François M. M. Morel Slides by Ja-Myung Kim

Years before µatm 400 µatm Vostok paleo Petit et al. 1999, Keeling et al. Mauna Loa from ice core & modern data Changes in atm. CO 2 concentration pCO 2 (µatm) 400 µatm

Seawater pCO 2 time-series monitoring stn.ESTOC ( ) BATS ( ) ALOHA ( )

Decadal changes at time-series stations ESTOC ( ) BATS ( ) ALOHA ( ) Year pCO 2 (µatm) ALOHA ( ) ESTOC ( ) Bates NR, Byrne RH, Dore JE, Feely RA, Gonzalez-Davila M, Karl DM, Lee K, Kleypas JA, Orr J (IPCC ARS) Year pCO 2 (µatm) BATS ( )

Atlantic Pressure (db) 60°50°40°30°20°10°0°10°50° 60° N40°30°20° IndianPacific Pressure (db) 60°50°40°30°20°10°0°10°50°40°30°20° 60°50°40°30°20°10°0°10°20° Latitude Pressure (db) Latitude Vertical distributions of CO 2 in the ocean Anthropogenic CO 2 conc. (μmol kg -1 ) “Half of the CO 2 stored in the oceans is found in the upper 10% of the ocean” Sabine et al. 2004

Anthropogenic carbon emissions are increasing atmospheric CO 2 Ocean is a CO 2 sink Why and How does that affect ocean chemistry ? Ocean acidification

CO 2 (aq) HCO 3 - CO H 2 O+HCO 3 - H+H+ CO 2 (aq) CO 2 (g) Effect of CO 2 on carbonate system H+H+ + CO 2 increases CO 3 2- decreases H+H+ increases (pH decreases)

ESTOC ( ) BATS ( ) ALOHA ( ) Decadal changes of pH & CO 3 2- at time-series monitoring stn. pH decrease: yr -1 CO 3 2- decrease : µmol kg -1 yr -1

CO 3 2- pH CO 2 CO 3 2- What biological consequences ? Photosynthesis Calcification Other physiological effects

What biological consequences ? Photosynthesis Calcification Other Physiological effects CO 3 2- pH

Experimental approaches Molecular mechanisms Lab cultures Coastal in-situ perturbation Open ocean monitoring Bottles Big bags Natural env.

Open ocean monitoring

Univ. of Bergen Univ. of Washington EPOCA POSTECH Mesocosm

Open ocean mesocosm, Baltic sea U. Riebesell (GEOMAR) In situ ecosystem-based CO 2 perturbation experiment MESOCOSM

Laboratory cultures Low CO 2 High CO 2 Mechanismstudy

What biological consequences ? Photosynthesis Calcification Other Physiological effects CO 3 2- pH

Photosynthesis CH 2 O Organic matter Light reaction Dark reaction e-e-e-e- photons H2OH2OH2OH2O O2O2O2O2 CO 2

Sediments Atmosphere Org C Phytoplankton Surface Ocean CO Depth (m) CO 2 (µM) Biological pump

Photosynthesis Light reaction Dark reaction e- e- e- e- H2OH2OH2OH2O O2O2O2O2 CO 2 CH 2 O organic matter RubisCO Poor affinity for CO 2 K m ≈ 50 µM >> [CO 2 ] seawater

Carbon concentrating mechanism Chloroplast CO 2 80 µM HCO 3 - CO 2 10 µM HCO 3 - CA CH 2 O CA RubisCO 2 mM

CA Skeletonema costatum CA activity U (mg Chl a) ppm Enzyme Rost et al Response of CCM to increasing CO 2 Growth rates Labculture ppm Growth rate (d -1 ) Skeletonema costatum Rost et al Growth rates ppm Growth rate (d -1 ) Skeletonema costatum 40% In-situ Kim et al Growth rates ppm Growth rate (d -1 ) Natural assemblage Ocean Tortell et al Growth rates Low CO 2 High CO 2 Growth rate (d -1 ) ? Future growth rate

What biological consequences ? Photosynthesis Calcification Other Physiological effects CO 3 2- pH

Calcium carbonate (CaCO 3 ) production & dissolution Main overall reaction: +Ca 2+ CO 3 2- CaCO 3 (s) [CO 3 2- ] > [CO 3 2- ] sat [CO 3 2- ] < [CO 3 2- ] sat Calcite Aragonite

Future projection for saturation state Turley et al [CO 3 2- ] = [CO 3 2- ] sat [CO 3 2- ] / [CO 3 2- ] sat Aragonite [CO 3 2- ] / [CO 3 2- ] sat Calcite

Tropical corals Coraline algae Molluscs Pteropods Coccolithophores Responses of marine calcifiers to increasing CO 2

Mussels & Oysters Gazeau et al Mussels (Mytilus edulis) Oysters (Crassostrea gigas)

Coccolithophores Low CO 3 2- Ambient CO 3 2- High CO 3 2- Coccolith size (µm) Coccolith Engel et al. 2005

Adapted from Doney et al Major groups Tropical corals Coraline red algae Molluscs Pteropods Coccolithophores Responses at increasing CO 2 Different responses of marine calcifiers to increasing CO 2

Poor understanding of the mechanisms responsible for the sensitivity Seawater pH Calcifying pH Seawater Skeleton inside H+H+H+H+ Ca 2+ CaCO 3 CO HCO H + + H + CO 3 2- Seawater Venn et al Stylophora pistillata (reef coral)

What biological consequences ? Photosynthesis Other Physiological effects pH Calcification CO 3 2-

l all pH homeostasis External enzymes Metalavailability Physiologicalprocesses pH

l allPhysiologicalprocesses pH Metal availability Fe(OH) 3 + H + Fe pH homeostasis External enzymes

Photosynthesis Light reaction Dark reaction e-e-e-e- H2OH2OH2OH2O O2O2O2O2 CO 2 Fe Organic matter

Effect of pH on Fe chemistry CaFe + 2H + → + Fe(OH) H + → Ca-EDTAFe-EDTA + 2H + + Y → Bound Fe Free Fe + 2H + + Y → Bound Fe

Shi et al Thalassiosira weissflogii kton The rate of Fe uptake by phytoplankton + 2H + + Y → Bound Fe Free Fe + 2H + + Y → Bound Fe Total Fe (nM) µmol Fe mol C -1 day -1 pH 7.7 pH Free Fe (pM) :1 pH 8.6 Fe uptake rate

pH effect depends on mature of chelator Shi et al. 2010

Weak effect of pH on Fe uptake in field Shi et al. 2010

Complications of OA research Time scales Adaptation Ocean warming Temperature Mixing CO 3 2- pH

Phytoplankton Succession Phytoplankton Succession Photochemistry C-fixation Transporter Enzyme Expression Enzyme Expression Cell Growth Competition Acclimation Adaptation Genetic mutation Lab. cultures Field monitoring Predictions Time scales Log 10 Days geological epoches nano seconds years centuries Timescales secondsdays

Today Year to 6°C Mixing Nutrient input Irradiance Stratification Surface temperature ++++/- Ocean warming: Temperature & Mixing Temperature

Morel Group Ja-Myung Kim

Biologically complicated… Chemically simple,