Macrozoobenthos of the Pechora Sea (SE Barents Sea): community structure and spatial distribution in relation to environmental conditions

Extensive investigations on macrozoobenthic communities of the Pechora Sea (SE Barents Sea), carried out between 1991 and 1995, indicate that it is rich in terms of diversity, with a total of 712 taxa observed (505 identified to species level). Biomass distribution of zoobenthos varied greatly (2.6 to 1200 g m -2 wet wt). Average values recorded for the offshore areas are high for an Arctic environment, implying that the influence of the large Pechora River may extend far into the offshore area. In addition, intensive sedimentation of organic matter during the retreat of the highly productive ice-edge zone in the summer may also contribute to the observed high biomass. A method combining the abundance and biomass values of species was used to calculate an index approximat- ing the production of each species. This index was used to distinguish the different community types in the area. In the study area, 13 benthic community types were identified, of which 2 main types covered most of the offshore areas. The concentration of total organic carbon (TOC) in the sediment was shown to have a strong influence on the diversity of the benthic communities, while both TOC and water depth affected the distribution of communities and the feeding mode of the dominant species. A community type consisting of surface deposit-feeders is the most widely distributed type in the area. Suspension feeders, however, dominate an extensive shallow offshore area. Boreal-Arctic species show a marked predomination (68.9%) in the whole Pechora Sea. The share of Arctic species is greater in the northern part influenced by cold water currents, while boreal species predominate in areas affected by warmer coastal waters. These observations indicate that the Pechora Sea functions as a transitional zone between boreal and Arctic biogeographic regions.