Bioerosion of submerged lapideous artefacts. Role of endolithic rhizoids of Acetabularia acetabulum (Dasycladales, Chlorophyta)

The endolithic activity of the green alga Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952 (Ulvophyceae, Dasycladales, Polyphysaceae) was documented on different lithotypes recovered in the Underwater Archaeological Park of Baiae (Naples). The results show that rhizoids of A. acetabulum penetrate several micrometres deep into marble and limestone creating characteristic ramified boreholes, while they colonized only the surface of brick. Resin casts of tunnels bored by rhizoids, known as the ichnospecies Fascichnus grandis Radtke, 1991, were described in detail. The study reports for the first time the significant role of A. acetabulum in the bioerosion process of underwater archaeological artefacts.