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Kisakürek, B; Eisenhauer, Anton; Böhm, Florian; Hathorne, Ed; Erez, Jonathan (2011): Seawater carbonate chemistry and biological processes of foraminifera, Globigerinoides ruber and Globigerinella siphonifera during experiments, 2011. doi:10.1594/PANGAEA.763297,
Supplement to: Kisakürek, B et al. (2011): Controls on calcium isotope fractionation in cultured planktonic foraminifera, Globigerinoides ruber and Globigerinella siphonifera. Geochimica et Cosmochimica Acta, 75(2), 427-443, doi:10.1016/j.gca.2010.10.015

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Specimens of two species of planktic foraminifera, Globigerinoides ruber and Globigerinella siphonifera, were grown under controlled laboratory conditions at a range of temperatures (18-31 °C), salinities (32-44 psu) and pH levels (7.9-8.4). The shells were examined for their calcium isotope compositions (d44/40Ca) and strontium to calcium ratios (Sr/Ca) using Thermal Ionization Mass Spectrometry and Inductively Coupled Plasma Mass Spectrometry. Although the total variation in d44/40Ca (~0.3 per mill) in the studied species is on the same order as the external reproducibility, the data set reveals some apparent trends that are controlled by more than one environmental parameter. There is a well-defined inverse linear relationship between d44/40Ca and Sr/Ca in all experiments, suggesting similar controls on these proxies in foraminiferal calcite independent of species. Analogous to recent results from inorganically precipitated calcite, we suggest that Ca isotope fractionation and Sr partitioning in planktic foraminifera are mainly controlled by precipitation kinetics. This postulation provides us with a unique tool to calculate precipitation rates and draws support from the observation that Sr/Ca ratios are positively correlated with average growth rates. At 25 °C water temperature, precipitation rates in G. siphonifera and G. ruber are calculated to be on the order of 2000 and 3000 µmol/m**2/h, respectively. The lower d44/40Ca observed at 29 °C in both species is consistent with increased precipitation rates at high water temperatures. Salinity response of d44/40Ca (and Sr/Ca) in G. siphonifera implies that this species has the highest precipitation rates at the salinity of its natural habitat, whereas increasing salinities appear to trigger higher precipitation rates in G. ruber. Isotope effects that cannot be explained by precipitation rate in planktic foraminifera can be explained by a biological control, related to a vacuolar pathway for supply of ions during biomineralization and a pH regulation mechanism in these vacuoles. In case of an additional pathway via cross-membrane transport, supplying light Ca for calcification, the d44/40Ca of the reservoir is constrained as -0.2 per mill relative to seawater. Using a Rayleigh distillation model, we calculate that calcification occurs in a semi-open system, where less than half of the Ca supplied by vacuolization is utilized for calcite precipitation. Our findings are relevant for interpreting paleo-proxy data on d44/40Ca and Sr/Ca in foraminifera as well as understanding their biomineralization processes.
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).
#NameShort NameUnitPrincipal InvestigatorMethodComment
1SpeciesSpeciesKisakürek, B
2IdentificationIDKisakürek, B
3Sample IDSample IDKisakürek, B
4ReplicatesRepl#Kisakürek, BShells
5Globigerinoides ruber, shell, weightG. ruber shell WµgKisakürek, B
6Globigerinella siphonifera, shell, weightG. siphonifera shell WµgKisakürek, B
7Growth rateµmg/dayKisakürek, Bsee reference(s)
8Growth rate, standard deviationµ std dev±Kisakürek, B
9SalinitySalKisakürek, BMeasured
10Temperature, waterTemp°CKisakürek, BMeasured
11Alkalinity, totalATmmol(eq)/lKisakürek, Bsee reference(s)
12Alkalinity, total, standard deviationAT std dev±Kisakürek, B
13Carbon, inorganic, dissolvedDICµmol/lKisakürek, Bsee reference(s)
14Carbon, inorganic, dissolved, standard deviationDIC std dev±Kisakürek, B
15pHpHKisakürek, BCalculated using CO2SYSNBS scale
16pH, standard deviationpH std dev±Kisakürek, B
17Carbonate ion[CO3]2-µmol/lKisakürek, BCalculated using CO2SYS
18Carbonate ion, standard deviation[CO3]2- std dev±Kisakürek, B
19Carbonate system computation flagCSC flagNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
20pHpHNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)Total scale
21Carbon dioxideCO2µmol/kgNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
22Partial pressure of carbon dioxide (water) at sea surface temperature (wet air)pCO2water_SST_wetµatmNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
23Fugacity of carbon dioxide (water) at sea surface temperature (wet air)fCO2water_SST_wetµatmNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
24Bicarbonate ion[HCO3]-µmol/kgNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
25Carbonate ion[CO3]2-µmol/kgNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
26Carbon, inorganic, dissolvedDICµmol/kgKisakürek, BCalculated
27Alkalinity, totalATµmol/kgKisakürek, BCalculated
28Aragonite saturation stateOmega ArgNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
29Calcite saturation stateOmega CalNisumaa, Anne-MarinCalculated using seacarb after Nisumaa et al. (2010)
30delta 44/40 Cad44/40 Caper mil SRM 915aKisakürek, BFinnigan TRITON thermal ionization mass spectrometer (TIMS)
31delta 44/40 Ca, standard deviationd44/40 Ca std dev±Kisakürek, B
32ReplicatesRepl#Kisakürek, BSr/Ca samples
33Strontium/Calcium ratioSr/Cammol/molKisakürek, Bsee reference(s)
906 data points

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