Remineralization at the bottom is assumed to be proportional to the amount of available benthic detritus, at a constant rate rD. The set of constants is given in Appendix A. There now follow a few remarks regarding their choice. For the grazing formulation, the threshold value Phyto and the half-saturation value kPhyt have been changed according

to data reported by Dzierzbicka-Głowacka (2005). The nitrogen to carbon ratio gN is assumed to be 0.013 mmolN (mgC)−1, the half-saturation constant for total inorganic nitrogen is 0.5 mmolN m−3, and the optimal light intensity for the phytoplankton community is set at 60 W m−2. For the remineralization rates in the water and at the KU-60019 molecular weight bottom (following Postma & Rommets (1984)) ca 20% of the average labile particulate organic carbon (POC) is mineralized daily. Thus, 20% of the POC formed as detritus is remineralized instantaneously (pF = pM = pZ = 0.2), whereas the remaining 80% is transported immediately to the bottom. There is no

explicit sinking of living phytoplankton, because this is already included in the instantaneous transfer to the bottom ( Figure 2). Ingested material is divided equally between dead zooplankton, faecal pellets and soluble excretion following Steele (1974). The benthic nutrient mineralization rD is taken to be 0.0005 day−1 exp(0.005°C−1T) ( Savchuk & Wulff 1996). The intention was to simulate selleck screening library production in a physical environment that would be as realistic as possible. Actual oceanic forces are required for reliable simulations of phytoplankton dynamics (Figure 2). The external forcing is taken from ECMWF (ERA 40 reanalysis, www.ecmwf.int). The biological reaction terms are

not implemented in the circulation model. The primary production model is an independent transport model that uses the circulation model output, so there is no feedback from Evodiamine the biology to the physics, which makes the simulations easier to implement. Another important force for primary production simulations is solar radiation with its own daily cycle. The total irradiance at the surface is calculated using the model by Rozwadowska & Isemer (1999). The local weather conditions were recorded on board Voluntary Observing Ships, and these data have been used to estimate the climatological characteristics of the solar radiation flux at the sea surface. The monthly loads were interpolated to give daily values. Nutrient contributions from rivers are not included in this model, but the initial values for nutrients have been based on the SCOBI 3D-model. Phytoplankton production is limited in the model by light and total inorganic nitrogen. The phytoplankton biomass is restricted by mesozooplankton grazing. The zooplankton biomass is prescribed as a force and the model uses the abundance data from Mańkowski (1978), Ciszewski (1983) and Mudrak (2004) for the southern Baltic Sea.