Trophic structure of polychaetes in the Sao Sebastiao Channel (southeastern Brazil)

Between November 1993 and August 1994, the spatial and seasonal trophic str uctures of polychaete annelids were studied in the Sao Sebastiao Channel, s outheastern Brazil, located between the mainland of Sao Paulo State and Sao Sebastiao Island. Four sampling surveys were carried out with a van Veen g rab of 0.1 m(2) at 15 stations. A total of 12 003 individuals (126 species) was recorded and separated into 14 feeding guilds. Data were analysed with univariate and multivariate techniques (cluster and canonical corresponden ce analysis). Results showed a strong correlation between trophic groups an d sediment variables such as grain size and organic carbon content. The Cha nnel was dominated by surface deposit-feeders, followed by carnivores. Susp ension-feeders were confined to medium and coarse sandy sites, environments with high energy. Bottoms where silt, clay and organic carbon predominated showed low polychaete densities. In these places the pollution induced by the sewage discharge from Araca underwater emissions and by the oil termina l Dutos e Terminals Centro Sul was evident. There were no significant seaso nal variations in the trophic structure over the study period, except in fa ll when densities were low. The polychaetes' relationships within the benth ic system are discussed.