Climate change impact on seaweed meadow distribution in the North Atlantic rocky intertidal

The North-Atlantic has warmed faster than all other ocean basins and climatechange scenarios predict sea surface temperature isotherms to shift up to600 km northwards by the end of the 21st century. The pole-ward shift hasalready begun for many temperate seaweed species that are important intertidalfoundation species. We asked the question: Where will climate change have thegreatest impact on three foundational, macroalgal species that occur alongNorth-Atlantic shores:Fucus serratus,Fucus vesiculosus,andAscophyllum nodo-sum? To predict distributional changes of these key species under three IPCC(Intergovernmental Panel on Climate Change) climate change scenarios (A2,A1B, and B1) over the coming two centuries, we generated Ecological NicheModels with the program MAXENT. Model predictions suggest that these threespecies will shift northwards as an assemblage or “unit” and that phytogeo-graphic changes will be most pronounced in the southern Arctic and the south-ern temperate provinces. Our models predict that Arctic shores in Canada,Greenland, and Spitsbergen will become suitable for all three species by 2100.Shores south of 45°North will become unsuitable for at least two of the threefocal species on both the Northwest- and Northeast-Atlantic coasts by 2200.If these foundational species are unable to adapt to the rising temperatures,they will lose their centers of genetic diversity and their loss will trigger anunpredictable shift in the North-Atlantic intertidal ecosystem.