The current status of the macrozoobenthos around the Atlantic walrus haul-outs in the Pechora Sea (SE Barents Sea)

Although benthic fauna in the Pechora Sea (SE Barents Sea) is generally well-studied, information on the bottom communities in the shallows near islands and the mainland is still sparse. Shallow marine areas in the Pechora Sea serve as important feeding grounds for numerous benthophagous fish, waterfowl and marine mammals, including the Atlantic walrus (Odobenus rosmarus rosmarus). To study the patterns of macrozoobenthic distribution in the shallows and evaluate the ecological state of the zoobenthic populations close to walrus haul-outs, sampling was performed in 2014 and 2016 around an archipelago in the Pechora Sea. In 2014, the average biomass, the Shannon's Diversity Index and the predominance of filter feeders in benthic communities were, in general, similar to the respective characteristics in neighboring deeper areas studied in the 1990s. In 2016, significant differences in species number and in biomass were recorded compared to 2014. An increase was observed in Atlantic boreo-Arctic species. Analysis of the trophic structure showed a slight decrease in the proportion of filter feeders and a significant increase in the proportion of subsurface deposit feeders. However, the Shannon's Diversity and Ecological Stress Indices indicated that the macrozoobenthos in the study area was in a state of equilibrium. Changes in the zoobenthos may result from several factors, such as an increase in water temperature, sediment re-deposition under wind-induced waves and the plowing of bottom sediments by walruses during their foraging.