Transcript Carbon Dioxide, Global Warming and Coral Reefs

Carbon Dioxide, Global Warming and
Coral Reefs: Prospects for the Future
Dr. Craig D. Idso, Chairman
Center for the Study of Carbon Dioxide and Global Change
Concerns About Global Warming
and Coral Reefs
• Magnify the intensity, frequency and duration
of environmental stresses
– Leading to more cases of coral disease, bleaching
and death
• Alter ocean water chemistry, ultimately
leading to reduced rates of coral calcification
– Leads to slower-growing and weaker corals, and
possibly death
How Do We Proceed?
• Must first have a correct
understanding of the
scientific basis for the
problems that are
predicted
– We have been reviewing
papers on CO2 and coral
reefs for more than a
decade, recently
releasing a major report
Coral Bleaching in Guam
Noted Causes of Coral Bleaching
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Anomalously high water temperature
Anomalously low water temperature
High levels of solar irradiance
Combined solar radiation-temperature stress
Reduced salinity
Bacterial infections
Increased sedimentation
Exposure to toxicants
The Power of Adaptation
• Responding to the stress of high solar
irradiance
– Corals exhibit a zonation of their symbiont taxa
with depth, with less tolerant species in corals at
greater depths
– Zooxanthellae possess light quenching
mechanisms
– Both produce amino acids that act as natural
“sunscreens”
The Power of Adaptation
• Responding to the thermal stress
– Coral bleaching event in 2002 was 30-100% lower
than a bleaching event in 1998 even though the
thermal stress was more than double that in 1998
– The two corals most susceptible to bleaching in
1998 exhibited the least amount of bleaching in
2002
– Findings are consistent with other literature
examining bleaching events across the globe
The Power of Adaptation
• Responding to the thermal stress
– “on the basis of the present knowledge of genetic
variation in performance traits and species’
capacity for evolutionary response, it can be
concluded that evolutionary change will often
occur concomitantly with changes in climate as
well as other environmental changes”
(Skelly et al., 2007, Conservation Biology 21: 1353-1355)
The Power of Adaptation
• Symbiont Shuffling
– Replace the zooxanthellae expelled during the
stress event with varieties more tolerant of the
stress
• Produce heat shock proteins
• Bacterial Shuffling
– Rearranging bacterial populations in a process
akin to symbiont shuffling
Corals have successfully adapted
for the past 450 million years
Ocean Acidification Hypothesis
• Higher atmospheric CO2 concentrations will
lead to …
– More CO2 dissolved into surface waters of the
world’s oceans, which leads to …
– Lower oceanic pH, which leads to …
– Reduced calcification rates, which leads to …
– Slower, weaker growing corals and perhaps even
coral death
• Is there any real-world evidence to support
such claims?
Calcification Observations
Calcification Observations
(1903-1922 vs 1979-1998)
1°C SST rise = 0.45 g cm-2 yr-1
rise in calcification
Why has Coral Calcification
Increased?
• “observed increases in coral reef calcification
with ocean warming are most likely due to an
enhancement in coral metabolism and/or
increases in photosynthetic rates of their
symbiotic algae”
• Coral calcification is a biologically-driven
process that can overcome physical-chemical
limitations, which in the absence of life would
appear to be insurmountable
Photosynthesis increases the pH of
marine waters making them less acidic
The 20th Century Impact on Corals
• Rising CO2 and rising temperatures …
– have not been anywhere near as catastrophically
disruptive as alarmists suggest they should have
been
– actually appear to have been helpful
• But what about other calcifying marine
organisms? Have they been harmed in any
way?
The 20th Century Impact on Other
Calcifying Marine Life
• Determined particulate
organic and inorganic
carbon produced for a
coccolithophore at 750
ppm CO2
• Also examined historic
growth trends in this
species over the 90
ppm rise in CO2 over
the past two centuries
Emiliania huxleyi
The 20th Century Impact on Emiliania huxleyi
• A doubling of both particulate organic and inorganic carbon
was observed for an approximate doubling of atmospheric CO2
• Field evidence revealed a 40% increase in average coccolith
mass over the past 220 years as temperatures and CO2 rose
Similar Results Obtained by Other
Researchers for Emiliania huxleyi
Elevated Temp. & CO2
Elevated CO2
Elevated Temp.
Ambient
Low-Light Environment
Similar Results Obtained by Other
Researchers for Emiliania huxleyi
Elevated Temp. & CO2
Elevated CO2
Elevated Temp.
Ambient
High-Light Environment
Concluding Comments
www.co2science.org
Concluding Comments
• Neither increases in temperature, nor
increases in atmospheric CO2 concentration,
nor increases in both of them together, have
had any lasting ill effects on the important
processes of calcification and growth in
marine organisms
– Out in the real world of nature, these processes
have actually been enhanced
Carbon Dioxide, Global Warming and
Coral Reefs: Prospects for the Future
Dr. Craig D. Idso, Chairman
Center for the Study of Carbon Dioxide and Global Change