Predicting the consequences of nutrient

reduction on the eutrophication status of

the North Sea D. K. Mills, H. J. Lenhart, J.G. Baretta-Bekker, S. M. van Leeuwen, J. van der Molen, M. Blaas, W. Kühn, F.J. Los, G. Lacroix, A. Ménesguen, R. Neves, R. Proctor, P. Ruardij, J. W. Baretta, M. D. Skogen, M.T. Villars and S. L. Wakelin

Cefas, POL (UK);RWS, Deltares, NIOZ (NL), MUMM (BE), IFREMER (FR), IFM (DE), IMR (NO), IST (PT)

OSPAR – Regional Convention

Convention for the protection of the marine environment of the North-East Atlantic

Strategy: to make every effort to combat eutrophication in the maritime area, in order to achieve, by the year 2010, a healthy marine environment where eutrophication does not occur.

OSPAR definition of eutrophication: “the enrichment of water by nutrients, especially nitrogen and/or phosphorus, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of water concerned”

PARCOM Recommendation 88/2: where eutrophication diagnosed then a reduction (of the order of 50%) in inputs of phosphorus and nitrogen.

Intersessional Correspondance Group on Eutrophication Modelling

(ICG-EMO)an assessment in 2006 of the expected eutrophication status of the OSPAR maritime area following the implementation of agreed measures

1st Workshop in Hamburg (IfM, September 2005)

2nd Workshop in Lowestoft (Cefas, September 2007)3rd Workshop, September 2009 (MUMM, Belgium)

OSPAR ICG-EMO Planning Group:D. Mills (Chair), J. van der Molen, S. van Leeuwen (UK, Cefas,)

H. Barretta-Bekker (NL, RWS), H. Lenhart (DE,IfM)

OSPAR class. according to Common Procedure

Problem Area

Potential Problem Area

23 participants, 10 institutes, 7 nationalities, 8 models

ICG-EMO: use common forcingProvided by ICG-EMO

boundary conditions riverine loads atmospheric deposition fields meteorological forcing spin up procedure calibration and validation data

DE: ECOHAM

N: NORWECOM

UK Cefas:GETM-BFM

NL: Delft3D

PT: MOHID

B: MIROFR: ECO-MARS

UK POL: POLCOMS-ERSEM

ammonium

Provided by ICG-EMO boundary conditions (POL) riverine loads atmospheric deposition fields meteorological forcing spin up procedure calibration and validation data

Different load reductions for TOxN (NO2+NO3), NH4 and PO4

Different load reductions for each country

1985 2002

ICG-EMO: use common forcing

Nutrient reduction scenarios

Contracting Party TOxN (%) NH4 (%) PO4 (%)

(a) Reductions achieved between 1985 and 2002

Netherlands 0 70 70

Germany 0 90 50

UK 0 20 0

France 0 10 60

(b) Scenario 1: Reductions of 2002 national loads necessary to achieve 50% reduction compared to 1985

Netherlands 50 0 0

Germany 50 0 0

UK 50 40 50

France 50 40 0

(c) Scenario 2: Reductions of 2002 national loads necessary to achieve 70% reduction compared to 1985

Netherlands 70 0 0

Germany 70 0 40

UK 70 60 70

France 70 70 20

ICG-EMO: procedure

reference run 50% reduction with respect to 1985 70% reduction with respect to 1985

Standard year 2002

Provided by ICG-EMO boundary conditions (POL) riverine loads atmospheric deposition fields meteorological forcing spin up procedure calibration and validation data

≥ 3 yearsNSP 1989 and ‘monitoring’ data for 2002

Comparable results due to common forcing and procedure

ECMWF operational reanalysis

-4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

48.5

49

49.5

50

50.5

51

51.5

52

52.5

Longitude (°E)

Latit

ude

(°N

)

WinterDIN (M50-STD)/STD

%

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

-4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 548.5

49

49.5

50

50.5

51

51.5

52

52.5

Longitude (°E)

Latit

ude

(°N

)

WinterDIN (M50-STD)/STD

%

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

Winter DIN results 50% red.-standardstandard

DE NL

UK Cefas BE

OSPAR target areas

Water body definitions:

Catchment, hydrography & salinity

O = offshore (>34.5 salinity)

C=coastal (30-34.5 salinity)

e.g. NLO2 is the Netherlands Offshore target area 2.

NL-O2UK-C1

10 target areas for model intercomparison

UK-C1 - parameter response to 50% nutrient load reduction

0

10

20

30

40

50

60

70

DIN DIP Chl O2min

red

uct

ion

(%

)

BE UK-Cef DE NL UK-POL mean

UK-C1 - parameter response to 70% nutrient load reduction

0

10

20

30

40

50

60

70

DIN DIP Chl O2min

red

uct

ion

(%

)

BE UK-Cef DE NL UK-POL mean

UK-C1 - mean winter DIN at surface

0

5

10

15

20

25

30

0 20 40 60 80

nutrient load reduction (%)

µm

ol/l

UK-C1 - mean winter DIP at surface

0

0.4

0.8

1.2

1.6

2

0 20 40 60 80

nutrient load reduction (%)

µm

ol/l

UK-C1 - mean summer chlorophyll at surface

02468

10121416

0 20 40 60 80

nutrient load reduction (%)

µm

ol/l

BE UK-Cef DE

NL NO UK-P OL

FR ass. level

UK-C1 - annual oxygen minimum at bottom

4

5

6

7

8

0 20 40 60 80

nutrient load reduction (%)

µm

ol/l

BE UK-Cef DE

NL NO UK-P OL

FR ass. level

Mean winter DIN at surface

Mean winter DIP at surface

Mean summer Chl at surface

Annual O2 mini- mum at bottom

Parameter response to 50% reduction

Parameter response to 70% reduction

0

1

2

3

4

5

0 20 40 60 80

UK-Cef DE NL

NO UK-P OL ass. level

0

10

20

30

40

50

DIN DIP Chl O2min

UK-Cef DE NL UK-POL mean

UK-C1 results

Assessment of eutrophication

DIN DIP N/P min O2

maxChla

meanChla

50%

70%

0%

threshold

Cefas GETM-BFM results for UK-C1

Assessment of eutrophication

DIN DIP N/P min O2

maxChla

meanChla

0

+

threshold

Cefas GETM-BFM results for UK-C1

Harmonised assessment

parameters of the Common Procedure

DataCommo

nProce-dure2002

GermanyECOHAM4

NetherlandsDelft3D-GEM

UK (POL)POLCOMS-

ERSEM

UK (Cefas)GETM-BFM

NorwayNORWECO

M

2002

Sc1

Sc2

2002

Sc1 Sc2 2002

Sc1

Sc2

2002

Sc1 Sc2

2002

50%

red

Cat. I

Winter DIN - - - - - - - - - - - - - -

Winter DIP - + + 0 - - - - - - - - - - -

N:P ratio - - - - - - - - - - + - - - -

Cat. II

Chl mean - - - - - - - - - - 0 0 - - -

Chl max - - - - + + + + + + + + + - -

Indicator species

-/+ n/a n/a n/a 0 0 0 n/a n/a n/a n/a n/a n/a n/a n/a

Cat. III

Oxygen min + + + - + + + + + + + - - + +

Organic matter

+ n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a na na

NL-O2 results

Model results presented in OSPAR Comprehensive Procedure reporting format

Results

Largest reductions in nutrients parameters are seen in the coastal water target areas.

A strong, almost linear response in winter DIN concentrations to the reduced loads (less in DIP).

Winter DIP concentrations do not respond as strongly to the load reductions as DIN with a decrease of up to 30% with 70% reduction in UK coastal waters but results are typically < 30% for all other areas and scenarios.

The range of responses in mean summer chlorophyll concentration is 4% - 25% with similar minimum decreases in coastal and offshore waters but the maximum decreases in coastal waters are nearly double those achieved in offshore areas for both scenarios.

Minimum dissolved oxygen concentration increased by a maximum of 12% for 70% reduction in coastal waters. Offshore and coastal waters gave similar results for both scenarios.

In general all models exhibit the following characteristics:

Conclusions Comparability of models improved through common

boundary conditions, calibration and validation data Models can support (in part) formal assessments of

eutrophication Setting wider context to assessment outcome Determine robustness of eutrophication indicators Improve interpretation of indicator values e.g. min O2 conc Help set background levels i.e. pristine values of indicator

Insight into future eutrophication status for some target areas

Only quantitative method for evaluating mitigation measures i.e. nutrient reduction

Trends more reliable that than absolute values

See ‘www.cefas.co.uk/eutmod’ for full report on workshop

Forward look

3rd workshop to be held in Belgium (MUMM), September 2009Focus on calculating transboundary nutrient transport

2nd ICG-EMO workshop report on www.cefas.co.uk/eutmod/

Revised 2nd workshop report submitted (including French and Belgium target areas) as stand-alone

document

Approach budgets across transects tagged nutrients – trace to source

Thank you for your attention!

Thanks to the OSPAR ICG-EMO workshop participants

1st row: M. Skogen (NO), L. Fernand (UK), H. Los (NL), S. M. van Leeuwen (UK), H. Lenhart (DE), H. Baretta-Bekker D.Mills (UK), S. Wakelin (UK), B. Bernardes (PT), A. Ménesguen (F), R. Neves (PT)

2nd row: A. Weiss (OSPAR), R. Proctor (UK), B. Brinkman (NL), M. Villars (NL), W. Kühn (DE), G. Lacroix (B), J. Baretta (NL), M. Blaas (NL), T. Prins (NL), M. Sourisseau (F), P. Ruardij (NL), J. van der Molen (UK)

NL-O2 results

NL-O2 - parameter response to 50% nutrient load reduction

0

10

20

30

40

50

DIN DIP Chl O2min

red

uct

ion

(%

)

NL-O2 - parameter response to 70% nutrient load reduction

0

10

20

30

40

50

DIN DIP Chl O2min

red

uct

ion

(%

)

NL-O2 - mean winter DIN at surface

02468

10121416

0 20 40 60 80

nutrient load reduction (%)

µm

ol/l

NL-O2 - mean winter DIP at surface

0

0.2

0.4

0.6

0.8

1

0 20 40 60 80

nutrient load reduction (%)

µm

ol/l

NL-O2 - mean summer chlorophyll at surface

0

1

2

3

4

5

0 20 40 60 80

nutrient load reduction (%)

µg

/lNL-O2 - annual oxygen minimum at

bottom

4

5

6

7

8

9

0 20 40 60 80

nutrient load reduction (%)

mg

/l

0

1

2

3

4

5

0 20 40 60 80

UK-Cef DE NL

NO UK-P OL ass. level

0

10

20

30

40

50

DIN DIP Chl O2min

UK-Cef DE NL UK-POL mean

Mean winter DIN at surface

Mean winter DIP at surface

Mean summer Chl at surface

Annual O2 mini- mum at bottom

Parameter response to 50% reduction

Parameter response to 70% reduction

Harmonised assessment

parameters of the Common Procedure

DataCommonProcedur

e2002

BelgiumMIRO&CO-3D

GermanyECOHAM4

Netherlands Delft3D-GEM

UK (POL)POLCOMS-

ERSEM

UK (Cefas)GETM-BFM

FranceECO-MARS3D

NorwayNORWECO

M

2002

Sc1

Sc2

2002

Sc1

Sc2

2002

Sc1

Sc2

2002

Sc1

Sc2

2002

Sc1

Sc2

2002

50% red

70%

red

2002

50% red

Cat. I

Winter DIN + + + + + - - + + 0 + + + + - - - - - - -

Winter DIP + + + + + + - + + + + + + 0 - - + - - + +

N:P ratio + - - - - - - - - - - - - - - - - - - - -

Cat. II

Chl mean + - - - - - - - - - - - - - - - - - - - -

Chl max + + + + - - - + + + - - - + + - - - - - -

Indicator species- n/a n/a

n/a

n/a n/a n/a - - - n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a

Cat. III

Oxygen min- n/a n/a

n/a + + + + + + - - - - - - n/a n/a n/a + +

Organic mattern/a n/a n/a

n/a

n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a

UK-C1 results

Model results presented in OSPAR Comprehensive Procedure reporting format