Impact of elevated environmental pollutants on carbon storage in mangrove wetlands: A comprehensive review

Mangrove wetlands are vital blue carbon sinks within the global carbon cycle, contributing approximately 10 % of the total organic carbon buried in coastal marine environments. However, rapid urbanization and industrialization discharge pollutants such as heavy metals, microplastics, organic contaminants, and oil spills, threatening these carbon and biodiversity functions. In this review, synthesizing 38 global studies reveals that heavy metals (e.g., Hg, Pb, Cd, Cr, Zn, Ni, As) reduce sediment organic carbon by 0.57–8.06 % and increase CH₄ emissions by 90–150 μg g⁻¹ d⁻¹ by microbial alterations and impairing normal growth and development of mangrove plants. Microplastics diminish carbon stocks by 1–12 % through impaired photosynthesis and sediment destabilization, while organic pollutants (i.e., PBDEs, PAHs) inhibit plant growth and microbial carbon processing. Oil spills reduce photosynthetic capacity by more than 50 %, accelerating biomass loss. These impacts collectively destabilize mangrove carbon storage capacity, a key climate mitigation function. We propose evidence-based mitigation strategies, including pollution regulation of land-sea discharge pathways, restoration using resilient species (e.g., Avicennia marina), and community-led conservation programs. Urgent interdisciplinary collaboration is needed to address multi-pollutant interactions and safeguard interconnected blue carbon ecosystems (salt marshes, seagrass beds) under intensifying anthropogenic pressure.