Changes in cell volume of bacteria and heterotrophic nanoflagellates in a hypereutrophic pond

Changes in cell volume of planktonic bacteria and heterotrophic nanoflagell ates (HNF) were examined in a hypereutrophic pond from April to October, 19 97. There were marked changes in the abundance of bacteria, HNF and ciliate s and in protistan bacterivory during this period. The cell volume of free- living bacteria (0.121 +/- 0.031 mu m(3), mean +/- SD) was large relative t o that reported in the literature. The cell volumes of HNF was 71.1 +/- 24. 8 mu m(3). Both cell volumes did not follow a seasonal trend. The dominant size class of bacteria was seasonally variable, whereas density of filament ous bacteria was relatively high between August and September. Biomass of f ilamentous bacteria accounted for up to 33.6% of total bacterial biomass. A correlation analysis for cell volume of bacteria and HNF, density of filam entous bacteria and some microbial variates was performed. The positive cor relations detected (p<0.05) were between density of bacteria and cell volum e of HNF, and between density of filamentous bacteria and cell volume of HN F.