Interactive effects of biotic and abiotic environmental stressors on carbamazepine toxicity in the non-biting midge Chironomus riparius

Pharmaceuticals and endocrine disrupting compounds modulate adverse effects of climate change on resource quality in freshwater food webs

Freshwater biodiversity, ecosystem functions and services are changing at an unprecedented rate due to the impacts of vast number of stressors overlapping in time and space. Our study aimed at characterizing individual and combined impacts of pollution with pharmaceuticals (PhACs) and endocrine disrupting compounds (EDCs) and increased water temperature (as a proxy for climate change) on primary producers and first level consumers in freshwaters. We conducted a microcosm experiment with a simplified freshwater food web containing moss (Bryophyta) and shredding caddisfly larvae of Micropterna nycterobia (Trichoptera). The experiment was conducted with four treatments; control (C), increased water temperature + 4 °C (T2), emerging contaminants' mix (EC = 15 PhACs & 5 EDCs), and multiple stressor treatment (MS = EC + T2). Moss exhibited an overall mild response to selected stressors and their combination. Higher water temperature negatively affected development of M. nycterobia through causing earlier emergence of adults and changes in their lipidome profiles. Pollution with PhACs and EDCs had higher impact on metabolism of all life stages of M. nycterobia than warming. Multiple stressor effect was recorded in M. nycterobia adults in metabolic response, lipidome profiles and as a decrease in total lipid content. Sex specific response to stressor effects was observed in adults, with impacts on metabolome generally more pronounced in females, and on lipidome in males. Thus, our study highlights the variability of both single and multiple stressor impacts on different traits, different life stages and sexes of a single insect species. Furthermore, our research suggests that the combined impacts of warming, linked to climate change, and contamination with PhACs and EDCs could have adverse consequences on the population dynamics of aquatic insects. Additionally, these findings point to a potential decrease in the quality of resources available for both aquatic and potentially terrestrial food webs.

Combined effects of climate warming and pharmaceuticals on a tri-trophic freshwater food web

Multiple anthropogenic stressors influence the functioning of lakes and ponds, but their combined effects are often little understood. We conducted two mesocosm experiments to evaluate the effects of warming (+4 °C above ambient temperature) and environmentally relevant concentrations of a mixture of commonly used pharmaceuticals (cardiovascular, psychoactive, antihistamines, antibiotics) on tri-trophic food webs representative of communities in ponds and other small standing waters. Communities were constituted of phyto- and zooplankton and macroinvertebrates (molluscs and insects) including benthic detritivores, grazers, omnivorous scrapers, omnivorous piercers, water column predators, benthic predators, and phytophilous predators. We quantified the main and interactive effects of warming and pharmaceuticals on each trophic level in the pelagic community and attributed them to the direct effects of both stressors and the indirect effects arising through biotic interactions. Warming and pharmaceuticals had stronger effects in the summer experiment, altering zooplankton community composition and causing delayed or accelerated emergence of top insect predators (odonates). In the summer experiment, both stressors and top predators reduced the biomass of filter-feeding zooplankton (cladocerans), while warming and pharmaceuticals had opposite effects on phytoplankton. In the winter experiment, the effects were much weaker and were limited to a positive effect of warming on phytoplankton biomass. Overall, we show that pharmaceuticals can exacerbate the effects of climate warming in freshwater ecosystems, especially during the warm season. Our results demonstrate the utility of community-level studies across seasons for risk assessment of multiple emerging stressors in freshwater ecosystems.

300-fold higher neuro- and immunotoxicity from low-redox transformation of carbamazepine

Current challenges in (eco)toxicology are in understanding the transformation of (reactive) substances, and how transformation affects toxic modes of action. Empirical assessment of transformation products of, practically an infinite number of substances, via experimentation, is impossible. Predicting transformation products for (benchmarking) compounds from conditions, facilitates risk analyses. This study applied calculus to predict transformation products of an important environmental and medicinal/toxicological marker, carbamazepine. As radicals are ubiquitous in humans and the environment, we looked into radical-mediated transformations of carbamazepine as a benchmark. We calculated proportions of their speciation states as function of redox conditions, which we took as pH and O2 concentration, describing transformation via covalent and ionic interactions. Formation of ring-contracted products with neuro-immunological activity is thermodynamically favored under anaerobic conditions and at low pH. Experimentally observed product distributions and toxicities reflect that pattern. Our predictive method may support toxicity predictions for other substances and conditions 'similar' to the current case study via interpolation. This paves the way for a more coherent, effective and easier risk assessment of transformation products.

Co-exposure of environmental contaminants with unfavorable temperature or humidity/moisture: Joint hazards and underlying mechanisms

In the context of global climate change, organisms in their natural habitats usually suffer from unfavorable climatic conditions together with environmental pollution. Temperature and humidity (or moisture) are two central climatic factors, while their relationships with the toxicity of contaminants are not well understood. This review provides a synthesis of existing knowledge on important interactions between contaminant toxicity and climatic conditions of unfavorable temperature, soil moisture, and air humidity. Both high temperature and low moisture can extensively pose severe combined hazards with organic pollutants, heavy metal ions, nanoparticles, or microplastics. There is more information on the combined effects on animalia than on other kingdoms. Prevalent mechanisms underlying their joint effects include the increased bioavailability and bioaccumulation of contaminants, modified biotransformation of contaminants, enhanced induction of oxidative stress, accelerated energy consumption, interference with cell membranes, and depletion of bodily fluids. However, the interactions of contaminants with low temperature or high humidity/moisture, particularly on plants and microorganisms, are relatively vague and need to be further revealed. This work emphasizes that the co-exposure of chemical and physical stressors results in detrimental effects generally greater than those caused by either stressor. It is necessary to take this into consideration in the ecological risk assessment of both environmental contamination and climate change.

The effect of temperature on toxicokinetics and the chronic toxicity of insecticides towards Gammarus pulex

A comprehensive understanding of chemical toxicity and temperature interaction is essential to improve ecological risk assessment under climate change. However, there is only limited knowledge about the effect of temperature on the toxicity of chemicals. To fill this knowledge gap and to improve our mechanistic understanding of the influence of temperature, the current study explored toxicokinetics and the chronic toxicity effects of two insecticides, imidacloprid (IMI) and flupyradifurone (FPF), on Gammarus pulex at different temperatures (7-24 °C). In the toxicokinetics tests, organisms were exposed to IMI or FPF for 2 days and then transferred to clean water for 3 days of elimination at 7, 18, or 24 °C. In the chronic tests, organisms were exposed to the individual insecticides for 28 days at 7, 11, or 15 °C. Our research found that temperature impacted the toxicokinetics and the chronic toxicity of both IMI and FPF, while the extent of such impact differed for each insecticide. For IMI, the uptake rate and biotransformation rate increased with temperature, and mortality and food consumption inhibition was enhanced by temperature. While for FPF, the elimination rate increased with temperature at a higher rate than the increasing uptake rate, resulting in a smaller pronounced effect of temperature on mortality compared to IMI. In addition, the adverse effects of the insecticides on sublethal endpoints (food consumption and dry weight) were exacerbated by elevated temperatures. Our results highlight the importance of including temperature in the ecological risk assessment of insecticides in light of global climate change.

Combined effects of polyethylene microplastics and natural stressors on Chironomus riparius life-history traits

Several studies have shown that ingestion of microplastics causes adverse effects in aquatic organisms, including sediment-dwelling invertebrates. Most studies focus on evaluating the effects of plastic particles alone without testing the mediating effects of different natural stressors and thus lacking realistic exposure scenarios. The present study addresses the interactive effects of exposure to polyethylene microplastics (PE-MPs; 2.5 g/kg) in the midge Chironomus riparius life history traits under different temperatures (15, 20 and 25 °C), a salinity gradient (0, 1 and 3 g L^-1 sodium chloride - NaCl) and different levels of food (0.5, 0.25 and 0.125 mg macerated fish food larva^-1day^-1). By the analyses of linear models and independent action models applied to different life-history traits, such as larval growth, development time and imagoes body weight, the present work reveals that under temperatures lower than 20 °C or severe food shortage (<0.25 mg macerated fish food larva^-1day^-1), microplastics' effects can be stronger than those observed at standard toxicity test conditions (20 °C and 0.5 mg food larva^-1day^-1). Additionally, we also found that, in general, toxicity induced by PE-MPs to C. riparius larvae was reduced under warmer temperature (25 °C) and salinity. As observed, MPs toxicity can be mediated by natural stressors, which underlines the importance of co-exposure studies. In this sense, these results contribute to a more accurate risk assessment of microplastics. Despite the complex interactions between microplastics and natural factors here tested, were not found evidence that the deleterious effects of PE-MPs on C. riparius life cycle history are aggravated under increased temperature, food shortage, or salinisation of freshwaters.

Bioflocculation effect of Glyptotendipes tokunagai on different Microcystis species: Interactions between secreted silk and extracellular polymeric substances

Cyanobacterial blooms are a major problem in many lakes and can negatively impact public health and ecosystem services. The bioflocculation technique has proven to be a cost-effective, environmentally friendly technique with no secondary pollution to harvest multiple microalgae; however, few studies have focused on its effect on and potential for controlling cyanobacterial blooms in eutrophic lakes. In this study, the bioflocculation efficiencies of different Microcystis species under Glyptotendipes tokunagai (Diptera, Chironomidae) stress conditions and the interactions between secreted silk from Chironomid larvae and extracellular polymeric substances (EPS) from Microcystis were compared. The results indicated that G. tokunagai presented better bioflocculation efficiency on M. wesenbergii than on M. aeruginosa. The formation of "Large Algal Aggregate" flocs was promoted by the derived-soluble extracellular polymeric substances (i.e., proteins and polysaccharides, sEPS) from M. wesenbergii and silk from G. tokunagai. Both M. wesenbergii and midge silk had abundant functional groups, which was beneficial to the formation of the large aggregate. G. tokunagai secreted a large amount of silk to bridge with the sEPS of M. wesenbergii, forming a network structure via interaction between filamentous substance (i.e., complex of sEPS and silk) that plays an important role in the aggregation of Microcystis and the removal of the Microcystis biomass in the water column. The findings provide further insights that will benefit the existing efforts of combating Microcystis blooms in the water column via bioflocculation and will provide a new sustainable approach for inhibiting early bloom formation from the perspective of its provenance in the sediment-water interface.

Environmental pharmaceuticals and climate change: The case study of carbamazepine in M. galloprovincialis under ocean acidification scenario

Contaminants of emerging concern and ocean changes are key environmental stressors for marine species with possibly synergistic, but still unexplored, deleterious effects. In the present study the influence of a simulated ocean acidification scenario (pH = 7.6) was investigated on metabolism and sub-lethal effects of carbamazepine, CBZ (1 µg/L), chosen as one of the most widely diffused pharmaceuticals in marine organisms. A multidisciplinary approach was applied on mussels, M. galloprovincialis, integrating measurement of drug bioaccumulation with changes in the whole transcriptome, responsiveness of various biochemical and cellular biomarkers including immunological parameters, lipid and oxidative metabolism, onset of genotoxic effects. Chemical analyses revealed a limited influence of hypercapnia on accumulation and excretion of CBZ, while a complex network of biological responses was observed in gene expression profile and functional changes at cellular level. The modulation of gamma-aminobutyric acid (GABA) pathway suggested similarities with the Mechanism of Action known for vertebrates: immune responses, cellular homeostasis and oxidative system represented the processes targeted by combined stressors. The overall elaboration of results through a quantitative Weight of Evidence model, revealed clearly increased cellular hazard due to interactions of CBZ with acidification compared to single stressors.

Laboratory-to-field extrapolation: Increase in carbamazepine toxicity in a higher tier, multiple-stress experiment

The toxicity and environmental risk of chemicals, such as the antiepileptic drug carbamazepine (CBZ), is commonly assessed using standardized laboratory tests and laboratory-to-field extrapolation. To investigate the toxicity of CBZ to aquatic key organisms in a more complex and environmentally relevant scenario, we conducted a 32-day multiple-stress experiment in artificial indoor streams. We exposed the non-biting midge Chironomus riparius, the blackworm Lumbriculus variegatus, and the New Zealand mud snail Potamopyrgus antipodarum to 80 and 400 μg CBZ/L in six artificial indoor streams. In addition to hydraulic stress, species' interaction, and low organic content in the sediment, organisms were co-exposed to the herbicide terbutryn (TBY) as a second chemical stressor at a concentration of 6 μg/L. The exposure to CBZ under multiple stress conditions resulted in a 10- to more than 25-fold higher toxicity in C. riparius and P. antipodarum when compared to a previous, standardized laboratory experiment. The co-exposure to TBY enhanced the adverse effects of CBZ on snails (reduced production of embryos). This effect was additive as the single exposure to TBY also reduced the reproduction of snails, most likely through the reduction of biofilm biomass. The emergence of C. riparius declined at a CBZ concentration of 400 μg/L (without the co-exposure to TBY) and at 80 μg/L in combination with TBY. The difference in sensitivity between laboratory and indoor stream experiments is indicative of a potential underestimation of risk when toxicity data are extrapolated to field conditions. The present results suggest the inclusion of non-chemical and chemical stressors in environmental hazard and risk assessments.