Macrobenthos of the sublittoral in the Astafiev and Srednyaya Bights of Peter the Great Bay, Japan Sea (Far Eastern Marine Biosphere State Nature Reserve)

Species composition, abundance, ecological structure and spatial distribution of macrobenthos are considered in landscape and ecological conditions of the Astafiev and Srednyaya Bights in the eastern part of the Far Eastern Marine Biosphere State Nature Reserve. The main types of landscapes are identified on the data of landscape profiling. Granulometric composition of soils and organic matter content in the bottom sediments are analyzed. A total of 77 species are found in the macrobenthos of both bights. There are 28 species of epibenthos (similarity between bights by Jaccard index is 93 %) and 53 species of infauna (similarity 23 %), including 4 species common for both biotopes. Different ecological processes in the bottom-macrobenthos system occur in these nearby bights that affects biological diversity, abundance and structure of soft-soil benthos. Despite geomorphological similarity of the bights, the bottom environment in the Astafiev Bight is more enriched in organic matter, but taxonomic composition and abundance of infauna is poorer there. Bulk release of terrigenous matter from the eroded shore of Gamov Peninsula to this bight after rains destabilizes and jeopardizes its bottom environments and prevents formation of biologically stable, diverse and abundant benthos. In the neighbor Srednyaya Bight with a less erosive coastline, the bottom sediments are formed by marine processes mostly, so the macrobenthos on soft soils is distinguished there by great biodiversity. The epibenthos in both bights has no such differences and is represented by the most common species for Peter the Great Bay.