An Investigation of the Effects of Patch Size, Local Adult Abundance, and Grazing Patterns of Interdidal Algal Succession

The patterns and mechanisms of succession in clearings in mussel beds are being investigated with field experiments. Patches cleared in the dominant cover of mussels constitute the major source of heterogeneity in the distributions of species in the mid-intertidal zone. Three factors largely determine the patterns of succession which follow such local disturbances: the size of the clearing, the local abundances of adult plants whose spores can disperse into the clearing, and the abundance of grazers within the clearing. By experimentally creating patches of different sizes and then manipulating the densities of grazers, I have been able to demonstrate strong patch size-grazer interaction effects. These result in markedly different successional patterns in patches of different size. I am continuing to monitor these patches to see if the amount of recruitment to a patch is correlated to the abundances of adult plants surrounding it. If so, this will be some of the first solid evidence of the limited dispersal of spores by marine algae.