[Coral-List] Question Thermal vs PH shift
James Cervino PhD.
jcervino at whoi.edu
Mon Jan 14 09:03:43 EST 2008
Hi Simon, You are correct! It is depressing, however, I spoke to a few science
writers, polititians and students at the undergrad level and they all think
that we have another 75-100 years to control atmospheric CO2 to levels that
will save the corals and their habitat.
This attitude is what allowed to what happen in Bali happen, which is more time
to monitor the situation thereby not putting anything in clear writing that
give us reef scientists a %cut number, and a serious target date to reduce.
Talk of 65% reduction is all pretty, however, this needs to happen if we want
to see the remaining gene pool of 100+ species of Acroporids remain. My course
coordinator at Columbia recently asked me to include "sustainability" in my
last lecture for this field course we are running and I said sustainability
begins at controlling atmospheric CO2, which is the number one killer. I dont
want my son to look through 1000s of slide images of these reefs and see what
they used to look like, I want him to see them in real time in 10 yrs.
Quoting Simon Donner <simon.donner at gmail.com>:
* It is rather depressing to read scientists arguing over which threat (T vs.
* pH) is worse. I will say that the discussion of poleward movement of corals
* confuses geological and socio/ecological thinking. Even if corals could all
* move poleward, that would not mean establishment, in the near or even the
* future, of coral reef ecosystems as we know them. And even if that could
* happen, the more equatorial human communities that had depended on
* (presumably degraded) coral reefs are still in trouble.
* Coral-List mailing list
* Coral-List at coral.aoml.noaa.gov
Hi Ken long time since NYU,
You make some very valid points in your post. However, what concerns me is the
terminology pertaining to corals establishing themselves poleward in a more
tolerable environment. The key question is, what types of corals will even be
able to take this journey? For the purposes of addressing the students,
policymakers, and journalists reading this healthy discussion, I would like to
point out a very important factor. Lets use the 100+ different species of
Acroporids (the most sensitive to thermal stress). The success of these
organisms reproductive productivity can be determined by factors specific to
global and coastal adaptive pressures, i.e., thermal stress, sedimentation,
nutrient enrichment & pathogens. Because these factors are occurring at such a
rapid rate, these thermally sensitive species will not move/adapt within the
time you are hypothesizing.
Sensitive species (all species, really) need time to adapt! As Steven J. Gould
so eloquently stated in the Return of the Hopeful Monster: The essence of
Darwinism lies in a single phrase: natural selection is the major creative
force of evolutionary change and no one denies that natural selection will play
a negative role in eliminating the unfit. However, selection occurs by building
gradual adaptations in a series of steps (again time), preserving at each
stage, the advantageous part in a random spectrum of genetic variability.
For those who are thinking optimistically, what is the time frame in which
youre thinking that corals will adapt and move northward? Did the surviving
corals of the 1998 Indian Ocean Hot-Spot bleaching pass some of these
heat-tolerant genes north and establish themselves there, thereby escaping the
heat? Is there evidence of this genetic drift? Lets look at the real-time
observations since the 1982-83 major thermal bleaching event. This will be
important to investigate the reality of whats occurring. The thermal hot-spot
events have been growing more severe year after year since 1982-83 and I have
not seen documentation of these keystone species (as we know them) mass
northward migration to escape from the heat. Does anyone have evidence of this
adaptation and drift?
>From our recent clade sub-type experiments I can identify a more heat tolerant
Symbiodinium spp. as shown by (Sotka and Thacker, 2005) and one that resists
Vibrio pathogens during short-term exposure due to unknown defense mechanisms.
However, as shown by Baker et al. & LaJeunesse et al., major reef-building
corals can be found hosting multiple symbiont species at the clade level.
However, radiation or drift of these symbioants northward escaping the heat
thereby taking up residence on the top of some algal lawn has to take time, and
not at the time scale some optimists want to think. The projected increases in
the frequency and severity of thermal bleaching events and coral resilience
depends, on whether phenotypic and genotypic changes in hostsymbiont
associations can match the time factors at which their cellular biochemical
processes can adapt. In conclusion, given what we are seeing in real-time, this
genetic adaptation and migration northward to preserve these 100+ Acroporid spp.
as we know them, is highly un-probable and will die long before the oceans
Dr. James M. Cervino
Pace University & Visiting Scientist
Woods Hole Oceanographic Inst.
Department of Marine Chemistry
Woods Hole MA.
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