Department of Environmental Science and Analytical Chemistry, Stockholm University , Svante Arrhenius väg 8, SE-106 91 Stockholm, Sweden.
Mass Spectrometry Laboratory, Center for Physical Science and Technology , Savanoriu 231, LT-02300 Vilnius, Lithuania.
Environ Sci Technol. 2016 Aug 2;50(15):8296-304. doi: 10.1021/acs.est.6b01731. Epub 2016 Jul 12.
Trophic magnification factor (TMF) analysis employs stable isotope signatures to derive biomagnification potential for environmental contaminants. This approach relies on species δ(15)N values aligning with their trophic position (TP). This, however, may not always be true, because toxic exposure can alter growth and isotope allocation patterns. Here, effects of PCB exposure (mixture of PCB18, PCB40, PCB128, and PCB209) on δ(15)N and δ(13)C as well as processes driving these effects were explored using the cladoceran Daphnia magna. A two-part experiment assessed effects of toxic exposure during and after exposure; juvenile daphnids were exposed during 3 days (accumulation phase) and then allowed to depurate for 4 days (depuration phase). No effects on survival, growth, carbon and nitrogen content, and stable isotope composition were observed after the accumulation phase, whereas significant changes were detected in adults after the depuration phase. In particular, a significantly lower nitrogen content and a growth inhibition were observed, with a concomitant increase in δ(15)N (+0.1 ‰) and decrease in δ(13)C (-0.1 ‰). Although of low magnitude, these changes followed the predicted direction indicating that sublethal effects of contaminant exposure can lead to overestimation of TP and hence underestimated TMF.
营养级放大倍数（TMF）分析利用稳定同位素特征来推断环境污染物的生物放大潜力。这种方法依赖于物种 δ(15)N 值与其营养级（TP）相一致。然而，这并不总是正确的，因为有毒物质的暴露会改变生长和同位素分配模式。在这里，使用枝角类动物大型溞研究了 PCB 暴露（PCB18、PCB40、PCB128 和 PCB209 的混合物）对 δ(15)N 和 δ(13)C 的影响，以及驱动这些影响的过程。一个两部分的实验评估了在暴露期间和暴露后的有毒暴露的影响；幼年溞类在 3 天内（积累阶段）暴露，然后允许它们在 4 天内净化（净化阶段）。在积累阶段后，没有观察到对生存、生长、碳和氮含量以及稳定同位素组成的影响，但在净化阶段后，成年溞类出现了显著变化。特别是，观察到氮含量显著降低和生长抑制，同时 δ(15)N 增加（+0.1 ‰）和 δ(13)C 减少（-0.1 ‰）。尽管幅度较小，但这些变化符合预期方向，表明污染物暴露的亚致死效应可能导致 TP 的高估，从而低估 TMF。
