Stability of diatom composition in a variable lake environment: Lake Chascomús, Argentina

Abstract

Water and surficial sediment samples of Lake Chascomús and its tributaries were analyzed in order to relate changes in diatom community structure to chemical variables. Over the course of 13 months of sampling, the lake exhibited major changes in water level (1.15-1.98m average depth), total dissolved solids (821-1972 mg1-1), silica (0.098-8.22 mg1-1), and total algal biomass (21.4-145.9 μg Ch1 a 1-1). However, despite these large fluctuations, the diatom species composition was relatively stable. The dominant species in the water column was always Synedra berolinensis (68.9%-90.1% total frustules), with Fragilaria construens and F. brevistriata as subdominants. In the sediments the latter two species dominated the frustule counts. These results indicate an unusual floristic stability of this eutrophic ecosystem, with persistent dominance by broadly tolerant, generalist species.