Ecotoxicological effects and uptake of metals (Cu +, Cu 2+, Mn 2+, Mo 6+, Ni 2+, V 5+) in freshwater alga Scenedesmus quadricauda

Abstract

The ecotoxicological effects of six metals (Cu +, Cu 2+, Mn 2+, Mo 6+, Ni 2+, V 5+) expressed as growth inhibition, respiratory rate, and total chlorophyll, chlorophyll a and b contents by alga Scenedesmus quadricauda were determined. Besides these parameters, the uptake of tested metals by alga was determined by using RXFA. On the base of the calculated EC 50 values, the following rank orders of inhibition were arranged: for algal growth: Cu 2+>Cu +>Ni 2+>V 5+-Mo 6+>Mn 2+; for total chlorophyll content: Cu 2+>Ni 2+>Cu +>Mn 2+>V 5+>-Mo 6+; for chlorophyll a content: Cu 2+>Ni 2+>Cu +>V 5+>Mn 2+>Mo 6+; for chlorophyll b content: Cu 2+=Cu +>Ni 2+>Mn 2+>Mo 6+>-V 5+. Respiratory rate was measured for metal concentrations corresponding with EC 50 values for growth inhibition by oxygen electrode. The most intensive respiration was observed for V 5+ and less for Mo 6+. When the uptake of metals from the medium was determined, in the highest percentage were uptaken Ni 2+ (20%), Cu 2+ (17,6%) and Mn 2+ (15,19%). Other metals were only uptaken in the amounts lower than 5.5 % from the metal concentration added into the cultivation medium. For uptake determination as well as for respiratory rate measurements, concentrations corresponding with calculated EC 50 values for growth inhibition were used.