Assessment on seasonal acidification and its controls in the Muping Marine Ranch, Yantai, China

Abstract

Ocean acidification has emerged as a major challenge affecting the development of the marine aquaculture. Seasonal variations of seawater pH and aragonite saturation (Ωarag) were investigated in the Muping Marine Ranch, Yantai. The results showed that the seasonal variations of pH and Ωarag were distinct. The temperature exerted opposite effects on pH and Ωarag and played a dominant role in pH variation, while limited role in Ωarag. The air-sea exchange had a syntropic effect on pH and Ωarag but less impact on their seasonal variations. Biological activities affected seasonal variations of surface seawater pH and Ωarag, but they largely canceled each other out with other non-temperature effects; while bottom seawater Ωarag was mainly controlled by biological respiration in summer. This study demonstrates that pH is primarily controlled by seasonal temperature changes, whereas Ωarag would be a better indicator for ocean acidification caused by non-temperature processes.