Effects of commercial scale bivalve aquaculture on the microbial carbon pump: implications for climate change mitigation

The ocean, the world's largest carbon pool, plays a critical role in regulating the global climate. Within this system, the microbial carbon pump (MCP) is a key mechanism for long-term carbon sequestration, converting organic carbon into diverse and structurally complex dissolved molecules that persist in the environment. Despite the dramatic expansion of bivalve aquaculture in recent decades, its contribution to carbon sequestration through the MCP remains poorly understood and understudied. This article critically assesses the impact of bivalve aquaculture on the carbon cycle, particularly its role in enhancing the MCP. Bivalve aquaculture influences the carbon cycle in several ways. First, it increases dissolved organic carbon (DOC) in surrounding waters through direct excretion by bivalves and enhances primary productivity, particularly in oligotrophic waters. These changes boost microbial biomass and may potentially accelerate the production of recalcitrant dissolved organic carbon (RDOC), a key component of long-term carbon storage; however, increased DOC release and microbial activity do not by themselves demonstrate RDOC production, and direct evidence from bivalve aquaculture is currently lacking. Second, intensive bivalve aquaculture alters phytoplankton community structure, shifting dominance from diatoms to cyanobacteria and picophytoplankton. These smaller phytoplankton groups tend to release more RDOC into the environment compared to diatoms and microphytoplankton, further contributing to carbon sequestration. By elucidating the mechanisms through which bivalve aquaculture enhances carbon sequestration via the MCP, this article provides valuable insights for developing sustainable bivalve fisheries and aquaculture management strategies. Such strategies can harness the potential of bivalve aquaculture to mitigate climate change impacts while supporting global food security.