Greenhouse gas emissions from fed mollusk mariculture: A case study of a Sinonovacula constricta farming system

Expanded shellfish mariculture is an important strategy to improve global food security. However, greenhouse gas (GHG) emissions associated with mariculture are a concern when evaluating the benefits of protein production. In this study, we conducted two field campaigns in a constricted tagelus (Sinonovacula constricta) farming system (March 3-5 and April 21-23, 2021) to observe the changes in GHGs. In a routine cycle of water exchange, the CO2 fluxes varied and followed a diurnal pattern (-7.6 to 23.1 mmol/m(2)/d), which is related to changes in the concentrations of dissolved inorganic carbon (DIC) and total alkalinity (TA). Non-CO2 GHGs were significantly released (CH4: 0.1-1.0 mmol/m(2)/d; N2O: similar to 0.1 mmol/m(2)/d) during the farming period and were responsible for over 75% of the net global warming potential over a centurial period. We argue that the significant GHG emissions in the constricted tagelus farming system were mainly attributed to the farming mode, which loads many nutrients to make algae blooms for tagelus feeding and disturbs the sediment surface by water draining/bivalve activity, increasing the possibility of GHG production and emissions. We suggest improving the monoculture mode and tempering the adoption of water drainage to ameliorate the current situation. We recommend that further research in mariculture consider non-CO2 GHGs, including CH4 and N2O, to evaluate the potential of GHG emissions and their local importance.

Automated summary

Expanded shellfish mariculture is important for global food security, but it also contributes to greenhouse gas (GHG) emissions. A study on a constricted tagelus farming system found significant emissions of non-CO2 GHGs, such as CH4 and N2O, which account for over 75% of the system's net global warming potential. The farming mode, nutrient loading, and water drainage activities were identified as the main factors contributing to the emissions. Improving the farming mode and reducing water drainage could help mitigate the emissions. Further research should consider non-CO2 GHGs in mariculture.