[Coral-List] causes of Acropora loss
eweil at caribe.net
Wed Oct 3 11:59:14 EDT 2007
I just want to expand a little on John's comment about the frequent A.
cervicornis mortalities in PR. Bleaching is just one factor that has only
produced significant mortalities (large colonies and stands in relatively
shallow waters) after the 1998 and 2005 bleaching events. The 2005 event
wiped out the largest A.cervicornis and A.prolifera shallow populations in
La Parguera and produced partial and total mortality in several A. palmata
colonies. Mild events have produced minor partial mortalities in few
colonies only. Most of the mortality in the last several years has been
produced by recurrent white band disease, predation by snails and fireworms,
damsel fish territories and in some lagoon areas but less frequent, excess
sedimentation. Strong surge and wave action by storms and hurricanes have
also fragmented and killed several recovering colonies in reef platforms and
smothered others at intermediate depths. Nevertheless, we still see small
colonies all over the place, however, many are frequently hit by one or
several of these factors. We hope that some of them make it to reproductive
age at least, and to form large, more stable stands in some places. We have
not observed massive spawning in A. cervicornis in several years around La
Parguera. For those interested, there is a review ms on the status of
acroporids in Puerto Rico, the reference is:
Weil E, E Hernandez, A. Bruckner, A. Ortiz, M. Nemeth and H. Ruiz, 2003.
Status of Acroporid populations in Puerto Rico. Proc. of the Caribbean
Acropora Workshop: Potential Application of the US Endagered Species Act as
a Conservation Strategy. NOAA technical Memorandum NMFS-OPR-24: 71-92.
Ernesto Weil, Ph.D
Department of Marine Sciences
University of Puerto Rico
(787) 899-2048 ext. 241
(787) 899-5500 FAX
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of John Bruno
Sent: Tuesday, October 02, 2007 3:26 PM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] causes of Acropora loss
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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