NarrCHRP: Ecological Modeling
Mark J. BrushVirginia Institute of Marine Science
Annual Managers’ MeetingCHRP Narragansett Bay Project
October 2008
USE OF MODELS IN MANAGEMENT
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0
10
20
30
40
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60
1940 1950 1960 1970 1980 1990 2000
NU
MB
ER
OF
PU
BL
ICA
TIO
NS
.
Riley(1946, 1947)
Steele
(1974)a
Kremer & Nixon
(1978)b
ERSEM I d;Rigler & Peters
(1995)
ASFA SEARCH FOR "ECOSYSTEM MODEL"
Odum(1983)
Baretta &Ruardij
(1988)c
ERSEM II e
Odum(1994)
Chesapeake Bay Model f
(2007)
131
Generality
Realism
Precision
R. Levins
(1966, 1968)
Empirical Models
Complex, Mechanistic
SystemsModels
A Simplified, Intermediate Complexity Model
MODELS …
A TRADEOFF BETWEEN:
Phytoplankton
Nutrients
Oxygen BOD
Sed Carbon
Estuarine Eutrophication Model
1. Phyto
Production
5. MacroMetabolism
3. C flux to sediments
* Need to accurately model both states and rates
Estuarine Eutrophication Model
2. Water Column Respiration
4. Denitrification
6. Sediment Respiration
1
2
3
4 5
876 9
11 12
10
13 14
RI Sound
Boxing Scheme
Boxing Scheme: Physical Exchanges
3D ROMS ModelOfficer Box Model
Freshwater Inputs
• Watersheds delineated for each box
• 7 gauged rivers extrapolated to include ungauged areas.
• Flow in the completely ungauged watersheds was computed from flow/area for the Hunt watershed.
• 2001 - 2006
Box Model: Exchanges = f(freshwater, salinity)
Salinity Distributions
• Current: Simple seasonal functions using Insomniacs and GSO data.
• Future: include event-scale with buoy data
Box 3
0
5
10
15
20
25
30
35
J F M A M J J A S O N D
S3
B3
S_bulr
B_bulr
S3
B3
Box Model: Exchanges = f(freshwater, salinity)
2:56 PM Thu, Aug 14, 2008
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Days
1:
1:
1:
2:
2:
2:
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3:
3:
0
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100
1: RTprovriv 2: RTgbay 3: RTnbay
1 1 1 12
2
2 2
3
3
3
3
Computed Residence Times
Providence River (Box 1-3)
Greenwich Bay (Box 6-7)
Entire Narragansett BayR
T,
DA
YS
1/1/01 12/31/06
Box Model: Computed Residence Times
Ecological Model:
How are we doing?
Ecological Model: Surface Chl-a
Ecological Model: Surface DIN
Ecological Model: Surface DIP
Ecological Model: Bottom DO
Current Directions:
• Calibration to Chl-a, DIN, DIP, and rates
• Finish GEM Box and compare the physical approaches
• Formulation to translate predicted DO and metabolism to instantaneous criteria
Potential Applications:
• Understanding formation, spread, & alleviation of hypoxia in NB
• Effect of changes in nutrient loading
• Effect of climate warming
• Effect of loss of spring bloom
• Stochastic simulation to assess Pr.(criteria attainment)
Ecological Model
Stochastic Simulation
Bottom O2
Surface Chl- a, mg/m3
0
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70
J F M A M J J A S O N DBottom O2, mg/L
0
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4
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J F M A M J J A S O N D