title: Influence of phosphorus on copper toxicity to Selenastrum gracile (Reinsch) Korshikov.
abstract: Microalgae need a variety of nutrients for optimal growth and health. However, this rarely occurs in nature, and if nutrient proportions vary, biochemical changes can occur in phytoplankton community. This may result in modifications of zooplankton food quality, affecting aquatic food chains. Our aim was to investigate the toxicity of copper (Cu) to Selenastrum gracile, a common freshwater Chlorophyceae, at different physiological status induced by varying phosphorus (P) concentration in culture medium. Phosphorus was investigated at 2.3×10(-4), 1.1×10(-4), 2.3×10(-5), 4.6×10(-6) and 2.3×10(-6) mol L(-1) and Cu at six concentrations, ranging from 6.9×10(-9) mol L(-1) to 1.0×10(-7) mol L(-1) free Cu(2+) ions. To guarantee the cells would be in a physiological status that reflected the external P concentration, they were previously acclimated up to constant growth rate at each P concentration. Phosphorus acclimated cells were then exposed to Cu and toxicity was evaluated through population density, growth rates and chlorophyll a content. Free Cu(2+) ions concentrations were calculated through the chemical equilibrium model MINEQL(+). The results showed that higher Cu toxicity was obtained in P-limited than in P-replete cells, and that chlorophyll a/cell was higher in P-limited cells and excess Cu than in P-replete cells. This confirms the importance of microalgae nutritional status to withstand the negative effects of the trace metal.
authors.affiliation: Departamento de Hidrobiologia, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luís, Km 235, CEP 13565-905 São Carlos, SP, Brazil. Electronic address: swertsbio@gmail.com.
authors.forename: Giseli S
authors.initials: GS
authors.lastname: Rocha
authors.affiliation: Departamento de Botânica, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luís, Km 235, CEP 13565-905 São Carlos, SP, Brazil.
authors.forename: Ana T
authors.initials: AT
authors.lastname: Lombardi
authors.affiliation: Departamento de Hidrobiologia, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luís, Km 235, CEP 13565-905 São Carlos, SP, Brazil.
authors.forename: Maria da Graça G
authors.initials: Mda G
authors.lastname: Melão
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D000460:Chlorophyta / Q000187:drug effects* / Q000378:metabolism; D003300:Copper / Q000633:toxicity*; D005618:Fresh Water; D058086:Microalgae / Q000187:drug effects* / Q000378:metabolism; D010758:Phosphorus / Q000494:pharmacology*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D010758:Phosphorus; D003300:Copper; D000077194:Chlorophyll A
keywords: Acute toxicity; Chlorophyceae; Eutrophication; Free copper; Orthophosphate