The North Yellow Sea (NYS) is a western North Pacific continental margin of major ecological and economic importance, where monthly/bimonthly declines of subsurface-water pH and aragonite saturation state occur from spring to autumn. To quantify controlling processes of these variations, we employed a Redfield-based methodology to decompose the monthly/bimonthly declines of subsurface-water aragonite saturation state observed in 2011 and 2013. Results showed that the contributions of the NYS cold water mass community respiration, calcification and temperature changes to the monthly declines of aragonite saturation state from spring to summer were 84 ± 9%, 30 ± 16%, and -13 ± 10%, while the contributions of the community respiration, CaCO3 dissolution and temperature change to the bimonthly decline of aragonite saturation state from late summer to autumn were 103%, -5% and 1%. Our results also suggested that the NYS cold water mass net calcification rate declined to nearly zero when the seawater aragonite saturation state reached a critical level of 1.5-1.6. This is much different from a recently published coral reef case observed by Bradley et al. (2018, Science), which suggest that the seawater aragonite saturation state threshold of net calcification rate reaching zero should be 2.9-3.0 in coral reef systems. Thus the relations between biogenic CaCO3 dissolution rate and seawater aragonite saturation state may vary in different systems. Much remains to be investigated in order to quantitatively evaluate the effect of ocean acidification on marine CaCO3 cycles. Based on a future scenario projection to predict the possible impacts of future CO2 changes on seasonal variations in the NYS cold water mass aragonite saturation state, we suggested that the very low aragonite saturation state values of <1.5 may exist all year round in the NYS cold water mass in the 2050s, bringing much stress on local benthic fauna community.