Evolutionary Stress Ecology and Ecotoxicology, KU Leuven, Deberiotstraat 32, B-3000 Leuven, Belgium; Laboratory of Aquatic Ecology, Evolution and Conservation, KU Leuven, Deberiotstraat 32, B-3000 Leuven, Belgium.
Laboratory of Aquatic Ecology, Evolution and Conservation, KU Leuven, Deberiotstraat 32, B-3000 Leuven, Belgium.
Aquat Toxicol. 2018 Sep;202:90-96. doi: 10.1016/j.aquatox.2018.07.005. Epub 2018 Jul 7.
Effects of stressors on body stoichiometry are important as these may cascade through food webs. Contamination and global warming are two key anthropogenic stressors, yet their effects on body stoichiometry have been rarely tested. Further, while thermal evolution may increase the ability to deal with warming, it is unknown how thermal evolution modifies the effect of contaminants under warming. Using resurrection ecology, we studied two Daphnia magna subpopulations (old/recent) of which the recent subpopulation evolved a higher heat tolerance. We exposed both subpopulations to a sublethal concentration of nano zinc oxide (nZnO) and 4 °C warming and quantified their effects on body stoichiometry: carbon (C), nitrogen (N), phosphorus (P) contents and their ratios (C:N, C:P, N:P). In the old subpopulation, nZnO only marginally decreased the C content and had no effect on N and P contents and their ratios. In contrast, in the recent subpopulation nZnO strongly increased the body P content (+51%) and reduced the C:P (-34%) and N:P (-34%) ratios at 24 °C but not at 20 °C. Moreover, these stoichiometric changes were not explained by changes of corresponding macromolecules as assumed by theory. Our results indicate that the stoichiometric responses to nZnO in Daphnia are temperature-dependent and modified by rapid evolution. The observed changes in body stoichiometry may affect the food quality of this important prey and have the potential to cascade through food webs and shape nutrients cycling.
胁迫对生物体化学计量的影响很重要，因为这些影响可能会通过食物网级联放大。污染和全球变暖是两种关键的人为胁迫因素，但它们对生物体化学计量的影响很少得到检验。此外，尽管热进化可能会增加应对变暖的能力，但热进化如何在变暖条件下改变污染物的影响尚不清楚。我们利用复苏生态学，研究了两个大型溞（Daphnia magna）亚种群（老/新），其中新亚种群具有更高的耐热性。我们将这两个亚种群暴露于亚致死浓度的纳米氧化锌（nZnO）和 4°C 的升温环境中，并量化了它们对生物体化学计量的影响：碳（C）、氮（N）、磷（P）含量及其比值（C:N、C:P、N:P）。在老亚种群中，nZnO 仅略微降低了 C 含量，对 N 和 P 含量及其比值没有影响。相比之下，在新近进化的亚种群中，nZnO 强烈增加了体内 P 含量（增加了 51%），并降低了 C:P（减少了 34%）和 N:P（减少了 34%）比值，而在 20°C 时则没有这种影响。此外，这些化学计量变化不能用理论所假设的相应大分子的变化来解释。我们的研究结果表明，大型溞对 nZnO 的化学计量响应取决于温度，并受到快速进化的影响。观察到的生物体化学计量的变化可能会影响这种重要猎物的食物质量，并有可能通过食物网级联放大和塑造养分循环。
