Hydrodynamic interactions with coral topography and its impact on larval settlement

Many benthic larvae rely on ambient flow and turbulence for their dispersal to settlement sites. After reaching the seafloor, larvae must prevent predation as well as overcome flow forces which act to dislodge them in order to achieve successful settlement. Most oceanic benthic habitats are topographically complex and are characterized by a combination of tidally driven currents and wave-driven oscillatory flows, which can exert substantial forces along settlement surfaces. In this study, computational fluid dynamics was used to numerically model both wave-dominated and unidirectional flows over surfaces of varying topography designed to mimic the surface roughness of corals. Near-surface hydrodynamic parameters, including velocities, turbulence statistics, and surface shear stresses, were computed, along with forces on simulated larvae settled on surfaces. It was found that widely spaced surface roughness (characterized as a k -type roughness with roughness width/height > 1) yielded 50–100% higher surface shear stress than tightly spaced roughness (characterized as d -type with width/height