Caroline De Bodt, Quentin d’Hoop, Jérôme Harlay and Lei Chou Calcification and transparent exopolymer particles (TEP) production in batch cultures of Emiliania huxleyi exposed to different pCO2 Core theme IV Biogeochemical feedbacks on the oceanic carbon sinks 2nd annual CarboOcean meeting Caroline De Bodt, Quentin d’Hoop, Jérôme Harlay and Lei Chou

Outline of the presentation Introduction Description of the experiment Results of chl a, calcification and TEP for the 3 cultures Calcification in relation to the Ωcalcite Correlation between TEP, particulate organic and inorganic carbon Conclusions

Outline of the presentation Introduction Description of the experiment Results of chl a, calcification and TEP for the 3 cultures Calcification in relation to the Ωcalcite Correlation between TEP, particulate organic and inorganic carbon Conclusions

Outline of the presentation Introduction Description of the experiment Results of chl a, calcification and TEP for the 3 cultures Calcification in relation to the Ωcalcite Correlation between TEP, particulate organic and inorganic carbon Conclusions

Outline of the presentation Introduction Description of the experiment Results of chl a, calcification and TEP for the 3 cultures Calcification in relation to the Ωcalcite Correlation between TEP, particulate organic and inorganic carbon Conclusions

Outline of the presentation Introduction Description of the experiment Results of chl a, calcification and TEP for the 3 cultures Calcification in relation to the Ωcalcite Correlation between TEP, particulate organic and inorganic carbon Conclusions

Outline of the presentation Introduction Description of the experiment Results of chl a, calcification and TEP for the 3 cultures Calcification in relation to the Ωcalcite Correlation between TEP, particulate organic and inorganic carbon Conclusions

The coccolithophore E.huxleyi - Photosynthesis: sink for CO2 106CO2 ↓ + 16NO3- + H2PO4- + 17H+ + 122H2O ↔ (CH2O)106(NH3)16H3PO4 + 138O2 - Calcification: source of CO2 Ca2+ + 2HCO3- ↔ CaCO3 + CO2↑ + H2O - Extracellular release (Transparent exopolymer particles, TEP) http://www.soes.soton.ac.uk/staff/tt/ (Engel et al., 2004a)

Description of the Experiment Cultures were grown in filtered seawater enriched with NO3 and PO4 Irradiance : 150 µmol m-2 s-1 Temperature : 13°C Light/Dark cycle : 14h/10h Culture 1 Culture 2 Culture 3 Vol. batch reactor (L) 2 8 Initial pCO2 (µatm) 490 630 930

Measured parameters pH Total alkalinity pCO2, Ωcalcite Nutrient concentrations (NO3 and PO4) Chlorophyll a TEP POC pCO2, Ωcalcite

Evolution of the pCO2

Results 490 µatm 630 µatm 930 µatm

Results 490 µatm 630 µatm 930 µatm

Results 490 µatm 630 µatm 930 µatm

Results 490 µatm 630 µatm 930 µatm

Results 490 µatm 630 µatm 930 µatm

Link between calcification and Ωcalcite Ca2+ (aq) + CO32- (aq) ↔ CaCO3 (s) - Saturation state with respect to calcite: > 1 precipitation < 1 dissolution

Link between calcification and Ωcalcite Ca2+ (aq) + CO32- (aq) ↔ CaCO3 (s) - Saturation state with respect to calcite: > 1 precipitation < 1 dissolution

Link between calcification and Ωcalcite Culture 1 Culture 2 Culture 3 Key value : Ωcalcite = 3

Correlation between TEP and POC During the exponential growth phase, POC concentration increases linearly with chlorophyll a. After nutrient exhaustion, TEP continue to be produced and contribute to POC increase by 61%.

Correlation between TEP and CaCO3 TEP production is strongly correlated with CaCO3 concentrations. → Calcification may be considered as a source of TEP.

Conclusions E. huxleyi is sensitive to pCO2

Conclusions E. huxleyi is sensitive to pCO2 TEP concentrations continue to increase after the decline in E. huxleyi growth

Conclusions E. huxleyi is sensitive to pCO2 TEP concentrations continue to increase after the decline in E. huxleyi growth Very good correlation between TEP and calcite production

Conclusions E. huxleyi is sensitive to pCO2 TEP concentrations continue to increase after the decline in E. huxleyi growth Very good correlation between TEP and calcite production key value of 3 for the Ωcalcite

Thank you for your attention This study was partially supported by the PEACE project, funded the Belgian Science Policy Office.