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Effects of shoreline reef creation on edge erosion, marsh resilience and nekton assemblages in south Louisiana Megan La Peyre U.S. Geological Survey, Louisiana.

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Presentation on theme: "Effects of shoreline reef creation on edge erosion, marsh resilience and nekton assemblages in south Louisiana Megan La Peyre U.S. Geological Survey, Louisiana."— Presentation transcript:

1 Effects of shoreline reef creation on edge erosion, marsh resilience and nekton assemblages in south Louisiana Megan La Peyre U.S. Geological Survey, Louisiana Fish and Wildlife Cooperative Research Unit School of Renewable Natural Resources Louisiana State University Agricultural Center Baton Rouge, LA Austin Humphries School of Renewable Natural Resources Louisiana State University Agricultural Center Baton Rouge, LA

2 Photo by Tyrone Turner – National Geographic Wetland loss 64 – 91 km 2 y -1 25% of nation’s total fishery production in lower 48

3 Louisiana’s 2007 Master Plan: 1) hydrologic restoration 2) shore protection > 500 projects

4 Shore Protection Tires, Wooden Structures, Christmas trees, Concrete Limestone rock - costly ($1 million / mile) - heavy (sink) - imported from out-of-state Oyster reefs - native - sustainable - potential added ecosystem benefits

5 research objectives: examine effects of created reef size, shoreline orientation, and location on: 1. shoreline erosion 2. nekton (fish and decapod crustaceans) use 3. reef sustainability/oyster populations (Casas poster)

6 West South North Sister Lake Gulf of Mexico “low” energy shorelines “medium” energy shorelines

7 reef establishment: march 2009 Cost: < $300,000/linear mile “narrow” = 25 m x 1 m x 1 m “wide” = 25 m x 2 m x 1 m

8 Measured quarterly: Shoreline position Soil characteristics Vegetation Nekton use approach

9 0% 20% 40% 60% 80% 100% northwestsouth % species composition S. americanus J. roemerianus S. patens S. alterniflora D. spicata B. maritimus Similar production at all sites: ± 74.0 g m -2 marsh vegetation community

10 southnorthwest % soil organic matter A B B Universal soil loss equation: increase OM 1-3%, reduces erosion 20-33% marsh soil properties

11 MediumLow Shoreline retreat (cm d -1 ) Narrow Reef Wide Reef Reference AB A B B Energy Environment shoreline change **site interaction

12 Medium Energy NorthWest South Narrow Reef Wide Reef Reference Shoreline retreat (cm d -1 ) Gulf of Mexico April 2009-August 2010

13 shoreline effects - sites experienced extremely high erosion (1-3 m/18 mo) - at low energy sites reefs failed to reduce retreat - at medium energy sites, site-specific effects Restoration implications: 1)Need to understand local site environment, such as currents, morphology, bathymetry 2) Understand local weather patterns and in particular, dominant storm passages

14 TraysSeine shoreline reef Gillnet sampling nekton Quarterly: March, June, August, December 2009, 2010

15 fallwinter CPUE Water quality: only difference between sites in salinity Season West North South transient species Gulf of Mexico Spring SummerFall Winter 8.6 ± ± ± 0.5

16 Resident abundance CPUE JuneAugDecMarch Reef Mud

17 CPUE (# individuals/tray) Tray shell volume (L) Adj r 2 = 0.22 Does shell quantity impact resident abundance?

18 High Low Four treatments Mud bottom Cage structure Cage plus low volume Cage plus high shell volume

19 abundance diversity MudCageLowHigh MudCageLow High Shannon diversity (H’) Mean abundance (# of indˉ²) a a a b b b b b

20 Frequency of size distribution (%) M-N M-W L-N September 2010 Spat: < 25 mm Seed: mm Seed: mm Commercial: >75 mm West North South dead live West North South M-N M-W L-N M-N M-W L-N M-N M-W L-N M-N M-W L-N M-N M-W L-N M-N = medium energy, narrow reef M-W = medium energy, wide reef L-N = low energy, narrow reef June 2010 POSTER: Casas et al. nekton support - transient abundance not affected by reef presence - possible redundancy of marsh edge habitat - residents more abundant and diverse at reef sites - presence of structure per se most important factor determining assemblages Restoration implications: 1)How do spatial location and adjacent habitats affect added value of reefs to transients 2)Does added structure impact resident communities? 3)How might resident species, oyster population structure affect nekton communities?

21 What factors influence the value of restored fringing reefs for resident or transient nekton? 1) characteristics of structure 2) functional response of nekton What are the key parameters to consider to identify the most viable shorelines for shore protection ? 1) local site conditions: energy, currents, morphology 2) oyster population response

22 Vermilion Bay Grand Isle, Breton Sound, Biloxi Marsh Experimental lab and field studies: - Location effects (shoreline, nekton, oyster populations) - Base material, size, design - Link oyster physiology, oyster population structure with nekton use - Foraging success with different structure Sister Lake

23 Funding Louisiana Department of Wildlife and Fisheries Acknowledgments LA DWF – Heather Finley, Patrick Banks, Steve Hein, Willie Cheramie LSU – Shea Miller, Shannon Martin, Steve Beck, Ben Eberline, Anna Catalanello, John Gordon, Gary Decossas, Lainey Pitre, Matt Kimball Community - Wilson Voisin, Stephen Champagne, Antill Pipeline Construction Co. Collaborators Jerome La Peyre, Louisiana State University AgCenter Sandra Casas-Liste, Louisiana State University AgCenter


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