TEMPORAL VARIATION OF POLYCHAETES FROM PICINGUABA AND UBATUMIRIM INLETS (SOUTHEASTERN BRAZIL)
Petti, M. A. V. & Nonato, E. F.
Instituto Oceanográfico da Universidade de São Paulo, Praça do Oceanográfico, 191, 05508-900 - São Paulo, SP, Brasil
Recent results on the distribution patterns of the near shore benthic macrofauna of Southeastern Brazil have shown that physical features such as wind, waves and water masses play an important role in the structure and dynamics of shelf communities. This study describes the temporal variability of the polychaetes between May 1993 and April 1994, at two monthly intervals at seven sites from 3 - 17 m depth. The density and biomass of polychaetes was estimated. Species richness, diversity and evenness were calculated for each sampling station and sampling period. The sediment was composed mainly of silt and very fine sand. Maximum densities and biomass of polychaetes were recorded on November 1993 and January 1994 (late spring and beginning of the summer). The lowest values were observed in July 1993, September 1993 and April 1994. The surface dwelling species of Spionidae, Cirratulidae, Pilargidae and Poecilochaetidae were the main indicators of the temporal variability observed in the macrofauna community structure. Species with the highest contribution to the biomass, Owenia fusiformis and Spiochaetopterus costarum, persisted over the colder periods. The temporal distribution patterns were strongly associated to the hydrodynamic processes present in the study area. The occurrence of cold fronts, more intense and frequent in winter, cause bottom resuspension and extensive mortality of the surface life forms from shallow areas. Under similar conditions, burrowing infaunal species or carnivore species can predominate. The penetration of cold water masses during summer results in an increase of nutrients and recruitment of larval and juveniles.