The Hydrodynamics of Chemical Cues Among Aquatic Organisms

Chemical cues mediate many critical life processes, such as feeding, reproduction, and benthic settling, for aquatic organisms. Depending on the fluid velocity and flow regime, released chemicals are transported via diffusion, laminar advection, or turbulent advection prior to organism reception. Here, we review transport mechanisms and ecological consequences in each regime. We discuss cue structures in terms of concentration gradients, concentration fluctuations, and spatial patterns and draw conclusions about strategies that animals use to acquire information. In some cases, chemical transport occurs through a combination of mechanisms, which requires a multiscale analysis. Regime and scaling are major themes that emerge from recent research. In particular, nondimensional parameters that combine biological and physical variables reveal general principles under which organisms respond to chemical cues and facilitate defining regimes of behavior.