Hydrodynamic Regulation of Reproduction in Fucoid Algae: A Regional Model and Consequences for Population Structure

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Fucoid algae dominate most rocky shores across the north Atlantic and contribute substantially to structuring of the coastal ecosystem. Reproduction in fucoid algae is sensitive to hydrodynamic conditions, resulting in high fertilization success because gamete release occurs only under calm conditions. These findings have important implications for asynchrony in gamete release between populations and the scale of population isolation. This study will 1) test a nascent model describing when successful fucoid reproduction can occur, 2) determine whether hybridization between Fucus vesiculosus and other fucoid algae occurs when gamete release is delayed by turbulent conditions, and 3) analyze whether genetic differentiation in F. vesiculosus is correlated with variable hydrologic conditions due to coastal topography. Quantitative data on gamete release at multiple sites on opposite sides of coastal points (and smaller features) will be collected. This will determine whether gamete release in fucoids occurs at different times over small spatial scales due to variable wave and wind exposures across opposite sides of the undulating coastline. Species-specific monoclonal antibodies to recognize fucoid sperm are available; they and the required pump/concentration apparatus have been tested successfully at Pemaquid Point. Local environmental data (e.g., wind speed, light levels, water motion) will be collected and compared with data from monitoring systems such as NOAA's National Data Buoy Center stations. Maine shores have been stable for thousands of years; if the coastal F. vesiculosus is reproductively isolated in topographic fragments, population genetic structure may be affected. This will be tested with AFLP analysis of randomly collected adults. Storms delay gamete release from fucoid algae, and laboratory studies predict that natural hybridization will increase sharply if over-mature eggs participate in fertilizations. This will be tested in field studies of hybridization potential, achieved hybridization, and identification of hybrid position in the intertidal zone in F. spiralis versus F. vesiculosus (Maine) and F. serratus (an exotic) versus F. vesiculosus (Nova Scotia). The hypothesized environmental interaction with development as a regulator of hybridization and genetic structure in F. vesiculosus (and other fucoids) could have strong local and biogeographic effects on intertidal communities across the north Atlantic. Among the products of this research will be a robust regional model for fucoid reproduction as a function of relevant physical factors (i.e., wind speed and direction, wave height, light levels).