Cylindrospermopsin (CYN) is an emerging cyanotoxin increasingly being found in freshwater cyanobacterial blooms worldwide. Humans and animals are exposed to CYN through the consumption of contaminated water and food as well as occupational and recreational water activities; therefore, it represents a potential health threat. It exhibits genotoxic effects in metabolically active test systems, thus it is considered as pro-genotoxic. In the present study, the advanced 3D cell model developed from human hepatocellular carcinoma (HepG2) cells was used for the evaluation of CYN cyto-/genotoxic activity. Spheroids were formed by forced floating method and were cultured for three days under static conditions prior to exposure to CYN (0.125, 0.25 and 0.5 μg/mL) for 72 h. CYN influence on spheroid growth was measured daily and cell survival was determined by MTS assay and live/dead staining. The influence on cell proliferation, cell cycle alterations and induction of DNA damage (γH2AX) was determined using flow cytometry. Further, the expression of selected genes (qPCR) involved in the metabolism of xenobiotics, proliferation, DNA damage response, apoptosis and oxidative stress was studied. Results revealed that CYN dose-dependently reduced the size of spheroids and affected cell division by arresting HepG2 cells in G1 phase of the cell cycle. No induction of DNA double strand breaks compared to control was determined at applied conditions. The analysis of gene expression revealed that CYN significantly deregulated genes encoding phase I (CYP1A1, CYP1A2, CYP3A4, ALDH3A) and II (NAT1, NAT2, SULT1B1, SULT1C2, UGT1A1, UGT2B7) enzymes as well as genes involved in cell proliferation (PCNA, TOP2α), apoptosis (BBC3) and DNA damage response (GADD45a, CDKN1A, ERCC4). The advanced 3D HepG2 cell model due to its more complex structure and improved cellular interactions provides more physiologically relevant information and more predictive data for human exposure, and can thus contribute to more reliable genotoxicity assessment of chemicals including cyanotoxins.

Field survey-based ecological risk assessments for trace metals are conducted to examine the necessity and/or effectiveness of management intervention, such as setting of environmental quality standards. Observational datasets often involve confounders that may bias estimation of the effects of intervention (e.g., reduction of trace-metal concentrations through regulation). The field of ecotoxicology lags behind some other research fields in understanding proper analytical procedures for causal inference from observational datasets; there are only a few field survey-based ecotoxicological studies that have explicitly controlled for confounders in their statistical analyses. In the present study, we estimated the effect of intervention in nickel concentrations on Ephemeroptera, Plecoptera, and Trichoptera richness in rivers in Japan. We also provide detailed explanations for the backgrounds of spurious associations derived from confounders and on proper analytical procedures for obtaining an unbiased estimate of the targeted intervention effect by using regression analysis. We constructed a multiple regression model based on a causal diagram for aquatic insects and environmental factors, and on “the backdoor criterion,” that enabled us to determine the set of covariates required to obtain an unbiased estimate of the targeted intervention effect from regression coefficients. We found that management intervention in nickel concentrations may be ineffective compared to intervention in organic pollution, and that analysis ignoring the confounders overestimated the effect of intervention in nickel concentrations. Our results highlight the fact that confounders can lead to misjudging the necessity for management of anthropogenic chemical substances. Confounders should be explicitly specified and statistically controlled to achieve a comprehensive assessment of ecological risks for various substances.

Glyphosate, one of the most popular herbicides, has become a prominent aquatic contaminant because of its huge usage. The eco-safety of glyphosate is still in controversy, and it is inconclusive how glyphosate influences aquatic microbial communities. In the present study, the effects of glyphosate on the structure and function of microbial communities in a freshwater microcosm were investigated. 16S/18S rRNA gene sequencing results showed that glyphosate treatment (2.5 mg L⁻¹, 15 days) did not significantly alter the physical and chemical condition of the microcosm or the composition of the main species in the community, but metatranscriptomic analyses indicated that the transcriptions of some cyanobacteria were significantly influenced by glyphosate. The microbial community enhanced the gene expression in pathways related to translation, secondary metabolites biosynthesis, transport and catabolism to potentially withstand glyphosate contamination. In the low phosphorus (P) environment, a common cyanobacterium, Synechococcus, plays a special role by utilizing glyphosate as P source and thus reducing its toxicity to other microbes, such as Pseudanabaena. In general, addition of glyphosate in our artificial microcosms did not strongly affect the aquatic microbial community composition but did alter the community’s transcription levels, which might be potentially explained by that some microbes could alleviate glyphosate’s toxicity by utilizing glyphosate as a P source.

Lead bioavailability in contaminated soils varies considerably depending on Pb speciation and sources of contamination. However, little information is available on bioavailability of Pb associated with different fractions. In this study, the Tessier sequential extraction was used to fractionate Pb in 3 contaminated soils to exchangeable (F1), carbonate-bound (F2), Fe/Mn oxides-bound (F3), organic-bound (F4), and residual fractions (F5). In addition, soil residues after F1–F2 extraction (F₃₄₅), F1–F3 extraction (F₄₅), and F1–F4 extraction (F₅) were measured for Pb relative bioavailability (RBA) using a mouse kidney model. Based on the mouse model, Pb-RBA in the soils was 44–93%, which decreased to 43–89%, 28–75%, and 15–68% in the F₃₄₅, F₄₅, and F₅ fractions, respectively. Based on Pb-RBA in the soil residues, Pb-RBA in different fractions was calculated based on a mass balance. The data showed that Pb-RBA was the highest (∼100%) in the exchangeable and carbonate fraction, and the lowest (15–68%) in the residual fraction. In addition, Pb in the first three fractions (F1–F3) contributed most (83–89%) to bioavailable Pb in contaminated soils. Our study shed light on oral bioavailability of Pb in contaminated soils of different fractions based on sequential extraction and provide important information for soil remediation.

Benzo[a]pyrene (BaP), a widely existed polycyclic aromatic hydrocarbon pollutant in aquatic environment, has toxic effects on marine animals and their generations, but the intergenerational immunotoxic mechanism underlying has not been clearly understood. In the study, the offspring of marine medaka (oryzias melastigma) which were exposed to 0.5 μg L⁻¹ BaP suffered from circadian rhythm oscillation disorders and severe DNA damage. Many clock-associated genes like per1 were significantly modulated in offspring, both per1 and p53 were significantly inhibited that altered the progression of cell cycle and inhibited DNA repair, which possibly resulted in the increased mortality of offspring. The hypermethylation of the per1 promotor and abnormal levels of N⁶-methyladenosine (m⁶A) suggested that the underlying mechanism was probably related to the epigenetic modification. Moreover, the offspring from paternal BaP exposure had more severe DNA damage and a higher degree of hypermethylation than those from maternal exposure. F1 larvae from BaP-exposed parents were more sensitive to BaP exposure, showing that the expression of immune and metabolism-related genes were significantly up-regulated. Taken together, the parental toxicity induced by BaP could be passed to F1 generation and the mechanism underlying was probably associated with a characteristic circadian rhythm disorder.

Imidacloprid (IMI) is one of the most extensively used chlorinated organic pesticides and its widespread occurrence makes it attract increased public concern and scientific interest. Peroxymonosulfate (PMS) activation has been widely studied for the elimination of organic pollutants from water. But few studies are focused on their heterogeneous catalytic performance towards imidacloprid especially with the presence of silver ferrite nanoparticles (nAgFeO₂)-based catalysts. Herein, the catalyst, nAgFeO₂, was prepared via a co-precipitation method, and further applied to activate PMS for the removal of imidacloprid (IMI). Our results demonstrated that the prepared nAgFeO₂ significantly promoted the activation of PMS for removing IMI, and the removal of IMI followed a pseudo first-order kinetics model with the corresponding nAgFeO₂ dosage. Electron paramagnetic resonance (EPR) and quenching tests revealed the singlet oxygen (¹O₂)-mediated nonradical pathway, instead of hydroxyl radical (•OH) or sulfate radical (SO4•−), played the dominant role in the degradation of IMI. Eight products were identified and the degradation pathways of IMI were proposed. It is postulated that the primary site at the C-1 position of IMI was more easily attacked by the •OH yielding (6-chloropyridin-3-yl) methanol). While the site at the amidine nitrogen (2) of IMI was more likely attacked by the ¹O₂, and then reacted with •OH to produce 5-hydroxy imidacloprid. Overall, this study provides insights into the mechanisms of nonradical oxidation processes based on PMS for the elimination of pesticides from water, broadening the application of silver ferrite nanoparticles in wastewater treatment.

The present work reports microwave-assisted synthesis of SnO₂ nanoparticles via green route using Psidium Guajava extract. For the enhancement of catalytic activity, nanohybrids of SnO₂ were formulated using different ratios of polyaniline (PANI) via ultrasound-assisted chemical polymerization. Formation of nanohybrids was confirmed via IR and XPS studies. The UV–vis DRS spectra of PANI/SnO₂ revealed significant reduction in the optical band gap upon nanohybrid formation. Microwave-assisted catalytic efficiency of pure SnO₂, PANI, PANI/SnO₂ nanohybrids was investigated using DDT as a model persistent organic pollutant. The degradation efficiency of PANI/SnO₂ was found to increase with the increase in the loading of PANI. Around 87% of DDT degradation was achieved within a very short period of 12 min under microwave irradiation using PANI/SnO₂-50/50 as catalyst. The effect of DDT concentration was explored and the degradation efficiency of PANI/SnO₂-50/50 catalyst was noticed to be as high as 82% in presence of 100 mg/L of DDT. The effect of microwave power on the degradation efficiency revealed 79% degradation using the same nanohybrid when exposed to microwave irradiation for 5 min under 1110 W microwave power. Scavenging studies confirmed the generation of OH, O₂⁻ radicals. The fragments with m/z values as low as 86 and 70 were confirmed by LCMS analysis. Recyclability tests showed that PANI/SnO₂-50/50 nanohybrid exhibited 81% degradation of DDT (500 mg/L) even after the third cycle, which reflected high catalytic efficiency as well as remarkable stability of the catalyst. This green nanohybrid could therefore be effectively utilized for the rapid degradation of persistent organic pollutants.

Microalgal aggregation is a key to many ecosystem functions in aquatic environments. Yet mechanistic understanding of microalgae aggregation, especially the interactions with ubiquitous bacteria populations, remains elusive. We reported an experimental study illustrating how the emerging bacterial populations interacted with a model microalga (Chlamydomonas microsphaera) cells and the consequent aggregation patterns. Results showed that the emergence of bacterial populations significantly stimulated C. microsphaera aggregation. Both bacterial and C. microsphaera motilities were remarkably excited upon coculturing, with the mean cell velocity being up to 2.67 and 1.80 times of those of separate bacterial and C. microsphaera cultures, respectively. The stimulated bacterial and C. microsphaera cell velocity upon coculturing would likely provide a mechanism for enhanced probability of cell-cell collisions that led to amplified aggregation of C. microsphaera population. Correlation analysis revealed that bacterial resource foraging (for polysaccharides) was likely a candidate mechanism for stimulated cell motility in an organic carbon source-limited environment, whereby C. microsphaera-derived polysaccharides serve as the sole organic carbon source for heterotrophic bacteria which in turns facilitates bacteria-C. microsphaera aggregation. Additional analysis showed that bacterial populations capable of successive decomposing algal-derived organic matters dominated the cocultures, with the top five abundant genera of Brevundimonas (24.78%), Shinella (17.94%), Sphingopyxis (11.62%), Dongia (5.82%) and Hyphomicrobium (5.45%). These findings provide new insights into full understanding of microalgae-bacteria interactions and consequent microbial aggregation characteristics in aquatic ecosystems.

With increasing demand for aquaculture products, water reuse is likely to increase for aquaculture operations around the world. Herein, wastewater stabilization ponds (WSP) represents low cost and sustainable treatment technologies to reduce nutrients and various contaminants of emerging concern from effluent. In the present study, we examined bioaccumulation of selected pharmaceuticals from several therapeutic classes by two important fish species in aquaculture with different feeding preferences (Cyprinus carpio and Sander lucioperca) and their common prey to test whether species specific accumulation occurs. Forty and nineteen from 66 selected pharmaceuticals and their metabolites were positively found in water and sediment samples, respectively from the representative WSP. After a six-month study, which corresponds to aquaculture operations, fourteen pharmaceuticals and their metabolites were detected (at a frequency of higher than 50% of samples) in at least one fish tissue collected from the WSP. We observed striking differences for species and organ specific BAFs among study compounds. Though muscle tissues consistently accumulated lower levels of the target analytes, several substances were elevated in brain, liver and kidney tissues (e.g., sertraline) of both species. Low residual concentrations of these target analytes in aquaculture products (fish fillets) suggest WSPs are promising to support the water-food nexus in aquaculture.

Cyanobacterial blooms are an increasing problem in a more eutrophic world. It is still a challenge to fully understand the influence of cyanobacteria on the interactions between predator and prey at higher trophic levels. The present study was mainly undertaken to understand the inducible anti-predator responses of cladocerans while using cyanobacteria as part of food. Specifically speaking, we focused on the anti-predator strategies of Ceriodaphnia cornuta in response to different predators (fish and Chaoborus larvae) under food with different proportions of Microcystis aeruginosa. The morphological (i.e., body size and the induction of horns) and life history traits (e.g., time to first reproduction, offspring number, and survival time) responses were measured under different proportions of M. aeruginosa (i.e., 0%, 20%, 40%, 60%, 80%, and 100%). Our results showed that both the life history and the inducible anti-predator responses of C. cornuta were significantly affected by different concentrations of M. aeruginosa. Specifically, lower concentrations of Microcystis (20%–60%) can significantly promote the horns induction under Chaoborus predation risks, and higher Microcystis concentrations (60%–100%) tend to enhance reproduction in response to fish predation risks, such as larger body size, decreased time to first reproduction, and increased total offspring number. Additionally, an increasing concentration of M. aeruginosa decreased the ability of C. cornuta to reverse horns when predation risks removed. Our findings indicated that cyanobacteria affecting life history traits and the subsequent indirect effects on anti-predator responses in cladocerans could impact the interactions between predator and prey at higher trophic levels and may consequently contribute to shaping the structure of the community in a cyanobacteria bloom area.