Seasonal Variability and Future Projection of Ocean Acidification on the East China Sea Shelf off the Changjiang Estuary

• Published in: Frontiers in Marine Science
• Main Authors: Guo, Xianghui, Yao, Zhentong, Gao, Ying, Luo, Yaohua, Xu, Yi, Zhai, Weidong
• Other Authors: National Natural Science Foundation of China, State Oceanic Administration
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2021
• Subjects: Ocean acidification
• Online Access: http://dx.doi.org/10.3389/fmars.2021.770034; https://www.frontiersin.org/articles/10.3389/fmars.2021.770034/full

Ocean acidification (OA) occurs universally in the world’s oceans. Marginal seas are facing more serious OA than the open ocean due to strong anthropogenic and natural impacts. This study investigates carbonate dynamics on the East China Sea (ECS) shelf off the Changjiang Estuary using field observations made from 2015 to 2019 that cover all four seasons. In the low productivity cold seasons, the water was well-mixed vertically. The coastal area and the northern ECS were occupied by water characterized by high dissolved inorganic carbon (DIC), low pH 25 (pH at 25°C), and low Ω Ar (saturation state index of aragonite), and influenced by the coastal water from the Yellow Sea (YS). However, during highly productive warm seasons, pH 25 and Ω Ar increased in the surface water but decreased in the bottom water as a result of strong biological DIC uptake in the surface water and CO 2 production by strong organic matter remineralization in the bottom water. Strong remineralization decreased pH 25 and Ω Ar by 0.18 ± 0.08 and 0.73 ± 0.35 in the hypoxic bottom water in summer, even though the bottom water remained oversaturated with respect to aragonite (Ω Ar > 1.0) during the surveys. Under the context of global OA and the strong seasonal acidification, the projected bottom water on the ECS shelf will be corrosive for aragonite by mid-century.