Temporal dynamics of a Sabellaria wilsoni (Sabellariidae: Polychaeta) reef on the Brazilian Amazon Coast

Abstract

Polychaetes of the family Sabellariidae build extensive reefs in many coastal regions worldwide. These structures are dynamic systems that undergo a natural cycle of growth and destruction provoked by fluctuations in hydrodynamic conditions and biological factors. Here, we monitored a Sabellaria wilsoni reef over an annual cycle on Algodoal-Maiandeua Island on the Brazilian Amazon coast. We studied the impact of temporal variations in local environmental characteristics on the structure of the reef and the reef-building polychaete population. Metrics included the local climate (temperature, rainfall, and winds), hydrological variables (suspended particulate matter and salinity), and the output of a numerical model of the local hydrodynamics. There was increased hydrodynamic stress in the dry season due to changes in the direction and intensity of the wind and stronger waves. This in turn led to an accentuated decrease in sabellariid density, and the eventual erosion of the reef, which lost >80% of its original area. The reduction in the hydrodynamic energy at the end of the rainy season favoured the mass recruitment of sabellariids as well as the subsequent growth and recuperation of the reef. Oligohaline conditions also contributed to a reduction in worm density, but not to any loss in reef structure. These findings provide important insights into the thresholds of energy and salinity tolerated by the reef-building polychaete S. wilsoni and offer a useful baseline for future research on the ecology of this species and the monitoring of this important marine habitat.