U.S. Geological Survey, Columbia Environmental Research Center, Columbia, MO 65201, USA.
Department of Ecology, Montana State University, Bozeman, MT 59717, USA.
Sci Adv. 2020 May 15;6(20):eaaz4880. doi: 10.1126/sciadv.aaz4880. eCollection 2020 May.
Mercury (Hg) biomagnification in aquatic food webs is a global concern; yet, the ways species traits and interactions mediate these fluxes remain poorly understood. Few pathways dominated Hg flux in the Colorado River despite large spatial differences in food web complexity, and fluxes were mediated by one functional trait, predation resistance. New Zealand mudsnails are predator resistant and a trophic dead end for Hg in food webs we studied. Fishes preferred blackflies, which accounted for 56 to 80% of Hg flux to fishes, even where blackflies were rare. Food web properties, i.e., match/mismatch between insect production and fish consumption, governed amounts of Hg retained in the river versus exported to land. An experimental flood redistributed Hg fluxes in the simplified tailwater food web, but not in complex downstream food webs. Recognizing that species traits, species interactions, and disturbance mediate contaminant exposure can improve risk management of linked aquatic-terrestrial ecosystems.
汞（Hg）在水生食物网中的生物放大是一个全球性的问题；然而，物种特征和相互作用影响这些通量的方式仍知之甚少。尽管食物网的复杂性存在很大的空间差异，但在科罗拉多河中，只有少数几种途径主导了汞的流动，而且这些流动是由一种功能特征，即抗捕食性来调节的。在我们研究的食物网中，新西兰泥螺具有抗捕食性，是汞的营养末端。鱼类更喜欢黑蝇，即使在黑蝇稀少的情况下，黑蝇也占汞流向鱼类的 56%至 80%。食物网的特性，即昆虫产量与鱼类消费之间的匹配/不匹配，决定了汞在河流中被保留的量与被输出到陆地的量。一次实验性洪水重新分配了简化的尾部水食物网中的汞通量，但没有分配复杂的下游食物网中的汞通量。认识到物种特征、物种相互作用和干扰调节污染物暴露，可以改善对相互关联的水生-陆地生态系统的风险管理。
