—Inland Water Biology, Vol. 16, No. 3, pp. 462–472. © Pleiades Publishing, Ltd., 2023
The Tendency of an Increase in the Abundance of Macrozoobenthos Species in the Sevastopol Bay (Black Sea).
Shalovenkov N.
Centre for Ecological Studies, shaloven@rambler.ru
In the Sevastopol Bay, degradation of species composition and communities of the zoobenthos began to be shown in the 20’s–30’s years and has reached maximum demonstration in the 60s–90s years of the last century. Only five species of macrozoobenthos were the most resistant at high anthropogenous loadings and eutrophication in those years.
(Figure 4. Phase trajectory in the factorial plane of the variability of the species composition of macrozoobenthos in Sevastopol Bay for 100 years. T °C is the average monthly water temperature in the surface water layer in August)
The relative recovery of the species composition and the improvement of benthic biological parameters are observed in the bay since the beginning of the 21st century. The zoobenthos was replenished by 39 new species which here were not marked earlier. Mollusca, Crustacea and Polychaete, among taxonomic groups of zoobenthos, had the greatest quantity of new species. Registration of the zoobenthic animals even in areas, which were earlier as “dead zone”, indicates an improvement of habitat in the Bay. The reduction of the eutrophic level, the oxygen regime improvement and the area expansion with oxidizing conditions in bottom sediment were the major factors in improving benthic habitats in the Sevastopol Bay. These ecological changes coincided with increase of water temperature in the summer period. The positive tendencies for a zoobenthos are typical for the Romania, Bulgarian coasts in the last decade.
(Figure 5. Spatial distribution of the redox potential (Eh) of bottom sediments in the water area of Sevastopol Bay and its inner bays in 1985 and 2000.)