Delesalle B., Gattuso J.-P., Pichon M. & Frankignoulle M., 1993. Effects of a cyclone on coral reef phytoplankton biomass, primary production and composition (Moorea, French Polynesia). Journal of Plankton Research 15: 1413-1423.




Abstract

Whereas the effects of cyclones, the most destructive natural events on tropical coasts, on reef benthic and fish communities are been well considered (Harmelin-Vivien, in press), phytoplankton changes have been seldom investigated. Observations on the phytoplankton of a French Polynesian barrier reef, following the passage of cyclone Wasa in December 1991, lead to outline two successive effects: firstly, a transient wash out of the lagoonal waters replaced by oceanic ones, then an increase in phytoplankton biomass and primary production together with a predominance of diatoms over other phytoplankton classes. These results are compared and discussed with the few previous studies either concerning the same reef or other tropical reefs. The increase in biomass and primary production, however less pronounced than in other areas, is related to nutrient enrichment either from terrestrial runoff or resuspended sediments, and to a lower grazing pressure. The predominance of diatoms seems to be a general scheme and is explained by higher growth rates of diatoms compared to other phytoplankters, thus allowing diatoms to take adavantage of the nutrient enrichment in the first place. The phytoplankton increase is frequently followed by a bloom of benthic macroalgae. This mico- and macro- algal development is interpreted as a mechanism to prevent the loss of dissolved nutrients out of the reef ecosystem.


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