Effect of nonlinear mortality and self-grazing on the dynamics of a marine ecosystem

Phase-plane analysis of a class of basic marine ecosystem models was carried out to know whether the nonlinear terms arising from mortality or self-grazing of zooplankton have significant effect in suppressing limit cycles or auto-oscillations of marine ecosystem models that are observed under certain conditions. The results show that even a rather small nonlinear term describing nonlinearity in mortality or self-grazing can effectively alter the linear stability conditions and thus suppress the limit cycles.