Relative Tolerance of Mat-forming Algae to Copper

Mat-forming algae are major constituents of the aquatic weed flora. Excessive growths of these macrophytic algae, which occur alone or in association with vascular plants, can limit recreational activities, restrict culture and harvest activities in fish culture ponds, reduce flow and clog intakes in water conveyance systems, and reduce habitat diversity (Lembi et al. 1988). The major method used for the control of these and other types of algae is the application of copper, either as copper sulfate or copper chelates. Experiences of commercial applicators suggest that mat-forming algal genera differ in their susceptibility to copper, but to this point data to support or confirm these observations have not been available. This study documents the relative tolerance of the common, weedy mat-forming green algae Hydrodictyon, Oedogonium, Pithophora, Rhizoclonium, and Spirogyra to copper. In addition, the copper tolerance of the cyanobacterial (blue-green algal) mat-forming Oscillatoria was assessed. The frequency with which this organism occurs in Indiana and probably other parts of the midwest has increased over the past few years.