Educational Topic: What do these terms really mean?

[davelin315]

Tracy's thread on her bleaching monti has gotten me thinking about how we all have different interpretations of what various reef terms mean. Obviously, with this being an online community that gets together in person on the rare occasion as a whole, the problem is that many things take awhile to hash out as it's difficult to understand what exactly someone means when they type something out on the forum. With that in mind, let's try and come up with some narrow and specific definitions for terms we use on the forums.

 

Bleaching: Coral reef bleaching, the whitening of diverse invertebrate taxa, results from the loss of symbiotic zooxantheallae and/or a reduction in photosynthetic pigment concentrations in zooxanthellae residing within scleractinian corals. Coral reef bleaching is caused by various anthropogenic and natural variations in the reef environment including sea temperature, solar irradiance, sedimentation, xenobiotics, subaerial exposure, inorganic nutrients, freshwater dilution, and epizootics. Coral bleaching events have been increasing in both frequency and extent worldwide in the past 20 years. Global climate change may play a role in the increase in coral bleaching events, and could cause the destruction of major reef tracts and the extinction of many coral species.

 

To me, bleaching in our closed environments means that there is a total loss of coloration. I guess that I have used the term indiscriminately throughout my experience in this hobby, but in general, I think of bleaching as basically a dead coral. In using this term loosely, it seems that color shifts have been described as bleaching events. My gut tells me that this should not be the same thing, and that bleaching should be bleaching, kind of like dipping a coral in bleach... it's going to turn white which means there's no zooxanthellae left.

 

Necrosis (Rapid Tissue Necrosis or RTN and Slow Tissue Necrosis or STN): Death of cells or tissues through injury or disease, especially in a localized area of the body.

 

In a coral setting, this manifests itself in two ways. Rapid, which occurs very quickly, and slow, which means that it's slow... but what does this mean?!?!? How do you quantify rapid versus slow? I typically associate rapid with the tissue disappearing over a period of hours. Where does slow come into play, though? If it takes a couple of days, is this still RTN or is it STN? Also, I have always associated RTN and STN with the tissue simply disappearing or peeling off, but I think that many people look at a massive bleaching event as being the same thing as RTN or STN. With RTN, the tissue itself removes itself from the coral skeleton so there's nothing left at all (same with STN). Obviously, if the tissue is gone, the zooxanthellae is also gone, but do these always go hand in hand? Also, is "brown jelly" the same condition basically as RTN? I had a coral that came into contact with a mushroom the other day and it jellied up in a couple of hours. Would that constitute RTN or brown jelly?

 

These are just a couple of terms, feel free to comment and add your own.

[zotzer]

Great topic, Dave!!!

I guess since I started with the "bleaching" thing, and am a relative newbie.....

If you toss a red sock in bleach, it doesn't turn white, it turns pink. That's why I picked the word.

 

It is always preferable to have a common language, and I will be watching eagerly!

Tracy

[davelin315]

Toss in your definition (I was thinking the red sock in the bleach as well when I was writing this), it doesn't hurt to have more than one opinion. Who knows where consensus will be?

[treesprite]

I thought bleaching meant that the zooxanthellae have died off which would cause the coral to lose color, which could be caused by anything that could hurt it. For example a piece of oxypora ended up on the sand overnight with the clown sandstorms also having gotten sand on top of it... bottom is all white now and the top is patchy. Another example - the mean emerald crab picked the polyps off the pocillopora frags - one turned white and is now clearly dead, the other is mostly white but still has patches of polyps. I have a question about this but I don't want to go on a tangent so I'll hold onto it it for a better place.