Endolithic and epilithic sponges of archaeological marble statues recovered in the Blue Grotto, Capri (Italy) and in the Antikythera shipwreck (Greece)

摘要

Boring sponges are among the most important erosive organisms causing relevant damage on calcium carbonate substrates in marine environments. The present work offers a contribution to the knowledge of the bioerosive impact of sponges on archaeological artifacts such as the marble statues recovered from the shipwreck of Antikythera (Greece) and the Blue Grotto (Capri, Italy). These peculiar substrates lie on the seabed, but only little information is available about the risks during their underwater life. Bioeroding sponges caused the loss of substantial parts of the artifacts' lithic substrate (penetrating up to some centimeters depth), often in association with microborers and boring bivalves. The results highlighted that the bioeroding species in Capri were mostly Dotona pulchella mediterranea, Cliona janitrix, Cliona schmidtii, and Spiroxya levispira. Their chambers were often filled by secondary, non-eroding sponges such as Agelas oroides, Jaspis incrustans, Dercitus (Stoeba) plicatus, Erylus sp., and Pachastrella monilifera. In the Antikythera statues, C. schmidtii was the most frequent species, often easily recognized by its purple color. It was often associated with other excavating sponges such as Cliona vermifera, and Dotona pulchella mediterranea. Pachastrella monilifera and Jaspis incrustans were also present as insinuating species. Incomplete sets of spicules and bioerosion pits observed by SEM were referred to the genera Alectona and Siphonodictyon. The presence of the sciophilous epilithic species Petrobiona massiliana and Merlia normani in both sites revealed that these archeological sites have comparable environmental conditions. The study allowed the identification of the sponges involved in the colonization of calcareous artifacts and the definition of the important role they played in the damage of the statues.