by Marilyn Davis
 

Research often hits unexpected snags—like the day recently when a supplier delivered a shipment of earthworms to Scott Meister DOA. But dealing with problems is the nature of Meister’s research in wildlife toxicology.

A master’s student in zoology, Meister needed the worms to test the safety of sediment collected near the Paducah (Ky.) Gaseous Diffusion Plant, a uranium enrichment facility. His work is part of a larger project run by Richard Halbrook, a professor of zoology and wildlife toxicologist with SIUC’s Cooperative Wildlife Research Laboratory. Halbrook studies the effects of environmental contaminants on wildlife and the ways species can serve as monitors of pollution. 

Taking water and soil samples can tell regulators if pollutants are present at a site, but such sampling only gives a snapshot in time. "If contaminants are changing over time, you could miss that," Halbrook says. Doing continuous water monitoring is very costly, and soil sampling poses another problem: where do you take the samples? It’s possible to miss hot spots.

In contrast, says Halbrook, "Animals are good integrators of what’s happening in the environment over space and time. They’re in the water or drinking the water; they’re closely associated with their environment. There may be a lot of exposure that would be missed if we only collected water or soil samples." 

Wild animals’ exposure to pollutants can be much different from that of humans, Halbrook notes. Often, people’s exposure to contaminated land or water can be controlled by fencing areas and posting warning signs. But animals are no respecters of signs and fences. By moving in and out of polluted areas, they can spread contaminants geographically—as well as up the food chain.

Halbrook and a team of graduate and undergraduate students are using amphibians and starlings living near the Paducah Gaseous Diffusion Plant as "sentinel species" to assess contamination and its effects. The plant complex is polluted with PCBs (common but hazardous industrial pollutants), heavy metals such as lead and mercury, and even radioactive waste. 

What isn’t known is the extent to which contaminants are migrating off-site or affecting wildlife. The issue is complex. Contaminants may or may not be "bioavailable"—in a form readily ingested by and accumulated in animals. And accumulated concentrations may or may not be high enough to harm species.

Since frogs and toads spend part of their life in water and part on land, they’re a good bet for ecological monitoring. Master’s student Colette DeGarady has set up sampling sites along eight waste streams from the plant. Her work begins at sundown. By listening to the number of frogs calling, she can gauge abundance, and by identifying the different species calling, she can gauge diversity.

Then she collects specimens from the streams. Back in Carbondale, she and undergraduate assistants analyze tissue from the frogs and toads for heavy metals and PCBs. But they also check for physical abnormalities such as an enlarged liver, often a sign of prolonged exposure to toxins. And they run tests for biomarkers—physiological signs—of contaminant exposure. For example, contaminants can trigger elevated levels of certain liver enzymes or metal-binding proteins. This lab work will give a good picture of exposure over time.

Meanwhile, master’s student Moira McKernan is concentrating on starlings. These common birds readily use nest boxes and feed within about 150 feet of their nests—convenient traits for researchers, who can be sure what area they’re monitoring. In the field, McKernan is focusing on the birds’ reproduction, often a good indicator of contamination effects. She’s counting numbers of nests built, eggs laid, chicks hatched, and chicks surviving until fledging time. Then she’s bringing the chicks to campus to analyze tissue samples and look for biomarkers of contamination.

Both the starling and frog studies are also using similar but uncontaminated sites for comparison purposes. Field data and samples collected this past summer are now being analyzed, and a second field season will begin in spring 2001.

And Scott Meister’s earthworms—the live replacements, that is—will help test for sediment toxicity. Some worms will be kept in batches of soil collected from streams at the plant site; others will be kept in soil known to be uncontaminated. Meister will compare how many worms in each group survive over a 14-day period, and how many egg sacs the worms produce over a 28-day period.

The bioassay is a "first-tier" test to identify areas that may be contaminated. "If we get a response, it shows that invertebrates in the sediment are being adversely affected by something," Halbrook says. Then more-expensive chemical analyses can be done. The bioassay also can serve as a first test of the biological significance of known contamination.

The Kentucky Department of Fish and Wildlife Resources, which is funding most of the Paducah research, will use the SIUC findings to make decisions about cleanup or control of contaminants.

Previous work with starlings at Crab Orchard National Wildlife Refuge, near Carbondale, has shown the value of such research. PCB contamination at the refuge led to concern about possible effects on bird species. Halbrook measured PCB concentrations in starling chicks and found a close correlation to levels in the soil. He also found reproductive problems in starlings nesting on the contaminated area. 

After cleanup at Crab Orchard, Halbrook repeated the testing. This time he saw normal reproduction, as well as decreased PCB levels in the starling chicks. 

With baseline data from wild species, then, scientists not only can monitor contaminant movement and bioaccumulation over time, but they also can document the effectiveness of cleanup efforts. 

Such information helps protect our wildlife—and by telling us more about what’s going on in the environment, it also helps safeguard human health.

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