In the Flix Reservoir (Ebro River, Spain), ca. 300,000tons of industrial waste were dumped because of the activity of a factory plant in Flix. Within the recovery program implemented, this exceptional situation provides a unique opportunity to test the value of zebra mussel as sentinel organism. Ten metal concentrations were measured in mussels from different sites to assess spatial redistribution of metals and bioavailability to the food web. Our results showed an important metal uptake by mussels; metal concentrations (except As) measured in impacted sites were up to 10 times higher than in control sites, and Mn and Hg exceeded several times the levels previously reported for polluted waters. Concentrations increased downstream showing the metal mobilization from polluted sediments in Flix Reservoir. The higher metal concentrations measured in zebra mussel individuals clearly indicated their bioavailability to the food web, allowing the toxics transfer to predators and occasionally to humans. Thus, zebra mussel is a valuable sentinel organism to identify highly polluted waters, transport routes and trophic transfer.
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