Epigenetic mechanisms have been found to play important roles in environmental stress response and regulation. These can, theoretically, be transmitted to future unexposed generations, yet few ...studies have shown persisting stress-induced transgenerational effects, particularly in invertebrates. Here, we focus on the aquatic microcrustacean Daphnia, a parthenogenetic model species, and its response to salinity stress. Salinity is a serious threat to freshwater ecosystems and a relevant form of environmental perturbation affecting freshwater ecosystems. We exposed one generation of D. magna to high levels of salinity (F0) and found that the exposure provoked specific methylation patterns that were transferred to the three consequent nonexposed generations (F1, F2, and F3). This was the case for the hypomethylation of six protein-coding genes with important roles in the organisms’ response to environmental change: DNA damage repair, cytoskeleton organization, and protein synthesis. This suggests that epigenetic changes in Daphnia are particularly targeted to genes involved in coping with general cellular stress responses. Our results highlight that epigenetic marks are affected by environmental stressors and can be transferred to subsequent unexposed generations. Epigenetic marks could therefore prove to be useful indicators of past or historic pollution in this parthenogenetic model system. Furthermore, no life history costs seem to be associated with the maintenance of hypomethylation across unexposed generations in Daphnia following a single stress exposure.
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•The WFD bioassessment scheme is highly valuable, but effectiveness can be improved.•Environmental Risk Assessment can inspire the improvement of WFD bioassessment.•Complementary ...approaches that provide added-value to bioassessment are identified.•A possible course of action towards improving the WFD bioassessment is proposed.•The proposal entails a tiered approach, includes ecotoxicology and expert judgement.
The EU Water Framework Directive (WFD) assessment scheme has been putting in force the evaluation of freshwater ecosystems in Europe, including a new paradigm of ecological status. After almost 20 years since the WFD implementation, it is imperative to evaluate the efficiency of its standard assessment scheme and to explore the possibility of learning how to improve its effectiveness. That is the spirit of this review, aiming (i) to explore the existing literature on the WFD bioassessment scheme for assessing freshwater ecosystem health, particularly in lotic ecosystems (where the WFD scheme is most consolidated); (ii) to document which paths are suggested by the scientific community to improve the efficiency of the bioassessment in tackling current challenges. In the specific arena of bioassessment, we first identify the major constraints to the WFD full implementation in rivers. Second, we analyse retrospective Ecological Risk Assessment (ERA) as an evaluation approach supporting management actions that could inspire improvements in the WFD bioassessment scheme. Third, we review the advances and debate on complementary metrics to improve WFD evaluation protocols and/or the feasibility of the evaluation outcome. Fourth, a conceptual scheme for an improved evaluation strategy is presented. Our proposal essentially merges the WFD bioassessment scheme with the ERA philosophy, proposing a tiered approach of increasing complexity and spatial resolution, where expert judgement is included surgically at all decision stages. This scheme requires true integration of chemical, ecological and ecotoxicological LoE for a quantitative estimation of risks, and provides a comprehensive framework that accommodates tools and perspectives already suggested by other authors. Besides providing a literature review on the strengths and weaknesses of the current WFD bioassessment scheme, we wish to open way for the scientific discussion towards an improved conceptual scheme for the evaluation of ecosystem health.
Aquatic toxins are potent natural toxins produced by certain cyanobacteria and marine algae species during harmful cyanobacterial and algal blooms (CyanoHABs and HABs, respectively). These harmful ...bloom events and the toxins produced during these events are a human and environmental health concern worldwide, with occurrence, frequency and severity of CyanoHABs and HABs being predicted to keep increasing due to ongoing climate change scenarios. These contexts, as well as human health consequences of some toxins produced during bloom events have been thoroughly reviewed before. Conversely, the wider picture that includes the non-human biota in the assessment of noxious effects of toxins is much less covered in the literature and barely covered by review works. Despite direct human exposure to aquatic toxins and related deleterious effects being responsible for the majority of the public attention to the blooms' problematic, it constitutes a very limited fraction of the real environmental risk posed by these toxins. The disruption of ecological and trophic interactions caused by these toxins in the aquatic biota building on deleterious effects they may induce in different species is paramount as a modulator of the overall magnitude of the environmental risk potentially involved, thus necessarily constraining the quality and efficiency of the management strategies that should be placed. In this way, this review aims at updating and consolidating current knowledge regarding the adverse effects of aquatic toxins, attempting to going beyond their main toxicity pathways in human and related models’ health, i.e., also focusing on ecologically relevant model organisms. For conciseness and considering the severity in terms of documented human health risks as a reference, we restricted the detailed revision work to neurotoxic cyanotoxins and marine toxins. This comprehensive revision of the systemic effects of aquatic neurotoxins provides a broad overview of the exposure and the hazard that these compounds pose to human and environmental health. Regulatory approaches they are given worldwide, as well as (eco)toxicity data available were hence thoroughly reviewed. Critical research gaps were identified particularly regarding (i) the toxic effects other than those typical of the recognized disease/disorder each toxin causes following acute exposure in humans and also in other biota; and (ii) alternative detection tools capable of being early-warning signals for aquatic toxins occurrence and therefore provide better human and environmental safety insurance. Future directions on aquatic toxins research are discussed in face of the existent knowledge, with particular emphasis on the much-needed development and implementation of effective alternative (eco)toxicological biomarkers for these toxins. The wide-spanning approach followed herein will hopefully stimulate future research more broadly addressing the environmental hazardous potential of aquatic toxins.
•The occurrence of cyanobacteria and algal blooms in aquatic environments is rising, often leading to increased phytoplankton neurotoxins production.•Improved knowledge of the full toxic potential of aquatic neurotoxins for humans and also for aquatic biota is required.•The development of alternative biomarker-based methodologies are promising tools that can aid in safeguarding human and environmental health, serving as early-warning signs for neurotoxins presence and toxic effects.•The possibility of increased fatal poisonings in freshwater and marine environments amplifies the need for conducting additional research on aquatic toxins.
Wildfires can cause immediate and drastic impacts on the structure and functioning of ecosystems, and there has been an increasing interest in wildfire effects on water chemistry and aquatic biota. ...Wildfires are increasingly recognized as a diffuse source of contamination of aquatic ecosystems, through the production of deleterious pyrolytic substances and their subsequent transport, mostly attached to ashes. To study the deleterious effects of the ash-laden runoff from burnt areas on water quality, composite ash samples of ashes were collected immediately after a forest fire and then used to prepare aqueous extracts of ash (AEA). The AEA were analyzed with respect to a large group of chemical elements and the sixteen prioritized polycyclic aromatic hydrocarbons (PAHs). Ca, S, Mg, K and Na were found to be the principal elements in the AEA, while only two low molecular weight PAHs (phenanthrene and naphthalene) were present in quantifiable amounts. In parallel, an ecotoxicological screening of the AEA was performed with four standard aquatic species from different functional groups and trophic levels. The AEA was found to induce a statistically significant decrease in the growth of two primary producers – Pseudokirchneriella subcapitata and Lemna minor – and inhibited the luminescence of the bacteria Vibrio fischeri. By contrast, AEA did not produce a significant immobilization of Daphnia magna suggesting that short-term acute toxicity may be absent at higher trophic levels. Overall, the present results emphasize the role of wildfires as a potential source of diffuse contamination for downstream water bodies, compromising both chemical and ecological conditions. At the same time, this study highlights the need for further research into the complexity of the potentially deleterious ecological effects of wildfires on aquatic communities, with a particular focus on cascading effects along the trophic web.
•The impacts of wildfires on aquatic ecosystems were assessed.•Aqueous extracts of ash were used as a surrogate for ash-laden post-fire runoff.•Wildfires are a source of chemical elements and PAHs for downstream water bodies.•Aqueous extracts of ash were toxic for primary producers and bacteria.•Further research will clarify the negative effects of wildfires on aquatic systems.
Epigenetic mechanisms are moving to the forefront of environmental sciences, as environmentally induced epigenetic changes shape biological responses to chemical contamination. This work focused on ...Daphnia as a representative of potentially threatened freshwater biota, aiming to gain an insight into the involvement of epigenetic mechanisms in their response and eventual adaptation to metal contamination. Copper-induced DNA methylation changes, their potential transgenerational inheritance, and life-history traits were assessed. Organisms with different histories of past exposure to copper were exposed to toxic levels of the element for one generation (F0) and then monitored for three subsequent unexposed generations (F1, F2, and F3). Overall, methylation changes targeted important genes for counteracting the effects of metals and oxidative stress, including dynein light chain, ribosomal kinase and nuclear fragile X mental retardation-interacting protein. Also, contrasting overall and gene-specific methylation responses were observed in organisms differing in their history of exposure to copper, with different transgenerational methylation responses being also identified among the two groups, without apparent life-history costs. Taken together, these results demonstrate the capacity of copper to promote epigenetic transgenerational inheritance in a manner related explicitly to history of exposure, thereby supporting the development and incorporation of epigenetic biomarkers in risk assessment frameworks.
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•Direct and inherited effects of Cu in DNA methylation of Daphnia were explored.•Methylation changes targeted genes that offset metal toxicity and oxidative stress.•Distinct methylation effects noticed in daphnids differing in Cu exposure history.•Exposure history promoted transgenerational inheritance in a specific manner.
The number of wildfires has markedly increased in Mediterranean Europe, including in Portugal. Wildfires are environmentally concerning, not only due to the loss of biodiversity and forest area, but ...also as a consequence of environmental contamination by specific compounds including metals and polycyclic aromatic compounds (PAHs). These contaminants, mostly bound to ashes, can reach downstream water bodies, namely through surface runoff, being ultimately dispersed by vast areas and contacting with aquatic biota. Being toxicologically noteworthy, the potential toxic outcomes of the input of such chemicals across the aquatic compartment must be characterized. In this context, the present study used a biomarker-based approach to find early-warning signals of toxicity triggered by the exposure of the mosquitofish, Gambusia holbrooki, to affected aqueous runoff and stream water samples collected from a forest burnt area. The chemical analysis revealed concerning levels of metals and polycyclic aromatic hydrocarbons in both runoff and stream water samples. Biological responses elicited by the collected samples showed the occurrence of pro-oxidative modifications, specifically driven by enzymatic forms involved in the metabolism of glutathione. Despite these effects, no further signs of involvement of metals and PAHs were elicited in terms of neurotoxicity. The overall set of data implicates chemicals resulting from wildfires in clear deleterious effects in exposed fish.
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•Toxic chemicals from wildfires can induce clear toxicity towards aquatic species.•Pro-oxidative modifications are the most relevant toxic effects.•Triggered biological responses are of defensive nature.•No neurotoxicity effects were perceived from the exposure to ashes.•Biomarkers are adequate to depict exposure of organisms to ashes from wildfires.
Mysids have a high ecological importance, particularly by their role in marine food chains as a link between the benthic and pelagic realms. Here we describe the relevant taxonomy, ecological aspects ...such as distribution and production, and their potential as ideal test organisms for environmental research. We also highlight their importance in estuarine communities, trophic webs, and their life history, while demonstrating their potential in addressing emergent problems. This review emphasizes the importance of mysids in understanding the impacts of climate change and their role in the ecology of estuarine communities. Although there is a dearth of research in genomic studies, this review emphasizes the relevance of mysids and their potential as a model organism in environmental assessment studies of prospective or retrospective nature and highlights the need for further research to enhance our understanding of this group's ecological significance.
•Mysids have a high ecological importance, particularly by their role in food chains.•The rapid response of mysids to ecosystem alterations makes them an effective predictor of climate changes.•Mysids may contribute to the transfer of metals and MPs to higher trophic levels.•Mysids omics can offer mechanistic views on the physiological consequences of stress scenarios.
Wildfires are a complex environmental problem worldwide. The ashes produced during the fire bear metals and PAHs with high toxicity and environmental persistence. These are mobilized into downhill ...waterbodies, where they can impair water quality and human health. In this context, the present study aimed at assessing the toxicity of mimicked wildfire runoff to human skin cells, providing a first view on the human health hazardous potential of such matrices. Human keratinocytes (HaCaT) were exposed to aqueous extracts of ashes (AEA) prepared from ash deposited in the soil after wildfires burned a pine or a eucalypt forest stand. Cytotoxicity (MTT assay) and changes in cell cycle dynamics (flow cytometry) were assessed. Cell viability decreased with increasing concentrations of AEA, regardless of the ash source, the extracts preparation method (filtered or unfiltered to address the dissolved or the total fractions of contaminants, respectively) or the exposure period (24 and 48 h). The cells growth was also negatively affected by the tested AEA matrices, as evidenced by a deceleration of the progress through the cell cycle, namely from phase G0/G1 to G2. The cytotoxicity of AEA could be related to particulate and dissolved metal content, but the particles themselves may directly affect the cell membrane. Eucalypt ash was apparently more cytotoxic than pine ash due to differential ash metal burden and mobility to the water phase. The deceleration of the cell cycle can be explained by the attempt of cells to repair metal-induced DNA damage, while if this checkpoint and repair pathways are not well coordinated by metal interference, genomic instability may occur. Globally, our results trigger public health concerns since the burnt areas frequently stand in slopes of watershed that serve as recreation sites and sources of drinking water, thus promoting human exposure to wildfire-driven contamination.
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•Wildfire runoffs, reaching hydrographic basins, may pose a human health hazard.•The metal and particle burden of runoffs affect human skin cells.•Cell viability decreases significantly following exposure to ash extracts.•Cell cycle arrests following exposure to ash extracts.
•Parabens mixture present a high toxicity over different tested non-target species.•Single and catalytic ozonation reveal efficiency for parabens mixture degradation.•Catalytic ozonation treated ...samples are more toxic than those from single ozonation.•Hydroquinone and 1,4-benzoquinone may be the most toxic by-products.•The effect of by-products and parabens interaction depends on the species analyzed.
Parabens are widely used as antimicrobial and preservative ingredients in pharmaceutical and personal care products. Nevertheless, these compounds have been increasingly seen as emerging contaminants that can be toxic to a wide range of species. In this study, the toxic effect of a mixture of parabens (10 mg/L of each paraben: methyl-, ethyl-, propyl-, benzyl- and butylparaben) and its degradation products through single and catalytic ozonation (using volcanic rock as low-cost catalyst) was investigated over several non-target species: cladocerans, microalgae, clams, macrophytes and cress. The analysis of the toxicity of parabens mixture is relevant since usually these compounds are used as blends rather than individually. While parabens were totally removed both by single and catalytic ozonation the toxicity of the samples resulting from both treatments was generally high. This toxicity was still compared to the one obtained for several dilutions of the initial parabens mixture and it was concluded that the by-products formed are more toxic than the most diluted parabens mixture sample (0.625 mg/L). While catalytic ozonation allows reducing the amount of ozone (about 3-fold) required for total removal of parabens, the resulting treated solution was more toxic than the sample taken at the endpoint of the single ozonation treatment. This suggests that the highest amount of ozone used for single ozonation allowed the elimination of toxic by-products such as hydroquinone and 1,4-benzoquinone. Still, the effect of by-products and parabens interaction depends on the species analyzed due to their different tolerances to potentially toxic products.
Climatic and hydrological variation is of utmost importance in regions of the globe facing water scarcity and river intermittency (e.g. areas under Mediterranean influence). The main aim of this ...study was to compare the macroinvertebrate community structure and its bioindicator value (i.e. waterbody ecological status) in streams from three Portuguese regions (Regions C, N and S), representing distinct climatic features and water availability scenarios. Results showed that, overall, sampling sites differed in their climatic, hydromorphological and physical and chemical features, and environmental (abiotic) and ecological (community dissimilarities) gradients among regions were clearly identified. Sites from Regions C (wettest) and S (driest) represented non-overlapping clusters of samples, both in terms of their environmental context and ecological (dis)similarity; sites from Region N occupied an intermediate position, and their macroinvertebrate community was highly variable locally. This coincided with overall higher ecological quality and uniformity in Region C, whereas Regions N and S were more heterogeneous and generally presented lower ecological quality. Our data showed that climate (and associated water scarcity) is coupled with other environmental drivers of the macroinvertebrate community structure, highlighting a shared influence of the three environmental components (climatic, hydromorphological, and physical and chemical) in the modulation of macroinvertebrate communities.
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