**1. Introduction**

The Aegean Sea is an ideal archive to investigate climatic evolution at both global and local scale because of its intermediate position between the higher- and lower-latitude climate systems [1–3], high sedimentation rate marine records compared to the open Mediterranean Sea [4–7], and its paleo-latitudinal and land-locked configuration [8,9]. Such marginal seas are often more responsive to

paleoceanographic and paleoclimatic changes than global oceans, with climatic signals to be recorded in an amplified fashion in Mediterranean properties such as temperature, salinity and specific elemental concentrations, because of their smaller size and partial isolation [10], and therefore can be considered miniature oceans. In addition to interactions with the Black Sea, northern Aegean, and Levantine basins with remote and local atmospheric forcing [1,11], the south Aegean Sea is characterized by intense biogeochemical contrasts in its hydrology in response to a climatic gradient from mid-latitude to subtropical regimes that appears to be very sensitive to climate changes. However, most of the current paleoclimatic and paleoceanographic studies are still limited to deep marine records [6,12–15], and consequently little is known about the continental shelf and/or coastal areas within this marginal Sea [16–21].

Environmental changes related to the different water column and/or sediment characteristics can be recorded virtually instantaneously in paleoceanographic proxy data, such as stable isotope and other geochemical ratios [22–31], and micro-fossil abundances, such as planktonic foraminifera and pteropods [15,17,28,32–36]. This makes them extremely valuable for both stratigraphic correlations and paleoenvironmental/paleoclimate reconstructions [15,23,28,29,32,35,37–45]. Their significance in the study of modern and past marine ecosystems in the eastern Mediterranean Sea is well underlined [20,31,46–51]. Particularly, they are used as indicators of temperature, salinity, density, and nutrient content of the water column, making it possible to identify past circulation through the sedimentary record [7,15,29,47,52,53] and detect long- and short-term paleoclimatic and paleoceanographic changes in the study area [6,10,12,15,16,53–55] during the last glacial cycle.

Pteropods are widespread and abundant in the global ocean and entirely adapted to a pelagic life cycle [56,57]. Owing to the aragonite nature of their shells which increases their weight as settling particles and hence their sinking speed [58], their deposition is expected to be close to their habitat [59]. Particularly in the Mediterranean Sea, preservation of pteropods shells is excellent as a result of the relatively shallow water, high bottom water temperatures, and probably the limited number of mud feeders [60]. A considerable number of studies (e.g., [33,34,61–66]) have shown that Late Quaternary pteropod assemblages and their distribution pattern in the world oceans have changed with temperature and the overall climatic conditions that also affect the aragonite compensation depth (ACD). Recent studies [67] have shown that modern eastern Mediterranean pteropod communities are found to be more abundant than in those at western Mediterranean Sea. Their abundances are positively correlated with the aragonite saturation state (Ωar), O<sup>2</sup> concentration, pH, salinity and temperature, and negatively correlated with nutrient concentrations [67,68]. However, pteropod assemblages and their distribution in the Aegean Sea during the Late Quaternary are poorly documented.

The present study focuses on identifying and describing key environmental factors that control Late Quaternary planktonic foraminiferal and pteropod distribution in the south Aegean Sea, based on marine sediments retrieved by a 2-m long gravity (KIM-2A) core. In addition, paleoclimatic data were revealed from their distribution patterns coupled with variations of oxygen and carbon isotopic signals. The combination of the above data enables speculation on the factors' response to the climatic changes.

#### **2. Regional and Climatic Setting**

The Aegean Sea is in the northern sector of the eastern Mediterranean (Figure 1a), between the Turkish coastline to the east, the Greek mainland to the north and west, and bounded on the south by the island of Crete and Cretan Arc. It is connected to the Black Sea through the Straits of Bosporus and Dardanelles, and to the Levantine Sea through several larger and deeper straits between Peloponnesus, the islands of Crete and Rhodes, and south-western Turkey (Figure 1b). It is characterized, in general, by a cyclonic water circulation, although the most active dynamic features are the mesoscale cyclonic and anticyclonic eddies, either permanent and/or recurrent [8]. It is separated into two major sub-basins with different climatic conditions: the "north" and the "south" Aegean Sea. The north is more humid than the semiarid south [8].

′ ′ **Figure 1.** (**a**) Map of the Mediterranean Sea (including the Aegean Sea); (**b**) inset shows location of the south Aegean sediment core KIM-2A (36◦95.464′N, 24◦06.354′E, 640 m depth; in red), and the main patterns of sea surface-water circulation (grey arrows), cyclonic (solid grey circles) and anticyclonic gyres (dashed grey circles) in the Levantine and Aegean Seas. Location of the core NS-14 [7,16], that was used for the age model construction. Map contours show paleobathymetry (water depth in meters) of the study area.

The south Aegean (extend in between 35◦N and 37◦N) is one of the most oligotrophic areas in the Mediterranean Sea [8], with its surface water circulation mostly affected by arid climatic conditions, while it is also modulated by the effect of the Cretan gyre [69]. It mainly consists of the Cretan basin and the shallow shelf of the Cyclades Plateau, along with the Myrtoan Sea at the NW part of the region (Figure 1b). Milos and Kimolos islands lie in the westernmost sector of the Cyclades plateau. Both islands are part of the south Aegean Volcanic Arc; the most important geological structure of the Aegean Sea. The submarine area between Kimolos and Sifnos Islands is characterized by a rather

complex relief [70] as it is related to the volcanic arc. The sedimentary and Quaternary tectonic evolution of the aforementioned submarine area have been studied previously [71], and it is separated into three parts (the southern, the eastern, and the northern; [70]). The core studied derives from a submarine depression located at the northern part.
