THE BENTHIC BIOLOGICAL SUBMODEL IN THE EUROPEAN-REGIONAL-SEAS-ECOSYSTEM-MODEL

The submodel describing benthic biology including a bioturbation modul e as incorporated in the European Regional Seas Ecosystem Model (ERSEM ) is discussed. It is linked to a nutrient dynamic model. The structur e of the benthic model food web is presented. There are four macrobent hic functional groups, meiobenthos and aerobic and anaerobic bacteria. The modelling uses 'standard organisms' as basic building blocks, The choice of parameter values is discussed. The results demonstrate the dependence of the benthic system on the pelagic system. The importance of features such as predation within functional groups for stability of the system is investigated. Detritus input from the pelagic system and detritus recycling is most important in the benthic food web. The web of carbon and nutrient fluxes through the system is analysed. On t he basis of the food web analysis, the trophic positions of the functi onal groups are calculated. Besides the benthic biology, the mathemati cal formulation of the bioturbation and diffusion enhancement is discu ssed. Macrobenthic presence and activity enhance diffusion in the sedi ment and contribute essentially to vertical transport of particulate m atter. This is of great importance for the vertical distribution of de tritus, and as a consequence, for microbial activity in the sediment l ayers.