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.

Large-scale Lyngbya wollei (Cyanobacteria, Oscillatoriales) infestations are increasing throughout the USA and globally and causing significant obstruction of water resource uses. Decision makers and stakeholders encountering this nuisance organism often seek management options. Many approaches to L. wollei management may be ineffective or not applicable to specific field sites. Chemical control with United States Environmental Protection Agency registered algaecides has shown to be effective, although the specific formulation, concentration, and application frequency can all govern efficacy. This study summarizes results from a long-term and adaptive management program on extensive L. wollei infestations in three central Alabama, USA reservoirs (Lay Lake, Jordan Lake and Lake Mitchell) managed by Alabama Power Company. Multiple treatment strategies including numerous algaecides, combinations and addition of surfactants were used in attempts to control the nuisance cyanobacterium and preserve multiple beneficial functions of the resource. Ultimately, operational shift toward one technology, a double-chelated copper algaecide with surfactants and emulsifiers (Captain ® XTR) resulted in more efficient and economical control. There were significant (P < 0.05) decreases in historic L. wollei acres requiring treatment through time on each reservoir. Throughout this study period, a 51.4, 88.1 and 94.7% percent decrease in total nuisance acres treated was realized on Lay Lake, Jordan Lake and Lake Mitchell, respectively. The large-scale and long-term dataset presented herein, covering multiple candidate treatment programs, provides valuable information to guide management decisions on other water resources impacted by L. wollei infestations.