资源环境科技发展态势分析平台

We measured the carbonate system (between 2015-2018) in an isolated and a well-connected temperate estuary, both known for shellfish growth. We evaluated endmember model estimates of inorganic carbon, alkalinity, pH, mineral saturation states (Ω_a), and pH sensitivity (βDIC). We find winter conditions are estimated within observational uncertainty. Spring-summer primary productivity elevates observed pH and Ω_a above theoretical lines, beyond uncertainty. Both estuaries are sensitive in winter and likely to experience rapid pH changes with increased inorganic carbon inputs. Summer pH sensitivity is reduced by productivity and is least sensitive in the mid-salinity region. We estimate carbon increased by up to 49 µmol kg^-1 since the pre-industrial period resulting in significant decreases in pH (0.2) and Ω_a (0.5). The largest pH decrease occurred outside the minimum buffer zone, at higher salinities where carbon increase was greatest. The largest pH decrease occurred in winter, but the largest Ω_a decrease in summer.