Biomass and production of phyto‐ and bacterio‐plankton in eutrophic Lake Tystrup, Denmark

SUMMARY. Phytoplankton primary production and biomass were compared with bacterial secondary production estimated by means of frequency of dividing cells (FDC) in eutrophic Lake Tystrup. Denmark. In the upper part of the photic zone, bacterial secondary production constituted 12% of the carbon fixed by the phytoplankton. In vertical profiles, bacterial secondary production ranged from 7.6% (early spring) to 121% (during August) of the carbon fixed by the algae. A close relationship was found between occurrence and activity of bacteria and algae, suggesting that released organic products are of primary importance to the bacteria. The annual phytoplankton primary production was estimated as 227 g C m‐2 compared to 102 g C m‐2 assimilated by the bacteria, so 45% of the carbon fixed by the phytoplankton went through pelagic bacteria.