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Diuron is a widely used pesticide for weed control in Brazil, Australia, the USA, and EU; therefore, environmental consequences are of concern. The aim of the present study was to determine the potential toxic effects of diuron (as formulation Diuron Nortox® 500 SC) on tadpoles of the bullfrog Lithobates catesbeianus, considering three endpoints: lethality, swimming behavior, and avoidance (ability to escape from contaminant). Secondly, it was intended to compare the sensitivity of tadpoles with to fish and other amphibian species by applying species sensitive distribution (SSD). Five diuron concentrations (20, 30, 35, 40, and 45 mg a.i./L) were tested in triplicate to evaluate mortality, swimming speed, and distance traveled after 96 h of exposure to the herbicide. Two avoidance tests were conducted using a multicompartmented system (n = 6) containing three tadpoles per compartment. Dilution gradients were established at 0; 5; 25; 50; 75; and 100% for both systems, corresponding to 0; 0.5; 2.5; 5; 7.5; and 10 mg a.i./L in an experiment, taking into account the results of the acute toxicity test and 0; 5; 25; 50; 100; and 150 μg a.i./L for another experiment, considering reported environmentally relevant concentrations in Brazilian water bodies. The acute toxicity tests (n = 3) with diuron revealed an 96 h-LC50 of 31 ± 3.7 mg a.i./L. The decreased maximum speed was only observed in tadpoles exposed to 30 mg a.i./L (0.15 ± 0.04 m/s) when compared to the control (0.28 ± 0.06 m/s). In the avoidance tests, concentrations of 2.5 and 5 mg a.i./L caused the escape behavior of L. catesbeianus tadpoles. However, tadpoles were also able to avoid diuron contamination at environmental relevance, especially in concentrations of 25 and 50 μg a.i./L. As expected, avoidance and effects on swimming behavior ocurred at lower diuron concentrations than mortality. Sublethal diuron concentrations may thus lead to the displacement of organisms to more favorable areas when they are available and the ability to swim is not affected.

The production and release of chemical compounds by invasive plants can affect competitors and native species overall, destabilizing ecological interactions and harming ecosystem functioning. Hedychium coronarium is an invasive macrophyte common on Brazilian riparian areas that produces a wide variety of allelochemicals, but little is known about their effect on aquatic species. Here, we identified the major chemical compounds of the aqueous extract of H. coronarium rhizomes and assessed its toxicity, evaluating the growth inhibition of one alga (Raphidocelis subcapitata) and one macrophyte (Lemna minor), and the lethality of cladoceran (Ceriodaphnia silvestrii and Daphnia similis) and Chironomidae larvae (Chironomus sancticaroli). The majoritarian compounds of H. coronarium rhizomes were Coronarin D and Coronarin D Ethyl Ether. The aqueous extract was toxic for all tested species. We observed growth inhibition in R. subcapitata, as well as reduction in biomass in L. minor. Chironomus sancticaroli and cladoceran were the most sensible species. The aqueous extract of H. coronarium rhizomes was toxic on tested conditions, suggesting that the rhizome compounds may interfere on aquatic organisms and in the dynamic of trophic webs of aquatic ecosystems on invaded areas.

Aquatic environments are constantly exposed to a cocktail of contaminants mainly due to human activities. As polluted ecosystems may simultaneously present other multiple natural stressors, the objective of the present study was to evaluate joint effect of stressors (natural and anthropogenic) on life history traits of the Neotropical cladoceran, Ceriodaphnia silvestrii. For this purpose, the effects of water conditioned with predator kairomones (fish) and environmental concentrations (sublethal) of two pesticides widely used in sugarcane monoculture in Brazil, the insecticide Regent® 800 WG (active ingredient—a.i. fipronil) and the herbicide DMA® 806 BR (a.i. 2,4-D) were evaluated using chronic toxicity testing, isolated and in mixture, for this cladoceran species. The environmental risks of pesticides for tropical freshwater biota were also estimated from the risk quotient MEC/PNEC. Among the characteristics of the life history of C. silvestrii evaluated after 8 days of exposure, compared with the mean value of control, the age of primiparous females was not affected by any evaluated treatment. However, species average survival decreased in the treatment of kairomones mixed with fipronil (FK) and in the treatment with a mixture of fipronil, 2,4-D, and kairomones (MFKD). The body length of maternal females was shorter than in the control after exposure in treatments with only kairomones (K) and FK. Fecundity of this cladoceran was reduced when exposed to FK and MFKD treatments, and the intrinsic rate of population increase significantly decreased for organisms exposed to treatment with fipronil (F) and to mixtures of fipronil and 2,4-D (MFD), MFDK, and FK. The results indicated that the combination of anthropogenic and natural stressors causes changes in C. silvestrii life history traits, which can contribute to the decline in populations, and our preliminary risk assessment results are a matter of concern regarding biota conservation.

The toxic potential of four disinfectant agents (chlorine, ozone, peracetic acid and UV radiation), used in the disinfection of urban wastewater, was evaluated with respect to four aquatic organisms. Disinfection assays were carried out with wastewater from the city of Araraquara (São Paulo State, Brazil), and subsequently, toxicity bioassays were applied in order to verify possible adverse effects to the cladocerans (Ceriodaphnia silvestrii and Daphnia similis), midge larvae Chironomus xanthus and fish (Danio rerio). Under the experimental conditions tested, all the disinfectants were capable of producing harmful effects on the test organisms, except for C. xanthus. The toxicity of the effluent to C. silvestrii was observed to increase significantly as a result of disinfection using 2.5 mg L⁻¹ chlorine and 29.9 mg L⁻¹ ozone. Ozonation and chlorination significantly affected the survival of D. similis and D. rerio, causing mortality of 60 to 100 % in comparison to the non-disinfected effluent. In experiments with effluent treated with peracetic acid (PAA) and UV radiation, a statistically significant decrease in survival was only detected for D. rerio. This investigation suggested that the study of the ideal concentrations of disinfectants is a research need for ecologically safe options for the treatment of wastewater.

The mining sector has great importance to the economic activity in Brazil. However, it is also responsible for several environmental impacts such as the rupture of the Fundão dam (Mariana, Brazil) that resulted in the spillage of 50 million m3 of mining tailings in the Doce River Basin. This study evaluated the acute and chronic effects of Fundão tailings on growth, development, respiration rates, swimming performance, and avoidance behavior of Lithobates catesbeianus tadpoles. Results showed that 96-h exposure to different dilutions (10, 25, 50, 75, and 100%) of a stock solution containing mining tailings (50 g/L) caused no mortality of tadpoles; however, the most concentrated solution decreased the swimming speed of the animals. After 16 days, tadpoles exposed to 25, 50, and 100% treatments had both swimming speed and distance traveled reduced. Oxygen consumption was also decreased in tadpoles exposed to the 100% solution after 20 days. Avoidance test indicated that tadpoles avoided lower tailing concentrations, but a reduced avoidance response was attested to the higher concentrations, probably due to the toxic effects of the residues that prevented animals’ displacement. Chemical analysis confirmed the occurrence of cadmium (Cd), lead (Pb), iron (Fe), manganese (Mn), zinc (Zn), and aluminum (Al) in Fundão tailings and its presence in the mouth and inside the intestine of treated tadpoles indicated the ingestion of metals by these organisms. This study showed that even presenting low lethal toxicity, long-term exposure to mining tailings from Fundão dam caused morphophysiological and behavioral damage in tadpoles.

Conventional farming uses a large volume of pesticides that may reach aquatic ecosystems. This is also the case for the insecticide fipronil and the herbicide 2,4-D, which are widely used in many crops. This study aimed at evaluating the individual and mixture toxicity of these pesticides to the tropical amphipod Hyalella meinerti . To this end, acute toxicity tests (96 h) were conducted. Chronic bioassays (10 days) were also carried out, in which the body length and dry biomass were evaluated as endpoints. In addition, a complete factorial mixture chronic toxicity test was carried out. H. meinerti was sensitive to fipronil in the acute toxicity tests, with a LC 50 -96-h of 0.86 μg L −1 (95% CI 0.26–0.46), and no acute effects were observed after 2,4-D exposure even at the highest test concentration of 100 mg L −1 . In the chronic toxicity tests, all tested concentrations of both pesticides decreased the growth of H. meinerti , in which losses on biomass reached 45% and 65% for 2,4-D and fipronil, respectively. The pesticide mixture indicated antagonism although it still significantly decreased the body growth. The results obtained indicate a high sensitivity of H. meinerti exposed to environmentally realistic concentrations, demonstrating that there are risks for the species in real field conditions.

Despite that chironomids are the most widely used benthic insect test species worldwide, little research has been conducted so far with tropical chironomid representatives. This study was designed to evaluate the indigenous midge Chironomus sancticaroli as a candidate test species for use in tropical toxicity assessments. To this end, laboratory water-only toxicity tests were conducted evaluating copper and cadmium. Obtained lethal concentration values were overall comparable or lower than those reported for other chironomids, including those most commonly used in temperate regions (C. riparius and C. dilutus). In addition, C. sancticaroli was deployed in situ in the Monjolinho River (São Paulo State, Brazil), and toxicity of sediment from this river was evaluated in the laboratory. Several field water and sediment quality parameters also were measured to enable correlating these with the effects observed in these toxicity tests. Field sediment toxicity to C. sancticaroli appeared to be related with sediment endosulfan concentrations, whereas effects noted in the in situ test were likely due to low pH values measured in river water. Chironomus sancticaroli appears to be a suitable candidate for inclusion as a test species in tropical toxicity evaluations in both the laboratory and the field.

The insecticide fipronil and the herbicide 2,4-D are the most applied pesticides in sugarcane crops leading to aquatic contamination. The whole-body bioconcentration of fipronil and 2,4-D, single and in mixture, was evaluated in Danio rerio after 96-h exposure. The activities of catalase (CAT) and glutathione S-transferase(GST) in whole body and in the gills and the acetylcholinesterase (AChE) in muscle were determined. The gill histopathology and the morphology of the pavement (PVC) and the mitochondria-rich(MRC) cells at gill surface were analyzed. Bioconcentration occurred after exposure to fipronil (2.69 L kg −1 ) and 2,4-D (1.73 L kg −1 ) single and in mixture of fipronil (3.10 L kg −1 ) and 2,4-D (1.27 L kg −1 ). Whole-body CAT activity was unchanged, and its activity decreased in the gills after exposure to fipronil and increased after exposure to 2,4-D and mixture. GST and AChE increased after single exposure to each pesticide and mixture of both. Fish exposed to mixture increased the MRC fractional area (MRCFA) which suggested possible ionic regulation disturbance and reduced the microridge of the PVC surface. Synergistic interactions occurred in the CAT activity and MRCFA after exposure to mixture of pesticides. The results indicate that the recommended application dose of fipronil and 2,4-D, single or in mixture, for sugarcane crops affects this fish species altering its homeostasis.

In conventional agriculture, several pesticides can be applied at the same stage of plant development, either individually or in mixtures and these compounds also reach aquatic ecosystems. The aim of the present study was to investigate the short-term effects of the insecticide Kraft® 36 EC (active ingredient — a.i. abamectin) and the fungicide Score® 250 EC (a.i. difenoconazole) on the zooplankton community in outdoor freshwater microcosms. The potential risks related to the exposure to both compounds, isolated and in mixture, likely to occur in the field after runoff and spray drift events of their recommended doses were assessed in these microcosms through integrative analyses of the effects on the composition, density, and functional diversity of zooplankton. Namely, these endpoints were evaluated for eight different exposures, which were (1) Runoff control — RC; (2) Kraft-contaminated runoff — RK; (3) Score-contaminated runoff — RS; (4) Kraft and Score-contaminated runoff — RKS; (5) Spray drift Control — SC; (6) Kraft spray drift — SK; (7) Score spray drift — SS; and (8) Kraft and Score spray drift — SKS. Zooplankton taxa responded quickly to physical, chemical, and biological changes in the aquatic ecosystems. The principal response curves (PRC) analyses of the zooplankton community in the microcosms indicated significant effects after all insecticide treatments, both when applied individually and in a mixture with the fungicide. The insecticide treatment (RK and SK) demonstrated a decrease in the number of unique species (sing.sp) of zooplankton in the microcosms, and RK also decreased the functional divergence (FDiv). However, it was the treatment of mixtures (SKS) that caused a decrease in functional diversity (FD) and in the functional diversity indexes (divergence and richness) and sing.sp. Thus, the results showed the risk of the insecticide and their mixture to aquatic ecosystems.

Sugarcane crops are dependent on chemicals for maintaining plantations. Therefore, environmental consequences concern adjacent areas that can be affected by contaminants in common use, including pesticides and vinasse (i.e., a by-product from the ethanol industry). This study aimed to evaluate phytotoxicity through two plant bioassays with water from mesocosms contaminated with the herbicide 2,4-D (447.0 μg L−1), the insecticide fipronil (63.5 μg L−1), and sugarcane vinasse (1.3%). First, the germination test (4 d) with Eruca sativa L. assessed water samples collected three times after the contamination (2 h, 14 d, and 30 d), considering germination, shoot, and root growth. The results from this bioassay indicated higher phytotoxicity for 2,4-D as it fully inhibited the shoot and root growth even in low concentrations (0.2 μg L−1). However, no significant effect was reported for fipronil and vinasse. Also, the 2,4-D effects drastically decreased due to an expressive concentration reduction (99.4% after 30 d in mixture with vinasse). Second, the irrigation test with Phaseolus vulgaris L. and Zea mays L. considered shoot and root growth and biomass under 21 days after plants emergence. The herbicide 2,4-D inhibited the initial growth of tested species, especially the roots (up to 45% inhibition). Furthermore, sugarcane vinasse caused harmful effects on plant growth (up to 31% inhibition). Therefore, our data showed that these contaminants could inhibit plant germination and initial growth under our tested conditions. These evaluations can endorse risk assessments and water management in sugarcane crops surrounding areas.