a question

John McManus jmcmanus at rsmas.miami.edu
Sun Nov 12 19:34:42 EST 2000

In reply to the inquiry of Tom Oberding, let me see if I can outline the
major concerns briefly, and then perhaps my colleagues can fill in what I
leave out. The summary should be useful to a number of people recently bein=
exposed to a confusing array of reef concerns.

Most concerns can be divided into local-regional problems and global

Local-regional problems include a wide range of perturbations to reefs, suc=
as sedimentation, pollution, overfishing, coral predation, coral disease,
etc. These all occur throughout the range of coral reefs, but vary widely i=
relative importance place to place. Many of us are particularly concerned
about increasing numbers of coral reefs in which recovery from perturbation=
(resilience) seems to have been reduced by chronically high levels of
organic pollution and/or reductions of herbivores (to fishing and/or
disease), leading to increasing dominance by frondose macroalgae (seaweed)
and inhibition of coral settling to various degrees. There may even be
long-term (decadal?) permanence in some of these "phase-shifts" from coral
dominance (or at least prominence) to macroalgal dominance (or at least
coral reduction). However, most of us seem to be concerned here with
reductions in coral and associated biota, rather than total losses of
reef-building corals. The range of problems is summarized well in the recen=
status report edited by Clive Wilkinson and the phase-shift more
specifically in my paper in the latest ICES Journal of Marine Science. A
brief summary of the range and potential severity of the problems can be
found at the WRI website in the Reefs at Risk Report.

The "Global Effect" concerns generally center on either changes in seawater
chemistry or global warming. The former is centered on a recent study by
Kleypas, et al published in Science, indicating that climate change may lea=
to decreasing rates of calcification under certain circumstances. The
post-publication interpretations range from opposition to the idea, to
concerns about perceptible or imperceptible changes in calcification rates
among coral reefs at high latitudes (north and south), to concern about the
dissolution of broad expanses of reefs such as the Great Barrier Reef. Some
of the more extreme views have been expressed in newspaper interviews.

Global warming carries with it at least three concerns: 1. El Ni=F1os of
increasing severity and/or frequency, 2. warming in general leading to
widespread coral deaths and 3. changes in current patterns affecting the
viabilities of reef populations. Since the El Ni=F1o effects are highly
variable peaks spread over time, it is not clear to many that the evidence
points to increasing frequencies or increasing severities. However, many at
least expect both to be the case as the world becomes warmer. Regardless of
the trend regarding El Ni=F1os, it is now clear that warming the sea has le=
to very widespread and often very severe deaths among reef-building coral
populations.  Within the next century, it is likely that global warming wil=
cause mean temperatures in tropical seas will cross the thresholds that hav=
recently led to massive coral death. The more optimistic among us tend to
assume that reef-building corals will adapt toward increasing tolerance of
warm temperatures, perhaps via zooxanthellae adaptation, coral adaptation,
zooxanthellae substitution, coral substitution (as in changes in coral
dominance), or combinations of these. However, the evidence for and against
such optimism is not well-assembled. There are also concerns that increasin=
bleaching will mount with the pressures mentioned above to create a
particularly severe depletion of reef corals. Overviews of the problem can
be found in recent articles in Ambio and elsewhere (see
http://coral.aoml.noaa.gov/bulls/clive-bleaching.html), and you can find on=
via the website of the Conference on Biodiversity (a workshop in which we
tried to summarize the implications of the recent global bleaching and
subsequent documents).  Go to :   http://www.biodiv.org/ and search for
"bleaching" to see a list of downloadable documents. As for assembling the
evidence concerning adaptation and substitution potentials and related
chemical changes, a group of us are putting together a "state-of-the-art"
workshop for early 2001 for this purpose.

The concern about current changes related to climate change has to do with
the often complex and unique means by which many reef organisms return from
their early pelagic stages to settle reefs of origin, riding specific
current patterns, eddies, etc. Warming the seas would undoubtedly alter
these currents, and one would expect some populations of fish and some othe=
creatures to take decades to adapt accordingly. Some of us expect there to
be severe local problems with coral reef fisheries, etc. The effect on
corals is less obvious. There seems to be little written on the general
"current-shift" problem, so we are also putting together a
"state-of-the-art" workshop on that subject for mid-2001. However, the
effect of the current-shifting is likely to be highly variable place to
place and not particularly permanent, and yet another stress to add to the

Please forgive the paucity of specific references - my boxes are still
packed awaiting the opening of our new offices. However, this should get yo=



John W. McManus, PhD
Director, National Center for Caribbean Coral Reef Research (NCORE)
Rosenstiel School of Marine and Atmospheric Sciences (RSMAS)
University of Miami, 4600 Rickenbacker Causeway
Miami, Florida 33149.
jmcmanus at rsmas.miami.edu
Tel. (305) 361-4609
Fax (305) 361-4600

 -----Original Message-----
From: =09owner-coral-list at coral.aoml.noaa.gov
[mailto:owner-coral-list at coral.aoml.noaa.gov]  On Behalf Of mjrtom999
Sent:=09Sunday, November 12, 2000 6:29 AM
To:=09coral-list at coral.aoml.noaa.gov
Subject:=09a question

Hi all,
There was some mail being bounced around here recently about the corals
being gone in the next 20 years or so..? can someone please get me the
original refernce source for that "fact"?
I would be very much appreciative
thank you much
-tomas oberding

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