[Coral-List] Question Thermal vs pH shift
James Cervino PhD.
jcervino at whoi.edu
Sun Jan 13 00:22:10 EST 2008
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.
Quoting Ken Caldeira <kcaldeira at stanford.edu>:
* In the absence of dramatic reductions in CO2 emissions, the range of
* aragonite saturation in the entire surface ocean will not intersect the
* range of aragonite saturation in which coral reefs grew in the
* pre-industrial ocean.
* In contrast, areas of ocean will still be found with temperatures in the
* range in which coral grew pre-industrially (they will just be closer to the
* poles). If temperature were the only issue, we could imagine reefs
* establishing themselves poleward of their current range.
* So, while temperature is a threat (perhaps a lethal threat), if temperature
* were the only threat their would be some hope for adaptation and migration.
* While corals survive and recover in a fish tank at low pH, their growth
* rates are slowed and it is likely that they will be less fit to compete
* ecologically, so we may not see acute lethality but rather a weakening that
* leads to a loss of ecological competitiveness -- for example, less success
* at repopulating an area after disturbance.
* My sense is that temperature is more of a threat to reefs today but if CO2
* emissions continue eventually aragonite saturation will become more
* important than temperature.
* On Jan 11, 2008 1:29 PM, John McManus <jmcmanus at rsmas.miami.edu> wrote:
* > The recovery from pH changes is in line with the paper of Fine and
* > Tchernov
* > "Scleractinian Coral Species Survive
* > and Recover from Decalcification" SCIENCE VOL 315 30 MARCH 2007, in which
* > species of Oculina and Madracis corals lost skeletons at high pH and
* > regained them upon returning to low pH. They did not test major reef
* > builders, but the results are astounding anyway.
* > As for thermal stress, some glimmer of hope lies in the fact that
* > temperatures that kill a species in one locality may be tolerated by the
* > same species elsewhere, whether via coral physiological adaptation or
* > genetics, or via differences in Symbiodinium. There is also species
* > substitution (susceptible for tolerant) and natural temperature refugia
* > for
* > some species (mesophotic reefs, upwelling areas, etc.). Not to minimize
* > the
* > immense problems ahead, but the patient does still have a pulse...
* > Cheers! (at least for the optimists)
* > John
* > John W. McManus, PhD
* > Director, National Center for Coral Reef Research (NCORE)
* > Professor, Marine Biology and Fisheries
* > Coral Reef Ecology and Management Lab (CREM Lab)
* > Rosenstiel School of Marine and Atmospheric Science (RSMAS)
* > University of Miami, 4700 Rickenbacker Causeway, Miami, 33149
* > jmcmanus at rsmas.miami.edu http://ncore.rsmas.miami.edu
* > Phone: 305-421-4814 Fax: 305-421-4910
* > "If I cannot build it, I do not understand it."
* > --Richard Feynman, Nobel Laureate
* > -----Original Message-----
* > From: coral-list-bounces at coral.aoml.noaa.gov
* > [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of James Cervino
* > PhD.
* > Sent: Friday, January 11, 2008 9:06 AM
* > To: coral-list at coral.aoml.noaa.gov
* > Cc: arietta.Venizelos at noaa.gov; konrad Hughen; tyler.volk at nyu.edu; Michael
* > Robert Rampino; kcaldeira at stanford.edu
* > Subject: [Coral-List] Question Thermal vs pH shift
* > Dear Coral Scientists-
* > A while ago at the MBL when we compared pH shifts vs thermal stress to
* > investigate what will induce expulsion (bleaching) first I noticed the
* > following: During every trial exposing corals to thermal stress, heat
* > killed
* > the corals far faster than pH changes in vitro. I am not saying that acid
* > like
* > conditions are not seriously inducing cell impairments in corals or
* > carbonate
* > substrates as both arriving at the same conclusion, death for corals.
* > With that said, all the data (real time, not models) points to the corals
* > dying
* > of heat stroke far before acid like conditions take effect. Are we not
* > witnessing the death of reefs in real-time due to thermal stress?
* > Just a question Cheers, James
* > *************************************
* > Dr. James M. Cervino
* > Pace University & Visiting Scientist
* > Woods Hole Oceanographic Inst.
* > Department of Marine Chemistry
* > Woods Hole MA.
* > Cell: 917-620*5287
* > ************************************
* > ----------------------------------------------------------------
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* Ken Caldeira
* Department of Global Ecology
* Carnegie Institution
* 260 Panama Street
* Stanford, CA 94305 USA
* +1 650 704 7212; fax: +1 650 462 5968
* kcaldeira at stanford.edu
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