Dataset for: The presence of algae mitigates the toxicity of copper-based algaecides to a non-target organism

Copper-based algaecides are routinely applied to target noxious algal blooms in freshwaters. Standard toxicity testing data with copper suggest typical concentrations used to control algae can cause deleterious acute impacts to non-target organisms. These “clean” water experiments lack algae, which are specifically targeted in field applications of algaecides and contain competing ligands. This research measured the influence of algae on algaecide exposure and subsequent response of the non-target species Daphnia magna to copper sulfate and an ethanolamine-chelated copper algaecide (Captain®). Significant shifts (P< 0.05) in Daphnia magna 48-h LC50 values were found when algae were present in exposures along with a copper salt or chelated copper formulation. Copper sulfate 48-h LC50 values shifted from 75.3 to 317.8 and 517.8 µg Cu/L whereas Captain increased from 353.8 to 414.2 and 588.5 µg Cu/L in no algae, 5 x 105 and 5 x 106 cells/mL algae treatments, respectively. Larger shifts were measured with copper sulfate exposures, although Captain was less toxic to Daphnia magna in all corresponding treatments. Captain was more effective at controlling Scenedesmus dimorphus at most concentrations, and control was inversely proportional to toxicity to D. magna. Overall, incorporating target competing ligands (i.e., algae) into standard toxicity testing is important for accurate risk assessment, and copper formulation can significantly alter algaecidal efficacy and risks to non-target organisms.