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.

主要由于人类活动，水生环境不断暴露于一系列污染物中。由于受污染的生态系统可能同时呈现其他多种自然压力源，因此本研究的目的是评估压力源（自然的和人为的）对新热带clacerceran Ceriodaphnia silvestrii的生活史特征的联合影响 。为了这个目的，水的影响与广泛用于在巴西的甘蔗单作两种农药的捕食利他素（鱼）和环境浓度（亚致死），所述杀虫剂丽晶空调^® 800 WG（活性成分-AI氟虫腈）和除草剂DMA ^®使用慢性毒性测试对806 cl（ai 2,4-D）进行了分离和混合评估，用于该刺柏属物种。还根据风险商MEC / PNEC估算了农药对热带淡水生物区系的环境风险。西尔维梭菌的生活史特征  在暴露8天后进行评估，与对照组的平均值相比，任何评估的治疗方法均不影响初产雌性的年龄。但是，在混合有氟虫腈的海洛酮（FK）处理和以氟虫腈，2,4-D和海洛酮（MFKD）的混合物处理中，物种平均存活率下降。在仅使用海洛酮（K）和FK的治疗中，母体雌性的体长比对照组短。当暴露于FK和MFKD处理时，这种锁骨卵的繁殖力降低，暴露于氟虫腈（F）以及氟虫腈和2,4-D（MFD），MFDK，和FK。结果表明，人为和自然压力源的组合引起了C. silvestrii的生活史特征可能会导致种群减少，而我们的初步风险评估结果是有关生物群保护的一个令人关注的问题。