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“IGURE 8 
Neighted ensemble results for the pre-eutrophic state (+ 1900), for surface DIN (A), DIP (B) and Chl (C). The colour bar scale is identical to that of 
:igure 7 
may also affect the adjacent water bodies (Gulf of Biscay Coastal 
Waters or GBCW: -22.1%) 
3.5 Ecosystem sensitivity 
The presented results clearly show the elevated nutrient 
concentrations in the coastal zone in the current state, compared 
:o the pre-eutrophic state. The accompanying net primary 
»roduction values as a function of winter total N and P 
concentrations are displayed in Figure 11 for all areas calculated 
by each model. 
In the current state (Figure 11A) the relationship between 
modelled Total N and Total P tends to reproduce the Redfield 
ratio in offshore areas (characterized by low concentrations for both 
variables) but not in coastal areas where TN concentrations are high 
due to anthropogenic river loads. Areas showing N:P ratios far from 
Redfield are found close to the delta rivers outlets (Rhine, Meuse, 
Scheldt; areas RHPM, MPM, SCHPMI1, SCHPM22), but also in the 
Humber plume (HPM) and the Seine plume (SPM) areas. This is a 
direct result of the successful phosphate loads reduction and less 
successful nitrogen loads reduction (Conley et al., 2009), showing 
"rontiers in Marine Lcience 
higher impact in coastal than in offshore areas. N:P ratios for pre- 
zutrophic conditions (Figure 11B) are much lower in river plume 
areas than in the current state scenario. The N:P ratio varies 
between 55-25 molN molP-1 in the current state and between 30- 
15 molN molP-1 in the pre-eutrophic state in coastal areas (with 
sxception of the Meuse Plume and Seine Plume, which remain on 
high N:P ratios). Note that the Redfield ratio is an average value 
applicable to global oceanic conditions, and that it is subject to high 
variability in the short term especially in coastal waters (Falkowski, 
2000). There are exceptions where the dual reduction does not 
significantly change the N:P ratio, which remains as high as 42 
moIlN molP* or even 50 molN molP* for e.g. the Meuse Plume 
area. Despite differences between models (results not shown), net 
primary production (NPP) decreases in the pre-eutrophic scenario 
compared to present conditions (Figure 10B). 
Since all models apply the same river loads, the differences in 
IN and TP concentrations between models in coastal areas are due 
to other differences in the models’ ecological and hydrodynamic set- 
up, such as the model grid resolution and domain and ecological 
process formulations. The proximity of boundary conditions may 
"nfluence concentrations in an area, for some of the smaller domain 
models this can be near river plume areas. To focus on the impact of 
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