Microbial source tracking to evaluate links between human, animal and environmental health: Tuesday, February 25th

This past week’s One Health Intellectual Exchange Group’s topic focusing on microbial source tracking in bodies of water was presented by Dr. Jill Stewart.  As an Assistant Professor in the Department of Environmental Sciences and Engineering at the University of North Carolina, Dr. Stewart develops techniques to detect and track pathogens in water.  Dr. Stewart’s current research projects involve water quality evaluation associated with land application of waste products and water quality evaluation associated with urbanization on watersheds.  Her work with environmental sciences show how environmental impacts can affect human health.

During the presentation, Dr. Stewart addressed the following learning objectives:

• Name a standard indicator used to detect fecal pollution of surface waters.
• List three issues associated with the use of traditional fecal indicator bacteria to monitor water quality.
• Define microbial source tracking and name a marker that can be used to track human-source pollution in water.
• Describe how microbial source tracking can be used to mitigate water pollution.

The presentation began with an introduction on microbial pollution and microbial detection.  Dr. Stewart works with bacteria, viruses, and protozoa.  Microbial pollution on water and shellfish include various sources such as waste water treatment plants, marinas, wild and domestic animals, recreational use, and food (for example, oysters).  In order to detect the microbes, membrane filtration is performed and fecal coliform colonies are analyzed.  This technique is widely used; however, there are some drawbacks.  Disadvantages include time (it takes about twenty-four hours to complete), type of pathogen (it only works for bacteria), and determination of contamination source.  Microbial Source Tracking (MST) is the method to determine fecal pollution in water sources.  Molecular techniques such as PCR and assays are also incorporated.  Markers of fecal microorganisms are used for analysis.  Fecal indicator bacteria includes Escherichia coli.  Depending on the presence of markers, fecal pollution can be linked to land development or other human causes.

The remaining of the presentation focused on two of Dr. Stewart’s studies.  One of Dr. Stewart’s studies was conducted at Jordan Lake.  The purpose of the study was to determine storm water and land use effects on microbial contamination.  Water samples were collected at various types of area uses and different storm times.  The fecal indicator bacteria were compared at a regulatory threshold, and the markers used were Bacteroides sp. (HuBac) and Methanobrevibacter smithii (nifH).  There was a positive correlation between land development and microbial contamination.  Storms had more of a contaminant load, and loading occurred over the course of the storm.  Therefore, there was no difference in loading between dry conditions and stormy conditions.

A second study discussed by Dr. Stewart concerned fecal indicator bacteria and swine farms.  Eastern North Carolina has most of the state’s swine operations, and North Carolina is the nation’s second largest state in swine production.  To control swine fecal waste, common applications are swine lagoons and spraying fields.  Again, Dr. Stewart found that there were higher levels of fecal indicator bacteria with rain.  Swine genetic markers analyzed included pig-1-BAC, pig-2-BAC, and pig-BAC-2.  The markers pig-1-BAC and pig-2-BAC were found to be correlated with pig waste. 

In addition to her studies within North Carolina, Dr. Stewart also collaborates with researchers in the Galápagos Islands.  A few studies were conducted by measuring water quality around sewage pipes, which emptied into the ocean.  The water treatment plants also had fecal indicator bacteria.  Dr. Stewart along with students will continue research in the Galápagos Islands.

The presentation concluded with Dr. Stewart stressing that single-sample monitoring for water sources may be inadequate, and alternative indicators may be necessary.  These points are exemplified in her studies with land use and water contamination as well as storm water affects on water contamination.  Her presentation and studies support the One Health concept connecting environmental health and human health. 

Discussion and questions followed the presentation.  Questions included the following topics:

• The affect of tides and timing on the analysis of storm water leaving sewage pipes in the Galápagos Islands
• Analyzing antibiotics directly in samples
• Water pollution by tour boats in the Galápagos Islands
• Collaborative work with Engineers Without Borders in the Galápagos Islands
• The difference between indicators and pathogens
• Costs for molecular techniques
• The use of caffeine as an indicator

Post Authored by Erin Beasley

NC State University

Feedbacks between shallow water coastal ecosystems and human well-being: Tuesday, February 25th

On Tuesday, February 25^th the North Carolina One Health Collaboration welcomed two speakers for the evening’s Intellectual Exchange Group meeting.

Dr. Mike Piehler is dually appointed as an Associate Professor at the UNC Chapel Hill Institute of Marine Sciences in Morehead City, NC and as Head of the Program in Estuarine Ecology and Human Health and the UNC Coastal Studies Institute in Manteo, NC.  He is also the Director of Graduate Studies for the Curriculum for the Environment and Ecology at UNC Chapel Hill.  Dr. Piehler drove up from the coast last Tuesday to share his expertise and current research on microbially mediated processes in coastal land-water interfaces and their links to human health with the NC One Health Intellectual Exchange Group. 

Dr. Piehler explained the importance of maintaining coastal shallow water ecosystems as “transition zones” between land based and fresh water areas and marine environments.  These areas mediate the contents of rivers feeding into the sea that are increasingly bringing excess nutrients and pollutants from sources such as fertilized fields or wastewater treatment facilities.  Without these zones, the excess nutrients can facilitate harmful algal blooms, which then deplete oxygen levels in the water as they decay, causing fish and plant-life kills. 

Currently, the world has lost between fifty and seventy percent of its flatland estuaries and nearly ninety percent of its oyster reefs.  Damage to coastal shallow water ecosystems increases globally as human population density in those ecosystems increases.  Dr. Piehler showed that these transition ecosystems are crucial for maintaining a balance to the influx of nutrients, sediments, and salinity in the water in such a complex way that alternate human interventions are hard-pressed to be as comprehensive or effective.

Nitrogen

Dr. Piehler has focused on nitrogen fluctuation in studying the importance of wetland ecosystems at the UNC Costal Studies Institute and at the Camp Lejeune military base in eastern North Carolina.  Nitrogen is key to limiting primary productivity at the intersection of fresh and salt water.  A healthy nitrogen cycle is threatened by augmentation of nitrogen in the water sourced mainly from fertilizers in the form of nitrite or ammonium. 

More is not always better in the case of ecological nitrogen levels.  There is a threshold for the amount of fixed nitrogen that is a beneficial to human, animal, and environmental health (Figure 1).¹ Beyond this levels instances of pollution and disease are increased.

Camp Lejeune DCERP Study

With funding from the Defense Coastal/Estuarine Research Program (DCERP), Dr. Piehler and colleagues studied the footprint of a military base on an estuary at Marine Corps Base Camp Lejeune.  An increase in nitrogen levels and in total suspended solid load was visible in the five streams tested as increases in development were seen.  The relationship of ammonium levels to development was not as clear.  In all cases more loading was seen during storms.  Currently, laws to control high levels of nutrients and pollutants entering streams and estuaries as a result of storms are of a small scale and are poorly monitored/ enforced.  Using regression modeling the researchers were able to predict loading in areas with various amounts of development.

Importance of Wetland Restoration

Dr. Piehler estimates that the cost to remove excess nitrogen if not done by oyster reefs is $1600 per year, per hectacre.  Oyster Reefs have among the highest denitrification potential and thus if restored can rebalance eutrophication areas. Subtidal flats, although they have lower rates of denitrification, are just as important because they cover a large area.  Wetlands provide numerous services under four different categories outlined by Dr. Piehler: Provisioning, Regulating, Cultural, and Supporting.  While Dr. Piehler does acknowledge that there are drawbacks to wetlands, such as competition for land for development or the potential for infectious diseases to breed in these areas, he demonstrates that the services provided by wetlands make them extremely valuable and that they should be restored and protected.

Future Concerns

The effects of global warming, drought, rising sea levels, and natural disasters are all concerns for the future of wetland ecosystems.  Dr. Piehler noted many ways these effects could be predicted and buffered through research on topics including:

• The impact of intense wet periods and protracted dry periods on river and wetland life
• The impact of changing tide ranges on coastal shallow water life as overall sea levels change
• The change in patterns of natural disasters and storms and their effects

As Dr. Piehler and his colleagues believe, the number one “eutrophication commandment” is to protect costal ecosystems for biodiversity services.

Figure Reference:

1) Townsend, Alan R., et al.  “Human health effects of a changing global nitrogen cycle.” Frontiers in Ecology and the Environment 1.5 (2003): 240-246.

Paige Meier

Duke University