Seasonality of zooplankton communities in the Hudson Bay system

The strong seasonality of sub-Arctic seas needs to be considered understand their ecosystems. Hudson Bay system undergoes seasonal changes in 1) sea ice conditions, alternating between complete cover winter and open water summer; 2) river discharge, which peaks the spring influences stratification bay; 3) surface circulation that consists a weak double gyre summer cyclonic autumn. Recent studies included data collected during have shown annual primary productivity is higher than previously reported. Similarly, regional zooplankton assemblages been studied mostly late summer, possibly leading an underestimation secondary production. Here, we use five one six week-long expeditions CCGS Amundsen 2005 2018 describe mesozooplankton investigate how it depends on environmental variables. In general, small pan-Arctic boreal copepods such as Microcalanus spp., Oithona similis Pseudocalanus spp. dominated assemblages. From relative abundance Arctic-adapted Calanus hyperboreus glacialis decreased, while proportion Acartia increased. day year break-up date explained most variation Physical processes species distribution spring, lack lipid-rich autumn, especially coastal regions, suggests some top-down control. This season contrasts with other seasonally ice-covered seas. More are needed fully implications these dynamics under climate change, but this study establishes baseline against future can compared.