Aarhus University, Department of Bioscience, DK-8600, Silkeborg, Denmark.
Aarhus University, Department of Bioscience, DK-8600, Silkeborg, Denmark.
Environ Pollut. 2019 Nov;254(Pt B):113105. doi: 10.1016/j.envpol.2019.113105. Epub 2019 Aug 24.
Soil organisms are exposed to natural and anthropogenic stressors, such as xenobiotics. However, to simplify and make laboratory experiments easily reproducible, natural stressors are often excluded from ecotoxicological studies and risk assessment. This might underestimate the effect of chemicals, since synergistic interactions between chemicals and natural stressors might occur, creating a more severe impact than expected. Several studies have addressed simultaneous exposure to natural and chemical stressors, but very little is known of about the persistence of these interactions during recovery. Here, we examined if recovery after chemical stress exposure was important for the ability of springtails (Folsomia candida) to tolerate subsequent drought- and heat stress. Nonylphenol (NP) and phenanthrene (PHE) was tested and their isolated toxicity resulted in LC values of 206 mg NP kg dry soil and 109 mg PHE kg dry soil in a 7-day test. Elimination of NP and PHE was rapid and only trace amounts remained in springtail tissues after 3-7 days of recovery. Isolated studies of drought and heat shock on Folsomia candida resulted in a lethal effect for 50% of the animals (LRH) at a relative humidity (RH) of 97.9%, and 190 min at 34 °C was shown to be lethal for 50% of the test species (LT). The results showed, as expected, significant synergistic interactions between the effects of the chemicals and the effects of drought and heat stress. The negative effects of NP and PHE on the drought tolerance disappeared within 7 days post exposure. Springtails exposed to PHE also recovered their heat tolerance within 7 days post exposure, while NP exposed animals had not fully recovered their heat tolerance 14 days after exposure. Overall, a recovery period post chemical exposure was found to be very important for springtails in order to cope with natural stressors like heat and drought.
土壤生物会暴露在自然和人为压力源下，例如外源化合物。然而，为了简化并使实验室实验易于重现，生态毒理学研究和风险评估通常排除自然压力源。这可能会低估化学物质的影响，因为化学物质和自然压力源之间可能会发生协同相互作用，从而造成比预期更严重的影响。已有几项研究涉及同时暴露于自然和化学压力源，但对于这些相互作用在恢复过程中的持续时间知之甚少。在这里，我们研究了在经历化学胁迫暴露后的恢复是否对跳虫（Folsomia candida）耐受随后的干旱和热胁迫的能力很重要。测试了壬基酚（NP）和菲（PHE），它们的单独毒性导致在 7 天测试中，NP 的 LC 值为 206 mg NP kg 干土，PHE 的 LC 值为 109 mg PHE kg 干土。NP 和 PHE 的消除速度很快，在恢复 3-7 天后，跳虫组织中仅残留痕量。对 Folsomia candida 进行的单独干旱和热冲击研究表明，相对湿度为 97.9%时，有 50%的动物（LRH）致死，而 34°C 190 min 对 50%的测试物种（LT）致死。结果表明，正如预期的那样，化学物质的作用与干旱和热应激的作用之间存在显著的协同相互作用。NP 和 PHE 对耐旱性的负面影响在暴露后 7 天内消失。暴露于 PHE 的跳虫在暴露后 7 天内也恢复了对热的耐受性，而暴露于 NP 的动物在暴露后 14 天内尚未完全恢复对热的耐受性。总体而言，暴露于化学物质后需要一个恢复期，这对跳虫应对热和干旱等自然压力源非常重要。
