1 11/20/2015 Scott Libby, Battelle Candace Oviatt, URI Dave Borkman, URI Jeff Turner, UMD Water Column Overview OMSAP – June 29, 2009

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


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


-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



& 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



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





Yes, as expected


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






Yes

YesNo


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


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


• 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




• Have production rates changed in the nearfield

• and Boston Harbor?



Yes



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


DO

(% s

atu

rati

on

)

Baseline Mean

Post-Diversion Mean

6

7

8

9

10

11

12


DO

(mg

L-1

)

Baseline Mean

Post-Diversion Mean

70

80

90

100

110


DO

(% s

atu

rati

on

)

Baseline Mean

Post-Diversion Mean

32




• Have production rates changed in the nearfield

• and Boston Harbor?



Yes



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

Documents

1 11/20/2015 Scott Libby, Battelle Candace Oviatt, URI Dave Borkman, URI Jeff Turner, UMD Water Column Overview OMSAP – June 29, 2009