Model reconstruction and future evolution of Phaeocystis colony blooms in Belgian coastal waters as a function of human activity on the watershed

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1 Model reconstruction and future evolution of Phaeocystis colony blooms in Belgian coastal waters as a function of human activity on the watershed Christiane LANCELOT and Nathalie GYPENS Ecologie des Systèmes Aquatiques Université Libre de Bruxelles, Belgium ECOLOGIE DES SYSTEMES AQUATIQUES

2 Studied area Staging the Belgian coastal waters today: Located in the eutrophied Southern Bight of the North Sea Direct and transboundary loads of unbalanced nutrients Spring blooms of ungrazable Phaeocystis colonies in between diatom blooms ecosystem disturbance Source: ECOMAR GEM-IES Chl a in 25 May Phytoplankton biomass, mgc m Phaeocystis Diatoms J F M A M J J A S O N D Month

3 Studied area Staging the Belgian coastal waters today: Located in the eutrophied Southern Bight of the North Sea Direct and transboundary loads of unbalanced nutrients Spring blooms of ungrazable Phaeocystis colonies in between diatom blooms ecosystem disturbance Source: ECOMAR GEM-IES Phytoplankton biomass, mgc m Chl a in 25 May Phaeocystis Diatoms J F M A M J J A S O N D Month

4 Addressing the questions: Southern Bight of the North Sea Link? Channel Seine Nutrient loads and mitigation Undisturbed (healthy) Phaeocystis ecosystem? Link between Phaeocystis colony blooms in BCZ and nutrient loads of anthropogenic origin? Relative contribution of transboundary and local sources to the nutrient status of BCZ?

5 Methodology Staging the methodology: coupling 2 models RIVERSTRAHLER-MIRO simulations: [R-MIRO; Lancelot et al., 7] Global Solar Radiation Temperature Wind speed Global Solar Radiation Rainfall Temperature MIRO Model coastal sea RIVER STRAHLER Model river Point source Diffuse sources Industry, households w w treat. Land use fertilizer watershed North Sea WCH Channel FCZ Seine BCZ 33 * Somme Rhine 1 km N

6 Methodology Staging the methodology: coupling 2 models RIVERSTRAHLER-MIRO simulations: [R-MIRO; Lancelot et al., 7] Global Solar Radiation Temperature Wind speed Global Solar Radiation Rainfall Temperature 5-2 TOM BAC NO3 NH4 PO4 SiOH4 MIRO µzoo Model NF PHAE DIA coastal sea ZOO mineralisation TOM NO3 NH4 PO4 SiOH4 BAC RIVER CY NF µzoo STRAHLER Model DIA river ZOO Point source Diffuse sources Industry, households w w treat. Land use fertilizer Every 5 years Every 1 years Diagenesis Diagenesis watershed WCH Channel FCZ Seine Somme North Sea BCZ Rhine 33 * R-MIRO scenarios 5-2 historical reference: pristine 215 [implementation of WFD plans -France and Belgium] 1 km N Reference for Phaeocystis disturbance: 15 mgc m -3

7 Historical reconstruction Pristine reference 5-2

8 Nutrient loads RIVERSTRAHLER: Specific loads R-MIRO: BCZ enrichment 2 kt N km -2 y -1 1 kt N y Seine Atl.+ Seine kt P km -2 y kt P y Seine kt Si km -2 y kt Si y -1 1 Seine Pristine Pristine

9 Nutrient enrichment and phytoplankton blooms Nutrient enrichment and blooms in BCZ R-MIRO: Winter nutrient R-MIRO: Winter nutrient stoichiometry Pristine 3 35 mmole m mole:mole N:P; Si:P Si:N 55 6 Si:N 65 DIP 7 75 Si:P 8 DSi 85 DIN 9 95 N:P R-MIRO: Max phytoplankton blooms Pristine: healthy ecosystem; diatom annual production: 75% Enriched well-balanced N:P benefical for summer diatoms and Phaeocystis Elevetad N:P ratios limit summer diatoms more than Phaeocystis Pristine mgc m g C m -2 Phaeocystis Sum. dia Spr. dia diatom Phaeocystis 3 pristine R-MIRO: Annual Primary Production

10 Future scenario: Implementation of WFD for 215

11 R-MIRO scenarios in BCZ: WFD implementation in : P loads: close to pristine; N loads: 4 x pristine Still disturbed Phaeocystis blooms; relative dominance of Phaeocystis blooms Annual Inputs Winter nutrient phytoplankton blooms Kt N year mmolen m mgc m -3 Spring dia Summer dia Phaeo Kt P year mmolep m pristine g C m -2 y pristine pristine pristine 2 215

12 Concluding remarks and perspectives DIN, especially NO 3 is the nutrient to be targeted for decreasing the magnitude of Phaeocystis blooms in BCZ; The coupled RIVERSTRAHLER-MIRO = useful mathematical tool for testing - Realistic nutrient mitigation measures or to be taken on the watershed; - Millenium Ecosystem Assesment Scenarios [Global Orchestration, Order from Strength, Adapting Mosaic, TechnoGarden]

TIMOTHY (Tracing and Integrated Modeling of Natural and Anthropogenic Effects

13 Acknowledgements EU FP6 Thresholds of Environmental sustainability AMORE 3 (Advanced Modeling and Research on Eutrophication) Belgian Science Policy IAP TIMOTHY (Tracing and Integrated Modeling of Natural and Anthropogenic Effects on Hydrosystems (TIMOTHY) Case study:the River Basin and Adjacent Coastal North Sea

Past, present and future eutrophication in the North-East Atlantic coastal waters

Past, present and future eutrophication in the North-East Atlantic coastal waters Xavier Desmit, Geneviève Lacroix, Valérie Dulière Royal Belgian Institute of Natural Sciences (RBINS), OD Nature, Belgium