[Coral-List] Coral immortality

Delbeek, Charles CDelbeek at calacademy.org
Tue Mar 22 11:21:25 EDT 2011

Is there anything to suggest that these massive corals slow in growth rate once they reach a certain size as is seen in Tridacna clams?

I seem to recall reading somewhere that Pocillopora meandrina in Hawaii have a limited life space of about 10 years, which would explain why you do not see them above a certain size and why you often find dead specimens encrusted with corallines at about the same size.

Best regards,

J. Charles Delbeek, M.Sc.
Assistant Curator, Steinhart Aquarium
California Academy of Sciences

p 415.379.5303
f. 415.379.5304
cdelbeek at calacademy.org

55 Music Concourse Dr.
Golden Gate Park
San Francisco CA 94118

The world's only aquarium-planetarium-rainforest-living museum.

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Mark Spalding
Sent: Monday, March 21, 2011 3:23 PM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] Coral immortality

I commend Gene Shinn once again for getting us all thinking. Of course the
suggestion that that a polyphyletic group such as corals might all suddenly
die in a natural cycle of events rather like bamboos is a bit bizarre, and
the original paper (Perry and Smithers) he referred us to does not begin to
suggest that this is what is happening. We all know that corals die, and I
suppose we could also talk about reefs "dying" (in the sense only that
periods of active reef growth are interspersed with periods of non-growth or
even erosion). Most authors then look for indicators of cause, rather than
claiming old age. And throughout geological history there have been many

But I agree with Gene that we need to be a little more critical and avoid
bandwagons. When diving in the "dying" reefs of the Southern Seychelles
during the 1998 coral bleaching I remember noticing the lack of any large
corals whatsoever on the out reef slopes. Here there were lots of massive
corals (mostly bleached or recently dead), but none in colonies larger than
about 60-80cm diameter. (There were much bigger ones in the lagoons.) I
remember commenting that maybe this sort of coral die-off happens more
regularly than we think. Most of those reefs have made good recoveries, but
the individual corals died. An obvious and interesting study would be a very
large-scale analysis of maximum sizes of corals. My guess is that an old-age
hypothesis would produce a nice simple tailing off size-frequency curve, but
that if there are big global or regional events we might see some nice
breaks in those curves, with major drops in the numbers above certain sizes
indicating such events. (Maybe someone's already done that?).

That gets at the dying corals (regular natural or human induced
perturbance), but dying reefs need some level of sustained perturbance. I
have to admit that it worries me when a geologist says "don't worry, it'll
get better again". When exactly? Perhaps they've spent too long studying
near-immortality to realise that most people care about now, next year and
the next generation.

And just because some things happen naturally doesn't mean that we should
relax if we produce the same impact by human actions. Whether compounding
threats are synergistic or just mildly additive it's not a clever response
to say let's not worry, its happened before. Giant panda's survived
innumerable cycles of bamboo flowering, but not surprisingly now face
extinction because we added to the problem, mostly through habitat loss.
Think about it!


Mark D Spalding, PhD
Senior Marine Scientist, Global Marine Team
The Nature Conservancy
Conservation Science Group, University of Cambridge

Reefs at Risk Revisited - www.wri.org/reefs
Recent books: The World's Protected Areas; The Atlas of Global Conservation
World Atlas of Mangroves - www.earthscan.co.uk 

    Date: Fri, 18 Mar 2011 14:04:05 -0400
    From: Eugene Shinn <eshinn at marine.usf.edu>
    Subject: Re: [Coral-List] Coral immortality
    To: coral-list at coral.aoml.noaa.gov
    Message-ID: <a06230903c9a94e76aa1b@[]>
    Content-Type: text/plain; charset="us-ascii" ; format="flowed"

    Good! We got to express ourselves about technical aspects of corals
    and reefs. The subject received two kinds of responses. Those that
    agreed that corals die of old age (mainly off-line) and those that
    disagreed (all on-line). I would like to propose another question for
    discussion. What if all the bamboo on earth began to die at the same
    time? Would there be finger pointing and accusations as to who, and
    what, caused it? I think there would be if it were not for the
    Chinese who have been watching such events for centuries. Bamboo is a
    major construction material in Asia and also the main food for
    Pandas. Do some Google searching and you will find that one species
    dies worldwide at the same time about every 125 years (associated
    with flowering). Other species die on shorter time scales and one in
    northern India flowers and bears fruit once every 40 years leading to
    a plague of rats that consume much of the rice crops leading to
    famine. Now before you say bamboo is in no way related to coral I ask
    how do we know that corals do not naturally go through similar boom
    and bust cycles. Who was diving and paying attention to corals and
    coral recruitment 100 years ago? Unfortunately even the geologic
    record is of little direct help. It is only because of the Chinese
    historical records that we know about bamboo cycles that prevents us
    from becoming hysterical.
    As for Doug Fenners remarks about sea level he is correct,
    Massive corals in shallow water do reach the surface and can grow no
    more. That can be seen on patch reefs in the Florida Keys. In
    addition sea levels fluctuates and corals are killed when the sea
    goes down. However, for the vast majority of the reef tract bordering
    the clear blue Gulf stream the water is 20 to-30-ft deep and there
    are hundreds of widely scattered heads that are less than 200 years
    old. Coals there have had at least 6,000 years to grow! Why are they
    all about the same size? And why is the reef accumulation no more
    than 1 meter thick over the vast extent of the reef tract? Head coral
    growth-rate is much faster than the known rise in sea level so why
    did they not keep pace and make coral heads 20 ft high? Either, like
    bamboo, various species died synchronously on some schedule we are
    unaware of, or they were killed by some environmental factor i.e.
    Hurricanes, disease, cold fronts and/or warming evens. Either way it
    is clear that many non anthropogenic events have kept the Florida
    reef tact from outpacing the well-known rise in sea level since the
    last glacial maximum when sea level was more than the length of a
    foot ball field below present I contend that many mysteries remain!
    If only we were doing the science/research aimed at understanding non
    anthropogenic causes of coral death. In stead we keep hammering away
    at the "usual suspects" that is driven by NGOs and other funding
    The remarks concerning Enewetak demonstrate that the Atoll has
    been able to keep pace with the many sea level fluctuations that have
    occurred over the past 65 million years. I spent 2 months there
    involved in drilling and diving. Unfortunately there are many atolls
    that did not respond well or could not keep up with subsidence. They
    now lie hundreds of meters below sea level and are called guyots.
    A Clarification: I certainly was not suggesting that corals are
    immortal. Just the opposite! Just needed a snappy title. Also, most
    organisms do not die of old age. They die of any number of diseases
    when they become weakened by old age. Could that be what we are
    seeing today? It is interesting that A. cervicornis "sticks" exposed
    in deep trenches made by ship groundings and other causes are more
    robust and often 2 to 3 times the diameter of those that died
    recently. In our paper (Shinn et. Al., 2003) we carbon 14-dated 39
    randomly collected, (actually hap-hazard), fossil sticks in reef sand
    over a hundred mile long stretch of the Florida reef tract, We found
    specimens that dated from 6,000 years old to the present (all near
    the surface). What was most interesting was a convincing 500 year
    absence of Staghorn centered at 4,500 years ago and another less
    convincing 500 year absence centered at around 3,000 years. The
    4,500-year interval correlates well with a period of inferred ice
    rafting determined from deep sea sediment cores. There were probably
    many climate episodes during the Holocene. Gene

    Reference: Shinn, E. A., Reich, C. D., Hickey, T. D., and Lidz, B.
    H., 2003, Staghorn tempestites in the Florida Keys, Coral Reefs, 22:


    No Rocks, No Water, No Ecosystem (EAS)
    ------------------------------------ -----------------------------------
    E. A. Shinn, Courtesy Professor
    University of South Florida
    Marine Science Center (room 204)
    140 Seventh Avenue South
    St. Petersburg, FL 33701
    <eshinn at marine.usf.edu>
    Tel 727 553-1158----------------------------------


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