Toxicity of ionic copper to the freshwater microalga Scenedesmus acuminatus (Chlorophyceae, Chlorococcales)

• Published in: Phycologia (Oxford) Vol. 46; no. 1; pp. 74 - 78
• Main Authors: Lombardi, Ana Teresa, Hidalgo, Thais Moreira dos Reis, Vieira, Armando Augusto Henriques, Sartori, Antonio Luiz
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 01.01.2007; Taylor & Francis Ltd
• Subjects: Algae; bioavailability; Cells; Chlamydomonadales; Chlorococcales; Chlorophyceae; Chlorophyll; Copper; ecotoxicology; Environmental conditions; Free copper; freshwater; Freshwater ecology; Genotype & phenotype; median effective concentration; Metabolites; Metal concentrations; Microalgae; phenotype; Phenotypic plasticity; Scenedesmus; Scenedesmus acuminatus; specific ion electrodes; Toxicants; Toxicity; Toxicity testing
• ISSN: 0031-8884; 2330-2968; 2330-2968
• DOI: 10.2216/06-40.1

A.T. Lombardi, T.M.R. Hidalgo, A.A.H. Vieira and A.L. Sartori. 2007. Toxicity of ionic copper to the freshwater microalga Scenedesmus acuminatus (Chlorophyceae, Chlorococcales). Phycologia 46: 74-78. DOI: 10.2216/06-40.1 Metal ecotoxicity testing with microalgae is subject to interferences such as change in bioavailable metal fraction by excreted metabolites. Moreover, high metal loads are usually necessary for obtaining 50% effect concentration (EC50) values based on cell number or chlorophyll a. Thus, sensitive parameters, which promptly respond to low dissolved metal variations at environmentally relevant concentrations, are much needed. The genus Scenedesmus, a coenobium-forming freshwater microalga, is cosmopolitan and inhabits pristine and contaminated waters. The present investigation addressed cellular phenotypic alterations in Scenedesmus acuminatus (Largerheim) Chodat 1902 caused by the presence of copper. Copper toxicity to the alga was investigated under laboratory-controlled conditions using a concentration range of 10 −8 mol l −1 to 10 −3 mol l −1 total dissolved Cu 2+ , thus including environmentally relevant concentrations. Free Cu 2+ concentrations were determined using an ion-selective electrode calibrated with a metal ion buffer. The phenotypic plasticity of S. acuminatus was measured as the number of cells per coenobia and found to be readily affected at low copper concentrations. Under healthy conditions (10 −8 mol l −1 total dissolved Cu 2+ , 10 −11 mol l −1 free Cu 2+ ) S. acuminatus formed eight-celled coenobia, whereas at 10 −7 mol l −1 total dissolved Cu 2+ (3 × 10 −10 mol l −1 free Cu 2+ ) these were absent and at 10 −5 mol l −1 total dissolved Cu 2+ (5 × 10 −8 mol l −1 free Cu 2+ ) free cells were predominant. Chlorophyll a synthesis was affected by 5 × 10 −8 mol l −1 free Cu 2+ or higher. EC50 (3.3 × 10 −5 mol l −1 free Cu 2+ ) was obtained using chlorophyll a values after 96-h exposure to the toxicant. The number of cells per coenobia was a more sensitive parameter than chlorophyll a to assess Cu toxicity, and at concentrations that may be encountered in the environment.