NarrCHRP: Ecological Modeling

Mark J. BrushVirginia Institute of Marine Science

Annual Managers’ MeetingCHRP Narragansett Bay Project

October 2008

USE OF MODELS IN MANAGEMENT

-10

0

10

20

30

40

50

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

Untitled

Page 81.00 548.25 1095.50 1642.75 2190.00

Days

1:

1:

1:

2:

2:

2:

3:

3:

3:

0

50

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

10

20

30

40

50

60

70

J F M A M J J A S O N DBottom O2, mg/L

0

2

4

6

8

10

12

J F M A M J J A S O N D