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. 2013 Jun 11;8(6):e65987. doi: 10.1371/journal.pone.0065987

Figure 3. Effect of increasing CO2 concentrations on the stable isotope composition.

Figure 3

(A) 13C fractionation of organic carbon (εp) and calcite (εk), (B) 18O composition of calcite (δ18Ocalcite) and DIC (δ18ODIC), and (C) relationship between the oxygen isotopic composition of calcite (δ18Ocalcite-water) in Thoracosphaera from this study (open diamonds) and from Ziveri et al. [9] (grey diamonds). Horizontal lines in (B) indicate δ18O values for HCO3 − and CO3 2−, and dashed line indicates trend of curve. Solid lines indicate linear regressions (n = 12) with (A) εp: R2 = 0.75, P<0.001, and εk: R2 = 0.90, P<0.001, (B) δ18ODIC: R2 = 0.76, P<0.001, and (C) This study: R2 = 0.99, P<0.001, and Ziveri et al. (2012), (n = 7): R2 = 0.95, P<0.001.