Assessing the effects of extreme nutrients scenarios in European rivers for the ecosystem status of the Mediterranean Sea : putting the marine modelling framework to work

The main objective for the development of the Marine Modelling Framework (MMF) at the Joint Research Centre of the European Commission is the creation of a tool that allows evaluation of the impacts of policy options on the environmental status of EU regional seas. Within the remit of the MSFD AA (N° 11 06 61/ENV.C.2/2016/733192 & JRC No. 34131-2016 NFP) with DG Environment, one deliverable (#3.5) referred to 'A specific technical report will be produced summarizing the potential impacts of MS programs of measures on key environmental parameters including a gap analysis in relation to the targets set by each MS'. As the program of measures from MS are still not available, the JRC marine modelling team designed a set of simulations to test the potentialities of the MMF to simulate the effects of different eutrophication scenarios in EU rivers. Here, an extreme scenario concerning the chemical quality of EU rivers is evaluated for the period 1960 - 2013 and compared with the results of the 'standard' hindcast model run. The river scenario consists in a total clean-up of inorganic nutrients from the freshwater and constitutes an unrealistic lower boundary for any management strategy that could be implemented regarding freshwater quality in Europe. By comparing MMF simulations with the full nutrient loads in the rivers with this alternative scenario, the impact of allochthonous river-borne fertilization on Mediterranean ecosystems could be analyzed and quantified. Moreover, this comparison provides an envelope of the range of expected consequences any freshwater management plans could have on the ecosystems' status of marine waters downstream.