Consequences of Surf-Zone Turbulence for Settlement and External Fertilization

The models presented here predict that surf-zone turbulence can have important consequences for wave-swept organisms. The rapid mixing of the water column ensures that larvae and spores can be rapidly transported to the substratum in the absence of sinking velocities or directed swimming. Thus, turbulent mixing removes one potential bottleneck in the recruitment of planktonic organisms to the shore. In contrast, the rapid dilution of gametes by turbulent mixing in the surf zone may drastically limit the efficiency of external fertilization, with a variety of consequences for animals using this form of reproduction. The "educational" models presented here are simplifications of an exceedingly complex flow regime, but they appear to be sufficiently valid to provide a useful perspective on life in the surf zone. We hope that they will stimulate discussion of and research into the many important biological consequences of nearshore turbulence.