This project will investigate the interplay between larval production, distribution, settlement, and recruitment and to determine how these factors influence differences in the structure and species composition of subtidal benthic communities. Previous studies using a newly developed automated sampling device indicate that recruitment of many invertebrate species occurs during slack water periods, particularly at low tide. This pattern may explain how some benthic species can maintain locally persistent populations even in turbulent environments. To assess the generality of this finding, Dr. Osman and collaborators will conduct a series of field investigations with four primary objectives. First, they will examine tidal hydrodynamics and associated transport withip an embayment in order to establish the patterns and correlations among water movement, larval distributions, and recruitment. Second, the scientists will investigate the spatial and temporal relationships between larval production, release, availability, and recruitment. Experiments will focus on three distinct groups of species; one with strong local source areas and shortlived (hours) larvae (colonial ascidians, bryozoans), a second group with equally strong local sources but with longer-lived (days) larvae (some solitary ascidians), and the third with a distributed regional source of long-lived larvae (e.g. barnacles). Third, investigators will examine how recruitment influences the establishment and long-term maintenance of sub-populations within a larger regional population. Experiments will quantify the immigration of recruits into an area, determine their survival rates, evaluate their ability to replicate and become a local population, and examine subsequent population maintenance through multiple generations. The field studies will combine newly-developed devices for measuring larvae and recruits of benthic species with standard techniques for measuring large-scale currents and local turbulence intensities. Finally, a numerical model will be developed to predict spatial distributions of larvae and recruits for species with different life histories. The model will combine knowledge of tidal flows with quantitative descriptions of larval production, distribution, settlement, and recruitment obtained from experiments. The model's sensitivity to plausible variations in these factors will be used to assess our ability to predict spatial and temporal variability in marine population and community dynamics.
