Benthic Community Zonation in a Breakwater on the North Coast of the State of Rio de Janeiro, Brazil

The present study presents the vertical zonation pattern of the intertidal benthic organisms on granitic boulders in the Farol de São Tomé beach (22º02'S, 41º03’W), Rio de Janeiro State. Four sampling profiles using 20 x 20 cm quadrats through a photo quadrat technique revealed four horizontal bands: (1) Littoral Fringe characterized by empty space and Littorina; (2) Upper eulittoral mainly occupied by Chthamalus and bare rock; (3) Lower eulittoral characterized by Chthamalus, Phragmatopoma, Ulva and Centroceras; and (4) Sublittoral Fringe characterized by Ulva, Phragmatopoma and Hypnea. The high variability in the relative abundance of the dominant species among the profiles may be attributed to the high topographic irregularity, reflecting in different wave action intensity at the same height, and consequently favoring the establishment of different species. The frequent substrate alternation from granitic rock to Phragmatopoma sandy reefs might contribute to the small-scale spatial variability. The implantation of a breakwater on an area without natural rocky shores allowed the study of intertidal benthic communty zonation, and provide a baseline for the experimental studies