Larval Transport and Population Dynamics of Intertidal Barnacles: A Coupled Benthic/Oceanic Model

The dynamics of barnacle species inhabiting the rocky intertidal zone of central California are analyzed using an advection—diffusion model for barnacle larvae coupled to a space—limited model for barnacle adults. The model explores the link between physical transport processes and the population dynamics of coastal barnacle species and inspects the hypothesis that recruitment events result from the collision of upwelling fronts with the intertidal zone. Initially, a one—dimensional model is presented that incorporates eddy diffusion, offshore advection, and an offshore reflecting boundary representing an upwelling front. Physical movement of the front, in response to fluctuating upwelling, is modeled by varying the position of the reflecting boundary. Results show analytically that populations can sustain only very low levels of offshore flow when not bounded by an offshore front, and that increased advection can cause a population to go extinct. The criterion for population viability is dependent upon the strength of advection and position of the offshore front. The one—dimensional model is subsequently extended to two dimensions to allow for the spatial distribution of both larvae and adults in a more realistic context. Recruitment patterns, adult dynamics, and larval distribution patterns are loosely based on parameters from the study area bounded between the Monterey Peninsula and Point Sur. Upwelling/relaxation events are phenomenologically incorporated into the model by varying the position of the offshore boundary and the magnitude of cross—shelf advection. The analysis shows how the interaction of advective and diffusive processes and the location of the offshore front determines the dynamics of coastal barnacle populations. The two—dimensional model represents the next step toward assimilation of time—dependent remote sensing data and/or linking to numerical circulation models.