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Journal of Environmental and Public Health
Volume 2012 (2012), Article ID 760108, 7 pages
Research Article

Impact of Summer Cattle Grazing on the Sierra Nevada Watershed: Aquatic Algae and Bacteria

1Department of Environmental Science and Policy and the John Muir Institute of the Environment, University of California, Davis, CA 95616, USA
2Department of Emergency Medicine, University of California Davis Medical Center, 4150 V Street, PSSB 2100, Sacramento, CA 95817, USA

Received 21 May 2011; Accepted 7 November 2011

Academic Editor: Pam R. Factor-Litvak

Copyright © 2012 Robert W. Derlet et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Introduction. We evaluated periphytic algal and microbial communities to assess the influence of human and cattle impact on Sierra water quality. Methods. 64 sites (lakes and streams from Lake Tahoe to Sequoia National Park, California) were sampled for suspended indicator bacteria and algae following standardized procedures. The potential for nonpoint pollution was divided into three categories: cattle-grazing areas (C), recreation use areas (R), or remote wildlife areas (W). Results. Periphyton was found at 100% of C sites, 89% of R sites, but only 25% of W sites. Eleven species of periphytic algae were identified, including Zygnema, Ulothrix, Chlorella, Spirogyra, mixed Diatoms, and Cladophoria. Mean benthic algae coverage was 66% at C sites compared to 2% at W sites ( 𝑃 < 0 . 0 5 ). The prevalence of E. coli associated with periphyton was 100% at C sites, 25% of R sites, and 0% of W sites. Mean E. coli CFU/gm of algae detected was: C = 173,000, R = 700, W = 0. ( 𝑃 < 0 . 0 5 ). Analysis of neighboring water for E. coli bacteria >100 CFU/100 mL: C = 91%, R = 8%, W = 0 ( 𝑃 < 0 . 0 5 ). Conclusion. Higher periphytic algal biomass and uniform presence of periphyton-attached E. coli corresponded to watersheds exposed to summer cattle grazing. These differences suggest cattle grazing compromises water quality.