Cost assessment and ecological effectiveness of nutrient reduction options for mitigating Phaeocystis colony blooms in the Southern North Sea: an integrated modeling approach |
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Authors: | Lancelot Christiane Thieu Vincent Polard Audrey Garnier Josette Billen Gilles Hecq Walter Gypens Nathalie |
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Affiliation: | a Université Libre de Bruxelles, Ecologie des Systèmes Aquatiques, CP-221, Bd du Triomphe, B-1050 Brussels, Belgiumb Université Pierre et Marie Curie, UMR 7619 Sisyphe, 4 Place Jussieu, F-75005 Paris, Francec Université Libre de Bruxelles, Centre d'Etudes Economiques et Sociales de l'Environnement, CP 124, Avenue Jeanne 44, B-1050 Brussels, Belgiumd CNRS, UMR 7619 Sisyphe, 4 Place Jussieu, F-75005 Paris, France |
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Abstract: | Nutrient reduction measures have been already taken by wealthier countries to decrease nutrient loads to coastal waters, in most cases however, prior to having properly assessed their ecological effectiveness and their economic costs. In this paper we describe an original integrated impact assessment methodology to estimate the direct cost and the ecological performance of realistic nutrient reduction options to be applied in the Southern North Sea watershed to decrease eutrophication, visible as Phaeocystis blooms and foam deposits on the beaches. The mathematical tool couples the idealized biogeochemical GIS-based model of the river system (SENEQUE-RIVERSTRAHLER) implemented in the Eastern Channel/Southern North Sea watershed to the biogeochemical MIRO model describing Phaeocystis blooms in the marine domain. Model simulations explore how nutrient reduction options regarding diffuse and/or point sources in the watershed would affect the Phaeocystis colony spreading in the coastal area. The reference and prospective simulations are performed for the year 2000 characterized by mean meteorological conditions, and nutrient reduction scenarios include and compare upgrading of wastewater treatment plants and changes in agricultural practices including an idealized shift towards organic farming. A direct cost assessment is performed for each realistic nutrient reduction scenario. Further the reduction obtained for Phaeocystis blooms is assessed by comparison with ecological indicators (bloom magnitude and duration) and the cost for reducing foam events on the beaches is estimated. Uncertainty brought by the added effect of meteorological conditions (rainfall) on coastal eutrophication is discussed. It is concluded that the reduction obtained by implementing realistic environmental measures on the short-term is costly and insufficient to restore well-balanced nutrient conditions in the coastal area while the replacement of conventional agriculture by organic farming might be an option to consider in the nearby future. |
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Keywords: | Coastal eutrophication mitigation River-ocean modeling Ecological effectiveness Cost assessment Southern North Sea |
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