, Volume 724, Issue 1, pp 91–107

Biological interactions maintain the boundaries between kelp forests and urchin barrens in the Aleutian Archipelago

  • Brenda Konar
  • Matthew S. Edwards
  • James A. Estes
Primary Research Paper

DOI: 10.1007/s10750-013-1727-y

Cite this article as:
Konar, B., Edwards, M.S. & Estes, J.A. Hydrobiologia (2014) 724: 91. doi:10.1007/s10750-013-1727-y


This study used benthic surveys and manipulative experiments to examine (1) if boundaries between kelp forests and urchin barrens exist at multiple locations spanning the Aleutian Archipelago, (2) if these boundaries are spatially stable, and (3) how changes in algal density within the kelp forests influence the ability of urchins to invade them. Our results demonstrate that sharply punctuated kelp forest-urchin barren boundaries occur throughout the Archipelago, and they are spatially stable for at least 2 years. Further, when all macroalgae were experimentally removed from the kelp forest side of the boundaries, urchins rapidly moved into these clearings and excluded macroalgae for up to 2 years. However, these movements were not observed where 75% or less of the macroalgae was removed (leaving 25% or more in place), suggesting that even low macroalgal abundances can prevent urchins from invading the kelp forests. Further, urchin densities were negatively related to kelp density, again indicating that kelp can reduce urchin densities. While the ability of urchins to overgraze kelp forests is widely known, our results indicate that kelp can inhibit urchins, that these inhibitory influences are a widely recurrent phenomenon, and that this interaction is important to maintaining kelp forests across the Aleutians.


AgarumAleutian IslandsEualariaGrazingKelpUrchinBarrens

Supplementary material

10750_2013_1727_MOESM1_ESM.docx (18 kb)
Supplementary material 1 (DOCX 17 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • Brenda Konar
    • 1
  • Matthew S. Edwards
    • 2
  • James A. Estes
    • 3
  1. 1.School of Fisheries and Ocean SciencesUniversity of Alaska FairbanksFairbanksUSA
  2. 2.Department of BiologySan Diego State UniversitySan DiegoUSA
  3. 3.Department of Ecology and Evolutionary BiologyUniversity of CaliforniaSanta CruzUSA