DO–Temperature habitat loss due to eutrophication in Tenkiller Reservoir, Oklahoma, USA

Abstract

Tenkiller Reservoir became eutrophic between 1975 and 1986, primarily due to poultry litter practices in the watershed, resulting in rapid dissolved oxygen (DO) depletion in the meta- and hypolimnion. Depletion was driven largely by high riverine-zone algal production due to high phosphorus inflow and internal loading, and the subsequent plunging of riverine water to the meta- and hypolimnion. This process of DO depletion greatly reduced summer habitat for cool-water fish species. Optimal and suboptimal habitat for smallmouth bass (SMB) growth averaged only 10 and 25% of total reservoir volume, respectively, during mid-June to mid-September in 2005 and 2006. For walleye (WAL), acceptable (suboptimal) habitat was essentially absent (<1%) due to its lower temperature criterion. By contrast, habitat for both species was much greater in oligo-mesotrophic Broken Bow, a physically similar reference reservoir. Long-term catch rates for SMB and WAL during systematic surveys averaged 3-fold higher in Broken Bow, with greater acceptable DO–temperature habitat than in Tenkiller. Conversely, catch rates for largemouth bass, a warm-water species preferring eutrophic conditions, averaged 2-fold higher in Tenkiller than Broken Bow. These catch rate differences are consistent with the DO–temperature conditions available during the stratified period and the trophic states in these 2 reservoirs. Recovery of cool-water fish habitat in Tenkiller by ceasing poultry litter application is predicted to be slow. [Supplemental materials are available for this article. Go to the publisher's online edition of Lake and Reservoir Management to view the supplemental file.]