title: Cellular and aqueous microcystin-LR following laboratory exposures of Microcystis aeruginosa to copper algaecides.
abstract: Microcystin release from algal cells influences use of copper-algaecides in water resources. Accurate data regarding relationships between copper-algaecide exposures and responses of microcystin-producing algae are needed to make informed management decisions. Responses of Microcystis aeruginosa were measured in terms of cellular microcystin-LR (MC-LR), aqueous MC-LR, and chlorophyll-a following exposure to CuSO4 and copper-ethanolamine. Comparisons were made between treated and untreated samples, and copper formulations. EC50s and slopes for M. aeruginosa responses to copper exposures were calculated. Algal responses followed a sigmoidal exposure-response relationship, and cellular MC-LR and chlorophyll-a were negatively related to copper concentrations. Aqueous MC-LR increased with copper concentrations, although the increase in aqueous MC-LR was not proportional to decreases in cellular MC-LR and chlorophyll-a. Cellular MC-LR and chlorophyll a declined at a greater rate than aqueous MC-LR increased. Total MC-LR was less than untreated controls following copper exposure. Differences were measured between copper formulations in terms of aqueous and total MC-LR concentrations at concentrations of 0.5 and 1.0 mg Cu L-1. Aqueous and total MC-LR were greater (10-20%) following exposure to CuSO4 compared to copper-ethanolamine one day following exposure. The positive relationship between copper concentration and aqueous MC-LR at 0.07-1.0 mg Cu L-1 demonstrates that lower copper concentrations were as effective as higher concentrations in controlling M. aeruginosa while decreasing the total amount of MC-LR, and minimizing the proportion of MC-LR released to the aqueous-phase. Results serve to support more accurate risk evaluations of MC-LR concentrations when M. aeruginosa is exposed to copper-algaecides and when it is untreated.
authors.affiliation: Department of Forestry and Environmental Conservation, 261 Lehotsky Hall, Clemson University, Clemson 29634-0001, SC, USA. Electronic address: kiwinsk@g.clemson.edu.
authors.forename: Kyla J
authors.initials: KJ
authors.lastname: Iwinski
authors.affiliation: Department of Forestry and Environmental Conservation, 261 Lehotsky Hall, Clemson University, Clemson 29634-0001, SC, USA.
authors.forename: Alyssa J
authors.initials: AJ
authors.lastname: Calomeni
authors.affiliation: Department of Forestry and Environmental Conservation, 261 Lehotsky Hall, Clemson University, Clemson 29634-0001, SC, USA.
authors.forename: Tyler D
authors.initials: TD
authors.lastname: Geer
authors.affiliation: Department of Forestry and Environmental Conservation, 261 Lehotsky Hall, Clemson University, Clemson 29634-0001, SC, USA.
authors.forename: John H
authors.initials: JH
authors.lastname: Rodgers
mesh_terms: D000605:Amino Alcohols / Q000494:pharmacology; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D003300:Copper / Q000494:pharmacology*; D019327:Copper Sulfate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005618:Fresh Water / Q000737:chemistry*; D008387:Marine Toxins; D052998:Microcystins / Q000032:analysis* / Q000378:metabolism; D046931:Microcystis / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009942:Organometallic Compounds / Q000494:pharmacology; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism
chemical_list: D000605:Amino Alcohols; D008387:Marine Toxins; D052998:Microcystins; D009942:Organometallic Compounds; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; C046504:cutrine-plus; D003300:Copper; C057862:cyanoginosin LR; D019327:Copper Sulfate; D000077194:Chlorophyll A
keywords: Copper-algaecides; Cyanobacteria; Microcystin; Microcystin release