Larval transport and population dynamics of intertidal barnacles in central California.

摘要

Mathematical models and field work are presented which explore the link between physical transport processes in the offshore water column and population dynamics of barnacle species inhabiting the rocky intertidal zone of central California. Chapter 1 examines the vertical distribution of six barnacle species found in central California in relation to hydrographic features. The location of intertidal barnacle larvae in the Ekman layer is confirmed, supporting the assumption that intertidal larvae remain in the surface layer and can be influenced by surface currents. It is hypothesized that intertidal larvae are carried offshore by surface currents during periods of upwelling, accumulating at offshore fronts marking the convergence between upwelled and California Current waters. Larvae recruit into adult populations during periods of relaxation in winds when the fronts move onshore.;The second and third chapters examine this hypothesis by analyzing the effects of currents and offshore upwelling front locations on recruitment patterns and adult dynamics using an advection-diffusion model for barnacle larvae coupled to a space-limited model for barnacle adults. Chapter 2 presents a one-dimensional model which 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. The analysis shows how variation in the location of an upwelling front and in the strength of cross-shelf advection determines recruitment events to adult populations. This model offers a prototype for predicting how changes in an offshore oceanographic regime are propagated to coastal ecosystems.;Chapter 3 extends this one-dimensional model to two-dimensions to allow for the spatial distribution of both larvae and adults. The interaction of offshore and alongshore flows with a moving offshore boundary is explored. The illustrations support the hypothesis that recruitment is negatively correlated along the coast with distance from shore of the upwelling front. The model can now be forced with a time series of local oceanographic conditions using remote sensing technologies to produce a truly predictive model of barnacle population dynamics along the central California coast.