Excess Light Doesn't Cause Coral Bleaching

I believe it was studied in aiptasia because it is an easy organism to work with. I worked in a lab at a graduate school this summer where a masters student was working with the professor to study autism using yeast cells.. Obviously yeast cannot be autistic. Researchers are using drosophila (a type of fly) as a model for cancer research. I don't think aiptasia has much to do with it. And yes, there is a lot more to be worked out. I was just throwing out some of my understanding of the situation.

 

Good stuff, but logically if coral bleaches because of high light combined with another stressor, it wouldn't be correct to say that high light can cause coral to bleach to death.

Michael Rice
Marine Engineers Aquarium Blog
Sent from Tapatalk so excuse my poor English

 

What kind of other stressors? BTW thanks a lot for distracting me from studying for molecular genetics test.

 

It seems from most of what I've read, temperature. Always happy to help.

Michael Rice
Marine Engineers Aquarium Blog
Sent from Tapatalk so excuse my poor English

 

I dont think that M could have stated it better. I have been trying to tell people this for years now but they just dont want to believe it...

 

Thanks Trent, I think a lot of the evidence has been recent, and conflicting/confusing. A lot of views are based on experience, which doesn't consider the documented complexity. To really think about this you need to read the literature, but that can be pretty dry for most ;D

I've worked with a number of simple model organism and yes, they are a great tool for basic research. The utility for a given application depends on a lot of factors though. If you want to study a simple subsystem, shared genetic component etc.. they can be very useful. For more intricate, complex processes, the limitations become more apparent. Bleaching is a very complex process, with a number of mechansims, causes, pathways... I bring up that this was aptaisia, because this is one specific example. If you read through the literature, there are other examples, some conflict with this view and there can be alternative mechanisms. It's definitely an important part of the picture though.

Excess photosynthesis causes higher levels of Oxygen (and others such as nitrogen) radicals. Too much light, photoinhibition starts to occur and PSII starts to shut down and photosynthesis becomes less efficient. The issue, is if there is sufficient photosynthesis to produce radicals and insufficient means of removing these. Generally there is a buildup during the day as they don't pass through the tissue quickly, although this will depend on the thickness of the corals diffusive boundary layer, which is dependent on flow. Also, will depend on the corals and symbionts health and ability to produce enzymes such as SOD, or the current density of GFP. So, there tends to be sequence of synergistic effects required for this to cause enough damage to break down symbiosis. Independent factors, such as light intensity tend not to be sufficient by themselves.


There is a lot of debate though on the mechanisms. For example, what about other symboiants, for example microbes, viruses? How do these fit in? What about pathogens? One viewpoint is the microbial hypothosis of coral bleaching. There are a lot of factors show to be associated with bleaching, light, especially UV light, salinity, cyanide, bacteria etc... It interesting, generally, they all have some relationship to temperature though. To explain this, some hypothesize that temperature driven bacterial growth, is a primary driving factor. For example,look at Vibrio shiloi, a mucus-associated bacteria, which has been implicated in bleaching. The bacteria produces a toxin that inhibits photosynthesis and relies on expression of superoxide dismutase, both processes are temperature dependent. If the temp is low enough it doesn't happen. High enough, it creates a series of interactions, via bacterial mediation, that break down symbiosis. Other bacterial mediated mechanisms have also been studied and do seem to rely on increased bacterial growth, with increased temperature. Of course, there is also, low-temperature induced bleaching, adding an entirely different can of worms. There is still a lot to learn.

It seems to be pretty ubiquitous from what I've seen. The idea has only recognized in the last few years though.

If your interest, here are a few quick references to start:
Bou-Abdallah et al. (2006) Quenching of superoxide radicals by green fluorescent protein

Palmer CVet al. (2009) Coral Fluorescent Proteins as Antioxidants.

Roth et al. (2010) Green fluorescent protein regulation in the coral Acropora yongei during photoacclimation

D'Angelo et al (2008 ) Blue light regulation of host pigment in reef-building corals

 

Very informative thread, I have nothing intelligent to add so I will leave it at this:

 

LMAO!! ;D Is that Forrest Gump's little brother Swamp Gump?;D;DSorry guys but that was funny. Don't think that was face paint though. Great topic please continue now silly Mojoe.

 

Hmm interesting.. And thanks, I'll have to take a look at those. Just out of curiosity, what is your field of study? I am a cell and molecular biology major so this stuff really interests me. Although, it is hard to take on all the info at once. There should be a science section to this forum!

 

Mostly molecular biology and biostatistics. Currently in working in biostats though; so, I use reefkeeping for my biology fix ;D