Why Blue Light?

[billsreef]

There is no secret why blue bubble corals turn brown under bright(er) aquarium lights... and why electric colored shallow water sps turn brown under weaker captive lighting (UV blocking and total light altering/reducing) sheeting for the GH in this case.

The operative part of this is "total light altering/reducing". The zooxanthellae are brown. In the case of the bubble coral from a low light, i.e. little zoox's present, transferred to high light...the coral in brighter lighting is now growing more zoox's, hence the brown coloring. In the case of the "electric" sps, shallow water very bright lighting calls for a small numbers of zoox's. When it's placed in deeper water/lower light, it grows more zoox's to make up for the lower photosynthetic production of the individual zoox's.

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=11467319#post11467319 target=_blank>Originally posted</a> by samtheman
http://forum.marinedepot.com/Topic33101-13-4.aspx

The folks having trouble with browning corals did not do their homework. The problem is their sheeting or glazing (not to mention that apparent lack of understanding for principal mechanisms for coral pigmentation). There is no easy answer here either... their expectations in a GH are about as unrealistic as their expectations in aquaria when they mix corals from drastically different parts of the reef. There is no way you can expect a Euphylliid from 60ft that mfgs FPs to capture/retain weak light to be as colorful in the same tank as an Acroporid from 10 ft of water that mfgs FPs to reflect light. It may be impossible to get both to have optimal color under standardized lighting (UV blocked no less).

There is no secret why blue bubble corals turn brown under bright(er) aquarium lights... and why electric colored shallow water sps turn brown under weaker captive lighting (UV blocking and total light altering/reducing) sheeting for the GH in this case.

The matter is made worse by these cheap hobby greenhouses having really poor quality sheeting/glazing.

The folks with brown corals frankly got what they paid for (low investment in their education... low investment in their facility). I mean that literally... not as a slight (please don't take it out of context - to all).

.

Anthony Calfo

Indeed, some kinds of glass may be more or less ideal for use in a greenhouse intended to grow corals. Personally, I'd look for something with good light transmission and probably some ability to block UV.

Anthony is a wonderful aquarist and I have great respect for him, but the suggestion that UV intensity is important in promoting colorful pigment production in corals is simply incorrect. It seems he is making that suggestion here, and all I can say is that all the available data sharply disagree. These pigments aren't produced to deal with UV light nor does UV induce their production. Many fluorescent and non-fluorescent GFP-like proteins vary in production with incident PAR, not with UV. GFP doesn't show much correlation with light intensity or necessarily UV, and seems to have functions completely seperate from the fact that it interacts with light.

Chris

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=11468273#post11468273 target=_blank>Originally posted</a> by billsreef
The operative part of this is "total light altering/reducing". The zooxanthellae are brown. In the case of the bubble coral from a low light, i.e. little zoox's present, transferred to high light...the coral in brighter lighting is now growing more zoox's, hence the brown coloring. In the case of the "electric" sps, shallow water very bright lighting calls for a small numbers of zoox's. When it's placed in deeper water/lower light, it grows more zoox's to make up for the lower photosynthetic production of the individual zoox's.

Zoox. density shows no significant variation over a large range of depths (and hence light intensity). Zoox. density tends to vary with N availability, not light availability. Instead, in lower light the zoox. produce more and/or larger photosystems, so the zoox. that are there appear darker. A coral in shallow water and another colony of the same species in deep water will tend to have the same zoox. density in the tissue, but the pigment density (and hence pigment per zooxanthella) will be higher in deeper water. At all but extremely low light intensities (light intensities below which zoox. can survive) an increase in light should lead to a reduction of pigment density, not an increase.

Chris

 

[samtheman]

So all the money spent on non-UV blocking glazing is a hoax then?

 

[MCsaxmaster]

I couldn't say. I can say that the UV is not benefitting a person by causing the corals to produce more colorful proteins though (possibly with the exception of GFP, but that isn't even straightforward).

Chris

 

[samtheman]

So another reef myth exposed.

 

[MCsaxmaster]

Yeah, this has been a pervasive myth/misunderstanding. With many such misunderstandings (e.g., zooxanthellae give corals their pretty colors) there is limited potential to cause harm to the actual corals. With this misunderstanding there is the potential for serious harm: overexposing corals to UV will harm or kill them, just like it will to any organism.