COMPARISON OF THE PECHORA SEA BENTHIC COMMUNITIES’ TROPHIC STRUCTURE ON CLAY-SILT AND SANDY-SHELL SUBSTRATE

Abstract

Changes in the structure of benthic communities are increasingly observed in the modern global environment. They are driven by natural processes and anthropogenic factors, including climate change. The shallow Pechora Sea, characterized by high freshwater discharge, is particularly sensitive to such changes. Biodiversity and biomass of benthic organisms are traditionally used to describe communities, but changes at the level of trophic relationships, which underlie ecosystem interactions, play a key role in assessing ecosystem resilience. In this study, we investigated the trophic structure of two types of benthic communities in the feeding area of a recovering Atlantic walrus (Odobenus rosmarus rosmarus) population near Vaigach Island. Based on literature data and analysis of stable carbon and nitrogen isotopes, the trophic position and feeding type of mass species of macro- and megabenthos invertebrates were determined. Deposit-feeding holothurians and suspension-feeding bivalve molluscs dominated the sandy-shell substrate. In silty substrates, there is a higher level of organic sediment, a greater biomass of benthic organisms, a greater diversity of deposit-feeders, and the predominance of suspension-feeding bivalves. Large mobile predators, including the alien snow crab, are present at both stations and are competitors of walruses for food resources, predominantly mollusks. The obtained results provide a scientific basis for further studies of the trophic structure of the Pechora Sea, including monitoring of food chain dynamics and assessment of ecosystem stability under conditions of ongoing environmental changes.