[Coral-List] T. Goreau: Bleaching and Food, Light, Etc.

Jim Hendee Jim.Hendee at noaa.gov
Mon May 29 14:42:49 EDT 2006

[Tom Goreau has been trying for over a week to get this posted, with no
luck, so here it is, below.  I've guessed on the Subject title.  Please 
to him or to the list, not me--I still don't know exactly why some corals
bleach and others don't.  Thank you.]

From:  Thomas Goreau <goreau at bestweb.net>
To:  Coral-List
Subject:  Bleaching, Food, Light, Etc.

Jokiel and Coles basically worked this out in the 1970s with regard to
the effects of thermal power plant effluents. In the 1980s I did
experiments with corals in Jamaica at three different temperature
(ambient, ambient + 1C, ambient +2C) and 3 different light levels (full
sun, quarter shading, half shading) and found that bleaching took place
only above a threshold temperature, but above that temperature bleaching
rate was proportional to light intensity. I never published the data,
but have photographs someplace. A few years later Peter Glynn and
colleagues did a very similar experiment, but also included UV
shielding, and published it. They reached identical conclusions, and
also showed that Photosynthetically Active Radiation, not UV, was the
key. So all of this was nailed down a long time ago. As far as pure
light induced bleaching, that was well known to coral researchers in the

The recent paper that claims to have discovered "for the first time"
that corals eat zooplankton and can survive bleaching better if fed is
not new either. The fact that corals don't get their carbon from
zooxanthellae is also very old knowledge, but for decades people have
ignored the old literature and have mistaken the net oxygen balance to
assume that corals are also autotrophic in carbon. This recent error has
become dogma, despite being wrong, because nowadays people don't read
the literature or ask those who know it. The first radiocarbon tracer
experiments, done by Thomas F. Goreau and Nora I. Goreau more than 50
years ago showed that very little zooxanthella carbon translocation
contributed to coral carbon, and that corals relied on zooplankton for
the vast bulk of their carbon needs. They kept corals completely
bleached in the dark for years, feeding them on zooplankton. So survival
of bleached fed corals has been known for over half a century and is not
a "new discovery" at all. Like so much else in the current literature.

On this note it is now 16 years since our first paper showing from NOAA
satellite data that high temperatures were the cause of bleaching was
blocked from publication by the first Bush Administration. They still
seem to be trying to find out if bleaching might have any possible link
to global warming, despite our numerous (uncited, naturally)
publications showing this. Hopefully they will figure this out while
there are still a few last survivors left.

Thomas J. Goreau, PhD
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
goreau at bestweb.net

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