The macroalgae stem organization is very diversified, and we can find from microcopic up to until 60m in length. They can be found in most diverse environments. In the marine environment they can be a part of benthic or plâncton. Considering benthic organisms (seaweed and animals) the strip from the coast that occupy can be distinguished. Benthic seaweed can be found in the supratidal, intertidal and subtidal rocky shores. It can also be found in the pelagic environment, as the Sargassum pelagic seaweed of the Sargaço Sea which supports a rich and varied fauna, we can find organisms on blades of seaweed, branches, stems, holdfast besides some species between and under the stem. The macroalgaes are an important constituent in the marine ecosystem providing habitats for a large number of small invertebrate species, representatives of almost all the groups of known metazoários, offering a mild environment against certain physical ambient factors, such as the impact of waves and dessecation, particularly in the intertidal region. Generally in the fital communities macrofauna and meiofauna organisms can be found. Analyzing by number of individuals in macroalgae the meiofauna is superior to the macrofauna