Sponges associated withSargassumspp. (Phaeophyceae: Fucales) from the south-western Gulf of California

Abstract

This study constitutes a preliminary assessment of the abundance and species richness of sponges living on the brown seaweedSargassumspp. from the southern Gulf of California (Mexico). The diversity and abundance of sponges associated withSargassumwas investigated from November 2006 to November 2007. In addition, it was examined whether temporal variations in the abundance of associations were influenced by changes in size and density ofSargassumas well as environmental factors such as water temperature and salinity. Twelve sponge species (4 Haplosclerida, 3 Poecilosclerida, 4 Dictyoceratida and 1 Clathrinida) were found growing epiphytically on the lower portions ofSargassumplants and the most frequent species wereCallyspongia californicaandHaliclona turquoisia(38% and 27%, respectively). The abundance of associations showed significant temporal and spatial variations, being higher from June to November (postSargassumgrowth period), at depths from 0.5–2.5 m. The number of sponge species m−2(both epiphytic and non-epiphytic) inside the seaweed bed was 4.8 species m−2, while outside it, the absence of hard substrate for attachment severely restricted the number of sponges. These results suggest thatSargassumprovide substratum and habitat for the sponge community from this region, and that their seasonal growth patterns may influence the abundance and diversity of the associations.