Planktonic foraminifera response to Sapropel S1 in the south Adriatic Sea

Detailed climate and ecological changes during the last Sapropel (S1) formation, interruption and ending is studied in the Adriatic Sea. This study aims to unravel in detail the internal climate oscillations of this fascinating period in the Holocene evolution of the Eastern Mediterranean Sea. In this study we present a high resolution and multiproxy approach carried out on core ND_14_Q_AR, collected during the oceanographic cruise NEXTDATA 2014 conducted by Institute for Coastal Marine Environment (IAMC-CNR) on board by URANIA vessel. The core was recovered in the southern part of the Adriatic Sea at 1013 meters water depth. Planktonic foraminiferal distribution, U/Mn ratios, a proxy for deep sea oxigenation, combined with oxygen stable isotopes in Globigerinoides ruber allowed us to recognise and characterize the pre-sapropel phase, the two S1 intervals, S1 interruption and post-sapropel phase. High abundance percentages of warm planktonic foraminifer Globigerinoides ruber white variety and the decrease in abundance of species linked to deep vertical mixing and cold-deep water conditions such as Globorotalia inflata and Neogloboquadrina pachyderma, respectively, characterized the S1a and S1b. Relatively light ?18O during both S1a and S1b supports also the dominance of warm and potentially fresh surface conditions. Nevertheless, an ecological niche turnover between G. ruber white and G. ruber pink variety by the second part of the S1a and along the S1b support improved water mixing during these intervals. Higher percentages of G. quadilobatus and G. siphonifera during the S1b could indicate, opposed to S1a, a greater oxygenation of the upper part of the water column during winter and summer. The interruption phase, between the S1a and S1b, is characterized by a strong increase in cold and mixing water species (G. inflata and Neogloboquadrinds). These surface water conditions are consistent with the deep Adriatic Sea evolution according to the U/Mn record. Minimum in oxygenation (high U/Mn ratios) occurred at the first part of S1a while a ventilation improvement occurred during the second part of the S1a reaching conditions comparable to those of the S1b. Minimum U/Mn values during the S1 interruption confirms a deep re-ventilation event associated to this period. This multi-proxy approach proves to be a powerful tool to analyse parallel changes in both surface and deep marine conditions. This research was financially supported by ERC-Consolidator TIMED project (REP-683237).