Exposure of White-throated Dippers to heavy metals in acidified and non-acidified streams in Norway

We examined the exposure of White-throated Dippers ( Cinclus cinclus ) to aluminum and mercury in acidified and non-acidified streams in two regions of Norway. Both metals showed significantly higher concentrations in the body tissues of dippers in acidified streams at southern sites compared to non-acidified streams in central Norway. Elevated concentrations of aluminum in acidified areas could not be explained by a corresponding elevated level of aluminum in the invertebrate foods of dippers. During our study period in 1993–1995, deposition rates of mercury by long-range air pollution were higher in southern than central Norway. High levels of mercury in dippers could have been due to higher levels of atmospheric deposition or higher water acidity in southern Norway. We found a high correlation between mercury levels in body tissues of females and their eggs, but not for aluminum. Thus, eggs are suitable for monitoring mercury levels but not for aluminum in female dippers. Our data provide baseline estimates of exposure to heavy metals in freshwater ecosystems in Norway that will be useful for monitoring future trends.