Coral community dynamics at multiple scales

Our understanding of ecosystem dynamics is directly linked to the scale at which we make our ecological observations. The ecological dynamics of Pleistocene coral communities varies with spatial and temporal scale of study. Reef coral communities studied over small spatial and temporal scales show ecological chaos where disturbance prevents ecological equilibrium, and those studied at the largest biogeographic scales show large differences due to history, chance, dispersion, and regional-scale processes. However, communities that are located within tens of kilometers of one another appear to show a large degree of order, probably due to underlying principles of niche similarity. Similarly, temporal studies conducted over large temporal scales show persistence in coral community structure through tens of thousands of years. The history of Caribbean reef coral communities shows that this persistence has been recently interrupted by massive degradation of coral reef habitats. Whether such habitat reduction and change in species composition are unprecedented and due to the acceleration of human consumption and pollution, or whether they represent a short-term fluctuation in an otherwise predictable community structure, is one of the most important questions facing reef managers today. Investigations of coral community structure at different spatial scales illuminate the dependence of ecological dynamics on spatial scale, and at different temporal scales show that present trends are not predicted from history but may well be related to human-induced environmental modification.