N.C. State Researchers Work To Identify Source Of Pollution In Shellfish Beds
Posted January 29, 2003 1:33 a.m. EST
RALEIGH, N.C. — Researchers at North Carolina State soon may identify the source of pollution that has closed some shellfish beds to harvesting in eastern North Carolina for decades.
As indicated by high levels of fecal coliform bacteria, clams and oysters from closed shellfish beds are potentially dangerous for humans to eat.
According to North Carolina Sea Grant, 56,000 acres of shellfish beds are permanently closed in the state.
Shellfish beds in one area have been affected by a small creek named Jumping Run near the town of Newport. These shellfish beds have been closed to commercial harvesting since 1979.
This site and two other watersheds have become the testing ground for assessing new methods of microbial-source tracking.
The project is being led by the College of Design's Research, Extension and Engagement Office, supported by the North Carolina Department of Environment and Natural Resources and the U.S. Department of Agriculture.
Nancy White, a landscape ecologist at the College of Design, has worked for several years examining the problem of water quality at the mouth of the Bogue Sound.
With colleague Dan Line, an extension specialist at N.C. State, the researchers have monitored water after storms, tested levels of bacteria and conducted dye studies to determine the path of the runoff.
Now, using microbial-source tracking methods, White hopes to identify the source of the bacteria. This important new information will indicate whether contaminants are from failed or leaking septic tanks, wildlife, or domestic animal wastes.
"A key question is the source of bacteria - human or animal?" White said. "If we know the source, we can find ways to halt the process."
George Gilbert, recently retired chief of the state's Shellfish Sanitation and Recreational Water Quality Section in Morehead City, said the state is becoming more aggressive in determining the cause of pollutants closing so much of the estuarine waters.
The study sites for the project are representative of hundreds of shallow inland creeks along the coastline, many of which are carrying high levels of bacteria.
"We all look forward to the day when we will be able to open up these waters and give them back to the public," Gilbert said.
Toward that aim, a laboratory has been organized to perform fingerprinting analysis on bacterial DNA and to assay bacteria for antibiotic resistance.
The laboratory is located at the Center for Marine Sciences and Technology on the campus of the Carteret Community College in Morehead City.
Molecular microbiologists from the Center for Coastal Environmental Health and Biomolecular Research in Charleston, S.C., are training the N.C. State team on the use of these techniques and will run identical tests on samples to verify the new data.
Researchers Bill Kirby-Smith of Duke University Marine Laboratory in Beaufort, N.C., and Rachel Noble of UNC Institute of Marine Sciences in Morehead City, are also partners in the effort.
Noble's innovative testing uses viral pathogens as tracers of the presence of human fecal contamination in shellfish harvesting and beach waters.
"We're going to learn from each other," White said. "In South Carolina, they have begun to quantify what happens in the landscape to cause the pollution. They know sources and are beginning to understand how the bacteria are being spread.
"They also want to improve their technology. This will show how well these techniques identify the bacterial sources and over how large an area you can use them."
Geoff Scott, acting director for the Center for Coastal Environmental Health and Biomolecular Research at Charleston, said the project offers an opportunity to share the latest in scientific testing methods among academic circles and federal and state governments.
The microbial tracking process, which has only been investigated for the past few years, already has resulted in surprising data.
For example, high bacteria levels in one South Carolina watershed were long believed to be caused by septic tanks, until source-tracking results revealed that excrement from domestic pets was more likely to be the problem.
Another study in Virginia found that fecal matter from a large raccoon population affected the water quality.
"In the past, our methods of testing water quality have been non-specific," Scott said, "in that all we could say is the bacterial count is high.
"Now, we can identify whether the bacteria are naturally occurring or whether they are coming from man-made sources."
To gather the data, White and her colleague will collect fecal droppings, logging the geographic areas of collection and following a painstaking sampling protocol.
The work will be challenging; there are no shortcuts. But the effort will result in a large DNA library organized by species, location and season of sample collection.
In addition, scientists will test bacteria for antibiotic resistance. Human bacteria will generally have higher antibiotic resistance than bacteria from domestic animals or wildlife.
In describing the links between science and design, White explains that each depends on the other for solutions. Her early study of the creek relied heavily on a 30-year analysis of aerial photography and mapping that spatially quantified loss of wetlands.
This mapping makes apparent how development alters the natural, slower movement of water over land.
The more slowly water travels, the more bacteria are attenuated by association with soils, predation, sunlight or other biological processes.
A landscape architect with a Ph.D. in forestry, White brings a comprehensive perspective to land analysis.
"Ultimately, we hope this study will assist us with urban planning on the coast," White said, "telling us how densely we can develop, where we can and can't build septic tanks, and where we need buffers, wetlands and conservation.
"We have to gather hard data in order to address our concerns about the effects of growth. Hopefully, that will contribute to policies that will support both natural and built environments."
Curriculum materials for middle and high schools, as well as workshops for government agencies, will be developed at the study's conclusion by graduate students under the direction of Kirby-Smith.
"The information from this study may change the way we think about procedures for opening and closing shellfish areas," Kirby-Smith said. "Communities need the information to design strategies to improve water quality."
The project is supported for three years with grants from the U.S. Department of Agriculture and the North Carolina Department of Environment and Natural Resources.