NEEA/CRHEA/SHS and PPG-SEA, São Carlos Engineering School, University of São Paulo, Av. Trabalhador São-carlense, 400 - Pq. Arnold Schimidt, São Carlos, 13560-970, Brazil.
Department of Ecology and Evolutionary Biology, Federal University of São Carlos, Rodovia Washington Luis, km 235, São Carlos, SP, 13565-905, Brazil.
Arch Environ Contam Toxicol. 2020 Oct;79(3):298-309. doi: 10.1007/s00244-020-00754-7. Epub 2020 Aug 28.
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.
水生环境不断受到各种污染物的影响，主要是由于人类活动。由于受污染的生态系统可能同时存在其他多种自然胁迫因素，因此本研究的目的是评估胁迫因素（自然和人为）对新热带枝角类动物 Ceriodaphnia silvestrii 生活史特征的联合影响。为此，使用慢性毒性测试评估了用鱼类产生的化感物质调节的水和巴西甘蔗单一种植中广泛使用的两种农药（杀虫剂 Regent 800 WG（有效成分-a.i. 氟虫腈）和除草剂 DMA 806 BR（有效成分-a.i. 2,4-D））在单独和混合条件下对这种枝角类动物的影响。还根据风险商数 MEC/PNEC 估算了农药对热带淡水生物群的环境风险。在暴露 8 天后评估的 Ceriodaphnia silvestrii 生活史特征中，与对照平均值相比，初次产仔雌性的年龄不受任何评估处理的影响。然而，在混合了化感物质和氟虫腈的处理（FK）以及混合了氟虫腈、2,4-D 和化感物质的处理（MFKD）中，物种的平均存活率下降。在仅暴露于化感物质（K）和 FK 的处理中，母体雌性的体长比对照短。当暴露于 FK 和 MFKD 处理时，这种枝角类动物的繁殖力降低，当暴露于氟虫腈（F）和氟虫腈与 2,4-D（MFD）、MFDK 和 FK 的混合物处理时，种群的内禀增长率显著降低。结果表明，人为和自然胁迫因素的组合导致 Ceriodaphnia silvestrii 生活史特征发生变化，这可能导致种群数量下降，我们的初步风险评估结果令人关注生物多样性保护。
