Coastal nutrient enrichment has resulted in saltmarshes being one of the most endangered ecosystems in the world. This over enrichment has compromised the ability of saltmarshes to provide key ecosystem services such as buffering coastal cities from storms, providing habitat for fish and shellfish, and mitigating climate impacts by storing carbon. The U.S. is investing millions of dollars to reduce nitrogen to coastal regions and embarking on large-scale saltmarsh restoration costing millions to billions of dollars to restore lost ecosystem services. Currently, it is unknown how quickly or if ecosystem services will return after nutrient inputs are cut. This research will provide insight into nitrogen pollution as a cause of marsh loss and the potential for ecosystem recovery with management strategies. There are several education efforts associated with this project that will train students. The project enhances education by developing high school curriculum on "Research and Resiliency: Investigating the Local Effects of Global Changes" in collaboration with the Massachusetts Audubon Society. A program for mid-career journalists about environmental science will also be developed. This project will facilitate sustainability and provide a science-based foundation for state and federal nutrient standards. <br/><br/>This project will address how the effects of historical nutrient over enrichment influences the ability of marshes to recover their ability to provide ecosystem services. The project will use a combination of whole-ecosystem experimental manipulations, field measurements of key species, assays of genetic change, nutrient and carbon cycle processes, and food-web structure in six experimental sites to determine recovery trajectories. Researchers will measure changes in the decomposer community genetic diversity and activity by sequence amplicons of functional genes responsible for encoding key enzymes in the nitrogen cycling processes. The project will measure plant traits and genotypic diversity. The recovery of carbon and nitrogen cycling will be determined from marsh geomorphology, habitat-specific denitrification rates, nitrogen exchange with the open bay, and decomposition. Measuring the species diversity, abundance and productivity and stable isotope of invertebrates and fish will assess food web recovery.<br/><br/>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.