Microbial dynamics in the marine ecosystem model ERSEM II with decoupled carbon assimilation and nutrient uptake

A description of the improvements in the microbial complex of the dynamical simulation model ERSEM is given and the results for a 130-box setup of the North Sea are discussed. The improvements affecting the microbial food web are the decoupling of the carbon assimilation from the nutrient uptake dynamics in the phytoplankton groups and the incorporation of nutrient uptake dynamics in the bacterioplankton. Simulation results of ERSEM II are presented and discussed in comparison with those of ERSEM I and validation data. Based on model results and emergent properties of the system it was possible to conclude that ERSEM II is able to model the full range of food webs from a system dominated by the microbial loop in the relatively oligotrophic offshore areas to a system dominated by the omnivorous food web in the eutrophic continental coastal area.