LEAD INHIBITION OF CHLOROPHYCEAN MICROALGAE1

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Abstract
SUMMARY: The effects of lead on the growth of 9 microalgae representing 4 chlorophycean genera were investigated in axenic laboratory cultures. Variations in sensitivity to lead existed among the algae tested with availability of phosphate often limiting growth. Under conditions in which phosphate was growth limiting at pH 6.2, Chlorella pyrenoidosa Chick, C. ellipsoidea Gerneck, C. vulgaris Beij. Scenedesmus sp. (IUCC 1591).Sc. Obtusiusculus Chodat and Selenastrum capricornutum Printz first showed toxicity at 0.5 mg·l−1 pb. Two planktonic Scenedesmus spp. And an Ankistrodesmus sp. Were more tolerant, developing toxicity at 1 mg· l−1 Pb. The relationship of phosphate supply to Pb toxicity was investigated with S. capricornutum and Sc. Obtusiusculus. Al pH 8.0, Selenastrum developed toxicity at 3 mg·l−1 pb either with or without phosphate. When phosphate supply was growth‐limiting, 6 times as much pb (i.e., 3 vs. 0.5 mg l−1 was required to demonstrate toxicity with Selenastrum at pH 8.0 as opposed to pH 6.2 Sc. Obtusiusculus was inhibited at 0.5 mg· l−1 pb in phosphate‐limiting medium and developed toxicity at 1 mg·l−1 in media containing phosphate. Control of colonial morphology with Sc. Obtusiusculus was inhibited. Phosphate availability as well as pH would seem to be important factors determining lead toxicity with some algae.