Spatial and temporal distributions of the sponge fauna insouthern Italian lagoon systems

Περίληψη

The present work focused on the taxonomic composition, spatial distributions, and temporal distributions of the sponge fauna from the main lagoon systems of southern Italy: Lesina, Varano, Taranto, Alimini, Faro, Ganzirri, Tindari and Marsala. Overall, 62 sponge species were recorded, belonging to the classes Demospongiae (52 species), Calcarea (8) and Homoscleromorpha (2). All the lagoon systems studied hosted sponges, even if with marked differences. Species richness varied from one (Lesina) to 45 (Marsala). A large number of the species recorded during this study (52%) was found only at a single site, whereas a species only (Halichondria (H.) panicea) was present in all the environments studied. Sponges colonised all available substrates. Salinity was the ecological factort hat best explained the spatial distribution of sponges, even though the wide heterogeneity of sponge assemblages, strongly suggests an important role of stochastic factors acting on pre- and post-settlement phases. Comparison of the present data with lists available from the literature shows that sponge assemblages from most of the studied lagoons were quite persistent. However, in some of the lagoons remarkable extinction processes, probably related to massive and prolonged anthropogenic pressures, have contributed to large changes in the sponge patterns.