ENVIRONMENTAL IMPLICATIONS OF RECENT OSTRACOD DISTRIBUTIONS IN THE LARSEN ICE SHELF REGION, EASTERN ANTARCTIC PENINSULA MARGIN

Beginning in 1996 the Larsen Ice Shelf (LIS) system showed signs of a significant reduction in ice shelf area.  By March 2002 LIS-A had nearly disappeared and a significant area of LIS-B had collapsed.  Three cruises to the LIS region, Nathaniel B. Palmer 2000-03 (NBP00-03), NBP01-07 and Laurence M. Gould 2005-02 (LMG05-02) sailed to study the exposed areas of the LIS on the eastern Antarctic Peninsula margin.  Surface sediment samples were collected using a Smith McIntyre grab (SMG).  The surface sediment samples were sieved through a 63 micron sieve, dried and picked for ostracods.  The ostracods were identified using Brady (1880), Samolyk, and Olempska (2005), Sars (1866), and Hornibrook (1952) as references. A total of 27 samples were examined from the LIS region with 15 samples containing ostracods, 11 from the LIS-B and 4 from LIS-A.  The ostracod assemblages recovered are represented by 10 genera, including 18 podocopod species and one myodocopid species.  The most common genus is Cytheropteron (comprised of 6 different species), and the most common species Cytheropteron testudo (Sars).  In total, 253 specimens of C. testudo were found, making up 28.2% of all species. All species were analyzed using multidimensional-scaling and cluster analysis (Primer 5).  Results from these analyses are interpreted to represent four ostracod groups.  The LIS-A group is diverse, and abundant in Cytheropteron abyssorum (Brady).  A distal LIS-B group is nearly monospecific containing C. testudo.  The mid LIS-B group is diverse and abundant in C. testudo.  The near shore LIS-B group is diverse, and has an abundance of Polycope kinnetorgenis (Hartman).  Ice shelf break-up affects primary production and changes pelagic and benthic marine ecosystems.  Recent ostraocod distributions in the LIS-A and LIS-B regions will further our understanding of the affects of climate change on these organisms.