mobile bay sediment modeling for ecosystem …...mobile bay sediment modeling for ecosystem health...
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Mobile Bay Sediment Modeling for Ecosystem Health Evaluation
MSFC/SSC Coastal Applications Project Team
• Mr. Maurice Estes, Jr., USRA/MSFC• Dr. Mohammad Al-Hamdan, USRA/MSFC• Dr. Jean Ellis, SSC previously/USC• Dr. Dale Quattrochi, NASA/MSFC• Ms. Callie Hall, NASA/SSC
Other Partners
• Dr. Ron Thom, Battelle/PNNL• Ms. Roberta Swann, Mobile Bay National
Estuary Program• Ms. Chaeli Judd, Battelle/PNNL• Dr. Dana Woodruff, Battelle/PNNL• Mr. Steven Davie, Tetra Tech Engineering
Funding for this Project is provided by the NASA Applied Sciences Program, John Haynes
Program Manager
Project Background
• Previously, coastal resource managers in Mobile Bay and other areas recommended that temperature and salinity modeling be supplemented with data on total suspended solids (TSS)
• Sediment influence on light attenuation is a critical factor in the health of submerged aquatic vegetation
• Overarching goal is to support NASA’s Applied Sciences Program and utilize Earth observations to address coastal health issues
Outline
• Project Objectives
• Project Methodology
• Results
• Conclusions
Project Objectives
• The overall goal is to determine a measure for turbidity that can be used to evaluate the health of the aquatic ecosystem.
– Model TSS for the Mobile Bay study area for a three year period (2003-2005) using four Land Cover Land Use (LCLU) scenarios
– Evaluate LCLU impacts on TSS values– Perform statistical analyses to determine fluxes of TSS at
strategic locations in the Bay– Use in-situ and TSS modeled outputs to model habitat
suitability for seagrasses and submerged aquatic vegetation (SAV)
– Share results with policy and decision-makers
Project Methodology
Habitat Suitability Model
Prioritization End User Interface
Watershed Models
Precipitation
LCLU (Landsat derived)
Impervious Areas
Slope
Slope Types
Drainage Area
Spatial Growth Model
TSS
Hydrodynamic Model
Baseline (1992) Watershed - LSPC
Hydrodynamic - EFDC
“Present” (2001)Watershed - LSPC
Hydrodynamic - EFDC
Forecast (2030 BAU)Watershed - LSPC
Hydrodynamic – EFDC
Historic 1948Watershed - LSPC
Hydrodynamic - EFDC
Model Scenarios
Historical Submerged Aquatic Vegetation
Distribution
Submerged Aquatic Vegetation• Grow in shallow waters
• Provide critical habitat for crabs, fish, birds
• Structure to hold & trap sediments
• Range limited to areas which receive sufficient photosynthetically active radiation (PAR)
• PAR levels change with turbidity
• Used as indicators of water quality in some coastal areas (eg. Tampa Bay)
Ruppia maritima Photo credit: UMCES
Historical LCLU Scenario
LCLU Scenarios
2001 1992 2030
Results
•Land Cover Land Use Analysis
• TSS Change Analysis
• Impact of TSS changes on Seagrass and
SAVs in Aquatic Ecosystems
LCLU Change and Total Suspended Solids
• Increasing Urbanization and Agriculture/Pasture decreases = - TSS
• Increasing Urbanization and Forest decreases = + TSS
• Increasing Agriculture/Pasture and decreasing forest = +TSS
Total Suspended Solids (TSS)
• Result of soil conditions and precipitation events
• Mobile area is among wettest in the U.S.
• Climate data used in model is representative of normal or typical climate
• Silt/Clay 90 percent and sand 10 percent
-5.00
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
CM
S
Discharge Point
Change in TSS Spatially 2030-1948 LCLU
TSS Fluxes by LCLU Scenario and Wet vs. Dry
Conditions
0.00
500.00
1000.00
1500.00
2000.00
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3500.00
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8000.00
5/1
/2005
5/3
/2005
5/5
/2005
5/7
/2005
5/9
/2005
5/1
1/2
005
5/1
3/2
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5/1
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5/1
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5/1
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/2005
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/2005
6/6
/2005
6/8
/2005
6/1
0/2
005
6/1
2/2
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6/1
4/2
005
TS
S M
g/L
TSS for Bayou La Batre
1948 TSS
2001 TSS
2030 TSS
TSS Fluxes by LCLU Scenario and
Wet vs. Dry Conditions
0.00
500.00
1000.00
1500.00
2000.00
2500.00
3000.00
3500.00
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4500.00
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5500.005/1
/2005
5/3
/2005
5/5
/2005
5/7
/2005
5/9
/2005
5/1
1/2
005
5/1
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/2005
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/2005
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/2005
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TS
S M
g/L
TSS for Wolf Bay
1948 TSS
2001 TSS
2030 TSS
Average TSS in Shallow Aquatic Ecosystems
0
10
20
30
40
50
60
70
673 674 716 717 718 719 720
mg/
l
Cell ID
Average of All Layers Means TSS (Bayou La Batre)
1948
2001
2030
0
5
10
15
20
25
30
570 621 667 712 753
mg/
l
Cell ID
Average of All Layers Means TSS (Wolf Bay)
1948
2001
2030
TSS Flux in Shallow Aquatic Ecosystems
0
10
20
30
40
50
60
673 674 716 717 718 719 720
mg/
l
Cell ID
Standard Deviation of All Layers Means TSS (Bayou La Batre)
1948
2001
2030
0
5
10
15
20
25
30
570 621 667 712 753
mg/
l
Cell ID
Standard Deviation of All Layers Means TSS (Wolf Bay)
1948
2001
2030
Steps to understanding how development may impact SAVs
Develop Algorithm to Convert TSS to Kd
Use in situ data to develop regression equation between TSS values and the coefficient (Kd) which describes the rate of attenuation of light
Convert model values for TSS to KdUse algorithm to predict Kd values from modeled TSS concentrations
Evaluate predicted light levels with needed light levels
How would SAVs be impacted by the mean change in light?
• Suggested light limitation in Perdido Bay at levels less than 19% surface irradiance (SI) (Shafer 1999); 15-18% Texas
• Use Lambert – Beer’s Law
% SI = e –kz
k = attenuation coefficient (derived)
z= depth
To find depth limits at each time step (1948, 2001, 2030)
Results
• Two sites studies have predicted changes in maximum SAV depth > .1m
– Bayou La Batre
– Wolf Bay
Bayou La Batre
Clearer water, more habitat
In Bayou La Batre, the maximum depth at which SAVs grow is predicted to increase from 1948 -2030, potentially expanding its range.
Wolf Bay
More turbidity, less habitat
In Wolf Bay, the maximum depth at which SAVs grow is predicted to decrease from 1948 -2030, potentially decreasing its range.
Application of Research Results
Conclusions
• Land use changes are increasing freshwater flows into Mobile Bay.
• These increasing freshwater flows are causing increased fluctuations
of temperature, salinity, and TSS.
• Seagrasses and SAVs have decreased in Mobile Bay over the past
60 years.
• Greatest impact of land use change could potentially be on highly
dynamic edge areas.
• It is likely that understanding the frequency of light limiting events
rather than the average amount of light will help our understanding of
critical areas.
• This is cutting edge research that will benefit understanding and
conservation of valuable coastal resources and benefit stakeholders.
• Present research at the Oceans 2009 Marine Sciences
Conference.
•Publish results late in 2009.
• More study areas around the Gulf of Mexico.
• Investigate the impact of climate variability and nutrient
changes.
Future Work
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