Comparative assessment of Ni and As(III) mediated alterations in diazotrophic cyanobacteria, Anabaena doliolum and Anabaena sp. PCC7120

The comparative effects of nickel (Ni2+) and arsenite (As(III)) on two diazotrophic cyanobacterial species were investigated in terms of photosynthetic attributes. Both metals demonstrated inhibitory effects on growth, pigments (chl a and phycocyanin) and photosystem II (PS II) photochemistry. However As(III) exerted severe effects as compared to Ni reflected by (1) reduced growth (2) significant inhibition of chl a and phycocyanin, (3) reduction in maximum photochemical efficiency of PSII and (4) depleted plastoquinone pool, thus suggesting it as more toxic. Moreover, comparative analysis of two species also demonstrated interspecies variation in terms of stress adaptive strategies reflected through higher sensitivity of Anabaena doliolum over Anabaena PCC7120. Thus the study recommends application of A. PCC7120 as biofertilizer in Ni and As(III) contaminated paddy fields. Key words: Anabaena sp. PCC7120, Anabaena doliolum, Nickel, As(III), maximal photochemical yield (Fv/Fm).