The response of the biogeographic distribution of the copepod Calanus glacialis to a changing Arctic marine environment

The Arctic marine environment has been undergoing dramatic change in the past few decades, especially in terms of sea ice loss and ocean warming, which may modify the phenology of marine plankton and have potential cascading impacts on upper trophic levels. Here, we seek to understand how the biogeographic distribution of an Arctic endemic copepod species, Calanus glacialis, may respond to substantial inter-annual variability in ocean circulation, ocean temperature, sea ice, and its phytoplankton prey. We use a copepod individual-based model that is coupled to an ice-ocean-ecosystem model to simulate temperature- and food-dependent life history development for C. glacialis from 1980 to 2014. Annual biogeographic distributions of successfully diapausing C. glacialis individuals are analyzed in conjunction with four critical factors in copepod development: reproduction timing, growth season length, ambient temperature and food conditions. Model results agree with observed biogeographic distributions that show C. glacialis is a shelf and slope species and cannot colonize the vast majority of the central Arctic basins. Both capital- and income-breeding reproductive strategies are implemented in the model by inferring initial egg release timing from the occurrence of two primary production blooms (i.e. ice algal and phytoplankton blooms), in order to test the hypothesis of the impact of timing match-mismatch between emergence/reproduction of C. glacialis and snow melt, ice retreat, and availability of food on C. glacialis population success.