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 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 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 Must first have a correct understanding of the scientific basis for the problems that are predicted – We have been reviewing papers on CO 2 and coral reefs for more than a decade, recently releasing a major report

Coral Bleaching in Guam

Noted Causes of Coral Bleaching Anomalously high water temperature Anomalously high water temperature Anomalously low water temperature Anomalously low water temperature High levels of solar irradiance High levels of solar irradiance Combined solar radiation-temperature stress Combined solar radiation-temperature stress Reduced salinity Reduced salinity Bacterial infections Bacterial infections Increased sedimentation Increased sedimentation Exposure to toxicants Exposure to toxicants

The Power of Adaptation Responding to the stress of high solar irradiance 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 Responding to the thermal stress – Coral bleaching event in 2002 was % 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 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: ) (Skelly et al., 2007, Conservation Biology 21: )

The Power of Adaptation Symbiont Shuffling Symbiont Shuffling – Replace the zooxanthellae expelled during the stress event with varieties more tolerant of the stress Produce heat shock proteins Produce heat shock proteins Bacterial Shuffling 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 CO 2 concentrations will lead to … Higher atmospheric CO 2 concentrations will lead to … – More CO 2 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? Is there any real-world evidence to support such claims?

Calcification Observations

Calcification Observations ( vs )

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” “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 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 20 th Century Impact on Corals Rising CO 2 and rising temperatures … Rising CO 2 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? But what about other calcifying marine organisms? Have they been harmed in any way?

The 20 th Century Impact on Other Calcifying Marine Life Emiliania huxleyi Determined particulate organic and inorganic carbon produced for a coccolithophore at 750 ppm CO 2 Determined particulate organic and inorganic carbon produced for a coccolithophore at 750 ppm CO 2 Also examined historic growth trends in this species over the 90 ppm rise in CO 2 over the past two centuries Also examined historic growth trends in this species over the 90 ppm rise in CO 2 over the past two centuries

The 20 th Century Impact on Emiliania huxleyi A doubling of both particulate organic and inorganic carbon was observed for an approximate doubling of atmospheric CO 2 A doubling of both particulate organic and inorganic carbon was observed for an approximate doubling of atmospheric CO 2 Field evidence revealed a 40% increase in average coccolith mass over the past 220 years as temperatures and CO 2 rose Field evidence revealed a 40% increase in average coccolith mass over the past 220 years as temperatures and CO 2 rose

Similar Results Obtained by Other Researchers for Emiliania huxleyi Low-Light Environment Ambient Elevated Temp. Elevated CO 2 Elevated Temp. & CO 2

Similar Results Obtained by Other Researchers for Emiliania huxleyi Ambient Elevated Temp. Elevated CO 2 Elevated Temp. & CO 2 High-Light Environment

Concluding Comments

Neither increases in temperature, nor increases in atmospheric CO 2 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 Neither increases in temperature, nor increases in atmospheric CO 2 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