NSF Press Release

Julian Sprung JSprung at compuserve.com
Fri Aug 25 01:12:03 EDT 2000

Dear Phillip Taylor,

I write to you since you posted the attached article to our list. Do you or
anyone on the list know the author of this piece, Cheryl Dybas. Please
advise her that she is with good intentions perpetuating an often repeated
myth. Mass coral bleaching and subsequent coral death has nothing
whatsoever to do with starvation. Nor is water pollution a factor. It is
simply hot water and light that combined do the damage. 

The corals in a hot spot may bleach and die in a matter of just a few days.
Corals don't starve so quickly. Also, when you find survivors of bleaching
events they tend to be in more polluted (nutrient rich) habitats. That can
be explained at least partly by the fact that these habitats have lower
light penetration due to turbidity and may also have shading caused by
growths of macroalgae.


Julian Sprung

Please see:

Jones, R, Hoegh-Guldberg, O, Larkum, AWL and Schreiber, U. (1998)
Temperature induced bleaching of corals begins with impairment of dark
metabolism in zooxanthellae. Plant Cell and Environment.


   Recent evidence of "sunburned" Caribbean coral reefs seems to
confirm not only the gradual warming of the world's oceans, but
also the effect of warming on ocean ecology. "Coral is very photo-
and temperature-sensitive," explains marine ecologist William
Fitt, an NSF-funded researcher at University of Georgia. "We know
that if water temperature is too high for too long, everything
goes wrong very quickly -- like throwing a screwdriver into a
running engine."
  In addition to excessively warm water temperatures, a number
of other factors, including pollution, may be contributing to
widespread bleaching of corals. But Fitt says his research team
has now "caught the bandit in the act." A key protein in
photosynthesis, known as the D1 protein, is extremely temperature
sensitive. Tropical corals are actually made up of algae, living
inside a coral animal. If seawater temperatures during summer
remain too high for too long, photosynthesis in the coral's algae
breaks down, leaving the coral with less food.  The animal
starves, and its white skeleton becomes visible--hence the
bleached white color. "Tropical corals are already on the edge of
the 'temperature envelope' of life during most summers. If warmer
waters push it that little bit higher or longer, the results are
very evident," says Fitt. [Cheryl Dybas]

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