1 11/20/2015 scott libby, battelle candace oviatt, uri dave borkman, uri jeff turner, umd water...
TRANSCRIPT
104/21/23
Scott Libby, Battelle
Candace Oviatt, URI
Dave Borkman, URI
Jeff Turner, UMD
Water Column Overview
OMSAP – June 29, 2009
2
Water Column Results– “Typical” trends generally observed in WQ parameters
– Driven by seasonal events- Winter/spring blooms (diatoms and Phaeocystis)
- Alexandrium blooms
- Seasonal stratification and upwelling
- Fall blooms and mixing of water column
10 m
10 m
10 m
10 m
10 m
Phaeocystis pouchetiiChaetoceros debilis
Dactyliosolen fragilissima
Ceratium tripos
Asterionellopsis glacialis Skeletonema costatum
Alexandrium fundyense
DIN
Areal Chla DO
3
Monitoring Questions
• Have nutrients changed near the outfall or in the farfield?
• Has phytoplankton biomass changed?
• Have production rates changed in the nearfield and Boston Harbor?
• Has plankton community structure been altered?
• Has dissolved oxygen (DO) changed?
Yes, as expected
No
Changes observed related to regional trends/blooms
Changes observed related to regional trends/blooms
YesNo
44
Nutrient Loading
– Relatively constant load from outfall (<12K mt/yr)
– Nitrogen load mostly ammonium (~75% NH4; 5-10% NO2+NO3)
– Outfall contributes ~3% of TN entering the MB system
– Flow from GoM contributes 92% of TN load to MB system
– Dilution at outfall is as-designed
- Plume surfaces in winter, but dilution is greater
- Plume is isolated below pycnocline in summer
- Net transport is generally to south with high local variability
5
Outfall Plume – NH4 signature (M)
Feb 2003 May 2003
1 3 5 7 9 11 13 15 26
NH4 Concentration (µM)
N07
N04
N01
1 3 5 7 9 11 1 3 15 26
NH4 Concentration (µM)
N01
N04
N07
6
Physical processes
• Massachusetts Bay circulation influenced by seasonal and local winds plus runoff
• Nearfield area does not have a consistent mean flow
• Massachusetts Bay and the Gulf of Maine are coupled
• Interannual and regional factors contribute to spatial and temporal variability in key monitoring parameters (e.g. DO)
• Hemispheric scale processes imparting trends in MWRA monitoring data (e.g. NAO)
Low-frequency CurrentsWinter Summer
Butman et al. 2007
7
Modeled and observedNutrient distributions
ModelPredictions
MonitoringResults
WINTERSUMMER
Harbor Outfall Bay Outfall
(R. Signell, USGS)
8
Annual Mean Nutrients – NH4
• Post Diversion– Large Decrease in Boston
Harbor (red)
– Decrease in Coastal area (green)
– Initial doubling in nearfield (black)
– Unchanged elsewhere MB and CCB
• After 2003– Decrease across all areas
– Current nearfield levels comparable to 90’s
Ammonium has changed – what about the other nutrients?
9
Annual Mean Nutrients – NO3
• NO3 variable with a weak increasing trend over time in the bays (except Boston Harbor)
• SiO4 and PO4 (not shown) – more interannual variability and no long-term trends
Have seasonal trends in nutrient concentrations changed?
10
Nutrients – NO3
Cape Cod Bay
• High NO3 (& SiO4)in February and March 2008 across the Bays
• PCCS also observed higher NO3 in CCB 2008
• Late -February NO3 higher post-diversion vs. Baseline in CCB and offshore MB
• Attributed to decrease/ delay in diatom bloom
11
2008 Phytoplankton, Chla & POC
0
3
6
9
12
15
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Oct Nov
Boston Harbor Coastal Nearfield Offshore N. Boundary Cape Cod
12
POC – Baseline and Post-diversion
Nearfield
N. BoundaryOffshore
13
Boston Harbor
Coastal
Cape Cod Bay
POC – Baseline and Post-diversion
14
BACI Statistical Analysis (92-08)
• Grouped stations– “Impacted” area
- Inner nearfield: N16, N18 & N20
– Control areas
- Outer nearfield: N01, N04, N07 & N10
- MB Offshore: F12, F17, F19 & F28
- CCB: F01, F02 & F03
• Pre vs. Post comparisons
• Comparisons of differences between impacted and control areas pre vs. post
15
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-5 -3 -1 -0.5 0 0.5 1 3
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-5 -3 -1 -0.5 0 0.5 1 3
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-5 -3 -1 -0.5 0 0.5 1 3
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-5 -3 -1 -0.5 0 0.5 1 3
Nutrient Distribution – Pre-Post changes
Ammonium – Baseline vs. 2001-2008
M NH4
Winter/Spring Summer Fall
Inner Nearfield
Outer NearfieldCCB & MB Off
Inner Nearfield Inner Nearfield
MB OffBACI analysis indicated increases (p≤0.05) in NH4 above baseline levels in the Inner Nearfield compared to all three control areas for each season
16
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-1 -0.5 0 0.5 1
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-1 -0.5 0 0.5 1
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-1 -0.5 0 0.5 1
Nutrient Distribution – Pre-Post changes
Nitrate – Baseline vs. 2001-2008
M NO3
Winter/Spring Summer Fall
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-1 -0.5 0 0.5 1
Inner NearfieldOuter Nearfield
& MB Off
Inner Nearfield Inner NearfieldOuter Nearfield
& CCB
All groups trending in the same direction – no change (p>0.05) for Inner Nearfield compared to the three control areas for any season
17
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-50 -30 -10 10 30 50
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-50 -30 -10 10 30 50
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-50 -30 -10 10 30 50
Chla Distribution – Pre-Post changes
Areal Chla – Baseline vs. 2001-2008
mg m-2 Chla
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
Areal ChlaFall
-50 -30 -10 10 30 50
Winter/Spring Summer Fall
Inner NearfieldOuter Nearfield
& MB OffAll groups trending in the same direction – no change (p>0.05) for Inner Nearfield compared to the three control areas for any season
18
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-5 -3 -1 1 3
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-5 -3 -1 1 3
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-5 -3 -1 1 3
POC Distribution – Pre-Post changes
POC – Baseline vs. 2001-2008
M POC
-71 -70.9 -70.8 -70.7 -70.6 -70.5 -70.4 -70.3 -70.2
41.9
42
42.1
42.2
42.3
42.4
42.5
42.6
-5 -3 -1 1 3
AmmoniumFall
Winter/Spring Summer Fall
Inner NearfieldOuter Nearfield
Inner NearfieldAll groups trending in the same direction – no change (p>0.05) for Inner Nearfield compared to the three control areas for any season
19
Updated BACI by stations (92-08)• Ran analysis based on
proposed AMP revision
• Pre. vs. post station changes
– Changes for NH4 only (p≤0.05)
- Increase at N18 all seasons
- Decrease at F23 all seasons & W/S at F13 & N04
• BACI results
– Impact vs. Control sites
– Only changes were for NH4
- Increase at N18 (p≤0.05) relative to nearly all other stations/season groups
- No differences for N18 in fall vs. F06, F13, and N04
20
Monitoring Questions
• Have nutrients changed near the outfall or in the farfield?
• Has phytoplankton biomass changed?
• Have production rates changed in the nearfield and Boston Harbor?
Yes, as expected
Changes observed related to regional trends/blooms
21
Seasonal and Annual Production• Decreases in peak productivity on a seasonal basis
• Harbor summer peak productivity decreased by 56% (P=0.05)
• Harbor Annual production decreased >40% (P=0.03)
• Only a minor change in production at the nearfield stations
22
Monitoring Questions
• Have nutrients changed near the outfall or in the farfield?
• Has phytoplankton biomass changed?
• Have production rates changed in the nearfield and Boston Harbor?
• Has plankton community structure been altered?
Yes
YesNo
Changes observed related to regional trends/blooms
23
0
3
6
9
12
15
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
106 C
ells
L-1
Boston Harbor Coastal Nearfield Offshore N. Boundary Cape Cod
Phaeocystis Blooms
(D. Borkman)
Sept 2000
Transfer to
Bay Outfall
SeaWiFS
April 2004
24
• March 21 – mixed Phaeocystis/ diatom/microflagellate assemblage in nearfield (<1 million cells/L)
• High flow into MB from Gulf of Maine (GoMOOS A buoy) in late March & April
• Elevated chlorophyll levels were also observed at the buoy over this period
• April 10-11 – Phaeocystis bloom observed from nearfield to CCB (1-9 million cells/L)
• April 21-22 – Bloom continues – maxima at depth from Cape Ann to nearfield (max 12 million/L at F22)
• Chlorophyll lower in early May and no Phaeocystis in nearfield on May 23
• Phaeocystis also observed in Casco Bay and along NH coast – Regional Blooms
2007 Phaeocystis Bloom
March 21 March 29 April 6
April 11 April 20 May 2
25
Diatom and Phaeocystis trends
0
0.2
0.4
0.6
0.8
1
1990 1995 2000 2005 2010
Ab
un
da
nc
e (m
illi
on
cel
ls l-1
)Diatom Trend
Diatom Mean
Phaeocystis Trend
Phaeocystis Mean
• Diatom trend of long-term decline• Phaeocystis increasing• Inverse correlation (Pearson r = -0.54, P<0.0001)
26
Alexandrium fundyense
27
2005 Bloom
• Regional blooms – initiated in western Gulf of Maine and driven by physical forcing mechanisms
• Expect these blooms to continue with regularity in GoM and lead to frequent toxicity in Massachusetts Bay
Conceptual Model
28
Total zooplankton, 1992-2008
0
50,000
100,000
150,000
200,000
250,000
300,000
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
An
imal
s m
-3
Boston Harbor Coastal Nearfield Offshore N. Boundary Cape Cod
• Similar abundance trends across areas
• Abundances ≤150,000 92-98
• Peak abundances in 1999 & 2000
• Lower post-diversion <100,000
29
Cape Cod Bay
Trends in total zooplankton abundance
• Long-term trend of decreased abundance since 2001
• Increasing in recent years
• Similar trends observed throughout Massachusetts Bay and Boston Harbor
• No change in total zooplankton abundance in Cape Cod Bay
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
1990 1995 2000 2005 2010
To
tal
zoo
pla
nk
ton
tre
nd
(#
m-3
)
Nearfield Time-series
30
Monitoring Questions
• Have nutrients changed near the outfall or in the farfield?
• Has phytoplankton biomass changed?
• Have production rates changed in the nearfield
• and Boston Harbor?
• Has plankton community structure been altered?
• Has dissolved oxygen (DO) changed?
Yes
Changes observed related to regional trends/blooms
Changes observed related to regional trends/blooms
Yes
No
31
Baseline vs. Post-discharge – Nearfield and Stellwagen Basin
6
7
8
9
10
11
12
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DO
(mg
L-1
)
Baseline Mean
Post-Diversion Mean
70
80
90
100
110
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DO
(% s
atu
rati
on
)
Baseline Mean
Post-Diversion Mean
6
7
8
9
10
11
12
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DO
(mg
L-1
)
Baseline Mean
Post-Diversion Mean
70
80
90
100
110
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DO
(% s
atu
rati
on
)
Baseline Mean
Post-Diversion Mean
32
Monitoring Questions
• Have nutrients changed near the outfall or in the farfield?
• Has phytoplankton biomass changed?
• Have production rates changed in the nearfield
• and Boston Harbor?
• Has plankton community structure been altered?
• Has dissolved oxygen (DO) changed?
Yes
Changes observed related to regional trends/blooms
Changes observed related to regional trends/blooms
Yes
No
No
33
Conclusions• Obvious and expected changes in the nutrient regimes
following diversion. – Ammonium decreased in Boston Harbor (80%) and nearby coastal waters
– Increasing to a lesser degree in the nearfield
– NH4 signature of the plume confined to within 10-20 km of the outfall.
– Consistent with predictions.
• In Boston Harbor, concurrent decreases in other nutrients, chlorophyll, and POC.
• In the nearfield, concurrent changes in chlorophyll, POC, and phytoplankton, but….– BACI analysis found that the only change between impact and control areas
and stations was for NH4 concentrations
– The analyses did not find statistically significant changes in chlorophyll
– Primarily because the changes have been regional in nature – occurring throughout Massachusetts Bay and further offshore in the western Gulf of Maine
34
Conclusions• Productivity
– Reduction (>40%) in Boston Harbor productivity since diversion
– No change at nearfield stations
• Phytoplankton– Major observed trends occurring on a wider, western Gulf of Maine Scale
- Decrease in diatoms and coincident increase in Phaeocystis blooms
- Recent increase in occurrence of Alexandrium blooms and toxicity in the bays
• Zooplankton– Abundance and species composition generally similar interannually
– Long-term decrease in total zooplankton in Massachusetts Bay 2001-2006
– Unchanged in Cape Cod Bay
• Dissolved Oxygen– Post-diversion comparable to baseline in the nearfield and Stellwagen Basin
– No change in DO (interannual variability driven by regional processes)
35
AcknowledgementsThe data presented are the result of the efforts from many HOM team members including:– Battelle Field and Logistics Operations Group
– Battelle, subcontractor, and MWRA labs
– Matt Fitzpatrick for helping with data analysis & graphics