Contaminants of Emerging Concern in Bats from the Northeastern United States

A systematic review of trace elements in the tissues of bats (Chiroptera)

Bats constitute about 22% of known mammal species; they have various ecological roles and provide many ecosystem services. Bats suffer from several threats caused by anthropization, including exposure to toxic metals and metalloids. We analyzed 75 papers in a systematic literature review to investigate how species, diet, and tissue type impact bioaccumulation. Most studies documented element accumulation in fur, liver, and kidney; at least 36 metals and metalloids have been measured in bat tissues, among the most studied were mercury and zinc. Comparisons with known toxicological thresholds for other mammals showed concerning values for mercury and zinc in bat hair, lead and some essential metals in liver, and iron and calcium in kidneys. Moreover, accumulation patterns in tissues differed depending on bat diet: insectivorous bats showed higher metal concentrations in fur than in liver and kidney while frugivorous species showed higher values in liver and kidney than in fur. Finally, among the bat species that have been studied in more than two papers, the big brown bat (Eptesicus fuscus) show values of mercury in hair and copper in liver that exceed the known thresholds; as does copper in the liver of the little brown bat (Myotis lucifugus). Most studies have been conducted in temperate North America and Eurasia, areas with the lowest bat species diversity; there is a paucity of data on tropical bat species. This review points out several information gaps in the understanding of metal contamination in bats, including a lack of measured toxicity thresholds specific for bat tissues. Data on trace element bioaccumulation and its associated health effects on bats is important for conservation of bat species, many of which are threatened.

A Palearctic view of a bat fungal disease

The fungal infection causing white-nose disease in hibernating bats in North America has resulted in dramatic population declines of affected species, since the introduction of the causative agent Pseudogymnoascus destructans. The fungus is native to the Palearctic, where it also infects several bat species, yet rarely causes severe pathology or the death of the host. Pseudogymnoascus destructans infects bats during hibernation by invading and digesting the skin tissue, resulting in the disruption of torpor patterns and consequent emaciation. Relations among pathogen, host, and environment are complex, and individuals, populations, and species respond to the fungal pathogen in different ways. For example, the Nearctic Myotis lucifugus responds to infection by mounting a robust immune response, leading to immunopathology often contributing to mortality. In contrast, the Palearctic M. myotis shows no significant immunological response to infection. This lack of a strong response, resulting from the long coevolution between the hosts and the pathogen in the pathogen's native range, likely contributes to survival in tolerant species. After more than 15 years since the initial introduction of the fungus to North America, some of the affected populations are showing signs of recovery, suggesting that the fungus, hosts, or both are undergoing processes that may eventually lead to coexistence. The suggested or implemented management methods of the disease in North America have encompassed, for example, the use of probiotics and fungicides, vaccinations, and modifying the environmental conditions of the hibernation sites to limit the growth of the pathogen, intensity of infection, or the hosts' responses to it. Based on current knowledge from Eurasia, policy makers and conservation managers should refrain from disrupting the ongoing evolutionary processes and adopt a holistic approach to managing the epizootic.

Antifungal drugs in the aquatic environment: A review on sources, occurrence, toxicity, health effects, removal strategies and future challenges

Fungal infections pose a significant global health burden, resulting in millions of severe cases and deaths annually. The escalating demand for effective antifungal treatments has led to a rise in the wholesale distribution of antifungal drugs, which consequently has led to their release into the environment, posing a threat to ecosystems and human health. This article aims to provide a comprehensive review of the presence and distribution of antifungal drugs in the environment, evaluate their potential ecological and health risks, and assess current methods for their removal. Reviewed studies from 2010 to 2023 period have revealed the widespread occurrence of 19 various antifungals in natural waters and other matrices at alarmingly high concentrations. Due to the inefficiency of conventional water treatment in removing these compounds, advanced oxidation processes, membrane filtration, and adsorption techniques have been developed as promising decontamination methods.In conclusion, this review emphasizes the urgent need for a comprehensive understanding of the presence, fate, and removal of antifungal drugs in the environment. By addressing the current knowledge gaps and exploring future prospects, this study contributes to the development of strategies for mitigating the environmental impact of antifungal drugs and protecting ecosystems and human health.

Mercury Isotope Values in Shoreline Spiders Reveal the Transfer of Aquatic Mercury Sources to Terrestrial Food Webs

The transfer of aquatic contaminants, including mercury (Hg), to terrestrial food webs is an often-overlooked exposure pathway to terrestrial animals. While research has implemented the use of shoreline spiders to assess aquatic to terrestrial Hg transfer, it is unclear whether Hg sources, estimated from isotope ratios, can be successfully resolved to inform site assessments and remedy effectiveness. To examine aquatic to terrestrial Hg transfer, we collected shoreline spiders (Tetragnatha spp.) and aquatic insect larvae (suborder Anisoptera) across a mosaic of aquatic and shoreline habitats in the St. Louis River and Bad River, tributaries to Lake Superior. The fraction of industrial Hg in sediments was reflected in the δ202Hg values of aquatic dragonfly larvae and predatory fish, connecting benthic Hg sources to the aquatic food web. Shoreline spiders mirrored these aquatic Hg source signatures with highly positive correlations in δ202Hg between tetragnathids and dragonfly larvae (r2 = 0.90). Further assessment of different spider taxa (i.e., araneids and pisaurids) revealed that differences in prey consumption and foraging strategies resulted in isotope differences, highlighting the importance of spider taxa selection for Hg monitoring efforts.

Analyzing the potential environmental impact of NIOSH list of hazardous drugs (group 2)

For the first time, several pharmaceuticals have been defined as priority substances in the new proposal of the revision of the Water Framework Directive (WFD). Consequently, environmental quality standards have been determined for several drugs. This is the case with the antiepileptic carbamazepine, which is considered as hazardous in healthcare settings by The National Institute for Occupational Safety and Health (NIOSH). This organism considers as such drugs that have shown teratogenicity, carcinogenicity, genotoxicity or other developmental, reproductive, or organ toxicity at low doses in studies with animals or humans. This study has been focused on the non-carcinogenic drugs classified in group 2, and their presence in the environment. This group contains many different therapeutic agents such as antineoplastics, psychoactive drugs, immunosuppressants and antivirals, among others. Of the 116 drugs included in the list, 26 have been found in aquatic environmental matrices. Certain drugs have received most attention (e.g., the antiepileptic carbamazepine, progesterone and the antidepressant paroxetine) while others completely lack environmental monitoring. Carbamazepine, fluconazole, paroxetine and warfarin have been found in invertebrates' tissues, whereas carbamazepine, oxazepam and paroxetine have been found in fish tissues. The main aim of the NIOSH's hazardous drug list is to inform healthcare professionals about adequate protection measures to prevent occupational exposure to these pharmaceuticals. However, this list contains useful information for other professionals and researchers such as environmental scientists. The paucity of relevant environmental data of certain hazardous pharmaceuticals might be important to help in the prioritization of compounds that may demand further research.

Evaluation of Parabens and Bisphenol A Concentration Levels in Wild Bat Guano Samples

Parabens and bisphenol A are synthetic compounds found in many everyday objects, including bottles, food containers, personal care products, cosmetics and medicines. These substances may penetrate the environment and living organisms, on which they have a negative impact. Till now, numerous studies have described parabens and BPA in humans, but knowledge about terrestrial wild mammals' exposure to these compounds is very limited. Therefore, during this study, the most common concentration levels of BPA and parabens were selected (such as methyl paraben-MeP, ethyl paraben-EtP, propyl paraben-PrP and butyl paraben-BuP) and analyzed in guano samples collected in summer (nursery) colonies of greater mouse-eared bats (Myotis myotis) using liquid chromatography with the tandem mass spectrometry (LC-MS-MS) method. MeP has been found in all guano samples and its median concentration levels amounted to 39.6 ng/g. Other parabens were present in smaller number of samples (from 5% for BuP to 62.5% for EtP) and in lower concentrations. Median concentration levels of these substances achieved 0.95 ng/g, 1.45 ng/g and 15.56 ng/g for EtP, PrP and BuP, respectively. BPA concentration levels did not exceed the method quantification limit (5 ng/g dw) in any sample. The present study has shown that wild bats are exposed to parabens and BPA, and guano samples are a suitable matrix for studies on wild animal exposure to these substances.

Bioaccumulation and bioamplification of pharmaceuticals and endocrine disruptors in aquatic insects

Environmental fate of emerging contaminants such as pharmaceuticals and endocrine disrupting compounds at the aquatic terrestrial boundary are largely unexplored. Aquatic insects connect aquatic and terrestrial food webs as their life cycle includes aquatic and terrestrial life stages, thus they represent an important inter-habitat linkage not only for energy and nutrient flow, but also for contaminant transfer to terrestrial environments. We measured the concentrations of pharmaceuticals and endocrine disrupting compounds in the larval and adult tissues (last larval stages and teneral adults) of five Odonata species sampled in a wastewater-impacted river, in order to examine their bioaccumulation and bioamplification at different taxonomic levels. Twenty different compounds were bioaccumulated in insect tissues, with majority having higher concentrations (up to 90% higher) in aquatic larvae compared to terrestrial adults (reaching 88 ng/g for 1H-benzotriazole). However, increased concentration in adults was observed for seven compounds in at least one suborder (41% of the accumulated), confirming contaminants bioamplification across the metamorphosis. Both, bioaccumulation and bioamplification differed at various taxa levels; the order (Odonata), suborder (Anisoptera and Zygoptera) and species level. Highest variability was observed between Anisoptera and Zygoptera, due to the underlying differences in their ecology. Generally, Zygoptera had higher concentrations of contaminants in both larvae and adults. Additionally, we aimed at predicting effects of contaminant properties on bioaccumulation and bioamplification patterns using the commonly used physicochemical and pharmacokinetic descriptors on both order and suborder levels, however, neither of the two processes could be consistently predicted with simple linear models. Our study highlights the importance of taxonomy in studies aiming at advancing the understanding of contaminant exchange between aquatic and terrestrial food webs, as higher taxonomic categories include ecologically diverse groups, whose contribution to "the dark side of subsidies" could substantially differ.

Occurrence of persistent organic pollutants and chlorpyrifos in Tadarida brasiliensis tissues from an agricultural production area in Argentina

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are lipophilic and persistent compounds, with chronic toxicity that cause negative effects on the environment and organisms. The chlorpyrifos is an organophosphate insecticide and represent the main insecticide currently used in many countries. The concentrations of OCPs, PCBs, and chlorpyrifos were evaluated in liver, muscle, and gonad of females and males of Tadarida brasiliensis in an agricultural production area in Argentina. Pollutants were quantified by gas chromatography with electron capture detection. The general total concentration pattern among tissues was gonad > muscle > liver, with a higher ratio of pesticides (OCPs + chlorpyrifos) over PCBs in muscle and liver, while gonads showed higher concentrations of PCBs. The predominance of DDTs and endosulfans evidences the bioavailability of these compounds despite their use has ceased. Chlorpyrifos was the main pesticide detected in almost all samples of both sexes, probably due to its current intensive use. More researches about ecology and activity patterns is paramount in order to understand more accurately the accumulation and possible negative effects of these pollutants.

Are little brown bats (Myotis lucifugus) impacted by dietary exposure to microcystin?✰

The cyanobacterium, Microcystis aeruginosa, can produce the hepatotoxin microcystin. When toxic M. aeruginosa overwinters in the sediments of lakes, it may be ingested by aquatic insects and bioaccumulate in nymphs of Hexagenia mayflies. When volant Hexagenia emerge from lakes to reproduce, they provide an abundant, albeit temporary, food source for many terrestrial organisms including bats. Little brown bats, Myotis lucifugus, feed opportunistically on aquatic insects including Hexagenia. To determine if microcystin moves from aquatic to terrestrial ecosystems via trophic transfer, we combined a dietary analysis with the quantification of microcystin in bat livers and feces. In June 2014, coincident with the local Hexagenia emergence, bat feces were collected from underneath a maternity roost near Little Traverse Lake (Leelanau County, Michigan, USA). Insects in the diet were identified via molecular analyses of fecal pellets from the roost and from individual bats. Livers and feces were collected from 19 female M. lucifugus, and the concentrations of microcystin in these liver tissues and feces were measured using an enzyme-linked immunosorbent assay (ELISA) and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). We show that the majority of the bats' diets consisted of aquatic insects and that microcystin was detected in high concentrations (up to 129.9 μg/kg dw) in the bat feces by ELISA. Histopathological examination of three bat livers with the highest concentrations of microcystin showed no evidence of phycotoxicosis, indicating that M. lucifugus may not be immediately affected by the ingestion of microcystin. Future work could examine whether bats suffer delayed physiological effects from ingestion of microcystin.

Contaminant exposure as an additional stressor to bats affected by white-nose syndrome: current evidence and knowledge gaps

Bats are exposed to numerous threats including pollution and emerging diseases. In North America, the fungal disease white-nose syndrome (WNS) has caused declines in many bat species. While the mechanisms of WNS have received considerable research attention, possible influences of contaminants have not. Herein, we review what is known about contaminant exposure and toxicity for four species whose populations have been severely affected by WNS (Myotis sodalis, M. septentrionalis, M. lucifugus, and Perimyotis subflavus) and identify temporal and spatial data gaps. We determine that there is limited information about the effects of contaminants on bats, and many compounds that have been detected in these bat species have yet to be evaluated for toxicity. The four species examined were exposed to a wide variety of contaminants; however, large spatial and knowledge gaps limit our ability to evaluate if contaminants contribute to species-level declines and if contaminant exposure exacerbates infection by WNS.

Multiresidues of environmental contaminants in bats from Turkey

Bat populations have been steadily declining, most likely because of anthropogenic factors. Identification and classification of these risks have crucial importance in ensuring the survival of this species. Bats often coexist with humans in urban, industrial, and agricultural areas and are potentially exposed to a range of environmental pollutants. Two bat species widely distributed in Turkey were selected, and the residues of pesticides and organic contaminants in their carcasses were analyzed using: gas chromatography-mass spectrometry, gas chromatography-tandem mass spectrometry, and liquid chromatography-tandem mass spectrometry. Species and sex specific differences were evaluated along with their potential to be used as bioindicators. During the rigor mortis period, 23 adult Pipistrellus pipistrellus (11 female and 12 male) and 19 adult Myotis myotis (9 female and 10 male) were collected and 322 contaminants (pesticides and organic contaminants) were analyzed in whole carcasses of bats by using a validated method. Multiple pesticides and organic contaminants were detected in all collected 42 bats. The most frequent contamination was detected as 4,4-DDE, followed by ethoprophos, quinalphos, methidation, paraoxon-methyl, phosalone and tetramethrin. The least common compounds were as follows: 2,4-DDD, endrin, HCH-alpha, fenamiphos sulfoxide, parathion ethyl, bitertanol, oxycarboxin, procymidone, fluazifop-butyl, trifluralin, bifenazate, DMF, fenpyroximate, PBDE-47, benzo(a)anthracene, benzo(b)fluoranthene, and benzo(g,h,i) perylene; of these only one was found in each bat. In terms of frequency and concentration, there was no significant difference between species and sex. An average of 26.1 pollutants was found in each bat. Thus, it was concluded that bats can be used as potential bioindicators in determining environmental pollution.

Aquatic Insects Transfer Pharmaceuticals and Endocrine Disruptors from Aquatic to Terrestrial Ecosystems

A wide range of pharmaceuticals and endocrine disrupting compounds enter freshwaters globally. As these contaminants are transported through aquatic food webs, understanding their impacts on both aquatic and terrestrial ecosystems remains a major challenge. Here, we provide the first direct evidence of the transfer of pharmaceuticals and endocrine disruptors through the aquatic-terrestrial habitat linkage by emerging aquatic insects. We also show that the type of insect metamorphosis and feeding behavior determine the bioaccumulation patterns of these contaminants. Adult Trichoptera, an important food source for riparian predators, showed an increased body burden of pharmaceuticals and endocrine disruptors. This implies that terrestrial predators, such as spiders, birds, and bats, are exposed to mixtures of pharmaceuticals and endocrine disruptors of aquatic origin, which may impact their physiology and population dynamics. Overall, our study provides valuable insights into the bioaccumulation patterns and trophic cross-ecosystem transfer of these contaminants, from aquatic primary producers to terrestrial predators.

DDT poisoning of big brown bats, Eptesicus fuscus, in Hamilton, Montana

Dichlorodiphenyltrichloroethane (DDT) is an insecticidal organochlorine pesticide with; known potential for neurotoxic effects in wildlife. The United States Environmental Protection Agency (US EPA) registration for this pesticide has been cancelled and there are currently no federally active products that contain this ingredient in the U.S. We present a case of a colony of big brown bats (E. Fuscus) found dead in the attic roost of an administrative building; in the city of Hamilton, Montana from unknown cause. DDT and its metabolites; dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD) were detected in bat tissues by gas chromatography/mass spectrometry (GC-MS) and quantified by gas chromatography tandem quadrupole mass spectrometry (GC-MS/MS). Concentrations of 4081 ppm DDT and 890 ppm DDE wet weight were found in the brain of one bat and are the highest reported concentrations in such a mortality event to date. This case emphasizes the importance of testing wildlife mortalities against a comprehensive panel of toxicologic agents including persistent organic pollutants in the absence of other more common disease threats.

Alterations in the health of hibernating bats under pathogen pressure

In underground hibernacula temperate northern hemisphere bats are exposed to Pseudogymnoascus destructans, the fungal agent of white-nose syndrome. While pathological and epidemiological data suggest that Palearctic bats tolerate this infection, we lack knowledge about bat health under pathogen pressure. Here we report blood profiles, along with body mass index (BMI), infection intensity and hibernation temperature, in greater mouse-eared bats (Myotis myotis). We sampled three European hibernacula that differ in geomorphology and microclimatic conditions. Skin lesion counts differed between contralateral wings of a bat, suggesting variable exposure to the fungus. Analysis of blood parameters suggests a threshold of ca. 300 skin lesions on both wings, combined with poor hibernation conditions, may distinguish healthy bats from those with homeostatic disruption. Physiological effects manifested as mild metabolic acidosis, decreased glucose and peripheral blood eosinophilia which were strongly locality-dependent. Hibernating bats displaying blood homeostasis disruption had 2 °C lower body surface temperatures. A shallow BMI loss slope with increasing pathogen load suggested a high degree of infection tolerance. European greater mouse-eared bats generally survive P. destructans invasion, despite some health deterioration at higher infection intensities (dependant on hibernation conditions). Conservation measures should minimise additional stressors to conserve constrained body reserves of bats during hibernation.

Polychlorinated biphenyls (PCBs): impact on bat activity and foraging behaviour along the upper Hudson River, New York

Sediments of the upper Hudson River, New York, USA, contain polychlorinated biphenyls (PCBs). Consequently, elevated levels of PCBs have been found in the tissues of bats and their insect prey along this region. However, it is not clear whether bat activity and foraging behaviour have been affected. To assess possible effects of PCBs on bat activity and foraging behaviour, we measured the activity of little brown bats (Myotis lucifugus (LeConte, 1831)) and hoary bats (Lasiurus cinereus (Palisot de Beauvois, 1796)) along the upper Hudson River, as well as abundance of insect prey at the same locations. We also measured foraging duration and distances travelled by radio-tagged M. lucifugus. We found that bat activity and insect abundance did not differ with PCB concentration. We did, however, find that foraging behaviour along the Hudson River differed from a control site. Specifically, M. lucifugus foraging along PCB-contaminated areas of the Hudson River travelled shorter distances from their roosts and spent less time foraging than bats at an uncontaminated site. Our results show that while bats roost and forage in areas historically exposed to PCBs, this exposure has not adversely affected bat activity, foraging behaviour, or abundance of insect prey.