Forest fires can threaten amphibians because ash-associated contaminants transported by post-fire runoff impact both terrestrial and aquatic ecosystems. Still, the effects of these contaminants on the skin microbiome of amphibians have been overlooked. Thus, the main objective of this study was to assess the effects of ash from different severity wildfires (moderate and high) on the skin microbiome of the Iberian frog (Rana iberica). Bacterial isolates sampled from R. iberica skin microbiome were tested for their antimicrobial activity against the pathogen Aeromonas salmonicida. The isolates with antimicrobial activity were identified and further exposed to several concentrations (0, 6.25, 12.5, 25, 50, 75, and 100%) of Eucalypt (Eucalyptus globulus) aqueous extracts (AAEs) of ash from both a moderate and a high severity wildfire. The results showed that 53% of the bacterial isolates presented antimicrobial activity, with Pseudomonas being the most common genus. Exposure to AAEs had diverse effects on bacterial growth since a decrease, an increase or no effects on growth were observed. For both ash types, increasing AAEs concentrations led to an increase in the number of bacteria whose growth was negatively affected. Ash from the high severity fire showed more adverse effects on bacterial growth than those from moderate severity, likely due to the higher metal concentrations of the former. This study revealed that bacteria living in Iberian frogs' skin could be impaired by ash-related contaminants, potentially weakening the individual's immune system. Given the foreseen increase in wildfires' frequency and severity under climate change, this work raises awareness of the risks faced by amphibian communities in fire-prone regions, emphasising the importance of a rapid implementation of post-fire emergency measures for the preservation and conservation of this group of animals.

Environmental nanoplastics (NPs) can accumulate in soils, posing a potential risk to soil ecosystems. However, the ecotoxicity of NPs for soil organisms has received little research attention. This study investigated whether NP exposure in soil leads to reproductive decline in the soil nematode Caenorhabditis elegans and sought to determine the mechanisms by which it may occur. Wild-type N2 C. elegans L1 larvae were exposed to various concentrations of nano-sized polystyrene (100 nm) in soil (0, 1, 10, 100, and 1000 mg/kg dry weight) for 96 h. We show that nano-sized polystyrene (100 nm) labeled with red fluorescence significantly accumulated in the intestine of C. elegans in a dose-dependent fashion via soil exposure (8%–47% increase). In addition, NP soil exposure led to 7%–33% decline in the number of eggs in utero and 2.6%–4.4% decline in the egg hatching percentage. We also find that the number of germ cell corpses (31%–55% increase) and the mRNA levels of germline apoptosis marker gene ced-3 (14%–31% increase) were significantly higher with greater NP soil exposure (10, 100, and 1000 mg/kg), while intracellular ATP levels were significantly reduced. Finally, the DEBtox model, which is based on the dynamic energy budget theory, was applied to show that the increased reproductive costs for C. elegans caused by NPs in soil are associated with energy depletion and reproductive decline. The threshold value (4.18 × 10⁻⁶ mg/kg) for the energy budget also highlighted the potential high reproductive risk posed by NPs in terrestrial ecosystems. Our study provides new insights into how soil organisms interact with NPs in soil ecosystems.

Nitric oxide (NO) and ethylene are both important signaling molecules which participate in numerous plant development processes and environmental stress resistance. Here, we investigate whether and how NO interacts with ethylene during the development of endodermal barriers that have major consequences for the apoplastic uptake of cadmium (Cd) in the hyperaccumulator Sedum alfredii. In response to Cd, an increased NO accumulation, while a decrease in ethylene production was observed in the roots of S. alfredii. Exogenous supplementation of NO donor SNP (sodium nitroprusside) decreased the ethylene production in roots, while NO scavenger cPTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) had the opposite effect. The exogenous addition of NO affected the ethylene production through regulating the expression of genes related to ethylene synthesis. However, upon exogenous ethylene addition, roots retained their NO accumulation. The abovementioned results suggest that ethylene is downstream of the NO signaling pathway in S. alfredii. Regardless of Cd, addition of SNP promoted the deposition of endodermal barriers via regulating the genes related to Casparian strips deposition and suberization. Correlation analyses indicate that NO positively modifies the formation of endodermal barriers via the NO-ethylene signaling pathway, Cd-induced NO accumulation interferes with the synthesis of ethylene, leading to a deposition of endodermal barriers in S. alfredii.

This study showed that metal transport and partitioning are primarily controlled by suspended solids with seasonal flow regimes in plain river networks with sedimentary resuspension. Eight metal species containing iron (Fe), manganese (Mn), cadmium (Cd), chrome (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn), in multiple phases of sediments, suspended solids (>0.7 μm), colloids (1 nm-0.7 μm) and dissolved phase (<1 nm) were analysed to characterize their temporal-spatial patterns, partitioning and transport on a watershed scale. Metal concentrations were associated with suspended solids in the water column and decreased from low flow to high flow. However, metal partitioning between particulate phase (suspended solids) and dissolvable phases (colloids and dissolved phase) was reversed and increased from low flow to high flow with decreased concentration of total suspended solids and median particle size. Partition coefficients (kₚ) showed differences among metal species, with higher values for Pb (354.3–649.0 L/g) and Cr (54.2–223.7 L/g) and lower values for Zn (2.5–25.2 L/g) and Cd (17.3–21.0 L/g). Metal concentrations in sediments increased by factors of 1.2–3.0 from upstream to downstream in watersheds impacted by urbanization. The behaviours of metals in rivers provide deeper insight into the ecological risks they pose for downstream lakes, where increased redox potential and organic matter may increase metal mobility due to algal blooms. Areas with heavy pollution of metals and the transport routines of metals in the river networks were also revealed in our research.

Freshwater mussels are among the most endangered groups of fauna anywhere in world. The indiscriminate use of antibiotics has led to the emergence of resistant strains. These antibiotic-resistant bacteria play a key role in increasing the risk allied with the use of surface water and in spread of resistance genes. Two endangered freshwater mussel species, Margaritifera margaritifera and Potomida littoralis, were sampled at 4 sampling sites along a 50 km stretch of River Tua. Water samples were taken at same sites. Of the total of 135 isolates, 64.44% (39.26% from water and 25.19% from mussels) were coliform bacteria. Site T1, with the lowest concentration of coliform bacteria, and site T2 were the only ones where M. margaritifera was found. No E. coli isolates were found in this species and the pattern between water and mussels was similar. P. littoralis, which was present at T3/T4 sites, is the one that faces the highest concentration of bacterial toxins, which are found in treated wastewater effluents and around population centers. Sites T3/T4 have the isolates (water and mussels) with the highest resistance pattern, mainly to β-lactams. Water and P. littoralis isolates (T3/T4) showed resistance to penicillins and their combination with clavulanic acid, and to cephalosporins, precisely to a fourth generation of cephalosporin antibiotics. The analysis provides important information on the risk to water systems, as well as the need to investigate possible management measures. It is suggested that future studies on the health status of freshwater bivalves should incorporate measures to indicate bacteriological water quality.

Dissimilatory arsenate-respiring prokaryotes (DARPs) are considered to be the major drive of the reductive mobilization of arsenic from solid phases. However, it is not fully understood how phosphate, a structural analog of arsenate, affects the DARPs-mediated arsenic mobilization. This work aimed to address this issue. As-contaminated soils were collected from a Shimen Realgar Mine-affected area. We identified a unique diversity of DARPs from the soils, which possess high As(V)-respiring activities using one of multiple small organic acids as the electron donor. After elimination of the desorption effect of phosphate on the As mobilization, the supplement of additional 10 mM phosphate to the active slurries markedly increased the microbial community-mediated reductive mobilization of arsenic as revealed by microcosm tests; this observation was associated to the fact that phosphate significantly increased the As(V)-respiratory reductase (Arr) gene abundances in the slurries. To confirm this finding, we further obtained a new DARP strain, Priestia sp. F01, from the samples. We found that after elimination of the chemical effect of phosphate, the supplement of 10 mM phosphate to the active slurries resulted in an 82.2% increase of the released As(III) in the solutions, which could be contributed to that excessive phosphate greatly increased the Arr gene abundance, and enhanced the transcriptional level of arrA gene and the bacterial As(V)-respiring activity of F01 cells. Considering that phosphate commonly coexists with As in the environment, and is a frequently-used fertilizer, these findings are helpful for deeply understanding why As concentrations in contaminated groundwater are dynamically fluctuated, and also provided new knowledge on the interactions between the biogeochemical processes of P and As.

Arsenic (As) is a highly toxic metalloid adversely affecting the environment, human health, and crop productivity. The present study assessed the synergistic effects of salinity and As on photosynthetic attributes, stomatal regulations, and metabolomics responses of the xero-halophyte Salvadora persica to decipher the As-salinity cross-tolerance mechanisms and to identify the potential metabolites/metabolic pathways involved in cross-tolerance of As with salinity. Salinity and As stress-induced significant stomatal closure in S. persica suggests an adaptive response to decrease water loss through transpiration. NaCl supplementation improved the net photosynthetic rate (by +39%), stomatal conductance (by +190%), water use efficiency (by +55%), photochemical quenching (by +37%), and electron transfer rate (54%) under As stress as compared to solitary As treatment. Our results imply that both stomatal and non-stomatal factors account for a reduction in photosynthesis under high salinity and As stress conditions. A total of 64 metabolites were identified in S. persica under salinity and/or As stress, and up-regulation of various metabolites support early As-salinity stress tolerance in S. persica by improving antioxidative defense and ROS detoxification. The primary metabolites such as polyphenols (caffeic acid, catechin, gallic acid, coumaric acid, rosmarinic acid, and cinnamic acid), amino acids (glutamic acid, cysteine, glycine, lysine, phenylalanine, and tyrosine), citrate cycle intermediates (malic acid, oxalic acid, and α-ketoglutaric acid), and most of the phytohormones accumulated at higher levels under combined treatment of As + NaCl compared to solitary treatment of As. Moreover, exogenous salinity increased glutamate, glycine, and cysteine, which may induce higher synthesis of GSH-PCs in S. persica. The metabolic pathways that were significantly affected in response to salinity and/or As include inositol phosphate metabolism, citrate cycle, glyoxylate and dicarboxylate metabolism, amino acid metabolism, and glutathione metabolism. Our findings indicate that inflections of various metabolites and metabolic pathways facilitate S. persica to withstand and grow optimally even under high salinity and As conditions. Moreover, the addition of salt enhanced the arsenic tolerance proficiency of this halophyte.

Sediment phosphorus (P) release and retention are important in controlling whole-system P dynamics and budget in eutrophic lakes. Here we combine short- (seasonal) and long-term (years to decades) studies to quantify the internal P loading and P release potential in the sediments of Lake Chaohu and explore their controlling mechanisms. In the west region of the lake, short-term P diffusive fluxes ranged from 0.2 mg/m²·d⁻¹ to 6.69 mg/m²·d⁻¹ (averaged 2.76 mg/m²·d⁻¹) and long-term net P release ranged from 2.25 mg/m²·d⁻¹ to 8.94 mg/m²·d⁻¹ (averaged 5.34 mg/m²·d⁻¹); in the east region, short-term P diffusive fluxes varied from 0.73 mg/m²·d⁻¹ to 1.76 mg/m²·d⁻¹ (averaged 1.05 mg/m²·d⁻¹) and long-term P release ranged from 0.13 mg/m²·d⁻¹ to 4.15 mg/m²·d⁻¹ (averaged 1.3 mg/m²·d⁻¹). Both short- and long-term P releases were in the same order of magnitudes as the external P inputs (3.56 mg/m²·d⁻¹). Comparison of the long-term and short-term sediment P release indicates that while the high summer P release in the east might only represent a snapshot value, the sediments in the west contribute to large P release for years or even decades, impeding water quality recovery under lake management. Mobilization of surface sediment legacy P accounted for 81% of short-term P release. The long-term release was dominated by remobilization of iron bond P (BD-P) (average 52.1%) at all sites, while Aluminium-bound P (NaOH-rP) exhibited partly reactive and potentially mobile, releasing P to the water column in most sites in the west. Our study demonstrates the importance of sediments as P sources in lake Chaohu. The combination of short- and long-term P release studies can help understand the roles of sediments in regulating the water quality and eutrophication.

Surface water is one of the primary sources of irrigation water for produce production; therefore, its contamination by foodborne pathogens, such as Salmonella, may substantially impact public health. In this study, we determined the presence of Salmonella in surface water and characterized the relationship between Salmonella detection and environmental and anthropogenic factors. From April 2019 to February 2020, 120 samples from 30 sites were collected monthly in four watersheds located in two different central Chile agricultural regions (N = 1080). Water samples from rivers, canals, streams, and ponds linked to each watershed were obtained. Surface water (10 L) was filtrated in situ, and samples were analyzed for the presence of Salmonella. Salmonella was detected every month in all watersheds, with a mean detection percentage of 28% (0%–90%) across sampling sites, regardless of the season. Overall, similar detection percentages were observed for both regions: 29.1% for Metropolitan and 27.0% for Maule. Salmonella was most often detected in summer (39.8% of all summer samples tested positive) and least often in winter (14.4% of winter samples). Random forest analysis showed that season, water source, and month, followed by latitude and river, were the most influential factors associated with Salmonella detection. The influences of water pH and temperature (categorized as environmental factors) and factors associated with human activity (categorized as anthropogenic factors) registered at the sampling site were weakly or not associated with Salmonella detection. In conclusion, Salmonella was detected in surface water potentially used for irrigation, and its presence was linked to season and water source factors. Interventions are necessary to prevent contamination of produce, such as water treatment before irrigation.

In fish, the gut microbiome plays a crucial role in homeostasis and health and is affected by several organic and inorganic environmental contaminants. Amphidromous fish are sentinel species, particularly exposed to these stressors. We used whole metagenome sequencing to characterize the gut microbiome of wild European eels (Anguilla anguilla) at a juvenile stage captured from three sites with contrasted pollution levels in term of heavy metals and persistent organic pollutants. The objectives were to identify what parameters could alter the gut microbiome of this catadromous fish and to explore the potential use of microbiota as bioindicators of environment quality. We identified a total of 1079 microbial genera. Overall, gut microbiome was dominated by Proteobacteria, Firmicutes and Actinobacteria. Alpha and beta diversity were different amongst sites and could be explained by a reduced number of environmental and biological factors, specifically the relative abundance of fish preys in eels’ diet, PCB101, γHCH (lindane), transnonachlor and arsenic. Furthermore, we identified a series of indicator taxa with differential abundance between the three sites. Changes in the microbial communities in the gut caused by environmental pollutants were previously undocumented in European eels. Our results indicate that microbiota might represent another route by which pollutants affect the health of these aquatic sentinel organisms.