STATUS OF THE CHAMELEA GALLINA AND PITAR RUDIS COMMUNITIES IN THE NORTH-EASTERN BLACK SEA IN THE AUTUMN OF 2019

Abstract

. Spatial distribution and quantitative characteristics of the main bottom communities in the North-Eastern Black Sea, characterized by the prevalence of the native bivalve species Chamelea gallina and Pitar rudis , have been considered for the autumn season of 2019. Within the investigated region, at the depth of 18 m, the largest area of sandy biotopes with silt and shell admixture was occupied by a community dominated by the bivalve mollusc Ch. gallina . At the depth of 30 m, a community of the pelophilic bivalve mollusc P. rudis was observed on silty substrate with shells and, at times, sand admixture. In the Chamelea community, molluscs were the most prominent group in terms of abundance and biomass. In the Pitar community, polychaetes were the most abundant in the benthic community, while molluscs prevailed in terms of their biomass. If compared with the data of the 1960s, the contemporary analysis of the materials presented indicates a decrease in the biomass of the macrozoobenthos down to 93 g/m 2 and of the dominant species down to 41 g/m 2 in the Chamelea community, which is associated with the predominance of small individuals in the mollusc populations. In the autumn of 2019, despite the appearance of invading species, the native species prevailed in the main regional biocoenoses.