[Coral-List] Persistent algae, bleaching, and nutrient publications

Tim McClanahan tmcclanahan at wcs.org
Mon Nov 12 11:32:40 EST 2007

Coral listers

In response to John Bruno's request for information on algal persistence and
influences of algae on bleaching. I think the following are moderately good
examples from our work that show that algae can be quite persistent once it
begins to dominate coral reefs. In all cases herbivorous fishes did not
increase greatly in fishing closures until the big algae were removed. I
don't think one can expect that algae will be quickly reduced once fishing
closures are established because fish herbivores avoid feeding on the
late-successional algae that eventually dominate reefs after fishing or
coral mortality disturbances, which results in slow change or persistence.

McClanahan, T. R., V. Hendrick, M. J. Rodrigues, and N. V. C. Polunin. 1999.
Varying responses of herbivorous and invertebrate-feeding fishes to
macroalgal reduction on a coral reef. Coral Reefs 18:195-203.

McClanahan, T. R., K. Bergman, M. Huitric, M. McField, T. Elfwing, M.
Nystrom, and I. Nordemar. 2000. Response of fishes to algal reductions on
Glovers Reef, Belize. Marine Ecology Progress Series 206:273-282.

McClanahan, T. R., M. McField, M. Huitric, K. Bergman, E. Sala, M. Nystrom,
I. Nordemer, T. Elfwing, and N. A. Muthiga. 2001. Responses of algae, corals
and fish to the reduction of macro algae in fished and unfished patch reefs
of Glovers Reef Atoll , Belize. Coral Reefs 19:367-379.

McClanahan, T. R., J. N. Uku, and H. Machano. 2002. Effect of macroalgal
reduction on coral-reef fish in the Watamu Marine National park, Kenya.
Marine and Freshwater Research 53:223-231.

I have argued the same is true for sea urchin dominance on fished reefs.

McClanahan, T. R., A. T. Kamukuru, N. A. Muthiga, M. G. Yebio, and D. Obura.
1996. Effect of sea urchin reductions on algae, coral, and fish populations.
Conservation Biology 10:136-154.

McClanahan, T. R., N. V. C. Polunin, and T. Done. 2002. Ecological states
and the resilience of coral reefs. Conservation Ecology 6:18-.

The process can be quite slow, as are still seeing increases in surgeonfish
dominance 37 years after closures.

McClanahan, T. R., N. A. J. Graham, J. M. Calnan, and M. A. MacNeil. 2007.
Towards pristine biomass: reef fish recovery in coral reef marine protected
areas in Kenya. Ecological Applications 17:1055-1067.

We have also done some work showing that nutrient enhancement increases the
tolerance of corals to bleaching. I believe bleaching is partly caused by
competition for nutrients between the Symbiodinium and the coral host when
respiration/metabolism demands increase due to warm water and light. The
hypothesis makes the prediction that adding nutrients reduces the
competition and leads to higher bleaching thresholds.

McClanahan, T. R., E. Sala, P. Stickels, B. A. Cokos, A. Baker, C. J.
Starger, and S. Jones. 2003. Interaction between nutrients and herbivory in
controlling algal communities and coral condition on Glover's Reef, Belize.
Marine Ecology Progress Series 261:135-147.

The response of algae to nutrients and herbivory is complex and taxa
dependent, which is only recently being appreciated. Many of debates result
because we are talking in generalities and we would probably improve
understanding if we referred to specific types of algae and avoid words like
macro-algae or algae when referring to responses to specific forcing
factors. People debating this issue need to read the scientific literature
more and cite experimental field studies as opposed to anecdotes from field
observations to explain patterns and unravel the complexities..

McClanahan, T. R., B. A. Cokos, and E. Sala. 2002. Algal growth and species
composition under experimental control of herbivory, phosphorus and coral
abundance in Glovers Reef, Belize. Marine Pollution Bulletin 44:441-451.

McClanahan, T. R., R. S. Steneck, D. Pietri, B. Cokos, and S. Jones. 2005.
Interaction between inorganic nutrients and organic matter in controlling
coral reef communities in Glovers Reef Belize. Marine Pollution Bulletin

Carreiro-Silva, M., T. R. McClanahan, and W. E. Kiene. 2005. The role of
inorganic nutrients and herbivory in controlling microbioerosion of
carbonate substrate. Coral Reefs 24:214-221.

McClanahan, T. R., M. Carreiro-Silva, and M. DiLorenzo. 2007. Effect of
nitrogen, phosphorous, and their interaction on coral reef algal succession
in Glover¹s Reef, Belize. Marine Pollution Bulletin doi:10.1016/j.marpolbul.

Finally, we are not finding much evidence that either fisheries closures or
that high finfish herbivores are creating "resilience" for coral reefs in
the face of climate change.

McClanahan, T. R., J. Maina, C. J. Starger, P. Herron-Perez, and E. Dusek.
2005. Detriments to post-bleaching recovery of corals. Coral Reefs

McClanahan, T. R., E. Verheij, and J. Maina. 2006. Comparing management
effectiveness of a marine park and a multiple-use collaborative fisheries
management area in East Africa. Aquatic Conservation: Marine and Freshwater
Ecosystems 16:147-165.

McClanahan, T. R. 2007. Response of the coral reef benthos and herbivory to
fishery closure management and the 1998 ENSO disturbance. Oecologia DOI

There are other good examples from our colleagues, and I hope they will pass
them on for review and discussion.

I wish things were simpler and supported the standard coral reef
environmentalist position, but they are not, and we need to keep doing and
publishing the science, maintain an open mind, and keep the field data and
experiments coming to test the models, our preconceptions, and the
appropriate advocacy.


PS. Most of the above papers are in my public folder, if you want to read
them you can visit the public folder below.

Tim McClanahan, PhD
Senior Conservation Zoologist
Wildlife Conservation Society
Download my pdf publications and other shared files at

Web sites


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