Cave Guano Research Articles

Past anthropogenic impacts revealed by trace elements in cave guano

Natural and human-induced toxic elements can accumulate in the environment, posing significant risks to human health and ecosystems. This study explores cave bat guano, an unconventional and relatively under-researched environmental repository, to reveal historical pollution trends and sources. Through trace elements analysis of a 1.5-m-thick guano deposit from Zidită Cave (Romania), we track changes in mining and metallurgy from 1000 CE–2012. We identified substantial pollution primarily from porphyry copper and Au–Ag–Te mines, but also impacts from usage of leaded gasoline and agricultural practices. Our record shows disruptions caused by the Bubonic plague around 1250 CE and a major surge ∼ 1500 CE. After the decline triggered by the European silver market collapse in 1525 CE, our study reveals a brief mining revival. This resurgence was followed by a continuous decline lasting until the early 1800s, driven by socio-economic upheavals and recurrent outbreaks of the bubonic plagues. The Industrial Revolution sparked prolonged growth that lasted until 1989 CE, only briefly interrupted by the Great Depression and World War II. Consequently, cave bat guano proves to be a critical resource for understanding spatial pollution patterns, both locally and regionally, and for identifying specific pollution sources.

Rates of diagenesis of tropical insectivorous bat guano accumulations: implications for potential paleoenvironmental reconstruction

Cave guano deposits are increasingly being recognized as valuable repositories of paleo-climatic and paleo-environmental information. However, that value is constrained by rates of guano decomposition, and these rates have not been previously well-studied. Here we show that field and laboratory studies of deep insectivorous bat guano sequences in the caves of Borneo demonstrate the extreme dependence of decomposition rate on guano water content. Under tropical conditions, moist guanos exhibit decomposition coefficients (k) values of ~ 0.01, implying the loss of most of the organic content on decadal timescales. Under similar temperatures but drier conditions, k values drop to ~3 x 10-6, permitting significant organic (chitin) content to persist for tens of thousands of years. One of the implications of these findings for paleo-environmental records older than the limit of carbon dating is that a value for k can be calculated based on a single carbon date, which then allows an estimate of likely age at base of deposit.

Insights into the cultivable microbiota of Isverna cave guano deposits

Insights into the cultivable microbiota of Isverna cave guano deposits

Climate and vegetation and their impact on stable C and N isotope ratios in bat guano

Cave guano deposits represent a relatively untapped paleoecological archive that can provide information about past vegetation, climate, and bat diet over several millennia. Recent research suggests that carbon isotope values (δ13C) measured in guano accumulations from insectivorous bats reflect the relative abundance of C3 and C4 plants on the landscape while nitrogen isotope values (δ15N) may reflect precipitation amount. Together, these proxies can provide useful information for restoration practitioners seeking to understand how plant species composition has changed over time in relation to climate and land use. To better calibrate these proxies for use in restoration, we compared instrumental records of precipitation and satellite imagery of vegetation with isotope values measured in modern bat guano from Mary Lawson Cave, a large limestone cavern located in central Missouri. Mary Lawson Cave hosts a maternity colony of insectivorous gray bats (Myotis grisescens), and as such, contains significant guano accumulations. In the fall of 2018, we collected a 60 cm long guano core that dates to 1999 cal AD at its base. Guano core δ13C values decrease from the base toward the surface (from ~-26 to -27‰) whereas δ15N values increase toward the surface even after accounting for ammonia volatilization (from ~3 to 5‰). Presently, the landscape around Mary Lawson Cave is dominated by a deciduous forest and pasture. Given that the land cover has changed very little over this period, the decline in δ13C values toward the present likely reflects a shift in land management on farms and/or increases in invasive C3 species. Rainfall amounts from nearby Lebanon, Missouri, are significantly positively correlated with guano δ15N values, a relationship that is notably opposite that observed previously in soil and plants. We argue that heavy fertilizer application and significant grazing intensity could lead to the accumulation of large pools of excess labile nitrogen which would be vulnerable to leaching during precipitation events. The relationship between guano δ15N values and precipitation may differ for materials from less agriculturally impacted locations or periods and should be extended into the past with caution.

Tropical environmental change in North Sumatra at the Last Glacial Maximum: Evidence from the stable isotope composition of cave guano

Insular Southeast Asia is of critical importance to global biodiversity, climate, and socioeconomics. Past environmental histories are a crucial factor influencing contemporary patterns and, in this region, fluctuating sea-level and climate change during the Last Glacial Period (LGP) resulted in drastic changes in both land extent and vegetation cover. However, understanding the past environments of this tropical region is hampered by its sheer size and relative lack of traditional continental proxy records, such as lake sediments. To provide further insight into the response of vegetation to the changing environmental conditions, we use the stable carbon isotope composition (δ13C) of a bat guano sequence from Liang Mbelen Cave in North Sumatra, to determine whether tropical grass (C4 vegetation) or forest (C3 vegetation) was present in the area from c. 30 to 10 cal kyr BP. Our results confirm the presence of C4 vegetation during the LGP; however, we find that the timing of grass expansion was just prior to the Last Glacial Maximum (LGM; 23–19 kyr BP). Comparing Liang Mbelen with the other evidence from across the region, we find a generally consistent pattern of peak tropical grasses often occurring prior to the LGM in Sundaland, with the timing of forest encroachment variable, although beginning at c. 25 cal kyr BP. We find that the timing of the shift from savanna to forest systems in Sundaland is similar to changes in obliquity, likely resulting in a decrease or elimination of the dry season that favoured forest expansion. Understanding past vegetation history will help the management and protection of the fragile and ecologically valuable ecosystems of SE Asia.

Nontuberculous Mycobacteria Prevalence in Bats' Guano from Caves and Attics of Buildings Studied by Culture and qPCR Examinations.

A total of 281 guano samples were collected from caves (N = 181) in eight European countries (Bulgaria, Czech Republic, France, Hungary, Italy, Romania, Slovakia and Slovenia) and attics in the Czech R. (N = 100). The correlation of detection of mycobacteria between Ziehl–Neelsen (ZN) microscopy and culture examination and qPCR was strong. ZN microscopy was positive in guano from caves (58.6%) more than double than positivity in guano from attics (21.0%; p < 0.01). From 89 mycobacterial isolates (73 isolates from cave guano and 16 isolates from attics’ guano), 68 (76.4%) isolates of 19 sp., ssp. and complex were identified as members of three Groups (M. fortuitum, M. chelonae, and M. mucogenicum) and four complexes (M. avium, M. terrae, M. vaccae, and M. smegmatis). A total of 20 isolates (22.5%) belonged to risk group 1 (environmental saprophytes), 48 isolates (53.9%) belonged to risk group 2 (potential pathogens), and none of the isolates belonged to risk group 3 (obligatory pathogens). When comparing bat guano collected from caves and attics, differences (p < 0.01; Mann–Whitney test) were observed for the electrical conductivity, total carbon, total organic, and total inorganic carbon. No difference (p > 0.05; Mann–Whitney test) was found for pH and oxidation-reduction potential parameters.

Geochronological implications of 210Pb and 137Cs mobility in cave guano deposits

Some recent publications on the paleo- and historical environmental interpretation of bat guano sequences have relied on 210Pb and 137Cs distribution to establish age-depth models, even when these are at odds with radiocarbon models in the lower parts of the sequence. Here, we present both field and laboratory evidence for the unpredictable mobility of lead and cesium in decomposing bat guano deposits. We suggest that 210Pb- and 137Cs-based chronologies of bat guano deposits should only be used when independently supported, for example, by a robust radiocarbon age-depth model.

A review of the magnetic susceptibility of guano deposits in caves

The study of environmental magnetic methods using magnetic susceptibility parameters in cave guano deposits has not been widely discussed, especially in Indonesia. This method is relatively inexpensive, fast, affordable, and non-destructive. Environmental magnetism is associated with environmental changes such as climate change and anthropogenic effects. After a brief introduction to the fundamental of environmental magnetism, we describe several case studies regarding the properties of magnetic minerals and magnetic grains. This study was complemented with XRF results to identify the elemental composition.

Improved pretreatment method for the isolation and decontamination of pyrogenic carbon for radiocarbon dating using hydrogen pyrolysis

Abstract Pyrogenic carbon (charcoal, black carbon, elemental carbon) is one of the most common materials used for radiocarbon dating of terrestrial samples. However, exogenous carbon contamination can compromise the accuracy of radiocarbon ages. This study presents the results of two chemical pretreatments prior to hydrogen pyrolysis (hypy) as improved protocols for the isolation and decontamination of pyrogenic carbon, i) a simple acid-oxidation step (A-Ox/hypy) and ii) acid-base-acid (ABA/hypy). The A-Ox/hypy protocol uses HNO3 and H2O2, while ABA/hypy uses HCl and NaOH. Both pretreatments remove labile and inorganic carbon before hypy, decreasing the potential for in situ production of pyrogenic carbon during the hypy reaction. The effectiveness of each protocol was directly measured on charcoal artificially produced at 350 °C, 450 °C and 550 °C from radiocarbon-free wood, and exposed to environmental contamination for 1–3 yrs. The results show a >94% reduction in carbon contamination for the 450 °C and 550 °C charcoal samples occurred using A-Ox/hypy, but this treatment was less effective for the 350 °C charcoal. A >99% reduction in carbon contamination in all charcoal samples examined occurred using ABA/hypy. The A-Ox/hypy protocol was further tested on cave guano sediments, which had previously reported erroneous dates following simple organic solvent extraction followed by ABA pretreatment. Effective decontamination was achieved using A-Ox/hypy on the guano, which corrected a radiocarbon age reversal. Overall, ABA/hypy effectively decontaminated the charcoals and was a more efficient pretreatment for charcoal than A-Ox/hypy, however resulting in larger sample mass loss. Therefore, ABA/hypy is the recommended protocol for older (>30,000 14C yr BP) charcoal or sediment samples, or where date accuracy is imperative, while A-Ox/hypy represents an improved protocol for the quick and cost-effective measurement of younger samples (

Using ratios in cave guano to assess past environmental changes

Abstract Stable isotope ratios of cave bat guano reflect environmental influences at the soil and plant level within the foraging range of the bats. Carbon, nitrogen and hydrogen isotopes have utility in reconstructing precipitation and temperature as well as in tracing the influence of large-scale atmospheric circulation and climate variability. Guano-derived stable isotope time series have been demonstrated to effectively provide high-resolution records of palaeoenvironmental variation from the late Pleistocene to present. Owing to their influence on these isotopes, factors such as bat ecology, species foraging range and site location must be considered when interpreting such records. Research analysing the isotopic composition of guano has provided a highly resolved history of vegetation and climate dynamics previously less understood. In this chapter we discuss the factors influencing the δ 13 C, δ 15 N and δ 2 H values in guano and provide an up-to-date review of cave guano as palaeo-climate archive.

Guano-related phosphate-rich minerals in European caves

Guano is a typical deposit found in caves derived from the excretions of bats and in minor cases of birds. These organic deposits decompose and form a series of acid fluids and gases that can interact with the minerals, sediments, and rocks present in the cave. Over sixty phosphates are known and described from caves, but guano decay also often leads to the formation of nitrates and sulfates. In this study twenty-two European caves were investigated for their guano-related secondary minerals. Using various analytical techniques, seventeen phosphates, along with one sulfate (gypsum), were recognized as secondary products of guano decay. Among those minerals, some are very rare and result from the interaction of guano leachates with clays, fluvial deposits, or pyrite. Some of these minerals are even found only in the studied caves (spheniscidite, robertsite). The most common minerals belong to the apatite group. The common mineral association present in fresh decaying guano is brushite-ardealite-gypsum, minerals that usually are not present in older deposits because of their higher solubility. Most minerals are in hydrated form because of the wet cave environment; however, some specific dry conditions may favor the presence of dehydrated minerals, such as berlinite, formed during guano combustion. Investigation on the acidity of guano piles shows pH values as low as 3.5 with an increase of acidity with age and depth. Finally, cave guano deposits should be better studied in the future because of their role in paleoenvironmental and paleoclimatic reconstructions and because it is important to better understand the origin of guano-related minerals, especially the phosphates and sulfates. Among all of the caves studied, Corona ’e sa Craba (Italy) and Domica-Baradla Cave (Slovakia-Hungary) are considered to be outstanding sites with respect to their phosphate mineralogy.

Mineralogical and organic study of bat and chough guano: implications for guano identification in ancient context

The mineralogical and geochemical evolution of cave guano deposits in France has been investigated in detail. Two test pits were excavated in guano mounds from insectivorous bats and one in a guano mound from omnivorous choughs. Both bats and choughs are thought to be among the main accumulators of guano during the Pleistocene in southwest France. Thin section analysis, mineralogical identification and quantification, geochemical analysis, organic matter characterization through pyrolysis and thermochemolysis coupled to gas-chromatography, were conducted to better understand the evolution of guano in caves and to identify the underlying factors. Bat guano undergoes mineralization through loss of organic matter and precipitation of phosphate and sulfate minerals. The neoformed minerals include gypsum, ardealite, brushite, francoanellite, hydroxylapatite, monetite, newberyite, and taranakite, and vary according to the local availability of chemical elements released by the alteration of detrital minerals due to acidic solutions. Chough guano, located at higher altitude in a periglacial environment, does not show similar mineral formation. Organic geo-chemical analysis indicates strong differences between guano. Abundant hydrocarbons derived from insect cuticles were the dominant feature in bat guano, whereas a mostly vegetal origin typifies chough guano. Geochemical analysis points to an especially high content of copper and zinc in bat guanos, a few hundreds of µg/g and thousands of µg/g, respectively. Both organic matter analysis and geochemistry may help identification of bat guano in archeological contexts , where phosphate minerals can originate from multiple sources.

Stable isotope composition of cave guano from eastern Borneo reveals tropical environments over the past 15,000 cal yr BP

Insular southeast Asia is a key driver for global atmospheric and oceanic circulation, is a hotspot for biodiversity and conservation, and is likely to have played a unique and important role in early human dispersals. Despite this, partially due to its vast size and remote tropical location, very few continuous palaeoenvironmental records exist, especially in eastern Borneo. Therefore, we investigated δ13C and δ15N values, and geochemistry of two cave guano deposits to reconstruct palaeoenvironments in eastern Borneo. Firstly, a profile was recovered from Gomantong caves, Sabah, reflecting a continuous deposit over ~15calkyrBP. Secondly, a profile was recovered from Bau Bau cave, East Kalimantan, that ranged from ~15–5calkyrBP. The geochemical signature of each deposit confirmed the material to be ancient guano. δ13C values revealed that a continuous dense rainforest persisted over at least the last 15calkyrBP around the Gomantong site that was relatively insensitive to regional climate change. By contrast, δ13C values at Bau Bau indicate that, although rainforest remained dominant in the record, a significant drying occurred between 7.7 and 6.3calkyrBP, with up to 25% grasses present. Although most regional models suggest that sea-level rise and increased Holocene insolation led to an increase in monsoonal moisture, we find some evidence of more regional variability, and that a reduction in monsoonal precipitation could have occurred. However, we cannot discount the implementation of an anthropogenic fire regime that opened the canopy allowing more grasses to occur.

A Late Holocene environmental history of a bat guano deposit from Romania: an isotopic, pollen and microcharcoal study

A 1.5-m-long core from a bat guano deposit in Zidită Cave (western Romania) has provided a 900-year record of environmental change. Shifts in δ13C values of bulk guano (between −22.6 and −27.5‰) combined with guano-sourced pollen and microcharcoal information show significant changes in the structure of vegetation and plant biomass. Cave guano δ13C values reflect the dietary preferences of bats which are controlled by local vegetation dynamics, which in turn depend on local climatic conditions. Neither δ13C values nor pollen association in guano changed strikingly over the Medieval Warm Period (MWP) and Little Ice Age (LIA) transition. Instead, an overall decreasing trend of δ13C values between ca. AD 1200 and 1870–1900 defines the duration of LIA. A shift toward cooler and wetter conditions at ca. AD 1500 noticed in the pollen record by an increase in Fagus sylvatica and Alnus and the decrease of Carpinus betulus, may indicate the first major change at the beginning of the LIA. Evidence for two major cold spells occurring around AD 1500 and ca. AD 1870 comes from both δ13C and pollen record. In between these events, the cave region experienced a warmer and drier climate but colder and wetter than the MWP, favouring the expansion of Quercus, Fraxinus and Tilia simultaneously with the decrease of F. sylvatica and Poaceae. Human impact in the studied area is mainly related to agriculture, grazing and deforestation. The effects are most pronounced after AD 1845 when the pollen of cereals increases and Zea is recorded (AD 1845). Higher percentages of microcharcoal particles in the guano sequence are generally correlated with agricultural activities like land cleaning via controlled fires.

The biogeochemistry of insectivorous cave guano: a case study from insular Southeast Asia

Cave guano derived from insectivorous bats and birds contain unique geochemical and mineralogical signatures. We investigated the mineralogy, pH, C, N and metal abundance patterns of cave guano spatially and temporally (with depth) along a W–E transect in Malaysia and Palawan from five remote cave sites, each housing large populations of bats and Aerodramus spp.(cave swiftlets). Guano deposits were rich in phosphate and/or sulphate minerals (e.g., gypsum, bassanite) with leucophosphite, spheniscidite, and variscite present in most profiles. Metal abundances measured from modern and ancient bat guano revealed high concentrations of transition metals relative to the local environment. Highly enriched metals, however, were associated with phosphate rather than sulphate minerals. Copper and Zn were enriched in all profiles, whereas other metals were associated with specific caves consistent with known local mineral resources. For example, Sn, Pb, and Rb were particularly enriched in Batu Cave, located in the Peninsular Malaysian granitic tin belt, whereas Ni and Cr were high in regions associated with ultramafic ophiolites and Ni-laterites found on Palawan.

Structure and interactions in a cave guano–soil continuum community

Bat guano represents an important food resource for cave-dwelling organisms, hosting up to entire communities in a single deposit. Sampling conducted in guano and its interface with the adjacent soil revealed a wide variation in physicochemical parameters (nitrogen, phosphorus, organic matter, pH and moisture) along that continuum. The invertebrate orders that showed the greatest abundance and species richness were: Mesostigmata, Sarcoptiformes and Trombidiformes, all belonging to subclass Acari. The results clearly showed that mite species are the most abundant group in guano deposits. Such species can directly or indirectly feed on this food resource. The abiotic factors of the guano significantly explained some community parameters. Furthermore, moisture was the parameter that best explained the abundance distribution for the most common mite species. Lastly, a trophic web of the most abundant species in the guano was devised based on literature data, interspecies correlation, preferences for microhabitats and abundance rates of the populations. It was possible to observe that the temporal changes in the guano deposit determine a successional process in the community, including the trophic web structure.

Palaeoenvironmental information from the palynology of an 800 year old bat guano deposit from Măgurici Cave, NW Transylvania (Romania)

Pollen analysis of a 270cm deep guano deposit from Măgurici Cave (NW Romania) was performed to understand the vegetation dynamics and the influence of deforestation and farming activities that unfolded in the Transylvania area over the past 800years. The study discusses the value of cave guano as a source of palaeoclimate data and tests if guano sequences record the same signals as other proxies (tree rings, speleothems, lakes or peat). The pollen record extracted from Măgurici Cave guano is consistent with the known vegetation history during the Late Subatlantic period, exhibiting two climate events: the Medieval Climate Anomaly and the Little Ice Age. Human influence on vegetation is also revealed, especially in modern times, by the decrease of arboreal pollen, the increase of herbaceous taxa related to grazing and the occurrences of cereals. Cave bat guano is emphasized as a source of valuable palaeoclimate data, especially in areas where no conventional archives are available.

How to sample the carbon isotopes of tropical ecosystems without leaving your armchair

Well-dated records of terrestrial environmental change in Southeast Asia spanning the past 50 kyr (kyr = 1,000 y) are few and far between. The problem is often one of preservation. Organic-based paleoenvironmental proxies in warm and wet tropical environments are often subject to severe microbial degradation processes rendering them unsuitable for radiocarbon (14C) dating. Notable exceptions to this problem include tropical speleothems, which can be dated using the 230Th method (1) and can provide information on the relative intensities of isotopically depleted Asian monsoonal rainfall back to ∼400 kyr ago (2). Speleothem records tell us little about the specific ecosystem responses to past rainfall and temperature changes, however. How can we tell how much rain is needed to maintain dense tropical rain forest as opposed to more open grasslands? Pollen and charcoal records go some way toward filling this knowledge gap in tropical settings (e.g., refs. 3–5), but they can be affected by biases in the representation of local plant species and are sometimes difficult to date accurately. In PNAS, a relatively innovative technique is explored in insular Southeast Asia that uses the vegetation-derived carbon isotope (δ13C) records preserved in cave guano deposits (6).

Forest contraction in north equatorial Southeast Asia during the Last Glacial Period.

Today, insular Southeast Asia is important for both its remarkably rich biodiversity and globally significant roles in atmospheric and oceanic circulation. Despite the fundamental importance of environmental history for diversity and conservation, there is little primary evidence concerning the nature of vegetation in north equatorial Southeast Asia during the Last Glacial Period (LGP). As a result, even the general distribution of vegetation during the Last Glacial Maximum is debated. Here we show, using the stable carbon isotope composition of ancient cave guano profiles, that there was a substantial forest contraction during the LGP on both peninsular Malaysia and Palawan, while rainforest was maintained in northern Borneo. These results directly support rainforest "refugia" hypotheses and provide evidence that environmental barriers likely reduced genetic mixing between Borneo and Sumatra flora and fauna. Moreover, it sheds light on possible early human dispersal events.

Potential and Possibility of Direct Use of Guano as Fertilizer in Indonesia

Guano is a material originally from sea bird or bat excrement. This material is an important source of P fertilizerduring nineteenth century and the early part of twentieth century. The development of artificial fertilizers and the depletion of guano deposits in Peru caused guano negligibled from world fertilizers trading. Recently, guano appeared in fertilizers trading and sciencetific publications again due to the development of organic farming and increasing the price of energy sources for fertilizer manufacture. Based on its origin, guano is classified into sea bird and bat guanos; and based on its composition guano is grouped into nitrogenous dan phosphatic guanos. Moreover, guano deposits are divided into two types: cave guano and insular guano deposits. The main component of guano is N, P, and Ca elements, and the additional elements are K, Mg, and S. Both nitrogenous and phosphatic guanos are important organic fertilizers because the N content of nitrogenous guano and the P content of phosphatic guano are far higher than those of manure, agricultural waste, or muniCipal waste. In Indonesia guano deposits are widely distributed in Sumatera, Java, Kalimantan, Sulawesi, Nusatenggara, and Irian Jaya. The most deposits are cave guano deposits which contain thousands to hundred thousands tons of guano.Consequently, it is highly potential to develop direct use of guano in our country. Futhermore, results of experiments indicated that phosphatic guano has high possibility to be used directly as P fertilizer.