Fungal communities in the biofilms colonizing the basalt sculptures of the Leizhou Stone Dogs and assessment of a conservation measure

Abstract

AbstractThe Leizhou Peninsula in China is very famous for its unique folk art creation, especially for the stonework, like the basalt sculptures of the Leizhou Stone Dogs, which have a history of more than two thousand years. Since these sculptures are usually exposed outdoors, many of them are suffering from severe damage by lichen and fungi. To protect them from microbial attack, we determined fungal communities in the biofilms colonizing the stone dogs and explored an effective conservation measure. Specifically, the micromorphology analysis of the biofilms on the stone dogs was performed through both on-site and laboratory-based microscopies in order to provide an overview of the fungal community structure. High-throughput sequencing analysis revealed that the predominant fungi in the biofilms belong to the following genera Caloplaca, Chaetomium, Clitopilus, Acanthostigma, Tolypocladium, Aspergillus, and Toxicocladosporium. The energy dispersive X-ray spectrometry (EDS) showed that the basalt is mainly composed of silica (53% by weight), followed by Al2O3 (14.4%), Fe2O3 (10.1%), CaO (8.4%), and MgO (7.4%) that are oxides susceptible to corrosion of biogenic acids. The EDS analysis of the hyphae provided the direct evidence on the leaching of the minerals of the sculptures. To control microbial attack, three kinds of antimicrobial agents were tested for 2 years. As a result, the mixture of biocide and water repellent showed the best effectiveness. Our findings provide an overview of fungi diversity in the biofilms on the stone dogs and help the investigation of fungi-induced biodeterioration and the exploration of specific conservation measure.