Linking substrate topography and coral larval settlement in oscillatory flow

Marine larvae undergo passive transport in the water column and physical interactions with the benthic surface that influence recruitment and settlement. Using experiments and simulations, we discuss results from a 2D agent based model that was developed to investigate the effect of substrate topography and boundary layer flow on larval settlement. To model various benthic environments, we used a ridged substrate as a model topography and systematically varied the ridge height and ridge spacing from the micron to the millimeter scale. We found that substrate topography directly influenced settlement by modifying the boundary layer flow structures and the local fluid speed near the settlement surface. The effects of larval shape and larval swimming speed on settlement were also investigated. Our findings highlight how the materials used for underwater construction and habitat restoration can be designed intentionally with surface features to either promote or inhibit the settlement of marine invertebrate larvae.