Differences in Aquatic Invertebrate Diversity and Community Composition in Perennial Systems of the Rio Sonoyta Basin, Arizona and Sonora

Authors: Kelsey Hollien, Michael Bogan

Year: 2018

Abstract

Quitobaquito spring and pond and the nearby Rio Sonoyta are some of the only perennial water bodies in the western Sonoran Desert, and support populations of endangered Sonoyta mud turtle and pupfish. Quitobaquito is fed by a near constant flow from springs, while the Rio Sonoyta holds only a few perennial pools with intermittent flow after significant rainfall. We have started a comprehensive and comparative inventory of aquatic invertebrates in Quitobaquito and the Rio Sonoyta to understand how local food webs and, as a result, populations of mud turtles and pupfish, fluctuate through time. Since April 2017, we have had four seasonal sampling events at Quitobaquito and the Rio Sonoyta: April, June, October, and January. Each sampling event targeted the dominant microhabitat types present, including the headspring, pond, and spring channel riffles, runs, and pools at Quitobaquito and river pools and intermittent riffles at the Rio Sonoyta. Although Quitobaquito and the Rio Sonoyta are geographically adjacent, species richness and community composition differed between the locations. Quitobaquito was more taxonomically rich, with 124 species, whereas Rio Sonoyta only had 75 species. Species richness changed seasonally in the Rio Sonoyta, reaching its highest level during flowing periods in spring and lowest levels in the driest part of summer. In contrast, there appeared to be no predictable seasonal changes in species richness at Quitobaquito. Invertebrate communities in the Rio Sonoyta tended to be fairly distinct from those at Quitobaquito. However, pond samples at Quitobaquito more closely resembled the community of Rio Sonoyta pools than those of the other other microhabitat types at Quitobaquito. Understanding variability in invertebrate prey communities could help us better predict the needs of the imperiled species that depend on these perennial systems. Next steps in our research include stable isotope analyses to link potential prey items to pupfish and turtle populations.