This action funds an NSF Minority Postdoctoral Fellowship for FY 2008. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation in biology. The research and training plan for this fellowship to Marcelo Ardon-Sayao is entitled "Nutrient cycling in coastal wetland ecosystems under an accelerating hydrologic cycle." The sponsoring scientist is Dr. Emily S. Bernhardt at Duke University.
Global climate change is forecasted to impact society and ecosystems by altering the frequency and intensity of extreme weather events. Increased intensity and frequency of storms could impair the ability of coastal wetlands to prevent water quality problems, such as increased nutrient runoff to coastal ecosystems. The main goal of this research is to develop empirical relationships describing the effects of increasingly variable wetland hydrology on nitrogen (N) and phosphorus (P) retention in nutrient rich coastal plain ecosystems by addressing the following questions: 1) How does timing and frequency of storms affect the fate and transport of N and P across a recently restored wetland ecosystem? 2) How does the temporal variability of rainfall affect transformations of N and P in wetland soils? 3) How do landscape fluxes of N and P change during rapid experimental reductions of water level? Research will be conducted primarily within a 400-ha wetland mitigation project in Tyrell County, NC.
The training goals include learning new experimental and analytical techniques to examine the effects of altered hydrology on nutrient transformation in wetlands across different scales and establishing long-term collaborations with scientists in different disciplines, government officials, consultants, and land owners to further the application of research to public policy. Broader impacts include increasing the participation of under-represented minorities at the postdoctoral level and mentoring undergraduate students in ecological research, making an effort to involve underrepresented minority students. This research will aid predictions of the likely direction of change of nutrient exports as a result of a more hydrologically variable future for southeastern coastal plain ecosystems.
Nitrogen and phosphorus are important nutrients necessary for life. However, through agriculture, land use change, and burning of fossil fuels we have increased the amounts of nitrogen and phosphorus reaching aquatic ecosystems (lakes, streams and wetlands). Polluting levels of nitrogen and phosphorus in aquatic ecosystems can cause negative consequences such as high growth of algae and water plants, decreased water quality, and fish kills. Wetlands have the capacity to retain and remove nitrogen and phosphorus from aquatic ecosystems. Most naturally occurring wetlands, however, have been lost to development. Thus, wetland restoration is increasingly being used as a tool to recover some of the services that historically were provided by wetlands, such as the removal and storage of nitrogen and phosphorus. Wetland restoration seeks to recover lost services by reinstating wetland hydrology and planting of wetland species. Due to both market and regulatory forces, many wetland restoration projects are built in former agricultural fields. Recovery of wetland services in former agricultural fields is challenging due to the many alterations to hydrology and soils caused by agricultural practices. Vast systems of ditches and pumps were necessary to drain wetlands for agriculture. Fertilizer application and soil tilling alter the chemical and physical structure of soils. Wetland restoration must reverse these various insults in order recover lost services. This project examined the water quality consequences of a large wetland restoration project in the coastal plain of North Carolina. One of the main objectives was to determine if the reinstatement of wetland hydrology and planting of wetland plants in a former agricultural field would lead to the recovery of nutrient retention services provided by wetlands. We were interested in examining both potential benefits and unforeseen consequences. We examined whether re-flooding the former agricultural field as part of wetland restoration could recover the processes by which nitrogen is retained, while causing the release of phosphorus that accumulated in soils due to past fertilizer application. We measured all inputs and outputs of water and nutrients in the first three years after restoration. Our results indicated that the restored wetland did a good job at retaining nitrogen, but released phosphorus during spring months and after storms. This release of phosphorus is likely the result of past fertilizer application to the soils. It is likely that phosphorus release will decline over time, but it is unclear how long that will take. Reconnecting the former agricultural field to the downstream estuarine system was part of the restoration plan. This site had been actively pumped for approximately twenty years, while it was under agricultural production. While hydrologic connectivity is normally considered a positive aspect of restoration, because it allows the free upstream movement of fish and other aquatic organisms. In this case, due to the low topographic relief and changes in precipitation, hydrologic reconnection facilitated salt water intrusion into the site. During two drought years, we documented salt water intrusion into the site due to surface water mixing and wind driven tides. Salt water intrusion led to changes in the forms of nitrogen and decreases in the quantity and quality of carbon leaving the site. Ongoing research is examining the potential mechanisms that led to changes in the carbon and nitrogen export due to salt water intrusion. This research has advanced the academic training of a postdoctoral researcher, one graduate student, three undergraduate students, and one high-school student. Results have improved our understanding of nutrient cycling in a large restored wetland under changing hydrologic regimes by illustrating some of the unforeseen consequences associated with wetland restoration. Results from this project are being shared with government agencies, private mitigation bankers, and the general public to help inform the practice of wetland restoration. Results from this project extend beyond this particular site, because similar agricultural landscapes are being restored or abandoned throughout the southeast US.
