СЕЗОННАЯ ИЗМЕНЧИВОСТЬ ТАКСОЦЕНА MOLLUSCA РЫХЛЫХ ГРУНТОВ КОНТАКТНОЙ ЗОНЫ РЕКИ ЧЕРНОЙ И СЕВАСТОПОЛЬСКОЙ БУХТЫ (ЮГО-ЗАПАДНЫЙ КРЫМ)

Abstract

The seasonal dynamics of species composition, abundance and biomass of mollusks in contact zone of the river and simultaneously in the mouth of the river Chernaya and in the corner part of the Sevastopol bay was analyzed for the first time. The distribution of molluscs depending on salinity was researched. As the river flows into the Bay, the number of species, abundance and biomass increased. In the Chernaya river the factor of salinity plays more important role for distribution of Mollusca than temperature. In this area the Mollusca taxon includes 22 species belonging to 3 classes: Polyplacophora, Bivalvia and Gastropoda. The largest number of species is recorded in October, May and August, the smallest — in winter months. In 2006-2007, the quantitative indicators (number and biomass) were also in average quite high in the study area compared to the corner part of the Sevastopol Bay. The gastropod Hydrobia acuta is a dominant species in terms of abundance, and the bivalve Cerastoderma glaucum in terms of biomass. The seasonal maximum number of Mollusca is confined to the warm period (late spring – summer), the minimum to the cold (late autumn – winter), which is due to the predominance of thermophilic species in this area. The maximum seasonal dynamics of shellfish biomass was observed in summer; the minimum was registered in spring. The trophic structure of the Mollusca taxon was determined. It was very diverse and included 6 groups, with a predominance of phytophages, detritophages and sestonophages.