Looking at the soft-bottom around a coastal coral reef: the impact of terrigenous input on Polychaeta (Annelida) community

ABSTRACT Erosion on coral reefs produces fragments of the constructor organisms that are scattered all around, thus enlarging the reef boundaries. Statistical modelling approach was used to investigate whether the Polychaeta community around Sebastião Gomes reef (Abrolhos Bank, Brazil) is influenced equally by sediment characteristics and/or by position related to the reef, that are variables related to the terrigenous input influence. In July 2007, a period dominated by winds that resuspend fine sediment from the land to coastal reefs, sediment samples were taken on four transects perpendicular to the reef (S, W, N and E) and a total of 121 species of polychaetes were recorded. The most abundant species was the carnivorous Goniadides carolinae and the model selected for it approximates to the best models fitted for both total macrofauna and polychaete abundance. These models represented higher abundance in coarse carbonate sediments on windward reef faces, where there is almost no terrigenous sediment. On the other hand, the Polychaeta richness did not depend on the transects. Sebastião Gomes reef is one of the many coastal reefs from Abrolhos Bank, whose healthy is probably in danger because of the increase of mud related to human activities, as deforestation and, recently, mining waste