Marine bioerosion of lapideous archaeological artifacts found in the Grotta Azzurra (Capri, Naples, Italy): Role of microbiota and boring Porifera

• Micro-erosion of submerged archaeological marble artifacts was analysed.
• SEM observations show the process of bioerosion due to microbiota and boring Porifera.
• Endolithic activity is related to chemotrophic and phototrophic microflorabiota.
• Embedding casting procedure permitted the identification of different microborers.
• Chlorophytes, fungi and boring Porifera play an important role in biodeterioration and bioerosion processes.

This research has been conducted on archaeological artifacts collected from the Grotta Azzurra (Capri, Naples, Italy). Endolithic microbiota and boring Porifera responsible for bioerosion and micro-erosion were analysed. SEM observations permitted the analysis of biodegradation. Embedding casting procedure with polyester resins allowed the identification of three different microborer traces, corresponding to green algae, fungi and boring sponges. According to spicule complement two excavating species and other four sponge species were recorded inside the bored cavities. In addition, the species Cliona janitrix is here reported, for the first time, into archaeological artifacts. Traces of the green alga Ostreobium quekettii (ichnospecies Ichnoreticulina elegans) were found to dominate in all samples; traces of three species of microfungi were abundant. Microscopic pitting patterns and resin casts produced by different boring sponges into marble samples have been examined. Different kinds of micro-erosion are characterized by various types of ornamentation and sculpturing patterns. The data confirm that endolithic chlorophytes and fungi together with macroboring organisms, especially boring sponges, play a significant role in biodeterioration processes of submerged lapideous artifacts.