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.

A Comprehensive Ecotoxicity Study of Molybdenum Disulfide Nanosheets versus Bulk form in Soil Organisms.

The increasing use of molybdenum disulfide (MoS2) nanoparticles (NPs) raises concerns regarding their accumulation in soil ecosystems, with limited studies on their impact on soil organisms. Study aim: To unravel the effects of MoS2 nanosheets (two-dimensional (2D) MoS2 NPs) and bulk MoS2 (156, 313, 625, 1250, 2500 mg/kg) on Enchytraeus crypticus and Folsomia candida. The organisms' survival and avoidance behavior remained unaffected by both forms, while reproduction and DNA integrity were impacted. For E. crypticus, the individual endpoint reproduction was more sensitive, increasing at lower concentrations of bulk MoS2 and decreasing at higher ones and at 625 mg/kg of 2D MoS2 NPs. For F. candida, the molecular endpoint DNA integrity was more impacted: 2500 mg/kg of bulk MoS2 induced DNA damage after 2 days, with all concentrations inducing damage by day 7. 2D MoS2 NPs induced DNA damage at 156 and 2500 mg/kg after 2 days, and at 1250 and 2500 mg/kg after 7 days. Despite affecting the same endpoints, bulk MoS2 induced more effects than 2D MoS2 NPs. Indeed, 2D MoS2 NPs only inhibited E. crypticus reproduction at 625 mg/kg and induced fewer (F. candida) or no effects (E. crypticus) on DNA integrity. This study highlights the different responses of terrestrial organisms to 2D MoS2 NPs versus bulk MoS2, reinforcing the importance of risk assessment when considering both forms.

Daphnia magna Multigeneration Exposure to Carbendazim: Gene Transcription Responses.

The world population is experiencing colossal growth and thus demand for food, leading to an increase in the use of pesticides. Persistent pesticide contamination, such as carbendazim, remains a pressing environmental concern, with potentially long-term impacts on aquatic ecosystems. In the present study, Daphnia magna was exposed to carbendazim (5 µg L-1) for 12 generations, with the aim of assessing gene transcription alterations induced by carbendazim (using a D. magna custom microarray). The results showed that carbendazim caused changes in genes involved in the response to stress, DNA replication/repair, neurotransmission, ATP production, and lipid and carbohydrate metabolism at concentrations already found in the environment. These outcomes support the results of previous studies, in which carbendazim induced genotoxic effects and reproduction impairment (increasing the number of aborted eggs with the decreasing number of neonates produced). The exposure of daphnids to carbendazim did not cause a stable change in gene transcription between generations, with more genes being differentially expressed in the F0 generation than in the F12 generation. This could show some possible daphnid acclimation after 12 generations and is aligned with previous multigenerational studies where few ecotoxicological effects at the individual and populational levels and other subcellular level effects (e.g., biochemical biomarkers) were found.

Nanoplastics increase the toxicity of a pharmaceutical, at environmentally relevant concentrations - A mixture design with Daphnia magna.

In aquatic environments, nanoplastics (NPls) can adsorb pharmaceuticals. However, throughout the scientific community, there is scarce knowledge about the interactive effects of the mixture nanoplastics (NPls) with pharmaceuticals to aquatic organisms. Therefore, this study aimed to investigate if the pharmaceutical diphenhydramine (DPH) toxicological effects alters when in presence of polystyrene NPls (PSNPls). To achieve this, Daphnia magna immobilization and different biochemical biomarkers (48-hours exposure) were assessed. Synergistic interactions occurred at environmentally relevant concentrations, PSNPls+DPH induced oxidative damage, whereas no effect was observed at single exposures. With the increase of PSNPls concentration, the DPH concentration causing 50% of effect (EC50) for organisms' immobilization decreased to 0.001 mg/L. In silico analysis suggested that the DPH toxicity to D. magna occurs via the sodium-dependent serotonin transporter. The results showed interactive effects between PSNPls and DPH (implying harmful effects on D. magna), allowing more thoughtful decisions by society and policymakers regarding plastics and pharmaceuticals.

Toxicity assessment of binary mixtures of BP3 with 4-MBC (UV-filters), and BP3 with DEET (insect repellent) using the aquatic midge Chironomus riparius.

Personal care products have various organic ultraviolet filters (UV filters) in their composition to increase protection against ultraviolet radiation. Some of these products also contain insect repellents in their formulations. Consequently, these compounds reach freshwater ecosystems, exposing aquatic organisms to a cocktail of anthropogenic contaminants. In this study, the joint effects of two most frequently detected UV filters (Benzophenone - 3 (BP3) and Enzacamene (4-MBC)) and joint effects of BP3 combined with an insect repellent (N, N diethyl-3-methylbenzamide - DEET) were evaluated using life-history traits of the aquatic midge Chironomus riparius such as emergence rate, time to emergence and imagoes body weight. The results showed synergistic effects between BP3 and 4-MBC for C. riparius emergence rate. Regarding the effects of BP3 and DEET mixture, our analysis suggests synergism in the case of males but antagonism in the case of females' time to emergence. Our results imply that the effects of UV filters present in sediments within chemical mixtures are complex and that the evaluation of effects using different life-history traits can yield different patterns of responses. This study demonstrates the importance of assessing the combined effects of pollutants used/found concomitantly in aquatic systems for a more accurate risk assessment, as individual chemical testing can underestimate the toxicity of organic UV filters.

Toxicokinetics and bioaccumulation of silver sulfide nanoparticles in benthic invertebrates in an indoor stream mesocosm.

Mesocosms allow the simulation of environmentally relevant conditions and can be used to establish more realistic scenarios of organism exposure to nanoparticles. An indoor mesocosm experiment simulating an aquatic stream ecosystem was conducted to assess the toxicokinetics and bioaccumulation of silver sulfide nanoparticles (Ag2S NPs) and AgNO3 in the freshwater invertebrates Girardia tigrina, Physa acuta and Chironomus riparius, and determine if previous single-species tests can predict bioaccumulation in the mesocosm. Water was daily spiked at 10 µg Ag L-1. Ag concentrations in water and sediment reached values of 13.4 µg Ag L-1 and 0.30 µg Ag g-1 in the Ag2S NP exposure, and 12.8 µg Ag L-1 and 0.20 µg Ag g-1 in the AgNO3. Silver was bioaccumulated by the species from both treatments, but with approximately 1.5, 3 and 11 times higher body Ag concentrations in AgNO3 compared to Ag2S NP exposures in snails, chironomids and planarians, respectively. In the Ag2S NP exposures, the observed uptake was probably of the particulate form. This demonstrates that this more environmentally relevant Ag nanoform may be bioavailable for uptake by benthic organisms. Interspecies interactions likely occurred, namely predation (planarians fed on chironomids and snails), which somehow influenced Ag uptake/bioaccumulation, possibly by altering organisms´ foraging behaviour. Higher Ag uptake rate constants were determined for AgNO3 (0.64, 80.4 and 1.12 Lwater g-1organism day-1) than for Ag2S NPs (0.05, 2.65 and 0.32 Lwater g-1organism day-1) for planarians, snails and chironomids, respectively. Biomagnification under environmentally realistic exposure seemed to be low, although it was likely to occur in the food chain P. acuta to G. tigrina exposed to AgNO3. Single-species tests generally could not reliably predict Ag bioaccumulation in the more complex mesocosm scenario. This study provides methodologies/data to better understand exposure, toxicokinetics and bioaccumulation of Ag in complex systems, reinforcing the need to use mesocosm studies to improve the risk assessment of environmental contaminants, specifically NPs, in aquatic environments.

Toxicokinetics of Ag from Ag2S NP exposure in Tenebrio molitor and Porcellio scaber: Comparing single-species tests to indoor mesocosm experiments.

Determining the potential for accumulation of Ag from Ag2S NPs as an environmentally relevant form of AgNPs in different terrestrial organisms is an essential component of a realistic risk assessment of AgNP emissions to soils. The objectives of this study were first to determine the uptake kinetics of Ag in mealworms (Tenebrio molitor) and woodlice (Porcellio scaber) exposed to Ag2S NPs in a mesocosm test, and second, to check if the obtained toxicokinetics could be predicted by single-species bioaccumulation tests. In the mesocosms, mealworms and woodlice were exposed together with plants and earthworms in soil columns spiked with 10 µg Ag g-1 dry soil as Ag2S NPs or AgNO3. The total Ag concentrations in the biota were measured after 7, 14, and 28 days of exposure. A one-compartment model was used to calculate the Ag uptake and elimination rate constants. Ag from Ag2S NPs appeared to be taken up by the mealworms with significantly different uptake rate constants in the mesocosm compared to single-species tests (K1 = 0.056 and 1.66 g dry soil g-1 dry body weight day-1, respectively), and a significant difference was found for the Ag bioaccumulation factor (BAFk = 0.79 and 0.15 g dry soil g-1 dry body weight, respectively). Woodlice did not accumulate Ag from Ag2S NPs in both tests, but uptake from AgNO3 was significantly slower in mesocosm than in single-species tests (K1 = 0.037 and 0.26 g dry soil g-1 dry body weight day-1, respectively). Our results are of high significance because they show that single-species tests may not be a good predictor for the Ag uptake in mealworms and woodlice in exposure systems having greater levels of biological complexity. Nevertheless, single-species tests could be used as a fast screening approach to assess the potential of a substance to accumulate in biota before more complex tests are conducted.

Ecotoxicological effects of fluvial eroded bitumen sediments from the Alberta oil sands to model aquatic species.

To fully understand the ecological and cumulative effects of mining activities on the surrounding aquatic systems of the Canadian oil sands region, it is essential to understand the consequences of exposure to bitumen-containing soils/sediment from natural geomorphological processes. Both physical and chemical stress on aquatic biota can potentially result from exposure to natural bitumen, resulting from hillslope erosional processes and slumping of bankside soils into the rivers, affecting both riverbed habitat and water quality. The magnitude and duration of bitumen-containing soil's fluvial soils/erosional input into receiving watersheds depends on the interannual variability in the regional hydroclimatology and related seasonal and extreme flow events. The primary objective of this study was to evaluate the potential ecotoxicological effects associated with erosional input of riverbank bitumen soils using controlled exposures. A series of integrated, laboratory-based ecotoxicological bioassays were conducted using organisms with different ecological and functional traits (Daphnia magna (Cladocera), Physa acuta (Gastropoda), and Aliivibrio fischeri (Bacteria)). All model organisms were exposed to elutriates produced from natural bitumen from four different regional rivers: fresh bitumen from shoreline outcrops at the Steepbank River upper and lower reaches (STB-CF and STB-MF, respectively) and the lower-Ells River (EL-MF) and aged, fluvially processed/weathered bitumen from the shoreline of the Athabasca River (ATB-MF). All tested organisms responded negatively to STB-MF and EL-MF elutriates. Low toxicity was also observed in the STB-CF and ATB-MF samples. These results follow the chemical analysis of the parental material and elutriates, where higher levels of metals, polycyclic aromatic compounds and naphthenic acids were detected in the EL-MF sample. In summary, this study shows that eroded and transported bitumen-containing soils and sediments could be a natural source of contaminant exposure to aquatic biota. This fluvial pathway should be considered when assessing background toxicity and the toxicological and ecological effects of oil sands mining activities.

The effects of different temperatures in mercury toxicity to the terrestrial isopod Porcellionides pruinosus.

Climate changes and metal contamination are pervasive stressors for soil ecosystems. Mercury (Hg), one of the most toxic metals, has been reported to interact with temperature. However, compared to aquatic biota, little is known about how temperature affects Hg toxicity and bioaccumulation to soil organisms. Here, toxicity and bioaccumulation experiments were replicated at 15 °C, 20 °C, and 25 °C to understand how sub-optimal temperatures affect the toxicokinetics and toxicodynamics of Hg via soil. Genotoxicity and energy reserves were also assessed to disclose potential trade-offs in life-history traits. Results underpin the complexity of temperature-Hg interactions. Survival was determined mainly by toxicokinetics, but toxicodynamics also played a significant role in defining survival probability during early stages. The processes determining survival probability were faster at 25 °C: General Unified Threshold of Survival (GUTS) model identified an earlier/steeper decline in survival, compared to 20 °C or 15 °C, but it also approached the threshold faster. Despite potentiation of Hg genotoxicity, temperature promoted faster detoxification, either increasing toxicokinetics rates or damage repair mechanisms. This metabolism-driven increase in detoxification led to higher depletion of energy reserves and likely triggered stress response pathways. This work emphasized the need for comprehensive experimental approaches that can integrate the multiple processes involved in temperature-metal interactions.

Metal transfer to sediments, invertebrates and fish following waterborne exposure to silver nitrate or silver sulfide nanoparticles in an indoor stream mesocosm.

The fate of engineered nanomaterials in ecosystems is unclear. An aquatic stream mesocosm explored the fate and bioaccumulation of silver sulfide nanoparticles (Ag2S NPs) compared to silver nitrate (AgNO3). The aims were to determine the total Ag in water, sediment and biota, and to evaluate the bioavailable fractions of silver in the sediment using a serial extraction method. The total Ag in the water column from a nominal daily dose of 10 µg L-1 of Ag for the AgNO3 or Ag2S NP treatments reached a plateau of around 13 and 12 µg L-1, respectively, by the end of the study. Similarly, the sediment of both Ag-treatments reached ~380 µg Ag kg-1, and with most of it being acid-extractable/labile. The biota accumulated 4-59 µg Ag g-1 dw, depending on the type of Ag-treatment and organism. The oligochaete worm, Lumbriculus variegatus, accumulated Ag from the Ag2S exposure over time, which was similar to the AgNO3 treatment by the end of the experiment. The planarian, Girardia tigrina, and the chironomid larva, Chironomus riparius, showed much higher Ag concentrations than the oligochaete worms; and with a clearer time-dependent statistically significant Ag accumulation relative to the untreated controls. For the pulmonate snail, Physa acuta, bioaccumulation of Ag from AgNO3 and Ag2S NP exposures was observed, but was lower from the nano treatment. The AgNO3 exposure caused appreciable Ag accumulation in the water flea, Daphnia magna, but accumulation was higher in the Ag2S NP treatment (reaching 59 µg g-1 dw). In the rainbow trout, Oncorhynchus mykiss, AgNO3, but not Ag2S NPs, caused total Ag concentrations to increase in the tissues. Overall, the study showed transfer of total Ag from the water column to the sediment, and Ag bioaccumulation in the biota, with Ag from Ag2S NP exposure generally being less bioavailable than that from AgNO3.

Short-Term Responses of Soil Microbial Communities to Changes in Air Temperature, Soil Moisture and UV Radiation.

We analyzed the effects on a soil microbial community of short-term alterations in air temperature, soil moisture and ultraviolet radiation and assessed the role of invertebrates (species Enchytraeus crypticus) in modulating the community's response to these factors. The reference soil, Lufa 2.2, was incubated for 48 h, with and without invertebrates, under the following conditions: standard (20 °C + 50% water holding capacity (WHC)); increased air temperature (15-25 °C or 20-30 °C + 50% WHC); flood (20 °C + 75% WHC); drought (20 °C + 25% WHC); and ultraviolet radiation (UV) (20 °C + 50% WHC + UV). BIOLOG EcoPlates and 16S rDNA sequencing (Illumina) were used to assess the microbial community's physiological profile and the bacterial community's structure, respectively. The bacterial abundance (estimated by 16S rDNA qPCR) did not change. Most of the conditions led to an increase in microbial activity and a decrease in diversity. The structure of the bacterial community was particularly affected by higher air temperatures (20-30 °C, without E. crypticus) and floods (with E. crypticus). Effects were observed at the class, genera and OTU levels. The presence of invertebrates mostly resulted in the attenuation of the observed effects, highlighting the importance of considering microbiome-invertebrate interactions. Considering future climate changes, the effects described here raise concern. This study provides fundamental knowledge to develop effective strategies to mitigate these negative outcomes. However, long-term studies integrating biotic and abiotic factors are needed.

Toxicity of historically metal(loid)-contaminated soils to Folsomia candida under the influence of climate change alterations.

Global warming is drastically altering the climate conditions of our planet. Soils will be among the most affected components of terrestrial ecosystems, especially in contaminated areas. In this study we investigated if changes in climate conditions (air temperature and soil moisture) affect the toxicity of historically metal(loid)-contaminated soils to the invertebrate Folsomia candida, followed by an assessment of its recovery capacity. Ecotoxicity tests (assessing survival, reproduction) were performed in field soils affected by metal(loid)s under different climate scenarios, simulated by individually changing air temperature or soil moisture conditions. The scenarios tested were: standard conditions (20°C + 50% soil water holding capacity-WHC); increased air temperature (daily fluctuation of 20-30°C + 50% WHC); soil drought (20°C + 25% WHC); soil flood (20°C + 75% WHC). Recovery potential was assessed under standard conditions in clean soil. Increased temperature was the major climate condition negatively affecting collembolans performance (decreased survival and reproduction), regardless of metal(loid) contamination. Drought and flood conditions presented less pronounced effects. When it was possible to move to the recovery phase (enough juveniles in exposure phase), F. candida was apparently able to recover from the exposure to metal(loid) contamination and/or climate alterations. The present study showed that forecasted climate alterations in areas already affected by contamination should be considered to improve environmental risk assessment.

Microplastic Fibers Increase Sublethal Effects of AgNP and AgNO3 in Daphnia magna by Changing Cellular Energy Allocation.

The effects of combined exposure to microplastics and contaminants are still not completely understood. To fill this gap, we assessed the effects of polyethylene terephthalate microplastic fibers (100 mg/L; 360 µm average length) on the toxicity of silver nanoparticles (AgNPs; 32 nm) and silver nitrate (AgNO3 ; 0.1-10 µg Ag/L) to Daphnia magna. Acute immobilization (median effect concentration [EC50]) and cellular energy allocation (CEA; ratio between available energy and energy consumption) were determined in neonates (<24 h old) and juveniles (7 d old), respectively. The 48-h EC50 for AgNP and AgNO3 (2.6 and 0.67 µg Ag/L, respectively) was not affected by the presence of microplastic fibers (2.2 and 0.85 µg Ag/L, respectively). No decrease in the available energy was observed: lipid, carbohydrate, and protein contents were unaffected. However, a significant increase in energy consumption was observed in animals exposed to AgNO3 (250% compared with control) and to the combination of microplastic fibers with AgNP (170%) and AgNO3 (260%). The exposure to microplastic fibers alone or in combination with both Ag forms decreased the CEA (values were 55-75% of control values). Our results show that after short-term exposure (48 h), microplastic fibers increased Ag toxicity at a subcellular level (i.e., CEA), but not at the individual level (i.e., immobilization). These results highlight the importance of combining different levels of biological organization to fully assess the ecotoxicological effects of plastics in association with environmental contaminants. Environ Toxicol Chem 2022;41:896-904. © 2021 SETAC.

Mixture toxicity prediction of substances from different origin sources in Daphnia magna.

Due to several anthropogenic activities, water bodies have been heavily impacted by contaminants identified in aquatic ecosystems, including pharmaceuticals, personal care products, agricultural and industrial chemicals. Risk assessment based on chemical mixtures is still default in many monitoring studies, with decisions being based solely on a chemical-by-chemical basis. The present study aimed to improve risk assessment procedures in water bodies by focusing on mixtures of chemical substances of different origins. The goal was to analyze potential interactions occurring at different complexity levels (binary and quaternary mixtures) using standardised toxicity assays. Mixture toxicity effects were assessed using Daphnia magna as the model organism and the compounds sodium fluoride, boric acid, ammonium hydroxide and acetaminophen as general representatives of contaminants in the aquatic ecosystem. The results revealed interactions between the compounds, mainly showing antagonism but also dose level and dose ratio-dependent deviations. Overall antagonism was the dominant deviation pattern, particularly at low doses, though synergism was also detected at higher doses or specific ratios. Synergism at low doses was found for the binary mixture of ammonium hydroxide and acetaminophen, two common pollutants, which denotes an enhanced risk to aquatic ecosystems. Independent Action provided more accurate predictions for the quaternary mixture, whereas Concentration Addition overestimated the toxicity of the mixture. Regarding the environmental risk assessment of water bodies, the interaction between chemicals in a mixture should not be neglected. The complexity of the mixture interactions found in the present study highlights the importance of complementing chemical screenings of water bodies with mixture toxicity data, particularly when considering chemicals of multiple origins whose joint action remains unknown.

Site-specific hazard evaluation for improved groundwater risk assessment.

Groundwater represents one of the most important natural water resources worldwide. Contamination is a key driver in sustaining water quality to populations and the environment. Therefore, it is crucial to look at contamination and potential effects. Within the WaterJPI project "We-Need - WatEr NEEDs, Availability, Quality and Sustainability", the Cremona and the Bologna Aquifers (Italy) were chosen as case studies since both aquifers represent two major Italian water resources of the Emilia-Romagna region. Aiming for a site-specific groundwater hazard assessment, the groundwaters from the Cremona and Bologna aquifers were simulated by preparing synthetic waters, CSW and BSW, respectively. Boron (as boric acid), fluoride (as sodium fluoride), and ammonium (as ammonium hydroxide), detected in the aquifers, were used to assess potential negative impacts on groundwater systems using aquatic organisms. Acute toxicity tests with Daphnia magna and Fish Embryo Toxicity Tests (FET) with Danio rerio were performed in the CSW and BSW synthetic waters and respective culture media, and toxicity was assessed for each organism. Boron, fluoride and ammonium had no ecological hazard effects at the concentrations detected in the groundwaters. Besides, a crucial result from this study regards the use of different media when addressing toxicity assessment. In this case, it was observed that toxicity was media and organism dependent. Therefore, adapting testing protocols for higher relevance should be considered for site-specific hazard assessment.

Fire Suppression Agents Combined with Gasoline in Aquatic Ecosystems: A Mixture Approach.

Fire suppression agents are recommended for extinguishing fires by flammable liquids and frequently end in water bodies, combined with the fuels. There is a lack of toxicity information on these commercial formulations and the effects of mixtures of fire suppression agents and fuels. The aim of the present study was to evaluate the toxic effects of different fire suppression agents, the gasoline water-soluble fraction (GWSF), and mixtures of each fire suppression agent and GWSF. Individual tests were performed with Daphnia similis and Artemia sp.; the most toxic fire suppression agents to D. similis and Artemia sp. were F-500®, Cold Fire®, Agefoam®, and Kidde Sintex® 1%; the GWSF was the least toxic. The concentration addition model was used to predict the mixture effects and evaluate synergism/antagonism, dose ratio dependence, and dose level dependence. Cold Fire with GWSF showed dose level deviation to D. similis, marked mainly by synergism; for Artemia sp., the dose ratio pattern was predicted, with a synergistic response mainly by Cold Fire. Agefoam and GWSF behaved additively for D. similis and dose ratio for Artemia sp., with synergism being caused by Agefoam. Kidde Sintex 1% with GWSF were dose ratio for both organisms, with Kidde Sintex 1% being responsible for synergism. Our results show that some mixtures of fire suppression agents and GWSF may cause toxicity to aquatic organisms, posing risk in a real environmental scenario, such as a major fire combat. Environ Toxicol Chem 2021;40:767-779. © 2020 SETAC.

Effects of the organic UV-filter, 3-(4-methylbenzylidene) camphor, on benthic invertebrates and ecosystem function in artificial streams.

In the last decades, the use of organic ultraviolet-filters (UV-filters) has increased worldwide, and these compounds are now considered emerging contaminants of many freshwater ecosystems. The present study aimed to assess the effects of 3-(4-methylbenzylidene) camphor (4-MBC) on a freshwater invertebrate community and on associated ecological functions. For that, artificial streams were used, and a natural invertebrate benthic community was exposed to sediments contaminated with two concentrations of 4-MBC. Effects were evaluated regarding macroinvertebrate abundance and community structure, as well as leaf decomposition and primary production. Results showed that the macroinvertebrate community parameters and leaf decomposition rates were not affected by 4-MBC exposure. On the other hand, primary production was strongly reduced. This study highlights the importance of higher tier ecotoxicity experiments for the assessment of the effects of low concentrations of organic UV-filters on freshwater invertebrate community structure and ecosystem functioning.

Two-generational effects of Benzophenone-3 on the aquatic midge Chironomus riparius.

Organic UV-filters are emergent contaminants continuously released into the aquatic ecosystems. These compounds are persistent showing potential for bioaccumulation. Partial life-cycle tests may underestimate the toxicity of UV-filters especially since these compounds have shown to act as endocrine disruptors. In the present study, the benthic aquatic insect Chironomus riparius was exposed to a gradient of Benzophenone-3 (BP3) concentrations over two generations to assess effects over a full life cycle from the first-instar larvae in the parental (P) generation (emergence, fecundity and fertility) until emergence in the subsequent generation (filial - F1). Recovery from exposure was also assessed after one generational exposure. Our results showed that concentrations of up to 8mg BP3/kg, elicited no effects regarding emergence rate and development time of C. riparius in the P generation. Our results also showed that C. riparius fecundity was not affected by BP3 exposure, but a strong dose-response relationship was observed for fertility with none of the egg ropes hatching at 8mg BP3/kg. Regarding effects observed in the F1 generation, emergence and development time were impaired by continuous exposure to BP3. Moreover, reduced emergence and changes in development time were observed in the F1 generation maintained in control/clean conditions but whose parents were exposed to BP3. Results found in this two-generational study clearly show reproductive effects of BP3 on C. riparius that would not be detected using standard tests. Full life cycle and multigenerational assays are critical to properly evaluate the population level effects of endocrine disrupting compounds such as organic UV-filters.

Long-term exposure of Daphnia magna to carbendazim: how it affects toxicity to another chemical or mixture.

Aquatic organisms might be exposed episodically or continuously to chemicals for long-term periods throughout their life span. Pesticides are one example of widely used chemicals and thus represent a potential hazard to aquatic organisms. In addition, these chemicals may be present simultaneously in the environment or as pulses, being difficult to predict accurately how their joint effects will take place. Therefore, the aim of the present study was to investigate how Daphnia magna (clone k6) exposed throughout generations to a model pesticide (the fungicide carbendazim) would react upon an exposure to another chemical compound (triclosan) and to a mixture of both chemicals (carbendazim and triclosan). Responses of daphnids continuously exposed to carbendazim and kept in clean medium will be compared using immobilization tests and the comet assay (DNA integrity). The results showed that triclosan presented similar toxicity to daphnids exposed for 12 generations (F12) to carbendazim (similar 48-h-LC50 values for immobilization data), when compared with daphnids kept in clean medium. However, at subcellular level, daphnids previously exposed to carbendazim for 12 generations (F12) showed different responses than those from clean medium, presenting a higher toxicity; a general higher percentage of DNA damage was observed, after exposure to a range of concentrations of triclosan and to the binary combination of triclosan + carbendazim. The patterns of toxicity observed for the binary mixture triclosan + carbendazim were generally similar for daphnids in clean medium and daphnids exposed to carbendazim, with a dose level deviation with antagonism observed at low doses of the chemical mixture for the immobilization data and a dose ratio deviation with synergism mainly caused by triclosan for DNA damage. With this study, we contributed to the knowledge on long-term induced effects of carbendazim exposure, while looking at the organismal sensitivity to another chemical (triclosan) and to a mixture of carbendazim and triclosan using lethality as an endpoint at the individual level and DNA damage as a subcellular endpoint.

Multigenerational effects of carbendazim in Daphnia magna: From a subcellular to a population level.

Anthropogenic activities such as the use of pesticides may affect aquatic biota populations, due to potential agricultural runoffs or disposals. Carbendazim is one example of a widely used fungicide with a high potential to end up in aquatic ecosystems through runoff. Deleterious effects observed at the individual level are possibly explained by changes in homeostasis at the cellular level, and both factors can then be used to predict effects at the population level. In the present study, an isoclonal population of Daphnia magna (clone K6) was exposed to a concentration that mimics relevant levels of carbendazim in the environment over 12 generations. The effects of carbendazim were assessed in some generations using the following endpoints: biochemical biomarkers (cholinesterase, catalase, and glutathione-S-transferase), lipid peroxidation and energy-related parameters (carbohydrates, lipids, and proteins along with available energy and energy consumption), parental longevity, and population growth (r). Long-term exposure to carbendazim had no effect on the intrinsic rate of natural increase (r) of adult D. magna, but longevity was decreased at the F12 generation compared to that of control. Differences between the exposed and nonexposed populations were found for cholinesterase, glutathione-S-transferase, and lipid peroxidation. However, for catalase and energy-related parameters, no differences were observed between these 2 populations. Natural variability was seen throughout the test period, under control conditions, within the 12 generations. Overall, carbendazim induced some effects at the subcellular level that translated into changes in longevity but these later vanished in terms of population effects. Environ Toxicol Chem 2019;38:412-422. © 2018 SETAC.