Impact of shape and swimming speed on the transport and settlement of simulated marine larvae

Many sessile marine invertebrates employ a fascinating reproductive strategy, releasing microscopic swimming larvae that are dispersed by ocean currents. These larvae embark on a remarkable journey, seeking to settle on the benthic surface, where they interact with boundary layer flows and the surface topography. Using 2D agent-based simulations, we delve into the influence of larval shape and speed on their transport in flow and subsequent settlement on the surface. Millimeter scale surface features are used to create different boundary flows and settling larvae are simulated with systematically varied body aspect ratios and swimming speeds. Larval shape governs their rotation and alignment with the flow, while swimming speed allows them to traverse streamlines and swim against the current. These larval characteristics significantly alter their transport trajectories, settling positions, and overall settlement rates. Our model allows us to predict the best surface to promote or inhibit settlement of a swimmer for its specific characteristics. These results are important for understanding how transport and settlement dynamics change with different larvae, informing attempts to modify benthic communities from coral reef recovery to anti-fouling measures.