BACTERIAL PRODUCTIVITY IN FORESTED AND OPEN STREAMS IN SOUTHERN ONTARIO

Bacterial abundance, biomass, and heterotrophic production were measured in the water, sediment, and epilithon of forested and open streams in southern Ontario in summer 1988. Relationships of environmental variables to production were examined. The time course of nucleoside incorporation, recovery efficiency of bacterial DNA, isotope dilution, and disturbance artifacts were examined to compare bacterial production rates and to determine the appropriateness of the rate of [H-3]thymidine incorporation into bacterial DNA as an estimate of bacterial production in these habitats. Water column bacterial biomass (12-97 mug C. L -1) and heterotrophic production (0.21-67 mug C-L-1.h-1) were greater in open streams than in forested streams. Differences between open and forested stream sediment bacterial biomass (0.30-1.1 g C-m-2) and heterotrophic production (18-140 mg C. M-2 .h-1) were not as pronounced as they were in the water column. A methodological disturbance artifact may have introduced a minor bias in sediment production measurements. Epilithic bacterial biomass was 35-150 mg C.m -2, and heterotroph production was 1.3-51 mg C.m-2.h -1, significantly greater (P < 0.05) in open streams than in forested streams. Epilithic production and stream water temperature were positively correlated (P < 0.05). Heterotrophic bacterial production exceeded net primary production in forested streams, but not in