Heavy metal monitoring using Nerita crepidularia-mangrove mollusc from the Vellar estuary, Southeast coast of India

Abstract

ObjectiveTo estimate levels of the heavy metals such as Fe, Al, Mg, Mn, Cd, Cu, Pb, Zn, Cr and Ni in sediment, shell and soft tissues of the mangrove gastropod Nerta crepidularia (N. crepidularia) in mangroves at Vellar estuary, Southeast coast of India for the period of January 2007 to December 2007 covering four seasons. MethodsTo estimate the trace metal content, samples were digested (1g) with conc. HNO3 and conc. HClO4 as 4:1 and analysed by Optical Emission Spectrophotometer (Optima 2100DV). ResultsThe order of accumulation was Fe> Al> Mg> Mn> Cd> Cu> Cr> Zn> Ni> Pb. The variation in the accumulation of metals in sediment was due to their geographical location. The degree of accumulation of trace metals in the animal tissues was as follows: Fe> Al> Mg> Mn> Cd> Cu> Cr> Zn> Ni> Pb. The higher concentrations of metals in the monsoon season could be due to the heavy inflow of freshwater, which brought lot of effluents from irrigation channels and municipal drainage. The results of ANOVA showed a positive significant relationship between sediment and tissues in their metal concentration. Shells also had some practical advantages, the shell size and weight along with the age are important factors which determined bioaccumulation. The concentrations of Fe, Cd, Ni and Pb in shells were found to be 88.54-176.46, 0.34-0.76, 2.44-14.58, 0-0.22 μg/g, respectively. ConclusionsSince N. crepidularia accumulates high concentrations of heavy metals, in general, than the ambient environment and Cu & Mn, in particular, it may be used as a biomonitor of certain heavy metals in mangrove environment.