Collaborative Research: Eco-geomorphic coupling: Vegetation transition and sedimentary responses to faulting

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The ability of coastal wetlands to survive accelerated sea level rise is a critically important and open question. Coastal marshes, which are dominated by the marsh grass Spartina alterniflora, build the land vertically (accrete) through a combination of ecological, geological and hydrological processes. The U.S. Gulf Coast has numerous growth faults, where the sinking or subsidence of the land surface can be accelerated relative to other coastal areas. Contrasts in the rate of subsidence across these growth faults will result in spatially-identifiable effects on marsh vegetation and on the rate of relative sea level rise. The central hypothesis of this project is that the amount of accretion and vegetative change of Spartina alterniflora wetlands is directly related to the amount of fault displacement. The project will be centered at an established field research station in Matagorda Bay, Texas, where an active, known growth fault bisects a Spartina alterniflora marsh. The field site will be intensively studied using field surveys, the Global Positioning System (GPS), aerial LIght Detection and Ranging (LIDAR) data sets, and tidal gauge cross-referencing to document ongoing elevation changes due to fault displacement; litho- and biostratigraphic methods, combined with paleo-sea level estimates, and radio-carbon (14-C) to provide a historical, geologic context for fault displacement and sea level change; Rod Sediment Elevation Tables (RSET) to directly measure contemporary rates of erosion and accretion; fallout radionuclides (7-Be, 137-Cs, 210-Pb) to provide historical data on sediment accumulation and chronology; and remote sensing imagery and field vegetative inventories, which will provide information on plant community transitions. This project has both national and global implications for managing the productivity of fisheries, documenting the rates of coastal erosion, and developing land-use policies in coastal environments. The ability to determine the contemporary and historical relationships between variable rates of marsh subsidence, accretion and/or erosion, sediment supply, and ecosystem sustainability in terms of relative sea level fluctuation will aid in projecting changes for the future and developing effective adaptation strategies. This project will integrate research, professional training, public outreach and education by the participation of graduate, undergraduate, and K-12 students from the Gulf Coast region.