Interactions between effects of environmental chemicals and natural stressors: a review

Thermal adaptation affects the temperature-dependent toxicity of the insecticide imidacloprid to soil invertebrates

Terrestrial ectotherms are vulnerable to climate change since their biological rates depend on the ambient temperature. As temperature may interact with toxicant exposure, climate change may cause unpredictable responses to toxic stress. A population's thermal adaptation will impact its response to temperature change, but also to interactive effects from temperature and toxicants, but these effects are still not fully understood. Here, we assessed the combined effects of exposure to the insecticide imidacloprid across the temperatures 10-25 °C of two populations of the Collembola Hypogastrura viatica (Tullberg, 1872), by determining their responses in multiple life history traits. The con-specific populations differ considerably in thermal adaptations; one (arctic) is a temperature generalist, while the other (temperate) is a warm-adapted specialist. For both populations, the sub-lethal concentrations of imidacloprid became lethal with increasing temperature. Although the thermal maximum is higher for the warm-adapted population, the reduction in survival was stronger. Growth was reduced by imidacloprid in a temperature-dependent manner, but only at the adult life stage. The decrease in adult body size combined with the absence of an effect on the age at first reproduction suggests a selection on the timing of maturation. Egg production was reduced by imidacloprid in both populations, but the negative effect was only dependent on temperature in the warm-adapted population, with no effect at 10 °C, and decreases of 41 % at 15 °C, and 74 % at 20 °C. For several key traits, the population best adapted to utilize high temperatures was also the most sensitive to toxic stress at higher temperatures. It could be that by allocating more energy to faster growth, development, and reproduction at higher temperatures, the population had less energy for maintenance, making it more sensitive to toxic stress. Our findings demonstrate the need to take into account a population's thermal adaptation when assessing the interactive effects between temperature and other stressors.

Exposure to teflubenzuron reduces drought tolerance of collembolans

Chitin synthesis inhibitors (CSIs) are commonly used insecticides compromising cuticle formation and structure in arthropods. Arthropods rely on intact cuticles to maintain water balance and cellular homeostasis to survive in different weather conditions. We hypothesized that physiological impacts of CSIs may make arthropods more vulnerable to harsh environmental conditions, such as extreme heat, cold or drought. The aim of this study was to investigate if pre-exposure to teflubenzuron (a common CSI) would influence Folsomia candida's (Collembola: Isotomidae) sensitivity to natural stressors. Here, we exposed adult collembolans to teflubenzuron through food for two weeks, then survivors were immediately divided into three groups for subsequent acute heat, cold, and drought exposure. After acute exposure to these natural stressors, the collembolans were moved to optimal conditions for a one-week recovery period during which their survival, time to regain reproduction, and egg production were examined. We analyzed the interaction between effects of teflubenzuron and natural stressors using a multiplicative model. No interaction between effects of teflubenzuron and heat was observed in any test endpoints. A synergistic interaction between effects of teflubenzuron and cold was observed in the time to regain reproduction. Both survival and egg production, on the other hand, showed synergistic interaction between effects of teflubenzuron and drought, as well as a tendency for longer reproduction recovery times. Our results suggest that pre-exposure to teflubenzuron reduces drought tolerance in F. candida, while its impact on heat or cold tolerance is minor or absent. This study is among the first to explore the combined effects of CSI and natural stressors on soil arthropods, providing more insight on potential risks posed by such chemicals in the environment.

Predicting the Combined Effects of Multiple Stressors and Stress Adaptation in Gammarus pulex

Global change confronts organisms with multiple stressors causing nonadditive effects. Persistent stress, however, leads to adaptation and related trade-offs. The question arises: How can the resulting effects of these contradictory processes be predicted? Here we show that Gammarus pulex from agricultural streams were more tolerant to clothianidin (mean EC50 148 μg/L) than populations from reference streams (mean EC50 67 μg/L). We assume that this increased tolerance results from a combination of physiological acclimation, epigenetic effects, and genetic evolution, termed as adaptation. Further, joint exposure to pesticide mixture and temperature stress led to synergistic interactions of all three stressors. However, these combined effects were significantly stronger in adapted populations as shown by the model deviation ratio (MDR) of 4, compared to reference populations (MDR = 2.7). The pesticide adaptation reduced the General-Stress capacity of adapted individuals, and the related trade-off process increased vulnerability to combined stress. Overall, synergistic interactions were stronger with increasing total stress and could be well predicted by the stress addition model (SAM). In contrast, traditional models such as concentration addition (CA) and effect addition (EA) substantially underestimated the combined effects. We conclude that several, even very disparate stress factors, including population adaptations to stress, can act synergistically. The strong synergistic potential underscores the critical importance of correctly predicting multiple stresses for risk assessment.

Spatial-temporal change of river thermal environment and anthropogenic impact in China

River water temperature is important and closely related to river ecosystem, concerning fishery industry, human health, and the land-sea exchange of nutrients, especially for great powers with a good deal of heat emission from once-through cooling systems of thermal power plants. However, the changes in river water temperature under the joint action of climate change and human activity such as the heat emission have not been well investigated for rising powers, hampering environmental policy making for sustainable development. Therefore, we have taken advantage of a recently-developed land surface model including river water temperature calculation with anthropogenic thermal discharge and zonal statistics to quantitatively make out the river water temperature variation and the man-made influence over the past thirty years (1981-2010) in China for the first time. Results show that the estimated water temperature in major rivers is generally close to the observation with the r2 of 0.83, though the underestimation exists in some rivers. The river water in the Pearl River Basin was the warmest with the mean temperature of 19.2 °C and the others in order were in the Southeast Basin, the Huaihe River Basin, the Yangtze River Basin, the Haihe River Basin, the Yellow River Basin, the Southwest Basin, the Song-Liao River Basin, and the Continental Basin, ranging from 16.7 °C to 6.3 °C. The Huaihe River Basin had the fastest mean increase rate of ca. 0.27 °C decade-1, while the slowest mean increase rate of ca. 0.13 °C decade-1 existed in the Pearl River Basin. At the subbasin scale, a meridionally-distributed hot spot zone (along the 115°E) of the increasing water temperature has been identified, where the trends ranged from 0.2 °C decade-1 to 0.5 °C decade-1. Air temperature exerted a major control on the spatial pattern of climatological water temperature, while both air temperature and downwelling solar flux played a leading role in the distribution of water temperature change trends. Although anthropogenic thermal emission heated the rivers locally, the impacts in the Song-Liao River, the Haihe River, the Huaihe River, and the middle and lower reaches of Yellow River and Yangtze River had been raised up to ca. 4.5 °C, when comparing with those controlled by climate change only. In general, these results show an acceptable level of river water temperature simulation in the land surface model, and could provide a scientific reference for the assessment on riverine thermal environment under the climate change and social impact in China.

Impact of environmental factors changes induced by marine heatwaves and heavy precipitation on antibiotic toxicity to Isochrysis galbana: Implications for climate change adaptation

Isochrysis galbana, a crucial primary producer and food source in aquatic ecosystems, faces increasing challenges from climate change and emerging contaminants like antibiotics. This study investigates the combined effects of sudden temperature increase (representing marine heatwaves) and rapid salinity change (representing extreme precipitation events) on the toxicity of tetracycline (TC) and oxytetracycline (OTC) to I. galbana. Short-term experiments reveal heightened antibiotic toxicity at 31 °C or salinities of 18 PSU, surpassing algal tolerance limits. Long-term tests show decreased inhibition of algal growth on day 9, indicating algal adaptation to the environment. Analyses of photosynthesis II efficiency, pigment content, and macromolecular composition support this, suggesting adaptation mechanism activation. While algae acclimate to the environment during long-term antibiotic exposure, extreme weather conditions may compromise this adaptation. These findings have implications for managing antibiotics in aquatic environments under climate change.

Surviving in a multistressor world: Gene expression changes in earthworms exposed to heat, desiccation, and chemicals

An investigation of the effects of anthropogenic stress on terrestrial ecosystems is urgently needed. In this work, we explored how exposure to heat, desiccation, and chemical stress alters the expression of genes that encode heat shock proteins (HSPs), an enzyme that responds to oxidative stress (CAT), hypoxia-related proteins (HIF1 and HYOU), and a DNA repair-related protein (PARP1) in the earthworm Eisenia fetida. Exposure to heat (31°C) for 24 h upregulated HSPs and hypoxia-related genes, suggesting possible acquired thermotolerance. Desiccation showed a similar expression profile; however, the HSP response was activated to a lesser extent. Heat and desiccation activated the small HSP at 24 h, suggesting that they may play a role in adaptation. Simultaneous exposure to endosulfan and temperature for 7 h upregulated all of the evaluated genes, implicating a coordinated response involving multiple biological processes to ensure survival and acclimation. These results highlight the relevance of multistress analysis in terrestrial invertebrates.

Cross-talk between low temperature and other environmental factors

Low temperatures are rarely experienced in isolation. The impacts of low temperatures on insects can be exacerbated or alleviated by the addition of other environmental factors, including, for example, desiccation, hypoxia, or infection. One way in which environmental factors can interact is through cross-talk where different factors enact common signaling pathways. In this review, I highlight the breadth of abiotic and biotic factors that can interact with low-temperature tolerance in both natural and artificial environments; and discuss some of the candidate pathways that are possibly responsible for cross-talk between several factors. Specifically, I discuss three interesting candidates: the neurohormone octopamine, circadian clock gene vrille, and microbes. Finally, I discuss applications of cross-talk studies, and provide recommendations for researchers.

The Easily Overlooked Effect of Global Warming: Diffusion of Heavy Metals

Since industrialization, global temperatures have continued to rise. Human activities have resulted in heavy metals being freed from their original, fixed locations. Because of global warming, glaciers are melting, carbon dioxide concentrations are increasing, weather patterns are shifting, and various environmental forces are at play, resulting in the movement of heavy metals and alteration of their forms. In this general context, the impact of heavy metals on ecosystems and organisms has changed accordingly. For most ecosystems, the levels of heavy metals are on the rise, and this rise can have a negative impact on the ecosystem as a whole. Numerous studies have been conducted to analyze the combined impacts of climate change and heavy metals. However, the summary of the current studies is not perfect. Therefore, this review discusses how heavy metals affect ecosystems during the process of climate change from multiple perspectives, providing some references for addressing the impact of climate warming on environmental heavy metals.

Review: Progress towards research on the toxicology of pyrimethanil

Pyrimethanil is a persistent environmental pollutant that poses a significant threat to human health. In this review, we summarize the fungicidal mechanism of pyrimethanil and its toxicological effects on aquatic organisms and mammals, as well as its impact on growth and development as an endocrine disruptor. Additionally, we investigate the metabolism of pyrimethanil in mammals and its molecular mechanism in the occurrence of Alzheimer's disease. Furthermore, this review outlines the influence of climate change on the toxicity of pyrimethanil, emphasizing the need to consider the impact of mixtures of multiple compounds on human health. Finally, we propose several promising future directions for pyrimethanil research, believing that there is a better understanding of the interaction between pyrimethanil and organisms, as well as the development of techniques to remove pyrimethanil, may be the best approach to eliminating the threat posed by this compound.

Temperature-dependent toxicity of fluoxetine alters the thermal plasticity of marine diatoms

Anthropogenic activities have led to the emergence of pharmaceutical pollution in marine ecosystems, posing a significant threat to biodiversity in conjunction with global climate change. While the ecotoxicity of human drugs on aquatic organisms is increasingly recognized, their interactions with environmental factors, such as temperature, remain understudied. This research investigates the physiological effects of the selective serotonin reuptake inhibitor (SSRI), fluoxetine, on two diatom species, Phaeodactylum tricornutum and Thalassiosira weissflogii. Results demonstrate that fluoxetine significantly reduces growth rate and biomass production, concurrently affecting pigment contents and the thermal performance curve (TPC) of the diatoms. Fluoxetine reduces the synthesis of chlorophyll a (Chl a) and carotenoid (Car), indicating inhibition of photosynthesis and photoprotection. Furthermore, fluoxetine decreases the maximum growth rate (μmax) while increasing the optimum temperature (Topt) in both species, suggesting an altered thermal plasticity. This shift is attributed to the observed decrease in the inhibition rate of fluoxetine with rising temperatures. These findings emphasize the physiological impacts and ecological implications of fluoxetine on phytoplankton and underscore the significance of considering interactions between multiple environmental drivers when accessing the ecotoxicity of potential pollutants. The present study provides insights into crucial considerations for evaluating the impacts of pharmaceutical pollution on marine primary producers.

Unraveling stress resilience: Insights from adaptations to extreme environments by Astyanax mexicanus cavefish

Extreme environmental conditions have profound impacts on shaping the evolutionary trajectory of organisms. Exposure to these conditions elicits stress responses, that can trigger phenotypic changes in novel directions. The Mexican Tetra, Astyanax mexicanus, is an excellent model for understanding evolutionary mechanisms in response to extreme or new environments. This fish species consists of two morphs; the classical surface-dwelling fish and the blind cave-dwellers that inhabit dark and biodiversity-reduced ecosystems. In this review, we explore the specific stressors present in cave environments and examine the diverse adaptive strategies employed by cave populations to not only survive but thrive as successful colonizers. By analyzing the evolutionary responses of A. mexicanus, we gain valuable insights into the genetic, physiological, and behavioral adaptations that enable organisms to flourish under challenging environmental conditions.

Sensitivity of Daphnia spinulata Birabén, 1917 to glyphosate at different salinity levels

Daphnia spinulata Birabén, 1917 is an endemic cladoceran species, frequent in the zooplankton communities of the shallow lakes of the Pampean region of Argentina. These lakes have varying salinity levels and, being located in agricultural areas, are frequently subject to pesticide pollution. This study aimed to determine the effects of the herbicide glyphosate (Panzer Gold®) in combination with different salinity levels on the biological parameters of D. spinulata and its recovery ability after a short exposure. Three types of assays were performed: an acute toxicity test, a chronic assessment to determine survival, growth and reproduction, and recovery assays under optimal salinity conditions (1 g L-1). The LC50-48 h of glyphosate was 7.5 mg L-1 (CL 3.15 to 11.72). Longevity and the number of offspring and clutches were significantly reduced due to the combined exposure of glyphosate and increased salinity. The timing of the first offspring did not recover after glyphosate exposure. Our results reveal that D. spinulata is sensitive to the herbicide Panzer Gold® at concentrations well below those indicated in the safety data sheet of this commercial formulation, which causes stronger negative effects in conditions of higher salinity. Further research is needed to shed light on the sensitivity of this cladoceran to glyphosate and its variability under other interactive stress factors.

Metal nanoparticle-induced effects on green toads (Amphibia, Anura) under climate change: conservation implications

The toxicity of aluminum oxide (Al2O3), copper oxide (CuO), iron oxide (Fe3O4), nickel oxide (NiO), zinc oxide (ZnO), and titanium dioxide (TiO2) nanoparticles (NPs) on amphibians and their interaction with high temperatures, remain unknown. In this study, we investigated the survival, developmental, behavioral, and histological reactions of Bufotes viridis embryos and larvae exposed to different NPs for a duration of 10 days, using lethal concentrations (LC25%, LC50%, and LC75% mg/L) under both ambient (AT: 18 °C) and high (HT: 21 °C) temperatures. Based on LC, NiONPs > ZnONPs > CuONPs > Al2O3NPs > TiO2NPs > Fe3O4NPs showed the highest mortality at AT. A similar pattern was observed at HT, although mortality occurred at lower concentrations and Fe3O4NPs were more toxic than TiO2NPs. The results indicated that increasing concentrations of NPs significantly reduced hatching rates, except for TiO2NPs. Survival rates decreased, abnormality rates increased, and developmental processes slowed down, particularly for NiONPs and ZnONPs, under HT conditions. However, exposure to low concentrations of Fe3O4NPs for up to 7 days, CuONPs for up to 72 h, and NiO, ZnONPs, and TiO2NPs for up to 96 h did not have a negative impact on survival compared with the control group under AT. In behavioral tests with larvae, NPs generally induced hypoactivity at AT and hyperactivity at HT. Histological findings revealed liver and internal gill tissue lesions, and an increase in the number of melanomacrophage centers at HT. These results suggest that global warming may exacerbate the toxicity of metal oxide NPs to amphibians, emphasizing the need for further research and conservation efforts in this context.

Strobilurin fungicide increases the susceptibility of amphibian larvae to trematode infections

The global rise in fungal pathogens has driven the increased usage of fungicides, yet our understanding of their ecotoxicity remains largely limited to acute toxicity. While such data is critical for projecting the risk of fungicide exposure to individual species, the contamination of natural systems with fungicides also has the potential to alter species interactions within communities including host-parasite relationships. We examined the effects of the fungicide pyraclostrobin on the susceptibility of larval American bullfrogs (Rana catesbeiana) to trematode (echinostome) infections using a controlled laboratory experiment. Following a 2-wk exposure to 0, 1.0, 5.2, or 8.4 µg/L of pyraclostrobin, tadpoles were then exposed to parasites either in the 1) presence (continued/simultaneous exposure) or 2) absence (fungicide-free water) of pyraclostrobin. We found that when exposed to pyraclostrobin during parasite exposure, meta cercariae counts increased 4 to 8 times compared to control tadpoles. Additionally, parasite loads were approximately 2 times higher in tadpoles with continued fungicide exposures compared to tadpoles that were moved to fresh water following fungicide exposure. This research demonstrates that fungicides at environmentally relevant concentrations can indirectly alter host-parasite interactions, which could elevate disease risk. It also underscores the need for studies that expand beyond traditional toxicity experiments to assess the potential community and ecosystem-level implications of environmental contaminants.

SKN-1/NRF2 upregulation by vitamin A is conserved from nematodes to mammals and is critical for lifespan extension in Caenorhabditis elegans

Vitamin A (VA) is a micronutrient essential for the physiology of many organisms, but its role in longevity and age-related diseases remains unclear. In this work, we used Caenorhabditis elegans to study the impact of various bioactive compounds on lifespan. We demonstrate that VA extends lifespan and reduces lipofuscin and fat accumulation while increasing resistance to heat and oxidative stress. This resistance can be attributed to high levels of detoxifying enzymes called glutathione S-transferases, induced by the transcription factor skinhead-1 (SKN-1). Notably, VA upregulated the transcript levels of skn-1 or its mammalian ortholog NRF2 in both C. elegans, human cells, and liver tissues of mice. Moreover, the loss-of-function genetic models demonstrated a critical involvement of the SKN-1 pathway in longevity extension by VA. Our study thus provides novel insights into the molecular mechanism of anti-aging and anti-oxidative effects of VA, suggesting that this micronutrient could be used for the prevention and/or treatment of age-related disorders.

Contribution of combined stressors on density and gene expression dynamics of the copepod Temora longicornis in the North Sea

The impact of multiple environmental and anthropogenic stressors on the marine environment remains poorly understood. Therefore, we studied the contribution of environmental variables to the densities and gene expression of the dominant zooplankton species in the Belgian part of the North Sea, the calanoid copepod Temora longicornis. We observed a reduced density of copepods, which were also smaller in size, in samples taken from nearshore locations when compared to those obtained from offshore stations. To assess the factors influencing the population dynamics of this species, we applied generalised additive models. These models allowed us to quantify the relative contribution of temperature, nutrient levels, salinity, turbidity, concentrations of photosynthetic pigments, as well as chemical pollutants such as polychlorinated biphenyls and polycyclic aromatic hydrocarbons (PAHs), on copepod density. Temperature and Secchi depth, a proxy for turbidity, were the most important environmental variables predicting the densities of T. longicornis, followed by summed PAH and chlorophyll concentrations. Analysing gene expression in field-collected adults, we observed significant variation in metabolic and stress-response genes. Temperature correlated significantly with genes involved in proteolytic activities, and encoding heat shock proteins. Yet, concentrations of anthropogenic chemicals did not induce significant differences in the gene expression of genes involved in the copepod's fatty acid metabolism or well-known stress-related genes, such as glutathione transferases or cytochrome P450. Our study highlights the potential of gene expression biomonitoring and underscores the significance of a changing environment in future studies.

Zooplankton vulnerability to glyphosate exacerbated by global change

Anthropogenic activities generate a severe footprint at a global scale. Intensive agriculture is a global change driver that affects aquatic systems due to the discharge of pollutants. This situation can be modified or aggravated by other aspects, such as the disturbance history and other global change factors. Following our study line, it is necessary to evaluate how the disturbance history combined with temperature changes can affect the functioning of aquatic systems. The objectives of this study were divided into two phases. The objectives of phase 1 were to induce vulnerability in Daphnia magna populations through a disturbance history based on sublethal glyphosate concentration exposure under different temperature conditions (20 °C and 25 °C). In phase 2, vulnerability was assessed through the exposure to subsequent stressors (starvation, increased salinity and paracetamol) combined with changes in temperature. During the glyphosate exposure period in phase 1, differences were observed in the D. magna populations with respect to temperature, with lower abundance at 25 °C than at 20 °C. However, no differences were observed in abundance regarding glyphosate treatment. The results obtained in phase 2 with the new stressors combined with temperature changes in both directions, revealed stronger effects in vulnerable populations than in control populations. In addition, the temperature changes modulated the effects in the starvation and increased salinity tests. Agrochemical sublethal concentrations induce vulnerability in D. magna populations and inflicted temperature changes can act as a modulating factor for this vulnerability, showing the complexity in assessing the responses under the multiple scenarios associated with global change.

Impacts of neonicotinoid insecticides on bumble bee energy metabolism are revealed under nectar starvation

Bumble bees are an important group of insects that provide essential pollination services as a consequence of their foraging behaviors. These pollination services are driven, in part, by energetic exchanges between flowering plants and individual bees. Thus, it is important to examine bumble bee energy metabolism and explore how it might be influenced by external stressors contributing to declines in global pollinator populations. Two stressors that are commonly encountered by bees are insecticides, such as the neonicotinoids, and nutritional stress, resulting from deficits in pollen and nectar availability. Our study uses a metabolomic approach to examine the effects of neonicotinoid insecticide exposure on bumble bee metabolism, both alone and in combination with nutritional stress. We hypothesized that exposure to imidacloprid disrupts bumble bee energy metabolism, leading to changes in key metabolites involved in central carbon metabolism. We tested this by exposing Bombus impatiens workers to imidacloprid according to one of three exposure paradigms designed to explore how chronic versus more acute (early or late) imidacloprid exposure influences energy metabolite levels, then also subjecting them to artificial nectar starvation. The strongest effects of imidacloprid were observed when bees also experienced nectar starvation, suggesting a combinatorial effect of neonicotinoids and nutritional stress on bumble bee energy metabolism. Overall, this study provides important insights into the mechanisms underlying the impact of neonicotinoid insecticides on pollinators, and underscores the need for further investigation into the complex interactions between environmental stressors and energy metabolism.

Biochemical and behavioral effects of zinc oxide nanorods on the freshwater mussel Potomida littoralis

Our study aimed to investigate the impact of nano-zinc oxide (nZnO), a widely used pollutant in industry, pharmaceuticals, and personal care products, on the behavior and oxidative stress of freshwater mussels (Potomida littoralis) an indicator species and also a model non-target organism in ecotoxicology. To this end mussels were exposed to nZnO (50 and 100 µg/L) and Zn2+ from ZnSO4 (50 and 100 µg/L) for 7 days. ZnSO4 was used for comparison purposes and to determine if the toxicity of nZnO was due to the release of ions into the aquatic environment. We evaluated changes in oxidative stress markers, including catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and malondialdehyde (MDA) levels, on the mussel gills and digestive glands. Additionally, the effect of nZnO on the filtration rate of bivalves was studied. The findings showed that the mussel tissue's different parameters were significantly affected by exposure to various concentrations of nZnO, causing changes in their behavior that led to a decrease in filtration rate. Additionally, noteworthy increments were observed in CAT activity, AChE activity, and MDA levels, whereas GST activity displayed a decreasing trend, implying that oxidative stress contributes to the toxicity of nZnO. The purpose of this review is to present a framework for comprehending the toxicological impacts of nanoparticles from an environmental standpoint. Additionally, it includes novel information about the connections between nanoparticles (NPs) and bivalve species.

Synergistic effects of microplastic and lead trigger physiological and biochemical impairment in a mangrove crab

Microplastics (MP) are vectors for other environmental contaminants, such as metals, being a considerable problem, especially in the aquatic ecosystem. To investigate the combined effects of MP (high density polyethylene) with lead (Pb), we exposed the mangrove fiddler crab Minuca vocator to Pb (50 mg L-1), and MP (25 mg L-1) alone and in mixture, for 5 days. We aimed to determine Pb and MP bioaccumulation, as well as physiological (oxygen consumption and hemolymph osmolality) and biochemical (superoxide dismutase, catalase, glutathione peroxidase, and lipid peroxidation) traits effects. Co-exposure of MP and Pb significantly increased the bioaccumulation of Pb, but reduced MP tissue accumulation. Regarding the physiological traits, increasing osmolality and oxygen consumption rates compared to the control were observed, particularly in the combined Pb and MP exposure. As to biochemical traits, the combination of Pb and MP induced the most significant responses in the enzymatic profile antioxidant enzyme activity. The catalase (CAT), glutathione peroxidase (GPx), and dismutase superoxide (SOD) decreased compared to individual exposure effects; the combination of MP and Pb had a synergistic effect on promoting lipid peroxidation (LPO). The co-exposure of MP and Pb acted synergistically when compared to the effects of the isolated compounds. Due to the increasing MP contamination in mangroves, more severe physiological and biochemical effects can be expected on mangrove crabs exposed to metal contamination.

Cloning and characterization of heat shock transcription factor 1 and its functional role for Hsp70 production in the sea slug Onchidium reevesii

To investigate the regulatory role of heat shock transcription factor 1 of sea slug Onchidium reevesii (OrHSF1) on Hsp70 expression in the sea slug under stress , the OrHSF1 gene was cloned and bioinformatics analysis was performed, then the gene and protein expressions by RNA interference (RNAi) mediated knockdown of OrHSF1 expression were measured to clarify the regulatory relationship between OrHSF1 and Hsp70 under low-frequency noise (LFN) stress. Our study was the first to clone a 1572 bp sequence of the OrHSF1 gene, with the sequence coding for amino acids (CDS) being 729 bp, encoding 243 amino acids. O. reevesii shared a close evolutionary relationship with mollusks such as the Aplysia californica. OrHSF1 gene is widely expressed in different tissues of sea slugs, with the highest expression in the intestine and the lowest in the reproductive glands. Furthermore, we used RNA interference (RNAi) as a tool to silence the OrHSF1 gene in the central nervous system (CNS) and the results indicated that gene silencing was occurring systematically in the CNS and the suppression of OrHSF1 expression by RNAi-mediated gene silencing altered the expression of Hsp70; besides, the expression trends of OrHSF1 gene and Hsp70 were consistent in the 3 and 5-day RNAi experiment. Moreover, in sea slugs injected with siHSF1 and exposed to LFN, the mRNA expression and protein expression of Hsp70 in the CNS were significantly decreased compared to the low-frequency noise group (P < 0.05). This study demonstrated that OrHSF1 regulates Hsp70 expression in marine mollusks under low-frequency noise, and HSF1-Hsp70 axis plays a key role in stress response.

Structural and Functional Shifts in the Microbial Community of a Heavy Metal-Contaminated Soil Exposed to Short-Term Changes in Air Temperature, Soil Moisture and UV Radiation

The interplay between metal contamination and climate change may exacerbate the negative impact on the soil microbiome and, consequently, on soil health and ecosystem services. We assessed the response of the microbial community of a heavy metal-contaminated soil when exposed to short-term (48 h) variations in air temperature, soil humidity or ultraviolet (UV) radiation in the absence and presence of Enchytraeus crypticus (soil invertebrate). Each of the climate scenarios simulated significantly altered at least one of the microbial parameters measured. Irrespective of the presence or absence of invertebrates, the effects were particularly marked upon exposure to increased air temperature and alterations in soil moisture levels (drought and flood scenarios). The observed effects can be partly explained by significant alterations in soil properties such as pH, dissolved organic carbon, and water-extractable heavy metals, which were observed for all scenarios in comparison to standard conditions. The occurrence of invertebrates mitigated some of the impacts observed on the soil microbial community, particularly in bacterial abundance, richness, diversity, and metabolic activity. Our findings emphasize the importance of considering the interplay between climate change, anthropogenic pressures, and soil biotic components to assess the impact of climate change on terrestrial ecosystems and to develop and implement effective management strategies.

Can warming accelerate the decline of Odonata species in experimental paddies due to insecticide fipronil exposure?

Systemic insecticides are one of the causes of Odonata declines in paddy fields. Since rising temperatures associated with global warming can contribute to strengthen pesticide toxicity, insecticide exposures under increasing temperatures may accelerate the decline of Odonata species in the future. However, the combined effects of multiple stressors on Odonata diversity and abundance within ecosystems under various environmental conditions and species interactions are little known. Here, we evaluate the combined effects of the insecticide fipronil and warming on the abundance of Odonata nymphs in experimental paddies. We show that the stand-alone effect of the insecticide exposure caused a significant decrease in abundance of the Odonata community, while nymphs decreased synergistically in the combined treatments with temperature rise in paddy water. However, impacts of each stressor alone were different among species. This study provides experimental evidence that warming could accelerate a reduction in abundance of the Odonata community exposed to insecticides (synergistic effect), although the strength of that effect might vary with the community composition in targeted habitats, due mainly to different susceptibilities among species to each stressor. Community-based monitoring in actual fields is deemed necessary for a realistic evaluation of the combined effects of multiple stressors on biodiversity.

Low-dose exposure to malathion and radiation results in the dysregulation of multiple neuronal processes, inducing neurotoxicity and neurodegeneration in mouse

Neurodegenerative disorders are a debilitating and persistent threat to the global elderly population, carrying grim outcomes. Their genesis is often multifactorial, with a history of prior exposure to xenobiotics such as pesticides, heavy metals, enviornmental pollutants, ionizing radiation etc,. A holistic molecular insight into their mechanistic induction upon single or combinatorial exposure to different toxicants is still unclear. In the present study, one-month-old C57BL/6 male mice were administered orally with malathion (50 mg/kg body wt. for 14 days) and single whole-body radiation (0.5 Gy) on the 8th day. Post-treatment, behavioural assays for exploratory behaviour, memory, and learning were performed. After sacrifice, brains were collected for histology, biochemical assays, and transcriptomic analysis. Transcriptomic analysis revealed several altered processes like synaptic transmission and plasticity, neuronal survival, proliferation, and death. Signalling pathways like MAPK, PI3K-Akt, Apelin, NF-κB, cAMP, Notch etc., and pathways related to neurodegenerative diseases were altered. Increased astrogliosis was observed in the radiation and coexposure groups, with significant neuronal cell death and a reduction in the expression of NeuN. Sholl analysis, dendritic arborization and spine density studies revealed decreased total apical neuronal path length and dendritic spine density. Reduced levels of the antioxidants GST and GSH and acetylcholinesterase enzyme activity were also detected. However, no changes were seen in exploratory behaviour or learning and memory post-treatment. Thus, explicating the molecular mechanisms behind malathion and radiation can provide novel insights into external factor-driven neurotoxicity and neurodegenerative pathogenesis.

Combined impact of elevated temperature and zinc oxide nanoparticles on physiological stress and recovery responses of Scylla serrata

Global climate change is the major cause behind unexpected fluctuations in temperature. In recent years, application of nanotechnology also has become widespread and nanomaterials are constantly being released into aquatic environments, posing a potential risk to various organisms and ecosystems. The lack of detailed understanding of how multiple stressors work, and how they differ from single stressors, impede to assess their combined effect on aquatic organisms and ecosystems. The prime aim of the current investigation is to decipher the toxicity of ZnO-NP after simultaneous exposure to a global environmental stressor, elevated temperature for 14 days, followed by a 7 days recovery period, on the eco-physiological responses of mud crab Scylla serrata collected from Sundarbans. Physiological energetics such as ingestion, assimilation, absorption, respiration, and excretion rates were measured to determine the Scope for growth (SfG). Additionally, we assessed various biomarkers from different levels of biological organisation (antioxidant, detoxification defence mechanisms, and lipid peroxidation levels) of the species. Combined stress attenuated the SfG in crabs which deteriorated further in the recovery phase. Oxidative stress also exacerbated under coalesced stress condition. Recovery was not observed in crabs with increased lipid peroxidation level under combined stress conditions. Elevated temperature disturbed the energy budget of crabs as mirrored by diminished energy left for compensatory actions under added metal stress, ultimately sensitizing the animals to ZnO NP pollutants. The current results advocate future ocean temperature to aggravate the impact of metal NP pollution and induce oxidative damage in S. serrata.

Higher temperature and daily fluctuations aggravate clothianidin toxicity towards Limnodrilus hoffmeisteri

In nature, aquatic organisms may suffer from chemical pollution, together with thermal stress resulted from global warming. However, limited information is available on the combined effects of pesticide with climate change on aquatic organisms. In this study, the acute toxicity of clothianidin to Limnodrilus hoffmeisteri as well as its effect on the induction of oxidative stress under both constant temperature and daily temperature fluctuation (DTF) regimes was investigated. Results showed that clothianidin exhibited the minimal toxicity to L. hoffmeisteri at 25 °C, which was magnified by both increased or decreased temperatures and 10 °C DTF. At different temperatures (15 °C, 25 °C and 35 °C), clothianidin exposure led to the elevated reactive oxygen species (ROS) levels and activated the antioxidant enzymes to resist against the oxidative stress. However, the antioxidant response induced by clothianidin was overwhelmed at high temperature as evidenced by decreased glutathione (GSH) content. Significant elevation of catalase (CAT) and peroxidase (POD) activities but depletion of GSH was also observed in worms treated with clothianidin under DTF after 24 h. The results indicated that high temperature and DTF could aggravate the clothianidin-induced oxidative stress. Moreover, the critical thermal maximum (CTmax) of the worms decreased with the increasing clothianidin concentrations, suggesting that exposure to clothianidin could reduce the heat tolerance of L. hoffmeisteri. Our work highlights the crucial importance to integrate temperature changes into risk assessment of pesticides under global warming.

The role of marine pollution on the emergence of fish bacterial diseases

Marine pollution and bacterial disease outbreaks are two closely related dilemmas that impact marine fish production from fisheries and mariculture. Oil, heavy metals, agrochemicals, sewage, medical wastes, plastics, algal blooms, atmospheric pollutants, mariculture-related pollutants, as well as thermal and noise pollution are the most threatening marine pollutants. The release of these pollutants into the marine aquatic environment leads to significant ecological degradation and a range of non-infectious disorders in fish. Marine pollutants trigger numerous fish bacterial diseases by increasing microbial multiplication in the aquatic environment and suppressing fish immune defense mechanisms. The greater part of these microorganisms is naturally occurring in the aquatic environment. Most disease outbreaks are caused by opportunistic bacterial agents that attack stressed fish. Some infections are more serious and occur in the absence of environmental stressors. Gram-negative bacteria are the most frequent causes of these epizootics, while gram-positive bacterial agents rank second on the critical pathogens list. Vibrio spp., Photobacterium damselae subsp. Piscicida, Tenacibaculum maritimum, Edwardsiella spp., Streptococcus spp., Renibacterium salmoninarum, Pseudomonas spp., Aeromonas spp., and Mycobacterium spp. Are the most dangerous pathogens that attack fish in polluted marine aquatic environments. Effective management strategies and stringent regulations are required to prevent or mitigate the impacts of marine pollutants on aquatic animal health. This review will increase stakeholder awareness about marine pollutants and their impacts on aquatic animal health. It will support competent authorities in developing effective management strategies to mitigate marine pollution, promote the sustainability of commercial marine fisheries, and protect aquatic animal health.

Winter is coming: Interactions of multiple stressors in winter and implications for the natural world

Winter is a key driver of ecological processes in freshwater, marine and terrestrial ecosystems, particularly in higher latitudes. Species have evolved various adaptive strategies to cope with food limitations and the cold and dark wintertime. However, human-induced climate change and other anthropogenic stressors are impacting organisms in winter in unpredictable ways. In this paper, we show that global change experiments investigating multiple stressors have predominantly been conducted during summer months. However, effects of anthropogenic stressors sometimes differ between winter and other seasons, necessitating comprehensive investigations. Here, we outline a framework for understanding the different effects of anthropogenic stressors in winter compared to other seasons and discuss the primary mechanisms that will alter ecological responses of organisms (microbes, animals and plants). For instance, while the magnitude of some anthropogenic stressors can be greater in winter than in other seasons (e.g. some pollutants), others may alleviate natural winter stress (e.g. warmer temperatures). These changes can have immediate, delayed or carry-over effects on organisms during winter or later seasons. Interactions between stressors may also vary with season. We call for a renewed research direction focusing on multiple stressor effects on winter ecology and evolution to fully understand, and predict, how ecosystems will fare under changing winters. We also argue the importance of incorporating the interactions of anthropogenic stressors with winter into ecological risk assessments, management and conservation efforts.

Copper-contaminated soil compromises thermal performance in the springtail Folsomia candida (Collembola)

The widespread agricultural and industrial emissions of copper-based chemicals have increased copper levels in soils worldwide. Copper contamination can cause a range of toxic effects on soil animals and influence thermal tolerance. However, toxic effects are commonly investigated using simple endpoints (e.g., mortality) and acute tests. Thus, how organisms respond to ecological realistic sub-lethal and chronic exposures across the entire thermal scope of an organism is not known. In this study, we investigated the effects of copper exposure on the thermal performance of a springtail (Folsomia candida), regarding its survival, individual growth, population growth, and the composition of membrane phospholipid fatty acids. Folsomia candida (Collembola) is a typical representative of soil arthropods and a model organism that has been widely used for ecotoxicological studies. In a full-factorial soil microcosm experiment, springtails were exposed to three levels of copper (ca. 17 (control), 436, and 1629 mg/kg dry soil) and ten temperatures from 0 to 30 °C. Results showed that three-week copper exposure at temperatures below 15 °C and above 26 °C negatively influenced the springtail survival. The body growth was significantly lower for the springtails in high-dose copper soils at temperatures above 24 °C. A high copper level reduced the number of juveniles by 50 %, thereby impairing population growth. Both temperature and copper exposure significantly impacted membrane properties. Our results indicated that high-dose copper exposure compromised the tolerance to suboptimal temperatures and decreased maximal performance, whereas medium copper exposure partially reduced the performance at suboptimal temperatures. Overall, copper contamination reduced the thermal tolerance of springtails at suboptimal temperatures, probably by interfering with membrane homeoviscous adaptation. Our results show that soil organisms living in copper-contaminated areas might be more sensitive to thermally stressful periods.

Generating Monoclonal Antibodies against Buprofezin and Developing Immunoassays for Its Residue Detection in Tea Samples

The synthesis of a hapten and antigen for the preparation of a monoclonal antibody (mAb) for buprofezin is described. The recognition mechanism of hapten and buprofezin by monoclonal antibodies (mAb-19F2) is described. The effectiveness of the mAb-19F2 immunoassay technique was assessed, and the effective detection of buprofezin in tea samples was achieved through the establishment of indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and colloidal gold immunochromatography assay (GICA). The mAb-19F2 subtype was IgG1, with an IC50 of 1.8 ng/mL and a linear range (IC20-IC80) of 0.6-5.4 μg/L, and had a cross-reaction rate of less than 0.18% with 29 other pesticides (neonicotinoids and insect growth regulators). The study identified π-π stacking interactions between hapten and TYR-61 at the mAb-19F2 site and alkyl/phosphate interactions with TRP-105 and ARG-103. The ic-ELISA had an IC50 of 12.9 ng/mL in green tea and 5.65 ng/mL in black tea, with a recovery rate of 92.4%-101.0% and RSD of 2.1%-4.8%. The GICA had a limit of detection (LOD) was 500 ng/mL, with the complete disappearance of the test lines visible to the naked eye. The limit of quantitation (LOQ, IC20) was determined to be 16.8 ng/mL. Additionally, the developed GICA showed no cross-reactivity with neonicotinoid pesticides. The recovery rate of tea spiked recovered samples was 83.6%-92.2%, with an RSD of 5.3%-12.6%, and the results were consistent with the LC/MS method. This study is important for the real-time detection of buprofezin residues to ensure food safety and human health.

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.

Chemical Mixtures and Multiple Stressors: Same but Different?

Ecosystems are strongly influenced by multiple anthropogenic stressors, including a wide range of chemicals and their mixtures. Studies on the effects of multiple stressors have largely focussed on nonchemical stressors, whereas studies on chemical mixtures have largely ignored other stressors. However, both research areas face similar challenges and require similar tools and methods to predict the joint effects of chemicals or nonchemical stressors, and frameworks to integrate multiple chemical and nonchemical stressors are missing. We provide an overview of the research paradigms, tools, and methods commonly used in multiple stressor and chemical mixture research and discuss potential domains of cross-fertilization and joint challenges. First, we compare the general paradigms of ecotoxicology and (applied) ecology to explain the historical divide. Subsequently, we compare methods and approaches for the identification of interactions, stressor characterization, and designing experiments. We suggest that both multiple stressor and chemical mixture research are too focused on interactions and would benefit from integration regarding null model selection. Stressor characterization is typically more costly for chemical mixtures. While for chemical mixtures comprehensive classification systems at suborganismal level have been developed, recent classification systems for multiple stressors account for environmental context. Both research areas suffer from rather simplified experimental designs that focus on only a limited number of stressors, chemicals, and treatments. We discuss concepts that can guide more realistic designs capturing spatiotemporal stressor dynamics. We suggest that process-based and data-driven models are particularly promising to tackle the challenge of prediction of effects of chemical mixtures and nonchemical stressors on (meta-)communities and (meta-)food webs. We propose a framework to integrate the assessment of effects for multiple stressors and chemical mixtures. Environ Toxicol Chem 2023;42:1915-1936. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Combined threats of climate change and contaminant exposure through the lens of bioenergetics

Organisms face energetic challenges of climate change in combination with suites of natural and anthropogenic stressors. In particular, chemical contaminant exposure has neurotoxic, endocrine-disrupting, and behavioral effects which may additively or interactively combine with challenges associated with climate change. We used a literature review across animal taxa and contaminant classes, but focused on Arctic endotherms and contaminants important in Arctic ecosystems, to demonstrate potential for interactive effects across five bioenergetic domains: (1) energy supply, (2) energy demand, (3) energy storage, (4) energy allocation tradeoffs, and (5) energy management strategies; and involving four climate change-sensitive environmental stressors: changes in resource availability, temperature, predation risk, and parasitism. Identified examples included relatively equal numbers of synergistic and antagonistic interactions. Synergies are often suggested to be particularly problematic, since they magnify biological effects. However, we emphasize that antagonistic effects on bioenergetic traits can be equally problematic, since they can reflect dampening of beneficial responses and result in negative synergistic effects on fitness. Our review also highlights that empirical demonstrations remain limited, especially in endotherms. Elucidating the nature of climate change-by-contaminant interactive effects on bioenergetic traits will build toward determining overall outcomes for energy balance and fitness. Progressing to determine critical species, life stages, and target areas in which transformative effects arise will aid in forecasting broad-scale bioenergetic outcomes under global change scenarios.

Impact of nanopesticide CuO-NPs and nanofertilizer CeO2-NPs on wheat Triticum aestivum under global warming scenarios

Concurrent effect of nanomaterials (NMs) and warming on plant performance remains largely unexplored. In this study, the effects of nanopesticide CuO and nanofertilizer CeO₂ on wheat (Triticum aestivum) under optimal (22 °C) and suboptimal (30 °C) temperatures were evaluated. CuO-NPs exerted a stronger negative effect on plant root systems than CeO₂-NPs at tested exposure levels. The toxicity of both NMs could be attributed to altered nutrient uptake, induced membrane damage, and raised disturbance of antioxidative related biological pathways. Warming significantly inhibited root growth, which was mainly linked to the disturbance of energy metabolism relevant biological pathways. The toxicity of NMs was enhanced upon warming, with a stronger inhibition of root growth and Fe and Mn uptake. Increasing temperature increased the accumulation of Ce upon CeO₂-NP exposure, while the accumulation of Cu was not affected. The relative contribution of NMs and warming to their combined effects was evaluated by comparing disturbed biological pathways under single and multiple stressors. CuO-NPs was the dominant factor inducing toxic effects, while both CeO₂-NPs and warming contributed to the mixed effect. Our study revealed the importance of carefully considering global warming as a factor in risk assessment of agricultural applications of NMs.

Influence of climate change and pesticide use practices on the ecological risks of pesticides in a protected Mediterranean wetland: A Bayesian network approach

Pollution by agricultural pesticides is one of the most important pressures affecting Mediterranean coastal wetlands. Pesticide risks are expected to be influenced by climate change, which will result in an increase of temperatures and a decrease in annual precipitation. On the other hand, pesticide dosages are expected to change given the increase in pest resistance and the implementation of environmental policies like the European ´Farm-to-Fork` strategy, which aims for a 50 % reduction in pesticide usage by 2030. The influence of climate change and pesticide use practices on the ecological risks of pesticides needs to be evaluated making use of realistic environmental scenarios. This study investigates how different climate change and pesticide use practices affect the ecological risks of pesticides in the Albufera Natural Park (Valencia, Spain), a protected Mediterranean coastal wetland. We performed a probabilistic risk assessment for nine pesticides applied in rice production using three climatic scenarios (for the years 2008, 2050 and 2100), three pesticide dosage regimes (the recommended dose, and 50 % increase and 50 % decrease), and their combinations. The scenarios were used to simulate pesticide exposure concentrations in the water column of the rice paddies using the RICEWQ model. Pesticide effects were characterized using acute and chronic Species Sensitivity Distributions built with toxicity data for aquatic organisms. Risk quotients were calculated as probability distributions making use of Bayesian networks. Our results show that future climate projections will influence exposure concentrations for some of the studied pesticides, yielding higher dissipation and lower exposure in scenarios dominated by an increase of temperatures, and higher exposure peaks in scenarios where heavy precipitation events occur right after pesticide application. Our case study shows that pesticides such as azoxystrobin, difenoconazole and MCPA are posing unacceptable ecological risks for aquatic organisms, and that the implementation of the ´Farm-to-Fork` strategy is crucial to reduce them.

Temperature related toxicity features of acute acetamiprid and thiacloprid exposure in Daphnia magna and implications on reproductive performance

This study investigated the potential for elevated temperature to alter the toxicity of acetamiprid (ACE) and thiacloprid (Thia) in the ecotoxicity model Daphnia magna. The modulation of CYP450 monooxygenases (ECOD), ABC transporter activity (MXR) and incident cellular reactive oxygen species (ROS) overproduction was screened in premature daphnids following acute (48 h) exposure to sublethal concentrations of ACE and Thia (0.1-, 1.0 μM) at standard 21 °C and elevated 26 °C temperatures. Delayed outcomes of acute exposures were further evaluated based on the reproduction performance of daphnids monitored over 14 days of recovery. Exposures to ACE and Thia at 21^o C elicited moderate induction of ECOD activity, pronounced inhibition of MXR activity and severe ROS overproduction in daphnids. In the high thermal regime, treatments resulted in significantly lower induction of ECOD activity and inhibition of MXR activity, suggesting a suppressed metabolism of neonicotinoids and less impaired membrane transport activity in daphnids. Elevated temperature on its own, caused a three-fold rise in ROS levels in control daphnids, while ROS overproduction upon neonicotinoid exposure was less accentuated. Acute exposures to ACE and Thia caused significant decreases also in the reproduction of daphnids, indicating delayed outcomes even at environmentally relevant concentrations. Both the cellular alterations in exposed daphnids and decreases in their reproductive output post exposures evidenced closely similar toxicity patterns and potentials for the two neonicotinoids. While elevated temperature elicited only a shift in baseline cellular alterations evoked by neonicotinoids, it significantly worsened the reproductive performance of daphnids following neonicotinoid exposures.

Synergistic survival-related effects of larval exposure to an aquatic pollutant and food stress get stronger during and especially after metamorphosis and shape fitness of terrestrial adults

To improve the ecological risk assessment of aquatic pollutants it is needed to study their effects not only in the aquatic larval stage, but also in the terrestrial adult stage of the many animals with a complex life cycle. This remains understudied, especially with regard to interactive effects between aquatic pollutants and natural abiotic stressors. We studied effects of exposure to the pesticide DNP (2,4-Dinitrophenol) and how these were modulated by limited food availability in the aquatic larvae, and the possible delayed effects in the terrestrial adults of the damselfly Lestes viridis. Our results revealed that DNP and low food each had large negative effects on the life history, behaviour and to a lesser extent on the physiology of not only the larvae, but also the adults. Food limitation magnified the negative effects of DNP as seen by a strong decline in larval survival, metamorphosis success and adult lifespan. Notably, the synergism between the aquatic pollutant and food limitation for survival-related traits was stronger in the non-exposed adults than in the exposed larvae, likely because metamorphosis is stressful itself. Our results highlight that identifying effects of aquatic pollutants and synergisms with natural abiotic stressors, not only in the aquatic larval but also in the terrestrial adult stage, is crucial to fully assess the ecological impact of aquatic pollutants and to reveal the impact on the receiving terrestrial ecosystem through a changed aquatic-terrestrial subsidy.

Toxic temperatures: Bee behaviours exhibit divergent pesticide toxicity relationships with warming

Climate change and agricultural intensification are exposing insect pollinators to temperature extremes and increasing pesticide usage. Yet, we lack good quantification of how temperature modulates the sublethal effects of pesticides on behaviours vital for fitness and pollination performance. Consequently, we are uncertain if warming decreases or increases the severity of different pesticide impacts, and whether separate behaviours vary in the direction of response. Quantifying these interactive effects is vital in forecasting pesticide risk across climate regions and informing pesticide application strategies and pollinator conservation. This multi-stressor study investigated the responses of six functional behaviours of bumblebees when exposed to either a neonicotinoid (imidacloprid) or a sulfoximine (sulfoxaflor) across a standardised low, mid, and high temperature. We found the neonicotinoid had a significant effect on five of the six behaviours, with a greater effect at the lower temperature(s) when measuring responsiveness, the likelihood of movement, walking rate, and food consumption rate. In contrast, the neonicotinoid had a greater impact on flight distance at the higher temperature. Our findings show that different organismal functions can exhibit divergent thermal responses, with some pesticide-affected behaviours showing greater impact as temperatures dropped, and others as temperatures rose. We must therefore account for environmental context when determining pesticide risk. Moreover, we found evidence of synergistic effects, with just a 3°C increase causing a sudden drop in flight performance, despite seeing no effect of pesticide at the two lower temperatures. Our findings highlight the importance of multi-stressor studies to quantify threats to insects, which will help to improve dynamic evaluations of population tipping points and spatiotemporal risks to biodiversity across different climate regions.

Adverse effects of the pesticide chlorpyrifos on the physiology of a damselfly only occur at the cold and hot extremes of a temperature gradient

Ecotoxicological studies considerably improved realism by assessing the toxicity of pollutants at different temperatures. Nevertheless, they may miss key interaction patterns between pollutants and temperature by typically considering only part of the natural thermal gradient experienced by species and ignoring daily temperature fluctuations (DTF). We therefore tested in a common garden laboratory experiment the effects of the pesticide chlorpyrifos across a range of mean temperatures and DTF on physiological traits (related to oxidative stress and bioenergetics) in low- and high-latitude populations of Ischnura elegans damselfly larvae. As expected, the impact of chlorpyrifos varied along the wide range of mean temperatures (12-34 °C). None of the physiological traits (except the superoxide anion levels) were affected by chlorpyrifos at the intermediate mean temperatures (20-24 °C). Instead, most of them were negatively affected by chlorpyrifos (reduced activity levels of the antioxidant defense enzymes superoxide dismutase [SOD], catalase [CAT] and peroxidase [PER], and a reduced energy budget) at the very high (≥28 °C) or extreme high temperatures (≥32 °C), and to lesser extent at the lower mean temperatures (≤16 °C). Notably, at the lower mean temperatures the negative impact of chlorpyrifos was often only present or stronger under DTF. Although the chlorpyrifos effects on the physiological traits greatly depended on the experimentally imposed thermal gradient, patterns were mainly consistent across the natural latitude-associated thermal gradient, indicating the generality of our results. The thermal patterns in chlorpyrifos-induced physiological responses contributed to the observed toxicity patterns in life history (reduced survival and growth at low and high mean temperatures). Taken together, our results underscore the importance of evaluating pesticide toxicity along a temperature gradient and of taking a mechanistic approach with a focus on physiology, to improve our understanding of the combined effects of pollutants and temperature in natural populations.

Increased daily temperature fluctuations exacerbate the toxicity of phenanthrene in Enchytraeus albidus (Enchytraeidae)

Temperature variability in soils is expected to increase due to the more frequent occurrence of heat waves, putting species under thermal stress. In addition, organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) are released into the environment due to anthropogenic activities. Both stressors negatively impact terrestrial organisms and may interact with each other. Here, we subjected the soil living enchytraeid, Enchytraeus albidus, to combined exposure to phenanthrene (PHE; 0, 10, 20, 40, and 80 mg kg^-1 dry soil) and a range of temperature treatments (constant temperature (CT): 10, 15 and 20 °C; different mean temperature with the same daily temperature fluctuation (DTF-5): 10 ± 5, 15 ± 5 and 20 ± 5 °C; daily temperature fluctuation with the same mean, but different amplitudes (DTF-A): 20, 20 ± 2, 20 ± 5 and 20 ± 7 °C). We measured internal PHE concentration in adults and found that an increase in mean temperature significantly increased the internal PHE concentration. The production of juveniles was measured using a standardized test. We found a synergistic interaction between the temperature amplitude (DTF-A treatments) and PHE on the reproduction of E. albidus. The EC₅₀ of reproduction decreased with increasing amplitude. These results show that the negative effects of PHE on E. albidus can be magnified if stressful temperatures are reached (although briefly) during diurnal fluctuations of soil temperature. Our results highlight the importance and inclusion of extreme thermal events in the risk assessment of pollutants.

Evaluation of life-history traits in Folsomia candida exposed to combined repeated mild heat shocks with phenanthrene

Climate change increases the frequency and intensity of extreme weather events. In nature, organisms are often exposed to climatic stressors and contaminants simultaneously, and the effects of contaminants may be modified by climate change and vice versa. Here, the effects of repeated mild heat shocks (0-5 times, 30 °C for 6 h), alone or combined with phenanthrene (PHE) (80 mg kg^-1 dry soil), on life-history traits of the springtail Folsomia candida were investigated. The survival, growth, maturation, and reproduction of single juvenile springtails were assessed over a period of 37 days. Increasing number of heat bouts or PHE exposure did not have significant negative effects on overall survival at the termination of the experiment, but the interaction between the two stressors led to complex interactions for the dynamics of survival during the test. Neither body growth nor time to first oviposition was influenced by heat or PHE, but a reduction of egg production with increasing number of heat bouts was observed, and there was an interaction between the two stressors. Further, a trade-off between the number of eggs produced and egg size was observed, indicating that females invested the same amount of energy in reproduction despite exposure to stressful temperature and PHE. These results indicate that egg production (in terms of the number of eggs) was a more sensitive indicator of the combined effects of mild heat shocks and PHE than growth, and there was a trade-off between survival and egg production.

Effects of elevated temperature and decreased soil moisture content on triclosan ecotoxicity to earthworm E. fetida

Emerging pollutants and climate change are two main challenges affecting soil organisms today. Changes in temperature and soil moisture with climate change are key factors determining activity and fitness of soil dwelling organisms. The occurrence and toxicity of antimicrobial agent triclosan (TCS) in terrestrial environment is of high concern, while no data are available on TCS toxicity changes to terrestrial organisms under global climate change. The study's aim was to assess the impact of elevated temperature, decreased soil moisture content, and their complex interaction on triclosan-induced changes in Eisenia fetida life cycle parameters (growth, reproduction, and survival). Eight-week TCS-contaminated soil (10-750 mg TCS kg^-1) experiments with E. fetida were performed at four different treatments: C (21 °C + 60% water holding capacity (WHC)); D (21 °C and 30% WHC); T (25 °C + 60% WHC); and T + D (25 °C + 30% WHC). TCS had negative impact on the earthworm mortality, growth, and reproduction. Changing climate conditions have altered TCS toxicity to E. fetida. Drought and drought in combination with elevated temperature enhanced the adverse effects of TCS on earthworm survival, growth rate, and reproduction, while single elevated temperature slightly reduced TCS lethal toxicity as well as toxicity to growth rate and reproduction.

Can pharmaceutical pollution alter the spread of infectious disease? A case study using fluoxetine

Human activity is changing global environments at an unprecedented rate, imposing new ecological and evolutionary ramifications on wildlife dynamics, including host-parasite interactions. Here we investigate how an emerging concern of modern human activity, pharmaceutical pollution, influences the spread of disease in a population, using the water flea Daphnia magna and the bacterial pathogen Pasteuria ramosa as a model system. We found that exposure to different concentrations of fluoxetine-a widely prescribed psychoactive drug and widespread contaminant of aquatic ecosystems-affected the severity of disease experienced by an individual in a non-monotonic manner. The direction and magnitude of any effect, however, varied with both the infection outcome measured and the genotype of the pathogen. By contrast, the characteristics of unexposed animals, and thus the growth and density of susceptible hosts, were robust to fluoxetine. Using our data to parameterize an epidemiological model, we show that fluoxetine is unlikely to lead to a net increase or decrease in the likelihood of an infectious disease outbreak, as measured by a pathogen's transmission rate or basic reproductive number. Instead, any given pathogen genotype may experience a twofold change in likely fitness, but often in opposing directions. Our study demonstrates that changes in pharmaceutical pollution give rise to complex genotype-by-environment interactions in its influence of disease dynamics, with repercussions on pathogen genetic diversity and evolution. This article is part of the theme issue 'Infectious disease ecology and evolution in a changing world'.

Speed it up: How temperature drives toxicokinetics of organic contaminants in freshwater amphipods

The acceleration of global climate change draws increasing attention towards interactive effects of temperature and organic contaminants. Many studies reported a higher sensitivity of aquatic invertebrates towards contaminant exposure with increasing or fluctuating temperatures. The hypothesis of this study was that the higher sensitivity of invertebrates is associated with the changes of toxicokinetic processes that determine internal concentrations of contaminants and consequently toxic effects. Therefore, the influence of temperature on toxicokinetic processes and the underlying mechanisms were studied in two key amphipod species (Gammarus pulex and Hyalella azteca). Bioconcentration experiments were carried out at four different temperatures with a mixture of 12 exposure relevant polar organic contaminants. Tissue and medium samples were taken in regular intervals and analysed by online solid-phase extraction liquid chromatography high-resolution tandem mass spectrometry. Subsequently, toxicokinetic rates were modelled and analysed in dependence of the exposure temperature using the Arrhenius equation. An exponential relationship between toxicokinetic rates versus temperature was observed and could be well depicted by applying the Arrhenius equation. Due to a similar Arrhenius temperature of uptake and elimination rates, the bioconcentration factors of the contaminants were generally constant across the temperature range. Furthermore, the Arrhenius temperature of the toxicokinetic rates and respiration was mostly similar. However, in some cases (citalopram, cyprodinil), the bioconcentration factor appeared to be temperature dependent, which could potentially be explained by the influence of temperature on active uptake mechanisms or biotransformation. The observed temperature effects on toxicokinetics may be particularly relevant in non-equilibrated systems, such as exposure peaks in summer as exemplified by the exposure modelling of a field measured pesticide peak where the internal concentrations increased by up to fourfold along the temperature gradient. The results provide novel insights into the mechanisms of chemical uptake, biotransformation and elimination in different climate scenarios and can improve environmental risk assessment.

Previous stress causes a contrasting response to cadmium toxicity in the aquatic snail Potamopyrgus antipodarum: lethal and behavioral endpoints

In aquatic ecosystems, animals are often exposed to a combination of stressors, including both natural and anthropogenic factors. Combined stressors may have additive or interactive effects on animals, either magnifying or reducing the effects caused by each stressor alone. Therefore, standardized bioassays can lead to overestimations or underestimations of the risk of toxicants if natural stressors are not bear in mind. The inclusion of natural stress in laboratory bioassays may help to extrapolate the laboratory results to ecosystems. This study assesses the effects of successive exposure to two sources of stress (high water conductivity and cadmium toxicity) on the behavior and survival of the aquatic snail Potamopyrgus antipodarum (Tateidae, Mollusca). I conducted a bioassay consisting on exposure to high conductivity (5000 mg NaCl/L, 7 days), followed by exposure to cadmium (0.03, 0.125, and 0.25 mg Cd/L for 7 days) and by a post-exposure period (7 days). Mortality, inactivity, and the time to start activity of active animals were monitored in each animal. In general, cadmium lethality was higher in animals previously undergoing high conductivity than in non-stressed ones. Previously stressed animals showed longer time to start activity, with a noticeable effect at the two highest cadmium concentrations. Animals submitted to the two highest cadmium concentration both, stressed and non-stressed, showed a moderate recovery during the post-exposure period. It is concluded that previous stress caused a worsening of the cadmium toxicity on the aquatic snail Potamopyrgus antipodarum, which is especially noticeable for mortality. However, there was no interactive effect between cadmium and conductivity on snail activity, which may be indicative of recovery after cadmium exposure regardless the previous stress suffered by the snails.

Influence of Soil Moisture on Bioaccumulation, Growth, and Recruitment of Folsomia candida Exposed to Phenanthrene-Polluted Soil

Climate change has resulted in an increased occurrence of summer droughts in large parts of the world. Low soil moisture has marked impacts on the physiology of soil invertebrates and lowers degradation rates of organic contaminants in soil. Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic contaminants that readily accumulate in the lipids of soil organisms. Here, we exposed springtails (Collembola, small soil living arthropods) to phenanthrene (a common PAH) in combination with a range of soil water contents to investigate the combined effects of these factors on the bioaccumulation, survival, recruitment, and body growth in a full factorial experiment. The results showed that phenanthrene up to 60 mg/kg dry soil had moderate effects on survival (<20%), whereas dry soil (4% soil water content) caused approximately 60% mortality. The bioaccumulation of phenanthrene increased almost 3-fold when soil water content decreased from 22 to 4%. We observed a joint effect of low soil water content and phenanthrene on recruitment, suggesting a synergistic interaction. The recruitment EC50 values of phenanthrene decreased from approximately 40 mg/kg dry soil at 22% soil water content to approximately 10 mg/kg dry soil at 12% soil water content. Our results show that the effects of phenanthrene are more pronounced in dry soil partly because bioaccumulation is enhanced when soils become dry.

Thermal Performance Curves in a Polluted World: Too Cold and Too Hot Temperatures Synergistically Increase Pesticide Toxicity

Ecotoxicological studies typically cover only a limited part of the natural thermal range of populations and ignore daily temperature fluctuations (DTFs). Therefore, we may miss important stressor interaction patterns and have poor knowledge on how pollutants affect thermal performance curves (TPCs), which is needed to improve insights into the fate of populations to warming in a polluted world. We tested the single and combined effects of pesticide exposure and DTFs on the TPCs of low- and high-latitude populations of Ischnura elegans damselfly larvae. While chlorpyrifos did not have any effect at the intermediate mean temperatures (20-24 °C), it became toxic (reflecting synergisms) at lower (≤16 °C, reduced growth) and especially at higher (≥28 °C, reduced survival and growth) mean temperatures, resulting in more concave-shaped TPCs. Remarkably, these toxicity patterns were largely consistent at both latitudes and hence across a natural thermal gradient. Moreover, DTFs magnified the pesticide-induced survival reductions at 34 °C. The TPC perspective allowed us to identify different toxicity patterns and interaction types (mainly additive vs synergistic) across the thermal gradient. This highlights the importance of using thermal gradients to make more realistic predictions about the impact of pesticides in a warming world and of warming in a polluted world.

Negative but antagonistic effects of neonicotinoid insecticides and ectoparasitic mites Varroa destructor on Apis mellifera honey bee food glands

Collaborative brood care by workers is essential for the functionality of eusocial Apis mellifera honey bee colonies. The hypopharyngeal food glands of workers play a crucial role in this context. Even though there is consensus that ubiquitous ectoparasitic mites Varroa destructor and widespread insecticides, such as neonicotinoids, are major stressors for honey bee health, their impact alone and in combination on the feeding glands of workers is poorly understood. Here, we show that combined exposure to V. destructor and neonicotinoids antagonistically interacted on hypopharyngeal gland size, yet they did not interact on emergence body mass or survival. While the observed effects of the antagonistic interaction were less negative than expected based on the sum of the individual effects, hypopharyngeal gland size was still significantly reduced. Alone, V. destructor parasitism negatively affected emergence body mass, survival, and hypopharyngeal gland size, whereas neonicotinoid exposure reduced hypopharyngeal gland size only. Since size is associated with hypopharyngeal gland functionality, a reduction could result in inadequate brood care. As cooperative brood care is a cornerstone of eusociality, smaller glands could have adverse down-stream effects on inclusive fitness of honey bee colonies. Therefore, our findings highlight the need to further study how ubiquitous stressors like V. destructor and neonicotinoids interact to affect honey bees.

Post-exposure Period as a key Factor to Assess Cadmium Toxicity: Lethal vs. Behavioral Responses

The exposure of animals to pollution in ecosystems is not always chronic. Toxicants can remain in aquatic ecosystems for a short-term. To improve the extrapolation of laboratory results to natural scenarios the inclusion of post-exposure periods is a relevant issue. The present study focuses on the assessment of cadmium toxicity on survival and behavior of the aquatic snail Potamopyrgus antipodarum (Tateidae, Mollusca) during exposure and post-exposure. Animals were exposed for 48 h to cadmium (0.05, 0.14, 0.44 and 1.34 mg Cd/L) and 168 h of post-exposure. During the post-exposure period an increase in mortality in all concentrations was observed. The effects observed during the post-exposure period on the LC50 and EC50 were significant. During the post-exposure, behavior showed a clear recovery in surviving animals exposed to 0.44 mg Cd/L. Animals exposed to 0.05 mg Cd/L did not show differences with control. Therefore, mortality after exposure should be included in the ecotoxicological bioassays for a more realistic estimation of the cadmium effects. To assess the degree of animal recovery after cadmium exposure, behaviour has been shown as an adequate parameter.

Heat stress delays detoxification of phenanthrene in the springtail Folsomia candida

Climate change has intensified the occurrence of heat waves, resulting in organisms being exposed to thermal and chemical stress at the same time. The effects of mild heat shock combined with sublethal concentrations of phenanthrene (PHE) on defense mechanisms in springtails Folsomia candida were investigated. The transcription of Heat Shock Protein 70 (HSP70) was significantly upregulated by heat shock but tended to reach the control levels after 42 h of recovery. The transcription of cytochrome P450 3A13 (CYP3A13) was upregulated 3-13 fold by PHE but suppressed by heat shock. The suppression by heat shock might contribute to the reduced detoxification of PHE during high-temperature exposure. In line with this, we found that the internal PHE concentration was approximately 70% higher in heat-shocked springtails than in animals kept at control temperature. In general, the transcription of genes encoding enzymes of detoxification phase Ⅱ (glutathione S-transferase 3) and phase Ⅲ (ABC transporter 1) and the activity of antioxidant defense enzymes (superoxide dismutase and catalase) were less influenced than genes encoding phase I detoxification mechanisms (CYP3A13). These results indicate that heat shock delays the detoxification of PHE in springtails.