The Ecotoxicity of Pyrimethanil for Aquatic Biota

Via the application of agrochemicals, farmers currently guarantee high productivity of fruit and vegetable crops. However, pest reduction using excessive amounts of such chemicals has a negative effect on aquatic organisms. The spray-drift, leaching, run-off or accidental spills occurring during or after application has become a serious and increasing problem for aquatic ecosystems. Pyrimethanil (PYR) is one of the most used fungicides. Such increase has heightened the interest in studying the potential risk and influence of PYR on the environment. In this chapter information on the PYR environmental risks for aquatic organisms was divided into three different approaches: (i) assessment of toxic effects of the pure active ingredient or the commercial formulation on primary producers, (ii) assessment of toxic effects of the pure active ingredient and PYR formulation on aquatic animals, and (iii) estimation of the role of PYR as an environmental disturber by triggering avoidance response. The available data provide evidences that PYR is potentially toxic for many aquatic species, affecting survival, reproduction, feeding, growth, and that it can disturb the environmental quality with no direct effect at the individual level by inducing organisms to migrate to less impacted areas

Impact of temperature on the toxicity of Kraft 36 EC® (a.s. abamectin) and Score 250 EC® (a.s. difenoconazole) to soil organisms under realistic environmental exposure scenarios

Pesticides can affect all receiving compartments, especially soils, and their fate and effects may be enhanced by temperature, increasing their risk to ecological functions of soils. In Brazil, the most widely used pesticides are the insecticide Kraft 36 EC® (a.s. abamectin) and the fungicide Score 250 EC® (a.s. difenoconazole), which are commonly used in strawberry, often simultaneously as a mixture. The aim of this study was to evaluate the toxicity of realistic environmental applications, single and in mixtures, for both pesticides to the springtail Folsomia candida and the plant species Allium cepa (onion) and Lycopersicum esculentum (tomato). Mesocosms filled with Brazilian natural soil (lattosolo) were dosed with water (control), Kraft (10.8 g a.s/ha), Score (20 g.a.s/ha) and Kraft + Score (10.8 + 20 g a.s./ha). The applications were repeated every 7 days, during 18 days of experiment, and simulating rainfall twice a week. Collembola reproduction tests were conducted with soils from the first (day 1) and last day (day 18) of experiment for each treatment. Plant toxicity tests were carried out in the experimental units. The experiments were run at 23 °C and 33 °C. Kraft, alone and in the binary mixture, showed high toxicity to the springtails in soils from both days 1 and 18, especially at 23 °C where it caused 100% mortality. Score however, was not toxic to the springtails. Plant growth was reduced by Score, but responses varied depending on temperature. This study indicates a high environmental risk of the insecticide Kraft, particularly at lower temperatures (23 °C), and an influence of temperature on pesticide fate and effects

Copper affects photosynthetic parameters of N- or P-limited Ankistrodesmus densus

Algae require micro- and macronutrients for optimal growth and metabolism. Under limitation or excess of the nutrients in the environment, they can adapt their photosynthetic machinery to cope with the new concentrations available to decrease damage to their performance. In the present study, to evaluate a microalga's responses to a macronutrient's limitation and the excess to a micronutrient, we acclimated the well-distributed freshwater microalga Ankistrodesmus densus to N- or P-limited medium before exposing it to sublethal copper (Cu) concentrations. Our results indicate that Cu affected the chlorophyll a concentration in N- and P-replete conditions, while the N- or P-limitation affected chlorophyll a concentration, maximum and effective quantum yield of photosystem II (PS II). Within the time frame of 72 h, and the maximum Cu concentration used (1.26 µM Cu2+), the addition of Cu to N- or P-limited algae resulted in synergism in all of these parameters, except in chlorophyll concentration under P limitation. In addition, the combination of Cu with N- or P-limited algae decreased the photochemical quenching (qP) and increased the non-photochemical quenching (qN and NPQ). The values obtained in Y (NPQ) – i.e., the quenching of regulated energy loss in PS II – indicate that the combination of Cu and N- or P-limited algae induced the activation of photoprotective mechanisms. Under the highest Cu exposure, the changes obtained from N- or P-limited algae were similar, indicating that under low metal concentrations, the concentration of macronutrient is responsible for changing the chlorophyll concentration, qN, NPQ, and Y (NPQ); however, at higher concentrations of metal, Cu apparently drives these changes. All of the parameters evaluated were affected under N or P limitation and Cu combination, indicating a synergism. Based on the present study results, we suggest using Ankistrodesmus densus in ecotoxicological studies due to its sensitivity and adaptation to adverse scenarios

Copper-driven avoidance and mortality in temperate and tropical tadpoles

Amphibians have experienced an accentuated population decline in the whole world due to many factors, one of them being anthropogenic contamination. The present study aimed to assess the potential effect of copper, as a worldwide and reference contaminant, on the immediate decline of exposed population due to avoidance and mortality responses in tadpoles of three species of amphibians across climatic zones: a South American species, Leptodactylus latrans, a North American species, Lithobates catesbeianus, and a European species, Pelophylax perezi. A non-forced exposure system with a copper gradient along seven compartments through which organisms could freely move was used to assess the ability of tadpoles to detect and avoid copper contamination. All species were able to avoid copper at a concentration as low as 100 ␮g L −1 . At the lowest (sublethal) concentrations (up to 200 ␮g L −1) avoidance played an exclu-sive role for the population decline, whereas at the highest concentrations (>450 ␮g L −1) mortality was the response determining population decline. The median concentrations causing exposed population immediate decline were 93, 106 and 180 ␮g L −1 for Le. latrans, Li. catesbeianus and P. perezi, respectively. Contaminants might, therefore, act as environmental disruptors both by generating low-quality habitats and by triggering avoidance of tadpoles, which could be an important response contributing to disper-sion patterns, susceptibility to future stressors and decline of amphibian populations (together with mortality)