Ocean acidification on carbonate chemical disruption and its implications for marine calcifiers and shellfish farming

Mollusc aquaculture is a lucrative business experiencing tremendous output growth in Europe and beyond. In recent years, there has been discourse over the extensive environmental advantages of this method of food production. An area of concern in Mollusk Aquaculture (MA) is the generation of calcareous shells (CaCO3). The formation of mollusc shells has occasionally been characterized as a reservoir for atmospheric CO2, as it sequesters carbon in a solid crystalline state. More comprehensive carbonate chemistry modeling, incorporating simultaneous variations in seawater CO2, pH, soluble inorganic carbon, and overall alkalinity, indicates that calcification is a net CO2 supply to the atmosphere. The discourse surrounding the inclusion of MA respiration in carbon footprint modeling suggests that more comprehensive knowledge is necessary before incorporating shellfish farming into carbon trading systems and footprint assessments. This study demonstrates that regional variations in the marine carbonate ecosystem can influence the quantity of CO2 emitted per unit of CaCO production. The carbonate chemistry modeling indicates that a coastal mussels farm in southern Portugal emits approximately 0.3 g of CO2 per gram of CaCO3 shell produced. In contrast, a similar farm on the coastline of the Baltic Ocean would generate up to 34% more CO2 per gram of CaCO3: CaCO3 g-CO2. This regional heterogeneity must be considered if MA is incorporated into future carbon pricing systems and the manufacturing expansion strategy.