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Living coccolithophores were collected from eight stations along a transect in the gulf of Korthi (southeastern Andros island, Aegean Sea, Eastern Mediterranean) in August 2001. Samples were collected from 0–120 m water depth to determine the cell density, the species composition and the biogeographical (spatial and vertical) distribution of the coccolithophore biocommunities in coastal marine ecosystems. The studies revealed an impressive heterococcolith–holococcolith combination coccosphere (SEM micrograph) involving the species Algirosphaera robusta and Sphaerocalyptra quadridentata. In addition, a second association was observed by light microscopy. This discovery verifies the suggestions of Kamptner (1941) and provides strong proof on the assignment of these two ‘species’ in a common life cycle, increasing significantly our knowledge of life-cycle pairings ecology.

Bay Akrotiri section represents a thick terrigenous sequence laying along the southern part of Paliki peninsula (southwest Cefallinia). The data of the calcareous nannofossil quantitative analysis indicate that the studied sediments are ranging in terms of age between 1.95 Ma and 1.238 Ma approximately. The provided distribution patterns clearly depict an apparent evolutionary lineage close to the Plio/Pleistocene boundary, from small Gephyrocapsa placoliths to larger forms of gephyrocapsids.

Spanochorion composite section (NE Lefkas) and Aghios Vassilios section (W Lefkas) have been studied semiquantitatively for their calcareous nannofossil content. The calcareous nannofossil biostratigraphy, performed at the Paxos unit atypical flysch sediments of Aghios Vassilios section, permits their biostratigraphic correlation with the uppermost part of NN4 biozone and the lower part of NN5 biozones (Martini, 1971) or MNN4b and MNN5a (Fornaciari and Rio, 1996), which chronostratigraphically point to Early Langhian age and range between 15.974 and 14.53 Ma. Τhe most interesting biostratigraphic result is the detection of the Sphenolithus heteromorphus Paracme End at the base of Aghios Vassilios section, a biohorizon that marks the basal Langhian deposits in the Mediterranean region. The mollasic sediments of Spanochorion section are more or less of the same age, ranging between 15.5 and 14.53 Ma. The biostratigraphic results of the present study reinforce the hypothesis that the molassic sediments of NE Lefkas Island behind the Ionian thrust were isochronously deposited with Paxos atypical flysch sequences deposited in front of Ionian thrust, at least until Early Langhian times.

Detailed quantitative analyses of coccolithophores performed on the shallow deposits of the southeastern Aegean region (core NS-14, 505 m depth), evidenced that the distribution of calcare-ous nannoplankton assemblages during the last 13 ka BP reflects paleoenvironmental changes which are directly related to parameters such as temperature, salinity, productivity and nutrient flux in the water column. Analysis enabled the separation of the assemblages in four groups. Group A consists of Emiliania huxleyi and the subtropical species Syracosphaera spp. and Rhabdosphaera clavigera, Group B is composed of Helicospaera spp. and Florisphaera profunda, typical species for high productivity conditions in the middle-lower photic zone, Group C consists of Gephyrocapsa oceanica and Braarudosphaera bigelowii, that characterise low salinity conditions and Group D includes Umbilicosphaera spp. and Calcidiscus spp. which are described as relatively eutrophic species. The Holocene assemblages differ distinctly from the living coccolithophore communities in the coastal ecosystems of the Aegean Sea, where only Group A coccolithophores are thriving in the seasonally controlled marine environment.

International audience; Information stored in sedimentary records provides evidence on climate and environmental variability at decadal to centennial time scales. The eastern Mediterranean Sea and the related Aegean Sea exhibit high sedimentation rates in certain areas and are considered as sensitive regions to record paleo-environmental and -climatic changes. The aim of our study is to reconstruct high-frequency paleoclimatic variations and identify associated changes in the physical, chemical and biological environment in selected basins of the eastern Mediterranean Sea, using molecular biogeochemical proxies. Here we present a high-resolution multi-proxy study along two Aegean Sea cores (north (152SL) and southeast (NS-14)) and a Libyan Sea core (HCM2/22). An important time marker and indicator of remarkable climatic and environmental changes is sapropel S1, a sediment layer rich in organic carbon. Depending on the water column depth, the sediment accumulation rates and the proximity to freshwater and water formation sources, S1 deposited between ~9.8 to 6.4 kyr BP, with an apparent interruption in the S1 deposition that occurred from ~8.6 to 7.6 kyr BP. SSTs based on alkenone unsaturation index Uḱ 37, ^15tot, ^13Corg and various marine and terrestrial biomarkers are used to investigate the region's climatic variability, and the modifications in the biogeochemical functioning of the eastern Mediterranean Sea. Uḱ 37 SST distribution in our records reveals significant fluctuations in temperature over the last 20.000 yrs. Organic carbon stable isotopes values span a narrow range over the whole sequence, with values varying to typical marine origin. The distributions of land-plant biomarkers are indicative of variable terrigenous organic matter supply and the concomitant transport of nutrients to surface waters. Furthermore, the distribution patterns and characteristic ratios of marine biomarkers exhibit differences in the paleoproductivity trends and ventilation changes over the last 20 kyr. Low ^15N values within the sapropel layers reflect a significant contribution of N-fixation to the N-cycle, related probably to higher demand for nitrogen due to denitrification and sedimentary phosphorous regeneration processes under low-oxygen conditions.

International audience; Much interest has been concentrated recently on the Aegean Sea, an eastern Mediterranean basin situated within a climatic transition zone which represents an important source area of new deep water for the entire eastern Mediterranean. Recent paleoceanographic research has shown that the Aegean Sea sediment record, although featuring organic-rich sapropel layers that demonstrated periodically different productivity, circulation and preservation conditions in the past, provides a direct link to the high-latitude Holocene climate influences. This is superimposed on the underlying subtropical/tropical control on the eastern Mediterranean Sea hydrography and ecosystem, suggesting that paloclimatic conditions that accompanied sapropel deposition were not always uniform. This research uses the inorganic and organic chemistry of coccolithophores to monitor changes in sea water chemistry and ecology during the sapropel S1 deposition in the Aegean Sea. In particular d18O on coccoliths of Emiliania huxleyi has been analyzed from a number of samples spanning S1 from the SE Aegean core NS-14 and the North Aegean core 152SL. Age model, marine biogeochemical conditions and SSTs derived from alkenones, are well determined in both cores. The calculated d18Ow variability is related to both changes in freshwater input and carbonate ion concentration. d18Ow decreases (approx. 0.6 o/oo) before S1 deposition, demonstrating fresher conditions and a possible runoff source for nutrient delivery. Here we will present various lines of coccolithophore evidence in support of this conclusion, as well as corroborating planktonic foraminiferal d18O data from the surface-dwelling species, Globigerinoides ruber.

An apparently unambiguous combination coccosphere from the Eastern Mediterranean (Aegean Sea, Greece) is documented involving Syracosphaera protrudens Okada & McIntyre, 1977 and Syracosphaera pulchra Lohmann, 1902 HOL pirus-type. This finding is difficult to interpret in terms of the current understanding of Syracosphaera taxonomy and adds evidence to the hypothesis of a distinctly complex Syracosphaera pulchra life cycle.

Στα πλαίσια της παρούσας εργασίας πραγματοποιήθηκε δειγματοληψία από το κατώτερο τμήμα των Σχιστολίθων της Βίγλας, από την τομή Φρύγανο {νήσος Ιθάκη). Η ανάλυση με βάση τα ασβεστολιθικά ναννοαπολιθώματα επιτρέπει τον βιοστρωματογραφικό συσχετισμό της βάσης των Σχιστολίθων της Βίγλας στη w τομή Φρύγανο, με το ανώτερο τμήμα των βιοζωνών BC21 (Bown et al., 1998) και NC7 (Roth, 1978), που χρονοστρωματογραφικά συσχετίζονται με το Ανώτερο Απτιο. Η πιστοποίηση της ηλικίας της βάσης των Σχιστολίθων της Βίγλας στη νήσο Ιθάκη (εξωτερικό περιθώριο της Ιονίου λεκάνης) ως Ανώτερο Απτιο, ενισχύει την υπόθεση ότι η απόθεση των Σχιστολίθων της Βίγλας είναι ισόχρονη., The calcareous nannofossil biostratigraphy, performed at the basal part of the Vigla Shale Member (Frygano section, Ithakl Island), permits its biostratigraphic correlation with the uppermost part of BC21 biozone (Bown et al., 1998) and the upper part of NC7 biozone (Roth, 1978), which chronostratigraphically point to Late Aptian. This result reinforces the hypothesis that the deposition of Vigla Shales is isochronous in the Ionian zone.