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Science

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General scientific background about the caverns

Ongoing studies

Previous studies

How to do research in Kartchner Caverns

General scientific background about the caverns

Cavern Formation

It all began with a few drops of water. A shallow inland sea covered this area 330 million years ago, depositing layers of sediment and fossils that eventually hardened into limestone, known as the Escabrosa limestone. Over the last 10-15 million years, this Escabrosa limestone, along with other rock layers, uplifted to form the Whetstone Mountains. However, a block of the Escabrosa limestone and other associated rock layers was dropped down via a fault thousands of feet below the peaks of the mountains above. Kartchner Caverns eventually formed in this down-dropped block of limestone and other sedimentary rocks.

Rainwater, made slightly acidic by absorbing carbon dioxide from the air and soil, penetrated cracks in the down-dropped limestone block, mixed with groundwater, and slowly dissolved rooms and passages. Later, groundwater levels lowered, and some of the rock ceilings collapsed (forming piles of “breakdown”) leaving behind vast air-filled rooms.

Once the rooms were filled with air, water slowly dripping into the cave began to deposit a wide variety of decorations, called “speleothems,” over hundreds of thousands of years. Water seeping from the surface dissolves minerals on its trip through the limestone. When the drop enters the cave, it can lose its carbon dioxide and deposit a tiny mineral load. Over time, these minerals have created the beautiful speleothems and variety of colors found in the cave. Kartchner Caverns is a “living” cave; the formations are still growing!

Bats

During the summer, the cave's Big Room serves as a nursery roost for over 1,000 female cave myotis  (Myotis velifer) bats. The pregnant females return to Kartchner Caverns around the end of April, where they give birth to a single pup in late June/early July. The babies remain in the roost each evening while their mothers forage for insects outside the cave. Over their 5-6 month residence, the colony consumes about half a ton of insects, consisting of moths, flying ants, beetles, mosquitoes, and termites. Mothers and their offspring will leave mid-September, to begin their migration for their winter hibernation roost.

The presence of bats in Kartchner Caverns means the cave ecosystem has a steady supply of fresh nutrients every summer. After returning to the bat roost from their nightly forays, the bats excrete waste, forming large guano piles. Most of the other life forms found in the cave depend on these guano piles for their food. Fungi and bacteria consume the guano first. These are in turn eaten by nematodes, mites, isopods, amphipods, and book lice. These are then eaten by spiders, scorpions, mites, millipedes, and centipedes. Scavengers, like crickets and beetle larvae, clean up the leftovers. The bat guano provides the energy needed to run this complex food chain. For more information, read the feature story about bats.

Bats across the United States have recently come under threat from a fungal disease known as white-nose syndrome (WNS). First appearing in New York in 2007, the disease is caused by a fungus called Pseuogymnoascus destructans (Pd), which prefers cold, damp, and dark environments. The disease has been spreading from New York since 2007 and as of 2019 is found in 33 states and 7 Canadian provinces and the fungus has been detected in an additional three states with no confirmed disease yet.  As the fungus grows on the bats, it causes them to wake up more frequently from hibernation and depletes their finite resources. Bats die as a result of not being able to make it through hibernation. In some places, more than 90% of bats have died, totaling more than 6 million dead bats since 2019.

The spread of the fungus Pd is still being studied. Most scientists think the fungus is transmitted bat-to-bat, but there’s no reason to believe people can’t also accidentally spread it by moving infected dirt from one cave or mine site to another. For this reason, since 2018 all visitors to Kartchner Caverns have been asked whether they are wearing the same shoes as they wore in another cave or mine. If so, the rangers will spray down their shoes with a 70% rubbing alcohol solution. If you are going into caves or mines, please follow recommended decontamination protocols developed and tested by the US Fish & Wildlife Service: https://www.whitenosesyndrome.org/static-page/decontamination-information.

Are the bats of Kartchner Caverns at risk from WNS?

The fungus that causes WNS prefers colder caves than Kartchner Caverns. Currently the closest sites with Pd are in Texas. However, as recently as 2018, Myotis velifer bats, like the ones we have in Kartchner Caverns, were shown to develop the full-blown WNS from an infection of Pd. This means our bats could pick up the fungus here or elsewhere, then carry it back to their hibernaculum in the mountains to the south of the park. If this happens, they could die off at their hibernation site and not come back one summer. We are tracking our bat colony through the work of our bat biologist, and we’ve started an extensive acoustic bat monitoring program to track the other bat species that use the park. Not many treatments have proven effective to kill off WNS yet, so the best we can do is protect the bat colony and the caverns as habitat for our bats as they face this serious threat.  

To view the most up to date map of the spread of white-nose syndrome, please visit the site: www.whitenosesnydrome.org

Paleontology of the cave

While exploring the cave, paleontologists, those who study prehistoric life, uncovered an 86,000-year record of the local faunal community. The finds included the following: skeletons of an 86,000-year-old Shasta ground sloth, a 34,000-year-old horse, and an 11,000-year-old bear, as well as terrestrial snails, a clam, a toad, lizards, rabbits, snakes, a coyote, a ringtail, and many species of rodents. These discoveries have lead paleontologists to declare Kartchner Caverns a treasure house of information on the local fossil history of the uplands around the San Pedro River Valley.Back to top

Ongoing studies

Dripwater hydrology of Kartchner Caverns, with Jonathan King, University of Arizona

Kartchner Caverns is known for being a very humid (>99% humidity) cave, despite the outside desert air being very dry (often a humidity of less than 6%). Aboveground, we have two rainy seasons—winter rains are slow and soaking, whereas our summer monsoon from July-Sep brings high intensity thunderstorms. Since 2011, we have been studying drip water in the cave. How does water get into the cave? How long after it rains on the surface does the water get into the cave? How much does summer rain vs. winter rain contribute to the water balance of the cave? How does the water chemistry affect the growth of cave formations such as stalagmites? These and other questions we hope to be able to answer using detailed analyses of water chemistry over approximate 7 years of drip water collection. Additionally, we have developed a gamified model of stalagmite growth that responds to differences in cave environment and water chemistry. We hope this model will help us understand cave formation growth and help interpret the process for speleothem growth for all visitors.

Cave air carbon dioxide variability and Kartchner Caverns ventilation, with Dr. Kevin Webster, University of Arizona

Carbon dioxide (CO2) concentrations in natural caves trend higher than atmospheric concentrations. CO2 sources include dripwater degassing, soil CO2 diffusion, organic matter decay, geothermal outgassing, and tourism; sinks include mixing with atmospheric air. Cave ventilation is thought to be controlled by air density, driven by seasonal changes in temperature/pressure relative to cave air. Kartchner Caverns is a show cave in southern Arizona that exhibits annual CO2 concentration cycles with highs in August/September and lows January. Kartchner Caverns hosts 134,000 visitors every year and holds multiple tours per day that could influence CO2 concentrations at higher frequencies than the routinely collected biweekly monitoring data. Thus, we used a single Omega AQM-100 CO2 meter to obtain high-resolution snapshots of CO2 concentrations in four key locations. Although our data are as yet insufficient to comment on the impact of tourism, we observed a strong correlation between ventilation and average surface wind speed but not temperature/pressure as measured by an on-site weather station. This suggests that an air density gradient created by temperature/pressure variability may prime the cave air system, but the addition of wind allows for more significant ventilation than by simple diffusion alone. Windiness may increase in southern Arizona with global change, which may lead to more frequent or deeper ventilation of Kartchner Caverns, suggesting active management of humidity levels into the future may be necessary.

Trace Elements in mud of Kartchner Caverns, with Stephan R. Hlohowskyj, Central Michigan University

Trace elements (e.g., Fe, Mn, Ti, Cr, Mo) are essential for life on earth, however their availability in extreme environments, like caves, could be a limiting factor for ecosystem growth and health. Our research aims to measure trace elements distribution in cave muds and formations to better understand how these elements might be concentrated, transformed, and used within the cave system. Additionally, our objective is to better characterize the elemental ‘fingerprint’ of new minerals such as calcite, aragonite, and clays that form within Kartchner.

Photofluorescence of speleothems with Tom Kaye, Foundation for Scientific Advancement

This is an exploratory study. We are using lasers to force formations to fluoresce (not usually enough to see, except on film), which allows us to develop hypotheses about why different formations fluoresce differently--is it mineralogy? Is it microbes? Is it chemistry of the water? etc. This kind of study often opens up new research directions in the future.

Effective cave and karst conservation messaging, with Dr. Rebecca Niemiec, Colorado State University, Ft. Collins

Recent research has shown that the manner in which environmental conservation is presented to different audiences affects how people behave. That is, depending how people learn about conservation, they may be more or less likely to engage in conservation-friendly behaviors such as recycling, using less water, driving less, etc. Kartchner Caverns State Park is partnering with Dr. Rebecca Niemiec, from Colorado State University, to conduct conservation psychology research in the park. Through our research, we are examining how different messaging strategies influence tourists' non-compliant behavior (i.e. touching the cave) and willingness to report non-compliant behavior to minimize damage to cave ecosystems. After the first phase of the study focused on not touching in the cave, we will study whether the way we talk about caves, karst, and water on our cave tours is the effective at encouraging people to change their behaviors after their cave tour experience. Our hope is that the simple act of discussing cave/karst/water conservation in a specific way will lead people to see the value of conserving these resources in the long term.

Bats, with Debbie Buecher, Buecher Biological Consulting

Kartchner Caverns Cave Unit is involved in a wide variety of bat-related conservation and research. Primarily, we do weekly bat counts of our colony size during the summer months from April-October, to track the health of the colony. With bat biologist Debbie Buecher in 2018 we re-started a microchipping project where we inject Passive Integrated Transponder (PIT) tags into the bats to be able to tell when they fly in and out of the cave.

We also contribute to the North American Bat Monitoring Program through our acoustic bat call recording project, and we keep track of when different species of bat-pollinated plants are blooming for the Flowers for Bats Campaign with the National Phenology Network.

Other Partnerships

In addition to the above projects, we also run an iNaturalist Project, and we partner with the Southwest Monarch Study and the Western Monarch Working Group to protect our monarch butterfly populations and the American Kestrel Partnership to protect kestrels using our land.Back to top

Previous studies

Kartchner Caverns Macro-Invertebrate Project

The Kartchner Caverns Macro-Invertebrate Project is a collaborative research venture among Arizona State Parks, the University of Arizona Insect Collection, and scientists and educators at a number of other institutions. Project research includes study and documentation of the biology and ecology of macro-invertebrates occurring within Kartchner Caverns State Park.

The project provides information to Arizona State Parks and supports a science-based approach to management and preservation of this remarkable and irreplaceable publicly-owned resource. We also support public outreach to further understanding and appreciation of the fascinating and often unique, endemic arthropods occurring within the park. The initial focus of our studies is on macro-invertebrates living in the cave, but studies involving surface invertebrates will eventually be integrated into project efforts.

Kartchner Caverns: A Living Microbe Laboratory

By Shelley Littin, NASA Space Grant intern, University Communications

In a hole in the ground, there lives a microbe. Actually, there live several microbes. What are they and how do they survive in conditions practically devoid of resources or other forms of life? Doctoral candidate Marian Ortiz in the University of Arizona's department of soil, water and environmental science is trying to find out.

Photo right: Doctoral candidate Marian Ortiz in the UA's department of soil, water and environmental science samples microbes that live on the surface of stalactites and other mineral deposits in Kartchner Caverns.

Her study site is Kartchner Caverns, designated a National Science Foundation Microbial Observatory in 2006. Ortiz's findings indicate that some of the cave-dwelling microbes could produce compounds with antimicrobial and antifungal properties. If so, the microbes could be a valuable resource for substances to help fight new diseases and pests.

In the first extensive genetic survey of microbes living in Kartchner Caverns, UA doctoral candidate Marian Ortiz has shown that some of the cave-dwelling microbes may have anti-microbial and anti-fungal properties.

Bacterial Poster

An inter-agency study examined variations in bacteria on the various formation at Kartchner Caverns. Download poster (below) to learn more.

Abstract: Kartchner Caverns is a 3.9 km long wet living carbonate cave in the southwestern USA near Benson, Arizona. The cave represents an oligotrophic environment with high humidity (average 99.4 percent) and elevated CO2. Because of its unique geology, Kartchner Caverns contains minerals from six different chemical classes: carbonates, sulfates, oxides, nitrates, silicates and phosphates, and is considered as one of the top 10 caves in the world in terms of mineral diversity. Furthermore, Kartchner is also characterized by its variety of speleothems (secondary mineral deposits). In 2006, the cave was added to the National Science Foundation’s Microbial Observatory Program. One goal of our studies in Kartchner is to characterize the heterogeneity of bacterial communities on speleothems. The objective of this study was to explore both, intra- and inter-speleothem variability in the bacterial community structure. Ten different formations located in a single cave room within an area of approx. 10 m (length) x 2 m (width) were examined. A chemical element profile of a surface sample scraped from each formation was performed using ICP-MS analysis. The analysis revealed differences in the elemental content of the ten formations. Bacterial DNA community fingerprints were generated from each speleothem using DGGE analysis of PCR-amplified 16S rRNA gene fragments. The intra-speleothem analysis revealed that the community profiles from the same formation are more similar to each other than to profiles from different speleothems. For the inter-speleothem analysis, bacterial community clusters were observed that appear to be influenced by the spatial location of the formation in the room.

Bacterial and Archaeal Community Structure of Two Adjacent Calcite Speleothems in Kartchner Caverns, Arizona, USA

Approximately 20 percent of the earth’s dry ice-free surface is composed of karst terrain (Ford and Williams 2007) with sinkholes and caves being typical features of these regions. Kartchner Caverns, one of the world’s 10 most interesting caves from a mineralogical standpoint (Hill and Forti 1997), is a 3.9 km long cave developed into a block of Escabrosa Limestone (Lower Carboniferous) in the Basin and Range of southeastern Arizona (Jagnow 1999). The relative humidity inside the cave averages 99.4 percent. The atmospheric CO2 is elevated (varying seasonally from approx. 1,000 to over 5,000 ppm) and the mean average temperature throughout the cave is 19.8 degrees C.  (Buecher 1999).

Culturable Microbial Diversity and the Impact of Tourism in Kartchner Caverns, Arizona

Kartchner Caverns in Benson, Ariz., was opened for tourism in 1999 after a careful development protocol that was designed to maintain predevelopment conditions. As a part of an ongoing effort to determine the impact of humans on this limestone cave, samples were collected from cave rock surfaces along the cave trail traveled daily by tour groups (200,000 visitors year–1) and compared to samples taken from areas designated as having medium (30–40 visitors year–1) and low (2–3 visitors year–1) levels of human exposure. Samples were also taken from fiberglass moldings installed during cave development. For more information, visit SpringerLink.

Kartchner Caverns Microbial Observatory

In 2006, Kartchner Caverns was added to the National Science Foundation's worldwide network of Microbial Observatories. The goal of the Microbial Observatories program is to study and describe the phylogenetic (who is there) and functional (what do they do) diversity of microbial communities on the beautiful formations found in the cave. Kartchner Caverns is the only cave in the network. The Kartchner Caverns Microbial Observatory is a collaboration between the laboratories of four investigators at the University of Arizona: Dr. Raina Maier, Dr. Leland S. Pierson III, Dr. Barry M. Prior, and Dr. Rod Wing.

Mycology Science & Research Brief

Joe Vaughan

Joe Vaughan samples a sizeable guano deposit in the Big Room. This pile, covered with a fungal-rich layer, was deposited last summer by cave Myotis (mytosis velifer).

Some of you may know that mycology is the study of fungi. However, did you also know that even though all molds are fungi, not all fungi are molds? So, we invite you to stay tuned on this project and others taking place at Kartchner Caverns State Park that support the park’s mission for continuing discovery, promoting science-informed and adaptive cave management, building advocacy for conservation and education, and showcasing only a portion of a more extensive and beautiful cavern system that is so worth protecting.

This recent mycology program is in partnership with graduate student, Joseph Vaughan, who is working under the direction of Dr. Barry Pryor from the Department of Plant Sciences at the University of Arizona. Although micro-fungi make up an essential portion of the microbial population in many ecosystems, not enough is known about the different types, distributions, life cycles, and intricate linkages that fungi play in caves and their supporting surface environments. Kartchner Caverns, having been developed and maintained in order to protect a range of biological communities, provides an excellent laboratory venue to examine microscopic cave-inhabiting microbes and fungi in a nearly pristine environment. This project proposes to investigate fungal communities living in association with bat guano, an essential nutrient source for many cave ecosystems. In addition to exploring the species richness of fungi living on or near the guano, this project will examine fungal community diversity and life cycle changes across a gradient from the Sink Hole entrance of the Big Room complex, where our bats raise their young during the summer months. The project will address questions about the source of various fungi in Kartchner Caverns and how these fungi are distributed through the cave. The idea is to learn if types and locations of different fungi in the cave are constrained to only bats as vectors, to learn if and why fungal types vary in their distribution on the piles and throughout the cave, and if locations and growth vary in time and space check out Joseph's research brief.

Controlling and quantifying lampenflora in show caves: a cave study from Kartchner Caverns State Park, AZ, USA

Undergraduate intern Colleen Birmingham joined us in 2018 to undertake a study on different methods to control lampenflora (algae) that unnaturally grows in caves. This is an abstract from her work, which she was able to present at the Geological Society of America meeting in Fall 2018:

Show caves (caves developed for tourism) around the world are frequently susceptible to colonies of phototrophic organisms known as lampenflora due to high humidity and artificial lighting. Algae is one particularly common type of lampenflora, as it thrives in the wettest areas of show caves that are frequently and heavily lit. These organisms have the potential to damage cave formations and prevent further speleothem growth as well as pose a threat to delicate cave ecosystems. Currently, there is no clear agreement on which method is the most eco-friendly and efficient for treating and removing algae from show caves. Similarly, there are not many highly accurate methods to measure the effectiveness of different treatments on a particular patch of algae, other than visual comparisons. As a result, this study was designed to test five different chemical and physical solutions (chlorine bleach, oxygen bleach, 3% hydrogen peroxide, 12% hydrogen peroxide and an industrial heat gun) on five algae populated areas throughout the mined tunnels of Kartchner Cavern State Park, located in southern Arizona. Following four weeks of treatments, we were able to quantify the success of algae removal for each method tested by using geographic information systems software, ArcMap. The most successful treatment was 12% H2O2, applied for thirty minutes then rinsed with zero-chlorine water.Back to top

How to do research in Kartchner Caverns

Many different disciplines of science are useful for the scientific study of caves, or “speleogy.” If you are interested in partnering with Arizona State Parks and Trails on a research study in or around Kartchner Caverns, please contact Cave Resource Manager, Dr. Sarah Truebe at (520)-586-4111 to begin the process. Back to top