Estudo da comunidade de corais na zona do Farol da Ilha do Ibo

Abstract

The structure of the coral community located in the northeastern part of the island of Ibo was analyzed in terms of profile structure, zonation, coverage and diversity. In a section of the reef in the lighthouse area, in November 1995, 18 transects were carried out during low tide, 9 in the exposed area and 9 in the non-exposed area, at three different depths. In the exposed area, the point transect method was used and, in the non-exposed area, the video-transect method using diving with a scuba diving suit. The studied area presented a geomorphological structure typical of a fringe reef: shallow lagoon, flat reef top and slope, ending in a sand platform. It is a shallow reef, where the distribution of the coral community does not exceed 16m. In the exposed area, seagrasses in the lagoon dominated, with an average coverage of 35%, and macroalgae on the top of the reef, with 43%. On the slope, unexposed zone, the dominant benthic communities were corals and octocorals, with mean percentages of coverage of 24% and 21%, respectively. The most common scleractinid coral genera were Acropora and Porites. The reef presented a well-defined zonation between lagoon, top and slope. Within the slope, group hierarchical analysis based on the Bray-Curtis dissimilarity index did not find a clear relationship between transects of the same depth. Twenty genera of scleractinid corals and 5 of octocorals were recorded. It was found that there is no relationship between diversity and depth. There were found to be many scarred corals, very small corals and other dead ones. The reef does not appear to be in the best condition. The main problem affecting the Ibo island reef is thought to be sedimentation. (TRADUÇÃO NOSSA)