Features of Development of the Zoobenthos in Shagany and Burnas Lagoons (Northern Black Sea)

Abstract

The qualitative composition and features of the quantitative development of zoobenthos of the salt Shagany and Burnas lagoons in the summer season of 2018 were determined. For comparison, the zoobenthos of the freshwater Maly Sasyk lagoon, connected by a channel to the Shagany lagoon, was studied. These reservoirs belong to the Tuzlovskaya group of lagoons, located in the Northern Black Sea region in the middle part of the Danube-Dniester interfluve. The depth in the sampling areas was 0,3 – 0,5 m. It was noted that the water temperature in these reservoirs during the study period was about 30 °C. Salinity in the Shagany and Burnas lagoons ranged from 24,55 to 32,56 ‰, and in the Maly Sasyk lagoon – from 4,79 to 7,06 ‰. As a part of the benthic community of lagoons, 21 species of invertebrates belonging to 9 taxes were found. The species composition of the zoobenthos of Shagany and Burnas lagoons did not differ much in view of the fact that these reservoirs are interconnected by wide straits passing through the Alibey lagoon. The largest number of species found belonged to Polychaeta worms, Amphipoda crustaceans and Bivalve mollusks. One hundred percent occurrence was characteristic of eight invertebrate species. These species under conditions of shallow lagoons reached the greatest quantitative development. It was shown that a small species diversity of the bottom community of these lagoons was accompanied by high abundance and biomass of several invertebrate species. The mass invertebrate species was gastropod mollusks Hydrobia acuta (Draparnaud, 1805), the abundance of which ranged from 1450 to 3675 ind.·m^-2. Most of the species found belonged to eurybiotic invertebrates, able to survive in a wide range of fluctuations of abiotic environmental factors. The nature of bottom sediments influenced not only quantitative development parameters, but also the size structure of bivalve mollusk populations living in the Shagany and Burnas lagoons. The discovered invertebrate species, due to their ecological features during growth and development, actively contributed to increasing the resistance of the studied lagoons to eutrophication.