| Autor(es): |
Tonietto, Alessandra Emanuele
[1]
;
Lombardi, Ana Teresa
[2]
;
Henriques Vieira, Armando Augusto
[2]
;
Parrish, Christopher C.
[3]
;
Choueri, Rodrigo Brasil
[4, 5]
Número total de Autores: 5
|
| Afiliação do(s) autor(es): | [1] Univ Fed Sao Carlos, Dept Chem, BR-13565905 Sao Carlos, SP - Brazil
[2] Univ Fed Sao Carlos, Dept Bot, BR-13565905 Sao Carlos, SP - Brazil
[3] Mem Univ Newfoundland, Dept Ocean Sci, St John, NF - Canada
[4] Univ Fed Sao Paulo, BR-11060001 Sao Paulo - Brazil
[5] Univ Santa Cecilia, Dept Ecotoxicol, BR-11045907 Sao Paulo - Brazil
Número total de Afiliações: 5
|
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 (C-L) 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 C-L was for Cd, but the greatest affinities were for Cu and Zn. In the 10-3 kDa fraction, higher C-L 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. (C) 2013 Elsevier Ltd. All rights reserved. (AU) |