Large schools of goatfish, mullet, surgeonfish, and other plant and plankton feeders are a common sight. Preying on unwary or disabled members of these schools are the carnivorous fish -- the groupers, tuna, jacks and sharks. Ultimately the waste products and carcasses of these and other carnivores are returned to the lagoon and reef to complete the cycle. Little or no time is lost between steps in the biological cycling of materials for there is not only an abundance of organisms but also a wide variety of species -- some 700 amongthe fishes alone (Schultz et al., 1953) other. -- so that whatever is not utilized by one is quickly taken by anThere is here a perfect economy of use of substances essential to life. Available substances are rapidly taken up by the biota, never re- maining long in the water to be diluted and washed away. This is dra- matically demonstrated following an atomic test in which radioactive materials are deposited in the water. Within hours, the great bulk of these materials is to be found in the living organisms. Plankton and some of the algae, which are the key organisms in the food chain, may concentrate within themselves more than a thousand times the amount of radioactive substances found in the sea water. The herbivorous fish and invertebrates have lower concentrations of radionuclides at any given time than do the plants on which they feed, and progressing along