High-intensity tourism activities can cause a significant increase in cave air CO2 concentration, thereby affecting the cave micro-environment and secondary carbonate deposition in these environments. During the 2023 National Day Golden Week, high-frequency continuous monitoring of cave air CO2 partial pressure (PCO2(A)) and visitor numbers was conducted in Dawang Cave, Anhui Province. Wavelet transform and cross-correlation analyses were used to reveal the multi-scale response characteristics of CO2 concentration to tourism activities. The results show that: (1) PCO2(A) exhibited clear diurnal variations (higher during the day, lower at night) and decreased spatially with enhanced ventilation, controlled jointly by cave morphology, ventilation conditions, and tourist activity. (2) Wavelet periodicity analysis revealed that all three monitoring sites (DW1# near entrance, DW2# rest area, DW3# deep chamber) showed a 24-hour diurnal period, but with different intensities; DW2# exhibited a distinct semi-diurnal period during the peak tourist period, while DW3# showed longer-period (>48 h) signals. (3) Coherence spectrum analysis indicated that the coherence coefficient between CO2 and visitor numbers at the diurnal period exceeded 0.6 for all three sites (p<0.05), with the highest value (>0.8) at DW2#. (4) Cross-correlation analysis showed that the lag time of CO2 behind visitor numbers during the peak tourist period was 3-6 h (DW1#: 6 h, DW2#: 3 h, DW3#: 5 h), whereas the full-period average lag was as long as 54-72 h, the latter being controlled by a "memory effect" during off-peak hours. This study provides a scientific basis for assessing environmental carrying capacity, visitor management, and sedimentary landscape protection in tourist caves.
'Fossil' cave pearls in the Fairgrounds Room of Fort Stanton Cave form two distinct layers in a flowstone sample, FS-14-2. The flowstone in the Fairgrounds Room covers a mud-silt bank and the extinct streambed that extends across the room. Uranium-series dates of two pieces of flowstone from this room, one piece from the higher end of the flowstone (FS-14-1, devoid of pearls), and another piece from the lower end of the flowstone (FS-14-2, rich in pearls), show that the flowstone was deposited during the Last Glacial period (60,000 to 11,000 yr BP). The two cave-pearl layers in FS-14-2 yielded U-series ages of 31,132 +/- 305 and 31,682 +/- 608 yr BP for the older layer and 26,441 +/- 295 yr BP for the younger layer. A uranium-series date on the thin layer of gypsum that coats the flowstone shows that the gypsum was deposited during the warmer and effectively drier later Holocene. The cave pearls formed along the lower extent of the flowstone in a flat cave-floor setting suitable for cave pearl formation. A vast majority of the pearls are restricted to two layers, which seems to suggest that climate was the driver, where wetter-than-normal glacial climate similar to 31,500 and similar to 26,700 yr BP resulted in increased dripping from the ceiling and greater water flow and flow variability on the flowstone. Cave pearl growth coincides with Glacial Stadials GS-5.2 and GS-3, respectively, suggesting that the glacial stadials delivered greater effective moisture to the region.
There is currently limited knowledge of the biological communities inhabiting cave ecosystems in South America. This study examines the vertebrate community composition of 21 caves across diverse subterranean ecosystems in Colombia using environmental DNA (eDNA) analysis. Water was collected from water bodies inside caves and subterranean systems in six of the eight speleological regions of Colombia in eight departments. Water was filtered manually through a 0.8 m pore size filter and preserved with Longmire solution. A 170-base pair (bp) fragment of the 12s mitochondrial gene specific for vertebrate identification was amplified by PCR and sequenced by Illumina (metabarcoding). Data corresponding to 208 OTUs were obtained from 21 caves or subterranean ecosystems. In total, 33 orders, 56 families, 81 genera, and 110 species were detected. Thirteen orders, 22 families, 31 genera, and 51 species of fish were identified, with Trichomycterus being the most representative genus. For tetrapods, 20 orders, 34 families, 50 genera, and 59 species were identified, where the bird genus Steatornis was the most commonly detected. For fish, the predominant orders were Siluriformes and Characiformes, with Loricariidae being the family with the highest detection. In the case of tetrapods, the most prevalent orders were Anura, Rodentia, and Chiroptera and among these taxa, the most numerous families corresponded to Leptodactylidae, Cricetidae, and Phyllostomidae, respectively. Environmental DNA proved to be an effective tool to quickly obtain information on diversity in areas that are difficult to access and sample, such as underground systems, allowing identification of difficult to detect species by traditional observation methods in these systems.
Cave ecosystems host specialized phototrophic biofilms structured primarily by light availability, yet quantitative assessments of aerophytic microalgal community organization in tropical limestone caves remain limited. This study investigated spatial variation in the structure of aerophytic microalgal communities across fourecologically distinctzones (entrance, transition, penetration, and low light) of Gua Tempurung, Malaysia. Stratified sampling was conducted during three seasonal periods. Dominant phototrophic morphospecies were identified using microscopy, and community composition was analyzed in relation to key environmental variables. Twenty-three dominant microalgal morphospecies were recorded across the cave gradient. Cyanobacteria constituted the major component of both richness and abundance, followed by chlorophytes and other algal groups. Community composition differed significantly among cave zones and was strongly associated with light intensity, which delineated distinct photic habitats. Species richness exhibited a unimodal response along the light gradient, with peak values observed at intermediate irradiance levels (similar to 15.0 mu mol/m(2) & times; s). Multivariate analyses indicated clear compositional turnover from illuminated entrance regions to low-light interior zones (PERMANOVA: F = 8.47, p = 0.001, R2 = 0.76), reflecting strong environmental filtering driven primarily by light availability and moisture conditions. Artificial illumination associated with tourist infrastructure created locally modified microhabitats that supported additional phototrophic taxa relative to naturally dark areas, underscoring the ecological consequences of cave lighting. Together, these findings demonstrate that light availability is a primary driver of aerophytic microalgal community structure and zonation in this tropical limestone cave and provide a baseline ecological framework for future integrative studies of cave phototrophic systems.
Coming from over 10 years of experience in cave monitoring in northeast Italy, Gruppo Speleologico Talpe del Carso, has designed Riki and Dolphin: customizable, low cost, and easy to assemble tools for getting real time data transmission from the bottom of a cave, even underwater, to a webserver. Their use has been tested to monitor air temperature inside the Abisso Bonetti Cave (Classical Karst, Italy), proving for the first time that a cave in Gorizian Karst can systematically be colder than the outdoor temperature even in winter, recording an internal temperature even lower than 0 degrees C. The Dolphin device can be installed hundreds of meters deep inside a cave, transmitting data with standard Modbus protocol over an Ethernet cable to Riki, the external ground station, which also supplies power to the entire system with a battery that lasts many months. Riki then sends data through the LoRaWAN network (with a Dragino transmitter) straight to a webserver for data collection and visualization in real time (using Grafana). This allows cavers to enter the cave once and then get data every few minutes ideally forever. The Riki-Dolphin-Dragino-Grafana is a fully integrated solution, where each step is documented and released as Free Open-Source hardware and software.
