Benthic carbon demand and community structure across the Pacific Arctic continental shelves

Abstract

High latitude continental shelves are experiencing rapid environmental change. The Pacific Arctic, which includes the northern Bering and southern Chukchi Sea continental shelves, is undergoing warming temperatures, reductions in sea ice, and changes to the marine ecosystem. Fieldwork was conducted across the northern Bering and southern Chukchi Sea continental shelves in June 2017 and June 2018 on the R/V Sikuliaq. The overall objective of this dissertation was to characterize benthic community structure, function, and carbon demand in the Pacific Arctic to serve as baselines for assessing impacts of environmental change. Spatial patterns of macrofauna and meiofauna were characterized, including abundances, biomass, composition, and vertical distribution within the sediment. Polychaete structure and function were assessed in detail by identifying polychaetes to family level and assigning each a functional guild based on feeding mode, motility, and feeding structures. Nematodes were identified to genus level and characterized by feeding type and life-history strategy. Clusters of polychaete functional guilds and nematode genera assemblages were similar and occupied different general regions within the Pacific Arctic: northern Bering Sea, Bering Strait, offshore Chukchi Sea, and coastal Chukchi Sea. These polychaete and nematode assemblages were associated with different depositional and food environments, characterized by grain size and the amount and quality of sediment organic matter. In addition, metabolic and carbon demand of dominant macrofaunal were estimated based on oxygen consumption rates. Species-specific rates suggest that shifts in macrofaunal community composition in the region will impact benthic carbon demand. Overall, the research presented here provides critical baseline data for benthic community structure, function, and carbon demand in the Pacific Arctic and can be used to evaluate change and constrain region-specific ecosystem models, especially in the context of a rapidly changing environment.