I used to teach science for a living, so ... like Iwan ... I too have an interest in presenting both historical and contemporary research-based literature in an effort to counter-balance the mind-numbing array of opinions which masquerade as information in reefkeeping cyberspace.
With due respect to Iwan's obvious mastery (where's the "bowdown" smilie when I need it?), one of his recent posts includes some assertions which ... while being easily digestible to the magazine reading crowd ... are significantly
incomplete in terms of the peer-reviewed literature.
Please note that I didn't say his post contained information that was
wrong ... I said "incomplete." I also don't mean to perpetrate a thread "hijack" ... apologies if it comes across that way ... and profound apologies if I come across as disrespectful to either Iwan or the RC community engaged with this thread.
That being necessarily said ...
Stone corals have the ability to build chromo proteins (Pocciloporine). These pigments determine the colors. The symbiosis algae (zooxanthellae) don't determine the color. ...
While it is true that nonzooxanthellate derived pigments profoundly impact coloration of corals (more so than many high post-count RC regulars acknowledge), pocciloporins are but a group of a much larger set of compounds. Pocciloporins are but one of MANY chromoproteins which influence what humans perceive as coral "coloration." Astaxanthins, ketones, carotenoids, xanthophylls, melanins, purines, ommochromes, porphyrins, to list but a few, are ALL involved ... and the list becomes more defined in the literature each year. To assert that pocciloporins are the
determinant compounds for coral coloration is ... well ... forgive me ... misleading.
BTW ... pocilloporins are related to the monomeric green fluorescent protein and the tetrameric DsRed fluorescent proteins, which have widespread use as biotechnological tools. They do NOT constitute the
exclusive set of fluorescent pigments in corals.
(SCIRUS search results for keyword "pocciloporin")
Zooxanthellae DO in fact directly synthesize proteins that are directly expressed in terms of fluorescence ... among these are MAA (mycosporine-like amino acids), flavines, urobilines, and pterines. "These compounds are responsible for some of the blue, green, and pink fluorescent colors found in so many corals of the reef. ... Many corals in the aquarium become fluorescent green under strong lighting, and it is likely that these pigments are responsible for the color change (Borneman 2001)." Just because a compound is colorless in a test tube does NOT mean that it lacks either fluorescent or refractory properties
in situ.
This is to say nothing of the role that pigment precursors synthesized by zooxanthellae play in the synthesis of nonzooxanthellate pigments within cnidarian cells.
I have no objection to the assertion that nonzooxanthellate derived pigments may end up being the most significant influence of a given specimen's coloration, but to say that "these pigments determine the colors" is ... well ... incomplete.
Too many nutrients cause an increase of the zooxanthellae. The result is a covering of the colors.
No problem with the first part (having recently asserted it myself), but ... is it being suggested that zooxanthellae (the vast majority of which reside in the gastrodermis
below the epidermis) are "covering the colors" of nonzooxanthellate pigments (which are primarily located in the epidermis
above the zooxanthellae)? Hmmm ... maybe a German-English translation glitch involving "covering"? Even so ... if the CSD of zooxanthellae are capable of determining the color of a coral specimen, not because of pigmentation, but because of the CSD's
effect on the refraction of light, how can it be asserted that MAA is not doing the same thing?
The zooxanthellae give the coral their colors:
Wrong!The zooxanthellae (symbiosis algae) fulfils other functions. They are responsible for the brown ground shade. This means: More symbiosis algae results in a covering of the colors. We have brown corals.
See above responses ... I would respectfully assert that it is not that simple and that zooxanthellae are directly involved in the biosynthesis of compounds which result in what we refer to as "color". The literature simply
abounds with references to the functioning of zooxanthellae in what Humans refer to as "coloration."
For example, anyone interested in the biochemical mechanisms that I'm refering to might also be interested in this ...
The Symbiotic Anthozoan: A Physiological Chimera between Alga and Animal.
Paola Furla, Denis Allemand, J. Malcolm Shick, Christine Ferrier-Pagès, Sophie Richier, Amandine Plantivaux, Pierre-Laurent Merle and Sylvie Tambutté
Integrative and Comparative Biology 2005 45(4):595-604
(Single ZeoPost with link to the article)
The coral needs energy for the formation of pigments. It makes sense that a coral only put this energy into the production of color giving pigments if it has met its basic requirements sufficiently. The formation of color is a "luxury good". A hungry coral won't waste valuable energy for the synthesis of color constituents.
"Formation of color" is hardly a "luxury good".
Consider ... "Invertebrates may contain more chemical forms of pigments than vertebrates, and they are largely involved in cryptic coloration or aposematic coloration adaptations. These defenses operate by camouflaging the corals or by warning predators not to come near or eat them, respectively (Borneman 2001)."
Aposematic: Coloration or other features that advertise noxious properties; warning coloration. Marked with bright or contrasting colors as a warning that the animal is venomous or noxious.
(Google Definitions of "Aposematic" Link)
In other words ... coloration is a SURVIVAL mechanism. This is NOT something we biologists refer to as a mere "luxury." Expending energy resources into a survival mechanism is hardly a waste of valuble energy.
Not meaning to "nit-pick" here ... Iwan is great, I love his posts, and the awesome mastery of his captive ecosystem
and his methodology speaks for itself (More pictures please).
But let's get the
science straight ... yes?
Not JMO ... this is the
science.
Your description of washed out, dull, more brown leads me to believe that an excess nutrient problem exists. Where, really light, bleached, transparent seem like nutrient starvation. HTH
Share ware your brain
I have a facility to place aragonite under the modules containing the carbon which should act to sequester any leached PO4.
