Seawater carbonate chemistry and silica during an experiment with a marine diatom Thalassiosira weissflogii, 2004

• Main Authors: Milligan, Allen J, Varela, Diana E, Brzezinski, Mark A, Morel, Francois M M
• Format: Dataset
• Language: English
• Published: PANGAEA 2004
• Subjects: Alkalinity; total; Aragonite saturation state; Bicarbonate ion; Biogenic silicate quota in diatom; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; Colorimetry; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Event label; EXP; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Laboratory experiment; Laboratory strains; Measured; Milligan_etal_04/F2A; Milligan_etal_04/F2B; Milligan_etal_04/F5A; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Other metabolic rates; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phytoplankton; Radiation; photosynthetically active; Salinity; Silicate efflux in diatom; Silicate quota in diatom; Single species; Temperature; water; Thalassiosira weissflogii; Time in minutes; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.721775; https://doi.org/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.