title: Cylindrospermopsis raciborskii (Cyanobacteria) exudates: chemical characterization and complexation capacity for Cu, Zn, Cd and Pb.
abstract: Cylindrospermopsis raciborskii is a cosmopolitan and potentially toxic planktonic Cyanobacteria that produces and exudes copious amounts of dissolved organic materials. This organism dominates the eutrophic reservoir Barra Bonita (Brazil), where it normally blooms throughout the year. This investigation focused on the characterization of such exudates analyzing their capacity to complex copper, zinc, lead and cadmium through the determination of ligand concentration (CL) and conditional stability constant (logK'ML), as well as elemental composition (C, H, N and S), the content of carbohydrates, proteins, lipids and dissolved organic carbon (DOC). The dissolved organic material was fractionated into 3 molecular weights (>30 kDa; 30-10 kDa; 10-3 kDa) and each fraction was analyzed. The results showed that in the >30 kDa and 30-10 kDa fractions carbohydrates dominate over proteins and lipids. Different CL and logK'ML were obtained for the different molecular weight fractions of the excreted organic materials, suggesting high diversity of ligands. In the >30 kDa, there were more complexing sites (CL) for Cu, but higher affinity (K') for Zn. In the 30-10 kDa fraction, the higher CL was for Cd, but the greatest affinities were for Cu and Zn. In the 10-3 kDa fraction, higher CL was obtained for Cd and Zn, while Cu and Cd had the highest strengths of association. In the environment, such diversity of ligands and strengths of association can result in a displacement of metals weakly bound to the EOM, and increase metal buffering capacity of the environment, supporting higher metal inputs before toxic effects are detected in the biota.
authors.affiliation: Department of Chemistry, Federal University of São Carlos, Via Washington Luis km 235, PO Box 676, CEP 13565-905 São Carlos, São Paulo, Brazil. Electronic address: aletonietto@gmail.com.
authors.forename: Alessandra Emanuele
authors.initials: AE
authors.lastname: Tonietto
authors.affiliation: Department of Botany, Federal University of São Carlos, Via Washington Luis km 235, PO Box 676, CEP 13565-905 São Carlos, São Paulo, Brazil.
authors.forename: Ana Teresa
authors.initials: AT
authors.lastname: Lombardi
authors.affiliation: Department of Botany, Federal University of São Carlos, Via Washington Luis km 235, PO Box 676, CEP 13565-905 São Carlos, São Paulo, Brazil.
authors.forename: Armando Augusto Henriques
authors.initials: AA
authors.lastname: Vieira
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, Canada.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Parrish
authors.affiliation: Federal University of São Paulo, Santos Campus, Avenue D. Ana Costa, 95, Vila Mathias, CEP 11060-001 Santos, São Paulo, Brazil; Department of Ecotoxicology, University Santa Cecília, Via Oswaldo Cruz, 266, CEP 11045-907 Santos, São Paulo, Brazil.
authors.forename: Rodrigo Brasil
authors.initials: RB
authors.lastname: Choueri
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000302:isolation & purification; D003300:Copper / Q000302:isolation & purification; D046891:Cylindrospermopsis / Q000737:chemistry*; D005227:Fatty Acids / Q000032:analysis; D007854:Lead / Q000302:isolation & purification; D008024:Ligands; D019216:Metals, Heavy / Q000302:isolation & purification*; D008970:Molecular Weight; D009930:Organic Chemicals / Q000737:chemistry*; D015032:Zinc / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D005227:Fatty Acids; D008024:Ligands; D019216:Metals, Heavy; D009930:Organic Chemicals; D002104:Cadmium; D007854:Lead; D003300:Copper; D015032:Zinc
keywords: Complexation capacity; Cyanobacteria; Cylindrospermopsis raciborskii; Exudates; Heavy metal