Potential Impacts of Ocean Acidification on Coral Reef and Calcifying Organisms ー ICRI, April, 24, Tokyo Yoshimi Suzuki ・ Beatriz Casareto Shizuoka University,JCRS

Ocean acidification The ongoing decrease in the pH of the oceans has been caused by their uptake of anthropogenic CO 2 from the atmosphere Over the past 200 years, the pH of surface sea water has decreased by 0.1 units (equivalent to a 30% increase in the concentrations of H + ions) Increase pCO 2, reduces the carbonate ion concentration and thus reduce calcium carbonate saturation of the seawater These processes are affecting the life and structure of marine ecosystems and the regulation of C cycling.

Recent research reports 1)UNEP WCMC on cold water coral reefs mentions atmospheric CO2 as a potential impacts (2004) 2)A brief overview report (Hauganhj, 2004) was presented to OSPAR 3)IOC/SCOR Symposium (May, 2004) 4)Royal Society Report (June, 2005) 5)US Workshop on impacts on coral reefs and other marine calcifiers (April, 2005) 6 ） Ｆｉｒｓｔ ＩＧＢＰ－ＳＣＯＲ workshop Ocean acidification-modern observation and past experiences (Spt. 2006) 7) Second workshop for synthesis (May, 2007, France)

1.Ocean acidification is a predictable consequence of increased atmospheric CO2. 2. Ocean acidification depends on the chemistry of CO2. 3.Ocean chemistry is changing at least 100 times more rapidly than it has changed in the 100, 000 yrs. preceding our industrial era. 4. Ocean acidification could be expected to have major negative Impacts on corals and other marine organisms that build calcium carbonate shells and skeletons. 5. Research is needed to better understand the vulnerabilities, resilience, and adaptability of marine organisms and ecosystems.

CO2 effects on marine organisms and ecosystems: physiological background and affected processes Question: complete lack of field observations, scenarios of CO2 effects on marine ecosystems developed based on laboratory, mesocosms and model. We have a large gaps in knowledge, there is considerable demand for research In this area to reach exact predictability. Dissolution and changes of photosynthesis under the lowered pH –values are due to the ability to adapt to Increasing CO2 concentrations on time scales Key processes are foodweb and adaptation

Calcification vs dissolution

pH Ambient pCO2 400ppmHigh pCO2 1000ppm After 8days, pH was back to more than 8 under the incubation experiments (organisms :cocolith)

Chl-a Chl-a and biomaas of cocolith Increased under the high CO2 Concentrations (1000ppmCO2) Without grayzer With grayzer Cell of Cocolith Biomass of Cocolith We expect that abundance of zooxanthellae increases With increase of CO2 concentration. Is it right ?

mmol C m -2 d GPP 呼吸 溶解 Coral CO 2 Orgaqnic GPP 呼吸 CO Orghanic Carbon balance at 450ppmCO2Carbon balance at 650ppm CO2 溶解 GC CaCO CaCO 3 Gross primary production increased to 40% Ｇｒｏｓｓ ｃａｌｃｉｆｉｃａｔｉｏｎ increased ｔｏ 40% More dissolution

cyanobacteria Zooxanthelloae Bacteria Virus Bentos phytoplank ton Fish /Shell Large zoopllankton Protozoa Microzooplanton Coral 滲出物・排泄物・屍 骸など 溶存態有機物質 Organic matter Ecosystem and organic matter cycling in Coral Reef Cyanobacteria (Prochlorochoccus) Nutrients Nitrogen fixation CO 2 increase

Forcing factors As pCO2 Is increasing, other environmental variables will also changes. increased temperature, changes in availability of nutrients (due to changes in redox conditions, ocean mixing, patterns of precipitation, dust inputs, and increased stratification). 1.Ecological aspects Effects on community structure and composition Effects on genetic diversity, species diversity, and the diversity of functional groups Will they be able to adapt to the evolve quickly enough to change now occuring ? Can adaptation occur under a continually and rapidly changing environment verus one that eventually stabilizes?

2. Key biogeochemical processes Primary production : Will increasing pCO2 in the surface ocean fertilize phytoplankton ? For high tropic levels ? C/N/P ratio ? Remineralization ? Nitrogen fixation ? DOM transfromations (aggregation, solubilization, biological turnover ?) Calcification ? Dissolution? Role of bacteria and grazer ?

3. Approches on reseaqrch Laboratory experiments Mesocosm experiments Short-term perturbation experiments ? Model developments 4. Action plan of ICRI Advanced monitoring system ( pH, Chl-a, bacteria, nutrients) Increase of primary producers (zooxanthellae, cyanobacteria, algae, gravel etc.) Fertilization of nutrients (N:P:Si) Avoiding human pollution

Subjects in discussion 1.How do we get an evidence of impact to coral reef ? Understanding of impacts on coral, sea grass, zooxanthellae, fish, benthos, other animals-- 2. What monitoring is required ? Physical, chemical, biological, geological,-- 3. Do we need a new method for conservation of coral and coral reef ? 4 How to educate an importance of ocean acidification ?