[Coral-List] bleaching and acidification

[Thomas Goreau]

Dear Chris,

I fully agree with what you say below based on lab studies. The Elat  
field data of Silverman et al. clearly showing less net calcium  
carbonate accumulation when waters have higher pCO2 makes this even  
clearer.

However this small reduction must be contrasted with the fact that  
bleached corals completely stop growing (Goreau & Macfarlane) or  
reproducing (Szmant-Froelich) for at least one year, and it takes a  
couple years to fully recover even if they survive and high  
temperatures don't ever come back.......

Best wishes,
Tom

Thomas J. Goreau, PhD
President, Global Coral Reef Alliance
Coordinator, United Nations Commission on Sustainable Development  
Partnership in New Technologies for Small Island Developing States
37 Pleasant Street, Cambridge MA 02139
617-864-4226
goreau at bestweb.net
http://www.globalcoral.org

Date: Sun, 15 Feb 2009 17:49:56 -0500 (EST)
From: "Chris Langdon" <clangdon at rsmas.miami.edu>
Subject: [Coral-List] Bleaching vs acidification
To: coral-list at coral.aoml.noaa.gov
Message-ID:
	<2975.129.171.118.2.1234738196.squirrel at webmail.rsmas.miami.edu>
Content-Type: text/plain;charset=iso-8859-1

It is very clear that bleaching events have resulted in significant loss
of live coral cover around the globe.  We know that within the
environmentally probable range of pH that coral mortality does not  
result.
However, acidification may play an important role in the amount of
recovery that is possible between bleaching events which have been
occurring with a frequency of 3-7 years since 1982. The average  
saturation
state of the tropical ocean has dropped from a pre-industrial value of  
4.6
to a present day value of 3.9-4.0.  This is sufficient to have caused on
average a 17% decrease in calcification for the twelve or so species  
that
have been studied in the lab.  In a world where the balance between
production and loss of carbonate on many reefs is thought to be close  
and
where the replacement rate of new coral colonies on many reefs is not
keeping up with the rate of mortality a 17% reduction in fitness may be
significant.  While acidification does not kill corals it does result in
slower development of coral larvae into juvenile colonies (Albright et  
al.
2008) and slower development of juvenile colonies to sexual maturity.
While bleaching is a very important threat I don't we know enough at  
this
time to ignore the possibility that acidification has already played a
role in the lack of recovery that we are seeing on many reefs.






Chris Langdon
Assoc. Professor
RSMAS/MBF
Uni. of Miami
4600 Rickenbacker Cswy
Miami,FL 33149
Ph: 305-421-4614
Fax: 305-421-4239