Coastal regions range from the continental shelf to estuarine systems, comprising complex ecosystems, with the interaction of several climatic, geomorphological and biological variables and processes. Extensive macroalgae banks are found on rocky shores in the infralittoral zone, these algae are considered ecosystem "engineers", as they are important primary producers enhancing marine benthic richness and diversity. Variations occur in their extension according to the variation of the slope structure and texture of the rocky coast and the local hydrodynamics, more than increasing the substrate of fixation of the organisms, the macroalgae banks serve as shelter and food source. The brown macroalgae(Sargassum) have a wide distribution in tropical and subtropical regions, are characterized by having branched fronds and varied length, due to this structural complexity, macroalgae have a high richness and diversification of marine invertebrates with emphasis on species of mollusks and crustaceans among them the spider crab(Epialtus brasiliensis).