Local primary production hotspot in the coastal waters of Southampton Island, Nunavut, Canada, in summer 2019

The marine region surrounding Southampton Island, northwestern Hudson Bay, Canada supports relatively large populations of marine mammals and seabirds. However, little information exists about primary production at the base of the marine food web. We estimate phytoplankton primary production from data collected around Southampton Island during August 2019 and consider the influence of physical and biological factors in explaining observed spatial variations. Differences in physical characteristics around the island, including ice conditions and surface stratification strength, resulted in differences in phytoplankton bloom stage. On average, the integrated euphotic zone phytoplankton production around Southampton Island was approximately 1.5 times higher than previous estimates for neighboring basins Hudson Bay and Foxe Basin. This difference was largely driven by tidal and wind-mixing along the constricted waterways of Frozen Strait and Roes Welcome Sound supporting a local hotspot of phytoplankton production, which was more than double that around the island and more comparable to estimates for the productive Hudson Strait. This research highlights the potential role of coastal hotspots and their contribution to regional primary production estimates, and the important role of stratification-disrupting processes in driving spatial variability in summertime primary production and, possibly, bloom phenology in Arctic areas.