July 1994 SUMMARY OF PROGRESS TO DATE AND WORK TO BE PERFORMED DURING THE SUCCEEDING PERIOD The 1993-1994 season was characterized by three periods of field activity that included winter and summer cruises in the LTER marine sampling grid, and the standard 6-month research effort including nearshore sampling and bird work at penguin and skua colonies in the vicinity of Palmer Station. The late winter cruise also completed our planned survey of the seasonal cycle on a large (regional) spatial scale: spring (November 91), summer (January 93), fall (April/May 1993) and late winter (August/September 1993). Following the annual cruise, we hosted our mid-grant site review, at both University of California at Santa Barbara (4 of the 10 member executive committee) and at Palmer Station (8 members). Site review committee and executive committee members had the opportunity to observe and experience the types of research undertaken as part of the nearshore sampling for temporal variability in the water column and the research on population dynamics and reproductive success in the seabirds nesting around Palmer Station. General research results One of the concepts underlying the Palmer LTER is that ice is the dominant physical variable influencing the structure and function of the pelagic ecosystem in the Southern Ocean, in part because the annual advance and retreat of the ice edge is the largest physical process in the world's oceans. This year a month-long research cruise was conducted to investigate interactions among the various components of the ecosystem, from ice to seabirds, in the late austral winter. During this late winter cruise, an area of about 400 km alongshore by 160 km offshore, ranging from Anvers Island south to Adelaide Island, was surveyed with both traditional oceanographic equipment and with divers using SCUBA to survey and sample the under-ice environment to look at the processes in both the water column and right under the ice. The northern region of the study area is one of unpredictable sea ice, whereas the southern area is predictably covered by ice in the winter every year. In winter 1993, the northern area was not covered by ice until mid-August, so the ice was young and the ice biota presumably not fully developed. Major survey data sets include: light, hydrographic characteristics of the water, microbial activity in both water and ice, food availability in both ice and water, primary production and community composition in the water column, larval and adult krill (the dominant macro-grazer) concentrations and physiological condition, and predator concentrations and diets. Results from this cruise will be used to test two important LTER hypotheses concerning the interaction of key species (krill and Adelie penguins) and the ice habitat: 1) In winters with a greater extent in pack ice cover, larval and juvenile krill (young-of-the-year) will be in better physiological condition, have faster growth and development rates, and greater winter-over survival than in winters of low ice cover. Because the larvae graze on ice biota, great sea ice extent means larger "pastures". 2) Winter-over survival and physiological condition of adult Adelie 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). Preliminary results reinforce the hypothesis that ice is a critical factor for some components of the ecosystem. Differences exist in the water column versus ice habitats, and both alongshore (unpredictable to predictable winter ice) and offshore gradients exist for many of the key organisms and processes, for example microbial activity (bacteria and viruses) and gas chemistry, microalgal concentrations, grazers (larval krill), and seabirds. In January 1994, the month-long annual time-series cruise was composed of both the long-term surveys for interannual variability in ecosystem activity on a regional scale, and of a fine scale investigation of an area representing the foraging range of the Adelie penguins nesting near Palmer Station on Anvers Island. We also retrieved and redeployed three sediment traps that measure sediment flux over a year-long deployment. Two traps were redeployed in the same area, one was moved to an area where winter ice is predictable. Data from the sediment traps is relevant to many of our questions concerning the fate of primary production, whether it is grazed or sinks to the benthos. Component research results Hydrography and ocean circulation The second important physical factor in this ecosystem is the oceanic circulation, with its impact on many characteristics of the water habitat and on the distribution of organism, directly or indirectly. During the past year, analysis of the existing hydrography, taken from cruises in November 1991; January, 1993; March, 1993 and August, 1993, has lead to a number of papers and posters presented at national (AGU Ocean Sciences, Feb 1994) and international meetings (SCOR/SCAR 1994). Additional analysis is proceeding with the data taken from January, 1994 but postprocessing has not been completed, so these data have not been included in this analysis. Further analysis of the hydrographic observations are in progress. These analyses will be extended to include the most recent observations from the January, 1994 cruise. Three water masses are known to exist over the peninsula region which are found in predictable places with well known temperature and salinity (T-S) values: Circumpolar Deep Water (CDW), Winter water and Bransfield Strait water. Over the inshore areas, water tends to be fresher due to the input of melt water from glaciers. The near surface water masses change in characteristics with season as expected by surface heating and cooling, ice freezing and thawing, and the changing frequency of atmospheric storms which deepen the mixed layer. Budgets of heat and fresh water clearly show these effects due to surface forcing. An unexpected result is the influence of the relatively warm CDW which heats the mixed layer from below. Calculations show that this heating from below can be as important as surface heating, especially early in the season when surface warming is weak and most of the heat goes to melting ice. The character of the surface water is strongly influenced by the amount of fresh water that comes from ice and glacier melt. The dividing line between the fresher inshore surface water and the offshore surface water is very clear. The summer 1993, observations show an extensive volume of this fresher water, indicating influence from nearshore. The structure of the summer mixed layer has been studied extensively to show that multiple mixing zones exist during some times. These zones are created by surface warming and freshening due to ice melt. Summer storms can, on occasion, mix all of these layers to form a single, traditional mixed layer. The more common case is a more complicated structure, with several relic mixed layers which are capped by shallower, more recent, mixed layers. The extensive hydrographic survey from the March, 1993 was used to estimate the circulation over the LTER region. The dynamic topography at 200m relative to 400m shows the geostrophic flow for water below the mixed layer. A relatively convoluted flow pattern appears which bears some resemblance to the two-gyre pattern that was proposed from earlier, but sparcer, observations. There is a generally clockwise circulation on the shelf east of Anvers Island. This circulation is strongly influenced by a deep topographic cut across the shelf which causes the circulation to turn back on itself twice. Further to the south off Renaud Island, the offshore circulation is counter-clockwise. On the inshore side of each of these gyres, there is a suggestion of a coastal current or an oppositely turning gyre. This near shore circulation is more extensive in the southern part of the region. All of the circulation in the southern half of the region also appears to be steered by bottom topography. Secondary production Adult and larval krill differ in their tolerance to starvation and their vulnerability to starvation. The indirect effect of the difference in the balance between the need to eat and the need to avoid predation has been predicted to generate habitat segregation between adults and larvae during the winter (Quetin and Ross, ASLO 1990 talk) This habitat segregation was confirmed during the Aug/Sept 93 cruise. Larval krill were found feeding on the ice biota at every station surveyed by SCUBA divers, and in numbers predicted by reproductive output. The under-ice habitat, as predicted, houses the young-of-the-year during winter. Adults, however, were seldom found under the ice, and were also not common in the water column under the ice. Length frequency and growth rates of one and two-year old krill collected from late November through January from the first three field season show distinct differences in years in the size of the larvae/juveniles after their first winter (AC0+), their growth rates and their numbers. In both 1991/92 and 1993/94 ACO+ were a significant part of the catch of small krill, whereas in 1992/93, there were no AC0+ krill. These results suggest that recruitment of the year classes born in 1991 and 1993 was higher than in 1992. Recruitment is a combination of reproductive output of the females and survival of that output, and is linked in a complex fashion the extent of winter ice. The pelagic fish community in the Southern Ocean is not as abundant as in most of the world's oceans, as antarctic krill appear to occupy the niche usually taken by small fish such as anchovy or sardines. Fish catch data from the first two years show some distinct patterns of abundance and distribution that have major implications for the seabirds that depend on these prey items. Two species in similar abundances compose 75% of the catch: antarctic silverfish (Pleuragramma antarcticum, ~30%), and a myctophid (Electrona antarctica, ~45%). Their distributions, however, are quite different. Silverfish are found in the nearshore stations along the Antarctic Peninsula in cold shelf waters, whereas the myctophid is found throughout the entire region in waters deeper than 500 m, whether seaward of the shelf break or in deeper waters on the shelf itself. Such patterns of occurrence are strong indicators of where seabirds that prey on these species must forage. Seabird component: Based on seabird diet data obtained during the winter cruise, it is apparent that the fish Electrona antarctica supports much of the avian biomass (excluding penguins) in the LTER grid. These results, previously unknown, have fundamentally changed our perceptions about the relative availability and distribution of fish prey species in the LTER grid. These findings are particularly relevant to our research on South Polar Skuas, as they provide the basis for understanding the relative function and importance of various skua prey species in food web interactions that might affect long-term fitness and population change. Indeed, it now seems clear that our LTER hypotheses relating aspects of the ecology of skuas to a single prey species (Antarctic Silverfish) may represent too narrow a focus to properly address the issue of long-term variability in sea ice conditions and its effect on interactions between this predator and its prey. Modeling Modeling/oceanic circulation. The first steps towards a circulation model have been taken. The bottom topography from ETOPO5 has been interpolated onto a grid of locations with a resolution of 5km. These locations match the grid used by the LTER observational program. The required forcing for the model (surface wind, heat flux, etc.) have been located (at NCAR) and identified, but have not been obtained. We will use the European Met Center (ECMWF) analysis products, which are available twice a day, to construct climatological forcing for the circulation model. Due to the large size of these files, considerable effort will be required to transfer and reduce the information to a form needed by the model along the Antarctic Peninsula. Optics and remote sensing. In anticipation of the launch of SeaWiFS ocean color satellite sensor,an oceanic net primary productivity (NPP) model has been created and tested. Using historical data from the Coastal Zone Color Scanner (CZCS) for the spatial and seasonal distribution of oceanic chlorophyll concentration and International Satellite Cloud Climatology Project (ISCCP) data for the sun's irradiance at the earth's surface the NPP for the LTER area has been computed. These model results are being compared with shipboard observations from both historical and LTER data. The goal is to provide a robust model for optimum estimation of seasonal NPP for the whole LTER area that will make use of both satellite and surface observations. Synthesis of historical data Seabird component: The seabird component began the second synthesis of long-term data sets related to the ecology of Adelie Penguins. The first synthesis (Fraser et al, 1992) related changes in penguin populations to environmental warming and its effect on winter sea ice conditions. The second synthesis, currently in preparation, relates long-term changes in penguin diets (variability in krill size classes) to specific annual trends in the formation and persistence of sea ice during the last 20 years. This synthesis links the relative proportions of particular krill size classes in the diets of Adelie Penguins to specific, episodic events in the development and persistence of sea ice during the last two decades. Briefly, the data indicate that the proportion of smaller krill in penguin diets increases significantly following years of heavy sea ice, but then exhibits a progressive decrease during the next several years until another heavy ice year occurs. We are interpreting these results as being indicative of the effects that heavy ice years have on krill recruitment. Moreover, because this pattern appears to be cyclical, we have been able to categorize and group the last 20 years of our data on other aspects of penguin ecology according to these episodic events for analysis. This approach is providing evidence linking variability in sea ice extent to krill recruitment and availability, and the subsequent effect of this variability on penguin foraging ecology and reproductive biology. Optics and remote sensing component: Sea-ice is a key component of the Palmer LTER ecosystem where the climate system consists of three freely interacting physical systems: atmosphere, sea-ice and ocean. The extent, variability, and ecological importance of sea-ice coverage for the Southern Ocean in general, and the LTER region in particular, have been investigated using both passive microwave and infrared remote sensing. While the Southern Ocean as a whole shows little interannual variability in ice coverage, there is significant regional variability that drives regional ecosystems through the advance and retreat of sea-ice. Sea-ice for LTER region has been investigated in detail (Stammerjohn, 1993), and both low and high-resolution data are being investigated for linkage to ecological indices and for use in ice-driven models for the LTER region. ABSTRACTS FROM SCOR/SCAR 6TH SYMPOSIUM ON ANTARCTIC BIOLOGY All in SCAR SIXTH BIOLOGY SYMPOSIUM, Antarctic Communities: Species, Structure and Survival (titles and abstracts have been entered into the lter palmer datainfo system so are accessible via gopher) Human disturbance and long-term changes in Adelie penguin populations: a natural experiment at Palmer Station, Antarctic Peninsula. p. 95. William R Fraser and Donna L Patterson PALMER LTER: abundance and distribution of larval krill, Euphausia superba, associated with annual sea ice in winter. p. 96 TK Frazer, LB Quetin, RM Ross, RC Smith Palmer LTER: Seasonal changes in the hydrographic structure of the upper 100m of the water column. p. 127 EE Hofmann, CM Lascara, BL Lipphardt, Jr., JM Klinck, DA Smith, RA Locarnini, RC Smith Palmer LTER: Circulation west of the Antarctic Peninsula. p. 128 EE Hofmann, DA Smith, BL Lipphardt, Jr., RA Locarnini, RC Smith Palmer LTER: Heat budgets and implications for circulation on the continental shelf west of the Antarctic Peninsula. p. 152 JM Klinck, RC Smith Palmer LTER: Seasonal and geographic variability in the distribution of Antarctic krill, Euphausia superba, west of the Antarctic Peninsula. p. 161 CM Lascara, EE Hofmann, JM Klinck, RM Ross and LB Quetin Temporal dynamics of coastal Antarctic phytoplankton: physical/chemical/biological linkages through a summer diatom bloom. p. 189 MA Moline, BB Prezelin, O. Schofield, RC Smith Palmer LTER: Fine-scale distribution of Antarctic krill, Euphausia superba, within coastal waters near Palmer Station off the Antarctic Peninsula. p. 225 LB Quetin, RM Ross and CM Lascara Palmer LTER: Hydrography in the region west of the Antarctic Peninsula. p. 249 DA Smith, EE Hofmann, JM Klinck, BL Lipphardt, Jr., RA Locarnini and RC Smith The Impact of Pack ice on the Distribution of Adelie Penguin Populations. p. 269 W.Trivelpiece, S.Trivelpiece, W.Fraser, S.Emslie, N.Karnovsky LTER CONTRIBUTION LIST (some items were published earlier than 1993/94 but were not in previous annual reports) Papers in Print 35. Fraser WR, WZ Trivelpiece, DG Ainley, SG Trivelpiece: Increases in Antarctic penguin populations: Reduced competition with whales or a loss of sea ice due to environmental warming? Polar Biology 11:525-531, 1992. Palmer LTER Contribution #35. Fraser, WR. and WZ Trivelpiece. In preparation. Long-term changes in the diets of Adelie Penguins: implications for Southern Ocean ecosystems Theses Completed 39. Stammerjohn SE: Spatial and temporal variability in Southern Ocean sea ice coverage. Master Thesis, University of California, Santa Barbara, Santa Barbara, CA 93106. 1993. Palmer LTER Contribution #39. Manuscripts Accepted: 14. Ross RM, LB Quetin, KS Baker: PALMER Long-Term Ecological Research (LTER): an Overview of the 1992-1993 Season. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #14 (submitted 1993). 15. Smith DA, RA Locarnini, BL Lipphardt, Jr., DA Smith, EE Hofmann: Palmer LTER: Hydrography in the LTER region. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #15 (submitted 1993). 16. Lascara CM, EE Hofmann, RM Ross, LB Quetin: Palmer LTER: Overview of krill acoustic studies and results from the Peninsula grid. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #16 (submitted 1993). 17. Lascara CM, LB Quetin, RM Ross: Palmer LTER: Krill distribution and biomass within coastal waters near Palmer Station. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #17 (submitted 1993). 18. Haberman KL, RM Ross, LB Quetin: Grazing by the Antarctic Krill, Euphausia superba, on Nitschia sp. and Phaeocystis sp. Monocultures. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #18 (submitted 1993). 19. Karl DM, J Resing, G Tien, R Letelier, D Jones: Hydrogen peroxide in the Palmer-LTER region: I. An introduction. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #19 (submitted 1993). 20. Karl DM, J Resing, G Tien, R Letelier, D Jones: Hydrogen peroxide in the Palmer-LTER region: II. Water column distributions. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #20 (submitted 1993). 21. Tien G, DM Karl: Hydrogen peroxide in the Palmer-LTER region: III. Local sources and sinks. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #21 (submitted 1993). 22. Karl DM, J Resing: Hydrogen peroxide in the Palmer-LTER region: IV. Photochemical interactions with dissolved organic matter. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #22 (submitted 1993). 23. Christian JR, DM Karl: Bacterial exoprotease activity in the Palmer Peninsula during austral autumn 1993. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #23 (submitted 1993). 24. Bird DF, R Maranger, DM Karl: Aquatic virus abundances near the Antarctic Peninsula. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #24 (submitted 1993). 25. Asper VL, AR Diercks, DM Karl: The first profiles of marine snow aggregate abundance from Antarctica. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #25 (submitted 1993). 26. Houlihan T, DM Karl: Palmer LTER: Dissolved silicic acid-nitrate relationships during Austral Fall 1993. Antarctic Journal of the United States, 1993. Palmer LTER Contribution #26 (submitted 1993). Technical Reports 27. Lascara CM, RC Smith, D Menzies, KS Baker: Oceanographic data collected aboard RV Polar Duke November 1991. CCPO Technical Report No. 93-01, Crittenton Hall, Old Dominion University, Norfolk, VA 23529. 1993. SIO Reference No. 93-40, Palmer LTER Contribution #27. 28. Lascara CM, RC Smith, D Menzies, KS Baker: Oceanographic data collected aboard RV Polar Duke January-February 1993. CCPO Technical Report No. 93-02, Crittenton Hall, Old Dominion University, Norfolk, VA 23529. 1993. SIO Reference No. 93-41, Palmer LTER Contribution #28. 29. Lascara CM, RC Smith, D Menzies: XBT Data Collected Aboard RV Polar Duke January-February 1993. CCPO Technical Report No. 93-03, Crittenton Hall, Old Dominion University, Norfolk, VA 23529. 1993. SIO Reference No. 93-42, Palmer LTER Contribution #29. 30. Smith DA, RA Locarnini, BL Lipphardt, Jr., EE Hofmann: Hydrographic data collected aboard R/V Nathaniel B. Palmer March-May 1993. CCPO Technical Report No. 93-04, Crittenton Hall, Old Dominion University, Norfolk, VA 23529. 1993. SIO Reference No. 93-43, Palmer LTER Contribution #30. 31. Smith DA, RC Smith, D Menzies: Oceanographic data collected aboard RV Nathaniel B Palmer March-May 1993. CCPO Technical Report No. 93-05, Crittenton Hall, Old Dominion University, Norfolk, VA 23529. 1993. SIO Reference No. 93-44, Palmer LTER Contribution #31. 32. Smith DA, RA Locarnini, BL Lipphardt, Jr., EE Hofmann: XBT data collected aboard R/V Nathaniel B. Palmer March-May 1993. CCPO Technical Report No. 93-06, Crittenton Hall, Old Dominion University, Norfolk, VA 23529. 1993. SIO Reference No. 93-45, Palmer LTER Contribution #32. 38. Karl D: Project S-046 University of Hawaii field and laboratory protocols manual. Palmer Peninsula Long-Term Ecological Research (LTER) Program, 1992. Palmer LTER Contribution #38. 40. Baker K, WR Fraser, EE Hofmann, DM Karl, JM Klinck, RM Ross, LB Quetin, BB Prezelin, RC Smith, WZ Trivelpiece: Palmer Station Site Visit, February 1994. In: Quetin LB, RM Ross, Eds: PALMER LTER Briefing Book, 1994. Palmer LTER Contribution #40. MEETINGS ATTENDED 1993 Jul 15-17 Seabird Workshop, Monticello, Minnesota Bill Fraser 1993 Jul 29-31 Data Manager's Meeting, Madison, Wisc. Karen Baker 1993 Jul 30-31 LTER PI Meeting/10 year Review, Madison, Wisc. Robin Ross 1993 Sep 18-22 LTER All Scientists Meeting, Estes Park, CO Robin Ross, Karen Baker, Tim Newberger, Karen Haberman, Sharon Stammerjohn 1993 Sep 18-22 LTER Executive and Coordinating Committees, Estes Park, CO Robin Ross 1993 Dec 12-16 Palmer LTER Executive Committee Meeting Palmer LTER Steering Committee Meeting, Santa Barbara, CA Karen Baker, Bill Fraser, Eileen Hofmann, , Dave Karl, John Klinck, Barbara Prezelin, Robin Ross, Langdon Quetin, Ray Smith, Wayne Trivelpiece 1994 Feb ASLO Ocean Sciences, San Diego, CA Langdon Quetin, Eileen Hofmann, John Klinck, Barbara Prezelin Cathy Lascara, David Smith 1994 Mar 18-20 NASA/LTER Sunphotometer Workshop, Sevilleta Research Center, Albuquerque, NM Phil Handley/Ray Smith 1994 Apr 22-24 LTER CC Meeting, Washington, D.C. Robin Ross 1994 Apr 25 Crary Science and Engineering Center Users' Committee, Denver Karen Baker 1994 May 25-29 SCAR-Bird Biology Sub-committee (BBS), Padua, Italy Bill Fraser 1994 May 30-Jun 3 SCOR/SCAR, Sixth Symposium on Antarctic Biology, Venice, Italy 6 Principal Investigators, 6 graduate students, and 4 associates attended; 10 posters/talks were presented (Mike Anghera, Nic Boucher, Steve Emslie, Bill Fraser, Tom Frazer, Eileen Hofmann, Nina Karnovsky, John Klinck, Cathy Lascara, Mark Moline, Langdon Quetin, Donna Patterson, Barbara Prezelin, David Smith, Wayne Trivelpiece, Susan Trivelpiece) 1994 Jun 16-19 LTER PAL PI Meeting Karen Baker, Bill Fraser, Eileen Hofmann, Dave Karl, John Klinck, Robin Ross, Ray Smith, Wayne Trivelpiece, Maria Vernet 1994 June 21 ASA Regional Planning Meeting Denver, CO Robin Ross, Ray Smith, Dave Karl, Bill Fraser, Wayne Trivelpiece, Maria Vernet