Odor transport in turbulent flows: Constraints on animal navigation

Odor plumes are common features of aquatic and terrestrial environments, fo rming an olfactory landscape through which animals must navigate to locate resources and avoid potential hazards. Time-averaged concentration profiles suggest that plumes consist of stable gradients in odor that animals may u se for orientation. However, the lime scales necessary to generate such pro files are much longer than those typically associated with the neural or be havioral components of odor-mediated search. In contrast, plume measurement s made at biologically relevant scales have indicated that turbulent plumes consist of discrete odor filaments separated by clean water. in addition, certain characteristics of individual odor filaments may vary consistently with distance from the odor source, thus providing directional information to a navigating organism. Unfortunately, there is no method to predict the distribution of these putative chemical cues, and our knowledge of odor dis persal is limited to very few laboratory flume studies. Here, we present th e results of a held study during which we measured the distributions of the time-averaged concentration, properties of odor filaments, conditional sta tistics, and relevant hydrodynamic mixing parameters. Many of the observed odor plume characteristics have similar spatial distributions through a ran ge of hydrodynamic conditions. The high degree of similarity in the distrib ution of many odor plume characteristics suggests that organisms can rely o n any number of metrics to successfully orient in an odor plume. However, t he temporal and spatial scales of odor dispersal may constrain the strategi es used by navigating organisms and influence the efficiency of odor-mediat ed search. These field results should provide the basis for further empiric al and theoretical work on chemosensory-mediated behavior of aquatic animal s.