WAVE-INDUCED KELP MOVEMENT AND ITS IMPORTANCE FOR COMMUNITY STRUCTURE

In the course of a distributional survey within a kelp forest off the west coast of South Africa qualitative changes in kelp distribution with increasing depth were noted. There was a decreasing proportion of juvenile Laminarians with depth, and although the mean Laminarian biomass decreased, maximum values per m2 were comparable throughout. This was attributed to a definite trend towards patchiness with depth. In part, this is the result of changes in species composition, since Ecklonia maxima declines with depth, until below 8 m only Lamirwria pallida remains. Examinations of individual Laminaria patches revealed a consistent form of large central plants with progressively smaller individuals towards the margins. A distinct belt of bare rock separates these kelp patches from patches of herbivorous animals. The barren interfaces between patches was found to be the result of sweeping action by the peripheral plants as these are bent by incoming swells. This sweeping effect provides protection against herbivory and it is a mechanism by which areas suitable for kelp colonization are prepared, allowing existing kelp patches to expand over time. © 1979, Walter de Gruyter. All Rightes Reserved.