The Spill Doctor

Spiders

One MTSU professor uses spiders to find truth in the ashes of Tennessee’s worst environmental disaster

In early 2009, Dr. Ryan Otter (Biology) stood awestruck on the banks of the Emory River in Roane County. What two months earlier had been a serene fishing alcove now looked like a lunar landscape or a present-day Pompeii. Under his boots, where there should have been vegetation, there was gray sludge. And the water in the alcove was simply gone, displaced by wet fly ash, a thick chemical stew that had spilled into the river when an earthen retention pond ruptured at the TVA Kingston Fossil Plant.

The scope of the spill was unlike anything Otter, an environmental toxicologist, had ever seen. It was also unlike anything the United States had ever seen. The slurry blanketed everything in its path, pushing homes off foundations, choking two tributaries of the Tennessee River, and burying a 300-acre ecosystem. For the people who lost their homes, the event was a life-changing disaster. But for the area’s quieter (and far more numerous) residents—the water and land animals— the prognosis wasn’t so clear. Despite the ubiquity of fossil fuel plants worldwide, Otter says, there had been very little research on fly ash, a byproduct of coal combustion that contains trace amounts of many potentially dangerous elements including arsenic, lead, and mercury.

Dr. Ryan Otter
Dr. Ryan Otter

Weeks after the spill, Otter joined a coordinated effort of several agencies
to answer a slightly different version of his gut-level question: Is this an environ- mental catastrophe? He found the answer in an unexpected place, and that answer surprised everyone.

When analyses of toxin levels in fish proved inconclusive, he knew he needed a different animal—something whose diet was more closely connected with the fly ash. Then he remembered his Ph.D. work with researchers from the Environmental Protection Agency, who used a commonly found spider to measure contamination at polluted sites. The spiders are ideal indicators, Otter says, because they have high fat levels that store toxins.

The spiders, known as long-jawed orb weavers, are easy to find on any riverbank in the country. Shy and harmless, they hide in trees near the water during the day, and at night they spin webs to catch mosquitoes, black flies, and other bugs that live in and feed on sediment. With the help of two students, Otter spent two days on the river, shaking tree branches and bagging several hundred spiders, which he sent to a lab for chemical analysis.

Otter says he tries to conduct research with no expectations about the outcome. But when the lab results came in, he was as shocked as anyone. The spiders tested negative for every toxin but selenium— levels of which, while concerning, weren’t “off the charts,” he says. Further field and controlled studies supported his initial findings. Apparently, the other toxins had bound with carbon in the fly ash and settled, uneaten, on the river bottom.

While media images of the Kingston site were terrifying, the spiders told a more accurate story. Because they bridge the ecosystems of river and land, says Otter, spiders reveal more than most animals can.

“All fish can tell you is the impact on fish . . . and how contamination moves through water systems in one way,” he says. “But how is that contamination impacting things on the land? Fish can’t really help with that.”

Long-jawed orb weavers aren’t the only creatures that eat aquatic bugs, he says. So do birds and bats, which then become part of the terrestrial food chain. “So these spiders are really cool indicators,” Otter says. “They can tell a story about what’s going on in the water and how much is leaving the water to come onto the land.”

Thanks in great part to Ryan Otter, there’s no longer a dearth of research on the environmental effects of fly ash. And while his work on the Kingston spill site is complete, he’s just beginning research with long-jawed orb weavers, which he considers invaluable but overlooked subjects in the study of food-chain dynamics. “They can tell a huge story that typically has not been told,” he says.

 

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