Date of Award

5-2005

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Jody Jellison

Second Committee Member

Cynthia Loftin

Third Committee Member

Terry Haines

Abstract

The objective of this investigation was to study mercury bioaccumulation and habitat use in lotic and lentic amphibians at Acadia National Park (ANP). I report concentrations of methyl Hg (MeHg – at ANP only) and total mercury (Hg) in larval northern two-lined salamanders (Eurycea bislineata bislineata) collected from streams in Acadia National Park (ANP), Maine, Bear Brook Watershed, Maine (BBWM; a paired, gauged watershed treated with bimonthly applications {25 kg/ha/yr} of ammonium sulfate [(NH4)2SO4]) since 1989), and Shenandoah National Park (SNP), Virginia. MeHg comprised 73-97% of total Hg in the larval salamander composite samples from ANP. At BBWM I detected significantly higher Hg levels in larvae from the (NH4)2SO4 treatment watershed. At ANP Hg concentrations in salamander larvae were significantly higher from streams in unburned watersheds in contrast with samples collected from streams located in watersheds burned by the 1947 Bar Harbor fire. Hg levels were higher in salamander larvae collected at ANP in contrast with SNP salamanders and ANP lentic amphibians (bullfrog - Rana catesbeiana and green frog - Rana clamitans tadpoles ~1 year of age). At ANP, 44% of the ponds (n = 9) had methylation efficiency rates greater than 10%, suggesting that some wetlands in ANP are likely susceptible to high levels of Hg bioaccumulation. Microhabitat data indicate that salamander larvae were generally found< 9 cm. Larval salamander density was greater in streams draining watersheds burned by the 1947 fire (hardwood dominated) in comparison to streams from unburned, conifer dominated watersheds. Among streams, the best approximating model for both occurrence and abundance of salamander larvae included pH (+), % embeddedness (-), and fish abundance (-). Among watersheds, percent conifer forest (+) in the watershed was the best approximating model for total Hg bioconcentration factors in salamander larvae. Overall, this investigation suggests that stream heterogeneity influences patterns of distribution, abundance and biomass of larval two-lined salamanders at multiple spatial scales. Risk assessment models should include a watershed perspective since headwater streams and their associated receiving wetlands and ponds may have substantial differences in rates of mercury bioaccumulation and biomagnification.

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