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Milligan, Allen J; Varela, Diana E; Brzezinski, Mark A; Morel, Francois M M (2004): Seawater carbonate chemistry and silica during an experiment with a marine diatom Thalassiosira weissflogii, 2004. PANGAEA, https://doi.org/10.1594/PANGAEA.721775, Supplement to: Milligan, AJ et al. (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, https://doi.org/10.4319/lo.2004.49.2.0322

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Abstract:
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.
Keyword(s):
Bottles or small containers/Aquaria (<20 L); Chromista; Laboratory experiment; Laboratory strains; Not applicable; Ochrophyta; Other metabolic rates; Pelagos; Phytoplankton; Single species; Thalassiosira weissflogii
Funding:
Seventh Framework Programme (FP7), grant/award no. 211384: European Project on Ocean Acidification
Sixth Framework Programme (FP6), grant/award no. 511106: European network of excellence for Ocean Ecosystems Analysis
Event(s):
Milligan_etal_04/F2A * Method/Device: Experiment (EXP)
Milligan_etal_04/F2B * Method/Device: Experiment (EXP)
Milligan_etal_04/F5A * Method/Device: Experiment (EXP)
Comment:
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).
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1Event labelEvent
2Time in minutesTimeminMilligan, Allen J
3Temperature, waterTemp°CMilligan, Allen JMeasured
4SalinitySalMilligan, Allen JMeasured
5Radiation, photosynthetically activePARµmol/m2/sMilligan, Allen JMeasured
6Carbonate system computation flagCSC flagNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
7pHpHMilligan, Allen JMeasuredNBS scale
8pHpHNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)Total scale
9Alkalinity, totalATµmol/kgMilligan, Allen JCalculated using CO2SYS
10Carbon, inorganic, dissolvedDICµmol/kgMilligan, Allen JCalculated using CO2SYS
11Carbon dioxideCO2µmol/kgNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
12Carbonate ion[CO3]2-µmol/kgNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
13Bicarbonate ion[HCO3]-µmol/kgNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
14Partial pressure of carbon dioxide (water) at sea surface temperature (wet air)pCO2water_SST_wetµatmMilligan, Allen JMeasured
15Partial pressure of carbon dioxide (water) at sea surface temperature (wet air)pCO2water_SST_wetµatmNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
16Fugacity of carbon dioxide (water) at sea surface temperature (wet air)fCO2water_SST_wetµatmNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
17Aragonite saturation stateOmega ArgNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
18Calcite saturation stateOmega CalNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
19Silicate quota in diatomSi quotapmol/#Milligan, Allen JColorimetry
20Biogenic silicate quota in diatombSiO2 quota%/#Milligan, Allen JColorimetry
21Silicate efflux in diatomSi effluxfmol/#/minMilligan, Allen JMeasured
Status:
Curation Level: Enhanced curation (CurationLevelC)
Size:
371 data points

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