coral reefs doomed?

[Bob Buddemeier]

Jim, et al.,

Good questions, good points, -- and like it or not, a pretty good if disturbing
article.

On your question about range expansion to compensate for temperature increase
and inhospitably hot tropics -- there are unfortunately 3 geographic factors
that work against that.
1.  The available shallow water benthic area decreases rather significantly as
you move to higher latitudes (no atolls, narrower shelves, etc.)
2.  Light -- see the Kleypas et al analysis -- Kleypas, J.A., McManus, J.W. and
Menez, L.A.B., 1999. Environmental limits to coral reef development: Where do we
draw the line? American Zoologist, 39(1): 146-159.  Maximum reef depth shoals
dramatically at higher latitudes, even within the thermal mixed layer.  This
presumably reflects light limitations due to sunangle and day lenght variations
-- which aren't going to change.
3.  Carbonate saturation state decrease is squeezing from the high latitude
sides -- see the US National Assessment,
http://www.cop.noaa.gov/pubs/coastalclimate.PDF, section 4.4.

So there is little basis for optimism there.

With acknowledgment of the terminological problems, some form of
adaptation/acclimatization probably does have real potential to ensure the
survival of corals , but not necessarily "reefs as we know them."   The Ware et
al article and its precursor, Buddemeier, R.W. and Fautin, D.G., 1993. Coral
Bleaching as an Adaptive Mechanism: A Testable Hypothesis. BioScience, 43:
320-326, are looking more solid as experimental tests come in (Kinzie et al in
Biol. Bull. earlier this year, Baker in Nature more recently), but for some
reason this concept has been anathema to some reef cology and conservation
types.  (see also Buddemeier, R.W., Fautin, D.G. and Ware, J.R., 1997.
Acclimation, Adaptation, and Algal Symbiosis in Reef-Building Scleractinian
Corals. In: J.C. den Hartog (Editor), Proceedings of the 6th International
Conference on Coelenterate Biology (16-21 July 1995, Noordwijkerhout, The
Netherlands). National Museum of Natural History, Leiden, pp. 71-76 for a
related issue).  This may be because it is seen as diminishing the seriousness
of the bleaching problem, but in my view your position is the more valid --
without some mechanistic reason to believe that corals CAN survive, there is
very little justification for investing money in research and conservation.

This also relates to my tired old hobby horse of the non-reef coral habitats --
I don't think we are getting the real picture, or doing ourselves any favors, by
exclusive concentration on reefs; corals have survived many periods of
non-reef-building, and we had better figure out how, why and where.

Thanks for bringing this up.

Bob Buddemeier


Jim Hendee wrote:

> Dear Coral Colleagues,
>
> I know I'll get raked over the coals on this (especially because I don't
> have all the literature at my fingertips), but the content and tone of the
> news article below is troublesome to me, even though such a tone helps to
> gain attention, as well as funding, so that we can more thoroughly study
> the problem of coral bleacing and global warming.  Of course I respect our
> colleague's right to a viewpoint, but when I see this, I can't help but
> have these thoughts:
>
> Such a projection gives no "credit" to adapatation and natural selection,
> even though such adaptation would have to occur under a relatively short
> time span (50 years).  I believe Ware et al (1996), among others, have
> addressed this.
>
> As Dr. Al Strong and I have discussed, and as alluded to but unfortunately
> not expanded upon in the last sentence of the article, if the seas are
> warming, then you might expect the zoogeography of corals to expand
> (relocate?) into the cooler areas, as long as the substrate, circulation,
> light and water quality regimes are conducive.  (I would imagine some
> coral researchers have modeled these possibilities, and I apologize for
> not referencing your work.)
>
> Even though high sea temperatures are the primary cause and indicator of
> coral bleaching, that is not the only cause, and no credit is given to the
> evidence in the literature (e.g., Lesser 1996, among others) that high UV
> is also an agent in coral bleaching.  Higher UV, especially in the
> tropics, is part of the problem as it relates to the earth's ozone layer.
> There is evidence that high sea temperatures that elicited coral bleaching
> at some localities in the past did not elicit coral bleaching during
> extended cloudy periods (Mumby et al, in press). (Perhaps the cooler areas
> mentioned in the above paragraph might also have lower UV?)
>
> There are other causes of coral bleaching (e.g., see Glynn 1993, 1996) and
> this manifestation of stress is complex and to my mind public statements
> on coral bleaching should emphasize this.
>
> Would an annual update to the ITMEMS statement on coral bleaching
> (http://coral.aoml.noaa.gov/bulls/ITMEMS-bleach.html) be helpful for the
> public in this regard?  It is my opinion that it would, that we should
> address the topics above (among others, e.g., coastal effects), and that
> it would behoove us to widely circulate the update among the press as a
> consensus opinion (if that is possible!).
>
> Just my two cents worth...
>
>         Cheers,
>
>         Jim Hendee
>         NOAA/AOML
>         Miami, FL
>
> Glynn, P. (1993). Coral reef bleaching: ecological perspectives. Coral
> Reefs 12, 1-17.
>
> Glynn, P. (1996). Coral reef bleaching: facts, hypotheses and
> implications. Global Change Biology 2, 495-509.
>
> Lesser, M.P. (1996).  Elevated temperatures and ultraviolet radiation
> cause oxidative stress and inhibit photosynthesis in symbiotic
> dinoflagellates.  Limnol Oceanogr. 41(2): 271-283.
>
> Mumby, P.J., Chisholm, J.R.M., Edwards, A.J., Andrefouet, S. & Jaubert, J.
> 2001. Cloudy weather may have saved Society Island reef corals during the
> 1998 ENSO event.  Mar Ecol Prog Ser (in press).
>
> Ware, J.R., Fautin, D.G., & Buddemeier, R.W. (1996). Patterns of coral
> bleaching: modeling the adaptive bleaching hypothesis. Ecological
> Modelling 84, 199-214.
>
> -------- Original Message --------
>
> World coral reefs to die by 2050, scientist warns
> By Ed Cropley, Reuters
> Thursday, September 06, 2001
>
> GLASGOW, Scotland — The world's coral reefs will be dead within 50 years
> because of global warming, and there is nothing we can do to save them, a
> scientist warned Wednesday.
>
> "It is hard to avoid the conclusion that most coral in most areas will be
> lost," Rupert Ormond, a marine biologist from Glasgow University, told a
> science conference. "We are looking at a loss which is equivalent to the
> tropical rain forests."
>
> Only the coral reefs in nontropical regions such as Egypt stand any chance
> of lasting beyond 2050, Ormond said, but even the days of the stunning
> marine parks of the Red Sea are numbered as sea temperatures continue to
> creep up.
>
> In the past, reefs have suffered from sediment buildup and the coral-eating
> crown-of-thorns starfish, whose numbers have exploded due to the
> over-fishing of their predators.
>
> Now the main threat to the delicate structures that harbor some of nature's
> most stunning creations comes from warmer seas, which cause coral bleaching.
>
> Microscopic algae that support the coral polyps cannot live in the warmer
> water, and the polyps, the tiny creatures who actually create the reefs, die
> off within weeks.
>
> Scientists agree the world's oceans are now warming at a rate of between one
> and two degrees Celsius every 100 years due to the increased amounts of
> greenhouse gases in the atmosphere which trap the sun's rays.
>
> But even if humans stopped pumping out greenhouse gases such as carbon
> dioxide tomorrow in a bid to halt the process, it would still be too
> late to
> save the reefs, Ormond said. "I don't know what can be done, given that
> there's a 50-year time lag between trying to limit carbon dioxide levels and
> any effect on ocean temperature," he told the conference, held by the
> British Association for the Advancement of Science.
>
> The implications stretch far beyond the death of the colorful coral
> structures themselves. The weird and wonderful eels and fish which inhabit
> the nooks and crannies will become homeless, and many species will die out.
> "We are looking at a gradual running down of the whole system. Over time,
> the diversity of coral fish will die," Ormond said.
>
> Humankind will also suffer directly as the dead reefs are eroded and
> shorelines that have been protected for the last 10,000 years face the wrath
> of the oceans without their natural defenses.
>
> In an age of relatively cheap scuba-diving holidays, this also means many
> developing countries in the tropics, such as Kenya or those in the
> Caribbean, face losing a major source of revenue.
>
> The only cause for optimism was that new coral reefs could start to emerge
> in colder waters such as the north Atlantic Ocean and Mediterranean Sea.
>
> Copyright 2001 — Reuters
>
> ~~~~~~~
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--
Dr. Robert W. Buddemeier
Kansas Geological Survey
University of Kansas
1930 Constant Avenue
Lawrence, KS 66047 USA
Ph (1) (785) 864-2112
Fax (1) (785) 864-5317
e-mail:  buddrw at kgs.ukans.edu