The presence of algae mitigates the toxicity of copper‐based algaecides to a nontarget organism

Abstract

Copper-based algaecides are routinely applied to target noxious algal blooms in freshwaters. Standard toxicity testing data with copper suggest that typical concentrations used to control algae can cause deleterious acute impacts to nontarget organisms. These "clean" water experiments lack algae, which are specifically targeted in field applications of algaecides and contain competing ligands. The present research measured the influence of algae on algaecide exposure and subsequent response of the nontarget species Daphnia magna to copper sulfate and an ethanolamine-chelated copper algaecide (Captain®). Significant shifts (p < 0.05) in D. magna 48-h median lethal concentration (LC50) values were found when algae were present in exposures along with a copper salt or a 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 × 10 , and 5 × 10 cells/mL algae treatments, respectively. Larger shifts were measured with copper sulfate exposures, although Captain was less toxic to D. 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 nontarget organisms. Environ Toxicol Chem 2018;37:2132-2142. © 2018 SETAC.

Bench-scale assessment of three copper-based algaecide products for cyanobacteria management in source water

“…Nonetheless, the increase is consistent with the trend observed by other researchers [1,4]. Bishop et al [2] attributed the trend to the mode of action in ethanolamine-chelated copper algaecide being more selective toward cyanobacteria than non-target species.…”

Controlling Lyngbya wollei in three Alabama, USA reservoirs: summary of a long-term management program

“…The formulation also results in increased internalized copper into L. wollei biomass which is significantly correlated with control (Bishop et al 2018a) and less likely to desorb back into the water (Bishop et al 2018b). The ethanolaminechelated copper in the formulation is innately less toxic to nontarget organisms, and the rapid/sustained sorption further decreases copper availability to water-column species (Wagner et al 2017;Bishop et al 2018c). There is no water use restrictions following application of Captain XTR (e.g., irrigation, swimming/other recreation, livestock watering, potable source water), and therefore compatible with the diverse use objectives of the reservoirs (SePRO 2014).…”

Early Toxic Effects of Cd²⁺ on Photosynthetic Activity of Six Freshwater Algae Species

“…Algae are primary producers in aquatic ecosystems. Damage to algae cells and bioaccumulation of heavy metals in algae will negatively influence higher trophic levels and finally endanger human beings [19]. Although algae had bioremediation potential in Cd 2+ -polluted areas [20], Cd 2+ revealed obvious toxicity to algae in most cases.…”