[Coral-List] Bleaching vs acidification

Chris Langdon clangdon at rsmas.miami.edu
Sun Feb 15 17:49:56 EST 2009

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
Uni. of Miami
4600 Rickenbacker Cswy
Miami,FL 33149
Ph: 305-421-4614
Fax: 305-421-4239

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