This talk is based on recent discoveries regarding spatial biogeography of Phaeocystis spp. via molecular monitoring in the North Sea, North Atlantic, Fram Strait and Central Arctic Ocean. The cosmopolitan micro algal genus Phaeocystis plays a crucial role in the ecology and biogeochemistry in nearly all marine ecosystems. It harbors three bloom- and colony-forming species, two cold and one `warm` water species. All three species: P. pouchetii in the Arctic, P. antarctica in the Southern Ocean and P. globosa in cold/warm temperate and tropical waters, are known to be key species within their habitats. P. pouchetii and P. globosa are believed to be species complexes. P. globosa has been physiologically widely studied, indicating eurythermal features due to a broad temperature span from -4 °C to more than +20 °C. This arises the question if present day populations of P. globosa could be dispersed via oceanic current regimes into the Arctic Ocean which is known to be an open oceanic system. Does P. globosa have the guts to enter the Arctic?