Summary
In January 2004 the microplankton community from the coastal waters of Terre Ade´lie and Georges V Land (139!E–145!E) was studied. Results showed a diatomdominated bloom with chlorophyll a levels averaging 0.64 lg l-1 at 5 m depth (range 0.21–1.57 lg l-1). Three geographic assemblages of diatoms were identified, based on principal diatom taxa abundances. The stratified waters near the Mertz Glacier presented highest phytoplankton biomasses (0.28–1.57 lg Chl a l-1 at 5 m) and diatom abundances (6,507–70,274 cells l-1 at 5 m), but low diversity, dominated by Fragilariopsis spp. Lower biomasses (0.38–0.94 lg Chl a l-1 at 5 m) and abundances (394–9,058 cells l-1 at 5 m) were observed in the mixed waters around the Astrolabe Glacier with a diverse diatom community characterised by larger species Corethron pennatum and Rhizosolenia spp. Finally an intermediate zone between them over the shallower shelf waters of the Ade´lie Bank represented by Chaetoceros criophilus, where biomasses (0.21–0.35 lg Chl a l-1 at 5 m) and abundances (1,190–5,431 cells l-1 at 5 m) were lowest, coinciding with the presence of abundant herbivorous zooplankton.