Division of Soil and Water Management, KULeuven, Heverlee, Belgium.
Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, Gent, Belgium.
Environ Toxicol Chem. 2018 Aug;37(8):2153-2164. doi: 10.1002/etc.4171. Epub 2018 Jul 13.
Ecological interactions and abiotic stress factors may significantly affect species sensitivities to toxicants, and these are not incorporated in standard single-species tests. The present study tests whether a model, calibrated solely on single-species data, can explain abiotic stress factors in a two-species microcosm, a test applied to the effects of nutritional stress (phosphorus [P] limitation) on zinc (Zn) toxicity to Daphnia magna. A population model was developed based on P- and Zn-dependent algal and daphnid growth. Two separate two-species (phytoplankton Pseudokirchneriella subcapitata and consumer D. magna) microcosm experiments with P × Zn factorial combinations and a different pH (7.3 and 7.8) were set up to validate the model. The 21-d daphnid population size was considerably reduced by increased Zn and by decreased P supply, with a significant (p < 0.001) interaction between the 2 factors. The observed median effective concentration (EC50) of Zn on D. magna population size varied 12-fold (25 to 310 μg Zn L ), with the lowest EC50 values found at the highest pH and high P treatments. For both experiments, Zn toxicity to D. magna was correctly predicted within a factor of 2 for EC50 values, and this is explained by the model through 1) a higher phytoplankton Zn sensitivity at higher pH, affecting food supply to D. magna, and 2) an increased algal P content at higher Zn, offering a nutritional benefit to daphnids that counteracts direct Zn toxicity under P limitation. The present study illustrates that indirect effects of Zn via producer-consumer relationships can outweigh the direct toxic effects and that models calibrated solely on single-species test data can help with interpreting these results in two-species systems. Environ Toxicol Chem 2018;37:2153-2164. © 2018 SETAC.
生态相互作用和非生物胁迫因素可能会显著影响物种对毒物的敏感性，而这些因素并未纳入标准的单一物种测试中。本研究检验了一种模型，该模型仅通过单一物种数据进行校准，是否可以解释两种生物微宇宙中的非生物胁迫因素，该测试应用于营养胁迫（磷[P]限制）对大型溞（Daphnia magna）的锌（Zn）毒性的影响。根据 P 和 Zn 依赖性藻类和溞类生长，建立了种群模型。进行了两个单独的具有 P×Zn 因子组合和不同 pH 值（7.3 和 7.8）的两种生物（浮游植物假微囊藻（Pseudokirchneriella subcapitata）和消费者大型溞）微宇宙实验，以验证模型。Zn 浓度增加和 P 供应减少都会导致 21 天溞类种群数量显著减少（p<0.001），这两个因素之间存在显著的相互作用。观察到的 Zn 对大型溞种群数量的中位有效浓度（EC50）变化了 12 倍（25 至 310μg Zn L），在最高 pH 值和高 P 处理下发现的 EC50 值最低。对于这两个实验，Zn 对大型溞的毒性在 EC50 值的 2 倍内被正确预测，这是通过模型解释的，原因是 1）较高 pH 值下浮游植物对 Zn 的敏感性更高，从而影响到大型溞的食物供应，以及 2）较高 Zn 下藻类的 P 含量增加，为 P 限制下的溞类提供了营养益处，从而抵消了直接的 Zn 毒性。本研究表明，通过生产者-消费者关系产生的 Zn 的间接影响可能大于直接毒性影响，并且仅通过单一物种测试数据校准的模型有助于解释这些在两种生物系统中的结果。环境毒理化学 2018；37：2153-2164。版权所有 2018 SETAC。
