Zonation and Seasonal Variation of the Commonest Algae on Tiahura Reef (Moorea Island, French Polynesia)

Zonational patterns, season occurrences and peak period of abundance were observed, for the commonest algae, on reefs on Moorea Island between May 1980 and October 1981. Of the seven species studied, four inhabited several zones of the reef complex while the others occurred in only one zone. Terrestrial and oceanic influences play a major pari in distributing the species. Hydroclathrus clathratus, Chnoospora implexa and Boodlea siamensis occurred during the spring and were absent with the change of season. B. siamensis had not been found on the inner reef before December 1980. Padina tenuis, Turbinaria ornata, Sargassum sp. and Halimeda incrassata persisted throughout the year; their abundance peaks coinciding with their maximum growth during winter. During summer, only vegetative thallii, holdfasts and main axes were present. The degeneration of H. incrassata populations followed fruiting periods. Climatic factors such äs rainfall and desiccation seem to be the main causes for seasonal Variation.