Environmental factors affecting the distribution of Spongillidae (Porifera) in an artificial channel (in north-western Italy)

The hydrographic network of the upper Po Valley (NW Italy) is characterized by the presence of numerous hydroelectric plants, often powered by artificial channels. These man-made water courses, which range from a few hundred meters to several kilometers in length, are used to convey water from the rivers to the electricity production plant. Power canals are usually characterized by concrete banks and bottoms, a geometric profile, and the absence of riparian vegetation so that they host peculiar invertebrate communities, often extremely well adapted to life in a completely artificial habitat. Sponges are an often little considered component of the freshwater macroinvertebrate fauna, whose functions and role within communities can be of considerable interest. These sessile, filterfeeding organisms can colonize artificial channels, but little is known about the local environmental characteristics that influence their distribution. In this study, we investigated the distribution of a freshwater sponge family Spongillidae, in a 4.5 km long artificial channel in Rocca Grimalda (Alessandria, NW Italy). A total of 863 specimens were localized and measured, and selected environmental characteristics were recorded. Results suggested that the distribution of sponges depends mainly on the lighting rather than the type of substrate or other local factors, so that this taxon is well-suited to colonizing artificial environments with good water quality conditions.