Features of spatial distribution of plankton ciliates in the humic lake of the southern taiga (Middle Volga region)

The paper presents data on the planktonic ciliates in various habitats of humic stratified lakes -”wetland window”, in a strictly protected area of the Volga-Kama state natural biosphere reserve. The maximum values of abundance and biomass were 3914 thousand ind./m3 and 392 mg/m3 in 2006, and - 5716 thousand ind./m3 and 822 mg/m3 in 2007 respectively. Average values of abundance and biomass are 1225 thousand ind./m3 аnd 130 mg/m3. The specific characteristics of the ciliates community are the predominance of mixotrophic ciliates among the structure-forming species in the entire water column of the lake in the species number, ciliates abundance and biomass. At the same time, under condition of greater water chromaticity, the contribution of mixotrophic ciliates to the average abundance and biomass in the water column was higher (74% of the number and 91% of biomass), compared with “less colored” water (59% of the number and 87% of biomass, respectively). The formation of significant aggregates of large species-mixotrophs is characteristic for overgrown biotopes of the lake. In contrast to the stratified, including meromictic water bodies (where the narrow maxima of the ciliates community is concentrated at the boundary of oxygen and anoxic zones) the abundance and biomass maxima in lake Dolgoe are concentrated in the oxygen zone and cover a wide area. In general, the vertical distribution of the ciliates community in the water column is more heterogeneous than the horizontal one.