[Coral-List] Survival of corals without zooxanthellae
RichardPDunne at aol.com
RichardPDunne at aol.com
Sun Jan 9 17:28:00 EST 2005
You will find some useful information on this in:
C M Yonge 1931 The effect of starvation in light and in darkness on the
relationship between corals and zooxanthellae. Scientific Reports of the Great
Barrier Reef Expedition 1928-29. Vol I no 7. Corals kept in the dark but fed
lost a high percentage of their zooxanthellae (colourless to the eye) but
survived until the end of the experiment ( 228 days). Variable according to
species.
See also:
C M Yonge and A G Nicholls 1931 The structure, distribution and physiology
of the zooxanthellae. Scentific Reports of the Great Barrier Reef Expedition
1928-29. Vol I no 6. They constructed a light tight box on the reef flat
through which the seawater could flow. after 152 days many of the species contained
very few zooxanthellae but were otherwise in good condition. Their
conclusion in this respect was "without any doubt that individual reef-building corals
at any rate can flourish without contained zooxanthellae."
I doubt however that corals ever loose ALL their zooxanthellae - the best
that Yonge noted was "almost completely absent". And in our own work even a
reduction of 86% of the seasonal maximum density following severe bleaching can
leave 0.026 x 10^7 algae per sq cm of tissue area (260,000). (Brown et al
1999 MEPS 191:53-69).
The evidence seems to point to an ability to survive without zooxanthellae
if a source of food is available, and presuming the stress which caused the
zooxanthellae loss does not persist or at least does not have a directly
deleterious effect on the coral host itself.
Richard Dunne
Tel: 01833 650059
RichardPDunne at aol.com
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