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

OMSAP Public MeetingSeptember 1999

Benthic Nutrient Cycling in Boston Harbor and Massachusetts Bay

Anne Giblin, Charles Hopkinson& Jane Tucker

The 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

Piscivorous Fish

Zooplankton

Phytoplankton

Planktivorous Fish

Epibenthos

Demersal Fish

RegenerationRegeneration

DetritusDetritusParticulateParticulate

Microbes

Dissolved

WATER COLUMN

Sources Rivers BoundaryBoundary Nonpoint EffluentsEffluents

Gas ExchangeExchangeN2, | O2, CO2

ATMOSPHERE

N, P, Si, ON, P, Si, O22, CO, CO22 MicrobesMicrobes


Nutrient Cycling Nitrogen Cycle in Coastal Waters


$#

N

0 2 4km

BH02BH03

QB01 BH08A

Nutrient Cycling Boston Harbor Stations for Benthic Fluxes


Nutrient Cycling Sediment Oxygen Demand - Northern Harbor

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

m2 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

m2 d-1

b. BH03


Nutrient Cycling Sediment Oxygen Demand - Southern Harbor

050

100150200250300350

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 O

2 m2 d

-1 c. BH08A

050

100150200250300350

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 O 2

m2 d

-1 d. QB01


Nutrient Cycling DIN Fluxes - Northern Harbor

-5

0

5

10

15

20

25Ja

n-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 N

m2 d-1

NO3NH4

a. BH02

-5

0

5

10

15

20

25

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 N

m2 d

-1

NO3NH4

b. BH03


Nutrient Cycling DIN Fluxes - Southern Harbor

-5

0

5

10

15

20

25Ja

n-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

NO3NH4

c. BH08A

-5

0

5

10

15

20

25

Jan-

95A

pr-9

5Ju

l-95

Oct

-95

Jan-

96A

pr-9

6Ju

l-96

Oct

-96

Jan-

97A

pr-9

7Ju

l-97

Oct

-97

Jan-

98A

pr-9

8Ju

l-98

Oct

-98

Jan-

99A

pr-9

9Ju

l-99

Oct

-99

Jan-

00

mm

ol N

m2 d

-1 NO3NH4

d. QB01


0.02.04.06.08.0

10.012.014.016.0

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

mm

ol N

m2 d

-1 a. BH02

0.02.04.06.08.0

10.012.014.016.0

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

mm

ol N

m2 d

-1

b. BH03

Nutrient Cycling Denitrification Losses


0.0

2.0

4.0

6.0

8.0

10.0

12.0

May Jun Jul Aug Sep Oct

mm

ol N

m2 d

-1

StoichiometryGCDGA

a. BH02

0.0

2.0

4.0

6.0

8.0

10.0

12.0


mm

ol N

m2 d

-1

StoichiometryGCDGA

b. BH03

0.0

2.0

4.0

6.0

8.0

10.0

12.0


mm

ol N

m2 d

-1

StoichiometryDGA

c. BH08A

0.0

2.0

4.0

6.0

8.0

10.0

12.0


mm

ol N

m2 d

-1

StoichiometryDGA

d. QB01

Nutrient Cycling Denitrification - Methods Comparisons


-1.0

0.0

1.0

2.0

3.0

4.0

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

mm

ol P

m-2 d

-1 7.8a. BH02

-1.0

0.0

1.0

2.0

3.0

4.0

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

mm

ol P

m-2 d

-1

b. BH03

-1.0

0.0

1.0

2.0

3.0

4.0

Jan-

95

Jul-9

5

Jan-

96

Jul-9

6

Jan-

97

Jul-9

7

Jan-

98

Jul-9

8

Jan-

99

Nutrient Cycling Phosphate Fluxes - Northern Harbor


-1.0

0.0

1.0

2.0

3.0

4.0

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

-1.0

0.0

1.0

2.0

3.0

4.0Ja

n-95

Jul-9

5

Jan-

96

Jul-9

6

Jan-

97

Jul-9

7

Jan-

98

Jul-9

8

Jan-

99

mm

ol P

m-2 d

-1 c. BH08A

-1.0

0.0

1.0

2.0

3.0

4.0

Jan- 95 Jul-

95 Jan- 96 Jul-

96 Jan- 97 Jul-

97 Jan- 98 Jul-

98 Jan- 99

mm

ol P

m-2 d

-1

d. QB01

Nutrient Cycling Phosphate Fluxes - Southern Harbor


a. DIC vs O2

020406080

100120140

0 20 40 60 80 100 120 140O2 (mmol m-2 d-1)

DIC

(mm

ol m

-2 d

-1)

DIC/O2=1BH02BH03BH08QB01

b. DIC vs DIN

020406080

100120140

0 4 8 12 16 20

DIN (mmol m-2 d-1)

DIC

(mm

ol m

-2 d

-1)

DIC/DIN = 6.6BH02BH03BH08AQB01

c. DIN vs DIP

-100

1020304050

-1 0 1 2 3

DIP (mmol m-2 d-1)

DIN

(mm

ol m

-2 d

-1) DIN/DIP=16

BH02BH03BH08AQB01

d. DIN vs Si

0

5

10

15

20

25

0 5 10 15 20 25Si (mmol m-2 d-1)

DIN

(mm

ol m

-2 d

-1) DIN/Si=1

BH02BH03BH08AQB01

Nutrient Cycling Flux Ratios


a. BH02

-14

-12

-10

-8

-6

-4

-2

00.0 2.0 4.0 6.0

H2S (mM)

Dep

th (c

m)

JulyAug

b. BH03

-14

-12

-10

-8

-6

-4

-2

00.0 0.5 1.0 1.5

H2S (mM)

Dep

th (c

m)

JulyAug

c. BH08A

-14

-12

-10

-8

-6

-4

-2

00.0 0.5 1.0 1.5

H2S (mM)

Dep

th (c

m)

JulyAug

d. QB01

-14

-12

-10

-8

-6

-4

-2

00.0 0.5 1.0 1.5

H2S (mM)

Dep

th (c

m)

JulyAug

Nutrient Cycling Dissolved Sulfides in Porewaters


The current four sites are representative of depositional and reworked areas in the Harbor and therefore may over-represent the role of the Harbor sediments somewhat. Based upon these four stations, we estimate that the sediments could supply 35% of the N and 58% of the P required for primary production. However, new inputs from the current Deer Island outfall contribute much more than needed for NPP. The importance of sedimentary recycled nutrients in supporting NPP will increase when the outfall moves offshore.

Nutrient Cycling Harbor Role


Harbor sediments are an active site of denitrification and more than half of the nitrogen mineralized in the sediments is subsequently denitrified and lost from the ecosystem. Although the proportion of nitrogen lost from the sediments is high, it is typical of marine sediments. However, because most of the nitrogen entering Boston Harbor are not cycled through the sediments only a relatively minor percentage of the N inputs to Boston Harbor from sewage and other sources is lost by denitrification. Hence, moving the outfall should not have a large effect on the N budget of Massachusetts Bay as a whole.

Nutrient Cycling Harbor Role (cont’d)


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

Interannual oxygen uptake rates continue to be variable at most stations, however, the extremely high rates observed in the early part of the study (1993-1995) have not been repeated. Highest oxygen uptake rates are usually associated with a dense cover of tube building amphipods. Although the amphipods continue to be present the lower rates we are now observing near the Long 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 cyclingAmount of nutrients released relative to NPP needsRatios 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 dynamicsImportance as an oxygen sinkStorage of reduced endproducts

Determine patterns of annual and interannual variability

Determine how the role of the sediments changes with outfall relocation

Nutrient Cycling Massachusetts Bay – Goals


Nutrient Cycling Benthic Flux Stations

BH02BH03

QB01

MB01MB02

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 Kilometers

Benth ic Flux Stations

LEGEND


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) MB01

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) MB02


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 Massachusetts Bay during 1998. Previous measurements had shown that benthic respiration rates exhibited low interannual variability, less than 20%. This suggested that any change due to the outfall relocation would be readily detectable. Benthic respiration rates measured in 1999, however,have been higher than average, and may reflect greater carbon loading to the sediments from an unusually large diatom bloom, and warmer than usual bottom water temperatures. October rates will be needed to determine if this year’s rates would have fallen outside what was considered normal based upon the 1992-1997 data.

Nutrient Cycling Bay Role

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

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