[Coral-List] causes of Acropora loss

John Bruno jbruno at unc.edu
Tue Oct 2 15:26:18 EDT 2007

Mike Risk wrote:

> Acropora is threatened by a host of things-and there is ample
> evidence to this effect-but not (so far) by global warming.
> The Caribbean-wide decline of reefs has nothing to do with global
> change, and a lot to do with things like land-based sources,
> overfishing, etc. It is easier to arm-wave about CO2 than it is to
> advocate controlling development.

Three quick points;

First, Mike is (probably accidentally) conflating global warming and  
global change.  Global change includes warming but also many other  
changes like increased sediment and nutrients, novel diseases and  
disease outbreaks, etc.  (wasn't there a discussion about this just a  
few weeks ago?).

Second, I am unaware of any evidence supporting Mike's contention  
that the Caribbean-wide loss of Acropora in the 1980s was caused by  
land-based sources (assuming he means nutrients) or by fishing.  If I  
am missing some published work in support of this hypothesis, I'd  
really like to hear about it.  I have long been convinced, based on  
my reading of the literature and the patterns I have observed, that  
the loss of Acropora was caused overwhelmingly by the white band  
epidemic, which as far as we know was not related to any human  
alterations to the environment.  If humans are to blame, I'd bet it  
would have something to do with introducing a novel pathogen.

Third, I have heard from several colleagues about recent bleaching- 
related mortality of Acropora cervicornis over the last few years.   
Ernesto Weil has noted frequent mass-Acropora bleaching in Puerto  
Rico that nearly eliminates cervicornis every time it begins to  
recover.   Thus I think temperature and possibly climate change could  
be playing some role in retarding the Acropora recovery, even if it  
was not the principle cause of the decline.  Is anyone aware of  
recent studies of Caribbean bleaching and subsequent mortality of  
Acropora species that would support this?



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

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