bleaching witness request!!!
Hsieh Chia-i
ch141 at york.ac.uk
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
present
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 york.ac.uk
with grateful thanks for your time,
Sincerely,
Joyce Chia-I Hsieh
Tropical Marine Research Unit,
Biology Department,
University of York,
YORK YO1 5DD
e-mail ch141 at york.ac.uk
fax 00-44-1904-432860
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