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Brown Marsh Update 14 September 2000

Brown Marsh Update 14 September 2000. Dr. Robert R. Twilley University of Louisiana at Lafayette Center for Ecology and Environmental Technology. List of Panel Participants 12 September 2000.

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Brown Marsh Update 14 September 2000

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  1. Brown Marsh Update14 September 2000 Dr. Robert R. Twilley University of Louisiana at Lafayette Center for Ecology and Environmental Technology www.LAcoast.gov/brownmarsh

  2. List of Panel Participants12 September 2000 Don Cahoon, Ph.D.Robert Chabreck, Ph.D.Woody Gagliano, Ph.D.Paul Kemp, Ph.D.Greg LinscombeMike MaterneIrv Mendelsohn, Ph.D.Jim Morris, Ph.D.Denise Reed, Ph.D.Robert Twilley, Ph.D. www.LAcoast.gov/brownmarsh

  3. Overview of Presentation • Extent of Brown Marsh • Coastal Conditions • Possible Causes • Nature of Recovery • Recommendations • Conclusions www.LAcoast.gov/brownmarsh

  4. Extent of Salt Marsh Damage • Aerial survey of salt marshes in the Barataria and Terrebonne basins Greg Linscombe( Dept Wildlife & Fisheries) Robert Chabreck (LSU -retired) www.LAcoast.gov/brownmarsh

  5. Sample point www.LAcoast.gov/brownmarsh

  6. Examples of Class Types www.LAcoast.gov/brownmarsh

  7. Percent Occurrence www.LAcoast.gov/brownmarsh

  8. Graph of Categories www.LAcoast.gov/brownmarsh

  9. Dist of Dead Patches www.LAcoast.gov/brownmarsh

  10. Dead Salt Marsh Patches www.LAcoast.gov/brownmarsh

  11. Local Patterns of Salt Marsh Dieback • Pattern first observed in May 2000 • Typical die-back of Spartina occurs in the marsh interior • Fringe Marsh usually remains healthy www.LAcoast.gov/brownmarsh

  12. Coastal Conditions - La Nina • Decrease in Precipitation over the last two years • Two Years of Water Deficits resulting in present condition of severe drought • Increased presence of Gulf High over coast of Louisiana • Increase number of clear days www.LAcoast.gov/brownmarsh

  13. Drought Index www.LAcoast.gov/brownmarsh

  14. Coastal Conditions - River Flow • River flow is one of lowest on record - probably between 8-10 lowest since 1931 • Lack of seasonal flow in spring has resulted in the movement of salinity regimes inland www.LAcoast.gov/brownmarsh

  15. Low River Flow 7 8 9 6 3 5 2 1 4 www.LAcoast.gov/brownmarsh

  16. Atch Slide www.LAcoast.gov/brownmarsh

  17. -1 SD www.LAcoast.gov/brownmarsh

  18. +1 SD www.LAcoast.gov/brownmarsh

  19. Historical Miss. River Discharge www.LAcoast.gov/brownmarsh

  20. Houma Canal DCP www.LAcoast.gov/brownmarsh

  21. Other Global Patterns of Coastal Wetland Dieback www.LAcoast.gov/brownmarsh

  22. Similar Local Patterns www.LAcoast.gov/brownmarsh

  23. Freshwater Diversions – Restoration Programs www.LAcoast.gov/brownmarsh

  24. Biotic Factors Herbivory Pathogens Low Genetic Diversity www.LAcoast.gov/brownmarsh

  25. Abiotic Factors Chemical Spills Buildup of Sulfide High Salinity Extreme Water Levels www.LAcoast.gov/brownmarsh

  26. Low Water Levels • Evidence for low water levels: Records indicate low water levels at some locations during early part of year. www.LAcoast.gov/brownmarsh

  27. Low Water Levels Marsh Drought - conditions with lower water level and increased temperatures have set up periods of water deficits in marsh soils - leading to toxic soil conditions - the exact nature of these soil conditions needs more information Tides Rain www.LAcoast.gov/brownmarsh

  28. Some species of plants have been able to maintain a presence in brown marsh areas • Avicennia germinans. • Batis maritima • Juncus roemarianus www.LAcoast.gov/brownmarsh

  29. Avicennia germinans Distichlis spicata www.LAcoast.gov/brownmarsh

  30. Interacting Environmental & Biotic Factors • Marsh drought, water level, and temperature are possibly all contributing factors that interact to develop stress plant conditions – the exact nature of which is not conclusive at this time. www.LAcoast.gov/brownmarsh

  31. Summary • Factors least likely to be involved: achemical spill, herbivory • Factors possibly involved, but with little or no data from a broad survey of current die-back sites: pathogens, low genetic diversity • Factors possibly involved, with some evidence from several sites: water level extremes, salinity, natural toxins (e.g., sulfide) www.LAcoast.gov/brownmarsh

  32. Nature of Recovery • Some small patches have recovered • Recovery potential is unknown – limited by duration of La Nina • Extensive restoration programs are limited by the magnitude of dieback • Small scale restoration strategies do exist and are under consideration • Erosion control is a high priority www.LAcoast.gov/brownmarsh

  33. Recommendation • Identify extent and severity of damage • Identify causes • Identify impacts – economics, social, biological • Identify restoration strategies www.LAcoast.gov/brownmarsh

  34. Conclusions • Based on the combined scientific experience of panel members and participants – this dieback event is most unique in terms of temporal and spatial scale • Understanding the extent, causes, and consequences of this unique event will require the collaboration of State,Federal, and University scientists and natural resource managers www.LAcoast.gov/brownmarsh

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