A morphometric and x-ray energy dispersive approach to monitoring pH-altered cadmium toxicity inAnabaena flos-aquae

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Abstract
Cadmium toxicity and uptake as influenced by different pH values have been studied in the freshwater cyanobacteriumAnabaena flos-aquae, using the techniques of morphometric analysis, x-ray energy dispersive analysis and atomic absorption spectrophotometry. A general reduction in cell dimension, thylakoid surface area, number and volume of polyhedral bodies, polyphosphate bodies, cyanophycin granules, lipid bodies, membrane limited crystalline inclusions, volume and number of wall layers and mesosomes was observed. These reductions were more pronounced in both acidic and alkaline medium than at pH 7.2. At 0.12 μM Cd, the uptake increased with alkaline pH values, and uptake was greater at pH 7.2 than at either acid or alkaline pHs. Lysis of cell wall at 1.18 μM Cd showed the following decreasing trend: pH 4.0 > pH 5.5 > pH 10.0 > pH 9.0 > pH 7.2. There was a total loss of lipid bodies at 1.18 μM Cd at all pH values listed. It is suggested that these techniques can be successfully employed for bioassay studies of metal toxicity to algae. In particular, cell wall lysis and loss of lipids by algae are good indicators of pH effects and metal toxicity in the aquatic ecosystem.