Effect of Cu 2+ on cell number and chlorophyll a content of green alga Scenedesmus obliquus

Aquatic environments are often exposed to heavy metals, this can affect aquatic organisms. The effect of Cu 2+ on cell density and chla content of  S.obliquus was studied. The algae were grown for 5 days at temperature of 2± 23  ˚c and light intensity of 300 lux on z8 medium .Copper  treatment was carried out at a concentration of 0 (control) ,2,4,,6 and 8 mgl-1. Cell counting was performed at 0,24,48,72 and 96 hours using heamocytometer and amount of chla was determined at the same hours. There was a significant difference between time and treatments (p< 0.05). The difference of cell density was significant between control and metal concentrations, 2,4 mgl-1 with 6,8 mgl-1. In control groups, the cell density and chla content were increased with time. On the other hand, the content of chla and cell number reduced with Cu2+ . The concentration of Cu2+ from 2 to 8 mgl-1 inhibited cell density from 72.09% ( 2mg.l-1 , 96 h) to 92.33% ( 8mgl-1,96 h), respectively. In the Cu2+ treatments the death of algal biomass was observed in 24 h, but there was an increase in cell numbers of S.obliquus in control and the algae were still on exponential phase at 96 h.