Download presentation
1
with contributions from:
An innovative modeling approach for simulating hypoxia/anoxia in estuarine ecosystems Mark J. Brush James N. Kremer Scott W. Nixon with contributions from: John Brawley Nicole Goebel Jamie Vaudrey
2
USE OF MODELS IN MANAGEMENT
Chesapeake Bay Model Baretta & Ruardij (1988) ERSEM I (1995) ERSEM II (1997) Odum (1983) (1994) Riley (1946, 1947) Steele (1974) Kremer & Nixon (1978) Rigler & Peters Also: Reckhow (1994 & others) Håkanson (1995, 2004) Hofmann & Lascara (1998) Pace (2001) Duarte et al. (2003) Fulton et al. (2003) NUMBER OF PUBLICATIONS USE OF MODELS IN MANAGEMENT
3
Trade-off between realism & predictability:
Increasing complexity / realism # of parameters predictability Loss of utility at lowest complexity? Generality Precision Realism Because this is certainly one of the more challenging topics I’ve had to talk about, I’ve sketched roadmap to help us all navigate these tricky waters. R. Levins (1966, 1968)
4
Published Gmax Functions
Phytoplankton Primary Production Published Gmax Functions Brush et al. (2002) elevated Eppley Gmax , d-1 Eppley Curve TEMPERATURE, oC
5
Duarte et al. (2003) “The Limits to Models in Ecology”
6
Can we find a middle ground?
Empirical “Stressor-Response” Models Can we find a middle ground? Generality Precision Question: Can a simplified eutrophication model be useful as a heuristic and management tool? R. Levins (1966, 1968) Parsimony Principle Ockam's Razor Realism Complex, Mechanistic Systems Models
7
Estuarine Eutrophication Model
8
* Need to accurately model
Estuarine Eutrophication Model * Need to accurately model both states and rates Phyto Production Pelagic Respiration C flux to sediments Macro Metabolism Denitrification
9
Light x Biomass (“BZI”) Models … capped by available nutrients
Phytoplankton Primary Production Light x Biomass (“BZI”) Models Pd = *Chl*Zp*PAR + … capped by available nutrients Cole & Cloern (1987) MEPS v. 36 Brush et al. (2002) MEPS v. 238
10
Water Column Respiration Rd = *e kT*Chl10
11
Estuaries and Nutrients
Carbon Flux to Sediments & Benthic Respiration Nixon (1981) Estuaries and Nutrients The Humana Press Csed = 0.25*Pd Rsed = *e kT
12
Denitrification DENIT = Nload*f(RT) Nixon et al. (1996)
Biogeochemistry 35(1) DENIT = Nload*f(RT)
13
… a hybrid, empirical-mechanistic
Empirical Functions Robust, data-driven, & apply across several systems - ideal when mechanistic formulations are insufficient or poorly constrained. Reduce model complexity by integrating multiple processes (which are often poorly constrained) into simplified, bulk functions. Produce output we can measure and test. Excellent tools for model validation. … a hybrid, empirical-mechanistic approach
14
Greenwich Bay Eutrophication Model
Greenwich Bay, RI (Avg Z = 3 m)
15
Surface Phytoplankton
Lower West Passage Chl-a
16
Surface DIN
17
Bottom O2
18
Bottom O2 with Forced Maximum Chlorophyll a
original run max chl
19
* Need to accurately model Annual Primary Production
both states and rates Rate Processes In the absence of flux measurements model MERL fcn of T, Chl, NPP Annual Primary Production g C m-2 y-1 Observed: 281 – 326 Modeled:
20
System-Level Validation: Nutrient Reduction Scenarios
Keller (1988) Nixon et al. (2001) Nixon et al. (1996)
21
Empirical-Mechanistic
Empirical Models Complex, Mechanistic Systems Models A Simplified, Hybrid Empirical-Mechanistic Systems Model Generality Precision R. Levins (1966, 1968) Realism Multiple, parallel modeling approaches, e.g.: Latour, Brush & Bonzek (2003) Scavia et al. (2003) Borsuk et al. (2002, 2004)
22
Models for Hypoxia Applied in Narragansett Bay
Oviatt et al. Models for Hypoxia Applied in Narragansett Bay NOAA Coastal Hypoxia Research Program Because this is certainly one of the more challenging topics I’ve had to talk about, I’ve sketched roadmap to help us all navigate these tricky waters.
23
Full 3D resolution in ROMS:
Because this is certainly one of the more challenging topics I’ve had to talk about, I’ve sketched roadmap to help us all navigate these tricky waters.
24
Nutrient Reduction Scenarios
Bottom O2, mg/L 0% watershed N,P 0% Narr. Bay N,P 0% Narr. Bay N,P & saturating O2
25
LOWER NARRAGANSETT BAY PROVIDENCE RIVER
26
Scope for Improvement: Pre-Colonial Inputs
Bottom O2 Nixon (1997) Estuaries 20(2)
27
Effect of Macroalgal Decomposition
Bottom O2 Bottom O2
28
Effect of Macroalgal Decomposition
29
Stochastic Simulation
Kremer (1983) Bottom O2
30
Dr. Brush’s wardrobe provided by:
Acknowledgements James N. Kremer Scott W. Nixon John Brawley Nicole Goebel Jamie Vaudrey Dr. Brush’s wardrobe provided by: Bay St. Louis Kmart
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.