Conditions of estuarine rivers of the Abkhazia Republic and their impact on the Black Sea coast

Abstract

Estuaries play an important role in formation of coastal water quality and the conservation of biological diversity. In 2013–2014 the study of estuarine rivers in Abkhazia Black Sea region and their possible impacts was supported by RFBR grant. A number of large (Bzyb, Kodor, Gumista Kelasur, Galizga) and medium (Aapsta, Hypsta, Basle and others.) Abkhazia rivers have a significant impact on the ecological state of the Black Sea coast because of the runoff of sediments. We have studied a total of 35 rivers flowing into the Black Sea on the coast of Abkhazia and identified hydrological characteristics of these. The maximum flow rate was observed for the Kodor River. Even in the low-flow period the water flow in estuarine areas ranged from 0.323 to 161.3 m³/s. Turbidity in the river at low water was 0,003–0,010 g/m³, for Kelasur river – 0.28 g/m³. Hydrocarbonate-calcium type of water is typical for the rivers of Abkhazia, salinity of most rivers is average. Well water quality characterizes by Galizga, Reprua, Gvandra and Hashipsa rivers. In the phytoplankton of investigated river estuaries were have identified 84 taxa below the rank of genus, in zooplankton – 19 species, in zoobenthos – 105 species and 23 species of fish fauna. In relation to phytoplankton most of the rivers appear to be oligotrophic. When using zoobenthic organisms as bioindicators the rivers were marked as having unfavorable conditions (Suhumka, Aapsta, Maanikvara et al.). The local impact on water quality of the Black Sea has a river experiencing pollution from receipt of sewage, waste and experiencing the impact of grazing. Rivers Bzyb, Kodor, Kelasur and Galizga bring large volumes of high mountain glacier water, which contributes to improving of the state of the Black Sea coast.

Keywords: Black Sea, river Abkhazia, estuarine areas, hydrochemical parameters, phytoplankton, zooplankton, zoobenthos, fish fauna