Variations in Tissue Mercury Contents in Three Species of Adult Salamanders in Streams in Western Maryland

The purpose of this study was to improve our understanding of the relationship between mercury in three species of adult salamanders and relatively pristine first-order streams in western Maryland. We measured the tissue mercury content of 106 northern two-lined salamanders (Eurycea bislineata bislineata), 111 northern dusky (Desmognathus fuscus), and 107 Allegheny mountain dusky (Desmognathus ocrophaeus) salamanders collected during three sampling periods. Averaged over our entire data set, northern two-lined salamanders had significantly greater tissue mercury contents (29.57 ± 1.32 ng g^-1) than northern dusky (20.95 ± 0.78 ng g^-1) and Allegheny mountain dusky salamanders (22.84 ± 1.23 ng g^-1). This may be due in part to the longer larval period of the northern two-lined salamanders (24-36 vs. 0-10 months). A longer larval period suggests that the northern two-lined larvae were consuming a fully aquatic diet for a longer time period, which is likely to be higher in mercury compared with a more terrestrial diet. The tissue mercury content in northern two-lined and northern dusky salamanders were strongly correlated with the average total mercury, methyl mercury, and dissolved organic carbon concentrations in stream water. In contrast, the tissue mercury content of the more terrestrial salamander, the Allegheny mountain dusky, was not correlated with stream water chemistry. This suggest that the mercury in the terrestrial prey consumed by the Allegheny mountain dusky salamanders is not directly linked to the mercury in stream water. Our results also suggest that the aquatic salamanders could be important bioindicators of mercury contamination of small streams.