Ciliates in the plankton of the shallow zone of the Rybinsk Reservoir in spring: long-term changes in the community structure and the contribution of ciliates to the formation of the total biomass of the plankton community

Abstract

In spring (April 28‒May16, 2022) plankton of the shallow-water zone of the Rybinsk Reservoir, the biomass of large, predatory ciliates with symbiotic algae was 5‒8 times lower than that in the periods of late April‒May of 1971 and 1977, and their share in the total biomass of ciliates (Bcil) decreased from 46.5−47.1% to 8.9%. At the same time, the biomass of algophagous ciliates in the plankton increased by 1.8−2.0 times and their proportion in Bcil – from 15.7−24.5% to 44.6%. In April‒May 2022, ciliates were the main component of the planktonic community of heterotrophic organisms and viruses. In the planktonic food web of the reservoir shallow zone, they played a key role in the transformation of organic carbon of primary producers and detritus to a higher trophic level.

Keywords

• species diversity
• size composition
• trophic groups
• food webs