Оценка экологического состояния восточной части Финского залива по гидробиологическим показателям в летний период 2022 года

The eastern part of the Gulf of Finland represents a transitional area from freshwater to brackish water. The hydrological characteristics of the Gulf of Finland largely determine the distribution of representatives of different ecological complexes of hydrobionts in the gulf – freshwater, brackish water, and marine forms. The eastern part of the Gulf of Finland is of exceptional importance for the city of Saint-Petersburg, as it is one of the most important transportation arteries in the northwest of Russia. The gulf is subjected to significant anthropogenic pressure, driven by high population density and concentration of economic activities in the watershed. The most common responses of ecosystems to anthropogenic influences are pollution or changes in their typological status, primarily towards its elevation. Therefore, monitoring the state of the aquatic environment is of great importance for the assessment of the state of aquatic ecosystems and the prevention of negative ecosystem changes. This article presents the results of hydrobiological studies conducted in the eastern part of the Gulf of Finland during the summer period of 2022 (June−July). To assess the ecological state of the gulf, hydrobiological indicators such as chlorophyll-a, phytoplankton, and zooplankton were used, which are reliable indicators of the state of aquatic ecosystems. During the study period, the salinity of the water in the gulf increased in the surface horizon from east to west, from 0.18 to 3.91 ‰, and in the near-bottom horizon from 3.91 to 6.73 ‰. The distribution characteristics of chlorophyll “a”, phytoplankton, and zooplankton in the eastern part of the Gulf of Finland were identified taking into account the hydrological conditions prevailing in different parts of the water body. It was established that during the study period, the shallow-water area of the eastern part of the Gulf of Finland corresponded to eutrophic conditions, the transitional area corresponded to the boundary between mesotrophic and eutrophic conditions, and the deep-water area corresponded to mesotrophic conditions. For the eastern part of the Gulf of Finland, especially for its shallow-water area, eutrophication is a serious environmental problem. The main cause of eutrophication of the gulf is excessive biogenic loading from terrestrial sources.