Chemical composition and trophic status of urban lakes of the Arctic zone of the Russian Federation (Murmansk)

The chemical composition and seasonal dynamics of the water in Murmansk urban lakes (Murmansk region, Russia) under the anthropogenic load of varying intensity was analysed. The studies were conducted in the period from 2018 to 2020. The chemical composition of the water in the studied lakes differed significantly from that of the lakes located in the background territories of the region. High values of pH and mineralization, increased concentrations of major ions and elevated content of nitrogen and phosphorus compounds were recorded in the surface waters. The nutrient concentrations were subject to noticeable seasonal fluctuations, mainly due to their consumption by phytoplankton, as well as to the changes in the ratios of surface and underground runoff. Lake Ledovoe (the central part of Murmansk) was the most polluted among the studied lakes, and Lake Bolshoe (used for drinking supply of the city) was the least polluted. Assessing the trophic status of the Murmansk lakes showed that the studied lakes are mostly mesotrophic, except for Lake Bolshoe (oligotrophic) and Lake Ledovoe (hypertrophic). In most of the lakes, phosphorus was the limiting factor for the growth and development of phytoplankton. The data obtained can be useful for understanding the fundamental processes of water composition transformation in the urbanized territories of the Arctic regions of the world and for making managerial (practical) decisions to create a comfortable urban environment in the North of Russia.