NarrCHRP: Ecological Modeling Mark J. Brush Virginia Institute of Marine Science Annual Managers’ Meeting CHRP Narragansett Bay Project October 2008

USE OF MODELS IN MANAGEMENT

Generality Realism Precision R. Levins (1966, 1968) Empirical Models Complex, Mechanistic Systems Models A Simplified, Intermediate Complexity Model MODELS … A TRADEOFF BETWEEN:

Phytoplankton Nutrients OxygenBOD Sed Carbon Estuarine Eutrophication Model

1. Phyto Production 5. Macro Metabolism 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

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 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 Model: Exchanges = f(freshwater, salinity)

Computed Residence Times Providence River (Box 1-3) Greenwich Bay (Box 6-7) Entire Narragansett Bay RT, DAYS 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 O 2