Plankton in Coral-Reef Waters

Abstract

For a long time an absolute predomination of bottom communities in functioning coral-reef ecosystems has been accepted axiomatically (Odum and Odum 1955; Johannes et al. 1970). But this opinion contradicted observations of the obvious abundance of planktonovore animals in reef communities. In fact, about half of the reef benthic animals are the filterers, or the sedimentary feeders, which feed on plankton. Among them are bivalves, some gastropods, sedentary pelychaetes, brittle stars and crinoids, many crustaceans, bryozoans, tunicates, and also corals, hydroids, and zoantharians. The Zooplankton is a main source of food for the pelagic larvae of most bottom animals, of fish larvae, and of a dense population of such common reef planktonovore fish like Alanetta, Chromis, Caesio. Nevertheless, the plankton of coral-reef waters has been studied less than that of oceanic waters. Its real quantitative studies have started comparatively recently in 1968–72, and those of the microzooplankton only in 1981. The data, which we now have, are still scarce and patchy, and not only on metereotrophic microplankton but also on the traditional objects of plankton studies, phytoplankton and zoo-plankton. Still, even so we can also recognize that plankton in reef-waters is abundant, has high specific productivity and plays a sighificant role in reef trophodynamics and metabolism.