Impact of Seasonal Ice on the Structure of the Dreissena polymorpha (Pallas, 1771) Beds in the Swash-Ice Zone of the Curonian Lagoon and the Peculiarities of Formation of the Zebra-Mussel Bed

摘要

The swash-ice zone of the Curonian Lagoon comprises the depths from a lower margin of the supralittoral to a lower margin of the swash subzone (0.7 m). This zone extends from a few meters to 250 m. This zone is the area of expatriation of Dreissena polymorpha because of its complete freezing in winter. However, this species prevails in the swash-ice zone in terms of the frequency of occurrence and the ratio in the total abundance and biomass of macrozoobenthos. Zebra mussels form large beds; their abundance and biomass reach 1420 ind./m(2) and 74.334 g/m(2), respectively. Population replenishment in this zone occurs sporadically due to adult individuals brought here from the consortium communities, where zebra mussel + Unionidae and zebra mussel + Viviparidae are the determining centers, as well as due to the settling of the mollusks of the veliconch stage.