Ocean margins cover only 5% of the ocean surface, but as much as 50% of integrated oceanic new production occurs over continental shelves and slopes, intimately tied to the close connection to land. We are interested in the mitigation and removal of nutrients during their passage through the subsurface, precluding eutrophication of the coastal ocean. Our work combines subsurface hydrology and biogeochemistry to better understand the role of marshes and the fresh-saltwater transition zone as material filters and critical interfaces between the land and the ocean. Gulf of Mexico/Big Bend saltmarsh with Hammock Georgia Coastal Ecosystems LTER The GCE-LTER program documents long-term patterns and processes at the coast of Georgia on and around Sapelo Island. In this collaborative effort involving many scientisits from a wide range of disciplines, our focus is on marsh hydrology and the associated nutrient fluxes in the marsh subsurface, and its connectivity to the upland and the tidal creeks. For more information visit the GCE-LTER project site. Dissolved Organic Carbon Outwelling from Salt Marshes A key variable to understanding the coupled terrestrial and marine carbon cycles lies in the transfer of carbon from land to ocean. Little is known about the magnitude and fate of organic matter that originates in coastal marshes and enters the coastal ocean, even as over half of the US coastal wetlands have been destroyed in the last 50 years. In a collaboration with J. Cable (UNC), J. Cherrier (FAMU) and R. Chen (UMass Boston), we combined high spatial and temporal resolution observations with discrete biogeochemical sampling and spatially explicit modeling to assess the role of salt marshes in the global carbon cycle. Methane emissions from tidal freshwater marshes Methane is an atmospheric greenhouse gas that is an integral part of the global carbon cycle. Much of the methane is produced biologically, and globally, between 20-40% of the annual methane flux to the atmosphere originates from freshwater wetland sediments. However, critical aspects of the factors regulating methane production and release from freshwater wetlands remain poorly understood. In a project led by the Joye Lab(UGA), we complemented in-situ sampling in Florida, Georgia and Massachusetts and laboratory experimentation with reactive transport modeling to evaluate how temperature, an important aspect of modern global change, organic carbon availability and microbial populations interact to regulate mineralization of complex organic matter and production of methane. Where groundwater meets the ocean Increase in population pressure at and near the coastline lead to increased anthropogenic input to the coastal ecosystem, including introduction of organic and nutrient rich material to the groundwater discharging into the coastal surface waters. More on what happens at the Georgia coast can be found here.
