In the investigation interactions of 12 pesticides with 37 strains of fresh water algae were studied in an effort to determine something of the variability in responses of fresh water algae to the variety of pesticides in use or projected to be used in the future. Three interactions were investigated. One was the toxicity of the pesticides to these algae. Another was the sorption of several of the pesticides by some of the species of algae. The third was the possibility that some of the pesticides can be degraded by action of algae. In general it was found that sensitivity of algae to pesticides varied greatly with the strains tested. Sorption of methoxychlor appeared to be mainly physical, since much of the methoxychlor sorbed was exchangeable. The butoxyethyl ester of 2,4-D (2,4-DBE) was not sorbed to a significant extent by two green algae tested, and sorption of carbaryl was very slow. Malathion can be degraded by algae in the presence of light. One breakdown product, malathion monoacid (beta form), appeared as the malathion was being degraded, and later disappeared.

Prepared by Department of Biology, University of Alabama, University (Tuscaloosa), Alabama, under grant no. R800371. Tables. Includes bibliographical references (pages 37-40).