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

Dr. Craig D. Idso, ChairmanCenter for the Study of Carbon Dioxide and Global Change

Concerns About Global WarmingConcerns About Global Warmingand Coral Reefsand Coral Reefs

• Magnify the intensity, frequency and duration Magnify the intensity, frequency and duration of environmental stressesof environmental stresses– Leading to more cases of coral disease, bleaching Leading to more cases of coral disease, bleaching

and deathand death

• Alter ocean water chemistry, ultimately Alter ocean water chemistry, ultimately leading to reduced rates of coral calcificationleading to reduced rates of coral calcification– Leads to slower-growing and weaker corals, and Leads to slower-growing and weaker corals, and

possibly deathpossibly death

How Do We Proceed?How Do We Proceed?

• Must first have a Must first have a correct understanding correct understanding of the scientific basis for of the scientific basis for the problems that are the problems that are predictedpredicted– We have been reviewing We have been reviewing

papers on COpapers on CO22 and coral and coral reefs for more than a reefs for more than a decade, recently decade, recently releasing a major reportreleasing a major report

Coral Bleaching in GuamCoral Bleaching in Guam

Noted Causes of Coral BleachingNoted Causes of Coral Bleaching

• Anomalously Anomalously highhigh water temperature water temperature• Anomalously Anomalously lowlow water temperature water temperature• High levels of solar irradianceHigh levels of solar irradiance• Combined solar radiation-temperature stressCombined solar radiation-temperature stress• Reduced salinityReduced salinity• Bacterial infectionsBacterial infections• Increased sedimentationIncreased sedimentation• Exposure to toxicantsExposure to toxicants

The Power of AdaptationThe Power of Adaptation

• Responding to the stress of high solar Responding to the stress of high solar irradianceirradiance– Corals exhibit a zonation of their symbiont taxa Corals exhibit a zonation of their symbiont taxa

with depth, with less tolerant species in corals at with depth, with less tolerant species in corals at greater depthsgreater depths

– Zooxanthellae possess light quenching Zooxanthellae possess light quenching mechanismsmechanisms

– Both produce amino acids that act as natural Both produce amino acids that act as natural “sunscreens”“sunscreens”

The Power of AdaptationThe Power of Adaptation

• Responding to the thermal stressResponding to the thermal stress– Coral bleaching event in 2002 was 30-100% lower Coral bleaching event in 2002 was 30-100% lower

than a bleaching event in 1998 even though the than a bleaching event in 1998 even though the thermal stress was more than double that in 1998thermal stress was more than double that in 1998

– The two corals most susceptible to bleaching in The two corals most susceptible to bleaching in 1998 exhibited the 1998 exhibited the leastleast amount of bleaching in amount of bleaching in 20022002

– Findings are consistent with other literature Findings are consistent with other literature examining bleaching events across the globeexamining bleaching events across the globe

The Power of AdaptationThe Power of Adaptation

• Responding to the thermal stressResponding to the thermal stress– ““on the basis of the present knowledge of genetic on the basis of the present knowledge of genetic

variation in performance traits and species’ variation in performance traits and species’ capacity for evolutionary response, it can be capacity for evolutionary response, it can be concluded that evolutionary change will often concluded that evolutionary change will often occur concomitantly with changes in climate as occur concomitantly with changes in climate as well as other environmental changes”well as other environmental changes”

(Skelly (Skelly et alet al., 2007, Conservation Biology 21: ., 2007, Conservation Biology 21: 1353-1355)1353-1355)

The Power of AdaptationThe Power of Adaptation

• Symbiont ShufflingSymbiont Shuffling– Replace the zooxanthellae expelled during the Replace the zooxanthellae expelled during the

stress event with varieties more tolerant of the stress event with varieties more tolerant of the stressstress

• Produce heat shock proteinsProduce heat shock proteins• Bacterial ShufflingBacterial Shuffling

– Rearranging bacterial populations in a process Rearranging bacterial populations in a process akin to symbiont shufflingakin to symbiont shuffling

Corals have successfully adapted Corals have successfully adapted for the past 450 million yearsfor the past 450 million years

Ocean Acidification HypothesisOcean Acidification Hypothesis

• Higher atmospheric COHigher atmospheric CO22 concentrations will concentrations will lead to …lead to …– More COMore CO22 dissolved into surface waters of the dissolved into surface waters of the

world’s oceans, which leads to …world’s oceans, which leads to …– Lower oceanic pH, which leads to …Lower oceanic pH, which leads to …– Reduced calcification rates, which leads to …Reduced calcification rates, which leads to …– Slower, weaker growing corals and perhaps even Slower, weaker growing corals and perhaps even

coral deathcoral death• Is there any real-world evidence to support Is there any real-world evidence to support

such claims?such claims?

Calcification ObservationsCalcification Observations

Calcification ObservationsCalcification Observations(1903-1922 vs 1979-1998)(1903-1922 vs 1979-1998)

1°C SST rise = 0.45 g cm1°C SST rise = 0.45 g cm-2-2 yr yr-1-1

rise in calcificationrise in calcification

Why has Coral Calcification Why has Coral Calcification Increased?Increased?

• ““observed increases in coral reef calcification observed increases in coral reef calcification with ocean warming are most likely due to an with ocean warming are most likely due to an enhancement in coral metabolism and/or enhancement in coral metabolism and/or increases in photosynthetic rates of their increases in photosynthetic rates of their symbiotic algae”symbiotic algae”

• Coral calcification is a biologically-driven Coral calcification is a biologically-driven process that can overcome physical-chemical process that can overcome physical-chemical limitations, which in the absence of life would limitations, which in the absence of life would appear to be insurmountableappear to be insurmountable

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

The 20The 20thth Century Impact on Corals Century Impact on Corals

• Rising CORising CO22 and rising temperatures … and rising temperatures …– have not been anywhere near as catastrophically have not been anywhere near as catastrophically

disruptive as alarmists suggest they should have disruptive as alarmists suggest they should have beenbeen

– actually appear to have been actually appear to have been helpfulhelpful

• But what about But what about otherother calcifying marine calcifying marine organisms? Have they been harmed in any organisms? Have they been harmed in any way?way?

The 20The 20thth Century Impact on Other Century Impact on Other Calcifying Marine LifeCalcifying Marine Life

Emiliania huxleyi

• Determined particulate Determined particulate organic and inorganic organic and inorganic carbon produced for a carbon produced for a coccolithophore at 750 coccolithophore at 750 ppm COppm CO22

• Also examined historic Also examined historic growth trends in this growth trends in this species over the 90 species over the 90 ppm rise in COppm rise in CO22 over the over the past two centuriespast two centuries

The 20The 20thth Century Impact on Century Impact on Emiliania huxleyiEmiliania huxleyi

• A doubling of both particulate organic and inorganic carbon A doubling of both particulate organic and inorganic carbon was observed for an approximate doubling of atmospheric COwas observed for an approximate doubling of atmospheric CO22

• Field evidence revealed a 40% increase in average coccolith Field evidence revealed a 40% increase in average coccolith mass over the past 220 years as temperatures and COmass over the past 220 years as temperatures and CO2 2 roserose

Similar Results Obtained by Other Similar Results Obtained by Other Researchers for Researchers for Emiliania huxleyiEmiliania huxleyi

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Concluding CommentsConcluding Comments

www.co2science.orgwww.co2science.org

Concluding CommentsConcluding Comments

• Neither increases in temperature, nor Neither increases in temperature, nor increases in atmospheric COincreases in atmospheric CO22 concentration, concentration, nor increases in both of them together, have nor increases in both of them together, have had any lasting ill effects on the important had any lasting ill effects on the important processes of calcification and growth in processes of calcification and growth in marine organismsmarine organisms– Out in the real world of nature, these processes Out in the real world of nature, these processes

have actually been enhancedhave actually been enhanced

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

Dr. Craig D. Idso, ChairmanCenter for the Study of Carbon Dioxide and Global Change