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The Risk of Hypoxia in Narragansett Bay. A Synthesis of Available Data. Objectives:. To assess whether hypoxia poses a risk to aquatic life in Upper Narragansett Bay Obtain an estimate of the spatial extent of this risk

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The risk of hypoxia in narragansett bay l.jpg

The Risk of Hypoxia in Narragansett Bay

A Synthesis of Available Data


Objectives l.jpg
Objectives:

  • To assess whether hypoxia poses a risk to aquatic life in Upper Narragansett Bay

  • Obtain an estimate of the spatial extent of this risk

  • Outline some approaches to integration of existing dissolved oxygen datasets with the EPA saltwater DO criteria (2000)


Available data l.jpg
Available Data

  • “Insomniac” surveys – Prell, Deacutis, Murray (1999-2003)

  • Nu-shuttle cruises – Berman, Oviatt, Melrose (1998-2004)

  • Monitoring Buoys – Bergondo, Kester (1999-2004)

  • Ambient Aquatic Life Water Quality Criteria for Dissolved Oxygen (Saltwater): Cape Cod to Cape Hatteras

    – EPA (2000)



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What do the EPA Criteria Tell Us

  • EPA criteria address both growth and mortality for different life stages:

    • Larvae – growth and mortality effects are incorporated into a larval recruitment model

    • Juveniles and Adults are considered together

  • Both persistent and cyclic/episodic hypoxia are accounted for in the criteria


Experimental mortality data l.jpg

2.9 mg/L - Limit for Protection against Larval Mortality

2.3 mg/L Limit for Protection against Juvenile Mortality

Winter

flounder

Tautog

Experimental Mortality Data

  • Plot from the EPA criteria document including protective limits

  • Shows DO concentrations associated with 50% mortality (LC50) for species that commonly inhabit estuaries between Cape Cod and Cape Hatteras


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Where the July and August Insomniac surveys fit into the structure of a hypoxic event at the Bullock’s Reach buoy


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Large regions of the bay show a coherent pattern with DO measured at the Bullock’s Reach Buoy



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Conclusions River to the south end of Prudence Island

  • Aquatic life in Upper Narragansett Bay is at risk from hypoxia - both mortality and growth effects

  • The spatial extent of this risk is large – including almost all areas northward from the south tip of Prudence Island

  • Integration of the existing data can provide information about patterns of hypoxia in Upper Narragansett Bay and guide future monitoring efforts


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Acknowledgements River to the south end of Prudence Island

Many thanks for the free exchange of data and ideas:

Deanna Bergondo Mark Berman

Dana Kester Chris Melrose

Chris Deacutis Heather Stoffel

Warren Prell Heidi Travers

David Murray Robin Weber

Don Pryor Catherine Walker

Candace Oviatt Peter August


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Additional River to the south end of Prudence IslandMaterial


Comparison of insomniac summer averages and summer averages from monitoring buoys l.jpg
Comparison of Insomniac Summer Averages and River to the south end of Prudence IslandSummer Averages from Monitoring Buoys

  • The Insomniacs data and Buoy data are completely independent, yet they give a very similar summer average at the Bullock’s Reach and North Prudence Buoy sites


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Larval Time-to-death Curves from the EPA criteria River to the south end of Prudence Island

  • These time-to-death curves are based upon studies done on larvae

  • Mortality after 24 hours does not increase significantly at a given DO concentration


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Absolute Minimum DO measured at each station in any “Insomniac” Survey.

Note that areas in red are below 1.2 mg/L

(from the EPA VPDO criteria Implementation Guidance document)


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Large regions of the bay show a coherent pattern with DO measured at the Bullock’s Reach Buoy



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GSO dock does not show on this slide very well correlated

Roger Williams is a future location


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