Disturbing hard and soft bottom communities: A comparison of marine and freshwater environments

For communities of intertidal rock surfaces, inshore soft sediments and streams, disturbance is regarded as an important community‐structuring force. Care needs to be taken in defining disturbance to avoid confusion with other processes such as predation. In the environments discussed, there have been many descriptive studies of disturbance and relatively few experimental studies. The latter have yielded interesting insights. Disturbance generates patches and thus may alter the outcome of biotic interactions, especially competition, by providing refuges for poor competitors and beleaguered prey. Between the three environments, colonization and succession differ — a difference no doubt related to the proportion of mobile versus sedentary biota in each environment. In succession on hard intertidal surfaces inhibition appears to be most important, whereas facilitation is dominant on soft sediments and tolerance is the most plausible mechanism of succession in streams. Across the three environments there are some striking similarities in the colonization dynamics of the mobile fauna. Disturbance is a key part of several hypotheses proposed to explain the regulation of community diversity, and for communities in the environments examined none of the hypotheses has been found to have general application.