Overview: Salt marshes play a significant role in the climate feedback system. Salt marshes are efficient at carbon burial and emit greenhouse gases. Under predicted climate change, sea level rise will potentially alter the carbon burial capacity of these systems. Nutrient loading is an additional external stressor in these systems which may impact carbon and greenhouse gas cycling. In this project, the fellow will study the impact of sea level rise and nitrogen enrichment on subsurface cycling of greenhouse gases and carbon in salt marshes with Kevin D. Kroeger, PhD at the United States Geological Survey.
The fellow plans to install a network of observing wells within a salt marsh system across nitrogen enrichment and inundation levels, and collect samples monthly for two years for dissolved carbon and nitrogen. In addition, she will quantify subsurface production of greenhouse gases in these salt marsh sediments with an installation of hydrophilic, gas permeable tubing attached to gas analyzers during the same monthly sampling. Measurements will be taken of porewater flux both within the salt marsh subsurface and out of the marsh to determine fluxes of these constituents to receiving estuarine waters and ultimately the coastal ocean. The study site exists in a sea level rise hot spot and, therefore, an ideal location to determine how enhanced rates of sea level rise over the past twenty-five years have changed carbon burial in salt marshes. Sediment cores will be collected from sites that undergo a range of nitrogen loadings and seawater inundation levels to synthesize the salt marsh carbon burial response through time to these two stressors (nutrient enrichment and sea level rise). Results from this study will further understanding of the potential climate impacts on the ecosystem services of salt marshes.
Intellectual Merit: The earth is faced with a high CO2 future, with potential climate impacts resonating through global coastal ecosystems via increasing temperatures and rising sea level. Population growth in coastal regions places added stress on ecosystems via nutrient enrichment. Salt marshes are regions of high carbon burial, and as such their carbon storage potential is of interest to both the scientific community and to stakeholders making decisions about carbon remediation. The direct impact of climate change on salt marsh ecosystems is unknown, however, potentially significant. In addition to their ability to store carbon, salt marsh ecosystems also produce and emit greenhouse gases, such as methane and nitrous oxide. Research results from this project will help to determine if carbon burial in salt marshes will be resilient in the face of climate change and if the net impacts of greenhouse gas emissions will reduce or negate the value of salt marshes as a carbon sink.
Broader Impacts: This project is synergistic with a larger established project evaluating surface greenhouse gas evasion and lateral carbon fluxes from salt marsh ecosystems across a gradient of nitrogen loading. A key component of this project is to use collaborative learning to transform the scientific results into useable products for policy makers and others interested in the economics of salt marsh ecosystem services. With this framework in place, the results of this work will be directly linked to coastal policy decisions regarding salt marshes. In addition, broadening participation educational opportunities are a significant component of this project. The second field season will include participation of an undergraduate student from the Woods Hole Partnership in Education Program. The student will conduct original research within the framework of this project and attend a national conference to present the findings of their research. The fellow will also serve as a lecturer and mentor in the Waquoit Bay National Estuarine Research Reserve Women in Science Program throughout the project. This program allows young women in grades 7-9 to explore science in the context of estuarine research at the Reserve.
