[Coral-List] Coral Immortality

Douglas Fenner douglasfenner at yahoo.com
Thu Mar 17 03:32:20 EDT 2011

    I think the author of the original study does us a favor, showing us that 
what looks like a dead reef to us, does not mean people killed it.  It can 
happen completely naturally.  Makes sense to me, conditions can get bad 
naturally- if a dry coastline with a lot of exposed soil (like a desert) started 
having rain in huge rainstorms that washed off lots of mud, it could kill nearby 
reefs.  Long before humans were doing anything.
    Gene is right, science does have fashion sometimes, something new is 
discovered and if it is exciting enough, people rush to work on it, and start 
interpreting everything in terms of it, and can forget that it doesn't explain 
     Gene makes some comments about corals perhaps dying of old age and maybe we 
just happen to be around when a group of geriatric corals are naturally dying.  
But my impression is that for a lot of corals, they continue to grow and have no 
set specific maximum size or age.  Adult human size is pretty uniform, we grow 
until we reach an adult size, then stop growing.  And human ages are pretty well 
limited too, people don't on rare occasions just go on living to 150, 200, or 
500 years old.  But some corals certainly do.  We recently documented a Porites 
lutea in American Samoa with a girth of 41 meters (Brown et al. 2009).  Far as I 
know the largest girth yet documented.  A Porites lobata was documented in 
Taiwan that is 12 meters tall (Soong et al. 1999).  That's a lot of coral.  And 
I know of no reports where living, healthy coral, reaches a maximum size and 
stops growing.  Some fish do, such as some surgeonfish (e.g., Ochavillo et al 
2011).  Corals seem to be more like some trees, like Redwoods.  Redwoods as far 
as I know have no maximum size or age, they don't stop growing, they just keep 
growing until something gets them, like the soil underneath them gives way, or 
strong winds blow them over, or disease kills them, etc.  Vertebrates typically 
have maximum sizes and stop growing.  Not all species of corals get to the huge 
sizes I mentioned, those are the champions, and only a few species of Porites 
get to those sizes, and I'd bet Montastrea annularis complex corals in the 
Carribean gets to huge sizes at times.  Most individuals of those same species 
are vastly smaller, and won't make it to that size.  But they grow every year as 
long as they live, and they die at a wide variety of ages, not at a specific 
size or age.  But it is also clearly true that different species of corals grow 
to different typical sizes and maximum sizes.  There are some small 
zooxanthellate corals in the Caribbean like Favia fragum, also called "golfball 
coral" due to its typical small size.  Scolymia cubensis doesn't get very big 
either, and Siderastrea radians is usually small.  The champion small colonial 
zooxanthellate coral as far as I know is Stylaraea punctata, an Indo-Pacific 
coral that is often less than 1 cm diameter and a really big one might reach 2 
      The original geology paper that stimulated this discussion reports on 
reefs near shore in the Great Barrier Reef, which live in very high sediment 
environments.  Like any reef, when they reach the surface, that upper surface 
can no longer grow.  Corals don't grow well in air.  These reefs stopped growing 
on their slopes as well, perhaps because of the sedimentary conditions, and some 
restarted later.  I work in American Samoa, on a relatively young (only 1.5 
million years old) island, which has lots of fringing reefs.  The reefs have 
reef flats that have reached the surface, and indeed although there is coral 
cover on the reef flat currently, it is not high cover, and you can see why, 
when the lowest tides of the year come, corals that are exposed to air too long 
in the hot sun don't survive.  The reef slopes, however, are in relatively clear 
water and a low sediment environment (at least outside the harbor!).  Those 
slopes have fairly decent coral cover (about 30% average), large and small 
colonies, coral cover has not been going down in the last few years, very little 
macroalgae, lots of coralline algae and what looks to this non-geologist like a 
reef slope that is growing geologically as well as biologically.  My guess is 
that many islands and atolls around the Pacific have reefs that are growing 
geologically on their slopes, but I am certainly guessing and not a qualified 
      For a longer time span perspective, consider Eniwetok Atoll in the 
Marshall Islands.  When it was drilled, the carbonate reef rock was about 1200 m 
thick, and on top of volcanic rock, fitting with Darwin's theory.  The reef rock 
just above the volcanic rock was about 65 million years old.  The reef at the 
top is at the surface, with a few islands in the atoll that stick up a couple 
meters or so above the water.  So, the reef there began growing 65 million years 
ago, and it has kept growing enough for the top to still be at the surface, even 
though if it stopped growing and didn't restart, it would have subsided until it 
was deep enough not to have enough light to grow back up to the surface.  The 
Pacific is dotted with atolls that have done the same sort of thing, and the 
Indian O. has quite a few too.  So over the time span of tens of millions of 
years, there are lots of reefs that have managed to "keep up."  Which is not to 
say they may not have stopped growing and started again several times or even 
many times.  But an awful lot of them must have started again after each stop or 
there would be few left at the surface, I think.
      On an even longer time scale, there are long periods in the geological 
record in which there are no fossil reefs anywhere.  Veron (2008) correlates 
these with periods when water conditions were bad, primarily chemically.  But 
you might have to hang around for 100 million years or so to see such a hiatus.
      All of which does not say that some reefs don't naturally stop growing 
from time to time.
      I recommend the popular article Gene's post pointed to, and the comments 
posted below it, all interesting.
      Cheers,  Doug

 Brown, D. P., Basch, L., Barshis, D., Foresman, Z., Fenner, D., Goldberg, J.  
    American Samoa’s island of giants: massive Porites colonies at Ta’u island.  
    Reefs 28: 735.
Soong K, Chen CA, Chang J-C (1999) A very large poritid colony at Green Island, 
Taiwan. Coral Reefs 18:42

Ochavillo, D., Tofaeono, S., Sabater, M., and Trip, E.L.  2011.  Population 
structure of Ctenochaetus striatus (Acanthuridae) in Tutuila, American Samoa: 
the use of size-at-age data in multi-scale population size surveys.  Fisheries 
Research 107: 14-21.

Veron, JEN.  2008.  Mass extinctions and ocean acidification: biological 
constraints on geological dilemmas.  Coral Reefs 27: 459-472.

Douglas Fenner, Ph.D.
Coral Reef Monitoring Ecologist
Dept Marine & Wildlife Resources
American Samoa

Mailing address:
PO Box 3730
Pago Pago, AS 96799

work phone 684  633 4456

Faster ice melt, higher sea levels

Ice loss on Greenland and Antarctica is accelerating at three times the rate of 
mountain ice loss. If it continues, this melting will dominate sea-level rise 
this century.

Eric Rignot at the University of California, Irvine, and his colleagues compared 
calculations based on 18 years' worth of data on climate and ice discharge with 
8 years' worth of data from the Gravity Recovery and Climate Experiment, which 
uses satellite measurements to assess ice mass. The authors estimate that the 
rate of loss is increasing by around 36..3 gigatonnes of ice a year, with a 
cumulative loss of 475 gigatonnes in 2006.


From: David M. Lawrence <dave at fuzzo.com>
To: coral-list at coral.aoml..noaa.gov
Sent: Wed, March 16, 2011 2:27:12 AM
Subject: Re: [Coral-List] Coral Immortality

First, you have to come up with a relevant definition of immortality.  I 
doubt the concept of immortality, which applies to individuals, makes 
any sense when applied to corals.

Also note this paragraph from the story:

"In many areas of the world, reef degradation is clearly down to human 
activities like over-fishing, pollution and rising sea temperatures. In 
the Caribbean, 80 per cent of reefs have declined since the mid-1970s 
and this is almost certainly down to pollution and over-fishing."

The story also offers an explanation for the growth declines:

"Two main things can slow their growth - lack of sunlight penetrating 
the water and lack of space. The shallow and muddy waters of the 
inner-shelf of the Great Barrier Reef mean that the space into which 
reefs can grow is relatively limited. This means they can pass through 
their different evolutionary stage rapidly - young to mature to senile 
in only a couple of 1,000 years."

This sounds a hell of a lot more than Liebig's law of the minimum coming 
into play than some kind of natural "life span" limit on coral growth.  
Which, if that is the case, is no surprise to anyone familiar with 
ecological literature.


On 3/15/2011 1:12 PM, Eugene Shinn wrote:
> Dear Coral-Listers, Here is a stimulating break from the incessant
> job advertisements. See
> <http://planetearth.nerc.ac.uk/news/story.aspx?id=907>   It is
> interesting because the vast majority of head corals in the Florida
> Keys suffered mortality over the past 35 years, especially during the
> 1980s at places like once-thriving Carysfort reef where there were
> hundreds in the 200 to 300 year-old range. More than a dozen of the
> living Montastrea sp heads there were cored and their growth rates
> measure and published by Hudson (1981). In addition brain corals also
> perished or are hanging on by a thread (see
> <http://gallery.usgs.gov/videos/334>). It is interesting to note that
> similar head corals grew during the Pleistocene and built the Florida
> keys when sea level was more than 20 ft higher than today.
> Interestingly those heads that built the reef grew no larger than
> those that recently died in the Florida Keys. Why do we not see head
> corals that grew 15 to-20-feet in height (or even 50 ft) back when
> there were no anthropomorphic influences? Does it mean corals are not
> immortal? Could it mean that corals die of old age like all other
> organisms on earth and we just happen to be living at the right time
> to observe the current age class of geriatrics demise?  Is that why
> more than 95 percent of what we call the Florida reef tract is less
> than 1 meter thick when it had the past 6 to 7,000 years to grow? I'm
> sure there are those who think today's corals should be immortal but
> why weren't they immortal in the past? Just something to think about!
> Gene
> Reference: Hudson, J. H., 1981, Growth rates in Montastraea
> annularis, a record of environmental change in the Key Largo Coral
> Reef Marine Sanctuary, Florida. Bulletin of Marine Science, v. 31,
> pp. 444-459

  David M. Lawrence        | Home:  (804) 559-9786
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