Seawater carbonate chemistry and silica during an experiment with a marine diatom Thalassiosira weissflogii, 2004, supplement to: Milligan, Allen J; Varela, Diana E; Brzezinski, Mark A; Morel, Francois M M (2004): Dynamics of silicon metabolism and silicon isotopic discrimination in a marine diatom as a function of pCO2. Limnology and Oceanography, 49(2), 322-329

• Main Authors: Milligan, Allen J, Varela, Diana E, Brzezinski, Mark A, Morel, Francois M M
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2004
• Subjects: Bottles or small containers/Aquaria <20 L; Chromista; Laboratory experiment; Laboratory strains; Not applicable; Ochrophyta; Other metabolic rates; Pelagos; Phytoplankton; Single species; Thalassiosira weissflogii; Event label; Time in minutes; Temperature, water; Salinity; Radiation, photosynthetically active; Carbonate system computation flag; pH; Alkalinity, total; Carbon, inorganic, dissolved; Carbon dioxide; Carbonate ion; Bicarbonate ion; Partial pressure of carbon dioxide water at sea surface temperature wet air; Fugacity of carbon dioxide water at sea surface temperature wet air; Aragonite saturation state; Calcite saturation state; Silicate quota in diatom; Biogenic silicate quota in diatom; Silicate efflux in diatom; Experiment; Measured; Calculated using seacarb after Nisumaa et al. 2010; Calculated using CO2SYS; Colorimetry; European network of excellence for Ocean Ecosystems Analysis EUR-OCEANS; European Project on Ocean Acidification EPOCA; Ocean Acidification International Coordination Centre OA-ICC; Varela; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.721775; https://doi.pangaea.de/10.1594/PANGAEA.721775

Opal accumulation rates in sediments have been used as a proxy for carbon flux, but there is poor understanding of the factors that regulate the Si quota of diatoms. Natural variation in silicon isotopes (delta.lc.gif - 54 Bytes30Si) in diatom frustules recovered from sediment cores are an alternative to opal mass for reconstructing diatom Si use and potential C export over geological timescales. Understanding the physiological factors that may influence the Si quota and the delta.lc.gif - 54 Bytes30Si isotopic signal is vital for interpreting biogenic silica as a paleoproxy. We investigated the influence of pCO2 on the Si quota, fluxes across the cell membrane, and frustule dissolution in the marine diatom Thalassiosira weissflogii and determined the effect that pCO2 has on the isotopic fractionation of Si. We found that our Si flux estimates mass balance and, for the first time, describe the Si budget of a diatom. The Si quota rose in cells grown with low pCO2 (100 ppm) compared with controls (370 ppm), and the increased quota was the result of greater retention of Si (i.e., lower losses of Si through efflux and dissolution). The ratio of efflux : influx decreased twofold as pCO2 decreased from 750 to 100 ppm. The efflux of silicon is shown to significantly bias measurements of silica dissolution rates determined by isotope dilution, but no effect on the Si isotopic enrichment factor (epsilon.lc.gif - 51 Bytes) was observed. The latter effect suggests that silicon isotopic discrimination in diatoms is set by the Si transport step rather than by the polymerization step. This observation supports the use of the v signal of biogenic silica as an indicator of the percentage utilization of silicic acid. : In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne and Gattuso, 2011) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI).