Intra-annual variation of intertidal benthic community in a breakwater zone on the north coast of Rio de Janeiro, Brazil

The present study investigated the vertical distribution of intertidal benthic organisms in different periods of the year, relating them to environmental variables (tide, air temperature, wave height and period) on a breakwater zone on the northern coast of Rio de Janeiro State. Quadrats of 400 cm2 were superposed along four vertical profiles and sampled by a photoquadrat method. A seasonal difference was identified in the degree of air exposure, which was higher in October 2005 and February 2006. Air temperature and wave height and periodicity differed significantly among the four studied periods. Some species occurred only in one period as Fissurella clenchi in July 2005 and October 2005, Gracilaria domingensis in July 2005, Grateloupia sp. in October 2005) and Porphyra acanthophora in October 2005 and February 2006. Species richness and diversity values were higher in the intermediary quadrats in all the studied periods. The intermediate benthic strip occupied a narrower zone, changing its spatial location according to the season of the year: in May 2005 it was closer to the lower zone, in July and October 2005 it occupied an intermediate position, and in February 2006 it was nearest to the upper quadrats. The hypothesis of intra-annual variation of the benthic community distribution according to the seasonal variability of tides, air temperatures, wave height and periodicity was accepted for the intermediate strip of the intertidal zone, related to taxonomic differences and on the abundance of dominant species considering the four studied seasons