| The influence of ocean circulation on planktonic organisms is explored through three numerical model studies. The purpose of these studies is to uncover basic qualities of physical-biological interactions which may have general relevance for marine ecosystems and efforts to model them.; A simple predator-prey model which exhibits limit cycle oscillations is investigated in a Lagrangian framework in the setting of the Stommel Gyre. The physical-biological coupling is provided by advecting the biological oscillators across a gradient in prey growth rate. Advection is found to mediate the de-synchronization and resynchronization of neighboring biological oscillations along a streamline.; After establishing the role of advection, an advection-diffusion-reaction study is performed on this biological system, in a steady two-dimensional double gyre circulation. Here the constant-coefficient diffusion introduces a spatial coupling of biological oscillations producing patterns of correlation which can be intermittent and spatially irregular. In the smaller scale recirculation cells, such as the eddies surrounding the meandering zonal jet, advection and diffusion combine to produce highly phase-correlated biological oscillations. Elsewhere in the domain, oscillations become highly irregular or nearly completely damped out.; The noteworthy alteration of these biological dynamics due to the addition of diffusion raises issues as to how sensitive biological systems in general may be to the specific levels of mixing. A biological model representing a phytoplankton which may bloom or not dependent on nutrient and population levels is explored in the setting of a two-dimensional shallow continental shelf upwelling process. Coupled physical-biological simulations are performed with two different parameterizations of vertical mixing. One, the K-profile parameterization [25], is modified here for application to coastal environments (primarily by the inclusion of bottom boundary layer physics). The physical circulation and passive tracer field evolution produced by the two schemes in this setting are quite similar. However, the difference in phytoplankton dynamics can be dramatic, depending on biological parameter value choice. The modified K-profile parameterization in some cases can produce a strong frontal bloom and a subsurface maxima in the pycnocline, while the Mellor-Yamada formulation produces neither. |
