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Oxpemul is an archaeological site with pre‐Hispanic legacy located in the Calakmul biosphere reserve in Mexico. The stelae in this site have important epigraphic records of the Mayan culture. However, this information can be lost due to weathering processes that these structures undergo. In this work, ion chromatography analysis of ions extracted from samples obtained in situ using cotton poultices was used to discuss the weathering processes involved in four stelae located in Oxpemul. The plots of Ca2+vs SO42−, (Ca2+ + Mg2+) vs HCO3− and Ca2+vs HCO3− and the mineral phases found by x‐ray diffraction (XRD) revealed that the dissolution of carbonates from the limestone and the recrystallization processes of these phases are the main weathering processes that occur in the stelae. Furthermore, it was found that the hydrolysis of silicates by cation exchange reactions to form montmorillonite contributes to the weathering process. The presence of oxalate crystals found by XRD and electron microscopy revealed that biodeterioration reactions also contribute to the weathering of the stelae. This is the first study carried out to identify and understand the weathering processes that occur in these stelae. This information could be useful to establish strategies for preserving, conserving, and restoring these vestiges. [ABSTRACT FROM AUTHOR]

Microorganisms naturally colonize rock-based materials in outdoor environments, thereby contributing to their degradation. Fungi, especially in tropical environments with abundant water and favorable temperatures, play a significant role in biodegradation. However, many aspects of the microorganism-stone interaction, including fungal colonization dynamics and the impact of treatment applications, remain unclear. This study conducted a four-year in-situ evaluation of fungal community dynamics on limestone surfaces in the Temple of the Warriors at the Chichén Itzá archaeological site in Mexico, focusing on cleaning and treatment using nanoparticles (NPs). These NPs included zinc oxide (ZnO) and CaZn 2 (OH) 6 ·2H 2 O (CZ)-based NPs synthesized via sol-gel (CZ-SG) and mechanochemical methods (CZ-MC), as well as CZ/Ca(OH) 2 -based products (CZ:Ca-SG). The microbial colonization cover was assessed using colorimetric measurements, and the surface was sampled for fungal community isolation and identification. The results demonstrated significant impacts of cleaning and nanomaterial applications on cultivable fungal communities (melanized filamentous, hyaline, and microcolonial fungi), altering composition, dynamics, and stone surface coloration. In particular, ZnO NPs caused 50 % decline in fungal species and individuals, whereas CZ:Ca-SG NPs displaced most species, indicating effective inhibition of the cultivable fungal community. Microcolonial fungi (MCF), known for their tolerance to withstand harsh environmental conditions, were the only fungal group found in the CZ:Ca-SG treatment. In contrast, CZ-SG and CZ-MC increased the abundance of melanized species, resulting in darkening and reduced color intensity. This study highlights the importance of microcolonial fungi that are tolerant to cleaning and coating procedures in the preservation of stone cultural heritage. These findings enhance our understanding of fungal colonization dynamics following treatment and provide valuable insights into the challenges associated with preserving stone materials in tropical environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

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Surfaces of buildings at the archaeological site of Palenque, Mexico, are colonized by cyanobacteria that form biofilms, which in turn cause aesthetic and structural damage. The structural characterization and species composition of biofilms from the walls of one of these buildings, El Palacio, are reported. The distribution of photosynthetic microorganisms in the biofilms, their relationship with the colonized substratum, and the three-dimensional structure of the biofilms were studied by image analysis. The differences between local seasonal microenvironments at the Palenque site, the bioreceptivity of stone and the relationship between biofilms and their substrata are described. The implications for the development and permanence of species capable of withstanding temporal heterogeneity in and on El Palacio, mainly due to alternating wet and dry seasons, are discussed. Knowledge on how different biofilms contribute to biodegradation or bioprotection of the substratum can be used to develop maintenance and conservation protocols for cultural heritage. [ABSTRACT FROM PUBLISHER]

The Copàn Hieroglyphic Stairway, one of the most important monuments of the Mayan culture, was excavated at the end of the 1800s. After a few decades it was extensively attacked by mosses and lichens. Different biocide treatments were applied in the late 1970s, and consolidation and stabilization works were carried out in the 1980s and 90s; a tarp was installed in 1985 over the Stairway for protection from rain. The present investigation shows an almost total death of lichens and a heavy reduction of the biodeterioration phenomena on the stone surfaces of this monument. The most frequent species presently growing are cyanobacteria and a few green algae. Notwithstanding this relatively low level of superficial colonization, cross-section staining and SEM analyses at times revealed a heavy biological growth just below the surface. The main structures found were exo-polymeric substances, fungal hyphae and moss protonema. Through a comparative analysis of the biodeteriorative phenomena of other monuments at the site, and with historical records, the relationships between the main ecological factors (water and light) and the biological colonization at the Copàn archaeological site are described. The ecological analysis and the changes that seem to have occurred in the biodeterioration of the Stairway provide useful information for planning future conservative interventions. [ABSTRACT FROM AUTHOR]

Biofilms on the salted ceiling of a limestone tunnel at the Mayan site of Edzna, Mexico, were characterised using SEM, EDS, chemical analysis, light microscopy, culture and pigment analysis. Major superficial biomass was pigmented, scytonemin-rich Subsection II cyanobacteria. Main endolithic phototrophs were Subsection I and II cyanobacteria and the alga Nanochlorum . Bacteria and actinomycetes of the Geodermatophilus , nocardioform, and streptomycete groups were present at all levels. Salt crystals, mainly sulfates, were found throughout the stone. Microbial ion transport, metabolite production, chelation, and water retention caused degradation and salt deposits. Exfoliation is the major erosion process. [ABSTRACT FROM AUTHOR]

The microbial epilithic communities associated with Uxmal Mayan stone monuments (Yucatan, Mexico) were preliminarily characterized by chemical and biochemical methods. The organic matter, organic carbon, and nitrogen content were within the respective ranges reported for other stone buildings, indicating that oligotrophic conditions prevailed at Uxmal's buildings. Quantitative differences in both total and phototrophic biomass were observed between stone and mortar (stucco) substrata, between indoor and outdoor locations, and between seasons. Microbial biomass and organic matter content were greater on indoor surfaces associated with more suitable microenvironmental conditions (availability of water and protection from direct sunlight) for microbial growth. Cyanobacterial photosynthesis, microbial debris, and bird droppings are the most probable sources of organic carbon and organic nitrogen in Uxmal's stone buildings. The epilithic communities appear to be dominated by phototrophs (mainly cyanobacteria) populations and associated bacteria. The latter are probably trophically dependent on the release of organic matter by photosynthetic production. These microbial biofilms and their activity may be responsible, in part, for the degradation of these stone monuments. [ABSTRACT FROM AUTHOR]