**6. Conclusions**

The results of the analysis of planktonic foraminifera and pteropods, combined with the results of principal component analysis and oxygen and carbon isotopic signals, describe the key factors controlling the formation of the micropaleontological assemblages, and therefore the paleoenvironmental and paleoclimatic changes during the last ~21 ka BP. Our data suggests that the sea surface temperature, stratification of the water column, seasonality, and productivity are the main controlling factors of the faunal distribution. During the Late Glacial, all the records indicate the occurrence of cold and eutrophicated waters. The time interval of 15.9–11.7 ka BP, corresponding to the deglaciation phase, was characterized by gradual climatic amelioration. During this interval, the warm interstadial Bølling–Allerød was identified, while low SST records at 12.9 ka BP revealed the onset of the YD. During this event, mild climate conditions were observed for around 400 years, and are attributed to the displacement of the polar front by a few degrees north. With the onset of the Holocene, a general climatic amelioration can be observed, with the gradual development of stratified oligotrophic surface waters. These conditions were intensified during the sapropel S1 deposition, which appears in two layers (S1a and S1b). The faunal and isotopic data suggest that conditions were more arid towards the end of S1a than at the onset of the S1a and the S1b. The interruption of sapropel deposition (S1i) and the post-sapropel interval are characterized by lower SST and stronger seafloor oxygenation due to vertical mixing.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2077-1312/8/9/709/s1, Figure S1: Planktonic foraminiferal PCA biplot of environmental factors of Temperature (Component 1) and Stratification (Component 2), Figure S2: Planktonic foraminiferal PCA biplot of environmental factors of Temperature (Component 1) and Seasonality (Component 3), Figure S3: Pteropods PCA biplot of environmental factors of Temperature (Component 1) and Productivity (Component 2), Figure S4: Pteropods PCA biplot of environmental factors of Temperature (Component 1) and Stratification (Component 3), Table S1: PCA scores based on planktonic foraminifera raw data, Table S2: PCA scores based on pteropods raw data.

**Author Contributions:** Conceptualization, C.G., G.K.; methodology, C.G., G.K., A.A.; software, C.G., G.K.; validation, C.G., G.K., A.A.; formal analysis, C.G., G.K., A.A.; investigation, C.G.,G.K., C.I., A.A.; resources, C.G., C.I.; data curation, C.G., G.K.; writing—original draft preparation, C.G., G.K.; writing—review and editing, C.G., G.K., E.K., A.A.; visualization, C.G., G.K.; supervision, E.K., A.A.; project administration C.G., A.A.; funding acquisition, E.K., C.I. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by EU/ESPA (NSRF; 2007–2013), YPOTHER project (351008) realized at the Institute of Geology and Mineral Exploration recent H.S.G.M.E. E.K. was funded by EU/ESPA (EPAnEK; 2014–2020), INNOVEXPO project (T1EDK-02363). The APC was funded by the Special Account for Research Grants, National and Kapodistrian University of Athens (Grant No. 16599).

**Acknowledgments:** We wish to thank the captain and crew of R/V Aegaeo (HCMR) for their technical assistance during the YPOTHER cruises, and N. Xirocostas and K. Vallianatou (H.S.G.M.E.) for the organic carbon analysis. We also thank M. Dagla for the English proofreading of the manuscript. Constructive comments by three anonymous reviewers have been essential in improving this manuscript and Victoria Li (Assistant Editor) is thanked for her editorial handling.

**Conflicts of Interest:** The authors declare no conflict of interest.
