The Role Of Obstacle Wakes In Enhancing Gamete Coalescence In Broadcast Spawning
Kawakami, Tanaya R 1 ; Crimaldi, John P 2
1 University of Colorado, Boulder
2 University of Colorado, Boulder
Many benthic invertebrates reproduce by broadcast spawning: egg and sperm are released at separate locations and must coalesce before fertilization can take place. In the case of corals, the gametes are typically released into the flow in the presence of neighboring coral heads which act as obstacles that alter the flow and subsequent stirring of the gametes. We present a numerical model of the stirring and mixing of gamete plumes in the structured wake of a circular obstacle. The model is a direct numerical simulation of the Navier-Stokes equations coupled with a pair of advection-diffusion-reaction equations with second-order fertilization kinetics. The results show that the obstacle wake serves as an effective reaction vessel that significantly enhances fertilization rates relative to the no-cylinder case. We quantify the fertilization enhancement as a function of initial separation of the gamete plumes, non-dimensional reaction rate, and Reynolds number. The role of this mixing mechanism in successful broadcast spawning can be used to help understand other mixing processes and shows the importance of the relationship between physics and ecology.