Principles of biogeographical regionalization of World Ocean are widely discussed in the literature. In works of Spalding et al (2007) for lower unit of regionalization adopted ecoregions - large marine ecosystems. These are very large water areas, as a rule, the whole sea basins, and analogs of physiographic countries on the land. In our view, large marine ecosystems comprise a hierarchical system of smaller units’ regionalization, which corresponds to a natural distribution of hydrobionts communities. In the continuing process of regionalization of large marine ecosystems is proposed to use the bionomic approach that takes into consideration the link of communities of marine organisms with habitats that allows a meaningful comparison of areas at different levels of hierarchy. System of biogeographical regionalization should be based on natural, historical and bionomic features of water areas (Petrov, 2004). Originality of bionomic area, in view of authors, is determined by its position in system of units of