Award: OCE-1459393

Many commercially important species (lobsters, crabs, urchins, mussels, oysters, etc.) have larvae that drift with the ocean currents. The question is, how do these drifting larvae ever get back to shore to become adults? Previous work has demonstrated the importance of ocean physical processes in moving the larvae on shore, but the actual mechanisms are still poorly understood. Using swarms of underwater robots to mimic drifting organisms, we discovered a previously unknown mechanism for the transport of swimming organisms such as plankton. This mechanism involved the interaction of the flows from internal waves, background flows, and the swimming of the organisms. Internal waves are large (1-50 m), slowly propagating waves inside the ocean. They move water up and down as they propagate. We showed that these waves can move fast-flowing water (such as created by the blowing of the wind on the surface of the ocean) down to the depths of the organisms. If the organisms swim against the vertical movements of the wave, they will enter a region of faster velocities, and be pushed along with the wave for up to 1 kilometer. Analyzing data from our month-long field program we showed that organisms that swim - even a little -against the internal-wave flows moved onshore much farther and faster than passive organisms. This new mechanism would have been difficult to discover without our swarm of underwater robots. The robots were programmed to behave like some larvae: they "swam" against the internal-wave currents. We recorded several events when the robots suddenly moved on shore, faster and farther than our ?normal? data would have predicted. We used our data to help build mathematical models of the flows and organism behaviors, and now have a good understanding of the conditions under which organisms will be moved onshore - or offshore - in the coastal ocean. During our project we worked with Middle School students from City Heights in San Diego through the Ocean Discovery Institute. We developed course modules for the students focused on computer programming and internal waves. The students did oral presentations of the results of their work at the end of their course. The course modules we developed are continuing to be used at the Ocean Discovery Institute to engage Middle School students in oceanography. Last Modified: 09/30/2020 Submitted by: Peter J Franks