Brown marsh update 14 september 2000
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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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Brown marsh update 14 september 2000

Brown Marsh Update14 September 2000

Dr. Robert R. Twilley

University of Louisiana at Lafayette

Center for Ecology and Environmental Technology

www.LAcoast.gov/brownmarsh


List of panel participants 12 september 2000

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


Overview of presentation

Overview of Presentation

  • Extent of Brown Marsh

  • Coastal Conditions

  • Possible Causes

  • Nature of Recovery

  • Recommendations

  • Conclusions

www.LAcoast.gov/brownmarsh


Extent of salt marsh damage

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


Sample point

Sample point

www.LAcoast.gov/brownmarsh


Examples of class types

Examples of Class Types

www.LAcoast.gov/brownmarsh


Percent occurrence

Percent Occurrence

www.LAcoast.gov/brownmarsh


Graph of categories

Graph of Categories

www.LAcoast.gov/brownmarsh


Dist of dead patches

Dist of Dead Patches

www.LAcoast.gov/brownmarsh


Dead salt marsh patches

Dead Salt Marsh Patches

www.LAcoast.gov/brownmarsh


Local patterns of salt marsh dieback

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


Coastal conditions la nina

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


Drought index

Drought Index

www.LAcoast.gov/brownmarsh


Coastal conditions river flow

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


Low river flow

Low River Flow

7

8

9

6

3

5

2

1

4

www.LAcoast.gov/brownmarsh


Atch slide

Atch Slide

www.LAcoast.gov/brownmarsh


Brown marsh update 14 september 2000

-1 SD

www.LAcoast.gov/brownmarsh


Brown marsh update 14 september 2000

+1 SD

www.LAcoast.gov/brownmarsh


Historical miss river discharge

Historical Miss. River Discharge

www.LAcoast.gov/brownmarsh


Houma canal dcp

Houma Canal DCP

www.LAcoast.gov/brownmarsh


Other global patterns of coastal wetland dieback

Other Global Patterns of Coastal Wetland Dieback

www.LAcoast.gov/brownmarsh


Similar local patterns

Similar Local Patterns

www.LAcoast.gov/brownmarsh


Freshwater diversions restoration programs

Freshwater Diversions – Restoration Programs

www.LAcoast.gov/brownmarsh


Biotic factors

Biotic Factors

Herbivory

Pathogens

Low Genetic Diversity

www.LAcoast.gov/brownmarsh


Abiotic factors

Abiotic Factors

Chemical Spills

Buildup of Sulfide

High Salinity

Extreme Water Levels

www.LAcoast.gov/brownmarsh


Low water levels

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


Low water levels1

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


Some species of plants have been able to maintain a presence in brown marsh areas

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


Brown marsh update 14 september 2000

Avicennia

germinans

Distichlis spicata

www.LAcoast.gov/brownmarsh


Interacting environmental biotic factors

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


Summary

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


Nature of recovery

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


Recommendation

Recommendation

  • Identify extent and severity of damage

  • Identify causes

  • Identify impacts – economics, social, biological

  • Identify restoration strategies

www.LAcoast.gov/brownmarsh


Conclusions

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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