A Functional Analysis of the Benthic Macrofauna of the Sa ˜ o Sebastia ˜o Channel (Southeastern Brazil) Emilia Arasaki 1,* , Pablo Muniz 2,3 & Ana Maria S. Pires-Vanin 3 1 Escola Polite ´cnica da Universidade de Sa ˜o Paulo, Laborato ´rio de Hidra ´ulica; Av. Prof. Lu ´ cio Martins Rodrigues, 120. CEP 05508-900, Sa ˜o Paulo, Brazil. 2 Seccio ´ n Oceanologı ´a, Departamento de Ecologı ´a, Facultad de Ciencias; Igua ´ 4225, Montevideo, 11400, Uruguay. 3 Instituto Oceanogra ´fico da Universidade de Sa ˜o Paulo, Caixa Postal 66149, CEP 05315-970, Sa ˜o Paulo, Brazil. With 2 figures and 5 tables Keywords: Benthic macrofauna, distribution patterns, biotic index, Sa ˜o Sebastia ˜o Channel, Brazil. Abstract. The major problem in coastal areas of developing countries is disturbance caused by anthropogenic influence. This disturbance can be quantified by analysing the distribution and composition of marine communities using uni- and multivariate techniques and the biotic index. A study of benthic macrofauna was carried out along the Sa ˜o Sebastia ˜o Channel, northern coast of Sa ˜o Paulo State, Brazil, in an area with a submarine outfall, a petroleum terminal and a commercial harbour. Sampling was undertaken seasonally, by means of a van Veen grab (0.1 m 2 ) at 15 oceanographic stations, from November 1993 to August 1994. A total of 392 species were identified (129 Polychaeta, 127 Mollusca, 98 Crustacea, 28 Echinodermata and 10 other phyla). The sedimentary pattern recorded for the Sa ˜o Sebastia ˜o Channel is very heterogeneous, influenced mainly by strong wind-driven currents, and differs from nearby shelf areas. The study area could be divided into three regions based on sediment texture and fauna: one region dominated by medium and coarse sand with low values of organic carbon; a second area where pelitic fractions were dominant with high values of organic carbon and nitrogen; and a third region characterised by fine and very fine sand, presenting intermediate organic carbon values. No temporal significant variation in abundance and species composition was found, except in autumn. The use of the Ômarine Biotic CoefficientÕ showed the same ecological trend as the faunal abundance and demonstrated that the central continental region of the channel is affected by human activities. *Author to whom correspondence should be addressed. E-mail: earasaki@usp.br P.S.Z.N.: Marine Ecology, 25 (4): 249–263 (2004) Ó 2004 Blackwell Verlag, Berlin ISSN 0173-9565 Accepted: August 13, 2004 U. S. Copyright Clearance Center Code Statement: 0173-9565/2004/2504–249/$15.00/0