Coral Growth in Response to Increased Atmospheric CO 2 Jim Billingsley Biology 881 University of Nebraska, Kearney

Introduction Overview Coral Structure Seawater Chemistry Affects of CO 2 on Seawater Conclusions

Overview –CO 2 emissions –Physiology of marine organisms.  CO 2  CO 3 2-

Overview Photosynthesis and calcification problems Sealevel rise Faster growing algae Boring organisms and storm damage

Trends in Atmospheric CO 2 Mauna Loa, Hawaii and Law Dome, Antarctica (Etheridge et al, 1998); (Keeling and Whorf, 2001) Vostok, Antarctica Ice Core Atmospheric CO 2 Record (Petit, et al, 1999)

Global Emission of CO 2 (Marland, Boden and Andres 2001)

Coral Structure Polyps Colony Nematocysts

Coral Structure Animal Calcium carbonate skeleton Symbiotic plant

Zooxanthellae Dinoflaggellate Photosynthetic Pigments

Seawater Chemistry H 2 O + CO 2 (aq)  H 2 CO 3  HCO H +

Dissolution of calcium carbonate Temperature, pressure and partial pressure of carbon dioxide CaCO 3 + H CO 2  Ca HCO 3 - Higher pressures and cooler temperatures Corrosive

CO 2 Emissions and Calcification in the Oceans Rising atmospheric CO 2 Carbonate equilibrium Decrease in alkalinity Reduces the CaCO 3 saturation Harder for coral reefs to grow 1880 Present Future – Double CO 2

Calculated changes seawater carbonate chemistry ( assuming S=35, TA=3.5 meq/L)  arag CO 2 aq

Observations at the Hawaii Ocean Times Series Station

Chemical treatments n weeks pCO 2  atm HCO 3 -  mol kg -1 CO 3 2-  mol kg -1 pH sws             0.06

Effect of CO 2 on community calcification

Coral Response (Marubini et al., 2001) 200  atm 700  atm Porites compressa

Effect of a doubling in CO 2 ( ) on calcification, (% decrease) Calcareous macroalgae Amphiroa foliacea-36 Borowitzka, 1981 Porolithon gardineri-16 Agegian, 1985 Corallina pilulifera-44 Gao et al., 1993 Corals Stylophora pistillata -3 Gattuso et al., 1998 Porites porites-16 Marubini & Thake, 1999 Porites compressa-27 Marubini et al., 2001 Acropora sp.-37 Schneider & Erez, 2000 Porites/Montipora-50 Langdon & Atkinson, in prep. Coccolithophorids Emiliania huxleyi -10 Riebesell et al., 2000 Gephyrocapsa oceanica -29 “ “ Natural pop. (N. Pac.) -38 “ “ Emiliania huxleyi -17 Zondervan et al., 2001 Gephyrocapsa oceanica –29 “ “ Community Biosphere Langdon et al., 2000 Monaco mesocosm -21 Leclercq et al., 2000 Bahama Bank -30 Broecker & Takahashi, 1966

Future pH Changes Burn all known stocks of fossil fuels –Atmospheric CO 2 would exceed 1,900 parts per million around the year 2300 pH reduction at the ocean surface –Calcium carbonate skeletons Unabated CO 2 emissions – Changes in ocean pH

Conclusions  CO 2  Calcification for 200 to 280  atm pCO 2  Calcif.  34% for 350 to 700  atm pCO 2  Calcif.  58%

Conclusions Saturation state (  ) controls calcification Consequences of reduced calcification –Space and light –Sealevel rise –Erosion and damage Decomposition of Calcium Carbonate

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