Changes in sponge fauna over a half-century from a rocky cliff of the Portofino Promontory (Ligurian Sea; Western Mediterranean)

Increasing anthropogenic impact and climate change have led to a depletion of the Mediterranean Sea’s benthic communities and mass mortality events of organisms in recent decades, and the consequent loss of three-dimensionality of habitats. Medium- and long- term monitoring studies are essential to investigate these changes and understand their ecological effects. The sponge fauna of a vertical section of a rocky cliff in the Protected Marine Area of Portofino (Italy) was analysed and compared with the communities observed 47 years earlier. A loss of the massive/erect forms and a general decrease in biodiversity in the upper half of the transect was evident. In contrast, the deeper section showed greater stability due to the presence of coralligenous reefs. In addition, a shift of some species from shallower depths to deeper areas was observed. This study thus allowed us to observe the evolution that the area’s sponge community has undergone in recent decades.