Program

Sub-arctic and polar region has faced to one of the most serious reductions of saturation degree (omega) of CaCO₃ in the world. The reduction of sea ice in the Arctic Ocean, which has progressed more rapidly than previously predicted, has the potential to cause multiple environmental stresses, including not only acidification but also warming. For acidification, the saturation horizon in the subarctic North Pacific has become the shallowest not only for aragonite but also calcite (~150m) in the world’s pelagic ocean (Wakita et al., 2013). Observations by time-series sediment trap experiments and model simulations have both helped to clarify the impact of environmental stressors on the dynamics of marine organism processes and biogeochemical cycles. In this presentation, we focus on the western Arctic, which has experienced the most rapid retreat of sea ice in the Arctic Ocean, and the western subarctic North Pacific, where under-saturation of CaCO₃ is causing problems for marine calcifiers. We will introduce a new evaluation method of acidification using micro X-ray computer tomography (MXCT) for marine calcifiers and represent their rapid response associated with seasonal change in omega condition from the western subarctic North Pacific (maybe from the Arctic Ocean, too). We estimated the carbonate density of marine calcifier especially planktic foraminifera and pteropods by MXCT. As a result, the remarkable reduction (~40%) of planktic foraminifera's carbonate density was observed during winter season from the western North Pacific. In terms of pteropods, the result of genetic analysis shows a potential warning under the progressed acidification in future.

Reference:

Wakita et al., 2013 Biogeosciences, doi:10.5194/bg-10-7817-2013