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Microplastics represent one of the main environmental concerns of our time and their presence is well known in all freshwater ecosystems. However, there is still a lack of knowledge about the interference with some environmental dynamics, such as the leaf litter decomposition, which represents a key process in freshwater ecosystems. The work presented herein analyzed the leaf litter decomposition in a lotic ecosystem, in relation to water physicochemical parameters, macrobenthic invertebrate functional feeding guilds (FFG) and, as a novelty, the microplastics as additional factor. Physicochemical features were monitored every 15 days for one year. Phragmites australis decomposition rates were investigated during four seasons (summer, autumn, winter, and spring) using the leaf bag technique. Microplastic items were also collected within the leaf bags (used as retaining tool) and within macrobenthic invertebrate colonizers. Shredders were the most contaminated FFG in summer and autumn, while scrapers showed high microplastics levels in autumn and winter. Decomposition rates significantly differed among seasons (0.007 < k < 0.022) and water temperature was the main driver of the decomposition dynamics (relative importance = 70.3 %), positively affecting the decay rates, followed by pH (9.7 %), which showed a negative contribution. Microplastics showed a negative effect (3.1 %), with a relative importance similar and opposite to that observed for the shredders (3.9 %), which value was similar to those recorded for scarpers (2.7 %). This study represents a field investigation regarding the microplastic effects on the organic matter decomposition rates in freshwater environments carried out directly on field. Our results provide new insights about the microplastic interference on environmental dynamics and could represent a starting point for further studies.

Microplastic (MP) pollution is a major environmental concern for mountain ecosystem and for high-mountain lakes in particular, which are recognized indicators of global change. In this study, the presence of MPs was assessed in abiotic (water and sediment) and biotic (zooplankton, tadpoles, fish) compartments of two high-mountain lakes (Upper Lake Balma and Lower Lake Balma) in the Cottian Alps (northwest Italy). No MPs were found in water and zooplankton samples, whereas the mean MPs in sediment samples was 1.33 ± 0.67 items/m3 and 1.75 ± 0.62 items/m3 in Lower and Upper Lake Balma, respectively. The mean MPs in tadpoles of Rana temporaria was 0.33 ± 0.58 items/individual and 0.66 ± 0.58 items/individual in Lower and Upper Lake Balma, respectively. The mean number of MPs items found in the gastrointestinal tract (GIT) of fish (Salvelinus fontinalis) was considerably higher in specimens from the Lower (0.45 items/g GIT) than in those from the Upper Lake (0.20 items/g GIT). There was a negative relationship between fish size (weight and age) and MPs abundance in the GIT of fish, indicating that young fish accumulated more MP items probably due to the high prey ingestion rate compared to adults. The same MPs color (blue, white, black), shape (fibers and fragments), and chemical type (polypropylene and polyethylene) were found in the compartments of both lakes. Our findings suggest the use of S. fontinalis as an indicator of MP pollution in high-mountain lakes. Further studies are needed to better understand the sources and the effects of MPs in these remote ecosystems.

High-altitude lakes have been studied intensively over the last decades both in terms of their biota and general physicochemical patterns and the importance of detailed knowledge of the small scale-regional fauna was underlined. In the present study the littoral macrobenthic invertebrate communities of two alpine lakes placed in the same geographical context (Upper and Lower Balma Lakes, Cottian Alps, Italy) were seasonally characterized, and the observed diversity was investigated in relation to site-specific abiotic features. During the ice-free period, two seasonal sampling campaigns (summer and autumn) were carried out at each lake along the littoral zones: macrobenthic invertebrate were collected and abiotic features (main physicochemical water parameters and main substrates) were monitored. PERMANOVA test disclosed significant differences in the invertebrate assemblages between the lakes, and SIMPER test highlighted that the observed dissimilarity was mainly related to Oligochaeta and Chironomidae taxa. The application of the RDA and VPA showed that differences were mainly due to littoral substrate composition and nutrient concentrations (i.e., phosphorus and nitrates) which could heavily affect both the structures and densities of the macrobenthic invertebrate communities in these environments. Findings from this study improve the knowledge about the macrobenthic invertebrate assemblages in the western area of the European Alps, highlighting the role of site-specific factors in small scales studies, and the importance of detailed knowledge of their local variability. The better understanding of the variation patterns in regional/ subregional biodiversity and their drivers are of pivotal importance and have implications in the decision of conservation policies.

Microplastics (MPs) pollution is arousing growing attention, yet knowledge about its occurrence in amphibians is scant to date. With this study, we aimed to determine whether plastic (>5000 μm) and MPs (10–5000 μm) could be detected in adult Rana temporaria from a high-mountain ecosystem (the Cottian Alps, northwest Italy). To do this, aquatic compartments and the digestive tract of adult R. temporaria were analyzed. Water, sediment, periphyton, aquatic macroinvertebrates, and tadpoles tested negative for plastic and MPs. Microplastics were detected in all the adult frogs (n = 5); all the identified items (one per specimen) were fibers (size range: 550.91–2355.51 µm). A statistically significant positive correlation between the particle length and frog size was recorded. The predominant fiber color was blue. The chemical composition was polyamide (60%), polyethylene (20%), and polyethylene terephthalate (20%). Since both the biotic and the abiotic freshwater compartments (tadpoles included) revealed the absence of MPs, it can be assumed that adult frogs ingest MPs from the surrounding terrestrial environment.

Climate change has direct effects on aquatic systems where increased water temperature leads to range shifts and changes in the distribution of aquatic organisms. The effects of climate change on aquatic ecosystems are expected in all biomes, and in Alpine environments in particular. Anthropogenic pressure (e.g., chemical pollution) besides climate change impact on the state and quality of aquatic systems in which climate change and environmental contaminants can interact. To better understand the effect of increases in temperature and environmental pollution on high-mountain lakes, we performed an ecotoxicological assay on Daphnia middendorffiana collected during summer 2021 in a high-mountain lake (Upper Balma Lake, Cottian Alps, 2212 m a.s.L.). Samples were exposed to two temperature values (15 °C and 20 °C), potassium chloride (KCl) as the reference toxicant, and D. magna as the model organism for comparison. Findings showed immobilization after exposure to KCl in both species, but exposure to non-optimal water temperature (20 °C and 15 °C for D. middendorffiana and D. magna, respectively) enhanced this effect. The mean half-maximal effective concentration (EC50; 24 h) for D. middendorffiana was significantly lower than that recorded for D. magna exposed to 20 °C (KCl) (46.9 mg/L vs 255 mg/L). A significantly higher EC50 (273.4 mg/L; 24 h) was recorded for D. middendorffiana exposed to 15 °C (KCl) compared to D. magna (EC50 50.6 mg/L; 24 h). Our findings suggest that the combined effects of temperature and chemical pollution may severely affect the occurrence of D. middendorffiana, which occupies a central position in the food webs of high-mountain lakes in the Alps.

Fish can be highly vulnerable to environmental pressures because they are exposed to oxidative stressors in the aquatic environment. Such stressors can affect the levels of antioxidant biomarkers against reactive oxygen species (ROS). With this study we investigated the oxidative stress ecology in Danube barbel (Barbus balcanicus) from the Barbucina creek (northeast Italy), a watercourse in the Collio winegrowing district. To do this, superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) activity was measured in gills, liver, and muscle, while metallothioneins (MT) and trace and rare earth elements (REEs) levels were determined in muscle. The effect of environmental factors (physicochemical parameters of water, trace elements and REEs) on oxidative stress biomarkers was thus assessed. High concentrations were determined for cerium (Ce), scandium (Sc), neodymium (Nd), lanthanum (La), yttrium (Y), and praseodymium (Pr) among the REEs. Among the trace elements, arsenic (As), copper (Cu), and mercury (Hg) levels were higher compared to published data, suggesting their role as stressors. The multiple linear regression (MLR) model showed a statistically significant association (R2 = 0.858; F = 10.07; p = 0.015) between As, Cu, Hg, and Pr and SOD activity in the gills, indicating a functional relationship between them. Differently, CAT activity was significantly higher in the liver, probably in response to long-term Cu contamination of the watercourse. This was confirmed by the MLR model that showed a significant association (R2 = 0.638; F = 8.152; p = 0.02) between the concentration of MT and of Cu. Our data show a biochemical defensive response by Danube barbel to the disturbances in the aquatic ecosystem of the Barbucina creek. These insights advance our understanding of the role and the effects of environmental factors as trace elements and REEs on oxidative stress in fish.

Microplastics (MPs) pose biological and chemical hazards in aquatic and terrestrial food webs across the globe. Research on microplastic contamination has long focused on marine ecosystems, whereas the toxicological impact on freshwater organisms is still little explored. In this study, the lethal and sublethal response of the freshwater macroinvertebrate Hydropsyche pellucidula exposed to polypropylene MPs after different pre-conditioning treatments was assessed. Field samples were collected in a riverine system (Vipacco river; northeast Italy) to assess the characteristics of the MPs in the aquatic environment Both water and sediment were contaminated by MPs (3.73 ± 2.11 items m−3 per min and 3.33 ± 4.16 items dm−3, respectively). The chemical MPs composition included polystyrene, polyethylene terephthalate, polyurethane, polyamide, polypropylene, and polyethylene. Polypropylene (PP), although not the most abundant polymer recorded in the study area, was preferred over the other types according to its abundance in freshwater and H. pellucidula feeding behavior. A housing test was performed to recreate the natural conditions of larvae sampled for a reliable response to the ecotoxicological tests. The microplastics underwent either preconditioning with Vipacco River water (PP-river) and surfactant Triton X-100 (PP-sf) or no pre-treatment (PP). Submersion of microplastics in 10 µg L−1 of surfactant solution for 24 h was sufficient to induce consistent spectral changes and modify the chemical profile of the plastic surface. Mortality rate differed according to treatment: PP and PP-river > positive control > PP-sf > negative control. Integrated biomarker response (IBRv2) and analysis of oxidative stress biomarker levels showed a greater response of superoxide dismutase and lipid peroxidation (malondialdehyde) in larvae treated with PP conditioned in surfactant. Our findings enhance knowledge on the toxicity of PP and conditioning phases on H. pellucidula larvae.