Meeting Abstract

S1-5.4  Jan. 6  Facing Up to the Reynolds Rap: Foiling Faux Pas in Formulation Fouling Forces DENNY, MW; Stanford University, Hopkins Marine Station mwdenny@stanford.edu

Reconsideration of the Reynolds-number-dependent drag coefficient of wiffle balls has led to a re-evaluation of velocities associated with breaking waves. Modulated by the topography of rocky shores, local velocities in the surf zone may reach 35 m/s, considerably higher than previously suspected. The spatial and temporal variation in the imposition of these maximum wave-induced velocities can have substantial consequences for benthic organisms. Drag associated with a velocity of 35 m/s is sufficient to eliminate some algal species altogether, and can dislodge a substantial fraction of mussels, the dominant competitor for space. When drag is coupled with the temporally random effects of impingement forces, biological consequences are even more severe: even acorn barnacles can be dislodged. The upwardly modified velocity estimates reported here help to explain the role hydrodynamic forces play in maintaining the spatially and temporally variable pattern of species abundances on wave-swept intertidal shores