Cleaning of Phototrophic Biofilms in a Show Cave: The Case of Tesoro Cave, Spain

Show caves have different grades of colonization by phototrophic biofilms. They may receive a varied number of visits, from a few thousand to hundreds of thousands of visitors annually. Among them, Tesoro Cave, Rincon de la Victoria, Spain, showed severe anthropic alterations, including artificial l...

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Bibliographic Details
Published in:Applied sciences 2022-08, Vol.12 (15), p.7357
Main Authors: Jurado, Valme, Hernandez-Marine, Mariona, Rogerio-Candelera, Miguel Angel, Ruano, Francisco, Aguilar, Clara, Aguilar, Juan, Saiz-Jimenez, Cesareo
Format: Article
Language:English
Subjects:
Algae
Aquatic plants
Biofilms
Bryophytes
Calcite
Carbon dioxide
Caves
Chemical treatment
chlorophytes
Cleaning
Colonization
Cyanobacteria
Humidity
Hydrogen peroxide
Lighting
Microorganisms
Nostoc
Paleolithic
Phylogenetics
Physicochemical treatment
Sediments
Sodium
Sodium hypochlorite
surface cleaning
Taxonomy
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Summary:Show caves have different grades of colonization by phototrophic biofilms. They may receive a varied number of visits, from a few thousand to hundreds of thousands of visitors annually. Among them, Tesoro Cave, Rincon de la Victoria, Spain, showed severe anthropic alterations, including artificial lighting. The most noticeable effect of the lighting was the growth of a dense phototrophic community of cyanobacteria, algae and bryophytes on the speleothems, walls and ground. The biofilms were dominated by the cyanobacterium Phormidium sp., the chlorophyte Myrmecia israelensis, and the rhodophyte Cyanidium sp. In many cases, the biofilms also showed an abundance of the bryophyte Eucladium verticillatum. Other cyanobacteria observed in different biofilms along the cave were: Chroococcidiopsis sp., Synechocystis sp. and Nostoc cf. edaphicum, the green microalgae Pseudococcomyxa simplex, Chlorella sp. and the diatom Diadesmis contenta. Preliminary cleaning tests on selected areas showed the effectiveness of hydrogen peroxide and sodium hypochlorite. A physicochemical treatment involving the mechanical removal of the thickest layers of biofilms was followed by chemical treatments. In total, 94% of the surface was cleaned with hydrogen peroxide, with a subsequent treatment with sodium hypochlorite in only 1% of cases. The remaining 5% was cleaned with sodium hypochlorite in areas where the biofilms were entrapped into a calcite layer and in sandy surfaces with little physical compaction. The green biofilms from the entire cave were successfully cleaned.
ISSN:2076-3417
2076-3417
DOI:10.3390/app12157357