In this project the Principle Investigator will determine how the physics of free-surface oceanic turbulence impacts the success of a reproductive strategy (broadcast spawning) used by corals and other marine invertebrates. The timeliness of the research is punctuated by the worldwide demise of coral reefs. The goals are to use a physics-based investigation to learn about reproduction in the living system and to see how evolutionary adaptations to complex turbulent physics shed light on subtleties of the physics themselves. Broadcast-spawning adult males and females simultaneously extrude sperm and ova into the surrounding flow. Subsequent fertilization relies primarily on turbulent stirring to mix the gametes. Most reef-building corals release buoyant gametes that rise to the free surface, where they are stirred by the free-surface turbulent flow. Buoyant particle paths in free-surface turbulence are compressible, even when the underlying 3D flow is incompressible. This results in regions of buoyant particle coalescence and divergence (corresponding to upwelling). This physical phenomena plays a role in the structure of floating and near-surface particles in the ocean, including foam streaks, oil spills, and the infamous garbage patch in the Pacific, but its effect on fertilization success is unknown. This research program will integrates laboratory experiments and numerical simulations to study the effect of free-surface turbulence on coalescence of initially distant buoyant scalars, and to predict fertilization rates for broadcast spawning corals. The Principle Investigator will integrate research methods into the teaching curriculum as an effective tool for learning fluid mechanics, and use the topic of broadcast spawning as a vehicle for getting K-16 students interested in engineering and science. A hands-on interactive module demonstrating the role of surface turbulence on the spreading and aggregation of buoyant scalars will be developed and used as part of the on-going effort to integrate research topics into outreach activities, many of which directly target women and other underrepresented K-16 students.
