Cross-Shelf Transport Causes Recruitment to Intertidal Populations in Central California

The control of recruitment to intertidal barnacle populations along the central California Coast was examined from April to mid-October 1988. Four recruitment pulses occurred during periods of relaxation in alongshore winds and cessation of coastal upwelling. In each case recruitment ended when strong equatorward winds reappeared and upwelling resumed. Data on SST, salinity, adjusted sea level, and satellite (AVHRR) images revealed alternating periods of onshore and offshore transport of the surface water layer. The onset of the largest recruitment pulse was associated with the advection of warm, clear, low-salinity water into the nearshore region. This oceanic water mass also contained a different zooplankton assemblage than the water mass it replaced.