Program

To quantify driving factors of the seasonal variation of aragonite saturation state (ΔΩarag) in the North Yellow Sea (NYS), a shallow marginal sea of the western North Pacific, where acidification-sensitive bivalve molluscs are of major ecological and economic importance, we revisited carbonate parameters and ancillary data obtained in the NYS in spring, summer and autumn in 2011. The bottom-water ΔΩarag values were -0.11 ± 0.27 from May to July and -0.40 ± 0.16 from July to October. As we reported earlier, very low Ωarag values of 1.13 to 1.40 dominated the bottom waters in October. From summer to autumn, changes of salinity-normalized dissolved inorganic carbon (ΔnCT) and alkalinity (ΔnAT) were the two most important contributors to the ΔΩarag. The contribution rates were calculated as 69 ± 20% (ΔnCT) and 26 ± 23% (ΔnAT) respectively from July to October. The contributions of ΔT were estimated as 5 ± 7% from July to October, while the contributions of ΔS were negligible (0.6 ± 0.6% from July to October. Further decomposition of ΔnCT from July to October showed that ΔnCT was enhanced by the changes of acid carbon (ΔAC) due to organic matter remineralization which increased the DIC/TA ratio, thus decreased Ωarag. Considering the IS92a scenario for CO2 emissions and the global warming by the year 2100, the NYS Ωarag would decline by 35-56% in surface waters (decreasing from 2.60 ± 0.42 to 1.14 ± 0.10 in May, 2.96 ± 0.20 to 1.92 ± 0.13 in July and 2.60 ± 0.22 to 1.51 ± 0.10 in October) and by 48-63% in bottom waters (decreasing from 1.85 ± 0.15 to 0.68 ± 0.20 in May, 1.75 ± 0.27 to 0.91 ± 0.19 in July and 1.41 ± 0.31 to 0.65 ± 0.30 in October) by the end of this century. Therefore, surface waters will remain supersaturated with respect to aragonite, but most of the bottom waters will be always aragonite-undersaturated. This change will bring much stresses on the local benthic fauna community.