[Coral-List] Artificial Reefs
szmanta at uncw.edu
Wed Oct 30 10:29:10 EDT 2013
Thanks for your clear write up, which perfectly captures my assessment of the various terms as I use them (and teach). Too many people either do not know about or have forgotten the term "bioherm" which in my mind captures structures like the deep Oculina and Lophelia structures, which are too deep to sink anything other than a submarine, and so in my book, are not 'coral reefs' shallow or deep.
Dr. Alina M. Szmant
Professor of Marine Biology
Center for Marine Science and Dept of Biology and Marine Biology
University of North Carolina Wilmington
5600 Marvin Moss Ln
Wilmington NC 28409 USA
tel: 910-962-2362 fax: 910-962-2410 cell: 910-200-3913
From: coral-list-bounces at coral.aoml.noaa.gov [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Douglas Fenner
Sent: Tuesday, October 29, 2013 5:58 PM
To: Eugene Shinn
Cc: coral list
Subject: Re: [Coral-List] Artificial Reefs
I think one other distinction needs to be made. And that is the difference between a coral reef as a geological structure, and a coral reef as a living ecosystem. People commonly use the term "coral reef" to mean either or both. They are two quite distinct things, although the living ecosystem builds the geological structure, so the are very much connected.
Since they are two distinct things, you can have both together, or just one or the other present. So you can have a geological "coral reef" which is an accumulation of calcium carbonate that was produced by a coral reef ecosystem in the past, but which no longer has a coral reef ecosystem living on it today. A Pleistocene coral reef which has almost no corals on it today, such as Gene was pointing out in Florida, would be an example.
It might be called a "hardground" or a "dead coral reef." On the other hand, you can have a coral reef ecosystem, without a geological coral reef. So an ecosystem of living corals and other organisms, in which corals are abundant enough to make it a coral reef ecosystem instead of say, an algae bed, but which is growing directly on rocks that are not carbonates. So there is no carbonate buildup beneath the corals, yet there are enough corals that there is a coral reef ecosystem. As John says, that is often referred to as a "coral community." And then you can have both together, which is what most of us are most familiar with. But they are two distinct things, and are separable.
I would think that something humans build and put into the water could easily become a coral reef ecosystem if enough corals settle on it, but would require a lot of time to become a coral reef geological structure, the corals would have to build so much carbonate that the coral carbonate was what the structure was mostly made of. Could certainly happen, but would take a lot of time.
The other aspect is the "reef" aspect. A "reef" being a natural structure in the water that is shallow enough you can run your boat aground on it. "Coral reefs" can be considered a type of reef that is made of coral. However, this is a relatively superficial use of terms that doesn't acknowledge the distinction above between a geological structure and an ecosystem.. Plus it gets into the problem of what to call a geological structure with a coral ecosystem on top of it, which doesn't reach shallow enough depths to run a boat aground on. There are places like that, surely plenty. In my view, they should still be called "coral reefs" even if they are too deep to run a boat aground on.
Then there is the distinction that we have become aware of, that there are deep water, cold water, places that have corals growing, and a structure built by corals. Those corals do not have zooxanthellae, they have to catch food. The corals are typically thin branching species, and that ecosystem has a very low diversity of coral species, probably most are dominated by just one species on a structure. But the structures they build (I think they're called "bioherms") can be fairly large. But clearly this is a distinct, though somewhat similar, thing to the tropical, shallow water, coral reefs most of us work on. Often they are called "deep water reefs" or "cold water reefs" or something like that.
Hope that helps a little. Cheers, Doug
On Tue, Oct 29, 2013 at 4:04 AM, Eugene Shinn <eugeneshinn at mail.usf.edu>wrote:
> John, That is a well reasoned response to my questions, thank you and
> congratulations. I especially appreciate your comment about
> Pleistocene coral reefs. I continually rant about how little growth
> there is on the so-called Florida reef tract that has had 6,000 years
> to grow and have often suggested it be called a hard bottom coral
> community rather than a reef. In this case the hard bottom is slowly
> forming on a thick Pleistocene age coral reef so geologically
> speaking it could all be lumped together and called a coral reef. It
> is a coral reef which contains an 80 to 110 thousand year old hiatus
> between a Pleistocene coral reef tract that was exposed and populated
> by air breathing plants and animals when sea level dropped a few hundred feet below present.
> The mystery is how did this thick coral reefs develop during the
> Pleistocene in a location where where corals have been doing poorly
> for the past 6,000 years? I can only guess that it was warmer during
> the Pleistocene interglacial period. Gene
> 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>
> Tel 727 553-1158
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