1
LTER Review Site Visit Book (03-15 February 1994)

I.  Introduction 
	The annual advance and retreat of pack ice, a characteristic 
feature of polar marine environments, affects about 50% of the 
Southern Ocean as well as vast areas of the Arctic Ocean and Bering 
Sea.  In these polar environments, pack ice provides marine habitats 
that are clearly distinct from those of the open-water (Smith 1987, 
1990; Murphy et al. 1988), and where microbial communities abound.  
Annual pack ice may also be the major physical determinant of 
temporal/spatial changes in the structure and function of polar 
biota (Ainley et al. 1986; Fraser and Ainley 1986; Smith and Vidal 
1986; Smith and Nelson 1986; Walsh and McRoy 1986; Garrison et al. 
1987; Ainley et al. 1988; Smith 1990).  Thus, interannual cycles 
and/or trends in the annual extent of pack ice are likely to have 
significant effects on all levels of the food web, from total annual 
primary production (Smith et al. 1988) to breeding success in 
seabirds (Ainley et al. 1983; Trivelpiece et al. in press, 1990).
A. Palmer Long-Term Ecological Research Project (LTER)
	Research at the antarctic marine LTER site, Palmer Station and 
surrounding waters, focuses on the pelagic marine ecosystem and 
the ecological processes which link the extent of annual pack ice 
with the biological dynamics of different trophic levels.  
	The central hypothesis for all Palmer LTER research is that 
interannual variations in physical processes like the extent of pack 
ice and oceanic circulation affect all levels of the food web of the 
Southern Ocean.
Our general objectives are
(1) to document interannual variability in the development and 
extent of annual pack ice and in life-history parameters of primary 
producers and populations of key species from different trophic 
levels in the antarctic marine food web;
(2) to quantify the processes that underlie natural variation in these 
representative populations;
(3) to construct models that link ecosystem processes to physical 
environmental variables, and that simulate the spatial/temporal 
relationships between representative populations; and 
(4) to employ such models to predict and validate the impacts of 
altered periodicities in the annual extent of pack ice on ecosystem 
dynamics.
	To achieve our objectives we require data from several 
spatial/temporal scales, including remote sensing, a field approach 
that includes both an annual monitoring program and a series of 
research cruises, and a modeling effort to provide linkages on 
multiple spatial and temporal scales between biological and 
environmental components of the ecosystem.  Linkages between the 
models will be based on resource limitation, and will track the 
effects of interannual variation in the extent of pack ice cover on 
marine populations.
B.  Ecosystem description:  physical environment and food web
	The amplitude and phase of interannual variability in the 
regional extent of pack ice is not the same in all sectors of the 
Southern Ocean (Zwally et al. 1983a).  The Palmer LTER study region 
surrounds Palmer Station (64ˇ40'S, 64ˇ03'W), on the southwest side 
of Anvers Island midway down the Antarctic Peninsula, and runs 
from the southern end of the Bransfield Strait to south of Marguerite 
Bay (Fig. 1).  Observations spanning 15 years confirm that the 
maximum extent of ice cover in the Palmer LTER study area varies 
widely, ranging from near zero to halfway across Drake Passage 
(Quetin and Ross 1991; Stammerjohn 1993) (Fig. 2).  This variation 
appears to be on a 6 to 8 year cycle, with colder winters and greater 
interannual variability in the 1970's (Zwally et al. 1983b; Smith et 
al. 1988; Stammerjohn 1993).  The current regime is less well 
known, but there appears to be a SW setting flow offshore of Anvers 
Island, with the possibility of one or two cyclonic gyres (one near 
Anvers and Brabant Islands and one west of Adelaide Island) seaward 
of the SW setting flow (Stein 1988, 1991; Hofmann et al. 1992).  The 
Antarctic Circumpolar Current flows NE on the outside of this gyre 
and forms the northern boundary of the study region.  Our study area 
is thus well situated to take advantage of "natural experiments" to 
test our hypotheses on the local and regional implications of the 
interactions between physical structure (ice cover and currents) and 
biological populations.
	Current views of the antarctic marine food web with plankton-
benthos coupling (Clark 1985) and energy flow through the microbial 
loop (Hewes et al. 1985) are certainly more complex than the simple 
and linear marine food chain from large phytoplankton cells to 
antarctic krill to larger predators first proposed (Tranter 1982).  
Nevertheless, the links in the food web between primary producers, 
grazers and larger predators (seabirds, seals and whales) are often 
short and may involve fewer than three or four species (Smith 
1990). The number of basic prey types available to predators is 
limited in the Southern Ocean (Croxall 1980). Predators tend to 
concentrate on a core group of species, especially some extremely 
abundant euphausids and fish residing close to the base of the food 
chain (Ainley et al. 1988; Croxall 1980, Croxall et al. 1988).  This 
specialization and the dominance of a few predators allows us to 
represent major energy flow and interactions with a few species 
from each trophic level. For example, AdŽlie penguins comprise 60 to 
70% of the entire antarctic avian biomass (Prevost 1981), and their 
diets are dominated by krill, i.e. 98% in the summer (Emison 1968; 
Volkman et al. 1980; Trivelpiece et al. 1987).  Croxall et al. (1988) 
suggest that the apparent close coupling between trophic levels 
means that long-term studies of these predator-prey relationships 
and their environment will be critical to understanding variability in 
Southern Ocean ecosystems and generating a monitoring base for 
predicting the impact of man-induced perturbations on this 
ecosystem.  The underlying assumption is that these apex predators 
sum and reflect environmental changes, whether cycles or trends, 
and are easier to monitor than the environmental changes 
themselves.
Primary Production.  The base of the pelagic food web is the 
phytoplankton, primary producers responsible for the entry of 
inorganic carbon (CO2, HCO3) into marine food chains.  In the 
Southern Ocean, pack ice causes differences in primary production in 
open water communities, ice-edge blooms, and ice algae.  The 
physical barrier formed by pack ice between the atmosphere and 
polar seas dampens wind-forced turbulence in the water column in 
the winter.  Melting pack ice at the ice edge during spring/summer 
creates a shallow, highly-stable, upper mixed layer over bottom 
water of higher salinity.  Coupled with increased incident radiation, 
these physical factors promote ice-edge blooms of phytoplankton 
throughout the austral spring that generally precede those seen in 
surrounding seas during summer months.  Ice-edge phytoplankton 
blooms are believed to contribute significantly to the overall 
productivity of the Southern Ocean throughout the austral spring and 
summer months (El-Sayed 1971, 1978; Smith and Nelson 1986; 
Wilson et al. 1986; Smith 1987).  Thus variation in the extent of the 
pack ice is a significant factor in estimating interannual variation 
in total primary production (Smith and Nelson 1986; Smith et al. 
1988; Stammerjohn 1993).
	The dynamics of ice-edge blooms are complex (Garrison et al. 
1987). Independent studies of the sea-ice column have revealed the 
presence of a unique microbial community comprised largely of 
algae and bacteria (Palmisano and Sullivan 1983; Grossi et al. 1984; 
Garrison et al. 1986; Kottmeier et al. 1987) which may provide both 
a food supply for higher trophic levels as well as a seed stock for 
the initiation of ice-edge spring blooms when the sea ice retreats.  
Algal blooms appear to be restricted to the near surface waters of 
the marginal ice zone of Antarctica by the strong vertical 
stratification (El-Sayed 1978; Niebauer and Alexander 1985; Smith 
and Nelson 1985a, b, 1986; Wilson et al. 1986; Smith 1987).  The 
center of the bloom proceeds southward with the receding ice edge 
and the seaward edge of the bloom is presumably diluted by deeper 
mixing processes.  As such, the areal extent of any marginal ice-
edge bloom is a passive tracer of the spatial balance between 
stratification processes induced by ice melting and the physical 
processes which promote vertical mixing (Wilson et al. 1986).  This 
paradigm was supported by a three- season investigation of the ice-
edge zone by AMERIEZ (Antarctic Marine Ecosystem Research at the 
Ice Edge Zone), and, as expected, the frontal zone of enhanced 
biological productivity exhibited seasonal variability and was 
highest in the spring (Nelson et al. 1989).
	Open-water primary production in the Southern Ocean is 
thought to be limited by wind-induced turbulence and available light, 
not macro-nutrients (Hayes et al. 1984; Heywood and Whitaker 1984; 
Koike et al. 1986; Holm-Hansen et al. 1989; Karl et al. 1992). 
Although our basic assumption is that nutrients are non-limiting in 
antarctic waters, there are reports that inorganic nutrients are 
significantly depleted as ice-edge blooms develop (Smith and Nelson 
1986; Perrin et al. 1987).  Since nutrients are rapidly but not 
entirely depleted, the nutrient-status of these blooms is a debatable 
issue.  On average, summer productivity is higher in nearshore 
coastal regions, in regions of upwelling, and at the ice edge than in 
the open ocean (El-Sayed 1985; Smith and Nelson 1986; Smith et al. 
1988).  Although low levels of primary production are detectable in 
winter (Kottmeier and Sullivan 1987), food availability for 
herbivores is intensely seasonal and spatially variable.
	During the austral spring and summer, nearshore and highly 
productive blooms are either unialgal in composition or a mixture of 
phytoplankton species in which the relative dominance of small and 
large phytoplankton species changes over the season.  Prior to the 
spring bloom of large size diatoms in October to December, smaller 
(<20 µm) phytoplankton can account for more than 80% of water 
column chlorophyll a (Chl a) biomass, shifting to < 30% in summer 
when phytoplankton abundance is greatest (Perrin et al. 1987).  The 
variability in dominant algal size class has direct implications for 
predictions of the impact of interannual variability in phytoplankton 
dynamics on the overall trophodynamic interactions in water column 
food webs.  Adult and larval antarctic krill (Euphausia superba) are 
more efficient at ingesting larger phytoplankton cells than smaller 
flagellates (Quetin and Ross 1985), and the smaller phytoplankton 
components are most likely grazed by microzooplankton and 
invertebrate larvae (Siegfried et al. 1985).
Primary consumers.  Unlike most other oceans where much of the 
primary production is grazed by copepods, antarctic krill, Euphausia 
superba, can be over 50% of the total zooplankton biomass in the 
epipelagic layer in the Southern Ocean (Hopkins 1985), and thus 
represent both an important grazer and about half the total animal 
matter available for larger carnivores to eat (Laws 1985).  
Antarctic krill reach 50 to 60 mm in total length, have a life-span 
of 6 to 8 years (Ettershank 1984; Siegel 1987), and can swim as 
well as small fish such as anchovy or sardines (Hamner et al. 1983).  
For most of their life krill occur in discrete schools of swarms that 
vary in size from several individuals (Hamner 1984) to the rare 
"super swarm" over 12 km long (Macaulay et al. 1984).  Although 
circumpolar in distribution, high concentrations of krill are found in 
only a few locations (Laws 1985), mostly within the area covered by 
the annual advance and retreat of sea ice - which suggests a close 
coupling between krill populations, ice dynamics and the associated 
ice-edge blooms.
	Seasonal cycles of growth and reproduction in E. superba are 
marked and keyed to seasonal cycles of light and food in the 
environment (Quetin and Ross 1991).  If herbivores are food-limited, 
as appears to be true for antarctic krill (Ross and Quetin 1986; Price 
et al. 1988; Quetin and Ross 1991), variability in phytoplankton 
biomass and production will cause variability in reproduction, 
growth and survival.  Survival of the young-of-the-year during the 
first year is affected primarily by environmental conditions during 
two critical periods:  (1) mid-summer when larvae first molt into 
the first feeding stage with its point-of-no-return of 10-14 d (Ross 
and Quetin 1989), and (2) the first winter, with a 6-mo period of 
low food availability coupled with the inability of larvae to starve 
for long periods (Ross and Quetin 1991).  Although questions remain 
about the quantitative importance of ice algae, larvae and juveniles 
do feed on ice algae both winter and spring (Guzman 1983; Kottmeier 
and Sullivan 1987; Quetin and Ross 1991; Daly and Macaulay 1988; 
Marschall 1988).
	Even though recruitment and reproductive success vary with 
environmental conditions, for animals with lifespans of more than 
several years, like krill and penguins, total biomass in an 
undisturbed population can be assumed to be constant, oscillating 
about a mean value (Priddle et al. 1988).  Thus, fluctuations in the 
mesoscale abundance of antarctic krill (Sahrhage 1988) are usually 
attributed to redistribution of krill by physical forces, not to 
intrinsic features of krill biology (Priddle et al. 1988).  These 
mesoscale changes occur on the order of twice per decade, the same 
temporal scale as natural cycles of variation in environmental 
conditions such as El Nino Southern Oscillations, ENSO's, (Priddle et 
al. 1988) and interannual variation in ice cover (Zwally et al. 1983a, 
b).
	Pleuragramma antarcticum, the antarctic silverfish, has 
clupeid characteristics and ecology, and is one of the most abundant 
fish in high-antarctic marine environments (DeWitt 1970).  As a 
consequence it is also an important prey item for many consumers 
(Eastman and DeVries 1981;Volkman et al. 1980), including south 
polar skuas (Ainley et al. 1984; Pietz 1986, 1987).  Although time 
and locations of spawning are not well known, spawning probably 
occurs during spring in the permanent pack ice zone near coastal 
waters of the antarctic continent, and larvae hatch in December 
(Kellermann 1986).  Post-larval silverfish in their first year (Age 
Class 0 - AC0) and juveniles in their second year (AC1) remain in the 
surface layers of cold shelf water.  However, older juveniles and 
sub-adult fish (AC2+ to AC11+, 6 to 20 cm) are commonly found in 
the same areas as krill, eating larval krill and other euphausiids 
(Hubold 1985; Williams 1985).  Thus, changes in water mass 
distributions may alter fish distributions near seabird rookeries.
	Larval abundance, growth and year class strength in silverfish 
appear to be related to the melting of the pack ice, and at least in 
the southern Weddell Sea are higher in warm years when the ice 
melts earlier (Hubold 1985, Hubold and Tomo 1989).  Year class 
strength of antarctic silverfish should thus be the inverse of that of 
antarctic krill.  
Secondary consumers.  AdŽlie penguins (Pygoscelis adŽliae ) and 
south polar skuas (Catharacta maccormicki ) represent the Palmer 
LTER secondary consumers.  AdŽlie penguins are long-lived (Ainley 
et al. 1983), highly philopatric birds (Ainley et al. 1983; Trivelpiece 
et al. in preparation), that migrate annually to their natal rookeries 
to breed.  AdŽlie penguins remain associated with these rookeries 
during the entire 4 to 5 month summer reproductive season, October 
through February.  However, they are dependent on pack ice for 
winter survival (Fraser et al. 1992; Trivelpiece et al. in preparation) 
and during critical stages in their reproductive cycle (Ainley et al. 
1983; Trivelpiece et al. in press).  AdŽlie penguins are shallow-
diving, offshore foragers, with a maximum foraging range of about 
50 km  and depend primarily on krill for food during summer.  In 
some years krill are scarce within the foraging area, which affects 
aspects of the reproductive biology of AdŽlie  penguins.
	Multiannual patterns in the physical environment, the temporal 
and spatial availability of the micronekton, and the breeding success 
of the large populations of seabirds dependent on these organisms 
have been described (El-Sayed 1988; Kellermann and Kock 1988; 
Rakusa-Suszczewski 1988; Stein 1988; Trivelpiece et al. 1990).  For 
example, the long-term historical data on AdŽlie penguins collected 
from 1981 to 1989 at Admiralty Bay at the north end of the South 
Shetland Islands suggest that winter-over survival was higher (50-
87%) during years of heavy ice than during years of light ice (<40%; 
Fig. 3a).  At Palmer Station the number of breeding AdŽlie penguin 
pairs at 21 colonies monitored from 1988-1992 increased during 
summers following heavy ice years (1991) and decreased during 
summers following light ice years (1989, 1990, 1992; Fig. 3b).
	The south polar skua feeds primarily on fish, with antarctic 
silverfish (primarily 10 to 13 cm long, of AC6+ to 8+) an important 
part of their diet for reproductive success (Young 1963; Ainley et al. 
1984; Pietz 1986, 1987; Hubold and Tomo 1989).  Upon arrival of the 
nesting pair at the rookery from their wintering areas, the male 
feeds the female with local food resources found within their 
foraging range of 160 km (Ainley et al. 1984).  Only with sufficient 
food at this time is the female able to lay eggs, unlike the penguins 
that arrive at the rookery ready to lay eggs.
	We hypothesize that the reproductive success of south polar 
skuas is linked to the extent of pack ice through the abundance of 
subadult (AC8+) antarctic silverfish in the foraging area (Fig. 3a).  
Thus high recruitment in silverfish in a warm year will produce high 
prey availability for the south polar skuas eight years later i.e. high 
abundance of AC8+.  The one exception to this predicted trend was 
during the 83-84 summer which was also noted for the lack of krill 
in the Bransfield Strait region and major shifts in water masses 
(Sahrhage 1988).
	In AdŽlie penguins, parental fitness is primarily a function of 
winter-over and spring conditions.  The physiological condition of 
birds during spring determines their ability to fast during incubation 
of the eggs and to forage at sea.  South polar skuas, on the other 
hand, are unable to store large amounts of fat, so they depend on 
prey availability during spring.  If prey availability is low, they will 
not attempt to breed.  In south polar skuas, breeding success 
(number of chicks per pair) is more variable than in AdŽlies, perhaps 
because the ability to breed depends on prey availability during a 
short period of time.
Microbial loop.  Heterotrophic bacteria and other microorganisms are 
ubiquitous in the marine environment, regardless of latitude, water 
depth or distance from continental land masses.  Antarctic marine 
habitats are no exception, and bacteria are an important component 
of the indigenous microbial assemblage (McLean 1918; Darling and 
Siple 1941; cf Sieburth 1965, and Bunt 1971).  During the past 
several years, in situ investigations designed to gain a general 
appreciation for the existence and metabolic activities of the 
microheterotrophic component of the food web have created a more 
coherent picture of microbial processes and rates.  Substantial 
regional/temporal variability exists in bacterial biomass, substrate 
uptake rates, productivity and specific growth rates for microbial 
assemblages from a variety of habitats within the Southern Ocean 
(Tables 1 and 2).  However, the numbers fall within the ranges 
measured in temperate and tropical marine ecosystems, indicating 
that antarctic bacterial assemblages are not unique (Table 2).  The 
extremely wide ranges observed, even within seasons and over short 
distances, suggest that there may be strong local controls on 
bacterial rate processes.
	The relatively long turnover times of one to several weeks of 
organic substrates found in a majority of Southern Ocean habitats 
argue for either slow uptake rates, large ambient pools or both.  
Without direct estimates of the ambient pools, however, turnover 
times may be overestimated by the common radiotracer techniques 
which add 14C or 3H to the ambient pool.  Direct measurements of 
either the total dissolved organic carbon (DOC) or specific 
constituents range from 0.5 to 12 mg C l-1 (El-Sayed and Taguchi 
1981; Dawson et al. 1985; Zdanowski 1985; Bolter and Dawson 
1982).  However, there appears to be no direct correlation between 
DOM pools and microheterotrophic activity (Morita et al. 1977; 
Bolter and Dawson 1982; Bird and Karl 1991), which argues that 
either we may not be able to distinguish between the total and 
'microbiologically available' pools (King and Klug 1982; Karl 1986) 
or that a temporal uncoupling exists between organic matter 
production by phototrophs and consumption by heterotrophs.
	The relative importance of the 'microbial' loop (heterotrophic 
bacteria, protozoans, and viruses) and the linear food chain 
associated with net phytoplankton production and macrozooplankton 
grazers to biogeochemical cycling and food chain dynamics varies 
widely within different marine ecosystems.  In most systems, 
microbial loop activity is positively correlated with phytoplankton 
production and the release of DOM, and is higher under certain 
environmental conditions (Bird and Kalff 1984; Cole et al. 1988).
	However, because the coastal waters of the Southern Ocean are 
routinely characterized by (1) saturating concentrations of 
macronutrients, (2) phytoplankton blooms dominated by large-sized 
diatoms that cannot be consumed by protozoans, (3) secondary 
production dominated by herbivorous macrozooplanktonic and 
micronektonic grazers, and (4) bacterial respiration limited by 
temperature, the microbial loop in the Southern Ocean may play a 
lesser role in nutrient cycling and secondary production than in 
other oceans.  Low bacterial activity is currently hypothesized to be 
either substrate or temperature limited in these waters (Karl 1993).  
The increasing body of knowledge on growth dynamics of 
bacterioplankton and microzooplankton in antarctic pelagic waters 
will help in evaluating the role of the microbial loop in the Southern 
Ocean.

C.  Conceptual Model and General Approach
	Our central hypothesis states that many significant biological 
processes in the antarctic marine environment are strongly affected 
by physical factors, particularly the annual advance and retreat of 
pack ice and variations in ocean currents.  Our conceptual model (Fig. 
4) of the interaction between these physical processes and the 
components of the ecosystem is based on our present knowledge of 
interannual variability in the extent of pack ice and in the 
reproductive success of the species that dominate energy flow (Fig. 
3).  Timing and maximum extent of pack ice (sea ice) and the 
strength of various currents (oceanic circulation) are forced to a 
great extent by large scale atmospheric processes (meteorology) 
(Sahrhage 1988).  Since type and abundance of species found in 
identifiable water masses are different, a decrease or increase in 
the strength of the current can change the type and abundance of 
prey in the foraging area of penguins and south polar skuas.  Oceanic 
circulation, meteorology (wind speed, mixing), sea ice and incident 
radiation, but not nutrients, also affect the timing and extent of 
primary production (phytoplankton).  Each of the apex predators is 
dependent on the presence of one of the two prey species for 
reproductive success.  And recruitment success in our two prey 
species is linked directly to the presence or absence of ice.  One 
predator/prey pair, antarctic krill and AdŽlie penguins, is positively 
affected by the presence of ice, whereas the other, antarctic 
silverfish and south polar skuas, are negatively affected by pack ice 
extent in a complex manner.  At present bacteria are the most 
significant members of the microbial loop in our conceptual model 
because bacteria recycle nutrients in the upper layers.  Within this 
conceptual model we also include parameters, such as nutrient 
concentrations and bacterial numbers, that are of interest but that 
we do not believe control ecosystem functioning.
General approach
	To achieve our objectives we must use data from a long-term 
program of comprehensive measurements for several 
spatial/temporal scales.  The program includes measurements from 
remote sensing, a field approach that includes an annual monitoring 
program, a series of process-oriented research cruises (Table 3), 
and a modeling effort to provide linkages on multiple spatial and 
temporal scales between biological and environmental components 
of the ecosystem.
	The annual nearshore monitoring program occurs throughout 
the austral spring and summer (mid-October to mid-March) within 
the 2 nmi (3 km) boating limit for Palmer Station when small boat 
operations are possible.  Research in the nearshore marine 
environment surrounding Palmer Station focuses on hydrographic and 
optical characterisitics of the water column, phytoplankton 
populations, primary production, the prey of the seabirds, and the 
seabirds.  During this 5-mo period, seabird colonies are monitored 
regularly and two transects within the Palmer grid (stations A-E 
and F-J, Fig. 5) are sampled either weekly or biweekly.  We monitor 
processes (reproduction, recruitment) and parameters (food 
availability) that are sensitive to environmental change and are 
important in the structure and function of the communities.
	Satellite imagery is used to provide important data for several 
environmental parameters on regional spatial scales and roughly 
daily temporal scales.  These satellite data include information on: 
meteorology, sea ice, surface and cloud reflectance and incident
surface irradiance, aerosol climatology and water vapor, ozone 
concentrations and corresponding surface UV flux, sea surface 
temperature and ocean color for the estimation of phytoplankton 
biomass and production.
	The annual nearshore monitoring within the Palmer grid is 
linked to the mesoscale Peninsula grid during both an annual time-
series cruise in mid-summer (January) and less frequent process 
research cruises.  Within the Peninsula grid sampling stations are 
spaced at 20 km intervals along transects spaced every 100 km 
along the peninsula (Fig. 6) (Waters and Smith 1992).  One of the 
objectives of both types of cruises is to confirm that monitoring of 
critical environmental parameters on the scale of the Palmer grid 
will allow modeling of regional processes.  We are particularly 
interested during the annual cruise to learn how well our continuous 
measurements of the nearshore marine environment represent 
Palmer Basin and the 30 to 160 km foraging area of the seabirds.  
The cruise also serves as a time-series cruise to assess interannual 
variation over the middle of the Peninsula grid in zooplankton 
populations, water column properties, primary production estimates, 
and hydrographic and optical measurements.
	Specific objectives of the process research cruises include 
mesoscale observations of the distribution and abundance of the two 
prey species, seabird distribution and ecology, and the density field 
and surface circulation.  The first of two pairs of cruises, in fall and 
late winter of 1993, represent a year when winter ice formed late 
(mid-August) and quickly.  We plan to schedule a second pair around 
a winter of early and high ice extent during the next funding cycle of 
the Palmer LTER.

II.  Description of Research
A.  Remote sensing and environmental optics (Ray Smith, University 
of California at Santa Barbara)
	Remote Sensing and Environmental Optics Satellite sensors 
provide a means of obtaining synoptic information on regional and 
global scales and over long time periods.  Multiplatform sampling 
strategies utilizing contemporaneous buoy, zodiac, research ship, 
aircraft and satellite sensors are essential to cover the range of 
space/time scales of physical and biological processes relevant to 
the Palmer LTER (Smith et al. 1987).  Available, or potentially 
available, satellite data include visible and infrared imagery, 
passive and active microwave as well as spectrometer data.  A key 
component of the Palmer LTER effort is the development and testing 
of models linking sea ice dynamics, ocean circulation, primary 
production, population energetics of krill and population 
characteristics of avian predators.  Satellite data and algorithms 
are an important element in this modeling effort.
	The spatial and temporal variability of Southern Ocean sea ice 
coverage is a major physical determinant of the ecology of the 
Palmer LTER.  Low resolution (25km) sea ice coverage for the whole 
Southern Ocean is available from passive microwave satellite data 
since the mid-70's and has been analyzed from the Palmer LTER 
perspective by Stammerjohn (1993).  These data provide more than a 
decade of consistent information on the extent and timing of sea ice 
coverage in the LTER area, are expected to be available into the 
forseeable future, and are valuable for a number of purposes.  First, 
these data provide the "large scale" extent of pack ice.  We are 
currently working to develop objective and quantitative "indices" of 
sea ice extent, coverage, and duration for the LTER area.  Second, 
these data provide an important input for a model of phytoplankton 
productivity based upon a receding ice edge (Smith and Nelson 1985; 
Smith et al. 1988).  Stammerjohn (1993) provides an example of 
such a model for the LTER area.  Third, relatively low resolution 
passive microwave data provide a basis for investigating ice 
coverage on smaller spatial scales by means of both visible/infrared 
imagery and active microwave sensors.  Our ability to link the large 
scale LTER grid to the Palmer area (small scale) grid is an important 
problem and an effort is underway to tie high resolution (1 km) 
estimates of ice coverage to the large scale, low resolution passive 
microwave estimates.  Our objective is to make this linkage so that 
we have an objective and quantitative methodology to describe the 
space/time variability of sea ice on scales from the whole Southern 
Ocean to Palmer-specific ice indices related to krill distributions 
and avian predator rookeries.
	Weather (temperature, precipitation, calm or storm, clear or 
cloudy) is a major short term (days) physical forcing factor 
influencing the ecology of the Palmer LTER.  Average or long-term 
(months to years) weather patterns may be related to sea ice 
distributions and ocean circulation.  Weather is also a pervasive 
element of all antarctic research logistics. Imagery from visible and 
infrared (IR) polar-orbiting satellites has been interpreted to 
provide current conditions and medium range forcast weather 
analyses which are immediately valuable for logistical planning and 
longer range for retrospective analyses of weather influences.  In 
particular, these images are a vital tool for monitoring storms or 
signs of storm development in the Southern Ocean and evaluating 
their impact.  These visible/infrared data are available from the 
TeraScan system at Palmer (Bob Whritner, Antarctic Research 
Center/Scripps Institute of Oceanography) and from Bruce Sinkula 
(Antarctic Meteorology Center, Univ. of Wisconsin).  Our intent is to 
utilize past satellite weather records for the purpose of 
investigating correlations with sea ice, ocean circulation and other 
possible relevant LTER variables.  When clear, the IR data also can be 
analyzed to provide areal sea surface temperature (SST) 
information.
	Incident solar radiation at the ocean surface is of fundamental 
importance to climate, ocean and ice dynamics and the biosphere.  A 
number of research groups (eg. Gautier et al. 1980; Bishop and 
Rossow 1991) have developed methods for utilizing visible and 
infrared satellite data for the quantitative estimation of incident 
solar irradiance.  The distribution of clouds and their brightness is 
an important component of these models, and such data are available 
from the TeraScan system operated since 1989 at Palmer Station by 
Bob Whritner.  These data are currently being analyzed for the 
purpose of developing a cloud climatology specifically for the 
Palmer LTER area.  In addition, these data can also be used for the 
estimation of photosynthetic available radiation  (PAR, Frouin et al. 
1989), which is a key parameter in various models used for the 
estimation of phytoplankton production (Platt 1986; Bidigare et al. 
1987; Morel and Berthon 1989; Smith et al. 1989; Balch et al. 1989).  
Bidigare, Prezelin and Smith (1991) provide a review of bio-optical 
models with specific consideration of past and future ocean color 
satellite sensors.  Sullivan et al. (1993) have provided an estimate 
of the distribution of phytoplankton blooms in the Southern Ocean 
using Coastal Zone Color Scanner (CZCS) imagery.  It is anticipated 
that the Palmer TeraScan system will provide near real time access 
to ocean color imagery after the launch of the SeaWiFS sensor 
scheduled for July 1994.  These data will be utilized to estimate 
pigment biomass (chlorophyll concentrations) and to drive bio-
optical models of phytoplankton productivity.  In addition, the 
irradiance data are available for climate, ocean heat budget and ice 
thermodynamics modeling.
	Optical signals provide the proxy parameters for important 
biological  constitutents in bio-optical models.  Our environmental 
optics sampling strategy is geared toward determining the energy 
available for photosynthesis and optically characterizing the water 
for accurate bio-optical modeling.  In addition, under NASA funding 
(to RCS), we are developing SeaWiFS inwater and atmospheric 
algorithms and providing "optical surface validation" for the 
Antarctic region.  Our in-situ work provides both the small scale 
observations for local modeling and the data necessary to optimally 
utilize ocean color satellite imagery.
	The antarctic ozone hole and the consequent increase in 
ultraviolet radiation has been shown to impact natural 
phytoplankton communities.  The Total Ozone Mapping Spectrometer 
(TOMS, now available from NASA Goddard Space Flight Center from 
the Russian Meteor satellite) provides global coverage of column 
ozone concentration.  These data, in concert with visible data to 
estimate solar irradiance, may be used to estimate areal 
distributions of incident UVB.  Our aim is to develop and test a 
model, using a UVB bio-optical model as input, to estimate the areal 
impact of the antarctic ozone hole on phytoplankton in the Southern 
Ocean.  Further, the TOMS data permit an important correction to be 
made in the SeaWiFS atmospheric algorithm.  In short, TOMS data 
available from NASA/GSFC are a very useful component of our 
modeling.
	Marine environments, with plant populations that can double 
and/or be advected from one location to another in days, have a 
stronger day-to-day variability than the distributions and 
production of biomass on land.  As a consequence, remote sensing 
plays an especially important role by filling a critical gap in the 
space/time sampling domain of marine environments (Smith et al. 
1987).  Also, logistical difficulties associated with antarctic 
research argue for the use of satellite sampling.  Our objective is to 
utilize these satellite data to link both across space/time scales 
and the various component models of the LTER. 


B.  Microbial processes and carbon flux.  (David Karl, University of 
Hawaii)
Microbial processes.  Research during the Antarctic Marine 
Ecosystem Research at the Ice Edge Zone (AMERIEZ) has helped 
establish the various temporal and spatial scales on which microbial 
processes vary.  During three research cruises to the marginal ice-
edge zone of the Weddell Sea in austral spring, autumn and winter, 
microbial assemblages seaward of the ice-edge influence, within 
the ice-melt region and beneath the pack ice were sampled and 
compared.  The enhanced levels of phytoplankton biomass and 
production at the ice-edge margin, especially in spring, were 
expressed at both higher trophic levels of the food web (Ainley et al. 
1986; Fraser and Ainley 1986) and within various components of the 
detrital-based microbial loop.  Bacterioplankton showed large scale 
spatial heterogeneity in austral spring (Sullivan et al. 1990).  
However, bacteria were a relatively small percentage of the 
available standing stock of particulate matter during the initial 
period of the spring bloom at the ice-edge margin.  During spring 
positive correlations were observed between time-and-space 
coupled autotrophic and heterotrophic processes, and 
bacterioplankton production averaged about 11% of the 
contemporaneous rate of primary production.
	In autumn 1986, the ice-edge was close to its seasonal 
extreme, and heterotrophic microbial assemblages showed biomass 
and activity maxima that were generally coherent with those 
measured for the photoautotrophic assemblage, with higher values in 
the open water regions of the ice-edge margin (Cota et al. 1990).  
Minimal values for biomass, productivity and growth rate were 
recorded under the pack ice or at depth in the water column.  In 
contrast to spring, however, depth-integrated bacterial production 
often exceeded rates of primary production.  Clearly a 
microheterotrophic succession followed the spring/summer bloom.  
However, information on the sources of carbon and energy required 
for this net heterotrophic ecosystem metabolism are not available, 
so interpretation of these events is uncertain.
	The current conceptual model for the role of heterotrophic 
bacteria in the Southern Ocean microbial loop distinguishes between 
high and low molecular weight organic substrates for 
microheterotrophic populations, the "HSB" model of Billen and 
Fontigny (1987) (Fig. 8).  This conceptual model as incorporated into 
an "ecophysiological" model of phytoplankton and bacterioplankton 
growth (Lancelot et al. 1989) has proven useful for determining 
microbial rate processes and control mechanisms.  One interesting 
and unexpected result of a study in Prydz Bay based on this model 
and that focused on several distinct habitats - the open sea, the 
divergence frontal region, and the marginal ice zone - was the 
relationship discovered between phytoplankton and bacterioplankton.  
The phytoplankton and bacterioplankton biomasses were not 
positively correlated, contrary to what is often observed (Bird and 
Kalff 1984; Cole et al. 1988).  Billen and Becquevort (1991) 
hypothesized that these results could be due to a lagged response in 
the growth of bacterioplankton following the spring phytoplankton 
bloom caused by the composition of the dissolved organic matter 
(DOM) pools, and not to a differential temperature inhibition as 
suggested by Pomeroy and Deibel (1986).  There are several 
alternative hypotheses that may be formulated to explain these 
results:
H1:  The decoupling of the phytoplankton and bacterioplankton 
biomasses is due to the composition of the DOM pools.  During the 
initiation of the bloom, predominantly high molecular weight DOM is 
produced by the phytoplankton requiring hydrolysis by exozymes 
(extracellular enzymes) before the carbon and energy is available for 
bacterial growth.  This effect would cause about a 1 mo temporal 
separation between the phytoplankton and bacterial biomass and 
activity peaks.
H2:  The decoupling of the phytoplankton and bacterioplankton 
biomasses is due to delayed production of extracellular carbon by 
the phytoplankton population and temporally coupled utilization by 
microheterotrophs.
H3:  The decoupling of the phytoplankton and bacterioplankton 
biomasses is due to delayed growth of micro- and macrozooplankton 
populations, relative to the initiation of the spring bloom, followed 
by a period of intense feeding and a rapid response of 
microheterotrophs to the organic substrates generated during the 
grazing processes.
	The surprising results of Billen and colleagues have clearly 
focused attention on several important parameters of carbon and 
energy flow through plankton assemblages, namely:  the importance 
of direct and indirect production of dissolved organic matter by 
phytoplankton populations, the importance of characterizing the 
molecular composition of the total dissolved organic carbon (DOC) 
pool and the importance of temporal lags and successional stages in 
Southern Ocean ecosystems.
	Similar comparisons between bacterial cell numbers and 
chlorophyll (chl) a concentrations for the AMERIEZ, in the Weddell 
Sea, and RACER programs, west of the Antarctic Peninsula in the 
north of Anvers Island but in the northern part of the Palmer LTER 
Peninsula grid, also revealed empirical relationships (Fig. 9) that 
were different from previous analyses of similar data from a 
variety of marine and freshwater ecosystems (Cota et al. 1990; Karl 
et al. 1991a).  The RACER database showed a deficiency in bacterial 
cells at chl a concentrations >2.5 µg Chl a l-1 of up to an order of 
magnitude (Fig. 9).  At the present time we do not know whether this 
is a fundamental difference between non-polar and polar habitats, or 
whether the eutrophic coastal regions of the Antarctic Peninsula are 
unique in this regard.
	As part of the Palmer LTER microbial loop research, we are 
investigating standing stocks, production rates and possible control 
mechanisms.  Standing stock estimates are derived from a 
combination of lipopolysaccharide (LPS) concentrations, bacterial 
enumeration by dual-laser flow cytometry, and closure calculations 
of microbial biomass from particulate organic carbon (POC), ATP, 
Chl a, and LPS measurements using inverse modelling techniques.  
Production rate investigations include determination of dissolved 
organic carbon (DOC), estimates of microheterotrophic activity from 
amino acid (leucine) incorporation, exoenzyme activities (beta-
glucosidase and leucine aminopeptidase), the stoichiometry of 
oxygen/carbon dioxide dynamics, bacterial starvation assays, and 
the effects of temperature on growth processes.  In addition, 
experiments on the effects of addition of organic substrates on 
bacterial growth will help elucidate whether the observed 
bacterial/algal decoupling is due to resource limitation.  Bacterial 
biomass is removed by the combined effects of grazing by 
protozoans and higher trophic levels, death and autolysis, and viral 
infection.
Carbon flux and the Southern Ocean biological pump.  The oceans act 
as a regulator of atmospheric carbon dioxide (CO2) and thus occupy a 
central role in the debate over the effects of increasing levels of 
greenhouse gases.  Both physical and biological processes control 
the rate of removal of atmospheric CO2.  First, the exchange can be 
rapid, and is influenced by ocean circulation and oceanic biological 
activity (Sarmiento and Toggweiler 1984; Siegenthaler and Wenk 
1984; Karl et al. 1991b).  Second, biological processes in the surface 
ocean produce particulate carbon that sinks into the deep ocean 
where it is either remineralized en route to the seabed or buried in 
deep-sea sediments (Brewer 1983).  Consequently, the ocean's 
interior is continuously enriched with a variety of bioelements (e.g., 
C, N, P, Si) resulting from surface ocean production, particulte 
matter flux and dissolution/remineralization - a series of processes 
that has been termed the "biological pump" (Moore and Bolin 1987).  
Variation in the rate and efficiency of the biological pump is thought 
to be controlled by inorganic nutrient inputs from outside the 
euphotic zone.
	Recent box models of the ocean-atmosphere system have 
demonstrated the potential importance of the Southern ocean in the 
regulation of atmospheric CO2 (Ennever and McElroy 1985), so the 
rate and efficiency of the biological pump in the Southern Ocean is a 
topic of great importance in the study of oceanic carbon cycles.  
However, the factors controlling the biological pump in polar 
environments appear to be different from those in other oceanic 
regions, and the biological pump in polar regions appears to be 
functioning at less than full capacity (Knox and McElroy 1984).  Most 
of the Southern Ocean is characterized by high surface nutrient 
concentrations, but low rates of primary production and export 
production (Holm-Hansen et al. 1977; Honjo 1990).  If all the surface 
nutrients in the Southern Ocean were used by the phytoplankton, the 
biological pump activity could transfer significant amounts of 
atmospheric CO2 to the ocean's interior.  Instead it appears as  if 
the excess inorganic nutrients are ultimately removed during the 
formation of Antarctic Deep and Antarctic Intermediate water 
masses.  A resolution of this Southern ocean biological pump enigma 
is a topic of great importance in the study of oceanic carbon cycles.
	Some recent studies are relevant to the activity of the 
biological pump in the Southern Ocean.  Studies of pCO2 fluctuations 
during the spring bloom of antarctic coastal ecosystems during 
RACER in a region in the northern part of the LTER Peninsula grid 
revealed a substantial decrease in the surface water pCO2 (surface 
water concentrations <100 µatm compared to atmospheric 
concentrations of about 325 µatm) (Fig. 10).  The air-to-sea flux of 
carbon during the height of the spring bloom was estimated to be 
about 10 mmol C m-2 d-1 (Karl et al. 1991b).  The large pCO2 
gradients during the spring bloom may be enhanced by a large flux of 
carbon to the atmosphere by air-breathing birds and mammals, the 
dominant predators in the spring bloom food web of antarctic 
coastal waters.  This flux has been described as a 'leak' in the 
biological carbon pump for the Southern Ocean (Huntley et al. 1991), 
and because the oxygen used by the predators is derived from the 
atmosphere rather than from the ocean, this leak should result in an 
uncoupling of the anticipated dissolved seawater O2:CO2 
relationships and may also affect quantitative C:N and C:P 
stoichiometries (Sambrotto et al. 1993).
	Another important component of the biological pump, the 
export of particulate organic matter from the surface waters, also 
referred to as "export production", can be measured with sediment 
traps positioned near the base of the euphotic zone (Eppley 1989).  
Particle flux measurements in antarctic coastal waters and at the 
ice-edge boundary have revealed a tremendous seasonality and 
interannual variability (Fig. 4), which is likely related to variations 
in the ice-edge blooms.
	On Palmer LTER research cruises several measurements 
relevant to carbon flux and questions concerning the biological pump 
in the Southern Ocean are measured.  Gases (oxygen, total dissolved 
inorganic carbon and alkalinity) are measured at the same stations 
as all other parameters for estimates of air-to-sea carbon flux.  In 
addition three sediment traps have been moored in Palmer Basin 
about a points two/thirds of the way seaward of the bottom of the 
600.* transect and at a points the retreating ice edge should pass in 
the spring after winters of high ice cover.  These traps were first 
deployed in November of 1992, and recovered in April 1993 after the 
end of the 1992-1993 season's high production.  The three traps 
were redeployed in April 1993 and will be retrieved and redeployed 
during the January 1994 LTER cruise.  The cups on the sediment 
traps are programmed to rotate at periods varying from 4 days 
during the anticipated periods of high production to up to 4 weeks 
during the winter when production and thus "export production" is 
expected to be low.
C. Phytoplankton Productivity and Community Dynamics (Barbara 
PrŽzelin, University of California at Santa Barbara)
	Given the evidence that led to the central LTER hypothesis that 
interannual variation in the extent of the pack ice is a major 
determinant of interannual variation in primary production (sect. 
IB), three general  working hypotheses were proposed which  
provided the initial framework for developing a preliminary field 
strategy of data collection and hypothesis testing. 
H1:  Neritic phytoplankton dynamics reflect spatial/temporal 
changes in the distribution and nature of frontal boundaries between 
antarctic oceanic water masses and nearshore currents, as well as 
episodic ice-edge phytoplankton blooms that occur sequentially over 
the short growing season.
H2:  The components of antarctic primary production include 
contributions from open water phytoplankton and ice edge blooms 
and sea ice algae.  Total primary production may therefore vary with 
the extent of the pack ice during the previous winter and spring as 
the spatial and temporal extent of the ice-edge phytoplankton 
blooms should be greater in years with greater ice pack coverage.
H3:  The size composition and abundance of phytoplankton biomass 
change with the season.  During blooms, larger sized phytoplankton 
will dominant the community.
Background and Initial Conceptual Approach.  This primary 
productivity research team had little or no prior Antarctic research 
experience at the time the Palmer LTER proposal was written.  
Solicitation for our participation was based largely upon our prior 
laboratory and field studies of potential mechanisms controlling the 
photoadaptive physiology and rates of primary productivity of in situ 
phytoplankton communities in diverse and highly variable waters of 
temperate and subtropical oceans (PrŽzelin et al. 1987, 1991; Smith 
et al. 1987, 1989; PrŽzelin and Glover 1991; Bidigare et al. 1992; 
PrŽzelin 1992). These regulation studies combined intensive field 
monitoring and experimental studies to define and/or model the 
mechanisms underlying the time/space variability in phytoplankton 
distribution, community structure, photosynthetic physiology and 
rates of whole cell carbon fixation. Results emphasized the light-
dependent and, to a lesser extent, the nutrient-dependent and cell 
cycle-dependent nature of phytoplankton productivity.  Studies 
(Fronts '85, Watercolors '88) done in collaboration with Ray Smith 
(UCSB) and Bob Bidigare (University of Hawaii) led to a bio-optical 
model of primary productivity that accurately predicted directly 
measured instantaneous, daily, and daily integrated rates of carbon 
fixation in diverse coastal waters (PrŽzelin et al. 1987; Smith et al. 
1987, 1989; Bidigare et al. 1992).  We proposed that a similar 
combination of bio-optical monitoring, experimental, and modeling 
approaches could be applied to a mechanistic study of  primary 
productivity in the Southern Ocean, with the caveat that there were 
unusual properties of antarctic phytoplankton ecosystems that 
would have to be considered. 
First, Tilzer and co-workers (1985) had shown that the 
photosynthetic capacity (Pmax) and maximum quantum efficiency of 
photosynthesis were much lower in natural antarctic phytoplankton 
compared to nonpolar phytoplankton (Jacques 1983; Hoepffner 1984; 
Wilson et al. 1986).  They suggested that inefficient low-light 
photosynthesis was due to temperature-controlled processes, i. e.  
possible alterations in the fluidity of photosynthetic membranes 
which in turn disrupted the functional arrangement of 
photosynthetic components.  Thus photochemistry could become 
temperature rather than light-limited.  Such observations left us 
wondering how generalized temperature hypersensitivity might be in 
antarctic phytoplankton communities and to what degree small 
and/or sudden temperature changes (ie. associated with the freezing 
and thawing of sea ice) might induce large changes in primary 
productivity.  It seemed important to test assumptions about 
temperature-independent and purely bio-optical regulation of 
quantum yield which would affect the abilities of a bio-optical 
model to predict accurately in situ rates of carbon fixation over a 
range of time and space scales.  Preliminary Q10 experiments in the 
first year indicated photosynthesis-irradiance (PI) relationships 
were hypersensitive to small changes in environmental temperature; 
however, the patterns were inconsistent for samples collected at 
different times and places.  Reality was that such experimental 
studies could not be supported past the first field season as limited 
resources were refocused on maintaining a redefined core data base 
of inorganic nutrient, cell composition and production measurements 
(Table 4, Fig. 12). 
Second, Antarctic literature suggested some groups of polar 
phytoplankton might be capable of relatively high rates of light-
independent carbon fixation via b-carboxylation reactions which 
could supplement photosynthetic carbon fixation by as much as 30% 
(Mortrain-Bertrand 1988).  Should b-carboxylation occur, it might 
contribute to an overwintering strategy for antarctic phytoplankton 
and, if undetected, would lead to overestimates of the apparent 
quantum efficiency of photosynthesis and to an underestimate of the 
rates of primary production predicted solely on the basis of a bio-
optical model.  Hundreds of spring and summertime determinations, 
based upon measurements of carbon fixation in the light in the 
presence of a photosynthetic inhibitor DCMU, indicated b-
carboxylation rarely exceeded 5-10% of the total carbon fixed in the 
absence of a photosynthetic inhibitor.  Several measurements were 
made in a separate study (Icecolors '90) which indicated that  spring 
time communities along the MIZ excreted little if any of the organic 
carbon formed by photosynthesis (PrŽzelin, unpubl. observation).  The 
phyto-plankton appeared to be surviving and growing largely as 
obligate photoautotrophs. 
Third, it is widely recognized that significant and often repeatable 
variations in phytoplankton biology are often induced and commonly 
observed on time scales less than a day, i.e. diel or diurnal 
periodicities (PrŽzelin 1992).  Given that diurnal patterns vary 
significantly with taxonmic group, cell cycles, physiological state, 
environmental time keepers (i.e. photoperiod, temperature), and the 
rate of change of many enviromental variables (ie. irradiance, 
ammonia or nitrate pulses), it is of considerable importance to  
assess and define linkages between the daily variability in 
phytoplankton growth and productivity and their possible driving 
forces.  A number of studies have shown that attempts to predict in 
situ rates of primary productivity would err significantly if the 
daytime variations in photosynthesis were not taken into account 
(Fee 1975; Harding et al. 1982; Brown and Field 1985; PrŽzelin et al. 
1987a and 1989b; Smith et al. 1987, 1989; PrŽzelin and Glover 
1991; PrŽzelin 1992) and attempts were made to include this 
variability.  For instance, the pattern of daytime periodicity may 
change dramatically with rapid changes in photoperiod, with one 
study (Rivkin and Putt 1987) suggesting the timing of peak Pmax for 
antarctic phytoplankton shifts from ca local noon to ca local 
midnight as the natural photoperiod lengthened from a few hours to 
continuous illumination.  While the resulting impact on sampling 
strategies and productivity estimates is obvious, the universality of 
such seasonally-dependent changes in production patterns is 
unknown.  We made a concerted effort to get some preliminary 
indication of the magnitude and seasonal variation in photosynthetic 
periodicity in the first field season.  To date, time and personnel 
constraints have precluded detailed analyses of this portion of the 
database.  Also, limited resources and shifting priorities have 
reduced the number of diurnal measurements significantly.  At 
present diurnal measurements are made sparsely through the season 
and will be used only to time-correct productivity measurements 
made at different times of day (PrŽzelin et al. 1987; Smith et al. 
1987).  In the context of the longer term goals of the LTER, which 
will focus on interannual comparisons of seasonal patterns of 
primary productivity, a complete understanding of the seasonal 
regulation of patterns of daytime periodicity in primary production 
will be required eventually in order to assure the predictive 
accuracy of bio-optically modeled datasets which rely on satellite 
(i.e. SeaWifs) measurements made at a fixed time of day over a 
season.
Lastly, the potentially harmful effects of ultraviolet radiation on 
primary productivity needs extra consideration in the Southern 
Ocean where the UVB dosage is artificially increased each spring due 
to the photolysis of atmospheric ozone by polluting aerosols (CFCs).  
The study of "UV Radiation, Ozone Depletion and Phytoplankton 
Biology" has been addressed in the recent Icecolors '90 and '93  
studies of Smith and PrŽzelin and are outside the scope of the 
Palmer LTER. (see section VII, C).
Initial Strategy.  Over the 6 year period, which should include years 
with significant variability in the extent of maximum pack ice cover 
in the antarctic winter, we proposed to 1) monitor the spring to fall 
temporal/spatial variability in the abundance, size-distribution, 
composition and productivity of the phytoplankton communities 
within nearshore waters; 2) use traditional radiolabel measures of  
productivity to calibrate a bio-optical model;
 3) bio-optically monitor as continuously as possible the spring to 
fall in situ  temporal/spatial variability in hydrography, light 
availability and utilization, and primary productivity; 4) employ bio-
optical data to model phytoplankton production in the region around 
the study site as a function of space and time; 5) extend the spatial 
scale of the measurements and model during cruises in the fall and 
spring of two years, one with heavy and one with light ice cover; and 
6) verify and refine the model with data from # 1-4.  These studies 
would be accompanied by an extensive array of experiments to test 
the validity, define the limitations, and determine acceptable 
modifications for a bio-optical model to predict accurately the 
rates of Antarctic primary productivity over a wide range of time 
and space scales. 
Temporal/Spatial Variability.  Table 4 summarizes the present LTER 
productivity database collected and analyzed during the last 3 field 
seasons.  Like other Antarctic researchers (El-Sayed l971, l978; 
Tilzer et al. 1985; Smith and Nelson l986; von Bodungen 1986; 
Wilson et al. l986; Perrin et al. l987; Smith l987), we can show that 
nearshore phytoplankton biomass, size distribution, species 
composition and rates of carbon fixation showed significant regional 
variations throughout the austral spring and summer in the 
Antarctic (Figs. 12-15) that is unrelated to the nutritional status of 
the cell (Fig. 16).  Our time and space coverage represents the most 
extensively and highly resolved assemblage of quantitative data on 
phytoplankton seasonal succession, photophysiology, and primary 
productivity collected to date in the Southern Ocean. Furthermore, 
this data can be linked to several hydrographic and optical 
properties of the water column for further studies of both bio-
optical models of primary production and circulation/water column 
stratification based models of primary production (see sect. IIF).
The ability to predict patterns of phytoplankton distribution and in 
situ productivity for different regions of the LTER grid are presently 
problematic for at least two reasons.  First, the present correlative 
databases are sufficient to document the co-occurrence of physical, 
biological and chemical events, but are not sufficiently 
experimental to test apparent mechanistic linkages that underly 
long term ecolological modeling.
Second, correlative analyses and casual observation indicate that 
the priority of determinant factors controlling primary production 
likely changes through seasons and that frequent episodic events do 
occur of sufficient magnitude to quickly alter phytoplankton 
dynamics within distinct areas of the LTER grid.  There are times 
when the phytoplankton biomass at a given location can change by 
orders of magnitude with the horizontal advection of sea ice laden 
with ice algae.  We have documented such events occurring within a 
few hours near Palmer Station, which last for a few to several days 
and then suddenly are blown away.  At other times in the same 
season at the same location, the horizontal advection or local 
formation of sea ice is essentially void of ice algae and thus 
contributes little to local productivity while having a profound 
effect on the optical and hydrographic characteristics of the 
previously ice-free water column (Fig. 15).  Episodic disruption of 
phytoplankton dynamics in the water column appears to be the norm 
for Antarctic ecosystems and provides intriguing challenges for 
future ecosystem studies.
D.  Secondary production.  (Robin Ross and Langdon Quetin, University 
of California at Santa Barbara)
	Several hypotheses guide our approach to the study of the 
effects of interannual differences in the extent of pack ice on two 
species chosen to represent secondary production.  The two 
hypotheses concerning recruitment in antarctic krill and its 
population dynamics, the survival of the larvae (H1) and recruitment 
potential or population reproductive output (H2), are based on the 
concept that food availability at critical times is linked to either 
winter or spring ice dynamics.  Two hypotheses address mechanisms 
underlying the interannual variability in distribution of prey species 
within the summer foraging ranges of the dependent apex predators, 
krill and AdŽlie penguins (H3) and antarctic silverfish and south 
polar skuas (H4).
H1:  In winters with a greater extent in pack ice cover, larval and 
juvenile krill (young-of-the-year) in waters west of the Antarctic 
Peninsula will be in better physiological condition, have faster 
growth and development rates, and greater winter-over survival 
than in winters of low ice cover.
H2:  In years with greater food availability, reproductive output of 
adult krill will be greater.  Abundance and duration of food 
availability within the mesoscale LTER grid will be greater after 
winters with a greater extent in pack ice cover than after winters 
of low ice cover.
H3:  Interannual variation in krill abundance within the penguin 
foraging area near rookeries is primarily related to changes in the 
distribution of water masses dominated by krill, not to variations in 
recruitment to the krill population.  Water mass distributions, the 
extent of pack ice cover in winter, and meteorological conditions 
will follow the same cycle.
H4:  In winters and springs with a greater extent of pack ice cover, 
recruitment in antarctic silverfish will be lower than after winters 
with low ice cover.  Interannual variation in abundance of the size 
fish eaten by the south polar skuas within the summer foraging area 
will be related to variation in recruitment 8 to 10 years previous, 
and to the distribution of water masses.
	Annual and geographical variations in recruitment in antarctic 
krill may be due either to variations in reproductive output 
(spawning success) and/or survival of the larvae during critical 
periods during the early life history (Ross and Quetin 1991).  
Summers of high reproductive output are predicted to follow 
winters of high ice extent and presumably more extensive ice edge 
blooms.  Winter-over survival of larvae would be higher after a 
winter of high ice cover with the ice biota providing good winter 
grazing.  Together the two predictions suggest that if several 
winters of heavy ice cover alternate with several of low ice cover 
(Stammerjohn 1993), recruitment may fail in at least two 
consecutive years.  Changes in adult biomass from such a failure 
will not be detectable with current techniques (Priddle et al. 1988).  
However, differences in recruitment will be seen in length frequency 
distributions of subadult and adult krill from the annual cruises.  
Two years after a failure in recruitment, a higher average size will 
result from a lack of krill in their third summer (25-35 mm), and 
two years after a successful year, the average size will decrease 
with the addition of large numbers of small krill (Priddle et al. 
1988).
Survival of larvae.  Physiological condition (condition factor as a 
measure of robustness or carbon per length cubed (volume), percent 
lipid as a measure of stored reserves, and instantaneous growth 
rates as an index of nutrition during the intermolt period (2-4 
weeks)) of larvae during a winter with extensive ice cover was 
higher than during one with low ice cover (Ross and Quetin 1991), 
evidence for the idea that larvae must find a source of food other 
than open water phytoplankton or starve during their first winter 
(Elias 1990).  One commonly suggested alternate source of food is 
ice algae.  In years with no or late ice cover and thus low winter 
food availability, recruitment may fail entirely even if reproductive 
output was high.  Physiological condition of larvae and juveniles 
collected each austral spring is an annual index of a year class's 
ability to survive the winter.  The quantitative relationship between 
physiological condition and imminent starvation is currently being 
explored under a separate grant to Quetin and Ross.
	In addition to the annual index, during the first pair of pre- and 
post-winter cruises (1993) winter-over survival of the year's 
cohort will be quantified and related to physiological condition.  A 
second pair of cruises in the next funding cycle would repeat the 
study under different winter conditions.  Quantification of the 
distribution of larval and juvenile krill and ice algae under first 
year ice is done by divers who also collect krill for physiological 
condition.  Mortality during the first winter will be estimated from 
total numbers and stage composition in the survey area fall and 
spring, and known developmental times under winter conditions 
(Elias 1990).
Reproductive output.  Inter-school variability in the spawning 
frequency during the 3+ months summer reproductive season (Ross 
and Quetin 1986) is of the same magnitude within years as between 
years, suggesting that the major variables affecting reproductive 
output are length of the spawning season and percent of the 
population spawning, not interannual differences in the spawning 
frequency.  Krill need relatively high food concentrations to 
reproduce (Ross and Quetin 1986), thus temporal and spatial 
availability of food, particularly ice edge blooms in austral spring, 
may be an important determinant of both the length of the spawning 
season, and the percent of the population spawning (Quetin, Ross and 
Clarke 1993).  Over the past decade we have seen large interannual 
variability in the percent of the population of mature adults 
reproducing that are consistent with observed interannual 
differences in reproductive output (Brinton et al. 1987; Amsler, 
Quetin, Ross and Cuzin-Roudy in preparation), although not solely 
with winter ice extent.  Annual estimates of the percent of the 
population in the 'resting' stage (Cuzin-Roudy and Amsler 1991) 
during the LTER summer cruise, timing and concentration of food 
available, and the extent of pack ice cover in the winter will allow 
us to investigate this hypothesized linkage.
Prey availability.  The third and fourth hypotheses address the 
cause(s) of variations in the distribution of adult antarctic krill and 
of sub-adult silverfish within the summer foraging range of their 
respective predators.  Changes in mesoscale distributions and 
abundances of krill and silverfish may be linked to the ice cycle in a 
complex manner through changes in oceanic circulations linked to 
atmospheric changes (Sahrhage 1988) and/or the direct effect of 
pack ice on survival and/or behavior of the prey.
	The causes of seasonal and interannual variations in the size 
and number of aggregations of krill are poorly understood, yet the 
distribution and size of schools may play an important role in 
population dynamics of krill (Okubo pers. comm.), and prey 
availability for the seabird predators.  Purely physical models of 
turbulent redistribution cannot explain observed krill distribution 
patterns at small scales (Levin et al. 1989), but models of biological 
diffusion in a variable environment such as those of Davis et al 
(1991) may provide better simulations.  Therefore, local krill 
availability will result from the interaction between variation in 
recruitment, water mass distribution caused by large scale changes 
in atmospheric circulation, and seasonal and interannual changes in 
school size and distribution.
	Bioacoustics (BioSonics, 120 kHz transducer) are being used to 
quantitatively map the spatial and temporal distribution of 
antarctic krill, both during research cruises and from the zodiac 
throughout the spring and summer.  Seasonally, biomass values over 
the peninsula grid change a great deal, and were higher in summer 
than in either fall or spring (Fig. 17).  However, the pattern of 
distribution and biomass of krill schools does hold constant over 
shorter periods, as evidenced by a repeat set of transects in January 
1993 (Lascara et al. in press).  Length frequency distributions of 
krill also varied seasonally.  Larger and reproductively mature 
individuals were found further offshore than subadults and 
immatures in both spring and summer, but not in austral fall.  During 
the first summer cruise (Jan.-Feb. 1993), reproducing krill were 
found primarily at offshore stations in the southern reaches of the 
Peninsula grid (300.* and 200.* transects, refer to Fig. 6) which 
coincidentally is covered by ice each winter (Stammerjohn 1993).  
Reproductive success in krill may be greater and less variable in 
areas covered by ice every winter then in areas where ice cover is 
more variable.
	Although similar climatic and recruitment factors may affect 
fish distributions, historical records of pelagic fish, especially 
antarctic silverfish, in the Palmer LTER region are sparse.  For 
silverfish, densities are not high and not all length classes have 
been found in the region (Kellerman 1986; Hubold and Tomo 1989; 
Reisenbichler 1994).  Initial objectives for the net collections and 
for otoliths from guano samples from south polar skuas were (1) to 
document interannual variation in distribution and abundance of 
pelagic fish with a midwater trawl throughout the grid and 
particularly in shelf waters where adult silverfish were thought to 
occur, (2) to measure physiological condition and age distribution of 
subadult silverfish populations, i.e., those eaten by the south polar 
skuas, and (3) to investigate whether interannual variability in 
growth rates from otolith analysis of either larval or adult fish 
would allow us to test whether recruitment in silverfish followed 
the pattern predicted by the hypothesis, i.e. that recruitment is 
higher (as implied by higher growth rates for fish in their first year 
(AC1+)) after years of low winter ice extent.  Our present and 
proposed future approach reflects the current state of our 
knowledge and an evaluation of various possible techniques.
	Initially fish in January/February 1993 were sampled at all 
possible stations, onshore and offshore, on transects 600.*, 500.*, 
400.* and 300.* Since in other regions subadult silverfish had been 
found with krill schools offshore in the East Wind Drift (Hubold 
1985) and the shelf stations inside the Biscoe Islands had been 
suggested as a possible spawning ground for silverfish populations 
west of the Antarctic Peninsula (Fig. 18).  However, silverfish were 
only found in shelf waters near the Antarctic Peninsula.  Other fish, 
primarily the myctophid, Electrona antarctica, were found 
throughout the region in low abundances.  In March/May 1993 the 
sampling design reflected what we had learned about the 
hydrography and fish distributions and was based on concurrent 
hydrographic measurements.  The midwater trawl was primarily 
fished in waters landward of the continental water boundary, in 
either continental zone or shelf water, the supposed habitat of 
silverfish.  However, silverfish were again restricted to 'shelf' 
waters within 40 to 50 km of the mainland (Fig. 18).
	Midwater trawls yield large spatial scale sampling over a 
short time scale that does not include the critical time for egg 
laying for the south polar skuas.  During the first two seasons south 
polar skuas were evaluated as 'collectors of fish' over a longer time 
frame.  Otoliths from the guano of about 20 pairs of south polar 
skuas on Bonaparte Point were sorted from weekly guano 
collections, and otoliths identified, counted and measured.  Results 
were compared to less frequent diet samples from skua pairs 
monitored for reproductive success by the seabird component to 
verify that similar fish populations were being preyed upon by all 
south polar skuas.  Otolith species composition and relative 
abundance represents the fish community available to these seabirds 
within their foraging range of about 160 km.  The combination of 
large spatial scale sampling over a short time scale and a long 
temporal sampling regime over a spatial scale defined by the 
foraging range and depth of the south polar skua has proven valuable 
in understanding possible factors affecting fish distribution, and in 
developing an approach to test our hypothesis on interannual 
variability in fish availability.
	Two fish species dominate catches, both from nets and from 
guano, but the patterns for the two differ, both in time and in space.  
Antarctic silverfish are restricted in their spatial distribution, 
whereas Electrona antarctica is found over the entire grid in both 
the same areas as silverfish and further offshore (Fig. 18).  
Silverfish are also more restricted in their temporal availability 
(Fig. 19).  In both years, E. antarctica was the most abundant species 
in guano samples in spring and early summer.  Antarctic silverfish 
were a significant proportion of the total catch in early summer, 
although 1992-1993 proportions never reached the levels of 1991-
1992, and did not increase throughout the season (Fig. 19).  Thus 
silverfish distributions were variable on all scales measured 
(temporal, spatial and interannual), whereas E. antarctica has a more 
homogeneous distribution.
	Our approach to testing the hypothesis about the mechanism 
underlying interannual variability in silverfish availability to south 
polar skuas requires both net and guano collections, and age analysis 
of silverfish otoliths.  The age composition of silverfish in the 
guano samples will tell us if recruitment or distribution shifts is 
behind the variability observed in the proportion of silverfish in the 
fish community available to skuas.  If the age distribution remains 
the same each year, then physical factors controlling horizontal or 
vertical movements in silverfish that in turn affect their 
availability to south polar skuas is the most likely explanation for a 
'poor silverfish year'.  Alternatively, if the age composition changes, 
and we can follow a decrease in a certain year class through several 
years, then a recruitment failure of that year class is the most 
likely explanation.  We are in the process of evaluating several 
methods for otolith analysis for the adults, an essential part of our 
approach.
	Otolith analysis will not only help distinguish causes of 
interannual variability in fish availability to a particular group of 
birds, but also be useful for physiological measurements.  Condition 
factor and percent lipid are estimates of the more recent nutritional 
history of the fish, whereas standard otolith analysis (Hubold and 
Tomo 1989) will yield the relative growth rates of the fish during 
the last 8 years or so.  Since growth of fish of AC2+ and older is 
restricted to summer months, the otolith rings record the effect of 
environmental conditions, and represent a record of the past 
nutritional history.  Such patterns may help us establish a 
relationship between recruitment success and growth rates in 
silverfish and prey availability for the south polar skuas and 
environmental factors such as timing of the ice retreat.
E.  Seabird ecology and vertebrate predators.  (William R. Fraser and 
Wayne Z. Trivelpiece, Montana State University)
	Two seabird species were selected to represent the LTER apex 
predators.  These are AdŽlie penguin (Pygoscelis  adeliae) and south  
polar skua (Catharacta maccormicki).  AdŽlie penguins and south 
polar skuas hold different trophic positions in the region, with the 
former being essentially a planktivore that feeds almost exclusively 
on the antarctic krill (Euphausia superba), and the latter being a 
piscivore that relies primarily on the antarctic silverfish 
(Pleuragramma antarcticum).  AdŽlie penguins are year-round 
residents within the region of interest to the LTER, and winter in 
association with the pack ice.  South  polar skuas, however, are only 
summer residents that winter in arctic  waters.  These  two 
wintering strategies have important implications to aspects of the  
data being obtained on the ecology of each species, and in particular 
on the effects of pack ice on these predators.  Four hypotheses guide 
the predator research:
H1:  Winter-over survival and physiological condition of adult AdŽlie 
penguins upon their return to the rookeries to breed is a function of 
winter and early spring food availability in the pack ice and on the 
location of winter pack ice relative to the rookeries (sea ice extent).  
Adult winter- over survival, physiological condition and the percent 
of young birds that attempt to breed will be higher when pack ice 
extent is greater during winter.
H2:  Breeding success of AdŽlie penguins, barring the effects of 
spring snow conditions and catastrophic summer storms, is linked to 
the extent of sea ice through its effects on spring and summer krill 
availability.  Krill availability will be lower during cold summers 
and higher during warm summers.  Fledgling weights and the number 
of chicks fledged per pair will thus increase during warm summers, 
while the duration of foraging trips will decrease.
H3:  The physiological condition of south polar skuas during the pre-
egg stage is a function of the availability of the  antarctic 
silverfish within the skua's spring foraging range.  Territory 
occupancy will be earlier and more constant, and the onset of 
reproduction earlier when silverfish are more available.
H4:  Breeding success of the south polar skua will exhibit cycles 
different from those of AdŽlie penguins.  Recruitment of their 
primary prey, the antarctic silverfish, is affected negatively by pack 
ice during the spring of cold years.  Because south polar skuas 
primarily eat subadult fish, breeding success will be a function of 
ice conditions 8-10 years prior to the current breeding season.
	The approach in testing these hypotheses capitalizes on 
abundant, easily accessible AdŽlie penguin and south polar skua 
breeding populations (12,000 and 1,000 pairs, respectively), and on 
the measurement of ecological variables (Table 5) that are likely to 
be sensitive indicators of change in the marine system.  These data 
are obtained using protocols that have been instrumental in the 
development of long-term databases in the region since 1977.  These 
methods, now standardized as part of the CCAMLR  Ecosystem 
Monitoring Program, are implemented annually in both apex predator 
species as part of a terrestrial, colony-based  research effort that 
covers the October-March  period.  A  marine-based complement to 
the terrestrial work occurs each January coincident with peak food 
demands by these predators.  The key objectives are to examine 
variability in pelagic abundance and distribution, reproductive 
success, foraging ecology and winter-over survival and recruitment 
relative to annual changes in sea ice conditions, and within the 
broader context of change in other physical and biological features 
of the marine environment.
	The pattern emerging as the predator research develops 
continues to support the view that sea ice may be critical not only 
to the ecology of AdŽlie penguins and south polar skuas, but to a host 
of other southern ocean, upper-trophic level predators as well 
(Fraser  et al. 1992).  Coupling the current LTER predator data with 
data obtained as part of complementary  research programs initiated 
in the mid-1970's and 1980's suggests that, in effect, sea ice 
mediates the abundance and availability of prey (Fraser et  al. 1989, 
1992).  Long-term changes in predator populations, and in the diets 
of a select group of predators, can be linked to changing sea ice 
conditions during the last two decades within the LTER sampling 
area.  These findings may have broad implications to the function of 
Antarctic marine ecosystems (Ainley et al. 1988), to the direction 
of future research initiatives, and to the management and use of 
antarctic marine living resources (Fraser and Trivelpiece in  
preparation; Fraser et al. in preparation).
F.  Modeling  (Eileen Hofmann and John Klinck, Old Dominion 
University; Barbara Prezelin and Ray Smith, University of California 
at Santa Barbara) 
	The modeling component of the Palmer LTER program is 
designed to provide an approach for integrating and analyzing the 
many and varied data sets that are now becoming available from the 
program and to test the program core hypotheses.  Consequently, the 
modeling component consists of a hierarchy of models.  These 
models consider the physical environment, primary production, krill 
distribution and higher predator effects.  The efforts in the modeling 
component during the first part of the Palmer LTER program have 
been directed towards identifying and formulating the models that 
will be used. 
	The models being developed for the physical environment 
consist of a regional scale circulation model and a coupled sea-ice 
and mixed layer model.  The circulation model considers the three-
dimensional, time-dependent flow in the LTER grid region.  This 
model is based upon a semi-spectral primitive equation model 
(Haidvogel et al. 1991) that has been applied successfully to a 
variety of oceanic environments.  This model is now being configured 
for the LTER region.  The model allows for bottom bathymetry, 
surface wind stress and thermodynamic effects on the flow.  The 
simulated circulation fields obtained from this model will be 
calibrated and analyzed using the hydrographic data sets collected 
as part of the LTER field program.  The simulated circulation fields 
will provide a basis for understanding the patterns observed in the 
the water mass and property distributions seen in the hydrographic 
distributions as well as providing input to the biological models 
described below. 
	The coupled sea-ice and mixed layer model is based upon 
existing models described by Price et al. (1986) and Hakkinen 
(1990).  This model will be used to simulate the temperature and 
salinity structure of the upper part of the water column.  Analysis 
of the LTER hydrographic data has shown that this part of the water 
column exhibits considerable seasonal variability.  Also, the 
episodic nature of the forcing within the LTER region (e.g. storms) 
results in erosion and re-establishment of the mixed layer several 
times within a given season, such as the austral summer.  The 
seasonal and within-season variability will be investigated with the 
coupled sea-ice and mixed layer model.  This model will also be used 
to analyze and interpret patterns that are observed in primary 
production and pigment measurements made in the LTER region.  
Stability (or not) is considered to be one of the major factors 
regulating primary production in antarctic waters.  Once the coupled 
sea-ice and mixed layer model is implemented and calibrated, it is 
anticipated that it will be interfaced with bio-optical model being 
developed by Smith and Prezelin.
	As briefly discussed in Section II A, marine systems span such 
a large range of space/time scales that remote sensing and modeling 
are essential in order to cover this range of scales (Table 6).  Smith 
et al. (1987) compares the sace/time domains of several physical 
and biological processes with sace/time samling regimes of various 
measurement platforms (Fig. 7).  For the LTER, an understanding of 
the space/time distributions of our key indicator species and the 
environmental and biological processes that  affect these 
distributions, is fundamental to a complete understanding of and 
linkage between the various trophic levels.
	Further, the harsh environment and limited resources for 
sampling require that we develope a robust and accurate method for 
estimating primary production over a range of space/time scales.  
Development of the primary production model has several 
components: a model of production for the marginal ice zone which 
can provide a temporal estimate for the entire LTER region as well 
as the Southern Ocean; high-latitude ocean color algorithms for use 
with the SeaWiFS ocean color satellite sensor for high spatial (but 
limited temporal) estimation of pigment biomass and primary 
production; and local and mesoscale bio-optical estimates of 
pigment biomass and primary productivity based upon ship and 
Palmer Station area data.  A key objective will be to apropriately 
link the resolution of these productivity models to circulation 
models and the higher trohic level models at space/time scales best 
suited to the objectives of the LTER.  We have already shown that 
bio-optical models can be used to predict rates of light-dependent 
carbon fixation from field measurements of water-column optical 
properties and phytolankton absorption properties combined with 
verifiable assumptions regarding photosynthetic quantum yield 
(Smith et al. 1990).  Adaptation of these models to the high-latitude 
and low temperature polar environment is another key objective and 
is in progress.
	The modeling efforts underway for the prey (krill) component 
are focused on understanding the processes that contribute to the 
spatial distribution of krill swarms that have been observed in the 
acoustic data sets collected during the LTER cruises.  This modeling 
effort will build upon models developed for krill swarming, which 
are described in Levin et al. (1988) and Morin et al. (1988).  Results 
from the circulation and coupled sea-ice and mixed layer model as 
well as the results from the bio-optical and primary production 
modeling efforts will be interfaced with the output of the coupled 
sea-ice and mixed layer model.
	The modeling effort for the higher predators (penguins) 
consists of an energetics-based model for the AdŽlie  penguin.  This 
model has been implemented and is now at the point of doing 
simulations for calibration purposes.  It is anticipated that the 
results from the krill swarming model will eventually be interfaced 
with the penguin energetics model.  A second modeling effort that 
considers the effects of the size class structure of the prey (krill) 
on penguin foraging is currently under development.  This model 
builds upon the size class models described in Hofmann et al. (1992) 
and Dekshenieks et al. (in press).  The krill size frequency 
distributions obtained from stomach content analysis of penguins in 
the Palmer Basin area and those at King George Island provide the 
observational basis for implementing and calibrating this model.  
The model will be used to investigate the effect of fishing krill for 
a particular krill size class on penguin survivability.

III.  Relationship of research to the five core areas
Core area 1.  Pattern and control of primary production
	One of the objectives of the Palmer LTER is to better define 
the seasonal pattern and control of primary productivity in antarctic 
waters near Palmer Station.  To do this we are gathering data from 
several spatial and temporal scales and using many approaches.  
Remote sensing techniques provide geographic and temporal/spatial 
data on scales that would otherwise not be available.  Several 
satellite derived products are or will provide coverage of sea-ice 
extent and thickness, pigment biomass and primary productivity, and 
hydrographic characteristics of near surface layers of the ocean.  
Direct measurements of nutrient, biomass, and primary production 
are determined weekly or biweekly near Palmer Station, annually 
during summer in a 200 by 300 km area of the LTER grid, and 
periodically in the austral spring and autumn of winters with 
different sea ice extent in an area of the LTER grid larger than in 
summer.  The contribution of sea-ice phytoplankton to the total 
carbon budget of the Southern Ocean is unknown.  We are approaching 
this difficult problem presently by pursuing an accurate estimate of 
sea-ice distribution, selectively collecting samples of 
phytoplankton biomass from the underside of sea ice (available to 
grazers), and making light measurements to develop bio-optical 
models for the estimation of under-ice production.  Understanding 
the seasonal control of primary productivity will come from the 
integration of the field data with experimental studies conducted in 
the field and laboratory to define the physiological characteristics 
of phytoplankton at different times during an annual cycle.  
Variability of some of the physiological characteristics of 
phytoplankton are presently being analyzed as a first step to 
developing a regional bio-optical model of primary production.

Core area 2.  Spatial and temporal distribution of populations 
selected to represent trophic structure
	Based on our understanding of the antarctic pelagic marine 
food web, two pairs of predator/prey species have been chosen for 
detailed studies within the Palmer LTER study region:  the AdŽlie 
penguin and antarctic krill pair is thought to be positively impacted 
by winters of extensive ice cover, and the south polar skua and 
antarctic silverfish pair negatively impacted.  One prey item, 
Euphausia superba, or antarctic krill, is an herbivorous 
macrozooplankter that is widespread and abundant, dominates the 
diets of many predators, and is an important grazer of the 
phytoplankton community.  The other, Pleuragramma antarcticum or 
antarctic silverfish, although a dominate member of the sparse 
epipelagic fish fauna and an important component of the diet of 
several seabirds and seals, is not abundant and is reported to be 
restricted in its distribution.
	The research program for antarctic krill covers multiple 
spatial and temporal scales.  The larger spatial scales are important 
for understanding the population dynamics of the species, and the 
smaller scales of more interest to specific food web interactions, 
with krill either as prey or consumer.  Temporal scales are both 
interannual, such as the indices for reproductive effort and post-
winter status, as is appropriate for a long-lived species, and also 
seasonal to understand the impact of interannual variability in 
phytoplankton bloom dynamics on secondary production in krill.  
Antarctic krill have a circumpolar distribution and are not 
genetically different throughout their range.  However, population 
centers may be aligned with the series of large gyres around the 
continent, for example the gyre(s) found off the west coast of the 
Antarctic Peninsula within the Palmer LTER grid.  The gyre off 
Adelaide Island includes the 300.* and 200.* transect lines (Fig. 6), 
areas that are consistently covered with ice in the winter 
(Stammerjohn 1993), and where we believe reproduction occurs 
every year, possibly because of a more dependable food supply.  
Reproduction and larval survival may or may not be successful in the 
northern region of the LTER Peninsula grid, depending on ice 
dynamics and food availability.  Given the potential impact of 
interannual variability in winter ice cover on population dynamics, 
and the implications of a possible population center off Adelaide 
Island, sampling for parameters vital to understanding population 
dynamics of krill must be on the mesoscale, and include regions that 
exhibit consistent and variable ice cover in the winter, i.e. from the 
600.* to 300.* lines (Fig. 6).  Finer spatial scale sampling is 
conducted within the foraging range of the AdŽlie penguins during 
the critical period for chick rearing, as part of a joint exploration of 
predator/prey interactions.  In addition, the finer temporal sampling 
possible from zodiacs over the Palmer grid yields estimates of 
growth in the krill population.  These growth estimates, determined 
both experimentally and by following modal lengths over time, 
represent the sum of food availability in the area during the season.  
We anticipate that these growth rates will show interannual and 
within season variability dependent on the timing and availability of 
food which in turn is linked to both ice dynamics and climate 
variables like wind and clouds.
	The sampling approach and design to generate both relevant 
annual measurements of the fish populations within the LTER grid 
and to test the hypothesis about silverfish availability within the 
foraging range of the south polar skuas from Palmer Station has 
changed during our first two years of sampling.  The current 
sampling scheme reflects what we have learned about silverfish 
distributions, the understanding that south polar skuas have a 
maximum foraging range during chick raising of about 160 km, some 
preliminary observations of south polar skuas from near Palmer 
Station foraging behind the islands near the Peninsula, and the 
analysis of otoliths from two years of south polar skua guano 
samples.  Stations sampled for fish populations include all those 
within 160 km of Palmer Station to include the fish community that 
may be available to the skuas, and those for silverfish dynamics 
include all stations on the shelf and within 60 km of the Peninsula 
on the standard transect lines plus additional stations within the 
known habitat of silverfish (shelf) and where south polar skuas have 
been observed foraging.  Depths sampled with the midwater trawl 
are consistent with our objective of understanding silverfish 
population dynamics, not just the availability of those size fish 
preyed upon by the south polar skuas.  South polar skuas serve as 
collectors over the longer temporal or seasonal scale important to 
understanding patterns of fish availability to the seabirds, and these 
samples yield adequate otoliths to test the hypothesis concerning a 
narrow size range of fish.  Whether the narrow size/age range of 
fish found in south polar skua guano is due to behavior of the fish or 
of the seabird is not yet known.
	AdŽlie penguins and south polar skuas have a circumpolar 
distribution, and throughout Antarctica tend to be the dominant 
components of avian communities in terms of both abundance and 
biomass.  Within the LTER region of interest on the Antarctic 
Peninsula, populations of these two predators represent 
approximately  80% of the avian biomass, and are thus two of the 
region's key avian consumers.  As current LTER hypotheses suggest, 
the ecology of these predators is tied to sea ice dynamics and the 
availability of krill and silverfish.  Issues related to the spatial and 
temporal scales over which sea ice impacts prey abundance and/or 
availability, and thus the ecology of these predators, have been 
addressed by selecting parameters for measurement (Table 5) with 
inherent response times that accommodate the desired range of 
spatial and temporal scales potentially important to these 
predators.  The  measurement of chick growth rates, for example, 
provides an index of prey availability in the marine environment 
every 3-5 days within the predator's summer foraging range.  The 
measurement of over-winter survival, on the other hand, provides a 
similar index, but it represents an intergrated value encompassing a 
minimum of 6 months within the predator's winter foraging range.  
The data being obtained thus encompass temporal scales covering 
days to years, and spatial scales covering meters to thousands of 
kilometers.



Core area 3.  Pattern and control of organic matter accumulation in 
surface layers and sediments 
	Organic matter accumulation in the surface layers and 
sediments is the most difficult of the six core research areas to 
directly compare to the other LTER sites.  In the subtidal in the 
immediate vicinity of Palmer Station accumulation of sediments is 
rare.  Because this is a high energy environment and scour from 
icebergs is common, most beaches are composed of pebble-size 
rocks or larger.  This trend continues subtidally.  Sediments are 
found at depth (500 m) in Palmer Basin, but interaction between 
these sediments and surface waters is one-way, from the pelagic to 
the benthic realm.  For the Palmer LTER we consider the "surface 
layers" to mean the surface layers of the ocean and the associated 
sea ice, a seasonal component.
	Particulate organic matter does not accumulate in these 
surface layers permanently.  In cold winters pack ice forms early 
and sea ice microbial communities (SIMCO's) develop, and significant 
accumulation and production of particulate organic matter (both 
living and detritus) in sea ice occurs.  When the pack ice melts in the 
spring, the accumulated organic matter (algal cells, bacteria, 
protozoans, detritus, fecal pellets) is released into the water 
column.  How much of this material is recycled within the surface 
layers and how much reaches the bottom is unknown.  Downward 
vertical flux of particulate organic matter was only 8% of 
integrated water column production in this region in the summer 
(RACER overview 1987).  Many investigators believe that the melting 
sea ice provides the seed stock for the ice-edge plankton blooms 
(Garrison et al. 1987).  Although the same close link between algal 
and bacterial production exists in SIMCO's as in the water column 
(Garrison et al. 1986), algal biomass and presumably primary 
production is much less in the ice than in the ice-edge blooms, so 
production of detritus and microbial activity will also be less.

Core area 4.  Patterns of inorganic inputs and movements of 
nutrients through soils, groundwater and surface waters
	In the surface waters of Antarctica, most of the inorganic 
nutrients are derived from upwelling of nutrient-rich water masses.  
By comparison to other coastal regions worldwide, terrestrial 
inputs to the Palmer LTER region are relatively minor.  The upwelled 
waters contain high concentrations of dissolved inorganic carbon 
(C=2 mM), nitrate (N=30-40 uM) and phosphate (P=2-3 uM).  By 
comparison, partially reduced forms of N (i.e., NH4 and NO2) are 
negligible (<0.5 uM).  The C:N:P molar stoichiometry is generally 
constrained within narrow limits and approximates the 
"Redfield"ratio of 106C:16N:1P.  This empirical relationship and 
elemental consistency derives from the fact that the nutrient 
composition of the deep water masses is the result of the 
accumulated regeneration at depth of particulate organic matter 
that is exported from the near surface waters.  In this way, the 
inorganic and organic nutrient flows of the polar ocean are closely 
linked.
	The concentration of silicic acid in upwelled waters varies 
considerably from water mass to water mass.  In the Palmer LTER 
region, silicic acid (Si) is always found in excess of that needed for 
diatom growth (typically concentrations in upwelled waters exceed 
75 uM).  At the point of total exhaustion of N or P from the water 
column, a residual Si of 30-50 uM is generally observed.  
Nevertheless, the sediments of the Southern Ocean are known to be a 
major sink for Si compared to C or N.  The reason(s) for this 
uncoupled burial stoichiometry are not known.  Other required 
inorganic trace nutrients appear to be poresent in sufficient 
concentrations to sustain high rates of primary production, 
especially in the seasonal ice pack and, subsequently, injection into 
the water column during spring melting may comprise an important 
mechanism.  Finally, for selected regions trace elements may be 
supplied from glacial runoff or for regions of Bransfield Strait from 
hydrothermal venting.
	As antarctic phytoplankton (eg. diatoms) grow and reproduce in 
the water column inorganic nutrients are assimilated in an 
approximate molar ratio of 106C:16N:1P:16Si.  The amount of Si 
uptake will depend to a large extent on the species composition and 
growth rate.  For example, under conditions of diatom spore 
formation more Si may be removed from the water column per mole 
of C than during exponential growth.  If diatoms are not present in 
the water column, then very little Si is removed.  The accumulated 
plant biomass in part  sinks out of the water column either as whole 
inactive cells or as egestion, an end product of zooplankton grazing 
processes.  Grazing also leads to the formation of ammonium, a 
metabolic by-product.  Because ammonium is taken up in preference 
to nitrate, the accumulation of ammonium acts to supress nitrate 
assimilation.  Consequently, even though nitrate may exceed 
ammonium by a factor of 10, phytoplankton derive nitrogen largely 
from ammonium.
	Our inorganic nutrient sampling strategy in the LTER program 
to date has been to obtain data on the concentrations of the major 
inorganic nutrient pools at all stations where we collect 
phytoplankton biomass and species composition data, or where we 
measure the light  dependent uptake of 14C.  In this way we can 
quantify the net nutrient removal rates and independently determine 
net primary production.  In addition, the measurement of the 
dissolved inorganic carbon pool and water column alkalinity allow us 
to calculate the partial pressure of carbon dioxide and the derived 
flux of CO2 into or out of the ocean surface.  Previous research in 
the coastal region of the Antarctic Peninsula has documented strong 
CO2 sink in coastal waters.  Additional nutrient samples are 
collected from deep hydrocasts in order to characterize the 
independent water masses.
Core area 5.  Patterns and frequency of disturbance to the research 
site
	With the exception of tourism and research, the LTER region of 
interest on the Antarctic Peninsula has not been subjected to any 
disturbance originating with human commercial interests or 
activities.  Where disturbance has occurred, it has almost 
exclusively been the result of sharp increases in the populations of 
southern fur seals (Arctocephalus  gazella) and southern elephant 
seals (Mirounga leonina), which in the last 20 years have increased, 
respectively, by 800% and 300% (Fraser et al. in preparation b).  
Because these seals use terrestrial sites as loafing and haul-out 
areas, two types of impacts have been recorded.  The most obvious 
have been the effects on vegetation and terrestrial freshwater 
ecosystems.  Some islands, for example, have lost 80% of their 
original vegetation, and virtually all freshwater ponds now exhibit 
high turbidity and a loss of the original flora and fauna.  Less 
obvious but equally apparent, have been the effects on some colonies 
of AdŽlie penguins and other seabirds, where competition from seals 
for space has effectively divided the colonies into significantly 
smaller units.  This effect has in some cases increased chick and egg 
exposure to predators, and accelerated the rate at which colonies 
move towards extinction (Fraser and Patterson 1993).  The primary 
cause for these changes in seal populations appears to be linked to 
changing climate and sea ice conditions (Fraser et  al. 1992; Fraser 
and Patterson 1993; Fraser et al. in prep)

IV.  Data Management
	Data management has been a consideration for the Palmer LTER 
since its inception three years ago because of the certainty of a 
continuing stream of related data.  Further, as the eighteenth LTER 
site we benefit from the collective experience of the other LTER 
sites and the funding agency which encourages data planning.  It is 
recognized that there is both a need to facilitate current research as 
well to provide for the long-term aspects of the program.  Further, 
our data management is designed to take advantage of the existing 
strengths of the team members and foster an integration of data as 
well as data handling.  The Palmer LTER data management is 
organized around several distinct concepts including:  1) acceptance 
of a diversity of computer platforms and tools, 2) establishment of 
a distributed system of communication, 3) development of an 
electronically available central database.
Personnel.  Currently there is one half-time position which is the 
data manager who develops and maintains the central data structure 
in co-ordination with the individual investigators' data analysts who 
reside at their home sites.  The data manager was made a member of 
the Executive Committee this year in recognition of the significant 
role data management must play in the development of an LTER site.  
The data manager, Karen Baker, has been a member of the marine 
bio-optics research team of Raymond C. Smith for eighteen years as 
a research participant and data analyst.  Two of the CRSEO computer 
system analysts, Steve Miley and Jim Davidson, have been available 
on an as-needed basis and have provided significant input on 
networking, software tools as well as hardware configurations.
History.  The Palmer LTER participants joined together with diverse 
scientific backgrounds permitting consideration of a significant 
portion of the antarctic food web from light to microbial activity to 
phytoplankton to krill to silverfish and birds.  Each group has 
undergone development of a unique, independent hardware and 
software organization specifically optimized for their own 
particular research questions over a long period of time.  Each group 
had adapted computer technology with reference to the local 
environment prior to joining together as the Palmer LTER team.  
Accepting the reality of these diverse computer platforms (unix, 
mac and pc) and tools means leaving local environment development 
in the hands of the individual research group and accepting the 
challenge of providing the methods for such a variety of systems to 
communicate (Table 7).  Thus the data management is mandated with 
providing as powerful a connectivity as possible rather than 
promoting a standardization of equipment.  Indeed a variety of 
platforms creates an enrichment of options in terms of data 
analysis and display.
	The Palmer LTER participants reside in different physical 
locations including UC Santa Barbara (CA), Scripps Institution of 
Oceanography (CA), Old Dominion University (VA,MN and CA), 
University of Hawaii (HA) while the field work is conducted at 
Palmer Station (Antarctica) and aboard the research vessels R/V 
Polar Duke  and Nathanial B. Palmer  (Fig. 20).  Given such a 
distribution, the development of the internet and the recent increase 
in reliable network software has played a critical part in the flow 
of data between individuals.
	In order to gain an overview, a list was generated of the 
Palmer LTER software and hardware (Table 7).  This simple survey 
was valuable enough that a Site Capability List was created by each 
LTER site at the data managers' group meetings.  This list is 
maintained by the Palmer LTER as part of the LTER network online 
database (gopher lternet.edu; (2) Basic LTER documentation; (4) 
SiteCapabilities).
Connectivity.  It was necessary first to insure physical connections 
to internet for each group. This has been accomplished in several 
different manners (Fig. 20):
1) direct campus broadband connection;
2) for two of the groups with heavy mac use, gatorboxes provide 
tunneling across the internet permitting appletalk networks to 
interface with the CRSEO unix network and providing remote disk 
mounting;
3) for those depending upon dial-up modems, tools such as gopher for 
browsing and ftp for file transfer are being used.
Such connectivity makes electronic mail and file transfer 
immediately available, but as the connectivity becomes exercised, 
we find also a transfer of both computer knowledge and computer 
resources which makes a significant contribution toward integrating 
the group and the data.
	The principal investigators for the group, Robin Ross and 
Langdon Quetin, are located at UC Santa Barbara as are two of the 
other co-investigatorsincluding Raymond C. Smith who is also 
director of the Center for Remote Sensing and Environmental Optics 
(CRSEO) which is a research unit at UC Santa Barbara organized by 
earth scientists interested in making available a state-of-the-art 
computer technology to address their scientific pursuits.  Further, 
several CRSEO investigators and many UC scientists have formed a 
multiyear collaboration with Digital Computer Company to 
investigate an EOS-era database project called Sequoia 2000.  The 
Palmer LTER benefits from this effort in terms of available 
hardware, software, personnel and database planning.  While storage 
of large datasets such as satellite data is available at Berkeley, a 
500 Megabyte disk is available to serve as an initial local data hub.
Database.  The goal of the centralized documentation and data 
storage is to make data and information available easily regardless 
of platform.  To further this goal, all Palmer LTER investigators 
have accounts on the CRSEO server to provide direct access to the 
Palmer LTER central archive.  The central data disk is divided in two 
sections:  datainfo and data (Fig. 21). Information in both sections is 
maintained in flat ascii files so they are easily available to all 
investigators with their current hardware capabilities.  Quality 
control for both metadata and the data itself is the responsibility of 
the individual investigator.  The central data archive is itself a 
backup of each individual investigator's dataset but is itself backed 
up on a regular schedule.  After considering the other LTER site data 
policies, the Palmer LTER group developed a data policy this year in 
order to help define the rules of data sharing.
	The datainfo section contains general information pertinent to 
the LTER as well as the metadata which is documentation describing 
the data taken for each field study.  The datainfo section is available 
to the general internet users through a gopher connection:
				gopher lter.crseo.ucsb.edu
choosing (6) Palmer LTER datainfo.  This internet gopher provides a 
menu driven browse for selecting resources, viewing and accessing 
from most platforms with internet access.  By enlarging the base of 
information from metadata about the data to include LTER 
bibliographies, reports, and lists this information is available not 
only for investigator reference but also for student education.
	In order to organize the metadata, a common vocabulary was 
developed and documented (Table 8).  A study consists of a ship 
cruise or a season at Palmer Station.  Within each study, data sets 
exist either as part of the predefined core data sets or as part of the 
non-core-opportunity data sets.  The study types and dataset 
definition list is maintained online (Coreform Definition Table).  
Describing each study is a corelist listing the measurements made 
(Table 9), a participant list describing who was on site for the study 
and an eventlog listing chronologically the type and location of 
measurements made during the study.  Efforts are still underway to 
streamlineand simplify documentation in order to make sure it gets 
done, which includes providing forms while at sea or on station so 
documentation may be done while data is being taken.
	The data itself is stored in a directory to which only the LTER 
investigators have access.  The plan is to facilitate data storage and 
exchange in order to promote more rapid data assimilation between 
groups.  There is ongoing discussion as to what stage of analysis the 
data should be before being entered onto this common data disk.
Future.  Future efforts will include continuing to find ways to 
encourage connectivity and to facilitate the submission of dataset 
forms and datasets.  Since the gopher connection has proven useful, 
a wais type server will be considered to enhance the search/browse 
capabilities.  Also, consideration will be given as to whether data 
should be made available online through a gopher link which has the 
advantage of bypassing any personnel time needed to fulfill data 
requests. Although we have been primarily concerned in these first 
years with the establishment of data taking, organization, storage, 
and availability, it is recognized that as the amount of data in the 
database increases, we need to consider the possibility of a 
relational database such as the Sequoia 2000 postgress or the 
Digital rdb, especially as user interfaces are evolving rapidly.  The 
database now is organized in such a way as to facilitate conversion 
to a relational database.  There will continue to be attention paid to 
maintaining as robust and powerful a system as possible while 
requiring as little maintenance and support as possible.  An 
emphasis on publically available software will continue with an eye 
toward maintaining data convertibility, meaning data is available to 
be entered into whatever software package any particular user 
wishes to use.

V.  Educational activities
A.  Graduate student thesis topics
Nicolas Boucher, Ph.D. student
	University of California at Santa Barbara
	Advisor Barbara Prezelin
The thinning of the stratospheric ozone layer is predicted to 
continue into the next century.  Due to atmospheric current patterns, 
ozone depletion is most prominent over Antarctica during the 
austral spring and leads to increased levels of UVB radiation 
reaching the surface of the earth.  During the austral spring 1990, I 
participated in a study that measured the impact of UVB radiation on 
the water column primary production (IcecolorsĘ'90).  Preliminary 
results showed that phytoplankton photosynthesis was decreased by 
6-12% due to the increased levels of UVB radiation over the Marginal 
Ice Zone in the Bellinsghausen Sea, Antarctica (Smith et al. 1992).  
The approach used in this study also allowed us to quantify the 
effects of background levels of UVA radiation on primary production 
in natural communities.  I propose to use existing data from two 
austral spring cruises (Icecolors '90, LTER '91) to develop and test a 
UVA and UVB dependent bio-optical model of primary production in 
antarctic waters.
The specific aims are: 
	1) to combine a PAR dependent model with UV dependent 
fractional inhibition algorithms into a single UVB, UVA and PAR 
dependent bio-optical model of in situ rates of primary production in 
antarctic waters and
	2) to use the model to estimate measured rates of production 
in the presence and absence of UVA and/or UVB radiation over the 
time and space scale of the LTER '91 austral spring cruise.
The results of such a modeling effort with 'real world' data should 
advance significantly any attempt to estimate the temporal and 
spatial variability of in situ primary production in antarctic waters.  
It is also likely that advancing a predictive approach to UV 
dependent primary productivity in antarctic waters would benefit 
similar attempts in other marine environments where UV radiation 
is a significant environmental factor.
Thomas Frazer, Ph.D. student
	University of California at Santa Barbara
	Advisors Robin Ross Langdon Quetin
	The larvae of Euphausia superba are found feeding on the 
underside of sea ice during the austral winter.  This observation has 
been observed many times in the past decade and the presence of sea 
ice and the food sources associated with it may be important to the 
winter-over survival of larval krill (Ross and Quetin 1991).  My 
thesis will focus on the winter ecology of larval krill and contribute 
to a more detailed and quantitative understanding of the role of ice-
associated food resources in their winter diet.  The results of the 
research will be of interest to krill biologist as well as those with 
an interest in direct and indirect interactions between biotic and 
physical components of food webs.
	The thesis will consist of four related chapters.  The first will 
provide a quantitative characterization of the abundance and 
distribution of krill larvae under annual sea ice during early and late 
winter.  The second and third chapters will evaluate the use of 
stable isotopes as a chemical tool to quantify the long-term 
assimilation of ice-associated food resources consumed by larval 
krill during winter.  The second chapter will rely heavily on field 
collected data.  The third chapter will make use of laboratory 
experiments to more rigorously assess the conclusions drawn from 
the field.  The final chapter will make use of a suite of physiological 
measures, e.g. growth, ingestion and respiration, to investigate the 
energetics of larval krill during early and late winter.
Karen L. Haberman, Ph.D. student
	University of California Santa Barbara
	Advisors Robin Ross and Langdon Quetin
	Previous studies suggest that growth and reproduction of 
antarctic krill, Euphausia superba, are food limited in the Southern 
Ocean.  However, a knowledge of whether certain phytoplankton 
types or groups are better utilized by krill is important to 
understanding how patterns of phytoplankton abundance and species 
composition affect the krill's food availability and thus, overall 
fitness in krill.   This thesis is designed to compare the ingestion 
and assimilation of different types of phytoplankton by the antarctic 
krill, and to determine whether they selectively feed on certain 
types or physiological stages of phytoplankton, with an emphasis on 
the prymnesiophyte Phaeocystis, and diatoms.  The reason for this 
focus is twofold:   first, both Phaeocystis and diatoms occur in large 
blooms in the Southern Ocean, and both are in the size range grazed 
most effectively by krill;  second, available evidence suggests that 
the edibility and nutritional value of Phaeocystis for various grazers 
are low compared to diatoms.
	During preliminary experiments,  krill did not ingest 
Phaeocystis colonies (mean diameter 100-µm) in stationary growth 
phase.  In a Phaeocystis/ diatom mixture, total ingestion rate was 
negligible when the mix contained Phaeocystis from a culture not 
ingested as a unialgal food source.  Visual observations indicate that 
this lack of feeding may be due to clogging of the feeding basket by a 
mucousy exudate from the Phaeocystis colonies.  The importance of  
Phaeocystis' physiological state to its ingestion and assimilation by 
krill will be examined in detail.   I also intend to evaluate 
immunochemical techniques to compare gut contents of field-caught 
krill to the phytoplankton pigment profiles collected concurrently as 
part of the LTER core data set.  This comparison will enable me to 
determine whether krill are selective feeders.
	One major objective is to determine whether species 
composition and physiological state of phytoplankton influence 
ingestion and assimilation by krill.  I will conduct long-term grazing 
experiments during which krill growth will be measured to assess 
the impact of different phytoplankton community composition on 
secondary production, and facilitate more accurate modeling of krill 
growth and reproduction based on phytoplankton distribution.  
Information from this thesis will also help us assess the influence 
of krill grazing on the composition of the phytoplankton community.
Cathy M. Lascara, Ph.D student
	Old Dominion University
	Advisor  Eileen Hofmann
	The PhD research project being undertaken will focus on 
investigation of processes important to the distribution and 
dynamics of antarctic krill in waters west of the Antarctic 
Peninsula.  The approach will be multi-phase, involving several 
specific objectives and require synthesis of field observations, 
literature review and simulation modeling experiments.  Analysis of 
a multi-disciplinary data set collected by the LTER will form the 
foundation of the first phase of this dissertation research.  The 
objective is to quantitatively map the spatial and temporal 
distribution of krill and to interpret krill distribution patterns in 
relation to other habitat characteristics; in particular, the 
concentration and composition of food resources, ice history, large-
scale flow regimes, and hydrographic and optical properties of the 
upper ocean.  The second phase will be to develop a conceptual model 
which illustrates the biological and physical processes that 
determine the environmental variability experienced by krill.  This 
model will be formulated as a set of modules or sub-models that 
consider specific processes.  It is envisioned that  the entire model 
will be too complicated to tackle as a single problem.  However, 
understanding of krill dynamics may be greatly improved through 
simulation models designed to examine single processes.  But the 
frame work of a complete conceptual model is necessary so that 
sub-modeling efforts can be interpreted in the context of the entire 
system.  The final phase of this research project will concentrate on 
the development of a series of time- and space-dependent modules 
to determine appropriate mathematical formulations and coefficient 
parameterizations for several key processes identified in the 
conceptual model.  Initial modeling efforts will focus on the 
processes of growth and biological diffusion in a variable 
environment. 


Mark A. Moline, Ph.D. student
	University of California at Santa Barbara
	Advisor Barbara Prezelin
	Although macronutrients in the Southern Ocean are in ample 
supply to sustain a large phytoplankton standing stock, the region is 
typically one of low primary productivity and large episodic blooms 
account for the majority of the annual productivity.  Mechanisms and 
processes explaining both the 'Antarctic Paradox' and the formation 
and dissipation of 'megablooms' have emerged (Sullivan et al. 1988, 
Smith et al. 1990, Mitchell et al. 1991, Sakshaug et al. 1991, 
Smetacek et al. 1992).  Most of these studies, however, have been 
conducted shipboard and as a result have been restricted to 
describing the above in a spatial context.  A few have concentrated 
on the temporal variability of phytoplankton dynamics but have 
either limited there studies to a few parameters of interest or to 
time scales too large for the processes themselves.
	With the existing datasets (including hydrographic, optical, 
and primary productivity components) collected over the first three 
LTER field seasons (9192PAL, 9293PAL, 9394PAL), I propose to 
develop and advance the understanding of the mechanisms 
controlling primary productivity in Antarctica.  Specific goals 
working with the data sets are:
	(1)  To examine the multiple feedback mechanisms between the 
physical, chemical, and biological systems and to determine the 
time scales on which they occur (9192PAL dataset).
	(2)  To examine the above mechanisms on annual time scales 
using the data collected from 1991-1994 and to identify the major 
determinants driving phytoplankton biomass and primary 
productivity.
	(3)  To test existing models of antarctic productivity with the 
LTER 9192PAL dataset and to develop a temporal model based on 
integrating the hydrography, optics, and primary production.
	(4)  To verify the predictive strength of the developed model 
using the 9293PAL and 9394PAL datasets.
	Results from the PAL datasets should significantly advance 
present knowledge of the time scales of processes governing 
antarctic primary productivity.  They will also provide the Palmer 
LTER and others a criterion to increase the efficiency of future 
sampling efforts.
David A. Smith, PhD student
	Old Dominion University
	Advisor John Klinck
	The research project being done will consider the hydrography 
and circulation in the LTER region.  This analysis will consist of 
three general sub-studies: analysis of historical observations of 
water properties, analysis of time and space dependence of surface 
exchanges that force the circulation and numerical modelling of the 
circulation.
	The analysis of historical data will be accomplished with 
observations from three general data sources, which contain some 
overlap: National Ocean Data Center, Southern Ocean Atlas (Arnold 
Gordon) and Southern Ocean Atlas (Dirk Olbers).  Attempts will be 
made to obtain hydrographic observation from other sources such as 
the British Antarctic Survey and the RACER project.  These 
historical observations will be combined with the hydrographic and 
nutrient measurements taken as part of the various LTER cruises. 
Analysis of this data will focus on tracking the path of Circumpolar 
Deep Water as it moves onto the shelf and on an estimation of the 
depth of the mixed layer during various seasons.
	The circulation and physical environment in the Bellingshausen 
Sea is affected by surface wind stress, heat exchange with the 
atmosphere, solar heating and ice cover. Each of these processes can 
be estimated from climatologies or atmospheric analyses (or 
forecasts).  The monthly variability of ice cover is being considered 
by other investigators in the LTER project, so these results will be 
used without further analysis.  The twice daily analyses of the 
Australian Meterological Service will be obtained to estimate 
surface wind stress, air temperture, humidity and cloud cover.  
These values will allow an estimation of the heat flux at the ocean 
surface.  The crudest analysis will be to use the values of pressure 
and temperature at the ocean surface to estimate fluxes.  If 
possible, we will obtain the estimated surface flux values that are 
used in the boundary layer part of the atmospheric model.  These 
should provide better estimates of the twice daily fluxes of heat and 
momentum.
	The final part of this study will be the implementation of a 3-
d circulation model, specifically, SPEM (semi-spectral primitive 
equation model) written by Dale Haidvogel for the Bellingshausen 
Sea.  This model includes at thermodynamically active mixed layer 
and ice.  A series of experiments will be used to see the influence on 
the physical properties in this area of offshore ocean circulation, 
surface wind stress, ice cover, redistribution of ice by wind and 
circulation, surface thermodynamic exchanges and ice production.  
The offshore circulation will be estimated from the monthly 
solutions from FRAM (fine resolution antarctic model) which has 
been run by British scientists.  This is a full model of the Southern 
Ocean which is forced by seasonally varying wind and heat fluxes.  
Forcing for the other model cases will come from estimates 
obtained in the second part of this study.
Sharon Stammerjohn, M.A. student (completed thesis December 
1993)
	University of California at Santa Barbara
	Advisor Ray Smith
Abstract.  Spatial and temporal variability in Southern Ocean sea ice 
coverage is analysed from October, 1978 to December, 1991.  Sea ice 
coverage is calculated from passive microwave satellite data, using 
Scanning Mulit-Channel Microwave Radiometer (SMMR) and Special 
Sensor Microwave/Imager (SSM/I) data.  Spatial variability in sea 
ice coverage was based on the following eight regions:  Southern 
Ocean, Weddell, Indian, West Pacific, Ross, Amundsen and 
Bellingshausen regions, as well as the subregion of the 
Bellingshausen, the Long term Ecological Research (LTER) study area 
located west of the Antarctic Peninsula.  The six adjacent Southern 
Ocean regions all show unique interannual variability which is 
confirmed by cross spectral analysis of monthly anomalies, and no 
two regions have the same anomalous years of extreme maximum or 
minimum ice coverage.  Regional interannual variability appears to 
be a yearly re-distribution of near constant ice coverage for the 
whole Southern Ocean, and in extreme high or low ice years there are 
asymmetries in southern ocean ice coverage.  Spectral analysis of 
monthly anomalies confirmed that most of the variance in regional 
ice coverages is due to interannual variability.  Several patterns in 
interannual and annual variability are observed in the 13.25-year 
time series of southern ocean ice coverage, and possible climatic 
forcings contributing to these patterns are discussed.  A thorough 
characterization of LTER ice coverage in comparison to the other 
regional ice coverages is provided, and possible ice-ocean-air and 
ice-ecosystem dynamics in the LTER region are explored.
B.  Research Experience for Undergraduates (REU) Site 
	The Palmer LTER was an REU site during the 1991-1992 and 
1992-1993 austral seasons, years two and three of the Palmer LTER.  
We recruited undergraduates to become integral members of four 
research teams within the Palmer LTER.  The research areas 
included:  hydrography, optical characteristics of the water column, 
primary production and phytoplankton physiology, and secondary 
production (pelagic zooplankton and fish).  The overall objective was 
to provide an educational experience to acquaint students with all 
aspects of the research process and to encourage them to continue 
their education in science.  The experiences included:  a seminar 
series, pre-season training in the advisor's laboratory, 10 weeks in 
Antarctica as an essential member of a research team, and 
independent research projects with data analysis and preparation of 
publications in the home laboratory.  One of the benefits to the 
student participants was the integrative aspects of the LTER as an 
interdisciplinary research program.  Seven undergraduates joined 
three research teams in 1991-1992 and eleven undergraduates four 
research teams in1992-1993, joining the Palmer LTER research 
teams for research either at Palmer Station or on one of two 
research vessels.  Students evaluated the program at the end of their 
award and the majority believe that their experience was beneficial 
in either helping them find a focus within aquatic science or 
deciding to continue in science as either technicians or graduate 
students.

VI.  Evidence of historical literature being considered and 
incorporated; intersite and network activities; leadership, 
management and organization
A.  Historical Literature.
	The existing long-term databases on upper-trophic level 
predators in  the  vicinity  of Palmer Station stem from  research  
on  the ecology of seabirds initiated in the early 1970's by Parmelee 
et al. 1977.  Originally focusing on species other than  penguins, this  
research established the earliest evidence linking aspects of  the 
ecology of south polar skuas with  antarctic silverfish.  Subsequent  
work  by Neilson  (1983) and  Pietz (1986, 1987) demonstrated that 
sea ice may also be important to the foraging ecology of south polar 
skuas, and thus play a role in determining reproductive success.  
Intensive studies on AdŽlie penguins did not  begin  in  the area until 
the CCAMLR (Convention  for  the Conservation  of  Antarctic Marine  
Living  Resources) Ecosystem Monitoring  Program  (CEMP) was 
established in 1987  (Fraser  and Ainley  1988).  The United States 
component of CEMP is known  as AMLR (Antarctic Marine Living 
Resources) and is discussed in  another section.  Although focused on 
AdŽlie  penguins, this  program provided the vehicle for continued 
studies on south polar  skuas and  other  predators, inluding marine 
mammals and terrestrial ecosystems.  As a result, and particularly 
in view of the recent establishment of the Palmer LTER, the 
databases developed at Palmer Station on upper-trophic level 
predators include some of the oldest, most  complete, coincident  
terrestrial, pelagic and environmental records available for the 
Southern Ocean.

American Geophysical Union (AGU) volume, "Foundations for 
Ecological Research in the Western Antarctic Peninsula Region", by 
the Palmer LTER accepted.  Manuscripts are due in late March.  The 
Preface and Table of Contents are are provided below.
Preface
	The LTER (Long-Term Ecological Research) Program was 
established in 1981 by the National Science Foundation of the United 
States because of the need to study some ecological processes that 
occur over longer time spans than the normal three year grant 
duration.  Today the LTER Network consists of 18 sites that span a 
variety of ecosystem types in the continental United States, Alaska, 
Puerto Rico and Antarctica.  The addition of the Palmer LTER at 
Palmer Station, Antarctica in October of 1990 extended the 
geographical and ecological range of the LTER Network, and provided 
the opportunity to link physical and ecological processes in the 
northern hemisphere to those in the southern hemisphere.
	One of the criteria for establishment of an LTER site is the 
existence of historical data and observations that serve to guide 
future research programs.  In this monograph we bring together in 
one place the meteorological, hydrographic, biological and ecological 
observations made in the general area of the Bellingshausen Sea and 
Antarctic Peninsula, and discuss the natural processes underlying 
those observations. This compilation of available data and 
observations in conjunction with our present understanding of 
processes provides the foundation for long-term studies of the 
ecosystem west of the Antarctic Peninsula.  In this context this 
monograph also provides a place for informal historical observations 
often so important to our understanding of long-term variability and 
change.
	The area of study of the Palmer LTER is bounded by the 
southern end of the Bransfield Strait extending south to Marguerite 
Bay, and from the Antarctic Peninsula seaward for 200 km.  The 
northern end of the area of discussion is the southern edge of a gap 
in the distribution of AdŽlie penguin (Pygoscelis adeliae) 
populations that extends to Livingston Island.  The seaward limit of 
the area is at the seaward limit of krill (Euphausia superba) 
distributions, includes probable spawning grounds for antarctic 
silverfish (Pleuragramma antarcticum) in the Biscoe Islands, and 
contains hydrographic features of the Southern Ocean that are 
uniquely antarctic.  The Palmer LTER has as its central hypothesis 
that interannual variability in the annual extent of the pack ice has 
major impacts on all levels of the marine ecosystem, and 
interannual variability in the extent of winter ice cover is high in 
the chosen region.  This monograph does not contain reviews of the 
larger geographic distributions, but instead restricts the 
geographical breadth of the data summaries and extends the depth 
and multidisciplinary nature of the coverage.  Even with the stated 
geographical restrictions and our intent to look at a small area in 
depth, there will be limitations.  For example, the monograph is 
primarily marine oriented, a choice made to accurately reflect 
differences in habitat area and species richness between the marine 
and terrestrial ecosystem.  The geographically restricted 
observations on patterns and distributions are placed in the context 
of our knowledge to date of the underlying processes that affect 
them, and this knowledge comes from many regions in the Southern 
Ocean.  To achieve this aim, the chapters are organized around 
several general themes introduced by a historical overview of 
research and more informal observations in the region.  Chapters 
describing the various habitats precede chapters describing the 
distribution of biological populations.  Chapters reviewing and 
evaluating the current state of our knowledge of processes 
controlling the distributions follow.  The role of man's impact on the 
region, whether commercial fishing or tourism, is another feature 
and must be included in the context of this long-term 
multidisciplinary program.  A final chapter summarizes the state of 
our knowledge and the design and objectives of the Palmer LTER 
with comments about other large research initiatives such as 
GLOBEC and BOFS in the area. 

Draft Table of Contents - one author has not yet confirmed

Preface	authors - R. Ross, E. Hofmann, L. Quetin

Part I.  Historical Description and Perspective

author - S. El-Sayed, Texas A and M University

Part II.  Habitat Description

Chapter 1.  Terrestrial Habitat

author - D. Walton, British Antarctic Survey

Chapter 2.  Terrestrial Biotic Components

author - R. Lewis Smith, British Antarctic Survey
(invited, decision pending)

Chapter 3.  Water Mass Distributions and Circulation

authors - E.E. Hofmann, J.M. Klinck, C.M. Lascara, D. Smith, Old 
Dominion University

Chapter 4.  Sea Ice Distribution

authors - R. Smith and S. Stammerjohn, University of California, 
Santa Barbara

Chapter 5.  Climate and Meteorology

authors - R. Smith and K. Baker, University of California, Santa 
Barbara

Chapter 6.  Benthic Habitat

authors - M. White and A. Clarke, British Antarctic Survey

Chapter 7.  Sedimentary Record

author - E. Domack, Hamilton College

Part III.  Distributions of Biological Populations (Horizontal and 
Vertical)

Chapter 1.  Microbial communities

author - Dave Garrison, National Science Foundation and University 
of California at Santa Cruz

Chapter 2.  Standing Stock of Phytoplankton

author - Greta Fryxell, Texas A and M University, and others


Chapter 3.  Standing Stock of Zooplankton plus Krill

authors - L. Quetin, R. Ross  of University of California at Santa 
Barbara, C. Lascara of Old Dominion University, and V. Marine, 
University of Chile

Chapter 4.  Benthic Communities

author - M. White, British Antarctic Survey

Chapter 5.  Standing Stock of Fish

author - A. Kellerman, Nationalparkamt Wattenmeer
(invited, decision pending)

Chapter 6.  Marine Birds

authors - W. Fraser and W. Trivelpiece, Old Dominion University

Chapter 7.  Marine Mammals

authors - ?

Part IV.  Control of Biological Distributions (Horizontal and 
Vertical)

Chapter 1.  Microbial Processes

author - D. Karl, University of Hawaii at Manoa

Chapter 2.  Primary Production

authors - B. PrŽzelin and R. Smith, University of California at Santa 
Barbara

Chapter 3.  Pelagic Secondary Production

authors - R. Ross and L. Quetin,  University of California at Santa 
Barbara, and others

Chapter 4.  Benthic Production (fish, macroalgae, invertebrates)

author - A. Clarke, British Antarctic Survey

Chapter 5.  Marine Birds

authors - W. Trivelpiece and W. Fraser, Old Dominion University

Chapter 6.  Marine Mammals

authors - D. Costa, ONR and University of California at Santa Cruz

Part V.  Human Disturbance

Chapter 1.  Terrestrial Disturbances

Ron Naveen, Oceanites, and Wayne Trivelpiece, Old Dominion 
University

Chapter 2.  Marine Disturbances - Hydrocarbons

author - C. Kennicutt, Texas A and M University

Chapter 3.  Marine Disturbances - Commercial Fishing

authors - S. Nicol, Australian Antarctic Division, and D. Agnew, 
CCAMLR

Part VI.  Summary and Synthesis

			authors - Palmer LTER Group


B.  LTER Coordinating Committee meetings, All Scientists Meetings
LTER Network All Scientists Meeting
The Palmer LTER participated in both the 1990 and 1993 All 
Scientists Meetings.  For each meeting, five people attended and we 
presented posters about our site and ongoing research.  One strong 
difference between the 1990 and 1993 All Scientists Meetings is 
that there is a more widespread acceptance of the antarctic LTERs 
as having relevant things to contribute to the Network.  The ten 
minute site bite with pictures of the ecosystem at work and some 
sample data helped others see how antarctic LTERs (both Palmer and 
McMurdo Dry Valleys) might fit into the range of ecosystems.  In 
September 1993 we actively participated in several of the 
workshops, and see intersite comparisions or studies developing in 
the following areas:
o  El Nino - (Bruce Hayden from Virginia Coast Reserve is the leader.)  
Everyone agreed to look for possible effects in their ecosystems.
o  Food Webs - (Robert Waide from Luquillo, Tom Frost from North 
Lakes)  A small group will try a cross site comparison of food webs.  
The comparison will be in two parts:  
(1) construct food webs and compare basic food web parameters 
such as food chain length,
(2) plan a cross-site experiment (a proposal will be necessary)
o  LTER and NASA/EOS Collaborative Research - Karen Baker managed 
to obtain two of the four sun photometers from the NASA/EOS 
workshop committed to the Antarctic, one for Palmer and one for 
McMurdo Dry Valleys.  They will switch out with the two arctic sites 
so all four sites have coverage for the spring and summer months.
o  Biodiversity - also in several parts, and with no long time series 
yet, we can best participate at the level of looking at biodiversity 
and how increasing the spatial scale of sampling increases 
diversity.
C.  Organization
	The Executive Committee consisting of the ten principal 
investigators is the primary governing body of the Palmer LTER (Fig. 
22).  The committee provides general scientific direction and budget 
guidelines.  Issues are decided in the Executive Committee by 
majority vote.  Formal communication is maintained between 
principal investigators with a monthly agenda sent by email and two 
annual meetings.  The co-managers of the LTER are the direct 
administrative contacts of the Palmer LTER to the LTER Network and 
the National Science Foundation.  The co-managers coordinate the 
monthly agenda, Executive and Steering Committee meetings, the 
overall field season and perform other general administrative 
funcitions.  The research, modeling and data management activities 
of the Palmer LTER are divided into several components with each 
administered by one to two principal investigators.  The principal 
investigators of each component plan the detailed logistics for a 
field season and are responsible for the collecting specific data 
sets, and entry of data and results into the Palmer LTER data base.  
Field work at Palmer Station is often the responsibility of 
technicians or graduate students in the absence of the principal 
investigator.  Undergraduate student volunteers comprise the 
majority of the field teams and are of great importance to our 
success.
D.  International interactions 
CCAMLR and SCAR
	The Scientific Committee on Antarctic Research (SCAR) and 
the Convention for the Conservation of Antarctic Marine Living 
Resources (CCAMLR) are international governing  bodies that receive 
recommendations on a host of issues related to the Southern Oceans 
through a diverse network of specialists and working groups.  Two 
LTER PI's, William R. Fraser and Wayne Z. Trivelpiece are, 
respectively, United States representatives to SCAR and CCAMLR, 
and address these bodies through participation in the Bird Biology 
Subcommittee of the Scientific Committee on Antarctic Research 
(WRF) and the CCAMLR  Ecosystem Monitoring Program (WRF and 
WZT).  The most direct interactions with the LTER occur primarily 
through the CCAMLR Ecosystem Monitoring Program (CEMP), which 
seeks annual data on the ecology of AdŽlie penguins as part of its 
efforts to develop long-term monitoring programs.  These data are 
delivered to CEMP through the Antarctic Marine Living Resources 
Program (AMLR), which  provides U.S. funding for its collection, 
analysis and the preparation of an annual report (see reports by 
Fraser et al. 1988-1993).



JGOFS (Joint Global Ocean Flus Study - Palmer LTER as a high 
latitude time series station 
	JGOFS may be interested in sponsoring the Palmer LTER as a 
high latitude time series station.  A preposal is now being 
considered by NSF program managers, and if both the JGOFS Steering 
Committee and the program managers approve, a full proposal will 
be required.  Most time-series stations for JGOFS are supposed to 
have biweekly or monthly sampling. However, our weekly sampling 
from station for spring and summer will satisfy requirements for a 
high latitude station.

VII.  Related research projects
A.   The Antarctic Marine Living Resources Program (AMLR).
	Palmer Station is one of two active sites on the western side 
of the Antarctic Peninsula where proposed long-term  monitoring of 
seabird populations has been initiated in support  of U.S. 
participation in CCAMLR.  The U.S. participates in CCAMLR through 
the United  States Antarctic Marine Living Resources Program 
(AMLR), a national program of the  National Marine Fisheries Service 
(NMFS) that emphasizes directed research on key component species 
in the Antarctic marine ecosystem.  Recognizing that many Antarctic 
marine  species are drawing  increasing  international interest  due  
to  their  commercial  fisheries  potential,   the principal objectives 
of directed research are to provide the U.S. and  CCAMLR  with the 
information needed to detect,  monitor  and predict  the  effects  of 
fishing and  associated  activities  on target  and  dependent  
populations  in  the  marine   ecosystem, including fish, squid, krill, 
seabirds and marine mammals.
	AMLR  research at Palmer Station, initiated in 1987,  focuses  
on aspects of the ecology of AdŽlie penguins that are  
complementary to the scope of research and objectives outlined by 
CCAMLR.  This research,  which is independently funded, shares many  
objectives with  the LTER, and, through cost-sharing, has facilitated  
long-term  data  collection on AdŽlie penguins on a scale  that  
would otherwise  have  been difficult for any single program  to  
fund.  The  result  has been a mutually beneficial program  with  
strong basic and applied components.
 
B.   The  Impacts of Tourism on Wildlife  Populations  at  Palmer 
Station.
	Tourism  in Antarctica has been showing a steady  increase  
since the  late  1960's.  However, despite rising  concern  that  
human activity  may  negatively impact  wildlife populations, 
studies designed to address this issue have been lacking.  The 
purpose of this study is to examine the feasibility of coupling 
research  on the effects of tourism on AdŽlie penguin populations on 
Torgersen Island with two long-term ecosystem oriented programs 
already  in existence  in the area, namely the AMLR and LTER 
programs.  The rationale  for  this approach  is based  on the premise  
that understanding and defining the natural variability  inherent  in 
the  ecosystem  is a necessary prerequisite for identifying and 
interpreting the  effects  of  human  activity.  By employing 
identical  technologies and methodologies, this study seeks to 
develop identical, coincident  databases at  sites visited by tourists 
to compare with databases developed as part of the two ecosystem 
studies at sites not visited by tourists.  The  latter will thus 
provide the background ecosystem data needed to discern and  
interpret  the  former.  This  arrangement  is likely to establish the 
proposed research as one of the key studies addressing human 
impacts in Antarctica, and serve as a model  for future research of a 
similar nature.

C. Icecolors II, 1993
	The Antarctic Ozone Hole is recognized as an unambiguous 
example of how human activities in one part of the globe can 
influence processes in another part.  The springtime stratospheric 
ozone layer over the Antarctic is thinning by over 50%, resulting in 
increased midultravioled (UVB) radiation reaching the surface of the 
Southern Ocean.  Two LTER PI's, Barbara Prezelin and Ray Smith, are 
also co-PI's on a study to investigate the possible influence of 
ozone-related increases in UVB on phytoplankton communities.  This 
work has been carried out in the LTER area, and many components of 
Prezelin's and Smith's research, both equipment and personnel, share 
common components between the LTER and Icecolors projects.  For 
example, the LTER Aug/Sept 1993 cruise immediately preceeded the 
Ice'93 Oct/Nov cruise with some team members participating in 
both, providing a distinct savings in logistics and training of 
personnel.  With this arrangement, the LTER cruise was able to 
provide exploratory information, having covered a significant part of 
the LTER grid, for the planning of Ice'93 while the latter cruise 
provided an additional month of selected hydrography and optics data 
to the LTER effort.  The intellectual interactions are also strong, 
especially in understanding processes related to the spectrally 
dependent phytoplankton processes, including photoinhibition, 
photoreactivation, photoprotection, and photosynthesis.  Further, the 
impact of UVB on phytoplankton communities, especially the 
possibility of long term effects, is clearly a concern for the LTER 
which will initially be addressed by the Icecolors research.

D.  Energetics of adult and larval Euphausia superba (krill)
	This research project with L. Quetin and R. Ross as co-PIs is 
focused on quantification of the role of ice biota in winter-over 
survival of krill larvae.  Observed interannual differences in 
physiological condition of the larvae during the winter could lead to 
differences in survival of the young-of-the-year, and thus in the 
strength of any one year class.  We proposed to investigate and 
compare the processes underlying such differences during early and 
late winter (June versus September).  Low food availability in the 
fall after the summer phytoplankton blooms suggests that larvae in 
early winter will have experienced several months of near 
starvation conditions.  Without an additional food source such as ice 
biota in the underside of the sea ice these larvae may not survive 
the winter.  However, larvae under the ice in late winter of a heavy 
ice year will have had this additional food source, and may be in 
better physiological condition than the beginning of the winter.  We 
will compare environmental conditions in open water and under ice, 
sample larval krill and determine their physiological condition, and 
quantify the nutritional contribution of the ice biota to total energy 
demand of the larvae on two month-long cruises to the Southern 
Ocean.  In the laboratory at Palmer Station we will conduct 
experiments on the starvation tolerance of the late calyptopis and 
furcilia larvae, the stages present at the beginning of winter.  We 
will establish what several measures of physiological condition 
(condition factor and lipid content) mean in terms of the nutritional 
history of the larvae, including the range of carbon content in a 
particular larval stage from close to the Point-of-No-Return (PNR) 
to well-fed.  If larvae are starved beyond the PNR they can no longer 
recover, even if food subsequently becomes available.  The proposed 
research will address several significant questions about the 
winter-over energetics of larval krill, in particular the role of ice 
biota in winter-over survival and subsequent recruitment.

E.  Program for International Polar Oceans Research (PIPOR)
	High resolution (30m) all weather sea ice data would be an 
enormously valuable asset to the Palmer LTER.  Such data are now, in 
principle, available from an active microwave system on the 
European Remote Sensing Satellite (ERS-1).  Ray Smith, with the 
recommendation of and collaboration with Dr. Frank Carsey at JPL, is 
a new member of the PIPOR team.  This team includs the planning 
staff for the German SAR (Synthetic Aperature Radar) receiving 
station at O'Higgins on the Antarctic Peninsula who carry out field 
work on sea ice conditions in the Weddell and the 
Bellingshausen/Amundsen Seas.  It is anticipated that this 
collaborative effort will make high resolution sea ice data available 
to the LTER in exchange for providing the PIPOR group with on site 
surface ice observations during the LTER season.  A joint objective 
will be to enhance the accuracy of sea ice estimates from both 
active and passive microwave data in the Southern ocean.


F.  Long-Term Ecological Research (LTER) on the Antarctic Marine 
Ecosystem:  Microbiology and carbon flux.
	This research with David Karl as the principle investigator 
focuses on biogeochemical cycling of carbon and associated 
elements at the Palmer LTER.  This grant comprises the microbiology 
and carbon flux component of the LTER and will provide 
measurements of a suite of core parameters related to the carbon 
cycle and will test several hypotheses pertaining to carbon fluxes, 
including bacterial productivity and nutrient regeneration.

VIII.  Site description, structures and facilities 
	The LTER site region surrounds Palmer Station, located in a 
protected harbor on the southwest side of Anvers Island midway 
down the Antarctic Peninsula.  Within a 9-km radius of Palmer 
Station are two exposed, prominent points, and groups of islands 
that extend to the edge of the Bismarck Strait to the southeast.  
These islands have a diverse topography which extends into the 
intertidal and subtidal zones surrounding and linking the islands.  
Palmer Basin, 22 km southwest of Palmer Station, is the only deep 
basin in the area.  The maximum depth is 1,280 m, and the basin is 
connected to the open ocean on the west side of Anvers Island, and 
to the southern end of the strait between Anvers Island and the 
Antarctic Peninsula to the northeast.  Both channels are about 450 m 
deep.  
	The climate is typically maritime antarctic, with snow and 
rain common any time of the year.  The temperature at Palmer is 
relatively mild, averaging about -10ˇC in July and 2ˇC in January, 
with temperature extremes recorded at -31ˇC and 9ˇC.  Annual 
rainfall averages about 20 inches and snowfall about 14 inches.
	Palmer is especially well-situated for studies of birds, seals, 
and other components of the marine ecosystem, and it is equipped 
with a large, well-outfitted laboratory and seawater aquaria.  The 
station consists of two major and several smaller buildings.  Peak 
population is 43, including support personnel.  Many Palmer-based 
research project are undertaken in conjunction with the research 
ship Polar Duke, a 205 foot ice-strengthened research vessel or the 
Nathaniel B. Palmer, a 310 foot ice class research vessel.  Small 
boats support research near Palmer Station.

IX.  National and international presentations on Palmer LTER 
research

Christian, J. R., and D. M. Karl.  1993.  Bacterial exoenzymes in 
marine waters:  implications for global biogeochemical cycles.  
American Society for Limnology Meeting xx:xx.

Fraser, W. and D. Patterson.  1994.  Human disturbance and long-term 
changes in AdŽlie penguin populations:  a natural experiment at 
Palmer Station, Antarctic Peninsula.  Sixth SCAR Biology 
Symposium.  Life History Strategies.  May/June 1994.  Venice, Italy.  
Accepted oral presentation.

Frazer, T. L., L. B. Quetin, R. M. Ross, and R. C. Smith.  1994  Poster:  
Palmer LTER:  Larval antarctic krill, Euphausia superba, and winter 
ice.  Sixth SCAR Biology Symposium.  Life History Strategies.  
May/June 1994.  Venice, Italy.  Submitted abstract.

Haberman, K., R. M. Ross, and L. B. Quetin.  1993.  Poster:  Grazing by 
the antarctic krill Euphausia superba, on Nitschia spp. and 
Phaeocystis spp. monocultures.  LTER All Scientists Meeting and 
International Summit.  September 18-24, 1993.  Estes Park, 
Colorado.

Hofmann, E. E., D. A. Smith, B. L. Lipphardt, Jr., J. M. Klinck, R. A. 
Locarnini, and R. C. Smith.  1994.  Circulation and heat distributions 
on the continental shelf west of the Antarctic Peninsula.  February 
21-25, 1994.  Ocean Sciences Meeting.  San Diego, California.  
Submitted abstract.

Hofmann, E. E., D. A. Smith, B. L. Lipphardt, Jr., R. A. Locarnini, and R. 
C. Smith.  1994.  Palmer LTER:  Circulation west of the Antarctic 
Peninsula.  Sixth SCAR Biology Symposium.  Life History Strategies.  
May/June 1994.  Venice, Italy.  Submitted abstract.

Klinck, J. M. and R. C. Smith.  1994.  Palmer LTER:  Heat budgets and 
implications for circulation on the continental shelf west of the 
Antarctic Peninsula.  Sixth SCAR Biology Symposium.  Life History 
Strategies.  May/June 1994.  Venice, Italy.  Submitted abstract.

Klinck, J. M., C. M. Lascara, and R. C. Smith. 1993.  Hydrography and 
krill distributions in the Bellingshausen Sea as part of a long-term 
ecological research program.  European Geophysical Society, May 3-
7, 1993, Viesbaden, Germany.  Annales Geophysicae, Supplement II 
11(149):.

Lascara, C. M., E. E. Hofmann, R. M. Ross, and L. B. Quetin.  1992.  
Acoustically-derived distribution of krill (Euphausia superba) 
swarms off the Antarctic Peninsula during austral spring 1991 
(LTER Program).  EOS 73(43):319.

Lascara, C. M., E. E. Hofmann, R. M. Ross, and L. B. Quetin.  1993.  
Poster:  Distribution of antarctic krill within the Palmer LTER study 
region based on bioacoustics.  LTER All Scientists Meeting and 
International Summit.  September 18-24, 1993.  Estes Park, 
Colorado.

Lascara, C. M., E. E. Hofmann, R. M. Ross, and L. B. Quetin.  1994.  
Seasonal changes in the mesoscale distribution of Antarctic krill in 
the waters west of the Antarctic Peninsula.  February 21-25, 1994.  
Ocean Sciences Meeting.  San Diego, California.  Submitted abstract.

Lascara, C. M., E. E. Hofmann, J. M. Klinck, R. M. Ross, and L. B. Quetin.  
1994.  Palmer LTER:  Seasonal and geographic variability in the 
distribution of Antarctic krill, Euphausia superba, west of the 
Antarctic Peninsula.  Sixth SCAR Biology Symposium.  Life History 
Strategies.  May/June 1994.  Venice, Italy.  Submitted abstract.

Lipphardt, Jr., C. M. Lascara, D. A. Smith, J. M. Klinck, E. E. Hofmann, R. 
A. Locarnini, and R. C. Smith.  1994.  Palmer LTER:  Seasonal Changes 
in the hydrographic structure of the upper 100 m of the water 
column.  Sixth SCAR Biology Symposium.  Life History Strategies.  
May/June 1994.  Venice, Italy.  Submitted abstract.

Quetin, L. B., R. M. Ross, and C. M. Lascara.  1994.  Palmer LTER:  Fine-
scale distribution of Antarctic krill, Euphausia superba, within 
coastal waters near Palmer Station off the Antarctic Peninsula.  
Sixth SCAR Biology Symposium.  Life History Strategies.  May/June 
1994.  Venice, Italy.  Submitted abstract.

Quetin, L. B., R. M. Ross, and T. A. Newberger.  1994.  Palmer LTER:  
Variability in the distribution of length classes and maturity stages 
of adult antarctic krill, Euphausia superba, with season and 
environmental factors.  Sixth SCAR Biology Symposium.  Life History 
Strategies.  May/June 1994.  Venice, Italy.  Submitted abstract.

Ross, R. M.  1993.  Site presentation discussing research near Palmer 
Station.  LTER All Scientists Meeting and International Summit.  
September 18-24, 1993.  Estes Park, Colorado.

Ross, R. M., L. B. Quetin, and M. O. Amsler.  1994.  Physiological 
condition of larval antarctic krill, Euphausia superba, throughout the 
year.    Sixth SCAR Biology Symposium.  Life History Strategies.  
May/June 1994.  Venice, Italy.  Submitted abstract.

Smith, D. A., E. E. Hofmann, J. M. Klinck, R. A Locarnini, and R. C. 
Smith.  1994.  Palmer LTER:  Water mass distribution west of the 
Antarctic Peninsula.  February 21-25, 1994.  Ocean Sciences 
Meeting.  San Diego, California.  Submitted abstract.

Smith, D. A., E. E. Hofmann, J. M. Klinck, B. L. Lipphardt, Jr., R. A 
Locarnini, R. C. Smith.  1994.  Palmer LTER:  Hydrography in the 
region west of the Antarctic Peninsula.  Sixth SCAR Biology 
Symposium.  Life History Strategies.  May/June 1994.  Venice, Italy.  
Submitted abstract.

Stammerjohn, S.  1993.  Poster:  Variability in sea ice areal 
coverage along the western Antarctic Peninsula.  LTER All Scientists 
Meeting and International Summit.  September 18-24, 1993.  Estes 
Park, Colorado.

Trivelpiece, W., S. G. Trivelpiece, and W. Fraser.  1994.  The impact 
of pack ice on the demography and distribution of AdŽlie penguin 
populations.  Sixth SCAR Biology Symposium.  Life History 
Strategies.  May/June 1994.  Venice, Italy.  Submitted abstract.


X.  Literature Cited

Ainley, D. G., E. F. O'Connor and R. J. Boekelheide.  1984.  The marine 
ecology of birds in the Ross Sea, Antarctica. Am. Ornithol. Un 
Ornithol. Monogr.32:97pp.

Ainley, D. G., R. E. LeResche and W. J. L. Sladen.  1983.  Breeding 
Biology of the AdŽlie penguin.  Los Angeles: University of California 
Press. 

Ainley, D. G., W. R. Fraser, C. W. Sullivan, J. J. Torres, T. L. Hopkins, 
and W. O. Smith, Jr.  1986.  Antarctic mesopelagic micronekton:  
Evidence from seabirds that pack ice affects community structure. 
Science 232:847-849.

Ainley, D. G., W. R. Frazer, and K. K. Daly.  1988.  Effects of pack ice 
on the composition of micronektonic communities in the Weddell 
Sea. In D. Sharhage (ed.), Antarctic ocean & resources variability.  pp. 
140-146.  Springer-Verlag, Berlin, Heidelberg.

Balch,W.M., M.R.Abbott, and R.W.Eppley.  1989.  Remote sensing of 
primary production,I, A comparison of empirical and semi-analytical 
algorithms, Deep-Sea Res. 36: 281-  .

Bidigare, R.R., B. B. Prezelin, and R. C. Smith.  1992.  Bio-optical 
models and the problems of scaling, in P. G. Falkowski and A. D. 
Woodhead (eds.), Primary Productivity and Biogeochemical Cycles in 
the Sea..  pp 175-212.  Plenum Press, NY.

Bidigare,R. R., R. C. Smith, K. S. Baker, and J. Marra.  1987.  Oceanic 
primary production estimates from measurements of spectral 
irradiance and pigment concentrations.  Global Biogeochemical 
Cycles 1:171-186.

Billen, G. and A. Fontigny.  1987.  Dynamics of a Phaeocystis-
dominated spring bloom in Belgian coastal waters. II.  
Bacterioplankton dynamics.  Marine Ecology Progress Series 37:249-
257.

Billen, G. and S. Becquevort.  1991.  Phytoplankton-bacteria 
relationship in the Antarctic marine ecosystem.  Pro Mare 
Symposium on Marine Arctic Ecology, Trondheim, Norway. 

Bird, D. F. and J. Kalff.  1984.  Empirical relationships between 
bacterial abundance and chlorophyll concentration in fresh and 
marine waters.  Canadian Journal of Fisheries Aquatic Science 
41:1015-1023.

Bird, D. F. and D. M. Karl.  1991.  Spatial patterns of assimilation of 
exogenous glutamate and thymidine in the western Bransfield Strait, 
Antarctica, during and following the austral spring bloom. Deep-Sea 
Research.  in press. 

Bishop, J. K. and W. B. Rossow.  1991.  Spatial and temporal 
variability of global solar irradiance.  JGR 96:16,839-16,858.

Bolter, M. and R. Dawson.  1982.  Heterotrophic utilisation of 
biochemical compounds in Antarctic waters. Netherlands Journal of 
Sea Research 16:315-332.

Brewer, P. G.  1983.  Carbon dioxide in the oceans.  In Changing 
climate: Report of the Carbon Dioxide Assessment Committee.  pp. 
175-212.  National Academy Press, Washington, D.C.

Brown, P.C. and J. G. Field.  1985.  Diel variation in production rates 
of natural phytoplankton populations in the southern Benguela 
upwelling region.  Botanica Mar. 28:201-208.

Brinton, E. V. J. Loeb, M. C. Macaulay, and E. Shulenberger.  1987.  
Variability of Euphausia superba  populations near Elephant Island 
and the South Shetlands: 1981 vs. 1984.  Polar Biology 7:345-362.

Bunt, J. S.  1971.  Microbial productivity in polar regions.  Society 
for General Microbiology Symposium 21:333-354.

Clarke, A.  1985.  Energy flow in the Southern Ocean food web.  In W. 
R. Siegfried, P. R. Condy, and R. M. Laws, (eds.). Antarctic nutrient 
cycles and food webs.  pp. 573-580.  Springer-Verlag, Berlin, 
Heidelberg.

Cole, J. J., S. Findlay, and M. L. Pace.  1988.  Bacterial production in 
fresh and saltwater ecosystems: a cross-system overview.  Marine 
Ecology Progress Series 43:1-10. 

Cota, G. F., S. T. Kottmeier, D. H. Robinson, W. O. Smith, Jr., and C. W. 
Sullivan.  1990.  Bacterioplankton in the marginal ice zone of the 
Weddell Sea:  Biomass, production and metabolic activities during 
austral autumn.  Deep-Sea Research 37:1145-1167.

Croxall, J. P.  1980.  The food of gentoo penguinos Pygoscelis papua 
and macaroni penguins Eudyptes chrysolophus  at South Georgia.  
Ibis.  122:245-253.

Croxall, J. P., T. S. McCann, P. A. Prince, and P. Rothen.  1988.  
Reproductive performance of seabirds and seals at South Georgia and 
Signy Island, South Orkney Islands, 1976-1987.  Implications for 
Southern Ocean monitoring studies.  In D. Sahrhage (ed.), Antarctic 
ocean and resources variability.  pp. 261-285.  Springer-Verlag, 
Berlin.

Cuzin-Roudy, J. and M. A. O'Leary Amsler.  1991.  Ovarian 
development and sexual maturity staging in antarctic krill, 
Euphausia superba dana (Euphausiacea).  J. of Crust. Biol. 11(2):236-
249.

Daly, K. L. and M. C. Macaulay.  1988.  Abundance and distribution of 
krill in the ice edge zone of the Weddell Sea, austral spring 1983.  
Deep-Sea Research 35:21-41.

Darling, C. A., and P. A. Siple.  1941.  Bacteria in Antarctica.  Journal 
of Bacteriology 42:83-98.

Davis, C.S., G.R. Flierl, P.H. Wiebe, and P.J.S. Franks.  1991.  
Micropatchiness, turbulence, and recruitment in plankton.  Journal of 
Marine Research 49:109-151.

Dawson, R., W. Schramm, and M. Bolter.  1985.  Factors influencing 
the production, decomposition and distribution of organic and 
inorganic matter in Admiralty Bay, King George Island.  In W. R. 
Siegfried, P. R. Condy, and R. M. Laws, (eds.), Antarctic nutrient 
cycles and food webs..  pp. 109-114.  Springer-Verlag, Berlin, 
Heidelberg.

Dekshenieks, M. M., E. E. Hofmann, and E. N. Powell.  1993.  
Environmental effects of the development of larvae of Crassostrea 
virginicia:  A modeling study.  Journal of Shellfish Research.  In 
press.

DeWitt, H. H.  1970. The character of the midwater fish fauna of the 
Ross Sea, Antarctica.  In M. W. Holgate (ed.), Antarctic Ecology.  
1:305-314. London:  Academic Press.  

Eastman, J.T. and A.L. DeVries. 1981.  Buoyancy adaptations in a 
swim-bladderless Antarctic fish.  Journal of Morphology 167:91-
102.

Elias, M. C.  1990.  Effects of photoperiod, phytoplankton level and 
temperature on the growth, development and survival of larval 
Euphausia superba  (dana).  Master of Science, University of 
California at Santa Barbara.

El-Sayed, S. Z.  1971.  Observations on phytoplankton bloom in the 
Weddell Sea.  In G. A. Llano and I. E. Wallen (eds.), Biology of the 
Antarctic Seas.  Antarctic Research Series.  17: 301-312.  Am 
Geophys Union.  .

El-Sayed, S. Z.  1978.  Primary productivity and estimates of 
potential yields of the Southern Ocean.  In M. A. McWhinnie (ed.), 
Polar Research.:  to the present, and the future.  AAAS  Select Symp 
7.  pp. 141-160. Westview Press, New York.

El-Sayed, S. Z.  1985.  Plankton of the Antarctic seas.  In W. N. Bonner 
and D. W. H. Walton (eds.), Antarctica.  pp. 135-153.  Pergamon Press, 
Oxford, New York, Toronto, Sydney, Paris, Frankfurt.

El-Sayed, S. Z.  1988.  Seasonal and interannual variabilities in 
Antarctic phytoplankton with reference to krill distribution.  In  D. 
Sahrhage (ed.), Antarctic ocean and resources variability .  pp. 101-
119.  Springer-Verlag, Berlin Heidelberg New York London Paris 
Tokyo.

El-Sayed, S. Z. and S. Taguchi.  1981.  Primary production and 
standing crop of phytoplankton along the ice-edge in the Weddell 
Sea.  Deep-Sea Research 28A:1017-1032.

Emison, W. B.  1968. Feeding preferences of the AdŽlie penguin at 
Cape Crozier, Ross Island.  In O. L. Austin (ed.), Antarctic Bird 
Studies .  Antarctic Research Series 12:191-212.  Washington D.C.:  
American Geophysical Union.  

Ennever, F. K. and M. B. McElroy.  1985.  Changes in atmospheric CO2:  
Factors regulating the glacial to interglacial transition. In E. T. 
Sundquist, and W. S. Broecker (eds.), The carbon cycle and 
atmospheric CO2:  Natural variations archaen to present, Geophysical 
Monograph 32, American Geophysical Union, Washington, D.C.  pp. 
154-162. 

Eppley, R. W.  1989.  New production:  History, methods, problems.  In 
W. H. Berger, V. S. Smetacek, and G. Wefer (eds.), Productivity of the 
ocean:  Present and past.   pp. 85-98.  John WIley & Sons Ltd.

Ettershank, G.  1984.  A new approach to the assessment of longevity 
in the antarctic krill Euphausia superba.  J. Crust. Biol. 4(spec. No. 
1):295-305.

Fee, E. J., 1975.  The importance of diurnal variation of 
photosynthesis vs light curves to estimates of integral primary 
production. Verh. int. Verein Theor. Angew. Limnol. 19:39-46

Fraser, W. R. and D. G. Ainley.  1986.  Ice edges and seabird 
occurrence in Antarctica. BioScience 36:258-263.

Fraser, W. R. and D. L. Patterson.  1993.  Human  disturbance and  
long-term changes in Adelie Penguin populations:  A  natural 
experiment  at Palmer Station, Antarctic Peninsula.  Workshop  on 
seabird-researcher  interactions.  Monticello, Minnesota  14-18 July 
1993.

Fraser, W. R., D. G. Ainley, and R. L. Pitman.  1989.  Seabird and fur 
seal responses to vertically migrating winter krill swarms in 
Antarctica.  Polar Biology 10:37-41.

Fraser,  W.R. and LTER PI's.  1994.  Changes in the populations of 
upper-trophic  level predators at  Palmer Station, Antarctic 
Peninsula:  The effects of long-term climate change.  In preparation.

Fraser,  W. R. and  W. Z. Trivelpiece.  1994  A.  Long-term changes in  
the  diets of Pygoscelid   penguins:  Implications for Southern Ocean 
ecosystems.  In  preparation.

Fraser, W. R., W. Z. Trivelpiece, D. G. Ainley, and S. G. Trivelpiece.  
1992.  Increases in antarctic penguin populations:  Reduced 
competition with whales or a loss of sea ice due to environmental 
warming.  Polar Biology 11:525-531.

Frouin, R., D. W. Ligner, C. Gautier, K. S. Baker, and R. C. Smith.  1989.  
A simple analytical formula to compute clear sky total and 
photosynthetically active solar irradiance at the ocean surface, JGR 
94, 9731-9742.

Garrison, D. L., C. W. Sullivan, and S. F. Ackley.  1986.  Sea ice 
microbial communities in Antarctica.  BioScience 36:243- 250.

Garrison, D. L., K. R. Buck, and G. A. Fryxell.  1987.  Algal assemblages 
in antarctic pack ice and in ice-edge plankton.  Journal of Phycology 
23:564-572.

Gautier, C., G. Diak, and S. Masse.  1980.  A Simple physical model to 
estimate incident solar radiation at the surface from GOES satellite 
data.  J. Appl. Meteor. 19:1005-1012.

Grossi, S. M., S. T. Kottmeier, and C. W. Sullivan.  1984.  Sea ice 
microbial communities. III. Seasonal abundance of microalgae and 
associated bacteria, McMurdo Sound, Antarctica.  Microbial Ecology 
10:231-242.

Guzman, O.  1983.  Distribution and abundance of antarctic krill 
(Euphausia superba) in the Bransfield Strait.  In S. B. Schnack (ed.), 
On the biology of krill  Euphausia superba.  pp. 169-190.  Alfred-
Wegener-Institute for Polar Research, Bremerhaven, FRG.

Haidvogel, D.B., J. Wilkin, and R. E. Young.  1991.  A semi-spectral 
primitive equation ocean circulation model using vertical sigma and 
orthogonal curvilinear coordinates.  J. Comp. Phys. 94:151-185.

Hakkinen, S.  1990.  Models and Their Applications to Polar 
Oceanography.  In W. O. Smith, Jr. (ed.), Polar Oceanography. Part A:  
Physical Science.  pp. 335-384.  Academic Press, Inc., London.

Hamner, W. M.  1984.  Aspects of schooling in Euphausia superba.  J. 
Crust. Biol. 4(Spec. No. 1):67-74.

Hamner, W. M., P. P. Hamner, S. W. Strand, and R. W. Gilmer.  1983.  
Behaviour of Antarctic krill, Euphausia superba  chemoreception, 
feeding, schooling, and moulting.  Science 220:433-435.

Harding, L. W. J., B. B. PrŽzelin, B. M. Sweeney, and J. L. Cox.  1982.  
Primary production as influenced by diel periodicity of 
phytoplankton photosynthesis.  Mar. Biol. 67:179-186.

Hayes, P. K., T. M. Whitaker, and G. E. Fogg.  1984.  The distribution 
and nutrient status of phytoplankton in the Southern Ocean between 
20 degrees and 70 degrees W.  Polar Biology 3:153-165.

Heywood, R. B. and T. M. Whitaker.  1984.  the antarctic marine flora.  
In R. M. Laws (ed.), Antarctic Ecology.  (2) pp. 373-419.  London New 
York:  Academic Press.  

Hewes, C. D., E. Sakshaug, and O. Holm-Hansen.  1985.  Alternative 
pathways at lower trophic levels in the Antarctic food web. In W. R. 
Siegfried, P. R. Condy, and R. M. Laws (eds.),  Antarctic nutrient 
cycles and food webs.  pp. 277-283.  Springer-Verlag, Berlin.

Hoepffner, N. J.  1984.  Strategies d'adaptation photosynthetique 
chez des diatomes de l'ocean Antarctique: variations du nombre et de 
la taille des unites photosynthetique.  Journal of Plankton Research 
6:881-895.

Hofmann, E.E., E. N. Powell, J. M. Klinck, and E. A. Wilson.  1992.  
Modeling oyster populations. III. critical feeding periods, growth and 
reproduction.  Journal of Shellfish Research 11(2):399-416.

Holm-Hansen, O., S. Z. El-Sayed, G. A. Franceschini, and R. L. Cuhel.  
1977.  Primary production and the factors controlling phytoplankton 
growth in the Southern Ocean.  In G. A. Llano (ed.), Adaptations 
within antarctic ecosystems: Proceedings of the third SCAR 
symposium on antarctic biology.  pp. 11-50.  Gulf Publishing 
Company, Houston, Texas.

Holm-Hanses, O., B. G. Mitchell, and M. Vernet.  1989.  Ultraviolet 
radiation in antarctic waters:  Effect on rates of primary production.  
Antarctic Journal of the United States 24(4):177-181.

Honjo, S.  1990.  Particle fluxes and modern sedimentation in the 
Polar Oceans. In W. O. Smith, Jr., (ed.), Polar oceanography. Part B: 
Chemistry, biology and geology.  pp. 687-739.  Academic Press, Inc., 
San Diego, CA.

Hopkins, T. L.  1985.  Food web of an Antarctic midwater ecosystem. 
Marine Biology 89:197-212.

Hubold, G.  1985. The early life history of the high antarctic 
silverfish, Pleuragramma antarcticum.  In W. R. Siegfried, P. R. Condy 
and R. M. Laws (eds.), Antarctic nutrient cycles and food webs.  pp. 
445-451.  Springer-Verlag, Berlin, Heidelberg, New York, Tokyo.

Hubold, G.  and  A. P. Tomo.  1989.  Age and growth of antarctic 
silverfish, Pleuragramma antarcticum Boulenger, 1902, from the 
Southern Weddell Sea and Antarctic Peninsula.  Polar Biology 9: 205-
212.

Huntley, M. E., M. D. G. Lopez, and D. M. Karl.  1991.  Top predators in 
the Southern Ocean: A major leak in the biological carbon pump.  
Science, in press.

Jacques, G.  1983.  Some ecophysiological aspects of the Antarctic 
phytoplankton.  Polar Biology 2:27-33.

Karl, D. M.  1986.  Determination of in situ microbial biomass, 
viability, metabolism, and growth. In J. S. Poindexter and E. R. 
Leadbetter (eds.), Bacteria in nature, vol. 2.  pp. 85-176.  Plenum 
Publishing Corporation. 

Karl, D. M.  1993.  Microbial processes in the Southern Ocean. In E. I. 
Friedmann (ed.),  Antarctic Microbiology.  pp. 1-63.  John Wiley and 
Sons, Inc. 

Karl, D. M. and G. Tien.  1992.  MABIC:  A sensitive and precise method 
for measuring dissolved phosphorus in aquatic environments.  
Limnology and Oceanography 37:105-116.

Karl, D. M., O. Holm-Hansen, G. T. Taylor, G. Tien, and D. F. Bird.  
1991a.  Microbial biomass and productivity in the western 
Bransfield Strait, Antarctica during the 1986-87 austral summer.  
Deep-Sea Research 38:1029-1055.

Karl, D. M., B. D. Tilbrook, and G. Tien.  1991b.  Seasonal coupling of 
organic matter production and particle flux in the Bransfield Strait, 
Antarctica.  Deep-Sea Research 38:1097-1126.
Kellermann, A.  1986.  Geographical distribution and abundance of 
postlarval and juvenille Pleuragramma antarcticum (Pisces, 
Notothenioidei) off the Antarctic Peninsula.  Polar Biology 6:111-
119.

Kellermann, A. and K.-H. Kock.  1988. Patterns of spatial and 
temporal distribution and their variations in early life stages of 
antarctic fish in the Antarctic Peninsula region.  In  D. Sahrhage 
(ed.), Antarctic ocean & resources variability.  pp. 147-159.  
Springer-Verlag, Berlin,  Heidelberg,  New York, London, Paris, Tokyo.

Koike, I., O. Holm-Hansen, and D. C. Biggs.  1986.  Inorganic nitrogen 
metabolism by Antarctic phytoplankton with special reference to 
ammonium cycling.  Marine Ecology Progress Series 30(2/3):105-
116.

King, G. M. and M. J. Klug.  1982.  Glucose metabolism in sediments of 
a eutrophic lake:  Tracer analysis of uptake and product formation.  
Applied and Environmental Microbiology 44:1308-1317.

Knox, F. and M. B. McElroy.  1984.  Changes in atmospheric CO2:  
Influence of the marine biota at high latitude.  Journal of 
Geophysical Research 89:4629-4637.

Kottmeier, S. T., S. M. Grossi, and C. W. Sullivan.  1987.  Sea ice 
microbial communities. VIII. Bacterial production in annual sea ice 
of McMurdo Sound, Antarctica. Marine Ecology Progress Series 
35:175-186.

Kottmeier, S. T. and C. W. Sullivan.  1987.  Late winter primary 
production and bacterial production in sea ice and seawater west of 
the Antarctic Peninsula.  Marine Ecology Progress Series 36:287-
298.

Lancelot, C., G. Billen, and S. Mathot.  1989.  Ecophysiology of phyto- 
and bacterioplankton growth in the Southern Ocean. Belgian 
Scientific Research Programme on Antarctica Scientific Results of 
Phase One (Oct 85 - Jan 89), Volume 1: Plankton Ecology, 97 pp.

Lascara, C. M., L. B. Quetin, and R. M. Ross.  1993.  Palmer LTER:  Krill 
distribtuion  and biomass within coastal waters near Palmer 
Station.  Antarctic Journal of the United  States.  Palmer LTER 
Contribution #17.  In press.

Laws, R. M.  1985.  The ecology of the Southern Ocean.  Am. Sci. 
73:26-40.

Levin, S. A., A. Morin, and T. M. Powell.  1988.  Patterns and processes 
in the distribution and dynamics of antarctic krill.  In Part I. 
Selected Scientific Papers.(ed.), Scientific Committee for the 
Conservation of Antarctic Marine Living Resources.  pp. 281-299. 

Macaulay, M. C., T. S. English, and O. A. Mathisen.  1984.  Acoustic 
characterization of swarms of antarctic krill (Euphausia superba) 
from Elephant Island and Bransfield Strait.  J. Crust. Biol. 4(Spec. no. 
1):16-44.

Marschall, H. -P.  1988.  The overwintering strategy of antarctic 
krill under the pack-ice of the Weddell Sea.  Polar Biol. 9:129-135.

McLean, A. L.  1918.  Bacteria of ice and snow in Antarctica.  Nature 
102:35-39. 

Moore, B. and B. Bolin.  1987.  The oceans, carbon dioxide and global 
climate change. Oceanus 29:9-15.

Morel, A. and J. F. Berthon.  1989.  Surface pigments, algal biomass 
profiles, and potential production of the euphotic layer: 
Relationships reinvestigated in view of remote-sensing 
applications.  Limnol. Oceanogr. 34:1545-1562.

Morin, A., A. Okubo, and K. Kawaski.  1988.  Acoustic Data Analysis 
and Models of Krill Spatial Distribution.  Scientific Committee for 
the Conservation of Antarctic Marine Living Resources.  Selected 
Scientific Papers, Part I, SC-CAMLR-SSP/5:311-329.

Morita, R. Y., R. P. Griffiths, and S. S. Hayasaka.  1977.  Heterotrophic 
activity of microorganisms in Antarctic waters. In G. A. Llano (ed.), 
Adaptations within Antarctic ecosystems: proceedings of the third 
SCAR symposium on Antarctic biology.  pp. 99-113.  Smithsonian 
Institution.

Mortrain-Bertrand, A.  1988.  Photosynthetic metabolism of an 
Antarctic diatom and its physiological responses to fluctuations of 
light.  Polar Biology 9:253-260.

Murphy, E. J., D. J. Morris, J. L. Watkins, and J. Priddle. 1988.  Scales 
of interaction between antarctic krill and the environment.  In D. 
Sahrhage (ed.), Antarctic ocean & resources variability.  pp. 120-
130.  Springer-Verlag, Berlin, Heidelberg, New York, London, Paris, 
Tokyo.

Nelson, D. M., W. O. Smith, Jr., R. D. Muench, L. I. Gordon, C. W. Sullivan, 
and D. M. Husby.  1989.  Particulate matter and nutrient distributions 
in the ice-edge zone of the Weddell Sea:  relationship to hydrography 
during late summer. Deep- Sea Research 36:191-209.

Niebauer, H. J. and V. Alexander.  1985.  Oceanographic frontal 
structure and biological production at an ice edge.  Continental Shelf 
Research 4:367-388.

Palmisano, A. C. and C. W. Sullivan.  1983.  Sea ice microbial 
communities (SIMCO). 1. Distribution, abundance, and primary 
production of ice microalgae in McMurdo Sound, Antarctica in 1980.  
Polar Biology 2:171-177.

Perrin, R. A., P. Lue, and H. J. Marchant.  1987.  Seasonal variation in 
marine phytoplankton and ice algae at a shallow antarctic coastal 
site.  Hydrobiologia 143:33-46.

Pietz, P. J.  1986.  Daily activity patterns of south polar and brown 
skuas near Palmer Station, Antarctica.  Auk 103:726-736.

Pietz, P. J.  1987.  Feeding and nesting ecology of sympatric south 
polar and brown skuas.  Auk 104(4):617-627.

Platt, T.  1986.  Primary production of the ocean water column as a 
function of surface light intensity: algorithms for remote sensing, 
Deep-Sea Res. 33:149-.

Prevost, J. 1981.  Population biomass and energy requirements of 
Antarctic birds.  In S.Z. El-Sayed (ed.), Biomass. II:.  pp. 125-137.   
Cambridge: Scott Polar Research Institute.

PrŽzelin, B. B. (l992) Review: Diel periodicity in phytoplankton 
productivity:. Hydrobiologia  238:1-35.

PrŽzelin, B. B., R. R. Bidigare,  H. A. Matlick,  M. Putt, and B. Ver 
Hoven.  1987.  Diurnal patterns of size-fractioned primary 
productivity across a coastal front.  Mar. Biol. 96:563-574 

PrŽzelin, B. B.  and H. E. Glover.  Variability in time/space estimates 
of phytoplankton, biomass, and productivity in the Sargasso Sea.  J. 
Plankton Res. 13S:45-67.

PrŽzelin, B.B., M. M. Tilzer, O. Schofield,  and C. Haese.  1991.  Control 
of the production process of phytoplankton by the physical structure 
of the aquatic environment, with special  reference to its optical 
properties.  Aquatic Sci. 53:36-186. 

Price, J. F., R. A. Weller, and R. Pinkel.  1986.   Diurnal Cycling: 
Observations and Models of the Upper Ocean Response to Diurnal 
Heating, Cooling, and Wind Mixing, J. Geophys. Res. 91:8411-8427.

Priddle, J. J. P. Crozall, I. Everson, R. B. Heywood, E. J. Murphy, P. A. 
Prince, and C. B. Sear.  1988.  Large-scale fluctuations in 
distribution and abundance of krill- A discussion of possible causes.  
In. D. Sharhage (ed.), Antarctic resources and variability.  pp. 139-
182.  Springer-Verlag, Berlin.

Quetin, L. B. and R. M. Ross.  1985.  Feeding by antarctic krill, 
Euphausia superba:  Does size matter?  In  Antarctic nutrient cycles 
and food webs.  pp. 372-377.  Springer-Verlag, Berlin, Heidelberg.

Quetin, L. B. and R. M. Ross.  1991.  Behavioral and physiological 
characteristics of the antarctic krill, Euphausia superba.  American 
Zoologist 31(1):117-146.

Quetin, L. B., R. M. Ross, and A. Clarke.  1993.  Krill energetics:  
seasonal and environmental aspects of the physiology of Euphausia 
superba.  In El-Sayed (ed.) Southern ocean ecology, the BIOMASS 
perspective.  Cambridge University Press. (In press).

Rakusa-Suszczewski.  1988.  Differences in the hydrology, biomass, 
and species distribution of plankton, fishes, and birds in the 
Bransfield Strait and the Drake Passage during FIBEX 1981 and SIBEX 
1983/84.  In D. Sharhage (ed.), Antarctic ocean and resources 
variability.  pp. 214-218.  Springer-Verlag, Berlin.

Reisenbichler, K. R.  1993.  Growth and chemical composition in two 
populations of the antarctic silverfish, Pleuragramma antarcticum  
(Pieces, Nototheniidae).  Masters thesis.  University of California at 
Santa Barbara.

Rivkin, R. B. and M. Putt.  1987.  Diel periodicity of photosynthesis in 
polar phytoplankton: influence on primary production.  Science 
238:1285-1288.

Ross, R. M. and L. B. Quetin.  1986.  How productive are antarctic 
krill?  BioScience 36 (4):264-269.

Ross, R. M. and L. B. Quetin.  1989.  Energetic cost to develop to the 
first feeding stage of Euphausia superba Dana and the effect of 
delays in food availability.  J. Exp. Mar. Biol. Ecol. 133:103-127.

Ross, R. M. and L. B. Quetin.  1991.  Ecological physiology of larval 
euphausiids, Euphausia superba (Euphausiacea).  Memoirs of the 
Queensland Museum 31:321-333.

Sahrhage, D.  1988.  Some indications for environmental and krill 
resources variability in the Southern Ocean.  In D. Sahrhage (ed.), 
Antarctic ocean and resources variability.  pp. 33-40.  Springer-
Verlag, Berlin.

Sambrotto, R. N., G. Savidge, C. Robinson, P. Boyd, T. Takahashi, D. M. 
Karl, C. Langdon, D. Chipman, J. Marra, and L. Codispoti.  1993.  
Elevated consumption of carbon relative to nitrogen in the surface 
ocean. Nature 363:248-250.
 
Sarmiento, J. L. and J. R. Toggweiler.  1984.  A new model for the 
role of the oceans in determining atmospheric PCO2.  Nature 
308:621-624.

Sieburth, J. McN.  1965.  Microbiology of Antarctica. In J. van 
Mieghem and P. van Oye (eds.), Biogeography and Ecology in 
Antarctica.  pp. 267-295.  Dr. W. Junk Publ., The Hague.

Siegel, V.  1987.  Age and growth of Antarctic Euphausiacea 
(Crustacea) under natural conditions.  Marine Biology 96:483-496.

Siegenthaler, U. and T. Wenk.  1984.  Rapid atmosheric CO2 variations 
and ocean circulation.  Nature 308:624-626.

Siegfried, W. R., P. R. Condy, and R. M. Laws (eds.).  1985.  Antarctic 
nutrient cycles & food webs.  Springer-Verlag, Berlin, Heidelberg, 
New York, Toronto.

Smith, R. C., B. B. Prezelin, R. R. Bidigare, and K. S. Baker.  1989.  bio-
optical modeling of photosynthetic production in coastal waters.  
Limnology & Oceanography 34:1526-1544.

Smith, R.C., B. B. PrŽzelin, R. R. Bidigare,  and K.S.  Baker.  l989.  Bio-
optical modeling of photosynthetic production in coastal waters  
Limnology & Oceanography 38: 1526-1546.

Smith, R. C., B. B. PrŽzelin, R. R. Bidigare, and K. S. Baker.  1989.  Bio-
optical modeling of photosynthetic production in coastal waters.  
Limnology & Oceanography 34(8):1524-1544.

Smith, R. C., O. B. Brown, F. E. Hoge, K. S. Baker, R. H. Evans, R. N. 
Swift, andW. E. Esaias.  1987.   Multiplatform Sampling (ship, 
aircraft, and satellite) of a Gulf Stream warm core ring.  Applied 
Optics 26:2068-2081.

Smith, R. C., R. R. Bidigare,  B. B. PrŽzelin,  K. S. Baker, and J. M. 
Brooks.  l987.  Optical characterization of primary productivity 
across a coastal front.  Mar.  Biol. 96:563-574 

Smith, S. J. and J. Vidal.  1986.  Variations in the distribution, 
abundance, and development of copepods in the southeastern Bering 
Sea in 1980 and 1981.  Continental Shelf Research  5:215-239.

Smith, W. O., Jr.  1987.  Phytoplankton dynamics in marginal ice 
zones. Oceanography and Marine Biology Annual Review 25:11- 38.

Smith, W.O., Jr. (ed.)  1990.  Polar Oceanography.  Orlando: Academic 
Press. 

Smith, W. O., Jr. and D. M. Nelson.  1985a.  Phytoplankton bloom 
produced by a receding ice edge in the Ross Sea: spatial coherence 
with the density field.  Science 227:163-166.

Smith, W. O., Jr. and D. M. Nelson.  1985b. Phytoplankton biomass near 
a receding ice-edge in the Ross Sea.  In W. R. Siegfried, P. R. Condy 
and R. M. Laws (eds.), Antarctic nutrient cycles & food webs.  pp. 70-
77.  Springer-Verlag, Berlin, Heidelberg, New York, Tokyo.

Smith, W. O., Jr. and D. M. Nelson.  1986.  Importance of ice edge 
phytoplankton production in the Southern Ocean.  BioScience 36:251-
257.

Smith, W. O., N. K. Keene, and J.C. Comiso.  1988.  Interannual 
variability in estimated primary production of the Antarctic 
marginal ice zone.  In  D.Sahrhage (ed.), Antarctic Ocean and 
Resources Variability.  pp. 131-139.  Springer-Verlag, Berlin.

Stammerjohn, S. E.  1993.  Spatial and Temporal Variability in 
Southern Ocean Sea Ice Coverage, Masters Thesis,  University of 
California at Santa Barbara.

Stein, M.  1988.  Variation of geostrophic circulation off the 
Antarctic Peninsula and in the southwest Scotia Sea, 1975-1985.  In 
D. Sahrhage (ed.), Antarctic ocean and resources variability.  pp. 81-
91.  Springer-Verlag, Berlin.

Stein, M.  1991.  Variability of local upwelling off the Antarctic 
Peninsula, 1986-1990.  Archiv fur Fischereiwissenschaft, in press.

Sullivan, C. W., G. F. Cota, D. W. Krempin, and W. O. Smith, Jr.  1990.  
Distribution and activity of bacterioplankton in the marginal ice 
zone of the Weddell-Scotia Sea during austral spring.  Marine 
Ecology Progress Series 63:239-252.

Sullivan, C. W., K. R. Arrigo, C. R. McClain, J. C. Comiso, and J. 
Firestone.  1993.  Distributions of phytoplankton blooms in the 
Southern Ocean.  Science 262:1832-1852.

Tilzer, M. M., B. von Bodungen and V. Smetacek.  1985. In W. R. 
Siegfried, P. R. Condy and R. M. Laws (eds.), Antarctic nutrient cycles 
& food webs.  pp. 60-69.  Springer-Verlag, Berlin, Heidelberg, New 
York, Tokyo.

Tranter, D. J.  1982.  Interlinking of physical and biological 
processes in the Antarctic Ocean.  Oceanography and Marine Biology 
Annual Review 20:11-35.

Trivelpiece, W. Z., S. G. Trivelpiece, and N. J. Volkman.  1987.  
Ecological segregation of AdŽlie, Gentoo, and Chinstrap penguins at 
King George Island, Antarctica.  Ecology 68(2):351-361.

Trivelpiece, W. Z., G. Geupel, J. Kjelmyr, and S. J. Trivelpiece.  1994.  
Proceedings  of the First International Conference on Penguins, 
Dunedin, New Zealand.  In press.

Trivelpiece, W., D. G. Ainley, W. R. Fraser, and S. G. Trivelpiece.  1990.  
Skua survival.  Nature 345:211.

Trivelpiece, W. Z., G. R. Geupel, S. G. Trivelpiece, J. Kjelmyt, and N. J. 
Volkman.  AdŽlie  and chinstrap penguins:  Their potential as 
monitors of the southern ocean marine ecosystem.  In K. Kerry G. 
Hempel (eds.), Ecological Change & the Conservation of Antarctic 
Ecosystems: Proceedings of the Fifth Symposium on Antarctic 
Biology.  Springer-Verlag, Berlin.

Volkman, N. J., P. Pressler, and W. Trivelpiece.  1980.  Diets of 
Pygoscelid penguins at King George Island, Antarctica.  Condor 
82:373-378.

Walsh, J. J. and C. P. McRoy.  1986.  Ecosystem analysis in the 
southeastern Bering Sea.  Continental Shelf Research 5:259-288.

Waters, K. and R. Smith.  1992.  Palmer LTER:  A sampling grid for the 
Palmer LTER program.  Antarctic Journal of the United States 
27:236-239.



Williams, R.  1985.  Trophic relationships between pelagic fish and 
euphausiids in Antarctic waters.  In W. R. Siegfried, P. R. Condy, and 
R. M. Laws (eds.), Antarctic nutrient cycles and food webs.  pp. 452-
459.  Springer-Verlag, Berlin, Heidelberg, New York, Tokyo.

Wilson, D. L., W. O. Smith Jr., and D. M. Nelson.  1986.  Phytoplankton 
bloom dynamics of the western Ross Sea ice edge:  1.  Primary 
productivity and species specific production.  Deep-Sea Research  
33:1375-1387.

Young, E. C.  1963.  feeding habits of the south polar skua Catharacta 
maccormicki.  Ibis.  105:301-318.

Zwally, H. J., C. L. Parkinson, and J. C. Comiso.  1983a.  Variability of 
antarctic sea ice and changes in carbon dioxide.  Science 220:1005-
1012.

Zwally, H. J., J. C. Comiso, C. L. Parkinson, W. Campbell, F. Carsey, and 
P. Gloerson. 1983b. Antarctic sea ice cover from Satellite Passive 
Microwave.  In G. Kukla, A. Hecht, D. Wiesnet (eds.), NOAA 
Environmental data and information service. Sea Ice, 1973-1976.  pp. 
79-85.  Satellite Passive Microwave Observations.  Boulder, CO.  
USA. 

Zdanowski, M. K.  1985.  Distribution of bacteria, organic carbon and 
amino acids in the southern art of Drake assage and in Bransfield 
Strait during the BIOMASS-SIBEX (December 1983- January 1984).  
Polish  Polar Research 6:43-63.

XI.  Palmer LTER Publications

Asper, V. L., A. R. Diercks, and D. M. Karl. 1993. The first profiles of 
marine snow aggregate abundance from  Antarctica.  Antarctic 
Journal of the United States.  Palmer LTER Contribution #25 
(submitted 1993).

Bird, D. F., R. Maranger, and  D.  M.  Karl.  1993.  Aquatic virus  
abundances near the Antarctic Peninsula. Antarctic Journal of the 
United States.  Palmer LTER Contribution #24 (submitted 1993).

Christian, J. R. and D. M. Karl.  1993.  Bacterial  exoprotease activity 
in the Palmer Peninsula during austral autumn 1993.  Antarctic 
Journal of the United States.  Palmer LTER Contribution #23 
(submitted 1993).

Fraser, W. R., W. Z. Trivelpiece, B. R. Houston, and D  R. Patterson.  
1992.  Palmer LTER:  Seabird research undertaken during 1991-1992 
at  Palmer Station, Antarctic Peninsula.  Antarctic Journal of the 
United States 27(5):249-250.  Palmer LTER Contribution #09.

Fraser, W. R., W. Z. Trivelpiece, D. G. Ainley, and S. G. Trivelpiece.  
1992.  Palmer LTER:  Increases in Antarctic penguin populations:  
Reduced competition with whales or a loss of sea ice due to 
environmental warming?  Polar Biology 11:525-531.  Palmer LTER 
Contribution #35.

Haberman, K. L., R. M. Ross, and L. B. Quetin.  1993.  Grazing by the 
Antarctic Krill, Euphausia superba, on Nitschia sp. and Phaeocystis 
sp. monocultures.  Antarctic Journal of the United States.  Palmer 
LTER Contribution #18 (submitted 1993).

Hofmann, E. E., C. M. Lascara, and J. M. Klinck.  1992.  Palmer LTER:  
Upper  ocean circulation in the LTER region from historical sources.  
Antarctic Journal of the United  States 27(5):239-241 Palmer LTER 
Contribution #05.

Hofmann, E. E., B. L. Lipphardt, R. A. Locarnini, and D. A. Smith.  1993.  
Palmer LTER:  Hydrography in the LTER region.  Antarctic Journal of 
the United States.  Palmer LTER Contribution #15 (submitted 1993).

Houlihan, T. and D. M. Karl.  1993.  Palmer LTER:  Dissolved silicic 
acid-nitrate relationships during Austral Fall 1993.  Antarctic 
Journal of the United States.  Palmer LTER Contribution #26 
(submitted 1993).

Karl, D. M., J. Resing, G. Tien, R. Letelier, and D. Jones.  1993.  
Hydrogen peroxide in the Palmer-LTER region:  II.  Water column 
distributions.  Antarctic Journal of the United States.  Palmer LTER 
Contribution #20 (submitted 1993).

Karl, D. M. and J. Resing.  1993.  Hydrogen peroxide  in  the Palmer-
LTER region:  IV.  Photochemical interactions with dissolved organic 
matter.  Antarctic Journal of the United States.  Palmer LTER 
Contribution #22 (submitted 1993).

Karl, D. M., J. Resing, G. Tien, R. Letelier, and D. Jones.  1993.  
Hydrogen  peroxide in the Palmer-LTER region:  I.  An  introduction.  
Antarctic Journal of the United States.  Palmer LTER Contribution 
#19 (submitted 1993).

Lascara, C. M., E. E. Hofmann, R. M. Ross, and L. B. Quetin.  1993.  
Palmer LTER:  Overview of krill acoustic studies and results from 
the Peninsula grid.  Antarctic Journal of the United States.  Palmer  
LTER Contribution #16 (submitted 1993).

Lascara, C. M., L. B. Quetin, and R. M. Ross.  1993.  Palmer LTER:  Krill 
distribtuion  and biomass within coastal waters near Palmer 
Station.  Antarctic Journal of the United  States.  Palmer LTER 
Contribution #17 (submitted 1993).

Porter, J. H. and J. T. Callahan.  Confounding a  Dilemma:  Historical 
Approaches to Data  Sharing in Ecological Research.  Draft Palmer 
LTER Contribution #(none).

Prezelin, B. B., M. Moline, K. Seydel, and K. Scheppe.  1992.  Palmer  
LTER:  Temporal variability in HPLC pigmentation and inorganic 
nutrient distribution in surface waters adjacent to Palmer Station, 
Decmeber 1991 - February 1992.  Antarctic Journal of the United 
States 27(5):245-248.  Palmer LTER Contribution #08.

Prezelin, B. B., N. P. Boucher, M. Moline, E. Stephens, K. Seydel, and K. 
Scheppe.  1992.  Palmer LTER:  Spatial variability in phytoplankton 
distribution and surface photosynthetic potential with the peninsula 
grid, November 1991.  Antarctic Journal of the  United  States 
27(5):242-244.  Palmer LTER Contribution #06.

Quetin, L. B., R. M. Ross, B. Prezelin, K. L. Haberman, K. L. Hacecky, and 
T. Newberger.  1992.  Palmer LTER:  Biomass and community 
composition of euphausiids within the peninsula grid, November 
1991 cruise.  Antarctic Journal of the United States 27(5):244-245. 
Palmer LTER Contribution #07.

Quetin, L. and R. Ross.  1992.  A  Long-Term  Ecological Research 
Strategy for Polar Environmental Research.  Marine Pollution 
Bulletin 25:233-238.  Palmer LTER Contribution #13.

Ross, R. M. and L. B. Quetin.  1992.  Palmer long-term ecoogical  
research  (LTER):  an overview of the 1991-1992 season.  Antarctic 
Journal of the United States 27(5):235-236. Palmer LTER 
Contribution #03.

Ross, R. M., L. B. Quetin, and K.  S.  Baker.  1993.  Palmer Long-Term  
Ecological Research  (LTER):  an Overview of the 1992-1993 season.  
Antarctic Journal of  the  United States.  Palmer LTER Contribution 
#14 (submitted 1993).

Smith, R. C., K. S. Baker, K. K. Hwany, D. Menzies, and  K. J. Waters.  
1992.  Palmer LTER:  Hydrography and optics within the peninsula 
grid, November 1991 cruise.  Antarctic Journal of the United States 
27(5):250-253.  Palmer LTER Contribution #10.

Smith, R. C., K. S. Baker, P. Handley, and T. Newberger.  1992.  Palmer 
LTER:  ROZ sampling of the hydrography and optics over the Palmer 
grid during the 1991/92 LTER field season.  Antarctic Journal of the 
United States 27(5):253-255.  Palmer LTER Contribution #11.

Tien, G. and D. M. Karl.  1993.  Hydrogen peroxide in the Palmer-LTER 
region:  III.  Local sources and sinks.  Antarctic Journal of the  
United States.  Palmer LTER Contribution #21 (submitted 1993).

Waters, K. J. and R. C. Smith. 1992.  Palmer LTER:  A sampling grid 
for the Palmer LTER program.  Antarctic Journal of the United States 
27(5):236-239.  Palmer LTER Contribution #04.

LTER REPORTS

Andrews, M., K. Baker, B. Benson, E. Boose, J. Brunt, C. Bledsoe, J. 
Briggs, G. Calabria, A. Elhaddi, D. Henshaw, R. Ingersoll, T. Kirchner, 
M. Klingensmith, L. Krievs, J. Laundre, R. Lent, E. Melendez, W. 
Michener, B. Nolen, R. Nottrott, J. Porter, S. Stafford, and C. Veen.  
1992.  In:  R. Nottrott, and R. J. Porter (eds.), Proceedings of the 
1992 LTER Data Management  Workshop.  Long-Term  Ecological 
Research Network Office, College of Forest Resources, AR-10, Univ. 
of Washington, Seattle, WA, 98195.  45 p.  Report of a Workshop, 7-
9August  1992, Honolulu, Hawaii.

Anonymous.  1993.  Conducting Time-Series in the Antarctic:  The 
Palmer Long-Term Ecological Research Project.  pp. 5-6.  U.S. JGOFS 
NEWS.

Baker, K., B. Benson, C. Bledsoe, E. Boose, C. Bowser, J. Briggs, J. 
Brunt, G. Calabria, Elhaddi, J. Gorentz, J. Greenlee, D. Henshaw, R. 
Ingersoll, T. Kirchener, M. Klingensmith, M. Klopsch, W. Michener, B. 
Moller, M. Murillo, R. Nottrott, J. Porter, J. V. Castle, C. Veen, and R. 
Waide.  1991.  In:  W. Michener, and J. Brunt  (eds.), Proceedings of 
the 1991 LTER Data  Management Workshop:  LTER Publication  No. 
13.  Chapal, Long-Term Ecological Research Network Office, College 
of Forest Resources, AR-10, Univ. of Washington, Seattle, WA, 
98195.  46 p.  Report of a Workshop, 1-3August 1991, San Antonio, 
TX.

Baker, K., B. Benson, C. Bledsoe, E. Boose, J. Brunt, J. Briggs, G. 
Calabria, J. Hastings, D. Henshaw, R. Ingersoll, J. Jefferson, D. Jones, 
T. Kirchener, M. Klingensmith, L. Krievs, R. Lent, M. Mackenzie, T. 
Maddux, B. Meeson, E. Melendex, B. Nolen, R. Nottrott, J. Porter, S. 
Stafford, J. V. Castle, and C. Veen.  1993.  In:  R. W. Nottrott, and J. H. 
Porter (eds.), Proceedings of the 1993 LTER Data  Management  
Workshop.  Long-Term Ecological Research Network Office, College 
of  Forest  Resources, AR-10, Univ. of Washington, Seattle, WA, 
98195.  Report of a Workshop, 29-31July 1993, Madison, Wisconsin.

Fraser, W. R.  1991.  Palmer LTER:  U.S. seabird research undertaken 
as part of the CCAMLR ecosystem monitoring program at Palmer 
Station, 1991-1992.  Annual  report submitted to the National 
Marine Fisheries Service, La Jolla, CA., USA. xx p.  Palmer LTER 
Contribution #36.

Fraser, W. R.  1991.  Palmer LTER:  U.S. seabird research undertaken 
as part of the CCAMLR ecosystem monitoring program at Palmer 
Station, 1990-1991.  Annual  report submitted  to the National 
Marine Fisheries Service, La Jolla, CA., USA. xx p.  Palmer LTER 
Contribution #34.

Fraser, W. R., B. R. Houston, D. R.  Patterson, and  W.  Z. Trivelpiece.  
1993.  Palmer LTER:  U.S. seabird research undertaken as part of the 
CCAMLR ecosystem monitoring program at Palmer Station, 1992-
1993. Annual report submitted to the National Marine  Fisheries 
Service, La Jolla, CA., USA. xx p.  Palmer LTER Contribution #37.

Hofmann, E. E.  1991.  p. 3.   The Antarctic Marine LTER:  Studying an 
Ecosystem Dominated by Ice.  BIOMASS Newsletter, Vol. 13. Palmer 
LTER Contribution #02. 

Klinck, J. M., and R. C. Smith.  1993.  Oceanographic data collected 
aboard R/V Polar Duke August-September 1993.  CCPO Technical 
Report No. 93-07.  Old  Dominion  University, Norfolk, VA. xx p.  SIO 
Reference No. 93-46, Palmer LTER Contribution #33 (pending 1993).

Lascara, C. M., R. C. Smith, D. Menzies, and K. S. Baker.  1993.  
Oceanographic data collected aboard R/V Polar Duke January-
February 1993.  CCPO Technical  Report  No.  93-02.  Old Dominion 
University, Norfolk, VA.  xx p.  SIO Reference No.  93-41, Palmer 
LTER Contribution  #28 (pending 1993).

Lascara, C. M., R. C. Smith, and D. Menzies.  1993.  XBT Data Collected 
Aboard R/V Polar Duke January-February 1993.  CCPO Technical 
Report No. 93-03.  Old Dominion University, Norfolk, VA. xx p.  SIO 
Reference No. 93-42, Palmer LTER Contribution #29 (pending 1993).

Lascara, C. M., R. C. Smith, and D. Menzies, and K. S. Baker.  1993.  
Oceanographic  data collected aboard R/V Polar Duke November 1991.  
CCPO Technical  Report  No.  93-01.  Old Dominion University, 
Norfolk, VA.  xx p.  SIO Reference No. 93-40, Palmer LTER 
Contribution  #27 (pending 1993).

Ross, R. and L. Quetin.  1991.  p. 178.  In  K. V. Cleve and S. Martin 
(eds.), Long-Term Ecological Research in the United States.  Long-
Term Ecological Research Network Office, Seattle, Washington.  
Palmer LTER Contribution #12.

Ross, R. and L. Quetin.  1991.  p. 1.  Palmer  Station:  The Antarctic 
Marine LTER:  An Ecosystem Dominated by Ice.  LTER Network News, 
Spring, Issue 9. Palmer LTER Contribution #01.

Smith, D. A., R. A. Locarnini, B. L. Lipphardt, and E.  E. Hofmann.  1993.  
XBT data collected aboard R/V Nathaniel B. Palmer March-May 1993.  
CCPO  Technical  Report  No. 93-06.  Old Dominion University, 
Norfolk, VA.  xx p.  SIO Reference  No. 93-45, Palmer LTER 
Contribution #32 (pending 1993).

Smith, D. A., R. C. Smith, and  D. Menzies.  1993.  Oceanographic data 
collected aboard R/V Nathaniel B Palmer March-May 1993.  CCPO 
Technical Report  No.  93-05.  Old Dominion University, Norfolk, VA. 
xx p.  SIO Reference No. 93-44,  Palmer LTER Contribution #31 
(pending 1993).

Smith, D. A., R. A. Locarnini, B. L. Lipphardt,  and E. E. Hofmann.  1993.  
Hydrographic data collected aboard R/V Nathaniel B. Palmer March-
May 1993.  CCPO  Technical Report No. 93-04.  Old Dominion 
University, Norfolk, VA.  xx p.  SIO Reference No. 93-43,  Palmer 
LTER Contribution #30 (pending 1993).