Dr. Angela Hayes, Dr. Teresa Broggy and Prof. Michal Kucera

1. Mary Immaculate College Research Showcase Late Quaternary Investigation of PlanktonicForaminiferal Assemblages from the Western Mediterranean Sea Dr. Angela Hayes, Dr. Teresa Broggy and Prof. Michal Kucera

2. Research Area: The Mediterranean Sea

3. The Late Quaternary

4. Planktonic Foraminifera (from Coloma et al., 2005) Protozoa Non-spinose Spinose

5. BiogeographicRegions (from Kucera, 2007)

6. Globorotaliatruncatulinoides Sinistral Dextral

7. Transitional Subtropical Tropical Ericson et al., 1954

8. Genetic Diversity De Vargas et al. (2001) Ujiie and Lipps (2009)

9. Distribution of G.truncatulinoides(Type 2) Pujol and Vergnaud-Grazzini, 1995

10. Core Locations

11. Methodology • All samples were dried at 40 °C, disaggregated in demineralised water and wet sieved through a 63 µm mesh before drying. Finally, samples were dry sieved through a 150 µm mesh. Using a random splitter, were possible, 100 specimens of G. truncatulinoideswere counted to obtain a coiling record for each core. • 16 radiocarbon dates

12. Results

13. It’s all about the Thermocline!

14. Assumptions • Occurrence of G. truncatulinoidesis governed by the stability of the water column (mixed or stratified). Winter convective overturning facilitates the transference of both nutrients and juvenile populations of G. truncatulinoidesinto the surface waters where maximum abundances of the species develop. • Observed variation in coiling, appears to be related to the depth/presence of the thermocline. Dominant dextral populations tend to coincide with overall lower abundances of G. truncatulinoidespossibly a residual population associated with increased stratification of the water column. The effects of SSTs are a potential secondary factor.

15. Phase 2: Characterised by the near absence of G. truncatulinoidesfrom the faunal record . The absence of the species is attributed to enhanced stratification of the water column. The strong water stratification in the western Mediterranean Sea at this time could have developed due to the combined result of postglacial sea level rise (and subsequent reduction in sea surface salinities) and increased precipitation (and subsequent river runoff). Significance of G. truncatulinoidesin the Western Mediterranean Sea Phase 1: Characterised by low numbers of G. truncatulinoidesboth coiling variants exist, but the sinistral variant dominates the faunal assemblage. Suggests seasonal mixing in the water column. However, the relatively low abundances and the presence of the dextral coiling variant may imply weakened vertical mixing associated with the formation of a shallow thermocline. Phase 3: Significant increase in the abundances of G. truncatulinoides corresponding with the end of the African Humid Period which marks the transition from a more humid climate to the semi-arid climate that exists in the Mediterranean region today. Modern day hydrographic conditions in the western Mediterranean Sea support the development of deep vertical mixing.

16. Conclusions • Recolonisation of G. truncatulinoidespost glaciation in the western Mediterranean Sea • The presence and absence of the species during the Holocene suggests a sequence of hydrological events associated with sea level rise. • Basin-wide temporal and spatial similarities of recolonisation

17. Thank you 