Global warming is forcing rapid change to Canada’s marine Arctic icescape and its associated ecosystem, while the increasing ice-free season is supporting an ever-increasing industrial presence in the North. With over two thirds of Canada’s coastline being located in the North and the fact that near shore waters represent some of the most productive Arctic regions, there is a need to improve our understanding of marine ecosystem processes in the sensitive Arctic coastal zone. The marine region around Southampton Island, northwest Hudson Bay (Nunavut), encompasses one of Canada’s largest summer and winter aggregations of Arctic marine mammals, providing multiple ecosystem services. This biological hotspot has supported local human habitation for millennia with confirmed Dorset, Thule, and Sadlermiut occupation sites. The region has also been a marine mammal management focus of Fisheries and Oceans Canada (DFO) for decades and supports two sea bird sanctuaries, yet we know surprisingly little of the region’s oceanography, productivity or biological community below these top trophic levels. This fact highlights a major management risk, severely limiting our ability to understand and predict changes to this unique and productive marine ecosystem. Adding complexity to this risk are pressures posed by the ongoing climate changes and an increasing industrial presence. Therefore, we undertook an oceanographic study called the Southampton Island Marine Ecosystem Project (SIMEP), funded by the MEOPAR Network of Centres of Excellence (NCE), Canada Foundation for Innovation through the Churchill Marine Observatory (CMO), Research Manitoba, Natural Science and Engineering Research Council of Canada (NSERC) ship time, BiodivERsA Belmont Forum, and individual research grants, Fisheries and Oceans Canada (DFO), and individual and international research grants from participants from USA, UK, and Norway.

The SIMEP network assumed a bottom up driven ecosystem, hypothesizing that the hotspot can be explained by:

• Winter pre-conditioning of surface waters associated with large polynyas that form along the western coasts of Foxe Basin and Hudson Bay. Also known as ice factories, these polynyas produce dense salty brine that can sink, ventilating deeper waters while associated mixing replenishes surface nutrients and therefore, primary production.

• Tidal and wind-driven mixing along shallow near shore as well as shoaled and constricted waterways of Rose Welcome Sound, Frozen Strait and Fisher Strait. Some of the world’s largest tides are observed in Hudson Bay and as they move water back and forth across these areas, currents and mixing intensify, increasing water mass exchange and thus nutrient supply and advective flux in the area.

• East and north of Southampton Island, water masses originating in Atlantic (via Hudson Strait) and Pacific (via Foxe Basin) oceans are mixed and modified, and greatly influence production as large inventories of new nutrients are imported to the region.

To test these hypotheses, we assembled a network of University and government scientists seeking to obtain a food web-based understanding of the ecosystem.