Researchers at the LSU Agricultural Center are looking for better ways to assess possible sources of pollution in the Tangipahoa River.
Dr. Caye Drapcho, an assistant professor in the Ag Center's Department of Biological and Agricultural Engineering, is leading a team of scientists trying to help maintain the delicate balance between recreational activities and the needs of livestock producers, who also enjoy the outdoors and don't want to be responsible for disrupting the environmental equilibrium.
The Tangipahoa River has had problems with high levels of coliform bacteria for many years, and the Louisiana Department of Environmental Quality has identified the dairy industry as a source of the contamination along with municipal wastewater.
Drapcho is working with Dr. Jim Beatty, resident director of the Ag Center's Southeast Research Station in Franklinton, and Dr. Eric Achberger, associate professor in the Ag Center's Department of Biological Sciences, on a five-year project studying the environmental effects of the Southeast Station's dairy farm.
The researchers are investigating the impact of animal wastes on the river system and designing ways to manage these wastes, Drapcho says. They're evaluating such management practices as vegetative buffers, retention ponds and other deterrents to allowing animal wastes to reach waterways. They also want to help producers continue grazing their cattle without affecting water quality.
"We want to create an atmosphere where dairying and recreation can coexist," Drapcho says.
Drapcho's work focuses both on identifying and assessing non-point source pollution and on designing control systems for point source pollution such as animal feedlots and confinement facilities.
As part of their work in the Tangipahoa watershed, the Ag Center researchers have installed automated water sampling equipment to measure both natural runoff and "agricultural storm water" that collects in a natural drainage channel near the research station to evaluate the amount of runoff and to develop methods to remediate any problems, Drapcho says.
Drapcho explains that part of the challenge stems from south Louisiana's combination of warm weather and wetlands.
Because the methods for testing water for fecal coliforms were developed in cooler climates, researchers are trying to modify the testing procedures to improve their ability to accurately measure potential problems and identify their sources in sub-tropical Louisiana.
The Ag Center research centers around E. coli, bacteria that naturally occur in human and animal feces.
"There are many pathogens involved with fecal contamination-- including viral and bacterial pathogens-- but fecal coliform is an indicator of the others," Achberger says. "If E. coli is present, then other pathogens are, too.
"We're really concerned about all pathogens, but we can't test for all of them," he adds. "So we monitor one organism-- E. coli-- that's indicative of fecal contamination."
The standard test for fecal coliform consists of taking a water sample and incubating it at high temperatures where the bacteria readily grow. The number of coliform cultures that result is considered to be a measure of the fecal coliform content in the water. The test is believed to be effective because fecal coliform can live in warmer environments than other coliforms in nature.
Researchers have discovered that the tests used to monitor contamination in waterways can be tainted by test methods that appear to measure more than what they're expected to measure. They're finding high instances of false positives, where non-fecal coliforms also colonize at the higher temperatures. The researchers believe this occurs because the warmer climate in the South has allowed these forms of coliform to thrive.
The test in general use was developed in New Jersey to measure the safety of sea water on beaches.
The standard for drinking water is zero E. coli while the standard for primary contact recreational use, such as swimming, is not more than 200 average E. coli per 100 milliliters of water with no single sample more than 400 fecal coliforms per 100 milliliters of water for swimming, Achberger says. The standard for fishing and boating is higher.
Drapcho says the Ag Center research has found that roughly two thirds of the time the concentration of coliform is higher than the DEQ standard for primary contact recreational use of waters even without the impact of dairying.
"These results can be attributed to wildlife and to natural soil organisms that appear to adapt and grow in the south Louisiana climate differently from similar organisms in northern areas," she says.
"When we're looking for E. coli we're finding a lot of interference from Klebsiella," Achberger says.
Klebsiella is a bacterium similar to E. coli, but it can be free-living and can give a false positive for fecal contamination, Achberger says.
"We're learning what other tests can be used to determine the concentration of E. coli without measuring the background contamination of Klebsiella," he adds.
Even a river away from farms and municipalities could have a high background from Klebsiella, so this non-fecal bacteria may indicate a problem that doesn't exit.
"Our work will allow people like DEQ to evaluate data and make recommendations based on evidence," Drapcho says.
Achberger is developing a more sophisticated test using microbiological techniques rather than cultures. He's evaluating different techniques-- comparing molecular analysis with classical bacteriology-- to find the best method for south Louisiana studies. One promising procedure uses an additive that can allow testing without incubating samples and can differentiate between fecal coliform and coliforms.
"There's a body of evidence that in tropical and sub-tropical climates, the standards can't be considered reliable," Achberger says. "The problem we've been running into is that in south Louisiana, our sub-tropical climate may cause re-growth of fecal coliform.
"We're looking at a second indicator in the Bacteroides fragilis group that's high in humans and low in animals to be able to get a better idea of the source of contamination," Achberger says.
The researchers are also investigating ways to differentiate between sources of coliform.
"Wildlife can and do contribute fecal coliform and disease-causing organisms to the environment," Drapcho adds.
Drapcho's research is funded from a U.S. Department of Agriculture Tillage, Silviculture and Waste Management Special Grant.
Contact:
Dr. Caye Drapcho at (225) 388-3153 or cdrapcho@agctr.lsu.edu
Dr. Eric Achbertar at (225) 388-2601 or eachber@lsuvm.sncc.lsu.edu
Writer: Rick Bogren at (225) 388-5839 or rbogren@agctr.lsu.edu