Calcite layer forming

[Namyar]

Anyone out there. I have been searching the internet to find information on the formation of the calcite layer on corals.

If anyone has any information they are aware of and are wiling to share it that it would be helpfull. Just trying to educate myself.

[Boomer]

What do you mean by calcite layer on corals ? All corals are layers of Aragonite not Calcite.

[Namyar]

What I am looking for is information on the secreted layer that forms on corals (typicly SPS) when the lights go out. Hoep this helps.

[Boomer]

Corals do have a small amount of intermixed Hi-Mg -Calcite but is a very small amount. I would PM MCsaxmaster to come here for a look. His thesis is more or less on this subject.

MCsaxmaster
http://reefcentral.com/forums/private.php?s=&action=newmessage&userid=24545

[Namyar]

Thank you boomer I sent him a PM I will see if he can help me with this.

[Boomer]

Be prepared for a very long answer :lol:

[MCsaxmaster]

I guess I'm a little confused too. There are 3 common polymorphs of CaCO3 produced in calcifying organisms: high-Mg calcite, low-Mg calcite and aragonite. Corals produce almost entirely aragonite, perhaps with some calcite as well (though these are final products--amorphous CaCO3 and maybe vaterite are probably the initial phases which eventually reorganize to aragonite).

If you're intersted in the process of biomineralization, we can discuss it here, but note that there are literally entire symposia and many books dedicated to the subject. Even so, significant unknowns still remain in spite of work done to date.

Chris

[MCsaxmaster]

<a href=showthread.php?s=&postid=13103875#post13103875 target=_blank>Originally posted</a> by Boomer
Be prepared for a very long answer :lol:

You know me too well :lol:

[Boomer]

But Chris, I love your long answers :D One is suppose to cover all and try not to leave things out. I *use* to do that :lol:

[Namyar]

Here is some reading that I am looking for does anyone have an idea where I can get a copy of it.

Barnes, D.J. 1972. The structure and formation of growth-ridges in scleractinian coral skeletons. Proc Roy Soc Lond B 182: 331-50.

[MCsaxmaster]

Try a local university library.

[Boomer]

Title:
The Structure and Formation of Growth-Ridges in Scleractinian Coral Skeletons
Authors:
Barnes, D. J.
Publication:
Proceedings of the Royal Society of London. Series B, Biological Sciences, Volume 182, Issue 1068, pp. 331-350
Publication Date:
10/1972
Origin:
JSTOR
Bibliographic Code:
1972RSPSB.182..331B

Abstract
The external surface of the epitheca in modern and fossil corals is marked by tiny ridges lying parallel to the epithecal rim. These ridges have been assumed to be daily growth increments, and have been linked with supposed lunar and seasonal events recorded in the skeleton, to compute aspects of the history of the Earth's rotation. This communication presents structural and experimental evidence to show that the growth-ridges in the epithecae of modern hermatypic scleractinian corals, particularly Manicina areolata (Linnaeus), are formed as a result of daily changes in the shape of the tissues secreting the epithecae. The changes in shape of the tissues are an integral part of the mechanism by which the body wall of these corals is adjusted in position to accommodate for epithecal growth. This adjustment takes place in concert with a daily cycle of expansion and contraction of the animals. Because the epitheca is formed at the perimeter of the skeleton-secreting layer, its growth involves certain fundamental requirements. The presence of growth-ridges in all coral epithecae suggests that all corals meet, or met, these requirements with a similar mechanism to that which operates in the hermatypic species studied. However, the mechanism is not necessarily linked to a daily cycle of expansion and contraction.

And this article is 35 yeras old :)

[Boomer]

Skeletal Microstructure of Galaxea fascicularis Exsert Septa: A High-Resolution SEM Study
http://www.biolbull.org/cgi/content/full/204/2/146

The Chemical and Biochemical Mechanisms of Calcification
http://www.advancedaquarist.com/issues/apr2002/chem.htm

[Namyar]

Thank you both for the information I found this one also.

http://jeb.biologists.org/cgi/content/full/209/17/3413

[Boomer]

You did good on that one :)