Influence Of Lake Inflow On The Benthic Communities Of Varna Bay

Abstract

As a result of high urbanization and industrialization the Varna Bay is one of the most influenced by anthropogenic activity region of the Bulgarian Black Sea area. Simultaneously the Varna Lake nutrient-enriched inflow contributes additionally to the negative changes of the ecological situation, especially in summer. To establish the state of the benthic communities in contact with lake waters in 2019, samples of macrozoobenthos were collected. The quantitative parameters of macrozoobenthos in Varna Bay established: taxonomic structure dominated by Polychaeta , spring abundance 2.5 twice higher that in autumn, built mainly by Oligochaeta , known as indicators for eutrofication. During both seasons the biomass maintains low values, due to predominance of small-sized mollusks. According to statistical indices the ecosystem status is slightly or moderately disturbed, with better results for the North region. Cluster analysis clearly defines 2 groups, according to the bottom substrata, with stations along the way of lake inflow waters forming an independent cluster. In conclusion, despite the total state of the Varna Bay ecosystem, the most negatively influenced stations are along the lake inflow way.