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

人类对河流生态系统的改变是全世界关注的一个重大问题。本研究的重点是新墨西哥州的中里约热内卢格兰德（MRG），该地区自20世纪初以来已经发生了严重的变化。该研究的总体目标是记录MRG水生食物网的现状和重建过去的状况，以了解河流管理（例如，水坝和堤坝建设，大规模的人类用水转移）如何影响生活在那里的生物。天然存在的稳定同位素将被用作生化示踪剂，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，我们将比较现今鱼类的同位素特征与西南生物博物馆保存的历史鱼类标本（长达63年），以评估(i)由于洪水周期改变而进入食物网的碳源随时间的变化，（ii）由于非本地鱼类丰富度增加而许多本地鱼类减少而鱼类食物网的变化，以及（iii）随着时间的推移农业氮肥投入的变化。这项研究将推进水生群落如何在十年时间跨度内对河流调节作出反应的知识。更广泛地说，本研究的重点是开发一种新的方法来解决河流生态系统变化后重建群落食物网结构和功能的挑战性问题。

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.