Dispersion of micro-organisms, like plankton and fish larvae, nutrients, (re)suspended (often chemically contaminated) particulate matter, and pollutants in oceans, estuaries and stratified lakes is governed by turbulent geophysical flows. In geophysical flows, the presence of the Coriolis force due to the rotation of the Earth and buoyancy force, as a result of temperature or salt stratification of the fluid, modifies the turbulence properties and the dispersion process of (biologically) active tracers. Prediction of phytoplankton (algae capable of photosynthesis) blooms, i.e. events of rapid production and accumulation of phytoplankton biomass, and their dispersion is of uttermost importance for economical activities (the fisheries industries, tourism), public health issues and ecology. The role of turbulent dispersion of micro-organisms on marine-population dynamics is classically investigated with a top-down approach where eddy diffusivity models have usually been used as the most simple parameterisation of dispersion. Such models fail to predict phytoplankton blooms and dispersion as illustrated in the satellite picture below. In order to improve large-scale computer models for prognostic purposes, a bottom-up approach to model turbulent dispersion is necessary that includes the strong anisotropic character of geophysical turbulence and the particle-flow and particle-particle interactions. In this colloquium I will illustrate the role of several geophysical processes on the dispersion of micro-organisms, the role of certain biological phenomena, and the different physical and biological mechanisms that may contribute to sudden blooms of phytoplankton.
|Title of host publication||Physics Seminar, TU/e, Eindhoven, 3 June 2004|
|Publication status||Published - 2004|