Effects of shoreline reef creation on edge erosion, marsh resilience and nekton assemblages in south...
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Transcript of Effects of shoreline reef creation on edge erosion, marsh resilience and nekton assemblages in south...
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 ResourcesLouisiana State University Agricultural Center
Baton Rouge, LA
Austin HumphriesSchool of Renewable Natural Resources
Louisiana State University Agricultural CenterBaton Rouge, LA
Photo by Tyrone Turner – National Geographic
Wetland loss
64 – 91 km2 y-1
25% of nation’s total fishery production in lower 48
Louisiana’s 2007 Master Plan:
1) hydrologic restoration
2) shore protection
> 500 projects
Shore ProtectionTires, Wooden Structures, Christmas trees, ConcreteLimestone rock
- costly ($1 million / mile)- heavy (sink)- imported from out-of-state
Oyster reefs - native - sustainable - potential added ecosystem benefits
research objectives:
examine effects of created reef size, shoreline orientation, and location on:
1. shoreline erosion2. nekton (fish and decapod crustaceans) use3. reef sustainability/oyster populations (Casas poster)
West
South
North
Sister Lake
Gulf of Mexico
“low” energy shorelines
“medium” energy shorelines
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
Measured quarterly:• Shoreline position• Soil characteristics• Vegetation• Nekton use
approach
0%
20%
40%
60%
80%
100%
north west south
% s
pec
ies
com
po
siti
on S. americanus
J. roemerianus
S. patens
S. alterniflora
D. spicata
B. maritimus
Similar production at all sites: 805.9 ± 74.0 g m-2
marsh vegetation community
5
15
25
35
southnorth west
% s
oil
org
anic
mat
ter
A
B B
Universal soil loss equation: increase OM 1-3%, reduces erosion 20-33%
marsh soil properties
0
0.2
0.4
0.6
Medium Low
Sh
ore
lin
e re
trea
t (c
m d
-1)
Narrow Reef
Wide Reef
Reference
AB
A
AB
BB
Energy Environment
shoreline change
**site interaction
0
0.2
0.4
0.6
0.8
Medium Energy
North West South
Narrow Reef
Wide Reef
Reference
Sh
ore
lin
e re
trea
t (c
m d
-1)
Gulf of Mexico
April 2009-August 2010
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, bathymetry2) Understand local weather patterns and in particular,
dominant storm passages
TraysSeine
shoreline
reef
Gillnetsampling nekton
Quarterly: March, June, August, December 2009, 2010
0
50
100
150
200
250
1
3
4
5
fall winter
CP
UE
Water quality: only difference between sites in salinity
Season
West
North
South
transient species
Gulf of Mexico
Spring Summer Fall Winter
8.6 ± 0.59.2 ± 0.4
12.4 ± 0.5
Resident abundance
0
20
40
60
80
100
CP
UE
June Aug Dec March
ReefMud
2009 2010
0 1 2 3 40
20
40
60
80
100
CP
UE
(#
in
div
idu
als/
tray
)
Tray shell volume (L)
Adj r2 = 0.22
Does shell quantity impact resident abundance?
High
Low
Four treatments
Mud bottomCage structureCage plus low volumeCage plus high shell volume
abundance
diversity
0
5
10
15
20
25
30
Mud Cage Low High
0
0.5
1
1.5
2
2.5
3
Mud Cage Low High
Shan
non
dive
rsity
(H’)
Mea
n ab
unda
nce
(# o
f ind
²)ˉ
aa
a
b
b
b
b b
Fre
qu
ency
of
size
dis
trib
uti
on
(%
)
0
25
50
75
100
M-N
M-W
L-N
September 2010
Spat: < 25 mm Seed: 25-50 mm Seed: 50-75 mm Commercial: >75 mm
West North South
Oys
ter
den
sity
(m
2 )
0
3000
6000
deadlive
West North South
M-N
M-W
L-NM
-NM
-WL-NM
-NM
-WL-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?
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, morphology2) oyster population response
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
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