Levels of taxonomic resolution and choice of transformation sufficient to detect community gradients: an approach to hard-substrata benthic studies

Many recent studies have demonstrated that, in monitoring surveys, identification of organisms to the lowest possible taxon may not always be necessary to describe spatial patterns. In this study we examine faunal patterns at different taxonomic levels by means of multivariate analysis. The study site was located in the Bay of Marina Grande (Scilla, Tyrrhenian Sea), in the proximity of an outlet of a drain of domestic sewage. Macrofaunal abundance data from four hard-bottom stations were analysed at the level of species, genus, family, class, and phylum. Transformation of data was also considered. The gradient of change in community structure was clearly detectable from matrices derived from species, genus, and family abundances constructed using identical transformation. This study, which is the first of this kind on Mediterranean hard-bottom macrofaunal communities, demonstrated that the taxonomic sufficiency for impact studies is similar to studies in soft-bottom benthic assemblages, and that identification of organisms to the level of family probably will be acceptable for most monitoring studies. © 2000 Taylor & Francis Group, LLC.