Taxonomic and functional patterns of macrobenthic communities on a high-Arctic shelf: A case study from the Laptev Sea

•We studied distribution of macrobenthos on 500-km transect in the eastern Laptev Sea.•Taxonomic and functional diversity and composition of macrofauna are strongly linked.•Riverine input and sedimentation regime are the main factors affected both community structure and functioning.•The benthic ecosystem exhibits long-term stability but low functional redundancy.•This makes the ecosystem potentially susceptible to a species loss or structural shifts.

The studies of functional structure of high-Arctic Ecosystems are scarce. We used data on benthic macrofauna from 500-km latitudinal transect in the eastern Laptev Sea, from the Lena delta to the continental shelf break, to describe spatial patterns in species composition, taxonomic and functional structure in relation to environmental factors. Both taxonomy-based approach and Biological Trait analysis yielded similar results and showed general depth-related gradient in benthic diversity and composition. This congruence between taxonomical and functional dimensions of community organization suggests that the same environmental factors (primarily riverine input and regime of sedimentation) have similar effect on both community structure and functioning. BTA also revealed a distinct functional structure of stations situated at the Eastern Lena valley, with dominance of motile, burrowing sub-surface deposit-feeders and absence of sedentary tube-dwelling forms. The overall spatial distribution of benthic assemblages corresponds well to that described there in preceding decades, evidencing the long-term stability of bottom ecosystem. Strong linear relationship between species and traits diversity, however, indicates low functional redundancy, which potentially makes the ecosystem susceptible to a species loss or structural shifts.