The Evolution of Redox Conditions in Stratified Water Bodies of Poria Gub Bay and Kandalaksh Coast of the White Sea

The results of hydrochemical studies of water bodies with varying degrees of development of anaerobic conditions (up to the appearance of meromixia with sulfide anoxia) located in the Porya Bay (Kandalaksha Bay of the White Sea, Kandalaksha State Nature Reserve) are presented. It is shown that these reservoirs, which are at different stages of isolation from the sea, have a unique hydrological and hydrochemical structure, which is formed at a certain stage of their evolution. The vertical stratification of waters, with the development of all phenomena accompanying stagnation, is more pronounced in the most distant parts of their water area from the sea, where an increased content of hydrogen sulfide (up to 16.5 mg/l), phosphates, silicon, nitrite and ammonium nitrogen is noted in the near-bottom anaerobic waters. However, the concentrations of all major ions are comparable to those in sea waters and practically do not change vertically. An analysis of the distribution of hydrochemical parameters of the distant reach of the Ozerki lagoon made it possible to conclude that, as a result of changes that have occurred with this reservoir over the past 90 years, it can now most likely be classified as meromictic.