Coloured Pigments and Coral Bleaching?

[Anya Salih]

Hi everyone,

For the last 6 yrs or so I've studied fluorescent pigments in corals
on the Great Barrier Reef, ecology and biology as well as
microstructure. I agree with Rob that during bleaching, not all
corals loose fluorescent pigments. Severely bleached or otherwise
stressed corals loose much fluorescent pigmentation as a result of
tissue degradation. When green fluorescent corals bleach, the
yellow-green hue of fluorescent pigments is clearly visible in
daylight. Blue fluorescent pigments (as in picture 1-2 at
http://www.emu.usyd.edu.au/research/figures.html) with emissions
476-484 nm, are generally invisible in daylight and bleached corals
appear white. Yellow, orange and red fluorescent pigmentation is
quite apparent in bleached corals. Expression of both fluorescent and
the weakly fluorescent pink/blue pigments is triggered by sunlight
(visible spectrum). Pigment expression, at least in some corals, is
up-regulated during bleaching, but only in corals exposed to sunlight.

regards
Anya

>Dear Coral Listers
>
>I would be grateful if any of the coral physiologists involved in bleaching
>work could offer any details on a question that's been put to me a couple
>of times.
>
>The colourful pigments (blues, pinks etc.) that are charateristic of many
>shallow water corals (Acropora etc.) are, as I understand it, located in
>the coral tissue itself.  Whereas the pigments present in the zooxanthellae
>are more or less brown in colour.  If coral bleaching (due to elevated
>SSTs) is principally the result of expulsion or loss of zooxanthellae, then
>why do the corals go completely white.  i.e. what happens to the more
>colourful coral pigments? Are they damaged as well but independently by
>temperature induced failure of protective systems?
>
>sincerely,
>
>Rupert Ormond
>
>
>
>
>Dr. Rupert Ormond
>Director,
>University Marine Biological Station Millport,
>Isle of Cumbrae,
>SCOTLAND
>UK  KA28 0EG
>
>email: rupert.ormond at millport.gla.ac.uk
>tel: (44)-01475-530581
>fax: (44)-01475-530601
>web: http://www.gla.ac.uk/Acad/Marine/
>
>
>
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--
Dr Anya Salih
APD(I) Research Fellow
Electron Microscope Unit
& The Australian Key Centre for Microscopy & Microanalysis
Madsen Building FO9                     Email: anya at emu.usyd.edu.au
The University of Sydney                Telephone: 02-93517540
Sydney, 2006, AUSTRALIA                 Facsimile: 02-93517682
http://www.emu.usyd.edu.au/research/anya_research.html
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