Change in the bottom biocenoses species composition in the Black Sea area before the Kerch Strait as a result of silting

Abstract

During the course of the late 80s - early 90s, the Black Sea area before the Kerch Strait was subjected to strong anthropogenic silting. As a result the area occupied by all the biocenoses, except for Terebellides stroёmi biocenosis, was reduced by 1.8 times from 4.399 thousand km2 to 2.491 thousand km2. Ascidiella aspersa biocenosis was completely lost. Its disappearance is also explained by the silt discharge from the Kerch Strait. Succession of Modiolus phaseolinus biocenosis and partially of Mytilus galloprovincialis one occurred into T. stroёmi biocenosis. A reduction of species diversity and abundance over all the silted biocenoses was observed. A decrease in the dominant species abundance was of great importance for the reduced number of the biocenoses. The species composition over the destroyed sites became more leveled in relation to the initial biocenoses. The net result was that communities of Pitar rudis and Spisula subtruncata were formed and the area of Terebellides stroёmi biocenosis was increased. It was found that Nephthys hombergii, N. longicornis and T. stroёmi are best tolerant of silting. Sponges do not withstand silting at all.