Glacier troughs as biodiversity and abundance hotspots in Arctic and subarctic regions

Arctic and subarctic Ecologically and Biologically Significant Areas usually comprise strong pelagic-benthic coupling. Currents, nutrient recycling, primary production, as well as excretion from zooplankton and fish occurring in the water column (pelagic) all contribute to carbon export at depth which, in turn, is exploited by animals living on the seafloor (benthic). On Arctic and subarctic shelves, this export is limited by shallow depths, but is greater in deeper areas with warmer nutrient-rich waters. Hence, the advection of deep ocean water in the numerous glacial troughs crossing the continental shelves likely provides favourable habitats for pelagic and benthic organisms. In contrast to submarine canyons, the importance of glacial troughs for harbouring biodiversity hotspots remain largely unknown, especially in Arctic regions. Here, we use large datasets comprising seafloor mapping and imagery, acoustic-trawl surveys, paleoceanography, and moorings to test two hypotheses: 1) glacial troughs allow deep waters to flow onto continental shelves, creating hotspots of abundance and biodiversity for pelagic and benthic organisms; 2) changes in hydrography, sea-ice, and productivity related to climate change may result in a decoupling between pelagic production and benthic habitats and biodiversity loss in some Arctic areas. As a case study transposable to other Arctic and subarctic regions, this project first focuses on observations from Baffin Bay and the Labrador Sea to develop a bio-physical model forecasting the impacts of climate change on deep-water habitats. It will then identify deep-water biodiversity hotspots at a panarctic scale and support the implementation of Protected Areas at northern latitudes.