Blue carbon ecosystems under pollution stress: Impacts and integrated carbon‐pollution monitoring

Abstract Coastal blue carbon ecosystems, including mangroves, seagrass meadows, and salt marshes, are globally important carbon sinks because they store organic carbon in vegetation biomass and waterlogged sediments over long timescales. However, nutrient enrichment, heavy metals, petroleum hydrocarbons, macroplastic and microplastic debris, and emerging contaminants increasingly threaten their capacity to sequester carbon. These pollutants reduce photosynthetic productivity, weaken root and rhizome systems, alter sediment redox conditions, disrupt microbial decomposition pathways, and may increase emissions of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O). This review synthesizes current evidence on how pollution alters carbon cycling across major blue carbon ecosystems, with emphasis on plant physiology, sediment stability, microbial processes, greenhouse gas (GHG) fluxes, and carbon stock permanence. It also evaluates monitoring, reporting, and verification (MRV) approaches that could integrate carbon measurements with pollutant diagnostics. In response to current methodological gaps, the review presents the Pollution‐Carbon Impact Framework (PCIF) as a conceptual decision‐support approach rather than a fully operational protocol. The PCIF is intended to guide future co‐located monitoring, indicator selection, site prioritization, and policy integration, while recognizing that standardized templates, open datasets, validated models, and Geographic Information System (GIS)‐based decision tools remain future requirements. The review concludes that reliable blue carbon accounting requires stronger integration between water‐quality governance, restoration planning, pollution control, and carbon‐credit verification.