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

Cecilia DAngelo cdangelo at gmx.de
Fri Sep 3 11:35:06 EDT 2010


Dear Sebastian, 

in several reef corals, an up-regulation of GFP-like fluorescent and non-fluorescent proteins (responsible for the "neon colors") is associated with an increase in light intensity. This up regulation can be measured at the transcriptional level already after two hours and is strongest in response to the blue part of the spectrum (D’Angelo et al 2008).  In the field, this effect can be nicely demonstrated by the increased fluorescence / color in the upper branch sides of many Acropora species (observations from the Great Barrier Reef and the Red Sea).  Especially in several table acroporas, the fluorescence is restricted to the upper side of the colony. 
 
As increased light levels can act synergistically with high temperatures (and other factors) to induce coral bleaching, the observation of increased fluorescence ahead of bleach might be indicative of light stress, for instance due to calm water conditions. It is important to note, though,  that not all corals and all GFP-like proteins respond the same way. Some pigments of Acropora millepora are downregulated at photonfluxes beyond 400 micromol/m2/s (D’Angelo et al., 2008) and the tissue concentrations of fluorescent pigments of other corals like Montastrea cavernosa do not respond at all to changes between medium and high light levels (Leutenegger et al., 2007). 
Interestingly, the visibility of the host pigments in this species can be enhanced when the tissue content of zooxanthellae is reduced under high light conditions (D’Angelo & Wiedenmann, in press). 

Taken together, there are potential explanations for the increase in colors observed ahead of bleaching. However, it would need some specific measurements to elucidate this particular case as also other factors might stimulate the production of fluorescent pigments.

Best wishes,

Joerg Wiedenmann

Cecilia D’Angelo


D’Angelo, C.; Denzel, A.; Vogt, A.; Matz M. V.; Oswald, F.; Salih, A.; Nienhaus, G.-U. & Wiedenmann, J. (2008). Blue light regulation of host pigment in reef-building corals. Mar. Ecol. Prog. Ser. 364, 97-106.

Leutenegger, A., D’Angelo, C., Matz, M.V., Denzel, A., Oswald, F., Salih, A., Nienhaus, G.U. & Wiedenmann, J. (2007). It’s cheap to be colorful: Anthozoans show a slow turnover of GFP-like proteins. FEBS Journal, 274, 2496–2505. 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PD Dr. Joerg Wiedenmann
National Oceanography Centre, Southampton    
University of Southampton, Waterfront Campus
European Way,  Southampton SO14 3ZH, UK 
http://www.noc.soton.ac.uk/corals/
http://www.carnuk.org/about.aspx
joerg.wiedenmann at noc.soton.ac.uk

Dr. Cecilia D’Angelo,
Institute for General Zoology,
University of Ulm,
89069 Ulm
Germany
C.D'angelo at soton.ac.uk



> 
> 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
> >
> >
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