Collaborative Research: Network Cluster: The Coastal Critical Zone: Processes that transform landscapes and fluxes between land and sea

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Coastal marshes are essential environments that preserve a fragile and highly valuable ecosystem. They are an integral part of the Critical Zone that regulates the conditions at the Earth’s surface and helps sustain life. Coastal marshes provide crucial services such as carbon storage and removal of nutrients and contaminants that would otherwise make their way to the ocean. Rising sea level is expanding these environments, but salt-water is also moving in, destroying woodlands, and damaging farm fields. Ghost forests and salt-damaged farm fields are stark indicators of these ecological changes along world coastlines that can adversely affect land use and economies. Less apparent, and perhaps even more important, are the concurrent changes in water and chemical cycling that are altering the functioning of the coastal Critical Zone. This research project will quantify the processes that occur in the changing coastal Critical Zone and associated alterations in cycling, fluxes, and storage of elements at the land-sea margin. The project will address important questions about how sea-level rise may alter the natural “plumbing” that occurs at the land-sea boundary and its implications with respect to coastal ecosystems. The results will assist decision-makers and stakeholders in planning for future environmental changes. This project will quantify the coupled processes and feedbacks that govern the hydrological, ecological, geomorphological, and biogeochemical transformations in the coastal Critical Zone and how rising sea level will translate to changes in cycling, fluxes, and storage of elements at the land-sea margin. Sea-level rise pushes salt and inundation fronts inland via storms and tides (fast processes) while gradually elevating the water table (slow processes). The complexity of the system, with its strong hydrologic transience (e.g. tides, storms), tightly coupled ecosystem and biogeochemical mosaics, and human influences, make functioning and response at the marsh-upland transition difficult to characterize and predict. The governing hypotheses of this project address (1) the major fast and slow hydrological drivers of coastal Critical-Zone transition, (2) the landscape feedbacks in which ecological change drives geomorphological evolution that feeds back into hydrological and biogeochemical processes, and (3) biogeochemical feedbacks in which salinization and redox shifts alter cycling, mobility, and sequestration of nutrients and carbon. These processes differ between areas where the marsh abuts forested uplands versus agricultural land. The hypotheses will be addressed through interdisciplinary field observations, experiments, and modeling that are fully integrated across three locations along the mid-Atlantic coast with paired marsh-forest and marsh-agriculture sites. The forested and agricultural sites at each location represent major differences in hydrology, geochemistry, and ecology, and are expected to respond differently to rising sea level. This project addresses pressing needs to determine how landscapes in the coastal Critical Zone may respond to sea-level rise and how Critical-Zone research can be applied to developing policies and actions to mitigate the effects.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.