Soil habitat function after innovative nanoagriproducts application: Effect of ageing on the avoidance behaviour of the soil invertebrates Enchytraeus crypticus and Folsomia candida

Research on nanotechnology with applications in agriculture has been gathering attention because it may achieve a good balance between agricultural production and environmental integrity. Among the vast nanomaterials, layered double hydroxides (LDHs) are a promising solution for supplying crops with macro- and/or micronutrients. Still, little is known about their safety implications for non-target organisms, such as soil invertebrates. The habitat function of soils might be impacted by potential stressors, which can be assessed through avoidance behaviour tests. This study aimed to assess the effect of two innovative agriproducts, Zn-Al-NO3 LDH and Mg-Al-NO3 LDH, on the avoidance behaviour of the enchytraeid Enchytraeus crypticus and the collembolan Folsomia candida, over time. Simultaneously, Zn and Mg potential release from LDHs to soil was evaluated. Overall, the behaviour of soil invertebrates differed between species, with enchytraeids being more sensitive to LDHs-treated soils than collembolans, possibly explained by their different physiological traits. The behaviour of soil organisms also depended on the LDH structural composition and was time-variable. Soil treated with Zn-Al-NO3 LDH was perceived as less favourable compared to Mg-Al-NO3 LDH, which was preferred to clean soil at most tested concentrations. LDHs toxicity was partly, but not exclusively, related to Zn and Mg release. Cations release over time was demonstrated in the chemical assessment. Still, LDHs toxicity to soil invertebrates decreased as increasing AC50 values were derived over time. Slower dissolution over time might explain the decrease in toxicity. Our study demonstrates that both soil invertebrates could sense LDHs in soil and eventually adapt their behaviour by avoiding or preferring, according to the type and level of LDH present.

Influence of soil organic matter content on the toxicity of pesticides to soil invertebrates: A review

A better understanding of how soil organic matter (OM) content influences pesticide toxicity to soil invertebrates is needed to improve the ecological relevance of risk assessment approaches. In the current study, soil invertebrate toxicity data (LC50 and EC50 values) were collected from studies determining the toxicity of organic chemicals in soils with varying OM content. Relevant studies were identified by performing a literature search and through the use of toxicity databases. The data were used to address the following questions: (1) Can the relationship between toxicity and soil OM content be quantified? (2) Does soil OM content influence different toxicity endpoints in a similar way? (3) Is the influence of soil OM content on sensitivity to pesticides different between species? The results indicate that toxicity-OM relationships are chemical dependent, differ between endpoints, and are species-specific. Hence, the grouping of chemicals based solely on their lipophilicity, as well as having only one correction factor for multiple species, may not be an appropriate approach to risk assessment. Integr Environ Assess Manag 2023;19:1457-1472. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

The contributions of enchytraeids and earthworms to the soil mineralization process in soils with fungicide

Pesticides may harm soil organisms such as earthworms and enchytraeids, but knowledge is lacking on their relative sensitivity to these chemicals and the consequences on soil functions. The aim of this study was to assess the impact of exposure to a commercial fungicide formulation (Swing® Gold, containing dimoxystrobin and epoxiconazole) on the function of earthworms (Aporrectodea caliginosa) and enchytraeids (Enchytraeus buchholzi) in soil organic matter (SOM) mineralization. The soil organisms were incubated alone and together in a 26-day laboratory experiment. At the recommended field rate, the fungicide induced a decrease in the SOM mineralization and a delay in the maximum daily CO₂ emissions compared to the control soil without fungicide. Soil fauna also influenced SOM mineralization with a higher cumulated CO₂ release after 26 days in the control soil with earthworms (by 21%) than without fauna. When both earthworms and enchytraeids were present, SOM mineralization did not increase, and there was a negative effect on earthworm weight gain. Finally, an alteration of fauna influence with treatment was observed from day 19, meaning that the effect of fauna on SOM mineralization changed with fungicide treatment. Earthworms no longer promoted SOM mineralization when fungicide was present at three-fold the recommended field rate. The effects of enchytraeids on SOM mineralization were similar with and without fungicide exposure. This study underlines the importance of considering the relative sensitivity of soil organisms to environmental factors and interactions between them when assessing soil functioning.

Chronic effects of clothianidin to non-target soil invertebrates: Ecological risk assessment using the species sensitivity distribution (SSD) approach

This study aimed to assess the chronic toxicity and risk of clothianidin in a seed dressing formulation to non-target soil invertebrates. The toxicity assays were performed with two oligochaetes (earthworms Eisenia andrei and enchytraeids Enchytraeus crypticus) and three collembolans (Folsomia candida, Proisotoma minuta and Sinella curviseta) species following ISO protocols. Risk assessment (via Hazard Quotient approach - HQ) was based on the hazardous concentrations for 95% of the species (HC₅), derived from chronic Species Sensitivity Distributions (SSD) for clothianidin, and on its predicted environmental concentrations (PEC). Four SSD scenarios were generated with literature and/or this study data, following different data selection criteria (i.e., general, only data from tests using similar formulations, similar soils, or identical soil/formulation). In our experiments, a higher clothianidin toxicity (EC₅₀-based) was found for collembolans (varying from 0.11 to 0.28 mg kg^-1 between species) followed by the earthworms (4.35 mg kg^-1), while the enchytraeids were the least sensitive (33.5 mg kg^-1). HQ indicated a significant risk of clothianidin to soil invertebrates because the estimated PEC were at least 16.6 times higher than HC₅ and are expected to affect the whole group of collembolans. Despite the criteria for data inclusion have influenced the HC₅ values, no substantial changes were observed for the risk outcomes. To our knowledge, this is the first study assessing the chronic ecological risk of clothianidin to beneficial soil fauna based on a probabilistic SSD approach. Data from this study can help to derive more reliable protection thresholds for clothianidin in soils.

Multiomics assessment in Enchytraeus crypticus exposed to Ag nanomaterials (Ag NM300K) and ions (AgNO3) - Metabolomics, proteomics (& transcriptomics)

Silver nanomaterials (AgNMs) are broadly used and among the most studied nanomaterials. The underlying molecular mechanisms (e.g. protein and metabolite response) that precede phenotypical effects have been assessed to a much lesser extent. In this paper, we assess differentially expressed proteins (DEPs) and metabolites (DEMs) by high-throughput (HTP) techniques (HPLC-MS/MS with tandem mass tags, reversed-phase (RP) and hydrophilic interaction liquid chromatography (HILIC) with mass spectrometric detection). In a time series (0, 7, 14 days), the standard soil model Enchytraeus crypticus was exposed to AgNM300K and AgNO₃ at the reproduction EC20 and EC50. The impact on proteins/metabolites was clearly larger after 14 days. NM300K caused more upregulated DEPs/DEMs, more so at the EC20, whereas AgNO₃ caused a dose response increase of DEPs/DEMs. Similar pathways were activated, although often via opposite regulation (up vs down) of DEPs, hence, dissimilar mechanisms underlie the apical observed impact. Affected pathways included e.g. energy and lipid metabolism and oxidative stress. Uniquely affected by AgNO₃ was catalase, malate dehydrogenase and ATP-citrate synthase, and heat shock proteins (HSP70) and ferritin were affected by AgNM300K. The gene expression-based data in Adverse Outcome Pathway was confirmed and additional key events added, e.g. regulation of catalase and heat shock proteins were confirmed to be included. Finally, we observed (as we have seen before) that lower concentration of the NM caused higher biological impact. Data was deposited to ProteomeXchange, identifier PXD024444.

Microplastic fibers influence Ag toxicity and bioaccumulation in Eisenia andrei but not in Enchytraeus crypticus

Microplastic fibers (MF) are released from synthetic textiles during washing and end up in the wastewater. Similarly, silver nanoparticles (AgNP), incorporated in textiles as antimicrobial agents, are released in washing machines, also reaching the wastewater treatment plants. Therefore, both MF and AgNP co-exist in the environment and enter the soil compartment mainly via the application of biosolids. Yet, the combined effect of MF and AgNP has not been studied. Here, we assessed the effects of polyester MF on the toxicity of AgNP and AgNO₃ to the earthworm Eisenia andrei and the enchytraeid Enchytraeus crypticus. The organisms were exposed to a range of concentration of AgNP (32, 100, 320, 1000, 3200 mg Ag/kg) and AgNO₃ (12.8, 32, 80, 200, 500 mg Ag/kg) in LUFA 2.2 soil in the absence or presence of MF (0.01% DW). Reproduction tests were conducted and the toxicity outcomes compared between soils with and without MF. The exposure to MF caused a decrease in the number of juveniles and changed the biochemical composition of earthworms. Moreover, the presence of MF increased the toxicity of AgNP to earthworm reproduction (EC50 = 165 mg Ag/kg) when compared to AgNP exposure alone (EC50 = 450 mg Ag/kg), but did not alter the toxicity of AgNO₃ (EC50 = 40 mg Ag/kg). For enchytraeids, no significant difference in Ag toxicity could be detected when MF was added to the soil for both AgNP and AgNO₃. Overall, Ag bioaccumulation was not affected by MF, except for a decrease in earthworm body concentration at the highest Ag soil concentration (3200 mg Ag/kg). Our results suggest that the presence of MF in the soil compartment may be a cause of concern, and that the joint exposure to Ag may be deleterious depending on the Ag form, organism, and endpoint. The present work provides the first evidence that a realistic MF concentration in soil lowers AgNP concentration necessary to provoke reproductive impairment in earthworms. The influence of MF on the risk assessment of AgNP should be considered.

Toxicokinetics of copper and cadmium in the soil model Enchytraeus crypticus (Oligochaeta)

Toxicokinetics information is key to understanding the underlying intoxication processes, although this is often lacking. Hence, in the present study the toxicokinetics of copper (Cu) and cadmium (Cd) was assessed in the soil invertebrate Enchytraeus crypticus. The animals were exposed in LUFA 2.2 natural soil spiked to the estimated EC₂₀ for reproduction effects in the Enchytraeid Reproduction Test (ERT), i.e. 80 mg Cu/kg soil Dry Weight (DW) and 20 mg Cd/kg soil DW. Tests followed the OECD guideline 317, including a 14-day uptake phase in spiked soil followed by 14 days elimination in clean soil, with samplings at days 0, 1, 2, 4, 7, 10, and 14. Exposure to Cu showed fast uptake, reaching a steady state after approx. 7 days, whereas for Cd, internal concentration increased and did not reach a clear steady state even after 14 days. When transferred to clean soil, Cu was rapidly eliminated returning to initial levels, while Cd-exposed animals still contained increased residue levels after 14 days. These differences in toxicokinetics have consequences for the toxicity and toxicodynamics and are indicative of the way essential and non-essential elements are handled by enchytraeids, likely also other soil invertebrates. This argues for the relevancy of longer exposure testing for elements like Cd compared to Cu, where phenotypical effects can well occur later at non-tested periods, e.g. after the 21 days' duration of the standard ERT using E. crypticus.

Testing of Eluates from Waterproof Building Materials for Potential Environmental Effects Due to the Behavior of Enchytraeus albidus

In order to determine the potential environmental impact of construction products, it is necessary to evaluate their influence on organisms exposed to them or their eluates under environmental conditions. The behavior of the white worm Enchytraeus albidus is a useful tool for assessing the potential environmental impact of construction products in contact with water and soil. This study investigates the environmental effects of eluates from two construction products, a reactive waterproofing product, and an injection resin, on the reproduction and avoidance behavior of E. albidus. The eluates were prepared according to existing guidelines. The soil used for the tests was moistened with the eluates of the construction products. The reproduction results of the worms were collected after six weeks of exposure. Offsprings were counted under the microscope and statistically analyzed. Results from the avoidance behavior were collected after 48 h of exposure, and results were compared with the reproduction results. The eluates from both construction products induced significant changes in the reproduction behavior of E. albidus. Undiluted or only slightly diluted eluates of the injection resin drastically reduced the reproduction of the worms, whereas the leaches of the reactive waterproofing product only had a minor effect. The avoidance results for the injection resin indicates that its presence in the habitat is clearly detrimental to the survival of E. albidus, while the avoidance results for the waterproofing resin showed an initial avoidance of the eluates, but no harmful effects were observed. The avoidance test is a way of rapid toxicity screening of environmental samples when time is a critical parameter to measure possible environmental effects. This study shows that ecotoxicological tests using Enchytraeids are a valuable and important tool for understanding the mode of action of eluates from construction products in the environment.

Impacts on reproduction of Enchytraeus crypticus in fertilized soils with chicken litter treated with synthetic and natural insecticide

Poultry litter is used as a fertilizer due to the high concentration of nutrients. However, this material receives application of medicines, whether they are used to treat animals or the litter itself. Thus, the objective was to evaluate if the application in soils of poultry litter doses treated with two insecticides (cypermethrin and cinnamon oil) used to control of the Alphitobius diaperinus, affect the reproduction of Enchytraeus crypticus, and the insecticides effects over time, trough of ecotoxicological tests using soils with different textural classes an Entisol and an Oxisol. In the Oxisol the application of poultry litter stimulated the E. crypticus reproduction regardless of the insecticide and the collection time. In Entisol the poultry litter showed a toxicity at 10 t ha^-1 when treated with cypermethrin and at 30 t ha^-1 with cinnamon oil. Entisol results show that cypermethrin affects non-target edaphic organisms soon after spraying, but over time has reduced toxicity unlike cinnamon oil.

Assessing toxicity of metal contaminated soil from glassworks sites with a battery of biotests

The present study addresses toxicological properties of metal contaminated soils, using glassworks sites in south-eastern Sweden as study objects. Soil from five selected glassworks sites as well as from nearby reference areas were analysed for total and water-soluble metal concentrations and general geochemical parameters. A battery of biotests was then applied to assess the toxicity of the glassworks soil environments: a test of phytotoxicity with garden cress (Lepidium sativum); the BioTox™ test for toxicity to bacteria using Vibrio fischeri; and analyses of abundancies and biomass of nematodes and enchytraeids. The glassworks- and reference areas were comparable with respect to pH and the content of organic matter and nutrients (C, N, P), but total metal concentrations (Pb, As, Ba, Cd and Zn) were significantly higher at the former sites. Higher metal concentrations in the water-soluble fraction were also observed, even though these concentrations were low compared to the total ones. Nevertheless, toxicity of the glassworks soils was not detected by the two ex situ tests; inhibition of light emission by V. fischeri could not be seen, nor was an effect seen on the growth of L. sativum. A decrease in enchytraeid and nematode abundance and biomass was, however, observed for the landfill soils as compared to reference soils, implying in situ toxicity to soil-inhabiting organisms. The confirmation of in situ bioavailability and negative effects motivates additional studies of the risk posed to humans of the glassworks villages.

Comparative toxicity of imidacloprid and thiacloprid to different species of soil invertebrates

Neonicotinoid insecticides have come under increasing scrutiny for their impact on non-target organisms, especially pollinators. The current scientific literature is mainly focused on the impact of these insecticides on pollinators and some aquatic insects, leaving a knowledge gap concerning soil invertebrates. This study aimed at filling this gap, by determining the toxicity of imidacloprid and thiacloprid to five species of soil invertebrates: earthworms (Eisenia andrei), enchytraeids (Enchytraeus crypticus), Collembola (Folsomia candida), oribatid mites (Oppia nitens) and isopods (Porcellio scaber). Tests focused on survival and reproduction or growth, after 3-5 weeks exposure in natural LUFA 2.2 standard soil. Imidacloprid was more toxic than thiacloprid for all species tested. F. candida and E. andrei were the most sensitive species, with LC50s of 0.20-0.62 and 0.77 mg/kg dry soil for imidacloprid and 2.7-3.9 and 7.1 mg/kg dry soil for thiacloprid. EC50s for effects on the reproduction of F. candida and E. andrei were 0.097-0.30 and 0.39 mg/kg dry soil for imidacloprid and 1.7-2.4 and 0.44 mg/kg dry soil for thiacloprid. The least sensitive species were O. nitens and P. scaber. Enchytraeids were a factor of 5-40 less sensitive than the taxonomically related earthworm, depending on the endpoint considered. Although not all the species showed high sensitivity to the neonicotinoids tested, these results raise awareness about the effects these insecticides can have on non-target soil invertebrates.

Mercury critical concentrations to Enchytraeus crypticus (Annelida: Oligochaeta) under normal and extreme conditions of moisture in tropical soils - Reproduction and survival

Soil provides many ecosystem services that are essential to maintain its quality and healthy development of the flora, fauna and human well-being. Environmental mercury levels may harm the survival and diversity of the soil fauna. In this respect, efforts have been made to establish limit values of mercury (Hg) in soils to terrestrial fauna. Soil organisms such as earthworms and enchytraeids have intimate contact with trace metals in soil by their oral and dermal routes, reflecting the potentially adverse effects of this contaminant. The main goal of this study was to obtain Hg critical concentrations under normal and extreme conditions of moisture in tropical soils to Enchytraeus crypticus to order to assess if climate change may potentiate their acute and chronic toxicity effects. Tropical soils were sampled from of two Forest Conservation Units of the Rio de Janeiro State - Brazil, which has been contaminated by Hg atmospheric depositions. Worms were exposed to three moisture conditions, at 20%, 50% and 80% of water holding capacity, respectively, and in combination with different Hg (HgCl₂) concentrations spiked in three types of tropical soil (two natural soils and one artificial soil). The tested concentrations ranged from 0 to 512mg Hg kg^-1 dry weight. Results indicate that the Hg toxicity is higher under increased conditions of moisture, significantly affecting survival and reproduction rate.

Influence of climate change on the multi-generation toxicity to Enchytraeus crypticus of soils polluted by metal/metalloid mining wastes

This study aimed at assessing the effects of increased air temperature and reduced soil moisture content on the multi-generation toxicity of a soil polluted by metal/metalloid mining wastes. Enchytraeus crypticus was exposed to dilution series of the polluted soil in Lufa 2.2 soil under different combinations of air temperature (20 °C and 25 °C) and soil moisture content (50% and 30% of the soil water holding capacity, WHC) over three generations standardized on physiological time. Generation time was shorter with increasing air temperature and/or soil moisture content. Adult survival was only affected at 30% WHC (∼30% reduction at the highest percentages of polluted soil). Reproduction decreased with increasing percentage of polluted soil in a dose-related manner and over generations. Toxicity increased at 30% WHC (>50% reduction in EC₅₀ in F0 and F1 generations) and over generations in the treatments at 20 °C (40-60% reduction in EC₅₀ in F2 generation). At 25 °C, toxicity did not change when combined with 30% WHC and only slightly increased with 50% WHC. So, higher air temperature and/or reduced soil moisture content does affect the toxicity of soils polluted by metal/metalloid mining wastes to E. crypticus and this effect may exacerbate over generations.

Toxicity of a metal(loid)-polluted agricultural soil to Enchytraeus crypticus changes under a global warming perspective: Variations in air temperature and soil moisture content

This study aimed to assess how the current global warming perspective, with increasing air temperature (20°C vs. 25°C) and decreasing soil moisture content (50% vs. 30% of the soil water holding capacity, WHC), affected the toxicity of a metal(loid)-polluted agricultural soil to Enchytraeus crypticus. Enchytraeids were exposed for 21d to a dilution series of the agricultural soil with Lufa 2.2 control soil under four climate situations: 20°C+50% WHC (standard conditions), 20°C+30% WHC, 25°C+50% WHC, and 25°C+30% WHC. Survival, reproduction and bioaccumulation of As, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn were obtained as endpoints. Reproduction was more sensitive to both climate factors and metal(loid) pollution. High soil salinity (electrical conductivity~3dSm^-1) and clay texture, even without the presence of high metal(loid) concentrations, affected enchytraeid performance especially at drier conditions (≥80% reduction in reproduction). The toxicity of the agricultural soil increased at drier conditions (10% reduction in EC10 and EC50 values for the effect on enchytraeid reproduction). Changes in enchytraeid performance were accompanied by changes in As, Fe, Mn, Pb and Zn bioaccumulation, with lower body concentrations at drier conditions probably due to greater competition with soluble salts in the case of Fe, Mn, Pb and Zn. This study shows that apart from high metal(loid) concentrations other soil properties (e.g. salinity and texture) may be partially responsible for the toxicity of metal(loid)-polluted soils to soil invertebrates, especially under changing climate conditions.

Salinity changes impact of hazardous chemicals in Enchytraeus albidus

Supralittoral ecosystems are among the most challenging environments for soil organisms, particularly when salinity fluctuations are involved, frequently combined with the presence of contaminants as a result of intense anthropogenic activities. Knowledge of how salinity influences the effect of contaminants in supralittoral species is crucial for determining the safety factors required when extrapolating results from optimal laboratory conditions to these natural ecosystems. The present study therefore evaluated the effects of 2 metals (copper and cadmium) and 2 organic compounds (carbendazim and 4-nonylphenol) in the absence or presence of 15‰ NaCl in the potworm Enchytraeus albidus, a model organism for ecotoxicology studies commonly found in supralittoral ecosystems, The potworms had a higher reproduction in saline soil than in control soil. Moreover, the effects of copper and carbendazim on reproduction were smaller than when they were tested in nonsaline soil. Potworms exposed to nonsaline soils also had significantly higher tissue concentrations of metals, which partly explains the effects on reproduction. The influence of salinity on effects of 4-nonylphenol was, however, less clear; effects on survival decreased in saline soil, but effects on reproduction were highest in saline soil. The latter slightly correlated with tissue concentrations of the chemical. The present study provides the first evidence that soil salinity has a significant influence on the impact of contaminants evaluated with the enchytraeid reproduction test.

Species composition of a soil invertebrate multi-species test system determines the level of ecotoxicity

A soil multi-species, SMS, experimental test system consisting of the natural microbial community, five collembolan species and a predatory mite along with either Enchytraeus crypticus or the earthworm Eisenia fetida were exposed to α-cypermethrin. A comparison of the performance of these two types of SMSs is given to aid the development of a standard test system. E. fetida had a positive effect on the majority of the species, reducing the negative insecticide effect. E. fetida affected the species sensitivity and decreased the degradation of the insecticide due to the organic matter incorporation of earthworm food. After 8 weeks, the EC50 was 0.76 mg kg(-1) for enchytraeids and ranged between 2.7 and 18.9 mg kg(-1) for collembolans, more sensitive than previously observed with single species. Changes observed in the community structure and function illustrates the strength of a multi-species test system as an ecotoxicological tool compared to single species tests.