Summary
The distribution and abundance of phytoplankton communities off east Antarctica were surveyed using CHEMTAX analysis of HPLC pigment profiles, supplemented by microscopy. Eight north--south transects were surveyed between 80°E and 150°E, from approximately 63°S to the sea-ice, during Jan.--Mar. 1996. Spatial resolution of 1--16 km along the shelf break allowed fine-scale resolution of features associated with the ice edge and the Antarctic Slope Front. The maximum concentration of chlorophyll a (Chl a ) was 3.4 µg l-1, although most transects had maxima <=s;1.0 µg l-1. Five `low chlorophyll transects had average integrated abundances of chl a <38 mg m-2, while three `high chlorophyll transects had average abundances >52 mg m-2. CHEMTAX software was used to estimate the contribution of the different algal classes to total chl a . Eight algal categories were operationally defined by their pigment content: Diatoms, Dinoflagellates, Cryptophytes, Prasinophytes, Chlorophytes, Cyanobacteria, and two categories of haptophytes: Hapto3s (typified by coccolithophorids) and Hapto4s (including Phaeocystis antarctica plus Parmales and other chrysophytes). Regions with melting pack ice typically had an algal bloom that was variable in composition and usually fairly uniform above a deep pycnocline. Significant quantities of detrital matter sank from beneath the melting ice. At each ice edge, there was a local minimum in surface Chl a concentration associated with krill and, in one case, salps. Most algal categories had concentration minima there, but Cryptophytes and often Dinoflagellates and Cyanobacteria had local maxima, perhaps due to selective grazing. North of the ice edge, strong subsurface Chl a maxima were the norm, with concentrations on average 170% of surface values (495% max.) Chlorophyll concentrations were lower in the eastern half of the survey area than the west, although the composition of communities was similar. The composition, concentration