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Anoxia in Narragansett Bay
Can we predict it?
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Narragansett Bay Fixed-Site Water Quality Monitoring Network
•Agencies: RIDEM-OWR,
URI/GSO, NBNERR, NBC,
NBNEP, & RWU
•Site Locations: West Passage,
East Passage, Providence River,
Seekonk River, West Greenwich
Bay, & Mt. Hope Bay
•Funding: NOAA Bay Window
Program, EPA Clean Water Act
(sections 319 & 106), & NOAA
National Estuary Program
10
9
8
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6
5
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3
2
1
0
Dissolved Oxygen at North Prudence Bottom: 2001-2003
DO mg/L
DO mg/L
North Prudence Bottom Oxygen Levels: 2001-2006
6/4/01
6/18/01
7/2/01
7/16/01
7/30/01
8/13/01
10
9
8
7
6
5
4
3
2
1
0
Dissolved Oxygen at North Prudence Bottom: 2004-2006
DO mg/L
DO Criteria (4.8 mg/L)
min daily limit (2.9 mg/L)
6/7/04
8/27/01
6/21/04
7/5/04
2001
6
5
4
3
2
1
0
8/30/04
3
2
1
0
6/17/02
7/1/02
7/15/02
7/29/02
8/12/02
8/26/02
6/6/05
6/20/05
7/4/05
7/18/05
8/1/05
8/15/05
8/29/05
2005
10
9
8
7
10
9
8
7
6
5
4
DO mg/L
DO mg/L
8/16/04
6
5
4
2002
3
2
1
0
6/2/03
8/2/04
10
9
8
7
DO mg/L
DO mg/L
10
9
8
7
6/3/02
7/19/04
2004
6
5
4
3
2
1
0
6/16/03
6/30/03
7/14/03
2003
7/28/03
8/11/03
8/25/03
6/5/06
6/19/06
7/3/06
7/17/06
2006
7/31/06
8/14/06
8/28/06
QuickTime™ and a
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Hypoxia Study Program Goals
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Predictive/modeling tools for decision makers
Models that predict susceptibility to hypoxia
Integrated parameterizations
Transferability of results across systems
Data to calibrate and verify models
Our approaches
• Hybrid Ecological-Hydrodynamic Modeling
– Ecological model: simple
•
•
•
•
Few processes, few parameters
Parameters that can be constrained by measurements
Few spatial domains (~20), as appropriate to measurements available
Net exchanges between spatial domains: from hydrodynamic model
– Hydrodynamic model: full physics and forcing of ROMS
• realistic configuration; forced by observed winds, rivers, tides, surface fluxes
• Applied across entire Bay, and beyond, at high resolution
• Passive tracers used to determine net exchanges between larger domains of
ecological model
• Empirical-Statistical Modeling
– Input-output relations, emphasis on empirical fit more than mechanisms
– Development of indices for stratification, hypoxia susceptibility
– Learn from hindcasts, ultimately apply toward forecasting
An alternative approach?
4 state variables, 5 processes
Processes of the model
& basis for formulations:
Temp, Light,
Boundary Conditions
Chl, N, P, Salinity
O2 coupled
stoichiometrically
Productivity
BZI
Phytoplankton
Photic zone
heterotrophy
Atmospheric
deposition
N
N P
ƒ(Chl10d)
Surface layer
DO2
mixing
- -flushing
-------
Flux to
bottom
ƒ[Chl]
.
Deep layer
Sediment
organics
Land-use
NP
Benthic
heterotrophy
ƒ(OM,T)
Physics
--------Denitrification
%
.
Bottom
sediment
Field Work in Support of
Ecological Models
Historical Hypoxia based on benthic forams
Water Column Metabolism
Sediment Oxygen Demand
Denitrification Rates
Oxygen Surveys ( some with other funding)
Survey of nutrient concentrations
Accomplishments
Physical model running.
Ecological model started.
Input output model started.
One year of denitrification measurements.
Historical foram survey completed.
Half a year of metabolism measurements.
Physical measurements made in the upper bay:
currents upper east and west passages.
water column profiling.
neap tide studies.
Intensive oxygen surveys conducted for two summers.
Workshop conducted with environmental mangers.

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