Benthic Macrofaunal and Megafaunal Distribution on the Canadian Beaufort Shelf and Slope




Nephin, Jessica

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The Arctic region has experienced the largest degree of anthropogenic warming, causing rapid, yet variable sea-ice loss. The effects of this warming on the Canadian Beaufort Shelf have led to a longer ice-free season which has assisted the expansion of northern development, mainly in the oil and gas sector. Both these direct and indirect effects of climate change will likely impact the marine ecosystem of this region, in which benthic fauna play a key ecological role. The aim of this thesis was to expand the current baseline knowledge of benthic fauna in the interest of developing the capacity to identify, predict and manage benthic change. The distribution of benthic macro- and megafauna was characterized utilizing community data from two recent benthic surveys on the Canadian Beaufort shelf and slope. Fauna were collected from 63 stations using box core and trawl sampling gear over the summers of 2009 through 2012 between depths of 30 and 1,000 m. Spatial patterns of abundance, biomass and α and β diversity metrics were examined. Megafaunal abundance and α diversity were elevated on the shelf compared to the slope while the macrofauna did not vary significantly with depth. Multivariate analyses illustrated that both macro- and megafaunal community composition varied more across the depth gradient than from east to west along the shelf. However the change across the depth gradient was greater for the megafauna than for the macrofauna. I proposed that megafaunal slope taxa were differentiated from shelf taxa, as faunal replacement not nestedness appeared to be the main driver of megafaunal β diversity across the depth gradient. The lack of correlation between macro- and megafauna in abundance, biomass and α and β diversity suggests that these faunal components vary at different spatial scales. These results demonstrate how separately sampling the different benthic components can yield different spatial patterns, with implications for future benthic monitoring in the region. This work contributes to the current regional baselines by providing the first comprehensive description of megafaunal distribution on the Canadian Beaufort shelf and by extending our knowledge of benthic distribution patterns deeper on the slope.



Marine ecology, Benthic ecology, Biodiversity, Macroecology, Benthic invertabrates, Canadian Beaufort Shelf