State of the geoecosystem of the Dniester Estuary as a component of the geoecotone «Black Sea—Land»

Abstract

The Dniester Estuary is a unique natural object that was formed and exists within the transitional area between the geoecosystems of the Black Sea and the mainland, which determines its hydrological regime, features of bottom sediments, quality characteristics of water and other properties. The Dniester Estuary should be considered as a separate and integral geoecosystem, which is composed of interdependent subsystems. Today, anthropogenic activity has a great influence on the state of the estuary, especially the role of the military factor is growing, which is explained by hostilities and destruction in the region where the reservoir is located. In order to assess changes and ensure effective use of reservoir resources in the future, a comprehensive analysis of the pre-war state of the Dniester Estuary is absolutely necessary. The article summarizes the existing information about the bottom sediments of the Dniester Estuary and the unknown results of the expedition research of the reservoir, which were carried out by the authors in 2020-2021. 35 samples of the rocks of the shore and the bottom of the reservoir, as well as 25 samples of water from the bottom layer, were taken. A primary lithological description, an analysis of the granulometric composition of sands, and the content of heavy metals (Pb, Cr, Cu, Cd, Zn) were carried out for samples of bottom and coastal sediments. Maps of the distribution of some of them in the bottom sediments of the reservoir were built, as well as a comparison of the content of these metals with the content in the bottom sediments of adjacent territories, adjacent soils, in the bottom sediments of other estuaries of the northwestern Black Sea region, as well as with existing regulatory characteristics. Elevated concentrations of Pb were established. In the article, the authors present the results of their own research into the regularities of the distribution of pH parameters, redox potential, salinity, and mineralization of water, and for some samples, the powers of the ambient equivalent dose of gamma radiation were determined. A map of the distribution of mineralization values of the southwestern part of the reservoir was constructed. Features of dependence of parameters of mineralization and salinity on pH values were established. The authors identified the main climatic and geomorphological factors affecting and controlling the geoecosystem of the estuary. The article is illustrated with the author's photographs.