Good news for humankind: We're not entirely to blame for Chesapeake Bay pollution. So says Virginia Tech biologist George M. Simmons, a former Antarctic explorer who now roams the tidal creeks of his state's Eastern Shore armed with a pooper scooper.
Simmons' surprising conclusion: Humans aren't always the source of the fecal coliform bacteria that contaminates some bay waters, forcing Maryland and Virginia officials to close thousands of acres of clam and oyster beds each year. Neither are geese and ducks, which often get blamed for fouling creeks and ponds. The most common culprits are cute, cuddly mammals: deer, otter and, most of all, raccoons.
To develop his findings, "I spend my weekends in the marshes, crawling around in the spartina on my hands and knees looking for animal scat," Simmons told a convention of agricultural and soil scientists gathering in Baltimore this week. "You get a lot of solitude that way."
Simmons' laboratory uses sophisticated DNA tests to analyze the collected scat for strains of E. coli, the common, rapidly mutating bacteria found in the waste of practically all vertebrate animals. Most types of E. coli are harmless, but a few can make people violently ill. A handful of virulent strains can kill children and adults with weak immune systems.
Because no simple test exists to sort harmful from harmless strains, the Food and Drug Administration requires states to close shellfish beds whenever high levels of fecal coliform are found. In Maryland, about 60,000 of the state's 1.2 million acres of shellfish beds are closed because of the contamination each year, said Maryland Department of the Environment spokesman Quentin Banks.
A few scientists are working to pinpoint the most dangerous bacteria sources. At the University of Washington in Seattle, researcher Mansour Samadpour has assembled a library of DNA fingerprints for more than 25,000 E. coli strains, taken from a Noah's Ark of creatures, including humans. Samadpour has used his DNA library to uncover improper dumping of raw sewage at a popular beach near Seattle, and to finger a colony of seals as the source of fecal coliform pollution in La Jolla, Calif.
A decade ago, researchers assumed septic tanks, sewage outfalls and livestock wastes were the source of most coliform bacteria, Simmons said. In some places that's true. But on Virginia's Eastern Shore, fecal coliform has contaminated creeks "in areas with no major human settlements," Simmons said. "I've been in marshes where there are absolutely no houses visible, but there's animal scat everywhere."
Using his collection of about 400 E. coli strains, Simmons finds raccoons are a common source of the bacteria. "You cannot believe how many raccoons can inhabit a given area of land, and they live quite nicely with humans. So as you get more people living on the water's edge, you get more raccoons, and more scat, and more contamination."
Because many strains of the bacteria are unidentified and their health effects are unknown, Samadpour and Simmons said, it's unlikely the DNA analysis will quickly replace fecal coliform counts as the standard for deciding when to close shellfish beds.
"Often there are multiple sources of contamination. What we can do is identify the sources," Samadpour said. "Then it's up to the people who make the decisions to see which ones they're capable of correcting." At that point, "it gets a little dicey," Simmons said. "Because if you say it's the deer, the raccoons and the otters that are causing the problem, who's going to go out there and kill them?"
Pub Date: 10/21/98