Factors affecting the algicidal and algistatic properties of copper.

Data from laboratory studies are presented to show that, whereas five different sources of copper appear to be equally effective as toxic agents for algae, the medium in which toxicity tests are carried out has a great influence on the toxicity of copper. A technique of subculture is described for determining whether a concentration of a chemical is algicidal, algistatic, or nontoxic in action against a specific alga, and demonstrations are given of tests with algae illustrating each class of action.