Trophic cascade facilitates coral recruitment in a marine reserve

doi:10.1073/pnas.0702602104

Trophic cascade facilitates coral recruitment in a marine reserve

*Marine Spatial Ecology Lab, School of BioSciences, University of Exeter, Prince of Wales Road, Exeter EX4 4PS, United Kingdom;
^‡National Center for Ecological Analysis and Synthesis, University of California, 735 State Street, Suite 300, Santa Barbara, CA 93101;
^§Hopkins Marine Station, Stanford University, Oceanview Boulevard, Pacific Grove, CA 93950-3094;
^¶Marine Protected Areas Science Institute, National MPA Center, 110 Shaffer Road, Santa Cruz, CA 95060;
^‖Center for Biodiversity and Conservation, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192;
**Perry Institute for Marine Science, 100 North U.S. Highway 1, Suite 202, Jupiter, FL 33477;
^††Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149; and
^‡‡Department of Probability and Statistics, University of Sheffield, Hicks Building, Sheffield S3 7RH, United Kingdom

Communicated by Robert T. Paine, University of Washington, Seattle, WA, March 22, 2007 (received for review November 15, 2006)

Abstract

Reduced fishing pressure and weak predator–prey interactions within marine reserves can create trophic cascades that increase the number of grazing fishes and reduce the coverage of macroalgae on coral reefs. Here, we show that the impacts of reserves extend beyond trophic cascades and enhance the process of coral recruitment. Increased fish grazing, primarily driven by reduced fishing, was strongly negatively correlated with macroalgal cover and resulted in a 2-fold increase in the density of coral recruits within a Bahamian reef system. Our conclusions are robust because four alternative hypotheses that may generate a spurious correlation between grazing and coral recruitment were tested and rejected. Grazing appears to influence the density and community structure of coral recruits, but no detectable influence was found on the overall size-frequency distribution, community structure, or cover of corals. We interpret this absence of pattern in the adult coral community as symptomatic of the impact of a recent disturbance event that masks the recovery trajectories of individual reefs. Marine reserves are not a panacea for conservation but can facilitate the recovery of corals from disturbance and may help sustain the biodiversity of organisms that depend on a complex three-dimensional coral habitat.

Footnotes

^†To whom correspondence should be addressed. E-mail: p.j.mumby{at}ex.ac.uk
Author contributions: P.J.M., A.R.H., D.R.B., F.M., and C.P.D. designed research; P.J.M., A.R.H., J.W., C.V.K., D.R.B., K.E.H., and C.P.D. performed research; P.J.M. and C.B.P. contributed new reagents/analytic tools; P.J.M., C.B.P., and P.G.B. analyzed data; and P.J.M. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/cgi/content/full/0702602104/DC1.
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