Carbon chemistry: carbonate systems

摘要

Both natural processes and human activities affect seawater calcium carbonate saturation state (Ω_(arag)), while the mechanisms are still far from being clearly understood. This study analysed the seawater surface Ω_(arag) during summer and winter in Jiaozhou Bay (JZB), China, based on two cruises observations performed in January and June 2017. The ranges of Ω_(arag) values were 1.55～2.92 in summer and 1.62～2.15 in winter. Regression analyses were conducted to identify the drivers of the change of Ω_(arag) distribution, and then the relative contributions of temperature, mixing processes and biological processes to the spatial differences in Ω_(arag). were evaluated by introducing the difference between total alkalinity (TA) and dissolved inorganic carbon (DIC) as a proxy for Ω_(arag). The results showed that biological processes were the main factor affecting the spatial differences in Ω_(arag), with relative contributions of 70% in summer and 50% in winter. The contributions of temperature (25% in summer and 20% in winter) and the mixing processes (5% in summer and 30% in winter) were lower. The increasing urbanization in offshore areas can further worsen acidification, therefore environmental protection in both offshore and onshore is needed.