THE INFLUENCE OF ENVIRONMENTAL-FACTORS ON SEASONAL-CHANGES IN BACTERIAL-CELL VOLUME IN 2 PRAIRIE SALINE LAKES

Bacterial biovolumes of hypertrophic Humboldt Lake (total dissolved so lids = 3.3 g liter-1; 6 m deep) and oligotrophic Redberry Lake (total dissolved solids = 20.9 g liter-1; 17 m deep), Saskatchewan, were meas ured concurrently with a variety of environmental variables to identif y the major factors correlated with volume changes. There was no diffe rence (P > 0.05) in mean bacterial volume between Redberry Lake (0.084 +/- 0.034 mum3 SD) and Humboldt Lake (0.083 +/- 0.021 mum3 SD). Stati stical analyses suggested there were marked differences in the factors associated with the pronounced seasonality of bacterial cell volumes in these two lakes. Variance in bacterial volume in the epilimnion of Redberry Lake was best explained by a multivariate regression model wh ich included ciliate abundance and chlorophyll concentration (r2 = 0.9 6). The model accounting for changes in hypolimnetic bacterial volume included ciliate numbers and primary production (r2 = 0.94), of the me asured variables. Bacterial volume in Humboldt Lake was most highly co rrelated with primary production (r2 = 0.59). Bacterial production (es timated as the rate of thymidine incorporation into DNA) and growth (t hymidine incorporation rate normalized to cell numbers) were not corre lated to cell volume, with the exception of cocci volume in Humboldt L ake.