Barriers to evidence use for sustainability: Insights from pesticide policy and practice.

Calls for supporting sustainability through more and better research rest on an incomplete understanding of scientific evidence use. We argue that a variety of barriers to a transformative impact of evidence arises from diverse actor motivations within different stages of evidence use. We abductively specify this variety in policy and practice arenas for three actor motivations (truth-seeking, sense-making, and utility-maximizing) and five stages (evidence production, uptake, influence on decisions, effects on sustainability outcomes, and feedback from outcome evaluations). Our interdisciplinary synthesis focuses on the sustainability challenge of reducing environmental and human health risks of agricultural pesticides. It identifies barriers resulting from (1) truth-seekers' desire to reduce uncertainty that is complicated by evidence gaps, (2) sense-makers' evidence needs that differ from the type of evidence available, and (3) utility-maximizers' interests that guide strategic evidence use. We outline context-specific research-policy-practice measures to increase evidence use for sustainable transformation in pesticides and beyond.

Wastewater microorganisms impact microbial diversity and important ecological functions of stream periphyton.

Effluents of wastewater treatment plants can impact microbial communities in the receiving streams. However, little is known about the role of microorganisms in wastewater as opposed to other wastewater constituents, such as nutrients and micropollutants. We aimed therefore at determining the impact of wastewater microorganisms on the microbial diversity and function of periphyton, key microbial communities in streams. We used a flow-through channel system to grow periphyton upon exposure to a mixture of stream water and unfiltered or ultra-filtered wastewater. Impacts were assessed on periphyton biomass, activities and tolerance to micropollutants, as well as on microbial diversity. Our results showed that wastewater microorganisms colonized periphyton and modified its community composition, resulting for instance in an increased abundance of Chloroflexi and a decreased abundance of diatoms and green algae. This led to shifts towards heterotrophy, as suggested by the changes in nutrient stoichiometry and the increased mineralization potential of carbon substrates. An increased tolerance towards micropollutants was only found for periphyton exposed to unfiltered wastewater but not to ultra-filtered wastewater, suggesting that wastewater microorganisms were responsible for this increased tolerance. Overall, our results highlight the need to consider the role of wastewater microorganisms when studying potential impacts of wastewater on the receiving water body.

Wastewater constituents impact biofilm microbial community in receiving streams.

Microbial life in natural biofilms is dominated by prokaryotes and microscopic eukaryotes living in dense association. In stream ecosystems, microbial biofilms influence primary production, elemental cycles, food web interactions as well as water quality. Understanding how biofilm communities respond to anthropogenic impacts, such as wastewater treatment plant (WWTP) effluent, is important given the key role of biofilms in stream ecosystem function. Here, we implemented 16S and 18S rRNA gene sequencing of stream biofilms upstream (US) and downstream (DS) of WWTP effluents in four Swiss streams to test how bacterial and eukaryotic communities respond to wastewater constituents. Stream biofilm composition was strongly affected by geographic location - particularly for bacteria. However, the abundance of certain microbial community members was related to micropollutants in the wastewater - among bacteria, micropollutant-associated members were found e.g. in Alphaproteobacteria, and among eukaryotes e.g. in Bacillariophyta (algal diatoms). This study corroborates several previously characterized responses (e.g. as seen in diatoms), but also reveals previously unknown community responses - such as seen in Alphaproteobacteria. This study advances our understanding of the ecological impact of the current wastewater treatment practices and provides information about potential new marker organisms to assess ecological change in stream biofilms.

What agro-input dealers know, sell and say to smallholder farmers about pesticides: a mystery shopping and KAP analysis in Uganda.

BACKGROUND: Pesticides can have negative effects on human and environmental health, especially when not handled as intended. In many countries, agro-input dealers sell pesticides to smallholder farmers and are supposed to provide recommendations on application and handling. This study investigates the role of agro-input dealers in transmitting safety information from chemical manufacturers to smallholder farmers, assesses the safety of their shops, what products they sell, and how agro-input dealers abide by laws and recommendations on best practices for preventing pesticide risk situations. METHODS: Applying a mixed-methods approach, we studied agro-input dealers in Central and Western Uganda. Structured questionnaires were applied to understand agro-input dealers' knowledge, attitude and practices on pesticides (n = 402). Shop layout (n = 392) and sales interaction (n = 236) were assessed through observations. Actual behavior of agro-input dealers when selling pesticides was revealed through mystery shopping with local farmers buying pesticides (n = 94). RESULTS: While 97.0% of agro-input dealers considered advising customers their responsibility, only 26.6% of mystery shoppers received any advice from agro-input dealers when buying pesticides. 53.2% of products purchased were officially recommended. Sales interactions focused mainly on product choice and price. Agro-input dealers showed limited understanding of labels and active ingredients. Moreover, 25.0% of shops were selling repackaged products, while 10.5% sold unmarked or unlabeled products. 90.1% of shops were lacking safety equipment. Pesticides of World Health Organization toxicity class I and II were sold most frequently. Awareness of health effects seemed to be high, although agro-input dealers showed incomplete hygiene practices and were lacking infrastructure. One reason for these findings might be that only 55.7% of agro-input dealers held a certificate of competency on safe handling of pesticides and even fewer (5.7%) were able to provide a government-approved up-to-date license. CONCLUSION: The combination of interviews, mystery shopping and observations proved to be useful, allowing the comparison of stated and actual behavior. While agro-input dealers want to sell pesticides and provide the corresponding risk advice, their customers might receive neither the appropriate product nor sufficient advice on proper handling. In light of the expected increase in pesticide use, affordable, accessible and repeated pesticide training and shop inspections are indispensable.

Impact of wastewater on the microbial diversity of periphyton and its tolerance to micropollutants in an engineered flow-through channel system.

Wastewater treatment plants (WWTPs) play an important role in retaining organic matter and nutrients but to a lesser extent micropollutants. Therefore, treated wastewater is recognized as a major source of multiple stressors, including complex mixtures of micropollutants. These can potentially affect microbial communities in the receiving water bodies and the ecological functions they provide. In this study, we evaluated in flow-through channels the consequences of an exposure to a mixture of stream water and different percentages of urban WWTP effluent, ranging from 0% to 80%, on the microbial diversity and function of periphyton communities. Assuming that micropollutants exert a selective pressure for tolerant microorganisms within communities, we further examined the periphyton sensitivity to a micropollutant mixture extracted from passive samplers that were immersed in the wastewater effluent. As well, micropollutants in water and in periphyton were comprehensively quantified. Our results show that micropollutants detected in periphyton differed from those found in water, both in term of concentration and composition. Especially photosystem II inhibitors accumulated in periphyton more than other pesticides. Although effects of other substances cannot be excluded, this accumulation may have contributed to the observed higher tolerance of phototrophic communities to micropollutants upon exposure to 30% and 80% of wastewater. On the contrary, no difference in tolerance was observed for heterotrophic communities. Exposure to the gradient of wastewater led to structural differences in both prokaryotic and eukaryotic communities. For instance, the relative abundance of cyanobacteria was higher with increasing percentage of wastewater effluent, whereas the opposite was observed for diatoms. Such results could indicate that differences in community structure do not necessarily lead to higher tolerance. This highlights the need to consider other wastewater constituents such as nutrients and wastewater-derived microorganisms that can modulate community structure and tolerance. By using engineered flow-through channels that mimic to some extent the required field conditions for the development of tolerance in periphyton, our study constitutes a base to investigate the mechanisms underlying the increased tolerance, such as the potential role of microorganisms originating from wastewater effluents, and different treatment options to reduce the micropollutant load in effluents.

Zebrafish early life stages as alternative model to study 'designer drugs': Concordance with mammals in response to opioids.

The number of new psychoactive substances (NPS) on the illicit drug market increases fast, posing a need to urgently understand their toxicity and behavioural effects. However, with currently available rodent models, NPS assessment is limited to a few substances per year. Therefore, zebrafish (Danio rerio) embryos and larvae have been suggested as an alternative model that would require less time and resources to perform an initial assessment and could help to prioritize substances for subsequent evaluation in rodents. To validate this model, more information on the concordance of zebrafish larvae and mammalian responses to specific classes of NPS is needed. Here, we studied toxicity and behavioural effects of opioids in zebrafish early life stages. Synthetic opioids are a class of NPS that are often used in pain medication but also frequently abused, having caused multiple intoxications and fatalities recently. Our data shows that fentanyl derivatives were the most toxic among the tested opioids, with toxicity in the zebrafish embryo toxicity test decreasing in the following order: butyrfentanyl>3-methylfentanyl>fentanyl>tramadol> O-desmethyltramadol>morphine. Similar to rodents, tramadol as well as fentanyl and its derivatives led to hypoactive behaviour in zebrafish larvae, with 3-methylfentanyl being the most potent. Physico-chemical properties-based predictions of chemicals' uptake into zebrafish embryos and larvae correlated well with the effects observed. Further, the biotransformation pattern of butyrfentanyl in zebrafish larvae was reminiscent of that in humans. Comparison of toxicity and behavioural responses to opioids in zebrafish and rodents supports zebrafish as a suitable alternative model for rapidly testing synthetic opioids.

Stream microbial communities and ecosystem functioning show complex responses to multiple stressors in wastewater.

Multiple anthropogenic drivers are changing ecosystems globally, with a disproportionate and intensifying impact on freshwater habitats. A major impact of urbanization are inputs from wastewater treatment plants (WWTPs). Initially designed to reduce eutrophication and improve water quality, WWTPs increasingly release a multitude of micropollutants (MPs; i.e., synthetic chemicals) and microbes (including antibiotic-resistant bacteria) to receiving environments. This pollution may have pervasive impacts on biodiversity and ecosystem services. Viewed through multiple lenses of macroecological and ecotoxicological theory, we combined field, flume, and laboratory experiments to determine the effects of wastewater (WW) on microbial communities and organic-matter processing using a standardized decomposition assay. First, we conducted a mensurative experiment sampling 60 locations above and below WWTP discharges in 20 Swiss streams. Microbial respiration and decomposition rates were positively influenced by WW inputs via warming and nutrient enrichment, but with a notable exception: WW decreased the activation energy of decomposition, indicating a "slowing" of this fundamental ecosystem process in response to temperature. Second, next-generation sequencing indicated that microbial community structure below WWTPs was altered, with significant compositional turnover, reduced richness, and evidence of negative MP influences. Third, a series of flume experiments confirmed that although diluted WW generally has positive influences on microbial-mediated processes, the negative effects of MPs are "masked" by nutrient enrichment. Finally, transplant experiments suggested that WW-borne microbes enhance decomposition rates. Taken together, our results affirm the multiple stressor paradigm by showing that different aspects of WW (warming, nutrients, microbes, and MPs) jointly influence ecosystem functioning in complex ways. Increased respiration rates below WWTPs potentially generate ecosystem "disservices" via greater carbon evasion from streams and rivers. However, toxic MP effects may fundamentally alter ecological scaling relationships, indicating the need for a rapprochement between ecotoxicological and macroecological perspectives.

Comparative Analysis of Pesticide Use Determinants Among Smallholder Farmers From Costa Rica and Uganda.

Pesticides are used globally in agriculture and pose a threat to the health of farmers, communities, and the environment. Smallholder farmers in low- and middle-income countries have generally a low socio-economic status and educational level. Consequently, they are particularly vulnerable to negative impacts of pesticides on their health, yields, or land. In a Knowledge, Attitude, and Practices study, we compared the pest management practices between a market-oriented farming system in Zarcero County, Costa Rica, and a subsistence-based farming system in Wakiso District, Uganda. We conducted a cross-sectional survey among smallholder farmers from Costa Rica (n = 300) in 2016 and from Uganda (n = 302) in 2017. We enrolled conventional and organic farmers, but also farmers with mixed practices and non-applicators of any pest management strategy. We found that the majority of pesticides used in both case studies are classified as highly hazardous by the World Health Organization. While more than 90% of smallholder farmers from both countries were aware of the negative health effects of pesticide exposure, <11% in Costa Rica and <2% in Uganda reported using personal protective equipment every time they handled or applied pesticides. Hygiene and other safe use practices were not adopted by all farmers (<61%), especially among farmers applying more hazardous pesticides. Conventional farmers from Costa Rica (14%) and Uganda (19%) reported disposing pesticide residuals into rivers. Using a logistic regression we found that organic farmers were more likely to having been trained on safe pesticide use practices. Using a robust regression, we observed that smallholder household income was primarily driven by education and not directly by the use of synthetic pesticides. Our results suggest that negative effects of pesticides can be managed over the whole life cycle, from purchase, via storage and application to residual and waste management by fostering professionalization of farmers. We advise future safe use and handling interventions to consider the pesticide use-related socioeconomic and demographic findings highlighted in this paper.

Microbial community shifts in streams receiving treated wastewater effluent.

Wastewater treatment plant (WWTP) effluents release not only chemical constituents in watersheds, but also contain microorganisms. Thus, an understanding of what microorganisms are released and how they change microbial communities within natural streams is needed. To characterize the community shifts in streams receiving WWTP effluent, we sampled water-column microorganisms from upstream, downstream, and the effluent of WWTPs located on 23 headwater streams in which no other effluent was released upstream. We characterized the bacterial community by sequencing the V3-V4 region of the 16S rRNA gene. We hypothesized that the downstream community profile would be a hydraulic mixture between the two sources (i.e., upstream and effluent). In ordination analyses, the downstream bacterial community profile was a mixture between the upstream and effluent. For 14 of the sites, the main contribution (>50%) to the downstream community originated from bacteria in the WWTP effluent and significant shifts in relative abundance of specific sequence variants were detected. These shifts in sequence variants may serve as general bioindicators of wastewater-effluent influenced streams, with a human-gut related Ruminococcus genus displaying the highest shift (30-fold higher abundances downstream). However, not all taxa composition changes were predicted based on hydraulic mixing alone. Specifically, the decrease of Cyanobacteria/Chloroplast reads was not adequately described by hydraulic mixing. The potential alteration of stream microbial communities via a high inflow of human-gut related bacteria and a decrease in autotrophic functional groups resulting from WWTP effluent creates the potential for general shifts in stream ecosystem function.

Exposure to Pesticides and Health Effects on Farm Owners and Workers From Conventional and Organic Agricultural Farms in Costa Rica: Protocol for a Cross-Sectional Study.

BACKGROUND: Pesticide use is increasing in low- and middle-income countries (LMICs) including Costa Rica. This increase poses health risks to farm owners, farm workers, and communities living near agricultural farms. OBJECTIVE: We aimed to examine the health effects associated with occupational pesticide exposure in farm owners and workers from conventional and organic smallholder farms in Costa Rica. METHODS: We conducted a cross-sectional study involving 300 owners and workers from organic and conventional horticultural smallholder farms in Zarcero County, Costa Rica. During the baseline study visit, we administered a structured, tablet-based questionnaire to collect data on sociodemographic characteristics, pesticide exposure, and health conditions (eg, respiratory and allergic outcomes and acute pesticide intoxication symptoms) and administered a neurobehavioral test battery (eg, Finger Tapping Test and Purdue Pegboard); we measured blood pressure, anthropometry (height, weight, and waist circumference), and erythrocytic acetylcholinesterase activity and also collected urine samples. In addition, a functional neuroimaging assessment using near-infrared spectroscopy was conducted with a subset of 50 study participants. During the follow-up study visit (~2-4 weeks after the baseline), we administered participants a short questionnaire on recent pesticide exposure and farming practices and collected hair, toenail, and urine samples. Urine samples will be analyzed for various pesticide metabolites, whereas toenails and hair will be analyzed for manganese (Mn), a biomarker of exposure to Mn-containing fungicides. Self-reported pesticide exposure data will be used to develop exposure intensity scores using an exposure algorithm. Furthermore, exposure-outcome associations will be examined using linear and logistic mixed-effects regression models. RESULTS: Fieldwork for our study was conducted between May 2016 and August 2016. In total, 113 farm owners and 187 workers from 9 organic and 83 conventional horticultural smallholder farms were enrolled. Data analyses are ongoing and expected to be published between 2019 and 2020. CONCLUSIONS: This study is one of the first to examine differences in health effects due to pesticide exposure between farm owners and workers from organic and conventional smallholder farms in an LMIC. We expect that this study will provide critical data on farming practices, exposure pathways, and how occupational exposure to pesticides may affect farm owners and workers' health. Finally, we hope that this study will allow us to identify strategies to reduce pesticide exposure in farm owners and workers and will potentially lay the groundwork for a future longitudinal study of health outcomes in farm owners and workers exposed to pesticides. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/10914.

Importance of Toxicokinetics to Assess the Utility of Zebrafish Larvae as Model for Psychoactive Drug Screening Using Meta-Chlorophenylpiperazine (mCPP) as Example.

The number of new psychoactive substances (NPS) increases rapidly, harming society and fuelling the need for alternative testing strategies. These should allow the ever-increasing number of drugs to be tested more effectively for their toxicity and psychoactive effects. One proposed strategy is to complement rodent models with zebrafish (Danio rerio) larvae. Yet, our understanding of the toxicokinetics in this model, owing to the waterborne drug exposure and the distinct physiology of the fish, is incomplete. We here explore the toxicokinetics and behavioral effects of an NPS, meta-chlorophenylpiperazine (mCPP), in zebrafish larvae. Uptake kinetics of mCPP, supported by toxicokinetic modeling, strongly suggested the existence of active transport processes. Internal distribution showed a dominant accumulation in the eye, implying that in zebrafish, like in mammals, melanin could serve as a binding site for basic drugs. We confirmed this by demonstrating significantly lower drug accumulation in two types of hypo-pigmented fish. Comparison of the elimination kinetics between mCPP and previously characterized cocaine demonstrated that drug affinities to melanin in zebrafish vary depending on the structure of the test compound. As expected from mCPP-elicited responses in rodents and humans, zebrafish larvae displayed hypoactive behavior. However, significant differences were seen between zebrafish and rodents with regard to the concentration-dependency of the behavioral response and the comparability of tissue levels, corroborating the need to consider the organism-internal distribution of the chemical to allow appropriate dose modeling while evaluating effects and concordance between zebrafish and mammals. Our results highlight commonalities and differences of mammalian versus the fish model in need of further exploration.

Dose-dependent effects of morphine on lipopolysaccharide (LPS)-induced inflammation, and involvement of multixenobiotic resistance (MXR) transporters in LPS efflux in teleost fish.

Opioid drugs, such as morphine (MO), detected in aquatic environments worldwide, may harm fish due to their semi-persistence and ability to potently interact with molecular targets conserved across vertebrates. Here, we established a waterborne bacterial lipopolysaccharide (LPS) challenge assay with zebrafish embryos as a model to investigate chemically-induced disruption of the innate immune system, and used it to study the effects of MO exposure. Exposure to 1 mg/L MO resulted in pronounced immunosuppression, reflected in downregulation of several inflammation-related genes, including myd88, trif, traf6, p38, nfκb2, il-1ß, il-8 and ccl34a. Fish exposed to 1 mg/L MO accumulated 11.7 ng/g (wet weight) of MO, a concentration comparable to that reported in blood of chronic drug abusers subject to higher infection rates. Surprisingly, exposure to lower MO concentrations (100 ng/L-100 µg/L) led to exacerbation of LPS-induced inflammation. Two ATP-binding cassette (ABC) transporters known to be involved in the xenobiotic efflux - abcb4 and abcc2, also known as multixenobiotic resistance (MXR) transporters - were downregulated at 100 ng/L MO. We hypothesized that ABC/MXR transporters could modulate the severity of inflammation by being involved in efflux of LPS, thus regulating its accumulation in the organism. Indeed, we could demonstrate that blocking of ABC/MXR transporters by an inhibitor, cyclosporine A, results in stronger inflammation, coinciding with higher LPS accumulation, as visualized with fluorescently labeled LPS. Our work demonstrates that MO can disrupt fish innate immune responses at environmentally relevant concentrations. We also provide evidence for a role of ABC/MXR transporters in LPS efflux in fish. These finding may be applicable across other taxa, as ABC transporters are evolutionary conserved. Since diverse environmentally present chemicals are known to interfere with ABC/MXR transporters' expression or activity, our discovery raises concerns about potential adverse effects of such compounds on the immune system responses in aquatic organisms.

Environmental context and magnitude of disturbance influence trait-mediated community responses to wastewater in streams.

Human land uses and population growth represent major global threats to biodiversity and ecosystem services. Understanding how biological communities respond to multiple drivers of human-induced environmental change is fundamental for conserving ecosystems and remediating degraded habitats. Here, we used a replicated 'real-world experiment' to study the responses of invertebrate communities to wastewater perturbations across a land-use intensity gradient in 12 Swiss streams. We used different taxonomy and trait-based community descriptors to establish the most sensitive indicators detecting impacts and to help elucidate potential causal mechanisms of change. First, we predicted that streams in catchments adversely impacted by human land-uses would be less impaired by wastewater inputs because their invertebrate communities should be dominated by pollution-tolerant taxa ('environmental context'). Second, we predicted that the negative effects of wastewater on stream invertebrate communities should be larger in streams that receive proportionally more wastewater ('magnitude of disturbance'). In support of the 'environmental context' hypothesis, we found that change in the Saprobic Index (a trait-based indicator of tolerance to organic pollution) was associated with upstream community composition; communities in catchments with intensive agricultural land uses (e.g., arable cropping and pasture) were generally more resistant to eutrophication associated with wastewater inputs. We also found support for the 'magnitude of disturbance' hypothesis. The SPEAR Index (a trait-based indicator of sensitivity to pesticides) was more sensitive to the relative input of effluent, suggesting that toxic influences of wastewater scale with dilution. Whilst freshwater pollution continues to be a major environmental problem, our findings highlight that the same anthropogenic pressure (i.e., inputs of wastewater) may induce different ecological responses depending on the environmental context and community metrics used. Thus, remediation strategies aiming to improve stream ecological status (e.g., rehabilitating degraded reaches) need to consider upstream anthropogenic influences and the most appropriate indicators of restoration success.

From the Cover: Zebrafish Larvae Are Insensitive to Stimulation by Cocaine: Importance of Exposure Route and Toxicokinetics.

Zebrafish (Danio rerio) larvae have been suggested as vertebrate model to complement or even replace mammals for rapidly assessing behavioral effects of psychoactive drugs. Yet, divergent responses have been reported in mammals and fish despite the conservation of many drug targets. Cocaine, eg, acts as stimulant in mammals but no such response has been documented for zebrafish larvae. We hypothesized that differences in exposure routes (inhalation or injection in mammals vs waterborne in fish) may be a reason for differences in behavioral responses. We characterized cocaine toxicokinetics by liquid chromatography-mass spectrometry and found its rapid uptake into larvae. We used Matrix-assisted laser desorption ionization-mass spectrometry imaging for the first time to characterize internal distribution of cocaine in zebrafish larvae. Surprisingly, eyes accumulated the highest amount of cocaine and retained most of it even after 48 h depuration. We attribute this to trapping by pigment melanin, a thus far little explored mechanism that may also be relevant for other basic drugs. Cocaine also reached the brain but with levels similar to those in trunk indicating simple passive diffusion as means of distribution which was supported by toxicokinetic models. Although brain levels covered those known to cause hyperactivity in mammals, only hypoactivity (decreased locomotion) was recorded in zebrafish larvae. Our results therefore point to cocaine's anesthetic properties as the dominant mechanism of interaction in the fish: upon entry through the fish skin and gills, it first acts on peripheral nerves rapidly overriding any potential stimulatory response in the brain.

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.

Acclimation of Chlamydomonas reinhardtii to ultraviolet radiation and its impact on chemical toxicity.

The toxicity of chemical pollutants can be modulated under stressful environmental conditions, such as increased temperature, salinity or ultraviolet radiation (UVR), due to the interaction of effects during simultaneous stressor exposure. However, organisms may acclimate to such conditions by activation of physiological and biochemical defence mechanisms. In sequential exposures, organisms acclimated to environmental stressors may display an increased sensitivity or co-tolerance towards chemical pollutants. It has been suggested that co-tolerance might be expected for similarly acting stressors due to common defence mechanisms. To test this for combinations of UVR and chemical stressors, we first acclimatized the model green alga Chlamydomonas reinhardtii to UVR and subsequently compared the sensitivity of UVR pre-exposed and control algae towards chemicals. Selected chemicals all act on photosynthesis and thus share a common physiological target, but display distinct toxicity mechanisms. Results showed that UVR pre-exposure for four days partially inhibited algal growth and photosynthesis, but also increased algal tolerance to higher UVR levels, confirming UVR acclimation. HPLC analysis of algal pigments indicated that UVR acclimation might in part be explained by the protective function of lutein while the contribution of UVR absorbing compounds was less clear. Challenge exposure to chemicals in the absence of UVR showed that acclimated algae were co-tolerant to the photosensitizer rose bengal, but not to the herbicides paraquat and diuron, suggesting that the fast physiological and biochemical defence mechanisms that conferred tolerance of algae towards higher UVR levels were related to singlet oxygen defence. The presented study suggests that knowledge of the molecular toxicity mechanisms of chemicals, rather than their general physiological target, is needed in order to predict co-tolerance between environmental and chemical stressors.

Multiple stressor effects in Chlamydomonas reinhardtii--toward understanding mechanisms of interaction between effects of ultraviolet radiation and chemical pollutants.

The effects of chemical pollutants and environmental stressors, such as ultraviolet radiation (UVR), can interact when organisms are simultaneously exposed, resulting in higher (synergistic) or lower (antagonistic) multiple stressor effects than expected based on the effects of single stressors. Current understanding of interactive effects is limited due to a lack of mechanism-based multiple stressor studies. It has been hypothesized that effect interactions may generally occur if chemical and non-chemical stressors cause similar physiological effects in the organism. To test this hypothesis, we exposed the model green alga Chlamydomonas reinhardtii to combinations of UVR and single chemicals displaying modes of action (MOA) similar or dissimilar to the impact of UVR on photosynthesis. Stressor interactions were analyzed based on the independent action model. Effect interactions were found to depend on the MOA of the chemicals, and also on their concentrations, the exposure time and the measured endpoint. Indeed, only chemicals assumed to cause effects on photosynthesis similar to UVR showed interactions with UVR on photosynthetic yield: synergistic in case of Cd(II) and paraquat and antagonistic in case of diuron. No interaction on photosynthesis was observed for S-metolachlor, which acts dissimilarly to UVR. However, combined effects of S-metolachlor and UVR on algal reproduction were synergistic, highlighting the importance of considering additional MOA of UVR. Possible mechanisms of stressor effect interactions are discussed.

Reducing the discharge of micropollutants in the aquatic environment: the benefits of upgrading wastewater treatment plants.

Micropollutants (MPs) as individual compounds or in complex mixtures are relevant for water quality and may trigger unwanted ecological effects. MPs originate from different point and diffuse sources and enter water bodies via different flow paths. Effluents from conventional wastewater treatment plants (WWTPs), in which various MPs are not or not completely removed, is one major source. To improve the water quality and avoid potential negative ecological effects by micropollutants, various measures to reduce the discharge should be taken. In this feature we discuss one of these measures; the benefits of upgrading WWTPs toward reduced MP loads and toxicities from wastewater effluents, using the recently decided Swiss strategy as an example. Based on (i) full-scale case studies using ozonation or powder activated carbon treatment, showing substantial reduction of MP discharges and concomitant reduced toxicities, (ii) social and political acceptance, (iii) technical feasibility and sufficient cost-effectiveness, the Swiss authorities recently decided to implement additional wastewater treatment steps as mitigation strategy to improve water quality. Since MPs are of growing global concern, the concepts and considerations behind the Swiss strategy are explained in this feature, which could be of use for other countries as well. It should be realized that upgrading WWTPs is not the only solution to reduce the discharge of MPs entering the environment, but is part of a broader, multipronged mitigation strategy.