Fixing broken ecosystems: Conservation and restoration in Fossil Creek and Cuatro Cienegas

Authors: Jane C. Marks, Eric Dinger, Allen Haden, Matthew W. O’Neill, Cinnamon Pace, Ken Adams, Zacchaeus Compson, Dean A. Hendrickson

Year: 2008 (xl)

Abstract

Our research program integrates food web ecology with biological monitoring to quantify the relative magnitude of different threats to freshwater biodiversity and study the restoration potential of management actions. In Fossil Creek, Arizona we combined stable isotope studies of food web structure with fish surveys to show that native fish were more threatened by the presence of exotic bass and sunfish than the reduction of flow. We tested this result using a before after control impact design following the restoration of Fossil Creek where flow was restored as part of dam decommissioning and exotic fish were removed from a large section of the river. Native fish responses were consistent with predictions, showing a fifty fold increase in native fish with the return of flow and the removal of exotic fish relative to a three fold increase due to restoration of flow alone where exotics never invaded. Native fish did not increase with the restoration of flow where exotic fish remain. In Cuatro Cienegas, Mexico, we combined stable isotope studies with field surveys and competition experiments to test how exotic fish affect native cichlids. We found that the effects of the exotic fish, Hemichromis guttatus were most pronounced on juvenile cichlids but relatively minor on adult cichlids. In a second experiment we tested whether native cichlids are essential to the persistence of stromatolites, a unique life form found only in a few freshwater habitats worldwide. We found that the molluscivore morph of this polymorphic fish maintains the integrity of stromatolites via a trophic cascade where molluscivores control snail densities thereby releasing stromatolites from intense grazing pressure