Daphnia magna metabolic profiling as a promising water quality parameter for the biological early warning system

Exploring the Relationship Among Lipid Profile Changes, Growth, and Reproduction in Folsomia candida Exposed to Teflubenzuron Over Time

The integration of untargeted lipidomics approaches in ecotoxicology has emerged as a strategy to enhance the comprehensiveness of environmental risk assessment. Although current toxicity tests with soil microarthropods focus on species performance, that is, growth, reproduction, and survival, understanding the mechanisms of toxicity across all levels of biological organization, from molecule to community is essential for informed decision-making. Our study focused on the impacts of sublethal concentrations of the insecticide teflubenzuron on the springtail Folsomia candida. Untargeted lipidomics was applied to link changes in growth, reproduction, and the overall stress response with lipid profile changes over various exposure durations. The accumulation of teflubenzuron in organisms exposed to the highest test concentration (0.035 mg a.s. kg-1 soil dry wt) significantly impacted reproductive output without compromising growth. The results suggested a resource allocation shift from reproduction to size maintenance. This hypothesis was supported by lipid shifts on day 7, at which point reductions in triacylglycerol and diacylglycerol content corresponded with decreased offspring production on day 21. The hypermetabolism of fatty acids and N-acylethanolamines on days 2 and 7 of exposure indicated oxidative stress and inflammation in the animals in response to teflubenzuron bioaccumulation, as measured using high-performance liquid chromatography-tandem mass spectrometry. Overall, the changes in lipid profiles in comparison with phenotypic adverse outcomes highlight the potential of lipid analysis as an early-warning tool for reproductive disturbances caused by pesticides in F. candida. Environ Toxicol Chem 2024;00:1-12. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Machine learning-based water quality prediction using octennial in-situ Daphnia magna biological early warning system data

Biological early warning system (BEWS) has been globally used for surface water quality monitoring. Despite its extensive use, BEWS has exhibited limitations, including difficulties in biological interpretation and low alarm reproducibility. This study addressed these issues by applying machine learning (ML) models to eight years of in-situ BEWS data for Daphnia magna. Six ML models were adopted to predict contamination alarms from Daphnia behavioral parameters. The light gradient boosting machine model demonstrated the most significant improvement in predicting alarms from Daphnia behaviors. Compared with the traditional BEWS alarm index, the ML model enhanced the precision and recall by 29.50% and 43.41%, respectively. The speed distribution index and swimming speed were significant parameters for predicting water quality warnings. The nonlinear relationships between the monitored Daphnia behaviors and water physicochemical water quality parameters (i.e., flow rate, Chlorophyll-a concentration, water temperature, and conductivity) were identified by ML models for simulating Daphnia behavior based on the water contaminants. These findings suggest that ML models have the potential to establish a robust framework for advancing the predictive capabilities of BEWS, providing a promising avenue for real-time and accurate assessment of water quality. Thereby, it can contribute to more proactive and effective water quality management strategies.

Traditional and new proposals for environmental microbial indicators-a review

The continuous increment in world population coupled with the greatest natural resource consumption and waste generation has an enormous impact on the environment. To date, using biological indicators (bioindicators) to evaluate the biological quality of natural environments is very common. Nonetheless, selecting those suitable for each ecosystem or contaminant is one of the most important issues for environmental sciences. Bacteria and helminths are mainly related to fecal contamination, while antibiotic-resistant bacteria, fungi, viruses, and microalgae are organisms used to determine deteriorated ecosystems by diverse contaminants. Nowadays, each bioindicator is used as a specific agent of different contaminant types, but detecting and quantifying these bioindicator microorganisms can be performed from simple microscopy and culture methods up to a complex procedure based on omic sciences. Developing new techniques based on the metabolism and physiological responses of traditional bioindicators is shown in a fast environmental sensitivity analysis. Therefore, the present review focuses on analyzing different bioindicators to facilitate developing suitable monitoring environmental systems according to different pollutant agents. The traditional and new methods proposed to detect and quantify different bioindicators are also discussed. Their vital role is considered in implementing efficient ecosystem bioprospection, restoration, and conservation strategies directed to natural resource management.

Evaluation of the probable synergistic toxicity of selected potentiated antiretroviral and antibiotics on some aquatic biomarker organisms

Environmental effects of active pharmaceutical compounds (APCs) in the environment are not well characterized, hence the need for comprehensive evaluation. This study employed three bioassays using three organisms, namely, Allium cepa, Daphnia magna, and Salmonella typhimurium, in the ecotoxicity study of lone and a mixture of selected APCs, namely, lamivudine (L), an antiretroviral, and ciprofloxacin (C) and sulfamethoxazole (S), antibiotics, at a concentration range between 10 and 100 ppb, in order to evaluate the potential of the lone and ternary mixture to exert synergistic toxicity. Study results from exposure to lone APCs showed that the L, C, and S trio individually had fatal impacts on daphnids, with mortality rates of 100, 75, and 95%, respectively, after 48 h. Sulfamethoxazole showed a mutagenic tendency, with a mutation ratio (background/sample ratio) of 2.0. Lamivudine showed a lethal impact on the root length of A. cepa (p > 0.05, p = 3.60E-3). Further microscopic examination of the A. cepa root tip revealed chromosomal aberrations on exposure to each compound. The LCS-mix ecotoxicology bioassays indicated a synergistic effect on the daphnids, probably due to potentiation. Although the LCS mix had a cytotoxic effect (evidenced by the absence of bacteria colonies) on exposed TA 98 P450 Salmonella typhimurium strain, this effect was not observed in other bacterial strains. Microscopic examination of A. cepa exposed to the LCS-mix revealed an aberration in the mitotic stage of the cell. The impact of combination of the pharmaceuticals in aqueous ecosystems was greater than when exposed to the tested individual pharmaceutical compounds. Study result showed that these compounds have tendencies to pose a higher risk to exposed living entities when in combined/potentiated forms, and this could lead to distortion of the regular functioning of the ecosystem, particularly bacterial and other microbial populations that are listed among primary producers of the aquatic food web.

Environmental metabolomics uncovers oxidative stress, amino acid dysregulation, and energy impairment in Daphnia magna with exposure to industrial effluents

Anthropogenic activities are regarded as point sources of pollution entering freshwater bodies worldwide. With over 350,000 chemicals used in manufacturing, wastewater treatment and industrial effluents are comprised of complex mixtures of organic and inorganic pollutants of known and unknown origins. Consequently, their combined toxicity and mode of action are not well understood in aquatic organisms such as Daphnia magna. In this study, effluent samples from wastewater treatment and industrial sectors were used to examine molecular-level perturbations to the polar metabolic profile of D. magna. To determine if the industrial sector and/or the effluent chemistries played a role in the observed biochemical responses, Daphnia were acutely (48 h) exposed to undiluted (100%) and diluted (10, 25, and 50%) effluent samples. Endogenous metabolites were extracted from single daphnids and analyzed using targeted mass spectrometry-based metabolomics. The metabolic profile of Daphnia exposed to effluent samples resulted in significant separation compared to the unexposed controls. Linear regression analysis determined that no single pollutant detected in the effluents was significantly correlated with the responses of metabolites. Significant perturbations were uncovered across many classes of metabolites (amino acids, nucleosides, nucleotides, polyamines, and their derivatives) which serve as intermediates in keystone biochemical processes. The combined metabolic responses are consistent with oxidative stress, disruptions to energy metabolism, and protein dysregulation which were identified through biochemical pathway analysis. These results provide insight into the molecular processes driving stress responses in D. magna. Overall, we determined that the metabolic profile of Daphnia could not be predicted by the chemical composition of environmentally relevant mixtures. The findings of this study demonstrate the advantage of metabolomics in conjunction with chemical analyses to assess the interactions of industrial effluents. This work further demonstrates the ability of environmental metabolomics to characterize molecular-level perturbations in aquatic organisms exposed to complex chemical mixtures directly.

The impact of amine and carboxyl functionalised microplastics on the physiology of daphnids

Plastic waste is considered a major threat for terrestrial, marine and freshwater ecosystems. Ingestion of primary or secondary microparticles resulting from plastic degradation can lead to their trophic transfer raising serious health concerns. In this study, the effect of amine and carboxy functionalized polystyrene microparticles on the physiology of daphnids was investigated with a combination of phenotypic and metabolic endpoints. Carboxy functionalized microparticles showed higher toxicity in acute exposures compared to their amine counterparts. Accumulation of both microparticles in animal gut was confirmed by stereo-microscopy as well as fluorescent microscopy which showed no presence of particles in the rest of the animal. Fluorescence based quantification of microparticles extracted from animal lysates validated their concentration-dependent uptake. Additionally, exposure of daphnids to amine and carboxy functionalized microparticles resulted in increased activities of key enzymes related to metabolism and detoxification. Finally, significant metabolic perturbations were discovered following exposure to microplastics. These findings suggest that polystyrene microparticles can hinder organism performance of the freshwater species and highlight the importance of seeking for holistic and physiological endpoints for pollution assessment.

Combined exposure of the bivalve Mytilus galloprovincialis to polyethylene microplastics and two pharmaceuticals (citalopram and bezafibrate): Bioaccumulation and metabolomic studies

Pharmaceuticals and microplastics constitute potential hazards in aquatic systems, but their combined effects and underlying toxicity mechanisms remain largely unknown. In this study, a simultaneous characterization of bioaccumulation, associated metabolomic alterations and potential recovery mechanisms was performed. Specifically, a bioassay on Mediterranean mussels (Mytilus galloprovincialis) was carried out with polyethylene microplastics (PE-MPLs, 1 mg/L) and citalopram or bezafibrate (500 ng/L). Single and co-exposure scenarios lasted 21 days, followed by a 7-day depuration period to assess their potential recovery. PE-MPLs delayed the bioaccumulation of citalopram (lower mean at 10 d: 447 compared to 770 ng/g dw under single exposure), although reaching similar tissue concentrations after 21 d. A more limited accumulation of bezafibrate was observed overall, regardless of PE-MPLs co-exposure (<MQL-3.2 ng/g dw). Metabolic profiles showed a strong effect of pharmaceuticals, generally independent of PE-MPLs co-exposure. Alterations of the citrate cycle (bezafibrate exposure) and steroid and prostaglandin metabolism (citalopram and bezafibrate exposures) were highlighted. PE-MPLs alone also impacted metabolic pathways, such as neurotransmitters or purine metabolism. After depuration, relevant latent or long-lasting effects were demonstrated as, for instance, the effect of citalopram on neurotransmitters metabolism. Altogether, the observed molecular-level responses to pharmaceuticals and/or PE-MPLs may lead to a dysregulation of mussels' reproduction, energy metabolism, and/or immunity.

The complexity of micro- and nanoplastic research in the genus Daphnia - A systematic review of study variability and a meta-analysis of immobilization rates

In recent years, the number of publications on nano- and microplastic particles (NMPs) effects on freshwater organisms has increased rapidly. Freshwater crustaceans of the genus Daphnia are widely used in ecotoxicological research as model organisms for assessing the impact of NMPs. However, the diversity of experimental designs in these studies makes conclusions about the general impact of NMPs on Daphnia challenging. To approach this, we systematically reviewed the literature on NMP effects on Daphnia and summarized the diversity of test organisms, experimental conditions, NMP properties and measured endpoints to identify gaps in our knowledge of NMP effects on Daphnia. We use a meta-analysis on mortality and immobilization rates extracted from the compiled literature to illustrate how NMP properties, study parameters and the biology of Daphnia can impact outcomes in toxicity bioassays. In addition, we investigate the extent to which the available data can be used to predict the toxicity of untested NMPs based on the extracted parameters. Based on our results, we argue that focusing on a more diverse set of NMP properties combined with a more detailed characterization of the particles in future studies will help to fill current research gaps, improve predictive models and allow the identification of NMP properties linked to toxicity.

An integrated supervision framework to safeguard the urban river water quality supported by ICT and models

Models and information and communication technology (ICT) can assist in the effective supervision of urban receiving water bodies and drainage systems. Single model-based decision tools, e.g., water quality models and the pollution source identification (PSI) method, have been widely reported in this field. However, a systematic pathway for environmental decision support system (EDSS) construction by integrating advanced single techniques has rarely been reported, impeding engineering applications. This paper presents an integrated supervision framework (UrbanWQEWIS) involving monitoring-early warning-source identification-emergency disposal to safeguard the urban water quality, where the data, model, equipment and knowledge are smoothly and logically linked. The generic architecture, all-in-one equipment and three key model components are introduced. A pilot EDSS is developed and deployed in the Maozhou River, China, with the assistance of environmental Internet of Things (IoT) technology. These key model components are successfully validated via in situ monitoring data and dye tracing experiments. In particular, fluorescence fingerprint-based qualitative PSI and Bayesian-based quantitative PSI methods are effectively coupled, which can largely reduce system costs and enhance flexibility. The presented supervision framework delivers a state-of-the-art management tool in the digital water era. The proposed technical pathway of EDSS development provides a valuable reference for other regions.

Molecular Responses of Daphnids to Chronic Exposures to Pharmaceuticals

Pharmaceutical compounds are among several classes of contaminants of emerging concern, such as pesticides, heavy metals and personal care products, all of which are a major concern for aquatic ecosystems. The hazards posed by the presence of pharmaceutical is one which affects both freshwater organisms and human health-via non-target effects and by the contamination of drinking water sources. The molecular and phenotypic alterations of five pharmaceuticals which are commonly present in the aquatic environment were explored in daphnids under chronic exposures. Markers of physiology such as enzyme activities were combined with metabolic perturbations to assess the impact of metformin, diclofenac, gabapentin, carbamazepine and gemfibrozil on daphnids. Enzyme activity of markers of physiology included phosphatases, lipase, peptidase, β-galactosidase, lactate dehydrogenase, glutathione-S-transferase and glutathione reductase activities. Furthermore, targeted LC-MS/MS analysis focusing on glycolysis, the pentose phosphate pathway and the TCA cycle intermediates was performed to assess metabolic alterations. Exposure to pharmaceuticals resulted in the changes in activity for several enzymes of metabolism and the detoxification enzyme glutathione-S-transferase. Metabolic perturbations on key pathways revealed distinct groups and metabolic fingerprints for the different exposures and their mixtures. Chronic exposure to pharmaceuticals at low concentrations revealed significant alterations of metabolic and physiological endpoints.

The Effects of Single and Combined Stressors on Daphnids-Enzyme Markers of Physiology and Metabolomics Validate the Impact of Pollution

The continuous global increase in population and consumption of resources due to human activities has had a significant impact on the environment. Therefore, assessment of environmental exposure to toxic chemicals as well as their impact on biological systems is of significant importance. Freshwater systems are currently under threat and monitored; however, current methods for pollution assessment can neither provide mechanistic insight nor predict adverse effects from complex pollution. Using daphnids as a bioindicator, we assessed the impact in acute exposures of eight individual chemicals and specifically two metals, four pharmaceuticals, a pesticide and a stimulant, and their composite mixture combining phenotypic, biochemical and metabolic markers of physiology. Toxicity levels were in the same order of magnitude and significantly enhanced in the composite mixture. Results from individual chemicals showed distinct biochemical responses for key enzyme activities such as phosphatases, lipase, peptidase, β-galactosidase and glutathione-S-transferase. Following this, a more realistic mixture scenario was assessed with the aforementioned enzyme markers and a metabolomic approach. A clear dose-dependent effect for the composite mixture was validated with enzyme markers of physiology, and the metabolomic analysis verified the effects observed, thus providing a sensitive metrics in metabolite perturbations. Our study highlights that sensitive enzyme markers can be used in advance on the design of metabolic and holistic assays to guide the selection of chemicals and the trajectory of the study, while providing mechanistic insight. In the future this could prove to become a useful tool for understanding and predicting freshwater pollution.

Omics-based ecosurveillance for the assessment of ecosystem function, health, and resilience

Current environmental monitoring efforts often focus on known, regulated contaminants ignoring the potential effects of unmeasured compounds and/or environmental factors. These specific, targeted approaches lack broader environmental information and understanding, hindering effective environmental management and policy. Switching to comprehensive, untargeted monitoring of contaminants, organism health, and environmental factors, such as nutrients, temperature, and pH, would provide more effective monitoring with a likely concomitant increase in environmental health. However, even this method would not capture subtle biochemical changes in organisms induced by chronic toxicant exposure. Ecosurveillance is the systematic collection, analysis, and interpretation of ecosystem health-related data that can address this knowledge gap and provide much-needed additional lines of evidence to environmental monitoring programs. Its use would therefore be of great benefit to environmental management and assessment. Unfortunately, the science of 'ecosurveillance', especially omics-based ecosurveillance is not well known. Here, we give an overview of this emerging area and show how it has been beneficially applied in a range of systems. We anticipate this review to be a starting point for further efforts to improve environmental monitoring via the integration of comprehensive chemical assessments and molecular biology-based approaches. Bringing multiple levels of omics technology-based assessment together into a systems-wide ecosurveillance approach will bring a greater understanding of the environment, particularly the microbial communities upon which we ultimately rely to remediate perturbed ecosystems.

Crayfish tissue metabolomes effectively distinguish impacts of wastewater and agriculture in aquatic ecosystems

Environmental metabolomics has been proposed as a tool for biomonitoring because organisms regulate production or consumption of metabolites in response to environmental conditions. We evaluated the efficacy of the metabolome of three tissues (hepatopancreas, gill, and tail muscle) from the northern crayfish (Faxonius virilis) to detect and differentiate between impacts of human activities (i.e., reference, municipal wastewater, and agriculture). We conducted a reciprocal transfer study exposing crayfish for 1 or 2 weeks in three streams with different amounts and types of human activities in southern Manitoba, Canada. Tissue samples were analyzed using nuclear magnetic resonance spectroscopy to generate a metabolic profile. Findings indicated the gill tissue metabolome best detected and differentiated between human activities. In particular, the gill metabolome was able to rapidly integrate abrupt changes in environmental conditions associated with municipal wastewater activity. In contrast, the tail metabolome best differentiated between crayfish collected at the reference site from those collected at the two impacted sites. Metabolites extracted from hepatopancreas tissue showed limited and inconsistent detection of among site differences. Based on our findings, we conclude that the metabolome of the northern crayfish can be an effective biomonitoring tool, but monitoring purpose will dictate tissue selection. Indeed, we recommend the gill metabolome be used for short-term assays aimed at detecting acute effects, whereas the tail be applied for survey monitoring aimed at detecting deviations in ecological condition at test sites from reference site conditions.

Targeted Metabolomic Assessment of the Sub-Lethal Toxicity of Halogenated Acetic Acids (HAAs) to Daphnia magna

Halogenated acetic acids (HAAs) are amongst the most frequently detected disinfection by-products in aquatic environments. Despite this, little is known about their toxicity, especially at the molecular level. The model organism Daphnia magna, which is an indicator species for freshwater ecosystems, was exposed to sub-lethal concentrations of dichloroacetic acid (DCAA), trichloroacetic acid (TCAA) and dibromoacetic acid (DBAA) for 48 h. Polar metabolites extracted from Daphnia were analyzed using liquid chromatography hyphened to a triple quadrupole mass spectrometer (LC-MS/MS). Multivariate analyses identified shifts in the metabolic profile with exposure and pathway analysis was used to identify which metabolites and associated pathways were disrupted. Exposure to all three HAAs led to significant downregulation in the nucleosides: adenosine, guanosine and inosine. Pathway analyses identified perturbations in the citric acid cycle and the purine metabolism pathways. Interestingly, chlorinated and brominated acetic acids demonstrated similar modes of action after sub-lethal acute exposure, suggesting that HAAs cause a contaminant class-based response which is independent of the type or number of halogens. As such, the identified metabolites that responded to acute HAA exposure may serve as suitable bioindicators for freshwater monitoring programs.

Untargeted metabolomics changes on Gammarus pulex induced by propranolol, triclosan, and nimesulide pharmaceutical drugs

The presence of pharmaceuticals and personal care products (PPCPs) in natural water resources due to incomplete removal in Wastewater Treatment Plants (WWTPs) is a serious environmental concern at present. In this work, the effects of three pharmaceuticals (propranolol, triclosan, and nimesulide) on Gammarus pulex metabolic profiles at different doses and times of exposure have been investigated by liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). The complex data sets generated in the different exposure experiments were analyzed with the ROIMCR procedure, based on the selection of the MS regions of interest (ROI) data and on their analysis by the Multivariate Curve-Resolution Alternating Least Squares (MCR-ALS) chemometrics method. This approach, allowed the resolution and identification of the metabolites present in the analyzed samples, as well as the estimation of their concentration changes due to the exposure experiments. ANOVA Simultaneous Component Analysis (ASCA) and Partial Least Squares Discriminant Analysis (PLS-DA) were then conducted to assess the changes in the concentration of the metabolites for the three pharmaceuticals at the different conditions of exposure. The three tested pharmaceuticals changed the concentrations of metabolites, which were related to different KEGG functional classes. These changes summarize the biochemical response of Gammarus pulex to the exposure by the three investigated pharmaceuticals. Possible pathway alterations related to protein synthesis and oxidative stress were observed in the concentration of identified metabolites.

Reproduction stage specific dysregulation of Daphnia magna metabolites as an early indicator of reproductive endocrine disruption

Rapid biomolecular observation in model indicator organisms has been considered as a potential predictor of water pollution from chronic and trace toxicants. This study evaluated the use of Daphnia magna metabolomic measurements as indicators for exposure to reproductive endocrine disruptors by using the model juvenile hormone analogue fenoxycarb. Because D. magna reproduction controls metabolic regulation, the reproduction stage was also carefully considered in metabolic observations and data analysis to examine differences. Comparisons of metabolite abundance regulation between 1 and 12 days of fenoxycarb exposure were performed to investigate the predictability of the sub-chronic (12 days) adverse impacts on reproduction and metabolic regulation based on acute (1 day) metabolic observations. ANOVA-simultaneous component analysis (ASCA) detected reversed patterns in direction of time-course metabolite abundance regulation with fenoxycarb exposure. For example, decreases in the abundances of leucine, asparagine, methionine, and isoleucine which then changed to increases were observed with time during fenoxycarb exposures. The reversed regulation pattern was observed at the last reproduction stage (stage 3), exclusively. Pearson correlation analysis showed that correlations of pairwise metabolites were disrupted with fenoxycarb exposure. Similar to ASCA, data normalization based on the reproduction stage improved the detectability of significant correlations. The disruption on ambient metabolite regulation patterns and pairwise metabolite correlations was consistently observed with both 1 and 12 days of fenoxycarb exposures for sets of select metabolites. The observed regulatory disruptions to these specific metabolites suggest altered oogenesis as the affected metabolites and the specific reproduction stage are related to successful oogenesis. This study demonstrates that D. magna metabolic dysregulation is a predictor of water contamination by endocrine disrupting compounds. The high predictability of sub-chronic (12 days) endocrine disruption was confirmed based on acute (1 day) metabolic observations. Furthermore, integration of the reproduction cycle information in D. magna metabolomics was validated by observing a reproduction stage specific dysregulation in metabolite abundance regulation, which was not observable from the broader data analysis. Consequently, this study confirms the potential for establishing a quantitative relationship between water quality and indicator species metabolic observations. Additionally, it was found that constraining variables relevant to toxicity mechanisms of interest, such as the reproduction stage, is a key consideration for extraction of ecologically meaningful information in environmental metabolomics.

Enhanced lipid extraction from the biodiesel-producing microalga Chlorella pyrenoidosa cultivated in municipal wastewater via Daphnia ingestion and digestion

Herein, a novel innovative lipid co-extraction strategy using the biodiesel-producing microalga Chlorella pyrenoidosa and planktonic cladoceran Daphnia was proposed. Co-extraction occurred as Daphnia ingested and digested microalgal cells in a pre-treatment process; thereafter, lipids from these organisms were extracted. Composition of fatty acids from C. pyrenoidosa and Daphnia were appropriate as potential biodiesel feedstocks. Daphnia had different absorption and conversion capacities of various fatty acids from C. pyrenoidosa, which showed potential for improving biodiesel characteristics. Linoleic acid (LA, C18:2n-6) and alpha-linolenic acid (ALA, C18:3n-3) were absorbed significantly into the body of Daphnia. The optimal lipid extraction and fatty acid methyl esters (FAMEs) recovery rates were up to 41.08% and 12.35%, respectively, which were greater than that of the traditional lipid extraction method due to the rich oil content of Daphnia. Overall, this lipid co-extraction process serves a potential Daphnia utilization as an economical, green, low-energy way for microalgae biodiesel production.

Time-dependent biomolecular responses and bioaccumulation of perfluorooctane sulfonate (PFOS) in Daphnia magna

Perfluorooctane sulfonate (PFOS) is a persistent pollutant which is potentially harmful and bioaccumulative to aquatic organisms. To evaluate the regulatory alteration of select metabolites with PFOS exposure at early and typical acute exposure periods in an aquatic indicator species Daphnia magna, the hourly abundance of the twenty-three metabolites was investigated over 24 h. To evaluate the bioaccumulation potential of PFOS at a sub-lethal concentration in D. magna, the daily accumulation into D. magna for 16 days was also evaluated. Twenty-three targeted metabolites were quantified over 1 to 4 h and 21 to 24 h of PFOS exposure using liquid chromatography tandem mass spectrometry (LC-MS/MS). Daphnid to water PFOS concentration ratios were monitored separately over different days and life stages at 0 to 76 h and 2 to 16 days of PFOS exposure. The observed metabolite abundance and bioaccumulation in the exposed groups was compared between sampling times. The results reveal that sub-lethal PFOS exposure at 2 mg/L and 20 mg/L alters regulation of arginine, tyrosine and adenosine monophosphate which are directly and indirectly related to energy status. The temporal metabolic responses observed for the early exposure period (4 h), but not for the typical acute exposure period (24 h), suggest the dysregulation potency of PFOS on metabolite regulation of D. magna and the importance of early time-course monitoring approaches. Sixteen days of bioaccumulation monitoring showed that PFOS is more bioaccumulative in younger D. magna. The observation of time-dependent bioaccumulation of PFOS in D. magna requires further studies to define its precise mechanism. Interestingly, the bioaccumulation potential of PFOS was found to be consistent between 72 h and 16 day exposure periods. No difference on the body burden to water concentration ratio during about one third of the life span time (16 days), compared to the 72 h exposure, suggests that the prolonged exposure did not increase the bioaccumulation of PFOS in D. magna. This study demonstrates that the Daphnia metabolites are rapidly responding to sub-lethal PFOS exposure and provides information on life stage and time-dependent bioaccumulation potential of PFOS. As such, metabolite regulation is a sensitive indicator to sub-lethal PFOS exposure and can be informative when combined with other measures of toxicity.