[Coral-List] What is a coral reef and about "geological reef"?

Vassil Zlatarski vzlatarski at gmail.com
Wed Nov 2 15:59:17 EDT 2016

Dear colleagues,
Hope the end of the exchange concerning "geological reef" and a text from
coming book referring "What is a coral reef" are of interest.

8:23 PM (15 hours ago)
to Eugene, me
Indeed, that has been my view until recently.  Problem is, people,
including me, commonly refer to "reefs" or "coral reefs" and make
statements like "reefs are all going to (or not going to) die in a few
decades."  Or "coral reefs will disappear (or not) by 2100".  Reading or
hearing those, they do not tell you whether the author is saying that the
coral reef ecosystem will die or disappear, or whether the carbonate
buildup will die or disappear.  Yet obviously, the carbonate buildup, which
is what a reef is, will not die or disappear in our lifetimes.  It was
never alive in the first place, and it won't disappear any time soon.  The
corals could, and the coral reef ecosystem, could die.  But the way we use
the terms, we have to guess which one the author meant, and many people
haven't been making the distinction, and I think they are very different
systems, with very different time courses and processes.  Related, yes,
dependent on each other, yes, intermingled (life in holes), for sure.  But
you can easily have one without the other.  Fossil reefs on land, and
carbonate caps on guyotes have cabonate buildups originally produced by
coral reef ecosystems, but no living reef building corals. "Coral
communities" on terrestrial rocks, have live corals and many other
organisms, but not carbonate buildups.  They are usually associated, but
they are separable.  I think we need to distinguish them.  I probably
shouldn't have written "geological reefs", maybe coral-ecossytem-produced
carbonate buildups would be better, maybe there is another term.  But
"reef" or "coral reef" is commonly used for either or both, and I think we
need to distinguish them.   Cheers,  Doug

On Tue, Nov 1, 2016 at 9:08 AM, Eugene Shinn <eugeneshinn at mail.usf.edu>

> Thanks, Yes I forgot worm reefs. Over the years there have been sessions
> at national geological meeting having to do with "What is a reef" Nothing
> ever got resolved So I finally decided I would not worry about it very
> much.
> On 11/1/16 2:27 PM, Douglas Fenner wrote:
> I like it!  Clear.  I'd just add that the ecological community that
> produces the reef is a distinct thing from the reef itself.  The ecological
> community can die, but the reef can't.  The reef can exist whether it is in
> the water or out.  Ah, you forgot one kind of reef, "worm reefs."  Also,
> there is the question of deep coral reefs.  They are clearly bioherms, but
> deep coral reefs never get near to the surface.  So by the navigator
> tradition they are not reefs, though they are coral reefs for sure, just
> not zooxanthellate coral reefs, rather they are azooxanthellate coral
> reefs.
>      I remember that there was an article published on defining coral
> reefs several decades ago, but have been unable to find it.
>     Cheers, Doug
> On Tue, Nov 1, 2016 at 7:08 AM, Eugene Shinn <eugeneshinn at mail.usf.edu>
> wrote:
>> Doug, I just finished the final touches on a requested book I am doing
>> with Barbara Lidz for the University Press of Florida. We include in chapt
>> 4 a discussion of what a reef is and is not. The  title of the book is
>> "Geology of the Florida Keys: A Natural Laboratory" Below is our section on
>> that subject. Best Wishes, Gene
>> Before proceeding, we should ask an age-old question, “What is a reef?”
>> More specifically, “What is a coral reef?” This seemingly simple question
>> lacks easy answers. Answers remain fuzzy and divided and are confused by
>> maritime history and lore. The traditional sailor’s term for reefs includes
>> any topographic feature upon which a vessel may become grounded. Because of
>> this vagueness, areas such as submerged rocks or mountaintops can be called
>> reefs. For example, “Bligh Reef,” on which the 274-m (900-ft) EXXON
>> *Valdez* oil tanker grounded on March 25, 1989, is simply a submerged
>> mountaintop—not a true reef. Sand bars have also been called reefs. For the
>> purposes of geology, a more precise definition has long been debated, yet a
>> precise one remains elusive. Geologists lean toward organically created
>> topography, often called bioherms in geologic literature. The key
>> distinction hinges on whether a topographic feature is created by growth of
>> an organism rather than a non-living object. Thus, there are oyster reefs,
>> sponge reefs, bryozoan reefs, stromatolite reefs, algal reefs, rudistid
>> reefs, and so forth. A sand pile is not a reef. In the Florida Keys, we are
>> concerned mainly with reefs built by corals. On the other hand, there are a
>> few cases where mud banks capped by branching corals have been called
>> reefs.
>> --
>> No Rocks, No Water, No Ecosystem (EAS)
>> ------------------------------------ -----------------------------------
>> E. A. Shinn, Courtesy Professor
>> University of South Florida
>> College of Marine Science Room 221A
>> 140 Seventh Avenue South
>> St. Petersburg, FL 33701<eugeneshinn at mail.usf.edu> <eugeneshinn at mail.usf..edu>
>> Tel 727 553-1158

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