Time between Sequential Exposures to Multiple Stress Turns Antagonism into Synergism

Environmental Science & Technology, vol. 56, pp. 14660–14667

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.

Authors 2

1. Florian Schunck corresponding Aachen Institute of Ecology & Computational Life Science

   RWTH Aachen University · Helmholtz Centre for Environmental Research

   Affiliation as printed

   Department of System-Ecotoxicology, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, 04318 Leipzig, Germany

   Institute of Ecology & Computational Life Science, Rheinisch-Westfälische Technische Hochschule (RWTH), Templergraben 55, 52056 Aachen, Germany

2. Matthias Liess Aachen Institute of Ecology & Computational Life Science

   RWTH Aachen University · Helmholtz Centre for Environmental Research

   Affiliation as printed

   Department of System-Ecotoxicology, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, 04318 Leipzig, Germany

   Institute of Ecology & Computational Life Science, Rheinisch-Westfälische Technische Hochschule (RWTH), Templergraben 55, 52056 Aachen, Germany