Abstract

The health of Caribbean coral reefs has significantly declined for the last 30 years. This phenomenon is characterized by a shift from benthic communities dominated by corals to macroalgae communities. Several causes, such as herbivorous fish overfishing, eutrophication of coastal waters, Diadema urchins epizooty, among others have been evoked. A long term monitoring study of Stegastes planifrons on a reef of Guadeloupe Island shows a significant decrease of the abundance of that species between 1988 to 2010. The density of Stegastes decreased from 28.6 ± 1.2 individuals for 300 m2 of reef surface, in 1988, to 1.89 ± 1.2 individual for 300 m2 between 2005 to 2010. Main negative turn points in the tendency correspond to the year 1989 (hurricane Hugo) and 1995 (hurricanes Luis and Marylin). These phenomena were the cause of important architectural destructuring of the reef habitat. Field observations of the territories of Stegastes planifrons led to an estimate on the average size of a territory of 1.26 ± m2. Cross-calculation between these data shows that the reef surface controlled by Stegastes planifrons decreased from an estimate of 8% to 0.8% over a period of 22 years. Stegastes planifrons is known to significantly control algal communities. On their territories, the algal diversity is higher than outside and above all macro-algae are replaced by turf. The strong decline of Stegastes planifrons on the reefs of the French Antilles might have played a significant role in the shift between corals to macroalgae observed these last decades in the reef communities.

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