PARENT SESSION
MA2 - Aquatic Toxicology
Chair: Spehar, Bob¹, ¹ U.S. EPA, Duluth, MN
Co-chair: Henry, Mary², ² U.S. Fish and Wildlife Service, Arlington, VA
8:00 AM to 12:00 PM - Monday, 18 November 2002
Room Ballroom J

(172) Toxicity of five copper-containing algaecides to selected algae and animal species.

Heatley, John¹, Murray-Gulde, Cynthia¹, Rodgers, John^*,1, ¹ Clemson University, Pendleton, SC, United States

ABSTRACT- The bioconcentrated dose of copper, rather than the aqueous concentration of copper in surrounding media, is responsible for copper's toxicity to aquatic organisms. This observation supports the concept of the Biotic Ligand Model (BLM); however, the BLM assumes that chelation of copper decreases copper toxicity for aquatic organisms. For this study, the toxicities of copper sulfate and four chelated copper algaecides (Cutrine^®-Plus, Cutrine^®-Plus (Ultra), Algimycin^® and Clearigate^®) were evaluated for three algal species (Raphidocelis subcapitata, Pseudoanabaena sp. and Pithophora sp.). Specific objectives of this study were: 1) to measure the toxicity of five copper-containing algaecides to three target algal species; and 2) to measure the critical burden of the three algaecides required to obtain control of R. subcapitata, Pseudoanabaena sp. and Pithophora sp. Algal "control" (EC₁₀₀) for R. subcapitata was achieved at aqueous concentrations ranging from 62.5 to 250 g Cu/L, and critical burdens ranged from 0.6 to 7.9 g Cu/mg algae. For Pseudoanabaena sp., EC₁₀₀s ranged from 62.5 to 125 g Cu/L, while critical burdens ranged from 0.4 to 1.8 g Cu/mg algae. Pithophora sp. was effectively controlled at concentrations ranging from 125 to 500 g Cu/L and critical burdens were achieved at dosages ranging from 0.9 to 6.1 g Cu/mg algae. Critical burdens can be used for predicting copper concentrations sufficient to control specific densities in field situations without imposing unnecessary risks for non-target species. Algal toxicity experiments using site-specific waters provide prescription treatments for specific algal species and densities, and efficient and effective algal treatment with a greater "margin of safety" for non-target species.

Key words: aquatic herbicides, algae, R. subcapitata, critical burden