Harnessing mangrove phytoremediation for coastal heavy metal pollution: A chemical environmental perspective

Abstract

Mangrove ecosystems play a vital role in mitigating heavy metal (HM) contamination in coastal regions due to their unique biological and ecological characteristics. This review synthesizes current knowledge on the phytoremediation capacity of mangrove species, with a focus on their mechanisms of HM uptake, accumulation, and translocation. Various species, such as Avicennia marina, Kandelia candel, and Rhizophora stylosa, demonstrate notable bioconcentration factors (e.g., BCFroot up to 12.3 for Cd) and selective metal compartmentalization, particularly in roots, thereby minimizing translocation to aerial parts (e.g., TF as low as 0.05 for Pb). The analysis of metal concentrations across different mangrove sites worldwide reveals that sediment composition, sampling depth, and anthropogenic activities significantly influence HM distribution. Mechanistic processes including redox potential modulation, rhizosphere oxidation, and associations with microbial communities further enhance the immobilization and detoxification of metals such as Cd, Pb, Cr, Cu, and Hg. As a narrative review, this article consolidates global findings and highlights species-specific strategies (e.g., tolerance differences among Avicennia and Rhizophora) and ecological thresholds (e.g., salinity tolerance ranges of 10-35 PSU, optimal redox potential above –100 mV, and metal concentration limits beyond which growth declines). Future prospects include integrating molecular tools, designing engineered mangrove wetlands, and developing policy-driven restoration initiatives. Ultimately, mangrove-based phytoremediation contributes not only to coastal pollution control, but also to the achievement of Sustainable Development Goals (SDGs), particularly SDG 14 (Life Below Water) and SDG 13 (Climate Action), while supporting real-world applications, such as coastal restoration planning and nature-based solutions.