PARENT SESSION
Poster Session #21: Riparian and Wetland Restoration.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Aiding Rio Grande restoration by using stable isotope analyses to characterize the past and present condition of the river food web.

Edwards, Melanie^*,1, Turner, Thomas^1,2, ¹ University of New Mexico, Albuquerque, NM² University of New Mexico, Albuquerque, NM

ABSTRACT- Obtaining information on the pre-disturbance condition of altered ecosystems is often difficult. A lack of this type of information can hinder ecosystem restoration efforts. The Rio Grande River of New Mexico has been severely altered and is in dire need of restoration or rehabilitation. The aim of our research is to provide information on the prior condition of the Rio Grande aquatic food web. Because no reference systems exist for the Rio Grande, we developed an alternative method for assessing change over time in the food web. We are using stable isotope analyses of museum preserved fish specimens, along with analyses of recently collected fishes, to construct a timeline of change in the Rio Grande food web. Results of the first step in this research, which indicated that formalin-induced changes in carbon, nitrogen, and sulfur isotope values of fish tissue are small (< 1.5 ‰) compared to changes expected from natural fractionation processes that are of interest in ecosystem studies, will be presented. Upon completion of this phase of the project, we performed stable isotope analyses (C, N, and S) on preserved fishes from 1940 to present in order to observe changes in the aquatic food web of the Rio Grande. Additionally, we analyzed many components of the current food web, including invertebrates, plants, and fishes. The preliminary results of this study of the past and present Rio Grande food web will be presented, along with causal factors that may have contributed to these changes. We will also address the possible effects of restoration on the Rio Grande food web.

KEY WORDS: stable isotopes, restoration, river, food web