GEOGRAPHIC-DISTRIBUTION OF THE PLANKTONIC COPEPOD UNDINULA-VULGARIS (DANA) IN 3 TYPES OF CORAL-REEF ENVIRONMENTS

The local geographic distribution of the planktonic copepod Undinula v ulgaris is studied in three types of coral reef zones: two atoll lagoo ns (Mataiva and Moruroa) in Tuamotu archipelago (South Pacific), one b arrier-reef lagoon in Tahiti and one coastal reef zone in the Red Sea (Dear Yembo, Saudi Arabia). The distribution of this species is hetero geneous and the limits of abundance zones are clearly drawn. In the tw o atoll lagoons, the abundance is one order higher in zones of oceanic water input to the lagoon. In the barrier reef lagoon, abundance is a t least four times higher near the exchange routes with the ocean. In the coastal zone of the Red Sea, the abundance gradient of distributio n decreases from the fringing reef towards the open sea. We discuss ho w oceanic water inputs determine this distribution; analysis of physic o-chemical parameters converge with bibliographical data to show that concentrations of organic nitrogen can account for the distribution of the species. U. vulgaris should rightly be considered as a species of neritic zones submitted to oceanic influence; in coral reef zones, th is influence is necessary because it brings compounds with a highly ni trogen content from coral reefs.