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.

Understanding trait selection factors is vital for decoding the processes shaping species’ assemblages. However, trait-based studies in freshwater crustacean copepod assemblages are scarce, especially in groundwater environments. We explored how environmental filtering influences functional traits in copepod assemblages across four freshwater habitats (an alluvial aquifer, a hyporheic zone, a stream benthic zone and a lake littoral) along a depth gradient. Each habitat had distinct environmental templates based on light, temperature and dissolved oxygen. We analysed 4898 individuals from 43 copepod species and examined 12 morphological and life history traits. The results revealed significant differences in copepod traits among habitats, notably in ovigerous female biomass, egg biomass and ovigerous female percentages. Furthermore, despite some statistical uncertainty, notable differences were also observed in the number of juveniles, male-to-female abundance ratios and overall biomass. No significant differences were observed in juvenile biomass, egg characteristics, body size dimorphism or juvenile-to-adult ratios among habitats. The trait variations offer insights into copepod-mediated ecosystem services, particularly carbon recycling. To gain a deeper understanding of copepod adaptations to environmental features and anthropogenic changes, future research should consider additional functional traits, such as locomotion and feeding habits.

Groundwater communities residing in contaminated aquifers have been investigated mainly through taxonomy-based approaches (i.e., analyzing taxonomic richness and abundances) while ecological traits have been rarely considered. The aim of this study was to assess whether a trait analysis adds value to the traditional taxonomy-based biomonitoring in N-contaminated aquifers. To this end, we monitored 40 bores in the Vomano alluvial aquifer (VO_GWB, Italy) for two years. The aquifer is a nitrate vulnerable zone according to the Water Framework Directive. The traditional taxonomy-based approach revealed an unexpectedly high biodiversity (38 taxa and 5725 individuals), dominated by crustaceans, comparable to that of other unpolluted alluvial aquifers worldwide. This result is in contrast with previous studies and calls into question the sensitivity of stygobiotic species to N-compounds. The trait analysis provided an added value to the study, unveiling signs of impairments of the groundwater community such as low juveniles-to-adults and males-to-females ratios and a crossover of biomasses and abundances curves suggestive of an intermediate alteration of the copepod assemblages.

Copepods are the dominant crustacean group in groundwater, where they perform valuable ecosystem services related to carbon recycling. The life-history traits of stygobitic (groundwater-obligate dweller) copepods, however, have only been casually studied in the past. In addition, next to nothing is known about the responses of stygobitic copepods to climate change. In this study, we investigated the life-history traits and respiratory metabolism of a species of harpacticoid copepods, Moraria sp., endemic to the Corchia Cave in the Apuan Alps (Italy). We collected the specimens of Moraria sp. from the dripping waters of the cave and observed their development, survival, and reproduction rates in the laboratory for one year. We also evaluated the acclimation ability of adult females of Moraria sp. by measuring their oxygen consumption in a temperature range from 8 °C (average annual temperature of the dripping water in the Stalactites Gallery of the Corchia Cave) to 12.5 °C (maximum temperature of the dripping water of the cave expected according to climate change scenarios in 2100). Our results indicate that Moraria sp. Is a stenothermal species showing remarkable stygobitic traits (long life span, low metabolic rates). We noted that the metabolism of this species is significantly affected by small (+1.5 °C) thermal changes. Our results showed no metabolic compensation occurring in this species over two weeks of exposure to temperatures higher than 8 °C. The outcomes of this study suggest that Moraria sp. May not be able to tolerate thermal changes brought on by climate change.

Copepods (Crustacea: Copepoda) are widespread in aquatic ecosystems worldwide and represent an important component of the meiobenthic metazoan assemblages of lake littorals. Yet, little is currently known about the diversity of benthic copepods in lentic habitats. We gathered information on the benthic copepod assemblages of the littoral zone of Lake Maggiore as part of the Interreg Italy-Switzerland 2014-2020 Parchi Verbano Ticino project (ID: 481668), funded by the European Regional Development Fund (ERDF). Lake Maggiore is a large and deep temperate lake in north-western Italy human-managed from mid-March to mid-September. This contributes to substantial changes in water levels in relation to human activities such as hydropower, industrial and agricultural uses. We compiled a dataset listing 234 occurrences of benthic copepod species recorded from three littoral sampling sites situated in three protected areas, two of which are part of the Natura 2000 network in Italy and one is part of the Emerald Network in Switzerland. We collected the specimens during the summer-autumn period in 2019-2021. We identified the copepods at the species level and created a dataset with individual georeferenced occurrence records for each species, organized in a standardized Darwin Core Archive format. We made available, through the Global Biodiversity Information Facility (GBIF), a total of 13 distinct taxonomic entities and 234 unique georeferenced occurrence records related to the benthic copepod assemblages of the littoral zone of Lake Maggiore (Tabilio Di Camillo et al., 2023). The dataset has the potential to support the authorities in charge of managing Lake Maggiore’s water levels in addressing the ecological risk relevant to the littoral zone and in developing shared implementation strategies for sustainable water management.

This study explores the metabolic response and carbon budget of two cyclopoid copepod species, Diacyclops belgicus Kiefer, 1936 (a stygobitic, groundwater-adapted species) and Diacyclops crassicaudis crassicaudis (Sars G.O., 1863) (a stygophilic, predominantly surface-associated species). We measured oxygen consumption rates (OCRs), carbon requirements (CRs), ingestion (I) rates, and egestion (E) rates at 14 °C and 17 °C, representing current and predicted future conditions in the collection habitats of the two species. Diacyclops belgicus displayed OCRs (28.15 and 18.32 µL O₂/mg DW × h at 14 and 17 °C, respectively) and carbon budget (CR: 0.14 and 0.10 µg C/mg × d at 14 and 17 °C) lower than those of D. crassicaudis crassicaudis (OCR: 55.67 and 47.93 µL O₂/mg DW × h at 14 and 17 °C; CR: 0.3 and 0.27 µg C/mg × d at 14 and 17 °C). However, D. belgicus exhibited metabolic rates and carbon requirements comparable to those of other epigean species, challenging the assumption that low metabolic rates are universal among stygobitic species. Temperature variations did not significantly affect the metabolic responses and carbon requirements of the two species, suggesting that they may cope with moderate temperature increases.