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Eutrophication is a considerable stressor of marine ecosystems at local and continental scales. In the North East Atlantic waters (NEA), most countries sustain systematic coastal eutrophication with toxic algae blooms and ecological nuisances. Marine eutrophication in the NEA directly relies on nutrient enrichment at the river outlets, which is linked to human activities and land use in the watersheds. Nitrogen emissions to Western Europe rivers are mainly stemming from agricultural practices. The sustainable governance of marine ecosystems and human societies requires to quantify these nutrient emissions and their impact at sea. The question rises of whether the human society can reduce its nutrient emissions by changing its land use without compromising its food security. To address this question, a new generic river model (pynuts/Riverstrahler) was designed to estimate the point and diffuse nutrient emissions (N,P) to the rivers. Nutrient emissions were computed according to land use in the watersheds across Western Europe (agro-food systems, urban structures, waste-water treatment plants). The river loads from the river model have been used as inputs to three marine ecological models (BioPComs, eco-mars3d, miro&co) covering together a large part of the NEA from the Portuguese shelf to the Southern North Sea and Celtic Sea [35°N-53°N, 13°W- 5°E]. Such a description of the land-ocean continuum allowed quantifying the impact of changes in land use across Western Europe on marine eutrophication in the NEA. A 'pristine-like' scenario was tested to scale the current level of eutrophication with respect to an absolute 'natural' level. Three 'future' scenarios were also tested to appraise the impact of the actual EU recommendations (WFD, MSFD), and to propose a more radical but still 'realistic' scenario. It is shown that a paradigmatic change in agricultural practices combined with a large-scale demitarian diet might sensibly reduce both riverine and marine eutrophication levels.

D5, Descriptor 5, modelling, eutrophication, North East Atlantic, toxic algae blooms, algae blooms, nitrogen, nutrient emissions, nitrogen,

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20/01/2016

Workshop of the Network of Experts for ReDeveloping Models of the European Marine Environment

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201604194622

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