Abstract
This study presents novel findings on the drivers of the calcitic planktonic foraminiferal and aragonitic pteropod Holocene assemblages of the North Aegean Trough (northeastern Mediterranean), an area recording the interaction between dynamic water masses as they exchange between the northern and southern Mediterranean sub-basins. Both of these groups of microorganisms are the major producers of calcium carbonate in the ocean, and are particularly sensitive to climate and oceanographic changes over the late Quaternary. Downcore micropaleontological data from the gravity core AEX-15, supplemented with multivariate statistical Q-mode cluster and principal component analyses (PCA) results, provide significant insights on the water column dynamics during the Holocene. Focusing on the last ~10 calibrated thousands of years before the present day (ka cal BP), our integrated study reveals that primary productivity is the dominant factor controlling the planktonic foraminifera distribution in the North Aegean Sea, whereas water column stratification, and particularly the intensity of the oxygen minimum zone, seems to be the major driver on the pteropod distribution. Besides productivity and thermal stratification, which show the highest explanatory power for planktonic foraminifera and pteropod communities, respectively, though they affect both groups to a different extent, upwelling seems to further affect both faunal groups. Overall, our findings are consistent with those derived by published late Quaternary eastern Mediterranean records, highlighting in parallel a useful additional dimension on planktonic foraminiferal and pteropod ecology, which is inextricably linked with the factors of primary productivity and vertical stratification of the warm Holocene water column.
Highlights
The Aegean Sea is a physical laboratory to investigate climatic oscillations at both a global and local scale due to its intermediate position between the higher- (i.e., NorthAtlantic-influenced) and lower-latitude climate systems [1,2,3], high sedimentation rate marine records compared to the open Mediterranean Sea [4,5,6], and its latitudinal and land-locked configuration [7]
17 species of planktonic foraminifera lumped in 12 groups and 11 species of pteropods were identified (Table S1; Supplementary Materials)
Plankton foraminiferal and pteropod faunas have been studied in core AEX-15, from the North Aegean Trough, to evaluate their relationship with surface water dynamics, and to decipher the control of the Holocene productivity and stratification changes coupled with the impact of the regional eastern Mediterranean climate regime
Summary
The Aegean Sea is a physical laboratory to investigate climatic oscillations at both a global and local scale due to its intermediate position between the higher- (i.e., NorthAtlantic-influenced) and lower-latitude (i.e., monsoonally-influenced) climate systems [1,2,3], high sedimentation rate marine records compared to the open Mediterranean Sea [4,5,6], and its latitudinal and land-locked configuration [7]. The basin’s limited communication with the open ocean implies that any paleoceanographic signals will be recorded in an amplified fashion, and, this heightened sensitivity to the effects of climate variability further underlies the prominent role of such marginal basins in the understanding of the global climatic evolution. Planktonic foraminifera are excellent bio-eco-stratigraphic [32,33,34,35], paleoceanographic [31,36,37,38,39,40], and paleoclimatic [41,42,43,44,45,46] indicators, due to their wide distribution in the world oceans, the good fossilization potential for their calcitic shells, their long geological record, their upper water column habitat, and their preservation in the deep-sea sedimentary record [47,48]. Pteropods are holoplanktonic aragonitic molluscs, widespread and abundant in the world’s oceans, [49,50,51]
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