Development of the Three
Dimensional Advanced Aquatic
Ecosystem Model (A2EM-3D) to
Address Multiple Stressors in
Saginaw Bay
Ed Verhamme*
Joe DePinto
Todd Redder
LimnoTech
Ann Arbor, MI
May 21, 2009
Conference on Great Lakes
Research. Toledo, OH
Overview
 Project background
 Need for refined model
 Model development
 Addition of several sub-models for
Dreissenids and Cladophora
 Other modeling advancements
 Preliminary application and results
 WQ parameters
 Dreissenids and Cladophora
 Future work
Saginaw Bay Multistressor
Project
 Five year project funded by NOAA-CSCOR

Goal: Bring together managers and policy makers at all
levels with engineers and scientists to develop an
Adaptive Integrated Framework for addressing multiple
stressors - Saginaw Bay is testbed
 Primary Focus: develop a quantitative
relationship between multiple stressors
(nutrients, hydrology, solids, and invasive
species) and production of “muck” on bay
shoreline


Apply multiple models with a range of complexities in
conjunction with monitoring and experimentation data
LimnoTech tasked with developing the most complex
mechanistic model of Saginaw Bay
Current Management Concerns…
“Muck” along shoreline at Bay City State Park
Advanced Aquatic Ecosystem
Model (A2EM-3D) Framework
 Hydrodynamic Model (EFDC)

Public domain, open source model maintained by USEPA

Includes temperature sub-model
 Water quality (modified-RCA)

RCA is a generalized water quality model maintained by
Hydroqual, Inc.

Includes sub models for phytoplankton and the full cycling of
nutrients and other parameters in water column and
sediments.
 LimnoTech additions to RCA

Increase to five phytoplankton functional groups

Addition of three zooplankton functional groups

Benthic filter feeder (Dreissenids) - SAGEM

Benthic algae (Cladophora) – M. Auer at MTU
Modeling Framework: A2EM-3D
Forcing
Functions
Forcing
Functions
EFDC
Modified
RCA
Water Column
Nutrients
Phyto & Zoo
Hydrodynamics
Dreissenid
Cladophora
Temperature
Initial
Conditions
Sediment
Nutrients
Diagenesis
Original Model Grid - SAGEM
Grid Facts
• 7 segments
• 2-Dimensional
• Dates to ~1984
• Designed to be “simple”
Updated Model Grid – A2EM-3D
New Grid Facts
• 2x2 km
• 747 active cells
• Up to 10 vertical layers
(GVC)
GVC System
 Combines advantages of
sigma and Z systems



Captures vertical
gradients better than
sigma grid
Hydraulically isolates
deep “holes”
Able to “cap” the number
of vertical layers
 LimnoTech created a
custom linkage from
EFDC to modified-RCA
Number of vertical layers
GVC Grid – Conceptual Model
Sigma Region
Implementation of GLCM in A2EM-3D
 Great Lakes Cladophora Model (GLCM)
developed by M. Auer (Michigan Tech)


Refinement of late 1970s model
Integrated as a sub-model of RCA
 Adaptation to A2EM-3D
 Sub-grid growth calculations (light and
nutrients)
 Separate state variable to track sloughed
Cladophora biomass and contribution to
“muck”
Sub-grid benthic algal growth
Au gres
River
Dimensions = 2 x 2km
Avg. Depth = 2.2 m
Med. Depth= 1.1 m
Min Depth = 0.0 m
Max Depth = 4.0 m
Cladophora
growth is
strongly
dependent on
available light at
the bottom and
hence depth
Sub-grid benthic algal growth
20%
10%
25%
45%
Model can simulate available light growth parameters at
up to 10 different depth bins per grid cell.
Implementation of GLCM in A2EM-3D
 Sloughed biomass is tracked as a state
variable

Allowed to move between grid cells, decay,
and settle.
 Mass balance of carbon and nutrients is
maintained when sloughed biomass decays.
 Accumulation patterns can be compared with
field estimates of “muck” deposition.
 Considering addition of another benthic
“unattached” algae state variable Spirogyra
SAGEM veruss A2EM3D
Category
SAGEM
A2EM-3D
Hydrodynamic
model
2D with 7 cells
No vertical resolution
3D with 747 cells
10 vertical layers
Water Quality
Model
Customized
framework
Documented and highly
tested framework. Full
sediment diag. sub-model
Benthic Algae
Sub-model
Simple kinetics,
attached green alga
not specific to
Cladophora
“Best available” Cladophora
model with tracking of
sloughed biomass
Filter Feeder
Sub-model
1 class with 3
cohorts
2 classes with 3 cohorts
Complete mass balance
Warning: The following results
are for Illustrative purposes
only. Calibration has NOT been
completed yet.
Preliminary Results - Chloride
May
Inner Bay Outer Bay
July
Inner Bay Outer Bay
Preliminary Results - DIP
May
Inner Bay Outer Bay
July
Inner Bay Outer Bay
Preliminary Results – Chl a
May
Inner Bay Outer Bay
July
Inner Bay Outer Bay
Fraction of Green Algae
Dreissenid: Select Filtration
Inner Bay Outer Bay
BG Fraction of Total
Mussel model off
Mussel model on
Inner Bay Outer Bay
Cladophora Sloughing (July 17, 1991)
Layer #1
Cladophora Sloughing July 22, 1991
Layer #1
Total Detrital Deposition - 1991
Next Steps
 Test the model framework using boundary
conditions for tributaries and Lake Huron from
1991 – 1996 (NOAA database)
 Calibrate model to data collected as part of the
project
 Apply model for diagnostic analysis, model
comparisons, and management questions
Questions?
For more information:
www.glerl.noaa.gov
www.limno.com