Based upon surveys conducted in November 2012 and June 2013, the distribution and dynamics of aragonite saturation state ($Ømega$arag) were investigated in the southern Yellow Sea (SYS) of China. In summer, surface water $Ømega$arag ranged from 2.1–3.8 and enhanced biological production fueled by Changjiang River freshwater input increased $Ømega$arag to 3.8 in the southern SYS. However, subsurface water $Ømega$arag was \textless 2.0 in the central SYS. During autumn, surface water $Ømega$arag was 2.0–2.9, lower than that in summer due to ventilation between surface and low $Ømega$arag (1.0–1.4) subsurface waters in the central SYS. Community respiration and/or aerobic remineralization dominated low $Ømega$arag in subsurface waters, while water stratification influenced the level and scale of acidity accumulation. By the end of this century, waters with $Ømega$arag \textgreater 2.0 could disappear from the SYS with increasing atmospheric CO2, while bottom waters $Ømega$arag may become undersaturated due to the impact of eutrophication.
