[Coral-List] Corals upgrade algae to 'beat the heat': how 'adaptation' is an ally, not an enemy, of effective policy action
abaker at rsmas.miami.edu
Tue May 26 14:21:41 EDT 2009
"Swapping out" tends to imply "exogenous acquisition" (or "switching", see
Baker 2003). Although this has been shown fairly conclusively in gorgonians
(Lewis and Coffroth 2004), this has not yet been demonstrated in
scleractinians. Of course, this does not mean that it does not occur.
However, in reality, the distinction between "switching" and "shuffling" is
not so straightforward: many corals seem to host a variety of symbionts in
the background (as an increasing number of qPCR studies are starting to
show), and it is my view that this phenomenon is very common (Baker and
Romanski 2007). Many of these symbionts are just "passing through", and
their functional importance to the system (if any) is not clear, even though
they may remain present in the community for some time. We dont, for
example, know what their role might be in maintaining coral health under
unusual circumstances (see below), or in perhaps interacting with other
microbial components of the coral holobiont.
I think it's probably quite likely that most (if not all) symbiont community
responses to bleaching are dominated by symbiont "shuffling" mechanisms
(i.e. shifts in existing symbionts), see Jones et al. (2008). However,
because ongoing "switching" is going on in the background prior to a
bleaching event, ascribing importance to either "switching" or "shuffling"
misses the point that its a mixture of both, acting on different
timescales, that really explains what is going on.
We need more studies of bleaching using high resolution techniques (qPCR) to
tease all this out. This will also help us understand "specificity", which
is not an all-or-nothing phenomenon, but rather a gradient, in which
different coral species show different degrees of selectivity. It is my
contention that some coral colonies of very "specific" coral species can
still have unusual symbionts in the background, but the low density of these
symbionts makes it very difficult for these symbionts ever to make it to
dominance, except under very unusual conditions.
Of course, it just so happens that we are entering a period of very unusual
conditions, so that makes it all the more interesting. There will of course
be tradeoffs (Little et al. 2004), but that doesnt mean to say that we
should dismiss these phenomena as unlikely to be important to coral reef
futures. We simply dont know.
And of course, dont forget the importance of the coral host in all this, as
the recent review by Baird et al. (2008) emphasizes.
What's important is that the variety of responses that coral-algal symbioses
exhibit under warmer and more acidic conditions all contribute to a more
informed understanding of reef response to climate change.
This suite of responses is important. The continued adage that "reefs can't
adapt" quickly enough to climate stressors suggests that committed warming
(the warming we can expect from fossil fuels we have already burnt) will
result in widespread coral demise, whether we get emissions under control in
the future or not.
Even fairly dramatic reductions in emissions may still result in the
widespread disappearance of reefs, if you assume reefs have absolutely no
effective way of responding (Simon Donner gave a very effective presentation
on this at 11ICRS). This severely limits policy makers' enthusiasm for the
kinds of actions we would like to see happen.
I believe we should welcome the findings of Oliver and Palumbi as valuable
ingredients in a scientific argument for effective emissions reduction.
Whether you believe their press release stretches things too far, or not,
the important thing is that these kinds of findings show that we may still
have time to act. By embracing these findings as part of our arsenal of
arguments for action, we not only increase the probability of real action
being taken, but also provide a more unified scientific front on the most
important issue: that climate change is an extreme threat, that dramatic
losses have already occurred, and that we need to do something quickly if we
hope to stem or reverse these declines.
On these points we all agree, and that's what really counts.
Baird AH, Bhagooli R, Ralph PJ, Takahashi S (2008) TREE 24: 16-20
Baker AC (2003) Annu Rev Ecol Evol Syst (2003) 34:66189
Baker AC, Romanski AM (2007) MEPS 335: 237242
Donner S (2008) 11th Int Coral Reef Symp Abstracts: 228
Jones AM, Berkelmans R, van Oppen MJH, Mieog JC, Sinclair W (2008) Proc R
Soc B 275: 13591365
Lewis CL, Coffroth MA (2004) Nature 304: 1490-1492
Little AF, van Oppen MJH, Willis BL (2004) Nature 304: 1492-1494
Andrew C. Baker, Ph.D.
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Cswy.
Miami, FL 33149, USA
Office: +1 (305) 421-4642
Lab: +1 (305) 421-4226
Cell: +1 (305) 989-5488
Fax: +1 (305) 421-4600
Email: abaker at rsmas.miami.edu
Associate Conservation Scientist
Wildlife Conservation Society
For more information on coral reef research at the University of Miami,
The National Center for Coral Reef Research: ncore.rsmas.miami.edu
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Thomas Moore
Sent: Sunday, May 24, 2009 10:28 PM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] Corals upgrade algae to 'beat the heat'
i've just read the following article in the New Scientist magazine,
about how corals can 'upgrade their symbiotic algae so that they can
survive the bleaching that occurs in waters warming under climate
do you agree that this means that the corals are 'able to adapt to
their local conditions', as well as adapt to projected climate change?
looks like professor ove hoegh-guldberg doesn't agree:
'To somehow imply that coral reefs are not facing problems from
climate change because Oliver and Palumbi found a few tough coral
genotypes in a rock pool, verges on the incredible.'
I already posted this to ove hoegh-guldberg's site, but: how is
'swapped out' defined? i thought that 'exogenous acquisition' of
entirely 'new' symbionts was still to be proven? if so, this means
that the corals that don't contain 'heat sensitive' algae are
selectively weeded out under warming seas? what proportion of corals
contain 'heat sensitive' algae?
><((((º> ----- ><((((º> ------ ><((((º> ------ ><((((º>
thomasmooreis at gmail.com
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