•The total length of the D. magna genome was about 123 Mb with N50 = 10.1 Mb.•The number of scaffolds was 4,193 including 10 LGs.•A total of 15,721 genes were annotated after manual curation.•Defense ...related genes such as 43 CYP, 22 GST, and 62 ABC genes were identified.
The water flea Daphnia magna is a small planktonic cladoceran. D. magna has been used as a model species for ecotoxicology, as it is sensitive to environmental stressors and environmental changes. Since Daphnia is affected by culture environment and each population/strain has its own ecological and genetic characteristics, its population/strain-based genome information is useful for environmental genomic studies. In this study, we assembled and characterized the genome of D. magna. Using a high-density genetic map of D. magna xinb3, the draft genome was integrated to 10 linkage groups (LGs). The total length of the integrated genome was about 123 Mb with N50 = 10.1 Mb, and the number of scaffolds was 4193 including 10 LGs. A total of 15,721 genes were annotated after manual curation. Orthologous genes were characterized in the genome and compared with other genomes of Daphnia. In addition, we identified defense related genes such as cytochrome P450 (CYP) genes, glutathione S-transferase (GST) genes, and ATP-binding cassette (ABC) genes from the assembled D. magna genome for its potential use in molecular ecotoxicological studies in the freshwater environment. This genomic resource will be helpful to study for a better understanding on molecular mechanism in response to various pollutants.
Research has demonstrated the presence of viruses in wastewater (WW), which can remain viable for a long period, posing potential health risks. Conventional WW treatment methods involving UV light, ...chlorine and ozone efficiently reduce microbial concentrations, however, they produce hazardous byproducts and microbial resistance that are detrimental to human health and the ecosystem. Hence, there is a need for novel disinfection techniques. Antimicrobial Photodynamic Inactivation (PDI) emerges as a promising strategy, utilizing photosensitizers (PS), light, and dioxygen to inactivate viruses. This study aims to assess the efficacy of PDI by testing methylene blue (MB) and the cationic porphyrin TMPyP as PSs, along a low energy consuming white light source (LED) at an irradiance of 50 mW/cm2, for the inactivation of bacteriophage Phi6. Phi6 serves as an enveloped RNA-viruses surrogate model in WW. PDI experiments were conducted in a buffer solution (PBS) and real WW matrices (filtered and non-filtered). Considering the environmental release of the treated effluents, this research also evaluated the ecotoxicity of the resulting solution (post-PDI treatment effluent) on the model organism Daphnia magna, following the Organisation for Economic Cooperation and Development (OECD) immobilization technical 202 guideline. Daphnids were exposed to WW containing the tested PS at different concentrations and dilutions (accounting for the dilution factor during WW release into receiving waters) over 48 h. The results indicate that PDI with MB efficiently inactivated the model virus in the different aqueous matrices, achieving reductions superior to 8 log10 PFU/mL, after treatments of 5 min in PBS and of ca. 90 min in WW. Daphnids survival increased when subjected to the PDI-treated WW with MB, considering the dilution factor. Overall, the effectiveness of PDI in eliminating viruses in WW, the fading of the toxic effects on daphnids after MB’ irradiation and the rapid dilution effect upon WW release in the environment highlight the possibility of using MB in WW PDI-disinfection.
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•The study proposes PDI as a promising approach to overcome the limitations of the conventional wastewater treatment methods.•The photosensitizers Methylene Blue and cationic porphyrin TMPyP showed efficacy in inactivating the enveloped RNA-virus.•The survival of Daphnia magna increased when exposed to the PDI-treated WW with MB. • The fading of toxic effects are related to the MB irradiation and the dilution effect upon WW release into environment.
Microplastic exposure leads to various toxic effects in Daphnia magna; however, the effects of microplastics on the metabolic processes in D. magna and the corresponding molecular toxicity mechanisms ...remain unclear. In the present study, the effects of acute exposure to polyethylene microplastics with different particle sizes (20 μm MPs-20 and 30 μm MPs-30) on metabolites in D. magna and the mechanisms of toxicity were investigated by combining metabolomics and traditional toxicology techniques. Exposure to both MPs-20 and MPs-30 resulted in significant accumulation of microplastics in the gut of D. magna and significantly reduced D. magna survival and heart rate. Metabolomics analysis revealed that MPs-20 and MPs-30 induced significant changes in up to 88 and 91 differential metabolites, respectively, and collectively induced significant changes in 75 metabolites in D. magna. Among lipid metabolites, MPs-20 specifically downregulated phosphatidylcholine and upregulated phosphatidylethanolamine, which mainly affected phospholipid metabolism, whereas MPs-30 specifically downregulated amino acid metabolites l-glutamine, l-glutamate and malic acid, which mainly interfered with energy metabolism. The results of this study provide novel insights into the mechanism of effects of microplastics on metabolic processes in D. magna.
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•Particle size dominated the toxic effects of microplastics on D. magna.•Waterborne exposure led to significant accumulation of microplastics in the gut of D. magna.•MPs-20 specifically downregulated phosphatidylcholine and upregulated phosphatidylethanolamine.•MPs-30 mainly induced the degradation of amino acid metabolites.•Exposure to 100 mg/L T-80 induced considerable negative effects on D. magna.
Graphene oxide (GO) possesses versatile applicability and high hydrophilicity, thus may have frequent contact with aquatic organisms. However, the ecological risks of GO in aquatic ecosystems remain ...largely unexplored currently. This study evaluated the comprehensive toxicological effects of GO on Daphnia magna, a key species in fresh water ecosystem. The results revealed nonsevere acute toxicities, including immobility (72 h EC50: 44.3 mg/L) and mortality (72 h LC50: 45.4 mg/L), of GO on D. magna. To understand the underlying mechanism of GO exposure, changes in superoxide dismutase (SOD) and lipid peroxidation (LPO) of D. magna exposed to GO were correlated, which revealed elevated GO-mediated oxidative stress and damages, especially in the long-time and high-dose exposure groups. The observations of in vivo fluorescence labeled with 2′, 7′-dichlorofluorescin further demonstrated that reactive oxygen species were concentrated in daphnia guts, which corresponded with the high bioaccumulation level (5 mg/L, 24 h body burden: 107.9 g/kg) of GO in daphnia guts. However, depuration of GO from daphnia was not difficult. Daphnia almost released all GO within 24 h after it was transferred to clean water. These results hence suggest that GO could accumulate and induce significant oxidative stress in the gut of D. magna, while D. daphnia can also relieve the acute toxicity by depurating GO.
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•Graphene oxide (GO) can be quickly uptaken and easily depurated by D. magna.•GO induces nonsevere acute toxicity in D. magna.•GO mediates the production of oxidative stress in D. magna.•The GO-induced oxidative stress coincides with its accumulation in daphnia guts.
This study investigated the accumulation of graphene oxide (GO) in Daphnia magna and the oxidative stress and acute toxicity induced by GO.
Microplastic fibers (MP) from textile weathering and washing are increasingly being recognized as environmental pollutants. The majority of studies on the bioavailability and effects of microplastic ...focused on small polystyrene spherical plastic particles, while less data are available for fibers and for other materials besides polystyrene. We investigated the ingestion and effects of ground polyethylene terephthalate (PET) textile microfibers (length range: 62–1400 μm, width 31–528 μm, thickness 1–21.5 μm) on the freshwater zooplankton crustacean Daphnia magna after a 48 h exposure and subsequent 24 h of recovery in MP free medium and algae. The majority of ingested fibers by D. magna were around 300 μm, but also some very large twisted MP fibers around 1400 μm were found inside the gut. Exposure to these fibers results in increased mortality of daphnids after 48 h only in the case where daphnids were not pre-fed with algae prior to experiment, but no effect was found when daphnids were fed before the experiments. Regardless of the feeding regime, daphnids were not able to recover from MP exposure after additional 24 h incubation period in a MP free medium with algae. The uptake and effects of PET textile MP on D. magna are presented here for the first time.
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•D. magna ingests very long polyethylene terephthalate textile microfibers (even 1400 μm long).•Ingestion of fibres results in increased mortality.•Daphnia die even after 24 h of exposure in MP free medium following 48 h of MP exposure.
Daphnia magna ingest long textile microplastic fibers.
Even though microplastics are intensively studied, the focus of the research is mainly on relatively short term effects at high doses. Therefore there is a need to shift the focus toward more ...realistic, longer-term endpoints. Studies with a range of chemicals have shown that the response of populations often differs from studies in which a single organism is exposed in an individual container (as often described within standard ecotox screening assays). Here we investigate the impact of primary microplastics (1–5 μm in size) on a population of Daphnia magna. We first allowed a stable population of D. magna to develop over 29 d, after which the populations were exposed to microplastics for three weeks (concentrations ranging from 102 to 105 particles mL−1 and a control). We found a significant impact of microplastics on the total population of D. magna, with a reduction in the amount of adult daphnids. Importantly, when expressed as total biomass, exposure to 105 microplastics mL−1 resulted in a 21% reduction in total biomass compared to control. These results indicate that exposure to microplastics can result in significant adverse effects on the population of D. magna, including a reduction in the number of individuals as well as total biomass. Given the importance of D. magna in freshwater food webs, both as a grazer as well as a food source, this can potentially impact the functioning of the ecosystem.
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•Populations of D. magna at carrying capacity were exposed to microplastics for 21 d.•The number of adults within the population declined at high exposure levels.•There were no impacts on the length of adults or the number of ephippia.•Exposure resulted in significant reductions in total biomass of exposed populations.
In this work, we aimed to study photocatalytic degradation of Microcystin-LR (MC-LR), a cyanotoxin known to cause acute as well as chronic toxicity and even mortality. The nanocomposite (NC) based on ...zinc ferrite (ZnFe2O4) was modified with graphene oxide (GO) and Ag nanoparticles (NPs) to enhance its photocatalytic properties under visible light. The so-formed ZnFe2O4-Ag/rGO NC exhibited superior performance in visible light allowing complete degradation of MC-LR within 120 min of treatment with pseudo rate constant, k = 0.0515 min−1, several times greater than other photocatalysts, TiO2 (k = 0.0009 min−1), ZnFe2O4 (k = 0.0021 min−1), ZnFe2O4-Ag (k = 0.0046 min−1) and ZnFe2O4/rGO (k = 0.007 min−1) respectively. The total organic carbon analysis revealed that only 22% of MC-LR was mineralized on 120 min of treatment time indicating presence of different intermediate by-products. The intermediates formed during photocatalytic treatment were identified using liquid chromatography–mass spectrometry (LCMS) based on which probable degradation pathways were proposed. The attack from OH radicals formed during the photocatalytic process resulted to hydroxylation and subsequent cleavage of diene bond. The toxicity assessment with Daphnia magna revealed that the degradation process has alleviated toxicity of the MC-LR and no toxic intermediates were formed during the treatment which is very important from eco-toxicological view point. Therefore, ZnFe2O4-Ag/rGO has a good potential in the field of environmental applications as visible light active and magnetic photocatalyst with enhanced performance.
Before photocatalytic treatment, MC-LR solution was toxic to D. magna, whereas after the treatment the toxicity was alleviated as indicated by the survival of all D. magna due to cleavage of the diene bond associated with the toxicity of the MC-LR. Display omitted
•ZnFe2O4 modified with GO and Ag NPs to enhance visible light photocatalysis.•ZnFe2O4-Ag/rGO NC exhibited enhanced degradation of MC-LR within 120 min.•MC-LR was not completely mineralized and intermediates were identified.•Toxicity assessment revealed, intermediate byproducts were not toxic to D. magna.•MC-LR degradation was driven by .•OH subsequently cleaving diene bond.
The commercial herbicide formulation Betanal registered Expert and its active ingredients (a.i.s) ethofumesate, phenmedipham and desmedipham were focused in this study. Following questions yielding ...from a previous study, an in-depth analysis of the reproductive toxicity of the pesticide was made. Long-term exposures of Daphnia magna and Daphnia longispina to Betanal registered Expert, to each a.i. and to a customised mixture matching the a.i.s ratio within the commercial formulation were carried out, and deleterious effects in the offspring were recorded. This intended to clarify whether (1) the tested compounds induce reproductive injury; (2) there is interspecific variation in daphnids tolerance to the compounds; (3) there is an interaction between chemicals in combined treatments; and (4) the so-called inert ingredients added to the commercial formulation contribute to the toxicity of the herbicide. Generally, developmental impair was observed in both species (egg abortion and release of undeveloped embryos or dead offspring) at concentrations of any of the a.i.s below 1 mg L super(-1). Ethofumesate was invariably the least toxic pesticide, and D. magna tended to be of slightly higher sensitivity to the exposures compared to D. longispina. Joint exposures indicated that the a.i.s can interact, inducing more than and less than additive effects for Betanal registered Expert and the customised a.i. mixture, respectively. This indicates that inert ingredients co-formulating the commercial pesticide (which are absent from the customised a.i. mixture) actually contribute to its overall toxicity. This study constitutes an add-on to the discussion on the ecotoxicological framework required for authorisation of pesticide trade and usage. The results support the need to consider test species, long-term hazardous potential and toxicity of commercial formulations rather than solely that of active ingredients, as relevant variables in pesticide regulation.
The drastic increase of microplastics (MPs) in aquatic environment has become a serious threat to marine and freshwater ecosystems. However, little information is available regarding the potential ...detrimental effects of polyvinyl chloride microplastics (PVC-MPs) on aquatic organisms. This study investigated the changes of reproduction parameters, oxidative stress and the expression of reproduction and detoxification-related genes in Daphnia magna after exposed to 2 ± 1 and 50 ± 10 μm PVC-MPs. The results showed that chronic exposure to 2 ± 1 μm PVC-MPs prolonged days to the first brood, increased total number of broods per female and frequency of molting per adult, decreased offspring number at first brood and total number of offspring per female in D. magna. Moreover, 2 ± 1 μm PVC-MPs also disturbed the activities of SOD and CAT, increased GSH and MDA levels. The expression of Vtg, SOD, CAT, CYP314 and CYP360A8 genes also exhibited different response patterns depending on exposure time. Furthermore, 50 ± 10 μm PVC-MPs decreased offspring at first brood and Vtg mRNA level, increased the transcription levels and activities of SOD and CAT. These results suggest that the presence of PVC-MPs in aquatic environment may cause reproduction toxicity by disrupting the reproduction and detoxification-related genes expression and inducing oxidative stress in D. magna.
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•PVC-MPs disturb the reproduction of D. magna.•PVC-MPs were found to exhibit size-dependent toxicity toward D. magna.•Oxidative stress may play an important role in PVC-MPs-induced reproduction toxicity.•PVC-MPs affect the reproduction and detoxification-related genes in D. magna.
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