Microplastic particles are a global problem, which has been widely found in marine and terrestrial environments. However, microplastic pollution in caves and karst aquifers is still poorly studied. To improve the current knowledge of microplastic pollution, we investigated the sediments of a show cave in Italy. We developed a methodology based on a cave-adapted version of the methods used in several studies to detect microplastics from sediments of different environments and with various laboratory tests. The microplastics were extracted from sediments via density separation and subjected to organic matter removal. Filters were observed with and without UV light under a microscope, before and after organic matter removal, and the microplastics were characterised according to shape, colour, and size, with visual identification. About 55% of the fibres observed under the microscope on filters were removed via organic matter removal. An average of 4390 items/kg dry weight was calculated for the touristic zone and 1600 items/kg dry weight for the speleological/research section. Fibre (84.9%) was the most abundant shape, and most microplastics were smaller than 1 mm, accounting for 85.4%, of which 58.4% were shorter than 0.5 mm. The highest microplastic abundance was fluorescent under UV light (87.7%); however, 12.3% of the microplastics observed on filters were not fluorescent. Most fluorescent fibres were transparent (84%), whereas blue (46.1%) and black (22.4%) fibres were more common for the non-fluorescent ones. Our results highlight the presence of microplastics in show caves, and we provide a valid non-invasive and non-expensive analytical technique for the preparation and isolation of microplastics from cave sediments, giving useful information for evaluating the environmental risks posed by microplastics in show caves.

Microplastic (MP) pollution is a growing concern in every known ecosystem. However, MP presence in groundwaters and the ecological impact they can have on groundwater fauna is still poorly investigated. Here, we assess the presence of MPs in three Italian groundwater bodies, comprising two karst caves and two monitoring bores of a saturated alluvial aquifer. In addition to water samples, groundwater invertebrates were collected to assess their potential ingestion of MPs. For water samples, chemical characterization of polymers was done by Fourier Transform Infrared Spectroscopy (FTIR) 2D imaging, while fauna samples were analyzed with a tandem microscopy approach (fluorescence microscopy and FTIR). The abundance of MPs in water samples varied from 18 to 911 items/L. The majority of MPs were fibers (91%), with a mean size in the range of 100 µm and 1 mm. Black, red, and blue were the most abundant colors (30%, 25%, and 19%, respectively). The most abundant polymer was artificial/textile cellulose (65%), followed by PET (21%). MPs were found in every groundwater taxon. Pellets were the most abundant in each specimen (87% on average), while the largest were fragments, with a mean dimension of 26 µm. Cellulose was found to be the most abundant polymer (51%). This study is the first to highlight the presence of MPs ingested by groundwater fauna. Further investigations are urgently required to assess the potential ecological impact MPs can have on the resident fauna in these sensitive ecosystems.

Microplastic pollution in karst systems is still poorly studied, despite the presence of protected species and habitats, and important water reserves. Vulnerable key species hosted in these habitats could consume or assimilate microplastics, which can irreversibly damage management efforts, and thus ecosystems functionality. This can be particularly true for subterranean water habitats where microplastic pollution effects on wildlife management programs are not considered. The aim of this study is to provide a case study from the Classical Karst Region, which hosts peculiar habitats and key species protected at European level, such as the olm Proteus anguinus. As this area has been deeply exploited and modified over time, and is adjacent to highways, roads and railways, which could contribute to pollution within the karst system, threatening the ecosystems, it provides a perfect model system. In this study we collected and investigated water and sediment samples from aquatic environments of surface and subterranean habitats hosting several subterranean environment-adapted organisms. Examined particles were counted and characterized by size, color and shape via visual identification under a microscope, with and without UV light. Furthermore, spectroscopic analyses were carried out in order to identify microplastics typology. Microplastics were found in all examined habitats. In water, microplastics concentration ranged from 37 to 86 items/L, in sediments from 776 to 2064 items/kg. Fibre-shape was the main present, followed by fragments and beads, suggesting multiple sources of pollution, especially textile products. Most of the particles were fluorescent under UV light and were mainly transparent, while not-fluorescent ones were especially black, blue or brown. Samples contained especially polyesters and copolymers. These results highlight intense MP pollution in karst areas, with significant impacts on water quality, and potential effects on subterranean environment-dwelling species. We stress the importance of monitoring pollution in these critical environments for biodiversity and habitat conservation: monitoring in karst areas must become a priority for habitat and species protection, and water resources management, improving analyses on a larger number of aquatic surface and subterranean habitats.

The touristic use of caves causes multiple environmental alterations to the subterranean ecosystem, having potential effects on all components, from the atmosphere to lithosphere, hydrosphere, and biosphere. Setting a baseline on the current knowledge of the ecological status of world show caves is pivotal to implement monitoring and management programs aiming at their conservation. However, information on this topic is scattered throughout several publications, making it difficult to access data and ultimately delaying advances towards a sustainable touristic use of show caves. We provide a literature-based dataset relative to the knowledge on the ecological status of 265 show caves worldwide. Data were collated from 289 papers selected through a systematic literature survey of an initial set of more than 1,000 scientific papers. We made the compiled information available through two complementary datasets, reporting: (i) references of the selected papers and (ii) 44 fields relative to the main characteristics of show caves investigated in literature. These fields encompass information about geographic locations, cave general characteristics, natural heritage, and the specific environmental components—and related environmental parameters—investigated in each of the considered study. Such a dataset improves our accessibility to the basic information provided by literature on the ecological status of show caves, also pointing out some literature gaps that should be addressed by future research. By making these data freely available and re-usable, we hope to stimulate research in the field of cave tourism, cave conservation, and cave-based ecology.