[Coral-List] two questions for coral listers

guillermo.diaz at unimagdalena.edu.co guillermo.diaz at unimagdalena.edu.co
Sat Nov 10 08:43:29 EST 2007

Dear John,

Inshore coral reefs of the Great Barrier Reef have dense stands of the brown
seaweed Sargassum during the austral summer. During the coral bleaching of
1998, we observed that shading by Sargassum canopy protected corals from
beaching. Jompa & McCook (1998) and McCook, Jompa & myself (2001) published
preliminary experimental results of this particular coral-algal interaction.
While certainly high abundance of macroalgae is usually associated to reef
degradation, especially in reefs formerly dominated by corals, this particular
observation illustrates the complexity of mechanisms by which they compete.


Jompa J, McCook LJ (1998) Seaweeds save the reefs?!: Sargassum canopy 
coral bleaching on inshore reefs. Reef Res 8: 5.

McCook LJ, Jompa J, Diaz-Pulido G (2001) Competition between corals and 
algae on
coral reefs: a review of evidence and mechanisms. Coral Reefs 19: 400-417

Quoting John Bruno <jbruno at unc.edu>:

> First, is anyone aware of an example (preferably published) where
> macroalgae have alleviated some stress or otherwise benefitted corals
> in terms of growth, survival, etc?  I have heard people talk about
> observing that shading by macroalgae can reduce bleaching and
> bleaching-related mortality, but don't recall seeing any studies on
> this and have not been able to dig any up using various search engines.
> Second, is anyone aware of an example in which after herbivore
> populations were replenished (either naturally or via management)
> macroalgal cover/biomass remained "high"?  This question really gets
> at whether "phase shifts" to macroalgal dominance are "permanent
> states" or simply responses to the removal of top down control.
> Every example I can think of clearly indicates that once herbivores
> return (e.g., Diadema to the north coast of Jamaica ala Edmunds and
> Carpenter 2001, Carpenter and Edmunds 2006) macroalge immediately
> return to formerly very low cover and abundance (which also suggests
> that top down rather than bottom up forces were the primary cause of
> the change in macroalgal cover in the first place).
> Thanks for any examples, ideas or advise you might have.
> JB
> John Bruno, Ph.D.
> Associate Professor
> Department of Marine Science
> The University of North Carolina at Chapel Hill
> Chapel Hill, NC 27599-330
> jbruno at unc.edu
> www.brunolab.net
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Dr. Guillermo Diaz-Pulido

Postdoctoral Research Fellow
Pew Program in Marine Conservation
ARC Centre of Excellence for Coral Reef Studies
Centre for Marine Studies
The University of Queensland
Brisbane, St Lucia 4072 QLD, Australia
Ph:   +61 7 33653378; Fax +61 7 33654755
Mob: 04-25296530
Email: g.diazpulido at uq.edu.au

Assistant Professor
Universidad del Magdalena, Colombia

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