Seth Cowall, University of Delaware

Abstract

Phytoplankton are the base of the marine food web. They are also responsible for almost half of the oxygen we breathe and they remove carbon dioxide from the atmosphere. A macroscale plankton ecology model is constructed consisting of coupled, nonlinear reaction-diffusion equations with spatially and temporally changing coefficients. An example of an NPZ model, this model simulates biological interactions between nutrients, phytoplankton and zooplankton. It also incorporates seasonally varying, physically driven forces that affect the phytoplankton growth: solar radiation and depth of the ocean’s upper mixed layer. The model’s predictions are dependent on the parametric functional behavior of the model. The model is analyzed using seasonal oceanic data with the goals of understanding the model’s dependence on its parameters and of understanding seasonal changes in plankton biomass. The model is tested on different regions of the world’s oceans so that appropriate choices can be made for parameters that correspond to physical/biological quantities in those regions. A study of varying parameter values and the resulting effects on the solutions, stability, and the timing of blooms is carried out. This modeling effort can be helpful for understanding the ecological structure of plankton communities and the timing of seasonal phytoplankton blooms, which are debated topics in oceanography.