Coming home - Boreal ecosystem claims Atlantic sector of the Arctic

Highlights: • Marine ecosystems of the European Arctic homogenise with those of the North Atlantic. • The biological messages of the Atlantification are expressed on all trophic levels. • The change is rather slow and quantitative towards more complicated food webs. • Neonative taxa are reappearing at sites, from where they retreated during the LGM. • Floating plastic debris may serve as a new way of transport for expanding boreal taxa. The Atlantification of the European Arctic has been an increasingly discussed topic in polar science over the past two decades. The alteration of local marine ecosystems towards a more temperate state and the appearance/range expansion of subarctic-boreal species at higher latitudes is a complex phenomenon induced mainly by the changing properties of Atlantic water (AW) transported from the south. Areas under the direct influence of AW experience biological Atlantification of their communities on all trophic levels, resulting in the growing complexity of arctic food webs. Here, besides summarising the main documented messages of biological Atlantification, we take a critical view on the threat posed on Arctic marine communities. We take into account the formation of the Arctic marine fauna, as well as the nature of (re)colonisation of Arctic sites by boreal organisms when evaluating the extent of the issue. We take a look at the history of Arctic colonisations by boreal organisms in an attempt to identify 'neonative taxa returning home'. We also highlight the role of floating plastic debris as an 'instrument from the toolbox of the Anthropocene' aiding the distribution of marine taxa.