Key Environmental Factors Controlling Planktonic Foraminiferal and Pteropod Community’s Response to Late Quaternary Hydroclimate Changes in the South Aegean Sea (Eastern Mediterranean)

Christina Giamali,Chryssanthi Ioakim,George Kontakiotis,Efterpi Koskeridou,Assimina Antonarakou

doi:10.3390/jmse8090709

Abstract

A multidisciplinary study was conducted in order to investigate the environmental factors affecting the planktonic foraminiferal and pteropod communities of the south Aegean Sea. Aspects of the Late Quaternary paleoceanographic evolution were revealed by means of quantitative analyses of planktonic foraminiferal and pteropod assemblages (including multivariate statistical approach; principal component analysis (PCA)), the oxygen (δ18O) and carbon (δ13C) isotopic composition of planktonic foraminifera and related paleoceanographic (planktonic paleoclimatic curve (PPC), productivity (E-index), stratification (S-index), seasonality) indices, extracted by the gravity core KIM-2A derived from the submarine area between Kimolos and Sifnos islands. Focusing on the last ~21 calibrated thousands of years before present (ka BP), cold and eutrophicated conditions were identified during the Late Glacial period (21.1–15.7 ka BP) and were followed by warmer and wetter conditions during the deglaciation phase. The beginning of the Holocene was marked by a climatic amelioration and increased seasonality. The more pronounced environmental changes were identified during the deposition of the sapropel sublayers S1a (9.4–7.7 ka BP) and S1b (6.9–6.4 ka BP), with extremely warm and stratified conditions. Pteropod fauna during the sapropel deposition were recorded for the first time in the south Aegean Sea, suggesting arid conditions towards the end of S1a. Besides sea surface temperature (SST), which shows the highest explanatory power for the distribution of the analyzed fauna, water column stratification, primary productivity, and seasonality also control their communities during the Late Quaternary.

Highlights

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 [1,2,3], high sedimentation rate marine records compared to the open Mediterranean Sea [4,5,6,7], and its paleo-latitudinal and land-locked configuration [8,9]
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
A useful additional dimension of planktonic foraminifera ecology that is underlined by the principal component analysis (PCA) conducted in this study is the degree of vertical stratification of the water column and the way it is recorded, which are inextricably linked with the factors of primary productivity and seasonality

Summary

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 [1,2,3], high sedimentation rate marine records compared to the open Mediterranean Sea [4,5,6,7], and its paleo-latitudinal and land-locked configuration [8,9]. 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 [22,23,24,25,26,27,28,29,30,31], and micro-fossil abundances, such as planktonic foraminifera and pteropods [15,17,28,32,33,34,35,36] This makes them extremely valuable for both stratigraphic correlations and paleoenvironmental/paleoclimate reconstructions [15,23,28,29,32,35,37,38,39,40,41,42,43,44,45]. 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 [6,10,12,15,16,53,54,55] during the last glacial cycle

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Discussion

Conclusion