Effects of the morphology and structural cycles of Sabellaria wilsoni Lana & Gruet, 1989 (Annelida: Sabellariidae) reefs on the associated macrofauna.

Despite their ecological importance, there has been insufficient investigation of reefs constructed by polychaetes of the family Sabellariidae in tropical regions. The present study compared macrofauna associated with Amazonian Sabellaria wilsoni reefs with focus on different morphologies (platform vs. hummock reefs) during distinct annual phases of structural development (preserved, eroded, and recuperation). The two types of reefs had dissimilar assemblages over the course of the structural phases. The platform reef had more muddy sediments and higher proportions of organic matter and phaeopigments, which favored soft-bottom infaunal groups, such as the polychaetes. The hummock reef had denser and taxonomically richer macrofauna, which was typical of consolidated substrates and dominated by crustaceans and bivalves. Temporal changes in the characteristics of the macrofauna were driven by physical disturbance of the reef morphology resulting from local increases in hydrodynamic intensity. The macrofauna associated with periods of reef growth (preserved and recuperation phases), which coincided with the rainy season, was less taxonomically rich in both reef types. In the erosion phase (in the dry season), degradation of the reef structure led to an increase in the complexity of the habitat and thus species richness. In the platform reef, erosion was accompanied by an increase in the density of the assemblage, while in the hummock reef, the density decreased. The present study offers important insights into the biodiversity and ecological function of this important marine habitat, as well as a baseline for future ecological research and the monitoring of tropical sabellariid reefs.