Influence of pesticides on Chlorella, Chlorococcum, Stigeoclonium (Chlorophyceae), Tribonema, Vaucheria (Xanthophyceae) and Oscillatoria (Cyanophyceae)
An examination was made of the influence of atrazine, simazine, malathion and 2,4-D on total chlorophyll production by Chlorella vulgaris, Chlorococcum hypnosporum, Stigeoclonium tenue, Tribonema sp., Vaucheria geminata and Oscillatoria lutea. The herbicide 2,4-D in concentrations up to 100 mg/1 did not alter chlorophyll production by the algae. Chlorococcum was not influenced by the pesticides. When added individually, atrazine, simazine and malathion inhibited chlorophyll production at a concentration of 1 mg/l or greater except for Stigeoclonium, in which production was not influenced by 1 mg/1 simazine. Results were variable when the pesticides were present individually at a concentration of 1 μg/l. The three pesticides stimulated chlorophyll production by Chlorella when present individually at 0·1 and 0·5 μg/1. The same was true for simazine and malathion on Tribonema and Oscillaloria. A complete examination was not made for all the algae in these lower concentrations of pesticides. A significant interaction was present among atrazine, simazine and malathion. Combinations of two pesticides resulted in more inhibition, less inhibition or stimulation of chlorophyll production depending upon the concentrations used. Treatment of Vaucheria with 1 μg/1 malathion caused a production of brown crystals inside the cytoplasm, a formation of a second cell wall inside the first and distortion of gametangia developing at the time of initial treatment.