restoring coastal alabama: different approaches for...
TRANSCRIPT
Restoring Coastal Alabama: Different Approaches for Different
Needs
1. Dauphin Island Sea Lab2. University of South Alabama3. ADCNR-State Lands Division
Just Cebrian1,2, Shailesh Sharma1,2, Josh Goff1Carl Ferraro3, Ken Heck1,2 and Sean Powers1,2
Abundant refuge and food
Coastal builders
Filters of land-derivednutrients
Carbon sinks
We are losing precious habitat…
How can restore these precious habitatsin cost-effective ways…or how can we
get “the most bang for the buck”?
calmer andclearer water
What improvements could we expect aswe build oyster reefs (subtidal breakwaters)?
Helen Wood Park
Northeast Point aux Pins
South Point aux PinsCoffee Island
Alabama Port
ReefsMarshes Shoreline Submerged habitat Fisheries
accrual/erosion water-column
bottom
gillnetting
seining oysterrecruitment
footprintlow/high marshsuspended solidsparticulate organic matterphytoplankton
transparencynutrients
granulometryparticulate organic matter
benthic microalgaeseagrass
nutrients
infauna
floral zonation
Spartina density,morphology,biomassand nutrient storagenutrients in sedimentnekton and infauna
Northeast Point aux Pins
Block 1
Block 2
Block 3
Block 4
Loose Shell Aggregate: South and Northeast Point aux Pins
Reef footprint
2013 Reef footprint 2013 Reef footprint
Oyster density
0
.001
.002
.003
.004
.005
.006
0
.001
.002
.003
.004
.005
.006
Pre-construction Post-construction
Blue Crab
Speckled Trout
CPU
E(fis
h/m
2 )
CPU
E(fis
h/m
2 )
Seine Abundance
Reef
Control
Pre-construction Post-construction
Positive impact on some economically important species
4” Gillnet Abundance
0
.05
.1
.15
.2
.25
.3
.35
Pre-construction Post-construction
Reef
Control
Speckled Trout
CPU
E(fis
h/hr
)
2-way ANOVAp= 0.0049
Pre-construction Post-construction
Silver Perch
CP
UE
(fish
/hr)
Striped Mullet
Pre-construction Post-construction
Sheepshead
Post-constructionPre-construction0
.005
.01
.015
.02
.025
.03
.035
0
.005
.01
.015
.02
.025
.03
.035
0
.005
.01
.015
.02
.025
.03
.035
Positive impact on some economically important species
Water quality and seagrasses
No significant impact on water clarity (lightpenetration) and quality (TSS, POM,chlorophyll and nutrients)
No significant effect on seagrassabundance and growth
When comparing reef vs. control plots:
Shadow effect ? Reef deployment
Shoreline and MarshesNo promoted values in reef vs. control plots after reefdeployment: sustained erosion across experimental area
need to look for evidenceof shadow effects
Are the subtidal breakwaters at Northeast Point aux Pins working as expected?
they do for fisheries, perhaps for water qualityand seagrasses, but thus far no evidence forshoreline erosion and marshes
?
Coffee Island
0
500
1000
1500
2000
2500
3000
3500
Live Adults Live Spat
Tota
l # o
f ind
ivid
uals
Total oyster abundance over time
6/23/2010
9/16/2010
1/19/2011
5/10/2011
Oyster abundance
0
100
200
300
400
500
600
2- Reefball 3- BaggedShell
4- Reefblk 5- Reefblk 6- Reefball 8- BaggedShell
Extension-Reefball
Extension-Bagged
Shell
Mea
n O
yste
r A
bund
ance
Oyster abundance among treatment types
0
0.5
1
1.5
2
2.5
3
3.5
Control Oyster Shell Reef Ball REEFBLKM
ean
CPU
E (fi
sh/m
2 )
Seine
Pre-Restoration
Post-Restoration
0
1
2
3
4
5
6
7
8
9
10
5cm 10cm 5cm 10cm
Mea
n C
PUE
(fish
/hr)
Gillnet
Control
Bagged Shell
Reef Ball
Reef Blk
Pre-Restoration Post-Restoration
Fisheries
Water quality, seagrass, shoreline and marshes
No promoted values in reef vs. control plots after reefdeployment need to look for evidence of shadow effects
Are the subtidal breakwaters at Coffee Island working as expected?
and this is also the case the other sites withsubtidal reefs: South Point aux Pins, Alabama Port and Helen Wood Park
they do for fisheries, but thus far no evidence forwater quality, seagrasses, shoreline erosion and marshes
So the subtidal reefs deployed in all of these projects dodefinitely enhance fisheries. There is potential evidence they may also enhance water quality, seagrass, shorelines andmarshes, but more work is needed for conclusive results
An alternative approach: breakwaters right by the shoreline Marshes Shoreline
accrual/erosionlow/high marsh
floral zonationSpartina density
sediment characteristics
nekton
oysterrecruitment
Breakwater
elevation profiles
Helen Wood Park
Northeast Point aux Pins
South Point aux PinsCoffee Island
Alabama Port
Little Bay
February 2008January 2012 0.2 km
Wave Attenuating Units (WAU): Little Bay
January 2012 0.2 km50 m
Restored Marsh
Original Marsh
WAU Complex
Wave Attenuating Unit
1 3 52 4
Elevation profiles
April 20131
2
3
4
5
WAU
Nekton• Fish:
– Mullet– Croaker– Pinfish– Bay Anchoy– Silverside– Sheepshead Minnow– Killifish sp.– Sailfin Molly– Darter Goby– Tongue fish
• Invertebrates– Blue Crab– White Shrimp– Grass Shrimp– Mud Crab
Intertidal breakwaters at Little Bay
• Sediment is compacting and stabilizing; erosion gaps between consecutive WAD complexes does not seem to be a problem
• Marsh plants are well established ; mostly Spartina alterniflorabut there are others (S. patens, Distichlis spicata, succulents)
• Oysters are settling on the WAUs and seem to maintain fair survivorship, although the settling densities are not high.
• Large amounts of nekton visiting the restored marsh
seem to be enhancing the marsh
So wrapping it all up togetherSubtidal reefs: definite fisheries enhancement and potentially other benefits (seagrasses, marshes)… at any rate it seems clear they may have some limitations, such as fully reverting shoreline erosion
Intertidal reefs: definite shoreline stabilization perhaps methodof choice if shoreline/marsh stabilization is the main goal?
Different living shoreline designs offer different options to managers given their priority needs and budget requirements
More research needed for a better “a la carte” menu, particularlyintegrating multidisciplinary approaches and parties
Thank You!!!!!• ADCNR State Lands, Coastal Section• TNC• Marine Resources Division• NOAA• Numerous techs, interns and graduate
students at DISL: Stan Bosarge, Lynn Moore, Jared McKee, Rachel Gamble, Nick Bawden, Luke Dodd, Kate Nixon, Carrie Robbins, Michelle Beumer, and Nicole Waite
• J & W Marine (Reef Construction)– Reed, Jessie, and Jason