A unifying framework for marine ecological model comparison

Abstract The complex network of the marine food chain with all the details of the behavior of individuals and the interactions with physical processes cannot be included into one generic model. Modelling requires simplification and idealization. The reduction of complex problems to simpler, but tractable problems are guided by the questions being addressed. Consequently, a variety of different models have been developed with different choices of state variables, process formulations, and different degree of physical control. In the last decade a multitude of studies were based on biogeochemical models, population models, and individual based models. There are now models available that cover the full range from individual based models, to population models, to biomass models, to combinations thereof. The biological model components are linked to physical models ranging from 1d water column models to full 3d general circulation models. This paper attempts to develop an unifying theoretical framework that elucidates the relationships among the different classes of models. The theory is based on state densities, which characterize individuals in an abstract phase space. Integration of the state densities over spatial or biological variables relates population densities, abundance or biomass to individuals.