Hydrodynamic context for considering turbulence impacts on external fertilization

Wave-swept shores in the marine environment are characterized by turbulent water motion. This turbulence influences external fertilization in benthic organisms by diluting gametes and producing hydrodynamic shear that is believed to have the capacity to disrupt egg-sperm interaction. However, although turbulence levels associated with decreases in fertilization due to this latter process (shear) have been identified in the laboratory, estimates of the intensities of turbulence in intertidal habitats have been based primarily on scaling arguments of limited precision and unknown accuracy. In the present study, values of energy dissipation rate (a standard measure of the strength of turbulence) were determined for three locations in the surf zone of a rocky shore. These measurements suggest a potential correspondence between threshold levels of turbulence that impair the ability of sperm to fertilize eggs, and actual intensities of turbulence arising in nature.