Vernal pools are a unique wetland type at tremendous risk due to habitat degradation and loss, a situation that has triggered recent legislation in Maine aimed at vernal pool conservation. Vernal pools host a diversity of biota (e.g., wood frogs [Rana sylvatica], ambystomatid salamanders [Ambystoma spp.], fairy shrimp [Eubranchipus spp.]) adapted to larval development in temporary waters, but these wetlands are endangered by a subtle threat to their function: non-point source pollution. Our study examines one such potential “invisible” risk in Acadia National Park (ANP), Maine: the role of mercury (Hg) in the broader context of vernal pool water chemistry and its effects on amphibian larval development. Our overarching goal is to understand the vernal pool chemical environment, the transport of Hg through vernal pool biota, the linkages between food web structure and Hg concentration in biota, and the potential toxicity of Hg to amphibians in vernal pools of the northeastern U.S. where atmospheric deposition of Hg is a well-documented phenomenon.
We will characterize the chemical environment (including Hg) of short-hydroperiod vernal pools in ANP, including potentially large Hg contributions from snow and seasonal snow melt. Changes in Hg concentrations in the water, leaf litter, biofilm, sediment, and developing embryos and larvae will be determined over time Developmental abnormalities in amphibian embryos and larvae and time-to-metamorphosis will be related to vernal pool chemistry. This exploratory research project will contribute to our knowledge about relationships between chemistry and biology in pool environments and will lead to refined hypotheses for future studies about potential synergistic interactions of the vernal pool chemical environment. This information could be applied to regions outside the Park to aid in conservation of pools with risks of chemical pollution due to physical setting or pool chemistry.
Project objectives are:
1) Describe the water chemistry of short-hydroperiod amphibian breeding pools.
2) Characterize relationships among vernal pool chemical and physical environments (e.g., pool substrate, forest cover type, size, hydroperiod).
3) Document the presence and bioaccumulation of Hg in vernal pool food webs.
4) Identify relationships between the vernal pool chemical environment and amphibian developmental condition.