Interactions Between Turbulent Mixing And Broadcast Spawning
Soltys, Michael 1 ; Crimaldi, John P 2
1 University of Å·ÃÀ¿Ú±¬ÊÓƵ
2 University of Å·ÃÀ¿Ú±¬ÊÓƵ
Turbulent fluid flow plays an important role in many physical and biological mixing processes. This is exemplified by broadcast spawning, the reproductive strategy used by corals and many other marine invertebrates. When spawning, male and female invertebrates release their gametes into a flow and then rely on the physics of turbulence to bring eggs and sperm close enough to promote fertilization. Current biological models predict that the efficiency of broadcast spawning is vastly insufficient to sustain coral populations (Denny, 1988), but the existence of these animals suggests otherwise. It is likely that the role of instantaneous turbulent stirring, missing from current models, is responsible for the under-prediction of spawning efficiency. In order for broadcast spawning to be successful it is necessary that the sperm and the eggs be brought together in high concentrations. It has been shown that over short time scales structured filaments of high concentration form in turbulent flow before being dispersed to low concentrations at longer times (Crimaldi and Koseff, 2006). It is hypothesized that when two scalars (e.g., sperm and eggs) are released into turbulent flow, coherent velocity structures will initially bring high-concentration filaments of these two scalars together. This Hypothesis is studied using a specially developed two-channel planar laser-induced fluorescence system which tracks two dyes as surrogates for coral sperm and egg. Preliminary results confirm the importance of coherent structures and their effects on mixing.