UC San Diego

Many coastal, benthic species, such as mussels and lobsters, have larval stages that rely on physical mechanisms for their cross-shore transport to suitable adult habitats. One of these physical mechanisms include internal waves. Because they transport mass, only highly nonlinear internal waves were traditionally assumed to induce significant cross-shore transport. However, the work presented in this dissertation shows that by deforming ambient velocities, even weakly nonlinear internal waves may enhance cross-shore transport of depth-keeping organisms. This mechanism was first observed in situ using novel, subsurface, trackable larval mimics, the mini-Autonomous Underwater Explorers. Results from the larval mimics were then related to mooring observations, using virtual swimming organisms and established theoretical wave models. Following this model validation, the total cross-shore transport of both passive and depth-keeping organisms was estimated for > 500 observed, shallow-water, weakly nonlinear internal waves during a 14-day deployment. Results show that in these waves, depth-keeping promoted onshore transport throughout the water column, compared to passive organisms. Moreover, the largest transport estimates for depth-keepers were on the same order of magnitude as average transport estimates for passive organisms in highly nonlinear internal waves. This dissertation also highlights the importance of considering larval horizontal displacement throughout an internal wave, and not only in bulk, to properly assess the environmental conditions planktonic organisms experience.