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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