Clam farming generates CO2: A study case in the Marinetta lagoon (Italy)

► We assessed the importance of the farmed Ruditapes philippinarum as CO2 sink/source. ► Biomass and calcimass were established by monthly harvests in 2009. ► CO2 fluxes produced by the clam were higher than CO2 sequestered in shell formation. ► Clam farming seems a significant additional source of CO2 to seawater.