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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 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 • • • • • • • • 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