Ecological models as tools for assessing and managing coastal eutrophication
The formulation of ecological quality indicators relies on the definition of good reference conditions. The general lack of present-day natural (non-impacted by human-induced eutrophication) sites in the NEA has prevented the formulation of well-sounded reference conditions needed for scaling the current status of NEA sub-areas.
Coupled river-ocean models applied to the Southern North Sea have been shown successful to formulate virtual pristine conditions for both the river inputs (Thieu et al., 2010) and the coastal ecosystem (Lancelot et al., 2009, 2011) and to explore realistic nutrient reduction scenarios applied to the Seine, Somme and Scheldt river watersheds (Thieu et al., 2010) and scale their effect on the Phaeocystis-dominated ecosystem (Lancelot et al., 2011).
Coupling between SENEQUE/Riverstrahler and MIRO models to explore nutrient reduction scenarios (credit: Billen et al., 2009)
We intend to extend this approach to the NEA watershed and coastal waters. Marine ecological models have been successfully implemented in each NEA sub-area (Lacroix et al., 2007, Ménesguen et al., 2007, Mateus et al., 2012) by using observed river inputs as forcings.
The coupling with pristine and nutrient reduction scenarios will provide an ecosystem-based mathematical tool for guiding the assessment and management priorities in the NEA as a whole.
In addition, two successful tools already developed by the French and Dutch partners in their zone will be tested for identifying eutrophication-related responsible nutrient sources and their control in the different NEA sub-areas. These are (i) the numerical tracking method of any nutrient sources (Ménesguen et al., 2006) for pointing specifically, through a transboundary approach, the river(s) responsible for the eutrophication nuisances in a given sub-area and (ii) the simplex method (Annex in Lenhart et al., In prep, Los in prep.) implemented to evaluate the subregion-specific "distance to target", i.e. the optimal river load reduction to be undertaken to achieve a GES.
References
Billen, G., Thieu, V., Garnier, J., Silvestre, M. (2009) Modeling the N cascade in regional watersheds: the case study of the Seine, Somme, and Scheldt rivers. Agricuture, Ecosystems & Environment, 133: 234-256
Lacroix, G., Ruddick, K., Park, Y., Gypens, N. and Lancelot, C., 2007. Validation of the 3D biogeochemical model MIRO&CO with field nutrient and phytoplankton data and MERIS-derived surface chlorophyll a images. Journal of Marine Systems, 64(1-4): 66-88.
Lancelot, C., Rousseau, V. and Gypens, N., 2009. Ecologically based indicators for Phaeocystis disturbance in eutrophied Belgian coastal waters (Southern North Sea) based on field observations and ecological modeling. Journal of Sea research, 61: 44-49.
Lancelot, C., Thieu, V., Polard, A., Garnier, J., Billen, G., Hecq, W. and Gypens, N., 2011. Ecological and economic effectiveness of nutrient reduction policies on coastal Phaeocystis colony blooms in the Southern North Sea: an integrated modeling approach. Science of the Total Environment, 409: 2179–2191.
Lenhart, H., Desmit, X., Grosse, F., Mills, D., Lacroix, G., Los, H.J., Ménesguen, A., Pätsch, J., Troost, T., van der Molen, J., van Leeuwen, S. and Wakelin, S., in prep. Report on “distance to target” modelling assessment by ICG-EMO.
Mateus, M., Riflet, G., Chambel, P., Fernandes, L., Fernandes, R., Juliano, M., Campuzano, F., de Pablo, H. and Neves, R., 2012. An operational model for the West Iberian coast: products and services. Ocean Science Discussion, 9: 1651-1689.
Ménesguen, A., Cugier, P. and Leblond, I., 2006. A new numerical technique for tracking chemical species in a multisource, coastal ecosystem, applied to nitrogen causing Ulva blooms in the Bay of Brest (France). Limnology and Oceanography, 51(1, part 2): 591-601.
Ménesguen, A., Cugier, P., Loyer, S., Vanhoutte-Brunier, A., Hoch, T., Guillaud, J.-F. and Gohin, F., 2007. Two- or three-layered box-models versus fine 3D-models for coastal ecological modelling? A comparative study in the English Channel (Western Europe). J.Mar. Sys., 64: 47-65.
Thieu, V., Garnier, J. and Billen, G., 2010. Assessing the effect of nutrient mitigation measures in the watersheds of the Southern Bight of the North Sea. Science of the Total Environment, 408: 1245–1255.