Effects of river drying on aquatic food web structure in the Rio Grande, New Mexico

Authors: Jennifer S. Kraus, Ayesha S. Burdett, Thomas F. Turner

Year: 2010 (xlii)

Abstract

The Rio Grande that flows through Albuquerque, New Mexico is subject to harsh, dry conditions and seasonal drought. During the dry season, river habitats can be reduced to small pools where aquatic food webs are potentially affected by harsh abiotic conditions and negative biotic interactions (e.g. competition and predation). To examine effects of dry-down on food web dynamics, weekly surveys were conducted in the river channel during summer 2006. In 2009, drying pool environments were examined in experimental mesocosms (n=12), and samples were collected over a 6 week period. Isotopic ratios (Á¤¹³C & Á¤¹⁵N) from algae, detritus, invertebrates and fishes in the Rio Grande in 2006 and the 2009 mesocosm experiment were used to evaluate temporal dynamics of aquatic interactions in drying pools. Stable isotope signatures changed significantly over time in the 2006 main channel data, whereas isotopic data from the 2009 mesocosm experiment showed no differences in food web structure over time, perhaps due to limited data. However, dramatic changes in species richness, abundance, and resource availability occur over very short timescales in drying aquatic habitats. The efficacy of isotopic analysis to identify key temporal changes in species interactions will be discussed.