Affinity and Efficacy of Copper Following an Algicide Exposure: Application of the Critical Burden Concept for Lyngbya wollei Control in Lay Lake, AL

Abstract

Accurate predictions of nuisance algae responses to algicide exposures are needed to guide management decisions. Copper sorption and responses of Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck were measured in the laboratory and two areas in Lay Lake (AL, USA) to treatments of Captain(®) XTR (SePRO Corporation; chelated copper algicide) and a sequential treatment of GreenClean(®) Liquid (BioSafe Systems, LLC; peroxygen algicide) combined with Hydrothol(®) 191 (United Phosphorus, Inc.; endothall algicide) followed by Captain XTR. Measured filament viability in laboratory exposures predicted Captain XTR alone could control L. wollei in Lay Lake, with 2 mg Cu/g algae EC75. This produced a targeted field treatment of 9.7 kg Cu/ha which was divided into three applications of 0.3 mg Cu/L as Captain XTR in the treatment areas. Laboratory and field experiments indicated treatments of Captain XTR alone and the combination treatment resulted in comparable copper sorption and responses of L. wollei. Copper adsorbed greater to L. wollei in laboratory experiments than in the treated areas of Lay Lake with comparable exposures (2 mg Cu/g L. wollei). However, responses and infused copper were similar and correlated in laboratory experiments and treated areas of Lay Lake indicating infused copper is critical for governing toxicity. Laboratory exposures as mg Cu/g algae accurately predicted the necessary algicide exposure required to attain the critical burden of infused copper and elicit desired responses of L. wollei in treated areas of Lay Lake.

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

“…L. wollei is a very resilient and adaptable cyanobacterium that is extremely difficult to control. Alabama Power Company has spent a significant amount of time focused on research into L. wollei control in these reservoirs and identifying most effective, economically feasible and ecologically appropriate solution for management (Duke 2007;Tedrow 2007;Bishop et al 2015;Calomeni et al 2015). Evaluating multiple treatment concepts, novel products/technologies and unique use patterns has helped establish an effective Alabama Power Company treatment program.…”

“…Significant differences in algaecide formulations, including those with similar listed active ingredients, have been documented (Bishop et al 2018a). Chelated copper-based algaecides are common components of L. wollei management programs and are often combined with surfactants to aid penetration (Duke 2007;Bishop et al 2015;Calomeni et al 2015). The chelation is designed to improve stability of the copper ion in solution and alter charge properties of resulting copper complexes to passively penetrate cell membranes (Stauber and Florence 1987;Straus and Tucker 1993;Mastin and Rodgers 2000).…”

“…Regimented algaecide applications, often > 5 applications per year, have been used to target infested areas of these systems for over two decades (Iwinski et al 2016). Multiple algaecide treatment programs have been researched and utilized in Lay Lake, Jordan Lake and Lake Mitchell with the goal of decreasing L. wollei biomass to preserve management objectives (Duke 2007;Tedrow 2007;Bishop et al 2015;Calomeni et al 2015). The overall goal of this research was to summarize the primary treatment programs utilized in Alabama Power Company reservoirs as well as resultant effectiveness through time.…”

Understanding Fate and Effects of Copper Pesticides in Aquatic Systems

“…concentration, duration) to non-target organisms will concomitantly be measured. Operational evaluations will investigate strategic use patterns of copper products and specifically calculate the most effective formulation to achieve desired results with lowest amounts of copper applied [44]. Furthermore, research will build on site specific fate assessments of copper in a variety of field sites in order to provide data on the weight of evidence approach in risk assessment.…”

Evaluation of copper dissipation, exposure factor, and algaecidal efficacy in an irrigation canal following pulse ‘slug’ application of a chelated copper algaecide

“…To account for these dynamic exposures encountered by algae at different downstream points, we used a factor exposure assessment where the copper concentration is multiplied by the exposure duration (Bishop et al 2017). These exposure data coupled with efficacy testing according to the mass of algae present (critical burden concept; Bishop and Rodgers 2012;Bishop et al 2015) can provide a framework to predict algaecidal efficacy in a range of canal systems based on site-specific parameters (e.g., algal biomass, type of algae, flow). This research will increase efficiency of copper use through a better understanding of exposure characteristics (e.g., formulation, duration, concentration) toward minimizing environmental load of copper while achieving management objectives.…”