The utility of behavioral studies for aquatic toxicology testing: a meta-analysis

Field-realistic exposure to the androgenic endocrine disruptor 17β-trenbolone alters ecologically important behaviours in female fish across multiple contexts

The capacity of pharmaceutical pollution to alter behaviour in wildlife is of increasing environmental concern. A major pathway of these pollutants into the environment is the treatment of livestock with hormonal growth promotants (HGPs), which are highly potent veterinary pharmaceuticals that enter aquatic ecosystems via effluent runoff. Hormonal growth promotants are designed to exert biological effects at low doses, can act on physiological pathways that are evolutionarily conserved across taxa, and have been detected in ecosystems worldwide. However, despite being shown to alter key fitness-related processes (e.g., development, reproduction) in various non-target species, relatively little is known about the potential for HGPs to alter ecologically important behaviours, especially across multiple contexts. Here, we investigated the effects of exposure to a field-realistic level of the androgenic HGP metabolite 17β-trenbolone-an endocrine-disrupting chemical that has repeatedly been detected in freshwater systems-on a suite of ecologically important behaviours in wild-caught female eastern mosquitofish (Gambusia holbrooki). First, we found that 17β-trenbolone-exposed fish were more active and exploratory in a novel environment (i.e., maze arena), while boldness (i.e., refuge use) was not significantly affected. Second, when tested for sociability, exposed fish spent less time in close proximity to a shoal of stimulus (i.e., unexposed) conspecific females and were, again, found to be more active. Third, when assayed for foraging behaviour, exposed fish were faster to reach a foraging zone containing prey items (chironomid larvae), quicker to commence feeding, spent more time foraging, and consumed a greater number of prey items, although the effect of exposure on certain foraging behaviours was dependent on fish size. Taken together, these findings highlight the potential for exposure to sub-lethal levels of veterinary pharmaceuticals to alter sensitive behavioural processes in wildlife across multiple contexts, with potential ecological and evolutionary implications for exposed populations.

Influence of Diltiazem on Fathead Minnows Across Dissolved Oxygen Gradients

Water resources in many arid to semi-arid regions are stressed by population growth and drought. Growing populations and climatic changes are influencing contaminant and water chemistry dynamics in urban inland waters, where flows can be dominated by, or even dependent on, wastewater effluent discharge. In these watersheds, interacting stressors such as dissolved oxygen and environmental contaminants (e.g., pharmaceuticals) have the potential to affect fish physiology and populations. Recent field observations from our group identified the calcium channel blocker (CCB) diltiazem in fish plasma exceeding human therapeutic doses (e.g., C_min ) in aquatic systems impaired because of nonattainment of dissolved oxygen water quality standards. Therefore our study objectives examined: 1) standard acute and chronic effects of dissolved oxygen and diltiazem to fish, 2) influences of dissolved oxygen at criteria levels deemed protective of aquatic life on diltiazem toxicity to fish, and 3) whether sublethal effects occur at diltiazem water concentrations predicted to cause a human therapeutic level (therapeutic hazard value [THV]) in fish plasma. Dissolved oxygen × diltiazem co-exposures significantly decreased survival at typical stream, lake, and reservoir water quality standards of 5.0 and 3.0 mg dissolved oxygen/L. Dissolved oxygen and diltiazem growth effects were observed at 2 times and 10 times lower than median lethal concentration (LC50) values (1.7 and 28.2 mg/L, respectively). Larval fathead minnow (Pimephales promelas) swimming behavior following low dissolved oxygen and diltiazem exposure generally decreased and was significantly reduced in light-to-dark bursting distance traveled, number of movements, and duration at concentrations as low as the THV. Individual and population level consequences of such responses are not yet understood, particularly in older organisms or other species; however, these findings suggest that assessments with pharmaceuticals and other cardioactive contaminants may underestimate adverse outcomes in fish across dissolved oxygen levels considered protective of aquatic life. Environ Toxicol Chem 2018;37:2835-2850. © 2018 SETAC.

Comparative behavioral toxicology with two common larval fish models: Exploring relationships among modes of action and locomotor responses

Behavioral responses inform toxicology studies by rapidly and sensitively detecting molecular initiation events that propagate to physiological changes in individuals. These behavioral responses can be unique to chemical specific mechanisms and modes of action (MOA) and thus present diagnostic utility. In an initial effort to explore the use of larval fish behavioral response patterns in screening environmental contaminants for toxicity and to identify behavioral responses associated with common chemical specific MOAs, we employed the two most common fish models, the zebrafish and the fathead minnow, to define toxicant induced swimming activity alterations during interchanging photoperiods. Though the fathead minnow (Pimephales promelas) is a common model for aquatic toxicology research and regulatory toxicology practice, this model has received little attention in behavioral studies compared to the zebrafish, a common biomedical model. We specifically compared behavioral responses among 7 different chemicals (1-heptanol, phenol, R-(-)-carvone, citalopram, diazinon, pentylenetetrazole (PTZ), and xylazine) that were selected and classified based on anticipated MOA (nonpolar narcosis, polar narcosis, electrophile, specific mechanism) according to traditional approaches to examine whether these comparative responses differ among chemicals with various structure-based predicted toxicity. Following standardized experimental guidelines, zebrafish embryos and fathead minnow larvae were exposed for 96 h to each compound then were observed using digital behavioral analysis. Behavioral observations included photomotor responses, distance traveled, and stimulatory, refractory and cruising locomotor activity. Though fathead minnow larvae displayed greater behavioral sensitivity to 1-heptanol, phenol and citalopram, zebrafish were more sensitive to diazinon and R-(-)-carvone. Both fish models were equally sensitive to xylazine and PTZ. Further, the pharmaceuticals citalopram and xylazine significantly affected behavior at therapeutic hazard values, and each of the seven chemicals elicited unique behavioral response profiles. Larval fish behaviors appear useful as early tier diagnostics to identify mechanisms and pathways associated with diverse biological activities for chemicals lacking mechanistic data.

Escherichia coli's water load affects zebrafish (Danio rerio) behavior

Traditional physico-chemical sensors are becoming an obsolete tool for environmental quality assessment. Biomonitoring techniques, such as biological early warning systems present the advantage of being sensitivity, fast, non-invasive and ecologically relevant. In this work, we applied a video tracking system, developed with zebrafish (Danio rerio), to detect microbiological contamination in water. Using the fishs' behavior response, the system was able to detect the presence of a non-pathogenic environmental strain of Escherichia coli, at three different levels of contamination: 600, 1800 and 5000 CFU/100 mL (colony forming units/100 mL). Data was collected during 50 min of exposure and analyzed with the artificial neural networks Self-organizing Map and Multi-layer Perceptron. The behavior of exposed fish was more erratic, with pronounced and rapid changes on movement direction and with significant less exploratory activity. The accuracy, sensitivity and specificity values regarding the detection capability (distinction between presence or absence of contamination) ranged from 89 to 100%. Regarding the classification capability (distinction between experimental conditions), the values ranged from 67 to 89%. This research may be a valuable contribution to improve water monitoring and management strategies, by taking as reference the effects on biosensors, without a biased anthropocentric perspective.

Neurobehavioral Alterations in Zebrafish Due to Long-Term Exposure to Low Doses of Inorganic Arsenic

Inorganic arsenic (As) is one of the most ubiquitous and toxic substances with widespread health effects on human populations and biodiversity. Although arsenic is a frequent surface water pollutant, there is scant evidence about neurotoxicity in aquatic species in different stages of development. In the present study, we investigated the neurobehavioral effects of chronic exposure to environmentally relevant doses of arsenic. We exposed zebrafish to 50 and 500 ppb during the larval, juvenile, and adult stage (from 4 h to 150 days postfertilization). We then used broad behavioral screening to evaluate motor function, social behavior, learning and memory, and anxiety-like behaviors. Our results show that arsenic exposure to 500 ppb alters motor function from the embryo to the adult stage. Furthermore, during the adult phase, associative learning and the sensorimotor response are affected with both high and low doses of As, respectively. Notably, exposure to 500 ppb of As induces behaviors associated with anxiety, during the juvenile and adult phase but not the larval stage, without changes in whole-body cortisol levels. These results indicate that chronic exposure to arsenic during their lifespan is capable of producing alterations in different behavioral markers in aquatic vertebrates.

Species-specific behaviours in amphipods highlight the need for understanding baseline behaviours in ecotoxicology

Behavioural studies in ecotoxicology are increasing with techniques and endpoints used in pharmacology being translated to other vertebrate and invertebrate species. Despite this, data on the baseline behaviours of model organisms, and inter-species variability in behaviour are currently under-studied. This study assessed a range of behaviours associated with anxiety including swimming speed, phototaxis and thigmotaxis in a marine and freshwater amphipod (Echinogammarus marinus and Gammarus pulex). Differences in sensitivity to these assays were observed between species with E. marinus showing a greater sensitivity to the phototaxis assay than G. pulex, while in thigmotaxis assays G. pulex appeared better suited than E. marinus for measuring differences in the use of central zones. Significant inter-species differences were also observed in swimming patterns when breaking the data into ten second time bins but not when data was broken into two-minute time bins. The results of this study provide evidence of phototactic and thigmotactic behaviours in two model crustacean species with potential for use in behavioural ecotoxicology. Inter-species variability in sensitivity to behavioural assays highlights the importance of systematic assessment of baseline responses for all model species used in behavioural studies. Careful analysis of data is also required when performing behavioural studies so as not to lose sensitivity in your data.

Direct and indirect effects of chemical contaminants on the behaviour, ecology and evolution of wildlife

Chemical contaminants (e.g. metals, pesticides, pharmaceuticals) are changing ecosystems via effects on wildlife. Indeed, recent work explicitly performed under environmentally realistic conditions reveals that chemical contaminants can have both direct and indirect effects at multiple levels of organization by influencing animal behaviour. Altered behaviour reflects multiple physiological changes and links individual- to population-level processes, thereby representing a sensitive tool for holistically assessing impacts of environmentally relevant contaminant concentrations. Here, we show that even if direct effects of contaminants on behavioural responses are reasonably well documented, there are significant knowledge gaps in understanding both the plasticity (i.e. individual variation) and evolution of contaminant-induced behavioural changes. We explore implications of multi-level processes by developing a conceptual framework that integrates direct and indirect effects on behaviour under environmentally realistic contexts. Our framework illustrates how sublethal behavioural effects of contaminants can be both negative and positive, varying dynamically within the same individuals and populations. This is because linkages within communities will act indirectly to alter and even magnify contaminant-induced effects. Given the increasing pressure on wildlife and ecosystems from chemical pollution, we argue there is a need to incorporate existing knowledge in ecology and evolution to improve ecological hazard and risk assessments.

Shape and size of the arenas affect amphipod behaviours: implications for ecotoxicology

The use of behaviour in ecotoxicology is expanding, however the lack of standardisation and validation of these assays currently presents a major drawback in moving forward in the development of behavioural assays. Furthermore, there is a current paucity of control data on test species, particularly invertebrate models. In this study we assessed a range of behaviours associated with spatial distribution and locomotion in relation to arena size and shape in two species of amphipod crustacean (Echinogammarus marinus and Gammarus pulex). Arena shape had significant effects on almost all behavioural parameters analysed. Increasing arena size resulted in an increased mean velocity and activity plus increased proportional use of the central zones. These results indicate that 'ceiling effects' may occur in some ecotoxicological studies resulting in potentially 'false' negative effects if careful consideration is not paid to experimental design. Differences in behaviours were observed between the two species of amphipod. For example, G. pulex spend approximately five times (∼20%) more of the available time crossing the central zones of the arenas compared to E. marinus (∼4%) which could have implications on assessing anxiolytic behaviours. The results of this study highlight several behaviours with potential for use in behavioural ecotoxicology with crustaceans but also underscore the need for careful consideration when designing these behavioural assays.

Comparison of the behavioural effects of pharmaceuticals and pesticides on Diamesa zernyi larvae (Chironomidae)

Several studies have indicated the presence of contaminants in Alpine aquatic ecosystems. Even if measured concentrations are far below those that cause acute effects, continuous exposure to sub-lethal concentrations may have detrimental effects on the aquatic species present in these remote environments. This may lead to a cascade of indirect effects at higher levels of the ecological hierarchy (i.e., the community). To improve the determination of ecologically relevant risk endpoints, behavioural alterations in organisms due to pollutants are increasingly studied in ecotoxicology. In fact, behaviour links physiological function with ecological processes, and can be very sensitive to environmental stimuli and chemical exposure. This is the first study on behavioural alteration in a wild population of an Alpine species. In the present study, a video tracking system was standardized and subsequently used to identify contaminant-induced behavioural alterations in Diamesa zernyi larvae (Diptera, Chironomidae). Diamesa zernyi larvae, collected in an Italian Alpine stream (Rio Presena, Trentino Region), were acclimated for 24 h and successively exposed to several aquatic contaminants (pesticides: chlorpyrifos, metolachlor, boscalid, captan; pharmaceuticals: ibuprofen, furosemide, trimethoprim) at concentrations corresponding to their Lowest Observed Effect Concentration (LOEC). After 24, 48, 72, and 96 h of exposure, changes in the distance moved, the average speed, and the frequency of body bends were taken to reflect contaminant- and time-dependent effects on larval behaviour. In general, metolachlor, captan, and trimethoprim tended to reduce all the endpoints under consideration, whereas chlorpyrifos, boscalid, ibuprofen, and furosemide seemed to increase the distances moved by the larvae. This could be related to the different mechanisms of action of the investigated chemicals. Independently of the contaminant, after 72 h a general slowing down of all the behavioural activities occurred. Finally, we propose a behavioural stress indicator to compare the overall behavioural effects induced by the various contaminants.

Environmentally relevant concentrations of tramadol and citalopram alter behaviour of an aquatic invertebrate

Environmental pollution by pharmaceutically active compounds, used in quantities similar to those of pesticides and other organic micropollutants, is increasingly recognized as a major threat to the aquatic environment. These compounds are only partly removed from wastewaters and, despite their low concentrations, directly and indirectly affect behaviour of freshwater organisms in natural habitats. The aim of this study was to behaviourally assess the effects of an opioid painkiller (tramadol) and antidepressant drug (citalopram) on behaviour patterns of a clonal model species, marbled crayfish. Animals exposed to environmentally relevant concentrations of both tested compounds (∼1 μg l^-1) exhibited significantly lower velocity and shorter distance moved than controls. Crayfish exposed to tramadol spent more time in shelters. Results were obtained by a simple and rapid method recommended as suitable for assessment of behaviour in aquatic organisms exposed to single pollutants and combinations.

Effects of UV filter 4-methylbenzylidene camphor during early development of Solea senegalensis Kaup, 1858

The inclusion of organic UV filters in personal care products (PCPs) has increased in recent years. 4-Methylbenzylidene camphor (4MBC) is one of the most used UV filters, and thus it is commonly found in aquatic ecosystems, with proved negative effects on aquatic organisms. Effects on early life stages of marine vertebrates are largely unknown. Therefore, the main goal of this work was to evaluate 4MBC effects on Senegalese sole (Solea Senegalensis Kaup, 1858) larvae at different levels of biological organization. S. senegalensis were exposed to increasing concentrations of 4MBC from egg stage until 96 h. Mortality, growth, malformations, behaviour and biochemical responses, including enzymatic biomarkers were studied. The exposure to 4MBC until 96 h post-fertilization (hpf) induced mortality and malformations in a dose-response manner. Besides, reduced growth with increasing concentrations was observed. The exposure to 4MBC also caused alterations on behaviour, including overall lower swimming time during light and dark periods. Biomarker alterations caused by 4MBC included imbalance of neurotransmission related endpoints (increased acetylcholinesterase activity) and decreased activity of enzymes related to anaerobic metabolism (lower cellular lactate dehydrogenase activity) at the lower concentrations tested. Furthermore, our results suggest that 4MBC do not induce oxidative stress in S. senegalensis larvae, since catalase and lipid peroxidation levels were not significantly altered by 4MBC. S. senegalensis revealed to be a good model species for vertebrate animal testing in the marine environment. Sub-lethal concentrations of 4MBC induced toxic effects at all organizational levels. Swimming behaviour was a sensitive endpoint and showed that exposure to 4MBC causes impairment on response to light stimulus which is possibly linked with the observed imbalances on cholinesterase activity in larvae. Conservation concerns along distribution range of S. senegalensis should consider that increasing levels of UV filters in marine environment might have impact on the ecology of the species.

Alterations of secondary sex characteristics, reproductive histology and behaviors by norgestrel in the western mosquitofish (Gambusia affinis)

Synthetic hormones in wastewater effluents released into the aquatic environments may interfere with the normal endocrine systems of fish in receiving streams. Norgestrel (NGT) is a synthetic progestin widely used in oral contraceptives and frequently detected in wastewater effluents. In this study, adult female mosquitofish (Gambusia affinis) were exposed to three environmentally relevant concentrations of norgestrel (NGT) (i.e., 3.6, 35.8, and 368.0 ng L-1) for 42 d, fin morphology, histology of the ovary, and reproductive behaviors were evaluated. The results showed that NGT at all three concentrations caused an increased frequency of atretic follicular cells in ovaries and impaired mating behaviors exhibited by males toward the NGT-exposed females. In mosquitofish exposed to NGT at 35.8 and 368 ng L^-1, the anal fin of females had an increased length ratio of ray4/ray 6, an increased width of ray 3, and increased number of segments in ray 3. The histopathological analysis showed that exposure to NGT increased the incidence of spermatogenesis in ovaries. Mating behavior was impaired 58.4%, 65.7%, and 76.4% (P < 0.01 in all cases) when mosquitofish were exposed to NGT at 3.6, 35.6 and 368.0 ng L^-1, respectively. The rapid masculinization, the increased frequency of atretic follicles, the incidence of spermatogenesis in the ovary of female fish, and the altered reproductive behaviors suggest that wild populations of mosquitofish could be similarly affected inhabiting in NGT contaminated environments.

Single and combined effects of microplastics and mercury on juveniles of the European seabass (Dicentrarchus labrax): Changes in behavioural responses and reduction of swimming velocity and resistance time

Microplastics and mercury are environmental pollutants of great concern. The main goal of the present study was to investigate the effects of these pollutants, both individually and in binary mixtures, on the swimming performance of juvenile European seabass, Dicentrarchus labrax. Microplastics alone, mercury alone and all the mixtures caused significant reduction of the swimming velocity and resistance time of fish. Moreover, changes in behavioural responses including lethargic and erratic swimming behaviour were observed. These results highlight that fish behavioural responses can be used as sensitive endpoint to establish the effects of contamination by microplastics and also emphasizes the need to assess the combined effects of microplastics and other environmental contaminants, with special attention to the effects on behavioural responses in fish and other aquatic species.

Transgenerational Effects of Toxicants: An Extension of the Daphnia 21-day Chronic Assay?

The assessment of transgenerational effects should be incorporated in standard chronic toxicity protocols for the sake of a realistic extrapolation of contaminant effects to the population level. We propose a simple add-on to the standard 21-day chronic Daphnia magna assay, allowing the assessment of the reproductive performance of the offspring (F₁ generation) born from the first clutch of the parental (F₀) generation. The extended generational assay was performed simultaneously with the standard reproduction assay. With this design, we evaluated the lethal, reproductive, and transgenerational effects of four widespread and extensively used substances: a biocide/anti-fouling (copper sulphate), an industrial oxidizing agent (potassium dichromate), a pharmaceutical (paracetamol), and a quaternary ammonium compound (benzalkonium chloride). Benzalkonium chloride was the most toxic in terms of lethality, whereas paracetamol, copper sulphate, and potassium dichromate caused deleterious effects in the reproductive performance of exposed D. magna. Adverse effects in the fitness of the daughter (F₁) generation were observed in the case of maternal exposure to paracetamol and copper sulphate, although they were not very pronounced. These findings highlight the usefulness of our approach and reinforce the view-shared by other authors-of the need for a generalised formal assessment of the transgenerational effects of pollutants.

Charting a path towards non-destructive biomarkers in threatened wildlife: A systematic quantitative literature review

Threatened species are susceptible to irreversible population decline caused by adverse sub-lethal effects of chemical contaminant exposure. It is therefore vital to develop the necessary tools to predict and detect these effects as early as possible. Biomarkers of contaminant exposure and effect are widely applied to this end, and a significant amount of research has focused on development and validation of sensitive and diagnostic biomarkers. However, progress in the use biomarkers that can be measured using non-destructive techniques has been relatively slow and there are still many difficulties to overcome in the development of sound methods. This paper systematically quantifies and reviews studies that have aimed to develop or validate non-destructive biomarkers in wildlife, and provides an analysis of the successes of these methods based on the invasiveness of the methods, the potential for universal application, cost, and the potential for new biomarker discovery. These data are then used to infer what methods and approaches appear the most effective for successful development of non-destructive biomarkers of contaminant exposure in wildlife. This review highlights that research on non-destructive biomarkers in wildlife is severely lacking, and suggests further exploration of in vitro methods in future studies.

No evidence of increased growth or mortality in fish exposed to oxazepam in semi-natural ecosystems

An increasing number of short-term laboratory studies on fish reports behavioral effects from exposure to aquatic contaminants or raised carbon dioxide levels affecting the GABA_A receptor. However, how such GABAergic behavioral modifications (GBMs) impact populations in more complex natural systems is not known. In this study, we induced GBMs in European perch (Perca fluviatilis) via exposure to a GABA agonist (oxazepam) and followed the effects on growth and survival over one summer (70days) in replicated pond ecosystems. We hypothesized that anticipated GBMs, expressed as anti-anxiety like behaviors (higher activity and boldness levels), that increase feeding rates in laboratory assays, would; i) increase growth and ii) increase mortality from predation. To test our hypotheses, 480 PIT tagged perch of known individual weights, and 12 predators (northern pike, Esox lucius) were evenly distributed in 12 ponds; six control (no oxazepam) and six spiked (15.5±4μgl^-1 oxazepam [mean±1S.E.]) ponds. Contrary to our hypotheses, even though perch grew on average 16% more when exposed to oxazepam, we found no significant difference between exposed and control fish in growth (exposed: 3.9±1.2g, control: 2.9±1g [mean±1S.E.], respectively) or mortality (exposed: 26.5±1.8individuals pond^-1, control: 24.5±2.6individuals pond^-1, respectively). In addition, we show that reduced prey capture efficiency in exposed pike may explain the lack of significant differences in predation. Hence, our results suggest that GBMs, which in laboratory studies impact fish behavior, and subsequently also feeding rates, do not seem to generate strong effects on growth and predation-risk in more complex and resource limited natural environments.

Unsuitable use of DMSO for assessing behavioral endpoints in aquatic model species

Dimethyl sulfoxide (DMSO) is a universally used aprotic solvent with the ability to permeate biological membranes and thus is commonly used to achieve appropriate biological availability of hydrophobic toxicants. While DMSO as a carrier medium has a reportedly low toxicity and is routinely employed in ecotoxicology, very little is known about its effect on dynamic behavioral parameters. This study presents a comparative analysis of the lethal and behavioral effects of exposures to DMSO concentrations of 0.1-10% on several test species such as: neonates of the freshwater crustacean Daphnia magna, nauplii of the marine crustacean Artemia franciscana, the marine crustacean Allorchestes compressa, embryos and larvae of the freshwater fish Danio rerio. The results demonstrated that DMSO did not cause statistically significant mortality even at concentrations close to 1% but induced clear and significant behavioral abnormalities in response to sublethal concentrations on all test species. These included hypoactivity syndrome in A. franciscana, A. compressa, D. magna and zebrafish larvae while a slight time-dependent hyperactivity response was observed in zebrafish embryos. For the majority of test species, behavioral changes such as moving distance, acceleration and burst movement were often observed during the first hours of exposure. These results indicate that caution should be exercised when using DMSO as a carrier solvent in experiments assessing behavioral endpoints.

Ecotoxicology Goes on a Chip: Embracing Miniaturized Bioanalysis in Aquatic Risk Assessment

Biological and environmental sciences are, more than ever, becoming highly dependent on technological and multidisciplinary approaches that warrant advanced analytical capabilities. Microfluidic lab-on-a-chip technologies are perhaps one the most groundbreaking offshoots of bioengineering, enabling design of an entirely new generation of bioanalytical instrumentation. They represent a unique approach to combine microscale engineering and physics with specific biological questions, providing technological advances that allow for fundamentally new capabilities in the spatiotemporal analysis of molecules, cells, tissues, and even small metazoan organisms. While these miniaturized analytical technologies experience an explosive growth worldwide, with a substantial promise of a direct impact on biosciences, it seems that lab-on-a-chip systems have so far escaped the attention of aquatic ecotoxicologists. In this Critical Review, potential applications of the currently existing and emerging chip-based technologies for aquatic ecotoxicology and water quality monitoring are highlighted. We also offer suggestions on how aquatic ecotoxicology can benefit from adoption of microfluidic lab-on-a-chip devices for accelerated bioanalysis.

Feeding Behavior of an Aquatic Snail as a Simple Endpoint to Assess the Exposure to Cadmium

One of the aims of ecotoxicology is the assessment of the effects of chemicals on the ecosystems. Bioassays assessing lethality are frequently used in ecotoxicology, however they usually employ supra-environmental toxic concentrations. Toxicity tests employing behavioral endpoints may present a balance between simplicity (i.e., laboratory bioassays) and complexity (i.e., relevant ecological effects). The aim of this study was to develop a feeding behavioral bioassay with the aquatic snail, Potamopyrgus antipodarum, which included a 2 days exposure to cadmium, followed by a 9 days post-exposure observational period. Several behavioral feeding endpoints were monitored, including percentage of actively feeding animals, percentage of animals in food quadrants and a mobility index. The percentage of actively feeding animals was reduced by the four cadmium treatments (0.009, 0.026, 0.091 and 0.230 mg Cd/L) with the stronger effect in the highest concentration. The two highest cadmium concentrations significantly reduced the percentage of animals in food quadrants and the mobility index. Therefore, the percentage of actively feeding animals was the most sensitive endpoint to cadmium toxicity as the four cadmium concentrations caused a significant decrease in this endpoint. It is concluded that feeding behavior is a useful endpoint to detect the exposure of aquatic snails to cadmium.

A Millifluidic System for Analysis of Daphnia magna Locomotory Responses to Water-born Toxicants

Aquatic toxicity testing in environmental monitoring and chemical risk assessment is critical to assess water quality for human use as well as predict impact of pollutants on ecosystems. In recent years, studies have increasingly focused on the relevance of sub-lethal effects of environmental contaminants. Sub-lethal toxicity endpoints such as behavioural responses are highly integrative and have distinct benefits for assessing water quality because they occur rapidly and thus can be used to sense the presence of toxicants. Our work describes a Lab-on-a-Chip system for the automated analysis of freshwater cladoceran Daphnia magna locomotory responses to water-born toxicants. The design combines a Lab-on-a-Chip system for Daphnia sp. culture under perfusion with time-resolved videomicroscopy and software tracking locomotory activity of multiple specimens. The application of the system to analyse the swimming behaviour of water fleas exposed to different concentrations of water-born toxicants demonstrated that Lab-on-a-Chip devices can become important research tools for behavioural ecotoxicology and water quality biomonitoring.

Evidence of low dose effects of the antidepressant fluoxetine and the fungicide prochloraz on the behavior of the keystone freshwater invertebrate Gammarus pulex

In recent years, behavior-related endpoints have been proposed as rapid and reliable ecotoxicological tools for risk assessment. In particular, the use of detritivores to test the toxicity of pollutants through feeding is currently becoming a well-known method. Experiments combining feeding with other behavioral endpoints can provide relevant information about direct and indirect toxicological effects of chemicals. We carried out a feeding experiment with the shredder Gammarus pulex in order to detect indirect (through leaf conditioning) and direct effects (through water exposure) of two pollutants at environmentally relevant concentrations: the fungicide prochloraz (6 μg/L) and the antidepressant fluoxetine (100 ng/L). Prochloraz inhibited fungal growth on leaves, but it did not affect either the microbial breakdown rates or the C:N ratio of the leaves. Individuals of G. pulex that were fed with treated leaves presented lower consumption rates, not only those fed with prochloraz-treated leaves, but also those fed with fluoxetine-treated leaves, and those fed with the mixture-treated leaves. Mixed-effects models revealed that the swimming velocity of the amphipods after the experiment was modulated by the exposure to fluoxetine, and also by the exposure to prochloraz. We demonstrate that both the antidepressant and the fungicide may cause significant sublethal effects at low concentrations. The combination of behavioral endpoints together with the application of mixed models provided a useful tool for early detection of the effects of toxicity mixtures in freshwater ecosystems.

The agricultural contaminant 17β-trenbolone disrupts male-male competition in the guppy (Poecilia reticulata)

Despite a growing literature highlighting the potential impact of human-induced environmental change on mechanisms of sexual selection, relatively little is known about the effects of chemical pollutants on male-male competition. One class of environmental pollutant likely to impact male competitive interactions is the endocrine-disrupting chemicals (EDCs), a large and heterogeneous group of chemical contaminants with the potential to influence morphology, physiology and behaviour at minute concentrations. One EDC of increasing concern is the synthetic, androgenic steroid 17β-trenbolone, which is used globally to promote growth in beef cattle. Although 17β-trenbolone has been found to cause severe morphological and behavioural abnormalities in fish, its potential impact on male-male competition has yet to be investigated. To address this, we exposed wild male guppies (Poecilia reticulata) to an environmentally realistic concentration of 17β-trenbolone (average measured concentration: 8 ng/L) for 21 days using a flow-through system. We found that, in the presence of a competitor, 17β-trenbolone-exposed males carried out more frequent aggressive behaviours towards rival males than did unexposed males, as well as performing less courting behaviour and more sneak (i.e., coercive) mating attempts towards females. Considering that, by influencing mating outcomes, male-male competition has important consequences for population dynamics and broader evolutionary processes, this study highlights the need for greater understanding of the potential impact of EDCs on the mechanisms of sexual selection.

Assessing the ecotoxicity of potentially neurotoxic substances - Evaluation of a behavioural parameter in the embryogenesis of Danio rerio

The pollution of the aquatic environment is currently characterised by a large number of contaminants, especially by mixtures of micro-pollutants including neurotoxins. The ecotoxicological consequences of this burden are not yet assessable. Within the present study, a new test method was applied which evaluates behavioural changes in zebrafish (Danio rerio) embryos to quantify the neurotoxic effect of selected chemicals. Changes in the frequency of spontaneous tail movements - a parameter of locomotion - occurring during embryogenesis was assessed as parameter for neurotoxic effects. Embryos were exposed in 24-microwell plates to neurotoxic compounds. Behaviour was examined after 24 h of exposure by videotaping and quantifying spontaneous locomotion. Additionally, acute toxicity was determined after 48 h of exposure by utilising the fish embryo toxicity test. Abamectin, emamectin benzoate, chlorpyrifos-oxon and carbamazepine were analysed using both: the new and classic acute test methods. The results showed the neurotoxic effect of the substances. Furthermore, an increased sensitivity compared to acute toxicity data was shown. The aim of the present study, to illustrate the sensitivity and specificity of the established endpoint to reliably assess adverse, neurotoxic effects of compounds on the model organism Danio rerio and to apply a new test method was achieved. Therefore, the present study is a substantial contribution to an effect-based risk assessment of contaminants in aquatic ecosystems.

Endocrine disruption in aquatic systems: up-scaling research to address ecological consequences

Endocrine‐disrupting chemicals (EDCs) can alter biological function in organisms at environmentally relevant concentrations and are a significant threat to aquatic biodiversity, but there is little understanding of exposure consequences for populations, communities and ecosystems. The pervasive nature of EDCs within aquatic environments and their multiple sub‐lethal effects make assessments of their impact especially important but also highly challenging. Herein, we review the data on EDC effects in aquatic systems focusing on studies assessing populations and ecosystems, and including how biotic and abiotic processes may affect, and be affected by, responses to EDCs. Recent research indicates a significant influence of behavioural responses (e.g. enhancing feeding rates), transgenerational effects and trophic cascades in the ecological consequences of EDC exposure. In addition, interactions between EDCs and other chemical, physical and biological factors generate uncertainty in our understanding of the ecological effects of EDCs within aquatic ecosystems. We illustrate how effect thresholds for EDCs generated from individual‐based experimental bioassays of the types commonly applied using chemical test guidelines [e.g. Organisation for Economic Co‐operation and Development (OECD)] may not necessarily reflect the hazards associated with endocrine disruption. We argue that improved risk assessment for EDCs in aquatic ecosystems urgently requires more ecologically oriented research as well as field‐based assessments at population‐, community‐ and food‐web levels.

Towards improved behavioural testing in aquatic toxicology: Acclimation and observation times are important factors when designing behavioural tests with fish

The quality and reproducibility of science has recently come under scrutiny, with criticisms spanning disciplines. In aquatic toxicology, behavioural tests are currently an area of controversy since inconsistent findings have been highlighted and attributed to poor quality science. The problem likely relates to limitations to our understanding of basic behavioural patterns, which can influence our ability to design statistically robust experiments yielding ecologically relevant data. The present study takes a first step towards understanding baseline behaviours in fish, including how basic choices in experimental design might influence behavioural outcomes and interpretations in aquatic toxicology. Specifically, we explored how fish acclimate to behavioural arenas and how different lengths of observation time impact estimates of basic swimming parameters (i.e., average, maximum and angular velocity). We performed a semi-quantitative literature review to place our findings in the context of the published literature describing behavioural tests with fish. Our results demonstrate that fish fundamentally change their swimming behaviour over time, and that acclimation and observational timeframes may therefore have implications for influencing both the ecological relevance and statistical robustness of behavioural toxicity tests. Our review identified 165 studies describing behavioural responses in fish exposed to various stressors, and revealed that the majority of publications documenting fish behavioural responses report extremely brief acclimation times and observational durations, which helps explain inconsistencies identified across studies. We recommend that researchers applying behavioural tests with fish, and other species, apply a similar framework to better understand baseline behaviours and the implications of design choices for influencing study outcomes.

Old model organisms and new behavioral end-points: Swimming alteration as an ecotoxicological response

Behavioral responses of aquatic organisms have received much less attention than developmental or reproductive ones due to the scarce presence of user-friendly tools for their acquisition. The technological development of data acquisition systems for quantifying behavior in the aquatic environment and the increase of studies on the understanding the relationship between the behavior of aquatic organisms and the physiological/ecological activities have generated renewed interest in using behavioral responses also in marine ecotoxicology. Recent reviews on freshwater environment show that behavioral end-points are comparatively fast and sensitive, and warrant further attention as tools for assessing the toxicological effects of environmental contaminants. In this mini-review, we perform a systematic analysis of the most recent works that have used marine invertebrate swimming alteration as behavioral end-point in ecotoxicological studies by assessing the differences between behavioral and acute responses in a wide range of species, in order to compare their sensitivity.

Effects of a glyphosate-based herbicide and predation threat on the behaviour of agile frog tadpoles

The widespread application of pesticides emphasises the importance of understanding the impacts of these chemicals on natural communities. The most commonly applied broad-spectrum herbicides in the world are glyphosate-based herbicides, which have been suggested to induce significant behavioural changes in non-target organisms even at low environmental concentrations. To scrutinize the behavioural effects of herbicide-exposure we exposed agile frog (Rana dalmatina) tadpoles in an outdoor mesocosm experiment to three concentrations of a glyphosate-based herbicide (0, 2 and 6.5mg acid equivalent (a.e.) / L). To assess whether anti-predator behaviour is affected by the pesticide, we combined all levels of herbicide-exposure with three predator treatments (no predator, caged Aeshna cyanea dragonfly larvae or Lissotriton vulgaris newt adults) in a full factorial design. We observed hiding, activity, proximity to the predator cage and vertical position of tadpoles. We found that at the higher herbicide concentration tadpoles decreased their activity and more tadpoles were hiding, and at least at the lower concentration their vertical position was closer to the water surface than in tadpoles of the control treatment. Tadpoles also decreased their activity in the presence of dragonfly larvae, but did not hide more in response to either predator, nor did tadpoles avoid predators spatially. Further, exposure to the herbicide did not significantly influence behavioural responses to predation threat. Our study documents a definite influence of glyphosate-based herbicides on the behaviour of agile frog tadpoles and indicates that some of these changes are similar to those induced by dangerous predators. This may suggest that the underlying physiological mechanisms or the adaptive value of behavioural changes may similar.

Integrative behavioral ecotoxicology: bringing together fields to establish new insight to behavioral ecology, toxicology, and conservation

The fields of behavioral ecology, conservation science, and environmental toxicology individually aim to protect and manage the conservation of wildlife in response to anthropogenic stressors, including widespread anthropogenic pollution. Although great emphasis in the field of toxicology has been placed on understanding how single pollutants affect survival, a comprehensive, interdisciplinary approach that includes behavioral ecology is essential to address how anthropogenic compounds are a risk for the survival of species and populations in an increasingly polluted world. We provide an integrative framework for behavioral ecotoxicology using Tinbergen’s four postulates (causation and mechanism, development and ontogeny, function and fitness, and evolutionary history and phylogenetic patterns). The aims of this review are: 1) to promote an integrative view and re-define the field of integrative behavioral ecotoxicology; 2) to demonstrate how studying ecotoxicology can promote behavior research; and 3) to identify areas of behavioral ecotoxicology that require further attention to promote the integration and growth of the field.

Impacts of the antidepressant fluoxetine on the anti-predator behaviours of wild guppies (Poecilia reticulata)

Chemical pollution from pharmaceuticals is increasingly recognised as a major threat to aquatic communities. One compound of great concern is fluoxetine, which is one of the most widely prescribed psychoactive drugs in the world and frequently detected in the environment. The aim of this study was to investigate the effects of 28-d fluoxetine exposure at two environmentally relevant levels (measured concentrations: 4ng/L and 16ng/L) on anti-predator behaviour in wild guppies (Poecilia reticulata). This was achieved by subjecting fluoxetine-exposed and unexposed guppies to a simulated bird strike and recording their subsequent behavioural responses. We found that exposure to fluoxetine affected the anti-predator behaviour of guppies, with exposed fish remaining stationary for longer (i.e. 'freezing' behaviour) after the simulated strike and also spending more time under plant cover. By contrast, control fish were significantly more active and explored the tank more, as indicated by the distance covered per minute over the period fish spent swimming. Furthermore, behavioural shifts were sex-dependent, with evidence of a non-monotonic dose-response among the fluoxetine-exposed fish. This is one of the first studies to show that exposure to environmentally relevant concentrations of fluoxetine can alter the anti-predator behaviour of adult fish. In addition to the obvious repercussions for survival, impaired anti-predator behaviour can have direct impacts on fitness and influence the overall population dynamics of species.

A Mixture of Persistent Organic Pollutants and Perfluorooctanesulfonic Acid Induces Similar Behavioural Responses, but Different Gene Expression Profiles in Zebrafish Larvae

Persistent organic pollutants (POPs) are widespread in the environment and some may be neurotoxic. As we are exposed to complex mixtures of POPs, we aimed to investigate how a POP mixture based on Scandinavian human blood data affects behaviour and neurodevelopment during early life in zebrafish. Embryos/larvae were exposed to a series of sub-lethal doses and behaviour was examined at 96 h post fertilization (hpf). In order to determine the sensitivity window to the POP mixture, exposure models of 6 to 48 and 48 to 96 hpf were used. The expression of genes related to neurological development was also assessed. Results indicate that the POP mixture increases the swimming speed of larval zebrafish following exposure between 48 to 96 hpf. This behavioural effect was associated with the perfluorinated compounds, and more specifically with perfluorooctanesulfonic acid (PFOS). The expression of genes related to the stress response, GABAergic, dopaminergic, histaminergic, serotoninergic, cholinergic systems and neuronal maintenance, were altered. However, there was little overlap in those genes that were significantly altered by the POP mixture and PFOS. Our findings show that the POP mixture and PFOS can have a similar effect on behaviour, yet alter the expression of genes relevant to neurological development differently.

Assessing ecotoxicity of biomining effluents in stream ecosystems by in situ invertebrate bioassays: A case study in Talvivaara, Finland

Mining of sulfide-rich pyritic ores produces acid mine drainage waters and has induced major ecological problems in aquatic ecosystems worldwide. Biomining utilizes microbes to extract metals from the ore, and it has been suggested as a new sustainable way to produce metals. However, little is known of the potential ecotoxicological effects of biomining. In the present study, biomining impacts were assessed using survival and behavioral responses of aquatic macroinvertebrates at in situ exposures in streams. The authors used an impedance conversion technique to measure quantitatively in situ behavioral responses of larvae of the regionally common mayfly, Heptagenia dalecarlica, to discharges from the Talvivaara mine (Sotkamo, Northern Finland), which uses a biomining technique. Behavioral responses measured in 3 mine-impacted streams were compared with those measured in 3 reference streams. In addition, 3-d survival of the mayfly larvae and the oligochaete Lumbriculus variegatus was measured in the study sites. Biomining impacts on stream water quality included increased concentrations of sulfur, sulfate, and metals, especially manganese, cadmium, zinc, sodium, and calcium. Survival of the invertebrates in the short term was not affected by the mine effluents. In contrast, apparent behavioral changes in mayfly larvae were detected, but these responses were not consistent among sites, which may reflect differing natural water chemistry of the study sites. Environ Toxicol Chem 2017;36:147-155. © 2016 SETAC.

Environmental relevant levels of a benzodiazepine (oxazepam) alters important behavioral traits in a common planktivorous fish, (Rutilus rutilus)

Environmental pollution by pharmaceuticals is increasingly recognized as a major threat to aquatic ecosystems worldwide. A complex mix of pharmaceuticals enters waterways via treated wastewater effluent and many remain biochemically active after the drugs reach aquatic systems. However, to date little is known regarding the ecological effects that might arise following pharmaceutical contamination of aquatic environments. One group of particular concern is behaviorally modifying pharmaceuticals as seemingly minor changes in behavior may initiate marked ecological consequences. The aim of this study was to examine the influence of a benzodiazepine anxiolytic drug (oxazepam) on key behavioral traits in wild roach (Rutilus rutilus) at concentrations similar to those encountered in effluent surface waters. Roach exposed to water with high concentrations of oxazepam (280 µg/L) exhibited increased boldness, while roach at low treatment (0.84 µg/L) became bolder and more active compared to control fish. Our results reinforce the notion that anxiolytic drugs may be affecting fish behavior in natural systems, emphasizing the need for further research on ecological impacts of pharmaceuticals in aquatic systems and development of new tools to incorporate ecologically relevant behavioral endpoints into ecotoxicological risk assessment.

Mimicking natural systems: Changes in behavior as a result of dynamic exposure to naproxen

Animals living in aquatic habitats regularly encounter anthropogenic chemical pollution. Typically, the toxicity of a chemical toxicant is determined by the median lethal concentration (LC₅₀) through a static exposure test. However, LC₅₀ values and static tests do not provide an accurate representation of exposure to pollutants within natural stream systems. In their native habitats, animals experience exposure as a fluctuating concentration due to turbulent mixing, temporal variations of contamination (seasonal inputs), and contaminant input type (point vs. non-point). Research has shown that turbulent environments produce exposures with a high degree of fluctuation in frequency, duration, and intensity. In order to more effectively evaluate the effects of pollutants, we created a dynamic exposure paradigm, utilizing both flow and substrate within a small mesocosm. A commonly used pharmaceutical, naproxen, was used as the toxicant and female crayfish (Orconectes virilis) as the target organism to investigate changes in fighting behavior as a result of dynamic exposure. Crayfish underwent either a 23h long static or a dynamic exposure to naproxen. Following exposure, the target crayfish and an unexposed size matched opponent underwent a 15min fight trial. These fight trials were recorded and later analyzed using a standard ethogram. Results indicate that exposure to sublethal concentrations of naproxen, in both static and flowing conditions, negatively impact aggressive behavior. Results also indicate that a dynamic exposure paradigm has a greater negative impact on behavior than a static exposure. Turbulence and habitat structure play important roles in shaping chemical exposure. Future research should incorporate features of dynamic chemical exposure in order to form a more comprehensive image of chemical exposure and predict the resulting sublethal effects from exposure. Possible techniques for assessment include utilizing flow-through experimental set-ups in tandem with behavioral or physiological endpoints as opposed to acute toxicity. Other possibilities of assessment could involve utilizing fine-scale chemical measurements of pollutants to determine the actual concentrations animals encounter during an exposure event.

Effect of antidepressants on circadian rhythms in fish: Insights and implications regarding the design of behavioural toxicity tests

Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs) are widely prescribed for the treatment of depression and anxiety disorders. Consequently, these compounds are frequently identified in global waterways where they may pose a hazard to aquatic biota. Evidence demonstrates these compounds to be capable of influencing the behaviour of fish, but the relevance of many reported behavioural endpoints is unclear and the value of some findings has been questioned. Since these compounds act on neuroendocrine-mediated pathways in vertebrates, the present study explored how exposure to two representative SSRIs (fluoxetine and sertraline) and an SNRI (venlafaxine) affect circadian rhythms in fish. Male mosquitofish (Gambusia holbrooki) were exposed to 1, 10 and 100μg/L concentrations of these compounds individually and when present as a full mixture, for a period of one week. Neither fluoxetine nor sertraline had an impact on diurnal activity patterns when fish were exposed to these compounds alone at any concentration, whereas venlafaxine significantly disrupted normal circadian rhythmicity but only at 100μg/L. When fish were exposed to the full mixture, significantly altered diurnal activity patterns were rapidly observed at nominal concentrations of 1 and 100μg/L, but there was no effect at 10μg/L. This sort of non-monotonic dose relationship is not altogether unusual for fish exposed to antidepressants, but it poses a problem when attempting to evaluate potential risks to the aquatic environment. To evaluate the possibility for misinterpretation when collecting behavioural data over short temporal scales, the data for each day of the experiment was analysed separately. The outcomes demonstrate the importance of longer periods of data collection, which may be necessary to capture the full range of natural behavioural variability that exists both amongst and within individual fish. More importantly, these findings may help reveal why discrepancies are commonly being reported in the literature with regards behavioural effects in fish exposed to antidepressants. It is thus suggested that research be aimed at documenting behavioural variability in fish species used in toxicity testing, to establish guidelines for quality control and where possible inform the development of standardised methodologies so that behavioural analysis can be more appropriately applied to the broad field of aquatic toxicology.

Exposure to SSRI-type antidepressants increases righting time in the marine snail Ilyanassa obsoleta

Exposure to human antidepressants has been shown to disrupt locomotion and other foot-mediated mechanisms in aquatic snails. We tested the effect of three selective serotonin reuptake inhibitor (SSRI)- and one selective serotonin-norepinephrine reuptake inhibitor (SNRI)-type antidepressants on the righting response in the marine snail, Ilyanassa obsoleta. All four antidepressants (fluoxetine, sertraline, paroxetine, venlafaxine) significantly increased righting time compared with controls with an exposure time as short as 1 h. Dose responses were nonmonotonic with effects seen mainly at the lowest exposure concentrations and shortest duration. The lowest concentration to show an effect was 3.45 μg/L fluoxetine with a 2-h exposure period and is about 3.71 times higher than environmental concentrations. Our results highlight rapid disruption of another foot-mediated behavior in aquatic snails by SSRI-type antidepressants. We discuss these and other reported nonmonotonic dose responses caused by antidepressants in terms of the various possible physiological mechanisms of action in nontarget aquatic species.

Development of a Low-Cost Ecotoxicological Bioassay Based on the Feeding Behaviour of the Aquatic Snail Potamopyrgus antipodarum (Hydrobiidae, Mollusca)

Conventional acute tests are not suited to assess the effects of toxicants, because they do not use the concentrations that are usually found in natural ecosystems. By contrast, nonlethal realistic concentrations may cause deleterious effects on animal fitness as a consequence of behaviour impairment. Behaviour is a good integrative variable of complex biochemical and physiological processes. Therefore, bioassays based on behaviour are a useful tool in ecotoxicology. In this study, two bioassays were conducted: (1) acute bioassay (48 h) of acetone on the aquatic snail Potamopyrgus antipodarum, and (2) video-recording behavioural bioassay with pulse exposures to acetone to assess its effects on feeding behaviour. In the latter, animals were exposed to three pulses of acetone (24 h each) with 6 days of postexposure after each pulse. This design allowed us to assess the degree of feeding behaviour recovery after exposure and the effects of repeated pulses. Our results show that postexposure periods have an important effect on the recovery of normal feeding behaviour and that this developed bioassay is an ecotoxicological tool with a relatively low-cost and a short-time consuming. The application of this new tool to different ecotoxicological requirements is discussed.

A meta-analysis synthesizing the effects of pesticides on swim speed and activity of aquatic vertebrates

Pesticide contaminants are ubiquitous in aquatic environments and pose a threat to biodiversity. Pesticides also have diverse mechanisms of action that make it difficult to identify impacts on exposed wildlife. Behavioral measures represent an important link between physiological and ecological processes, and are often used to generalize sub-lethal effects of pesticide exposure. In order to bridge the toxicological and behavioral literature, and identify chemical classes that denote the largest threat, we conducted a meta-analysis summarizing the effects of pesticides on swim speed and activity of aquatic vertebrates. We found that exposure to environmentally relevant concentrations of pesticides reduced the swim speed of exposed amphibians and fish by 35%, and reduced overall activity by 72%. There were also differences in the magnitude of this effect across chemical classes, which likely reflect underlying physiological processes. Pyrethroids, carbamates, and organophosphates all produced a large decrease in swim speed, where as phosphonoglycines and triazines showed no overall effect. Pyrethroids, carbamates, organophosphates, organochlorines, and organotins also produced a large decrease in activity, while phosphonoglycines had no overall effect, and triazines had the opposite effect of increasing activity. Our results indicate that even sub-lethal concentrations of pesticides have a strong effect on critical behaviors of aquatic vertebrates, which can affect fitness and alter species interactions. We expect our synthesis can be used to identify chemical classes producing the largest sub-lethal effects for further research and management.

Removal of trace organic contaminants from domestic wastewater: A meta-analysis comparison of sewage treatment technologies

Trace organic contaminants (TrOCs), such as endocrine disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs), represent global threats to aquatic animals and ecosystems. A major source of TrOCs in the aquatic environment is via the discharge of treated sewage, so there is an urgent need to evaluate the comparative efficiencies of the most widely used sewage treatment technologies as regards elimination of these compounds from wastewater. To address this need, 976 published articles were compiled focusing on estimates of removal (%) for 20 common environmental TrOCs, from five major sewage treatment technologies: conventional activated sludge (CAS), oxidation ditch (OD), membrane bioreactor (MBR), ponds and constructed wetlands (PCW), and trickling biological filters (TBF). A quantitative meta-analysis was performed to compare standardized relative removal efficiencies (SREs) of the compounds amongst these technologies, and where possible potential sources of heterogeneity were considered (e.g., flow rates and chemical sorption potential). The results indicate that the most widely used CAS treatment and the less common TBF provide comparatively poor overall removal of common organic micropollutants. Membrane bioreactors appear to be capable of achieving the greatest overall removal efficiencies, but the sustainability and economic viability of this option has been questioned. Treatment with OD systems may be more economical while still achieving comparatively high removal efficiencies, and the analysis revealed OD to be the best option for targeting highly potent estrogenic EDCs. This study offers a unique global assessment of TrOC removal via leading sewage treatment technologies, and is an important step in the identification of effective options for treating municipal sewage.

Effects of coal mine wastewater on locomotor and non-locomotor activities of empire gudgeons (Hypseleotris compressa)

Coal mining represents an important industry in many countries, but concerns exist about the possible adverse effects of minewater releases on aquatic animals and ecosystems. Coal mining generates large volumes of complex wastewater, which often contains high concentrations of dissolved solids, suspended solids, metals, hydrocarbons, salts and other compounds. Traditional toxicological testing has generally involved the assessment of acute toxicity or chronic toxicity with longer-term tests, and while such tests provide useful information, they are poorly suited to ongoing monitoring or rapid assessment following accidental discharge events. As such, there is considerable interest in developing rapid and sensitive approaches to environmental monitoring, and particularly involving the assessment of sub-lethal behavioural responses in locally relevant aquatic species. We therefore investigated behavioural responses of a native Australian fish to coal mine wastewater, to evaluate its potential use for evaluating sub-lethal effects associated with wastewater releases on freshwater ecosystems. Empire gudgeons (Hypseleotris compressa) were exposed to wastewater from two dams located at an open cut coal mine in Central Queensland, Australia and activity levels were monitored using the Multispecies Freshwater Biomonitor® (LimCo International GmbH). A general decrease in locomotor activity (i.e., low frequency movement) and increase in non-locomotor activity (i.e., high frequency movement including ventilation and small fin movement) was observed in exposed fish compared to those in control water. Altered activity levels were observable within the first hour of exposure and persisted throughout the 15-d experiment. Results demonstrate the potential for using behavioural endpoints as tools for monitoring wastewater discharges using native fish species, but more research is necessary to identify responsible compounds and response thresholds, and to understand the relevance of the observed effects for populations in natural receiving environments.

Oxidative stress, energy storage, and swimming performance of Limnodynastes peronii tadpoles exposed to a sub-lethal pharmaceutical mixture throughout development

Pharmaceutical contaminants represent emerging threats to aquatic animals and ecosystem health, and research exploring toxicological outcomes associated with these compounds in non-target wildlife has been flagged for prioritization. Amphibians represent particularly vulnerable organisms and many populations around the world are currently at risk of extinction. However, to date, relatively few studies have explored the consequences of exposures to common non-steroidal pharmaceuticals during sensitive amphibian life-stages. To address existing knowledge gaps, tadpoles of the Australian striped-marsh frog (Limnodynastes peronii) were exposed to control water and a mixture of the common pharmaceutical contaminants diclofenac, naproxen, atenolol and gemfibrozil at 0.1, 1, 10, 100 and 1000 μg/L throughout the developmental period. Effects on detoxification pathways, energy storage, growth and development, and swimming performance were assessed following exposure. Developmental rates and liver-somatic index (LSI) were significantly reduced in the highest exposure concentration, and condition factor (K) was increased at concentrations as low as 10 μg/L. Morphological endpoints were associated with significantly altered levels of hepatic triglycerides, which in turn were correlated with increased peroxidase activity in animals exposed to the highest concentration (1000 μg/L). The mixture had no significant effect on swimming performance, but a trend of decreased swimming velocity (average and maximum) was observed with increasing concentration, and this was correlated with effects on LSI. Results demonstrate that mixtures of common non-steroidal pharmaceuticals can elicit a range of physiological, metabolic and morphological responses in larval amphibians, and more research is therefore warranted to explore possible relationships between endpoints at different levels of organization.

Behaviour, development and metal accumulation in striped marsh frog tadpoles (Limnodynastes peronii) exposed to coal mine wastewater

Coal mining generates large quantities of complex effluent, and this often contains high levels of dissolved solids, suspended solids, metals, hydrocarbons, salts and other compounds. Substantial volumes of mine wastewater are periodically discharged into the environment, through both planned and accidental releases, and this raises concerns about the potential for adverse impacts on aquatic wildlife. There have been few attempts to explore sub-lethal effects of coal mine wastewater on amphibians compared to other organisms, and this is particularly true for Australian species. To address existing knowledge gaps, we exposed striped marsh frog (Limnodynastes peronii) tadpoles to 25, 50 and 100% coal mine wastewater collected from two holding dams (CMW1 and CMW2) located at an open cut mine in Central Queensland, Australia. The exposure lasted for four weeks, after which survival, growth and development, swimming behaviour, and concentrations of metals and metalloids in tail and liver tissues were assessed. Physico-chemical parameters varied considerably between sites, with higher turbidity, nutrients, total and dissolved organic carbon, alkalinity and arsenic (As) concentrations at CMW1, and higher conductivity, salinity, dissolved solids, hardness and sulfate levels at CMW2. There was no mortality in controls and less than 5% mortality in CMW1 treatments, whereas survival was significantly decreased in tadpoles exposed to CMW2 with 40 and 55% mortality in the 50 and 100% treatments, respectively. Development was significantly delayed in 100% CMW1 wastewater, but tadpole size (growth) was not influenced by the exposure. Hepatosomatic indices were significantly increased in tadpoles exposed to 25 and 50% CMW1 but not the 100% treatment group. Exposed tadpoles (predominantly those exposed to CMW1) exhibited increased activity after very short-term exposure (24h), but this did not persist as animals approached metamorphic climax. At the end of the experiment, tadpoles exposed to both wastewaters had elevated levels of selenium (Se), cobalt (Co) and As in tail and liver tissue compared to controls. Manganese (Mn) levels were also elevated in livers and tails of CMW2 exposed tadpoles. Hepatic tissue accumulated 8-9 times higher concentrations of Co, Mn and Se compared to tail tissue, irrespective of treatments. Future research is warranted to explore possible relationships between metal bioaccumulation, morpho-physiological effects during development, and subsequent higher-level outcomes related to individual performance and population fitness.

Psychotropic drugs in mixture alter swimming behaviour of Japanese medaka (Oryzias latipes) larvae above environmental concentrations

Psychiatric pharmaceuticals, such as anxiolytics, sedatives, hypnotics and antidepressors, are among the most prescribed active substances in the world. The occurrence of these compounds in the environment, as well as the adverse effects they can have on non-target organisms, justifies the growing concern about these emerging environmental pollutants. This study aims to analyse the effects of six psychotropic drugs, valproate, cyamemazine, citalopram, sertraline, fluoxetine and oxazepam, on the survival and locomotion of Japanese medaka Oryzias latipes larvae. Newly hatched Japanese medaka were exposed to individual compounds for 72 h, at concentrations ranging from 10 μg L(-1) to 10 mg L(-1). Lethal concentrations 50 % (LC50) were estimated at 840, 841 and 9,136 μg L(-1) for fluoxetine, sertraline and citalopram, respectively, while other compounds did not induce any significant increase in mortality. Analysis of the swimming behaviour of larvae, including total distance moved, mobility and location, provided an estimated lowest observed effect concentration (LOEC) of 10 μg L(-1) for citalopram and oxazepam, 12.2 μg L(-1) for cyamemazine, 100 μg L(-1) for fluoxetine, 1,000 μg L(-1) for sertraline and >10,000 μg L(-1) for valproate. Realistic environmental mixture of the six psychotropic compounds induced disruption of larval locomotor behaviour at concentrations about 10- to 100-fold greater than environmental concentrations.

Locomotor and behavioural responses of empire gudgeons (Hypseleotris compressa) exposed to coal mine wastewater

Coal mining generates large quantities of complex effluent and may pose a threat to aquatic wildlife. Despite this, few studies have explored the consequences of exposure to mine wastewater on aquatic organisms, and this is particularly true for the Australian environment. We investigated sub-lethal behavioural responses in a native Australian fish exposed to wastewater from two releasing dams (CMW1 and CMW2) located at an open cut coal mine in Central Queensland. Swimming activity and movement of empire gudgeons (Hypseleotris compressa) were assessed during a two-week exposure using video-tracking software. Increased activity was observed in exposed fish after 7 and 14 days. Specifically, we found a significant increase in the mean velocity and mobility of fish exposed to CMW1 treatments. Exposed fish also spent on average 23% more time in the peripheral zone compared to controls after 14-d exposures. A similar response pattern was observed in fish exposed to CMW2, but differences between treated and control fish did not generally reach statistical significance. Alterations to normal swimming activity and movement patterns can be indicative of a stress response in fish, and could subsequently lead to negative population-level impacts by increasing the conspicuousness of exposed individuals to predators, or by altering foraging abilities. More research is warranted to explore relationships between behavioural and physiological outcomes, including endocrine disruption, and subsequent population-level outcomes in aquatic organisms at risk of exposure to coal process-affected water.

Behavioural alterations from exposure to Cu, phenanthrene, and Cu-phenanthrene mixtures: linking behaviour to acute toxic mechanisms in the aquatic amphipod, Hyalella azteca

Phenanthrene (PHE) and Cu are two contaminants commonly co-occurring in marine and freshwater environments. Mixtures of PHE and Cu have been reported to induce more-than-additive lethality in the amphipod, Hyalella azteca, a keystone aquatic invertebrate, yet little is understood regarding the interactive toxic mechanisms that mediate more-than-additive toxicity. Understanding the interactions among toxic mechanisms among Cu and PHE will allow for better predictive power in assessing the ecological risks of Cu-PHE mixtures in aquatic environments. Here we use behavioural impairment to help understand the toxic mechanisms of Cu, PHE, and Cu-PHE mixture toxicity in the aquatic amphipod crustacean, Hyalella azteca. Our principal objective was to link alterations in activity and ventilation with respiratory rates, oxidative stress, and neurotoxicity in adult H. azteca. Adult amphipods were used for all toxicity tests. Amphipods were tested at sublethal exposures of 91.8- and 195-μgL(-1) Cu and PHE, respectively, and a Cu-PHE mixture at the same concentrations for 24h. Neurotoxicity was measured as acetylcholinesterase (AChE) activity, where malathion was used as a positive control. Oxidative stress was measured as reactive oxygen species (ROS) production. Phenanthrene-exposed amphipods exhibited severe behavioural impairment, being hyperstimulated to the extent that they were incapable of coordinating muscle movements. In addition, respiration and AChE activity in PHE-exposed amphipods were increased and reduced by 51% and 23% respectively. However, ROS did not increase following exposure to phenanthrene. In contrast, Cu had no effect on amphipod behaviour, respiration or AChE activity, but did lead to an increase in ROS. However, co-exposure to Cu antagonized the PHE-induced reduction in ventilation and negated any increase in respiration. The results suggest that PHE acts like an organophosphate pesticide (e.g., malathion) in H. azteca following 24h sublethal exposures, and that AChE inhibition is the likely mechanism by which PHE alters H. azteca behaviour. However, interactive aspects of neurotoxicity do not account for the previously observed more-than-additive mortality in H. azteca following exposure to Cu-PHE mixtures.

Exposure to an agricultural contaminant, 17β-trenbolone, impairs female mate choice in a freshwater fish

Despite the pivotal role sexual selection plays in population dynamics and broader evolutionary processes, the impact of chemical pollution on female mate choice is poorly understood. One group of chemical contaminants with the potential to disrupt the mechanisms of female mate choice is endocrine disrupting chemicals (EDCs); a broad class of environmental pollutants that can interfere with the endocrinology of organisms at extremely low concentrations. Recent research has revealed that estrogenic EDCs can affect female mate choice in fish, but the impact of androgenic EDC exposure is yet to be studied. To address this, we investigated the effects of an environmentally relevant concentration of trenbolone - an androgenic steroid used as a growth promoter in the cattle industry - on female mate choice in wild-caught guppies (Poecilia reticulata). We exposed male and female guppies to 17β-trenbolone for 21 days (measured concentration 4ng/L) via a flow-through system, and found that trenbolone-exposed female guppies spent less time associating with males, and were less choosy, compared to unexposed females. In contrast, trenbolone had no impact on male reproductive behavior or morphology. This is the first study to show that androgenic EDC exposure can disrupt female mate choice, highlighting the need for studies to investigate the behavioral impacts of environmental contaminants on both sexes.

Lipid nanocapsules for behavioural testing in aquatic toxicology: Time-response of Eurytemora affinis to environmental concentrations of PAHs and PCB

The increasing interest for behavioural investigations in aquatic toxicology has heightened the need for developing tools that allow realistic exposure conditions and provide robust quantitative data. Calanoid copepods dominate the zooplankton community in marine and brackish environments. These small organisms have emerged as attractive models because of the sensitivity of their behaviour to important environmental parameters and the significance of self-induced motion in their ecology. Estuarine copepods are particularly relevant in this context because of their incessant exposure to high levels of pollution. We used lipid nanocapsules to deliver sub-lethal concentrations of PAHs (pyrene, phenanthrene and fluoranthene) and PCB 153 into the digestive track of males and females Eurytemora affinis. This novel approach enabled us to achieve both contact and trophic exposure without using phytoplankton, and to expose copepods to small hydrophobic molecules without using organic solvent. We reconstructed the motion of many copepods swimming simultaneously by means of three-dimensional particle tracking velocimetry. We quantified the combined effects of contact and trophic toxicity by comparing the kinematic and diffusive properties of their motion immediately and after 3h and 24h of exposure. Despite the lack of toxicity of their excipients, both empty and loaded capsules increased swimming activity and velocity immediately after exposure. Laser microscopy imaging shows adhesion of nanocapsules on the exoskeleton of the animals, suggesting contact toxicity. The behavioural response resembles an escape reaction allowing copepods to escape stressful conditions. The contact toxicity of empty capsules and pollutants appeared to be additive and nanocapsules loaded with PCB caused the greatest effects. We observed a progressive accumulation of capsules in the digestive track of the animals after 3h and 24h of exposure, which suggests an increasing contribution of systemic toxicity. Nanocapsules filled with PAHs caused a smaller response compared to empty capsules, which we attribute to the narcotic properties of these toxicants. The sharp decrease in velocity after 24h of exposure to capsules loaded with PCB suggests physiological incapacitation following systemic toxicity. Clear differences are visible between genders in their response to empty and loaded capsules, for all exposure durations. Females appear to be less sensitive than males, suggesting different tolerance to stress conditions. Our results confirm the feasibility of using lipid nanocapsules to identify pollutant-induced behavioural alteration in the plankton. They also add new insights into the contact and systemic toxicity of common pollutants. We expect that our results will assist and evoke further research to develop suitable nanocarrier systems for behavioural testing.

Short-term exposure to municipal wastewater influences energy, growth, and swimming performance in juvenile Empire Gudgeons (Hypseleotris compressa)

Effectively treating domestic wastewater is paramount for preserving the health of aquatic ecosystems. Various technologies exist for wastewater treatment, ranging from simple pond-based systems to advanced filtration, and it is important to evaluate the potential for these different options to produce water that is acceptable for discharge. Sub-lethal responses were therefore assessed in juvenile Empire Gudgeons (Hypseleotris compressa) exposed for a period of two weeks to control, 12.5, 25, 50, and 100% wastewater treated through a multi-stage constructed wetland (CW) treatment system. Effects on basic energy reserves (i.e., lipids and protein), growth and condition, and swimming performance were quantified following exposure. A significant increase in weight and condition was observed in fish exposed to 50 and 100% wastewater dilutions, whereas whole-body lipid content was significantly reduced in these treatments. Maximum swimming velocity increased in a dose-dependent manner amongst treatment groups (although not significantly), whereas angular velocity was significantly reduced in the 50 and 100% dilutions. Results demonstrate that treated domestic wastewater can influence the growth and swimming performance of fish, and that such effects may be related to alterations to primary energy stores. However, studies assessing complex wastewaters present difficulties when it comes to interpreting responses, as many possible factors can contribute towards the observed effects. Future research should address these uncertainties by exploring interaction between nutrients, basic water quality characteristics and relevant contaminant mixtures, for influencing the energetics, growth, and functional performance of aquatic animals.

Early life exposure to PCB126 results in delayed mortality and growth impairment in the zebrafish larvae

The occurrence of chronic or delayed toxicity resulting from the exposure to sublethal chemical concentrations is an increasing concern in environmental risk assessment. The Fish Embryo Toxicity (FET) test with zebrafish provides a reliable prediction of acute toxicity in adult fish, but it cannot yet be applied to predict the occurrence of chronic or delayed toxicity. Identification of sublethal FET endpoints that can assist in predicting the occurrence of chronic or delayed toxicity would be advantageous. The present study characterized the occurrence of delayed toxicity in zebrafish larvae following early exposure to PCB126, previously described to cause delayed effects in the common sole. The first aim was to investigate the occurrence and temporal profiles of delayed toxicity during zebrafish larval development and compare them to those previously described for sole to evaluate the suitability of zebrafish as a model fish species for delayed toxicity assessment. The second aim was to examine the correlation between the sublethal endpoints assessed during embryonal and early larval development and the delayed effects observed during later larval development. After exposure to PCB126 (3-3000ng/L) until 5 days post fertilization (dpf), larvae were reared in clean water until 14 or 28 dpf. Mortality and sublethal morphological and behavioural endpoints were recorded daily, and growth was assessed at 28 dpf. Early life exposure to PCB126 caused delayed mortality (300 ng/L and 3000 ng/L) as well as growth impairment and delayed development (100 ng/L) during the clean water period. Effects on swim bladder inflation and cartilaginous tissues within 5 dpf were the most promising for predicting delayed mortality and sublethal effects, such as decreased standard length, delayed metamorphosis, reduced inflation of swim bladder and column malformations. The EC50 value for swim bladder inflation at 5 dpf (169 ng/L) was similar to the LC50 value at 8 dpf (188 and 202 ng/L in two experiments). Interestingly, the patterns of delayed mortality and delayed effects on growth and development were similar between sole and zebrafish. This indicates the comparability of critical developmental stages across divergent fish species such as a cold water marine flatfish and a tropical freshwater cyprinid. Additionally, sublethal effects in early embryo-larval stages were found promising for predicting delayed lethal and sublethal effects of PCB126. Therefore, the proposed method with zebrafish is expected to provide valuable information on delayed mortality and delayed sublethal effects of chemicals and environmental samples that may be extrapolated to other species.