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.

Biogeographic responses and niche occupancy of microbial communities following long-term land-use change.

Understanding the effects of forest-to-agriculture conversion on microbial diversity has been a major goal in soil ecological studies. However, linking community assembly to the ruling ecological processes at local and regional scales remains challenging. Here, we evaluated bacterial community assembly patterns and the ecological processes governing niche specialization in a gradient of geography, seasonality, and land-use change, totaling 324 soil samples, 43 habitat characteristics (abiotic factors), and 16 metabolic and co-occurrence patterns (biotic factors), in the Brazilian Atlantic Rainforest, a subtropical biome recognized as one the world's largest and most threatened hotspots of biodiversity. Pairwise beta diversities were lower in pastures than in forest and no-till soils. Pasture communities showed a predominantly neutral model, regarding stochastic processes, with moderate dispersion, leading to biotic homogenization. Most no-till and forest microbial communities followed a niche-based model, with low rates of dispersal and weak homogenizing selection, indicating niche specialization or variable selection. Historical and evolutionary contingencies, as represented by soil type, season, and dispersal limitation were the main drivers of microbial assembly and processes at the local scale, markedly correlated with the occurrence of endemic microbes. Our results indicate that the patterns of assembly and their governing processes are dependent on the niche occupancy of the taxa evaluated (generalists or specialists). They are also more correlated with historical and evolutionary contingencies and the interactions among taxa (i.e., co-occurrence patterns) than the land-use change itself.

Ecotoxicological effects of untreated pig manure from diets with or without growth-promoting supplements on Eisenia andrei in subtropical soils.

This study aimed to evaluate the effects of untreated pig manure from diets incorporating growth-promoting supplements (antibiotics and Zn oxide) on the survival and reproduction of Eisenia andrei earthworms. The tested manures were obtained from four different groups of pigs fed with four different diets: CS, a diet based on corn and soymeal; TR, a diet based on corn, soymeal, and ground wheat (15%); CSa, a diet based on corn and soymeal + 100 ppm of doxycycline + 50 ppm of colistin + 2500 ppm of Zn oxide; and TRa, a diet based on corn, soymeal, and ground wheat (15%) + 100 ppm of doxycycline + 50 ppm of colistin + 2500 ppm of Zn oxide. The study used two soils representative of the Southern region of Brazil (Oxisol and Entisol). In general, there were no significant differences between the different manures tested in each soil. However, there were differences in the toxicity manure on E. andrei between the soils, and the magnitude of this effect was dependent on the applied dose. In Oxisol, LC50 values were higher than 80 m3 ha-1, and EC50 varied from 9 to 27 m3 ha-1. In Entisol, the LC50 values were below the lowest dose tested (< 25 m3 ha-1), and EC50 remained around 5 m3 ha-1. It may be possible that the effects observed were attributed to an excess of nitrogen, copper, and zinc, promoted by the addition of the untreated manure and how these factors interacted with soil type.

Biogeographic Patterns of Arbuscular Mycorrhizal Fungal Communities Along a Land-Use Intensification Gradient in the Subtropical Atlantic Forest Biome.

Information concerning arbuscular mycorrhizal (AM) fungal geographical distribution in tropical and subtropical soils from the Atlantic Forest (a global hotspot of biodiversity) are scarce and often restricted to the evaluation of richness and abundance of AM fungal species at specific ecosystems or local landscapes. In this study, we hypothesized that AM fungal diversity and community composition in subtropical soils would display fundamental differences in their geographical patterns, shaped by spatial distance and land-use change, at local and regional scales. AM fungal community composition was examined by spore-based taxonomic analysis, using soil trap cultures. Acaulospora koskei and Glomus were found as generalists, regardless of mesoregions and land uses. Other Acaulospora species were also found generalists within mesoregions. Land-use change and intensification did not influence AM fungal composition, partially rejecting our first hypothesis. We then calculated the distance-decay of similarities among pairs of AM fungal communities and the distance-decay relationship within and over mesoregions. We also performed the Mantel test and redundancy analysis to discriminate the main environmental drivers of AM fungal diversity and composition turnover. Overall, we found significant distance-decays for all land uses. We also observed a distance-decay relationship within the mesoregion scale (< 104 km) and these changes were correlated mainly to soil type (not land use), with the secondary influence of both total organic carbon and clay contents. AM fungal species distribution presented significant distance-decays, regardless of land uses, which was indicative of dispersal limitation, a stochastic neutral process. Although, we found evidence that, coupled with dispersal limitation, niche differentiation also played a role in structuring AM fungal communities, driven by long-term historical contingencies, as represented by soil type, resulting from different soil origin and mineralogy across mesoregions.

Increasing level of liquid pig manure reduces Eisenia andrei and Enchytraeus crypticus reproduction in subtropical soils.

Wastes generated in pig production are widely used as agricultural fertilizers. Nevertheless, such form of disposal supplies large amounts of waste in soils annually and can cause environmental pollution. The ecological risk of this practice to soil organisms has received little attention. Ecotoxicological tests are used to evaluate the toxicity of contaminants added to the soil biota. The aimed to evaluate the effect of liquid pig manure (LPM) on the reproduction of Eisenia andrei and Enchytraeus crypticus when applied in natural soils. LPM doses caused effects on earthworm reproduction in both soils, with EC50 of 112 and 150 m3 ha-1 in the Entisol and Nitosol, respectively. On enchytraeids, LPM had bigger effects, leading to EC50 of 17.7 and 45.0 m3 ha-1 in the Entisol and Nitosol, respectively. The results emphasize the importance to consider the ecological risks of LPM of conducting studies with natural soils and edaphic fauna as indicators.

Assessing the most sensitive and reliable endpoints in plant growth tests to improve arsenic risk assessment.

Arsenic (As) is toxic to humans and the environment. Its toxicity has been assessed in many ways, including plant growth tests integrated in As risk assessments (RA). The tiered approach used in RA schemes assumes that lower tiers are more conservative than higher tiers. Plant growth tests may comprise lower tier of a RA and include the measurement of several endpoints. However, only few of these endpoints are highly sensitive and reliable, which makes them more appropriate to comprise lower tiers. Therefore, the selection of those endpoints is needed. The present study aimed to evaluate the most appropriate endpoints of plant growth tests to use in lower tier As RA schemes. This selection of endpoints was based on their sensitivity and reliability, using different tropical soils and plant species. In order to achieve this objective, six plant species were exposed to eight levels of As contamination (0; 8; 14.5; 26; 46.5; 84; 150; 270 mg kg-1), in three different tropical soils (Oxisol, Inceptisol, and tropical artificial soil). The endpoints measured were: first germination count (FrC), plant height (PH), relative leaf area (RLA), stem diameter (SD), total germination (TG), germination speed index (GSI), dry mass (DM), number of completely expanded leaves (CEL), plant survival (PS), soil plant analysis development chlorophyll level (SPAD), and the final germination count (FnC). Toxic values for 50% of effect were estimated for each endpoint within each species and test soil, to rank them according to their sensitivity and reliability. The most sensitive endpoints were: FrC, RLA, DM, GSI, PH, and FnC, while the most reliable endpoints were: FrC, DM, GSI, DM, PH, FnC, and TG. Our findings suggest that FrC, DM, GSI, PH, and FnC are the most adequate endpoints to be used in plant growth tests as lower tiers of As RA in tropical regions.

Assessing the Brazilian prevention value for soil arsenic: Effects on emergence and growth of plant species relevant to tropical agroecosystems.

One of the entry routes of arsenic (As) into the food chain is through the consumption of edible parts of crops contaminated by this element. Different plant species present distinctive As accumulation and tolerance capacities. These differences are also influenced by As availability and speciation in soils. This study assessed the effect of As contamination on plant emergence and initial growth, as well as on accumulated As contents in different crops grown in tropical soils. In addition, it was intended to verify the protection level of the current soil As prevention value adopted in Brazil, which should be applicable for conceivably other tropical soils in Latin America. Plants of maize, rice, sorghum, common bean, sunflower, and radish were cultivated in two different tropical soils (Oxisol and Inceptisol) and in a standard substrate (tropical artificial soil - TAS) dosed with As (0; 8; 14.5; 26; 46.5; 84; 150; 270 mg kg-1). Early germination, total dry mass, As content, and bioconcentration factor were evaluated. The EC20 and EC50 values (the As concentration for 20% or 50% of effect relative to control treatment) based on total As concentration were more variable among different soils than the corresponding EC20 and EC50 values based on extractable (phytoavailable) As concentration. From the studied species, common bean was the most sensitive and maize was the least sensitive to As. Those species were the ones that accumulated the lowest As levels in shoot tissues. Arsenic concentrations measured in plant tissues and estimated bioaccumulation factors were not related to relative As toxicity among species. Data obtained suggest that the current Brazilian prevention value for arsenic is adequate for soils with high arsenic adsorption capacity.

Ecotoxicological effects of fipronil, neem cake and neem extract in edaphic organisms from tropical soil.

Veterinary medicines are widely applied for the treatment and prevention of animal diseases. Consequently, animal manure contains significant amounts of environmental pollutants that are potential sources of environmental pollution when inappropriately applied in soils. This work aimed to evaluate ecotoxicological effects of doses of commercial fipronil, neem cake and neem extract in the survival and reproduction of earthworms (Eisenia andrei), enchytraeidae (Enchytraeus crypticus) and springtails (Folsomia candida) in Oxisol and tropical artificial soil (TAS). Applications of fipronil, neem cake and extract in soil were carried out according to standardized ISO methodologies by using a random experimental design with five replicates. Toxic effects of fipronil for springtails in Oxisol and TAS were observed with LC50 of 0.26 mg kg-1 (0.18-0.35 mg kg-1) and 0.29 mg kg-1 (0.22-0.37 mg kg-1), respectively. It was not observed significant toxic effects of fipronil for earthworms and enchytraeidae in both soils. However, significant amounts of juvenile earthworm and adult enchytraeidae decreased in fipronil doses higher than 10 mg kg-1. Neem cake and extract were not toxic for earthworms and enchytraeidae but, significant amounts of juvenile springtails decreased in neem cake doses from 500 to 1000 mg kg-1. It can be concluded that the use of veterinary medicines containing synthetic compounds for preventing diseases in animals needs to be controlled to avoid environmental pollution after applying manure in soil. Veterinary medicines containing natural compounds as neem cake and extract are eco-friendly and could be efficiently applied in soil in a sustainable way.

Ecotoxicological effect of fipronil and its metabolites on Folsomia candida in tropical soils.

The aim of this study is to evaluate the toxicity of the fipronil and its metabolites, fipronil sulfone and fipronil desulfinyl on Folsomia candida. Three types of soils were used to perform the ecotoxicological tests, two natural soils (Oxisol and Entisol), and an artificial substrate (Tropical Artificial Soil). The treatments consisted of increasing doses of a veterinary medicinal product with active ingredient based on fipronil, and of its two main metabolites, fipronil sulfone and fipronil desulfinyl. The doses of fipronil were 0.00, 0.02, 0.04, 0.08, 0.15, 0.30, 0.60, and 1.00 mg kg-1 of the active ingredient. For fipronil sulfone and fipronil desulfinyl the doses tested were: 0.00, 0.01, 0.02, 0.04, 0.06, 0.08, 0.15, 0.30, 0.60, 1.00, and 5.00 mg kg-1. The effects of toxicity on F. candida were evaluated by survival and reproduction tests, based on the methods described by ISO 11267. There was a completely randomized design, with six replicates for the fipronil tests and eight for the metabolites. We show that fipronil and its metabolites, even at very low concentrations, are toxic to F. candida. Reduction of reproduction can be observed at concentrations of 0.15 mg kg-1. There was little difference in toxicity (LC50 and EC50) between fipronil and its metabolites. Rather, differences were related more to soil type, where the artificial soil was more sensitive than the two natural soils (Oxisol and Entisol). We conclude that it is important to perform ecotoxicological tests in natural soils, in order to generate more realistic representations of veterinary drug toxicity on the environment.

Placing arbuscular mycorrhizal fungi on the risk assessment test battery of plant protection products (PPPs).

Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts considered a key group in soil systems involved in the provision of several ecosystem services. Recently they have been listed by EFSA as organisms to be included in the test battery for the risk assessment of plant protection product (PPPs). This study aimed to contribute to improve the ISO Protocol (ISO 10832: 2009) by assessing the feasibility of using other AMF species under different test conditions. Overall, results showed that AMF species Gigaspora albida and Rhizophagus clarus (selected out of five AMF species) are suitable to be used in spore germination tests using the ISO protocol (14 days incubation with sand or artificial soil as substrate) to test PPPs. However, several modifications to the protocol were made in order to accommodate the use of the tested isolates, namely the incubation temperature (28 °C instead of 24 °C) and the change of reference substance (boric acid instead of cadmium nitrate). The need for these changes, plus the results obtained with the three fungicides tested (chlorothalonil, mancozeb and metalaxyl-M) and comparisons made with literature on the relevance of the origin of AMF isolates in dictating the adequate test conditions, emphasize the importance of adjusting test conditions (AMF species/isolates and test temperature) when assessing effects for prospective risk assessment targeting different climatic zones. So, further studies should be conducted with different AMF species and isolates from different climatic regions, in order to better define which species/isolate and test conditions should be used to assess effects of a particular PPP targeting a given climatic zone.

Soil ecotoxicology in Latin America: Current research and perspectives.

Soils from some Latin American countries support the highest biodiversity levels on the planet and simultaneously have some of the most serious environmental impacts attributed to both historical and current agricultural practices and industrial activities. Soil contamination has resulted from intensive use of pesticides, extensive mining and other industrial activities, and uncontrolled management of waste within inappropriate regulatory frameworks. The present study presents an overview of the scientific research on soil ecotoxicology conducted in Latin America, summarizing the recent advances and highlighting the needs for further refinements in this research field. Most of the contributions to the scientific literature have been from Brazil. The most investigated issue is the ecotoxicity of pesticides and earthworms, which were the organisms most frequently used as test species. Needs identified by Latin American researchers include methods and procedures for: 1) identifying and collecting natural soils to be used as reference test-substrates in tests, 2) identifying and discerning the range of sensitivities of native test species to soil contaminants, 3) developing environmental guidelines applicable to tropical/subtropical conditions, and 4) developing methods and procedures for higher tier testing for full development and implementation of environmental risk assessment schemes. The protection of Latin American soils, including provision of goods and services, is currently framed in legislation and other regulations, but implementation requires significant improvement and additional training programs. Environ Toxicol Chem 2017;36:1795-1810. © 2017 SETAC.

Toxicity of four veterinary pharmaceuticals on the survival and reproduction of Folsomia candida in tropical soils.

This study aimed to evaluate the effect of veterinary pharmaceuticals (VPs) used to control endo- and ectoparasites in ruminants, on the survival and reproduction of the collembolan species Folsomia candida. Standard ecotoxicological tests were conducted in Tropical Artificial Soil and the treatments consisted of increasing dosages of four commercial products with different active ingredients: ivermectin, fipronil, fluazuron and closantel. Ecotoxicological effects were related to the class and mode of action of the different compounds. Fipronil and ivermectin were the most toxic compounds causing a significant reduction in the number of juveniles at the lowest doses tested (LOECreprod values of 0.3 and 0.2 mg kg-1 of dry soil, respectively) and similar low EC50 values (fipronil: 0.19 mg kg-1 dry soil, CL95% 0.16-0.22; ivermectin: 0.43 mg kg-1 dry soil, CL95% 0.09-0.77), although the effects observed in the former compound were possibly related to a low adult survival (LC50 of 0.62 mg kg-1 dry soil; CL95%: 0.25-1.06). For the latter compound no significant lethal effects were observed. Fluazuron caused an intermediate toxicity (EC50 of 3.07 mg kg-1 dry soil, CL95%: 2.26-3.87), and also here a decrease in adult survival could explain the effects observed at reproduction. Closantel, despite showing a significant reduction on the number of juveniles produced, no dose-response relationship nor effects higher than 50% were observed. Overall, all tested compounds, especially ivermectin, when present in soil even at sub-lethal concentrations, can impair the reproduction of collembolans and possibly other arthropods. However, the actual risk to arthropod communities should be further investigated performing tests under a more realistic exposure (e.g., by testing the dung itself as the contaminated matrix) and by deriving ecotoxicologically relevant exposure concentration in soil derived from the presence of cattle dung.

Ecotoxicological effects of pig manure on Folsomia candida in subtropical Brazilian soils.

The effects of pig manure, from diets incorporating veterinary pharmaceuticals, on survival and reproduction of Folsomia candida were evaluated. Manures derived from the following diets: corn and soymeal (CS); 85% CS diet+15% wheat meal (TR); CS diet+100ppm doxycycline+50ppm colistin+2500ppm Zn oxide (CSa); TR diet+100ppm doxycycline+50ppm colistin+2500ppm Zn oxide (TRa). Manures were tested in two subtropical soils representative of southern (Oxisol and Entisol). Despite the antibiotics no significant differences were found between the four manures within each soil. However, strong differences were found on the toxicity between soils. In Oxisol, LC50 values were around 100m(3)ha(-1), and EC50 values around 80m(3)ha(-1). In Entisol these were much lower, with LC50 values oscillating around 20m(3)ha(-1) and EC50 values between 10-15m(3)ha(-1). The observed toxicity on both soils was attributed to excess of nitrogen, Cu and Zn in the highest doses. The strong difference between soils could be explained by soil properties, namely CEC, organic matter, and clay contents that were lower in Entisol, indicating a poor ability to retain contaminants increasing their availability in soil. Results suggest that the application of these residues should be regulated not only using a volume-based criterion, but should incorporate data on soil properties, complemented by an ecotoxicological assessment.

Soil ecotoxicology in Brazil is taking its course.

Soil ecotoxicology has been motivated by the increasing global awareness on environmental issues. Northern Hemisphere has been the main driver of this science branch; however, the number and quality of contributions from the Southern Hemisphere are increasing quickly. In this case study, Brazil is taken as an example of how soil ecotoxicology has developed over the last 30 years. It starts with a brief historical overview depicting the main events on soil ecotoxicology in the country. Following, an overview on the Brazilian legislation related to soil ecotoxicology is given, covering regulations with prospective focus, mainly on the registration of pesticides. Regulations with retrospective focus in contaminated areas are also given. Then, an outline of the actors in soil ecotoxicology and examples of prospective ecotoxicological studies performed with soil organisms and plants are given by stressor groups: pesticides, pharmaceuticals, metals, and residues. Experiences from retrospective studies, mainly looking at the assessment of industrial sites, are also covered. Emphasis is given on methodological aspects, pointing to needed actions, mainly regarding the different biotic and abiotic conditions of a tropical country. Finally, the last session discusses how soil ecotoxicology could be improved in methodological adaptations as well as legal requirements.

Ecological Risk Assessment of a Metal-Contaminated Area in the Tropics. Tier II: Detailed Assessment.

This study presents data on the detailed evaluation (tier 2) of a site-specific ecological risk assessment (ssERA) in a former smelter area contaminated with metals (Santo Amaro, Bahia, Brazil). Combining information from three lines of evidence (LoE), chemical (ChemLoE), ecotoxicological (EcotoxLoE) and ecological (EcoLoE), in the Triad approach, integrated risk values were calculated to rank sites and confirm the potential risk disclosed with tier 1. Risk values were calculated for the habitat and for the retention functions in each sampling point. Habitat function included the ChemLoE calculated from total metal concentrations. The EcotoxLoE was based on reproduction tests with terrestrial invertebrates (Folsomia candida, Enchytraeus crypticus, Eisenia andrei), shoot length and plant biomass (Avena sativa, Brassica rapa). For the EcoLoE, ecological parameters (microbial parameters, soil invertebrate community, litter breakdown) were used to derive risk values. Retention function included the ChemLoE, calculated from extractable metal concentrations, and the EcotoxLoE based on eluate tests with aquatic organisms (Daphnia magna reproduction and Pseudokirchneriella subcapitata growth). Results related to the habitat function indicated that the metal residues are sufficient to cause risk to biota, while the low metal levels in extracts and the general lack of toxicity in aquatic tests indicated a high soil retention capacity in most sampling points. Integrated risk of tier 2 showed the same trend of tier 1, suggesting the need to proceed with remediation actions. The high risk levels were related to direct toxicity to organisms and indirect effects, such as failure in the establishment of vegetation and the consequent loss of habitat quality for microorganisms and soil fauna. This study shed some light on the selection of tools for the tier 2 of an ssERA in tropical metal-contaminated sites, focusing on ecological receptors at risk and using available chemical methods, ecological surveys and ecotoxicity tests.

Influence of cypermethrin on avoidance behavior, survival and reproduction of Folsomia candida in soil.

Cypermethrin is a pyrethroid widely used in agriculture and in control of animal ectoparasites, being effective against a large number of insects. Therefore, this study aimed to evaluate the effects of cypermethrin on soil fauna using reproduction and behavior ecotoxicological tests with the springtail Folsomia candida. The surface layer of a soil characteristic of the western region of the Santa Catarina State, classified as Typic Dystrupept, was used as test substrate. The treatments on both tests consisted of five concentrations of cypermethrin (0, 7.5, 15.0, 22.5, and 30.0mgkg(-)(1)) corresponding to 0, 1.5, 3.0, 4.5, and 6.0gm(-2), respectively. This range was chosen according to technical instruction for the use of this product in broilers beds (that are used afterwards as organic fertilizer in soil) that recommends 15mgkg(-1) (3.0gm(-2)). The results obtained with tests for F. candida showed toxicity at all doses tested, following a dose-related response resulting in reduction in survival rate (LC50 of 18.41mgkg(-1), equivalent to 3.8gm(-2)), in the number of juveniles (EC50 of 15.05mgkg(-1), corresponding to 3.01gm(-2)), and an increase in avoidance response (AC50 of 29mgkg(-1), corresponding to 5.8gm(-2)). Although more studies are needed focusing on the fate of cypermethrin in soil when the poultry beds are used as fertilizer and how it may affect soil fauna, data obtained in this study, by showing effects within the range of the doses that are recommended implies that caution and possible mitigation measures should be taken when using this compound.

Disposal of dredged sediments in tropical soils: ecotoxicological evaluation based on bioassays with springtails and enchytraeids.

Metal reference values established in Brazilian legislation for terrestrial disposal of dredged sediments and soil quality were derived for temperate regions. To evaluate the adequacy of such metal reference values to tropical soils, the ecotoxicity of a dredged sediment (from the Guanabara bay, Rio de Janeiro, Brazil) was investigated in two local soils (ferralsol and chernosol) by performing avoidance and reproduction tests using Folsomia candida and Enchytraeus crypticus. Test doses consisted of 0 %, 1.25 %, 2.5 %, 5, 10 %, and 20 %. Total and potentially bioavailable metal concentrations were determined in the test mixtures. Although the chernosol mixtures had the highest total metal concentrations, the influence of the expansive clay minerals (with high ability to adsorb metals) and the high contents of nutrients typical from this type of soils, seem to reduce the ecotoxicity. Collembolan avoidance behavior was the least sensitive endpoint. The lowest sediment doses increased the reproduction of F. candida in ferralsol mixtures. E. crypticus reproduction in the ferralsol mixtures were more pronounced at lower concentrations than in chernosol mixtures. Possibly the low nutrient content of the ferralsols, in connection with the addition of small amounts of sediment, created particular conditions that promoted reproduction of the test species. Data obtained in the ecotoxicological tests may support the establishment of a "safe" ecological dose of dredged sediments to be applied in tropical soils, supporting decision-makers in programs of environmental management.

Ecotoxicological assessment of a dredged sediment using bioassays with three species of soil invertebrates.

The ecotoxicity of a dredged sediment from the Guanabara Bay (Rio de Janeiro, RJ, Brazil) was evaluated using reproduction tests with Eisenia andrei, Folsomia candida and Enchytraeus crypticus, and avoidance and feeding inhibition tests with Folsomia candida. The sediment was mixed with artificial soil to obtain the following doses: 1.25, 2.5, 5.0, 10.0, 20.0 and 40.0 %. Lead, nickel, chromium, copper and zinc concentrations were determined in the test mixtures. In reproduction tests, E. andrei was the most sensitive species (EC50 = 2.94 %), followed by F. candida (EC50 = 7.72 %) and E. crypticus (EC50 = 10.10 %). The percentage of initial weight of earthworms was significantly higher in all test concentrations compared to the control except at the highest one where earthworms biomass significantly decreased. No feeding inhibition of F. candida was observed for any test mixture and the number of organisms with a dark gut (the fed collembolans) generally increased with the increasing dose of sediment. Significant avoidance responses of F. candida were observed towards all test mixtures, however, the avoidance behaviour was the less sensitive endpoint after feeding inhibition. The results showed that chemical analysis is not sufficient to foresee toxic effects in terrestrial systems resulting from sediment disposal in soil if not complemented with an ecotoxicological evaluation.

Disposal of dredged sediments in tropical soils: ecotoxicological effects on earthworms.

The upper limit concentrations of metals established by international legislations for dredged sediment disposal and soil quality do not take into consideration the properties of tropical soils (generally submitted to more intense weathering processes) on metal availability and ecotoxicity. Aiming to perform an evaluation on the suitability of these threshold values in tropical regions, the ecotoxicity of metal-contaminated dredged sediment from the Guanabara Bay (Rio de Janeiro, Brazil) was investigated. Acute and avoidance tests with Eisenia andrei were performed with mixtures of dredged sediment with a ferralsol (0.00, 6.66, 13.12, 19.98, and 33.30 %) and a chernosol (0.00, 6.58, 13.16, 19.74, and 32.90 %). Mercury, lead, nickel, chromium, copper, and zinc concentrations were measured in test mixtures and in tissues of surviving earthworms from the acute tests. While ferralsol test mixtures provoked significant earthworm avoidance response at concentrations ≥13.31 %, the chernosol mixtures showed significant avoidance behavior only at the 19.74 % concentration. The acute tests showed higher toxicity in ferralsol mixtures (LC50 = 9.9 %) compared to chernosol mixtures (LC50 = 16.5 %), and biomass increased at the lowest sediment doses in treatments of both test soils. Most probably, the expansive clay minerals present in chernosol contributed to reduce metal availability in chernosol mixtures, and consequently, the ecotoxicity of these treatments. The bioconcentration factors (BCF) for zinc and copper were lower with increasing concentrations of the dredged sediment, indicating the existence of internal regulating processes. Although the BCF for mercury also decreased with the increasing test concentrations, the known no biological function of this metal in the earthworms metabolism lead to suppose that Hg measured was not present in bioaccumulable forms. BCFs estimated for the other metals were generally higher in the highest dredged sediment doses.

Earthworm ecotoxicological assessments of pesticides used to treat seeds under tropical conditions.

Ecotoxicological laboratory tests (lower-tier tests) are fundamental tools for assessing the toxicity of pesticides to soil organisms. In this study, using these tests under tropical conditions, we quantified the impact of the insecticides imidacloprid, fipronil, and thiametoxam, and the fungicides captan and carboxin+thiram, all of which are used in the chemical treatment of crop seeds, on the survival, reproduction, and behavior of Eisenia andrei (Oligochaeta). With the exception of imidacloprid, none of the pesticides tested caused mortality in E. andrei in artificial soils. The LC(50) of imidacloprid was estimated as 25.53 mg active ingredient kg(-1) of dry soil. Earthworm reproduction rates were reduced by imidacloprid (EC(50)=4.07 mgkg(-1)), fipronil (EC(20)=23.16 mgkg(-1)), carboxin+thiram (EC(50)=56.38 mgkg(-1)), captan (EC(50)=334.84 mgkg(-1)), and thiametoxam (EC(50)=791.99 mgkg(-1)). Avoidance behavior was observed in the presence of imidacloprid (AC(50)=0.11 mgkg(-1)), captan (AC(50)=33.54 mgkg(-1)), carboxin+thiram (AC(50)=60.32 mgkg(-1)), and thiametoxam (AC(50)=>20 mgkg(-1)). Earthworms showed a preference for soils with the insecticide fipronil. Imidacloprid was the most toxic of the substances tested for E. andrei. The avoidance test was the most sensitive test for most pesticides studied, but results varied between pesticides. These results offer new insights on the toxicity of pesticides used to treat seeds in tropical regions. However, they should be complemented with higher-tier tests in order to reduce the uncertainties in risk assessment.