Rivers wildlife indicators

The average THg concentration of all tissue samples (n = 285) was 0.2482 0.2546 pg/g, wet weight, ww, ranging from 0.0148 to 0.8052 pg/g. The highest levels were found at the factory site, close to the waste dumping point, followed by the meander, wildlife reserve, and reference sites (Table 1). This fact indicates an important mercury uptake by zebra mussels at the hot spot and redistribution to areas located immediately downstream and near to the river bank opposite the dumping site. 

Fig. 2 Location of the lower Ebro River catchment, zebra mussel, crayfish, and fish species sampling sites in the Flix dam area. Samples were taken at several stations in the four areas (RF = control site upstream WR = wildlife reserve HS = hot spot or chlor-alkali plant, and MD = meander). Positions of dams (black bars) and overflow dams (grey bars) are indicated to illustrate the mutual isolation of aquatic organisms sampled...

The Use Attainability Assessment (UAA) as well as recent USEPA monitoring indicated that water quality standards in the basin were not being met due to a combination of the natural geologic conditions and metals contamination due to mining. The UAA also discussed historic aquatic life uses in the basin (6). Anecdotal evidence fiom local persons and a variety of other Forest Service, Division of Wildlife, and USEPA data are reported to indicate that the Alamosa River supported at least a limited fishery until 1990. While there is evidence of mining activity in the upper Alamosa River, it was determined to be a minimal influence of stream water quality. 

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