Protecting mud crabs from pollution by microplastics, per- and polyfluoroalkyl substances, polycyclic aromatic hydrocarbons, pesticides, and heavy metals in mangroves

Mangroves are essential ecosystems for coastal protection, carbon sequestration, biodiversity, and food production. In particular, mud crabs, with an annual global landing of over 100,000 metric tons, are crucial for the economic livelihoods and food security of millions of small-scale fishers in Southeast Asia. Here, we review the impact of pollutants on mud crab populations in mangrove ecosystems, with emphasis on pollutant sources, toxic effects on crabs, and remediation using microbes and biochar. Pollutants include microplastics, per- and polyfluoroalkyl substances, pesticides, polycyclic aromatic hydrocarbons, and heavy metals. Pollution originates from agricultural runoff, industrial discharges, mining activities, urbanization, and domestic waste. We present the use of biochar for pollutant remediation and enhancing carbon sequestration. We observe that heavy metals, pesticides, and microplastics induce oxidative stress, disrupt antioxidant defense mechanisms, and impair the growth, reproduction, and survival rates of mud crabs. Microbial bioremediation can remove more than 90% of polycyclic aromatic hydrocarbons. Biochar application reduces by 87% the bioavailability of heavy metal in contaminated soils.