Relationship between trans-generational effects of tetracycline on Daphnia magna at the physiological and whole organism level

Ecotoxicity of the fluoroquinolone antibiotic delafloxacin to the water flea Simocephalus vetulus and its offspring under the influence of calcium modulation

Delafloxacin (DFX), one of the latest additions to the fluoroquinolone antibiotics, is gaining heightened recognition in human therapy due to its potential antibacterial efficacy in a wide range of applications. Concerns have arisen regarding its presence in the environment and its potential interactions with multivalent metals, such as calcium (Ca). The present study investigated the trans- and multigenerational effects of environmentally projected concentrations of DFX (100-400 μg DFX L-1) on individual- and population-level responses of parental S. vetulus (F0) and its descendants (F1) under normal (26 mg L-1) and high (78 mg L-1) Ca conditions. Exposure of the F0 generation to DFX under the normal Ca condition resulted in reduced juvenile body length (JBL), increased age-specific survival rate (lx), indicating prolonged developmental time, reduced age-specific fecundity rate (mx), and decreased population growth rate (rm). Under the high Ca condition, JBL, mx, and rm were adversely affected. Transgenerational effects of DFX existed, as F1 individuals exhibited persistent suppressions in at least one endpoint under both Ca conditions even after being transferred to a clear medium. Continuous exposure of the F1 generation to DFX had negative impacts on JBL, mx, and rm under the normal Ca condition, and on JBL and rm under the high Ca condition. However, cumulative effects were not observed, suggesting the potential development of tolerance to DFX in the F1 organisms. These findings suggest that DFX is a harmful compound for the non-target model organism S. vetulus and reveal a potential antagonism between DFX and Ca. Nevertheless, the interaction between other (fluoro)quinolones and Ca remains unclear, necessitating further research to establish this phenomenon more comprehensively, including understanding the interaction mechanism in ecotoxicological contexts.

Direct and gut microbiota-mediated toxicities of environmental antibiotics to fish and aquatic invertebrates

The accumulation of antibiotics in the environment has ecological impacts that have received less attention than the human health risks of antibiotics, although the effects could be far-reaching. This review discusses the effects of antibiotics on the health of fish and zooplankton, manifesting in direct or dysbiosis-mediated physiological impairment. Acute effects of antibiotics in these organism groups are usually induced at high concentrations (LC₅₀ at ∼100-1000 mg/L) that are not commonly present in aquatic environments. However, when exposed to sub-lethal, environmentally relevant levels of antibiotics (ng/L-μg/L) disruption of physiological homeostasis, development, and fecundity can occur. Antibiotics at similar or lower concentrations can induce dysbiosis of gut microbiota which can affect the health of fish and invertebrates. We show that the data about molecular-level effects of antibiotics at low exposure concentrations are limited, hindering environmental risk assessment and species sensitivity analysis. Fish and crustaceans (Daphnia sp.) were the two groups of aquatic organisms used most often for antibiotic toxicity testing, including microbiota analysis. While low levels of antibiotics impact the composition and function of gut microbiota in aquatic organisms, the correlation and causality of these changes to host physiology are not straightforward. In some cases, negative or lack of correlation have occurred, and, unexpectedly, gut microbial diversity has been unaffected or increased upon exposure to environmental levels of antibiotics. Efforts to incorporate functional analyses of gut microbiota are beginning to provide valuable mechanistic information, but more data is needed for ecological risk assessment of antibiotics.

Combined exposure of polystyrene microplastics and carbamazepine induced transgenerational effects on the reproduction of Daphnia magna

Polystyrene microplastics (PS MPs) and carbamazepine (CBZ) are frequently detected in freshwater ecosystems. However, the transgenerational effects of PS MPs and CBZ on the reproduction of aquatic organisms and the corresponding mechanisms are still unclear. In the present study, Daphnia magna was used to evaluate the reproductive toxicity in two consecutive generations (F0, F1). The molting and reproduction parameters, the expression of reproduction, and the toxic metabolism genes were examined after 21-day exposure. A significantly enhanced toxicity was observed in the presence of 5 μm PS MPs and CBZ. Chronic exposure results showed that the 5 μm PS MPs alone, CBZ alone, and their mixtures exerted significant reproductive toxicity of D. magna. The results of RT-qPCR showed transcripts of genes related to reproduction (cyp314, ecr-b, cut, vtg1, vtg2, dmrt93b) and toxic metabolism (cyp4, gst) were altered in both the F0 and F1. In addition, for the F0, gene transcriptional changes of reproduction were not fully translated into physiological performance, probably due to the compensatory responses caused by the low dose of PS MPs alone, CBZ alone, and their mixtures. Whereas for the F1, the trade-off between reproduction and toxic metabolism at gene levels was observed, which translated into a significant reduction in the total neonate number of F1. These findings suggest that long-term exposure to MPs and CBZ can cause serious reproduction damage to aquatic animals, which needs to be given sufficient attention.

Freshwater crustacean exposed to active pharmaceutical ingredients: ecotoxicological effects and mechanisms

Concerns over the ecotoxicological effects of active pharmaceutical ingredients (APIs) on aquatic invertebrates have been raised in the last decade. While numerous studies have reported the toxicity of APIs in invertebrates, no attempt has been made to synthesize and interpret this dataset in terms of different exposure scenarios (acute, chronic, multigenerational), multiple crustacean species, and the toxic mechanisms. In this study, a thorough literature review was performed to summarize the ecotoxicological data of APIs tested on a range of invertebrates. Therapeutic classes including antidepressants, anti-infectives, antineoplastic agents, hormonal contraceptives, immunosuppressants, and neuro-active drugs exhibited higher toxicity to crustaceans than other API groups. The species sensitivity towards APIs exposure is compared in D. magna and other crustacean species. In the case of acute and chronic bioassays, ecotoxicological studies mainly focus on the apical endpoints including growth and reproduction, whereas sex ratio and molting frequency are commonly used for evaluating the substances with endocrine-disrupting properties. The multigenerational and "Omics" studies, primarily transcriptomics and metabolomics, were confined to a few API groups including beta-blocking agents, blood lipid-lowing agents, neuroactive agents, anticancer drugs, and synthetic hormones. We emphasize that in-depth studies on the multigenerational effects and the toxic mechanisms of APIs on the endocrine systems of freshwater crustacean are warranted.

Maternal Effect of Polyethylene Microplastic Fragments Containing Benzophenone-3 in Different Ages and Broods of Daphnia Magna

The maternal effect of microplastics (MPs) toxicity is likely influenced by age and brood of test species. This study investigated the maternal effect of polyethylene MP fragments (18.23 ± 8.02 μm) with benzophenone-3 (BP-3; 2.89 ± 0.20% w/w) on chronic toxicity to Daphnia magna over two generations. Neonate (< 24 h old) and adult (5 d old) daphnids in the F0 generation were exposed until 21 d old, then first and third brood neonates in the F1 generation were recovered in clean M4 medium for 21 d. Higher chronic toxicity and maternal effect of MP/BP-3 fragments were observed in the adult group compared with the neonate group, reducing growth and reproduction in both F0 and F1 generations. First brood neonates in the F1 generation showed a higher maternal effect of MP/BP-3 fragments than third brood ones, resulting in enhanced growth and reproduction relative to the control. This study provided insights into the ecological risk of MPs containing plastic additives in the natural environment.

Antibiotic Pollution of Planktonic Ecosystems: A Review Focused on Community Analysis and the Causal Chain Linking Individual- and Community-Level Responses

Antibiotic pollution has become one of the most challenging environmental issues in aquatic ecosystems, with adverse effects on planktonic organisms that occupy the base of the aquatic food chain. However, research regarding this topic has not been systematically reviewed, especially in terms of community-level responses. In this review, we provide an overview of current antibiotic pollution in aquatic environments worldwide. Then, we summarize recent studies concerning the responses of planktonic communities to antibiotics, ranging from individual- to community-level responses. Studies have shown that extremely high concentrations of antibiotics can directly harm the growth and survival of plankton; however, such concentrations are rarely found in natural freshwater. It is more likely that environmentally relevant concentrations of antibiotics will affect the physiological, morphological, and behavioral characteristics of planktonic organisms; influence interspecific interactions among plankton species via asymmetrical responses in species traits; and thus alter the structure and function of the entire planktonic ecosystem. This review highlights the importance of community analysis in revealing antibiotic toxicity. We also encourage the establishment of the causal relationships between impacts at multiple scales in the future for predicting the community-level consequences of antibiotics based on the currently available individual-level evidence.

A tiered probabilistic approach to assess antibiotic ecological and resistance development risks in the fresh surface waters of China

Exposure to antibiotics can result in not only ecotoxicity on aquatic organisms but also the development of antibiotic resistance. In the study, the ecotoxicity data and minimum inhibitory concentrations of the antibiotics were screened to derive predicted no-effect concentrations of ecological (PNEC_eco) and resistance development risks (PNEC_res) for 36 antibiotics in fresh surface waters of China. The derived PNEC_eco and PNEC_res values were ranged from 0.00175 to 2351 μg/L and 0.037-50 μg/L, respectively. Antibiotic ecological and resistance development risks were geographically widespread, especially in the Yongding River, Daqing River, and Ziya River basins of China. Based on the risk quotients, 11 and 14 of 36 target antibiotics were at high ecological risks and high resistance development risks in at least one basin, respectively. The higher tiered assessments provided more detailed risk descriptions by probability values and β-lactams (penicillin and amoxicillin) were present at the highest levels for ecological and resistance development risks. Although there was uncertainty based on the limited data and existing methods, this study can indicate the overall situation of the existing risk levels and provide essential insights and data supporting antibiotic management.

Chronic toxicity of diclofenac, carbamazepine and their mixture to Daphnia magna: a comparative two-generational study

The chronic toxicity of diclofenac (DCF) and carbamazepine (CBZ) as separate substances and in conjunction with their mixture on Daphnia magna was assessed in the parental (F0) and first filial (F1) generations. The second (F1-B2) and fifth (F1-B5) broods of F1 offspring were investigated and compared. Both drugs and their mixture were exposed to each generation of Daphnia magna for 21 days with life history, behavioural and gene expressions as measured endpoints. After the parental exposure, offspring from these two broods were transferred to a clean medium for a 21-day recovery. Exposure to diclofenac, carbamazepine and their mixture significantly inhibited growth, reproduction, swimming activities, heart rate, thoracic limb activities, reproductive and antioxidant-related genes in the parental as well as the first filial generations. These effects were relatively greater in the F1 generation. This indicates that Daphnia magna's sensitivity improved while its fitness declined over the two generations, which is an indicator of greater energy requirements for maintenance. Besides, the significant inhibition in the antioxidant-related genes implies that oxidative stress occurred in Daphnia magna under the exposure to these drugs. The significant reduction in the reproductive output, moulting frequency and cyp314 gene expression as a result of exposure to CBZ simultaneously obtained herein may indicate that this drug could act as an endocrine disruptor. Most of these significant effects were not recoverable after the 21-day recovery period. The findings reported herein highlight the necessity to include maternal effects in environmental risk assessment processes, considering that pollutant effects are underestimated during single-generational exposure.

Correlation analysis of single- and multigenerational endpoints in Daphnia magna toxicity tests: A case-study using TiO2 nanoparticles

Multigenerational toxicity tests provide more sensitive measures of population-level effects than conventional single-generation tests. Particularly for stressors which exhibit slow uptake rates (e.g. nanomaterials), multigenerational tests may also provide a more realistic representation of natural exposure scenarios. To date, the inherently high costs and labor intensity have however limited the use of multigenerational toxicity tests and thereby their incorporation in environmental risk assessment. The aim of the present study was therefore to determine to what extent short(er) term endpoints which are conventionally measured in Daphnia magna toxicity tests hold predictive capacity towards reproduction measured over longer timescales, including multiple generations. To assess this, a case-study was performed in which effects of TiO₂ nanoparticles (0, 0.02, 0.2, 2 and 5 mg L^-1) on D. magna life-history traits were assessed over five generations. Additionally, it was determined whether offspring derived from exposed parents exhibited sustained adverse effects when rearing them in clean (non-exposed) media after each generation of exposure. The present study showed that although various life-history traits correlate with the total reproductive output in the same- and subsequent generation under non-exposed conditions, these correlations were decoupled in presence of exposure to nTiO₂. In addition, it was found that nTiO₂ can induce adverse effects on population relevant endpoints at concentrations 1-2 orders of magnitude lower than previously found (i.e. 0.02 mg L^-1), and close to the range of concentrations occurring in natural freshwater ecosystems.

Intergenerational and biological effects of roxithromycin and polystyrene microplastics to Daphnia magna

The influence of microplastics (MPs) on transgenerational effects of pharmaceuticals are drawing growing attention, however, whether aged process will alter the carrier effects of MPs were unknown. In this study, the intergenerational toxicity of single and combined exposure of polystyrene microplastics (PS-MPs) and roxithromycin (ROX) were investigated at the environmentally related concentrations, using Daphina magna as test organism. In the presence of UV-aged PS-MPs, the survival of D. magna for maternal generation (F0) at ROX concentration of 0.1 and 10 µg/L were increased by 20% and 40%, respectively. Meanwhile, the inhibition effects of ROX on the number of offspring and intrinsic rate of natural increase were obviously moderated. All these reproductive toxicity of ROX and PS-MPs in the first offspring (F1) were further aggravated both for the single and combined exposure. And the adverse effects disappeared much easier for the single exposure compared to the co-exposure through subsequent recovery. The combined exposure resulted in the change of inhibition of ROX on the swimming velocity and acceleration of D. magna into induction, while the feeding behavior kept inhibited. The AChE activity was distinctly increased by 1.61-3.25 times for the single and combined treatments, and the induction level of UV-aged MPs was higher than that of original MPs. Oxidative stress of the single exposure of ROX and original PS-MPs was observed with obvious induction of T-AOC and SOD activity, while the significant increase of MDA content was observed for the co-exposure. Among all indicators, the biochemical biomarkers and time of first brood were attributed to a class among all indicators, indicating that the time of first brood might be the most sensitive reproductive toxicity index. These results illustrated that both maternal impacts and offspring quality need to be considered for assessment of interaction of emerging contaminants.

Acquiring an evolutionary perspective in marine ecotoxicology to tackle emerging concerns in a rapidly changing ocean

Tens of thousands of anthropogenic chemicals and wastes enter the marine environment each year as a consequence of the ever-increasing anthropogenic activities and demographic growth of the human population, which is majorly concentrated along coastal areas. Marine ecotoxicology has had a crucial role in helping shed light on the fate of chemicals in the environment, and improving our understanding of how they can affect natural ecosystems. However, chemical contamination is not occurring in isolation, but rather against a rapidly changing environmental horizon. Most environmental studies have been focusing on short-term within-generation responses of single life stages of single species to single stressors. As a consequence, one-dimensional ecotoxicology cannot enable us to appreciate the degree and magnitude of future impacts of chemicals on marine ecosystems. Current approaches that lack an evolutionary perspective within the context of ongoing and future local and global stressors will likely lead us to under or over estimations of the impacts that chemicals will exert on marine organisms. It is therefore urgent to define whether marine organisms can acclimate, i.e. adjust their phenotypes through transgenerational plasticity, or rapidly adapt, i.e. realign the population phenotypic performances to maximize fitness, to the new chemical environment within a selective horizon defined by global changes. To foster a significant advancement in this research area, we review briefly the history of ecotoxicology, synthesis our current understanding of the fate and impact of contaminants under global changes, and critically discuss the benefits and challenges of integrative approaches toward developing an evolutionary perspective in marine ecotoxicology: particularly through a multigenerational approach. The inclusion of multigenerational studies in Ecological Risk Assessment framework (ERA) would provide significant and more accurately information to help predict the risks of pollution in a rapidly changing ocean.

Daphnia magna model in the toxicity assessment of pharmaceuticals: A review

Daphnia magna is one of the most commonly used model organism to assess toxicity of wide range of pharmaceuticals such as antibiotics, anticancer drugs, antidepressants, anti-inflammatory drugs, beta-blockers and lipid-regulating agents. Currently, daphnia toxicity tests based on immobilisation and lethality standardised by OECD, acute immobilisation test and reproduction test, are mainly used in toxicological studies. Detailed analysis of Daphnia biology allows distinguishing the swimming behaviour and physiological endpoints such as swimming speed, distance travelled, hopping frequency, heart rate, ingestion rate, feeding rate, oxygen consumption, thoracic limb activity which could be also useful in assessment of toxic effects. The advantage of behavioural and physiological parameters is the possibility to observe sublethal effects induced by lower concentrations of pharmaceuticals which would not be possible to notice by using OECD tests. Additionally, toxic effects of tested drugs could be assessed using enzymatic and non-enzymatic biomarkers of daphnia toxicity. This review presents scientific data considering characteristics of D. magna, analysis of immobilisation, lethality, reproductive, behavioural, physiological and biochemical parameters used in the toxicity assessment of pharmaceuticals. The aim of this paper is also to emphasize usefulness, advantages and disadvantages of these invertebrate model organisms to assess toxicity of different therapeutic classes of pharmaceuticals. Also, various examples of application of D. magna in studies on pharmaceutical toxicity are presented.

The Combined and Single Effect of Marjoram Essential Oil, Ascorbic Acid, and Chitosan on Fresh-Cut Lettuce Preservation

Increasing demands by consumers for fresh, nutritional, and convenient food has led to the increase of fresh-cut produce market. Nowadays, there is a turn towards the investigation of natural products (i.e., essential oils, organic acids, and edible coatings) in an effort to lower the usage of chemical synthetic compounds (i.e., chlorine) as postharvest sanitizers. The aim of the present study was to assess the effectiveness of Origanum majorana essential oil (EO), ascorbic acid (AA), chitosan, and their combinations on quality attributes of fresh-cut lettuce stored for six days at 7 °C. When applied, Chitosan+AA resulted to a less acceptable product (visual quality and aroma), while the application of marjoram EO was able to preserve the visual quality of fresh-cut lettuce and at the same time resulted in a pleasant aroma. The application of EO+AA and Chitosan+AA increased total phenolics and antioxidant levels of fresh-cut lettuce on the fourth and sixth day of storage. The EO and EO+AA increased damage index (hydrogen peroxide and lipid peroxidation) of fresh-cut lettuce, while at the same time these treatments decreased the activity of enzymes related with plant tissue browning (i.e., peroxidase activity and polyphenol oxidase). Chitosan decreased total valuable counts and yeasts and molds counts on the sixth day of storage, while EO, AA, EO+Chitosan, and Chitosan+AA decreased yeasts and molds after four days of application. The findings of the present work indicating that the combination of marjoram EO, AA, and chitosan could be considered further as alternative means for fresh-cut produce preservation.

Transgenerational reproductive effects of two serotonin reuptake inhibitors after acute exposure in Daphnia magna embryos

The release of pharmaceuticals and personal care products (PPCPs) into aquatic environments has been a major concern for the health of ecosystems. Transgenerational plasticity is a potential mechanism for organisms to respond to changing environmental conditions, including climate change and environmental contaminants. The purpose of the present study was to determine the long-term transgenerational effects of an abundant freshwater zooplankton, Daphnia magna, to acute embryonic exposures of serotonin re-uptake inhibitors (SSRI - fluoxetine and sertraline). Both SSRIs have been used extensively to treat depression and anxiety disorders for decades and persist in freshwater ecosystems at physiologically relevant concentrations. Our results revealed that even short (72 h) embryonic exposures of D. magna embryos had long lasting consequences on life history and expression of 5HT related genes in the unexposed generation (F3). Moreover, we identified direct effects of SSRIs on heart rate and swimming behavior in the first generation that carried over from embryonic exposure. We also found that SSRI exposure resulted in a transient increase of ephippia formation in the F1 and F2 . Our results suggest that SSRI exposure has transgenerational consequences to the unexposed generation and potentially beyond, even at low concentration (10-100× lower than what can be found in natural ecosystems) and as a result of embryonic exposure. Because of the short reproductive period of D. magna and their integral role in aquatic food webs, these findings have population-level implications and deserve further investigation.

Effects of abamectin-based and difenoconazole-based formulations and their mixtures in Daphnia magna: a multiple endpoint approach

This study evaluated the toxicity of pesticide formulations Kraft® 36 EC (active ingredient-a.i. abamectin) and Score® 250 EC (a.i. difenoconazole), and their mixtures in Daphnia magna at different biological levels of organization. Survival, reproduction and biochemical markers (cholinesterase (ChE), catalase (CAT) and lipid peroxidation (LPO)) were some of the endpoints evaluated. Total proteins and lipids were also studied together with energy consumption (Ec). D. magna neonates were exposed for 96 h to Kraft (2, 4, and 6 ng a.i./L) and Score (12.5, 25, and 50 µg a.i./L) for the biochemical experiments, and for 15 days to abamectin (1-5 ng a.i./L) and to difenoconazole (3.12-50 µg a.i./L) to assess possible changes in reproduction. Exposures of organisms to both single compounds did not cause effects to antioxidant and detoxifying enzymes, except for LPO occurring at the highest concentration of difenoconazole tested. For ChE and CAT there was enzymatic induction in mixture treatments organisms, occurring at minor pesticides concentrations for CAT and at the two highest concentrations for ChE. There were no significant differences for total protein in D. magna but lipids showed an increase at the highest concentrations of pesticide mixture combinations. There was a significant increase of Ec in individuals of all treatments tested. In the chronic test, increased fecundity occurred for D. magna under difenoconazole exposures and mixtures. This study demonstrated that mixtures of these pesticides caused greater toxicity to D. magna than when tested individually, except for Ec. Therefore, effects of mixtures are very hard to predict only based on information from single compounds, which most possibly is the result of biological complexity and redundancy in response pathways, which need further experimentation to become better known.

Effects of nanoplastics at predicted environmental concentration on Daphnia pulex after exposure through multiple generations

The biological effects of nanoplastics are a growing concern. However, most studies have focused on exposure to high concentrations or short-term exposure. The potential effects of exposure to low environmental nanoplastic concentrations over the long-term and across multiple generations remain unclear. In the present study, Daphnia pulex was exposed over three 21-day generations to a typical environmental nanoplastic concentration (1 μg/L) and the effects were investigated at physiological (growth and reproduction), gene transcription and enzyme activity levels. Chronic exposure did not affect the survival or body length of D. pulex, whereas the growth rate and reproduction were influenced in the F2 generation. Molecular responses indicated that environmental nanoplastic concentrations can modulate the response of antioxidant defenses, vitellogenin synthesis, development, and energy production in the F0-F1 generations, and prolongation resulted in inhibitory effects on antioxidant responses in F2 individuals. Some recovery was observed in the recovery group, but reproduction and stress defenses were significantly induced. Taken together, these results suggest that D. pulex recovery from chronic exposure to nanoplastic may take several generations, and that nanoplastics have potent long-term toxic effects on D. pulex. The findings highlight the importance of multigenerational and chronic biological evaluations to assess risks of emerging pollution.

The xenobiotic doxycycline affects nitrogen transformations in soil and impacts earthworms and cultivated plants

The effects of doxycycline (DOX) on microbial biomass C and nitrates production in soil, on earthworms and cultivated plants were examined. The concentrations for the various tests were selected after preliminary experiments, to present impact and be close to the environmentally relevant. The results revealed impacts of the antibiotic on microbial biomass C and NO₃^- production at the concentration level of 7.2 mg/kg soil dry weight (d.w.), but these parameters recovered to normal values since the antibiotic was applied once as a pulse. Moreover, the drug had negative effects on earthworm juveniles' total number at the concentration level of 30 mg/kg soil d.w. In addition, the toxicity tests on plant seedling growth revealed negative effects of the antibiotic for tomato at the concentration level of 45.44 mg/kg soil d.w. However, DOX showed positive effects for corn seedling growth, showing that the results of such experiments are valuable for sustainable animal wastes management. Non-significant effects were observed for seedling growth of pea, pumpkin and bean plants. The results of the study are valuable for the impact assessment of the antibiotic in the terrestrial environment and the management of contaminated animal waste.

The concentration of dissolved organic matter impacts the metabolic response in Daphnia magna exposed to 17α-ethynylestradiol and perfluorooctane sulfonate

The pharmaceutical 17α-ethynylestradiol (EE2) and the industrial chemical perfluorooctane sulfonate (PFOS) are organic contaminants frequently detected in freshwater environments. It is hypothesized that hydrophobic organic contaminants can sorb to dissolved organic matter (DOM) and this may reduce the toxicity of these contaminants by reducing the contaminants' bioavailability. To investigate this hypothesis, ¹H nuclear magnetic resonance (NMR)-based metabolomics was used to determine how the metabolome of Daphnia magna changes when a range of DOM concentrations are added during EE2 and PFOS exposure experiments. D. magna were exposed for 48 h to sub-lethal concentrations of 1 mg/L EE2 or 30 mg/L PFOS in the presence of 0, 1, 2, 3 and 4 mg dissolved organic carbon (DOC)/L. EE2 exposure resulted in increased amino acids and decreased glucose in D. magna. All DOM concentrations were able to lessen these metabolite disturbances from EE2 exposure, likely due to reductions in the bioavailability of EE2 through interactions with DOM. Exposure to PFOS resulted in decreased amino acids, and the presence of 1 mg DOC/L did not alter this metabolic response. However, PFOS exposure with the higher DOM concentrations resulted in a different pattern of metabolite changes which may be due to combined impacts of PFOS and DOM on the metabolome or due to an increase in PFOS bioavailability and uptake in D. magna. These results suggest that the concentration of DOM influences the sensitive biochemical changes in organisms that occur during acute sub-lethal exposure to organic contaminants.

An adaptive transgenerational effect of warming but not of pesticide exposure determines how a pesticide and warming interact for antipredator behaviour

The impact of pesticides on organisms may strongly depend on temperature. While many species will be exposed to pesticides and warming both in the parental and offspring generations, transgenerational effects of pesticides under warming are still poorly studied, particularly for behaviour. We therefore studied the single and combined effects of exposure to the pesticide chlorpyrifos (CPF) and warming both within and across generations on antipredator behaviour of larvae of the vector mosquito Culex pipiens. Within each generation pesticide exposure and warming reduced the escape diving time, making the larvae more susceptible to predation. Pesticide exposure of the parents did not affect offspring antipredator behaviour. Yet, parental exposure to warming determined how warming and the pesticide interacted in the offspring generation. When parents were reared at 24 °C, warming no longer reduced offspring diving times in the solvent control, suggesting an adaptive transgenerational effect to prepare the offspring to better deal with a higher predation risk under warming. Related to this, the CPF-induced reduction in diving time was stronger at 20 °C than at 24 °C, except in the offspring whose parents had been exposed to 24 °C. This dependency of the widespread interaction between warming and pesticide exposure on an adaptive transgenerational effect of warming is an important finding at the interface of global change ecology and ecotoxicology.

Multigenerational effects of carbendazim in Daphnia magna: From a subcellular to a population level

Anthropogenic activities such as the use of pesticides may affect aquatic biota populations, due to potential agricultural runoffs or disposals. Carbendazim is one example of a widely used fungicide with a high potential to end up in aquatic ecosystems through runoff. Deleterious effects observed at the individual level are possibly explained by changes in homeostasis at the cellular level, and both factors can then be used to predict effects at the population level. In the present study, an isoclonal population of Daphnia magna (clone K6) was exposed to a concentration that mimics relevant levels of carbendazim in the environment over 12 generations. The effects of carbendazim were assessed in some generations using the following endpoints: biochemical biomarkers (cholinesterase, catalase, and glutathione-S-transferase), lipid peroxidation and energy-related parameters (carbohydrates, lipids, and proteins along with available energy and energy consumption), parental longevity, and population growth (r). Long-term exposure to carbendazim had no effect on the intrinsic rate of natural increase (r) of adult D. magna, but longevity was decreased at the F12 generation compared to that of control. Differences between the exposed and nonexposed populations were found for cholinesterase, glutathione-S-transferase, and lipid peroxidation. However, for catalase and energy-related parameters, no differences were observed between these 2 populations. Natural variability was seen throughout the test period, under control conditions, within the 12 generations. Overall, carbendazim induced some effects at the subcellular level that translated into changes in longevity but these later vanished in terms of population effects. Environ Toxicol Chem 2019;38:412-422. © 2018 SETAC.

Bioenergetics-adverse outcome pathway: Linking organismal and suborganismal energetic endpoints to adverse outcomes

Adverse outcome pathways (AOPs) link toxicity across levels of biological organization, and thereby facilitate the development of suborganismal responses predictive of whole-organism toxicity and provide the mechanistic information necessary for science-based extrapolation to population-level effects. Thus far AOPs have characterized various acute and chronic toxicity pathways; however, the potential for AOPs to explicitly characterize indirect, energy-mediated effects from toxicants has yet to be fully explored. Indeed, although exposure to contaminants can alter an organism's energy budget, energetic endpoints are rarely incorporated into ecological risk assessment because there is not an integrative framework for linking energetic effects to organismal endpoints relevant to risk assessment (e.g., survival, reproduction, growth). In the present analysis, we developed a generalized bioenergetics-AOP in an effort to make better use of energetic endpoints in risk assessment, specifically exposure scenarios that generate an energetic burden to organisms. To evaluate empirical support for a bioenergetics-AOP, we analyzed published data for links between energetic endpoints across levels of biological organization. We found correlations between 1) cellular energy allocation and whole-animal growth, and 2) metabolic rate and scope for growth. Moreover, we reviewed literature linking energy availability to nontraditional toxicological endpoints (e.g., locomotor performance), and found evidence that toxicants impair aerobic performance and activity. We conclude by highlighting current knowledge gaps that should be addressed to develop specific bioenergetics-AOPs. Environ Toxicol Chem 2019;38:27-45. © 2018 SETAC.

Parental diet affects embryogenesis of the great pond snail (Lymnaea stagnalis) exposed to cadmium, pyraclostrobin, and tributyltin

Diet quality has a strong impact on life-history traits, but it is not usually considered as a factor in toxicity tests. The purpose of the present study was to evaluate how diets differing in nutritional content affect sensitivity to cadmium, pyraclostrobin, and tributyltin in Lymnaea stagnalis offspring. Three groups were fed a different diet each: lettuce, high-caloric pellets, or a combination of both. Snails fed pellets and both diets had similar growth; however, snails fed lettuce showed lower growth until the fourth month. Egg masses were collected from adult snails fed each diet and exposed to 3 concentrations of either cadmium, pyraclostrobin, or tributyltin. We quantified time to hatch, hatching success, and the developmental stages of embryos. We measured fecundity in adults and total lipids, carbohydrates, and proteins in adult snails and egg masses. Adult snails fed different diets produced a similar number of egg masses, but the number of eggs per egg mass in snails fed pellets was lower than for snails fed the other 2 diets. We found that adult snails fed pellets had a higher lipid content compared to snails fed the other 2 diets. However, egg masses from parental snails fed pellets did not hatch, including those from the controls. Interestingly, egg masses exposed to the lowest concentration of tributyltin had low hatching success. These observations on offspring performance suggest that there are important diet effects that can strongly influence responses that could be diet- and chemical-dependent. Environ Toxicol Chem 2018;37:2428-2438. © 2018 SETAC.

Transgenerational interactions between pesticide exposure and warming in a vector mosquito

While transgenerational plasticity may buffer ectotherms to warming and pesticides separately, it remains unknown how combined exposure to warming and pesticides in the parental generation shapes the vulnerability to these stressors in the offspring. We studied the transgenerational effects of single and combined exposure to warming (4°C increase) and the pesticide chlorpyrifos on life-history traits of the vector mosquito Culex pipiens. Parental exposure to a single stressor, either warming or the pesticide, had negative effects on the offspring: parental exposure to both warming and the pesticide resulted in an overall lower offspring survival, and a delayed offspring metamorphosis. Parental exposure to a single stressor did, however, not alter the vulnerability of the offspring to the same stressor in terms of survival. Parental pesticide exposure resulted in larger offspring when the offspring experienced the same stressor as the parents. Within both the parental and offspring generations, warming made the pesticide more toxic in terms of survival. Yet, this synergism disappeared in the offspring of parents exposed to both stressors simultaneously because in this condition, the pesticide was already more lethal at the lower temperature. Our results indicate that transgenerational effects will not increase the ability of this vector species to deal with pesticides in a warming world. Bifactorial transgenerational experiments are crucial to understand the combined impact of warming and pesticides across generations, hence to assess the efficacy of vector control in a warming world.

Electronic-property dependent interactions between tetracycline and graphene nanomaterials in aqueous solution

Understanding the interactions between graphene nanomaterials (GNMs) and antibiotics in aqueous solution is critical to both the engineering applications of GNMs and the assessment of their potential impact on the fate and transport of antibiotics in the aquatic environment. In this study, adsorption of one common antibiotic, tetracycline, by graphene oxide (GO) and reduced graphene oxide (RGO) was examined with multi-walled carbon nanotubes (MWCNTs) and graphite as comparison. The results showed that the tetracycline adsorption capacity by the four selected carbonaceous materials on the unit mass basis followed an order of GO>RGO>MWCNTs>graphite. Upon normalization by surface area, graphite, RGO and MWCNTs had almost the same high tetracycline adsorption affinity while GO exhibited the lowest. We proposed π-electron-property dependent interaction mechanisms to explain the observed different adsorption behaviors. Density functional theory (DFT) calculations suggested that the oxygen-containing functional groups on GO surface reduced its π-electron-donating ability, and thus decreased the π-based interactions between tetracycline and GO surface. Comparison of adsorption efficiency at different pH indicated that electrostatic interaction also played an important role in tetracycline-GO interactions. Site energy analysis confirmed a highly heterogeneous distribution of the binding sites and strong tetracycline binding affinity of GO surface.

Multigenerational Effects of the Antibiotic Tetracycline on Transcriptional Responses of Daphnia magna and Its Relationship to Higher Levels of Biological Organizations

Given the risk of environmental pollution by pharmaceutical compounds and the effects of these compounds on exposed ecosystems, ecologically relevant and realistic assessments are required. However, many studies have been mostly focused on individual responses in a single generation exposed to one-effect concentrations. Here, transcriptional responses of the crustacean Daphnia magna to the antibiotic tetracycline across multiple generations and effect concentrations were investigated. The results demonstrated that tetracycline induced different transcriptional responses of daphnids that were dependent on dose and generation. For example, reproduction-related expressed sequence tags (ESTs), including vitellogenin, were distinctly related to the dose-dependent tetracycline exposure, whereas multigenerational exposure induced significant change of molting-related ESTs such as cuticle protein. A total of 65 ESTs were shared in all contrasts, suggesting a conserved mechanism of tetracycline toxicity regardless of exposure concentration or time. Most of them were associated with general stress responses including translation, protein and carbohydrate metabolism, and oxidative phosphorylation. In addition, effects across the dose-response curve showed higher correlative connections among transcriptional, physiological, and individual responses than multigenerational effects. In the multigenerational exposure, the connectivity between adjacent generations decreased with increasing generation number. The results clearly highlight that exposure concentration and time trigger different mechanisms and functions, providing further evidence that multigenerational and dose-response effects cannot be neglected in environmental risk assessment.

Validation of a two-generational reproduction test in Daphnia magna: An interlaboratory exercise

Effects observed within one generation disregard potential detrimental effects that may appear across generations. Previously we have developed a two generation Daphnia magna reproduction test using the OECD TG 211 protocol with a few amendments, including initiating the second generation with third brood neonates produced from first generation individuals. Here we showed the results of an inter-laboratory calibration exercise among 12 partners that aimed to test the robustness and consistency of a two generation Daphnia magna reproduction test. Pyperonyl butoxide (PBO) was used as a test compound. Following experiments, PBO residues were determined by TQD-LC/MS/MS. Chemical analysis denoted minor deviations of measured PBO concentrations in freshly prepared and old test solutions and between real and nominal concentrations in all labs. Other test conditions (water, food, D. magna clone, type of test vessel) varied across partners as allowed in the OECD test guidelines. Cumulative fecundity and intrinsic population growth rates (r) were used to estimate "No observed effect concentrations "NOEC using the solvent control as the control treatment. EC₁₀ and EC-₅₀ values were obtained regression analyses. Eleven of the twelve labs succeeded in meeting the OECD criteria of producing >60 offspring per female in control treatments during 21days in each of the two consecutive generations. Analysis of variance partitioning of cumulative fecundity indicated a relatively good performance of most labs with most of the variance accounted for by PBO (56.4%) and PBO by interlaboratory interactions (20.2%), with multigenerational effects within and across PBO concentrations explaining about 6% of the variance. EC₅₀ values for reproduction and population growth rates were on average 16.6 and 20.8% lower among second generation individuals, respectively. In summary these results suggest that the proposed assay is reproducible but cumulative toxicity in the second generation cannot reliably be detected with this assay.

A cost or a benefit? Counterintuitive effects of diet quality and cadmium in Lymnaea stagnalis

Diet quality can have a strong impact on organismal fitness although diet quality is infrequently considered as a factor in toxicity tests. The purpose of this study was to assess how diets differing in nutritional content affect sensitivity to Cd as measured by several sublethal responses related directly to bioenergetics. We evaluated feeding rate, growth rate, behavior and macronutrient content in the pond snail Lymnaea stagnalis exposed to Cd and fed two different diets. Hatchlings were fed either lettuce or high-caloric pellets, and exposed to 5, 10, and 20 µg/L Cd for 12 days. Length and weight were measured at the beginning and end of the test. The amount of food eaten and behavior were determined every two days. Total lipids, proteins and carbohydrates were biochemically measured at test end. For the second part of the study, snails were fed either lettuce or pellets for 2 weeks and then exposed to high challenge concentrations of Cd. Growth coefficients based on length and weight were significantly higher for snails fed pellets. In addition, snails exposed to Cd had significantly smaller growth coefficients than those in the control for both diets. Total carbohydrates and lipids were higher for snails fed pellets while the protein content was not significantly affected by Cd or diets. Even though snails fed pellets grew significantly faster, contrary to expectations they were significantly more sensitive to Cd compared to those fed lettuce. This study provides evidence that a bioenergetics-based approach can been used to better understand how diet can affect the ecotoxicity of chemical stressors to freshwater gastropods.

Transgenerational effects of two antidepressants (sertraline and venlafaxine) on Daphnia magna life history traits

The low levels of antidepressants detected in surface waters currently raise concern about their potential long-term risks to nontarget aquatic organisms. We investigated the transgenerational effects of sertraline, a selective serotonin reuptake inhibitor, and venlafaxine, a serotonin-norepinephrine reuptake inhibitor, on the life traits of Daphnia magna over two generations under environmentally realistic concentrations. We also studied the reversibility of the effect using recovery experiments. We assessed daphnid survival, growth, and reproduction over 21 days and evidenced detectable effects of the antidepressants. Sertraline increased the F0-daphnid fecundity whereas it decreased the offspring number of F1-daphnids. Transfer to clean medium caused negative effects on the offspring of daphnids exposed to 0.3 μg L(–1), but improved the fecundity of offspring of daphnids exposed to 100 μg L(–1). Venlafaxine exposure decreased the offspring number of F0-daphnids and resulted in drug tolerance in the F1 generation. Sertraline, unlike venlafaxine, may turn out to be a true environmental threat due to its accumulation in algae and the physiological weakness observed over generations. These effects across generations point out to the need to perform multigeneration tests to assess the environmental risk of pharmaceuticals in nontarget organisms.