Aquatic communities are exposed to repeated pulses of toxicants and environmental stressors. We hypothesize that the dose, order, and timing of stress events shape the interactions of these communities. For this, we conducted a fully-crossed, four-factorial, multiple stress exposure experiment to study the combined effects of Esfenvalerate and ultraviolet-B (UV-B) radiation related to the exposure timing and order on Daphnia magna. We revealed that initial exposure to low stress doses, independent of the stress type (UV-B or Esfenvalerate), significantly increased the resistance toward the second stressor. This beneficial effect was apparent only when the second stressor was applied immediately after the first stressor (p < 0.01). When the period between stressor applications was extended to 2 days, the antagonism between the two stressors turned into synergism. The stressor interaction could be predicted with an abstract-mechanistic model of the temporal dynamics of the early-stage stress response. With this model, the timing and order of exposures were able to successfully explain interactions observed in all treatments (model-R² = 1.0). We conclude that especially the duration of a break between exposures and the exposure dose have a decisive influence on interactions between toxicants and environmental stressors.

中文翻译：

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连续暴露于多重压力之间的时间将对抗转化为协同作用

水生群落暴露在毒物和环境压力源的反复脉冲中。我们假设压力事件的剂量、顺序和时间决定了这些社区的相互作用。为此，我们进行了全交叉、四因子、多重应力暴露实验，以研究依戊戊酸和紫外线-B (UV-B) 辐射对大型水蚤的暴露时间和顺序的综合影响。我们发现，与压力类型（UV-B 或 Esfenvalerate）无关的低压力剂量的初始暴露显着增加了对第二压力源的抵抗力。只有在第一个压力源之后立即应用第二个压力源时，这种有益效果才明显（p< 0.01)。当压力源应用之间的时间延长到2天时，两种压力源之间的对抗变成了协同作用。压力源的相互作用可以用早期压力反应的时间动态的抽象机械模型来预测。使用该模型，暴露的时间和顺序能够成功地解释在所有处理中观察到的相互作用（模型-R ² = 1.0）。我们得出结论，尤其是暴露之间的中断持续时间和暴露剂量对毒物和环境压力源之间的相互作用具有决定性影响。