31 December 2002 to 10 January 2003
Weekly SitRep

The central tenet of the Palmer LTER (Palmer Long Term 
Ecological Research) project is that the annual advance and 
retreat of sea ice is a major physical determinant of 
spatial and temporal changes in the structure and function 
of the Antarctic marine ecosystem.  We now recognize the 
region west of the Antarctic Peninsula as a premier example 
of a climate-sensitive region experiencing major changes in 
species abundance and composition due to changes in range 
and distribution that are occurring in response to regional 
climate change.  The regional climate change is manifested 
primarily as a southern migration of principal climate 
characteristics.  In effect, the maritime system of the 
northern WAP is replacing the continental, polar system 
along the Peninsula climate gradient.  This change is 
driven by regional warming, which is modulated by regional 
hydrography, sea ice processes and global teleconnections 
to lower latitude atmospheric variability.  We seek to 
understand the full ecological implications of climate 
migration in our study region west of the Antarctic 
Peninsula, and to uncover the mechanisms linking them 
through teleconnections to global climate variability.  

The focus of our research has been to identify and 
understand the mechanistic couplings by which the life 
histories of key species or functional groups (microbial 
foodwebs, phytoplankton, the grazers Antarctic krill 
(Euphausia superba) and Salpa thompsoni, and Adilie 
penguins (Pygoscelis adeliae) and flying seabirds, and 
biogeochemical processes (primary and secondary production, 
sedimentation, CO2 absorption) are affected by physical 
processes.  

This January cruise on the ASRV Laurence M. Gould (LMG03-
01) is the 11th annual summer cruise for the Palmer LTER. 
Our annual sampling program addresses multiple spatial 
scales within one regional scale 'grid' of about 55 
regularly occupied oceanographic stations between Anvers 
and Adelaide Islands at which core measurements are 
conducted, permitting repeated sampling on both seasonal 
and annual time scales, covering short and long-term 
ecological phenomena, and specific mechanistic studies.  
Transect lines are perpendicular to the land, 100 km apart, 
and named for the distance from the 000 transect below 
Marguerite Bay, e.g. 000.*. Stations are spaced 20 km apart 
going from inner shelf stations (*.000) to off shore 
stations (*.180 to *.260). During the annual cruise we 
occupy stations on the 600.*, 500.*, 400.*, 300.* and 200.* 
lines.  Annual cruises on the same mesoscale grid allow us 
to assess interannual variability in all aspects of the 
ecosystem sampling on (1) scales of 100s of kilometers on 
the shelf and outer shelf break, and behind the Biscoe 
Islands and in Crystal Sound and Marguerite Bay, and (2) 
10s of kilometers within the foraging range of the Adilie 
penguins nesting near Palmer Station.  Processes underlying 
the variability documented are investigated. 

In addition, the seasonal sampling based at Palmer Station 
is maintained on a less frequent sampling cycle.   The 
sediment trap deployed near Hugo Island will be retrieved, 
and a new sediment trap deployed.  Three process stations 
focused on food web dynamics are planned for Palmer Basin, 
the Grandidier Channel, and Marguerite Bay, along an inner 
shelf latitudinal gradient.  Diets of Adilie penguins 
nesting both near Palmer Station and at Avian Island, at 
the southern end of the summer study region, and the prey 
fields within the respective foraging areas will be 
quantified and compared.  A visit to Rothera in Marguerite 
Bay is planned to further LTER collaborations with BAS 
personnel. 

We departed Punta Arenas, Chile, at 1000 on 31 December, 
arriving at Palmer Station on 4 January 2003 at 0845.  The 
southbound crossing was one of the smoothest in memory, 
with both cruise participants and personnel bound for 
Palmer Station participating in the XBT transect conducted 
for J. Sprintall of Scripps. The new bioacoustic system, a 
BioSonics DT-X, was tested in southern Bransfield Straits.  
After a busy port call punctuated by a welcome break for 
'cross-town' pizza at the station, we headed for our first 
station at 600.040 (Palmer Basin area) at 1900 5 January.  
The following day we conducted sampling at the seasonal 
stations (CTD casts at Stations B and E, plus two 
bioacoustic transects), and continued to occupy stations 
along the 600.* line.  A long stretch of excellent weather 
allowed us to complete the standard stations along the 
600.* line and add stations out to 600.260 with CTD casts 
to the bottom at the far seaward end to document any signal 
from the Antarctic Circumpolar Current.  We also conducted 
our first process station, sited close to the 600.060 
station in the Palmer Basin area.  The station consisted of 
a series of CTD casts and net/bioacoustic tows with 
experiments on board to investigate multiple aspects of 
food web dynamics.
The support of the Raytheon support crew and the Captain 
and crew of the ASRV L. M. Gould has been excellent.  They 
have adjusted the level wind, installed the net depth 
sensor, redone terminations, and helped calibrate 
fluorometers - all cheerfully.  The Raytheon support staff 
has also played an important and critical in the collection 
of the hydrographic data for BP-021.  We thank them all!

From the Chief Scientist and field team leaders:
Robin Ross (Chief Scientist, BP-028), Hugh Ducklow (Lead PI 
for the Palmer LTER, BP-045), Wendy Kozlowski (BP-016 and 
BP-032), and Heidi Geisz (BP-013). Palmer LTER PIs also 
include: Karen Baker (information manager), Bill Fraser 
(BP-013), Doug Martinson (BP-021), Langdon Quetin (BP-028), 
Ray Smith (BP-032), and Maria Vernet (BP-016).