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