Pechora Sea polychaete worms: biodiversity and spatial distribution

The modern taxonomic and geographical composition, trophic mode and spatial distribution of polychaete worms - one of the most important components of the bottom ecosystems of the Pechora Sea, is studied. This area characterized by the special abiotic conditions, a high level of biological production, a variety of biotopes and numerous populations of rare and protected species. According to the materials of the last expeditions in the Pechora sea, 198 taxa of polychaete worms were identified including 165 species belonging to 113 genera, 34 families, and 14 orders. Everywhere the species diversity of polychaetes and stress stability of their populations was high, with the exception of small areas, located near entrance to the Pechora and Khaypudir bays with amount of river runoff. The density of settlements widely varied from 26 to 7144 ind./m(2). Density gradients are most pronounced in the south-eastern shallow part of the Pechora Sea and in a lesser extent in the north-western of region. The spatial distribution of polychaete biomass is also heterogeneous, but varies much less in absolute terms from 0.7 to 387 g/m(2). Four major groups represent the trophic mode of polychaete bioresources. More than half of the total biomass is created by surface detrivorous, a few less than a third - by subsurface detrivorous, 2% - by suspension feeders, and 10% - by carnivorous. The 80% of all polychaetes constituted only by six species, and the most significant of which are Spiochaetopterus typicus and Maldane sarsi. During the last 70 years the number ratio of species belonging to main biogeographic groups remains stable, although the taxonomic list is constantly increasing. The stable state of polychaete taxocene, playing the significant role in the bottom ecosystems, assumes the stable state of bottom biocenoses of the Pechora Sea in general.