Data from: Environmental context and contaminant biotransport by Pacific salmon interact to mediate the bioaccumulation of contaminants by stream-resident fish

1.The extent to which environmental context mediates the bioaccumulation of biotransported contaminants by stream-resident organisms is poorly understood. For example, it is unclear the extent to which contaminant type, instream characteristics, or resident fish identity interact to influence the uptake of contaminants deposited by Pacific salmon (Oncorhynchus spp.) during their spawning runs. 2.To address this uncertainty, we sampled four stream-resident fish species from 13 watersheds of the Laurentian Great Lakes in locations with and without salmon runs across a gradient of instream and watershed characteristics. We determined the polychlorinated biphenyl (PCB) and mercury (Hg) concentration along with the stable isotope ratios for salmon and stream-resident fish. 3.We found that stream-resident fish PCB concentrations were higher in reaches with salmon and were positively related to δ15N. In contrast, resident fish Hg concentrations were similar or lower in reaches with salmon compared to reaches lacking salmon and either exhibited a negative or no relationship with δ15N. 4.Based upon AICc, resident fish exhibited species-specific PCB concentrations that were positively related to salmon PCB flux. Hg burdens exhibited an interaction between fish length and salmon Hg flux – as salmon Hg inputs increased, Hg levels decreased with increasing resident fish length. Because salmon eggs are enriched in PCBs but depleted in Hg, contaminant loads of resident fish appear to be driven by consumption of salmon eggs. We found no support for models that included the mediating influence of instream or watershed factors. 5.Synthesis and applications. Our results highlight that contaminants bioaccumulate differently depending on contaminant type, species identity, and the trophic pathway to contamination. Consequently, consideration of the recipient food web and route of exposure is critical to understanding the fate of biotransported contaminants in ecosystems. The transfer of contaminants by migratory organisms represents an understudied stressor in ecology. Effective management of biotransported contaminants will require the delineation of hotspots of biotransport and implementation of best management practices to reduce inputs of salmon-derived pollutants.1. 环境背景对溪流定居生物（stream-resident organisms）富集生物转运污染物的介导程度，目前仍未得到充分认知。例如，尚不清楚污染物类型、溪流生境特征，以及定居鱼类种类之间的相互作用，会在多大程度上影响太平洋鲑（Oncorhynchus spp.）洄游产卵时沉积的污染物的摄取过程。 2. 为厘清这一认知空白，我们从圣劳伦斯五大湖（Laurentian Great Lakes）的13个流域中采样了4种溪流定居鱼类，采样点覆盖有无鲑鱼洄游的区域，且涵盖了不同梯度的溪流生境与流域特征。我们测定了鲑鱼及溪流定居鱼类体内的多氯联苯（polychlorinated biphenyl, PCB）、汞（mercury, Hg）浓度，以及稳定同位素比值。 3. 研究结果显示，有鲑鱼分布的河段中，溪流定居鱼类的PCB浓度更高，且与δ¹⁵N呈正相关关系。与之相反，相较于无鲑鱼分布的河段，有鲑鱼分布河段的定居鱼类Hg浓度相近甚至更低，且其与δ¹⁵N要么呈负相关，要么无显著相关性。 4. 基于AICc准则，定居鱼类的PCB浓度具有物种特异性，且与鲑鱼PCB通量呈正相关。鱼类体内的Hg负荷则与鱼体长度及鲑鱼Hg通量存在交互作用：随着鲑鱼Hg输入量增加，定居鱼类的Hg水平随其体长增加而降低。由于鲑鱼卵富含PCB但Hg含量较低，定居鱼类的污染物负荷似乎由捕食鲑鱼卵所驱动。我们未发现支持溪流生境或流域因素存在介导作用的模型证据。 5. 综合与应用。本研究结果表明，污染物的生物富集过程因污染物类型、物种种类以及污染营养通路的不同而存在差异。因此，要理解生态系统中生物转运污染物的归趋，需充分考虑受纳食物网及暴露路径。由洄游生物介导的污染物迁移，是生态学领域尚未得到充分研究的胁迫因子之一。对生物转运污染物进行有效管理，需明确生物转运热点区域，并实施最佳管理实践以减少鲑鱼源性污染物的输入。