Harpacticoida (Copepoda) of the northern East Sea (the Sea of Japan) and the southern Sea of Okhotsk: diversity, taxocenes, and biogeographical aspects

Based on novel data and a literature review, an inventory of Harpacticoida from the northern part of the East Sea and the southern part of Sea of Okhotsk is compiled. A total of 151 species belonging to 70 genera and 26 families, of which 16 species are deemed to be new to science, are recognized from the region. Twelve harpacticoid species assemblages are described from marine and brackish water soft sediments and the phytal zone. Estuarine faunas were similar throughout the East Sea and Sea of Okhotsk, both in species composition and dominant-taxon structure. Conversely, the fauna of marine soft sediment and phytal zones differed greatly throughout this region. This distinction may have been caused by differences in dispersal rates or by differences in environmental conditions. The distribution of littoral and sublittoral harpacticoids was determined primarily by climatic factors and the temperature of surface waters. Three basic sub-regions were distinguished within the survey area: Korean, which includes many tropical taxa (39%) and a smaller amount (about 20%) of boreal taxa; Primorye, where boreal and subarctic-arctic species (>40%) predominate, and representatives of the tropical complex are rare (17%); and Soya, with a mix of tropical (22%) and boreal (31%) faunal elements. The faunas of the Korean and the Primorye sub-regions are distinct, whereas that of the Soya has intermediate features.