Nearshore bleaching photos - Fiji

[Anya Salih]

James,

Had a look at your excellent photos and here's another possible difference
for the observed inter- and intraspecific variation in coral bleaching so
far not mentioned in the feedback - the degree of fluorescent pigmentation
in sp and morphs of the same species. For several years now I have been
researching the function of fluorescent pigmentation in corals and have
accumulated a lot of experimental and ecological evidence for at least one
function being that of photoprotection.

Given that temperature related bleaching involves light, corals with
sunscreening fluorescent pigmentation can be more resistant to bleaching. I
found this to be so in experiments where fluorescent and non fluorescent
species were exposed to high light and temperature, as well as when
temperature-induced bleaching of fluro- and non-fluorescent morphs of the
same species was compared. Similarly, during 1998 mass bleaching on Great
Barrier Reef in the majority of cases fluorescent morphs were unbleached or
partially bleached, while non fluorescent ones growing near-by, were
completely bleached (Salih et al 2000, Fluorescent pigments in corals are
photoprotective, Nature 408: 850-853).

>Photo 1596 shows an Acropora sp. bleaching from the center out.  Why is
>this?

The distribution of fluorescent pigmentation in any one colony is often
uneven; frequently the edges of colonies are more pigmented than the
center. This may be one reason for the observed difference in your photo

>Photos 1594 and 1595 show a monospecific stand of acropora.  I would expect
>either the whole colony to bleach, or perhaps the tops of branches - however
>the coral is only bleached in large "patches."  Why is this?

I found that monospecific stands of Acropora are frequently composed of
patches of fluorescent and non-fluorescent morphs eg intertidal lagoon,
reef front and slope of Heron and One Tree Islands, mid-shelf reefs such as
Cayley, Feather, Coats of Great Barrier Reef and also Red Sea reefs in
Hurghada, Egypt. In all these sites, patchy distribution of bleaching as
shown in your photos was correlated with concentration of fluorescent
pigmentation in Acropora colonies.

>Some of the photos show many different colonies in one patch reef.  Why is
>one coral bleached, and it appears that an identical species next to it is
>not (1599 and 1600).  Why did one coral bleach, and the other did not?

Similarly, some of the species in your photo may be fluorescently pigmented
while others are not. The easiest way to find out whether or not corals are
fluorescent is to look for the greenish tinge in their coloration. However
fluoresce is not always apparent in daylight. A reliable quick method is to
illuminate them with UV or blue light at night, for example using Charlie
Mazel's underwater torches (mentioned previously on this list) or more
simply, by covering a torch with a blue plastic filter. At present I am
conducting large scale surveys of distribution of fluorescent pigmented
corals on Great Barrier Reef and found them to be very abundant, in some
reef parts being more common than non fluorescent corals. It may be
speculated that reefs with highly fluorescent corals may be on the whole
much less susceptible than reefs with largely non fluorescent morphs.

I will be very interested to hear how these observations compare to records
of coral bleaching elsewhere.

regards

Anya Salih

Anya Salih                      Email:          anya at emu.usyd.edu.au
Electron Microscope Unit        Telephone:      02-93517540
Madsen Building FO9             Facsimile:      02-93517682
The University of Sydney
Sydney, 2006, AUSTRALIA


>Ladies and gentlemen,
>
>I have posted some photos of nearshore bleaching from a recent trip to Fiji.
>I decided to post them to a webpage yesterday as I think they are worth
>discussing as part of this recent "Factors in coral bleaching - nearshore
>vs. offshore reefs" discussion.
>
>The website (It is NOT commercial) shows ONLY the pictures and location map
>and some of my comments (temperature, some observations, etc).  Here is the
>URL:
>
>http://www.reefhabilitation.com/fiji/bleaching/index.htm
>
>
>Of particular interest to me are some of the photos showing "unusual"
>bleaching patterns.  Any feedback on these is much appreciated - as I would
>like to better understand coral bleaching.
>
>For example:
>Photo 1596 shows an Acropora sp. bleaching from the center out.  Why is
>this?
>Photos 1594 and 1595 show a monospecific stand of acropora.  I would expect
>either the whole colony to bleach, or perhaps the tops of branches - however
>the coral is only bleached in large "patches."  Why is this?
>Some of the photos show many different colonies in one patch reef.  Why is
>one coral bleached, and it appears that an identical species next to it is
>not (1599 and 1600).  Why did one coral bleach, and the other did not?
>
>The areas I dove in Fiji were in the North (Somosomo Straits and reefs
>around Savusavu and Namenala Isl.) and I did not observe any bleaching below
>20 foot water depth.
>
>Please feel free to use these photos for non-commercial use and high
>resolution digital photos are available upon request.
>
>James Wiseman
>Project Engineer
>Winmar Consulting Services
>www.winmarconsulting.com
>
>
>~~~~~~~
>For directions on subscribing and unsubscribing to coral-list or the
>digests, please visit www.coral.noaa.gov, click on Popular on the
>menu bar, then click on Coral-List Listserver.

Anya Salih                      Email:          anya at emu.usyd.edu.au
Electron Microscope Unit        Telephone:      02-93517540
Madsen Building FO9             Facsimile:      02-93517682
The University of Sydney
Sydney, 2006, AUSTRALIA
~~~~~~~
For directions on subscribing and unsubscribing to coral-list or the
digests, please visit www.coral.noaa.gov, click on Popular on the
menu bar, then click on Coral-List Listserver.