Plankton photosynthesis, extracellular release and bacterial utilization of released dissolved organic carbon (RDOC) in lakes of different trophy.

The major objective of these studies was to assess the extent of the flow of released dissolved organic carbon (RDOC) from phytoplankton to heterotrophic bacteria. The second aim was to test Nalewajko and Schindler's (1976) hypothesis that the percentage of extracellular release (PER) of RDOC by phytoplankton is higher in oligotrophic than eutrophic waters. The studies on the relationship between the bacterial assimilation of RDOC and productivity of phytoplankton in the lakes of different trophy have shown a direct correlation. It was observed that higher utilization rate of phytoplankton RDOC occurred in lakes with higher primary production. The inverse relationship between productivity of lakes, i.e. trophy of waters, and amount of RDOC or PER is closely dependent on the heterotrophic activity of bacteria in waters.