Numerical simulation of environment modulation of chemical signal structure and odor dispersal in the open ocean.

Hydrodynamic models were used to simulate the dispersal of a model fish pheromone at three characteristic depth regimes (mixed layer, and 300 and 1000 m) of broad extent in the open ocean at the scale of individual organisms. The models were calibrated to experimental studies of dye dispersal at these depths and the goldfish pheromone system was used as the model odorant. There are profound differences in the time course and geometry of dispersing odor fields with depths. Below the thermocline odor fields spread primarily as horizontal patches with dispersal rates about five times slower at 1000 m as compared to 300 m. In the mixed layer, odors disperse rapidly in all directions and the maximum radial distance of spread of a physiologically active odor patch is less than half of the deep water value. Increases in the threshold sensitivity of olfactory receptors can greatly increase effective odor field size. Chemical signals impact the encounter dynamics among oceanic organisms by affecting the distance at which the target (emitting) individual is perceived. Perception distances due to olfactory cues can be significantly greater than for other senses in pelagic oceanic environments. Environment specific modulation of odor fields then affects the signal properties and therefore utility of chemoreception that, in turn, bear on encounter probabilities and transfer functions in oceanic ecosystems.