Modeling zooplankton development using the monotonic upstream scheme for conservation laws

Numerical diffusion along the age/stage axis is recognized as a significant problem in the modeling of zooplankton populations in dynamic physical environments. We demonstrate the utility of borrowing schemes from numerical fluid dynamics to address this problem. In particular, we use the monotonic upstream scheme for conservation laws (MUSCL) to model the zooplankton Calanus finmarchicus in the Gulf of Maine. Applying this scheme to the molting term substantially reduces numerical diffusion without requiring the introduction of additional state variables. The improvement is on average equivalent to a 3- to 5-fold increase in the number of state variables, but without the run-time costs of such an increase. Basic strategies for assessing numerical schemes are discussed, and some consequences of numerical diffusion in the age domain are demonstrated.