SPATIAL DISTRIBUTION OF POLYCHAETES IN A SOFT-BOTTOM COMMUNITY AT SACO DO CÉU (ILHA GRANDE, RIO DE JANEIRO, BRAZIL)
Brasil, A. C. dos S.1 & Silva, S. H. G. da2
1Departamento de Biologia Animal, Instituto de Biologia, Universidade Federal Rural do Rio de Janeiro, Km 47, Antiga Rodovia Rio-São Paulo, 23851-970, Rio Janeiro RJ, Brazil.
2Departamento de Biologia Marinha/IB, Universidade Federal do Rio de Janeiro, CCS Bloco A, Cidade Universitária,21941-900, Rio Janeiro RJ, Brazil.
Polychaete worms represent an important group in soft bottom communities and their spatial structure is always closely related to grain size and other factors such as organic content. This study was perfomed to determine the spatial distribution of polychaetes in the bottom of a small, shallow bay (Saco do Céu), at Ilha Grande Island, Rio de Janeiro, Brazil. Thirty-nine stations were sampled throughout the bay at two seasons (January and July, 1992). A 0.1 m2 Petersen grab was used to collect biological samples and the sediment for granulometric analyses. Anesthetic was added to the samples before washing them through 1.0 and 0.5 mm mesh sieves. Samples were fixed in 10% formalin. The Mantel test was used to compare sediment and seasons for January and July. The sediments vary from fine to very coarse sand. The most abundant polychaete species were Glycinde multidens, Sigambra grubii, Paraprionospio pinnata, Mediomastus californiensis, and Armandia agilis in fine sand and Magelona papillicornis, Goniadides carolinae, and Eunice vittata in coarse sand. Cluster analysis showed different species groups associated with the two types of sediment. No correlation was found between the fauna/sediment type and period of year, thus suggesting that the spatial distribution of polychaetes at Saco do Céu is determined by grain-size characteristics and by organic matter content and not affected by season.