peer reviewed | Mercury (Hg) concentrations have significantly increased in oceans during the last century. This element accumulates in marine fauna and can reach toxic levels. Seafood consumption is the main pathway of methylmercury (MeHg) toxicity in humans. Here, we analyzed total Hg (T-Hg) concentrations in two oceanic squid species (Ommastrephes bartramii and Thysanoteuthis rhombus) of an increasing commercial interest off Martinique, French West Indies. Stable isotope ratios reveal a negative linear relationship between δ15N or δ13C in diamondback squid samples. No significant trend was observed between δ34S values and T-Hg concentrations, contrasting with the sulfate availability and sulfide abundance hypotheses. This adds to a growing body of evidence suggesting Hg methylation via sulfate-reducing bacteria is not the main mechanism driving Hg bioavailability in mesopelagic organisms. All squid samples present T-Hg levels below the maximum safe consumption limit (0.5 ppm), deeming the establishment of a commercial squid fishery in the region safe for human consumption.

Fluoride (F) is an emerging pollutant that originates from multiple sources and adversely affects plant growth and nutrient bioavailability in soil. This greenhouse study investigated the effects of soil F (0, 10, 20, 50, 100, 200 mg kg⁻¹) on morpho-physiological growth characteristics of wheat, soil F contents, and bioavailability and uptake of F, phosphorus (P), sulphur (S), potassium (K), calcium (Ca), magnesium (Mg), aluminium (Al), iron (Fe), manganese (Mn), silicon (Si) and zinc (Zn) by wheat. Higher F significantly reduced plant height and number of leaves particularly at early growth stages and increased visible leaf injury index. Powdery mildew infestation coincided with leafy injury and was higher in elevated soil F treatments. Fluoride treatments (>50 mg kg⁻¹) significantly increased water (H₂O)- and calcium chloride (CaCl₂)-extractable F contents in soil. Water-extractable soil F contents from soil in all concentration were higher than CaCl₂-extractable F. This increased F bioavailability resulted in significantly higher F uptake and accumulation in live leaves, dead leaves and grains of wheat which followed order: live leaves > dead leaves > grains. Leaf injury index and number of dead leaves correlated significantly positively with soil H₂O- and CaCl₂-extractable F contents. Patterns of nutrient (P, K, S) and trace metals (Al, Ca, Mg, Fe, Mn, Si, Zn) varied significantly with F concentrations and between live and dead leaves, and grains except for Zn. Dead leaves generally had higher nutrients and trace metals than live leaves and grains. Fluoride contents in live leaves, dead leaves and grains showed positive correlations with nutrient elements but negative with trace metals. Number of dead leaves correlated negatively with Al, Ca, Fe, Mg, S and Si but positively with P and Zn contents in dead leaves whereas leaf injury index showed positive correlation with Fe, K, P, Si, Zn, S but negative with Al, Ca and Mg contents. These observations provided evidence of higher F uptake and associated impairment in nutrient and trace metal accumulation which caused leaf injury accompanied by powdery mildew infestation in wheat. However, further research in the region is required to confirm the relationship between F pollution, leaf injury and trace metal accumulation in crops under field conditions.

The role of hydrogen sulfide (H₂S) is well known in the regulation of abiotic stress such as toxic heavy metal. However, mechanism(s) lying behind this amelioration are still poorly known. Consequently, the present study was focused on the regulation/mitigation of hexavalent chromium (Cr(VI) toxicity by the application of H₂S in wheat and rice seedlings. Cr(VI) induced accumulation of reactive oxygen species and caused protein oxidation which negatively affect the plant growth in both the cereal crops. We noticed that Cr(VI) toxicity reduced length of wheat and rice seedlings by 21% and 19%, respectively. These reductions in length of both the cereal crops were positively related with the down-regulation in the ascorbate-glutathione cycle, and were recovered by the application NaHS (a donor of H₂S). Though exposure of Cr(VI) slightly stimulated sulfur assimilation but addition of H₂S further caused enhancement in sulfur assimilation, suggesting its role in the H₂S-mediated Cr(VI) stress tolerance in studied cereal crops. Overall, the results revealed that H₂S renders Cr(VI) stress tolerance in wheat and rice seedlings by stimulating sulfur assimilation and ascorbate-glutathione which collectively reduce protein oxidation and thus, improved growth was observed.

Low sulfur fuel oils (LSFOs) with less than 0.5% sulfur content have been mandated for marine vessels by the International Maritime Organization since 2020. However, owing to the low dispersibility and high viscosity of LSFOs, their oceanic spills are difficult to clean using conventional response systems. In this study, we propose a superhydrophilic and hygroscopic ramie to clean spilled LSFO. To this end, a raw ramie fiber, which is intrinsically hydrophobic, was treated using a mild alkali to remove its waxy, rough, and gummy veneer and reveal a smooth surface. This substantially improved its hygroscopic nature, superhydrophilicity, and water-retention, while preserving its mechanical durability in dry and wet environments. The hygroscopic ramie exhibited underwater superoleophobicity and self-cleaning abilities against highly adhesive LSFOs. Two proofs-of-concept are demonstrated in this study—an oil-proof glove for maximizing oil repellency and a direct oil-scooping device for simple and continuous recovery of spilled oil with high efficiency.

Bacterial communities in antimony (Sb) polluted soils have been well addressed, whereas the important players fungal communities are far less studied to date. Here, we report different responses of bacterial and fungal communities to Sb contamination and the ecological processes controlling their community assembly. Soil samples in the Xikuangshan mining area were collected and subjected to high through-put sequencing of 16S rRNA and ITS1 to investigate bacterial and fungal communities, respectively, along an Sb gradient. Sb speciation in the soil samples and other physicochemical parameters were analyzed as well. Bacterial communities were dominated by Deltaproteobacteria in the soil with highest Sb concentration, whereas Chloroflexi were dominant in the soil with lowest Sb concentration. Fungal communities in high-Sb soils were predominated by unclassified Fungi, whilst Leotiomycetes were dominant in low-Sb soil samples. Multivariate analysis indicated that Sb, pH and soil texture were the main drivers to strongly impact microbial communities. We further identified Sb-resistant microbial groups via correlation analysis. In total, 18 bacterial amplicon sequence variants (ASVs) were found to potentially involve in biogeochemical cycles such as Sb oxidation, sulfur oxidation or nitrate reduction, whereas 12 fungal ASVs were singled out for potential heavy metal resistance and plant growth promotion. Community assembly analysis revealed that variable selection contributed 100% to bacterial community assembly under acidic or high Sb concentration conditions, whereas homogeneous selection dominated fungal community assembly with a contribution over 78.9%. The community assembly of Sb-resistant microorganisms was mainly controlled by stochastic process. The results offer new insights into microbial ecology in Sb-contaminated soils, especially on the different responses of microbial communities under identical environmental stress and the different ecological processes underlining bacterial and fungal community assembly.

Arsenic (As) and cadmium (Cd), two major carcinogenic heavy metals, enters into human food chain by the consumption of rice or rice-based food products. Both As and Cd disturb plant-nutrient homeostasis and hence, reduces plant growth and crop productivity. In the present study, As/Cd modulated responses were studied in non-basmati (IR-64) and basmati (PB-1) rice varieties, at physiological, biochemical and transcriptional levels. At the seedling stage, PB-1 was found more sensitive than IR-64, in terms of root biomass; however, their shoot phenotype was comparable under As and Cd stress conditions. The ionomic data revealed significant nutrient deficiencies in As/Cd treated-roots. The principal component analysis identified NH₄⁺ as As-associated key macronutrient; while, NH₄⁺/NO₃⁻ and K⁺ was majorly associated with Cd mediated response, in both IR-64 and PB-1. Using a panel of 21 transporter gene expression, the extent of nutritional deficiency was ranked in the order of PB-1(As)<IR-64(As)<PB-1(Cd)<IR-64(Cd). A feed-forward model is proposed to explain nutrient deficiency induced de-regulation of gene expression, as observed under Cd-treated IR-64 plants, which was also validated at the level of sulphur metabolism related enzymes. Using urea supplementation, as nitrogen-fertilizer, significant mitigation was observed under As stress, as indicated by 1.018- and 0.794-fold increase in shoot biomass in IR-64 and PB-1, respectively compared to that of control. However, no significant amelioration was observed in response to supplementation of urea under Cd or potassium under As/Cd stress conditions. Thus, the study pinpointed the relative significance of various macronutrients in regulating As- and Cd-tolerance and will help in designing suitable strategies for mitigating As and/or Cd stress conditions.

Evidence suggests that the invasion of Spartina alterniflora (S. alterniflora) poses potentially serious risks to the stability of coastal wetlands, an ecosystem that is extremely vulnerable to both biological and non-biological threats. However, the effects and mechanisms of sulfur (S) in mediating the growth and expansion of S. alterniflora are poorly understood, particularly when sediments are contaminated with cadmium (Cd). A 6-month greenhouse study was conducted to evaluate the mediating effect of S on Cd tolerance and growth of S. alterniflora. Treatments consisted of a factorial combination of three S rates (applied as Na₂SO₄; 0, 500, 1000 mg kg⁻¹ dry weight (DW), as S₀, S₅₀₀, and S₁₀₀₀) and four Cd rates (applied as CdCl₂; 0, 1, 2, 4 mg kg⁻¹ DW, as Cd₀, Cd₁, Cd₂, and Cd₄). Results showed that although the exogenous S supply obviously increased Cd accumulation in roots (up to 71.22 ± 6.43 mg kg⁻¹ DW) due to the decrease of Fe concentration in iron plaque (down to 4.02 ± 1.18 mg g⁻¹ DW), biomass reduction and oxidative stress in plant tissues were significantly alleviated. The addition of S significantly up-regulated the concentration of compounds related to Cd tolerance, including proline and glutathione. Therefore, the translocation of Cd was restricted, and plant growth was not impacted. The present study demonstrated that the exogenous sulfur supply could promote the growth of S. alterniflora and enhance its tolerance to Cd. Therefore, under the effects of S. alterniflora, the increased fluctuations of S pool caused by the release and deposition of S might further exacerbate S. alterniflora expansion in Cd contaminated coastal wetlands.

We investigated the biological response of soluble organic fraction (SOF) and water-soluble fraction (WSF) extracted from particulate matter (PM) emitted by an automotive diesel engine operating in a representative urban driving condition. The engine was fueled with ultra-low sulfur diesel (ULSD), and its binary blends by volume with 13% of butanol (Bu13), and with hydrotreated vegetable oil (HVO) at 13% (HVO13) and 20% (HVO20). Cytotoxicity, genotoxicity, oxidative DNA damage and ecotoxicity tests were carried out, and 16 polycyclic aromatic hydrocarbons (PAH) expressed as tbenzo(a)pyrene total toxicity equivalent (BaP-TEQ) were also analyzed. The Hepatocarcinoma epithelial cell line (HepG2) was exposed to SOF for 24 h and analyzed using comet assay, with the inclusion of formamidopyrimidine DNA glycosylase (FPG) and endonuclease III (Endo III) to recognize oxidized DNA bases. The WSF was evaluated through acute ecotoxicity tests with the aquatic microcrustacean Daphnia pulex (D. Pulex). Results showed that there was no cytotoxic activity for all tested SOF concentrations. Genotoxic responses by all the SOF samples were at same level, except for the HVO13 which was weaker in the absence of the enzymes. The addition of the FPG and Endo III enzymes resulted in a significant increase in the comet tail, indicating that the DNA damage from SOF for all tested fuel blends involves oxidative damage including a higher level of oxidized purines for ULSD and Bu13 in comparison with HVO blends, but the oxidized pyrimidines for HVO blends were slightly higher compared to Bu13. The WSF did not show acute ecotoxicity for any of the fuels. Unlike other samples, Bu13-derived particles significantly increase the BaP-TEQ. The contribution to the genotoxic activity and oxidative DNA from SOF was not correlated to BaP-TEQ, which means that the biological activity of PM might be affected also by other toxic compounds present in particulate phase.

Ants can influence ecological processes, such as the transfer of elements or radionuclides, in several ways. For example, they redistribute materials while foraging and maintaining their nests and have an important role in terrestrial food webs. Quantitative data of the transfer of elements into ants is needed, e.g., for developing improved radioecological models. In this study, samples of red wood ants (genus Formica), nest material, litter and soil were collected from a former uranium mining site in Eastern Finland. Concentrations of 33 elements were analyzed by Inductively Coupled Plasma-Mass Spectroscopy/Optical Emission Spectroscopy. Estimated element concentrations in spruce needles were used as a proxy for studying the transfer of elements into ants via aphids because spruces host the most important aphid farms in boreal forests. Empirically determined organism/medium concentration ratios (CRs) are commonly used in radioecological models. Ant/soil CRs were calculated and the validity of the fundamental assumption behind the of use of CRs (linear transfer) was evaluated. Elements that accumulated in ants in comparison to other compartments were cadmium, potassium, phosphorus, sulfur, and zinc. Ant uranium concentrations were low in comparison to soil, litter, or nest material but slightly elevated in comparison to spruce needles. Ant element concentrations were quite constant regardless of the soil concentrations. Non-linear transfer models could therefore describe the soil-to-ant transfer better than conventional CRs.

Airborne bacteria may absorb the substance from the atmospheric particles and play a role in biogeochemical cycling. However, these studies focused on a few culturable bacteria and the samples were usually collected from one site. The metabolic potential of a majority of airborne bacteria on a regional scale and their driving factors remain unknown. In this study, we collected particulates with aerodynamic diameter ≤2.5 μm (PM₂.₅) from 8 cities that represent different regions across China and analyzed the samples via high-throughput sequencing of 16S rRNA genes, quantitative polymerase chain reaction (qPCR) analysis, and functional database prediction. Based on the FAPROTAX database, 326 (80.69%), 191 (47.28%) and 45 (11.14%) bacterial genera are possible to conduct the pathways of carbon, nitrogen, and sulfur cycles, respectively. The pathway analysis indicated that airborne bacteria may lead to the decrease in organic carbon while the increase in ammonium and sulfate in PM₂.₅ samples, all of which are the important components of PM₂.₅. Among the 19 environmental factors studied including air pollutants, meteorological factors, and geographical conditions, PM₂.₅ concentration manifested the strongest correlations with the functional genes for the transformation of ammonium and sulfate. Moreover, the PM₂.₅ concentration rather than the sampling site will drive the distribution of functional genera. Thus, a bi-directional relationship between PM₂.₅ and bacterial metabolism is suggested. Our findings shed light on the potential bacterial pathway for the biogeochemical cycling in the atmosphere and the important role of PM₂.₅, offering a new perspective for atmospheric ecology and pollution control.