Time between Sequential Exposures to Multiple Stress Turns Antagonism into Synergism

Abstract

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-R 2 = 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.

The mechanistic basis and adaptive significance of cross-tolerance: a ‘pre-adaptation’ to a changing world?

“…For example, exposure to heat, hypoxia and ultraviolet-B radiation stress can heighten pesticide and pollutant resistance in a range of species, from nematodes to fishes (Fig. 1C; Alzahrani and Ebert, 2018;Dolci et al, 2013Dolci et al, , 2017Dolci et al, , 2014Fitzgerald et al, 2016;Schunck and Liess, 2022;Wang et al, 2020). Similarly, exposure to polystyrene microplastics over two generations can increase heat tolerance in Daphnia magna (Chang et al, 2023).…”

Chemical Mixtures and Multiple Stressors: Same but Different?

“…Toxicokinetic-toxicodynamic models and related bioenergetic models (details in next section) could be adapted for other stressors and then be useful for multiple stressor research (Goussen et al, 2020). Finally, a recent study introduced the concept of stressor action curves, based on the stressor addition null model, that successfully predicted synergistic effects for different sequential treatments of a chemical and nonchemical stressor on a single species (Schunck & Liess, 2022).…”