9409073 SQUIRES This research project will focus on the interaction between small- scale turbulence and the spatial distribution of phytoplanktonic particles. Preliminary results from Direct Numerical Simulations (DNS) of incompressible, isotropic turbulence have shown that particles of a density similar to that of algae develop non-random spatial distributions including aggregates at peak number densities of 40 times the global mean value when suspended in a simulated flow field. Laboratory tests to determine whether actual algal particles in real turbulent flow form patches and whether they behave as predicted from numerical simulations will be undertaken. A special apparatus which creates reproducible grid-generated turbulent flow and which allows for direct observation of suspended algal particles will be constructed and calibrated. The effect of particle size, shape, buoyant density, and inherent motility ("swimming" capacity) on particle spatial distributions will be evaluated. Empirical data will be compared to DNS predictions derived from a refined model. Results will provide pioneering insight into the role of small-scale fluid dynamics in influencing phytoplankton spatial distributions: such insight is essential for understanding the dynamics of resource acquisition by algae and herbivore-algal interactions in oceans and the Great Lakes. ***
