Salinity gradient meiobenthos distribution on the Razdolnaya River’s estuary

The paper studies salinity gradient meiobenthos distribution based on the results of the benthic surveys of the Razdolnaya estuary (the Sea of Japan, Amursky Bay). The density was increased with salinity growth on the Razdolnaya River’s estuary. Meiobenthos was comprised by 8 taxonomic groups (Nematoda, Copepoda, Ostracoda, Oligochaeta, Mollusca, Amphipoda, Polychaeta и Chironomidae) with the dominance of nematodes. Most of meiobenthic species are presented by marine euryhaline species and registered throughout the Razdolnaya River’s estuary. Fresh water species Dorylaimus chassanicus, Hofmaenneria gratiosa, Theristus brevisetosus and nematodes of the genera Paradontophora , widespread on estuaries of Far East of Russia, were dominated in meiobenthos in oligohaline zone of estuary; Monhystrella sp. Oncholaimium japonicum, Anoplostoma cuticularia, Daptonema inversum and Harpacticoid Copepods Remanea naksanensis, Onychocamptus mohammed, Huntemannia biarticulatus, Halectinosoma sp. were dominated in mesohaline zone. Nematode community are changed by zones throughout the estuary: Paradontophora genera are dominated in freshwater and olihaline zones, as well as freshwater species ( Dorylaimus chassanicus, Hofmaenneria gratiosa, Theristus brevisetosus ) were presented; Monhystrella sp. are dominated and freshwater spicies are decreased in the number at the mesohaline zone; Paracanthonchus macrodon, Onсholaimium paraolium, Sabatieria finitima, Dorylaimopsis peculiaris and S. palmaris are dominated at the euhaline zone. The nematocenes of inner part of estuarine zone aren’t characterized by specific species assemblage and consist of species typical for nematode community of shallow water and of marine zones.