Adult Demography and Larval Processes in Coastal Benthic Populations: Intertidal Barnacles in Southern California and Baja California

Fabian Tapia, Ph.D., 2005
Jesus Pineda, Advisor

This dissertation focused on patterns of nearshore larval distribution and regional demography of intertidal barnacles from Southern and Baja California. Nearshore larval distributions and mortality were assessed from short term (hours-days) small-scale observations (0.1-1 km). Spatial variability in adult demography was assessed over 1.5 years at scales of hundreds of kilometers. Stage-specific distributions and nearshore current velocities suggested that larvae experience limited dispersal. High mortality rates could further limit travel distances and the exchange of larvae among disjunct populations. Nauplii and cyprids were horizontally segregated, with consistently higher cyprid concentrations at the inshore station. Observed differences in vertical distribution between nauplii and cyprids, together with the vertical variability of horizontal flows, may explain this pattern. Differences in vital rates of adult Balanus glandula were observed between Dana Point (Southern California) and Punta Baja, a site located near the species' southern limit of distribution in Baja California. Analysis of a stage-structured matrix model indicated that Punta Baja barnacles are less robust to environmental stochasticity and more prone to local extinction than populations located further north. This thesis emphasizes the relevance of small-scale nearshore processes affecting the dispersal of larvae, and the importance of a multi-scale characterization of factors affecting benthic populations.