Carbon Dioxide, Global Warming and Coral Reefs: Prospects for the Future

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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
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Concerns About Global Warmingand 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

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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

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Coral Bleaching in Guam
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Noted Causes of Coral Bleaching

• 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

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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

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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

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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)

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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

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Corals have successfully adapted for the past 450
million years
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Ocean Acidification Hypothesis

• Higher atmospheric CO2 concentrations will lead
  to
• More CO2 dissolved into surface waters of the
  worlds 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?

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Calcification Observations
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Calcification Observations(1903-1922 vs
1979-1998)
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1C SST rise 0.45 g cm-2 yr-1rise in
calcification
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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

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Photosynthesis increases the pH of marine waters
making them less acidic
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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?

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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
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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

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Similar Results Obtained by Other Researchers for
Emiliania huxleyi
Low-Light Environment
Elevated Temp. CO2
Elevated Temp.
Elevated CO2
Ambient
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Similar Results Obtained by Other Researchers for
Emiliania huxleyi
High-Light Environment
Elevated Temp. CO2
Elevated Temp.
Elevated CO2
Ambient
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Concluding Comments
www.co2science.org
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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

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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