Although most marine organisms have external fertilization, very little is know about the processes that control fertilization success and early embryonic survival. Inter tidal fucoid algae represent an ideal model system in which to study these processes in nature. Periods of gamete release, current velocities during fertilization, and degree of aggregation of male/female plants will be determined and /or varied experimentally to determine how they influence fertilization success, which will be determined cytological. Whether fertilization can adapt to low salinity environments is unknown; of particular interest is how the polyspermy block is affected, because this is Na+-dependent in may marine species. Electrophysiological and physiological techniques will be used to study the polyspermy block in fucoid algae from low salinity habitats. The ability of embryos of intertidal algae to survive the stresses encountered in the intertidal zone is poorly known. Stage- specific survival of fucoid embryos during low tidal emersion will be studied in the laboratory and in nature. The role of the hormone abscisic acid (ABA) in conferring tolerance to desiccation and freezing will be examined by quantitative immunoassay and by treating sensitive stages with exogenous ABA. Taken together with existing data, this work will offer an unusually complete understanding of the ecological processes affecting recruitment of a marine organism.
