Trophic ecology of epibenthic communities exposed to different sea-ice concentrations across the Canadian Arctic Ocean

Abstract

Sea ice is one of the most critical environmental drivers shaping primary production and fluxes of organic inputs to benthic communities in the Arctic Ocean. Fluctuations in organic inputs influence ecological relationships, trophic cascades, and energy fluxes. However, changes in sea-ice concentration (SIC) induced by global warming could lead to significant shifts in trophic interactions, ultimately affecting the functioning of Arctic food webs. Despite the increasing concern over the need to understand benthic species and food web responses to rapid sea-ice loss, few studies have addressed this topic so far. Using multiple niche metrics based on stable isotopes, this research examined the trophic ecology of epibenthic communities in areas with different SIC across the Canadian Arctic Ocean. We found that trophic niches varied according to complex interactions between environmental conditions, resource supply, and biotic pressures such as predation and competition. Our results highlighted a lower isotopic richness (i.e., shorter food chain length and niche width) in low and high SIC areas, suggesting homogeneity of resources and a low diversity of food items ingested by individuals. In contrast, a higher isotopic richness (i.e., broad niche) was observed in the moderate SIC area, implying higher heterogeneity in basal food sources and consumers using individual trophic niches. Finally, our findings suggested a lower isotopic redundancy in areas with high SIC compared to low and moderate SIC. Overall, our results support the idea that sea ice is an important driver of benthic food web dynamics and reinforce the urgent need for further investigations of declining sea ice cover impacts on Arctic food web functioning.