Presentation Abstracts: Gulf Coast Science Conference
1: Understanding ecosystems and predicting ecosystem change: Ensuring the nation’s economic and environmental future
Large Scale Landscape Change and Natural Hazards in the Northern Gulf of Mexico
Brock, J.C.1, Lavoie, D.L.2, Barras J.3, and Nayegandhi, A.4
1 Coastal and Marine Geology Program, USGS National Center, Reston, Virginia
2 Gulf of Mexico Science Coordination Office, University of New Orleans, New Orleans, Louisiana
3 National Wetlands Research Center, Coastal Restoration Field Station, Baton Rouge, Louisiana
4 Jacobs Technology, Inc., Florida Integrated Science Center, St. Petersburg, Florida
Following the devastation wrought by Hurricanes Katrina and Rita in August –September 2005, a better understanding of the northern Gulf of Mexico (NGOM) coastal system is a basic requirement for sustainable restoration, redevelopment, and sound natural resource management strategies. Further impetus for investigations of the geomorphological structure, ecological function, and hazard vulnerability of the northern Gulf Coast stems from global climate projections that suggest more intense Atlantic hurricanes will occur over the next several decades. Moreover, dramatic landscape change in the NGOM region during the last century has reduced the level of hurricane protection afforded to NGOM human populations by coastal wetlands and barrier islands. The Coastal and Marine Geology Program is partnering with other USGS Disciplines and other federal and state agencies to investigate these highly societally relevant questions within the Northern Gulf Coast Northern Gulf Coast Ecosystem Change and Hazard Susceptibility project. This large interdisciplinary project is conducting research on 1) the reconstruction of Holocene geologic stratigraphy, paleoenvironments, climate, and sea-level histories, 2) the historical period evolution of the NGOM landscape, 3) forecasts of change in this landscape, and 4) the susceptibility of NGOM ecosystems and human communities to severe storms throughout the coming century.
Contact Information: John Brock, U.S. Geological Survey, 12201 Sunrise Valley Drive, MS 915B, Reston, VA 20192; phone: 703 648 6053; email: jbrock@usgs.gov
Biophysical Controls on Response of Coastal Wetlands to Climate Change, Elevated CO 2, and Sea-Level Rise
Karen L. McKee, U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
Global changes in climate, atmospheric CO2, and sea-level rise (SLR) will have multiple and complex effects on coastal wetlands. Assessments of vulnerability to submergence are typically based on simple physical models of projected sea-level intersecting with land topography and do not consider biological feedbacks that allow wetlands to maintain their elevations. This presentation (1) reviews how external drivers and internal biological feedbacks may interact to influence the capacity of coastal marshes to keep pace with SLR and (2) presents new data showing how CO2 enrichment may alter elevation dynamics. Soil accretion in most coastal wetlands occurs through both physical and biological processes, but in sediment-deficient systems, accumulation of organic matter through plant processes is an important contributor to soil volume. Thus, factors that influence plant processes (CO2, salinity, flooding) have the potential to alter soil volume and vertical land-building. An understanding of biological processes influencing elevation dynamics is especially important in subsiding and low-sediment geomorphic settings such as the Mississippi River deltaic complex. Field studies have identified the plant root zone as a key stratum where vertical adjustment to counter submergence occurs. Greenhouse studies have quantified interactive effects of atmospheric CO2 with edaphic factors of flooding, salinity, and nutrients to increase soil volume and upward soil expansion in freshwater, brackish, and saline plant communities. In addition, large disturbance events such as hurricanes deliver sediment to subsiding marshes, adding directly to soil volume and stimulating plant production, setting back the clock on elevation loss. These results show that as sea-level rises, biophysical processes and interactions with other global drivers may alter elevation dynamics in coastal marshes, in some cases improving their capacity to keep pace with SLR.
Contact Information: Karen McKee, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd, Lafayette, LA 70506; phone: 337 266 8662; email: mckeek@usgs.gov
How Does Restoration Affect the Resiliency of Coastal Louisiana Marshes?
Christopher M. Swarzenski1, William Orem2, Ken Krauss3, Tom Doyle3 and JoAnn Holloway4
1 U.S. Geological Survey, Louisiana Water Science Center, Baton Rouge
2 Geologic Division, Eastern Region, Energy Resources
3 Biologic Resources Division, National Wetland Research Center
4 Geologic Division, Central Region, Crustal Imaging and Characterization
Wetlands of the Mississippi River delta plain in coastal Louisiana currently are eroding at annual rates of less than 15 km2, less than the rates of between 45-75 km2 measured in the previous 30 years, but still substantial. The loss threatens New Orleans and other human settlements along the coast, an oil and gas infrastructure that delivers > 25% of the energy needs of the United States as well as the second ranked commercial fisheries in the United States. To mitigate the loss of the economically and ecologically valuable wetlands, large-scale restoration projects are being proposed and implemented.
One restoration approach integral to all coast-wide restoration plans for Louisiana is to divert freshwater from the Mississippi River across flood-control levees and into adjacent marshes to recreate the natural springtime overbank flooding that occurred before the levees were built. However, river water quality has changed appreciably since the river last flowed unencumbered into the estuaries, with nitrate and sulfate concentrations 2-3 x higher than in the early 1900s. Herbicides were only introduced in the 1950’s. How this shift in water quality may affect the marshes being restored currently is not well known. In co-operative studies with the National Park Service, and through a USGS Venture Capital Collaborative effort, we are studying the soil biogeochemical response both of organic-rich freshwater marshes and more brackish marshes. Results suggest river water introductions may enhance soil organic matter decomposition, resulting in a more degraded and weaker root mat than marshes not receiving this river water subsidy. Such a change makes these marshes more susceptible to erosion during infrequent high-energy events (for example hurricanes) and regular low-energy events, such as tides and the passage of weather fronts. In effect, freshwater diversions appear in some cases to weaken marshes and make them less resilient to extreme weather events.
Contact Information: Christopher M. Swarzenski, US Geological Survey, Louisiana Water Science Center, Baton Rouge, 3535 S. Sherwood Forest Blvd., Ste 120, Baton Rouge, Louisiana 70816; phone: 225 298 5481; email: cswarzen@usgs.gov
USGS Research Activities in Coastal Forest Ecosystems of the Northern Gulf of Mexico
Ken W. Krauss1, Thomas W. Doyle1, Thomas J. Smith2, Thomas C. Michot1, Helen M. Light2
1 U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
2 U.S. Geological Survey, Florida Integrated Science Center, St. Petersburg, Florida
Coastal forests along the northern Gulf of Mexico are among the most sensitive ecosystems to climate change. While tidal freshwater forests are undergoing dieback and decline at the upper intertidal ecotone in coastal areas, saltwater forests (i.e., mangroves) are migrating landward and poleward under general warming conditions and sea-level rise. Recent evidence suggests that hurricane surge events and sea-level anomalies during drought episodes contribute to increasing soil salinities that progressively eliminate certain freshwater tree species with different thresholds of tolerance within riverine outlets near the estuarine interface. This process of soil salinization of freshwater habitats along the upper estuary is related to land elevation and tidal influence on the short-term and relative sea-level rise and hurricane events over the long-term. A number of coastal forest types have exhibited similar die-off behavior and episodes in the last few decades including slash pine forests of the Florida Keys, coastal cabbage palms and hammock ecosystems of the Big Bend region of Central Florida, and bottomland hardwood and bald cypress dominated tidal forests of the Louisiana Deltaic region. Contrastingly, mangrove species also serve as an outstanding environmental indicator and sentinel tree species of climate change. Lapses in freeze events and extreme drought events related to recent warming trends account for increased mangrove establishment and expansion into subtropical salt marsh and freshwater ecosystems over the past decade. Historically, the ecological range of mangroves along the northern Gulf of Mexico have expanded and contracted, but populations in Florida, Louisiana, and Texas are currently undergoing unprecedented expansion landward and in latitudes above the tropical Everglades region. USGS field and modeling studies of tidal freshwater and mangrove forests predict that climate change impacts may lead to extensive shifts in habitat conditions along the northern Gulf of Mexico. Coastal parks and refuges, State and Federal, are at risk to coastal forest retreat and habitat shifts across the pan-Gulf region under changing climate that could have significant ecological and economic implications.
Contact Information: Ken W. Krauss, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, Louisiana 70506; phone: 337-266-8882; fax: 337-266-8586; email: kkrauss@usgs.gov
USGS Ecosystem Modeling Research and Applications in the Northern Gulf of Mexico
Donald L. DeAngelis1 and Thomas W. Doyle2
1 U.S. Geological Survey, Florida Integrated Science Center, Fort Lauderdale, Florida, USA
2 U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana, USA
USGS Science Centers and scientists are engaged in developing ecosystem models of coastal ecosystems along the northern Gulf of Mexico to forecast potential effects of climate change and restoration alternatives on Department of Interior (DOI) trust species and Federal lands. Several ecosystem models have been developed by the USGS to address potential sea-level rise effects on shoreline, habitat retreat, and shifts in boundaries between habitats at the local, park and regional scale. Sea-level inundation models of coastal habitats have been constructed at different landscape scales to forecast NGOM-wide changes at the state and county level to more sophisticated and process-based models at specific park and refuge scale. Ecosystem-specific modeling applications have been advanced for mangrove forests of NGOM to investigate the potential impacts of climate change and freshwater flow on the quality and distribution of future mangrove habitat. This USGS mangrove model predicts the tree and gap replacement process of natural forest succession at the local and landscape scale as influenced by sea-level rise, hurricanes, and other disturbances and as related to planned hydrological restoration of the Everglades. Other USGS models include the ATLSS, (Across-Trophic Landscape Spatial Simulation) models, designed for evaluating alternative scenarios for Everglades restoration. The majority of ATLSS models are spatially explicit and deal with habitat suitability and population dynamics of animal species of particular interest. Because they use information on habitat type, they can be used to determine the impacts of changes in habitat on the viability of these species.
Contact: Donald L. DeAngelis, U. S. Geological Survey, Florida Integrated Science Center, Department of Biology, University of Miami, P. O. 249118, Coral Gables, FL, 33124. Phone: 305-284-1690, Fax: 305-284-3039, E-mail: don_deangelis@usgs.gov
Thomas W. Doyle, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, LA, 70506, Phone: 337-266-8647, Fax: 337-266-8592, Email: tom_doyle@usgs.gov
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