The disturbance of aquatic ecosystems due to metal pollution from various sources such as industrial and domestic, cause loss of biodiversity as well as increases the bioaccumulation and magnification of toxicants in the food chain. The objective of the present investigation was to evaluate the effect of selenium on several physiological activities of Anabaena ambigua, Anabaena subcylindrica, Nostoc commune, Nostoc muscorum, Spirogyra sp, Spirulina sp. To carry out this research work, the algal strains were obtained from various sources. A standard initial inoculum of the isolated algal species were inoculated to culture flasks. The culture flasks were supplied with various concentrations (0.1, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mg/L) of selenium. At the end of the incubation period 10 ml of sample was taken and centrifuged at 6000 rpm for 15 minutes and the pellets were used for measurement of the various experimental parameters. The results show that, the lower doses of selenium had stimulatory effects on total chlorophyll, total protein, total carbohydrate, total starch and total free amino acids of all the tested algal species. All the biochemical parameters of the tested algal strains were gradually decreased in a manner dependent on the metal concentration in the culture medium. The inhibitory and stimulatory effects of either of the used heavy metals depends on concentration. Different organisms, however, have different sensitivities to the same metal and the same organisms may be more or less damaged by different metals.
