Distribution of diatoms in surface sediments of Prydz Bay, Antarctica

Four diatom assemblages are identified from the surface sediments of Prydz Bay and the Mac Robertson Shelf using multivariate analysis. A coastal assemblage is characterized by the sea-ice diatoms Fragilariopsis curia, F. angulata, F. cylindrus and Pseudonitzschia turgiduloides. A continental shelf assemblage is characterized by sea-ice and ice-edge diatoms, and an oceanic assemblage is characterized by the open-water diatoms Fragilariopsis kerguelensis, Thalassiosira lentiginosa, T. gracilis var. expecta and Trichotoxin reinboldii. The Cape Darnley assemblage contains both sea-ice and open-water diatoms, but all are characteristically large and heavily silicified. Multiple regression has been used to identify the relationships between the diatom assemblages and known environmental variables. There are strong correlations between the coastal, shelf and oceanic assemblages and ecological conditions, including latitude, sea-ice distribution and ocean currents. The Cape Darnley assemblage is thought to represent an assemblage from which the smaller and more lightly silicified species have been removed by current winnowing.