An attempt to evaluate the diffuse removal of mineral nitrogen and phosphorus from river catchments in the central part of the Russian Plain has been made. A rough esti-mate of the annual water-biogenic balance for the Linda and Kudma river catchments, which are the tributaries of the Cheboksary reservoir, and river catchments of the Kursk region is presented. It is shown that the diffuse removal of biogens from river catchments exceeds their removal into water bodies with wastewater, and in recent years (2008–2018) it reached 75–95 %. Along with the surface component of the runoff, the contribution of underground runoff and precipitation to this process is estimated. It is found that on the catchment area of the lateral tributary of the Cheboksary reservoir, the natural component in the diffuse removal of nutrients predominates comprising 55–75 % and more their total removal. Due to the intensive anthropogenic load in the Kursk region, the natural supply of biogens to the river catchments (30% nitrogen and 5% phosphorus) is much less than their anthropogenic input. The livestock business, poultry farming, urban areas (including the road network) and fertilization are the most significant sources of anthropogenic nutrient input. Resent chang-ers in nitrogen and phosphorus removal from river catchments are assessed. They have oc-curred mainly due to climatic changes in the water balance – due to decrease in the surface slope runoff and due to increase in the runoff of infiltration origin (underground runoff and vekhovodka). Annual biogens export from the Linda and Kudma river catchments has in-creased significantly (by 20–30 %). At the same time in the Kursk region, due to a reduction in the annual river flow (by 30–40 %), nutrient removal has decreased.
Phytoplankton of unique karst lakes (by the example of the Lake Klyuchik, the basin of the Cheboksary Reservoir)