Relationship between Phytoplankton, Heterotrophic Plankton, and Planktivorous Fish Productions in Different Water Bodies.

Examination of 14 lake-type water bodies at various latitudes of the Northern Hemisphere showed that the efficiency of phytoplankton production transformation through heterotrophic bacterioplankton and non-predatory zooplankton to predatory zooplankton and planktivorous fish increases in the direction from eutrophic to oligotrophic water bodies. The highest ratios between autotrophic and heterotrophic organism production were observed in lakes and reservoirs where the contribution of allochthonous substances to the total energy flow is relatively high. Bacterioplankton utilizing allochthonous dissolved organic matter (DOM) provides an additional source of energy for zooplankton, which serves as food for planktivorous fish. Therefore, to predict the total biological productivity and production of the fish community, it is necessary to take into account the production of not only autotrophic plankton, but also that part of heterotrophic bacterioplankton that is specialized in utilizing DOM entering the water body from the outside.