Silicoflagellate abundance, vertical distribution and morphology were studied during spring (March 2014) at three sampling stations locatedin the Northeast Aegean Sea adjacent to the Dardanelles Strait and characterized by a variable influx of cold, low-salinity Black Sea water.The silicoflagellate assemblage was dominated by Dictyocha stapedia and Stephanocha speculum with minor contribution of D. aculeata andOctactis pulchra. While specimens of D. stapedia were represented by the typical morphologies described in other areas of the Mediterranean Sea,populations of S. speculum displayed peculiar characters: they were large, predominantly 7-sided, with a small apical ring as well as apical ringspines, concave basal ring sides and non-rotated apical structure. Some of these features have been described for S. speculum at high latitudes, butthe combined characters make these specimens slightly different from the high latitude populations. Similar morphologies have been observed inthe western Black Sea, thus we can infer that the peculiar specimens detected in the Northeast Aegean are associated with the influx of Black Seawater masses.
Benthic foraminiferal composition assemblages and their temporal changes, ecological indices and foraminiferal densities are used to compare three coastal environments with different physicogeographical features in the Aegean Sea (coastal environment of Avdira–Vistonikos Gulf and Kitros–Thermaikos Gulf and open lagoonal environment of Vravron–South Evoikos Gulf). Three main foraminiferal assemblages have been recognized: a) “Assemblage A”; high degree of similarity between living and dead foraminiferal species, dominated byAmmonia beccarii, Elphidium spp. and relatively abundant and diverse miliolids, b) “Assemblage B1”; intermediate degree of similarity between live and dead assemblages, characterized by highly-abundant and well-diversified foraminiferal assemblages including the algal symbiont bearing Peneroplis pertusus together withAmmonia tepida and several small epiphytic rotaliids and miliolids, and c) “Assemblage B2”; absence of living individuals, strongly dominated by the opportunistic species A. tepida. Our results suggest a good comparison between living and dead assemblages from different coastal environments in the Aegean Sea, however the prevailing environmental conditions (vegetation cover, hydrodynamics, fresh water influx) have a strong impact on the taphonomic processes.
We provide new evidence on sea surface temperature (SST) variations and paleoceanographic/paleoenvironmental changes over the past 1500 years for the north Aegean Sea (NE Mediterranean). The reconstructions are based on multiproxy analyses, obtained from the high resolution (decadal to multi-decadal) marine record M2 retrieved from the Athos basin. Reconstructed SSTs show an increase from ca. 850 to 950 AD and from ca. 1100 to 1300 AD. A cooling phase of almost 1.5 °C is observed from ca. 1600 AD to 1700 AD. This seems to have been the starting point of a continuous SST warming trend until the end of the reconstructed period, interrupted by two prominent cooling events at 1832 ± 15 AD and 1995 ± 1 AD. Application of an adaptive Kernel smoothing suggests that the current warming in the reconstructed SSTs of the north Aegean might be unprecedented in the context of the past 1500 years. Internal variability in atmospheric/oceanic circulations systems as well as external forcing as solar radiation and volcanic activity could have affected temperature variations in the north Aegean Sea over the past 1500 years. The marked temperature drop of approximately ∼2 °C at 1832 ± 15 yr AD could be related to the 1809 ΑD ‘unknown’ and the 1815 AD Tambora volcanic eruptions. Paleoenvironmental proxy-indices of the M2 record show enhanced riverine/continental inputs in the northern Aegean after ca. 1450 AD.The paleoclimatic evidence derived from the M2 record is combined with a socio-environmental study of the history of the north Aegean region. We show that the cultivation of temperature-sensitive crops, i.e. walnut, vine and olive, co-occurred with stable and warmer temperatures, while its end coincided with a significant episode of cooler temperatures. Periods of agricultural growth in Macedonia coincide with periods of warmer and more stable SSTs, but further exploration is required in order to identify the causal links behind the observed phenomena. The Black Death likely caused major changes in agricultural activity in the north Aegean region, as reflected in the pollen data from land sites of Macedonia and the M2 proxy-reconstructions. Finally, we conclude that the early modern peaks in mountain vegetation in the Rhodope and Macedonia highlands, visible also in the M2 record, were very likely climate-driven.
Combined micropaleontological and geochemical analyses of the high-sedimentation gravity core M-4G provided new centennial-scale paleoceanographic data for sapropel S1 deposition in the NE Aegean Sea during the Holocene Climatic Optimum. Sapropel layer S1a (10.2–8.0 ka) was deposited in dysoxic to oxic bottom waters characterized by a high abundance of benthic foraminiferal species tolerating surface sediment and/or pore water oxygen depletion (e.g.,Chilostomella mediterranensis, Globobulimina affinis), and the presence of Uvigerina mediterranea, which thrives in oxic mesotrophic-eutrophic environments. Preservation of organic matter (OM) is inferred based on high organic carbon as well as loliolide and isololiolide contents, while the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. High inputs of terrigenous OM are attributed to north Aegean borderland riverine inputs. Both alkenone-based sea surface temperatures (SSTs) and δO18 G. bulloides records indicate cooling at 8.2 ka (S1a) and ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7–6.4 ka) is characterized by rather oxic conditions; abundances of foraminiferal species tolerant to oxygen depletion are very low compared with the U. mediterranea rise. Strongly fluctuating SSTs demonstrate repeated cooling and associated dense water formation, with a major event at 7.4 ka followed by cold spells at 7.0, 6.8, and 6.5 ka. The prominent rise of the carbon preference index within the S1b layer indicates the delivery of less degraded terrestrial OM. The increase of algal biomarkers, labile OM-feeding foraminifera and eutrophic planktonic species pinpoints an enhanced in situ marine productivity, promoted by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine OM along with fresher terrestrial OM inputs after ~7.7 ka imply sources alternative/additional to the north Aegean riverine borderland sources for the influx of organic matter in the south Limnos Basin, plausibly related to the inflow of highly productive Marmara/Black Sea waters.
Saronikos Gulf, including the industrial zone of Elefsis Bay and the Port of Piraeus, is one of the most anthropogenically impacted coastal regions of Greece. Distinct assemblages of benthic foraminifers in sediment samples, collected from this gulf in February 2012, defined three zones that reflect abiotic parameters of the sediments (e.g., organic carbon, metal content). A low-diversity assemblage, dominated by stress-tolerantAmmonia tepida and Bulimina spp., was characteristic of samples from Elefsis Bay. Samples from the western and central part of Saronikos Gulf were the most variable with respect to both abiotic parameters and the foraminiferal assemblage, characterized by a mix of stress-tolerant and more sensitive taxa, especially Bolivina spp. andNonion fabum. Samples from the coast of Salamis and at the eastern sector of the gulf were characterized by a diverse assemblage that included Peneroplis pertusus, miliolids, and a variety of small, epiphytic rotaliid taxa. A new biotic index, the Foram Stress Index (FSI), is based on the relative percentages of two ecological groups of benthic foraminiferal species, grouped according to their tolerance/sensitivity to organic matter enrichment and weighted proportionately to obtain a formula to define five ecological-status classes. The FSI produced three rankings for these samples (Poor, Moderate and Good), that strongly correlate with the macroinvertebrate-classification tool known as the BENTIX Index. The FSI provides a new tool to assess sediment or substrata quality based upon the benthic foraminiferal assemblages, which are a significant component of living meiobenthic communities that are generally not considered in most biotic benthic indices.
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.
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.
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.
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.
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).
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.
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.
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.
Marine and terrestrial biological and biogeochemical proxies in three sediment cores from North and SE Aegean and northern Levantine Seas record continuous warm and humid conditions between 5.5 and 4.0 ka BP related to the establishment of relatively stratified conditions in the upper water column. These conditions may have resulted from the concordant albeit weak Mid-Holocene South Asian monsoon forcing, combined with lighter Etesian winds. During this interval, sea surface temperatures fluctuate in the Aegean Sea, although exhibiting a strong positive shift at*4.8 ka BP. The warm and humid climatic conditions triggered upper water column stratification and enhancement of the deep chlorophyll maximum (DCM), leading to dysoxic conditions and the deposition of a sapropel-like layer, but only in the SE Aegean site. In contrast to the shallow water SE Aegean, the deeper North Aegean and the northern Levantine sites, although experiencing stratification in the upper parts of the water column, did not achieve bottom-water dysoxia. Thus, a top–bottom mechanism of stratification–DCM development accompanied by fast transport and burial of organic matter is a likely explanation for the preservation of productivity signal in the shallow sites of the SE Aegean and establishment of sapropelic conditions during the warm and humid Mid-Holocene. The termination of the Mid-Holocene warm and humid phase coincides with the ‘‘4.2 ka’’ climate event. Our data exhibit an N–S time transgressive aridification gradient around the Aegean Sea, most probably associated with the reorganization of the general atmospheric circulation during the Mid-Holocene.
Two specimens of the coccolithophore Calyptrolithophora pappilifera associated with single exothecal and endothecal coccoliths of Syracosphaera histrica,collected from the North Aegean Sea (NE Mediterranean), have been verified by Scanning Electron Microscopy. The two specimens strengthen previous reported hints that Syracosphaera histrica and Calyptrolithophora pappilifera represent a life-cycle association, documenting accordingly the relationships between the different phases within the genus Syracosphaera.
TheElefsis Bay is a typical coastal setting characterized by a semi-closed shallow environment with intense anthropogenic activity. This study describes a peculiar low cell density and species poor late-winter coccolithophore assemblages from Elefsis Bay compared to those from further offshore of the Aegean Sea. Helicosphaera carteri contributes significantly to the assemblage inside the Elefsis Bay and together with Emiliania huxleyi both represent the dominant component of the calcareous nannoplankton. Water column data confirmed the opportunistic behavior of H. carteri, thus providing new evidence for the ecology of the species. It is suggested that an increase in this species can be associated with distinct pollution in neritic environments.
The Collective Article ‘New Mediterranean Biodiversity Records’ of the Mediterranean Marine Science journal offers the means to publish biodiversity records in the Mediterranean Sea. The current article is divided in two parts, for records of alien and native species respectively. The new records of alien species include: the red alga Asparagopsis taxiformis (Crete and Lakonikos Gulf, Greece); the red alga Grateloupia turuturu (along the Israeli Mediterranean shore); the mantis shrimp Clorida albolitura (Gulf of Antalya, Turkey); the mud crab Dyspanopeus sayi (Mar Piccolo of Taranto, Ionian Sea); the blue crab Callinectes sapidus (Chios Island, Greece); the isopod Paracerceis sculpta (northern Aegean Sea, Greece); the sea urchin Diadema setosum (Gökova Bay, Turkey); the molluscs Smaragdia souverbiana, Murex forskoehlii, Fusinus verrucosus, Circenita callipyga, and Aplysiadactylomela (Syria); the cephalaspidean mollusc Haminoea cyanomarginata (Baia di Puolo, Massa Lubrense, Campania, southern Italy); the topmouth gudgeon Pseudorasbora parva (Civitavecchia, Tyrrhenian Sea); the fangtooth moray Enchelycore anatine (Plemmirio marine reserve, Sicily); the silver-cheeked toadfish Lagocephalus sceleratus (Saros Bay, Turkey; and Ibiza channel, Spain); the Indo-Pacific ascidian Herdmania momus in Kastelorizo Island (Greece); and the foraminiferal Clavulina multicamerata (Saronikos Gulf, Greece). The record of L. sceleratus in Spain consists the deepest (350-400m depth) record of the species in the Mediterranean Sea. The new records of native species include: first record of the ctenophore Cestum veneris in Turkish marine waters; the presence of Holothuria tubulosa and Holothuria polii in the Bay of Igoumenitsa (Greece); the first recorded sighting of the bull ray Pteromylaeus bovinus in Maltese waters; and a new record of the fish Lobotes surinamensis from Maliakos Gulf.
This is the first documentation of a combination coccosphere from samples collected in the field (North Aegean Sea, NE Mediterranean) between the heterococcolithophore species Coronosphaera mediterranea (Lohmann 1902) Gaarder in Gaarder & Heimdal (1977) and the holococcolithophore species “Zygosphaera hellenica”. This specimen verifies previous combination coccosphere evidence found in culture and again demonstrates that “Zygosphaera hellenica” can be developed from cells of Coronosphaera mediterranea in a life-cycle association.
Calcareous nannofossil biostratigraphy from Kotaphi Hill section allowed not only the biostratigraphic zonation of the Miocene units but also provided evidence for a distinct warm phase known as the Middle Miocene Climate Optimum (MMCO). Kotaphi Hill section is located in Agrokipia village (Nicosia region, Cyprus) and consists of cyclic marine deposits of the Pakhna Formation. High resolution sampling has been conducted and 84 samples were collected. Preliminary results indicated that several important calcareous nannofossil events can be consistently recognized along the studied section. High abundances of Discoaster druggii and Highest occurrence (HO) of Sphenolithus procerus suggest the presence of NN2 biozone while, LO of Sphenolithus belemnos has been used to recognize the base of biozone NN3. Upwards, Lowest Common Occurrence (LCO) of Sphenolithus heteromorphus marked the NN3-4 boundary-level. Biozone NN4 in Kotaphi Hill section is featured by high abundance of S. heteromorphus whereas total absence of the species together with the LO of Helicosphaera walbedorfensis mark the Paracme Beginning (PB) of S. heteromorphus interval. High abundance of warm indicators such as Discoasterids, S. heteromorphus, S. moriformis and Helicosphaera carteri observed in our material may partly reflect the warm phase of MMCO.
This paper concerns records of species that have extended their distribution in the Mediterranean Sea. The finding of the rare brackish angiosperm Althenia filiformis in the island of Cyprus is interesting since its insertion in the Red Data Book of the Flora of Cyprus is suggested. The following species enriched the flora or fauna lists of the relevant countries: the red alga Sebdenia dichotoma (Greece), the hydrachnid mite Pontarachna adriatica (Slovenia), and the thalassinid Gebiacanthatalismani (Turkey). Several alien species were recorded in new Mediterranean localities. The record of the burrowing goby Trypauchenvagina in the North Levantine Sea (Turkish coast), suggests the start of spreading of this Lessepsian immigrant in the Mediterranean Sea. The findings of the following species indicate the extension of their occurrence in the Mediterranean Sea: the foraminifer Amphistegina lobifera (island of Zakynthos, Greece), the medusa Cassiopea andromeda (Syria), the copepod Centropagesfurcatus (Aegean Sea), the decapod shrimp Melicertus hathor (island of Kastellorizo, Greece), the crab Menoethius monoceros (Gulf of Tunis), the barnacles Balanus trigonus, Megabalanus tintinnabulum, Megabalanus coccopoma and the bivalves Chama asperella, Cucurbitula cymbium (Saronikos Gulf, Greece).
The paleoenviromental conditions during the depositional interval of sapropel S1 in the northeastern Aegean (gravity core M-4, length 2.53 m; south Limnos basin) are studied based on quantitative micropaleontological (benthic and planktonic foraminifera) and geochemical (OC, δ13Corg) analyses. Special feature of core M-4 is the thickness of S1 layer (96 cm). Our study points that sapropelic layer S1a has been deposited in more dysoxic and warmer conditions in respect to S1b. Both primary productivity and preservation of organic material are more intense during the lower part of S1. An interruption of the sapropelic conditions at 8.0 Ka BP which is mainly characterized by the increase of agglutinated foraminiferal forms confirms both higher oxygen bottom conditions and freshwater input.
Benthic foraminiferal composition of sedimentary successions during the last 7500 years, was investigated from boreholes drilled in three rather tectonically stable coastal areas of the Aegean Sea (Alykes Kitros, Lafrouda Thrace and Vravron Attica). The quantitative analysis of foraminiferal fauna enabled separation into two different groups that are supported by the analysis of modern benthic foraminiferal communities in the studied sites. Group A consists of Ammonia tepida and Haynesina germanica (closed lagoon assemblage), whereas the most common species of Group B (open lagoon assemblage) are Aubignyna perlucida, miliolids, Elphidium spp. and Ammonia spp. The foraminiferal composition integrated with radiometric dating provides information on Holocene paleoenvironmental changes in the studied coastal plains, related to seaeland interaction. Alykes Kitros and Lafrouda Thrace boreholes show a similar trend, with an open lagoonal fauna in the lower part, transitional upwards to closed lagoonal conditions. This environmental change has taken place after 6500 cal BP in Alykes Kitros and around 3000 cal BP at Lafrouda Thrace. The benthic communities of Vravron Attica borehole sediments seem to represent continuously an open lagoon/shallow marine environment from 4700 to 400 cal BP.
Morphological abnormalities of recent and fossil benthic foraminiferal tests may be caused by environmental stress resulting from anthropogenic pollution and/or natural effects. In the present paper we document and describe morphological abnormalities of Ammonia tepida and some additional foraminiferal species from Holocene sedimentary successions of the Aegean Sea (Alykes Kitros and Vravron Attica). The abnormality types are manifested largely by siamese twins, whereas distorted chamber arrangement, overdeveloped or protruding chambers and the presence of multiple apertures have also been observed. Our observations on the distribution of abnormal tests in comparison to the characters of the accompanying fauna suggest that malformation was caused mainly by rapid and intense salinity fluctuations.
Ocean acidification and the related changes in seawater chemistry may disrupt calcification by coccolithophores and departure from the normal growth process causing malformed coccoliths. Coccospheres with malformed were coccoliths collected from different locations in the Aegean Sea. Although most of these specimens in our work are restricted to Emiliania huxleyi, scarce coccospheres of Rhabdosphaera clavigera, Syracosphaera pulchra, Discosphaera tubifera and Calcidiscus quadriperforatus have also been detected. In this study we discuss our observations on malformed distribution in relation to seawater carbonate chemistry.
Το ολοένα αυξανόμενο ενδιαφέρον σε Γεω-Περιβαλλοντικά θέματα, όπως η παγκόσμια κλιματική μεταβολή, η βιοποικιλότητα και η εξέλιξη των οικοσυστημάτων, που σχετίζονται με την ανθρωπογενή δραστηριότητα, συνέβαλαν στην ταχύτατη πρόοδο σε όλους τους τομείς της κατανόησης των θαλάσσιων μικροοργανισμών και των απολιθωμένων στοιχείων τους. Τα μικροαπολιθώματα, καθώς αποτελούν ή βρίσκονται κοντά στη βάση της τροφικής αλυσίδας και παρουσιάζουν γρήγορους ρυθμούς αναπαραγωγής, αναδεικνύονται ως ιδανικό εργαλείο στις περιβαλλοντικές και γεωπεριβαλλοντικές έρευνες, διαδραματίζοντας σημαντικό ρόλο στους βιογεωχημικούς κύκλους του άνθρακα, του πυριτίου και του ασβεστίου των ωκεάνιων συστημάτων και παράλληλα συμβάλλοντας στη βιογενή ανθρακική και πυριτική ιζηματογένεση. Το βιβλίο «Μικροπαλαιοντολογία και Γεωπεριβάλλον» πραγματεύεται αναλυτική εισαγωγή στην μελέτη των κύριων ομάδων μικροαπολιθωμάτων (κοκκολιθοφόρα/ασβεστολιθικό ναννοπλαγκτόν, τρηματοφόρα, διάτομα, πυριτομαστιγοφόρα, ακτινόζωα και δινομαστιγωτά) και στοιχεία φυσιολογίας, μορφολογίας, ταξινόμησης και βιοστρωματογραφίας. Ταυτόχρονα επιχειρείται συνοπτική παρουσίαση των δυνατοτήτων τους στη σύγχρονη γεω-περιβαλλοντική έρευνα - συμβολή στην ιζηματογένεση, αλληλεπίδραση με περιβάλλον και κλίμα - με έμφαση στις μελέτες στον ελλαδικό χώρο. Το βιβλίο κυκλοφορεί από τον εκδοτικό όμιλο ΙΩΝ
Members of the family Amphisteginidae have been nearly ubiquitous contributors to shelf carbonate facies through most of the Cenozoic. The most prolific carbonate producer of modern representatives is Amphistegina lobifera Larsen, which is the largest and shallowest dwelling of the Indo- Pacific taxa. This epiphytic, symbiont-bearing foraminifer is also a remarkably successful invasive species in coastal ecosystems of the eastern Mediterranean, where its shell production is altering the composition of shoreline sediment. This paper reports a temporal study of an A. lobifera population collected monthly between June 2008–May 2009 in the Vravron/Attica coastal ecosystem of the south Evoikos Gulf (Aegean Sea), where winter temperatures can drop below previously reported minima for the species. Monthly variations in size, frequency distribution, and abundance indicate that this population reproduced primarily during the summer (July–September), when both asexual and sexual reproduction occurred simultaneously, suggesting a predominantly coeval, one-year life span for each generation. However, a modest increase in juveniles in January indicates some winter reproduction. Comparison of these findings with previous studies shows that a) tolerance of low winter temperatures, b) adaptation of the life cycle to strong seasonality, and c) the mixotrophic feeding strategy have allowed A. lobifera to proliferate in the exceptionally clear, low nutrient, coastal waters of the Mediterranean Sea. These attributes elucidate how previous Cenozoic populations of Amphistegina were able to rapidly expand their latitudinal ranges and invade shallow epeiric seas during episodes of climatic warming.
Detailed quantitative analyses of calcareous nannofossils/coccolithophores performed on the deep sea deposits of the north eastern Mediterranean Sea; two gravity core from North Aegean Sea (SL 152) and south Cretan continental margin (HCMR 2/22), with a focus on the regional expression of sapropel S1 deposition. In both sites, higher values of Florisphaera profunda, Helicosphaera spp., Braarudosphaera bigelowii and the concomitant increase of stratification S index, within sapropel intervals can be interpreted as the result of elevated marine production and enhanced inflow of fresh water input during the S1 period. A series of cooling events detected within the S1 depositional interval, may be linked to outbursts of cold northerly air masses and relevant pulses in the deep-intermediate water ventilation that caused the temporary cessation of S1 deposition between 7.8-7.5 ka uncal. BP in North Aegean and 8.1-7.8 ka uncal. BP at the south Cretan margin. During this interval the peak of Braarudosphaera bigelowii, the decrease in abundance of Florisphaera profunda, Helicosphaera spp., Rhabdosphaera spp. and a general increase in NPP are related to a shoaling of the nutricline and higher production in the surface layer.
The species composition of the epiphytic benthic foraminiferal fauna was compared at two coastal locations in the Aegean Sea. Samples were collected during August 2001 and July 2003 along the southeastern coast of Andros Island at Korthi Gulf, where there are minimal anthropogenic activities, and at Kastro Gulf, with substantial anthropogenic influence. This study represents the first application of the FORAM Index (FI), which is a single-metric index for water quality originally developed for western Atlantic reef foraminiferal assemblages, to Mediterranean assemblages.
Multivariate analyses distinguished three clusters of sample sites representing three foraminiferal assemblages. Samples dominated by the mixotrophic species, A. lobifera, were collected primarily from sites along the northern coasts of both gulfs. Characteristics of this assemblage, including relatively high dominance (D=0.27–0.51), lower Shannon–Wiener diversity (H′=1.3–2.1) and high FI (6.6–8.2), all reflect oligotrophic environmental conditions typical of pristine waters of the Aegean Sea. A. lobifera was typically the most common species in the second assemblage, though relative abundances of heterotrophic taxa were higher, resulting in somewhat higher diversity (H′=1.6–2.4) and lower dominance (D=0.14–0.36). These indices, as well as the FI range of 3.5–7.0 indicated somewhat more prevalent organic carbon resources but still relatively high water quality. This assemblage was found along the southern coast of Korthi Gulf and at more interior sites in northern Kastro Gulf. The third assemblage was dominated by smaller heterotrophic species, including notable proportions of the stress-tolerant taxa Ammonia spp. and Elphidium spp., and had few or no A. lobifera. Diversity (H′=1.4–2.0) and dominance (D=0.22–0.47) indices were similar to those for the first assemblage, but FI values were much lower (2.0–3.4). Samples characterized by this assemblage were collected only from the southern Kastro Gulf, in the vicinity of the primary sewage outfall.
The results of this study document the sensitivity of benthic foraminiferal assemblages, and particularly A. lobifera populations, to sewage pollution in the Aegean Sea. These observations are consistent with studies from other biogeographic regions where the FORAM Index, which is based upon this genus and associated mixotrophic taxa, has been used as a water-quality indicator. This observation is particularly noteworthy because A. lobifera is an invasive species in the Mediterranean.
The present study provides additional data on the distributional range of six alien foraminiferal species in living assemblages from Greek coastal areas (Aegean Sea, Eastern Mediterranean). Amphistegina lobifera LARSEN 1976, Sorites orbiculus (FORSK L 1775) and Coscinospira hemprichii EHRENBERG 1839 are well established in Greek coastal areas, whereas Triloculina fichteliana D'ORBIGNY 1839, Planogypsina acervalis (BRADY 1884) and Cymbaloporetta plana (CUSHMAN 1924), are recorded for the first time in this paper. The occurrence of these species in a number of sites in the Aegean Sea establishes their presence in the Eastern Mediterranean.
In core ADE3-23 collected in the Libyan Sea, the nannofossil species Coccolithus pelagicus, Coronosphaera spp., Helicosphaera spp., Syracosphaera spp., Calcidiscus spp., small Gephyrocapsa spp., and the planktonic foraminifers Globigerina bulloides, Neogloboquadrina pachyderma, Globorotalia scitula, Turborotalita quinqueloba and Neogloboquadrina dutertrei prevail in sapropel S6 (midpoint at 172 ka B.P.), indicative of cold and highly productive surface conditions. Warm and highly stratified water-column conditions are recorded by the characteristic assemblage of Globigerinoides ruber, Globoturborotalita rubescens, Florisphaera profunda, Rhabdosphaera spp. during the sapropel S5 depositional interval (midpoint at 124 ka B.P.). Compared with S5, Globigerinita glutinata, Globorotalia inflata, Globigerinella siphonifera, Globorotalia truncatulinoides and the calcareous nannofossil Emiliania huxleyi characterise less stratified conditions within sapropel S1 (midpoint at 8.5 ka B.P.). Multivariate statistical analyses of calcareous nannofossil and planktonic foraminifers in core ADE3-23 identify planktonic assemblages which typify sapropels S6, S5 and S1 in the Libyan Sea. A warmer interval is recognised in the middle part of the cold S6, and can beassociated with an influx of less saline waters and the occurrence of a faint, temporary deep chlorophyll maximum. Evidence for enhanced surface productivity and breakdown of stratification is observed in the middle–upper part of the warm S5, associated with climatic deterioration. Moreover, an increase in surface productivity in the upper S1 implies weak stratification. Our combined calcareous nannofossil and planktonic foraminiferal data add to the evidence that climate variability was more pronounced than commonly considered to date for all the three studied Eastern Mediterranean sapropel depositional intervals.
Living coccolithophores were collected in February 2008, in surface waters from seven stations over the western Cretan Straits (South Aegean Sea, Eastern Mediterranean). The coccolithophore distribution was quantitatively documented through Scanning Electron Microscopy in terms of density, diversity and community structure. In the study period, the most abundant species was Emiliania huxleyi, followed by Rhabdosphaera clavigera and Syracosphaera pulchra, while additional important component of the winter assemblages were Helicosphaera carteri, Algirosphaera robusta and Syracosphaera molischii. The studied coccolithophore communities indicate a close relationship between coccosphere densities and surface water circulation, with the surface temperature gradient affecting species composition.
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 calcareous 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.
The Pissouri basin (Cyprus Island) corresponds to a small tectonically controlled depression elongated NNW-SSE and widening southward in the direction of the deep Mediterranean domain. In the centre of the basin, the section Pissouri South, about 100 m thick, consists of well-preserved cyclic marine sediments including laminated brownish layers alternating with grey homogeneous marls. Plankton biostratigraphy (calcareous nannofossil and planktonic foraminifera) revealed a remarkable number of biovents bracketing the Zanclean-Piacenzian boundary. In particular the Highest Occurrence (HO) of Reticulofenestra pseudoumbilicus suggests the presence of NN14/15-NN16 nannofossil biozone boundary, dated at 3.84 Ma. Additionally the defined planktonic foraminiferal MPL3-MPL4a and MPL4a-MPL4b zone boundaries point to ages between 3.81 and 3.57 Ma, in Pissouri North section. Zanclean/Piacenzian boundary (3.6 Ma) is placed at 75.8 m from the base of the section, considering Discoaster pentaradiatus top paracme (3.61 Ma) and Globorotalia crassaformis first influx (3.6 Ma) bioevents. The cyclically developed sapropelic layers around the Zanclean – Piacenzian boundary suggest a climate characterized by a period of warm temperate conditions and a highly stratified water column that occurred at times of precession minima.
A seasonal morphological variability is observed in Emiliania huxleyi var. huxleyi specimens, collected from discrete water samples in the Aegean Sea. Biometric analyses reveal a consistent pattern of increase in the size of coccoliths and coccospheres, including the thickness of the inner tube elements (INT), in winter/spring time low sea surface temperature and moderate productivity samples when compared with summer time high temperature–low productivity samples. The small range of salinity change in the Aegean Sea and the absence of seasonal pattern in nutrient content do not support any association with the observed increase in E. huxleyi coccolith size. A relatively increased [HCO3-] content is observed during spring-time interval related with the increase in the coccolith size, however it remains unclear which parameter of the carbonate system causes the observed effects.
New micropaleontological, palynological, and geochemical results from a relatively shallow (∼500 m) sediment core (NS-14) in the south-eastern Aegean Sea provide a detailed picture of the regional expression of sapropel S1 formation in this sub-basin of the eastern Mediterranean Sea. Specifically, freshwater input during ∼10.6–10.0 ka BP has preceded the deposition of S1. Further decrease in surface water salinity is evidenced between 10.0 and 8.5 ka BP at the lower part of S1a, which in respect to S1b, is featured by warmer (∼19.5 °C) and more productive surface waters associated with dysoxic bottom conditions. A series of coolings detected within the S1 depositional interval, may be linked to outbursts of cold northerly air masses and relevant pulses in the deep-intermediate water ventilation that caused the S1 interruption between 7.9 and 7.3 ka BP and culminated during the deposition of S1b, with the decline of deep chlorophyll maximum (DCM) at ∼6.5 ka BP. The climate instability and the relevant absence of anoxia weakened the organic matter preservation in the shallow south-eastern Aegean margin during the S1 times. NS-14 record provides evidence for a distinct mid Holocene warm (up to ∼25 °C) and wet phase associated with the deposition of the sapropel-like layer SMH (Sapropel Mid Holocene), between 5.4 and 4.3 ka BP. The SMH layer could represent evidence of on-going, albeit weak, African monsoon forcing, only expressed at the south-eastern edge of the Aegean Sea. Its end is associated with the 4.2 ka BP Northern Hemisphere megadrought event and the termination of the African Humid Period at 3.8 ka BP.
Quantitative analyses of coccolithophores, planktonic foraminifers, dinoflagellate cysts and pollen assemblages were carried out on shallow (NS-14) and deeper (NS-40) sediment cores from the south-eastern Aegean Sea. Nine coccolithophore (ACE 1–9) and nine planktonic foraminifer (APFE 1–9) ecozones, correlated with dinoflagellate cyst evidence, have been defined for the last ~14.5 cal. ka. Additionally, eight pollen assemblage zones (PAZ 1–8) have been recognised and correlated with the plankton ecozones. Although generally consistent with existing schemes for the central and eastern Mediterranean, the established high resolution ecostratigraphy has led to an expanded palaeoecological reconstruction of the Late Glacial–Holocene archive in the south-eastern Aegean Sea, defining two warm and humid phases at 9.3–8.6 and 7.6–6.4 cal. ka B.P., associated with the deposition of the early Holocene sapropel S1, and a third one between 5.2 and 4.2 cal. ka B.P. The high sedimentation rates which characterise the study area enabled the detection of even minor and brief climatic events in the Aegean Sea during S1 deposition times.
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.
A combined study of extant nannoflora (calcareous nannoplankton/coccolithophores) and microfauna (ostracods, benthic foraminifera) was conducted in summer period between 2001 and 2003 at Kastro and Korthi gulfs, Andros Island (central Aegean Sea). The results of our study showed that the studied three groups can provide evidence of stress on the natural assemblages and therefore can be used as proxies of declining coastal environments. In particular, the existence of coccolithophore communities with low species diversities, high dominance values and the predominance of Emiliania huxleyi with malformed coccoliths indicate unstable environmental conditions. The environmental stress in ostracod assemblages is mainly proved by the decreasing abundances of Xestoleberis spp. specimens. The response of benthic foraminifers was demonstrated by the increase of foraminiferal tests with morphological abnormalities and the replacement of Amphistegina lobifera – an environmental health proxy- by miliolids and small rotalliid forms.
During the last decades, hundreds of species of Indo-Pacific origin from the Red Sea have traversed the Suez Canal and settled in the Eastern Mediterranean. Nowadays, Amphistegina lobifera Larsen, the most common epiphytic, symbiont- bearing large foraminifer, is known to be a successful immigrant that is widely distributed in the coastal ecosystems of the Eastern Mediterranean Sea. In this study, we provide additional sites of occurrences on distributional range and settlement of A. lobifera in the Greek coastal ecosystems. The high relative abundances recorded are the result of very successful inhabitation of thisspecies in the Aegean ecosystems and suggest that it has become significant part of the epiphytic foraminiferal fauna.
Τhe main scope of this book is to illustrate a magnificent marine micro world in eastern Mediterranean Sea waters, the world of Coccolithophores. The eastern Mediterranean Coccolithophores presented in this book have been collected during several cruises and samplings in the Ionian and Aegean Sea at different seasons, between the years 1997-2006. The collected material has been analyzed and photographed by Scanning Electron Microscope and Light Microscope techniques. Αs a result 375 SEM and LM microphotographs are presented together with thorough systematic taxonomy and detailed description of 132 Coccolithophore species. A novelty of this book, compared to traditional atlases, is the trilingual approach of Coccolithophore taxonomy. Each species is described in three languages, English, Greek and Italian. In this way these astonishing beautiful marine microorganisms are getting introduced to a broad public and it becomes easier for non-native English speakers - students and researchers - to get acquainted with the scientific terminology. Additionally the combination of both scanning and light microscope techniques provides the most comprehensive documentation of Coccolithophore species morphology.
Two new possible hetero-holococcolithophore combinations are shown: Syracosphaera histrica withS. pulchra HOL oblonga type and S. molischii with Gliscolithus amitakareniae. In addition, an ambiguous combination of S. pulchra HOL oblonga type with S. pulchra HOL pirus type is recorded by light-microscope imaging. Although represented by ambiguous combinations, they potentially document new life-cycle associations within coccolithophores to add to the complexity of haplo-diplontic coccolithophore stages.
This study concerns the species composition and seasonality of extant coccolithophore communities in Eastern Mediterranean coastal environments and investigates their significance as environmental indicators. Water samples were collected during six one-day cruises carried out between 2001 and 2004, in two separate marine ecosystems (Gulfs of Korthi and Kastro, southeastern coast of Andros Island). High species diversities (65 species of heterococcolithophores and 45 species of holococcolithophores), associated with the dominant K-selected taxa, Rhabdosphaeraceae, and holococcolithophores, were recorded during summer whereas low diversities coupled with maximum concentration of cells and the predominance of r-selected species (Emilianiahuxleyi) were observed during late autumn-early spring. The coccolithophores of the upper photic zone have been grouped into four distinct communities (Emiliania huxleyi group, Palusphaera vandelii group, Rhabdosphaeraclavigera group and Helladosphaera cornifera group).A taxonomic study of the modern coccolithophores of Aegean Sea is presented. Several combination coccospheres of Algirosphaera robusta with Sphaerocalyptra quadridentata have been well documented, therefore their synonymy is proposed and the remaining species of Sphaerocalyptra have been transferred to the genus Holococcolithophora. One more holococcolith-heterococcolith association between Corisphaera sp. type A, Zygosphaera bannockii, Zygosphaera amoena and Syracosphaera bannockii is presented, recombining all taxa into Syracosphaera amoena comb. nov. A new species, Holococcolithophora kastriensis sp. nov. is described.
Living coccolithophores were collected in August 2001, at different photic depths (0-120 m), form 8 stations along a transect in the gulf of Korthi (Andros island). The analysis of the vertical distribution of coccolithophores certified high differentiation in density and diversity, as well as in the species composition at different depth levels. As a result, the photic zone is separated into three distinct sub-zones: upper (0-25 m depth), middle (45-60 m depth) and lower (90-120 m depth). The total cell density varies between 14.7x103 cells/l and 1.9x103 cells/l, and is usually higher in the upper and middle photic zone, while in the lower photic zone it gradually decreases. The highest species richness (max=34 taxa) was observed at the middle photic zone. Emiliania huxleyi, Rhabdosphaera clavigera and holococcolithophores preferred the upper photic zone. On the contrary, in the lower photic zone, the presence of Florisphaera profunda and Algirosphaera robusta becomes important, making up the typical deep community. Umbellosphaera tenuis is an additional important component of the summer heterococcolithophore nannoflora, especially in the middle photic zone. The studied coastal marine coccolithophore communities indicate that temperature and availability of nutrient concentrations are the most important controlling factors controlling their vertical distribution.
A quantitative analysis of coccolithophores, planktonic foraminifera and pollen assemblages was carried out on core NS-14 (SE Aegean Sea), recovered in the Western Kos Basin. Eleven coccolithophore (ACE1-11) and ten planktonic foraminifera (APFE1-10) ecozones have been recognized during the last 14 000 yrs using calcareous nannofossil and planktonic foraminifera abundances. Additionally eight pollen assemblage zones (PAZ1-8) have been recognised. The established high resolution ecozonal scheme allows a detailed paleoecological reconstruction for the Holocene archive in the SE Aegean Sea, defining two warm and humid phases (9300-8600 yr cal BP and 7600-6400 yr cal BP) associated with the deposition of S1 and a third one between 5200-4200 yr cal BP.
The main purpose of the present study was the detailed qualitative and quantitative analysis of coccolithophore distribution in the marine ecosystems of the island of Andros and in correlation to the Late Quaternary recording from the region lying central-south of the Aegean Sea region.
A first approach on the reconstruction of the climate history of SE Aegean Sea during the last 18kyrs is recorded in the 400cm-long high sedimentation NS14 core collected in the vicinity of Nisyros Island. The results concerning the sea surface conditions during late Pleistocene-Holocene are acquainted through multi-proxy analyses of algal and organic biomarkers and comparison with pollen assemblages, defining eight paleoenvironmental units that imply their response to climatic changes.
Living coccolithophores were collected, in August, 2001, from eight stations in the Gulf of Korthi (Andros Island, middle Aegean Sea, eastern Mediterranean), in order to determine the cell density, species composition and biogeographical (spatial and vertical) distribution in this coastal marine ecosystem. The holococcolithophore assemblages in the sampled stations sometimes reached more than 50% of the total standing crop, tending to be dominant especially at the shallower stations. Two new species of Sphaerocalyptra were identified and are described and figured here: Sphaerocalyptra dermitzakii sp. nov. and Sphaerocalyptra youngii sp. nov.
Water sampleswere collected for coccolithophore analysis at coastal environments, in August 2002, from 7 stations in the Gulf of Kastro (Andros Island, middle Aegean Sea, Eastern Mediterranean). The studies on coccolithophore regional dynamics in the middle Aegean Sea coastal environments have revealed a unique heterococcolith–holococcolith combination coccosphere indicating a life-cycle association of the taxa Syracosphaera halldalii in Gaarder and Hasle 1971 ex Jordan and Green 1994 and Calyptrolithina divergens var. tuberosa (Heimdal 1980) Jordan et al. 1993. Consequently their systematic taxonomy is emended and the name Syracosphaera halldalii is considered as the appropriate one for the well-established association.
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.
Benthic foraminifera widespread occurrence, numerical abundance and high fossilization potential rank them among the most powerful biological tools to reconstruct paleoenvironments. Their diversity and composition by suborder sometimes provide a general indication of the past environment, but the benthic taxonomic composition and recognition of faunal assemblages allow more detailed assessments of water depth, intertidal level, salinity, exposure to water turbulence, bottom oxygen concentrations, water temperature and carbon flux. The distribution of benthic foraminifera group is determined, and an analysis of the data is made in an effort to isolate and identify important relationships between the distribution of organisms studied and the parameters of the physical environment. Benthic Foraminifera of the Upper Pliocene Tsoutsouras section (southern Crete) are analysed in order to investigate their relationship with paleodepth, sediment grain size and climatic changes. This paper encompasses the first detailed quantitative paleoenvironmental analysis based on benthic foraminifera from this area. Q-mode analysis revealed the existence of three associations. A. beccarii-Miliolids association corresponds to a rather shallow marine environment with vegetation in the neighbourhood. A. planorbis-Agglutinants is characterized by a decline in the salinity and the existence of moderate environmental stress which is associated by oxygen depletion and increase of primary productivity. In the upper part of the section V.bradyana – C. carinata association represents theestablishment of a restricted environment with abundant nutrient, where organic matter accumulates and infaunal opportunistic species capable of surviving in stressed conditions dominate.
Water samples were collected for coccolithophore analysis in August 2001, from 8 stations along a transect in the gulf of Korthi (Andros Island, Aegean sea). Samples were collected from 0-120m water-depth to determine the spatial and vertical distribution of individual holococcolithophore species in coastal environments. Holococcolithophore absolute abundances usually range between 7.29x103 and 0.06x103 cells/l. The distribution patternsi ndicate that holococcolithophores may constitute a significant part of the summer flora in the upper photic zone of the coastal waters of Andros island, providing evidence of vertical distribution in the water column and showing affinities to shallower environments and rather normal nutrification conditions.
Water samples for coccolithophorid analysis were collected in August 2001, from 8 stations along a transect in the gulf of Korthi (Andros Island, Aegean sea). Samples were collected from 0-120m water-depth. Holococcolithophorid absolute abundances usually range between 7.29x103 and 0.06x103 cells/l. The derived distribution patterns indicate that holococcolithophorids bearing holococcoliths with convex cover above the tube, may constitute a significant part of the summer flora in the uppermost photic zone of the coastal waters of Andros island, showing affinities to shallower environments.
National and Kapodistrian University of Athens (+30) 210-7274920 Faculty of Geology and Geoenvironment Panepistimiopolis Zografou Athens, 15784 email@example.com