Meiobenthos of Lake Krivoe (Karelia) in the winter and vegetational periods

Our work is dedicated to the comparison of the quantitative development of meiobenthos during the vegetative season and in winter in the dimictic subpolar Lake Krivoe (Karelia). The winter meiobenthos turned out to be significantly poorer in species composition than the meiobenthos of the vegetative season (13 and 29 species, respectively). Of the 8 meiobenthic groups typical for the lake, Ostracoda and Cladocera were completely absent in winter. An analysis of the proportions of the dominant meiobenthos groups showed that the studied lake fits into the group of typical lakes in the North-West of Russia, and does not belong to the group of polar lakes, as would be expected based on its geographical coordinates. The peculiarity of Lake Krivoe that makes it unique among subpolar lakes is the high biomass in the profundal in winter – 0.14 g/m2, which does not significantly differ from that in the vegetative season – 0.2 g/m2. In the littoral and sublittoral in winter, compared with the vegetative season, there is a significant decrease in meiobenthos biomass from 0.47 g/m2 to 0.03 g/m2 and from 0.05 g/m2 to 0.001 g/m2, respectively. In winter, the largest biomass of meiobenthos is provided by the profundal of the lake – 71.5% of the total biomass of meiobenthos, littoral – 27.25%, and sublittoral zone – 1.2%. In the vegetative season, the opposite picture is observed: in the littoral zone of the lake, meiobenthos makes up 71.5% of the total meiobenthos biomass, in the sublittoral zone – 9.70%, and 18.78% in the profundal zone. The biomass of the winter meiobenthos significantly positively correlates with the meiobenthos biomass in September, r = 0.82 (p < 0.001), and with that in May of the next year, r = 0.56 (p < 0.03). Correlations between meiobenthos biomasses in various months of the vegetative season were non-significant.