Species composition comparisons and relationships of Arctic marine ecoregions

In the context of rapid climate change, a better understanding of the Arctic Ocean (AO) biodiversity patterns is of paramount importance. Here, we integrated and quality controlled the distribution records of well-represented marine taxa from OBIS and GBIF, from shallow (0–200 m) to deeper environments (>200–500 and > 500 m), across fifteen Marine Ecoregions of the World (MEOW) of the AO. We qualitatively compared patterns of species richness and unique species along those ecoregions, and based on species compositions: (i) assessed ecoregions validity by statistically comparing composition differences; and (ii) determined the relationships between ecoregions. We found less significant differences between ecoregion species compositions at greater depths suggesting a highest homogeneity of deeper environments and that the MEOW system, originally defined for shallow water (0–200 m), does not represent well the organization of deep-sea Arctic biodiversity. However, at shallower depths, some regions such as the Canadian and Greenland ecoregions neither showed clear species composition differentiation. At all analyzed depths, Arctic ecoregions cluster in two groups differentiating Eurasian and American ecoregions, respectively. At shallower depths, however, Siberian ecoregions tended to group highlighting their specific environment and more isolated waters. Our results suggest that AO biodiversity patterns and distribution match the paths and influence of the main oceanic currents entering from the Atlantic and Pacific. We identified the Siberian Arctic and the Canadian Arctic to be data scarce highlighting the need for sampling in these regions and mobilization of data to public repositories. This study helps to better understand the organization of the AO biodiversity and to guide future biodiversity assessments and management activities.