The Abrolhos Bank, located in the extension of the continental shelf in the northeastern region of Brazil, is the largest South Atlantic reef complex. This region is divided into the inner and outer arc, the last is formed by coral pinnacles called "chapeirões", that are isolated in shaped like a mushroom. Addition to the "chapeirões", other features of these reefs are the high endemism displayed by organisms and their resistance to extreme conditions such as high levels of turbidity. The unconsolidated sediment sand and mud adjacent to the reefs are rarely studied, but as shown in recent literature, can present a rich benthic fauna of Peracarida crustaceans, such as the Tanaidacea. This paper aims to describe the structure (species composition and distribution) of Tanaidacea communities in unconsolidated sediment from two areas of the Abrolhos Bank, correting with bottom type, distance from the reef and other environmental aspects. For this purpose, samples were taken between 19 and 29 July 2007, with 33 collection points located in two different reefs, Sebastião Gomes, situated in the innner arc (higher turbidity of the Abrolhos Bank) formed by bank reef, and Parcel dos Abrolhos, located in the outer arc and formed by isolated "chapeirões". The sediments were collected using van Veen grab (0.03 m² and 0.07 m²), launched in triplicate. The samples were sieved through 0.5 mm mesh and retained sediment was screened in the laboratory. The macrofauna was separated into groups to further identify the species of Tanaidacea. This work is inserted in subproject Bentos, Pro-Abrolhos Project, aimed to understanding the composition and diversity of benthic macrofauna community of the study area.
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