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The Pantanal (Brazil) is a wetland region characterized by seasonal flooding. Hydrological cycles influence the water physicochemical parameters, causing seasonal variations in pH and nitrites. Thus, the objective of this study was to evaluate the effects of varying pH and nitrite concentrations on the toxicity of the cypermethrin-based pesticide Barrage®, considering both lethal (mortality) and sublethal endpoints (growth and development). Larvae of the endemic shrimp Macrobrachium pantanalense and of the estuarine Amazonian congener Macrobrachium amazonicum were exposed to cypermethrin (through Barrage®) under several pH levels (6.5, 7.5 and 8.5) or nitrite concentrations (0.1, 0.2 and 0.4 mg/L). The pH had direct effects on all the tested endpoints for both species. For M. pantanalense, the lethal effects of the cypermethrin formulation were more pronounced at low pH (96-h LC 50  = 0.004 μg/L at pH 6.5, and 0.146 μg/L at pH 8.5). For M. amazonicum, an opposite response was observed, with increased toxicity of the formulation at high pH (96-h LC 50  = 0.110 μg/L at pH 6.5 and 0.044 μg/L at pH 8.5). Variations in pH also seemed to modify the sublethal effects of the formulation on larval growth and development of M. pantanalense. Nitrite concentrations affected larval growth of both species, modifying also the effects of the cypermethrin formulation on the larval development of M. amazonicum. This work shows the importance of considering abiotic factors for risk assessment either due to possible direct effects on the physiology of organisms and/or due to interactions with other stressors, particularly in fragile biomes such as Pantanal., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Ametryn (AMT) is one of the most widely used herbicides in tropical sugarcane crops, the main culture of São Paulo State, Brazil. It is known as a diffuse pollutant, being found in surface water and sediment of water bodies adjacent to the crop fields. In the present study, the toxicity of AMT to zebrafish (Danio rerio) embryos was evaluated using developmental and biochemical endpoints. At the biochemical level, lactate dehydrogenase responded at the lowest concentration tested (4 μg L -1 ) indicating a high demand of energy required to cope with the stress condition. Antioxidant enzyme levels were changed at intermediate/high concentrations while oxidative damage (lipid peroxidation) was observed at the last concentration tested (10 mg L -1 ). This suggests that, like for other herbicides from the triazine group, oxidative stress is a major pathway of toxicity for AMT. Several developmental effects such as oedemas and tail deformities were also observed. The 96 h-EC 50 values calculated for different developmental parameters were between 17 and 29 mg L -1 . AMT also affected hatching (96 h-EC 50  = 22.5 mg L -1 ) and positioning in the water column (96 h-EC 50  = 13.2 mg L -1 ). In a previous work of the group, lethal toxicity of AMT showed to be much higher to adults than to embryos. However, in the present work, sublethal endpoints assessed suggest that important effects are observed at lower concentrations, improving the sensitivity of the embryo test. Moreover, in this work, sublethal effects were observed for concentrations in the same range as the ones found in the environment, and thus, given that this chemical is widely used in tropical fields, a refined evaluation of risk should be performed based on the monitoring of sublethal and long-term parameters and considering mixture scenarios.