Effect of Heavy Metals on the Desmodesmus quadricauda Isolated from the River Nile, Egypt

Abstract

The wastewater of Iron and Steel Factories contains high level of metallic ions, especially Fe which represents the main component of the waste followed by Zn, Cu, Pb, Ni, Hg, Co, Cd, Mn and Cr. Bioassay experiment were achieved to determine the effect of industrial waste of Iron and Steel Factories at Helwan on growth, chlorophyll a and photosynthetic activity of one alga (Desmodesmus quadricauda) which represent one of the most dominant phytoplankton in the Nile River. The growth rate (counting and chlorophyll a) was more sensitive than photosynthetic activity. A synergistic effect was found between the trace metals of the waste. The toxicity of the waste decreased gradually by time. The EC50 of the growth rate values indicated that, the inhibitory effect of waste on growth of the alga showed slight decrease during the four days incubation, the phenomenon was enhanced on the 5th day when the EC50 reached to 46.84. The EC50 values of waste inhibited chlorophyll a showed a significant increase till the 3rd day when the EC50 reached to 47.79. The EC50 values had considerably decreased to 32.78 on the 4th day then abruptly increase to 47.32 on the 5th day. Industrial waste showed a significantly reduced the photosynthetic activity at 48% and 60% concentration. The maximum decreased observed on the 4th day and represented by 62.92% and 79.02% below their control values, respectively.