Harnessing the microbial carbon pump: prospects and challenges for coastal carbon sequestration

The Marine Microbial Carbon Pump (MCP) theory proposes a novel mechanism for long-term carbon sequestration in the ocean, wherein microbial processes convert labile dissolved organic carbon (LDOC) into recalcitrant dissolved organic carbon (RDOC). This review synthesizes recent advancements in technologies aimed at enhancing carbon sinks based on the MCP, with a specific emphasis on coastal ecosystems. Through a structured literature review, this paper evaluates the mechanisms of action, key environmental regulatory factors, and negative emissions technologies associated with utilizing the MCP to bolster the ocean carbon sink. Research indicates that the MCP significantly contributes to the global ocean carbon reservoir, with coastal systems accounting for 40–60% of RDOC production. However, this contribution is constrained by nutrient availability, temperature, light, and anthropogenic pollutants that suppress microbial activity. Current strategies for enhancing carbon sinks encompass nutrient addition, microbial community engineering, and integrated ecological engineering approaches, such as artificial upwelling and macroalgae cultivation. Major challenges remain—particularly low RDOC conversion efficiency (<5%), inadequate monitoring methods, and ecological risks such as harmful algal blooms—that must be addressed before MCP technologies can be deployed at scale. The MCP framework offers a novel and useful perspective for understanding the ocean carbon cycle and presents a potential pathway that requires further validation for achieving negative emissions. Among the strategies reviewed, integrated artificial upwelling with macroalgae cultivation appears most immediately actionable, with pilot studies demonstrating 15–25% increases in sediment carbon storage, though verification at environmentally relevant scales is still required.