Despite being remote, polar and sub-polar regions are increasingly threatened by global ecological change. For instance, South America’s sub-Antarctic forest ecoregion is considered one of the world’s last wilderness areas and a global reference site for pre-Industrial Revolution nutrient cycles. Nonetheless, the North American beaver (Castor canadensis) was introduced to Tierra del Fuego in 1946 and, as an invasive ecosystem engineer, has transformed the ecology of regional watersheds. Beavers’ engineering activities transform forested streams (FS) into beaver ponds (BP), where there is greater light and primary production (allochthonous organic matter) and, consequently, increased basal resource quality. To investigate this, we analyzed algal, diatom, fungal and bacterial fatty acid (FA) biomarkers in three basal resource categories (biofilm, very fine benthic organic matter, coarse benthic organic matter) and benthic consumers from four functional feeding groups (FFG). The amphipod Hyalella spp. was chosen as an indicator species due to its abundance and biomass in both habitats. Hyalella spp. had higher proportions of algal and bacterial FA in BP than FS. In FS, Hyalella spp. (gatherer) and Gigantodax spp. (filterer, Diptera) had greater contributions of higher quality FA (higher in polyunsaturated FA), while Rheochorema magallanicum (predator, Trichoptera) and Meridialaris spp. (scraper, Ephemeroptera) showed lower quality monounsaturated and saturated FA. All FFGs showed evidence of microbial FA and had higher levels of autochthonous FA biomarkers than their food resources. Scrapers had the greatest proportion of autochthonous FA. These data provide new insights into the utilization of basal resources by stream consumers in sub-Antarctic streams and how beavers modify these ecosystems.

中文翻译：

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脂肪酸阐明了北美海狸（Castor canadensis）入侵的亚南极河流底栖食物网动态

尽管地处偏远，极地和次极地地区正日益受到全球生态变化的威胁。例如，南美洲的亚南极森林生态区被认为是世界上最后的荒野地区之一，也是工业革命前营养循环的全球参考点。尽管如此，北美海狸 (Castor canadensis) 于 1946 年被引入火地岛，作为入侵生态系统工程师，改变了区域流域的生态。海狸的工程活动将森林溪流 (FS) 转变为海狸池塘 (BP)，在那里有更多的光照和初级生产（外来有机物质），从而提高了基础资源质量。为了对此进行研究，我们分析了三种基础资源类别（生物膜、非常细的底栖有机质、粗的底栖有机质）和来自四个功能性摄食组 (FFG) 的底栖消费者。片脚类 Hyalella spp。由于其在两个栖息地的丰富度和生物量而被选为指示物种。Hyalella spp. BP 中藻类和细菌 FA 的比例高于 FS。在 FS 中，Hyalella spp。（采集者）和 Gigantodax spp。（过滤器，双翅目）对更高质量的 FA（多不饱和 FA 的含量更高）有更大的贡献，而 Rheochorema magallanicum（捕食者，毛翅目）和 Meridialaris spp。(scraper, Ephemeroptera) 显示出较低质量的单不饱和和饱和 FA。所有 FFG 都显示出微生物 FA 的证据，并且比它们的食物资源具有更高水平的本土 FA 生物标志物。刮板具有最大比例的本土 FA。