Community structure and organization of tidepools

Abstract

Although tidepools are conspicuous components of rocky intertidal shores, their biotic communities have not been studied as extensively as those on emergent substrata. We examine processes regulating the structure of tidepool communities for comparison with emergent substrata. The physical environment of tidepools is highly regulated by the tidal cycle, although fluctuations in physical factors are smaller in tidepools, and the organisms remain submerged for the entire tidal cycle. As a result, the upper limits of the distribution of organisms are extended in tidepools and some species either tend to aggregate in pools or avoid them. The vertical zonation of organisms is not as pronounced in tidepools as on emergent substrata. Herbivory has been shown to influence the distribution and abundance of algal species in tidepools, but the effect of predation in regulating community structure has been less well documented. The importance of interspecific competition has been consistently shown in tidepools, particularly among algal species, which usually are the dominant space occupiers. Although the introduction of most species into tidepools depends upon recruitment from the surrounding water, the effects of variation in the supply of new individuals has not been examined. Aspects of the physical regime such as habitat complexity and wave exposure affect the community structure of tidepools, as they do communities on emergent substrata. However, the specific characteristics of tidepools such as pool depth, volume, orientation, shading and flushing rate make individual pools unique, resulting in large spatial variability in tidepool community structure. For this reason, replication in tidepool studies should be carefully selected. Because of their variable characteristics, well-defined boundaries and tidepools of manageable size can serve as experimental mesocosms to test general ecological theories about community organization.