Appl Environ Microbiol. 1983 June; 45(6): 1709-1721
Copyright © 1983, American Society for Microbiology. All Rights Reserved.
Institute of Limnology, Uppsala University, S-751 22 Uppsala, Sweden
ABSTRACT
Bacterioplankton abundance, [3H]thymidine incorporation, 14CO2 uptake in the dark, and fractionated primary production were measured on several occasions between June and August 1982 in eutrophic Lake Norrviken, Sweden. Bacterioplankton abundance and carbon biomass ranged from 0.5 x 109 to 2.4 x 109 cells liter1 and 7 to 47 µg of C liter1, respectively. The average bacterial cell volume was 0.185 µm3. [3H]thymidine incorporation into cold-trichloroacetic acid-insoluble material ranged from 12 x 1012 to 200 x 1012 mol liter1 h1. Bacterial carbon production rates were estimated to be 0.2 to 7.1 µg of C liter1 h1. Bacterial production estimates from [3H]thymidine incorporation and 14CO2 uptake in the dark agreed when activity was high but diverged when activity was low and when blue-green algae (cyanobacteria) dominated the phytoplankton. Size fractionation indicated negligible uptake of [3H]thymidine in the >3-µm fraction during a chrysophycean bloom in early June. We found that >50% of the 3H activity was in the >3-µm fraction in late August; this phenomenon was most likely due to Microcystis spp., their associated bacteria, or both. Over 60% of the 14CO2 uptake in the dark was attributed to algae on each sampling occasion. Algal exudate was an important carbon source for planktonic bacteria. Bacterial production was roughly 50% of primary production.
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