H-02 Constructed Wetland Studies:
Amphibians and plants
David Scott, Tracey Tuberville, Brian Metts, and Bill Hopkins
 The H-02 constructed treatment wetlands associated with the H-Area facilities.
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Construction of the H-02 treatment wetlands adjacent to H-Area on the Savannah River Site (SRS) began during FY-2007. The Savannah River Ecology Laboratory (SREL) initiated ecological studies related to the operation of the H-02 constructed wetlands in May 2008. Constructed wetlands are one method to treat and improve water quality at regulated outfalls on the SRS. Heavy metals such as copper, lead, and zinc are removed by adsorption to organic matter and clay particles, and sulfate reducing bacteria enable the precipitation of metal ions in the anaerobic soils. Constructed treatment wetlands proved effective at the A-01 outfall on the SRS, with removal efficiencies > 80% for copper, mercury, and lead within four years. Systematic monitoring has revealed that water quality is improved prior to discharge into streams, but the extent to which these constructed treatment wetlands also serve other “natural wetland” functions, such as providing wildlife habitat, has not been documented. |
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Water chemistry is extremely important to the successful development of amphibian eggs and young. Of particular interest are factors such as pH, dissolved oxygen (DO) concentration, and concentrations of metal ions such as copper (Cu) and zinc (Zn). The H-02 wetlands, now in their early phase of establishment, exhibit large fluctuations in some of these parameters. By assessing the response of amphibians to the water quality of the H-02 wetlands over time and comparing amphibian success in created versus natural wetlands, we will better understand the suitability of the H-02 created wetlands for wildlife habitat, especially amphibians. The H-02 wetlands were designed to comply with regulatory guidelines for process and storm water discharge from H-Area facilities, but they may also provide wildlife benefits.
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The SREL began amphibian and vegetation surveys at the site in
summer 2008. Ecological research conducted by SREL focuses primarily on four
questions related to these treatment wetlands: 1) Within 1˝ years of
construction, what amphibians, reptiles, and plants have become established
in the wetlands? 2) Is there any evidence that elevated metals levels in the
wetlands (e.g., copper and zinc) affect amphibian success? 3) How do the
amphibian diversity and numbers compare to other, more natural, wetlands? 4)
As the constructed wetlands age, how will changes in vegetation composition
and structure affect the amphibian community?
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We conducted amphibian and vegetation sampling at the H-02 treatment wetlands from May-September 2008. Permanent plots for monitoring vegetation and amphibians were established in each wetland cell, and drift fences were constructed adjacent to the area to determine amphibian use of the ponds as breeding sites. We recorded 617 captures of 17 amphibian and reptile species at the H-02 treatment wetlands in 2008, including successful production of juveniles by eight species. This level of reproductive success was higher than at the natural wetland reference site, which dried in mid-May. However, to date no salamander species have been recorded at the H-02 site. Our baseline vegetation sampling documented 18 vascular plant species plus algae in our plots.
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In 2009 we plan to continue the drift fence and aquatic trap
sampling, and supplement these techniques with night call surveys to
estimate numbers of breeding individuals [in FY-08 most amphibians species
had either completed breeding or were nearly finished prior to the
initiation of this project]. Some larvae will also be tested for the
presence of the chytrid fungus to compare to levels of this pathogen found
in bullfrog (Rana catesbeiana) larvae at the A-01 created wetlands.
Additional samples will be taken of selected species to assay copper levels
in tissues. In conjunction with studies by G. Mills and others, we will use
in situ toxicity tests to examine the effects of H-02 water chemistry
on several amphibian species (e.g., representative frog, toad, and
salamander species).
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Acknowledgements -- These studies of contaminant effects on amphibians are funded in part by the National Nuclear Security Administration (NNSA-DOE). |
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