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

Abstract

IntroductionThe accumulation of the heavy metals in aquatic organisms leads to danger effect on the aquatic food chain and endanger human health too. Heavy metals are considered the important reasons of the pollution in soil and aquatic ecosystem. The heavy metals cannot be biodegraded by micro-organisms into non-toxic or to volatile compounds as organic pollutants. Due to this reasons, these pollutants will eventually accumulate in the food chain.Industrial wastes, agricultural run-off, municipal waste and accidental spillage are the main sources of the aquatic pollution. As well as the appreciable amounts of pollutants to air come from human activity as factories and automobile exhausts may enter the aquatic water bodies through rainfall or dry fall-out. The Nile receives increasing amounts of waste discharges, from several sources, as the rivers travels northward. River pollution problems are primarily due to human activities as domestic and industrial waste discharge as well as River transportation and agricultural return flows.In the recent decades, the toxicity tests have been developed to expect the probable effect of industrial effluents on the aquatic ecosystem by using algae, crustaceans, mollusks and fishes [1,2]. The toxicity of heavy metals to phytoplankton was reviewed by Ref [3]. The toxicity of Copper and Cadmium was investigated on the alginateimmobilized algae. Ref [4] investigated the use of alginate-immobilized algae for testing the toxicity of cadmium and copper. The industrial wastes discharged on the banks of Periyar River in India were tested by using algal assays [5]. The effects of Zinc smelter waste to some diatoms were investigated by Rao and Mohanchand [6]. The effects of mercury on the cell population, chlorophyll a and photosynthesis of Dunaliella minuta was investigated by Gotsis [7]. The level of heavy metals in water and sediment was done by Sabri et al. [8] at River Tigris at Samarra impoundment (Iraq). Mingazzini [9] evaluated the different methods for quantitative toxicity of the pollutants on the River Po, Italy, by using Selenastrum capricornatum. The mutual effect of some heavy metals AbstractThe 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 EC 50 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 5 t...