Collaborative Research: Ecosystems on the Edge - Tidal wetland-estuary margins as buffers, reactors, and transformers of organic carbon and nitrogen

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Tidal wetlands are among the most productive, diverse and economically important ecosystems on Earth. They are also especially vulnerable to human pressures and environmental change. Wetlands contain large reservoirs of soil organic matter, an important source of carbon and nitrogen to estuaries and coastal oceans, but very little is known about the processes involved in the translocation of these nutrients. This project will advance understanding of tidal marsh-estuarine interactions by linking processes between tidal wetland soils and estuaries, and assessing where, when, and how dissolved organic compounds are retained, released and transformed within the marsh soil-estuarine system. Results from this study will be integrated into enhanced monitoring and management efforts through partnerships with the Environmental Protection Agency, the National Oceanic and Atmospheric Administration and the National Estuarine Research Reserve System. The project will improve models that predict the influence of wetlands on estuarine and coastal biology, geochemistry and pollution response. In collaboration with the Smithsonian Citizen Science program and teachers from middle schools serving minority students, the team will develop K-12 educational materials. Specialized training will be extended to undergraduate students, as well as graduate and postdoctoral researchers, with a particular focus on underrepresented groups in science. This study will test three key research hypotheses that are critical for understanding the role of marsh soils and tidal wetland-estuary margins as buffers, reactors, and transformers of dissolved organic C and N, and that could transform our ability to predict the influence of wetland ecosystems on estuarine biology, biogeochemistry, and ecology. An integrative approach will be used to test hypotheses that combines rich datasets, process-focused experiments, and a novel coupled hydrodynamic-photo-biogeochemical model to investigate three understudied aspects of marsh export that likely control the seasonality and fate of dissolved organic matter in estuaries: (i) soil and porewater organic matter composition, (ii) adsorption-desorption on soil surfaces, and iii) photo- and bio- degradation in estuarine waters. Proposed activities incorporate a system perspective and cover a broad range of marsh environments (i.e., different marsh vegetation characteristics, soil type, surface area and salinity regimes) providing the ability to scale up and assess tidal marsh biogeochemical fluxes and processes across a range of spatial and temporal scales. Results from this research will increase understanding of the contributions of wetlands and estuarine systems to coastal carbon and nitrogen budgets, and improve predictions of the influences of natural and man-made stresses on ecosystem processes, biogeochemical cycles and exchanges along the continuum of wetlands, estuaries and the coastal zone. This information is highly valuable to managing the coastal zone in the face of accelerated environmental change and continued human pressures and, in particular, to evaluating the potential for managed restoration of wetlands to mitigate climate change impacts.