Seawater acidification has the potential to disrupt the balance of coastal ecosystems and may pose a significant threat to mariculture activities, particularly shellfish farming. Our study aimed to investigate the regulation mechanisms of seawater pH and aragonite saturation state (Ω_arag) in a typical marine ranch in summer, with a focus on the influence of temperature, sea-air CO₂ exchange, and biological factors. The results suggested that the rise in temperature led to a decrease in surface and bottom seawater pH. Nevertheless, the temperature effect had a relatively minor impact on seawater Ω_arag. The process of sea-air CO₂ exchange exerted little influence on both seawater pH and Ω_arag on a monthly scale. Biological activities were considered to be the primary drivers of changes in both surface and bottom seawater pH and Ω_arag. These findings should contribute to identifying the causes of seawater acidification in the coastal marine aquaculture areas, and providing a scientific basis for predicting coastal seawater acidification trends and formulating environmental management policies.

carbonate system, ocean acidification, aragonite saturation state, mariculture