Adaptive Bleaching Hypothesis (1)
oveh at uq.edu.au
Fri Sep 21 19:41:51 EDT 2001
With great respect to you and your colleagues, the effort to discuss the
ABH should be seen not as an "attack" but as an attempt to clarify and
expand on this interesting area (aka "spirit of debate"). My intention in
responding to your broadcast message (Sep 16) was to also clarify the
implication that the resistance to the ABH was somehow not on scientific
terms. Given the interest in this area, I agree that it is important to
keep the discussions open and visible on the coral-list forum.
To begin with, let us put one assertion to rest. You suggest that I have
"consistently misstated" your hypothesis. I understand the hypothesis as
encapsulated in your own words (Ware, Fautin and Buddemeier 1996) as:
"Buddemeier and Fautin (1993) proposed that bleaching is not merely
pathological, but is also adaptive, providing an opportunity for
recombining hosts and algae to form symbioses better suited to altered
To the first issue - recombination involves re-mixing as well as
recombining. If part of the ABH involves shifts in the genotype
frequencies of populations of pre-existing mixed dinoflagellate symbionts,
then I would argue that "re-combining" as a term is not clear (and hence
perhaps the greater confusion) and that "remixing" should be included in
these descriptions of the ABH hypothesis. I spoke briefly (as I walked
out of a talk in Bali) to Daphne about this distinction in regard to the
"adaptation" versus "acclimation" (hence the recent reference to the
re-mixing genotypes as "acclimation" not "adaptation"). By the way, this
is the only time (prior to recent exchanges in September) that we (you, I
or Daphne) have corresponded on this issue. I enjoyed the conversation and
was unaware of any anxiety.
Secondly, according to your recent email, I need to also recognise the
expanded definition of "altered circumstances" to include a changed regime
(more frequent and/or intense bleaching events) as opposed to an on-going
stress. I have and have no problems with this. It does not remove the
problems, however. More on this in a second email to the list.
At the end of the day, however, we are left with a need (8 years after the
ABH was first formulated) to go beyond the partial verification of
assumptions and theoretical modelling (as per John Ware and co-authors) to
the critical testing of this hypothesis. While there has been attempts to
test the assumptions in at least one paper, the critical test for this
hypothesis is that new combinations of host-symbiont genotypes with
greater fitness arise from changed circumstances with respect to bleaching
events (be that changing patterns of frequency and/or severity). "The key
observations that corals, when heat stressed, expel one variety of
zooxanthellae and take on another more heat-tolerant variety while the
heat stress is still present, has never been made." (Hoegh-Guldberg 1999).
That statement is still correct but does address a restricted set of ABH
possibilities. This statement should be more inclusive given the above:
"The key observation: that corals after heat stress or a changed sea
temperature regime, shift toward more fit combinations of host-symbiont
genotype combinations, has never been made." Unless I am mistaken, no
observation like this has not been made. I suppose as a biologist, I
would expect this to be a visible and obvious feature of
coral-dinoflagellate symbioses, especially before and after the
substantial selective pressure of recent bleaching events.
In the spirit of scientific debate, I want to also discuss (in detail as
you request) your broadcast proposition (Sep 8 2001) that "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)." As requested, I
will "rely on direct quotes in context" but will do this directly in a
separate email to the list.
All the best,
From: buddrw [mailto:buddrw at kgs.ukans.edu]
Sent: Sunday, 16 September 2001 7:28 AM
To: oveh at uq.edu.au; Jim Hendee
Subject: RE: coral reefs doomed?
Ove, and others --
Part of the reason you are still waiting for hard experimental evidence
regarding the ABH is that you consistently misstate and/or misunderstand what
it is. Some specific examples:
"the definitive data that shows corals will bleach, get rid of one
dinoflagellate genotype and adopt another WHILE the thermal (or other) stress
is still being applied to the coral-dinoflagellate association." This is
part of the ABH only to the extent of requiring continuance of the stressful
REGIME (e.g., frequency of high temperature excursions), not of the stressful
bleaching-inducing CONDITION (e.g., continuous high temperature). It seems to
me that you are attacking the latter proposition, which is NOT what we
proposed or modeled (Ware et al).
"used light and could not prove (using RFLPs) that his corals had changed from
one dinoflagellate genotype to another (simply up-regulating one strain over
another is not sufficient - that is acclimation and is not surprising)."
Bleaching is a stress response, and we think that stress adaptation probably
doesn't care that much about light, temperature or whatever -- besides which,
there is certainly strong evidence for the synergism of light in temperature
even in the bleaching episodes attributed primarily to temperature. Sorry if
using light is a problem for you -- it's not for us. Further, we are willing
to plead guilty to having accepted that which is not surprising -- what you
refer to as 'up-regulation' we considered a shift in dominance or inertnal
competitve abilities among the varieties of zoocxanthellae that could or did
inhabit a host -- very much a part of ABH.
Rather than go on and nit-pick your counter-arguments, I'd like to suggest
that this is a good opportunity to set up and broaden the debate as a
discussion thread -- with the proviso that we rely on direct quotes in context
(since the subject is a bit complicated for one-line summaries) rather than on
strawman revisions to discuss what the ABH actually is or isn't.
>===== Original Message From <oveh at uq.edu.au> =====
>Dear Bob and others,
>I was triggered to respond by the inferences in your statement that some
>ecology and conservation" types have trouble with the Adaptive Bleaching
>Hypothesis. Any practicing experimental scientist would have an issue with
>state of play regarding support for this hypothesis. The basic problem at
>point is nothing to do with "culture" - it is more to do with hard evidence,
>which is almost completely lacking to support this still very soft and
>hypothetical explanation for why coral bleach. While experimental tests have
>been coming in, they have had serious problems in terms of design and the
>conclusions they draw. Us "reef ecology and conservation types" still wait
>the definitive data that shows corals will bleach, get rid of one
>genotype and adopt another WHILE the thermal (or other) stress is still being
>applied to the coral-dinoflagellate association. This has never been shown.
>Showing diversity in rDNA is interesting but irrelevant if diversity here
>not relate to relevant physiological differences. The recent paper by Baker
>(whom I greatly respect), for example, used light and could not prove (using
>RFLPs) that his corals had changed from one dinoflagellate genotype to
>(simply up-regulating one strain over another is not sufficient - that is
>acclimation and is not surprising). The experimental design was also
>by the fact that stressed corals were placed in the two contrasting and
>confounding (for the experiment) habitats (one, the deeper site, was at the
>extreme depth limit of the species concerned while the other was clearly more
>optimal after photo acclimation). It is therefore not surprising that the
>died more at deeper site - which has nothing to do with the fact that they
>Other issues abound and concern us "reef ecology and conservation types" -
>idea of range of expansion is limited (as outlined by several people so far)
>the fact that light may be a more important limiting than temperature. I
>want to stress that the issue of the decline of reefs (as you, Bob, did
>has nothing to do with the extinction of corals. As the "geo types"
>use here) tell us worse things have happened to corals and they have bounced
>back (but over thousands if not millions of years). The issue, however, is
>current human dependency on coral reef ecosystems - reefs disappearing for
>a few decades would present serious issues for several hundred million
>The idea of finding out how reefs survived major extinction events is
>interesting but largely irrelevant to the current discussion.
>So - out I come on my old hobby horse - we still have no evidence of unusual
>adaptive abilities of corals that will match the fast rate of change. Us
>ecology types keep looking. While looking for this evidence - perhaps we also
>need to focus on how reefs will change and how we can "adapt" as human
>to these changes. This research direction, if the projections of the future
>correct, will assume a major significance as we enter the next few decades.
>Professor Ove Hoegh-Guldberg
>Director, Centre for Marine Studies
>University of Queensland
>St Lucia, 4072, QLD
>Phone: +61 07 3365 4333
>Fax: +61 07 3365 4755
>Email: oveh at uq.edu.au
>From: owner-coral-list at coral.aoml.noaa.gov
>[mailto:owner-coral-list at coral.aoml.noaa.gov]On Behalf Of Bob Buddemeier
>Sent: Saturday, 8 September 2001 4:00 AM
>To: Jim Hendee
>Subject: Re: coral reefs doomed?
>Jim, et al.,
>Good questions, good points, -- and like it or not, a pretty good if
>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
>you move to higher latitudes (no atolls, narrower shelves, etc.)
>2. Light -- see the Kleypas et al analysis -- Kleypas, J.A., McManus, J.W.
>Menez, L.A.B., 1999. Environmental limits to coral reef development: Where do
>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
>-- 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
>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
>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
>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,
>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.
>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...
>> Jim Hendee
>> 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
>> Microscopic algae that support the coral polyps cannot live in the warmer
>> water, and the polyps, the tiny creatures who actually create the reefs,
>> off within weeks.
>> Scientists agree the world's oceans are now warming at a rate of between
>> 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
>> 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
>> 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
>> For directions on subscribing and unsubscribing to coral-list or the
>> digests, please visit www.coral.noaa.gov, click on Popular on the
>> menu bar, then click on Coral-List Listserver.
>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
>For directions on subscribing and unsubscribing to coral-list or the
>digests, please visit www.coral.noaa.gov, click on Popular on the
>menu bar, then click on Coral-List Listserver.
Dr. Robert W. Buddemeier
Senior Scientist, Geohydrology
Kansas Geological Survey
University of Kansas
1930 Constant Avenue
Lawrence, KS 66047
ph (785) 864-2112; fax (785) 864-5317
email: buddrw at kgs.ukans.edu
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