benthic nutrient cycling in boston harbor and ...omsap public meeting september 1999 benthic...

OMSAP Public MeetingSeptember 1999

Benthic Nutrient Cycling in BostonHarbor and Massachusetts Bay

Anne Giblin,Charles Hopkinson& Jane TuckerThe Ecosystems Center,Marine Biological LaboratoryWoods Hole, MA 02543

September 22, 1999


Nutrient Cycling Boston Harbor – Goals

Determine the role of the sediments in nutrient cycling• Amount of nutrients released relative to NPP needs• Ratios of nutrients released (e.g. N/Si)• Size of sink if appropriate (denitrification; N,P, and Si burial)

Determine the role of the sediments in oxygen dynamics• Importance as an oxygen sink• Storage of reduced endproducts

Determine how role of the sediments has changed over time• Sludge disposal ceased in 1991• Treatment being upgraded to secondary• Relocation of outfall to offshore

InflowOutflow

Light

ConcernsEcologicalEcological NutrientsNutrients Contaminants Organic MaterialOrganic Material Food Chain Community Structure Living Resources

Human Health Contaminants Bacteria Viruses Bioaccumulation

SEDIMENT

Mammals

Infauna

PiscivorousFish

Zooplankton

Phytoplankton

PlanktivorousFish

Epibenthos

DemersalFish

RegenerationRegeneration

DetritusDetritusParticulateParticulate

Microbes

Dissolved

WATER COLUMN

SourcesSources Rivers BoundaryBoundary Nonpoint EffluentsEffluents

GasExchangeExchangeN2, | O2, CO2

ATMOSPHERE

N, P, N, P, SiSi, O, O22, CO, CO22 MicrobesMicrobes


Nutrient Cycling Nitrogen Cycle in Coastal Waters


$#

N

0 2 4 km

BH02BH03

QB01 BH08A

Nutrient Cycling Boston Harbor Stations forBenthic Fluxes


0

50

100

150

200

250

300

350

Jan-

92

Jul-9

2

Jan-

93

Jul-9

3

Jan-

94

Jul-9

4

Jan-

95

Jul-9

5

Jan-

96

Jul-9

6

Jan-

97

Jul-9

7

Jan-

98

Jul-9

8

Jan-

99

Jul-9

9

Jan-

00

mm

ol O

2 m

2 d-1 a. BH02

0

50

100

150

200

250

300

350

Jan

-92

Jul-9

2

Jan

-93

Jul-9

3

Jan

-94

Jul-9

4

Jan

-95

Jul-9

5

Jan

-96

Jul-9

6

Jan

-97

Jul-9

7

Jan

-98

Jul-9

8

Jan

-99

Jul-9

9

Jan

-00

mm

ol O

2 m

2 d

-1

b. BH03

Nutrient Cycling Sediment Oxygen Demand -Northern Harbor


050

100150200250300350

Jan

-95

Ap

r-95

Jul-

95

Oct

-95

Jan

-96

Ap

r-96

Jul-

96

Oct

-96

Jan

-97

Ap

r-97

Jul-

97

Oct

-97

Jan

-98

Ap

r-98

Jul-

98

Oct

-98

Jan

-99

Ap

r-99

Jul-

99

Oct

-99

Jan

-00

mm

ol O

2 m

2 d-1

c. BH08A

050

100150200250300350

Jan

-95

Ap

r-95

Jul-

95

Oct

-95

Jan

-96

Ap

r-96

Jul-

96

Oct

-96

Jan

-97

Ap

r-97

Jul-

97

Oct

-97

Jan

-98

Ap

r-98

Jul-

98

Oct

-98

Jan

-99

Ap

r-99

Jul-

99

Oct

-99

Jan

-00

mm

ol O

2 m

2 d-1

d. QB01

Nutrient Cycling Sediment Oxygen Demand -Southern Harbor


-5

0

5

10

15

20

25

Jan

-92

Jul-

92

Jan

-93

Jul-

93

Jan

-94

Jul-

94

Jan

-95

Jul-

95

Jan

-96

Jul-

96

Jan

-97

Jul-

97

Jan

-98

Jul-

98

Jan

-99

Jul-

99

Jan

-00

mm

ol N

m2

d-1

NO3

NH4

a. BH02

-5

0

5

10

15

20

25

Jan

-92

Jul-

92

Jan

-93

Jul-

93

Jan

-94

Jul-

94

Jan

-95

Jul-

95

Jan

-96

Jul-

96

Jan

-97

Jul-

97

Jan

-98

Jul-

98

Jan

-99

Jul-

99

Jan

-00

mm

ol N

m2 d

-1

NO3

NH4

b. BH03

Nutrient Cycling DIN Fluxes - Northern Harbor


-5

0

5

10

15

20

25

Jan-

95

Apr

-95

Jul-9

5

Oct

-95

Jan-

96

Apr

-96

Jul-9

6

Oct

-96

Jan-

97

Apr

-97

Jul-9

7

Oct

-97

Jan-

98

Apr

-98

Jul-9

8

Oct

-98

Jan-

99

Apr

-99

Jul-9

9

Oct

-99

Jan-

00

mm

ol N

m2 d

-1 NO3

NH4

c. BH08A

-5

0

5

10

15

20

25

Jan-

95

Apr

-95

Jul-9

5

Oct

-95

Jan-

96

Apr

-96

Jul-9

6

Oct

-96

Jan-

97

Apr

-97

Jul-9

7

Oct

-97

Jan-

98

Apr

-98

Jul-9

8

Oct

-98

Jan-

99

Apr

-99

Jul-9

9

Oct

-99

Jan-

00

mm

ol N

m2 d

-1 NO3

NH4

d. QB01

Nutrient Cycling DIN Fluxes - Southern Harbor


0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0J

an

-92

Ju

l-9

2

Ja

n-9

3

Ju

l-9

3

Ja

n-9

4

Ju

l-9

4

Ja

n-9

5

Ju

l-9

5

Ja

n-9

6

Ju

l-9

6

Ja

n-9

7

Ju

l-9

7

Ja

n-9

8

Ju

l-9

8

Ja

n-9

9

mm

ol

N m

2 d

-1 a . BH02

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

Ja

n-9

2

Ju

l-9

2

Ja

n-9

3

Ju

l-9

3

Ja

n-9

4

Ju

l-9

4

Ja

n-9

5

Ju

l-9

5

Ja

n-9

6

Ju

l-9

6

Ja

n-9

7

Ju

l-9

7

Ja

n-9

8

Ju

l-9

8

Ja

n-9

9

mm

ol

N m

2 d

-1

b . B H 0 3

Nutrient Cycling Denitrification Losses


0 .0

2 .0

4 .0

6 .0

8 .0

10 .0

12 .0

May J u n J u l A u g Sep O c t

mm

ol

N m

2 d

-1

S t o i c h i o m e t r y

G C

D G A

a . B H 0 2

0 .0

2 .0

4 .0

6 .0

8 .0

10 .0

12 .0

M a y J u n J u l A u g S e p O c t

mm

ol

N m

2 d

-1


G C

D G A

b. BH03

0 .0

2 .0

4 .0

6 .0

8 .0

10 .0

12 .0

M a y J u n J u l A u g S e p O c t

mm

ol

N m

2 d-1


D G A

c . B H 0 8 A

0 .0

2 .0

4 .0

6 .0

8 .0

10 .0

12 .0

May J u n J u l A u g Sep O c t

mm

ol

N m

2 d

-1


D G A

d . Q B 0 1

Nutrient Cycling Denitrification - Methods Comparisons


-1.0

0.0

1.0

2.0

3.0

4.0

Ja

n-9

2

Ju

l-9

2

Ja

n-9

3

Ju

l-9

3

Ja

n-9

4

Ju

l-9

4

Ja

n-9

5

Ju

l-9

5

Ja

n-9

6

Ju

l-9

6

Ja

n-9

7

Ju

l-9

7

Ja

n-9

8

Ju

l-9

8

Ja

n-9

9

mm

ol

P m

-2 d

-1 7.8a . B H 0 2

-1.0

0.0

1.0

2.0

3.0

4.0

Ja

n-9

2

Ju

l-9

2

Ja

n-9

3

Ju

l-9

3

Ja

n-9

4

Ju

l-9

4

Ja

n-9

5

Ju

l-9

5

Ja

n-9

6

Ju

l-9

6

Ja

n-9

7

Ju

l-9

7

Ja

n-9

8

Ju

l-9

8

Ja

n-9

9

mm

ol

Pm

-2 d

-1

b . B H 0 3

4.0

Nutrient Cycling Phosphate Fluxes - NorthernHarbor


-1.0

0.0

1.0

2.0

3.0

4.0J

an

-95

Ju

l-9

5

Ja

n-9

6

Ju

l-9

6

Ja

n-9

7

Ju

l-9

7

Ja

n-9

8

Ju

l-9

8

Ja

n-9

9

mm

ol

P m

-2 d

-1

c . BH08A

-1.0

0.0

1.0

2.0

3.0

4.0

Ja

n-

95

Ju

l-

95

Ja

n-

96

Ju

l-

96

Ja

n-

97

Ju

l-

97

Ja

n-

98

Ju

l-

98

Ja

n-

99

mm

ol

P m

-2 d

-1

d . QB01

Nutrient Cycling Phosphate Fluxes - SouthernHarbor


a . D IC vs O2

0

2040

6080

1 0 0

1 2 0

1 4 0

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0

O2 (mmol m -2 d -1)

DIC

(m

mo

l m

-2 d

-1)

DIC/O2=1BH02BH03BH08Q B 0 1

b. DIC vs DIN

0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

1 4 0

0 4 8 1 2 1 6 2 0

D I N ( m m o l m -2 d -1)

DIC

(m

mo

l m

-2 d

-1)

DIC/DIN = 6.6

BH02BH03

B H 0 8 A

Q B 0 1

c . D I N v s D I P

- 1 0

0

1 0

2 0

3 0

4 0

5 0

-1 0 1 2 3

D I P ( m m o l m -2 d -1 )

DIN

(m

mo

l m

-2 d

-1) DIN/DIP=16

BH02

BH03

B H 0 8 AQ B 0 1

d . D I N v s S i

0

5

1 0

1 5

2 0

2 5

0 5 1 0 1 5 2 0 2 5

S i ( m m o l m -2 d -1 )

DIN

(m

mo

l m

-2 d

-1) DIN/Si=1

BH02

BH03

B H 0 8 A

Q B 0 1

Nutrient Cycling Flux Ratios


a . B H 0 2

-14

-12

-10

-8

-6

-4

-2

0

0.0 2.0 4.0 6.0

H 2S ( m M )

De

pth

(c

m)

J u l y

A u g

b . B H 0 3

- 1 4

- 1 2

- 1 0

- 8

- 6

- 4

- 2

0

0.0 0.5 1.0 1.5

H 2S ( m M )

De

pth

(c

m)

J u l y

A u g

c . B H 0 8 A

-14

-12

-10

-8

-6

-4

-2

0

0.0 0.5 1.0 1.5

H 2S ( m M )

De

pth

(c

m)

J u l y

A u g

d . Q B 0 1

-14

-12

-10

-8

-6

-4

-2

0

0.0 0.5 1.0 1.5

H2S (mM)

De

pth

(c

m)

J u l y

A u g

Nutrient Cycling Dissolved Sulfides in Porewaters


The current four sites are representative of depositionaland reworked areas in the Harbor and therefore mayover-represent the role of the Harbor sedimentssomewhat. Based upon these four stations, we estimatethat the sediments could supply 35% of the N and 58%of the P required for primary production. However, newinputs from the current Deer Island outfall contributemuch more than needed for NPP. The importance ofsedimentary recycled nutrients in supporting NPP willincrease when the outfall moves offshore.

Nutrient Cycling Harbor Role


Harbor sediments are an active site of denitrification andmore than half of the nitrogen mineralized in thesediments is subsequently denitrified and lost from theecosystem. Although the proportion of nitrogen lost fromthe sediments is high, it is typical of marine sediments.However, because most of the nitrogen entering BostonHarbor are not cycled through the sediments only arelatively minor percentage of the N inputs to BostonHarbor from sewage and other sources is lost bydenitrification. Hence, moving the outfall should nothave a large effect on the N budget of MassachusettsBay as a whole.

Nutrient Cycling Harbor Role (cont’d)


The ratio of N/Si is greater than 1.0 at most stations atmost times of the year, therefore sediments are releasingnutrients with an N/Si ratio favorable to diatoms.

Interannual oxygen uptake rates continue to be variableat most stations, however, the extremely high ratesobserved in the early part of the study (1993-1995) havenot been repeated. Highest oxygen uptake rates areusually associated with a dense cover of tube buildingamphipods. Although the amphipods continue to bepresent the lower rates we are now observing near theLong Island sludge disposal site suggest some “mining”of sediments organic stores may have taken place.

Nutrient Cycling Harbor Role (cont’d)


Determine the role of the sediments in nutrient cycling•Amount of nutrients released relative to NPP needs•Ratios of nutrients released (e.g. N/Si)•Size of sink if appropriate (denitrification; N,P, and Si burial)

Determine the role of the sediments in oxygen dynamics•Importance as an oxygen sink•Storage of reduced endproducts

Determine patterns of annual and interannual variability

Determine how the role of the sediments changes withoutfall relocation

Nutrient Cycling Massachusetts Bay – Goals


Nutrient Cycling Benthic Flux Stations

l

l

ll

l

l

l

l

BH02BH03

QB 01

MB01

MB02

MB03

MB05

BH08A

42°1

2'

42°12'

42°1

6'

42°16'

42°2

0'

42°20'

42°2

4'

42°24'

42°2

8'

42°28'

42°3

2'

42°32'

71°00 '

71°00 '

70°56 '

70°56 '

70°52'

70°52 '

70°48 '

70°48 '

70°44 '

70°44 '

70°40'

70°40 '

N

0 2 4 6 8 Kilometer s

Ben thic Flux Stat ionsl

LEGEND


0

5

10

15

20

25

30

35

Jan

-92

Jul-

92

Jan

-93

Jul-

93

Jan

-94

Jul-

94

Jan

-95

Jul-

95

Jan

-96

Jul-

96

Jan

-97

Jul-

97

Jan

-98

Jul-

98

Jan

-99

Jul-

99

Jan

-00

O2 (m

mol

m-2

d-1

) MB01

0

5

10

15

20

25

30

35

Jan

-92

Jul-

92

Jan

-93

Jul-

93

Jan

-94

Jul-

94

Jan

-95

Jul-

95

Jan

-96

Jul-

96

Jan

-97

Jul-

97

Jan

-98

Jul-

98

Jan

-99

Jul-

99

Jan

-00

O2 (m

mo

l m-2

d-1

) MB02

Nutrient Cycling Sediment Oxygen Demand


05

101520253035

Jan-

92

Jul-9

2

Jan-

93

Jul-9

3

Jan-

94

Jul-9

4

Jan-

95

Jul-9

5

Jan-

96

Jul-9

6

Jan-

97

Jul-9

7

Jan-

98

Jul-9

8

Jan-

99

Jul-9

9

Jan-

00

O2

(mm

ol m

-2 d

-1)

MB03

05

101520253035

Jan-

92

Jul-9

2

Jan-

93

Jul-9

3

Jan-

94

Jul-9

4

Jan-

95

Jul-9

5

Jan-

96

Jul-9

6

Jan-

97

Jul-9

7

Jan-

98

Jul-9

8

Jan-

99

Jul-9

9

Jan-

00

O2

(mm

ol m

-2 d

-1)

MB05

Nutrient Cycling Sediment Oxygen Demand


Sediment fluxes were not measured in MassachusettsBay during 1998. Previous measurements had shownthat benthic respiration rates exhibited low interannualvariability, less than 20%. This suggested that anychange due to the outfall relocation would be readilydetectable. Benthic respiration rates measured in 1999,however,have been higher than average, and may reflectgreater carbon loading to the sediments from anunusually large diatom bloom, and warmer than usualbottom water temperatures. October rates will beneeded to determine if this year’s rates would have fallenoutside what was considered normal based upon the1992-1997 data.

Nutrient Cycling Bay Role

benthic nutrient cycling in boston harbor and ...omsap public meeting september 1999 benthic...

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