Bringing a food web perspective to conservation science: Assessing threats and setting restoration targets.
Marks, Jane*,1, Haden, G1, Dinger, Eric1, Adams, Ken1, Carter, Cody1, 1 Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Flagstaff, AZ, USA
ABSTRACT- Freshwater ecosystems are in peril because they aggregate multiple threats in a watershed. In many systems, managers can identify the prominent threats and implement programs to mitigate them. Most assessment programs however monitor physical rather than biological responses, even when conservation of biodiversity is an explicit goal. We combined stable isotopes and manipulative experiments to bring a food web perspective to conservation and restoration of two ecosystems that face similar threats: water extraction and exotic species. In Cuatro Cienegas, Mexico we employed stable isotopes to identify which native species are most likely to be affected by an exotic fish and showed through manipulative experiments that the stable isotope analysis correctly predicted that the exotic would compete with juvenile cichlid fish. In Fossil Creek, AZ a stream slated for two major restoration actions: dam decommissioning and exotic fish removal. We used stable isotopes to compare food web structure in a pristine site (a reach above the dam with full flows and no exotic fish), with disturbed sites. Results indicate that the trophic level of native fish decreases and that there is more resource overlap among functional feeding groups of macroinvertebrates in disturbed relative to pristine sites. This food web analysis will be used to assess the success of the restoration actions.
Key words: isotope food webs, invasive species, aquatic restoration, dam decommissioning
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