Shallow-Water Benthic Communities on Soft Bottoms of a Sub-Arctic Fjord (Southern Barents Sea, Russia) along a Gradient of Ecological Factors

Abstract

Kola Bay is the most developed coastal area in the Russian part of the Barents Sea, but despite a long history of research, information about the local shallow-water benthic communities is lacking. For this reason, in this fjord area, we investigated the soft-bottom zoobenthos to determine its distribution and the factors influencing its abundance, biomass, and diversity. An analysis of 24 samples collected by divers at eight stations located at 7–8 and 10–15 m depths revealed 127 benthic taxa with an average abundance and biomass of 12,190 ± 4740 ind. m−2 and 30 ± 8 g m−2, respectively. The most severe abiotic conditions (high rates of sedimentation and eutrophication) were found at the head of the bay while the highest densities of predator red king crabs were registered in the middle part. The total benthic abundance and biomass, as well as the abundances of infauna, mobile taxa, subsurface deposit feeders, and surface deposit feeders, decreased towards the central part of the bay, reflecting gradients in the environmental conditions. In the inner part of the bay, we registered two communities: Cossura pygodactylata + Ciliatocardium ciliatum and Arctica islandica + Laonice cirrata, while the benthos of the middle part was less structured. Redundancy analysis indicated that the faunal abundances were influenced mainly by predator density (negative association) and the organic matter content (positive association). The total benthic biomass was negatively linked to water temperature due to the predominance of cold-water species in the area and a close positive association of this factor with crab abundance. In contrast, the highest diversity was registered at the warmer sites, which may have been a reflection of the borealization process in the Arctic. Our results contribute towards the proper management and conservation of the local benthic ecosystem and provide reference data for future monitoring programs and coastal management guidelines.