Effect of Nickel on Freshwater Cyanobacteria Under Stress Condition

Heavy metals occur in immobilized form in sediments and as ores in nature. Due to various human activities like ore mining and industrial processes, the natural biogeochemical cycles are disrupted causing increasing deposition of heavy metals in terrestrial and aquatic environment. Heavy metals even at low concentration cause toxicity to humans and other forms of life. The toxicity of metal ion is owing to their ability to bind with the protein molecules and to prevent replication of DNA and thus subsequent cell division. The metal of concern in this case is nickel. With increasing environmental awareness and legal constraints being imposed on discharge of effluents, a need for cost effective alternative is essential. Cyanobacterial biomass has emerged as an alternative for developing economic and ecofriendly waste treatment process. Effect of chlorophyll on heavy metal nickel, metal uptake by free living and immobilized cyanobacterial cells along with pH variation was studied. The cell morphology of metal treated Cyanobacteria was studied by SEM. It was observed that Ni uptake increased from 10mg/l upto 200 mg/l. Moreover, metal absorbance by free cyanobacterial cells was higher than that of immobilized cells.