Clapper rails as indicators of mercury and PCB bioavailability in a Georgia saltmarsh system

Abstract

Mills, Gary L.; Garvin, N.; Stephens, Warren L. Jr.; Novak, James N.; and Brisbin, I. L. Jr., "Clapper rails as indicators of mercury and PCB bioavailability in a Georgia saltmarsh system" (2008 Abstract Clapper rails (Rallus longirostris) were used as an indicator species of estuarine marsh habitat quality because of their strong site fidelity and predictable diet consisting of mostly benthic organisms. Mercury (Hg) and the polychlorinated biphenyl (PCB) Aroclor 1268 concentrations were determined for sediments, crabs, as well as clapper rail adults and chicks collected from salt marshes associated with the LCP Superfund site in Brunswick, Georgia. Home ranges were established for adult rails, and sediment and crab samples were taken from each individual's range. The study was designed to minimize the spatial variability associated with trophic transfer studies by choosing an endpoint species with a potentially small home range and specifically sampling its foraging range. The mean home range for clapper rails was 1.2 ha with a median of 0.28 ha. Concentrations of Hg and Aroclor 1268 were shown to increase with each trophic level. Transfer factors between media followed the same pattern for both contaminants with the highest between fiddler crabs and clapper rail liver. Hg and PCB transfer factors were similar between sediment to fiddler crab and fiddler crab to muscle, however the PCB transfer factor from fiddler crabs to liver was over twice as large as for Hg. PCB congener profiles did not significantly differ between media types.

Is the LCP Superfund Site an Ecological Trap for Clapper Rails?

“…Gaines et al (1999Gaines et al ( , 2000 assisted the US Fish and Wildlife Service (USFWS) to document the extent of the post-mitigation damage to wildlife resources, using Clapper Rails as an indicator of ecosystem health. Specifi cally, this research reported that birds had elevated levels of DNA strand-breakage, egg-shells had been weakened, and chicks had neurological damage and bone-structural problems (Cumbee et al 2008;Novak et al 2006;Rodriguez-Navarro et al 2002. Although this research helped the USFWS quantify damage to the ecosystem, it left many unanswered questions.…”

“…Clean-up plans often consider action levels to minimize chronic toxic effects, but fail to regard the broader impacts of long-term exposure to populations. The Clapper Rail population in this study has been used as an indicator population for acute effects (Cumbee et al 2008;Novak et al 2006;Rodriguez-Navarro et al 2002. However, the long-term consequences of this perturbation have not been examined.…”

“…All work summarized below has been performed post-mitigation in areas that were never physically disturbed by clean-up efforts. Studies performed post-mitigation have found that the Aroclor 1268 mixture is still present in the sediment throughout the marshes associated with LCP, has gone through little physical or chemical weathering, and is highly bioavailable (Cumbee et al 2008;Novak et al 2006;Rodriguez-Navarro et al 2002. Gaines et al (1999Gaines et al ( , 2000 assisted the US Fish and Wildlife Service (USFWS) to document the extent of the post-mitigation damage to wildlife resources, using Clapper Rails as an indicator of ecosystem health.…”

“…One hypothesis was that the LCP marsh had become an ecological trap. Previous studies reported that the LCP marsh has excellent habitat for Clapper Rail courtship and nesting (Cumbee et al 2008, Gaines et al 2003. However, the high levels of contaminants may be reducing or possibly eliminating successful nests (i.e., chick survival to recruitment).…”

Migrating and breeding bird use of restored shallow lakes in Iowa

“…There is also evidence that they are sensitive to certain habitat conditions, such as water quality, and so may be considered wetland quality indicators , Conway 1995, Cumbee et al 2008. Additionally, we examined the effect of vegetation on Marsh Wren (Cistothorus palustris), Yellow-headed Blackbird, and Virginia Rail separately; these are relatively common species in Iowa wetlands but are experiencing population declines elsewhere , Conway 1995).…”