Seawater carbonate chemistry and processes during experiments with Emiliania huxleyi (PML B92/11), 2000

• Main Authors: Riebesell, Ulf, Revill, Andrew T, Holdsworth, Daniel G, Volkman, J K
• Format: Dataset
• Language: English
• Published: PANGAEA 2000
• Subjects: Alkalinity; Gran titration (Gran; 1950); total; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated; see reference(s); Calculated after Freeman & Hayes (1992); Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbon per cell; Chromista; Coulometric titration; CTD; Sea-Bird SBE 911plus; Emiliania huxleyi; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; EXP; Experiment; Experimental treatment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Haptophyta; Isotopic fractionation; during photosynthis; Laboratory experiment; Laboratory strains; Mass spectrometer ANCA-SL 20-20 Europa Scientific; Mass spectrometer Finnigan Delta-S; Nitrogen/Carbon ratio; Nitrogen per cell; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Other studied parameter or process; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.727288; https://doi.org/10.1594/PANGAEA.727288

We have measured the stable carbon isotopic composition of bulk organic matter (POC), alkenones, sterols, fatty acids, and phytol in the coccolithophorid Emiliania huxleyi grown in dilute batch cultures over a wide range of CO2 concentrations (1.1-53.5 micromol L-1). The carbon isotope fractionation of POC (POC) varied by ca. 7 per mil and was positively correlated with aqueous CO2 concentration [CO2aq]. While this result confirms general trends observed for the same alga grown in nitrogen-limited chemostat cultures, considerable differences were obtained in absolute values of POC and in the slope of the relationship of POC with growth rate and [CO2aq]. Also, a significantly greater offset was obtained between the delta13C of alkenones and bulk organic matter in this study compared with previous work (5.4, cf. 3.8 per mil). This suggests that the magnitude of the isotope offset may depend on growth conditions. Relative to POC, individual fatty acids were depleted in 13C by 2.3 per mil to 4.1 per mil, phytol was depleted in 13C by 1.9 per mil, and the major sterol 24-methylcholesta-5,22E-dien-3beta-ol was depleted in 13C by 8.5 per mil. This large spread of delta13C values for different lipid classes in the same alga indicates the need for caution in organic geochemical studies when assigning different sources to lipids that might have delta13C values differing by just a few per mil. Increases in [CO2aq] led to dramatic increases in the alkenone contents per cell and as a proportion of organic carbon, but there was no systematic effect on values of U37k- used for reconstructions of paleo sea surface temperature.