Composition and structure of under-ice zooplankton of diverse lakes in Kenozersky National Park (Arkhangelsk Region)

The article presents the results of studies on zooplankton communities of diverse lakes in Kenozersky National Park in the ice-covered period of 2014–2016. The lakes differed in their genesis and morphometric characteristics. The species composition, quantitative characteristics, and vertical distribution of zooplankton were studied. Zoocoenoses are represented by winter and perennial forms of crustaceans and rotifers. In winter, zooplankton developed actively, and the communities contained egg-bearing female copepods and rotifers, aswell as nauplius copepods. Rotifers are the group represented by the largest number of speciesin the communities. The core that forms the structure of the communities is represented by 4–7 species. The number of species was the highest in Lake Lyokshmozero (19 species). In terms of numbers, the communities were dominated by copepods, except for Lyokshmozero, where rotifers quantitatively prevailed in 2015 and 2016. The biomass in the lakes was dominated by copepods in all years of the study. Depending on the year, the abundance of zooplankton in the lakes was 8,400–66,700 ind./m3, the biomass was 0.08–0.45 g/m3. The highest levels of abundance and biomass were found in Lake Vilna, which had the most favorable oxygen conditions. In the ice-covered period, zooplankton in the lakes was distributed unevenly. Most species formed clusters in the surface and bottom horizons. Some forms of zooplankton were numerous only at the bottom or at the surface. Surface aggregations of organisms are associated with the functioning of phytoplankton at the ice edge, bottom ones with the activity of anaerobic bacteria. The main factors in fluencing the development and distribution of zooplankton under ice were the duration of the autumn convection period, temperature and oxygen regimes in the lakes, and the food factor.