Recent observation of seasonal variability of plankton in Maloe More Strait (Lake Baikal)

In this paper, we describe the structure and quantitative characteristics of phyto- and zooplankton from Maloe More Strait of Lake Baikal studied in June-October, 2024. Maloe More is a popular recreational zone facing higher anthropogenic stress. In summer, phytoplankton in the littoral area of the strait showed continuous biomass maximum, starting from July until late August during cyanobacterial blooms. Two smaller maxima were observed in the strait pelagic zone, the first by the end of spring vegetation of phytoplankton, and second during excessive cyanobacterial growth in August. Elevated water temperatures resulted in prolonged cyanobacterial vegetation with a change of dominants. Restructuring of food resources and temperature fluctuations entailed transformations in the zooplankton structure. In June, the pelagic plankton was dominated by Epischura, a Baikal endemic. As the water temperature rose, the dominant position was occupied by Cyclops kolensis, the population of which was represented by mature specimens and nauplii. In summer, Cladocera reached its abundance peak in the nearshore. The highest number of rotifers was documented during maximal rise of nanoplanktonic flagellate concentrations in autumn.