This project will explore how the viscosity and longevity of sea urchin gametes interact with different flow regimes to determine where gametes contact and the resulting level of fertilization and polyspermy. Preliminary data suggest that under a range of field conditions, fertilization in echinoids is a time-integrated process that occurs largely on the aboral surface of the female or in flow structures (eddies) immediately downstream. Consequently, fertilization and polyspermy levels may be much greater than predicted by earlier experiments and existing models that treat fertilization as a water column process. Components of these hypotheses will be tested through a series of laboratory flume experiments that will assay the time course of gamete advection, the site of fertilization, and levels of fertilization and polyspermy under a range of turbulence conditions in both uni-directional and oscillatory flow regimes. Complementary field assays will explore the flow conditions under which natural spawning occurs.
The green sea urchin (Strongylocentrotus droebachiensis) is commercially harvested, and local population densities are consequently quite low along much of the Maine coast. Increased understanding of fertilization processes and temporal patterns of sperm availability will help managers evaluate the likelihood of fertilization failure in low density populations and the consequences for population dynamics. Two local sea urchin reserves will be used as study sites, so results will also help managers evaluate the reproductive potential of small, localized reserves. This project will also train students (both undergraduate and graduate) and post-docs.
