Numerous specimens of coccolithophore combination coccospheres in water samples collected from the North Aegean and Tyrrhenian (Mediterranean Sea) have been photographed using the scanning electron microscope.As a consequence a series of taxonomic revisions are proposed, in which the names of the heterococcolithophores and holococcolithophores involved in the same life-cycle are synonymized. This has resulted in synonymizing the genus Coronosphaera with Syracosphaera and establishing one new combination; Syracosphaera arethusae (Kamptner 1941) comb. nov.
We document surface coccolithophore species composition along a N-S transect from New Zealand to the Ross Sea, across the fronts of the Antarctic Circumpolar Current. Emiliania huxleyi is the most abundant coccolithophore species throughout, with high concentration in the northernmost samples, in the Polar Frontal Zone and at the Polar Front. Three E. huxleyi morphotypes, A, B/C and O were recognized and show different biogeographic distributions along the investigated transect. Coccolithophore distribution appears to be strongly controlled by the location of oceanographic fronts, with minor species (Calcidiscus leptoporus, Syracosphaera spp., Acanthoica quattrospina, Umbellosphaera tenuis, Corisphaera strigilis and other holococcolithophores) largely restricted to the northern Sub-Antarctic Zone, only showing minor occurrence in the southern Sub-Antarctic Zone and being very rare in the Polar Frontal Zone. Our data confirm previous findings and add new information on the biogeography of minor coccolithophore species in relation with oceanographic features. Overall, integration with previous data on the southern extent distribution of E. huxleyi showed no significant temporal shifts in the polar dynamic perspective of the species since early observations.
This study presents the species composition of living coccolithophore communities in the Aegean Sea (northeastern Mediterranean), investigating their spatial and temporal variations in various environmental conditions from mesotrophic to ultra- oligotrophic regions. Coccolithophores of the photic zone in the Aegean Sea are relatively diverse (65 heterococcolithophores and 34 holococcolithophores) and dominated mostly by Emiliania huxleyi, Syracosphaera spp., Rhabdosphaeraceae and holococcolithophores. Hierarchical classification using R-mode cluster analysis distinguished five coccolithophore groups: Group Ia (Emiliania huxleyi, Syracosphaera molischii and Syracosphaera ossa) prevails in the high cell density and low diversity assemblages during the winter and early spring, when low temperatures and high nutrient concentrations are prevailing. Particularly in the north Aegean, E. huxleyi is dominating the upper photic zone being affected by the Black Sea Water inflow and the associated control on the water column stratification. Group Ib (Florisphaera profunda, Algirosphaera robusta, Syracosphaera anthos and Syracosphaera lamina) becomes important in the lower photic zone, making up the typical deep assemblages, whereas Group Ic (mainly Helicosphaera carteri and Gephyrocapsa oceanica) implies an opportunistic behavior in distinctly polluted neritic regions. Group IIa (Rhabdosphaera clavigera, Syracosphaera protrudens, Syracosphaera halldalii and numerous holococcolithophores) dominates the late spring-early autumn low cell density and high diversity assemblages, mainly in the thermally-stratified south Aegean and/or shallow, coastal environments with normal/ oligotrophic conditions, while Group IIb (Umbellosphaera tenuis and Syracosphaera pulchra) dominates the coccolithophore assemblages mainly during the early autumn in the north Aegean, thus reflecting the influence of Levantine Intermediate Water masses in the middle-lower photic zone. Our results suggest that abundance and variability in Aegean Sea coccolithophore assemblages are primarily controlled by surface water circulation and the associated water column stratification,with the sea temperature gradient affecting species composition.
Quantitative analyses of calcareous nannofossils in the sediments of Pissouri South section on the island of Cyprus have produced a paleoceanographic record reflecting the paleoclimatic conditions during the Zanclean/Piacenzian transition. Pissouri South cyclical lithological alternations between organic-rich laminated layers and grey marls reflect the Earth’s orbital precession. According to the calcareous nannofossil biostratigraphy which has been performed, the studied section is correlated with MNN14/15 and MNN16 calcareous nannofossil biozones and is astronomically dated between 4.065 and 3.217 Ma. Intervals of increased organic carbon content, along with the positive values ofFlorisphaera profunda, Helicosphaera sellii, Discoaster spp. and the subsequent increase of stratification S-index, correspond to the sapropel deposition during periods of wetter climate and intense continental runoff, especially from the river Nile. These layers alternate with grey marly intervals, featured by the increased values of small placoliths of Reticulofenestra and Gephyrocapsaspecies, which are indicative of eutrophic conditions during intense surface-water mixing. Our data support the prevalence of a generally warm phase characterized by the absence of high-frequency climate variations in the southeastern Mediterranean during the Zanclean/Piacenzian (Early/Late Pliocene) transition.
Detailed pollen analyses were performed at the lower sapropelic deposits of the marine core SK-3 within theframework of a multiproxy palaeoceanographic-palaeoenvironmental study. Pollen flora is characterized byhigh arboreal pollen abundances, mainly deciduous Quercus, together with Pinus, Juniperus and otherdeciduous taxa. A transition is marked from vegetation where Mediterranean elements appear more abundanttowards mixed deciduous woodland. In the upper part of the deposits an expansion of Abies, Pinus and Fagushas been recorded. The overall vegetation pattern adds significant evidence about the terrestrialpalaeoenvironmental conditions during deposition of sapropel S5.
Paleoceanographic proxies, such as marine micropaleontology, sedimentology and organic geochemistry havebeen performed in the sediment record of SK-3 gravity core (total length 217cm, water depth 249m) in order toprovide possible determination of late interglacial-Holocene the paleoenvironmental changes, at the southwestern margin of Cyclades plateau in the SW Aegean Sea. The sediment core exhibits two sapropels layer; thefirst one is associated with sapropel S1. The second sapropelic layer which we focus on represents anoxicconditions during the high sea-level warm event associated with sapropel S5 deposition.
A study on living coccolithophores from the euphotic zone is conducted in the northeastern Aegean Sea, anarea under the direct influence of the Black Sea waters inflowing into the Aegean. A total of 53 planktonsamples from 5 stations have been collected during four sampling periods between 2011 and 2014. Highconcentrations of Emiliania huxleyi and low concentrations of oligotrophic species, such asholococcolithophores, are indicative of a direct influence of the Black Sea waters inflow on the coccolithophoreassemblages in the northeastern Aegean Sea.
ELNAIS is a dynamic online information platform aiming to collect and report spatial information on Aquatic Alien Species in Greek waters. It covers freshwater, marine and estuarine waters, including not only established aliens but also casual records and cryptogenic species. The ELNAIS system includes: News, List of Greek experts, Literature of findings in Greece, List of species with information on their first introduction date and source as well as photos and distribution maps. Data providers are the scientific community (publications, grey literature, and databases) as well as citizen scientists. ELNAIS provides a useful tool towards national obligations and commitments under both the European and global frameworks in respect to Non Indigenous Species (CBD, WFD, MSFD).
The Barremian and Aptianwere times of global plate reconfiguration and profound changes in the ocean–climate system, culminating in the worldwide deposition of lower Aptian black shale layers (OAE 1a). Based on high resolution lithostratigraphic and micropaleontological analyses, precursor conditions and timing of the anoxia are here reconstructed along a 33.06 m thick section in the proposed Barremian/Aptian boundary GSSP stratotype at Gorgo a Cerbara (Umbria–Marche Basin, Italy).
A non-uniform history of benthic foraminiferal diversification is interrupted by the Selli Level (= OAE 1a) and by three turnover points for both benthic and planktic organisms, each highlighted by prominent breaks in lithology and outcrop morphology. The first two points, at ~1.1 Myr and ~20–50 kyr prior to the onset of the OAE 1a, correspond respectively to the nannoconid (=bathypelagic calcareous nannofossils) ‘decline’ and ‘crisis’ events, and separate: (a) pelagic limestone/chert-claystone lithological cycles of the uppermost Maiolica Formation, showing frequencies reminiscent of orbital eccentricity and containing an oligotrophic Barremian benthic and planktic assemblage, dominated by k-selected nannoconids and Rhizammina; (b) greenish-grey cherty marls of the lowermost Marne a Fucoidi Formation, associated to declining sedimentation rates and eutrophic early Aptian assemblages dominated by radiolarians and lituolid benthic foraminifera; and (c) anoxic radiolarites and shales of the carbonate-free Selli Level. High magnitude and frequency assemblage fluctuations occur between the nannoconid crisis (~25 cm below the lowermost OAE 1a black shale layer) and the Selli Level base, with suggestions of bottom-water acidification. At ~800 kyr after the OAE 1a end, a third turnover point in the basal reddish member of the Marne a Fucoidi highlights ‘middle’ Aptian assemblages characterized by a bloom of early macroperforate planktic foraminifera (Hedbergella spp.) and appearances of new benthic species, marking a shift towards better oxygenation.
OAE 1a oxygen and pelagic carbonate factory crises are here suggested to have been step-wise and linked to global warming conditions.
National and Kapodistrian University of Athens (+30) 210-7274920 Faculty of Geology and Geoenvironment Panepistimiopolis Zografou Athens, 15784 firstname.lastname@example.org