Seawater carbonate chemistry and processes during experiments with coccolithophores (Emiliania huxleyi and Gephyrocapsa oceanica), 2000

• Main Authors: Riebesell, Ulf, Zondervan, Ingrid, Rost, Björn, Tortell, Philippe Daniel, Zeebe, Richard E, Morel, Francois M M
• Format: Dataset
• Language: English
• Published: PANGAEA 2000
• Subjects: Alkalinity; potentiometric; total; Aphrodite aculeata; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (<20 L); Calcification/Dissolution; Calculated; see reference(s); Calculated after Freeman & Hayes (1992); Calculated using seacarb after Nisumaa et al. (2010); Carbon; particulate; Carbon/Nitrogen ratio; Carbonate ion; Carbon dioxide; dissolved; Chromista; Coccolithophoridae; Counting; CTD; Sea-Bird SBE 911plus; Entire community; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; EXP; Experiment; Growth/Morphology; Haptophyta; Isotopic fractionation; during photosynthis; Laboratory experiment; Laboratory strains; Light; Mass spectrometer Finnigan Delta-S; Measured; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Open ocean; Other studied parameter or process; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Particulate inorganic carbon production per cell; Pacific; Hayes; Aphrodite; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.728092; https://doi.org/10.1594/PANGAEA.728092

The formation of calcareous skeletons by marine planktonic organisms and their subsequent sinking to depth generates a continuous rain of calcium carbonate to the deep ocean and underlying sediments1. This is important in regulating marine carbon cycling and ocean-atmosphere CO2 exchange2. The present rise in atmospheric CO2 levels3 causes significant changes in surface ocean pH and carbonate chemistry4. Such changes have been shown to slow down calcification in corals and coralline macroalgae5,6, but the majority of marine calcification occurs in planktonic organisms. Here we report reduced calcite production at increased CO2 concentrations in monospecific cultures of two dominant marine calcifying phytoplankton species, the coccolithophorids Emiliania huxleyi and Gephyrocapsa oceanica . This was accompanied by an increased proportion of malformed coccoliths and incomplete coccospheres. Diminished calcification led to a reduction in the ratio of calcite precipitation to organic matter production. Similar results were obtained in incubations of natural plankton assemblages from the north Pacific ocean when exposed to experimentally elevated CO2 levels. We suggest that the progressive increase in atmospheric CO2 concentrations may therefore slow down the production of calcium carbonate in the surface ocean. As the process of calcification releases CO2 to the atmosphere, the response observed here could potentially act as a negative feedback on atmospheric CO2 levels.