The polar seas are generally ice-covered waters with highly seasonal weather conditions, temperature, formation and extent of sea ice. To date, more than 8,000 marine species are estimated to occur in these waters (5,782–Arctic;> 8,200–Antarctic). A collaboration with the Alfred-Wegener-Institut resulted in a preliminary list of marine species in the polar seas (7,710 species), collated from published documentation and made available via FishBase and SeaLifeBase. This list includes 533 species of bony fishes, 10 sharks, 17 rays, 208 vertebrates (whales, dolphins and sea birds), and at least 6,816 invertebrates and 114 plant species. This report includes the polar sea species list, their marine ecoregions, and an overview of available data on ecology, life history, and population dynamics.