UNC scientists shed light on how humans are affecting the ecology of the Neuse River Estuary — and our health

The Neuse River Estuary is a valuable resource for North Carolinians: a source for food, recreation and, for many residents, their livelihoods.  But with coastal development and the growth of homes and industries along the Neuse River Basin, the ecology of this vital estuary is changing — and those changes may affect our health.

An estuary is the area at the mouth of a river into which ocean tides f low, mixing salt water from the ocean with fresh water from rivers and streams. Estuaries are important habitats for bird and marine life, including many fish and shellfish used for food. Estuaries also act as filters of the water coming downstream and provide a buffer from f looding. The slow-moving, brackish Neuse River Estuary f lows into the Pamlico Sound.

Over the past four years, an interdisciplinary team of UNC oceanographers, epidemiologists, environmental modelers and microbiologists have come together on the Ecology of Infectious Disease project to understand the changes taking place in the Neuse River Estuary. What happens to pathogens as they are released and travel through the Estuary? What happens to people who come into contact with these pathogens?

Dr. Douglas Crawford-Brown, professor of environmental sciences and engineering in the UNC School of Public Health and director of the UNC Institute for the Environment, is the principal investigator for the Ecology of Infectious Disease project, funded by the National Science Foundation and the National Institutes of Health.

Crawford-Brown and fellow UNC researchers have studied the growth, death and travel patterns of pathogens that enter the river through human influence (e.g., storm water runoff, wastewater spills) and bacteria that are native to estuaries like the Neuse. They also have studied the effects of wind, tides and the mixing of salt and fresh water on how far these pathogens travel through the estuary, how long they live, and the impact of excess nitrogen and phosphorus released into the river by nearby hog farms and agricultural fertilizer.

Several exciting results already have come out of the project. Applying the same approach they used in rapid detection tests for Enterococcus and E. coli bacteria, the UNC team is fine-tuning a rapid, accurate and sensitive test they have developed for Vibrio vulnificus, a potentially harmful bacteria native to estuaries like the Neuse. Vibrio infections are generally a problem only for people with compromised immune systems, including the very young or very old. Infections are rare but can be fatal. In the aftermath of Hurricane Katrina, four people died after suffering wounds in flood waters that contained Vibrio vulnificus. The test has garnered national interest as a tool to protect public health around waterways.

UNC investigators also shed light on how bacteria move through the estuary. “These pathogens ‘hitch a ride’ with other materials in the water,” explains Rachel Noble, a coinvestigator on the study and adjunct faculty member at the UNC School of Public Health. “If you’re a bacteria, and you attach onto a piece of algae, you’d be more likely to sink, so you won’t travel as far as if you attach yourself onto a very small, suspended particle that lets you float down the river.”

Another key finding: Likelihood that this contamination will affect humans increases significantly during and after “extreme events” such as heavy rainfall, heavy wind, hurricanes or tropical storms. These events bring more storm water runoff into the river and churn up pathogens that have settled to the bottom so they become re-suspended. Even after the rain or wind subsides, these pathogens continue to float downstream, creating a continuing risk, even as people think it’s safe to return to the water.

“We’ve made great advances through this project, but there’s a lot more to do,” notes Noble, who holds joint appointments with the UNC Institute of Marine Sciences and the UNC Institute for the Environment. The next step is to use emergency room data to see if there is a link between these findings and incidence of health problems in populations along the Neuse. It’s this crucial link to human health that makes this project so special.

Ultimately, findings from the Ecology of Infectious Disease project can benefit North Carolinians who live near or visit many of the state’s shallow estuaries or who enjoy food harvested from these waterways. While change along our waterways may be inevitable, there may be steps we can take to protect our health and our environment.

Dr. David Weber, professor of epidemiology in the UNC School of Public Health, is a co-investigator on this project. Weber is also professor of medicine and pediatrics in the UNC School of Medicine and medical director of the Departments of Hospital Epidemiology, Occupational Health, and Environmental Health and Safety at UNC Hospitals.

— by Laura Ertel 

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