The Georgia Coastal Ecosystems (GCE) Long-Term Ecological Research (LTER) project was established in 2000 as part of the U.S. LTER network to understand how long-term drivers of climate change, sea level rise, and human alterations affect ecosystems. The site encompasses three adjacent sounds on the South Atlantic coast of the U.S. and includes both intertidal marshes and estuaries. The University of Georgia Marine Institute on Sapelo Island serves as the base of field operations for the project, which includes scientists from multiple institutions (University of Georgia, Coastal Carolina University; Creighton University, University of Delaware, Duke University, University of Houston, Indiana University). The GCE-LTER is studying the effects of four perturbations in water delivery to coastal ecosystems that we anticipate will occur over the coming decades: (1) freshwater inflow will decrease due to population growth; (2) runoff and infiltration patterns will be altered due to increases in impervious surface and changes in groundwater input; (3) sea level rise will push salt water further upstream and also increase the depth and duration of flooding of salt marshes; and (4) precipitation and runoff patterns will be altered due to increased climate variability and shifts in mean climatology, leading to altered frequencies of droughts, storms, and floods. These changes in water delivery can be conceptualized as presses and pulses in river inflow, local runoff, groundwater input, and tidal inundation, all of which will affect coastal ecosystems. The GCE-LTER monitors a number of key variables to track long-term change in the study area (Fig. 1). In the water column, a network of sondes measures salinity, temperature, and pressure, and we regularly collect samples for analysis of nutrients, DIC, chlorophyll, and suspended sediment. In the intertidal marshes we measure soil accretion, accumulation, compaction, and decomposition; assess plant and animal biomass and density; and record disturbance. Together, these measurements allow us to evaluate how the study area is responding to variations in river inflow, sea level, and other boundary conditions. We also use a number of remote sensing approaches to extend our observations back in time and across large areas of the landscape. Map of the GCE-LTER domain on the coast of Georgia, U.S. showing locations of monitoring stations and field studies. SINERR: Sapelo Island National Estuarine Research Reserve. Inset shows the watershed of the Altamaha River in the state of Georgia. The Altamaha is the main source of freshwater to this area. The GCE-LTER conducts long-term field studies designed to characterize the responses of three key marsh habitats (Spartina marsh, fresh/brackish marsh, high marsh) to the pulses and presses in salinity and inundation that might be expected in the future. We have established an eddy correlation flux tower in a tract of Spartina marsh to assess marsh-atmosphere exchange as part of a larger-scale assessment of wetland C storage (Fig. 2). A variety of associated measurements will help interpret the flux tower data and lead to a better understanding of how marsh production, marsh-atmosphere exchange, and carbon export from marshes to the water column will change due to sea level rise and variation in climate. We have established a large-scale field manipulation in a region of fresh/brackish marsh transition to evaluate how pulses and presses of saline water, as might occur with sea-level rise and drought, affect ecological and geochemical processes in a tidal freshwater marsh (Fig. 3). We have conducted surveys to evaluate differences in the high marsh—upland transition areas adjacent to developed vs. undeveloped upland and are in the process of setting up an experimental manipulation to test the effects of altered upland runoff on the high marsh. The GCE-LTER eddy covariance flux tower is located in a Spartina alterniflora marsh on Sapelo Island. Photo by Wade Sheldon. Inset: Images of the marsh surface are taken every 30 min as part of the ecosystem phenology web camera network (http://phenocam.sr.unh.edu/webcam/) so that CO2 flux at the tower can be related to patterns of plant growth. The image was taken during flood tide. GCE scientists measuring net ecosystem exchange in stands of wild rice, Zizaniopsis milacea, in a tidal fresh marsh where we are experimentally simulating saltwater intrusion (SALTEx, Seawater Addition Long Term Experiment). Shown are Joel Craig (left, project technician) and Ellen Herbert (right, Ph.D. student who works with Dr. Christopher Craft at Indiana University). Photo by Chris Craft The GCE-LTER integrates these different types of data using a combination of modeling (two hydrodynamic models that track water movement through the GCE domain; a soil model that predicts porewater salinity in the intertidal marshes; plant models; landscape models) and scenarios that evaluate how changes in salinity and inundation may change habitat provisioning and carbon dynamics in the future. A variety of cruises, focused sampling programs, and short-term experiments provide data to parameterize and validate these models. GCE scientists have published more than 250 papers and almost 50 book chapters since the project began in 2000. Papers cover a range of disciplines, from ecology to anthropology to oceanography. (A complete list of publications can be found at http://gcelter.marsci.uga.edu/public/app/biblio_query.asp.) The GCE-LTER has a comprehensive information management program that supports the project. We have developed several software products, database systems and web applications that have been released as open source software and adopted across the LTER Network and in other environmental informatics programs. Examples include the GCE Data Toolbox, a MATLAB software library for metadata-based processing, analysis, quality control and synthesis of ecological data (https://gce-svn.marsci.uga.edu/trac/GCE_Toolbox) and the Metabase, a comprehensive metadata management, search and distribution system that supports the entire data life-cycle. At present there are 490 online datasets in the GCE-LTER data catalog, and 640 in our data portal, representing over 18 million data records that are freely and publically available. Finally, the GCE education and outreach program provides training and professional opportunities to K-12 educators, undergraduate students, graduate students, and international collaborators. There are currently 31 graduate students from eight institutions engaged in LTER activities, and there have been 34 Ph.D. dissertations, and 22 M.S. theses to date. We reach school children though our children's book, “And the Tide Comes In;” we work with coastal managers through the Georgia Coastal Research Council (www.gcrc.uga.edu); and we reach the general public through presentations, popular publications, and other events. The GCE is one of 25 LTER sites funded by the U.S. National Science Foundation to provide the scientific expertise, research platforms, and long-term datasets necessary to document and analyze environmental change (www.lternet.edu). The sites in the LTER network represent a range of ecosystems including deserts, prairies, forests, tundra, lakes, urban areas, estuaries, coastal reefs, the pelagic ocean, and production agriculture. Although the research focus varies across the network, each site collects data on primary production, population dynamics, the cycling of both organic and inorganic matter, and disturbance patterns. Long-term data in these core areas enable changes in critical ecological processes to be tracked over time and facilitate comparisons among sites. For more information, see www.lternet.edu. We thank all of the GCE personnel, both past and present, who have contributed to this effort. Funding was provided by the Georgia Coastal Ecosystems LTER Project (NSF Awards OCE-99-82133, OCE-0620959, and OCE-1237140). Merryl Alber, Department of Marine Sciences, University of Georgia, Athens, GA, 30602, USA Steven C. Pennings, Department of Biology and Biochemistry, University of Houston, Houston, TX, 77204, USA James T. Hollibaugh, Department of Marine Sciences, University of Georgia, Athens, GA, 30602, USA