Cost assessment and ecological effectiveness of nutrient reduction options for mitigating Phaeocystis colony blooms in the Southern North Sea: An integrated modeling approach

• Published in: The Science of the total environment 2011-05, Vol.409 (11), p.2179-2191
• Main Authors: Lancelot, Christiane, Thieu, Vincent, Polard, Audrey, Garnier, Josette, Billen, Gilles, Hecq, Walter, Gypens, Nathalie
• Format: Article
• Language: English
• Subjects: Agriculture; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Blooms; Coastal eutrophication mitigation; Conservation of Natural Resources - economics; Conservation of Natural Resources - methods; Conservation, protection and management of environment and wildlife; Cost assessment; Cost engineering; Costs and Cost Analysis; Ecological effectiveness; Ecological monitoring; Environmental degradation: ecosystems survey and restoration; Environmental Sciences; Eutrophication; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Geographic Information Systems; Haptophyta - growth & development; Mathematical models; Methods and techniques (sampling, tagging, trapping, modelling...); Models, Biological; Models, Chemical; Nitrogen - analysis; North Sea; Nutrients; Phaeocystis; Phosphorus - analysis; Reduction; River–ocean modeling; Southern North Sea; Waste Disposal, Fluid - economics; Waste Management - economics; Waste Management - methods; Water Pollutants, Chemical - analysis; Water Pollution, Chemical - prevention & control; Water Pollution, Chemical - statistics & numerical data; Watersheds
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2011.02.023

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. ► A coupled river-ocean biogeochemical model is used to assess coastal eutrophication. ► The model is embedded in a DPSIR loop to assess efficiency and cost of nutrient reduction options. ► We examine the effects of waste water treatment upgrading and changes in agricultural practices. ► Point source reduction is costly and insufficient to obviate coastal eutrophication. ► The further improvement with organic farming appears the best option to rest