bleaching witness request!!!

Hsieh Chia-i ch141 at
Wed Feb 25 19:13:24 EST 1998

Dear coral-health friends,

Last summer we received several reports from amatuer dive groups etc. of what 
sound like extensive coral bleaching events in different parts of the wider Indian 
Ocean Region including the Red Sea.   These were areas from which so far as we 
know bleaching had not previously been reported.  As a result I am planning to 
circulate dive schools, cruise boats, etc. in the region with a request to report any 
incidents of possible / probable bleaching that they observe.  With the request I 
hope to provide advice on how to distinguish coral bleaching from other forms of 
coral mortality.

I would very much welcome hearing details from anyone who has witnessed 
temperature related bleaching within the region in say the last 10 years?  (P.S. We 
have already liased with Alan Strong at NOAA regarding their data).

I would also appreciate any comments on what those who have witnessed such 
bleaching would regard as diagnostic features, distinguishing bleaching from other 
forms of coral mortality.  One difficulty might I think be in distinguishing 
mortality caused by say  6 month-old bleaching from 6 month-old 
mortality due to Crown-of-thorns attack?  Our thought is to mention the following:
a) affects very large areas - scale of kms to 10s of kms
b) usually affects the top metre to several metres of the reef
c)  when new looks blotchy often with variable degree of blanching but tissue still 
d) surface of coral skeleton remains intact (i.e. not eroded or broken)
e) often affects all the individuals of particular species in a depth zone, but not 
other species
f) small branching coral species such as  Acropora, Pocillopora most susceptible 
g) massive corals principally affected on upper surface(s)
h) if bleaching leads to mortality corals subsequently become patchily or 
extensively overgrown by algal turf / filamentous algae
i) no large numbers of Crown-of-thorns observed anywhere even though very large 
areas of dead coral present
j) patches of fresh bleaching not sharp-edged or with other characteristic features of 
Crown-of-thorns scars

to save disturbing others you may please respond to me directly at
ch141 at

with grateful thanks for your time,


Joyce Chia-I Hsieh
Tropical Marine Research Unit,
Biology Department,
University of York,
e-mail ch141 at
fax 00-44-1904-432860

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