My early research examined the effects of disturbance on the structure and dynamics of rocky seashore communities. My dissertation study was conducted in an intertidal boulder field on the seashore at Ellwood Beach, CA, near the UC Santa Barbara campus. The top surfaces of these boulders provide discrete habitat patches for a variety of algae and sessile invertebrate species. When they are overturned by winter storm waves, unoccupied space on their undersides becomes available for colonization, initiating a predictable successional sequence that ends in a low diversity climax state dominated by a single species of vegetatively reproducing red algae. Rates of disturbance by waves vary among boulders, being inversely related to their mass. Employing a mix of long-term sampling data and controlled field experiments, the study demonstrated that intermediate levels of disturbance maintain local species diversity in these algal/invertebrate assemblages. I also tested three alternative models of successional species replacement that had been formalized by Connell and Slatyer (1977, American Naturalist 111:1119-1144). The Inhibition Model best explained temporal changes in algal species composition: early colonizing species inhibited the recruitment of later arriving species, but early species suffered differentially from herbivory and physical stress, allowing later successional species to replace them over time.
Boulder field at Leo Carrillo State Park, Los Angeles Co, CA