field work in support of ecological models
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Field Work in Support ofEcological Models
Warren Prell - Historical Hypoxia based on benthic forams
Candace Oviatt - Water Column MetabolismWarren Prell - Sediment Oxygen Demand
Scott Nixon/Wally Fulweiler - Denitrification Gradient
Historical Hypoxia Based on
Benthic Forams
Warren Prell
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.
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
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# Benthic foraminifers per gram
Site # Providence Mid-Bay
Abundance (#/gram)• Lower in Providence
River, Greenwich Bay and embayments
• Higher in mid and upper Bay
• Reflects both environment and substrate
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4
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0 200 400 600 800 1000 1200 1400
Foraminifer Abundance (#/g)
Diversity vs. Abundance
Diversity
•Increases down Bay
•Low in Providence River and embayments
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0.2
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0.6
0.8
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0 200 400 600 800 1000 1200 1400
Foraminifer Abundance (#/g)
AE Index vs. Abundance
AE Hypoxia Index
•High in Providence River and embayments. Consistent with low DO
•AE Index increases at lower population abundance
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UpperWest
Passage
GreenwichBay
UpperBay
Upper East
Passage
79 132
13 3 3
x4x9
x8 x11
UpperWest
Passage
Abundance 1950 vs. 2003
UpperWest
Passage
GreenwichBay
UpperBay
Upper East
Passage
79 132
13 3 3
x4x9
x8 x11
UpperWest
Passage
Abundance 1950 vs. 2003
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.
Water Column Metabolism
Candace Oviatt
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.
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
http://www.nbnerr.org/propertieshome.htm
Water Column Assessment Methods
14C Primary Productivity Incubations
O2 Primary Productivity Incubations
Respiration Incubations
Surface Primary Productivity6/28/06
North Prudence 14C
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Irradiance (μ E m-2 s-1)
Productivity( mg C m
-3 h
-1)
North Prudence O 2
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1000
0 500 1000 1500
Irradiance (μ E m-2 s-1)
Productivity( mg O
2 m-3 h
-1)
Respiration Rates
-0.11
-0.06
-0.01
0.04
6/15/2006 6/29/2006 7/13/2006 7/27/2006
Bottom
Chl Max
Surface
North Prudence-0.17
-0.12
-0.07
-0.02
0.03
6/15/06 6/29/06 7/13/06 7/27/06 8/10/06 8/24/06 9/7/06 9/21/06
Date
mgO2/l/hr
Conimicut Point
-0.11-0.06-0.010.04
6/15/20066/29/20067/13/20067/27/20068/10/20068/24/20069/7/20069/21/2006
Date
mgO2/l/hr
Primary Production June & July
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1 2 3 4
Date
mg C/O
2 d
-1 m
-2
Conimicut C-14
Cominicut O2
No Prud C-14
No Prud O2
Sediment Oxygen Demand
Warren Prell
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).
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.
Denitrification in Upper Narragansett BayCHRP MEETING
Robinson W. FulweilerScott W. NixonOctober 2, 2006
Graduate School of Oceanography University of Rhode Island
240 g C m-2 y-1
520 g C m-2 y-1
560 g C m-2 y-1
PP data Oviatt et al. 2002
Denitrification Rates in Narragansett Bay (6-13ºC)
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N2-
N, μ
mol
m-2 h
-1N
2-N
, μm
ol m
-2 h
-1
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60
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120N
2-N
, μm
ol m
-2 h
-1
1979 1986 2005/06
Denitrification Rates in Narragansett Bay (6-13ºC)
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