The greatest single threat to water quality in coastal waters is fecal contamination — and the culprits, in the case of Virginia’s Eastern Shore, often are not human.
In the last several years, there have been many closings of tidal creeks to shellfish harvest because of high levels of contamination. "People couldn't figure out why this was occurring," says Virginia Tech Biology Professor George Simmons. "They thought it was human waste getting into groundwater.
"But contamination was happening even where there were no houses or only a few houses with well-designed septic tanks. So where were the E. coli coming from?"
Virginia Tech researchers led by Simmons are measuring the presence of the bacterium, Escherichia coli, known commonly as E. coli, to establish water quality — and are ‘DNA fingerprinting’ the bacteria to trace them to their source.
Simmons explains, "We use E. coli because it occurs in the intestinal tract of all warm-blooded animals (including humans) and it can be cultured and grown easily. If we find E. coli in water, there is a suggestion that we have fecal contamination and that other, more dangerous organisms such as viruses, bacteria, or protozoa may be present. So, if you find high levels of E. coli, you must close areas to shellfish harvesting, for example."
As well as being an indicator of other more harmful contamination, E. coli itself can be harmful. "There are some pretty bad strains that can cause anything from a mild stomach upset to death. Some strains are hemorraghic (cause internal bleeding)," Simmons says.
Contamination becomes extremely critical when talking about water quality in areas where shellfish are grown or harvested. Shellfish filter water, so contaminants like bacteria, viruses, and protozoa become concentrated in them. To be safe, shellfish must grow in extremely clean water.
Simmons and colleagues, including students, discovered that there have been dramatic increases in the populations of certain species of wildlife, many of which are active on the edge of the marsh. "The animals defecate there, then water covers their scat (feces) and the scat goes back out with the tide and contaminates the water."
Simmons, an Alumni Distinguished Professor, started looking for the source of coastal water contamination in 1990, working on a ground water project on the Eastern shore.
"When we first started, we were looking for leaky septic tanks," he says. "We thought if people fixed them, the problem would go away. But we couldn't find any leaks. So I started doing some basic field biology, going out and looking at the contaminated areas and designing experiments.
"I was working with a man who had a clam bed that had very high levels of E. coli. It was not from a septic tank. So, out of desperation, I covered the groundwater seeps (areas about the size of a bathtub where groundwater goes down into the water table). I made a sort of tent out of clam netting, a very fine mesh. The E. coli count went to almost zero in the seeps.
"I had found I could manipulate the E. coli count directly. Then I knew animals were using the groundwater seep areas to defecate," Simmons reports. "But we needed to know which animals were using them."
He had to learn what various scat deposits look like — deer, water fowl, raccoon, etc. By examining the scat, he found raccoon was dominant in the area of study.
"A man was about to lose his clam bed because of contamination. I showed him the data and said he must take some raccoons off his farm. He removed about 100, and about six months later the creek was reopened and another creek that bordered his land that was about to be closed was saved from closing," Simmons reports. The clam-bed owner has hired a trapper full time to keep the fur-bearing populations down around the marshes in the vicinity of the clam beds.
"One reason fur-bearing animals are such a problem is that no one traps them anymore," says Simmons. "An old oysterman told me that when he was a child, every kid trapped raccoons during the winter. Now, they don't do it any more."
While Simmons' research made clear the need to control the raccoon population in one area, the same research can help preserve wildlife in other areas.
"The field work was very strong on the Eastern Shore. High E. coli counts in natural areas mean you have one or more animal populations out of control. But what if you go to a place that has a high count and nobody knows where it's coming from?"
Simmons' group decided to collect scat from known animals such as goose, raccoon, muskrat, and deer. "Everybody thought waterfowl were causing the contamination and wanted to shoot the birds. But we exonerated this whole group of wildlife. It wasn't waterfowl.
"Everybody has an opinion. But if we don't have data, everybody's opinion is valid," Simmons points out. So the Virginia Tech researchers started building a library of E. coli DNA from animals. They collect scat, grow E. coli, and genetically fingerprint the E. coli from the different animals by analyzing the E. coli DNA.
"It's expensive and time-consuming to check water quality this way. It takes about a week to develop a DNA fingerprint and costs about $1,000 per sample," he explains. "But we have 15 or 20 animals' DNA now, including humans. In geographic areas where the field data is lacking or weak, DNA technology may be the only option to solve a water quality problem."
Contact for more information: George Simmons: at Eastern shore laboratory: 804-331-8328; on campus: 540-231-6407.
— Written by Netta Smith
