Metal pollution in the aquatic environment and impact on flora and fauna

Aquatic ecosystems, especially lentic, are the major sink to receive the municipal and industrial waste and wastewater. This wastewater contains a variety of hazardous substance including heavy metals (HMs), biochemical oxygen demand ions, acids, pesticides, dyes, etc., along with high content of total dissolved solids, and chemical oxygen demand. Among these, HMs are considered to be potential toxic due to their nondegradability nature. HMs like Cr, Cd, Ni, Cu, Co, Zn and some metalloids like As and Hg are some common toxicants that deteriorate the quality of water bodies. HMs gets accumulated easily in the living organisms and has potential to biomagnify at a higher trophic level in the food chain. Both aquatic flora and fauna gets affected in the presence of HMs. In aquatic plants, HMs cause growth inhibition, lipid peroxidation, reduction in photosynthetic rate and alterations in different metabolic activities. Inhibition in enzymatic activities, enhanced generation of reactive oxygen species, damages in DNA and central nervous system are the major adverse effects produced in aquatic animals by HMs.