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In recent years the Ash Plume Wetland (APW) and surrounding area in D-Area on the Savannah River Site (SRS) have been targeted for ecological studies due to the release of coal combustion wastes to the ecosystem several decades ago. High concentrations of trace metals (e.g., arsenic, selenium, and cadmium) in the waste may threaten the environmental health of the APW, especially for organisms such as amphibians that use both aquatic and terrestrial habitats during their life cycle. Our study builds on previous work by SREL scientists that examined the distribution of coal ash wastes in APW and adjacent floodplain, as well as concentrations of metals in soil, plants, invertebrates, and amphibians.
Although trace element uptake and accumulation has been well documented in different species and life stages of amphibians at the APW, potential biological effects are not known. Earlier sampling of the amphibian and reptile community revealed that the assemblage of species at the site is similar to a nearby reference site (Ellenton Bay); i.e., the number of species found at the APW is comparable to the “expected” number. However, with the exception of the leopard frog (Rana sphenocephala), newly metamorphosed individuals of amphibians were not found in earlier studies, possibly indicating that the APW is not suitable for successful egg and larval development of some pond-breeding amphibians. If the APW is an ecological trap, rather than a source pond for many species, the lack of recruitment of juveniles into the population may be connected to the elevated trace metal concentrations.
We are combining aquatic and drift fence sampling with artificial mesocosm pilot studies to 1) determine the species utilizing the APW and 2) begin assessment of the biological effects of the APW environment on pond-breeding amphibians. The study began in mid-March 2008, which was after most species had bred, laid eggs, and completed significant larval development. Nonetheless, we observed newly metamorphosed juveniles of two species (R. sphenocephala, and the southern toad, Bufo terrestris). In contrast, five species produced juvenile at the reference site during the same time frame (additional species were the ornate chorus frog, Pseudacris ornata; the spring peeper, P. crucifer; and the tiger salamander, Ambystoma tigrinum).
To date we have conducted egg hatching studies on five species (Spadefoot toad, Scaphiopus holbrookii; Southern chorus frog, Pseudacris nigrita; Southern toad, Bufo terrestris; Southern leopard frog, R. sphenocephala; and the Eastern narrowmouth toad, Gastrophryne carolinensis). Egg studies general protocol: 1) collection of sediment from the APW and an uncontaminated reference site (Ellenton Bay), 2) preparation of 0.5-L containers with ~10 cm of sediment from each treatment, 3) introduction of pond water to the containers, and 4) introduction of known numbers of eggs to containers. Each treatment was replicated five times. Different numbers of clutches were used depending upon species average clutch size and the availability of eggs. We observed 100% hatching success in the APW trial for all five species; results for Ellenton Bay trials were nearly the same (4 of 5 species had 100% hatching success), with only B. terrestris showing reduced success (64%). Thus, to date we have seen no evidence that the APW environment affects hatching success for the amphibian species tested.
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The ash plume wetland (APW).
The APW received coal combustion wastes from a breach in a receiving basin in the 1970s.
Several trace metals are elevated in sediments of the APW area, including arsenic, selenium, strontium and copper.
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