DISSERTATION RESEARCH: Stable Isotope Analysis of Current and Historical Aquatic Food Webs

人类活动对河流生态系统的影响是一个全球性的问题。 这项研究的重点是在中格兰德河（MRG）的新墨西哥州，这已严重改变自20世纪初。 研究的总体目标是记录MRG水生食物网的现状并重建其过去的状况，以了解河流调控（例如，大坝和堤坝的建设，大规模的引水供人使用）已经影响到生活在那里的生物。 天然存在的稳定同位素将被用作生物化学示踪剂，以记录从植物到鱼类的整个MRG生态系统中食物能量的生产和循环。 然后，我们将比较现代鱼类的同位素签名与西南生物博物馆中保存的历史鱼类标本（长达63年），以评估（i）由于洪水周期的改变，进入食物网的碳源随时间的变化，（ii）随着非本地鱼类数量的增加和许多本地鱼类数量的减少，鱼类食物网的变化，以及（iii）来自农业的氮肥投入随时间的变化。 这项研究将推进水生生物群落如何应对十年时间跨度的河流整治的知识。 更广泛地说，这项研究的重点是开发一种新的方法来解决具有挑战性的问题，重建社区食物网结构和功能的河流生态系统改变。

Human alteration of river ecosystems is an enormous concern worldwide. This study is focused in the Middle Rio Grande (MRG) of New Mexico, which has been severely altered since the early 1900s. The overall aim of the research is to document present conditions and reconstruct past conditions of the MRG aquatic food web to understand how river regulation (e.g., dam and levee construction, large-scale diversion of water for human use) has affected organisms that live there. Naturally occurring stable isotopes will be used as biochemical tracers to document production and cycling of food energy through the entire MRG ecosystem from plants to fishes. We will then compare isotope signatures of present day fishes to historical fish specimens held in the Museum of Southwestern Biology (up to 63 years) to evaluate (i) changes over time in carbon sources entering the food web due to altered flood cycles, (ii) changes in fish food web as non-native fish species increased in abundance and many native fishes declined, and (iii) variation in nitrogen fertilizer inputs from agriculture over time. This research will advance knowledge of how aquatic communities respond to river regulation over decadal time spans. More broadly, this research focuses on developing a novel method to address the challenging problem of reconstructing community food web structure and function following river ecosystem alteration.