Assessment of the current state of the northern Agrakhan by hydrochemical and hydrobiological indicators

Abstract

The northern part of the Agrakhan Bay belongs to one of the main fishery reservoirs of the Tersko-Caspian region, which plays a major role in the formation of stocks of valuable passing, semi-passing and lake-river fish species. In the last 2019-2022, due to a critical decrease in the flow of the Terek River and a drop in sea level, the hydrological regime deteriorated significantly, which led to a sharp shallowing and overgrowth of the Northern Agrakhan. The performed studies have shown that although, in general, the hydrochemical regime in the reservoir remains relatively favorable for the growth and development of hydrobionts, but over the past 8 years there has been a deterioration in a number of defining indicators, so a decrease in the content of dissolved oxygen in the water is recorded, especially in the summer, which sometimes dropped to critical levels. Hydrobiological studies have established that planktonic and benthic communities have not undergone significant changes and, as before, are subject to seasonal fluctuations, but the predominance of the highest tough vegetation of reeds and cattails covering more than half of the surface of the reservoir leads to a decrease in the bioproductivity of the northern part of the Agrakhan Bay.