Las variaciones de la pendiente topográfica, un factor a considerar en la evaluación de la estructura de una comunidad arrecifal

Abstract

We studied the effect of slope variations on the structure of a reef community.Four sections of a reef char­acterized by different topographic slopes were studied. The sampling design was systematic,using the transections and quadrate methods to estimate the frequency, as well as total and relative coverage of the following substrata cat­egories: coral species, gorgonians, sponges, briozooans, dead coral and sand. Simultaneously the depth gradient for each section were measured. A total of 29 species of petreous corals was found. The dominant coral species was Montastrea annularis, followed by Colpophyllia natans, and Madracis mirabilis. An Importance Value Index was estimated for the different substrate categories on each section of the reef, taking into accountthe average relative coverage and the occurrence frequency. The Kendall correlation tests pointed out the existence of significative dif­ferences in the relative importance of these categories when similar zones of the studied sections were compared. The comparison between steep and intermediate slopes produced the biggest difference (82.24%, p=0.1529). Our results suggest that the slope variations within a same reef must be taken into account to establish the sampling design for the evaluation of community structure.