4.5.1. Planktonic Foraminifera

The first varimax factor (PCA1; Figure 5a) accounts for 50.26% of the total variance (Table 2) and is interpreted as temperature indicator. Species with positive loadings (*N. pachyderma, T. quinqueloba, N. dutertrei, G. glutinata, G. inflata, G. bulloides*, and *G. scitula*; Table 4) thrive in cold–water masses, while the species with negative loadings (*O. universa, G. ruber* f. rosea, *G. siphonifera* gr., and *G. ruber* f. alba; Table 4) thrive in warm–water conditions. Factor PCA2 (Figure 5b) accounts for 22.5% of the total variance (Table 1), with the positive pole being expressed by species living in a highly stratified water column (*O. universa, G. ruber* f. rosea and Neogloboquadrinids) and negative pole by species typical of the weak development of these conditions (*G. ruber* f. alba and *G. bulloides* gr.). The third varimax factor (PCA3) describes 8.9% of the total variance (Table 2), and also display a bipolar character, with ts positive pole to be represented mainly by *G. ruber* f. alba and *N. pachyderma* and the negative pole by *G. bulloides*. The above species that characterize the PCA3 factor are the main exponents of the seasonal contrasts governing planktonic foraminiferal assemblages in the Mediterranean Sea during the last glacial cycle [94–96]. Thus, the third varimax factor (PCA3; Figure 5c) is referred to as a seasonality factor.

## 4.5.2. Pteropods

The first varimax factor (PCA1; Figure 5e) accounts for 58.66% of the total variance (Table 3) and was interpreted as a temperature indicator. Negative loadings consist mainly of the warm–water species *H. inflatus*, whereas positive loadings consist mainly of the subarctic species *L. retroversa* (Table 5). The second factor (PCA2; Figure 5e) describes 13.29% of the total variance (Table 3) and was interpreted as a productivity factor, as its positive pole is represented mainly by the mesopelagic oligotrophic *H. inflatus*. The third varimax factor (PCA3; Figure 5f) explains 10.27% of the total variance (Table 3). The positively loading taxa expressed by the epipelagic *Cavolinia* sp., *L. retroversa* and *B. chierchiae*, as well as the mesopelagic and tolerant to low oxygen concentration *H. inflatus,* whereas the negatively loading taxa (mesopelagic *C. pyramidata* and *D. trispinosa*) prefer a well-ventilated water column (Table 5). Thus, the third factor (PCA3) can be regarded as a stratification factor.

#### **5. Discussion**
