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Spatial and temporal variability at different scales of relevant biogeochemical properties are presented. The study is carried out by means of a 3D implementation of a numerical model (OGSTM-BFM). Several simulations are shown including hindcast and scenario simulations that reconstruct productivity and trophic regimes. Simulations show that, on a basin scale, the Mediterranean Sea is characterised by a high degree of spatial and temporal variability in terms of primary production. On a spatial scale, important horizontal and vertical gradients have been observed. According to the simulations over a 6 yr period, the developed model correctly simulated the climatological features of deep chlorophyll maxima and chlorophyll west-east gradients, as well as the seasonal variability in the main off-shore regions that were studied. According to the model, the western Mediterranean, in particular the Alboran Sea, can be considered mesotrophic, whereas the eastern Mediterranean is oligotrophic. Results show that the effects of atmospheric and terrestrial nutrient loads on the total integrated net primary production account for less than 5 % of the its annual value, whereas an increase of 30 % in the light extinction factor impacts primary production by approximately 10 %. The impacts of climate change and environmental management policies on the Mediterranean Sea were analysed in multi-annual simulations of carbon cycling in a planktonic ecosystem model. The scenario simulations span the periods 1990–2000 and 2090–2100, assuming the IPCC SRES A1B scenario of climatic change at the end of the century. All scenarios indicate that the increase in temperature fuels an increase in metabolic rates. The gross primary production increases approximately 5% over the present-day figures, but the changes in productivity rates are compensated by augmented community respiration rates, so the net community production is stable with respect to present-day figures. The 21st century simulations are characterized by a reduction in the system biomass and by an enhanced accumulation of semi-labile dissolved organic matter. The largest changes in organic carbon production occur close to rivers, at the coastal scale, where the influence of changes in future nutrient is higher and can potentially lead to eutrophication.

Mediterranean Sea, primary production, chlorophyll, D5, Descriptor 5, modelling, carbon cycling, plankton, climate change, organic carbon, euthrophication, modelling

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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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EN

201604193539

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