Structural and trophic characteristics of protozoan plankton in a subarctic Lake (Northern Karelia)

Abstract

The seasonal dynamics of ciliate abundance has been studied in Lake Krivoye (the White Sea coast). A high species diversity of ciliates and their maximal biomass in the plankton are observed in the early spring in spite of low water temperatures (5–7°C). In spring, infusoria comprise 90% of the zooplankton biomass; i.e., infusoria as primary consumers are the main consumers of algal and microzooplankton production and the major carriers of energy to the next trophic level. During this period, a significant portion of planktonic infusoria biomass is constituted by the species containing zoochlorella. The high biomass of symbiotic algae (25% of the total biomass of planktonic algae) in a spring cilioplankton testifies to the important role that algosymbionts play in the primary production in some parts of the year.