Assessment of metal pollution and bioaccumulation of metals by edible bivalve Polymesoda erosa in the Zuari Estuary, west coast of India.

The mangrove sediment cores from middle and upper Zuari Estuary were studied for grain size, organic carbon, total and bioavailable metals (Fe, Mn, Zn, Pb) to evaluate the metal enrichment and pollution, along with the bioaccumulation of metals by edible bivalve Polymesoda erosa to understand the toxicity of metals. The distribution of metals varied between middle and upper estuary and was attributed to difference in metal source, hydrodynamics and/or post-depositional behavior. The pollution indices viz., contamination factor and pollution load index revealed metal pollution at both middle and upper estuary. Speciation of Mn, Zn and Pb indicated their bioavailability in sediments, and the application of screening quick reference table and risk assessment code suggested possible harmful effects of Mn on biota. The concentration of metals in Polymesoda erosa was more than the standard permissible limit, at both middle and upper estuary indicating metal toxicity to Polymesoda erosa and human health.