Species composition and distribution of macroalgae on Atol das Rocas, Brazil, SW Atlantic

Abstract

This study, performed over the years 1999-2003, analyzed the species composition, spatial distribution and ecological aspects of macroalgal assemblages on Atol das Rocas reef, located 266 km off northeastern Brazil. It is the sole atoll in the South Atlantic and is almost completely built of coralline algae. Forty-seven new occurrences of macroalgae were recorded. Adding these to the previous studies, 143 taxa are now known for the local marine flora, with the Rhodophyta as the dominant group. New finds were mainly on the fore reef and in reef pools. The inner habitats (the reef flat, internal ridge and inner pools) harbored fewer macroalgal species than the outer habitats (the reef front, reef crest crevices and outer pools). Inner habitats are subject to prolonged desiccation and solar irradiation stress together with abrupt changes in temperature and salinity controlled by the water oscillations of the mesotidal regime within the atoll; the outer habitats are less affected by these short temporal impacts and are mainly governed by oceanic forcing. Atol das Rocas harbors some species unknown in other Brazilian waters, but these are common in Caribbean reef waters. © 2010 by Walter de Gruyter.