Comparison of Partitioning and Efficacy Between Copper Algaecide Formulations: Refining the Critical Burden Concept

Filamentous mat-forming algae are increasingly impairing freshwater resources. To restore water utility, reactive management programs often involve application of copper-based algaecides. Copper algaecide formulations can differ significantly, and this research outlined an advanced approach to evaluate formulation efficiency for controlling filamentous algae. Two common algal species ( Lyngbya wollei , Pithophora varia ) were used to assess copper internalization and adsorption as well as relation to control among copper formulations. Captain® XTR achieved control (7-day EC 85 ) of L. wollei with internal copper concentrations of 0.78 and 0.76 mg Cu/g based on chlorophyll a content or filament viability, respectively. Cutrine® Ultra achieved control of L. wollei based on filament viability only at 0.85 mg Cu/g. Internalized copper concentrations required for control following Captain XTR exposures were similar for P. varia , 0.81 and 0.95 mg Cu/g, whereas Cutrine Ultra and copper sulfate did not elicit control nor attain the critical internal copper threshold. The relationship between internalized copper and responses, among all formulations, was significant ( P