Ocean acidification limits temperature-induced poleward expansion of coral habitats around Japan
1Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Japan
2Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba, Japan
3Environmental Physics Group, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland
4School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, Alaska, USA
5Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland
6Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
Abstract. Using results from four coupled global carbon cycle-climate models combined with in situ observations, we estimate the effects of future global warming and ocean acidification on potential habitats for tropical/subtropical and temperate coral communities in the seas around Japan. The suitability of coral habitats is classified on the basis of the currently observed regional ranges for temperature and saturation states with regard to aragonite (Ωarag). We find that, under the "business as usual" SRES A2 scenario, coral habitats are projected to expand northward by several hundred kilometers by the end of this century. At the same time, coral habitats are projected to become sandwiched between regions where the frequency of coral bleaching will increase, and regions where Ωarag will become too low to support sufficiently high calcification rates. As a result, the habitat suitable for tropical/subtropical corals around Japan may be reduced by half by the 2020s to 2030s, and is projected to disappear by the 2030s to 2040s. The habitat suitable for the temperate coral communities is also projected to decrease, although at a less pronounced rate, due to the higher tolerance of temperate corals for low Ωarag. Our study has two important caveats: first, it does not consider the potential adaptation of the coral communities, which would permit them to colonize habitats that are outside their current range. Second, it also does not consider whether or not coral communities can migrate quickly enough to actually occupy newly emerging habitats. As such, our results serve as a baseline for the assessment of the future evolution of coral habitats, but the consideration of important biological and ecological factors and feedbacks will be required to make more accurate projections.