Bloom dynamics under the effects of periodic driving forces (Q6566678)

To explain phytoplankton bloom, the authors investigate a 3-dimensional ODE nutrient-phytoplankton-zooplankton (NPZ) model that is subject to a periodic driving force represented by the light-dependent growth rate of the phytoplankton, the solar radiation being modeled as a sinusoidal. The paper is essentially self contained, as it starts with a comprehensive review of the available NPZ models, including concrete examples of usual functional forms for phytoplankton light response and uptake, and for zooplankton grazing.\N\NThe stability of the equilibria is discussed along with a detailed bifurcation analysis, in terms of the total nitrogen concentration. Transcritical and Hopf bifurcations, respectively, are observed to occur for a certain parametric region, being noticed that the numerically simulated result closely resembles a real phytoplankton bloom event. Another periodic driving force, modeling the effect of sea surface temperature on phytoplankton growth, is also incorporated, its effect upon bloom dynamics being investigated theoretically, via further bifurcation analysis, and numerically. It is observed that the introduction of the second periodic driving force, although essentially leading to a similar qualitative picture, significantly improves the timing accuracy of the model.