Microbial and ecological fluid dynamics

Existing aquatic circulation models are designed for large, basin-size scales and therefore cannot resolve the planktic organism scales of A-H balance. The nonlinear kinetics of biological responses to physical and chemical variables are more appropriately described at micro-scales, at the level of molecular diffusion. It is striking to realize that typical computation grids in 3D numerical models for lakes and oceans are more than 106 times larger than the dimensions of planktic organisms. Therefore, there is a major difference between the typical computational grid scale with associated scale of resolved fluid motions and the majority of phytoplankton and bacteria. Further, both fluid motions and categories of plankton have significant temporal and spatial heterogeneities in aquatic ecosystems (Durham et al. 2009; Wüest and Lorke 2009). To what extent do physical and chemical processes guide formation, location, and duration of such heterogeneities? How do individual organisms “feel” the physical environment as they respond to it? Parameterization for smaller scales is therefore necessary, and there is an urgent need for modeling A-H processes at scales that are much smaller than those addressed by existing aquatic circulation models.