Assessment of the reproduction of six collembolan species in tropical soils naturally rich in potentially toxic elements

Laboratory ecotoxicological tests are important tools for the management of environmental changes derived from anthropogenic activities. Folsomia candida is usually the model species used in some procedures. However, this species may not be sufficiently representative of the sensitivity of the other collembolan species. This study aimed to evaluate (i) the effects of soils naturally rich in potentially toxic elements (PTE) and soil characteristics on the reproduction and survival of different collembolan species, (ii) whether the habitat function of these soils is compromised, and (iii) to what extent F. candida is representative of the other collembolan species. For this, reproduction tests with six collembolan species were conducted in 14 different samples of soils. In general, collembolan reproduction was not completely inhibited in none of the natural tested soils. Even soils with high pollution load index values did not negatively affect collembolan reproduction for most of the species. In contrast, the lowest collembolan reproduction rates were found in a visually dense soil (lowest volume/weight ratio), highlighting that soil attributes other than total PTE concentration also interfere in the reproduction of collembolans. Our results support the idea that the F. candida species might not be representative of other collembolan species and that laboratory tests to assess soil contaminations should be conducted using diverse collembolan species.

Evaluation of the ecotoxicological effects of biogenic amines derived from cadaverous putrefaction on springtails Folsomia candida

Necro-leachate, a liquid released during cadaveric decomposition, is considered the main culprit for impacts on cemetery environments. The biogenic amines cadaverine and putrescine make up part of the composition of necro-leachate and have a certain toxicity to different organisms. Springtails are among the most used bioindicators to assess the impacts of soil contaminants. As there are no data on the acute and chronic toxicity of springtails exposed to cadaverine and putrescine, the objective of this study was to evaluate the toxic potential of both amines, under the behavioral effect of avoidance and reproduction in the species Folsomia candida. Springtails were exposed to soils contaminated with different concentrations of cadaverine and putrescine, and different mixtures of these amines. To evaluate the avoidance and reproduction test, the individuals were exposed for periods of 48 h and 28 days, respectively. The results obtained in the avoidance test showed that springtails exhibited a preference for the treated soil in both isolated and mixed treatments. The chronic evaluation assays showed that the reproduction was affected, particularly in the treatments with combined amines, resulting in a reduction in the total number of juveniles. From the results, it is possible to infer that the methods applied in this research have provided information that will contribute to a better understanding of the toxicity of putrefactive biogenic amines, since there exist few ecotoxicological studies carried out with these amines, and especially with those from cemetery environments.

From the importance of organic carbon in reproduction tests with Eisenia fetida

The standard Eisenia fetida chronic toxicity reproduction test is normalized and needs up to 8 weeks of experimentation. Many matrixes have shown toxic effects on the earthworms' survey, growth and reproduction. But the food factor may affect the organisms' responses to contaminated media in such tests. We try to evaluate the effect, or not, of the organic carbon content present in the environment, as spreadable organic wastes added in soil, on the reproduction test of Eisenia fetida. We confirm the influence of the organic matter content on earthworm reproduction. This "food" factor must be considered when studying environmental samples rich in organic matter, since that could mask potentially harmful effects. To minimize this potential "food" effect during reproduction tests, we recommend an inverse gradient of organic matter contribution by the "horse dung" food applied in all conditions according to the dose of agricultural amendments tested.

Variation in chronic nickel toxicity to Daphnia magna among Japanese river waters and performance evaluation of bioavailability models in predicting the toxicity

Nickel (Ni) ecotoxicity is dictated by water chemistry characteristics such as pH, water hardness, and amount of dissolved organic carbon. Bioavailability models have been developed to predict Ni toxicity and validated for European, Australian, and US natural waters. In this study, chronic toxicity tests in Ni-spiked Japanese river waters were conducted on a strain of Daphnia magna to test whether the chronic toxicity differs among Japanese natural waters with different water chemistries. Based on the results of chronic Ni toxicity tests, we assessed the performance of existing D. magna bioavailability models, which were developed in artificial waters (Model 1) and calibrated in European natural waters (Model 2), in terms of the accuracy and the bias of model predictions. Furthermore, we also calibrated the two models by using toxicity test results to develop a bioavailability model for Ni chronic toxicity to the strain of D. magna in Japanese river waters. The 10%, 20%, and 50% effect concentrations (EC₁₀, EC₂₀, and EC₅₀) of dissolved Ni on reproduction of the D. magna strain were within ranges from 8.1 to 44.9 μg/L, 9.0 to 57.1 μg/L, and 10.9 to 86.1 μg/L, respectively. Results indicate that differences in water chemistry among Japanese river waters influenced chronic Ni toxicity to the model organism. Model 1predicted 43% of the observed EC₁₀, EC₂₀, and EC₅₀ values within a factor of 2 and 100%, 100%, and 43% within a factor of 3, respectively. Model 2 predicted 14%, 14%, and 29% of the observed EC₁₀, EC₂₀, and EC₅₀ values within a factor of 2 and 43% within a factor of 3. The values of model bias based on the geometric mean of ratios of EC₁₀, EC₂₀ and EC₅₀ values predicted by each of the two models and observed EC₁₀, EC₂₀, and EC₅₀ values were 0.71, 0.65, and 0.62 for Model 1 and 0.27, 0.26, and 0.29 for Model 2, respectively. After calibrating two models using the results of toxicity tests, refined Model 1 predicted 71%, 57%, and 57% of observed EC₁₀, EC₂₀, and EC₅₀ values within a factor of 2 and 100%, 86%, and 100% within a factor of 3; refined Model 2 predicted 71% of observed EC₁₀, EC₂₀, and EC₅₀ values within a factor 2 and 100%, 86%, and 86% within a factor of 3, respectively. Our results indicate that calibrating the Ni bioavailability models in Japanese natural waters increased their predictive capacity by a factor of up to approximately five.

Comparison of earthworm responses to petroleum hydrocarbon exposure in aged field contaminated soil using traditional ecotoxicity endpoints and 1H NMR-based metabolomics

(1)H NMR metabolomics and conventional ecotoxicity endpoints were used to examine the response of earthworms exposed to petroleum hydrocarbons (PHCs) in soil samples collected from a site that was contaminated with crude oil from a pipeline failure in the mid-1990s. The conventional ecotoxicity tests showed that the soils were not acutely toxic to earthworms (average survival ≥ 90%), but some soil samples impaired reproduction endpoints by >50% compared to the field control soil. Additionally, metabolomics revealed significant relationships between earthworm metabolic profiles (collected after 2 or 14 days of exposure) and soil properties including soil PHC concentration. Further comparisons by partial least squares regression revealed a significant relationship between the earthworm metabolomic data (collected after only 2 or 14 days) and the reproduction endpoints (measured after 63 days). Therefore, metabolomic responses measured after short exposure periods may be predictive of chronic, ecologically relevant toxicity endpoints for earthworms exposed to soil contaminants.