Anoxia in Narragansett BayCan we predict it?

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Narragansett Bay Fixed-Site Water Quality Monitoring NetworkNarragansett 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

North Prudence Bottom Oxygen Levels: 2001-2006

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Hypoxia Study Program Goals

• 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

N P

N

Land-use

Atmosphericdeposition

N P

Productivity

Temp, Light,Boundary Conditions

Chl, N, P, Salinity

Phytoplankton

Sedimentorganics

.

.

Physics

Surface layer

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Deep layer

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Bottom sediment

O2

Flux tobottom

Photic zoneheterotrophy

Benthicheterotrophy Denitri-

fication

O2 coupledstoichiometricallyBZI

ƒ(Chl10d)ƒ[Chl]

ƒ(OM,T) %

Processes of the model & basis for formulations:

mixing flushing

Field Work in Support ofEcological Models

Historical Hypoxia based on benthic foramsWater Column MetabolismSediment Oxygen DemandDenitrification RatesOxygen Surveys ( some with other funding)Survey of nutrient concentrations

AccomplishmentsPhysical 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.