GCE Research Program

Program Overview

In GCE-I we began to describe the patterns of variability in estuarine processes with an emphasis on water inflow as a primary environmental forcing function. During GCE-II, we are continuing our focus on patterns of variability, but we are also working to elucidate the mechanisms that underlie this variation and in particular the extent to which gradients in water inflow drive landscape patterns. In so doing, we recognize the necessity of evaluating the interaction of inflow-driven changes with other factors that influence estuarine processes (i.e. geologic setting, organismal interactions, etc.). The central paradigm of GCE-II is that variability in estuarine ecosystem processes is primarily mediated by the mixture of fresh and salt water flow across the coastal landscape.

Transformational Scientific Research

1. Salt Marsh Herbivores – GCE scientists discovered that herbivores such as grasshoppers are more abundant and do more damage to plants in salt marshes at low versus high latitudes. This finding helps explain geographic variation in the palatability of coastal plants and in herbivore body size. (more information)
2. Sea Level Rise – GCE scientists predict significant declines in wetland area in response to sea level rise. However, because different types of wetlands provide varying levels of ecosystem services, the loss of services due to sea level rise is actually less than forecast based on losses of total wetland area alone. (more information)
3. Nitrogen to the Coast – GCE scientists determined that only 9% of the nitrogen that enters watersheds in the southeastern US is transported to the coast, compared to 25% in the northeast. They suggest that the difference is due to increased temperatures in the south, and that global estimates of nitrogen export are too high. (more information)
4. Microbes & Nitrogen – GCE scientists are studying a novel group of microbes that appear to convert nitrogen from ammonium to nitrate. Very little is known about these organisms, but their potential importance has implications for both understanding nitrogen cycling and controlling nitrogen pollution. (more information)
5. To be or not to be – The density of marine organisms varies tremendously among and within habitats, leading to very different communities. GCE scientists combined ecological approaches with modern genetic analyses to reveal how abundance and genetic diversity of larvae vary from inland to offshore, with important implications for populations of snails, barnacles, and other organisms. (more information)

Signature Publications

Conceptual models guiding GCE research

Left: Longitudinal perspective showing relative contributions of river discharge, groundwater flow, oceanic influence and net flow in three coastal sounds.

Right: Lateral movement of water among subtidal, intertidal and upland habitats; A & B: river discharge and tidal flow combine to move water up and downstream, C: tidal exchange brings water on and off the marsh platform, D: precipitation, E: precipitation leads to overland flow (runoff) if soils are saturated or impermeable, F & G: groundwater may flow directly into the marsh or may transit under the marsh to emerge sub-tidally, H: evapotranspiration. By layering this model on top of the landscape model on the left, we will gain a more sophisticated understanding of spatial variation in ecosystem processes across the GCE landscape.

Current Research Questions

GCE Research Projects

Many long-term core research projects and individual investigator studies have been initiated to address components of these over-arching research questions. A database of GCE research projects, including all associated personnel, study sites and research products (publications, data sets and reports), was recently developed and is currently being populated. Project descriptions can be accessed from links on corresponding research question pages (above), or from a list of all ongoing and complated projects here.