Spatial and seasonal patterns of benthic food web structure in the Northern Barents Sea using stable isotope analysis

Abstract

Phytoplankton detritus constitutes the main food source for benthic invertebrates in the Northern Barents Sea, and high spatial and seasonal variability of this food source is likely to control patterns of benthic trophic relationships. Benthic invertebrates were collected during Nansen Legacy cruises in December and August, 2019 at 6 stations spanning 76-81°N in the Northern Barents Sea and were later analyzed for stable isotopes of carbon and nitrogen (δ13C, δ15N). Our results are used to describe the mega- and macro-benthic food web structure and to explore latitudinal changes in isotopic signatures during Summer. We find the highest trophic level is occupied by deposit-feeding echinoderms (e.g. Molpadia borealis) as well as predatory molluscs (Buccinum hydrophanum, Rossia sp.), shrimp (Sabinea septemcarinata, Sclerocrangon ferox) and demersal fish (Leptagonus decagonus). Lower trophic levels are a mix of suspension- and deposit-feeders that are highly variable in isotopic composition. Some taxa (Ophiacantha bidentata, Sabinea septemcarinata) have more enriched δ13C values at higher latitudes, while others (Boreogadus saida, Buccinum hydrophanum, Ctenodiscus crispatus) exhibit the opposite trend. In general, there is less isotopic variability (in both δ13C and δ15N) of predatory taxa than of deposit feeders, supporting the hypothesis that environmental conditions affecting the detrital baseline are most important for taxa directly reliant on this food source. Future analyses will focus on detailed comparisons of taxa across all seasons and the entire latitudinal transect.