Physiological responses of the cyanobacterium calothrix parietina and green alga scenedesmus dimorphus to iron, manganese, sulphate and sulphite

ABSTRACT

The uptake of manganese and iron ions by Scenedesmus dimorphus and Calothrix parietina was significantly increased by increasing the doses supplemented to the culture media of both algae up to 10[-5]molar concentration. The ability of Scenedesmus to accumulate the two metals was greater than that of Calothrix. Higher concentrations of sulphate, sulphite and manganese ions inhibited the accumulation of total carbohydrates in the two phytoplankter cells. All iron levels stimulated synthesis of total carbohydrates in Calothrix, but inhibited it in Scenedesmus. Under all concentrations of the four pollutant salts, nitrogen secretion by the two organisms, total nitrogen and almost all nitrogen fractions were increased particularly at moderate rates. However, 10[-4] M and 300 micro g S ml[-1] of iron and sulphite attenuated the synthesis of protein N in Calothrix, Sulphate, sulphite and iron suppressed phosphorus uptake by Calothrix but stimulated it in Scenedesmus. Manganese ions at all concentrations, encouraged phosphorus uptake from nutrient media by Calothrix. Sulphite, at al concentrations lowered total phosphorus content, total soluble and total insoluble phosphorus in the two organisms, a phenomenon that was associated with marked disturbances in phosphorus metabolism. Sulphite, at all concentrations inhibited the biosynthesis of nucleic acids [RNA, DNA] in Calothrix, while its low and moderate concentrations stimulated their biosynthesis in Scenedesmus. Sulphate and manganese on the other hand, stimulated their biosynthesis in the two phytoplankters. Iron, at 10[-8] M level encouraged the biosynthesis of nucleic acids in Calothrix, whereas 10[-6] M and 10[-4]M concentrations suppressed their formation in Scenedesmus. At all levels of manganese and sulphate, the cell length and width of both organisms and the diameters of heterocyst in Calothrix were increased. At all concentrations of iron and sulphite, the cell length and width of both organisms and also diameters of heterocysts in Calothrix were decreased