*4.4. Total Organic Carbon and Stable Isotopes*

Total organic carbon (TOC) in KIM-2A generally exhibits values around 1%. This pattern is interrupted in two intervals related to the sapropel sub-units deposition. The first interval (S1a; 89–64 cm) is characterized by high TOC concentration, ranging from 1.5% to 3.4%, and in the second interval (S1b; 52.5–40 cm), TOC concentration ranges from 1.8% to 2.4% (Figure 2a). Thus, the deposition of S1 sapropel layer started at 89 cm and terminated at 40 cm. The interruption of sapropel S1 layer (S1i) is detected between 64 cm and 52.5 cm, as suggested by the TOC content (~1.3%).

As shown in Figure 2a, between 196 cm and 159 cm, δ <sup>18</sup>O*G. ruber* values range from +2.9 to +3.2‰. From 157 cm to 115 cm, a depletion in δ <sup>18</sup>O*G. ruber* values is observed (up to +0.9‰) and persists until the 34 cm with even lower values. More precisely, the depleted values were recorded from two intervals (88.5–65.5 cm and 50.25–34 cm) with an average value of −0.08‰ and +0.25‰ respectively. In the interval corresponding to 66.5–61 cm, slightly heavier δ <sup>18</sup>O*G. ruber* values were observed (+0.6 to −0.1‰). In the final unit of the core, from 28 cm until the top, a core enrichment in δ <sup>18</sup>O*G. ruber* is recorded. The δ <sup>13</sup>C*G. ruber* values of KIM-2A core exhibit more scatter than the δ <sup>18</sup>O records. In the basal part of the core (200–88 cm) values range between +1.3 to +0.2‰. In the interval between 88 cm and 61 cm the δ <sup>13</sup>C*G. ruber* ranges between 0.3 and 0.9‰ with the exception of three high-positive peaks at 80.5 cm, 73.5 cm, and 71.5 cm with values of 1.4‰, 1.2‰, and 1.3‰ respectively. From 50.25 cm to the top of the core, δ <sup>13</sup>C*G. ruber* exhibits heavier values with an average of +1.29‰ (Figure 2a).

#### *4.5. Principal Component Analysis*

δ δ − δ − A standardized principal component analysis (PCA) was carried out on the total data set using the varimax method, in order to determine the impact of various environmental parameters on the planktonic distribution. The application of this statistical analysis yielded a three-factor model for both planktonic foraminiferal and pteropod communities (Supplementary Materials; including PCA scores and biplots). The interpretation of the three components in each case was based on the screen plots of eigen values, and the factor loadings of the planktonic foraminiferal and pteropod species respectively. The 3 distinguished factors were considered to account for 81.57% and 82.81% of the total variance in each category respectively (Tables 2 and 3), with their factor loadings showing the contribution of each factor in every sample and therefore the downcore contribution of each factor (Tables 4 and 5; Figure 5). In the case of a bipolar factor, which has extremes of positive and negative loadings, high positive factor scores are related to the positive pole and high negative scores to the negative pole, respectively.


**Table 2.** Principle component analysis (PCA) factors based on planktonic foraminifera and their percentages of the total variability for core KIM-2A.

**Table 3.** PCA factors based on pteropods and their percentages of the total variability for core KIM-2A.


**Table 4.** Ranking of the planktonic foraminiferal species and their factor loadings along the PCA factors in core KIM-2A. Bold data indicate the most important factor loadings in each factor.



**Table 5.** Ranking of the pteropod species and their factor loadings along the PCA factors in core KIM-2A. Bold data indicate the most important factor loadings in each factor.

**Figure 5.** Environmental factors controlling planktonic foraminifera and pteropod distribution resulting from the PCA. (**a**) PCA1 of planktonic foraminifera as a temperature factor; (**b**) PCA2 of planktonic foraminifera as a stratification factor; (**c**) PCA3 of planktonic foraminifera as a seasonality factor; (**d**) PCA1 of pteropods as a temperature factor; (**e**) PCA2 of pteropods as a productivity factor; and (**f**) PCA3 of pteropods as a stratification factor.
