Marine environmental chemistry and ecotoxicology of heavy metals

Metals, importantly heavy metals (HM), are the major cause of pollution in the marine environment. They are added into the marine system through various natural and anthropogenic sources such as weathering of rocks, volcanic eruptions, atmospheric deposition, domestic sewage, industrial effluents, agricultural discharge, mining, coastal construction activities, dredging, etc. In the marine system, metals enter the seawater and influence its chemistry. Different metal species are formed as they move from freshwater to seawater due to change in pH and salinity. Within the water column, biogeochemical processes govern the existence of HM in particulate or dissolved form. Some proportion of metals may get deposited in the marine sediments which are the major sink of these metals. Metals are taken up by marine biota through seawater or through food chain, which may adversely affect them by altering their abundance, diversity, and physiology. HM pollution is a serious concern due to its higher toxicity, nonbiodegradability, and tendency to bioaccumulate and biomagnify in the tissues of living organisms. It is important to quantify the toxic effect of these metals on different groups of marine organisms such as phytoplankton, zooplankton and fish, to know the extent to which marine biota is impacted by them. This would assist in taking timely measures to curb metal pollution in marine environment. The major areas impacted by metal pollution are the coastal and estuarine systems. Metal pollution indirectly affects the health of the human population, consuming fish and other seafood living in metal polluted seawater.