Long-Term Changes in the Composition and Distribution of Macrobenthic Communities in the Intertidal Zone of Vostok Bay, Sea of Japan

Studies were conducted in the intertidal zone of Vostok Bay in 2021–2023 at the same sampling stations as in 1990. Thirty-seven macrobenthos communities were identified, but only half of them were common to both 1990 and the 2020s. In the 2020s, communities that were not recorded in 1990 developed. In the upper intertidal subzone, the Gloiopeltis furcata community was found on hard sediments, the Ruditapes philippinarum community was typical for mixed sediments dominated by sand, and the Assiminea possietica community was associated with the silty-sandy intertidal zone. In the middle intertidal subzone, the rocky-bouldery sediment was occupied by the communities of Dictyota dichotoma, Laurencia nipponica, Symphyocladia marchantioides, etc.; the sandy-pebbly-bouldery sediment was occupied by the Gracilaria vermiculophylla and Campylaephora kondoi communities; and the silty-sandy sediment was occupied by the Batillaria cumingii community. In the lower intertidal subzone, the Sargassum pallidum and S. miyabei communities were found for the first time. The middle intertidal Hapterophycus primoriensis community was recorded in 2021, but it was absent in 2022 and 2023. The Silvetia babingtonii community of the middle intertidal subzone and the Saccharina angustata and Coccophora langsdorfii communities of the lower intertidal subzone were typical for Vostok Bay in 1990, but they were not found in the 2020s. A biomass similarity of the communities between 1990 and the 2020s exceeding 40% was recorded only for the upper intertidal subzone. The observed changes in the composition and distribution of communities were presumably caused by climate changes, anthropogenic impacts, and by the cyclic development of individual intertidal inhabitants.