Geographic Differences in Ecological Processes on Coral Reefs

Abstract

Although basic ecological processes are generally consistent on a local scale, there are geographic differences in geological processes, the physical environment, and dimensions of the areas involved that change the nature of coral-reef systems. The structure of reefs is affected by plate tectonics, e.g., there is a greater prevalence of atolls in the central Pacific and Indian Oceans than in the Atlantic or eastern Pacific. The vast dimensions of the Pacific Ocean produces a sharp gradient of decrease from west to east in species, generic, class, and habitat diversity across the Pacific that is not so pronounced in the smaller western Atlantic and Indian Oceans. Diseases are generally contained within distantly separated archipelagoes in the Pacific but quickly spread across the relatively small and interconnected greater Caribbean. The differences in sediment input into the oceans (2 % west coasts of continents, 82 % east coasts) and the degree to which river output affects biogeographic patterns (eastern vs western coasts of continents), show the overwhelming global influences of trade winds and the Coriolis effect on coral reefs. The relative prevalence of corals and other sessile photosymbiotic invertebrates compared to sessile heterotrophic invertebrates can be affected on a geographic scale as well as locally by the strength and dependability of nutrient input. Adult coral colonies can persevere in areas with substantial nutrient input such as upwelling, but recruitment in these areas is extraordinarily difficult in competition with algae and heterotrophic invertebrates in areas with abundant nutrients. The effects of disturbances and effects of altering the system, for example by reducing the stock of grazers, can be substantially greater in areas of high nutrient input.