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Other Titles: Evaluation of Trace metais and metallothionein Levels in Polychaetes collected in polluted areas in Guanabara Bay: potential use for biomonitoring
Keywords: Biodisponibilidade;  Baía de Guanabara;  Laeonereis culveri;  Metalotioneínas;  Bioavailabibity;  Guanabara Bay;  Laeonereis culveri;  Metallothioneins
Issue Date: 29-Jun-2010
Abstract: Short-term sediment test using polychaetes has been routinely used to assess marine sediment toxicity. However there are needs to develop long-term assays that measure the effects on sub-lethal endpoints, predicting impacts at population level. This study evaluated the potential use of polychaetes as indicators of metal contamination, using the determination of metal concentrations and molecular biomarkers (metalothioneins) in Laeonereis culveri (Polychaeta, Nereididae). Organisms and sediments were collected in two polluted sites located in Guanabara Bay, RJ (Jardim Gramacho e Mauá), to investigate the use of this species in environmental monitoring assessments and the influence of metal geochemical partitioning and acid volatile sulfides (AVS) in sediments on the metal bioavailability. A sequencial extraction was proposed, using in the first step an extraction in cold 6 mol L-1 HCl, corresponding to the metals simultaneously extracted to AVS (SEM), and the sediment residue was used in a second extraction, according to EPA 3051 method. This method allowed an evaluation of the metals in a weakly-bound fraction in sediments, assumed as potentially bioavailable. Sediment samples were analyzed for organic matter content, grain size and metals of environmental interest (Ag, Fe, Mn, Zn, Cd, Cu, Pb and Ni). Metal concentrations were determined in three size classes of organisms (<3 cm, 3-5 cm and 5-8 cm lenght). For Gramacho area, sampling was carried out in the wet (February/2009) and dry (June/2009) seasons, and two sampling were carried out in the other area (august/2009 and September/2009) in the dry season. Metal concentrations in worms were higher in Mauá, where sediments presented AVS levels not exceeding SEM levels. Only the Ag presented a well defined trend of concentration increase with the increase in organism length. In the present study, concentrations of metalothioneins (MTs) were presented according to the three size classes adopted. Organisms from Gramacho showed the higher levels of MTs. For Gramacho, organisms from the larger size showed more elevated MT concentrations (96,5 &#61549;g g-1) than other organisms (31,0 e 38,6 &#61549;g g-1). Organisms from Mauá presented low variability among size classes (means from 14,8 to 20,8 &#61549;g g-1). A total of 80% of organisms from Gramacho and 36% of organisms from Maua presented some kind of morphological alteration (atrophy of dorsal cirri, bifurcated ligule and tumors), reflecting the deleterious effects of the inhabited polluted environments. Therefore, an integration of polychaete molecular and systemic biomarkers presents a potential use in environmental quality assessments.
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