*3.2. Micropaleontological Quantitative Analysis*

The planktonic foraminiferal assemblages for the studied core-tops were picked from 10 cm<sup>3</sup> of wet sediment after washing through a 125 µm mesh sieve and cleaning using the HyPerCal protocol [87]. The 125 µm size fraction was selected in order to increase the reliability of studied planktonic foraminiferal assemblages that derived from such a subtropical oligotrophic-to-mesotrophic region with relatively low planktonic foraminiferal abundance [22,88,89] by avoiding over/under-estimations in the percentages of smaller (e.g., *Turborotalita quinqueloba*) or larger (e.g., *Trilobatus trilobus*) in size than the usual mean size of other species. The adopted size fraction is commonly used in relevant investigations within and beyond the Mediterranean Sea, which analyze the modern foraminiferal record [21,24,90–92] and implement a paleoclimatic analysis [8,9,93,94]. The dry residues (~3 g) were split using an Otto micro-splitter into aliquots of at least 300 planktonic foraminiferal specimens, which were identified to the species level according to the taxonomic concepts of Hemleben et al. [1] and Schiebel and Hemleben [95]. Raw data were transformed into percentages of the total absolute abundance, and relative percentage abundance curves were plotted versus latitude. Following Aurahs et al. [96], we distinguish *Globigerinoides ruber* pink (var. *rosea*) as a distinct morphotype, whereas for the white variety (var. *alba*), we follow the concept of Wang [97] by distinguishing *G. ruber* sensu stricto (s.s.) and *G. ruber* sensu lato (s.l.) morphotypes which have different depth preferences [98] and reflect distinctive environmental parameters [99,100]. We further note that *G. ruber* s.s. is equivalent to Morphotype A (type "Normal"), while those specimens

are grouped as *G. ruber* s.l. correspond to the Morphotypes B and C (type "Platys" and "Elongate") of Kontakiotis et al. [21] from the Mediterranean Sea. The *Globigerina bulloides* group includes the species *G. bulloides* and *G. falconensis* due to their similar ecological preferences [95]. Finally, the ecological interpretations and biogeographic implications for the studied species were based on the reference of [22,24,101–103].

#### *3.3. Morphometric Analysis*

For morphometric analysis, the picked specimens were transferred with a brush on a chapman micro-slide, where each species positioned in separate cells. Given the minimized difference in average areas for the umbilical or spiral sides for several species [104], we oriented the foraminiferal shells in umbilical or spiral position (species dependent) to capture the maximum silhouette area of each individual. The fixed specimens were photographed in transmitted light under a 50-fold magnification by a modular Leica M165 C fully apochromatic stereo microscope equipped with an integrated 10 megapixel (MP) Leica IC90 E color camera and processed using ImageJ software (version 1.50i). The derived images were parsed into objects by thresholding and their shape and size parameters were automatically extracted. Automated recognition of multiple foraminifera in the images was succeeded due to the contrast between the bright background and the dark silhouettes of the specimens. Following the pioneer work of Kucera and Kennett [105] and in accordance with a recent study of Zarkogiannis et al. [24] for the eastern Mediterranean, the Equivalent Circular Diameter (ECD) was measured as an aspect of the size of the species analyzed. Calibration for the silhouette area and diameter measurements was performed using a microscale image taken at the same magnification as the foraminiferal images optimizing the reproducibility and accuracy of the measurements. Additional to size analysis, image processing automatically performs planktonic foraminiferal counting, as well for each site, resulting in the overall changes in their assemblages for the study area during recent times.

#### **4. Results**

#### *4.1. Relative Abundance Data*

Thirteen planktonic foraminiferal species were identified at the studied core-tops along the N-S transect of the central Mediterranean Sea. The overall changes in their abundances are illustrated in Figure 2. Overall, the planktonic assemblages are dominated by *G. bulloides*, followed by *G. ruber* (including var. *alba* and *rosea*), while the species *Globigerinella siphonifera*, *Neogloboquadrina pachyderma*, *Orbulina universa*, *Globoturborotalita rubescens,* and *Globigerinita glutinata* are common. *Globorotalia inflata*, *Globorotalia truncatulinoides* and *Turborotalita quinqueloba* display a more sporadic faunal pattern with lower percentages.

**Figure 2.** Planktonic foraminifera species abundances in core-top samples from the eastern Mediterranean. The labels in the vertical axis are representative of the core-top locations presented in Table 1.

*G. bulloides* is the major contributor in the planktonic fauna in all samples with percentages up to 57%. However, the average contribution of this species significantly differs between the two study regions with a clear geographic signal to have emerged in its distribution. More explicitly, a sharp decrease in the abundance of *G. bulloides* with latitude is marked with the average values of 43.9% for the Adriatic to be diminished to 26.3% for the Ionian basin, respectively. It reaches high abundance values, constantly higher than 35% within the south Adriatic Sea, while its distributional pattern displays minor (almost half) percentages in the Ionian basin. *Globigerinoides ruber* (w) is the second ubiquitous and more abundant species showing an average abundance of 29.8% in the central Mediterranean. This species is continuously present throughout the transect, displaying almost an opposite distributional pattern compared to *G. bulloides*. Such an antagonistic pattern is documented for both s.s. and s.l. morphotypes. Except for two samples (H-03 and GeoB 10718), the s.s. morphotype is the main constituent in the *G. ruber* (w) morphospace. This intra-specific trend is more pronounced in the Adriatic basin, where the dominant morphotype presents higher frequencies (i.e., at least the double percentages) compared to *G. ruber* s.l. in most of the samples. *Globigerinoides ruber rosea* is present in lower percentages up to 11% being more abundant in the southern part of the Ionian basin. *Globigerinella siphonifera* is present in almost all locations, but its percentages become important by exceeded 10% only in the westernmost sites (H-04, H-05) within the Ionian basin. *Neogloboquadrina pachyderma* presents a highly variable distributional pattern, occasionally reaching significant percentages up to 20% (i.e., site H-11 at the northernmost part of the Ionian basin). *Orbulina universa*, *G. rubescens*, and *T. trilobus* show comparable patterns with continuous although limited presence (<8%) in both basins. *Globigerinita glutinata* is mostly found within the Ionian basin with restricted occurrence in relatively small percentages (<7%), and it is almost absent in the southern Adriatic Sea. *Turborotalita quinqueloba*, where present, exists with very small percentages around 3%. *Globorotalia inflata* shows a geographically sporadic distribution pattern with percentages stably less than 10% and the deep-dweller *G. truncatulinoides* is nearby absent from all regions, since it occasionally occurred at very low percentages (maximum 4%).
