This document summarizes a study on the impacts of land use change and climate change on the aquatic ecosystem of Mobile Bay in Alabama. The study used watershed and hydrodynamic models to analyze how increased urbanization and climate change could affect river outflows, water quality parameters like temperature and salinity, and submerged aquatic vegetation (SAV) in the bay. The models project increased runoff and decreased outflows from watersheds with more urban development compared to natural areas. Climate change is also expected to decrease precipitation and increase temperatures, further impacting outflows. Changes in flows, sediment loads, temperature and salinity could stress SAV communities in Mobile Bay that provide important habitat. The goal is to understand these stressors to

1. Clarisse M. Betancourt Roman¹, Maury Estes² and Mohammad Al-Hamdan²
1.University of Puerto Rico- Rio Piedras Campus and NASA/USRP; 2. USRA at Marshall Space Flight Center
Introduction
Mobile Bay is a significant resource for human uses with
important implications on commercial fisheries, coastal
development, industry and tourism. Submerged aquatic vegetation
(SAV) is one of the most important communities in an aquatic
ecosystem and is a vital food resource for wintering waterfowl,
native, exotic and endangered species. The factors generally
considered to the success of SAV are light, salinity, wave energy, and
nutrients (NC-DENR, 2005). The major stressors of lost coastal and
estuarine wetlands in Alabama are land cover/land use (LCLU)
change, climate change and surface water runoff (Dahl, 1990; Mobile
Bay NEP, 2007; Turner, 1997).The distribution and condition of the
SAV had been affected by the changes in land use (Orth et al., 2006).
The coastal systems of Alabama are increasing in population, which
comes with LCLU change in the surrounding areas of the coast,
causing a direct effect in the outflows of the rivers. Also, the climate
change impacts the outflows and the quality of the water in Mobile
Bay affecting the species that live there. In order to manage and plan
the recovery and restoration of the bay for the future, the effect of
these stressors to the bay must be understood.
Results
Type of Land Use
Water
Urban Low Residential Recreation
Urban Medium High Density Residential
Urban Commercial
Bare Soil Transitional
Deciuous Forest
Evergreen Forest
Mixed Forest Shrub
Agriculture and Pastures
Woody Wetlands
Emergent Herbaceous Wetlands
1992 2001 2030
Objectives
Determine:
(1) how the land use and climate changes affect the runoff of the
rivers;
(2) how the outflows of the rivers impact the quality of water in the
bay;
(3) how these changes in quality of water will affect the species in
the bay.
Discussion and Conclusions
•Times series of flows in each watershed showed that the difference
between these changes is significant; the outflows are less when the
temperature increases and the precipitation decreases.
•The outflow of the rivers varies from the type of land use: zones with
elevated percent of urban development had runoffs higher than zones
with higher percent of natural surface.
•These changes in freshwater flows cause fluctuations in temperature,
salinity and sediment concentrations in the water, changing the
habitat conditions.
•Seagrasses and SAVs in Mobile Bay have decreased and are being
stressed by increasing urbanization and climate change (USGS, 2007).
Acknowledgements
NASA Puerto Rico Space Grant Consortium (PRSGC)
Gerardo Morell and Mayra Martínez
NASA- Marshall Space Flight Center
Mona Miller and Tina Haymaker
NSSTC-National Space Science and Technology Center
Maury G. Estes and Mohammad Al-Hamdan
References
Dahl, T.E. 1990. Wetlands losses in the United States 1780's to 1980's. U.S.
Department of the Interior, Fish and Wildlife Service, Washington, D.C. Jamestown,
ND: Northern Prairie Wildlife Research Center Online.
MBNEP (Mobile Bay National Estuary Program). 2007. National Estuary
Program Coastal Condition Report, Chapter 5- Gulf of Mexico National Estuary.
Mobile Bay National Estuary Program, Mobile, AL.
MBNEP. 2008. A Status Report on Alabama’s Coastline from the Delta to Our
Coastal Waters. Mobile Bay National Estuary Program, Mobile, AL
MBNEP. 2009. Mapping of Submerged Aquatic Vegetation in Mobile Bay and
Adjacent waters of Coastal Alabama in 2008 and 2009. Mobile Bay National Estuary
Program, Mobile, AL.
NC-DENR (North Carolina Department of Environmental and Natural
Resources). 2005. North Carolina Coastal Habitat Protection Plan- Chapter 4
Submerged Aquatic Vegetation. North Carolina Department of Environmental and
Natural Resources, NC.
Orth RJ., Carruthers, T.J.B., Dennison, W.C., Duarte, C.M., Fourqurean, J.W.,
Heck, K.L., Hughes, A.R., Kendrick, G.A., Kenworthy, W.J., Olyarnik, S., Short, F.T.,
Waycott, M. and S.L. Williams. 2006. A global crisis for seagrass ecosystems.
Bioscience 56: 987-96.
Turner, R.E. 1997. Wetland loss in the northern Gulf of Mexico: multiple
working hypotheses. Estuaries. 20: 1-13.
USGS (U.S. Geological Survey). 2007. Global Change and Submerged Aquatic
Vegetation Research. U.S. Geological Survey.
Methodology
.
Climate
Change
(IPCC)
Outflows,
Sediment loads
Temperature,
salinity, and
sediment
concentrations
Watershed and hydrodynamic modeling
has been performed for Mobile Bay to
evaluate the impact of land use and climate
change in Mobile and Baldwin counties on
the aquatic ecosystem.
• The Loading Simulation Package in C++
(LSPC) model was used to provide change in
flow, temperature and general water quality.
•The land use scenarios used a common land
classification system developed by merging
the 1992 and 2001 National Land Cover Data
(NLCD). The Prescott Spatial Growth Model
(PSGM) was used to project the 2030 land
use scenario based on observed trends.
• The Environmental Fluid Dynamics
Computer Code (EFDC) hydrodynamic model
to generate data, in 4 vertical layers in the
depth of the bay. The models were calibrated
using in-situ data.
Medians for Climate Change- South Region
Scenario A2 Year 1990-2050
%
Precipitation
Temperature
(ºC)
Dec, Jan, Feb -2.19 1.75
June, July,
August -9.93 2.18
March,April,May -3.29 2.01
Sept, Oct, Nov -0.19 2.08
Sixteen different SAV species in Mobile Bay
0.002 % Acreage in the bay; found in
the survey 2002
28.7 % Acreage in the bay; most
abundant
(MB NEP, 2008)
Figure 1. Mobile Bay with land use classes for each year. LCLU for 2030 with the PSGM
Figure 2. Values of outflows, percent of land use and sediment load for each watershed in 2001
Figure 3. Descriptive statistics of outflow differences between the baseline (2005) and the future (2050) outflow
NLCD
LSPC MODEL
EFDC MODEL
Land Use Change (RS DATA) 0
10
20
30
40
50
60
70
80
90
100
110
120
Comparation of Outflows and Percent of Land Use per
Watershed in 2001
Outflow (in/year)
% All Urban
% natural surfaces (no water or wetlands)
% Agriculture
Sediment load (tons-year/area watershed)
-1,000
-900
-800
-700
-600
-500
-400
-300
-200
-100
0
-35
-30
-25
-20
-15
-10
-5
0
Outflow Differences Stats (2050-2005)
Mean
Minimum
Standard
Deviation
Maximum
Mean(cfs)
Min,Max,Staand.Desviation(cfs)