Seascape-level variation in turbulence- and wave-generated hydrodynamic signals experienced by plankton

• We synthesized geographic variation in the signals produced by turbulence and waves.
• Seascapes have typical co-occurring shears and accelerations with distinct ranges.
• We quantify dependence of flow sensing on plankter size, speed, and sensor types.
• We discuss implications of these patterns for zooplankton and larval sensory ecology.

Plankton exhibit diverse and dramatic responses to fluid motions, and these behaviors are likely critical for survival and fitness. Fluid motions can be generated by organisms or by physical processes, including turbulence and surface gravity waves. Physical processes vary geographically in their intensity and generate hydrodynamic signals experienced by plankton as fluid forces on their sensory receptors. In this synthesis, we review how turbulence and waves vary in space, the scales and statistics of their motions, and the forces exerted on plankton. We then quantify the hydrodynamic signals produced by turbulence and waves in four seascape types – surf zones, inlets and estuaries, the continental shelf, and the open ocean – using published dissipation rates, wind and wave data from buoys, and observations from two coastal sites in Massachusetts, USA. We relate these geographic patterns in signals to the observed behaviors of example species and to the forces sensed by typical plankters with different receptor types. Turbulence-generated shears are largest in the surf zone, inlets and estuaries, while wave-generated accelerations are larger offshore; as a result, each seascape exhibits some range of combined shears and accelerations that is distinct. These signals generate forces on plankton that vary among habitats and with plankton size and swimming speed. Spatial patterns in fluid forces create a potential mechanism for dispersing larvae to distinguish habitats by their hydrodynamic signatures. However, turbulence can be strong in all seascapes and may cause widespread interference in signaling among predators and prey. Plankton with a single receptor type could identify nearshore habitats, while those with multiple receptor types potentially could distinguish inshore vs. offshore seascapes or decode signals produced by physical processes and by other organisms.

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