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Journal of Marine Biology
Volume 2012, Article ID 492308, 12 pages
Research Article

Kelp Forests versus Urchin Barrens: Alternate Stable States and Their Effect on Sea Otter Prey Quality in the Aleutian Islands

1School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 905 N. Koyukuk Drive, 245 O’Neill Building, Fairbanks, AK 99775, USA
2Global Undersea Research Unit, University of Alaska Fairbanks, 905 N. Koyukuk Drive, 217 O’Neill Building, Fairbanks, AK 99775, USA

Received 11 August 2011; Revised 28 November 2011; Accepted 29 November 2011

Academic Editor: Andrew McMinn

Copyright © 2012 Nathan L. Stewart and Brenda Konar. 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.


Macroalgal and urchin barren communities are alternately stable and persist in the Aleutians due to sea otter presence and absence. In the early 1990s a rapid otter population decline released urchins from predation and caused a shift to the urchin-dominated state. Despite increases in urchin abundance, otter numbers continued to decline. Although debated, prey quality changes have been implicated in current otter population status. This study examined otter prey abundance, size, biomass, and potential energy density in remnant kelp forest and urchin-dominated communities to determine if alternate stable states affect prey quality. Findings suggest that although urchin barrens provide more abundant urchin prey, individual urchins are smaller and provide lower biomass and potential energy density compared to kelp forests. Shifts to urchin barrens do affect prey quality but changes are likely compensated by increased prey densities and are insufficient in explaining current otter population status in the Aleutians.