Gregg Snedden, Ph.D.
Ph.D., Oceanography and Coastal Sciences, Louisiana State University, 2006
M.S., Fisheries Science, Louisiana State University, 1997
B.S., Aquatic Ecology, University of Illinois, 1993
2007 - Present, Research Ecologist, USGS Wetland and Aquatic Research Center (formerly National Wetlands Research Center)
2005 - 2007, Post-Doctoral Research Fellow, UNC-Wilmington Center for Marine Science
2000 - 2005, Research Associate, Coastal Ecology Institute, Louisiana State University
1993 - 1997, Research Assistant, School of Forestry, Wildlife and Fisheries, Louisiana State University
Science and Products
Developing effective living shoreline restoration projects that can withstand hurricanes and storms requires a better understanding of how restoration structures reduce the impact of wave and current energy on marsh edges in estuaries and bays. Without this knowledge, existing living shoreline projects and adaptive management measures are more likely to fail, decreasing the possibility for...
USGS research in the Florida Everglades will provide information on how environmental conditions and disturbances impact carbon storage in mangrove systems.
Influence of Sea-Level Rise on Wetland Vegetation Community Structure, Primary Productivity, Organic Matter Decomposition and Carbon Storage
This study will employ a space for time substitution to show long-term effects of rising sea-level and increasing salinity on vegetation community structure, primary production and decomposition. Productivity and decomposition rates will be estimated for four wetland plant community types defined by salinity zones and dominant plant species.
Will wetland vertical accretion rates be enough to keep up with the predicted rates of sea level rise? USGS looks at soil properties and geochronology in Louisiana wetlands.
Surface Water Hydrology and Nitrate Dynamics in Delta Islands of Prograding Wax Lake Delta, Louisiana
The Wax Lake Delta is an ideal ecosystem to study the effects of a large-scale river diversion on the biogeochemistry of coastal wetlands, and the capacity of these wetlands to assimilate nutrients delivered by these diversions. USGS works to develop a better understanding of surface water hydrology and nitrate dynamics in this area.
Sediment and Nutrient Retention by Wetlands Receiving Inflows from a Mississippi River Diversion: A Mass Balance Approach
Diversions are currently used in the Mississippi River to stimulate delta growth via increased sediment supply. This technique may also help to reduce nutrient loads before its discharged into the ocean. Scientists at USGS assess how wetlands retain the sediment and nutrients that come from these diversions.
Diversions are being used to encourage Missippi River delta growth via increased sediment availability to coastal wetlands. USGS studies hydrodynamics and sediment transport in Louisiana to better understand how marshes and deltas respond to these sediment inputs.
Wetlands along the Gulf of Mexico coast play an important role in the global carbon cycle, but as they rapidly convert to open water, their potential for carbon storage is declining. USGS is working to provide accurate, long-term marsh soil carbon sequestration rates.
Wetlands are often classified by their vegetation, which can help scientists track how these landscapes change over time. USGS turns to unsupervised artificial neural networks to help guide this classification process.
Drivers of barotropic and baroclinic exchange through an estuarine navigation channel in the Mississippi River Delta Plain
Estuarine navigation channels have long been recognized as conduits for saltwater intrusion into coastal wetlands. Salt flux decomposition and time series measurements of velocity and salinity were used to examine salt flux components and drivers of baroclinic and barotropic exchange in the Houma Navigation Channel, an estuarine channel located in...Snedden, Gregg
Inundation and salinity impacts to above- and belowground productivity in Spartina patens and Spartina alterniflora in the Mississippi River Deltaic Plain: implications for using river diversions as restoration tools
Inundation and salinity directly affect plant productivity and processes that regulate vertical accretion in coastal wetlands, and are expected to increase as sea level continues to rise. In the Mississippi River deltaic plain, river diversions, which are being implemented as ecosystem restoration tools, can also strongly increase inundation in...Snedden, Gregg A.; Cretini, Kari Foster; Patton, Brett
Sediment discharge into a subsiding Louisiana deltaic estuary through a Mississippi River diversion
Wetlands of the Mississippi River deltaic plain in southeast Louisiana have been hydrologically isolated from the Mississippi River by containment levees for nearly a century. The ensuing lack of fluvial sediment inputs, combined with natural submergence processes, has contributed to high coastal land loss rates. Controlled river diversions have...Snedden, G.A.; Cable, J.E.; Swarzenski, C.; Swenson, E.
Subtidal sea level variability in a shallow Mississippi River deltaic estuary, Louisiana
The relative roles of river, atmospheric, and tidal forcings on estuarine sea level variability are examined in Breton Sound, a shallow (0.7 m) deltaic estuary situated in an interdistributary basin on the Mississippi River deltaic plain. The deltaic landscape contains vegetated marshes, tidal flats, circuitous channels, and other features that...Snedden, G.A.; Cable, J.E.; Wiseman, W.J.