Long-Term Dynamics of Macrozoobenthos in the Tyligul Estuary (the Northern Black Sea Region)

Long-term changes in the species composition and quantitative parameters of macrozoobenthos of the Tyligul estuary registered for the recent more than 40 years are analyzed in the paper. It has been shown that of the 56 species of benthic invertebrates that previously inhabited the estuary, only 20 remain now. It has been noted that of the 12 higher taxa of invertebrates previously represented in the estuary, only 7 remain now. Over the past period, such taxa as Turbellaria, Oligochaeta, Mysidacea, Decapoda and Cirripedia have disappeared. It has been shown that the bivalve mollusks <i>Mytilaster lineatus</i> (Gmelin, 1791), <i>Cerastoderma glaucum</i> (Bruguiere, 1789), and <i>Abra segmentum</i> (Recluz, 1843) are both previously and currently key species of the estuary macrozoobenthos. Currently the contribution of these mollusks to the total numbers of macrozoobenthos accounts for 70.4%, and their contribution to its total biomass is 93.5%. A potential threat to the existence of the key macrozoobenthos species <i>M. lineatus</i> coming from the invasive bivalve mollusk <i>Arcuatula senhousia</i> (Benson, 1842), which settled in this estuary in 2021, was noted.