Tests with fathead minnows, water fleas and bloodworms subjected to water and sediment near the Mayflower spill site are confirming what Arkansas state agencies are claiming more than eight months after the Pegasus pipeline burst — that the level of pollutants now likely constitutes more of an ecological concern than a public health hazard.
Researchers affiliated with Arkansas State University's Ecotoxicology Research Facility in Jonesboro reached their conclusion after conducting two rounds of tests with the three types of tiny creatures in late spring and early summer.
The first round of ecotoxicology tests indicated that there are likely environmental issues with the water and sediments in the cove of Lake Conway, said Jennifer Bouldin, the research facility's director and an associate professor of environmental biology.
"It's not acutely toxic but there is a little something in there," Bouldin said. "What that says to me is that the cove would be a place to watch and look at it again. So much of it was excavated but it makes you wonder if they got all of the oil out.
"I think the main part of the lake was probably OK. But I'm anxious because all the rain we had this summer could have washed oil from the cove into it."
Unlike the testing for compounds that ExxonMobil has been conducting since the spill, ecotoxicology tests look at the effect on animals. If the organisms die or fail to grow or reproduce, it is an indication that a compound or a mix of compounds has reached a toxic level.
"The beauty of ecotoxicology is that if an environment is safe for those tiny organisms, then you know it is safe for humans, even babies," Bouldin said.
Bouldin and graduate student Molly Kennon executed both sets of tests — officially called Whole Effluent Toxicity (WET) tests — with grant money provided by the Log Cabin Democrat, the daily newspaper in Conway, Bouldin said. The newspaper told her it was interested in pursuing independent research on the condition of water and soil in Mayflower after the ExxonMobil's Pegasus pipeline spewed 210,000 gallons of oil on March 29.
The Ecotoxicology Research Facility in Jonesboro is certified by the U.S. Environmental Protection Agency to conduct WET tests that measure what effects wastewater has on an organism's ability to survive, grow and reproduce. Usually, the facility conducts these tests for industries and municipalities with wastewater treatment utilities that are required to have a permit under the National Pollutant Discharge Elimination System.
Bouldin and Kennon first collected water and sediment samples from six sites in Mayflower on June 7 to use back in their lab. These included three spots in the lake, one near the railroad trestle near Northwoods subdivision, one in the drainage ditch near the shopping center with the Subway sandwich shop, and one at the edge of the cove near the Interstate 40 frontage road.
Once back at the lab, they set up controls and spent seven days measuring how the water samples affected the survival and growth of fathead minnows (Pimephales promelas) and the survival and reproduction of water fleas (Ceriodaphnia dubia). Both species, which were cultivated in the lab for these tests, live in the type of warm freshwater found in Arkansas and are part of EPA test protocols.
"Both species are used because each is sensitive to different contaminants," Bouldin explained. "It allows us to hit a broad range of what might be found."
The researchers repeated those same steps on Sept. 11, but were unable to collect water from near the railroad trestle because it was so dry. The first round of water tests revealed that reproduction of the water flea was lower in water collected from the cove than it was in the control experiment. Survival and growth of the fathead minnow wasn't significantly affected. The second set didn't detect any adverse effects on either the water flea or the fathead minnow.
Bouldin said it was hard to explain the second set of results. She speculated that the contaminants had been flushed out by large amounts of rain or consumed by microbes in the water column. With contaminants such as hydrocarbons, she said, the lighter parts float to the top and the heavier ones sink to the sediment.
For the sediment tests, Bouldin and Kennon measured how the samples affected a species of bloodworm (Chironomus dilutus), which actually eats the organic particles in the sediment. Like the two species used in the water tests, the bloodworms also were cultivated in the lab. Sediment tests take at least 10 days to process.
The first set of tests revealed that, compared to the control group, bloodworms subjected to the sediment in the cove had a significant decrease in growth. It's likely the bloodworms were reacting to heavier hydrocarbons that sank in the cove, Bouldin said.
Somewhat surprisingly, she said, the second round of tests showed decreased growth in bloodworms exposed to sediment in the main body of Lake Conway — about 80 to 100 yards from the boom near Highway 89 — and the site at the railroad trestle near Northwoods subdivision.
"What this indicates is that these organisms can survive but something is having a more subtle effect on them," Bouldin said. "There is a contaminant but it's not in a big enough concentration to kill the bloodworms, only to stunt their growth."
Bouldin said that while she and Kennon want to continue gathering data at Lake Conway, the grant they received was only enough to cover two rounds of testing.
The Arkansas Department of Environmental Quality is overseeing the Mayflower cleanup. However, Ryan Benefield, the agency's deputy director, said in an interview that he could not comment on Bouldin's findings because he had not seen a copy of the ecotoxicology testing, methods or results.
The ecotoxicology tests don't offer definitive answers for those directing the cleanup, Bouldin said, but they do confirm concerns that the Arkansas Game and Fish Commission has about long-term ecological effects.
Ricky Chastain, the deputy director of the commission, said his agency is especially worried about the toxicity of the impact of the oil — particularly polycyclic aromatic hydrocarbons — on the bacteria, mollusks and crustaceans that live in or near the sediment because "from a wildlife standpoint, that's the foundation of the ecosystem."