Changes in benthic communities in Blagopoluchiya Bay (Novaya Zemlya, Kara Sea): the influence of the snow crab

Until recently, the Kara Sea was a stable ecosystem unaffected by alien species invasions. However, at the beginning of the twenty-first century, the snow crab (Chionoecetes opilio) was detected. Studies conducted between 2013 and 2022 in Blagopoluchiya Bay (Novaya Zemlya Archipelago, Kara Sea) provided an opportunity to observe the establishment of a population of this species and its influence on benthic communities. Various sampling methods, such as trawl and grab surveys, as well as video observations, were used to study two main seabed habitats, one in the deep inner basin and the other at the sill at the bay’s exit. The study revealed significant changes in benthic ecosystems, including declines in integral benthic characteristics such as abundance, biomass, diversity, and shifts in dominant species. The response of megabenthos and macrobenthos varied between habitats, but in general, there was a sharp decline in the abundance of large bivalves and brittle stars. The observed changes were not related to environmental variability but most likely to the abundance and size structure of the snow crab. The taxonomic and size structure of the benthos changed as crab individuals increased in size, and the changes were faster and more pronounced in the area with higher crab abundance. These findings raise concerns about the potential long-term effects of the snow crab invasion on the Kara Sea ecosystem, including reduced biodiversity and changes in food webs.