Biogeochemical marine ecosystem models II: the effect of physiological detail on model performance

The level of detail required to efficiently capture system dynamics in ecosystem models has not been well defined. To this end an ecosystem model of a generalised temperate bay, Bay Model 2 (BM2), was constructed. It is a trophically diverse biogeochemical model built using the functional groups from another ecosystem model, the Integrated Generic Bay Ecosystem Model (IGBEM) and the general framework from a model of Port Phillip Bay (PPB), Australia. BM2 captures the essential features of real marine systems, it is also capable of reproducing realistic levels of biomass and conforms with known ecological relationships. The model’s performance is not as good for some of the poorly known groups (like infauna) or when environmental conditions undergo extreme change. Despite this, the overall performance of BM2 indicated, it is as capable of representing systems as accurately as more physiologically detailed ecosystem models, such as IGBEM. This shows that physiological detail is not always required and that simpler formulations, such as those employed in BM2, are generally adequate for learning and general predictive purposes. This is important because, in comparison with IGBEM, BM2 uses substantially fewer parameters and has lower development, computation and maintenance costs.