*3.3. Total Organic Carbon and Stable Isotopes*

Total organic carbon (TOC) was determined based on the [76] methodology with the [77] adaptation at the Laboratory of the Hellenic Survey of Geology and Mineral Exploration (H.S.G.M.E.). For stable oxygen and carbon (δ <sup>18</sup>O, δ <sup>13</sup>C) isotope measurements, 30 specimens of the planktonic species *G. ruber* f. alba were picked from the 250–300 µm size fraction. In particular, we exclusively used the morphotype "Normal" of [32] (equivalent to *G. ruber* sensu stricto [75]) in order to minimize potential morphotype-specific differential responses in stable isotope compositions [24,78,79]. This narrow size fraction was used to minimize ontogenetic and growth rate effects on shell geochemistry [80]. The analyses were carried out at the Laboratory of Geology and Geophysics at Edinburgh University. Foraminiferal δ <sup>18</sup>O and δ <sup>13</sup>C data were calibrated to National Bureau of Standards 19 (NBS19), and the isotope values are reported in ‰ relative to Vienna Pee Dee belemnite scale. The external standard errors of the stable carbon and oxygen isotope analyses are <0.06‰ and 0.08‰, respectively.
