[Coral-List] intensive coral colors at onset of bleaching?

[Bill Allison]

This paper is relevant to your comments as is the post to coral list from
about that time:

Salih, A., A. Larkum, et al. (2000). "Fluorescent pigments in corals are
photoprotective." *Nature* *408*(6814): 850-853.

Abst & Notes:

Abst

All reef-forming corals depend on the photosynthesis performed by their
algal symbiont, and such corals are therefore restricted to the photic zone..
The intensity of light in this zone declines over several orders of
magnitude-from high and damaging levels at the surface to extreme shade
conditions at the lower limit1. The ability of corals to tolerate this range
implies effective mechanisms for light acclimation and adaptation2. Here we
show that the fluorescent pigments3-9 (FPs) of corals provide a
photobiological system for regulating the light environment of coral host
tissue. Previous studies have suggested that under low light, FPs may
enhance light availability4,5. We now report that in excessive sunlight FPs
are photoprotective; they achieve this by dissipating excess energy at
wavelengths of low photosynthetic activity, as well as by reflecting of
visible and infrared light by FP-containing chromatophores.We also show that
FPs enhance the resistance to mass bleaching of corals during periods of
heat stress, which has implications for the effect of environmental stress
on the diversity of reef-building corals, such as enhanced survival of a
broad range of corals allowing maintenance of habitat diversity.
Coral List post:

Dear Tom

Coral colours are mainly due to tissue pigments - the greens, white, yellow
and red colours are from UV fluorescent pigment proteins; blues, pinks and
some reds are due to related non fluorescent pigments. A good web site on
coral fluorescent pigmentation and relevant references is by Charles Mazel
at http://www.nightsea.com.

I and my collegues recently showed that fluorescent pigmentation in corals
can protect them from excessive sunlight, results described in paper
"Fluorescent pigments in corals are photoprotective" Nature, DEC 14 2000;
408 (6814) : 850-853.

Given that light is important in the way corals are affected by many
stresses, pigmented morphs which can screen themselves and their
photosynthetic symbionts from excessive sunlight are less susceptible to
various stresses eg. during mass coral bleaching we found that fluorescent
corals bleached less than non fluorescent morphs.

My surveys on Australian reefs showed that almost all coral species have
several colour morphs, either visibly or fluorescently pigmented, or both,
but we are only beginning to understand the function and causes of such high
polymorphism on reefs. There is a probably a higher metabolic cost
associated with production of pigments, and these morphs are slower growing,
but pigmentation affords them higher protection during stressful conditions..
their non pigmented conspecifics may be more competitive by growing faster
when conditions are stable but are more susceptible during stressful events..

Anya Salih


On Wed, Sep 1, 2010 at 9:06 PM, Charles Mazel <mazel at psicorp.com> wrote:

> Dear Sebastian,
>
> This kind of observation of anomalously intense fluorescence in corals
> exposed to various kinds of stress has cropped up anecdotally for
> years. I have heard similar things from reef aquarium hobbyists who
> noted extreme color changes in corals suddenly shifted to increased
> light conditions. I do not know of any demonstration of the cause/
> effect mechanism behind this.
>
> There have been arguments for a photoprotective function for the
> fluorescent pigments, but also arguments against, at least as a
> general function. Similarly there have been suggestions that pigmented
> corals are less susceptible to bleaching, but also that they are more
> so (e.g.,Dove, S. G., 2004. Scleractinian corals with photoprotective
> host pigments are hypersensitive to thermal bleaching, Mar. Ecol.
> Prog. Ser., 272:99-116.)
>
> As usual, more observation and focused study needed.
>
> Best regards,
>
> Charlie
>
>
> Charles Mazel
> Physical Sciences Inc.
> 20 New England Business Center
> Andover, MA 01810
> tel: 978 738-8227
> fax: 978 689-3232
>
>
>
> On Sep 1, 2010, at 5:18 AM, Sebastian Ferse wrote:
>
> > Dear listers,
> >
> >
> >
> > An acquaintance has passed on a report from a dive resort owner in
> > Malaysia,
> > who observed that prior to each bleaching event all corals underwent a
> > spectacular color change, displaying bright neon colors. I am
> > assuming that
> > this is due to the higher amount of color pigments in the tissue
> > relative to
> > zooxanthellae, and possibly due to a stress response triggering higher
> > pigment production. Does anyone have further insights or own
> > observations on
> > this?
> >
> >
> >
> > Cheers
> >
> >
> >
> > Sebastian
> >
> >
> >
> > _________________________
> > Dr. Sebastian Ferse
> >
> >
> > Leibniz-Zentrum für Marine Tropenökologie (ZMT) GmbH
> > Leibniz Center for Tropical Marine Ecology
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> > e-mail: sebastian.ferse at zmt-bremen.de
> >
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