Characterizing Bacterial Communities in Beaufort Sea Sediments in a Changing Arctic

Reduced sea ice cover has shifted marine productivity patterns in the Arctic. These shifts affect the quality and quantity of organic matter (OM) deposited to the seafloor and available to the benthic organisms that rely on sinking material from overlying water masses for sustenance. Additionally, processes regulating the local remineralization and degradation of OM may be impacted. Sediment bacteria are the biogeochemical engineers of the benthos and play a vital role in OM and biogeochemical budgets. Although bacterial diversity and community structure can reflect local biogeochemical processes, environmental characteristics, physical disturbances, and chemical contaminants, they are largely understudied in the Beaufort Sea benthos. The overall goals of this study were to characterize broad-scale patterns in the diversity and community structure of benthic bacteria from the western Beaufort Sea into the Amundsen Gulf and to elucidate the environmental drivers of these patterns. To achieve these goals, sediment bacterial communities were characterized via the 16S rRNA gene using a next-generation DNA sequencing (NGS) approach. Diversity, community structure, and associated environmental correlates were assessed for 79 sampling sites across the Alaskan and Canadian regions of the Beaufort Sea shelf and slope to the Amundsen Gulf. Bacterial alpha-diversity exhibits overall positive correlations with depth, salinity, and δ15N and negative correlations with chl-a, chla/phaeopigments, and C/N across all sediments analyzed. Patterns of beta-diversity are not highly definitive, and bacterial communities appear to be loosely clustered with high overlap in nMDS ordination space. Overall, bacterial communities are more similar within Beaufort subregions including the Alaskan Beaufort Shelf, the Mackenzie Shelf, Amundsen Gulf, and Banks Island. Environmental variables identified as drivers of community structure differences were depth, salinity, δ15N, chl-a, C/N, and total organic carbon (TOC). As previously ice-covered Arctic waters become more accessible for human activities, particularly petroleum and gas exploration, there is an increased likelihood of contaminant exposure. Our study area included samples within and adjacent to areas with high oil and gas resource potential. In order to gain a general sense of oil biodegradation potential across the study area, bacterial community data generated were queried for putative oil-degrading taxa. Of the 14 taxa investigated, the majority were found sporadically throughout the study area, with more taxa found on the Alaskan Beaufort Shelf and the Amundsen Gulf than on the Mackenzie Shelf. Only three taxa were ubiquitously distributed across all samples.

USD: $25,000

2016-06-01 → 2018-01-01