Executive Summary : | The study aims to understand the implications of metal toxicity through bioavailability in sediments and bioaccumulation in benthic biota in tropical estuaries of Maharashtra, west coast of India. In estuaries, river and sea water confluence which induces various biogeochemical processes. The intertidal regions of estuaries often lead to the development of mudflat and mangrove sub-environments due to the deposition of fine sediments. The sub-environments act as sink and/or source for pollutants. Metal is one of such pollutants introduced in estuaries by means of natural and human-induced activities whose concentration has been enhanced by several times through anthropogenic means. The metals bound on the sediment surface can be desorbed by variations in salinity, pH, Eh, ionic composition, etc. The mobilization of metals from sediments to overlying water or pore water increases their bioavailability. The biota prefers ingestion of essential metals (Fe, Mn, Zn, Cu, Ni and Co) for their body functioning. However, the accumulation of essential and non-essential metals (Hg, Pb, Cd and As) above the threshold limit can induce toxicity to biota. The consumption of biota contaminated with metals can eventually transfer toxicity to humans. The metal toxicity can force the biota to migrate and also, affect their diversity. It decreases the availability of fish catch and influences the fishermen community's socio-economic life. Maharashtra has witnessed tremendous industrialization and urbanization in the proximity to estuaries in the last three decades. The generation of metal waste through industries and other human-induced activities has increased the level of bioavailable metals in the estuaries of Maharashtra. This has caused an overexposure of bioavailable metals to benthic biota. Therefore, it is crucial to determine metal bioavailability and bioaccumulation to understand the toxicity of metals to biota, and the implications of metal toxicity on socio-economic life of humans. The sediment and associated benthic biota will be collected from estuaries of Maharashtra (Ulhas, Patalganga, Amba, Kundalika, Savitri, Vashishti, Vaitarna, Shastri and Vaghotan estuaries) subjected to anthropogenic metal waste discharge. Sediment samples will be used for grain size, total organic carbon and total metal analysis. The metal speciation will be studied to quantify its chemical forms and to understand the metal source, bioavailability, mobilization, and toxicity. Also, metals in soft tissues of benthic biota will be studied to determine metal toxicity in the form of DNA damage and oxidative stress. The data will be processed using statistical software and interpreted to determine a relationship between the metal bioavailability and bioaccumulation. The project outcome will decide the need for awareness programs, regular monitoring and assessment of the environment, and management strategies to improve the living standards of the fishermen's community. |