title: Effects of two copper compounds on Microcystis aeruginosa cell density, membrane integrity, and microcystin release.
abstract: Microcystin release following Microcystis aeruginosa cell lysis after copper-based algaecide treatment is often cited as a concern leading to restricted use of algaecide in restoration of natural water resources. To examine this concern, bench-scale experiments were conducted to study responses of M. aeruginosa to 8-day copper exposures as copper sulfate and copper-ethanolamine (Cu-EA). M. aeruginosa UTEX 2385 was cultured in BG11 medium to cell density of 10(6)cells/mL with total and extracellular microcystin of 93 and 53μg/L, respectively. Exposures of copper concentration ranged from 40 to 1000μgCu/L. Cell membrane integrity was indicated by erythrosine B. In the end of experiment, total microcystin and cell density in untreated control (313μg/L and 10(7)cells/mL) was 3.3 and 10 times greater than pretreatment value, respectively. Minimum amount of copper required to reduce M. aeruginosa population within 8 days was 160μgCu/L as copper sulfate and 80μgCu/L as Cu-EA, where total and extracellular microcystin concentrations (47 and 44μg/L for copper sulfate; 56 and 44μg/L for Cu-EA) were degraded with degradation rate coefficient 0.1 day(-1) and were less than pretreatment values. Given a copper concentration at 80µgCu/L as Cu-EA, M. aeruginosa cells were intact and less microcystin were released compared to treatments at 160-1000µgCu/L, where lysed cells and relatively greater microcystin release were observed. Based on the laboratory results, a minimum amount of copper required for reducing M. aeruginosa population could decrease total microcystin concentration and not compromise cells and minimize microcystin release.
authors.affiliation: Baruch Institute of Coastal Ecology and Forest Science, Clemson University, 177 Hobcaw Road, Georgetown, South Carolina 29440, United States. Electronic address: kuot@clemson.edu.
authors.forename: Kuo-Pei
authors.initials: KP
authors.lastname: Tsai
mesh_terms: D015169:Colony Count, Microbial; D003300:Copper / Q000032:analysis / Q000633:toxicity*; D019327:Copper Sulfate / Q000032:analysis / Q000633:toxicity*; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004983:Ethanolamines / Q000032:analysis / Q000633:toxicity*; D008826:Microbial Sensitivity Tests; D052998:Microcystins / Q000096:biosynthesis*; D046931:Microcystis / Q000187:drug effects* / Q000302:isolation & purification* / Q000378:metabolism; D009942:Organometallic Compounds / Q000032:analysis / Q000633:toxicity*
chemical_list: D003470:Culture Media; D004983:Ethanolamines; D052998:Microcystins; D009942:Organometallic Compounds; C416547:copper-ethanolamine complex; C078588:microcystin; D003300:Copper; D019327:Copper Sulfate
keywords: Cell lysis; Copper; Degradation; Microcystin; Microcystis aeruginosa