Structure and Production Potential of Summer Phytoplankton of Lake Baikal in the Present Period

A study of the structure and production parameters of phytoplankton (biomass, photosynthesis rate, chlorophyll a content, and assimilation numbers) in the coastal and pelagic zones of the southern and central basins of Lake Baikal in the summer period 2018 has been performed. In the rivers and estuarine areas of the lake, the maximum concentration of dissolved organic matter reached 12.95 mg L –1 and was recorded near the southwestern coast, in the pelagic zone—in the central part of Maloye More—from 2.26 to 3.18 mg L –1 . At the pelagic stations, the quantitative indicators of phytopicoplankton were higher. The nanoplankton phytoflagellates, the development of which was facilitated by high concentrations of dissolved organic matter were the main producers of the coastal zone. The chlorophyll content in the phytoplankton at sampling most stations did not exceed the values revealed earlier for the summer phytoplankton of the lake (from 0.1 to 4 μg L –1 ), and the average rate of photosynthesis in the surface layer of the lake was 26.3 ± 8.7 μg C L –1 day –1 and exceeded the values of 18.5 ± 5.9 μg С L –1 day –1 published for the summer phytoplankton of the southern and central Baikal basins developing at the same depth. High production characteristics are provided both by an additional influx of nutrients and by the vegetation of small forms of microalgae.