Assessment of water quality in the rivers of Abkhazia, based on zooplankton

Abstract

Objective: A number of water objects of Abkhazia (the Western Caucasus) have been studied. Physicochemical indicators of water and characteristics of zooplankton community were investigated. Water bodies of Abkhazia are specified by high water quality, due to glacier-derived nourishment of rivers. In the mouth areas, the quality of water deteriorates, sometimes significantly, due to the pollution by sewage. However, most of the studied water bodies have high quality of water. The exceedance of maximum permissible concentration of biogenic elements was not revealed in rivers. In waterfalls water is ultra-fresh. In rivers, water is fresh with low hardness. Materials and Methods: A total of 17 zooplankton taxa were identified in the studied water bodies. The dominant species in various water objects were the following: Thermocyclops crassus, Pleuroxus aduncus, Pleuroxus trigonellus, Alona rectangula, Penilia avirostris, Macrothrix laticornis, and Eucyclops serrulatus. Zooplankton communities are characterized by low species richness. It is due to the high flow rate of mountain rivers, and their low temperature that creates unfavorable conditions for the development of zooplankton. Results and Discussion: The abundance of zooplankton varied from 5 specimens/m3 (the Mokva River) to 570 specimens/m3 (the Edyrtaa River). The biomass of zooplankton varied from 0.127 mg/m3 (the Mokva River) to 5.1 mg/m3 (the Akuna Channel). Quantitative indicators of zooplankton are low. Conclusions: According to the value of saprobity index, water in the Dzyguta, Edyrtaarivers, the channel from the Gali reservoir refers to β-mesosaprobic zone, and water in the Kudry Khuchi and Smyrakha rivers - to oligosaprobic zone.