Impact of chromium and tin on a nitrogen-fixing cyanobacterium Anabaena doliolum: interaction with bivalent cations

The toxicity of chromium and tin on growth, uptake of NO3- and NH4+, nitrate reductase and glutamine synthetase activity of Anabaena doliolum, and its interaction with bivalent cations, viz. Ca2+, Mg2+, Mn2+, Ni2+, Co2+, and Zn2+, has been studied. Some interacting cations, viz. Ca, Mg, and Mn, substantially antagonized the toxic effects of chromium and tin with reference to growth and nutrient (NO3- and NH4+) uptake in the hierarchical sequence Ca greater than Mg greater than Mn, whereas the sequence of hierarchy was Mn greater than Mg greater than Ca for nitrate reductase and glutamine synthetase activity of A. doliolum. A synergistically inhibitory pattern of interaction was noted for all the parameters, viz. growth, uptake of NO3- and NH4+, nitrate reductase and glutamine synthetase activity of A. doliolum, when Ni, Co, and Zn were used in combination with test metals in the growth medium. These bivalent cations followed the synergistic inhibition sequence Ni greater than Co greater than Zn and potentiated the toxicity of test metals in the N2-fixing cyanobacterium under study.