[Coral-List] causes of Acropora loss
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.
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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