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Morten D. Skogen

North Sea eutrophication assessment

OpNet, Geilo, 27-28/5-2009

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References:

Skogen, M.D. & Mathisen, L.R. (2009). Long term effects of reduced nutrient inputs to the North Sea. Estuarine, Coastal and Shelf Science, 82:433-442.

Almroth, E. & Skogen, M.D. A North Sea and Baltic Sea model ensemble Eutrophication Assessment. Accepted for publication in Ambio.

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Eutrophication: an increase in chemical nutrients -- typically compounds containing nitrogen or phosphorus -- in an ecosystem. Results often in an increase in the ecosystem's primary productivity – i.e. excessive plant growth and decay -- and even further impacts, including lack of oxygen and severe reductions in water quality and in fish and other animal populations.

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Eutrophication (first report):

“By this you will know that I am the Lord: I am going to strike the water of the Nile with the staff that is in my hand, and it will be turned into blood. Fish in the Nile will die, the Nile will stink, and the Egyptians will be unable to drink water from the Nile.”

2.Moses 7:17-18

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North Sea agreement:At the 2nd. International conference on the protection of the North Sea (London 1987), all countries around the North Sea agreed on reducing the input of nutrients by 50 % between 1985 and 1995 for those areas where nutrient cause, or are likely to cause, pollution, in order to combat eutrophication (PARCOM 88/2).

OSPAR further developed the Common procedure for the Identification of the Eutrophication Status of the Maritime Areas of the Oslo and Paris Convention in 1997, with an update in 2005.

Contracting partners to report ontotal loads of DIN and DIP intheir rivers.

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Reductions in North Sea nitrogen and phosphorous loads 1985-2000 (source approach)

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Reductions in North Sea nitrogen and phosphorous 1985-2000 measured from both sources and loads

Toxic Chrysochromulina sp. bloom

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Assessment criteria based on the OSPAR Common procedure

Areas categorised as problem area, potential problem area or non-problem area

Category Assessment criteriaI: Degree of nutrient enrichment • Riverine inputs and direct discharges (area-specific)

• Nutrient concentrations (area-specific)

• N:P-ratio (area-specific)

II: Direct effects (during growing season)

• ChlorophyllA concentration (area specific)

• Phytoplankton indicator species (area specific)

• Macrophytes including macroalgae (area specific)

III: Indirect effects (during growing season)

• Oxygen deficiencies

• Zoobenthos and fish

• Organic carbon/organic matter (area specific)

IV: Other possible effects (during growing season)

• Algal toxins

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EcoQO for winter nutrients (DIN and/or DIP) concentration

EQO: winter DIN and/or DIP should remain below elevated levels, defined as concentrations >50% above salinityrelatedand/or region-specific natural background concentrations.

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EcoQO for phyto-plankton ChlA

EQO: maximum and mean chlorophyllA conc. during the growing season should remain below elevated levels, defined as conc. > 50% above the spatial (offshore) and/or historical background conc.

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NORWECOM

The NORWegian ECOlogical Model systemhttp://www.imr.no/~morten/norwecom

A coupled physical-chemical-biological model system appliedto study primary production and dispersion of particles

(e.g. fish larvae and/or pollution)

Main partners:

Institute of Marine ResearchDept. of Fisheries and Marine Biology, Univ. of Bergen

Dept. of Mathematics, Univ of BergenThe Norwegian Meteorological institute

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NORWECOM (2)

• first coupled physical-chemical-biological model for the whole North Sea

• North Sea, North Atlantic, Benguela, Hardangerfjorden

• physics based on POM or ROMS• runs operational (7 days forecast) at met.no

http://moncoze.met.no

• environmental status, eutrophication issues, what-if scenarios, climate/fish relations,…..

• offline version coupled to Bergen Climate Model for paleo studies – potential oil fields

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• 2 types of phytoplankton (diatoms, flagellates)

• 3 nutrients (N, P, Si)

• Dead organic matter (DetN, DetP, diatom skeletals)

• Oxygen

• (IBM Calanus finm.) • Primary production

• Respiration

• Algae death

• Regeneration

• Self shading

• Turbidity

• Sedimentation

• Resuspension

• Denitrification

• ECMWF:

• Wind and Pressure

• SeaSurfaceRadiation

• Surface heat flux

• Precipitation

• Evaporation

• Tides (M2, S2, K1, O1)

• Freshwater (rivers)

• River nutrients

• Atmospheric N

• Waves (WINCH)

• Offline (U,V,S,T,ETA,SSR,wind)

NORWECOM

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North Sea primary production model

• Period 1985-2008• Spin-up: 4 x 1985• Horisontal 10x10km• Vertical 21 σ-layers• References:

– Skogen & Mathisen(2009)– Almroth & Skogen (accepted)

10 km horisontal resolution, 21 -layers

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NOORDWIJK 10, Winter DIP

0

0,5

1

1,5

2

2,519

85

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Model

PHO_10

Linear (PHO_10)

Linear (Model)

NOORDWIJK 10, Winter DIN

0

10

20

30

40

50

60

70

80

90

100

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Model

NIT_10

Linear (NIT_10)

Linear (Model)

Longterm changes of winter DIN and DIP at Noordwijk 10km station

Ele

vate

d le

vels

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NOORDWIJK 70, Winter DIP

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Model

PHO_70

Linear (Model)

Linear (PHO_70)

NOORDWIJK 70, Winter DIN

0

2

4

6

8

10

12

1419

85

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

Model

NIT_70

Linear (NIT_70)

Linear (Model)

Longterm changes of winter DIN and DIP at Noordwijk 70km station

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Model validation at Noordwijk 10 and 70, Longterm winter DIN and DIP

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OSPAR ICG-EMO: Target areas, GC1, GO2, NLC2, NLC3 and NLO2 for model statistics to perform a eutrophication assessment based on the OSPAR common procedure

Eutrophication in Potomac river

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Assessment simulations:• realistic simulation• 1985 fixed values• (fixed 1985, 10% reduced)• fixed 1985, 50% reduced• fixed 1985, 90% reduced

Caspian sea from orbit

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GC1

DIN

DIP

NLC2

XX

Effects of reduced N and P to winter DIN and DIP

Fixed 1985

90%

50%

Realistic

• 2-3 years for full effect• 50% reduction not sufficient!!

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NLC3

ChlA

ChlA, mean value through the growing season

NLO2

XX

Effects of reduced N and P to ChlA mean value

Fixed 1985

90%

50%

Realistic

• offshore gradient• immediate effect• lower response than winter nutrients

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GC1

O2, annual minimum value

GO2

XX

Effects of reduced N and P to oxygen minimum value

Fixed 1985

90%

50%

Realistic

• almost no effect• trend towards lower oxygen values (consistent with increased temperatures)

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Assessment summary:

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What controls inter annual variability??

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A North Sea and Baltic Sea model ensemble Eutrophication Assessment

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23 North Sea and Baltic subareas:

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Cost function:

)(

)(

dataSTD

DataModelC

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Modelled winter DIP:Also done for:

• winter DIN• DIN/DIP• Chlorophyll• Oxygen

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Integrated assessment:

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Integrated assessment:

Model mean: Weighted model mean:

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References:

Skogen, M.D. & Mathisen, L.R. (2009). Long term effects of reduced nutrient inputs to the North Sea. Estuarine, Coastal and Shelf Science, 82:433-442.

Almroth, E. & Skogen, M.D. A North Sea and Baltic Sea model ensemble Eutrophication Assessment. Accepted for publication in Ambio.

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THANK YOU FOR YOUR ATTENTION

Bergen seen from Mt. Ulriken

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Reductions of winter DIN at Helgoland (5-years mean) vs. NAO

(J.Aure, IMR, pers.comm)

5.15

18

12

17

28

35

42

2624

0

5

10

15

20

25

30

35

40

45

1965-70 1970-75 1975-80 1980-85 1985-90 1990-95 1995-2000 2000-2005

mm

ol/m

3

Middel nitrat Helgoland , jan- april

y = 0.15x - 20R2 = 0.8

0

5

10

15

20

25

30

35

40

45

50

200 250 300 350 400

He

lg N

O3

S o

bs

v ja

n-a

pr

NO3 Elbe NO3 mmol m-3

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21

28

35

47

32

20

0

5

10

15

20

25

30

35

40

45

50

1965-70 1970-75 1975-80 1980-85 1985-90 1990-95 1995-2000 2000-2005

NO

3 (

mm

ol/

m3 )

periode

Helgoland RedeNO3, jan-apr

middel salth : 32.0

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Eutrophication: an increase in chemical nutrients -- typically compounds containing nitrogen or phosphorus -- in an ecosystem. Results often in an increase in the ecosystem's primary productivity – i.e. excessive plant growth and decay -- and even further impacts, including lack of oxygen and severe reductions in water quality and in fish and other animal populations.

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Winter DIN Winter DIP

101 gC/m2/y

103 gC/m2/y

Annual primary prod.1

98

52

00

2