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Predicting the consequences of nutrient reduction on the eutrophication status of the North Sea

Predicting the consequences of nutrient reduction on the eutrophication status of the North Sea.

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Predicting the consequences of nutrient reduction on the eutrophication status of the North Sea

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  1. 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)

  2. OSPAR – Regional Convention Conventionfor 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. PARCOM Recommendation 88/2:where eutrophication diagnosed then a reduction (of the order of 50%) in inputs of phosphorus and nitrogen. OSPAR definition of eutrophication:“the enrichmentof water by nutrients, especially nitrogen and/or phosphorus, causing an accelerated growthof 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”

  3. 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 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 23 participants, 10 institutes, 7 nationalities, 8 models 1st Workshop in Hamburg (IfM, September 2005) 2nd Workshop in Lowestoft (Cefas, September 2007) 3rd Workshop, September 2009 (MUMM, Belgium) Problem Area Potential Problem Area

  4. N: NORWECOM UK Cefas: GETM-BFM PT: MOHID NL: Delft3D B: MIRO FR: ECO-MARS DE: ECOHAM ICG-EMO: use common forcing • Provided by ICG-EMO • boundary conditions • riverine loads • atmospheric deposition fields • meteorological forcing • spin up procedure • calibration and validation data UK POL: POLCOMS-ERSEM

  5. ICG-EMO: use common forcing • Provided by ICG-EMO • boundary conditions (POL) • riverine loads • atmospheric deposition fields • meteorological forcing • spin up procedure • calibration and validation data 1985 2002 ammonium Different load reductions for TOxN (NO2+NO3), NH4 and PO4 Different load reductions for each country

  6. Nutrient reduction scenarios

  7. ICG-EMO: procedure • Provided by ICG-EMO • boundary conditions (POL) • riverine loads • atmospheric deposition fields • meteorological forcing • spin up procedure • calibration and validation data ECMWF operational reanalysis ≥ 3 years NSP 1989 and ‘monitoring’ data for 2002 Standard year 2002 • reference run • 50% reduction with respect to 1985 • 70% reduction with respect to 1985 Comparable results due to common forcing and procedure

  8. 50% red.-standard standard Winter DIN results NL DE BE UK Cefas

  9. OSPAR target areas 10 target areas for model intercomparison 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. UK-C1 NL-O2

  10. UK-C1 results Parameter response to 50% reduction Parameter response to 70% reduction Annual O2 mini- mum at bottom Mean winter DIP at surface Mean winter DIN at surface Mean summer Chl at surface

  11. mean Chla max Chla min O2 DIN DIP N/P 0% 50% threshold 70% Assessment of eutrophication Cefas GETM-BFM results for UK-C1

  12. mean Chla max Chla min O2 DIN DIP N/P + 0 threshold Assessment of eutrophication Cefas GETM-BFM results for UK-C1

  13. NL-O2 results Model results presented in OSPAR Comprehensive Procedure reporting format

  14. 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. Results In general all models exhibit the following characteristics:

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

  16. Forward look 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 3rd workshop to be held in Belgium (MUMM), September 2009 Focus on calculating transboundary nutrient transport Approach • budgets across transects • tagged nutrients – trace to source

  17. Thank you for your attention! Thanks to the OSPAR ICG-EMO workshop participants 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) 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)

  18. NL-O2 results Parameter response to 50% reduction Parameter response to 70% reduction Mean winter DIN at surface Mean winter DIP at surface Mean summer Chl at surface Annual O2 mini- mum at bottom

  19. UK-C1 results Model results presented in OSPAR Comprehensive Procedure reporting format

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