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Field Work in Support of Ecological Models Warren Prell - Historical Hypoxia based on benthic forams Candace Oviatt - Water Column Metabolism Warren Prell.

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Presentation on theme: "Field Work in Support of Ecological Models Warren Prell - Historical Hypoxia based on benthic forams Candace Oviatt - Water Column Metabolism Warren Prell."— Presentation transcript:

1 Field Work in Support of Ecological Models Warren Prell - Historical Hypoxia based on benthic forams Candace Oviatt - Water Column Metabolism Warren Prell - Sediment Oxygen Demand Scott Nixon/Wally Fulweiler - Denitrification Gradient

2 Warren Prell - Historical Hypoxia based on benthic forams Historical Hypoxia Based on Benthic Forams Warren Prell

3 Objective: Develop a reliable historical record (pre-settlement to present) of the degree of NNB hypoxia based on benthic foraminifera populations in surface sediments and sediment cores.

4 Benthic Foraminifer Survey Completed sampling for mid-bay to lower bay Both abundance (#/g) and diversity tend to increase downbay AE (hypoxia?) Index increases at low abundance Abundance is 4 to 11 times the 1950 abundance in mid-Bay locations

5 Abundance (#/gram) Lower in Providence River, Greenwich Bay and embayments Higher in mid and upper Bay Reflects both environment and substrate

6 Diversity Increases down Bay Low in Providence River and embayments

7 AE Hypoxia Index High in Providence River and embayments. Consistent with low DO AE Index increases at lower population abundance

8 Comparison of abundance (#/g) from 1950 to 2003 shows increases of 4 to 11 fold in upper Bay and upper East and West Passages and Greenwich Bay.

9 Water Column Metabolism Candace Oviatt

10 Project Goal To estimate primary productivity and respiration along a gradient in Narragansett Bay to test the impacts of water column metabolism on hypoxic events.

11 Sampling Design Sampling 6 stations  Conimicut Point  North Prudence  Mount View  Bullocks Reach  Quonset Point  GSO Dock 3 depths at each station  Surface  Chlorophyll Max  Bottom Water collected monthly

12 Water Column Assessment Methods 14 C Primary Productivity Incubations O 2 Primary Productivity Incubations Respiration Incubations

13 Surface Primary Productivity 6/28/06

14 Respiration Rates

15 Primary Production June & July

16 Sediment Oxygen Demand Warren Prell

17 Objective: Measure the spatial variability of sediment oxygen demand (SOD) in the shoal parts of NNB and to relate SOD to the benthic environment (grain size and organic carbon content).

18 We will use simple benthic chambers with YSI CTD-DO sensors to measure bulk oxygen demand in sediments and the 0.2 m water column in the chamber. Preliminary chamber tests exhibit a smooth and systematic draw down of oxygen over a few hours. We will use existing maps of organic carbon as a guide to likely areas of high SOD and coordinate with the spatial surveys of DO and estimates of water column respiration. We plan to make measurements within each of the initial-phase spatial elements of the hybrid model.

19 Denitrification in Upper Narragansett Bay CHRP MEETING Robinson W. Fulweiler Scott W. Nixon October 2, 2006 Graduate School of Oceanography University of Rhode Island

20 240 g C m -2 y g C m -2 y g C m -2 y -1 PP data Oviatt et al. 2002

21

22 Denitrification Rates in Narragansett Bay (6-13ºC) N 2 -N,  mol m -2 h

23 N 2 -N,  mol m -2 h /06 Denitrification Rates in Narragansett Bay (6-13ºC)


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