Center for Limnology, University of Wisconsin, Madison, Wisconsin, United States of America.
PLoS One. 2012;7(7):e41829. doi: 10.1371/journal.pone.0041829. Epub 2012 Jul 27.
Organohalogen compounds are some of the most notorious persistent pollutants disturbing the Earth biosphere. Although human-made, these chemicals are not completely alien to living systems. A large number of natural organohalogens, part of the secondary metabolism, are involved in chemical trophic interactions. Surprisingly, the relationship between organisms' trophic position and synthetic organohalogen biotransformation capability has not been investigated. We studied the case for polybromodiphenyl ethers (PBDE), a group of flame-retardants of widespread use in the recent years, in aquatic food webs from remote mountain lakes. These relatively simple ecosystems only receive pollution by atmospheric transport. A large predominance of the PBDE congener currently in use in Europe, BDE-209, largely dominated the PBDE composition of the basal resources of the food web. In contrast, primary consumers (herbivores and detritivores) showed a low proportion of BDE-209, and dominance of several less brominated congeners (e.g. BDE-100, BDE47). Secondary consumers (predators) showed large biomagnification of BDE-209 compare to other congeners. Finally, top predator fish characterized by low total PBDE concentrations. Examination of the bromine stable isotopic composition indicates that primary consumers showed higher PBDE biotransformation capability than secondary consumers. We suggest that the evolutionary response of primary consumers to feeding deterrents would have pre-adapted them for PBDE biotransformation. The observed few exceptions, some insect taxa, can be interpreted in the light of the trophic history of the evolutionary lineage of the organisms. Bromine isotopic composition in fish indicates that low PBDE values are due to not only biotransformation but also to some other process likely related to transport. Our finding illustrates that organohalogen compounds may strongly disturb ecosystems even at low concentrations, since the species lacking or having scarce biotransformation capability may be selectively more exposed to these halogenated hydrophobic semi-volatile organic pollutants due to their high bioaccumulation potential.
有机卤化合物是一些最臭名昭著的持久性污染物，扰乱地球生物圈。虽然是人为的，但这些化学物质并不是完全与生命系统无关。大量的天然有机卤化物，作为次生代谢的一部分，参与了化学营养相互作用。令人惊讶的是，生物体的营养位置与合成有机卤化物生物转化能力之间的关系尚未得到研究。我们研究了近年来广泛使用的阻燃剂多溴二苯醚（PBDE）在偏远山区湖泊水生食物网中的情况。这些相对简单的生态系统只受到大气传输污染的影响。目前在欧洲使用的 PBDE 同系物的一个大优势，BDE-209，在很大程度上主导了食物网基础资源的 PBDE 组成。相比之下，初级消费者（食草动物和碎屑食者）的 BDE-209 比例较低，而几种溴化程度较低的同系物（如 BDE-100、BDE47）则占主导地位。次级消费者（捕食者）的 BDE-209 生物放大倍数明显高于其他同系物。最后，顶级掠食性鱼类的总 PBDE 浓度较低。对溴稳定同位素组成的研究表明，初级消费者比次级消费者具有更高的 PBDE 生物转化能力。我们认为，初级消费者对摄食抑制物的进化反应使它们预先适应了 PBDE 的生物转化。一些昆虫类群的少数例外情况可以根据生物体进化谱系的营养历史来解释。鱼类的溴同位素组成表明，低 PBDE 值不仅是由于生物转化，还由于其他一些可能与运输有关的过程。我们的发现表明，即使在低浓度下，有机卤化合物也可能强烈干扰生态系统，因为缺乏或缺乏生物转化能力的物种可能由于其高生物累积潜力而选择性地更容易受到这些卤代疏水性半挥发性有机污染物的影响。
