Article: Ecological stratification in the Pleistocene coral reefs of the Kenya coast

Ecological succession on small patch reef structures can be studied by employing the concept of ecological stratification. The component corals of a patch are divided into two basic categories, the B or C horizons (or strata). The former category represents the initial colonizers (or pioneers) on a soft substrate, and the latter the subsequent colonizers. The potential exists for studying the later stages of succession by finely subdividing the C horizon. Detailed mapping of vertical sections through patch reefs in the Pleistocene reef limestones of the Kenya coast provided stratification analyses in a variety of back-reef environments. Massive Porites proved to be the commonest B horizon coral throughout the region studied, and clearly was of fundamental importance in patch reef formation. Massive faviids and mussids were less frequent early colonizers. The most important C horizon corals were encrusting Montipora (in more open water areas), encrusting Cyphastrea (in quieter, deeper water areas), and tiny domes and patches of massive Favia. Many corals may be much more specialized in their habitat requirements than has previously been recognized. The principal coral types within the back-reef patches of the Kenya Pleistocene reef consistently adopt distinctive three-dimensional growth forms within either B or C horizons, and it is argued that they must have partitioned at least part of the available habitat space. Ecological stratification is a useful tool for determining the nature and extent of habitat resource partitioning by scleractinian corals.