Vacuum Effect: A Redistribution Process of Organic Carbon Mediated by Bivalve Farming

Bivalve farming affects the spatiotemporal distribution of organic carbon deposition to benthic environments, potentially altering ecosystem functioning. In this study, spatiotemporal patterns of benthic organic carbon flux of a bottom-based Manila clam (Ruditapes philippinarum) farm were estimated for a 1 year farming cycle using a carbon flux model coupled to a two-dimensional (2-D) hydrodynamic (MIKE-3) and a clam dynamic energy budget (DEB) model. The simulated flux was compared to the sediment total organic carbon (TOC) and contribution of biodeposits to sediment TOC based on stable isotope signatures. The outputs of the model illustrated a clear "vacuum effect" with increased carbon flux within and near the farming area (deposition area) and reduced flux outside the farm (depletion area), which could also correspond to changes in sediment TOC. Moreover, the contribution of biodeposits to the carbon flux was overall higher compared to that of biodeposits to sediment TOC, indicating a loss of biodeposits from deposition to storage in the sediment. This study highlights the role clam farming plays in the dynamics of organic carbon by linking vertical fluxes with sediment TOC, which addresses the current knowledge gaps related to the carbon footprint in coastal bivalve aquaculture systems.