Diversity of Microfungi in a High Radon Cave Ecosystem

Abstract

Castañar Cave is a clear example of an oligotrophic ecosystem with high hygrothermal stability both seasonal and interannual and the particularity of registering extraordinary levels of environmental radiation. These environmental conditions make the cave an ideal laboratory to evaluate both the responses of the subterranean environment to sudden changes in the matter and energy fluxes with the exterior and also any impact derived from its use as a tourist resource under a very restrictive access regime. In 2008, a fungal outbreak provoked by a vomit contaminated the sediments which were removed and subsequently treated with hydrogen peroxide. Fungal surveys were carried out in 2008 and 2009. The visits were resumed in 2014. Here, 12 years after the outbreak, we present an exhaustive study on the cave sediments in order to know the distribution of the different fungal taxa, as well as the prevalence and spatio-temporal evolution of the fungi caused by the vomit over the years under the conditions of relative isolation and high radiation that characterize this cave.

A Second Fungal Outbreak in Castañar Cave, Spain, Discloses the Fragility of Subsurface Ecosystems

“…The history of samplings in Castañar Cave shows that only three fungi retrieved in the first fungal outbreak in 2008 were also found in the following 2009 and 2020 campaigns, as well as during the second outbreak in 2021: N. solani , F. oxysporum , and M. alpina [ 6 , 17 ].…”

“…In a previous report, we stated that N. solani was a permanent dweller of Castañar Cave because this fungus was present in all samplings since 2008 [ 17 ]. Some studies confirmed that this is a widespread fungus in nature and is considered a natural dweller in caves and subterranean environments [ 3 ].…”

“…A recent study of the Castañar Cave fungal community conducted 12 years after the initial outbreak in 2008 revealed the persistence of several fungi, including Neocosmospora solani (= F. solani ), Fusarium oxysporum , and Mortierella alpina [ 17 ]. Unfortunately, a second outbreak occurred in Castañar Cave during the work on the installation of a steel grating walkway to protect the ground sediments and rocks from visitors’ footsteps.…”

Biodiversity of Phototrophs and Culturable Fungi in Gobustan Caves

“…Frequently occurring species are common in caves. Aureobasidium pullulans is an endophytic fungus common in various caves [ 50 , 52 ], including ice and volcanic caves, and is a primary colonizer of oligotrophic environments [ 53 , 54 ]. A. niger may exhibit keratinolytic activity [ 55 ], and Alternaria alternata may have lignolytic potency [ 56 ].…”

The geomicrobiology of limestone, sulfuric acid speleogenetic, and volcanic caves: basic concepts and future perspectives

“…Fungal taxa so far recognized in caves are those commonly found on the Earth’s surface, and air currents entering and circulating within caves can distribute spores from the outside environment. It has also been suggested that the presence of fungi in caves is an indirect consequence of the entry of organic matter vehicled by cave animals, human visitors, and airborne spores from outside ( Martin-Pozas et al, 2022 ). Fungi are not distributed evenly throughout caves, being commonly associated with organic debris and cave fauna.…”