Synergistic effect of abalone and macroalgae on carbon storage in a co-culture ecosystem

Shellfish are vital food sources that fix carbon within the shell and potentially remove marine dissolved carbon dioxide. Bivalves accelerate atmospheric carbon dioxide absorption at low and medium stocking densities, while the role of gastropods fed with macroalgae remains unclear. Here, we used mesocosm experiments to quantify the carbon storage potential of the gastropod abalone in monoculture and in co-culture with the macroalgae Gracilaria. Results showed that abalone monoculture acts as a source of atmospheric carbon dioxide, whereas the co-culture functions as a carbon dioxide sink. This transformation arose from higher net community productivity and the greater quantity of recalcitrant carbon in the co-culture system. When co-cultured, abalones and macroalgae exhibited synergistic effects on carbon storage due to abalones’ fertilization effect and the interaction between micro- and macroalgae. These findings reveal the role of gastropods in carbon storage, further facilitating the understanding of the marine carbon cycle. Co-culturing abalone with the seaweed Gracilaria turns the system from a carbon dioxide source into a carbon sink, as mesocosm experiments show higher community productivity and more stable carbon sediment than in abalone monoculture.