Abstract
Alaskan Arctic shelf communities are currently experiencing dramatic changes that will likely affect ecosystem functioning of Arctic marine benthic communities. Here, functional diversity based on biological traits was used to assess differences and similarities in ecosystem functioning between 2 shelf systems that are geographically close but vary in many environmental influences: the Arctic Beaufort and Chukchi Sea epibenthic communities. We hypothesized that (1) patterns of functional composition and diversity metrics reflect patterns in taxonomic composition and diversity metrics in these 2 shelf communities; and (2) patterns in functional diversity metrics are distinct between the 2 shelves. We evaluated 9 biological traits (body form, body size, feeding habit, fragility, larval development, living habit, movement, reproductive strategy, sociability) for 327 taxa in 2014 and 2015. For each trait, multiple modalities (specific expressions within a trait) were considered. Patterns in functional diversity metrics on both shelves reflected those in taxonomic diversity metrics. However, shelf communities were more similar in functional- than in taxonomic composition. Beaufort Sea communities had higher functional dissimilarity and functional evenness driven by differences in the modalities within body form, body size, larval development, and reproductive strategy. These traits primarily affect nutrient cycling, energy turnover, and recovery from disturbances, suggesting a stronger potential for future maintenance of ecosystem function, and indicating a more even use of resources in the Beaufort Sea. The combination of functional and taxonomic diversity metrics enabled a comprehensive understanding of how ecological niche space is used and how epibenthic communities function in Alaskan Arctic shelf systems.
Highlights
Arctic ecosystems are changing rapidly as the Arctic is warming twice as fast as the rest of the planet (Stroeve et al 2012), with continued decreases in sea ice extent (Carmack et al 2016) and changes in primary production (Arrigo & van Dijken 2015, Frey et al 2019)
Following previous studies on biological traits (Conti et al 2014, Kokarev et al 2017), we considered biological traits with correlation ratios > 0.1 as most representative of the variance captured by the fuzzy correspondence analysis (FCA) axes
All diversity metrics except Functional redundancy (FRed) had higher median values in the Beaufort Sea shelf community compared to the Chukchi Sea shelf community
Summary
Arctic ecosystems are changing rapidly as the Arctic is warming twice as fast as the rest of the planet (Stroeve et al 2012), with continued decreases in sea ice extent (Carmack et al 2016) and changes in primary production (Arrigo & van Dijken 2015, Frey et al 2019). Arctic benthic assemblages within the Beaufort and Chukchi Sea shelf communities are of great importance for these ecosystem processes, as they support important food webs, which can channel anthropogenic or climatic perturbations to upper trophic levels (Iken et al 2010, Divine et al 2015). These benthivorous upper trophic levels include ecologically and socially important bearded seals, walruses (Fay 1982, Oliver et al 1983), demersal fishes (Whitehouse et al 2017), crabs (Divine et al 2017), and birds (Lovvorn et al 2003). Changes in benthic assemblages within shelf communities or in the energy pathways supporting these assemblages will have effects on overall Arctic shelf ecosystem function
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