Sampling efficiency of several sieve mesh sizes (2, 1, 0.5, 0.2 and 0.1 mm) was tested in invertebrate assemblages associated to Sargassum stenophyllum. Samples of this brown algae were collected in southeastern Brazil to determine whether different sampling devices resulted in differences on the abundance and composition of the macrofauna. The 1 and 2 mm mesh sizes sampled less organisms, resulting in smaller abundances, densities, number of species and diversity, when compared to the other three mesh sizes, that achieved similar results. The most efficient sieve was the 0.5 mm mesh, sampling 85.8% and 94.5% of gammaridean and caprellidean amphipods, respectively, and 93.1% of gastropods. However, polychaetes and isopods were best sampled with the 0.2 mm sieve. Our results suggest that caution should be exercised when deciding on which sieve to use, as mesh sizes commonly used in benthic studies (1 and 0.5 mm) may result in very different estimates of diversity and abundance, as well as community structure patterns.
