Diversity of Parengyodontium spp. strains isolated from the cultural heritage environment: Phylogenetic diversity, phenotypical diversity, and occurrence.

Parengyodontium album is a fungal species that frequently occurs in the cultural heritage environment. Although three subclades were initially described in the species, no study has sought to determine the occurrence of each subclade in the cultural heritage context. These subclades are easily distinguishable phylogenetically, but their morphological identification is more difficult. Eighteen strains isolated from different cultural sites and initially identified as P. album were studied phylogenetically, morphologically, and in terms of their susceptibility to econazole nitrate 0.2%, an antifungal product used as preservation treatment in cultural heritage domain. The phylogenetic study revealed that all studied strains belonged to P. album subclade 1 or P. torokii (P. album subclade 3) and none belonged to P. album subclade 2. The morphological study revealed the best characteristics to differentiate the three subclades/species, namely, the ability of the strains to grow at 32 C and 35 C on potato dextrose agar (PDA) medium and the shape of conidia. Finally, the strains displayed variable susceptibilities to econazole nitrate, with no apparent link to any particular subclade/species.

Hydrogeological control on carbon dioxide input into the atmosphere of the Chauvet-Pont d'Arc cave.

Carbon dioxide (CO2) concentration (CDC) is an essential parameter of underground atmospheres for safety and cave heritage preservation. In the Chauvet cave (South France), a world heritage site hosting unique paintings dated 36,000 years BP, a high-sensitivity monitoring, ongoing since 1997, revealed: 1) two compartments with a spatially uniform CDC, a large volume (A) (40,000 to 80,000 m3) with a mean value of 2.20 ± 0.01% vol. in 2016, and a smaller remote room (B) (2000 m3), with a higher mean value of 3.42 ± 0.01%; 2) large CDC annual variations with peak-to-peak amplitude of 2% and 1.6% in A and B, respectively; 3) long-term changes, with an increase of CDC and of its annual amplitude since 1997, then faster since 2013, reaching a maximum of 4.4% in B in 2017, decreasing afterwards. While a large effect of seasonal ventilation is ruled out, monitoring of seepage at two dripping points indicated that the main control of CDC seasonal reduction was transient infiltration. During periods of water deficit, calculated from surface temperature and rainfall, CDC systematically increased. The carbon isotopic composition of CO2, correlated with water excess, is consistent with a time-varying component of CO2 seeping from above. The CO2 flux, which is the primary driver of CDC in A and B, inferred using box modelling, was found to confirm the relationship between water excess and reduced CO2 flux into A, compatible with a more constant flux into B. A buoyancy-driven horizontal CO2 flow model in the vadose zone, hindered by water infiltration, is proposed. Similarly, pluri-annual and long-term CDC changes can likely be attributed to variations of water excess, but also to increasing vegetation density above the cave. As CDC controls the carbonate geochemistry, an increased variability of CDC raises concern for the preservation of the Chauvet cave paintings.