Seawater carbonate chemistry and processes during experiments with Emiliania huxleyi (PML B93/11A)

• Main Authors: Riebesell, Ulf, Zondervan, Ingrid, Rost, Björn, Tortell, Philippe Daniel, Zeebe, Richard E, Morel, Francois M M
• Format: Dataset
• Language: English
• Published: PANGAEA 2002
• Subjects: Alkalinity; Gran titration (Gran; 1950); total; Aragonite saturation state; Bicarbonate ion; Bottles or small containers/Aquaria (<20 L); Calcification/Dissolution; Calcite saturation state; Calculated; see reference(s); Calculated after Freeman & Hayes (1992); Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; particulate; per cell; production per cell; organic; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbon organic/inorganic ratio; Chromista; Colorimetry; Entire community; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; EXP; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.726883; https://doi.org/10.1594/PANGAEA.726883

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 sediments. This is important in regulating marine carbon cycling and ocean-atmosphere CO2 exchange. The present rise in atmospheric CO2 levels causes significant changes in surface ocean pH and carbonate chemistry. Such changes have been shown to slow down calcification in corals and coralline macroalgae, 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.