AIM: The aim was to verify the geochemical composition of sediments samples (riverbed and bank) and the relationship of the following elements: Al, As, Cd. Cr, Cu, Fe, Mn, Ni and Zn with the zooplankton community. METHODS: Bank and riverbed sediments were collected in four sampling points along the studied area, in June/2010 (dry season) and March/2011 (rainy season). Three types of analysis were performed: granulometric, mineralogical (by X-Ray diffractometer) and geochemical (by ICPOES), where for the last two types, only a fraction of silt/clay (<0.062 mm) was used, and the results were compared with the following reference values: Local Reference Value (Costa et al., 2010), Quality Reference Values (São Paulo, 2005), PEC and TEC values (MacDonald et al., 2000). For identification of the zooplankton community, riverbed and bank samples were collected in polyethylene bottles, suspended with deionized water (bank sample only), stained with Rose Bengal and preserved in formalin at 4%. RESULTS: As concentrations at Col sampled point were 18 times greater than the Local Reference Value (3.84 mg.kg-1). Cd concentrations were greater than the values established by the QRV (<0.5 mg.kg-1) and PEC (4.98 mg.kg-1) in almost all the sampled points, regarding seasonality. The following zooplanktonic species were identified: Arcella costata (Ehrenberg, 1847), Arcella discoides (Ehrenberg, 1843), Arcella vulgaris (Ehrenberg, 1830), Centropyxis aculeata (Ehrenberg, 1838), Centropyxis ecornis (Ehrenberg, 1841), Difflugia sp., Difflugia acuminata (Ehrenberg, 1838), Euglypha laevis (Perty, 1849), Trynema enchelys (Ehrenberg, 1938), Asplanchna priodonta (Gosse, 1850), and Bedelloida, with, approximately 81% belonging to the Protozoa group. CONCLUSIONS: The studied area, with the exception of the Tripuí point, was found to be impacted by historical gold exploration in the region, as well as by the growing urbanization. Within the elements considered to be the most toxic to the biota, As and Cd violated all their reference values. In spite of high concentrations of major and trace elements encountered at downstream points, testacea species were identified, suggesting that this group has the capacity to adapt to adverse situations.
geochemistry; sediments; impacts, gold mining; zooplankton
