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EXPERIMENTAL TEST OF ALTERNATIVE STABLE STATES ON A CORAL REEF

An unresolved issue for coral reef ecosystems is whether a persistent phase shift, such as a transition to a macroalgae dominated community, represents an alternative stable state. Robust evidence for alternative stable states in a natural system can come from a pulse manipulation that reveals the same location can be occupied by qualitatively different, self-replacing communities. There have been relatively few such experimental tests in general, and very few on coral reefs in particular. To test whether macroalgae can be an alternative stable state on a coral reef, we undertook a pulsed manipulation in Moorea, French Polynesia where lagoon patch reefs (bommies) are either dominated by the brown macroalgae Turbinaria ornata or are occupied by a mixture of coral and turf algae. Replicate bommies at the same site were assigned haphazardly to one of 3 treatments: (1) all Turbinaria removed from bommies initially covered by the alga, (2) Turbinaria left unmanipulated on bommies dominated by the alga, and (3) bommies dominated by turf algae left unmanipulated. After a year (corresponding to several generations of Turbinaria), Turbinaria removal bommies were all dominated by turf algae and unmanipulated bommies remained in their respective original states. During this time caged bommies were rapidly colonized by macroalgae indicating that colonization of macroalgae would have been robust in the absence of herbivory, and that fish herbivores were responsible for maintaining the Turbinaria removal plots in the turf algae state. These data support the notion that macroalgae can represent an alternative stable state on coral reefs.

Authors

Adam, T. C., University of California Santa Barbara, USA, adam@lifesci.ucsb.edu

Holbrook, S. J., University of California Santa Barbara, USA, holbrook@lifesci.ucsb.edu

Schmitt, R. J., University of California Santa Barbara, USA, schmitt@lifesci.ucsb.edu

Brooks, A. J., University of California Santa Barbara, USA, ajbrooks@ucsb.edu

Details

Poster presentation

Session #:067
Date: 03/02/2017
Time: 15:30 - 16:30
Location: Poster/Exhibit Hall

Presentation is given by student: No

PosterID: 530