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Sample records for aegean sea eastern

  1. Static Stress Changes Inverted from Microseismicity in Eastern Aegean Sea

    NASA Astrophysics Data System (ADS)

    Leptokaropoulos, Konstantinos; Papadimitriou, Eleftheria; Orlecka-Sikora, Beata; Karakostas, Vassilios

    2014-05-01

    In this study we attempted to derive static stress field variations from the changes of earthquake production rates in Kusadasi bay and Samos island (eastern Aegean), by applying the Dieterich et al. (2000) Rate/State formulation. The calculation of stress changes from earthquake occurrence rates fluctuations should be obtained from catalogues which achieve adequate spatial and temporal resolution and well determined hypocenter coordinates. For this reason we took advantage of the data from a regional network operating since July of 2007, providing continuous monitoring of microseismicity, along with data available from seismological stations of the permanent Hellenic Unified Seismological Network (HUSN). The high accuracy and large sized regional catalogue is utilized for inverting seismicity rate changes into stress variation through a Rate/State dependent friction model. After explicitly determining the physical parameters incorporating in the modeling (reference seismicity rates, characteristic relaxation time, constitutive properties of fault zones) we investigated stress changes in both space and time regime and their possible connection with earthquake clustering and fault interactions. The main interest is focused on the June 2009 Samos Mw=5.1 event, which was followed by an intense seismic activity for several days. We attempt to reproduce and interpret stress changes both before and after the initiation of this seismic burst. The differences between the earthquake occurrence rates before and after the main shock are used as input data in a stress inversion algorithm based upon the Rate/State dependent friction concept in order to provide an estimation of stress changes. Diverse assumptions and combinations of the parameters values are tested for the model performance and sensitivity to be evaluated. The approach followed here could provide evidence of the robustness of the seismicity rate changes usage as a stress meter for both positive and negative

  2. Vertical distribution of marine cyanobacteria Synechococcus spp. in the Black, Marmara, Aegean, and eastern Mediterranean seas

    NASA Astrophysics Data System (ADS)

    Uysal, Zahit

    2006-08-01

    The vertical distributions of the unicellular cyanobacteria Synechococcus were studied in several highly contrasting seas: the Black Sea, Sea of Marmara, Aegean Sea, and Mediterranean Sea. Cell abundances varied significantly on both vertical and horizontal scales in all physically and spatially discrete water masses. Epifluorescence microscope cell counts from all seas clearly showed that majority of the population remains suspended in the surface-mixed layer and decreases gradually towards the base of the euphotic zone. Surface spatial distributions in the Black Sea were heterogeneous. Salinity, rather than temperature, seemed to have the greatest impact on the surface distribution of cells in this highly eutrophic sea. Changes in abundance in the mixed layer were small compared to the abrupt changes below the halocline, especially in the Black Sea and the Sea of Marmara. In contrast to the Black Sea, the major population remains suspended above the depth of fluorescence maximum in the Aegean and eastern Mediterranean seas. Significant correlations ( r>P0.01) were observed between cell counts and physical and chemical parameters with depth in the Black Sea. In all seas, cells at subsurface chlorophyll- a maximum layer (SCML) reflected brighter and longer fluorescence than those present at the surface and below. Cell size derived from flow cytometry indicated the presence of larger cells at the surface mixed layer compared to those at depth.

  3. Progress of KOERI Tsunami Warning System for the Eastern Mediterranean, Aegean and Black Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Meral Ozel, Nurcan; Ozer Sozdinler, Ceren; Yilmazer, Mehmet; Cokacar, Tulay; Comoglu, Mustafa; Pinar, Ali; Kekovali, Kivanc

    2016-04-01

    This presentation provides a progress report on the activities of the Bogazici University / Kandilli Observatory and Earthquake Research Institute - Regional Earthquake and Tsunami Monitoring Center (KOERI-RETMC) which provides services as a Candidate Tsunami Service Provider (CTSP) of ICG/NEAMTWS in the Eastern Mediterranean, Aegean and Black Seas since 1 July 2012. KOERI continues to operate 178 BB and 97 strong motion and 6 short period sensors and the regional coverage includes 77 stations from GFZ and additional 16 stations through bilateral agreements. One radar-type tide-gauge has been installed in Fethiye within the framework of "Inexpensive Device for Sea-Level Measurement" (IDSL) initiative offered as donation by the EC/JRC and planning is in progress for the possible installation of three more IDSLs in selected locations in the Aegean Sea coast of Turkey. The capabilities and the limitations of HF Radar technology for the purpose of tsunami detection in the Eastern Mediterranean has been identified and the maturity and the applicability of these systems for the possible use under the Tsunami Warning System has been determined. The development of the TsuComp as a user-friendly interface to be used in the assessment of tsunamigenic potential and as a single-point entry for message dissemination has been finalized. The work towards the creation of Tsunami Inundation Maps at the Tsunami Forecast Points in Turkey is near finalization. This work is partially funded by project ASTARTE - Assessment, Strategy And Risk Reduction for Tsunamis in Europe - FP7-ENV2013 6.4-3, Grant 603839. The authors would like to thank EC/JRC and Mr. Alessandro Annunziato for their continuous support in the operational activities of RETMC and IDSL initiative.

  4. Tsunami Warning System for the Eastern Mediterranean, Aegean and Black Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Meral Ozel, Nurcan; Kalafat, Dogan; Comoglu, Mustafa; Ozer Sozdinler, Ceren; Yılmazer, Mehmet; Cevdet Yalçıner, Ahmet

    2015-04-01

    Bogazici University - KOERI is providing a Tsunami Warning System to Eastern Mediterranean, Aegean and Black Seas since 1 July 2012 as a Candidate Tsunami Service Provider (CTSP) within the ICG/NEAMTWS Framework. KOERI continues to operate 129 BB and 86 strong motion and 6 short period sensors. The regional coverage includes 77 stations from GFZ and additional 16 stations through bilateral agreements. During 2014, Romania and Russian Federation have subscribed to its services thanks to 2nd Tsunami Exercise of NEAMTWS - NEAMWave14, reaching a total of 11 NEAMTWS Member States as subscribers. No further progress could have been made in 2014 in the integration of the existing national-tide gauge stations due to the updated plans of the General Command of Mapping in charge of the operation of the national tide-gauge network. Collaborative activities with EC-JRC continued where a comprehensive tsunami scenario database for the Eastern Mediterranean, Aegean and Black Seas has been produced. In addition, KOERI also participated in EC-JRCs Global Tsunami Informal Monitoring Service Project and analyzed 16 tsunamigenic events around the globe. CTSP-TR continued to participate in the Communication Test Exercises (CTE) and Regular CTEs (RegCTE), and acted as the Message Provider for the NEAMWave14 Black Sea Scenario, where Black Sea was covered fort he first time in a NEAMTWS Tsunami Exercise. New Operational Centre has been built and full integration is expected in the first half of 2015. Data preparation activities for the inundation maps at TFPs continued. KOERI also continued to improve its TWS through its involvement of EC funded FP-7 Projects ASTARTE and MARSite and currently focuses on a detailed NEAMTWS Performance Monitoring Framework with associated Key Performance Indicators. This presentation provides a status overview of the operational system while focusing on selected events, such as 12 October 2013 Mw 6.6 and 24 May 2014 Mw 6.9 Northern Aegean earthquakes

  5. Biodiversity of zoobenthic hard-substrate sublittoral communities in the Eastern Mediterranean (North Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Antoniadou, Chryssanthi; Chintiroglou, Chariton

    2005-03-01

    The spatial dispersion of zoobenthos from sublittoral hard substrate communities in the northern part of the Aegean Sea has been studied during summer 1997 and 1998. Material was collected by SCUBA diving, by totally scraping off five replicate quadrates (400 cm 2 each) at three depth levels (15, 30, 40 m) from six sites located in Chalkidiki peninsula, plus one in Kavala Gulf. The examination of the 19,343 living specimens collected revealed the presence of 314 species. Though the multivariate analyses showed high similarity between stations, the structure of this sciaphilic algal community seems to have an increased spatial heterogeneity. Four distinct facies were recorded in accordance with the occurrence of different algal forms, the degree of hard substrate inclination and the water clarity. A short review on the biodiversity of sublittoral communities in the Mediterranean revealed the affinity between the western and the eastern basin and also among the photophilic and the sciaphilic algal communities.

  6. Sea cliff erosion in the eastern part of the North Aegean coastline, Northern Greece.

    PubMed

    Xeidakis, George S; Delimani, P K; Skias, S G

    2006-01-01

    The coastal zone is an area where many human activities are taking place. Erosion of the coast obstructs, in various ways, these activities creating occasionally serious socioeconomic and environmental problems. In this paper the coastal erosion problems encountered in the eastern Greek part of the North Aegean Sea Coast, a stretch of about 51 km long adjacent to the city of Alexandroupolis, are discussed. Given the observed type and location of erosion and other sea-action phenomena, the coast under study is divided in two parts/stretches. The western stretch, where the city of Alexandroupolis is presently extending, presents, mainly, cliff erosion problems and retreat of the coastline, very serious in some sections; whereas, the eastern stretch (to the east of the city) exhibits deposition and progression seawards due to the abundance of sediments supplied by Evros river delta. A classification of the coastline according to its relief, geologic material, erosion characteristics and rate, slope failure phenomena as well as the wave energy potential, is presented together with suggestions for case-appropriate mitigation and protection measures regarding the coastal erosion problems. The paper is focusing on the cliff erosion phenomena, since varying in height coastal cliffs made of soft rocks, cover the major part of the investigated coastline (western stretch).

  7. Food-web traits of the North Aegean Sea ecosystem (Eastern Mediterranean) and comparison with other Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Tsagarakis, K.; Coll, M.; Giannoulaki, M.; Somarakis, S.; Papaconstantinou, C.; Machias, A.

    2010-06-01

    A mass-balance trophic model was built to describe the food-web traits of the North Aegean Sea (Strymonikos Gulf and Thracian Sea, Greece, Eastern Mediterranean) during the mid-2000s and to explore the impacts of fishing. This is the first food-web model representing the Aegean Sea, and results were presented and discussed in comparison to other previous ecosystems modelled from the western and the central areas of the basin (South Catalan and North-Central Adriatic Seas). Forty functional groups were defined, covering the entire trophic spectrum from lower to higher trophic levels. Emphasis was placed on commercial invertebrates and fish. The potential ecological role of the invasive ctenophore, Mnemiopsis leidyi, and several vulnerable groups (e.g., dolphins) was also explored. Results confirmed the spatial productivity patterns known for the Mediterranean Sea showing, for example, that the total biomass is highest in N.C. Adriatic and lowest in N. Aegean Sea. Accordingly, food-web flows and several ecosystem indicators like the mean transfer efficiency were influenced by these patterns. Nevertheless, all three systems shared some common features evidencing similarities of Mediterranean Sea ecosystems such as dominance of the pelagic fraction in terms of flows and strong benthic-pelagic coupling of zooplankton and benthic invertebrates through detritus. The importance of detritus highlighted the role of the microbial food-web, which was indirectly considered through detritus dynamics. Ciliates, mesozooplankton and several benthic invertebrate groups were shown as important elements of the ecosystem linking primary producers and detritus with higher trophic levels in the N. Aegean Sea. Adult anchovy was shown as the most important fish group in terms of production, consumption and overall effect on the rest of the ecological groups in the model, in line with results from the Western Mediterranean Sea. The five fishing fleets considered (both artisanal and

  8. Habitat Selection and Temporal Abundance Fluctuations of Demersal Cartilaginous Species in the Aegean Sea (Eastern Mediterranean)

    PubMed Central

    Maravelias, Christos D.; Tserpes, George; Pantazi, Maria; Peristeraki, Panagiota

    2012-01-01

    Predicting the occurrence of keystone top predators in a multispecies marine environment, such as the Mediterranean Sea, can be of considerable value to the long-term sustainable development of the fishing industry and to the protection of biodiversity. We analysed fisheries independent scientific bottom trawl survey data of two of the most abundant cartilaginous fish species (Scyliorhinus canicula, Raja clavata) in the Aegean Sea covering an 11-year sampling period. The current findings revealed a declining trend in R. clavata and S. canicula abundance from the late ′90 s until 2004. Habitats with the higher probability of finding cartilaginous fish present were those located in intermediate waters (depth: 200–400 m). The present results also indicated a preferential species' clustering in specific geographic and bathymetric regions of the Aegean Sea. Depth appeared to be one of the key determining factors for the selection of habitats for all species examined. With cartilaginous fish species being among the more biologically sensitive fish species taken in European marine fisheries, our findings, which are based on a standardized scientific survey, can contribute to the rational exploitation and management of their stocks by providing important information on temporal abundance trends and habitat preferences. PMID:22536389

  9. Temporal and spatial variations in provenance of Eastern Mediterranean Sea sediments: Implications for Aegean and Aeolian arc volcanism

    NASA Astrophysics Data System (ADS)

    Klaver, Martijn; Djuly, Thomas; de Graaf, Stefan; Sakes, Alex; Wijbrans, Jan; Davies, Gareth; Vroon, Pieter

    2015-03-01

    The Eastern Mediterranean Sea (EMS) is the last remnant of the Tethys Ocean that has been subducted to the north since the Jurassic. Subduction has led to the formation of multiple island arcs in the EMS region where the Aeolian and Aegean arcs are currently active. The EMS is surrounded by continents and receives a large sediment input, part of which is transported down with the subducting slab into the mantle and potentially contributes a major flux to the arc volcanism. An along-arc gradient in the composition of subducting sediment has been evoked to explain the distinct geochemical signature of the easternmost volcanic centre of the Aegean arc, but direct evidence for this proposal is lacking. We present a detailed study of the mineralogical, major-, trace elements and Sr-Nd-Hf-Pb isotope composition of 45 Neogene EMS sediment samples obtained from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill sites and box cores to characterise their geochemical composition, distinguish provenance components and investigate the temporal and spatial variation in provenance to evaluate the potential changing contribution of subducted EMS sediment to Aegean and Aeolian arc volcanism. Based on trace element characteristics of EMS sediments, we can distinguish four provenance components. Nile sediment and Sahara dust are the main components, but contributions from the Tethyan ophiolite belt and arc volcanic rocks in the north are also recognised. Pliocene and Quaternary EMS sediment records a strong geochemical gradient where Nile River sediment entering the EMS in the east is progressively diluted by Sahara Desert dust towards the west. Pre-Messinian samples, however, have a remarkably homogeneous composition with Nile sediment characteristics. We relate this rapid increase in Sahara dust contribution to a late Miocene climate shift leading to decreased Nile runoff and aridification of the Sahara region. EMS sediment has a restricted range in Pb isotopes

  10. Assessing the salinity effect on planktonic foraminiferal Mg/Ca: Evidence from Aegean Sea core-top samples (Eastern Mediterranean).

    NASA Astrophysics Data System (ADS)

    Kontakiotis, G.; Antonarakou, A.; Mortyn, P. G.; Triantaphyllou, M. V.; Martínez-Botí, M. À.; Dermitzakis, M. D.

    2009-04-01

    Recent work across the Mediterranean Sea has illustrated a salinity (S) effect on planktonic foraminiferal Mg/Ca, which potentially confounds the use of this as a temperature (T) proxy for paleoceanographic reconstructions. As a likely illustration of this, recent downcore work revealed Mg/Ca values that were unreasonably high to be explained by T variations alone over the last deglaciation and throughout the Holocene. Modern biochemical and oceanographic studies highlight the Aegean Sea as an especially sensitive part of the Mediterranean that is closely connected to global climatic variability. Especially focused on T and S variations in the upper hundred meters of the water column, where energy storage and heat transport occur, we analyse planktonic foraminiferal Mg/Ca from a series of Aegean core tops, spanning a strong S gradient and little T range along a N-S transect. The aim is to isolate and quantify the S influence on the Mg/Ca tracer as well as possible in a field study from the region. We have specifically targeted the tropical spinose species Globigerinoides ruber, since it is the most ubiquitous species in the eastern Mediterranean and generally occurs in a wide range of T and S conditions. From our initially high core-top Mg/Ca measurements, we estimated how much of this was "excess", defined by amount of Mg/Ca exceeding that predicted using modern observed average summer T and a G. ruber calibration equation from the Western Equatorial Pacific (WEP). We then determined excess S values by subtracting WEP salinity values from those observed in our core-top locations. We observed that our results were in close agreement with those previously found for the Mediterranean as a whole, such that excess Mg/Ca is positively correlated with excess S. In the present study we expand on previous core-top results for the Aegean Sea in order to confirm and better quantify the S effect on G. ruber Mg/Ca signatures, such that paleo-records from this region will be

  11. Recurrent intrusions of transitional waters of Eastern Mediterranean origin in the Cretan Sea as a tracer of Aegean Sea dense water formation events

    NASA Astrophysics Data System (ADS)

    Velaoras, Dimitris; Krokos, George; Theocharis, Alexander

    2015-06-01

    Available temperature and salinity data in the Cretan Sea from 1955 up to 2014 as well as literature sources were revisited in order to trace the appearance of low salinity, temperature, oxygen and nutrient-rich waters inside the basin at depths below the intermediate layer. First appearing as far back as 1961 in literature, these waters were found originating in the layers that separate intermediate and deep waters of the Eastern Mediterranean Sea (EMed) and were named Transitional Mediterranean Water (TMW) in the 1990s. Data analysis showed that the appearance of TMW in the Cretan Sea is a recurrent phenomenon connected to water mass exchanges between the Aegean Sea and the EMed. In particular, the inflow of TMW in the Cretan basin acts as compensation for the outflow of equally dense or denser masses from the Aegean. This export is a result of dense water formation (DWF) events taking place inside the Aegean Sea triggering TMW compensatory inflow into the Cretan Sea through the Cretan Straits. In this context, TMW intrusions in the Cretan basin can be used as a tracer of DWF in the Aegean Sea while the depth of the intrusion can provide valuable information about the intensity of the DWF event. The importance of TMW intrusions is not solely restricted to the tracing and evaluation of DWF events but could additionally expand to the impact on local ecological processes as TMW is a nutrient carrier for the oligotrophic Cretan Sea. It is obvious that this low salinity, temperature and oxygen layer is what was later named TMW. The core temperature, salinity and oxygen values reported by Miller (1974) fall within the range of values observed during the PELAGOS project in 1994, as noted in Section 'Presence of low salinity water masses below the intermediate layer in the Cretan Sea during the EMT event'. Using the same dataset provided by MEDATLAS 2002 database, a salinity transect along the Cretan Sea is reconstructed in Fig. 5. The bottle data originate from the

  12. On the recent seismic activity in North-Eastern Aegean Sea including the Mw5.8 earthquake on 8 January 2013

    PubMed Central

    SARLIS, Nicholas V.

    2013-01-01

    In the last week of November 2012, we announced that a strong electrotelluric disturbance, which we judged to be a Seismic Electric Signal (SES) activity, was recorded at station Assiros located in Northern Greece. This disturbance was actually followed by an Mw5.8 earthquake on 8 January 2013 in North-Eastern Aegean Sea. Here we show that, by analyzing this SES activity and employing the natural time analysis of subsequent seismicity, we estimated the epicentral location, magnitude and occurrence time which are reasonably compatible with those of the Mw5.8 event. PMID:24213207

  13. Depositional environment, foraminifer content and ESR ages of Quaternary Gediz Delta Sediments (Eastern Aegean Sea, İzmir-Western Turkey)

    NASA Astrophysics Data System (ADS)

    Gökçe Benli, Ekin; Aydın, Hülya; İşintek, İsmail; Engin, Birol; Şengöçmen, Berna

    2016-04-01

    Sediments and fossil content of Gediz Delta (Eastern Aegean Sea - İzmir) were examined based on the drilling core samples of the YSK-C and SK-246 drilling. W-SW part of the Delta is represented by continental delta sediments up to 6 meters and shallow marine detritic sediments up to 35 meters in the YSK-C drilling. Continental part consists of an soiled, graveled, muddy and sandy sediment in terms of rich organic substance. As for marine part, it consists of bioclast, muddy, fine graveled sand and by repetition of pebble, sand and bioclast bearing mud layers. Bioclasts comprise of bivalvia, echinoid, ostracod, gastropod, foramifer and bryozoa fragments. Benthic foraminiferal fauna determinated in the marine levels are represented by 55 bethic, 2 planktonic species. These foraminifers and bioclasts reflect that the W-SW part of the delta, has been occured in marine conditions between 8-31m deep. E-NE part of the delta is generally represented by continental sediments up to 43.5m in SK-246 drilling. In addition, it includes marine levels in 18-19 m, 23-24 m and 36-37,5 m intervals. Continental sediments of E-NE part is generally represented by calcareous and sandy mud rocks which mostly includes ash, tuff, and pebble derived from Neogene volcanic rocks. As for marine levels, it is composed of calcareous mud stones and calcareous clay stones including very thin gastropod, bivalvia and ostracod in 18- 19 and 36-37.5 meters whereas it is represented by sandy mud stones including a great deal of bentic foraminifer, bivalvia, bryozoa, echinoid, gastropod in 23-24 metres. Thus show that E-NE part of the delta is usually in continental condition but it is occasionally covered by sea. In aging studies of YSK-C core done by ESR method, age of 8-9 m interval is determined to be 11. 376 ± 0,067 Ka; however ages of 10-11m and 24-25 m intervals are revealed to be 16.466 ± 0,016 Ka and 15.344 ± 0,021 Ka respectively; finally age of 25-26 m interval is found to be 19.995 ± 0

  14. Total and inorganic arsenic levels in some marine organisms from Izmir Bay (Eastern Aegean Sea): a risk assessment.

    PubMed

    Kucuksezgin, Filiz; Gonul, Lutfi Tolga; Tasel, Didem

    2014-10-01

    The arsenic compounds in marine biota were evaluated from Izmir Bay (Eastern Aegean) and found that inorganic arsenic occurred as a minor fraction. No information is available on the annual variations of arsenic in important edible biota species from Izmir Bay. Fish and mussel samples were taken from different regions of Izmir Bay between 2009 and 2011 (n=854 individual specimens). The average percentages of inorganic arsenic to total arsenic for all biota samples were 3.43±3.38% with a range of 0.11-11.8%. The importance of speciation analysis for arsenic is supported by our work, because arsenic is ubiquitous in the ecosystem, and flexible toxicity of arsenic is based on chemical form. The average total As levels in Mullus barbatus were 6 times higher than Diplodus annularis and Mytilus galloprovincialis. This study also revealed that spatial variation influenced the arsenic levels in the fish samples and the highest concentrations of arsenic were found in Gediz site. Our study showed that estimated daily intakes of arsenic via consumption of flesh fish and shell fish were below the BMDL0.5 values established by FAO/WHO. PMID:25048921

  15. Simulating anchovy's full life cycle in the northern Aegean Sea (eastern Mediterranean): A coupled hydro-biogeochemical-IBM model

    NASA Astrophysics Data System (ADS)

    Politikos, D.; Somarakis, S.; Tsiaras, K. P.; Giannoulaki, M.; Petihakis, G.; Machias, A.; Triantafyllou, G.

    2015-11-01

    A 3-D full life cycle population model for the North Aegean Sea (NAS) anchovy stock is presented. The model is two-way coupled with a hydrodynamic-biogeochemical model (POM-ERSEM). The anchovy life span is divided into seven life stages/age classes. Embryos and early larvae are passive particles, but subsequent stages exhibit active horizontal movements based on specific rules. A bioenergetics model simulates the growth in both the larval and juvenile/adult stages, while the microzooplankton and mesozooplankton fields of the biogeochemical model provide the food for fish consumption. The super-individual approach is adopted for the representation of the anchovy population. A dynamic egg production module, with an energy allocation algorithm, is embedded in the bioenergetics equation and produces eggs based on a new conceptual model for anchovy vitellogenesis. A model simulation for the period 2003-2006 with realistic initial conditions reproduced well the magnitude of population biomass and daily egg production estimated from acoustic and daily egg production method (DEPM) surveys, carried out in the NAS during June 2003-2006. Model simulated adult and egg habitats were also in good agreement with observed spatial distributions of acoustic biomass and egg abundance in June. Sensitivity simulations were performed to investigate the effect of different formulations adopted for key processes, such as reproduction and movement. The effect of the anchovy population on plankton dynamics was also investigated, by comparing simulations adopting a two-way or a one-way coupling of the fish with the biogeochemical model.

  16. Eastern-Mediterranean ventilation variability during sapropel S1 formation, evaluated at two sites influenced by deep-water formation from Adriatic and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Filippidi, A.; Triantaphyllou, M. V.; De Lange, G. J.

    2016-07-01

    Present-day bottom-water ventilation in the Eastern Mediterranean basin occurs through deep-water convection originating from the two marginal basins, i.e. Adriatic and Aegean Seas. In the paleo record, long periods of enhanced deep-water formation have been alternating with shorter periods of reduced deep-water formation. The latter is related mainly to low-latitude humid climate conditions and the enhanced deposition and preservation of organic-rich sediment units (sapropels). This study focuses on sedimentary archives of the most-recent sapropel S1, retrieved from two sites under the direct influence of the two deep-water formation areas. Restricted oxygen conditions have developed rapidly at the beginning of S1 deposition in the Adriatic site, but bottom-water conditions have not persistently remained anoxic during the full interval of sapropel deposition. In fact, the variability in intensity and persistence of sedimentary redox conditions at the two deep-water formation sites is shown to be related to brief episodes of climate cooling. In the Adriatic site, sapropel deposition appears to have been interrupted twice. The 8.2 ka event, only recovered at the Adria site, is characterized by gradually increasing suboxic to possibly intermittently oxic conditions and decreasing Corg fluxes, followed by an abrupt re-establishment of anoxic conditions. Another important event that disrupted sapropel S1 formation, has taken place at ca. 7.4 cal ka BP. The latter event has been recovered at both sites. In the Adriatic site it is followed by a period of sedimentary conditions that gradually change from suboxic to more permanently oxic, as deduced from the Mn/Al pattern. Using the same proxy for suboxic/oxic sedimentary redox conditions, we observe that conditions in the Aegean Sea site shift to more permanently oxic from the 7.4 ka event onwards. However, at both sites the accumulation and preservation of enhanced amounts of organic matter have continued under these

  17. Marine pollution risk in a coastal city: use of an eco-genotoxic tool as a stress indicator in mussels from the Eastern Aegean Sea.

    PubMed

    Kacar, Asli; Pazi, Idil; Gonul, Tolga; Kucuksezgin, Filiz

    2016-08-01

    Coastal areas, such as bays, estuaries, and harbors, are heavily polluted since these areas are the settlements to which toxic chemicals from industrial and domestic wastes are discharged. The genetic damage was evaluated using bioindicator mussel Mytilus galloprovincialis caused by toxic chemicals (metals and polycyclic aromatic hydrocarbons) in İzmir and Çandarlı Bays (the Eastern Aegean Sea) through comet assay. Three sampling sites from the two bays were selected and the study was conducted during the spring and autumn periods. The highest levels of DNA damage expressed as %Tail-DNA were observed in İzmir Bay (34.60 % Tail-DNA) in the spring. Analysis of the correlation between PAHs and metals in mussels and %T-DNA in the hemolymph and gill cells showed a statistically significant positive correlation between %T-DNA and ∑PAH, chromium (p < 0.05). This study determined the pollution level of the İzmir and Çandarlı Bays by using the DNA damage to the mussel, which can identify the effects of environmental pollutants at the cellular levels. These results confirm that comet assay can be used to determine the temporal and spatial differences of DNA damage, and as a suitable tool for the measurement of genotoxicity in regions with low pollutant concentrations. PMID:27146544

  18. Marine pollution risk in a coastal city: use of an eco-genotoxic tool as a stress indicator in mussels from the Eastern Aegean Sea.

    PubMed

    Kacar, Asli; Pazi, Idil; Gonul, Tolga; Kucuksezgin, Filiz

    2016-08-01

    Coastal areas, such as bays, estuaries, and harbors, are heavily polluted since these areas are the settlements to which toxic chemicals from industrial and domestic wastes are discharged. The genetic damage was evaluated using bioindicator mussel Mytilus galloprovincialis caused by toxic chemicals (metals and polycyclic aromatic hydrocarbons) in İzmir and Çandarlı Bays (the Eastern Aegean Sea) through comet assay. Three sampling sites from the two bays were selected and the study was conducted during the spring and autumn periods. The highest levels of DNA damage expressed as %Tail-DNA were observed in İzmir Bay (34.60 % Tail-DNA) in the spring. Analysis of the correlation between PAHs and metals in mussels and %T-DNA in the hemolymph and gill cells showed a statistically significant positive correlation between %T-DNA and ∑PAH, chromium (p < 0.05). This study determined the pollution level of the İzmir and Çandarlı Bays by using the DNA damage to the mussel, which can identify the effects of environmental pollutants at the cellular levels. These results confirm that comet assay can be used to determine the temporal and spatial differences of DNA damage, and as a suitable tool for the measurement of genotoxicity in regions with low pollutant concentrations.

  19. Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux Variability on Daily Through Decadal Time Scales

    NASA Technical Reports Server (NTRS)

    Romanski, Joy; Romanou, Anastasia; Bauer, Michael; Tselioudis, George

    2013-01-01

    We analyze daily wintertime cyclone variability in the central and eastern Mediterranean during 1958-2001, and identify four distinct cyclone states, corresponding to the presence or absence of cyclones in each basin. Each cyclone state is associated with wind flows that induce characteristic patterns of cooling via turbulent (sensible and latent) heat fluxes in the eastern Mediterranean basin and Aegean Sea. The relative frequency of occurrence of each state determines the heat loss from the Aegean Sea during that winter, with largest heat losses occurring when there is a storm in the eastern but not central Mediterranean (eNOTc), and the smallest occurring when there is a storm in the central but not eastern Mediterranean (cNOTe). Time series of daily cyclone states for each winter allow us to infer Aegean Sea cooling for winters prior to 1985, the earliest year for which we have daily heat flux observations. We show that cyclone states conducive to Aegean Sea convection occurred in 1991/1992 and 1992/1993, the winters during which deep water formation was observed in the Aegean Sea, and also during the mid-1970s and the winters of 1963/1964 and 1968/1969. We find that the eNOTc cyclone state is anticorrelated with the North Atlantic Oscillation (NAO) prior to 1977/1978. After 1977/1978, the cNOTe state is anticorrelated with both the NAO and the North Caspian Pattern (NCP), showing that the area of influence of large scale atmospheric teleconnections on regional cyclone activity shifted from the eastern to the central Mediterranean during the late 1970s. A trend toward more frequent occurrence of the positive phase of the NAO produced less frequent cNOTe states since the late 1970s, increasing the number of days with strong cooling of the Aegean Sea surface waters.

  20. Black Sea and Mediterranean Sea interaction: influence of the North Aegean dynamics

    NASA Astrophysics Data System (ADS)

    Androulidakis, Yannis; Krestenitis, Yannis; Kourafalou, Vassiliki

    2013-04-01

    The brackish Black Sea Waters outflow to the Aegean Sea, through the Dardanelles Straits, affects and determines significantly the hydrodynamic and physical characteristics of the Aegean Sea. At the same time, it affects several biological parameters, like chl-a concentrations, and, therefore, the general quality of the marine environment. The investigation and mathematical simulation of the North Aegean's physical oceanography contributes to the knowledge and understanding of the buoyant waters' circulation initial conditions in the wider East Mediterranean region. The implementation and adaptation of the 3-d hydrodynamic mathematical model HYCOM (Hybrid Coordinate Ocean Model) in the North Aegean Sea (1/50οx1/50o), significantly contributes to the investigation of the area's hydrodynamic circulation. HYCOM, due to its hybrid coordinate operation, can describe at a satisfactory level, all the different topography and mixing cases of the complicated N. Aegean region. In addition, the high resolution atmospheric forcing and the nesting with a data assimilated broader Mediterranean HYCOM model along the southern open boundary of the North Aegean model, benefit the quality of the results and constitutes an important tool on the description and understanding of the Black Sea influence to the region's dynamics. A fundamental objective is the application and comparison of different Dardanelles outflow parameterizations based a) on the Black Sea water budget, b) on current measurements from a telemetric station in Limnos Island, and c) on historical time series. The Black Sea Waters plume evolution and the circulation patterns are dependant on the outflow rate magnitude, the flow distribution inside the straits and the prevailing winds. The long-term simulation covers the period of the last 20 years (1990-2010), investigating several physical characteristics of the North Aegean Sea, such as the deep water masses evolution, the major Black Sea waters circulation patterns

  1. Old stories and lost pieces of the Eastern Mediterranean puzzle: a new approach to the tectonic evolution of the Western Anatolia and the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Yaltırak, Cenk; Engin Aksu, Ali; Hall, Jeremy; Elitez, İrem

    2015-04-01

    During the last 20 or so years, the tectonic evolution of Aegean Sea and Western Anatolia has been dominantly explained by back-arc extension and escape tectonics along the North Anatolian Fault. Various datasets have been considered in the construction of general tectonic models, including the geometry of fault patterns, paleomagnetic data, extensional directions of the core complexes, characteristic changes in magmatism and volcanism, the different sense of Miocene rotation between the opposite sides of the Aegean Sea, and the stratigraphy and position of the Miocene and Pliocene-Quaternary basins. In these models, the roles of the Burdur-Fethiye Shear Zone, the Trakya-Eskişehir Fault Zone, the Anaximander Mountains and Isparta Angle have almost never been taken into consideration. The holistic evaluation of numerous land and marine researches in the Aegean Sea and western Anatolia suggest the following evolutionary stages: 1. during the early Miocene, Greece and western Anatolia were deformed under the NE-SW extensional tectonics associated with the back-arc extension, when core complexes and supra-detachment basins developed, 2. following the collision of the Anaximander Mountains and western Anatolia in early Miocene , the Isparta Angle locked this side of the western arc by generating a triangle-shaped compressional structure, 3. while the Isparta Angle penetrated into the Anatolia, the NE-striking Burdur-Fethiye Shear Zone in the west and NW-striking Trakya-Eskişehir Fault Zone in the north developed along the paleo-tectonic zones , 4. the formation of these two tectonic structures allowed the counterclockwise rotation of the western Anatolia in the middle Miocene and this rotation removed the effect of the back-arc extension on the western Anatolian Block, 5. the counterclockwise rotation developed with the early westward escape of the Western Anatolian reached up to 35-40o and Trakya-Eskişehir Fault Zone created a total dextral displacement of about 200

  2. Monitoring sea level fluctuation in South Aegean

    NASA Astrophysics Data System (ADS)

    Zacharis, Vangelis; Paradissis, Demitris; Drakatos, George; Marinou, Aggeliki; Melis, Nicolaos; Anastasiou, Demitris; Alatza, Stavroula; Papanikolaou, Xanthos

    2015-04-01

    The complexity of the geological setting of the South Aegean is well-known, among the scientific community. The subduction zone coupled with the latest unrest of the Santorini volcano, as well as the particular morphology of the earth's surface and seabed pose a poorly understood source of tsunami hazard. A sparse network of tide gauges that operate in the area for varying periods of time is strengthened by the establishment of new sensors at carefully selected locations, by the Institute of Geodynamics of the National Observatory of Athens, and the Dionyssos Satellite Observatory and the Laboratory of Higher Geodesy of the National Technical University of Athens. These new instruments, aided by a rather dense network of GNSS receivers, provide a more concrete basis for the development, testing and evaluation of a near real-time model of the sea level changes in the area. Moreover, integration with various other sensors allows to understand and assess the level of tsunami risk in the area.

  3. Physical and chemical processes of air masses in the Aegean Sea during Etesians: Aegean-GAME airborne campaign.

    PubMed

    Tombrou, M; Bossioli, E; Kalogiros, J; Allan, J D; Bacak, A; Biskos, G; Coe, H; Dandou, A; Kouvarakis, G; Mihalopoulos, N; Percival, C J; Protonotariou, A P; Szabó-Takács, B

    2015-02-15

    High-resolution measurements of gas and aerosols' chemical composition along with meteorological and turbulence parameters were performed over the Aegean Sea (AS) during an Etesian outbreak in the framework of the Aegean-GAME airborne campaign. This study focuses on two distinct Etesian patterns, with similarities inside the Marine Atmospheric Boundary Layer (MABL) and differences at higher levels. Under long-range transport and subsidence the pollution load is enhanced (by 17% for CO, 11% for O3, 28% for sulfate, 62% for organic mass, 47% for elemental carbon), compared to the pattern with a weaker synoptic system. Sea surface temperature (SST) was a critical parameter for the MABL structure, turbulent fluxes and pollutants' distribution at lower levels. The MABL height was below 500 m asl over the eastern AS (favoring higher accumulation), and deeper over the western AS. The most abundant components of total PM1 were sulfate (40-50%) and organics (30-45%). Higher average concentrations measured over the eastern AS (131 ± 76 ppbv for CO, 62.5 ± 4.1 ppbv for O3, 5.0 ± 1.1 μg m(-3) for sulfate, 4.7 ± 0.9 μg m(-3) for organic mass and 0.5 ± 0.2 μg m(-3) for elemental carbon). Under the weaker synoptic system, cleaner but more acidic air masses prevailed over the eastern part, while distinct aerosol layers of different signature were observed over the western part. The Aitken and accumulation modes contributed equally during the long-range transport, while the Aitken modes dominated during local or medium range transport. PMID:25460953

  4. An integrated multi-parameter monitoring approach for the quantification and mitigation of the climate change impact on the coasts of Eastern Crete, S. Aegean Sea (Project AKTAIA)

    NASA Astrophysics Data System (ADS)

    Ghionis, George; Alexandrakis, George; Karditsa, Aikaterini; Sifnioti, Dafni; Vousdoukas, Michalis; Andreadis, Olympos; Petrakis, Stelios; Poulos, Serafim; Velegrakis, Adonis; Kampanis, Nikolaos; Lipakis, Michalis

    2014-05-01

    The AKTAIA project aims at the production of new knowledge regarding the forms of manifestation of the climate change and its influence on the stability and evolution of the coastal landforms along the shoreline of eastern Crete (approximate length: 757 km), taking into account the various aspects of human intervention. Aerial photographs, satellite images and orthophotomaps have been used to produce a detailed coastline map and to study the morphological characteristics of the coastal zone of Eastern Crete. More than 100 beach zones have been visited during three field campaigns, which included geomorphological and human intervention mapping, topographic, meteorological and oceanographic measurements and sedimentological sampling and observations. In addition, two pilot sites (one in the north and one in the south part of Crete) are being monitored, via the installation of coastal video monitoring systems, shore-based meteorological stations and wave-tide recorders installed in the nearshore zone. Detailed seafloor mapping with the use of side scan sonar and scuba diving and bathymetric surveys were conducted in the two pilot sites. Meteorological and oceanographic data from all existing land-based meteorological stations, oceanographic buoys and the ERA-interim dataset are used to determine the wind and wave climate of each beach. The collected climatic, sedimentological and coastal environmental data are being integrated in a GIS database that will be used to forecast the climatic trends in the area of Crete for the next decades and to model the impact of the climatic change on the future evolution of the coastal zone. New methodologies for the continuous monitoring of land-sea interaction and for the quantification of the loss of sensitive coastal zones due to sea-level rise and a modified Coastal Vulnerability Index for a comparative evaluation of the vulnerability of the coasts are being developed. Numerical modelling of the nearshore hydrodynamics and the

  5. Wild fire effects on floristic diversity in three thermo-Mediterranean vegetation types in a small islet of eastern Aegean sea

    NASA Astrophysics Data System (ADS)

    Abraham, Eleni; Kyriazopoulos, Apostolos; Korakis, George; Parissi, Zoi; Chouvardas, Dimitrios

    2014-05-01

    Sclerophyllus scrub formations, the main vegetation type in many islands of the Aegean area, are characterized by their high biodiversity. Dominant shrub species of sclerophyllus formations are well adapted to dry season conditions by various anatomical and physiological mechanisms. As a result, their biomass acts as very flammable fine fuel, and consequently wild fires are very common in these ecosystems. Wildfire effects on vegetation and biodiversity in the Mediterranean basin have been studied and the results are diverse depending mainly on vegetation type and frequency of fire. The aim of this study was to evaluate the effects of wildfire on floristic diversity and species composition in three thermo-Mediterranean vegetation types 1) Sacropoterium spinosum phrygana, 2) low formations of Cistus creticus and 3) low formations of Cistus creticus in abandoned terraces. The research was conducted in Enoussa islet, which is located northeastern of Chios Island, in May 2013 (one year after the fire). Vegetation sampling was performed along five transects placed in recently burned and in adjacent unburned sites of each vegetation type. The plant cover and the floristic composition were measured, while diversity, evenness and dominance indices were determined for the vegetation data. Vegetation cover and the floristic diversity were significant lower and higher respectively in burned areas in comparison to the unburned. The woody species followed by the annual grasses and the annual forbs dominated in both burned and unburned areas. However, the woody species were significantly decreased in the burned areas in all vegetation types, while the annual grasses only in the burned areas of Sacropoterium spinosum phrygana and Cistus creticus in abandoned terraces. Inversely, the annual forbs significantly increased in the burned sites of Cistus creticus formations. The highest value of Morisita-Horn Index of similarity between burned and unburned sites (beta diversity) was

  6. Modeling of Tsunami Propagation and Inundation in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Aydin, B.; Moore, C. W.; Kalligeris, N.; Kanoglu, U.

    2011-12-01

    Several tsunami forecasting systems have been developed based on pre-computed tsunami scenario databases with the aim to provide early warning to tsunami-prone regions worldwide. NOAA's tsunami forecasting system for the United States is such a system, based on the concept of a pre-computed tsunami scenario database consisting of 100km x 50km fault planes with a slip value of 1m, referred to as tsunami source functions. These source functions are placed along the subduction zones in several rows, covering known faults throughout the major ocean basins. Linearity of the tsunami propagation in the open ocean allows scaling and/or combination of the pre-computed tsunami source functions since propagation of tsunamis in deep sea is linear. In real time, a specific tsunami scenario can be obtained by inverting deep-ocean buoy measurements providing initial and boundary conditions for site-specific, high-resolution, nonlinear forecast models. The database can also be used to generate different scenario events to produce tsunami inundation maps for target shorelines. To date, tsunami source functions have not been computed along the subduction zones in Aegean Sea even though there are considerable number of tsunami events causing damages. Although one might argue that the possibility of such an event is rare, the coastlines are densely populated, developed, and hosts millions of tourists during the summer months. Therefore, even though the risk of an event might be small, the hazard is high. Considering the long shorelines and the general lack of public knowledge about preparedness, a tsunami event in the region would be disastrous. A database for historical tsunami events in the Aegean Sea has been compiled, providing potential source locations. This data has allowed us to create a tsunami propagation database for Aegean Sea. Once finalized, this pre-computed scenario database will be extremely useful in developing tsunami resilient communities in the region.

  7. Major outputs of the recent multidisciplinary biogeochemical researches undertaken in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Lykousis, V.; Chronis, G.; Tselepides, A.; Price, N. B.; Theocharis, A.; Siokou-Frangou, I.; Van Wambeke, F.; Danovaro, R.; Stavrakakis, S.; Duineveld, G.; Georgopoulos, D.; Ignatiades, L.; Souvermezoglou, A.; Voutsinou-Taliadouri, F.

    2002-06-01

    The main outputs of a multidisciplinary and integrated studies are summarised. The results incorporate the latest biogeochemical researches, at basin scale, in the Aegean Sea (including thermohaline circulation studies, SPM dynamics, mass and energy fluxes, acknowledge biochemical processes in the euphotic and the benthic layer and benthic response to downward fluxes). The data were acquired within five (seasonal) research cruises, during 1997-1998. Data analysis and evaluation hence provided important new information on the functional processes of the Aegean ecosystem. In terms of water circulation, no new deep water formation in the Aegean Sea was observed, during 1997-1998, but rather intermediate water, due mainly to the mild winter conditions. All the biochemical parameters of the euphotic zone (nutrients, Particulate Organic Carbon (POC), chlorophyll- a, phytoplankton, primary and bacterial production), although high in the N. Aegean Sea reflect clearly the highly oligotrophic character of the Aegean Sea. In the N. Aegean, microbial food web was the main pathway of carbon, whereas in the S. Aegean, the food web could be classified as multivorous. An important Black Sea Water (BSW) signal was observed in the dissolved phase; this was especially pronounced in the Dissolved Organic Carbon (DOC), Mn and to a lesser degree to Cd, Cu and Ni concentrations. The downward material fluxes are higher in the N. Aegean, relative to the S. Aegean. Substantially higher values of near-bottom mass fluxes were measured in the deep basins of the N. Aegean, implying significant deep lateral fluxes of POM. The N. Aegean could be classified as a "continental margin" ecosystem, whilst the S. Aegean is a typical "oceanic margin" environment. There is a close relationship and, consequently, coupling between the near-bottom mass fluxes and the accumulation rates of organic matter (OM), with the near-bottom mineralisation, bioturbation, redox potential, oxygen consumption rates, the

  8. Particulate and dissolved primary production along a pronounced hydrographic and trophic gradient (Turkish Straits System-NE Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Lagaria, A.; Psarra, S.; Gogou, A.; Tuğrul, S.; Christaki, U.

    2013-06-01

    The rates of particulate (PPp) and dissolved primary production (PPd) were estimated along a trajectory of variable environmental regimes formed in a narrow shelf area, following the course of Black Sea water masses (BSW) passing through the Turkish Straits System (TSS) into the NE Aegean Sea (BS-AS outflow). Seven stations in total were sampled, covering a transect from the eastern edge of the Marmara Sea basin to the NE Aegean Sea, during two consecutive cruises performed in October 2008 within the framework of the EU SESAME project. Along the BS-AS outflow, depth-integrated over the surface BSW layer PPp decreased considerably from 91 to < 16 mg C m- 2 h- 1 whereas PPd increased from 3 to 10 mg C m- 2 h- 1. As a consequence, the relative importance of PPd over total production (percentage extracellular release, PER) increased from 6% (± 3% sd) in the Marmara Sea to 37% (± 4% sd) in the NE Aegean Sea. Total chlorophyll a concentration gradually decreased and phytoplankton community size-structure was modified, with pico-phytoplankton, that originally represented 35% (± 9% sd) in the Marmara Sea, gradually becoming dominant in the NE Aegean (77% ± 2% sd), substituting large nano- and micro-phytoplankton cells (> 5 μm). This study showed that PER increased along a gradient from mesotrophy to oligotrophy, probably due to nutrient deficiency constraining phytoplankton growth and was closely related to phytoplankton size-structure. In the oligotrophic NE Aegean Sea, phytoplankton exudation was a significant source of dissolved organic carbon for heterotrophic prokaryotes.

  9. Severe accidents due to windsurfing in the Aegean Sea.

    PubMed

    Kalogeromitros, A; Tsangaris, H; Bilalis, D; Karabinis, A

    2002-06-01

    Windsurfing is a popular sport and has recently become an Olympic event. As an open-air water activity that requires the participant to be in perfect physical condition, windsurfers may be prone to accidents when certain basic rules or procedures are violated. The current study monitored severe injuries due to windsurfing over a period of 12 months in the Aegean Sea in Greece. Our study revealed 22 cases of severe accidents due to windsurfing, with a wide range of injuries including head injuries, spinal cord injuries, and severe fractures of the extremities. Prolonged hospitalization, severe disability and two deaths occurred as consequences of these accidents. The study examined the characteristics of these patients and the possible risk factors and conditions associated with the accidents. We also focused on the most common types of injuries and reviewed the mechanisms that may provoke them. Water sports and particularly windsurfing represent a major challenge for the emergency medical system, especially in the Aegean Sea. Hundreds of islands, kilometres of isolated coasts, millions of tourists, an extended summer period and rapidly changing weather create conditions that constantly test the efficacy of the emergency services. The development of an appropriate infrastructure and maximum control of the risk factors causing these accidents could reduce the morbidity and mortality that, unfortunately but rather predictably, accompany this popular summer activity. PMID:12131638

  10. Assimilating Ferry Box data into the Aegean Sea model

    NASA Astrophysics Data System (ADS)

    Korres, G.; Ntoumas, M.; Potiris, M.; Petihakis, G.

    2014-12-01

    Operational monitoring and forecasting of marine environmental conditions is a necessary tool for the effective management and protection of the marine ecosystem. It requires the use of multi-variable real-time measurements combined with advanced physical and ecological numerical models. Towards this, a FerryBox system was originally installed and operated in the route Piraeus-Heraklion in 2003 for one year. Early 2012 the system was upgraded and moved to a new high-speed ferry traveling daily in the same route as before. This route is by large traversing the Cretan Sea being the largest and deepest basin (2500 m) in the south Aegean Sea. The HCMR Ferry Box is today the only one in the Mediterranean and thus it can be considered as a pilot case. The analysis of FerryBox SST and SSS in situ data revealed the presence of important regional and sub-basin scale physical phenomena, such as wind-driven coastal upwelling and the presence of a mesoscale cyclone to the north of Crete. In order to assess the impact of the FerryBox SST data in constraining the Aegean Sea hydrodynamic model which is part of the POSEIDON forecasting system, the in situ data were assimilated using an advanced multivariate assimilation scheme based on the Singular Evolutive Extended Kalman (SEEK) filter, a simplified square-root extended Kalman filter that operates with low-rank error covariance matrices as a way to reduce the computational burden. Thus during the period mid-August 2012-mid January 2013 in addition to the standard assimilating parameters, daily SST data along the ferryboat route from Piraeus to Heraklion were assimilated into the model. Inter-comparisons between the control run of the system (model run that uses only the standard data set of observations) and the experiment where the observational data set is augmented with the FerryBox SST data produce interesting results. Apart from the improvement of the SST error, the additional assimilation of daily of FerryBox SST

  11. Exploration of the Black, Aegean, and Mediterranean Seas Aboard E/V Nautilus

    NASA Astrophysics Data System (ADS)

    Bell, K. L.; Ballard, R. D.; Brennan, M. L.; Raineault, N. A.; Shank, T. M.; Mayer, L. A.; Roman, C.; Mitchell, G. A.; Coleman, D. F.

    2012-12-01

    In the summer of 2012, the Exploration Vessel (E/V) Nautilus undertook a two-month expedition to the Black, Aegean, and Mediterranean Seas. The primary goal of the Nautilus is to create a focus of international leadership for the development and integration of leading-edge technologies, educational programs, field operations, and public outreach programs for ocean exploration, in partnership with the NOAA Office of Ocean Exploration, National Geographic Society, Office of Naval Research, and corporate partners. To do so, the program uses a complement of deep submergence vehicle systems and telepresence technologies to engage scientists, educators and the public, both at sea and ashore, allowing them to become integral members of the on-board exploration team. When discoveries are made, experts ashore are notified and brought aboard virtually within a short period of time to help guide shipboard response before the ship moves on. The 2012 expedition is comprised of four areas of interest. Extensive sidescan mapping took place off the Turkish coasts of the southern Black Sea and eastern Aegean Sea, and was followed by remotely operated vehicle (ROV) dives on targets of archaeological, geological, and biological interest. In the Black Sea, additional work was done on the porewater chemistry of the sediments in the oxic, suboxic, and anoxic zones. Nautilus returned to the Anaximander Seamounts, including Kazan, Amserdam, Thessaloniki, and Athina, to further explore active and formerly active seep sites located in 2010. Finally, based on biological and geological discoveries made on Eratosthenes Seamount in the eastern Mediterranean Sea, we returned to further study chemosynthetic vent communities and tectonic processes.;

  12. Frequent underwater volcanism in the central Aegean Sea

    NASA Astrophysics Data System (ADS)

    Huebscher, C.; Ruhnau, M.; Dehghani, G. A.

    2012-04-01

    The extinction of the Minoan culture in the mid second millennium BCE is a well known consequence of the Plinian eruption of Thera volcano (Santorini Island). Santorini is a member of the South Aegean arc forming a chain from the Gulf of Saronikos (Susaki, Egina, Poros, Methana) at West, to an area close to the Anatolian coast at East (Kos, Nisyros and minor islands), through the central part (Milos and Santorini island groups). Underwater volcanic activity was manifested historically only once. During 1649-1650 CE the Kolumbo underwater volcano evolved about 8 km northeast of Santorini. As a consequence of this eruption volcanic ash covered the entire Aegean area and a hazardous tsunami was triggered. Here we show by means of reflection seismic and magnetic data that underwater volcanism occurred more frequently in the central Aegean Sea than previously assumed. Seismic data show that Kolumbo constitutes of five vertically stacked cones of pyroclastic sediment plus at least four smaller cones on the flank of the volcano. The formation of Kolumbo started synchronous with Santorini Island. The entire volume of the Kolumbo pyroclastic cones is estimated to more than 15 cubic-kilometers. Several small-scale cones have been detected in the Anyhdros Basin some km north-east of Kolumbo, being previously interpreted as mud volcanoes by other authors. However, the similarity of seismic and magnetic signatures of these cones and Kolumbo strongly suggest that these cones were also created by underwater volcanism. Volcanic cones, Kolumbo and Santorini are situated along a NE-SW striking graben system that evolved during five extensional tectonic pulses in the Pliocene.

  13. Source mechanism of the 2014 Aegean Sea earthquake

    NASA Astrophysics Data System (ADS)

    Nakano, Masaru

    2016-04-01

    Rapid determination of centroid moment tensor (CMT) of earthquakes, namely the source centroid location, focal mechanism, and magnitude is important for early disaster responses and issuing Tsunami warnings. In order to evaluate capability of Turkey seismic network for rapid determinations of CMT, I investigate the source mechanism of the 2014 Aegean Sea earthquake (Mw 6.9). Although this event occur out of Turkey seismic network, I obtained stable CMT solution. The CMT solution of this earthquake represents a strike-slip fault, consistent with the geometry of the North Anatolian Fault (NAF), and the source-time function indicates that this event comprised several distinct subevents. Each subevent is considered to have ruptured a different fault segment. This observation indicates the existence of a mechanical barrier, namely a NAF segment boundary, at the hypocenter. I also determined CMT solutions of background seismicity. CMT solutions of background seismicity beneath the Aegean Sea represent strike-slip or normal faulting along the NAF or its branch faults. The tensional axes of these events are oriented northeast-southwest, indicating a transtensional tectonic regime. Beneath the Sea of Marmara, the CMT solutions represent mostly strike-slip faulting, consistent with the motion of the NAF, but we identified a normal fault event with a tensional axis parallel to the strike of the NAF. This mechanism indicates that a pull-apart basin, marking a segment boundary of the NAF, is developing there. Because ruptures of a fault system and large earthquake magnitudes are strongly controlled by the fault system geometry and fault length, mapping fault segments along NAF can help to improve the accuracy of scenarios developed for future disastrous earthquakes in the Marmara region.

  14. Flux measurements in the surface Marine Atmospheric Boundary Layer over the Aegean Sea, Greece.

    PubMed

    Kostopoulos, V E; Helmis, C G

    2014-10-01

    Micro-meteorological measurements within the surface Marine Atmospheric Boundary Layer took place at the shoreline of two islands at northern and south-eastern Aegean Sea of Greece. The primary goal of these experimental campaigns was to study the momentum, heat and humidity fluxes over this part of the north-eastern Mediterranean Sea, characterized by limited spatial and temporal scales which could affect these exchanges at the air-sea interface. The great majority of the obtained records from both sites gave higher values up to factor of two, compared with the estimations from the most widely used parametric formulas that came mostly from measurements over open seas and oceans. Friction velocity values from both campaigns varied within the same range and presented strong correlation with the wind speed at 10 m height while the calculated drag coefficient values at the same height for both sites were found to be constant in relation with the wind speed. Using eddy correlation analysis, the heat flux values were calculated (virtual heat fluxes varied from -60 to 40 W/m(2)) and it was found that they are affected by the limited spatial and temporal scales of the responding air-sea interaction mechanism. Similarly, the humidity fluxes appeared to be strongly influenced by the observed intense spatial heterogeneity of the sea surface temperature.

  15. Reconstructing Holocene sea surface salinity changes in the Northern Aegean Sea: evidence from morphological variations of Emiliania huxleyi-coccoliths

    NASA Astrophysics Data System (ADS)

    Herrle, Jens O.; Gebühr, Christina; Bollmann, Jörg; Giesenberg, Annika; Kranzdorf, Philip

    2013-04-01

    The Aegean Sea is a key area for our understanding of the impact of changes in the hydrological cycle on ocean circulation in the Mediterranean Sea. The Aegean Sea appears to be very sensitive to climate changes in Europe because of its small volume and the position between high- and low-latitude climate regimes. Therefore, it is assumed to record environmental change, especially changes in sea surface water salinity (SSS) without a significant time lag with respect to the forcing process (Rohling et al., 2002). However, up to date, SSS cannot be easily reconstructed from geological archives because several assumptions need to be made that lead to a significant error of the salinity estimates (e.g. Rohling, 2000). Here, we present the first high resolution SSS reconstruction from a Holocene sediment core based on a recently developed transfer function using the morphological variation of Emiliania huxleyi coccoliths (Bollmann & Herrle 2007, Bollmann et al., 2009). The core is located in the northern Aegean Sea (eastern Mediterranean Basin) and covers the time period 3 -11ka ago. Sea surface water salinity in the Aegean Sea has varied in concert with temperature oscillations as recorded in Greenland ice cores (iGISP2 ice core δ18O record) with a periodicity of about 900 years (Schulz & Paull, 2002). Four major SSS events can be identified at about 3.9, 4.7, 6.4, 7.4, and 8.2 ka in the northern Aegean Sea that correlate with increases in GISP2 δ18O (Schulz & Paull, 2002) as well as decreasing percentages of tree pollen studied at the same core expect for 3.9 ka (Kotthoff et al., 2008). The most prominent salinity increase occurred during the short-lived 8.2 kyr cold event (e.g., Rohling & Pälike, 2005), which was most likely triggered by a melt-water related perturbation of the Atlantic Meridional Overturning and associated decrease of ocean heat transport to the North Atlantic. We suggest that the salinity fluctuations in the northern Aegean Sea are related to

  16. Anisakidae infection in fish of the Aegean Sea.

    PubMed

    Chaligiannis, Ilias; Lalle, Marco; Pozio, Edoardo; Sotiraki, Smaragda

    2012-03-23

    Nematode worms of the family Anisakidae are the causative agents of infections in humans when fish is consumed raw and of serious allergies up to the death, when fish is consumed raw or cooked by previously sensitized people. From April until November 2009, 462 fish belonging to 26 species, fished in three areas of the Aegean Sea were tested for Anisakidae larvae. Anisakidae larvae were detected in 87 (18.83%) fish of 13 species. These larvae were identified by morphology as the third-stage larvae of the genera Hysterothylacium sp. or Anisakis. Larvae of the genus Anisakis were identified by PCR-RFLP as belonging to A. simplex s.str., A. pegreffii, or as hybrids between A. simplex s.str and A. pegreffii. PMID:22030376

  17. The influence of Black Sea Water inflow and its synoptic time-scale variability in the North Aegean Sea hydrodynamics

    NASA Astrophysics Data System (ADS)

    Mavropoulou, Apostolia-Maria; Mantziafou, Anneta; Jarosz, Ewa; Sofianos, Sarantis

    2016-02-01

    The exchange water fluxes between the Black Sea and the North Aegean Sea through the Dardanelles Strait constitute an essential factor for the general circulation of the region. The Black Sea Water (BSW) inflow to the Aegean plays an important role in the hydrography and circulation of the basin and can affect the North Aegean deep water formation processes. Numerical experiments evaluating the influence of the time-scale variability (synoptic and seasonal) and the seasonality (period of maximum/minimum) of the Black Sea Water inflow on the dynamics of the North Aegean basin were performed. The experiments were carried out for the period from August 2008 to October 2009, using observed upper and lower-layer fluxes from the Dardanelles Strait, high-resolution atmospheric forcing, and boundary conditions derived from an operational system (ALERMO). The large-scale spatial patterns of the circulation and the seasonal variability of the North Aegean circulation show that dynamics of the basin can effectively absorb most of the Black Sea Water inflow variability. The overall cyclonic circulation of the North Aegean Sea and the predominant cyclonic and anti-cyclonic features are robust and are little affected by the different lateral fluxes. However, differences in the seasonality of the BSW inflow have an important impact in the North Aegean water column structure, while the synoptic variability observed in the Black Sea Water inflow affects the kinetic energy of the basin and the pathway of the Black Sea Water plume.

  18. Bacterial and organic matter distribution in the sediments of the Thracian Sea (NE Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Polymenakou, Paraskevi N.; Fragkioudaki, Glykeria; Tselepides, Anastasios

    2007-10-01

    Recently, black carbon has been introduced as the form of carbon that may be separated from the biologically mediated carbon cycle thereby representing the non-bioavailable fraction of the estimated organic carbon. It has been speculated that the bioavailability of organic matter may be a limiting factor for the presence of active bacteria within the sediments. In order to address this question, marine sediments were collected from the Thracian Sea (Eastern Mediterranean), a complex system impacted by riverine inputs and Black Sea water masses. In addition to counts of total bacteria, we estimated the fraction of active bacteria by using a destaining step to the DAPI staining method. Black carbon was also estimated following the thermal oxidation method in order to determine the fraction of the refractory organic matter. The fraction of black carbon to total organic carbon varied from 16% to 53% indicating that black carbon constitutes a significant pool of sedimentary organic carbon in the Thracian sea. A fraction ranging from 18% to 97% was scored as nucleoid containing cells. We did not record any significant differences in the fraction of nucleoid-containing bacteria among sediment depths ( P<0.05) indicating that there was no accumulation of dead bacterial cells with depth. The same was observed for the fraction of black carbon and bioavailable organic carbon with sediment depth ( P<0.05) indicating that benthic consumers are not the key regulators of the organic matter pool in these sediments but have a minor effect. A possible reason for these observations and for the uncoupling between the active bacterial fraction and the bioavailability of organic matter could be (i) the presence of refractory components in the estimated bioavailable organic matter and (ii) the hydrological and geological complexity of the study area. The North Aegean marginal slopes are highly unstable experiencing frequent seismic events. These events are capable of inducing sediment

  19. Tsunami Propagation Database for the Mediterranean and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Kanoglu, U.; Hoto, O.; Kalligeris, N.; Flouri, E.; Aydin, B.; Moore, C. W.; Synolakis, C. E.

    2012-12-01

    Pre-computed tsunami scenario databases are common tools to develop long- or short-term forecasting methodologies and hazard assessment approaches for tsunami-prone regions worldwide. The benefits of such databases include the possibility of probabilistic studies (Gonzalez et al., 2009, J. Geophys. Res. 114, Article Number: C11023), inundation mapping (Barberopoulou et al., 2011, Pure Appl. Geophys. 168(11), 2133-2146), or real-time forecasting (Wei et al., 2008, Geophys. Res. Lett. 35(4), Article Number: L04609). As a result, several tsunami propagation databases have been developed including one by NOAA's Pacific Marine Environmental Laboratory (PMEL), and another by the Australian Bureau of Meteorology (BOM). Pre-computed tsunami scenario databases utilize different approaches. PMEL's tsunami propagation database is based on the concept of a pre-computed tsunami scenarios consisting of propagation results from 100km x 50km fault planes with a slip value of 1m referred to as tsunami source functions. PMEL's source functions are placed along the subduction zones in several rows, covering known faults throughout the major ocean basins. Linearity of the tsunami propagation in the open ocean allows scaling and/or combination of the pre-computed tsunami source functions to generate a desired scenario. The BOM database considers five earthquakes with magnitudes changing from 7.0 to 9.0 at each location with 100km intervals along the subduction zone. However, to date, no similar approach has been computed along the subduction zones in the Aegean and Mediterranean Seas, even though, historically, there have been a considerable number of tsunami events which caused damage in the region (Ambraseys and Synolakis, 2010, J. Earthquake Eng. 14 (3), 309-330, Article Number: PII 919600673). A new project was initiated between Greece and Turkey supported by General Secretariat for Research & Technology, The Ministry for Development (GSRT) of Greece and The Scientific and

  20. Upper Cenozoic organic-rich sequences (offshore and onshore the south Aegean sea)

    SciTech Connect

    Anastasakis, G.

    1988-08-01

    The upper Cenozoic sedimentary column of the south Aegean Sea is composed mostly of marine sediments which have been deposited after the Seravallian breakup of the south Aegean landmass. Extensive submarine coring has revealed the frequent occurrence of Quaternary dark, organic-rich layers in the cores retrieved from water depths greater than 180 m. Moreover, deep-sea drilling (DSDP leg 42A) in the south Aegean basin recovered organic-rich layers as old as late Miocene. Onshore the south Aegean Sea islands, organic-rich sediments are found at the north and south territories of the region, on Milos and Crete islands. Especially on the island of Crete and south of it, on the smaller islands of Gavdos and Koufonisi, these organic-rich sediments represent a considerable portion of the widespread upper Cenozoic sediments. Stratigraphically they cover the interval between upper Seravallian and lower Pleistocene. The organic carbon content of all these mostly calcareous lithofacies, the so-called sapropels, ranges mostly between 0.5 and 6.5%. The most reliably chronostratigraphically correlated upper Pleistocene sapropels display similar compositional characteristics across the entire basin. Certain Pleistocene and older organic-rich layers contain increased proportions of siliceous tests. However the entire range of sapropels in the region (except those within the Messinian evaporites) can be described adequately by the same lithofacies association. To demonstrate this the authors compare the lower Tortonian Faneromeni Formation on Crete with the upper Quaternary sediments from the south Aegean Sea.

  1. Modelling the impact of Black Sea water inflow on the North Aegean Sea hydrodynamics

    NASA Astrophysics Data System (ADS)

    Tzali, Margarita; Sofianos, Sarantis; Mantziafou, Anneta; Skliris, Nikolaos

    2010-06-01

    The impact of the Black Sea Water (BSW) inflow on the circulation and the water mass characteristics of the North Aegean Sea is investigated using a high-resolution 3D numerical model. Four climatological numerical experiments are performed exploring the effects of the exchange amplitude at the Dardanelles Straits in terms of the mean annual volume exchanged and the amplitude of its seasonal cycle. Larger inflow of low salinity BSW influences the water characteristics of the whole basin. The largest salinity reduction is encountered in the upper layers of the water column, and the most affected region is the northeastern part of the basin. The winter insulation character of the BSW layer (low-salinity layer) is reduced by the seasonal cycle of the inflow (minimum during winter). The maximum atmospheric cooling coincides with the minimum BSW inflow rate, weakening the vertical density gradients close to the surface and thus facilitating the vertical mixing. The inflow rate of BSW into the North Aegean Sea constitutes an essential factor for the circulation in the basin. Increased inflow rate results into considerably higher kinetic energy, stronger circulation and reinforcement of the mesoscale circulation features. Although the position of the front between BSW and waters of Levantine origin does not vary significantly with the intensity of the BSW inflow rate, the flow along the front becomes stronger and more unstable as the inflow rate increases, forming meanders and rings. The changes in the intensity of BSW inflow rate overpower the wind and thermohaline forcing and largely determine the general circulation of the North Aegean Sea.

  2. Symbiosis of sea anemones and hermit crabs: different resource utilization patterns in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Vafeiadou, Anna-Maria; Antoniadou, Chryssanthi; Chintiroglou, Chariton

    2012-09-01

    The small-scale distribution and resource utilization patterns of hermit crabs living in symbiosis with sea anemones were investigated in the Aegean Sea. Four hermit crab species, occupying shells of nine gastropod species, were found in symbiosis with the sea anemone Calliactis parasitica. Shell resource utilization patterns varied among hermit crabs, with Dardanus species utilizing a wide variety of shells. The size structure of hermit crab populations also affected shell resource utilization, with small-sized individuals inhabiting a larger variety of shells. Sea anemone utilization patterns varied both among hermit crab species and among residence shells, with larger crabs and shells hosting an increased abundance and biomass of C. parasitica. The examined biometric relationships suggested that small-sized crabs carry, proportionally to their weight, heavier shells and increased anemone biomass than larger ones. Exceptions to the above patterns are related either to local resource availability or to other environmental factors.

  3. A new approach to the structural features of the Aegean Sea: Cellular neural network

    NASA Astrophysics Data System (ADS)

    Aydogan, Davut; Elmas, Ali; Albora, A. Muhittin; Ucan, Osman N.

    2005-03-01

    In this study, structural features in the Aegean Sea were investigated by application of Cellular Neural Network (CNN) and Cross-Correlation methods to the gravity anomaly map. CNN is a stochastic image processing technique, which is based on template optimization using neighbourhood relationships of pixels, and probabilistic properties of two-Dimensional (2-D) input data. The performance of CNN can be evaluated by various interesting real applications in geophysics such as edge detection, data enhancement and separation of regional/residual potential anomaly maps. In this study, CNN is used in edge detection of geological bodies closer to the surface, which are masked by other structures with various depths and dimensions. CNN was first tested for (prismatic) synthetic examples and satisfactory results were obtained. Subsequently, CNN/Cross-Correlation maps and bathymetric features were evaluated together to obtain a new structural map for most of the Aegean Sea. In our structural map, the locations of the faults and basins are generally in accordance with the previous maps from restricted areas based on seismic data. In the southern and southeastern parts of the Aegean Sea, E-W trending faults cut NE-SW trending basins and faults, similar to on-shore Western Anatolia. Also, in the western, central and northern parts of the Aegean Sea, all of these structures are truncated by NE-trending faults.

  4. Shallow structure and recent evolution of the Aegean Sea deduced from the seismic reflection analysis

    SciTech Connect

    Laure, M.; Mascle, J.

    1988-08-01

    Together with the Tyrrhenian Sea, the Aegean Sea represents one of two marine basins still developing as a consequence of the subduction of the African lithosphere beneath Europe. Despite many geophysical similarities with the Tyrrhenian Sea, the Aegean displays a specific structural segmentation characterized by two distinct domains separated by the central Aegean. To the north of the basin, the so-called North Aegean trough likely represents the western marine extension of the transtensive Anatolian transform fault zone. The northern margin of this area contains a series of disconnected, often thickly sedimented small basins that probably initiated during the late Miocene as a consequence of a dominantly north-south extension; typical uppermost Miocene (Messinian) formations can be observed on seismic grounds. To the south, the Cretan Sea shows clear evidence of important distensive events occurring during two main episodes and following two main trends; a dominantly north-south-directed extension is responsibile for most of the structural features detected along both the Cretan and southern Cyclades margins.

  5. Structure of flows in the Northern Aegean Sea from a pilot drifter array

    NASA Astrophysics Data System (ADS)

    Kourafalou, V.; Olson, D.; Johns, W.; Kontoyiannis, H.; Zervakis, V.

    2003-04-01

    An array of thirty drifters deployed in the northern Aegean are used to consider the circulation in a complex archipelago of islands. The circulation of the Aegean is largely influenced by a combination of buoyancy from freshwaters introduced from the Black Sea via the Dardenelles Straits and from coastal rivers and by wind forcing. The latter is highly structured as the winds along the axis of the Aegean Sea are channeled between the orography of the Greek peninsula and islands. The above mechanisms are revealed in the drifter tracts. Preferred pathways that mark transport and exchange between the northern and southern parts of the basin are also evident. The drifters equipped with hourly GPS location and holly sock drogues provide information of time and space scales that have not been routinely sampled before. After a brief review of the overall circulation outlined by the array, the statistics of the turbulent field and its variation for the various subbasins are described. Of special interest are coastal plumes, motions induced as fluid passes between sub-basins, and the nature of cyclonic flows trapped within deep topographic pockets through the Aegean. An initial comparison of eddy statistics in relationship to wind events is also reported.

  6. Microbial activities at the benthic boundary layer in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Bianchi, A.; Tholosan, O.; Garcin, J.; Polychronaki, T.; Tselepides, A.; Buscail, R.; Duineveld, G.

    2003-05-01

    During the Aegean Sea component of the EU MTP-MATER project, benthic samples were acquired along a depth gradient from two continental margins in the Aegean Sea. Sampling was undertaken during spring and summer 1997 and the microbial metabolic activities measured (Vmax for aminopeptidase activity, 14C-glutamate respiration and assimilation) displayed seasonal variability even in deep-sea conditions. The metabolic rates encountered in the North Aegean (average depth 566±234 m), were approximately five-fold higher than in the deeper (1336±140 m) Southern part of the Aegean. The aminopeptidase rates, however, were the exception with higher values recorded in the more oligotrophic sediments of the Southern stations (1383±152 vs. 766±297 nmol MCA cm -2 h -1). A discrepancy in bacterial metabolism also appeared in the near bottom waters. In the Southern stations, 80% of the glutamate uptake was used for energy yielding processes and only 20% devoted to biomass production, while in the North Aegean, most of the used glutamate was incorporated into bacterial cells. During the early burial stages, bacterial mineralization rates estimated from 14C-glutamate respiration decreased drastically compared to the rates of biopolymer hydrolysis estimated by aminopeptidase assays. Thus, at the 2-cm depth layer, these rates were only 32 and up to 77% of the corresponding average values, respectively, in the superficial layer. Such a discrepancy between the evolution of these two metabolic activities is possibly due to the rapid removal of readily utilizable monomers in the surface deposits. The correlation between bacterial respiration and total organic carbon, or total organic nitrogen, is higher in the surficial sediment (0-2 and 2-4 cm) than in the underlying layer. Conversely, it is only at 4-cm depth layer that the hydrolysis rates appear correlated with organic carbon and nitrogen concentrations. This pattern confirms the drastic degradation of organic matter during the

  7. On dense water formation in shelves of the Aegean Sea during the year 1987

    NASA Astrophysics Data System (ADS)

    Salusti, Ettore; Bellacicco, Marco; Anagnostou, Christos; Rinaldi, Eleonora; Tripsanas, Efthymios

    2015-04-01

    We here investigate the role of the rather virgin year 1987, when some modern data are available but before the main EMT event. A combination of field, satellite and numerical model temperature and salinity data from PROTHEUS, as well as a coupled ocean-atmosphere model, are used to implement theoretical models. After its formation over a sloping shelf of some important points in the Aegean Sea, due to the strong cold winter winds, a dense water patch can either have a dramatic downflow or can start a slow geostrophic descent along shelves and then following isobaths, best described by streamtube models. The most important, among these shelves characterized by a strong air sea interaction, have been identified from satellite data. The Northernmost shelves are those north of the island of Samothrace and in the Northern Thermaikos Gulf. In agreement with the field measuraments of Georgopoulos et al. (1987) also the shallow shelf between Limnos and Goceada was a source of very dense water, as well as thr shelf between Lesbos and the Turkish coast. Most probably also the shelves around the Cycladic Plateau were affected by strong winds and contributed to the Aegean Sea deep water formation. In addition, other theoretical models of wind-induced coastal upwelling allow to infer temperature and salinity information of dense water dynamics along the shallow coasts and shelves of the Aegean Sea. All this allows a heuristic application of classical T/S diagrams to estimate Northern Aegean dense water evolution and spreading, that nicely supports the early ideas of Zervakis et al. (2000). A complex situation about the Cycladic Plateau dynamics is also analyzed in correlation with sediment locations. Indeed seismic-reflection profiles confirm the presence of a contourite location along the northeast Cyclades Plateau shelves. All this interestingly opens novel prospective about the dense water coastal formation shelves. In synthesis such field, numerical and satellite data

  8. Large-scale bioprospecting of cyanobacteria, micro- and macroalgae from the Aegean Sea.

    PubMed

    Montalvão, Sofia; Demirel, Zeliha; Devi, Prabha; Lombardi, Valter; Hongisto, Vesa; Perälä, Merja; Hattara, Johannes; Imamoglu, Esra; Tilvi, Supriya Shet; Turan, Gamze; Dalay, Meltem Conk; Tammela, Päivi

    2016-05-25

    Marine organisms constitute approximately one-half of the total global biodiversity, being rich reservoirs of structurally diverse biofunctional components. The potential of cyanobacteria, micro- and macroalgae as sources of antimicrobial, antitumoral, anti-inflammatory, and anticoagulant compounds has been reported extensively. Nonetheless, biological activities of marine fauna and flora of the Aegean Sea have remained poorly studied when in comparison to other areas of the Mediterranean Sea. In this study, we screened the antimicrobial, antifouling, anti-inflammatory and anticancer potential of in total 98 specimens collected from the Aegean Sea. Ethanol extract of diatom Amphora cf capitellata showed the most promising antimicrobial results against Candida albicans while the extract of diatom Nitzschia communis showed effective results against Gram-positive bacterium, S. aureus. Extracts from the red alga Laurencia papillosa and from three Cystoseira species exhibited selective antiproliferative activity against cancer cell lines and an extract from the brown alga Dilophus fasciola showed the highest anti-inflammatory activity as measured in primary microglial and astrocyte cell cultures as well as by the reduction of proinflammatory cytokines. In summary, our study demonstrates that the Aegean Sea is a rich source of species that possess interesting potential for developing industrial applications. PMID:26902670

  9. Numerical simulations of tsunamis generated by underwater volcanic explosions at Karymskoye lake (Kamchatka, Russia) and Kolumbo volcano (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Ulvrová, M.; Paris, R.; Kelfoun, K.; Nomikou, P.

    2014-02-01

    Increasing human activities along the coasts of the world provoke the necessity to assess tsunami hazard from different sources (earthquakes, landslides, volcanic activity). In this paper, we simulate tsunamis generated by underwater volcanic explosions from (1) a submerged vent in a shallow water lake (Karymskoye Lake, Kamchatka), and (2) from Kolumbo submarine volcano (7 km NE of Santorini, Aegean Sea, Greece). The 1996 tsunami in Karymskoye lake is a well-documented example and thus serves as a case study for validating the calculations. The numerical model reproduces realistically the tsunami run-ups measured onshore. Systematic numerical study of tsunamis generated by explosions of the Kolumbo volcano is then conducted for a wide range of energies. Results show that in case of reawakening, the Kolumbo volcano might represent a significant tsunami hazard for the northern, eastern and southern coasts of Santorini, even for small-power explosions.

  10. Numerical simulations of tsunami generated by underwater volcanic explosions at Karymskoye lake (Kamchatka, Russia) and Kolumbo volcano (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Ulvrová, M.; Paris, R.; Kelfoun, K.; Nomikou, P.

    2013-11-01

    Increasing human activities along the coasts of the world arise the necessity to assess tsunami hazard from different sources (earthquakes, landslides, volcanic activity). In this paper, we simulate tsunamis generated by underwater volcanic explosions from (1) a submerged vent in a shallow water lake (Karymskoye Lake, Kamchatka), and (2) from Kolumbo submarine volcano (7 km NE of Santorini, Aegean Sea, Greece). The 1996 tsunami in Karymskoye lake is a well-documented example and thus serves as a case-study for validating the calculations. The numerical model reproduces realistically the tsunami runups measured onshore. Systematic numerical study of tsunamis generated by explosions of Kolumbo volcano is then conducted for a wide range of energies. Results show that in case of reawakening, Kolumbo volcano might represent a significant tsunami hazard for the northern, eastern and southern coasts of Santorini, even for small-power explosions.

  11. Assessment of ENSEMBLES regional climate models for the representation of monthly wind characteristics in the Aegean Sea (Greece): Mean and extremes analysis

    NASA Astrophysics Data System (ADS)

    Anagnostopoulou, Christina; Tolika, Konstantia; Tegoulias, Ioannis; Velikou, Kondylia; Vagenas, Christos

    2013-04-01

    The main scope of the present study is the assessment of the ability of three of the most updated regional climate models, developed under the frame of the European research project ENSEMBLES (http://www.ensembles-eu.org/), to simulate the wind characteristics in the Aegean Sea in Greece. The examined models are KNMI-RACMO2, MPI-MREMO, and ICTP - RegCM3. They all have the same spatial resolution (25x25km) and for their future projections they are using the A1B SRES emission scenarios. Their simulated wind data (speed and direction) were compared with observational data from several stations over the domain of study for a time period of 25 years, from 1980 to 2004 on a monthly basis. The primer data were available every three or six hours from which we computed the mean daily wind speed and the prevailing daily wind direction. It should be mentioned, that the comparison was made for the grid point that was the closest to each station over land. Moreover, the extreme speed values were also calculated both for the observational and the simulated data, in order to assess the ability of the models in capturing the most intense wind conditions. The first results of the study showed that the prevailing winds during the winter and spring months have a north - northeastern or a south - south western direction in most parts of the Aegean sea. The models under examination seem to capture quite satisfactorily this pattern as well as the general characteristics of the winds in this area. During summer, winds in the Aegean Sea have mainly north direction and the models have quite good agreement both in simulating this direction and the wind speed. Concerning the extreme wind speed (percentiles) it was found that for the stations in the northern Aegean all the models overestimate the extreme wind indices. For the eastern parts of the Aegean the KNMI and the MPI model underestimate the extreme wind speeds while on the other hand the ICTP model overestimates them. Finally for the

  12. Focal mechanism determinations of earthquakes along the North Anatolian fault, beneath the Sea of Marmara and the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Nakano, Masaru; Citak, Seckin; Kalafat, Doğan

    2015-09-01

    We determined the centroid moment tensor (CMT) solutions of earthquakes that occurred along the North Anatolian fault (NAF) beneath the Sea of Marmara and the Aegean Sea, using data obtained from Turkey's broad-band seismograph network. The CMT solution of the 2014 Aegean Sea earthquake ( Mw 6.9) represents a strike-slip fault, consistent with the geometry of the NAF, and the source-time function indicates that this event comprised several distinct subevents. Each subevent is considered to have ruptured a different fault segment. This observation indicates the existence of a mechanical barrier, namely a NAF segment boundary, at the hypocenter. CMT solutions of background seismicity beneath the Aegean Sea represent strike-slip or normal faulting along the NAF or its branch faults. The tensional axes of these events are oriented northeast-southwest, indicating a transtensional tectonic regime. Beneath the Sea of Marmara, the CMT solutions represent mostly strike-slip faulting, consistent with the motion of the NAF, but we identified a normal fault event with a tensional axis parallel to the strike of the NAF. This mechanism indicates that a pull-apart basin, marking a segment boundary of the NAF, is developing there. Because ruptures of a fault system and large earthquake magnitudes are strongly controlled by the fault system geometry and fault length, mapping fault segments along NAF can help to improve the accuracy of scenarios developed for future disastrous earthquakes in the Marmara region.

  13. Oblique opening of Skyros Basin in the North Aegean Sea, based on Morphotectonic Analysis

    NASA Astrophysics Data System (ADS)

    Papanikolaou, Dimitris; Nomikou, Paraskevi; Livanos, Isidoros; Papantoniou, George; Rousakis, Grigoris; Lampridou, Danai

    2015-04-01

    Detailed analysis of swath bathymetry and seismic reflection profiling has revealed the morphotectonic structure of the Skyros Basin in North Aegean Sea (Greece). The overall geometry of the basin is shaped by a major slope discontinuity, separating the continental platform from the continental slope at depths between 200-400m. The basin forms an equilateral triangle. Its base is 50km long NW-SE trending at the southwest, parallel to the Skyros Island, whereas its pic is located at the northeast, north of Lesvos Island. The basin comprises 9 sub-basins at depths varying from 1200m at the southwest to 600m to the northeast and is structurally divided into three parts: i) the eastern part forms a longitudinal semi-graben with one sub-basin trending ENE-WSW of 45km length, but only 5-8 Km width at depths varing between 600-700m. This sub-basin is bounded to the south by a marginal fault of >1.5km throw but with unknown horizontal displacement. ii) the central part that forms the predominant part of the triangle with 45 Km long NW-SE trending base and 70km long axis at the NE-SW direction. The central part corresponds to an assymetric graben with a 70km long major marginal fault with >1500m throw along its southern slopes and a 70 km long antithetic fault with >400m throw along its northern slopes. It comprises 5 sub-basins with depths ranging between 950-700m, bounded by important E-W trending strike slip fault zones, characterized by flower structures, with minor vertical components ranging from a few meters up to 200m. iii) the western part of the basin trends NW-SE, is 55 Km long and 25 Km wide, revealing a NW-SE tectonic graben. It comprises two sub-basins, oriented NW-SE separated by an intermediate transverse fault zone. The throw of the western marginal faults offshore Skyros Island exceeds 1200m, whereas the throw of the parallel faults creating the NW-SE tectonic graben is limited to a few hundreds meters. It should be emphasized that the Alpine basement was

  14. A new contribution to the Late Quaternary tephrostratigraphy of the Mediterranean: Aegean Sea core LC21

    NASA Astrophysics Data System (ADS)

    Satow, C.; Tomlinson, E. L.; Grant, K. M.; Albert, P. G.; Smith, V. C.; Manning, C. J.; Ottolini, L.; Wulf, S.; Rohling, E. J.; Lowe, J. J.; Blockley, S. P. E.; Menzies, M. A.

    2015-06-01

    Tephra layers preserved in marine sediments can contribute to the reconstruction of volcanic histories and potentially act as stratigraphic isochrons to link together environmental records. Recent developments in the detection of volcanic ash (tephra) at levels where none is macroscopically visible (so-called 'crypto-tephra') have greatly enhanced the potential of tephrostratigraphy for synchronising environmental and archaeological records by expanding the areas over which tephras are found. In this paper, crypto-tephra extraction techniques allow the recovery of 8 non-visible tephra layers to add to the 9 visible layers in a marine sediment core (LC21) from the SE Aegean Sea to form the longest, single core record of volcanic activity in the Aegean Sea. Using a novel, shard-specific methodology, sources of the tephra shards are identified on the basis of their major and trace element single-shard geochemistry, by comparison with geochemical data from proximal Mediterranean volcanic stratigraphies. The results indicate that the tephra layers are derived from 14 or 15 separate eruptions in the last ca 161 ka BP: 9 from Santorini; 2 or 3 from Kos, Yali, or Nisyros; 2 from the Campanian province; and one from Pantelleria. The attributions of these tephra layers indicate that 1) inter-Plinian eruptions from Santorini may have produced regionally significant tephra deposits, 2) marine tephrostratigraphies can provide unique and invaluable data to eruptive histories for island volcanoes, and 3) tephra from both Pantelleria and Campania may be used to correlate marine records from the Aegean Sea to those from the Tyrrhenian, Adriatic and Ionian Seas.

  15. Trichoptera biodiversity of the Aegean and Adriatic sea basins in the republic of Kosovo.

    PubMed

    Ibrahimi, Halil; Kučinić, Mladen; Gashi, Agim; Grapci-Kotori, Linda

    2014-01-01

    We present the first preliminary inventory of Trichoptera taxa in the Aegean and Adriatic Sea basins in Kosovo that have previously received poor and fragmentary attention. Adult caddisflies were collected using ultraviolet (UV) light traps in 13 stations in areas of the Aegean Sea and Adriatic Sea drainage basins in Kosovo. Nineteen species out of 82, reported in this article, are first records for the Kosovo caddisfly fauna. Five genera are recorded for the first time in Kosovo: Brachycentrus, Ecclisopteryx, Psilopteryx, Thremma, and Oecetis. During this investigation, we found several Southeastern European endemic and rare species whose previous known distribution was limited to particular areas of this region, as well as other species whose distribution is considerably enlarged by this investigation: Polycentropus ierapetra, Polycentropus irroratus, Chaetopteryx stankovici, Drusus schmidi, Drusus tenellus, Potamophylax goulandriourum, Oecetis notata, and Notidobia melanoptera. Even though this article is a result of a limited sampling effort, it increases the number of Trichoptera taxa recorded for the Republic of Kosovo to 131.

  16. Trichoptera biodiversity of the Aegean and Adriatic sea basins in the republic of Kosovo.

    PubMed

    Ibrahimi, Halil; Kučinić, Mladen; Gashi, Agim; Grapci-Kotori, Linda

    2014-01-01

    We present the first preliminary inventory of Trichoptera taxa in the Aegean and Adriatic Sea basins in Kosovo that have previously received poor and fragmentary attention. Adult caddisflies were collected using ultraviolet (UV) light traps in 13 stations in areas of the Aegean Sea and Adriatic Sea drainage basins in Kosovo. Nineteen species out of 82, reported in this article, are first records for the Kosovo caddisfly fauna. Five genera are recorded for the first time in Kosovo: Brachycentrus, Ecclisopteryx, Psilopteryx, Thremma, and Oecetis. During this investigation, we found several Southeastern European endemic and rare species whose previous known distribution was limited to particular areas of this region, as well as other species whose distribution is considerably enlarged by this investigation: Polycentropus ierapetra, Polycentropus irroratus, Chaetopteryx stankovici, Drusus schmidi, Drusus tenellus, Potamophylax goulandriourum, Oecetis notata, and Notidobia melanoptera. Even though this article is a result of a limited sampling effort, it increases the number of Trichoptera taxa recorded for the Republic of Kosovo to 131. PMID:25434031

  17. Volcano-tectonic evolution of the polygenetic Kolumbo submarine volcano/Santorini (Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Hübscher, Christian; Ruhnau, M.; Nomikou, P.

    2015-01-01

    Here we show for the first time the 3D-structural evolution of an explosive submarine volcano by means of reflection seismic interpretation. Four to five vertically stacked circular and cone-shaped units consisting mainly of volcaniclastics build the Kolumbo underwater volcano which experienced its first eruption > 70 ka ago and its last explosive eruption 1650 AD, 7 km NE of Santorini volcano (southern Aegean Sea). The summed volume of volcaniclastics is estimated to range between 13-22 km3. The entire Kolumbo volcanic complex has a height of ≥ 1 km and a diameter of ≥ 11 km. All volcaniclastic units reveal the same transparent reflection pattern strongly suggesting that explosive underwater volcanism was the prevalent process. Growth faults terminate upwards at the base of volcaniclastic units, thus representing a predictor to an eruption phase. Similarities in seismic reflection pattern between Kolumbo and near-by volcanic cones imply that the smaller cones evolved through explosive eruptions as well. Hence, the central Aegean Sea experienced several more explosive eruptions (≥ 23) than previously assumed, thus justifying further risk assessment. However, the eruption columns from the smaller volcanic cones did not reach the air and- consequently - no sub-aerial pyroclastic surge was created. The Anydros basin that hosts Kolumbo volcanic field opened incrementally NW to SE and parallel to the Pliny and Strabo trends during four major tectonic pulses prior to the onset of underwater volcanism.

  18. Growth and feeding patterns of European anchovy ( Engraulis encrasicolus) early life stages in the Aegean Sea (NE Mediterranean)

    NASA Astrophysics Data System (ADS)

    Catalán, Ignacio A.; Folkvord, Arild; Palomera, Isabel; Quílez-Badía, Gemma; Kallianoti, Fotini; Tselepides, Anastasios; Kallianotis, Argyris

    2010-01-01

    The objective of this work was to describe inter- and intra-annual variations in the environmental characteristics of the North-eastern Aegean Sea and to relate these changes to the egg and larval distributions, growth and feeding of larval anchovy ( Engraulis encrasicolus). Four cruises, two in July and two in September in 2003 and 2004 were performed. The distributions of eggs and larvae were associated with i) salinity fronts related to the Black Sea Water and ii) shallow areas of high productivity over the continental shelf, some of them with high riverine influence. The first published description of the anchovy larval diet in the Eastern Mediterranean was conducted in individuals ranging from 2.2 to 17 mm standard length. The number of non-empty guts was relatively high (between 20% and 30%), and the diet was described through 15 main items. The mean size of the prey increased with larval size, and was generally dominated by prey widths smaller than 80 μm (mainly the nauplii and copepodite stages of copepods). Small larvae positively selected copepod nauplii. As larvae grew, they shifted to larger copepod stages. At all sizes, larvae rejected abundant taxa like cladocerans. The average trophic level calculated for anchovy of all size ranges was 2.98 ± 0.16 (SE). Growth rates varied from 0.41 to 0.75 mm d -1, with the highest growth rates generally observed in September. Variability in the Black Sea Water influence and the recorded inter- and intra-annual changes in primary and secondary production, combined with marked changes in temperature over the first 20 m depth, are used to frame the discussion regarding the observed significant differences in growth rates in terms of both length and weight.

  19. Assessment of impact of geochemical and environmental properties on the meiofauna (benthic foraminifer, ostracod, mollusc) assemblages: A case study in The Late Quaternary Sediments In The Gulf Of Izmir (Eastern Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Yümün, Zeki Ü.

    2016-04-01

    The drilling samples collected from varying depths at 1.00-13.00 m at four different localities of Karsiyaka, Bayrakli, Inciralti and Urla (Çesmealti) in the Gulf of Izmir were studied for their geochemical, sedimantological and micropaleontological properties. The purpose of this study is to describe the meiofauna of the sediments, to determine the pollution history of the gulf and to show the effect of the pollution on the foraminifera and ostracoda. Examination of the loose sediments reveals that the gulf has been affected by the sea for a long time, and it had a rich microfaunal assemblages. Both foraminiferal tests and ostracod carapaces have coloring, and morphological abnormalities have been determined in foraminiferal tests. Peneroplis pertusus (Forskal) and P. planatus (Fichtel and Moll) have blue and black colored tests, while morphological abnormalities were observed on the tests of Ammonia compacta Hofker, Elphidium complanatum (d'Orbigny), E. crispum (Linné), E. macellum (Fichtel and Moll). The ostracod carapaces are generally gray-black colored. Heavy metal (Cr, Mn, Zn, Co, Ni, Cu) analyses have been carried out on the sediments of the Gulf of Izmir. Heavy metal concentrations are high in Bayrakli, and low in Urla (Çesmealti). Cr, Mn and Zn values are the highest in Bayrakli, whereas Co, Ni and Cu values are the highest in Inciralti. Scanning Electron Microscope (SEM) analyses were performed and no heavy metal was detected on the white and colored ostracod carapaces. When the white and colored ostracod carapaces are compared, the coloured ostracode carapace has higher Mg content, and also includes Fe, Al, N, Cl and K. Based on the results obtained, it is observed that the Bayrakli region have been more affected by the pollution than Urla (Çesmealti).

  20. Distribution of organotin compounds in the bivalves of the Aegean Sea, Greece.

    PubMed

    Chandrinou, S; Stasinakis, A S; Thomaidis, N S; Nikolaou, A; Wegener, J W

    2007-02-01

    Five bivalve species--Mytilus galloprovinciallis (Mediterranean mussels), Venus gallina (stripped venus), Modiola barbatus L. (bearded horse mussels), Pecten jacobeus (scallops) and Callista chione (hard clams)--were collected from seven areas in Aegean Sea, Greece, between August 2001 and January 2003 and analyzed for organotins (OTs). The concentrations (as geometric means) found were 17.1 ng g-1 for tributyltin (TBT), 18.8 ng g-1 for dibutytltin (DBT), 7.8 ng g-1 for monobutyltin (MBT) and 13.0 ng g-1 for triphenyltin (TPhT) (wet weight), which are at similar or lower levels than those reported worldwide. Studying OTs distribution between different bivalve species, lower concentrations were observed in mediterranean mussels, possibly due to their growth in water column (grown on sea net pens in mussel farms), in contrast to the free-ranging species, collected from fishing grounds. Concentrations of the OTs in the examined bivalves varied seasonally. PMID:17067676

  1. Model simulation of the drift and spread of the Aegean Sea oil spill near La Coruna

    SciTech Connect

    Daniel, P.

    1994-12-31

    On the 3 December 1992 the Greek oil tanker Aegean Sea ran aground at Torre de Hercules near the entrance to the Ria de Coruna and La Coruna harbor, Spain. The 291 m tanker of 114,036-dwt carrying 79,096 tons of Brent type crude oil, broke up and exploded. Practically all of the oil was released into the sea. Over 200 km of shore was affected. A two-dimensional depth-integrated model on a .25 ft. x .25 ft. grid was implemented with the capability of predicting wind driven movements in the area of La Coruna. It is driven by meteorological analysis from the European Centre for Medium Range Weather Forecasts (ECMRWF) global numerical weather prediction model.

  2. The Etesian wind system and wind energy potential over the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Dafka, Stella; Xoplaki, Elena; Garcia-Bustamante, Elena; Toreti, Andrea; Zanis, Prodromos; Luterbacher, Juerg

    2013-04-01

    The Mediterranean region lies in an area of great climatic interest since it is influenced by some of the most relevant mechanisms of the global climate system. In the frame of the three Europe 2020 priorities for a smart, sustainable and inclusive economy delivering high levels of employment, productivity and social cohesion, the Mediterranean energy plan is of paramount importance at the European level, being an area with a significant potential for renewable energy from natural sources that could play an important role in responding to climate change effects over the region. We present preliminary results on a study of the Etesian winds in the past, present and future time. We investigate the variability and predictability of the wind field over the Aegean. Statistical downscaling based on several methodologies will be applied (e.g. canonical correlation analysis and multiple linear regression). Instrumental time series, Era-Interim and the 20CR reanalyses will be used. Large-scale climate drivers as well as the influence of local/regional factors and their interaction with the Etesian wind field will be addressed. Finally, the Etesian wind resources on the present and future climate will be assessed in order to identify the potential areas suitable for the establishment of wind farms and the production of wind power in the Aegean Sea.

  3. Pelagic-benthic coupling and diagenesis of nucleic acids in a deep-sea continental margin and an open-slope system of the Eastern Mediterranean.

    PubMed

    Dell'anno, Antonio; Corinaldesi, Cinzia; Stavrakakis, Spyros; Lykousis, Vasilis; Danovaro, Roberto

    2005-10-01

    Downward fluxes of nucleic acids adsorbed onto settling particles play a key role in the supply of organic phosphorus and genetic material to the ocean interior. However, information on pelagic-benthic coupling, diagenesis, and processes controlling nucleic acid preservation in deep-sea sediments is practically nonexistent. In this study, we compared nucleic acid fluxes, sedimentary DNA and RNA concentrations, and the enzymatically hydrolyzable fraction of DNA in a bathyal continental margin (North Aegean Sea) and an open-sea system (South Aegean Sea) of the Eastern Mediterranean. The two systems displayed contrasting patterns of nucleic acid fluxes, which increased significantly with depth in the North Aegean Sea and decreased with depth in the South Aegean Sea. These results suggest that in continental margin and open-ocean systems different processes control the nucleic acid supply to the sea floor. Differences in nucleic acid fluxes were reflected by nucleic acid concentrations in the sediments, which reached extremely high values in the North Aegean Sea. In this system, a large fraction of DNA may be buried, as suggested by the large fraction of DNA resistant to nuclease degradation and by estimates of burial efficiency (ca. eight times higher in the North than in the South Aegean Sea). Overall, the results reported here suggest that the preservation of DNA in deeper sediment layers may be favored in benthic systems characterized by high sedimentation rates.

  4. Holocene Climatic Optimum centennial-scale paleoceanography in the NE Aegean (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Triantaphyllou, Maria V.; Gogou, Alexandra; Dimiza, Margarita D.; Kostopoulou, Sofia; Parinos, Constantine; Roussakis, Grigoris; Geraga, Maria; Bouloubassi, Ioanna; Fleitmann, Dominik; Zervakis, Vassilis; Velaoras, Dimitris; Diamantopoulou, Antonia; Sampatakaki, Angeliki; Lykousis, Vassilis

    2016-02-01

    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

  5. Macrofauna biodiversity of mussel bed assemblages in Thermaikos Gulf (northern Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Chintiroglou, Chariton-Charles; Damianidis, Panagiotis; Antoniadou, Chryssanthi; Lantzouni, Marina; Vafidis, Dimitris

    2004-02-01

    Biomonitoring of mussel bed assemblages can provide valuable information about the impact of pollution on hard substrate assemblages. This study of Mytilus galloprovincialis mussel beds in Thermaikos Gulf (northern Aegean Sea) deals with the spatial and temporal structure of the associated fauna. Samples were collected and abiotic factors were measured in two successive years. Common biocoenotic methods were employed to analyze the data. The samples could be separated into three groups, with summer and winter samples being clearly different. A total of 100 species were found: polychaetes and crustaceans were the most dominant taxa. The assemblage shows high diversity with respect to species abundance. Biotic interactions within the assemblage appear to influence its composition, although the total evenness remains unaffected in space and time. The M. galloprovincialis assemblages can be found in clean as well as in polluted waters and, therefore, are of great interest in biomonitoring studies.

  6. Centennial-scale paleoceanography during sapropel S1 deposition in the NE Aegean (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Triantaphyllou, Maria; Gogou, Alexandra; Dimiza, Margarita; Kostopoulou, Sofia; Parinos, Constantine; Roussakis, Grigoris; Geraga, Maria; Skampa, Elisavet; Bouloubassi, Ioanna; Fleitmann, Dominik; Zervakis, Vassilis; Velaoras, Dimitris; Diamantopoulou, Antonia; Sampatakaki, Angeliki; Lykousis, Vassilis

    2016-04-01

    Combined micropaleontological and geochemical analyses in the high-sedimentation gravity core M-4G, provided new centennial scale paleoceanographic data for the sapropel S1 deposition in the NE Aegean Sea. Sapropel layer S1a (10.2-8.0 ka) is deposited in dysoxic to oxic bottom waters; sediments are characterized by the high abundance of benthic foraminifers Chilostomella mediterranensis and Globobulimina affinis that are able to tolerate surface sediment and/or pore water oxygen depletion and the presence of the oxic mesotrophic-eutrophic U. mediterranea. Adequate preservation of organic matter is proven by the high organic carbon and loliolide and isololiolide contents, whereas the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. Both alkenone-based SSTs and δO18 G. bulloides records indicate coolings at 8.2 ka (S1a) and at ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7-6.4 ka) is characterized by rather oxic conditions marked by the prominent increase of U. mediterranea. The highly fluctuating SSTs demonstrate repeated coolings and associated dense water formation; major event at 7.4 ka, followed by cold spells at 7.0, 6.8, 6.5 ka. Besides, the increase of algal biomarkers, labile organic matter-feeding foraminifera and eutrophic planktonic species pinpoints rise in in situ marine productivity, which is enhanced by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine organic matter (OM) along with fresher terrestrial OM inputs after ~7.7 ka BP imply alternative/ additional than the north Aegean riverine borderland sources for the influx of organic matter at the south Limnos Basin, also related to the inflow of highly productive Marmara/Black Sea waters

  7. Performance of Statistical Temporal Downscaling Techniques of Wind Speed Data Over Aegean Sea

    NASA Astrophysics Data System (ADS)

    Gokhan Guler, Hasan; Baykal, Cuneyt; Ozyurt, Gulizar; Kisacik, Dogan

    2016-04-01

    Wind speed data is a key input for many meteorological and engineering applications. Many institutions provide wind speed data with temporal resolutions ranging from one hour to twenty four hours. Higher temporal resolution is generally required for some applications such as reliable wave hindcasting studies. One solution to generate wind data at high sampling frequencies is to use statistical downscaling techniques to interpolate values of the finer sampling intervals from the available data. In this study, the major aim is to assess temporal downscaling performance of nine statistical interpolation techniques by quantifying the inherent uncertainty due to selection of different techniques. For this purpose, hourly 10-m wind speed data taken from 227 data points over Aegean Sea between 1979 and 2010 having a spatial resolution of approximately 0.3 degrees are analyzed from the National Centers for Environmental Prediction (NCEP) The Climate Forecast System Reanalysis database. Additionally, hourly 10-m wind speed data of two in-situ measurement stations between June, 2014 and June, 2015 are considered to understand effect of dataset properties on the uncertainty generated by interpolation technique. In this study, nine statistical interpolation techniques are selected as w0 (left constant) interpolation, w6 (right constant) interpolation, averaging step function interpolation, linear interpolation, 1D Fast Fourier Transform interpolation, 2nd and 3rd degree Lagrange polynomial interpolation, cubic spline interpolation, piecewise cubic Hermite interpolating polynomials. Original data is down sampled to 6 hours (i.e. wind speeds at 0th, 6th, 12th and 18th hours of each day are selected), then 6 hourly data is temporally downscaled to hourly data (i.e. the wind speeds at each hour between the intervals are computed) using nine interpolation technique, and finally original data is compared with the temporally downscaled data. A penalty point system based on

  8. Hydrodynamic features of the South Aegean Sea as derived from Argo T/ S and dissolved oxygen profiles in the area

    NASA Astrophysics Data System (ADS)

    Kassis, Dimitris; Krasakopoulou, Evangelia; Korres, Gerasimos; Petihakis, George; Triantafyllou, George S.

    2016-11-01

    In this work, the hydrodynamic picture of the South Aegean Sea is examined through an analysis of recent measurements in its sub-basins, the Myrtoan and Cretan Sea. Both sub-basins play an important role in the water circulation, exchange, and formation processes that affect the dynamics of the whole Eastern Mediterranean. For the first time, Bio-Argo floats were deployed in the area under the Greek Argo Research Infrastructure coordination. The acquired profiles cover an almost 2-year period (November 2013-July 2015) and are compared with previous Argo profiles and the re-processed time-series data recorded from the E1-M3A POSEIDON observatory operating in the area since 2007. The spatio-temporal distribution of the physical and chemical properties in each sub-basin is examined. Dense water formation events are revealed in the northern part (Myrtoan), while the wider area can be characterized as pre-conditioned. In the Cretan basin, a strong inter-annual variability of the salinity field at intermediate and deep layers is observed that is associated with water exchange from its open boundaries. Furthermore, comparison of the dissolved oxygen (DO) distribution with physical water properties within both the mixed layer, and at greater depths, indicated that relatively high but still under-saturated DO values are more likely to be associated with convection events. Finally, an updated picture of the physical properties and the DO distribution is presented based on the last 5 years of measurements and the recent introduction of Bio-Argo floats with DO sensors in the area.

  9. Long-Term Marine Traffic Monitoring for Environmental Safety in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Giannakopoulos, T.; Gyftakis, S.; Charou, E.; Perantonis, S.; Nivolianitou, Z.; Koromila, I.; Makrygiorgos, A.

    2015-04-01

    The Aegean Sea is characterized by an extremely high marine safety risk, mainly due to the significant increase of the traffic of tankers from and to the Black Sea that pass through narrow straits formed by the 1600 Greek islands. Reducing the risk of a ship accident is therefore vital to all socio-economic and environmental sectors. This paper presents an online long-term marine traffic monitoring work-flow that focuses on extracting aggregated vessel risks using spatiotemporal analysis of multilayer information: vessel trajectories, vessel data, meteorological data, bathymetric / hydrographic data as well as information regarding environmentally important areas (e.g. protected high-risk areas, etc.). A web interface that enables user-friendly spatiotemporal queries is implemented at the frontend, while a series of data mining functionalities extracts aggregated statistics regarding: (a) marine risks and accident probabilities for particular areas (b) trajectories clustering information (c) general marine statistics (cargo types, etc.) and (d) correlation between spatial environmental importance and marine traffic risk. Towards this end, a set of data clustering and probabilistic graphical modelling techniques has been adopted.

  10. The Sponge Community of a Subtidal Area with Hydrothermal Vents: Milos Island, Aegean Sea

    NASA Astrophysics Data System (ADS)

    Pansini, M.; Morri, C.; Bianchi, C. N.

    2000-11-01

    Sponges were sampled by SCUBA diving at six subtidal rocky sites, three of which were close to hydrothermal vents, a common feature on the sea-floor off the south-east coast of Milos. Twenty-five species (2 Calcarea and 23 Demospongiae) were found, few compared with the 589 recorded for the Mediterranean, but an important addition to the scant information on the sponge fauna of the Aegean Sea. The number of species found at vent sites was consistently higher than that found at non-vent sites, but no vent-obligate species could be identified. However, Geodia cydonium and three species of Cliona ( C. copiosa, C. nigricans and C. rhodensis) showed a tendency to colonize vent areas. The former might take advantage of increased silica availability, the latter of the enhanced deposition of carbonates near vents. Substratum cover by sponges (estimated from wire-framed photographs of 0·7 m 2), varied greatly both among and within sites, mostly according to slope. Most sponge species preferred vertical to overhanging, shaded substrata. Proximity to vents seemed to have little or no influence on sponge cover, notwithstanding a primary effect on species diversity.

  11. Radioactivity and metal concentrations in marine sediments associated with mining activities in Ierissos Gulf, North Aegean Sea, Greece.

    PubMed

    Pappa, F K; Tsabaris, C; Ioannidou, A; Patiris, D L; Kaberi, H; Pashalidis, I; Eleftheriou, G; Androulakaki, E G; Vlastou, R

    2016-10-01

    Marine sediment samples were collected from Ierissos Gulf, N Aegean Sea, close to the coastal mining facilities. Measurements of radionuclide and metal concentrations, mineral composition and grain size distribution were performed. The concentrations of (226)Ra, (235)U and trace metals showed enhanced values in the port of Stratoni compared with those obtained near to Ierissos port. The dose rates received by marine biota were also calculated by the ERICA Assessment Tool and the results indicated no significant radiological risk. PMID:27474903

  12. GPS-Constrained Microplate Kinematics and Plio-Pleistocene Tectonic Evolution of the North Anatolian Fault and North Aegean Sea

    NASA Astrophysics Data System (ADS)

    Thatcher, W.

    2004-12-01

    Emerging evidence from Global Position System (GPS) survey measurements in the Aegean and elsewhere suggests that present-day active continental deformation occurs largely due to the relative motions of a small number of rigid blocks or microplates. However, it is not universally agreed whether the continental microplate description of the GPS data is superior to other proposed models, nor is it clear whether present-day movement patterns can be usefully extrapolated into the geologic past. Here I examine the known deformation history of the North Aegean over the past ~10 Ma and compare it with predictions based on the present-day microplate model. Agreement provides independent support for the GPS-based model and demonstrates its value in bettering our understanding of Aegean tectonics. If we knew nothing about late Cenozoic North Aegean tectonics and provisionally assumed the correctness of the Aegean microplate model of Nyst & Thatcher [2004 JGR], we would predict several features of the tectonic evolution that accord with geologic evidence. First, the North Aegean Sea would be created by extension due to SSW motion of the South Aegean and concomitant CW rotation of central Greece during the past 10 Ma. The same kinematic process would cause extension to be succeeded by strike-slip motion as the `ridge-transform-ridge' triple junction migrates WSW 24 km/Ma and the North Anatolian fault propagates into the region. The Plio-Pleistocene history of the North Aegean shows these same general features. Drilling and seismic imaging document the existence of young (< 10 Ma) and thick (up to 6 km) sedimentary sequences attributed to crustal extension by a factor of 3-4. Seismic profiling and bathymetric mapping show a mesh of roughly orthogonal faults with dip-slip offsets. Structural studies of sub-aerial exposures of these faults suggest an earlier episode of extension was followed by predominantly strike-slip motions. The plate kinematic reconstruction of late Cenozoic

  13. Aliphatic hydrocarbon levels in turbot and salmon farmed close to the site of the Aegean Sea oil spill

    SciTech Connect

    Alvarez Pineiro, M.E.; Gonzalez-Barros, S.T.C.; Lozano, J.S.

    1996-12-31

    After the Andros Patria oil spill, the most serious oil tanker accident to occur off the coast of Galicia (N.W. Spain) was the running aground and subsequent conflagration of the Aegean Sea supertanker outside the northern Spanish port of La Coruna (December 3rd 1992). Approximately 60,000 tonnes of Brent oil were spilled into the Atlantic Ocean in the cited coastal region. Subsequently, an impropitious combination of a high tide and a change in wind direction caused the resulting slick to rapidly spread into the port. Measures aimed at cleaning up affected areas and evacuating the ca. 11,215 tonnes of oil remaining in the supertanker were immediately implemented. However, within just a few days the resulting contamination had killed some 15000 turbot juveniles and larvae, which are cultivated in fish farms close to the accident site. The environmental impact of major oil spillages has been widely studied. Several scientists have suggested that, in terms of the negative effects on the seawater quality and productive capacity of the affected maritime regions, the magnitudes of the Aegean Sea and Amoco Cadiz accidents are comparable. This paper reports variations over time of aliphatic hydrocarbon levels in turbot and Atlantic salmon sampled from fish farms close to the site of the Aegean Sea oil spill. 6 refs., 2 figs., 1 tab.

  14. Earthquake Scenario-Based Tsunami Wave Heights in the Eastern Mediterranean and Connected Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Özel, Nurcan Meral

    2015-12-01

    We identified a set of tsunami scenario input parameters in a 0.5° × 0.5° uniformly gridded area in the Eastern Mediterranean, Aegean (both for shallow- and intermediate-depth earthquakes) and Black Seas (only shallow earthquakes) and calculated tsunami scenarios using the SWAN-Joint Research Centre (SWAN-JRC) code ( Mader 2004; Annunziato 2007) with 2-arcmin resolution bathymetry data for the range of 6.5—Mwmax with an Mw increment of 0.1 at each grid in order to realize a comprehensive analysis of tsunami wave heights from earthquakes originating in the region. We defined characteristic earthquake source parameters from a compiled set of sources such as existing moment tensor catalogues and various reference studies, together with the Mwmax assigned in the literature, where possible. Results from 2,415 scenarios show that in the Eastern Mediterranean and its connected seas (Aegean and Black Sea), shallow earthquakes with Mw ≥ 6.5 may result in coastal wave heights of 0.5 m, whereas the same wave height would be expected only from intermediate-depth earthquakes with Mw ≥ 7.0 . The distribution of maximum wave heights calculated indicate that tsunami wave heights up to 1 m could be expected in the northern Aegean, whereas in the Black Sea, Cyprus, Levantine coasts, northern Libya, eastern Sicily, southern Italy, and western Greece, up to 3-m wave height could be possible. Crete, the southern Aegean, and the area between northeast Libya and Alexandria (Egypt) is prone to maximum tsunami wave heights of >3 m. Considering that calculations are performed at a minimum bathymetry depth of 20 m, these wave heights may, according to Green's Law, be amplified by a factor of 2 at the coastline. The study can provide a basis for detailed tsunami hazard studies in the region.

  15. Source of the tsunami generated by the 1650 AD eruption of Kolumbo submarine volcano (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Ulvrova, Martina; Paris, R.; Nomikou, P.; Kelfoun, K.; Leibrandt, S.; Tappin, D. R.; McCoy, F. W.

    2016-07-01

    The 1650 AD explosive eruption of Kolumbo submarine volcano (Aegean Sea, Greece) generated a destructive tsunami. In this paper we propose a source mechanism of this poorly documented tsunami using both geological investigations and numerical simulations. Sedimentary evidence of the 1650 AD tsunami was found along the coast of Santorini Island at maximum altitudes ranging between 3.5 m a.s.l. (Perissa, southern coast) and 20 m a.s.l. (Monolithos, eastern coast), corresponding to a minimum inundation of 360 and 630 m respectively. Tsunami deposits consist of an irregular 5 to 30 cm thick layer of dark grey sand that overlies pumiceous deposits erupted during the Minoan eruption and are found at depths of 30-50 cm below the surface. Composition of the tsunami sand is similar to the composition of the present-day beach sand but differs from the pumiceous gravelly deposits on which it rests. The spatial distribution of the tsunami deposits was compared to available historical records and to the results of numerical simulations of tsunami inundation. Different source mechanisms were tested: earthquakes, underwater explosions, caldera collapse, and pyroclastic flows. The most probable source of the 1650 AD Kolumbo tsunami is a 250 m high water surface displacement generated by underwater explosion with an energy of ~ 2 × 1016 J at water depths between 20 and 150 m. The tsunamigenic explosion(s) occurred on September 29, 1650 during the transition between submarine and subaerial phases of the eruption. Caldera subsidence is not an efficient tsunami source mechanism as short (and probably unrealistic) collapse durations (< 5 min) are needed. Pyroclastic flows cannot be discarded, but the required flux (106 to 107 m3 · s- 1) is exceptionally high compared to the magnitude of the eruption.

  16. Source of the tsunami generated by the 1650 AD eruption of Kolumbo submarine volcano (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Ulvrova, Martina; Paris, Raphael; Nomikou, Paraskevi; Tappin, Dave

    2016-04-01

    The 1650 AD explosive eruption of Kolumbo submarine volcano (Aegean Sea, Greece) generated a destructive tsunami. In this paper we propose a source mechanism of this poorly documented tsunami using both geological investigations and numerical simulations. Sedimentary evidences of the 1650 AD tsunami were found along the coast of Santorini Island at maximum altitudes ranging between 3.5 m a.s.l. (Perissa, southern coast) and 20 m a.s.l. (Monolithos, eastern coast), corresponding to a minimum inundation of 360 and 630 m respectively. Tsunami deposits correspond to an irregular 5 to 30 cm thick layer of dark grey sand intercalated in soil at depths between 30 and 50 cm. Composition of the tsunami sand is similar to the composition of the present-day beach and clearly differs from the pumiceous gravelly soil. Spatial distribution of the tsunami deposits was confronted to available historical records and to the results of numerical simulations of tsunami inundation. Different scenarios of source mechanism were tested: earthquakes, underwater explosions, caldera collapse, and pyroclastic flows. The most probable source of the 1650 AD Kolumbo tsunami is a 250 m high water surface displacement generated by underwater explosion with an energy of ~2 E15 J at water depths between 20 and 150 m. The tsunamigenic explosion(s) occurred on September 29, 1650 during the transition between submarine and subaerial phases. Caldera subsidence is not an efficient source of tsunami, as short (and probably unrealistic) collapse durations (< 5 minutes) are needed. Pyroclastic flows cannot be discarded, but the required flux (E6 to E7 m³.s-1) is exceptionally high compared to the magnitude of the eruption.

  17. Bacterial pollution, activity and heterotrophic diversity of the northern part of the Aegean Sea, Turkey.

    PubMed

    Çiftçi Türetken, Pelin S; Altuğ, Gülşen

    2016-02-01

    Isolation and characterization studies of marine heterotrophic bacteria are important to describe and understand eco-metobolism of the marine environments. In this study, diversity and community structures of the culturable heterotrophic bacteria, metabollicaly active bacteria and bacterial pollution in the coastal and offshore areas of Gökçeada Island, in the Northern Aegean Sea, Turkey were investigated from March 2012 to November 2013. The primary hydrographic parameters were recorded in situ. The frequency of the metabolically active bacteria was determined by using a modified staining technique. The indicator bacteria were determined by using membrane filtration technique; 126 bacteria isolates, 24 of them first records for this region, were identified using an automated micro-identification system, VITEK2 Compact30. The results showed that detected bacterial community profiles were significantly different when compared with previous studies conducted in polluted marine areas of Turkey. High frequency of faecal bacteria detected at station 2 indicated that increasing human activities and terrestrial pollution sources are shaping factors for possible risks, regarding recreational uses of this region, in the summer seasons.

  18. Polychaetes associated with the sciaphilic alga community in the northern Aegean Sea: spatial and temporal variability

    NASA Astrophysics Data System (ADS)

    Antoniadou, C.; Nicolaidou, A.; Chintiroglou, C.

    2004-10-01

    Polychaete biodiversity has received little attention despite its importance in biomonitoring. This study describes polychaete diversity, and its spatial and temporal variability in infralittoral, hard substrate assemblages. Seven stations were chosen in the central area of the northern Aegean Sea. At each station, one to three depth levels were set (15, 30 and 40 m). Five replicates were collected by scuba diving with a quadrat sampler (400 cm2) from each station and depth level during summer for the spatial analysis, and seasonally for the study of temporal changes. Common biocoenotic methods were employed (estimation of numerical abundance, mean dominance, frequency, Margalef's richness, Shannon-Weaver index and Pielou's evenness). A total of 5,494 individuals, belonging to 79 species, were counted and classified. Diversity indices were always high. Clustering and multidimensional scaling techniques indicated a high heterogeneity of the stations, although these were all characterized by the sciaphilic alga community. A clear seasonal pattern was not detectable. Summer and autumn samples discriminate, while winter and spring form an even group. The abundance/biomass comparison indicated a dominance of k-strategy patterns, characteristic of stable communities.

  19. a Structural and Thermochronological Study of Santorini Detachment in Santorini Island, Aegean Sea

    NASA Astrophysics Data System (ADS)

    Marsellos, A.; Foster, D. A.; Min, K. K.; Kamenov, G. D.; Kidd, W. S.; Garver, J. I.; Kyriakopoulos, K.

    2012-12-01

    Extension in the Aegean has been very prominent since early Miocene expressed by a series of detachments, opening of the Cretan basin, arc expansion and plutons, with a peak of extensional activity at 10-16 Ma across the south Aegean. In Santorini, which is the southernmost Cyclades island and closest to the forearc, intrusion of an unexposed pluton to a depth equivalent to modern sea level took place at about 9.5 Ma (Skarpelis et al., 1992). In this study, Zircon fission-track (ZFT) and apatite (U-Th)/He (AHe) data from the Athinios metamorphic rocks exposed in Santorini caldera distinguish an upper metamorphic cooling unit associated with Early-Middle Eocene exhumation (46.3 ± 2.8 Ma, ZFT; 49.34 ± 2.9 Ma, AHe) from a lower metamorphic unit of Middle-Late Miocene (10.9 ± 0.7 Ma, ZFT; 9.4 ± 0.3 Ma, AHe) exhumation ages. The upper unit shows mineral lineations that range from N-S to NE-SW trending while the lower unit shows lineations ranging from N-S to NW-SE trending. U-Pb (LA-MC-ICP-MS) zircon data from mica-schists in the lower Santorini metamorphic unit show a prominent Pan-African signature similar to the Phyllite-quartzite unit (PQU) rocks exposed along the forearc in Kythera, Peloponnese and western Crete. The NW-SE stretching lineations in the lower unit imply an arc-parallel extension. Similar arc-parallel extension took place between 10-13 in PQU rocks in the west Crete-Kythera-south Peloponnese area (Marsellos et al., 2010). The lower unit shows ductile structures affected by top to the S shearing while the upper unit by top to the N shearing. A 3D projection of the mineral lineation dip angles along N-S direction shows a C' shear band of top to the N shearing that has affected the entire structural stack. Early brittle structures, which appear to be re-oriented normal faults, and show top to the S displacement. Later normal faults show similar shear sense. A tectonic model that could explain the above structures shows that initial exhumation of the

  20. Late Quaternary stratigraphic and tectonic evolution of the northeastern Aegean Sea

    NASA Astrophysics Data System (ADS)

    Isler, Ekrem Bursin

    The late Quaternary--Recent stratigraphic and tectonic evolution of the NE Aegean Sea, between the Islands of Bozcaada and Lesbos and the Biga Peninsula, is examined using ˜1600 km of seismic reflection and side scan profiles and six cores collected during cruises in 1998, 2000, 2002, and 2003. Detailed examination of the seismic reflection profiles showed that several vertically stacked depositional sequences developed within three NE-SW trending basins. These depositional sequences exhibit oblique- to complex oblique-sigmoid internal seismic reflection configuration and are separated from one another by shelf-crossing unconformities. The chronology of the depositional sequences is constrained by seven radiocarbon and two U/Th dates on in situ shell samples extracted from five cores. Sedimentation rates calculated by using these dates range between 19 cm/kyr and 30 cm/kyr. The ages and the stacked architecture of the depositional sequences, together with the correlations with the oxygen isotopic stages and global sea-level curve reveal that these seaward-prograded delta sequences were developed in a sufficiently rapidly subsiding shelf environment during successive global eustatic sea-level falls associated with late Quaternary glaciations. The progradation of the depositional sequences decelerated and eventually halted shortly after the subsequent major transgressions during which the shelf-crossing unconformities were generated. The terrigenous materials transported throughout the development of the depositional sequences originated from the Tuzla, Karamenderes, and Dumbek rivers draining the Biga Peninsula. Seismic reflection profiles showed no evidence for a major E--W-trending fault system, suggesting that the western continuation of the central strand of the North Anatolian Transform Fault does not exit into the Aegean Sea at Ezine. Detailed mapping of the seismic data showed that two major faults, A1 and beta8, constitute the main fault system in the study

  1. The advance of Kos Plateau Tuff ignimbrite into the marine realm of the Kalymnos Basin, SE Aegean Sea.

    NASA Astrophysics Data System (ADS)

    Markakis, Emmanouil; Anastasakis, George

    2013-04-01

    The 161 ka Kos Plateau Tuff (KPT) eruption is considered to be the largest explosive Quaternary event in the eastern Mediterranean. It produced pumice rafts followed by "non-welded ignimbrites" that are up to 30m thick, especially widespread on Kos island and covering an area of > 80 Km2 that includes mainly islands and present marine regions. Pyroclastic flows travelled from the proposed vent, that lies between and around Yali and Nisyros islands, across present land and sea, the total volume of the tuff has been estimated as at least 100km3. KPT products principally consist of rhyolitic ash and pumice. Post 2010 Athens University oceanographic missions have mapped the seafloor around the volcanic islands of the SE Aegean Sea. Here we present new data on seafloor morphology and Upper Quaternary seafloor stratigraphy of the Kalymnos basin that extends over an area over 70km2 and map the advance and deposition of the KPT that was previously unknown in this region. The Kalymnos basin is roughly triangular in shape and essentially consists of two sedimentation depocenters: a) a roughly elliptical 400 m deep northern segment that is developed sub-parallel to Kalymnos Island and its W-SW shelf; b) a rather physiographically complex western sector developed NE of Astipalea island and reaching depths of over 620m. High resolution sparker profiles from the west Kos-Kalymnos shelf reveal an outstanding seismic stratigraphy of stacked and prograded coastal clinoform packets capped by erosional transgressive surfaces that record Quaternary eustatic lowstands deposits of sea level with clinoforms developing during forced regression and the erosional surfaces during transgression. We show that a massive gravity flow deposit is intercalated with the shelf sediments. Above it low sea level MIS 6 and 2 sedimentary sequences are fully developed and below stage 8-10 sediments are erratically preserved over stages 12 and 16 sediments. This gravity flow deposit swept across the shelf

  2. Internal wave measurements on the Cycladic Plateau of the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Alford, Matthew H.; Gregg, Michael C.; Zervakis, Vassilis; Kontoyiannis, Harialos

    2012-01-01

    The internal wave climate in the southern Aegean Sea is examined with an array of two bottom-mounted acoustic Doppler current profilers and three profiling moorings deployed on the northern continental slope of the Cretan Sea for 3 months. Frequency spectra indicate an extremely weak internal wave continuum, about 4-10 times weaker than the Garrett-Munk and Levine reference levels. Spectra are instead dominated by semidiurnal internal tides and near-inertial waves, which are examined in detail by bandpass filtering. In the semidiurnal band, a barotropic tidal flow of ≈2 cm s-1 is observed, with a pronounced spring/neap modulation in phase with the lunar fortnightly cycle. One to two days following several of these spring tide periods, a distinct internal tide featuring 10-20 m vertical displacements and 15-20 cm s-1baroclinic velocities is detectable propagating upward and to the southeast. Time-mean energy increases a factor of 2-5 within about 100 m from the bottom, implying generation and/or scattering from the bottom, whose slope is nearly critical to semidiurnal internal waves over much of the array. Several strong, downward propagating near-inertial events are also seen, each of which occurs following a period of work done by the wind on the mixed layer as estimated from a nearby surface mooring. The high-frequency internal wave continuum is more temporally constant but increases substantially toward the end of the deployment. Significant but unexplained differences in kinetic energy occur between successive spring tide periods in the case of the internal tides and between successive wind events in the case of the near-inertial signals. Substantial variability is observed in the low-frequency flows, which likely contributes to the time variability of the internal wave signals.

  3. Evolution and fluxes of 137Cs in the Black Sea/Turkish Straits System/North Aegean Sea

    NASA Astrophysics Data System (ADS)

    Delfanti, R.; Özsoy, E.; Kaberi, H.; Schirone, A.; Salvi, S.; Conte, F.; Tsabaris, C.; Papucci, C.

    2014-07-01

    The vertical profiles of 137Cs were determined in the North Aegean, Marmara and Black Seas, to assess inventories and fluxes of the radionuclide in these basins. The inventory of 137Cs in the Western Black Sea integrated from the surface down to 400 m water depth is 3.4 ± 0.1 kBq m- 2, which is surprisingly close to the amount determined in 1988, decay corrected to 2007 (2.9 ± 0.1 kBq m- 2). On the other hand, based on the comparison of profiles roughly 20 years apart, it is estimated that about 1 kBq m- 2 has been transferred from above the halocline to depths below the halocline, emphasizing the effective redistribution of tracers within the same period. We estimate that about 12 TBq y- 1 of 137Cs presently leaves the Black Sea with the upper layer flow through the Bosphorus and only 2 TBq y- 1 is returned with the lower layer inflow of Mediterranean water from the Marmara Sea. Accounting for river fluxes, estimated on the order of 2 TBq y- 1 few years after the Chernobyl accident, and possibly decreased by now, we can thus estimate a net rate of loss of about 8-10 TBq y- 1. Investigating the effective redistribution in the upper water column, the supply by the inflowing Mediterranean water alone does not explain the increase of 137Cs concentration and inventory at intermediate depths in the Western Black Sea. The most important mechanism transferring 137Cs and dissolved contaminants from the surface water to the sub-pycnocline layer appears to be the turbulent entrainment of a larger quantity of Black Sea water into the inflowing plume of Mediterranean water through mixing processes on the southwestern shelf and continental slope following its exit from the Bosphorus. This process produces an extra export of some10 TBq y- 1 of 137Cs from the surface to the sub-pycnocline depths of the Black Sea, a quantity comparable in magnitude to the total export out from the basin. It is the entrainment flux resulting from the mixing, and the further advection and

  4. Geodynamic features along the Christianna-Santorini-Kolumbo tectonic line (South Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Nomikou, Paraskevi; Papanikolaou, Dimitrios; Carey, Steve; Bejelou, Konstantina; Sakellariou, Dimitris; Kilias, Stefanos; Camilli, Rich; Escartin, Javier; Bell, Kathrine; Parks, Michelle

    2013-04-01

    Numerous oceanographic surveys have been conducted in Santorini Volcanic Group (South Aegean Sea) since 2001, revealing the spectacular morphology of the seafloor (multibeam data) and the sub-seafloor stratigraphic horizons (seismic profiles). Technological advancements in seafloor exploration such as ROVs and a submersible, enabled us to observe products of submarine volcanism that were previously inaccessible. In addition, gravity and box coring, geological and biological samples have been collected from selected areas for further analysis. The offshore geophysical survey in Santorini shows that recent volcanism occurred along a NE-SW tectonic zone named as Christianna-Santorini-Kolumbo (CSK) line. Christiana islets and three newly discovered submarine volcanic domes, with small colonies of yellow, presumably sulfur-reducing hydrothermal bacteria, occur in the southwestern part of the line. The presently active intra caldera volcanic domes of Palea and Nea Kameni islands and the low temperature (17-24°C) vent mounds covered by yellowish bacterial mat occupy the middle part of the line. The Santorini vent field is linked with the Kolumbo normal fault onshore which is likely controlling the pathways of hydrothermal circulation within the caldera. The most prominent feature at the NE part of this zone, is Kolumbo submarine volcanic chain which is extended 20Km with several volcanic domes aligned along this direction. The Kolumbo volcano had an explosive eruption in 1650 that killed 70 people on Santorini. The hydrothermal vent field in the crater floor of Kolumbo consists dominantly of active and inactive sulfide-sulfate structures in the form of vertical spires and pinnacles, mounds and flanges along a NE-SW trend, with temperatures up to 220°C and vigorous CO2 gas emission. For several years, the highest frequency of earthquakes was concentrated mainly in the vicinity of Kolumbo volcano. However, during 2011-2012 both seismic and geodetic unrest began abruptly

  5. April 16, 2015 Crete Island Earthquake (Mw=5.9) Series and its Seismotectonic Significance, Southern Aegean Sea

    NASA Astrophysics Data System (ADS)

    Yalçın, Hilal; Kürçer, Akın; Gülen, Levent

    2016-04-01

    The active deformation of the southern Aegean Sea is a result of the northward motion of the African and Arabian Plates with respect to the Eurasian Plate in the Eastern Mediterranean Region. The Hellenic subduction zone plays a key role in the active tectonics of the region. On 16 April, 2015, a moderate earthquake occurred on the eastern part of Hellenic arc (south of Crete island), with a moment magnitude of Mw=5.9. A series of aftershocks were occurred within four months following the mainshock, which have magnitudes varying from Mw = 3.4 to 5.4. Source parameters of the 16 April 2015 earthquake have been modeled in order to reveal the regional stress tensor and the tectonic style of the region. In this study, the source parameters of the main shock and 36 aftershocks that have magnitudes M≥3.4 have been determined and modeled by seismic moment tensor waveform inversion method developed by Sokos and Zahradnik (2006) algorithm using the near-field and regional waveforms. The depth of earthquakes are varied from 2 to 61 km. Stress tensor can describe reliably principle stress axes (σ1, σ2, σ3), their relative size and stress field variations. Stress tensor inversions have been carried out using the Micheal method (1984, 1987). In this study, 16 April 2015 Crete Earthquake mainshock (Mw=5.9), a total of 36 earthquake moment tensor solutions that belong to the Crete earthquake sequence and 24 earthquake moment tensor solutions of previous main shocks in the region have been compiled and used in the stress inversion calculation. Orientations of σ1, σ2 and σ3 were computed and the principal directions are projected onto a lower hemisphere Wulff net. The best fit was attained for Phi = 0.38+/‑0.13609 and indicated that the stress regime revealed strike-slip faulting with reverse component and for the azimuth and plunge pair of (-161.6°, 21.7°) for σ1, (-11.1°, 65.4°) for σ2 and (103.8°, 10.9°) for σ3. At the final step of the study, Gutenberg and

  6. April 16, 2015 Crete Island Earthquake (Mw=5.9) Series and its Seismotectonic Significance, Southern Aegean Sea

    NASA Astrophysics Data System (ADS)

    Yalçın, Hilal; Kürçer, Akın; Gülen, Levent

    2016-04-01

    The active deformation of the southern Aegean Sea is a result of the northward motion of the African and Arabian Plates with respect to the Eurasian Plate in the Eastern Mediterranean Region. The Hellenic subduction zone plays a key role in the active tectonics of the region. On 16 April, 2015, a moderate earthquake occurred on the eastern part of Hellenic arc (south of Crete island), with a moment magnitude of Mw=5.9. A series of aftershocks were occurred within four months following the mainshock, which have magnitudes varying from Mw = 3.4 to 5.4. Source parameters of the 16 April 2015 earthquake have been modeled in order to reveal the regional stress tensor and the tectonic style of the region. In this study, the source parameters of the main shock and 36 aftershocks that have magnitudes M≥3.4 have been determined and modeled by seismic moment tensor waveform inversion method developed by Sokos and Zahradnik (2006) algorithm using the near-field and regional waveforms. The depth of earthquakes are varied from 2 to 61 km. Stress tensor can describe reliably principle stress axes (σ1, σ2, σ3), their relative size and stress field variations. Stress tensor inversions have been carried out using the Micheal method (1984, 1987). In this study, 16 April 2015 Crete Earthquake mainshock (Mw=5.9), a total of 36 earthquake moment tensor solutions that belong to the Crete earthquake sequence and 24 earthquake moment tensor solutions of previous main shocks in the region have been compiled and used in the stress inversion calculation. Orientations of σ1, σ2 and σ3 were computed and the principal directions are projected onto a lower hemisphere Wulff net. The best fit was attained for Phi = 0.38+/-0.13609 and indicated that the stress regime revealed strike-slip faulting with reverse component and for the azimuth and plunge pair of (-161.6°, 21.7°) for σ1, (-11.1°, 65.4°) for σ2 and (103.8°, 10.9°) for σ3. At the final step of the study, Gutenberg and

  7. Living benthic foraminifera as an environmental proxy in coastal ecosystems: A case study from the Aegean Sea (Greece, NE Mediterranean)

    NASA Astrophysics Data System (ADS)

    Koukousioura, Olga; Dimiza, Margarita D.; Triantaphyllou, Maria V.; Hallock, Pamela

    2011-12-01

    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

  8. Petroleum exploration and geology of the Aegean

    SciTech Connect

    Bartling, T.C.; Gips, J.

    1988-08-01

    The present-day Aegean Sea covers several graben and/or half-graben basins filled with more than 12,000 ft of sedimentary rocks. The normal faulting observed on seismic record sections indicates a tensional tectonic regime. There is a marked coincidence of modern basins and bathymetric highs with paleobasins and highs. A stratigraphic section of marine clastics of Eocene through Miocene-Pliocene age have been encountered in the seven wildcat wells drilled. Cretaceous-age rocks must be considered basement for petroleum exploration because, except for an area in the eastern Aegean, Cretaceous and older rocks were metamorphosed during the Alpine orogenies. The Eocene is a transgressive clastic sequence. The Oligocene is conformable with the underlying Eocene. The Miocene is predominantly a regressive clastic sequence. This series ended with evaporitic conditions. The Messinian evaporite is an excellent seismic marker and is the seal for the one producing field in the Aegean Sea. Source rocks and reservoir rocks are found in both the Eocene and the Miocene. Four of the seven wildcats drilled have encountered hydrocarbon shows. Prinos field, discovered in 1974, was put on production in 1981 and is currently producing at design capacity of 25,000 to 28,000 bbl of oil per day. Cumulative production is approximately 50 million bbl. Prinos field is only 7 mi from metamorphic basement outcrop, yet field wells have penetrated more than 10,000 ft of Tertiary marine clastics.

  9. Palaeomagnetic Results From Minoan Ash Deposits (Rv Vema) Cores V10-50 And V10-58 South Aegean Sea: A Comparison With Santorini Minoan Pumice Deposits.

    NASA Astrophysics Data System (ADS)

    Downey, W. S.

    Palaeomagnetic and anisotropy measurements were carried out on Minoan ash deposits ob-tained from the deep-sea cores, (V10-50 and V10-58), South Aegean Sea. Three distinct layers have been reported within the ash deposit in core (V10-50). Based primarily on grain-size differences, a link to three separate eruptive phases of Santorini has been suggested. Magnetic results were una-ble to resolve any differences between these layers which suggests that the eruption may have been a 'single event'. Some magnetic parameters indicate that the final ignimbrite phase of the eruption of Santorini is most likely to have been responsible for the bulk of the deep-sea ash deposits, alt-hough a contribution from the first phase (phreatomagmatic and/or Plinian air-fall) cannot be ex-cluded. Anisotropy of magnetic susceptibility measurements indicate a primary sedimentary fabric and quiet depositional conditions for V10-50 ash sediment. A more disturbed petrofabric is ob-served for V10-58 suggesting, bottom current activity and/or slumping. The mean palaeomagnetic inclination calculated from appropriate V10-50 results is:- 60.2° ± 4.3° (corrected for anisotropy and geographical location differences of sites). This is statistically identical to values obtained for burnt mud brick from destruction sites in eastern Crete but different to the mean palaeomagnetic inclina-tion obtained for central Cretan sites. A comparison with the secular variation (inclination) data for the Balkan region and for Greece, suggests that the eruption/s of Santorini occurred in the period between ~1540 and 1500 BC.

  10. Hydrodynamic features of the South Aegean Sea as derived from Argo T/S and dissolved oxygen profiles in the area

    NASA Astrophysics Data System (ADS)

    Kassis, Dimitris; Krasakopoulou, Evangelia; Korres, Gerasimos; Petihakis, George; Triantafyllou, George S.

    2016-09-01

    In this work, the hydrodynamic picture of the South Aegean Sea is examined through an analysis of recent measurements in its sub-basins, the Myrtoan and Cretan Sea. Both sub-basins play an important role in the water circulation, exchange, and formation processes that affect the dynamics of the whole Eastern Mediterranean. For the first time, Bio-Argo floats were deployed in the area under the Greek Argo Research Infrastructure coordination. The acquired profiles cover an almost 2-year period (November 2013-July 2015) and are compared with previous Argo profiles and the re-processed time-series data recorded from the E1-M3A POSEIDON observatory operating in the area since 2007. The spatio-temporal distribution of the physical and chemical properties in each sub-basin is examined. Dense water formation events are revealed in the northern part (Myrtoan), while the wider area can be characterized as pre-conditioned. In the Cretan basin, a strong inter-annual variability of the salinity field at intermediate and deep layers is observed that is associated with water exchange from its open boundaries. Furthermore, comparison of the dissolved oxygen (DO) distribution with physical water properties within both the mixed layer, and at greater depths, indicated that relatively high but still under-saturated DO values are more likely to be associated with convection events. Finally, an updated picture of the physical properties and the DO distribution is presented based on the last 5 years of measurements and the recent introduction of Bio-Argo floats with DO sensors in the area.

  11. Occurrence, sources and transport pathways of natural and anthropogenic hydrocarbons in deep-sea sediments of the eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Parinos, C.; Gogou, A.; Bouloubassi, I.; Pedrosa-Pàmies, R.; Hatzianestis, I.; Sanchez-Vidal, A.; Rousakis, G.; Velaoras, D.; Krokos, G.; Lykousis, V.

    2013-09-01

    Surface sediments collected from deep basins (1018-4087 m depth) of the eastern Mediterranean Sea (Ionian Sea, southern Aegean Sea and northwestern Levantine Sea) were analyzed for aliphatic and polycyclic aromatic hydrocarbons as tracers of natural and anthropogenic inputs. Concentrations of total aliphatic hydrocarbons, n-alkanes and the unresolved complex mixture (UCM) of aliphatic hydrocarbons varied significantly, ranging from 1.34 to 49.2 μg g-1, 145 to 4810 ng g-1 and 0.73 to 36.7 μg g-1, respectively, while concentrations of total polycyclic aromatic hydrocarbons (PAHs) ranged between 11.6 and 223 ng g-1. Molecular profiles of determined hydrocarbons reflect a mixed contribution from both natural and anthropogenic sources in deep-sea sediments of the eastern Mediterranean Sea, i.e., terrestrial plant waxes, degraded petroleum products, unburned fossil fuels and combustion of grass, wood and coal. Hydrocarbon mixtures display significant variability amongst sub-regions, reflecting differences in the relative importance of inputs from various sources and phase associations/transport pathways of individual hydrocarbons that impact on their overall distribution and fate. Hydrocarbon concentrations correlated significantly with the organic carbon content of sediments, indicating that the latter exerts an important control on their transport and ultimate accumulation in deep basins. Additionally, water masses' circulation characteristics also seem to influence the regional features and distribution patterns of hydrocarbons. Our findings highlight the role of deep basins/canyons as repositories of both natural and anthropogenic chemical species.

  12. Foraminifera eco-biostratigraphy of the southern Evoikos outer shelf, central Aegean Sea, during MIS 5 to present

    NASA Astrophysics Data System (ADS)

    Drinia, Hara; Antonarakou, Assimina; Tsourou, Theodora; Kontakiotis, George; Psychogiou, Maria; Anastasakis, George

    2016-09-01

    The South Evoikos Basin is a marginal basin in the Aegean Sea which receives little terrigenous supply and its sedimentation is dominated by hemipelagic processes. Late Quaternary benthic and planktonic foraminifera from core PAG-155 are investigated in order to understand their response to the glacial-interglacial cycles in this region. The quantitative analysis of planktonic foraminifera, coupled with accelerator mass spectrometry (14C-AMS) radiocarbon date measurements, provide an integrated chrono-stratigraphic time framework over the last 90 ka (time interval between late Marine Isotopic Stages 5 and 1; MIS5-MIS1). The temporary appearance and disappearance as well as several abundance peaks in the quantitative distribution of selected climate-sensitive planktonic species allowed the identification of several eco-bioevents, useful to accurately mark the boundaries of the eco-biozones widely recognized in the Mediterranean records and used for large-scale correlations. The established bio-ecozonation scheme allows a detailed palaecological reconstruction for the late Pleistocene archive in the central Aegean, and furthermore provides a notable contribution for palaeoclimatic studies, facilitating intercorrelations between various oceanographic basins. The quantitative analyses of benthic foraminifera identify four distinct assemblages, namely Biofacies: Elphidium spp., Haynesina spp. Biofacies, characterized by neritic species, dominated during the transition from MIS 5 to MIS 4; Cassidulina laevigata/carinata Biofacies dominated till 42 ka (transgressive trend from MIS 4 to MIS 3); Bulimina gibba Biofacies dominated from 42 ka to 9.5 ka (extensive regression MIS 3,2 through lowstand and early transgression; beginning of MIS 1); Bulimina marginata, Uvigerina spp. Biofacies dominated from 9.5 ka to the present (late transgression through early highstand; MIS 1)., This study showed that the South Evoikos Basin which is characterized by its critical depths and

  13. The trace-element characteristics of Aegean and Aeolian volcanic arc marine tephra

    NASA Astrophysics Data System (ADS)

    Clift, Peter; Blusztajn, Jerzy

    1999-10-01

    High-silica volcanic ashes are found within deep-sea sediments throughout the Eastern Mediterranean. Although coring by Ocean Drilling Program has penetrated Lower Pliocene (˜4 Ma) sediments, few ashes older than 400 k.y. have been recovered, suggesting a young initiation to subaerial Aegean Arc volcanism. Ashes derived from the Aegean volcanic front were cored south and east of the arc, and are typified by medium-K, calc-alkaline major-element compositions, contrasting with high-K ashes from the Aeolian Arc found in the Ionian Sea and as far east as Crete. Ion microprobe analysis of individual glass shards shows that all the ashes have a light rare earth element (LREE)-enriched pattern after normalizing against a chondrite standard. Aeolian Arc-derived ashes show greater enrichment than those from the Aegean area. Within the latter set, two groups are discernible, a mildly enriched set similar to the volcanoes of the arc volcanic front, and a more enriched group corresponding to lavas from the backarc region or possible from western Anatolia. Multi-element `spider diagrams' also show a bimodal division of enriched and depleted Aegean ashes, possibly caused by source depletion due to melt extraction in the Aegean backarc followed by remelting under the volcanic front. Relative Nb depletion, a characteristic of arc volcanism, is seen to be modest in Aegean and non-existent in Aeolian ashes. Using B/Be as a proxy for the flux of material from the subducting slab, this influence is seen to be low in the Aeolian Arc but higher than at Vesuvius. B/Be is higher again in the Aegean Arc. These differences may reflect the rate of subduction in each system. Data suggest caution is required when correlating ashes solely on the basis of major elements, as alkaline ashes from the central part of the study may be derived from Italy or from the Aegean backarc.

  14. Abyssal and deep circulation in the Eastern Mediterranean Sea (Ionian Sea)

    NASA Astrophysics Data System (ADS)

    Artale, Vincenzo; Bensi, Manuel; Falcini, Federico; Marullo, Salvatore; Rubino, Angelo

    2016-04-01

    In the mid-1990s, experimental evidences on the Eastern Mediterranean Transient (EMT) were presented and it was shown that the Mediterranean abyssal circulation is not in a steady state but can be subjected to episodic sudden changes (Roether et al., 1996). In the last 10 years the Ionian Sea, the central and deepest part of the Mediterranean Sea, was subjected to relevant scientific interests from a theoretical and experimental point of view. Among these, there is the discovery of the BiOS (Bimodal Oscillating System), one new mechanism that drives a periodic (almost decadal) redistribution of surface and subsurface waters in the Eastern Mediterranean, with considerable feedbacks in the variability of the deep-water formation both in the southern Adriatic and in the Levantine and Aegean sub-basins (Gačić et al., 2010). In the Ionian Sea, numerous recent observational campaigns have been conducted to investigate the behaviour of deep and abyssal waters, at depths between 2000-4000m that are comparable to the mean global ocean depth (Rubino and Hainbucher, 2007; Bensi et al., 2013). There, advection, diffusion and vertical stability of the water masses can assume an important role on the internal quasi-periodical variability, creating the preconditions for catastrophic events such as the EMT or reversals of the Ionian circulation (Pisacane et al., 2006). Since there are no significant deep heat sources in the world ocean, waters that fill the deep ocean can only return to the sea surface as a result of downward mixing of heat from the sea surface to the bottom and vice versa and this occurs through eddy diffusion. Along our presentation, mainly through the analysis of the deepest CTD casts taken from 2009 to 2011 in the eastern basins and in particular in the Ionian Sea, we will show a significant change in the deep thermohaline structure (including its biogeochemical and hydrological characteristics), giving an indication on the time scale of the renewal of deep

  15. Submarine canyon, slope, and shelf sedimentation in an upper Eocene-Oligocene progradational system (Limnos Island, north Aegean Sea, Greece)

    SciTech Connect

    Roussos, N.

    1988-08-01

    The only well-exposed outcrops of a post-Alpine late Eocene-Oligocene basin in the north Aegean Sea are at Limnos Island. These mostly consist of typical slope deposits overlain by remnants of shallow marine shelf and continental (braided-river) deposits. Three main slope lithofacies are distinguished. Canyon deposits consist of thick-bedded, massive, and pebbly sandstones (facies B), conglomerates (facies A), pebbly mudstone where the matrix shows flow (facies F), rock falls (nummulitic limestones), and zones of slump folds in sandstones (facies F). Channelized facies of massive sandstones, classical turbidites, and thin interbeds of sandstone and mudstone (facies E - probably overbank or levee deposits) are associated with canyon deposits. Pelagic and hemipelagic slope deposits consist of mudstone (facies G) and thin-bedded sandstone (facies D) with occasional small to medium-scale slump folds. These mud-rich slope deposits are incised by several channels filled with conglomerates, thick massive sandstones with well-developed dish structures, and turbidites interbedded with thin layers of mudstone (facies C). This unit composes a typical thinning and fining-upward sequence.

  16. Assessing enigmatic boulder deposits in NE Aegean Sea: importance of historical sources as tool to support hydrodynamic equations

    NASA Astrophysics Data System (ADS)

    Vacchi, M.; Rovere, A.; Zouros, N.; Firpo, M.

    2012-04-01

    Due to their importance in the assessment of coastal hazards, several studies have focused on geomorphological and sedimentological field evidence of catastrophic wave impacts related to historical tsunami events. Among them, many authors used boulder fields as important indicators of past tsunamis, especially in the Mediterranean Sea. The aim of this study was to understand the mechanism of deposition of clusters of large boulders, consisting of beachrock slabs, which were found on the southern coasts of Lesvos Island (NE Aegean Sea). Methods to infer the origin of boulder deposits (tsunami vs. storm wave) are often based on hydrodynamic models even if different environmental complexities are difficult to be incorporated into numerical models. In this study, hydrodynamic equations did not provide unequivocal indication of the mechanism responsible for boulder deposition in the study area. Further analyses, ranging from geomorphologic to seismotectonic data, indicated a tsunami as the most likely cause of displacement of the boulders but still do not allow to totally exclude the extreme storm origin. Additional historical investigations (based on tsunami catalogues, historical photos and aged inhabitants interviews) indicated that the boulders are likely to have been deposited by the tsunami triggered by the 6.7 Ms Chios-Karaburum earthquake of 1949 or, alternatively, by minor effects of the destructive tsunami produced by 1956's Amorgos Island earthquake. Results of this study point out that, at Mediterranean scale, to flank numerical models with the huge amount of the available historical data become a crucial tool in terms of prevention policies related to catastrophic coastal events.

  17. A review of tectonics and sedimentation in a forearc setting: Hellenic Thrace Basin, North Aegean Sea and Northern Greece

    NASA Astrophysics Data System (ADS)

    Maravelis, A. G.; Boutelier, D.; Catuneanu, O.; Seymour, K. St.; Zelilidis, A.

    2016-04-01

    Exposure of the forearc region of the North Aegean Sea, Greece, offers insight into evolving convergent margins. The sedimentary fill of the Thrace Basin during the Late Eocene to Oligocene time provides a record of subduction-driven processes, such as growth of magmatic arcs and construction of accretionary complexes. This large sediment repository received sediment from two sources. The southern (outboard) basin margin reflects the active influence of the exhumed accretionary prism (e.g. Pindic Cordillera or Biga peninsula), while the northern (inboard) margin records the effect of the magmatic arc in the Rhodope region. The forearc basin sedimentary fills shoal upward into shallow-marine strata but are dominated mainly by deep-marine facies. The depositional trend and stacking pattern are dominated by progradational patterns. This trend, which is observed in both basin margins, is related to tectonic deformation rather than sea-level fluctuations. Additional evidence for this tectonic uplift comes from the backstripping analysis. The accretionary complex provided material into the forearc basin. This material was transported northeast and formed a sand-rich turbidity system that evolved upslope into shallow-marine deposits. Stratigraphic data indicate that this turbidity system exhibits a successive landward (inboard) migration of the depocenter. Provenance data utilizing sandstone petrography, conglomerate clast composition, and bulk-rock geochemistry suggest that this system reflects an increased influx of mafic material into the basin. Volcanic arc-derived material was transported south and east and accumulated in deep-marine settings. Both stratigraphic and provenance data indicate a seaward (outboard) migration of the basin depocenter and a significant increase in felsic detritus into the forearc.

  18. Geomorphological characteristics of the onshore/offshore volcanic edifices with respect to their evolutionary stage in the South Aegean Sea, Greece.

    NASA Astrophysics Data System (ADS)

    Carey, S.; Nomikou, P.; Papanikolaou, D.; Alexandri, M.

    2014-12-01

    Volcanism in the South Aegean Sea first occurred about 3-4 million years ago, along four different volcanic island groups, including both onshore and recently discovered offshore volcanoes: 1) Starting from the west, the Methana group consists of the Methana stratovolcano, composed exclusively of volcaniclastics and lavas, creating cones and domes onland and the Paphsanias submarine cone in the Epidavros tectonic graben, bordered by E-W normal faults. It has a 2 km basal diameter at 400 m depth and its top rises to 150 m. 2) The Milos-Antimilos group consists of volcanic domes and calderas onland and three submarine domes to the east of Antimilos. A hydrothermal vent field is limited in the SE coastal zone of Milos, 3) The Santorini group consists of: (i) the older volcanic cones of Christianna islets and three submarine domes east of them, (ii) Santorini volcano which during the last 500 ka experienced repeated caldera collapses following Plinian eruptions and edifice rebuilding, represented by the growth of the Kamenes islands after the last catastrophic Late Bronze age eruption. (iii) a chain of about twenty submarine volcanic domes and craters in the Kolumbo zone northeast of Santorini. Kolumbo volcano is a 3 km diameter cone with a 1500 m wide crater, a crater rim as shallow as 18 m depth and a flat crater floor at 505 m depth containing an active hydrothermal vent field degassing 99% of CO2. 4) The Kos-Nisyros group at the eastern edge of the Hellenic Volcanic arc, comprises several domes and craters offshore and Nisyros volcano consists exclusively of alternating lava and pyroclastic deposits following several phases of reconstruction and caldera collapse. The rhyodacitic domes of Profitis Ilias are the latest evolutionary stage of Nisyros volcano which disrupted a pre-existed caldera and may be regarded as an earlier reconstruction phase similar to the Kameni islands at Santorini. The volcanic relief reaches 1100-1200 m in most cases. This is produced from

  19. Ductile nappe stacking and refolding in the Cycladic Blueschist Unit: insights from Sifnos Island (south Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Aravadinou, Eirini; Xypolias, Paraskevas; Chatzaras, Vasileios; Iliopoulos, Ioannis; Gerogiannis, Nikolaos

    2016-10-01

    New geological and structural mapping combined with kinematic and amphibole chemistry analyses is used to investigate the deformation history of the Cycladic Blueschist Unit (CBU) on Sifnos Island (Cyclades, Aegean Sea). We concentrate on north Sifnos, an area characterized by exceptionally well-preserved eclogites and blueschists. Our data show that the early, main phase (D2) of ductile deformation in the CBU occurred synchronous with the transition from prograde to close-to-peak retrograde conditions. This deformation phase took place at middle Eocene and is related to ESE-directed thrusting that emplaced the metavolcano-sedimentary subunit over the Marble subunit. The subsequent exhumation-related (D3) deformation is characterized by gently NE-plunging folds and NE-directed contractional shear zones that formed parallel to the axial planes of folds. NE-directed shearing occurred under blueschist and transitional blueschist-/greenschist-facies conditions during late Eocene-Oligocene and caused the restacking of the early nappe pile. We suggest that a mechanism of ductile extrusion of the CBU in a tectonic setting of net compression could explain better the recorded exhumation-related deformation than a mechanism of syn- and post-orogenic extension. Our new kinematic results in combination with previous works in the Cyclades area reveal a regional scale change in tectonic transport direction from (W)NW-(E)SE at Late Cretaceous-middle Eocene to (E)NE-(W)SW at late Eocene-Oligocene times. The observed change in transport direction may be governed by the relative motion of Africa with respect to Europe during Alpine orogeny.

  20. Zircon U-Pb, O, and Hf isotopic constraints on Mesozoic magmatism in the Cyclades, Aegean Sea, Greece

    NASA Astrophysics Data System (ADS)

    Fu, Bin; Bröcker, Michael; Ireland, Trevor; Holden, Peter; Kinsley, Leslie P. J.

    2015-01-01

    Compared to the well-documented Cenozoic magmatic and metamorphic rocks of the Cyclades, Aegean Sea, Greece, the geodynamic context of older meta-igneous rocks occurring in the marble-schist sequences and mélanges of the Cycladic Blueschist Unit is as yet not fully understood. Here, we report O-Hf isotopic compositions of zircons ranging in age from ca. 320 Ma to ca. 80 Ma from metamorphic rocks exposed on the islands of Andros, Ios, Sifnos, and Syros with special emphasis on Triassic source rocks. Ion microprobe (SHRIMP II) single spot oxygen isotope analysis of pre-Cretaceous zircons from various felsic gneisses and meta-gabbros representing both the marble-schist sequences and the mélanges of the study area yielded a large range in δ18O values, varying from 2.7 ‰ to 10.1 ‰ VSMOW, with one outlier at -0.4 %. Initial ɛHf values (-12.5 to +15.7) suggest diverse sources for melts formed between Late Carboniferous to Late Cretaceous time that record derivation from mantle and reworked older continental crust. In particular, variable δ18O and ɛHf( t) values for Triassic igneous zircons suggest that magmatism of this age is more likely rift- than subduction-related. The significant crustal component in 160 Ma meta-gabbros from Andros implies that some Jurassic gabbroic rocks of the Hellenides are not part of SSZ-type (supra-subduction zone) ophiolites that are common elsewhere along the margin of the Pelagonian zone.

  1. Radiometric dating of sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea.

    PubMed

    Ugur, Aysun; Miquel, Juan-Carlos; Fowler, Scott W; Appleby, Peter

    2003-05-20

    Sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea were dated using the 210Pb method. The average unsupported 210Pb inventory in the cores was calculated to be 3256 Bq m(-2). The corresponding mean annual 210Pb flux of 105 Bq m(-2) year(-1) is comparable to estimates of the atmospheric flux given in the literature. 210Pb fluxes calculated from the unsupported 210Pb inventories in cores are also comparable with the 210Pb vertical fluxes determined from settling particles off the coast of Milos Island. The highest unsupported 210Pb concentrations (89 Bq kg(-1)) were measured in the sediments nearest to the hydrothermal vent area suggesting that the sedimentation rate is lowest at this site. Direct gamma measurements of 210Pb were used to date three sediment cores that are located at different distances from the vent zone: one is in the immediate vicinity of the vent; and others are outside the zone. Sedimentation rates for these cores, calculated using the CRS and CIC models, ranged from 0.088+/-0.008 cm year(-1) to 0.14+/-0.01 cm year(-1). Where both models were applicable, the results given by the two methods were in good agreement. 137Cs concentrations in all three cores generally declined with depth but showed no clear signal of either the period of maximum fallout from weapons testing or the Chernobyl accident. 210Po activities were also measured and the maximum 210Po concentration was in the sediment surface layer (166 Bq kg(-1)).

  2. Ductile nappe stacking and refolding in the Cycladic Blueschist Unit: insights from Sifnos Island (south Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Aravadinou, Eirini; Xypolias, Paraskevas; Chatzaras, Vasileios; Iliopoulos, Ioannis; Gerogiannis, Nikolaos

    2015-10-01

    New geological and structural mapping combined with kinematic and amphibole chemistry analyses is used to investigate the deformation history of the Cycladic Blueschist Unit (CBU) on Sifnos Island (Cyclades, Aegean Sea). We concentrate on north Sifnos, an area characterized by exceptionally well-preserved eclogites and blueschists. Our data show that the early, main phase (D2) of ductile deformation in the CBU occurred synchronous with the transition from prograde to close-to-peak retrograde conditions. This deformation phase took place at middle Eocene and is related to ESE-directed thrusting that emplaced the metavolcano-sedimentary subunit over the Marble subunit. The subsequent exhumation-related (D3) deformation is characterized by gently NE-plunging folds and NE-directed contractional shear zones that formed parallel to the axial planes of folds. NE-directed shearing occurred under blueschist and transitional blueschist-/greenschist-facies conditions during late Eocene-Oligocene and caused the restacking of the early nappe pile. We suggest that a mechanism of ductile extrusion of the CBU in a tectonic setting of net compression could explain better the recorded exhumation-related deformation than a mechanism of syn- and post-orogenic extension. Our new kinematic results in combination with previous works in the Cyclades area reveal a regional scale change in tectonic transport direction from (W)NW-(E)SE at Late Cretaceous-middle Eocene to (E)NE-(W)SW at late Eocene-Oligocene times. The observed change in transport direction may be governed by the relative motion of Africa with respect to Europe during Alpine orogeny.

  3. Assessment of SMOS Salinity and SST in the Aegean Sea (Greece) and correlations with MODIS SST measurements. Exploring the SSS and SST correlation to 137Cs inventory

    NASA Astrophysics Data System (ADS)

    Sykioti, Olga; Florou, Heleni

    2014-05-01

    A program concept has been developed to utilize sea surface salinity (SSS) and sea surface temperature (SST) information for the inventory of artificial radionuclides, which are conservative and part of the sea salinity. As a pilot study, activity concentrations of 137Cs in the Aegean Sea (Greece) are combined to SMOS and other satellite data so as to develop an innovative tool for the remote radioactivity detection either for routine observations and emergency recordings. The presented first results are a part of an effort to attempt for the integration in space and time of field measurements to the respective satellite observations of salinity variations by model simulations, which might be also applicable for the prediction of the radiological impact of potential accidental events. The presented results involve the first assessment of SMOS SSS and SST measurements over the Aegean Sea. SMOS measurements are averaged over a surface of 40x40 sq km at an average distance of 100 km from the coastline. For this reason, totally thirty nine pixels from SMOS Level 2 data cover part of the Aegean Sea. Two time series are created that include all available measurements spanning December 2011 to current date, from descending and ascending passes, each one representing an acquisition frequency of about three days. The average SSS values in the Aegean Sea are 37-38psu following no distinct seasonal pattern. A general trend of increasing values is observed from north to south. Noise and uncertainty in the measurements are most probably due to land and RFI contamination. High island density is combined with radiofrequency interferences generated by illegal man-made emissions. The latter is a detected common issue in specific areas worldwide, such as the Mediterranean Sea. On the other hand, SST follows a clear typical seasonal variation pattern with maximum values observed in August and minimum ones around March and a general trend of increasing values from north to south

  4. Viruses in a deep oligotrophic sea: Seasonal distribution of marine viruses in the epi-, meso- and bathypelagic waters of the Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Magiopoulos, Iordanis; Pitta, Paraskevi

    2012-08-01

    Marine viruses and their main hosts were studied in the Eastern Mediterranean Sea (Ionian, Libyan and Aegean Seas) during two sampling cruises (mixing and water column stratification periods). Samples were collected from the surface to 4000 m depth. Total abundance of viruses and prokaryotes was determined by Flow Cytometry (FCM). Viruses were separated into three groups according to their fluorescence signal. Viral abundance ranged from 1.2×105 viruses ml-1 to 2.7×107 viruses ml-1 and varied significantly between areas, depth zones and seasons. Prokaryotic cell abundance varied from 1.7×104 cells ml-1 to 1.5×106 cells ml-1 presenting a strong positive correlation with viral abundance. Stations and depths influenced by the Black Sea Water in the North Aegean Sea presented the highest values of viral abundance and Viruses to Prokaryotes Ratio (VPR). Vertical distributions of VPR were attributed to different water masses. The increased viral abundance and VPR values that were detected during the stratification period may be explained by the seasonal changes in prokaryotic cell characteristics (cell size, nucleic acid content). These significant seasonal distributions were also found below 1000 m indicating a possible viral activity in the bathypelagic ocean.

  5. 137Caesium distribution in the eastern Mediterranean Sea: recent changes and future trends.

    PubMed

    Papucci, C; Delfanti, R

    1999-09-30

    A series of sampling campaigns were carried out in the eastern Mediterranean in the period 1995-1997, to examine the relationship between the distribution of 137Cs in the water column and water mass circulation. 137Cs concentration in the surface water ranges between 3.3 and 4.0 mBq/l all over the area, indicating that the input due to the Chernobyl accident has been transferred to deep water layers by convection processes. In fact, in the vertical profiles, relative maxima are observed in the intermediate (4 mBq/l) and deep waters (approximately 2.5 mBq/l) formed after the Chernobyl accident. A clear Chernobyl signal also traces the new deep waters formed in the Aegean Sea that, exiting from the Cretan Arc Straits, since 1991 are spreading in the bottom layer of the eastern Mediterranean. The changes in 137Cs vertical profiles related to the new thermohaline circulation of the intermediate and deep waters of the eastern Mediterranean are being monitored at a deep station in the western Ionian Sea. The 1997 profile shows a decrease in 137Cs concentration both in the Levantine intermediate water and in the eastern Mediterranean deep water with respect to 1996. The decrease in Levantine intermediate water is likely due to seasonal/interannual variability, while the changes in the deep layer are related to the spreading westward into the Ionian of the new Aegean dense water. Along the path towards the western Mediterranean, 137Cs content in the Levantine intermediate water decreases from approximately 4 mBq/l in the W-Ionian Sea to approximately 2 mBq/l at the western sill of the Sicily Straits, due to mixing with underlying water, with lower caesium content, near the Malta Sill. Time-series measurements at the western sill of the Sicily Straits show that, while 137Cs concentration in the surface water entering the eastern Mediterranean remained constant (approximately 3.5 mBq/l) in the period 1993-1997, its level in the Levantine intermediate water leaving the basin

  6. 137Caesium distribution in the eastern Mediterranean Sea: recent changes and future trends.

    PubMed

    Papucci, C; Delfanti, R

    1999-09-30

    A series of sampling campaigns were carried out in the eastern Mediterranean in the period 1995-1997, to examine the relationship between the distribution of 137Cs in the water column and water mass circulation. 137Cs concentration in the surface water ranges between 3.3 and 4.0 mBq/l all over the area, indicating that the input due to the Chernobyl accident has been transferred to deep water layers by convection processes. In fact, in the vertical profiles, relative maxima are observed in the intermediate (4 mBq/l) and deep waters (approximately 2.5 mBq/l) formed after the Chernobyl accident. A clear Chernobyl signal also traces the new deep waters formed in the Aegean Sea that, exiting from the Cretan Arc Straits, since 1991 are spreading in the bottom layer of the eastern Mediterranean. The changes in 137Cs vertical profiles related to the new thermohaline circulation of the intermediate and deep waters of the eastern Mediterranean are being monitored at a deep station in the western Ionian Sea. The 1997 profile shows a decrease in 137Cs concentration both in the Levantine intermediate water and in the eastern Mediterranean deep water with respect to 1996. The decrease in Levantine intermediate water is likely due to seasonal/interannual variability, while the changes in the deep layer are related to the spreading westward into the Ionian of the new Aegean dense water. Along the path towards the western Mediterranean, 137Cs content in the Levantine intermediate water decreases from approximately 4 mBq/l in the W-Ionian Sea to approximately 2 mBq/l at the western sill of the Sicily Straits, due to mixing with underlying water, with lower caesium content, near the Malta Sill. Time-series measurements at the western sill of the Sicily Straits show that, while 137Cs concentration in the surface water entering the eastern Mediterranean remained constant (approximately 3.5 mBq/l) in the period 1993-1997, its level in the Levantine intermediate water leaving the basin

  7. Estimation and Monitoring of Wind/Wave energy potential in the Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Zodiatis, George; Galanis, George; Galanis, George; Emmanouil, George; Emmanouil, George; Hayes, Dan; Nikolaidis, Andreas; Georgiou, Georgios; Kalogeri, Christina; Kallos, George

    2013-04-01

    Τhe adaptation and use of innovative methodologies for the exploitation of renewable energy marine resources is one of the main issues today for the environmental science community. Within this framework, the exploitation of wind and wave energy potential for coastal and island states seems to be one of the promising solutions and highly interesting from research and technological point of view. In this work, the activities of two projects focusing on the study of wind/wave energy over the area of Eastern Mediterranean Sea are presented. The "Integrated High Resolution System for Monitoring and Quantifying the Wave Energy Potential in the EEZ of Cyprus" (Ewave project) focuses on the estimation, monitoring and forecasting of the wave energy potential over the Levantine Basin with special emphasis to the Exclusive Economical Zone of Cyprus, while the "Development and application of new mathematical and physical models for Monitoring the wind and Sea wave Energy Potential" (MOSEP project) is a platform for developing new mathematical algorithms for the estimation of the wave energy over the Aegean Sea. In both projects, high resolution digital atlases of sea wave/wind climatological characteristics and the distribution of the wind and wave energy potential are developed for the coastal and offshore areas of the East Mediterranean sea . Moreover, new models for the prediction and quantification of wave energy in short and long forecast horizons are proposed. Statistical results concerning the probability density functions of the wind speed, the significant wave height, as well as the energy potential will be presented for selected sea areas in the Eastern Mediterranean Sea, while test case studies in certain regions favor to wind/wave renewable energy will be discussed.

  8. An integrated zircon geochronological and geochemical investigation into the Miocene plutonic evolution of the Cyclades, Aegean Sea, Greece: part 2—geochemistry

    NASA Astrophysics Data System (ADS)

    Bolhar, Robert; Ring, Uwe; Kemp, Anthony I. S.; Whitehouse, Martin J.; Weaver, Steve D.; Woodhead, Jon D.; Uysal, I. Tonguc; Turnbull, Rose

    2012-12-01

    Zircons from 14 compositionally variable granitic rocks were examined in detail using CL image-guided micro-analysis to unravel the complex magmatic history above the southward retreating Hellenic subduction zone system in the Aegean Sea. Previously published U-Pb ages document an episodic crystallisation history from 17 to 11 Ma, with peraluminous (S-type) granitic rocks systematically older than closely associated metaluminous (I-type) granitic rocks. Zircon O- and Hf isotopic data, combined with trace element compositions, are highly variable within and between individual samples, indicative of open-system behaviour involving mantle-derived melts and evolved supracrustal sources. Pronounced compositional and thermal fluctuations highlight the role of magma mixing and mingling, in accord with field observations, and incremental emplacement of distinct melt batches coupled with variable degrees of crustal assimilation. In the course of partial fusion, more fertile supracrustal sources dominated in the earlier stages of Aegean Miocene magmatism, consistent with systematically older crystallisation ages of peraluminous granitic rocks. Differences between zircon saturation and crystallisation temperatures (deduced from zircon Ti concentrations), along with multimodal crystallisation age spectra for individual plutons, highlight the complex and highly variable physico-compositional and thermal evolution of silicic magma systems. The transfer of heat and juvenile melts from the mantle varied probably in response to episodic rollback of the subducting lithospheric slab, as suggested by punctuated crystallisation age spectra within and among individual granitic plutons.

  9. Modelling tsunamis in the Eastern Mediterranean Sea. Application to the Minoan Santorini tsunami sequence as a potential scenario for the biblical Exodus

    NASA Astrophysics Data System (ADS)

    Periáñez, R.; Abril, J. M.

    2014-11-01

    A numerical model which simulates the propagation of tsunamis in the Eastern Mediterranean has been developed. Several tsunami sources have been considered: earthquakes associated to geological faults, submarine landslides, entry of pyroclastic flows into the sea and the collapse of a volcano caldera. The model has been applied to different past events for which historic data or previous simulations exist, to test its performance. Then it has been applied to simulate tsunamis triggered by the explosion of Santorini volcano (17th century BC) in the Aegean Sea. While the model accounts for run-ups in the Aegean coasts, it fails to explain the isochronous tsunamigenic deposits reported in eastern Sicily and the levantine coasts. A scenario of a sequence of intense tectonics strain release triggering a series of tsunamis could better fit the whole dataset. Thus, a submarine landslide at the Gulf of Sirte may explain the Augias megaturbidite and the sedimentary deposits reported in Augusta Bay (Sicily). Similarly, a sequential tsunami in the eastern Nile Delta may explain the tsunamigenic deposits found in Israel and Gaza. Considering the former coastline at 3500 years BP, it could also provide a plausible scenario for the biblical sea crossing related in the Exodus.

  10. Thermaikos Gulf Coastal System, NW Aegean Sea: an overview of water/sediment fluxes in relation to air land ocean interactions and human activities

    NASA Astrophysics Data System (ADS)

    Poulos, S. E.; Chronis, G. Th; Collins, M. B.; Lykousis, V.

    2000-04-01

    This study presents an overview of the Holocene formation and evolution of the coastal system of Thermaikos Gulf (NW Aegean Sea). The system is divided into the terrestrial sub-system and the oceanic sub-system; the former represents 90%, while the latter includes only 10% of the total area. This particular coastal zone includes the second most important socio-economic area of Greece and in the southern Balkans, the Thessaloniki region; this is in terms of population concentration (>1 million people), industry, agriculture, aquaculture, trade and services. The geomorphology of the coastal zone is controlled by sediment inputs, nearshore water circulation, and the level of wave activity. The large quantities of sediments (with yields >500 tonnes/km 2 per year), delivered annually by the main rivers (Axios, Aliakmon, Pinios, and Gallikos) and other seasonal streams are responsible for the general progradation of the coastline and the formation of the Holocene sedimentary cover over the seabed of the Gulf. Changes to the coastline can be identified on macro- and meso-time scales; the former include the evolution of the deltaic plains (at >1 km 2/year), while the latter incorporates seasonal changes along sections of the coastline (e.g. sandy spits), mostly due to the anthropogenic activities. The overall water circulation pattern in Thermaikos Gulf is characterised by northerly water movement, from the central and eastern part of the Gulf; this is compensated by southerly movement along its western part. The prevailing climate (winds and pressure systems) appears to control the surface water circulation, while near-bed current measurements reveal a general moderate (<15 cm/s) southerly flow, i.e. offshore, towards the deep water Sporades Basin. Waves approaching from southerly directions play also a role in controlling the shoreline configuration. Various human activities within the coastal system place considerable pressure on the natural evolution of the coastal

  11. Periodicities in sediment temperature time-series at a marine shallow water hydrothermal vent in Milos Island (Aegean Volcanic arc, Eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Aliani, Stefano; Meloni, Roberto; Dando, Paul R.

    2004-05-01

    Time-series data sets of total bottom pressure (tidal plus atmospheric), seawater temperature and sediment temperature from a marine shallow hydrothermal vent (Milos, Hellenic Volcanic Arc, Aegean Sea) were studied to determine factors influencing periodicity at the vents. Bottom pressure and vent temperature were mainly opposite in phase, with the main fluctuations of vent temperature occurring at tidal frequencies. Although the fluctuations in atmospheric pressure were of the same order as those due to tidal pressure, the contribution of atmospheric pressure was considerably weaker at diurnal frequencies. Some sudden discontinuities in sediment temperature were recorded, at least one of these may have been caused by seismic events. Seawater temperature changes were not reflected in the sediment temperature record. Transient loadings, such as tidal loadings, barometric pressure and earth tides, may affect the pore pressure in sediments, influencing fluid expulsion and sediment temperature as a consequence. Most of the contribution to the fluctuations in sediment temperature depends on tidal loadings. Gravitational forces, in the form of earth tides, can also be involved and barometric pressure is probably responsible for long period temperature oscillations.

  12. Lithospheric Response of the Anatolian Plateau in the Realm of the Black Sea and the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Ergun, Mustafa

    2016-04-01

    The Eastern Mediterranean and the Middle East make up the southern boundary of the Tethys Ocean for the last 200 Ma by the disintegration of the Pangaea and closure of the Tethys Ocean. It covers the structures: Hellenic and Cyprus arcs; Eastern Anatolian Fault Zone; Bitlis Suture Zone and Zagros Mountains. The northern boundary of the Tethys Ocean is made up the Black Sea and the Caspian Sea, and it extends up to Po valley towards the west (Pontides, Caucasus). Between these two zones the Alp-Himalayan orogenic belt is situated where the Balkan, Anatolia and the Iran plateaus are placed as the remnants of the lost Ocean of the Tethys. The active tectonics of the eastern Mediterranean is the consequences of the convergence between the Africa, Arabian plates in the south and the Eurasian plate in the north. These plates act as converging jaws of vise forming a crustal mosaic in between. The active crustal deformation pattern reveals two N-S trending maximum compression or crustal shortening syntaxes': (i) the eastern Black Sea and the Arabian plate, (ii) the western Black Sea and the Isparta Angle. The transition in young mountain belts, from ocean crust through the agglomeration of arc systems with long histories of oceanic closures, to a continental hinterland is well exemplified by the plate margin in the eastern Mediterranean. The boundary between the African plate and the Aegean/Anatolian microplate is in the process of transition from subduction to collision along the Cyprus Arc. Since the Black Sea has oceanic lithosphere, it is actually a separate plate. However it can be considered as a block, because the Black Sea is a trapped oceanic basin that cannot move freely within the Eurasian Plate. Lying towards the northern margin of orogenic belts related to the closure of the Tethys Ocean, it is generally considered to be a result of back-arc extension associated with the northward subduction of the Tethyan plate to the south. Interface oceanic lithosphere at

  13. Tsunami Hazard Analysis for the Eastern Mediterranean and its Connected Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Meral Ozel, Nurcan

    2015-04-01

    Accurate earthquake source parameters are essential for any tsunami hazard assessment and mitigation, including early warning systems. Complex tectonic setting makes the a priori accurate assumptions of earthquake source parameters difficult and characterization of the faulting type is a challenge. Information on tsunamigenic sources is of crucial importance in the Eastern Mediterranean and its Connected Seas, especially considering the short arrival times and lack of offshore sea-level measurements. In addition, the scientific community have had to abandon the paradigm of a ''maximum earthquake'' predictable from simple tectonic parameters (Ruff and Kanamori, 1980) in the wake of the 2004 Sumatra event (Okal, 2010) and one of the lessons learnt from the 2011 Tohoku event was that tsunami hazard maps may need to be prepared for infrequent gigantic earthquakes as well as more frequent smaller-sized earthquakes (Satake, 2011). We have initiated an extensive modeling study to perform a deterministic Tsunami Hazard Analysis for the Eastern Mediterranean and its Connected Seas. Characteristic earthquake source parameters (strike, dip, rake, depth, Mwmax) at each 0.5° x 0.5° size bin for 0-40 km depth (total of 310 bins) and for 40-100 km depth (total of 92 bins) in the Eastern Mediterranean, Aegean and Black Sea region (30°N-48°N and 22°E-44°E) have been assigned from the harmonization of the available databases and previous studies. These parameters have been used as input parameters for the deterministic tsunami hazard modeling. Nested Tsunami simulations of 6h duration with a coarse (2 arc-min) grid resolution have been simulated at EC-JRC premises for Black Sea and Eastern and Central Mediterranean (30°N-41.5°N and 8°E-37°E) for each source defined using shallow water finite-difference SWAN code (Mader, 2004) for the magnitude range of 6.5 - Mwmax defined for that bin with a Mw increment of 0.1. Results show that not only the earthquakes resembling the

  14. Biochemical biomarker responses to pollution in selected sentinel organisms across the Eastern Mediterranean and the Black Sea.

    PubMed

    Catherine, Tsangaris; Vanessa, Moschino; Evangelia, Strogyloudi; Valentina, Coatu; Andreja, Ramšak; Rana, Abu Alhaija; Susana, Carvalho; Serena, Felline; Alisa, Kosyan; Yiota, Lazarou; Ioannis, Hatzianestis; Andra, Oros; Daniela, Tiganus

    2016-01-01

    Pollution effects were assessed by means of biochemical biomarkers (catalase, glutathione S-transferase and acetylcholinesterase activities, and metallothioneins content) in five species at selected coastal sites across the Eastern Mediterranean and the Black Sea. The mussel Mytilus galloprovincialis, a well-established sentinel species, was investigated in the Adriatic Sea, Aegean Sea, and Black Sea. The mussel Brachidontes pharaonis and the striped red mullet Mullus surmuletus were used in the Levantine Sea where M. galloprovincialis is not present. The white seabream Diplodus sargus sargus and the gastropod Rapana venosa were additionally sampled in the Adriatic and the Black Sea, respectively. Mussels showed catalase, glutathione S-transferase, and acetylcholinesterase responses to pollution in most geographical areas while the response of metallothioneins was restricted to a few sites. R. venosa showed marked responses of catalase and metallothioneins whereas both fish species did not generally exhibit variations in biomarker values among sites. The approach based on the reference deviation concept using the "Integrated Biological Responses version 2" index was useful for the interpretation of overall biomarker responses.

  15. Biochemical biomarker responses to pollution in selected sentinel organisms across the Eastern Mediterranean and the Black Sea.

    PubMed

    Catherine, Tsangaris; Vanessa, Moschino; Evangelia, Strogyloudi; Valentina, Coatu; Andreja, Ramšak; Rana, Abu Alhaija; Susana, Carvalho; Serena, Felline; Alisa, Kosyan; Yiota, Lazarou; Ioannis, Hatzianestis; Andra, Oros; Daniela, Tiganus

    2016-01-01

    Pollution effects were assessed by means of biochemical biomarkers (catalase, glutathione S-transferase and acetylcholinesterase activities, and metallothioneins content) in five species at selected coastal sites across the Eastern Mediterranean and the Black Sea. The mussel Mytilus galloprovincialis, a well-established sentinel species, was investigated in the Adriatic Sea, Aegean Sea, and Black Sea. The mussel Brachidontes pharaonis and the striped red mullet Mullus surmuletus were used in the Levantine Sea where M. galloprovincialis is not present. The white seabream Diplodus sargus sargus and the gastropod Rapana venosa were additionally sampled in the Adriatic and the Black Sea, respectively. Mussels showed catalase, glutathione S-transferase, and acetylcholinesterase responses to pollution in most geographical areas while the response of metallothioneins was restricted to a few sites. R. venosa showed marked responses of catalase and metallothioneins whereas both fish species did not generally exhibit variations in biomarker values among sites. The approach based on the reference deviation concept using the "Integrated Biological Responses version 2" index was useful for the interpretation of overall biomarker responses. PMID:26396017

  16. Shorebirds of the eastern Bering Sea

    USGS Publications Warehouse

    Calder, J.A.; Hood, D.W.

    1981-01-01

    Largely on the basis of work conducted in western Alaska since 1975, we present an overview of the shorebird resources of the region and discuss their relationship to the littoral and supralittoral habitats of the area. Thirty species of shorebirds occur regularly and comprise an important component of the eastern Bering Sea ecosystem. For a third of these species the region supports the main Alaska population-for several species, the main North American population. In winter and spring littoral areas are generally ice-fast and little used by shorebirds. After breeding, there is a pronounced movement of shorebirds to coastal areas throughout the region. Populations regularly swell into the millions, many relying entirely on littoral habitats while undergoing molt and premigratory fat deposition. The extensive intertidal of the Yukon Delta and lagoons of the Alaska Peninsula are used by more species, in greater numbers, and for longer periods than other areas within the region. The timing of fall migration shows considerable variation by area, species, and age. The susceptibility of the most common shorebird species to disturbances from petroleum development is discussed.

  17. A biomarker study of high resolution sedimentary records in the eastern Mediterranean Sea since the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Katsouras, G.; Gogou, A.; Bouloubassi, I.; Emeis, K.-C.; Triantaphyllou, M. V.; Lykousis, V.

    2009-04-01

    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

  18. Viral Density and Virus-to-Bacterium Ratio in Deep-Sea Sediments of the Eastern Mediterranean

    PubMed Central

    Danovaro, Roberto; Serresi, Michela

    2000-01-01

    Viruses are now recognized as a key component in pelagic systems, but their role in marine sediment has yet to be assessed. In this study bacterial and viral densities were determined at nine deep-sea stations selected from three main sites (i.e., the Sporades Basin, the Cretan Sea, and the Ierapetra Trench at depths of 1,232, 1,840, and 4,235 m, respectively) of the Eastern Mediterranean. The three areas were characterized by different phytopigment and biopolymeric carbon concentrations and by changes in the protein and carbohydrate pools. A gradient of increasing trophic conditions was observed from the Sporades Basin (North Aegean) to the Ierapetra Trench (South Aegean). Viral densities (ranging from 1 × 109 to 2 × 109 viruses ml of sediment−1) were significantly correlated to bacterial densities (n = 9, r2 = 0.647) and reached values up to 3 orders of magnitude higher than those generally reported for the water column. However, the virus-to-bacterium density ratio in deep-sea sediments was about 1 order of magnitude lower (range of 2 to 5, with a modal value of 2.6) than in pelagic environments. Virus density decreased vertically with depth in sediment cores at all stations and was below detection limits at the 10-cm depth of the abyssal sediments of the Ierapetra Trench. Virus density in the sediment apparently reflected a gradient of particle fluxes and trophic conditions, displaying the highest values in the Sporades Basin. The low virus-to-bacterium ratios and their inverse relationship with station depth suggest that the role played by viruses in controlling deep-sea benthic bacterial assemblages and biogeochemical cycles is less relevant than in pelagic systems. PMID:10788350

  19. Implementation of a reduced order Kalman filter to assimilate ocean color data into a coupled physical-biochemical model of the North Aegean Sea.

    NASA Astrophysics Data System (ADS)

    Kalaroni, Sofia; Tsiaras, Kostas; Economou-Amilli, Athena; Petihakis, George; Politikos, Dimitrios; Triantafyllou, George

    2013-04-01

    Within the framework of the European project OPEC (Operational Ecology), a data assimilation system was implemented to describe chlorophyll-a concentrations of the North Aegean, as well the impact on the European anchovy (Engraulis encrasicolus) biomass distribution provided by a bioenergetics model, related to the density of three low trophic level functional groups of zooplankton (heterotrophic flagellates, microzooplankton and mesozooplankton). The three-dimensional hydrodynamic-biogeochemical model comprises two on-line coupled sub-models: the Princeton Ocean Model (POM) and the European Regional Seas Ecosystem Model (ERSEM). The assimilation scheme is based on the Singular Evolutive Extended Kalman (SEEK) filter and its variant that uses a fixed correction base (SFEK). For the initialization, SEEK filter uses a reduced order error covariance matrix provided by the dominant Empirical Orthogonal Functions (EOF) of model. The assimilation experiments were performed for year 2003 using SeaWiFS chlorophyll-a data during which the physical model uses the atmospheric forcing obtained from the regional climate model HIRHAM5. The assimilation system is validated by assessing the relevance of the system in fitting the data, the impact of the assimilation on non-observed biochemical parameters and the overall quality of the forecasts.

  20. The circulation of eastern Canadian seas

    NASA Astrophysics Data System (ADS)

    Wu, Yongsheng; Tang, Charles; Hannah, Charles

    2012-11-01

    The eastern Canadian seas including Baffin Bay, the Labrador Sea and shelf, the N.E. Newfoundland Shelf, the Scotian Shelf and the Gulf of St. Lawrence form an integrated hydro-dynamical system. The circulation is investigated using current meter data and a high resolution three dimensional coupled ice-ocean circulation model, CECOM (Canadian East Coast Ocean Model) covering the entire area. The model is forced with realistic atmosphere fluxes and the results are compared to the current meter data collected in four selected periods between 1987 and 2008. Many features of the model current fields are similar to those from the previous regional circulation models for the shelves. New findings from CECOM include seasonal differences of the circulation around Davis Strait, the detailed structure of the Labrador Current re-circulation, two cross-shelf currents on the Scotian Shelf, and strong currents in Halibut Channel which connects the waters of the western Grand Banks and Scotian Shelf. The annual variation of the circulation is investigated. Both the model and data show the Labrador Current is strong in fall and weak in spring. The outflow from the Gulf of St. Lawrence through Cabot Strait and the currents on the inner Scotian Shelf are strong in winter and fall and weak in spring, and are in phase with the Labrador Current. The model currents are compared to observations using a qualitative method of visual comparison, and a quantitative method based on statistical analysis. The comparisons indicate that the main features of the current fields from the observations are successfully reproduced by the model. The quantitative analysis indicates that the model currents are in reasonable agreement with the observations. Specifically, a good agreement is found in the Labrador shelf, Newfoundland Shelf and Flemish Pass, a fair agreement is found in Davis Strait, the inner Scotian Shelf and Sable Bank. However, the agreement for Cabot Strait and the Scotian Shelf break is

  1. Eemian sea-level highstand in the eastern Baltic Sea linked to long-duration White Sea connection

    NASA Astrophysics Data System (ADS)

    Miettinen, Arto; Head, Martin J.; Knudsen, Karen Luise

    2014-02-01

    Revised diatom and new dinoflagellate cyst and benthic foraminiferal data from the eastern Baltic Sea have refined our understanding of Eemian (Last Interglacial; 131-119.5 ka) sea-level change on the Russian Karelia, a former seaway linking the Baltic to the White Sea. Results from Peski, eastern Baltic show the initiation of marine conditions just before 131 ka in the latest Saalian, after the opening of a connection to the North Sea. Following the onset of the Eemian marine highstand and the opening of the White Sea connection at around 130.25 ka, near-fully marine conditions persisted in the eastern Baltic area for ca 6 kyr, until ca 124 ka. For most of the Eemian, a strong thermal stratification in the eastern Baltic resulted from an Arctic and possible North Atlantic water component from the White Sea merging with warmer waters from the North Sea. From ca 124 ka, decreasing salinity indicates the end of the marine highstand and a simultaneous closure of the Baltic Sea-White Sea connection, i.e. a duration of ca 6 kyr for this seaway. The main influence of White Sea inflow appears to be restricted to the eastern Baltic area, although a large submerged area in the Russian Karelia associated with temperate Atlantic waters could have assisted in creating a more oceanic climate for Central Europe.

  2. Evolution of freshwater crab diversity in the Aegean region (Crustacea: Brachyura: Potamidae).

    PubMed

    Jesse, Ruth; Grudinski, Melanie; Klaus, Sebastian; Streit, Bruno; Pfenninger, Markus

    2011-04-01

    The aim of this study was to estimate the influence of the palaeogeographic and climatic history of the Aegean region on the diversity of freshwater crabs of the genus Potamon and to test whether this area served as source or reservoir in species diversity. Necessary species delimitation was accomplished by phylogenetic analyses of the mitochondrial markers COX1 and ND1, partial 16S rRNA gene and the tRNALeu gene. We found 14 genetic lineages of which nine could be assigned to previously recognised species. Temporal estimates of the splitting pattern in the phylogeny of Potamon indicated that a combination of geological and climatic events influenced their diversification. Within Potamon, the lineages separated into a western group and an eastern group. This first split in the genus occurred approximately 8.3-5.5 Mya, thus possibly correlated with the Messinian salinity crisis. A likelihood approach to geographic range evolution suggested for most species, occurring in the Aegean area, an origin in the Middle East. Moreover, there were no insular endemics in the central Aegean archipelago, therefore low sea-levels during the Pleistocene glacial periods possibly enabled dispersal to these islands, but subsequent rise in sea-level did not cause speciation. Nevertheless, the diversification of most lineages occurred during the Pleistocene epoch thus coinciding with Quaternary fluctuations of the climate.

  3. The eastern Massachusetts sea breeze study

    NASA Astrophysics Data System (ADS)

    Thorp, Jennifer E.

    This study investigates many different aspects of the sea breeze at Logan Airport in Boston, Massachusetts (KBOS) and along the Massachusetts coastline. Part of the study adapts the method of predicting sea breeze events developed by Miller and Keim (2003) for Portsmouth, New Hampshire (KPSM) to KBOS. A nearly ten-year dataset of hourly KBOS surface observations (1998-2007) was used to identify 879 days when the sea breeze occurred or was likely to occur at the airport. These days were classified as sea breeze, marginal, or non-sea breeze events. Sea breeze events were further classified into fast and slow transitions, with a fast transition identified by a wind shift taking one hour or less to develop, and a slow transition identified by a wind shift taking two hours or more to develop. Marginal events were events that had a duration of 1 hour or less, no clear start or finish, or were interrupted by periods of "calm" or "light and variable" winds. Non-events were events in which the background conditions for a sea breeze to occur existed, but a sea breeze did not develop. Times of onset and event durations for the sea breeze events (fast, slow, and marginal) were calculated and used to create seasonal statistics by event type. It was found that seasonal variation did occur with both characteristics, but was more evident in the time of onset. Slow events occurred earliest in the day overall, while marginal events occurred a bit later, and fast events occurred the latest. Slow events had the longest duration overall, while marginal events, by definition, had the shortest duration. Seasonally, similar results were found for both characteristics with a few variations. United States surface analyses for each event at the time of onset (or average time of onset, 1500 UTC, for non-events) were classified using the seven synoptic classes developed by Miller and Keim (2003), and statistics were developed to evaluate the distribution of synoptic classes amongst the

  4. Tectono-stratigraphic evolution through successive extensional events of the Anydros Basin, hosting Kolumbo volcanic field at the Aegean Sea, Greece

    NASA Astrophysics Data System (ADS)

    Nomikou, P.; Hübscher, C.; Ruhnau, M.; Bejelou, K.

    2016-03-01

    The structural evolution of the South Aegean Sea is little explored due to the lack of marine seismic data. Our present day understanding is mainly based on some island outcrops and GPS measurements. In this study we discuss the rather incremental opening of the Anydros Basin in the Pliocene during six major tectonic pulses and the subsequent basin fill processes by interpreting seismic data and derived time isochore maps. Between the active pulses basin floor tilting persisted on a much lower rate. Seismic data illustrate the depositional processes in the emerging Anydros Basin. The observation of onlap fill strata, divergent reflection pattern, moat channels and contourite drifts imply that deposition was controlled by turbidity and contour currents as well as the tilting basin floor. The metamorphic Attico-Cycladic basement shows a rise that aligns along an NW-SE directed axis crossing Anydros island. This axis marks a structural change of the Santorini-Amorgos Ridge and thus represents a major structural boundary. Dip angles of NE-SW trending major faults, like the Santorini-Amorgos Fault, indicate normal faulting to be the superior mechanism forming the present horst and graben environment. Hence, the area is likely to be in a state of NW-SE directed extensional stresses forming the asymmetric graben structure of Anydros. Secondary fault clusters strike the same direction but show much steeper dip angles, possibly indicating strike-slip movement or resulting from deformational stresses along the hinge zones of the normal faults. The majority of the faults we discovered are located in the area of earthquake clusters, which is another indication of recent faulting. Ring faults around Kolumbo submarine volcano, result from caldera collapse and mark the diameter of the magma chamber approximately to 20 km.

  5. Impact of recent Global Digital Bathymetry and Topography Models on geoid modelling: Results from two case studies in Balearic and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Delikaraoglou, D.; Mintourakis, I.; Kallianou, F.

    2009-04-01

    geoid modelling of archipelagic (island) areas. We have concentrated in two test regions: (a) the Catalano-Balearic Sea (South of Spain in the NW Meditteranean), where adequate marine and land gravity data allow a detailed evaluation of our processing methodologies and their results and, (b) the Aegean Sea where the presence of many islands in varying distances from the mainland Greece and located on the continental shelf and/or divided by steep sea floor topography present some unique challenges for any high resolution geoid modelling efforts. For both test regions, we generated a combined DEM (C-DEM) using the IFREMER and SRTM 30 arcsec bathymetric data for the sea areas and SRTM 3 arcsec data for the surrounding land areas. In this contribution, we discuss various computational aspects relating to the so-called "Direct Topographical Effect" (DTE) and the "Indirect Topographical Effect" (ITE), the two most significant topographical effects that have to be evaluated when a precise geoid is being compiled. In addition, we outline the evaluation and the impact of the results obtained, especially with regard to the differences in the geoid models when different elevation data are used, and point out the main limitations and possibilities for further improvements in the use of the aforementioned satellite and terrestrial data for regional and local geoid mapping in coastal and island regions. Keywords: IFREMER, SRTM, terrain effects, free-air gravity anomalies, geoid modelling,Digital Bathymetry Models.

  6. Time-Domain Moment Tensors for shallow ( h ≤ 40 km) earthquakes in the broader Aegean Sea for the years 2006 and 2007: The database of the Aristotle University of Thessaloniki

    NASA Astrophysics Data System (ADS)

    Roumelioti, Zafeiria; Kiratzi, Anastasia; Benetatos, Christoforos

    2011-03-01

    We present a catalog of moment tensor (MT) solutions and moment magnitudes, Mw, for 119 shallow ( h ≤ 40 km) earthquakes in Greece and its surrounding lands (34°N-42°N, 19°E-30°E) for the years 2006 and 2007, computed with the 1D Time-Domain Moment Tensor inversion method (TDMT_INV code of Dreger, 2003). Magnitudes range from 3.2 ≤ Mw ≤ 5.7. Green's functions (GF) have been pre-computed to build a library, for a number of velocity profiles applicable to the broader Aegean Sea region, to be used in the inversion of observed broad band waveforms (10-50 s). All MT solutions are the outcome of a long series of tests of different reported source locations and hypocenter depths. Quality factors have been assigned to each MT solution based on the number of stations used in the inversion and the goodness of fit between observed and synthetic waveforms. In general, the focal mechanisms are compatible with previous knowledge on the seismotectonics of the Aegean area. The new data provide evidence for strike-slip faulting along NW-SE trending structures at the lower part of Axios basin, close to the heavily industrialized, and presently subsiding, region of the city of Thessaloniki. Normal faulting along E-W trending planes is observed at the Strimon basin, and in Orfanou Gulf in northern Greece. A sequence of events in the east Aegean Sea close to the coastline with western Anatolia sheds light on an active structure bounding the north coastline of Psara-Chios Islands about 20-25 km in length exhibiting right lateral strike-slip faulting.

  7. High-Temperature Hydrothermal Vent Field of Kolumbo Submarine Volcano, Aegean Sea: Site of Active Kuroko-Type Mineralization

    NASA Astrophysics Data System (ADS)

    Sigurdsson, H.; Carey, S.; Alexandri, M.; Vougioukalakis, G.; Croff, K.; Roman, C.; Sakellariou, D.; Anagnostou, C.; Rousakis, G.; Ioakim, C.; Gogou, A.; Ballas, D.; Misaridis, T.; Nomikou, P.

    2006-12-01

    Kolumbo submarine volcano is located 7 km north-east of the island of Santorini in the Hellenic arc (Greece), and comprises one of about twenty submarine cones in a NE-trending rift zone. Kolumbo erupted explosively in 1649-50AD, causing 70 fatalities on Santorini. Kolumbo's crater is 1700 m in diameter, with a crater rim at 10 m below sea level and crater floor at depth of 505 m. Recent marine geological investigations, using ROVs, reveal a very active high-temperature hydrothermal vent field in the northeastern part of the Kolumbo crater floor, about 25,000 m2. Vent chimneys up to 4 m high are vigorously emitting colorless gas plumes up to 10 m high in the water column. Temperatures up to 220oC are recorded in vent fluids. Some vents are in crater- like depressions, containing debris from collapsed extinct chimneys. The entire crater floor of Kolumbo is mantled by a reddish-orange bacterial mat, and bacterial filaments of a variety of colors cling to chimneys in dense clusters. Glassy tunicates and anemones are common in lower-temperature environments on the crater floor. Most chimneys show a high porosity, with a central conduit surrounded by an open and very permeable framework of sulfides and sulfates, aiding fluid flow through the chimney walls. In the sulfate-rich samples, blades of euhedral barite and anhydrite crystals coat the outside of the chimney wall, and layers of barite alternate with sulfide in the interior. The dominant sulfides are pyrite, sphalerite, wurtzite, marcasite and galena. Crusts on extinct and lower-temperature chimneys are composed of amorphous silica, goethite and halite. Sulfur isotope composition of sulfates is virtually at sea water values, whereas the sulfides are more depleted. Elevated levels of copper, gold and silver are observed in bulk composition of chimney samples. Both the structural setting, character of the vent field and sulfide/sulfate mineralogy and geochemistry indicate on-going Kuroko-type mineralization in the

  8. The 40Ar/39Ar and U/Pb dating of young rhyolites in the Kos-Nisyros volcanic complex, Eastern Aegean Arc, Greece: Age discordance due to excess 40Ar in biotite

    NASA Astrophysics Data System (ADS)

    Bachmann, O.; Schoene, B.; Schnyder, C.; Spikings, R.

    2010-08-01

    High-precision dating of Quaternary silicic magmas in the active Kos-Nisyros volcanic center (Aegean Arc, Greece) by both 40Ar/39Ar on biotite and U/Pb on zircon reveals a complex geochronological story. U/Pb ID-TIMS multi and single-grain zircon analyses from 3 different units (Agios Mammas and Zini domes, Kefalos Serie pyroclasts) range in age from 0.3 to 0.5 to 10-20 Ma. The youngest dates provide the maximum eruption age, while the oldest zircons indicate inheritance from local continental crust (Miocene and older). Step-heating 40Ar/39Ar experiments on 1-3 crystals of fresh biotite yielded highly disturbed Ar-release patterns with plateau ages typically older than most U/Pb ages. These old plateau ages are probably not a consequence of inheritance from xenocrystic biotites because Ar diffuses extremely fast at magmatic temperatures and ratios are reset within a few days. On the basis of (1) elevated and/or imprecise 40Ar/36Ar ratios, (2) shapes of the Ar release spectra, and (3) a high mantle 3He flux in the Kos-Nisyros area, we suggest that biotite crystals retained some mantle 40Ar that led to the observed, anomalously old ages. In contrast, sanidine crystals from the only sanidine-bearing unit in the Kos-Nisyros volcanic center (the caldera-forming Kos Plateau Tuff) do not appear to store any excess 40Ar relative to atmospheric composition. The eastern edge of the Aegean Arc is tectonically complex, undergoing rapid extension and located close to a major structural boundary. In such regions, which are characterized by high fluxes of mantle volatiles, 40Ar/39Ar geochronology on biotite can lead to erroneous results due to the presence of excess 40Ar and should be checked either against 40Ar/39Ar sanidine or U/Pb zircon ages.

  9. Iceberg Drift In The Eastern Weddell Sea: Observed And Modeled

    NASA Astrophysics Data System (ADS)

    Wesche, Christine; Rackow, Thomas; Dierking, Wolfgang

    2013-12-01

    The eastern Weddell Sea region is an alley for drifting icebergs, which calve further east along the coastline of East Antarctica. Our analysis is focused on the region north of the Ekstro ̈m Ice Shelf. Since at the Ekstro ̈m Ice Shelf a landing place is used for the supply of the German overwintering station Neumayer III and the South-African station Sanae IV, it is important to monitor the drifting routes taken by the icebergs in this region. We use a series of ENVISAT ASAR WSM data to follow a larger (D18) and a smaller (IB1) iceberg through the eastern Weddell Sea region in 2006. Model simulations are carried out to get more detailed information about the relative influence of different forces on the iceberg drift in this region.

  10. Subduction and slab tearing dynamics constrained by thermal anomalies in the Anatolia-Aegean region

    NASA Astrophysics Data System (ADS)

    Roche, Vincent; Guillou-Frottier, Laurent; Jolivet, Laurent; Loiselet, Christelle; Bouchot, Vincent

    2015-04-01

    Most previous geodynamic studies treat subduction zones with backward migration (rollback), slab tearing or slab breakoff by numerical or laboratory experiments and by integrating seismicity, tomography data and geochemical studies. Here we investigate these processes in the Aegean-Anatolian domain and particularly the western side of Turkey (western Anatolia) by incorporating thermal regime of the crust, and in particular the geothermal fields as anomalies that could reflect the thermal state of Aegean subduction zone at depth. This domain is characterized by 1) extensional crustal deformation which progressively localized during the Aegean slab retreat from late Eocene to Present, enabling the development of a hot backarc domain; this extension accelerated between 15 and 8 Ma coeval with a fast rotation of the Hellenides and 2) since the latest Miocene, extension is coupled with the development of the North Anatolian Fault that accommodates the westward escape of the Anatolian block. Both the acceleration of extension in the Middle Miocene and the recent escape of Anatolia have been proposed to result from several slab tearing events, the first one being located below western Turkey and the Eastern Aegean Sea, a second one below eastern Turkey and a last one below the Corinth Rift (Faccenna et al., 2006; Jolivet et al., 2013). The distribution of magmatism and mineral resources has been suggested to be largely controlled by these retreat and tearing events (Menant et al., submitted). The development of a widespread active geothermal province in western Anatolia is unlikely to simply result from the Quaternary magmatism whose volcanism part has a too limited extent. Conversely, the long wavelength east-west variation of surface heat flow density could reflect deep thermal processes in the lower crust and/or deeper, and we thus look for possible connections with larger-scale mantle dynamics. We use the distribution of thermal anomalies at different scales and the 3

  11. Evaluating drivers of Pleistocene eastern tropical Pacific sea surface temperature

    NASA Astrophysics Data System (ADS)

    Dyez, K. A.; Ravelo, A. C.; Mix, A. C.

    2016-08-01

    Sea surface temperature (SST) of the eastern equatorial Pacific is a key component of tropical oceanic and atmospheric circulation with global teleconnections. Forcing factors such as local and high-latitude insolation changes, ice sheet size and albedo feedbacks, and greenhouse gas radiation have been proposed as controls of long-term eastern tropical Pacific SST, though the precise role each mechanism plays is not fully known on glacial-interglacial or longer timescales. Here proposed mechanisms are evaluated by comparing orbital-scale records of eastern Pacific SST with forcing variability over the past 1.5 Ma. The primary SST records are a compilation of new and existing data from Ocean Drilling Program Site 1239 at the northeastern margin of the modern eastern Pacific cold tongue and Site 846 SST within the cold tongue. Using time series analysis, we test previously proposed mechanisms for control of long-term tropical SST change and SST gradients in the eastern Pacific. We find that within statistical uncertainties, in the precession band eastern Pacific SST is consistent with direct forcing by equatorial radiation changes in the tropical cold season (summer-fall) rather than inversely correlated as previously suggested. In the obliquity band high-latitude solar forcing leads or is in phase with eastern equatorial Pacific SST, while in the eccentricity band atmospheric greenhouse gas concentrations are closely associated with cold tongue SST. Pleistocene eastern Pacific SST gradients indicate that the gradient on the northern margin of the cold tongue strengthened through the mid-Pleistocene transition, a result compatible with the cold tongue becoming more focused at ~900-650 ka.

  12. Lithospheric Response of the Anatolian Plateau in the Realm of the Black Sea and the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Ergun, Mustafa

    2016-04-01

    The Eastern Mediterranean and the Middle East make up the southern boundary of the Tethys Ocean for the last 200 Ma by the disintegration of the Pangaea and closure of the Tethys Ocean. It covers the structures: Hellenic and Cyprus arcs; Eastern Anatolian Fault Zone; Bitlis Suture Zone and Zagros Mountains. The northern boundary of the Tethys Ocean is made up the Black Sea and the Caspian Sea, and it extends up to Po valley towards the west (Pontides, Caucasus). Between these two zones the Alp-Himalayan orogenic belt is situated where the Balkan, Anatolia and the Iran plateaus are placed as the remnants of the lost Ocean of the Tethys. The active tectonics of the eastern Mediterranean is the consequences of the convergence between the Africa, Arabian plates in the south and the Eurasian plate in the north. These plates act as converging jaws of vise forming a crustal mosaic in between. The active crustal deformation pattern reveals two N-S trending maximum compression or crustal shortening syntaxes': (i) the eastern Black Sea and the Arabian plate, (ii) the western Black Sea and the Isparta Angle. The transition in young mountain belts, from ocean crust through the agglomeration of arc systems with long histories of oceanic closures, to a continental hinterland is well exemplified by the plate margin in the eastern Mediterranean. The boundary between the African plate and the Aegean/Anatolian microplate is in the process of transition from subduction to collision along the Cyprus Arc. Since the Black Sea has oceanic lithosphere, it is actually a separate plate. However it can be considered as a block, because the Black Sea is a trapped oceanic basin that cannot move freely within the Eurasian Plate. Lying towards the northern margin of orogenic belts related to the closure of the Tethys Ocean, it is generally considered to be a result of back-arc extension associated with the northward subduction of the Tethyan plate to the south. Interface oceanic lithosphere at

  13. New boron isotopic evidence for sedimentary and magmatic fluid influence in the shallow hydrothermal vent system of Milos Island (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Wu, Shein-Fu; You, Chen-Feng; Lin, Yen-Po; Valsami-Jones, Eugenia; Baltatzis, Emmanuel

    2016-01-01

    Magmatic sources may contribute a significant amount of volatiles in geothermal springs; however, their role is poorly understood in submarine hydrothermal systems worldwide. In this study, new results of B and δ11B in 41 hydrothermal vent waters collected from the shallow hydrothermal system of Milos island in the Aegean Sea were combined with previously published data from other tectonic settings and laboratory experiments to quantify the effects of phase separation, fluid/sediment interaction and magmatic contribution. Two Cl-extreme solutions were identified, high-Cl waters (Cl as high as 2000 mM) and low-Cl waters (Cl < 80 mM). Both sets of waters were characterized by high B/Cl (~ 1.2-5.3 × 10- 3 mol/mol) and extremely low δ11B (1.4-6.3‰), except for the waters with Mg content of near the seawater value and δ11B = 10.3-17.4‰. These high-Cl waters with high B/Cl and low δ11B plot close to the vent waters in sediment-hosted hydrothermal system (i.e., Okinawa Trough) or fumarole condensates from on-land volcanoes, implying B addition from sediment or magmatic fluids plays an important role. This is in agreement with fluid/sediment interactions resulting in the observed B and δ11B, as well as previously reported Br/I/Cl ratios, supporting a scenario of slab-derived fluid addition with elevated B, 11B-rich, and low Br/Cl and I/Cl, which is derived from the dehydration of subducted-sediments. The slab fluid becomes subsequently mixed with the parent magma of Milos. The deep brine reservoir is partially affected by injections of magmatic fluid/gases during degassing. The results presented here are crucial for deciphering the evolution of the brine reservoirs involved in phase separation, fluid/sediment interaction and magmatic contribution in the deep reaction zone of the Milos hydrothermal system; they also have implications in the understanding of the formation of metallic vein mineralization.

  14. Chemical composition of Eastern Black Sea aerosol--preliminary results.

    PubMed

    Balcılar, Ilker; Zararsız, Abdullah; Kalaycı, Yakup; Doğan, Güray; Tuncel, Gürdal

    2014-08-01

    Trace element composition of atmospheric particles collected at a high altitude site on the Eastern Black Sea coast of Turkey was investigated to understand atmospheric transport of pollutants to this semi-closed basin. Aerosol samples were collected at a timber-storage area, which is operated by the General Directorate of Forestry. The site is situated at a rural area and is approximately 50 km to the Black Sea coast and 200 km to the Georgia border of Turkey. Coarse (PM2.5-10) and fine (PM2.5) aerosol samples were collected between 2011 and 2013 using a "stacked filter unit". Collected samples were shipped to the Middle East Technical University in Ankara, where Na, Mg, Al, Si, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Ba, Pb were measured by Energy dispersive x-ray fluorescence technique (EDXRF). Comparison of measured concentrations of elements with corresponding data generated at other parts of Turkey demonstrated that concentrations of pollution derived elements are higher at Eastern Black Sea than their corresponding concentrations measured at other parts of Turkey, which is attributed to frequent transport of pollutants from north wind sector. Positive matric factorization revealed four factors including three anthropogenic and a crustal factor. Southeastern parts of Turkey, Georgia and Black Sea coast of Ukraine were identified as source regions affecting composition of particles at our site, using trajectory statistics, namely "potential source contribution function" (PSCF). PMID:24373640

  15. Aquamarine waters recorded for first time in Eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Vance, T. C.; Schumacher, J. D.; Stabeno, P. J.; Baier, C. T.; Wyllie-Echeverria, T.; Tynan, C. T.; Brodeur, R. D.; Napp, J. M.; Coyle, K. O.; Decker, M. B.; Hunt, G. L., Jr.; Stockwell, D.; Whitledge, T. E.; Jump, M.; Zeeman, S.

    During the late summer of 1997, for the first time ever recorded, most of the continental shelf of the eastern Bering Sea was covered by aquamarine waters (Figure 1), resulting from a massive bloom of coccolithophores (Figure 2). Light reflecting off the calcium carbonate plates of the flagellated coccolithophores gave the water its anomalous color, which was first observed in July. The bloom was also clearly visible from space, as shown by some of the first images from the multispectral sea-viewing wide-field-of- view sensor (SeaWiFS) scanner in September.Light penetration into the water column, essential for primary production by diatoms and other phytoplankton, was markedly reduced. This shift potentially altered the trophic dynamics throughout the food web of one of world's most productive ecosystems.

  16. Aquatic animal resources in Prehistoric Aegean, Greece.

    PubMed

    Mylona, Dimitra

    2014-12-01

    This paper explores the early stages in the history of fishing in the Aegean Sea in Greece, and highlights its formative phases and its specific characteristics in different points in time. This is testified by various physical remains, such as fish bones, fishing tools, and representations in art, which are gathered in the course of archaeological research. The aquatic resources in the Aegean Sea have been exploited and managed for millennia by communities that lived near the water and often made a living from it. The earliest evidence for a systematic, intensive exploitation of marine resources in the Aegean Sea dates to the Mesolithic, eleven millennia ago. In the Neolithic period, the adoption of a sedentary, agro-pastoral way of life led to a reduction in the intensity of fishing and shellfish gathering. Its importance as an economic resource remained high only in certain regions of rich, eutrophic waters. In the Bronze Age, an era of social complexity and centralized economy, the exploitation of aquatic, mostly marine, resources became a complex, multi-faceted activity which involved subsistence, industry and ideology. The range of preferred fish and invertebrate species, the fishing technology, and the processing of fish and shellfish in order to produce elaborate foods or prestige items are all traceable aspects of the complex relationship between humans and the aquatic resources throughout the prehistory of fishing and shellfish gathering in the Aegean area. The broadening of collaboration between archaeology and physical sciences offers new means to explore these issues in a more thorough and nuanced manner. PMID:25984485

  17. Evolutionary processes in a continental island system: molecular phylogeography of the Aegean Nigella arvensis alliance (Ranunculaceae) inferred from chloroplast DNA.

    PubMed

    Bittkau, C; Comes, H P

    2005-11-01

    Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of past fragmentation, dispersal, and genetic drift on taxon diversification. We used phylogeographical (nested clade) and population genetic analyses to elucidate the relative roles of these processes in the evolutionary history of the Aegean Nigella arvensis alliance (= 'coenospecies'). We surveyed chloroplast DNA (cpDNA) variation in 455 individuals from 47 populations (nine taxa) of the alliance throughout its core range in the Aegean Archipelago and surrounding mainland areas of Greece and Turkey. The study revealed the presence of three major lineages, with largely nonoverlapping distributions in the Western, Central, and Eastern Aegean. There is evidence supporting the idea that these major lineages evolved in situ from a widespread (pan-Aegean) ancestral stock as a result of multiple fragmentation events, possibly due to the influence of post-Messinian sea flooding, Pleistocene eustatic changes and corresponding climate fluctuations. Over-sea dispersal and founder events appear to have played a rather insignificant role in the group's history. Rather, all analytical approaches identified the alliance as an organism group with poor seed dispersal capabilities and a susceptibility to genetic drift. In particular, we inferred that the observed level of cpDNA differentiation between Kikladian island populations of Nigella degenii largely reflects population history, (viz. Holocene island fragmentation) and genetic drift in the near absence of seed flow since their time of common ancestry. Overall, our cpDNA data for the N. arvensis alliance in general, and N. degenii in particular, indicate that historical events were important in determining the phylogeographical patterns seen, and that genetic drift has historically been relatively more influential on population structure than has cytoplasmic gene flow.

  18. Eddy analysis in the Eastern China Sea using altimetry data

    NASA Astrophysics Data System (ADS)

    Qin, Dandi; Wang, Jianhong; Liu, Yu; Dong, Changming

    2015-12-01

    Statistical characteristics of mesoscale eddies in the Eastern China Sea (ECS) are analyzed using altimetry sea surface height anomaly (SSHA) data from 1993 to 2010. A velocity geometry-based automated eddy detection scheme is employed to detect eddies from the SSHA data to generate an eddy data set. About 1,096 eddies (one lifetime of eddies is counted as one eddy) with a lifetime longer than or equal to 4 weeks are identified in this region. The average lifetime and radius of eddies are 7 weeks and 55 km, respectively, and there is no significant difference between cyclonic eddies (CEs) and anticyclonic eddies (AEs) in this respect. Eddies' lifetimes are generally longer in deep water than in shallow water. Most eddies propagate northeastward along the Kuroshio (advected by the Kuroshio), with more CEs generated on its western side and AEs on its eastern side. The variation of the Kuroshio transport is one of the major mechanisms for eddy genesis, however the generation of AEs on the eastern side of the Kuroshio (to the open ocean) is also subject to other factors, such as the wind stress curl due to the presence of the Ryukyu Islands and the disturbance from the open ocean.

  19. The surface circulation in the eastern basin of the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Hamad, N.; Millot, C.; Taupier-Letage, I.

    2003-04-01

    The POEM-schema of the Atlantic Water (AW, http://ciesm.org/events/RT5-WaterMassAcronyms.pdf) circulation in the eastern basin of the Mediterranean Sea widely referred to nowadays (Robinson et al., 1991, completed by Robinson and Golnaraghi, 1993, and by Malanotte-Rizzoli et al., 1997) represents, in particular, a jet meandering offshore across the whole basin. No information is given on the southern part of the basin and no mention is made of a possible overall alongslope anticlockwise flow there, as suggested by a contemporaneous analysis of infrared satellite images (Le Vourch et al., 1992; Millot, 1992). A roughly similar controversy was elucidated in the western basin where such imagery was proven reliable. This has motivated the detailed analysis of daily and weekly composite images (about 1000) during the period 1996-2000, and of monthly composites available since 1985. Our analysis shows that AW circulates alongslope and anticlockwise around the whole basin, as indicated by Nielsen (1912) who considered the Coriolis effect as dominant. This circulation, which is permanent from Tunisia to Turkey, exists more or less temporarily in the Aegean, in the Ionian around Greece and in the Adriatic, due to the Etesians. However, a branch having spread for years (up to early 1998) from the channel of Sicily towards the northern Ionian before vanishing represents marked interannual (not seasonal) variability. Being unstable during most of its circuit, the AW flow generates mesoscale eddies which had not been correctly described before and which represent a relatively large amount of AW. Other eddies are known to be generated by orographic effects on the wind field, especially the Etesians. Both kinds of eddies play a fundamental role in spreading AW from alongslope towards the open basin. Although these eddies have characteristics almost specific to each subbasin and/or generation mechanism, the largest ones are anticyclonic, both kinds reach diameters of a few 100s km

  20. Chemical speciation and ecological risk assessment of arsenic in marine sediments from Izmir Bay (Eastern Aegean Sea).

    PubMed

    Gonul, L T

    2015-12-01

    Total arsenic, arsenic(III) and (V), Fe, and Mn were measured in 17 surface sediment samples from Izmir Bay. The concentrations and ecological risk of As were characterized in the sediment affected by urban and agricultural activities. Total As ranged from 8.87 to 28.3 μg g(-1) dry weight (96.5-99.9 % as inorganic As). Distribution of total As and total As/Fe followed a different trend in sediments at all sampling sites. Arsenite (As(III)) was the most dominant form followed by As(V), while organic arsenic represented a minor constituent (0.03 to 3.49 %). The highest concentration of total As was observed at Gediz River estuary and exceeded lower threshold value (threshold effects level (TEL)). Due to the biological reduction of As(V) and abundance of Fe (oxyhydr)oxides in the sediments, most inorganic As in the Izmir Bay was present as As(III). Besides, the levels of As were >TEL and

  1. Paleoseismological investigation offshore eastern Sicily and south Calabria (Ionian Sea).

    NASA Astrophysics Data System (ADS)

    San Pedro, Laurine; Babonneau, Nathalie; Gutscher, Marc-André; Cattaneo, Antonio

    2016-04-01

    The Ionian Sea is a deep and narrow basin in the Central Mediterranean Sea, bounded by two accretionary wedges formed by the Calabrian and the Hellenic subduction zones, respectively to the North West and to the East. Eastern Sicily and Calabria have been repeatedly struck by destructive historical earthquakes and tsunamis (1693 AD Catania M7.4, 1908 AD Messina M7.2). The latter triggered a submarine landslide and turbidity current that ruptured submarine cables. In the Ionian Sea, preliminary sedimentological studies show that recent turbidite deposits could be directly correlated with large historical earthquakes. Other thick deposits imaged in seismic data as thick transparent layers in the Ionian abyssal plain have been termed megaturbidites or homogenites. This study is focused on the interpretation of turbidites and megaturbidites on the basis of new sediment cores located in the northwestern Ionian Sea. Understanding the sources and the origin of these deposits is crucial to interpret the paleoseismological record contained in the deep sediments of the Ionian Sea. The objective is to improve our understanding of the chronology and origin of large catastrophic events, which have affected the area. New data, including piston cores and CHIRP echosounder profiles, were collected during the CIRCEE cruise, with R/V Le Suroit in October 2013, in the western Ionian Sea, including the western part of Calabrian accretionary wedge and the base of the Malta Escarpment. With a wide regional distribution of the cores, this new dataset allows to refine the interpretation of gravity deposits in terms of sedimentary processes and to establish an event stratigraphy based on radiocarbon dating. The Augias megaturbidite was completely sampled in six cores: the origin of this deposit is associated to the 365 AD Crete mega-thrust earthquake. The sedimentological study and correlation of turbidite deposits provide the opportunity to obtain a paleoseismological record extending

  2. Distribution of phosphorus in the eastern Adriatic Sea sediments (Croatia)

    NASA Astrophysics Data System (ADS)

    Matijević, Slavica; Bogner, Danijela; Kušpilić, Grozdan; Veža, Jere

    2014-05-01

    Phosphorus (P) is very important nutrient for the eastern Adriatic Sea owing to its limiting role in the primary production. Orthophosphate concentrations are low (median HPO42- value: 0.039 µmol dm-3) as a consequence of relatively small number of freshwater inflows and cyclonic circulation of oligotrophic eastern Mediterranean water masses. Due to anthropogenic influence in coastal areas such as bays, estuaries and channel waters, P concentrations increment occurred leading to the formation of trophic gradient from the open sea towards the coast. As marine sediment presents the ultimate sink for particulate organic P from the water column, as well as for inorganic P forms, knowledge about distribution of different sediment P species is of great importance for understanding the burial, diagenesis and environmental geochemical significance of P. This paper presents results of P distribution at the eastern Adriatic sites of different trophic status (open sea, channel, estuary, semi-enclosed bay under the anthropogenic influence and fish farms) during 2002-2012. In the water column dissolved and particulate inorganic and organic P were analyzed. In all sediments total phosphorus (organic and inorganic P) was determined, while at certain sites beside organic P, inorganic P forms were examined using modified SEDEX methods (P in biogenic - P-FD; authigenic - P-AUT and in detrital apatite - P-DET; phosphorus bound to iron oxides and hydroxides - P-Fe). Various geochemical variables in the water column and sediment (HPO42- concentration, sediment redox potential, granulometric composition, carbonate content, iron, organic carbon and total nitrogen content) were also investigated. Results proved total P concentrations range between 3 and 161 µmol g-1, with highest values at sites under the strong anthropogenic impact including fish farms, estuaries and bay areas. Major inorganic P species in the eastern Adriatic was P-Fe form. Fish debris P species P-FD, prevailed in

  3. Ancient DNA Analysis of 8000 B.C. Near Eastern Farmers Supports an Early Neolithic Pioneer Maritime Colonization of Mainland Europe through Cyprus and the Aegean Islands

    PubMed Central

    Fernández, Eva; Pérez-Pérez, Alejandro; Gamba, Cristina; Prats, Eva; Cuesta, Pedro; Anfruns, Josep; Molist, Miquel; Arroyo-Pardo, Eduardo; Turbón, Daniel

    2014-01-01

    The genetic impact associated to the Neolithic spread in Europe has been widely debated over the last 20 years. Within this context, ancient DNA studies have provided a more reliable picture by directly analyzing the protagonist populations at different regions in Europe. However, the lack of available data from the original Near Eastern farmers has limited the achieved conclusions, preventing the formulation of continental models of Neolithic expansion. Here we address this issue by presenting mitochondrial DNA data of the original Near-Eastern Neolithic communities with the aim of providing the adequate background for the interpretation of Neolithic genetic data from European samples. Sixty-three skeletons from the Pre Pottery Neolithic B (PPNB) sites of Tell Halula, Tell Ramad and Dja'de El Mughara dating between 8,700–6,600 cal. B.C. were analyzed, and 15 validated mitochondrial DNA profiles were recovered. In order to estimate the demographic contribution of the first farmers to both Central European and Western Mediterranean Neolithic cultures, haplotype and haplogroup diversities in the PPNB sample were compared using phylogeographic and population genetic analyses to available ancient DNA data from human remains belonging to the Linearbandkeramik-Alföldi Vonaldiszes Kerámia and Cardial/Epicardial cultures. We also searched for possible signatures of the original Neolithic expansion over the modern Near Eastern and South European genetic pools, and tried to infer possible routes of expansion by comparing the obtained results to a database of 60 modern populations from both regions. Comparisons performed among the 3 ancient datasets allowed us to identify K and N-derived mitochondrial DNA haplogroups as potential markers of the Neolithic expansion, whose genetic signature would have reached both the Iberian coasts and the Central European plain. Moreover, the observed genetic affinities between the PPNB samples and the modern populations of Cyprus and

  4. Ancient DNA analysis of 8000 B.C. near eastern farmers supports an early neolithic pioneer maritime colonization of Mainland Europe through Cyprus and the Aegean Islands.

    PubMed

    Fernández, Eva; Pérez-Pérez, Alejandro; Gamba, Cristina; Prats, Eva; Cuesta, Pedro; Anfruns, Josep; Molist, Miquel; Arroyo-Pardo, Eduardo; Turbón, Daniel

    2014-06-01

    The genetic impact associated to the Neolithic spread in Europe has been widely debated over the last 20 years. Within this context, ancient DNA studies have provided a more reliable picture by directly analyzing the protagonist populations at different regions in Europe. However, the lack of available data from the original Near Eastern farmers has limited the achieved conclusions, preventing the formulation of continental models of Neolithic expansion. Here we address this issue by presenting mitochondrial DNA data of the original Near-Eastern Neolithic communities with the aim of providing the adequate background for the interpretation of Neolithic genetic data from European samples. Sixty-three skeletons from the Pre Pottery Neolithic B (PPNB) sites of Tell Halula, Tell Ramad and Dja'de El Mughara dating between 8,700-6,600 cal. B.C. were analyzed, and 15 validated mitochondrial DNA profiles were recovered. In order to estimate the demographic contribution of the first farmers to both Central European and Western Mediterranean Neolithic cultures, haplotype and haplogroup diversities in the PPNB sample were compared using phylogeographic and population genetic analyses to available ancient DNA data from human remains belonging to the Linearbandkeramik-Alföldi Vonaldiszes Kerámia and Cardial/Epicardial cultures. We also searched for possible signatures of the original Neolithic expansion over the modern Near Eastern and South European genetic pools, and tried to infer possible routes of expansion by comparing the obtained results to a database of 60 modern populations from both regions. Comparisons performed among the 3 ancient datasets allowed us to identify K and N-derived mitochondrial DNA haplogroups as potential markers of the Neolithic expansion, whose genetic signature would have reached both the Iberian coasts and the Central European plain. Moreover, the observed genetic affinities between the PPNB samples and the modern populations of Cyprus and Crete

  5. Occurrence of Diopatra marocensis (Annelida, Onuphidae) in the eastern Mediterranean

    PubMed Central

    Çinar, Melih Ertan; Fauchald, Kristian; Dagli, Ertan

    2014-01-01

    Abstract The present study deals with the presence of Diopatra marocensis in the eastern Mediterranean. This species is small-sized and inhabited muddy bottom near the opening of rivers or lagoons [salinity range: 33−39‰] in the Aegean and Levantine Seas, and reached a maximum density of 90 ind.m-2 in Mersin Bay. This species might be an alien species that was introduced from the East Atlantic (near Gibraltar) to the eastern Mediterranean via ballast water of ships, as it has never been reported from the western Mediterranean Sea. PMID:25349504

  6. Occurrence of Diopatramarocensis (Annelida, Onuphidae) in the eastern Mediterranean.

    PubMed

    Cinar, Melih Ertan; Fauchald, Kristian; Dagli, Ertan

    2014-01-01

    The present study deals with the presence of Diopatramarocensis in the eastern Mediterranean. This species is small-sized and inhabited muddy bottom near the opening of rivers or lagoons [salinity range: 33-39‰] in the Aegean and Levantine Seas, and reached a maximum density of 90 ind.m(-2) in Mersin Bay. This species might be an alien species that was introduced from the East Atlantic (near Gibraltar) to the eastern Mediterranean via ballast water of ships, as it has never been reported from the western Mediterranean Sea.

  7. NEAMWave12: The First Tsunami Exercise in the North-eastern Atlantic, the Mediterranean and Connected Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Matias Matias, Luis; Schindelé, François; Behrens, Jörn; Tinti, Stefano; Chouliaras, Gerasimos; Melis, Nicos; Carrilho, Fernando; Santoro, Francesca; Rudloff, Alexander; Crochet, Emilie; Gonzalez, Mauricio

    2013-04-01

    The first tsunami exercise of the Tsunami Early Warning and Mitigation System in the North-eastern Atlantic, the Mediterranean and connected seas (NEAMTWS) has been conducted on 27-28 November 2012 involving 19 of the 39 member countries of the Intergovernmental Coordination Group (ICG) for NEAMTWS. NEAMWave12 involved the simulation of the assessment of a tsunami, based on an earthquake-driven scenario followed by alert message dissemination by Candidate Tsunami Watch Provider (CTWP) (Phase A) and continued with the simulation of the National Tsunami Warning Center's/Tsunami Warning Focal Point's (NTWC/TWFP) and Civil Protection Authoritie's (CPA) actions (Phase B), as soon as the message produced in Phase A has been received. There were four earthquake triggered tsunami scenarios in NEAMWave12 in different parts of the NEAM Region, where each CTWP (CENALT-France, NOA-Greece, IPMA-Portugal and KOERI-Turkey) was responsible for a single scenario. The CENALT Scenario was based on a plausible worst-case scenario of magnitude 7.5 along the Western Mediterranean Algerian margin at a fault located close to 21-22 August 1856 Jijel earthquakes. The NOA scenario was based on an earthquake similar to the well-known Amorgos earthquake, which was followed by a tsunami that devastated the Aegean Sea on 9 July 1956. The IPMA scenario was based on the 1 November 1755 Lisbon event with the assumption that the event represents the worst-case tsunami scenario impacting the NE Atlantic region. Finally, the KOERI scenario was based on a Mw=8.4 worst-case interpretation of the 8 August 1303 Crete and Dodecanese Islands earthquake resulting in destructive inundation in the Eastern Mediterranean. Initial evaluation of the exercise indicates that all CTWPs successfully participated in the exercise, where existing operational and some future prototype systems were utilized. System end-users (NTWC/TWFP/CPA) benefited from the exercise considerably, demonstrating the first successful test

  8. Silica cycling in the ultra-oligotrophic eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Krom, M. D.; Kress, N.; Fanning, K.

    2014-08-01

    Although silica is a key plant nutrient, there have been few studies aimed at understanding the Si cycle in the eastern Mediterranean Sea (EMS). Here we use a combination of new measurements and literature values to explain the silicic acid distribution across the basin and to calculate a silica budget to identify the key controlling processes. The surface water concentration of ∼1 μM, which is unchanging seasonally across the basin, was due to the inflow of western Mediterranean Sea (WMS) water at the Straits of Sicily. It does not change seasonally because there is only a sparse population of diatoms due to the low nutrient (N and P) supply to the photic zone in the EMS. The concentration of silicic acid in the deep water of the western Ionian Sea (6.3 μM) close to the S Adriatic are an of formation was due to the preformed silicic acid (3 μM) plus biogenic silica (BSi) from the dissolution of diatoms from the winter phytoplankton bloom (3.2 μM). The increase of 4.4 μM across the deep water of the EMS was due to silicic acid formed from in situ diagenetic weathering of aluminosilicate minerals fluxing out of the sediment. The major inputs to the EMS are silicic acid and BSi inflowing from the western Mediterranean (121 × 109 mol Si yr-1 silicic acid and 16 × 109 mol Si yr-1 BSi), silicic acid fluxing from the sediment (54 × 109 mol Si yr-1) and riverine (27 × 109 mol Si yr-1) and subterranean groundwater (9.7 × 109 mol Si yr-1) inputs, with only a minor direct input from dissolution of dust in the water column (1 × 109 mol Si yr-1). This budget shows the importance of rapidly dissolving BSi and in situ weathering of aluminosilicate minerals as sources of silica to balance the net export of silicic acid at the Straits of Sicily. Future measurements to improve the accuracy of this preliminary budget have been identified.

  9. Meteotsunami-tide interactions and high-frequency sea level oscillations in the eastern Yellow Sea

    NASA Astrophysics Data System (ADS)

    Choi, Byoung-Ju; Hwang, Chorong; Lee, Sang-Ho

    2014-10-01

    While an air pressure jump was moving southeastward over the shallow water region of the eastern Yellow Sea in March 2007, a long ocean wave (meteotsunami) was generated and amplified due to the Proudman resonance. The long wave arrived at the coast during high tide with wave amplitude of 1.4 m and seawater overflew seawalls and inundated the land. High-frequency sea level oscillations continued for 8-9 h after the long wave hit a local coast. The Moon's age was 12 days, and the tidal range was about 4 m between neap and spring tides. Two-dimensional numerical simulations were performed, to reproduce amplification of the long ocean wave in offshore and oscillations of sea level at the coast. Both tidal elevation and tidal currents were found to affect the growth of the long wave amplitude by the interactions between tides and the long wave. Long wave-tides interactions are important processes for the accurate prediction of long wave arrival time and maximum height and for the reduction of coastal hazards in the macrotidal region. After the long wave hit the coast of remote regions, reflected waves propagated radially from remote regions to a local coast. The high-frequency sea level oscillations at a local observation station continued, until all of the reflected waves from remote regions had passed by. It was concluded that high-frequency oscillations of sea level are generated not only by local reflection of the long wave, but also by propagation of the reflected waves from remote regions.

  10. Magnetotelluric Investigation of the South Aegean Volcanic Arc, Greece

    NASA Astrophysics Data System (ADS)

    Kalisperi, Despina; Romano, Gerardo; Smirnov, Maxim; Kouli, Maria; Perrone, Angela; Makris, John P.; Vallianatos, Filippos

    2014-05-01

    The South Aegean Volcanic Arc (SAVA) is a chain of volcanic islands in the South Aegean resulting from the subduction of the African tectonic plate beneath the Eurasian plate. It extends from Methana, northwest, to the Island of Nisyros southeast (450 km total length). SAVA comprises a series of dormant and historically active volcanoes, with the most prominent to be Aegina, Methana, Milos, Santorini, Kolumbo, Kos and Nisyros. The aim of the ongoing research project "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)" is to contribute to the investigation of the geoelectric structure of Southern Aegean, and particularly to attempt to image the Hellenic Subduction Zone. In this context, onshore magnetotelluric (MT) measurements were recently carried out on the central and eastern part of SAVA (Milos, Santorini, Nisyros and Kos Islands). Data were collected using two MT systems running simultaneously plus a remote reference station installed in Omalos plateau (Western Crete). Robust MT data analysis of the broad-band MT soundings and the resulting model of the conductivity structure of the South Aegean Volcanic Arc is presented. The research is co-funded by the European Social Fund (ESF) and National Resources under the Operational Programme 'Education and Lifelong Learning (EdLL) within the context of the Action 'Supporting Postdoctoral Researchers' in the framework of the project title "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)".

  11. Holocene sea-level oscillations and environmental changes on the Eastern Black Sea shelf

    USGS Publications Warehouse

    Ivanova, E.V.; Murdmaa, I.O.; Chepalyga, A.L.; Cronin, T. M.; Pasechnik, I.V.; Levchenko, O.V.; Howe, S.S.; Manushkina, A.V.; Platonova, E.A.

    2007-01-01

    A multi-proxy study of four sediment cores from the Eastern (Caucasian) Black Sea shelf revealed five transgressive-regressive cycles overprinted on the general trend of glacioeustatic sea-level rise during the last 11,000??14C yr. These cycles are well represented in micro-and macrofossil assemblages, sedimentation rates, and grain size variations. The oldest recovered sediments were deposited in the Neoeuxinian semi-freshwater basin (??? 10,500-9000??14C yr BP) and contain a Caspian-type mollusk fauna dominated by Dreissena rostriformis. Low ??18O and ??13C values are measured on this species. The first appearance of marine mollusks and ostracodes from the Mediterranean is established in this part of the Black Sea at ??? 8200??14C yr BP, i.e., about 1000-2000??yr later than the appearance of marine microfossils in the deeper part of the sea. The Early Holocene (Bugazian to Vityazevian) condensed section of shell and shelly mud sediments with at least two hiatuses represent a high-energy shelf-edge facies. It contains a transitional assemblage representing a mixture of Caspian and Mediterranean fauna. This pattern suggests a dual-flow regime via the Bosphorus after 8200??14C yr BP. Caspian species disappear and oligohaline species decrease in abundance during the Vityazevian-Prekalamitian cycle. Later, during the Middle to Late Holocene, low sea-level stands are characterized by shell layers, whereas silty mud with various mollusk and ostracode assemblages rapidly accumulated during transgressions. Restricted mud accumulation, as well as benthic faunal composition and abundance, suggest high-energy and well-ventilated bottom water during low sea-level stands. A trend of 18O enrichment in mollusk shells points to an increase in bottom-water salinity during the Vityazevian to Kalamitian transgressions (??? 7000 to 5700??14C yr BP) due to a more open connection with the Mediterranean, while a pronounced increase in polyhaline species abundance is established during

  12. Submarine sand ridges and sand waves in the eastern part of the China Sea

    NASA Astrophysics Data System (ADS)

    Wu, Ziyin; Li, Shoujun; Shang, Jihong; Zhou, Jieqiong; Zhao, Dineng; Liang, Yuyang

    2016-04-01

    Integrated with multi-beam and single-beam echo sounding data, as well as historical bathymetric data, submarine bathymetric maps of the eastern part of the China Sea, including the Bohai Sea, Huanghai Sea, and East China Sea, are constructed to systematically study submarine sand ridges and sand waves in the eastern part of the China Sea, combined with high-resolution seismic, sub-bottom profile and borehole data. Submarine sand ridges are extraordinarily developed in the eastern part of the China Sea, and 7 sand ridge areas can be divided from north to south, that is, the Laotieshan Channel sand ridge area in the Bohai Sea, the Korea Bay sand ridge area in the southern Huanghai Sea, the sand ridge area in the eastern Huanghai islands and the Huanghai Troughs, the Jianggang sand ridge area in the western Huanghai Sea, the sand ridge area in the East China Sea shelf, and the sand ridge and sand wave area in the Taiwan Strait and Taiwan Banks. The distribution area of the sand ridges and sand waves covers more than 450,000 km2, wherein ~10,000 km2 in the Bohai Bay, ~200,000 km2 in the Huanghai Sea, ~200,000 km2 in the East China Sea shelf, and ~40,000 km2 in the Taiwan Strait and Taiwan Banks, respectively. The great mass of sand ridges are distributed within water depth of 5-160 m, with a total length of over 160 km and a main width of 5-10 km. The inner structure of the sand ridges presents features of high-angle inclined beddings, with main lithology of sands, sand-mud alternations partly visible, and a small number of mud cores. Dating results indicate that the sand ridges in the eastern part of the China Sea are mainly developed in the Holocene. Sea-level variation dominates the sand ridge evolution in the eastern part of the China Sea since the LGM, and the sand ridges developed in the area of < 60m water depth are appeared in bad activity, meanwhile sand ridges with good activity are still developed in large scale.

  13. Environmental selection of protistan plankton communities in hypersaline anoxic deep-sea basins, Eastern Mediterranean Sea.

    PubMed

    Filker, Sabine; Stock, Alexandra; Breiner, Hans-Werner; Edgcomb, Virginia; Orsi, William; Yakimov, Michail M; Stoeck, Thorsten

    2013-02-01

    High salt concentrations, absence of light, anoxia, and high hydrostatic pressure make deep hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea one of the most polyextreme habitats on Earth. Taking advantage of the unique chemical characteristics of these basins, we tested the effect of environmental selection and geographic distance on the structure of protistan communities. Terminal restriction fragment length polymorphism (T-RFLP) analyses were performed on water samples from the brines and seawater/brine interfaces of five basins: Discovery, Urania, Thetis, Tyro, and Medee. Using statistical analyses, we calculated the partitioning of diversity among the ten individual terminal restriction fragment (T-RF) profiles, based on peak abundance and peak incidence. While a significant distance effect on spatial protistan patterns was not detected, hydrochemical gradients emerged as strong dispersal barriers that likely lead to environmental selection in the DHAB protistan plankton communities. We identified sodium, magnesium, sulfate, and oxygen playing in concerto as dominant environmental drivers for the structuring of protistan plankton communities in the Eastern Mediterranean DHABs.

  14. Environmental selection of protistan plankton communities in hypersaline anoxic deep-sea basins, Eastern Mediterranean Sea

    PubMed Central

    Filker, Sabine; Stock, Alexandra; Breiner, Hans-Werner; Edgcomb, Virginia; Orsi, William; Yakimov, Michail M; Stoeck, Thorsten

    2013-01-01

    High salt concentrations, absence of light, anoxia, and high hydrostatic pressure make deep hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea one of the most polyextreme habitats on Earth. Taking advantage of the unique chemical characteristics of these basins, we tested the effect of environmental selection and geographic distance on the structure of protistan communities. Terminal restriction fragment length polymorphism (T-RFLP) analyses were performed on water samples from the brines and seawater/brine interfaces of five basins: Discovery, Urania, Thetis, Tyro, and Medee. Using statistical analyses, we calculated the partitioning of diversity among the ten individual terminal restriction fragment (T-RF) profiles, based on peak abundance and peak incidence. While a significant distance effect on spatial protistan patterns was not detected, hydrochemical gradients emerged as strong dispersal barriers that likely lead to environmental selection in the DHAB protistan plankton communities. We identified sodium, magnesium, sulfate, and oxygen playing in concerto as dominant environmental drivers for the structuring of protistan plankton communities in the Eastern Mediterranean DHABs. PMID:23239531

  15. Climate variability in the Eastern and Western Mediterranean Sea over the last two millennia: a contribution of PaleoMex/MISTRALS

    NASA Astrophysics Data System (ADS)

    Gogou, Alexandra; Sicre, Marie-Alexandrine; Triantaphyllou, Maria; Parinos, Konstantine; Bouloubassi, Ioanna; Dimiza, Margarita; Rousakis, Grigoris; Korres, Gerasimos; Kallel, Nejib; Jalali, Bassem; Kaberi, Helen; Ezat, Ullah; Lykousis, Vasilios

    2013-04-01

    Recent compilations of Mediterranean 2k paleoclimate archives (Luterbacher et al., 2012, MedClivar Book) stressed the lack of high-resolution/ continuous marine records. The two new high-resolution sea surface temperature (SSTs) time-series presented here from the shallow coastal shelf sediments of the Gulf of Lions and deeper ocean one of the Aegean Sea using alkenone paleothermometry, are thus an important contribution. SST values are roughly 2°C warmer in the Eastern than Western Mediterranean sites in agreement with our knowledge of the production pattern of the main alkenone producer Emiliania huxleyi in the two basins. Both SST-record reveal significant variability of cool/warm intervals, corresponding to the continental European and Northern Hemisphere climatic variability. While distant from each other, SSTs at the two sites show some degree of similarity: increasing SSTs from ~ 600 to 1300 AD followed by a significant cooling till the early 1600's marking the onset of an outstanding warm period reaching values similar to present day. After a sharp decrease ending around 1700 yrs AD, the last three centuries indicate gradually rising SSTs by about 1°C/100 yrs. To our knowledge the latter feature has been undocumented in North Atlantic cores but often observed in paleoclimate reconstructions of the European climate, though with different regional timing and amplitude. This unexpected finding may reflect feedbacks from the surrounding land-masses contributing to "continentalize" the Mediterranean climate. Another notable feature is the short-lived abrupt cooling in the Aegean record between 1816 and 1824 yr AD, possibly expressing the surface water cooling subsequent to the Tambora volcanic eruption of 1815 yrs AD. * We acknowledge financial support from MEDECOS (Marin-ERA, EU/FP6) Project and the Greek General Secretary of Research and Technology. Luterbacher J, Garcia-Herrera R, Allan R, Alvarez-Castro BG, Benito G, Booth J, Büntgen U, Colombaroli D

  16. Summer distributions of forage fish in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Parker-Stetter, Sandra L.; Horne, John K.; Farley, Edward V.; Barbee, David H.; Andrews, Alexander G.; Eisner, Lisa B.; Nomura, Jennifer M.

    2013-10-01

    Juvenile and small adult fish, typically called forage fish, are an important but poorly studied part of the eastern Bering Sea (EBS) ecosystem. Acoustic and trawl data from a non-target survey were used to evaluate distributions of capelin (Mallotus villosus), age-0 Pacific cod (Gadus macrocephalus), and age-0 walleye pollock (Theragra chalcogramma, herein pollock) in 2006-2010. Within the surface zone (15 m to ~35 m, evaluated 2006-2010), capelin occurred throughout the EBS but primarily in the middle shelf. Capelin were also present in the midwater zone (~35 m to 0.5 m off-bottom) in both 2009 and 2010 (evaluated 2009-2010), and resulted in water column zone (15 m to 0.5 m off-bottom) distributions that differed from surface zone characterizations. Age-0 Pacific cod occurred primarily in the surface zone of the middle and outer shelf regions in all years. As midwater and surface zone age-0 Pacific cod were often coincident, water column zone distributions in 2009-2010 were similar to surface zone distributions. Age-0 pollock were found in the EBS surface zone in all years, primarily in the middle and outer shelf regions. High densities of age-0 pollock occurred in the midwater zone in 2006-2007 and 2009-2010. Water column zone distributions of age-0 pollock were similar to surface zone distributions in 2006-2007, but differed in 2009-2010 due to low numbers of age-0 pollock in the surface zone and presence of high densities in the midwater zone of the outer shelf region. While general patterns in capelin distribution in the surface zone were similar between the present and the previous studies, the acoustic-trawl characterization suggested that capelin densities were high in the middle shelf region. As expected, surface zone distributions of age-0 Pacific cod and age-0 pollock were similar to previous characterizations. Observed high densities of midwater age-0 pollock have not been described by previous studies. Annual abundance indices based on bottom or

  17. Crust-mantle mechanical coupling in Eastern Mediterranean and eastern Turkey.

    PubMed

    Özeren, M Sinan

    2012-05-29

    Present-day crust-mantle coupling in the Eastern Mediterranean and eastern Turkey is studied using the Global Positioning System (GPS) and seismic anisotropy data. The general trend of the shear wave fast-splitting directions in NE Turkey and Lesser Caucaus align well with the geodetic velocities in an absolute plate motion frame of reference pointing to an effective coupling in this part of the region of weak surface deformation. Farther south, underneath the Bitlis Suture, however, there are significant Pn delays with E-W anisotropy axes indicating significant lateral escape. Meanwhile, the GPS reveals very little surface deformation. This mismatch possibly suggests a decoupling along the suture. In the Aegean, the shear wave anisotropy and the Pn anisotropy directions agree with the extensional component of the right-lateral shear strains except under the Crete Basin and other parts of the southern Aegean Sea. This extensional direction matches perfectly also with the southward pulling force vectors across the Hellenic trench; however, the maximum right-lateral shear directions obtained from the GPS data in the Aegean do not match either of these anisotropies. Seismic anisotropy from Rayleigh waves sampled at 15 s, corresponding to the lower crust, match the maximum right-lateral maximum shear directions from the GPS indicating decoupling between the crust and the mantle. This decoupling most likely results from the lateral variations of the gravitational potential energies and the slab-pull forces.

  18. Crust-mantle mechanical coupling in Eastern Mediterranean and Eastern Turkey

    PubMed Central

    Sinan Özeren, M.

    2012-01-01

    Present-day crust-mantle coupling in the Eastern Mediterranean and eastern Turkey is studied using the Global Positioning System (GPS) and seismic anisotropy data. The general trend of the shear wave fast-splitting directions in NE Turkey and Lesser Caucaus align well with the geodetic velocities in an absolute plate motion frame of reference pointing to an effective coupling in this part of the region of weak surface deformation. Farther south, underneath the Bitlis Suture, however, there are significant Pn delays with E-W anisotropy axes indicating significant lateral escape. Meanwhile, the GPS reveals very little surface deformation. This mismatch possibly suggests a decoupling along the suture. In the Aegean, the shear wave anisotropy and the Pn anisotropy directions agree with the extensional component of the right-lateral shear strains except under the Crete Basin and other parts of the southern Aegean Sea. This extensional direction matches perfectly also with the southward pulling force vectors across the Hellenic trench; however, the maximum right-lateral shear directions obtained from the GPS data in the Aegean do not match either of these anisotropies. Seismic anisotropy from Rayleigh waves sampled at 15 s, corresponding to the lower crust, match the maximum right-lateral maximum shear directions from the GPS indicating decoupling between the crust and the mantle. This decoupling most likely results from the lateral variations of the gravitational potential energies and the slab-pull forces. PMID:22592788

  19. Crust-mantle mechanical coupling in Eastern Mediterranean and eastern Turkey.

    PubMed

    Özeren, M Sinan

    2012-05-29

    Present-day crust-mantle coupling in the Eastern Mediterranean and eastern Turkey is studied using the Global Positioning System (GPS) and seismic anisotropy data. The general trend of the shear wave fast-splitting directions in NE Turkey and Lesser Caucaus align well with the geodetic velocities in an absolute plate motion frame of reference pointing to an effective coupling in this part of the region of weak surface deformation. Farther south, underneath the Bitlis Suture, however, there are significant Pn delays with E-W anisotropy axes indicating significant lateral escape. Meanwhile, the GPS reveals very little surface deformation. This mismatch possibly suggests a decoupling along the suture. In the Aegean, the shear wave anisotropy and the Pn anisotropy directions agree with the extensional component of the right-lateral shear strains except under the Crete Basin and other parts of the southern Aegean Sea. This extensional direction matches perfectly also with the southward pulling force vectors across the Hellenic trench; however, the maximum right-lateral shear directions obtained from the GPS data in the Aegean do not match either of these anisotropies. Seismic anisotropy from Rayleigh waves sampled at 15 s, corresponding to the lower crust, match the maximum right-lateral maximum shear directions from the GPS indicating decoupling between the crust and the mantle. This decoupling most likely results from the lateral variations of the gravitational potential energies and the slab-pull forces. PMID:22592788

  20. Changes in the distribution and abundance of albatrosses in the eastern Bering Sea: 1975-2010

    NASA Astrophysics Data System (ADS)

    Kuletz, Kathy J.; Renner, Martin; Labunski, Elizabeth A.; Hunt, George L.

    2014-11-01

    A number of marine species are showing poleward shifts in their distributions in response to climate warming. Three albatross species frequent the Bering Sea, the Laysan (Phoebastria immutabilis), the black-footed (Phoebastria nigripes), and the endangered short-tailed albatross (Phoebastria albatrus). To determine if albatrosses changed their distribution or abundance in the eastern Bering Sea between 1975 and 2010, we examined at-sea survey data using the North Pacific Pelagic Seabird Database. Within our study area, all three species of albatross occurred most frequently in the waters of the Aleutian Islands. In the eastern Bering Sea, all three species were most abundant near the shelf break, and in particular in the vicinity of the major submarine canyons in the shelf slope. Starting in the 1990s, population densities increased for all three albatross species, with a marked increase in the 2000s. In the 2000s, there was also an increase in the frequency at which albatrosses were recorded in the central and northern Bering Sea. Both black-footed and short-tailed albatrosses shifted the centers of their Bering Sea distributions northward. The Laysan albatross center of distribution shifted southward due to increased numbers along the southern shelf break, but densities also increased northward. We suggest that the observed changes in distribution and abundance of the three albatross species in the eastern Bering Sea may have been responses to an increase in the availability of squid, their primary prey, there. Additionally, the expansion of the distribution of the short-tailed albatross in the eastern Bering Sea may represent the reclamation of its previous range, now that the population is beginning to recover from near extinction caused by over harvesting. We suggest that predicted increases in ocean temperatures and northward movement of prey could result in albatrosses and other marine apex predators foraging farther north along the Bering Sea shelf and

  1. Accumulation of organochlorine contaminants in loggerhead sea turtles, Caretta caretta, from the eastern Adriatic Sea.

    PubMed

    Lazar, Bojan; Maslov, Luna; Romanić, Snježana Herceg; Gračan, Romana; Krauthacker, Blanka; Holcer, Draško; Tvrtković, Nikola

    2011-01-01

    We analyzed 15 polychlorinated biphenyls (PCBs) and five organochlorine pesticides (OCPs) in fat tissue of 27 loggerhead sea turtles (Caretta caretta) from eastern Adriatic Sea with the curved carapace length ranging from 25.0 to 84.5 cm. The PCB profile was dominated by hexa- and hepta-chlorinated congeners, with PCB-153 (median: 114.9 ng g⁻¹ wet mass), PCB-138 (80.0 ng g⁻¹ w.m.), and PCB-180 (26.7 ng g⁻¹ w.m.) detected with the highest levels. Toxic mono-ortho congeners PCB-118, PCB-105 and PCB-180 with dioxin-like toxicity were found in > 70% samples. 4,4'-DDE (81.0 ng g⁻¹ w.m.) prevailed the OCP signature, accounting for 80% of the total DDTs. A significant increasing trend in accumulation with size was found for PCB-52 (r(s) = 0.512, p < 0.01) and PCB-114 (r(s) = 0.421, p < 0.05). Comparison of our results with organochlorine contaminant (OC) pattern in some prey taxa suggest that contamination occurs primarily through the food web, with biomagnification factors of 0.14-6.99 which were positively correlated with the octanol-water partition coefficient (logK(ow); p < 0.05). This study, based upon a fairly large sample size collected mostly from incidentally captured animals over a short time period (June 2001-November 2002), present a temporal snapshot of OC contamination in wild, free-ranging loggerheads from Adriatic feeding grounds and provide a baseline for monitoring the regional OC trends in this endangered species.

  2. Trophodynamics of a deep-sea demersal fish assemblage from the bathyal eastern Ionian Sea (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Madurell, T.; Cartes, J. E.

    2005-11-01

    Daily food consumption of the eight dominant demersal fish species of the bathyal eastern Ionian Sea were determined from field data on four seasonal cruises (April 1999, July August 1999, November 1999 and February 2000). Daily ration (DR) estimates ranged from 0.198 to 4.273% WW/WW. Overall, DR estimates were independent of the model used, and they were comparable to the daily consumption of other deep-sea fauna (e.g. fish and crustaceans). Both sharks studied ( Galeus melastomus and Etmopterus spinax) exhibited the highest values of DRs, together with the macrourid Coelorhynchus coelorhynchus in August. Among osteichthyes, DR estimates were related (in a multi-linear regression model) to the nature of their diet (i.e. their trophic level deduced from δ15N isotopic composition, the mean number of prey and trophic diversity). Thus, species feeding at a lower trophic level, ingesting a large number of prey items and with a very diversified diet had higher DR than species from higher trophic level and feeding fewer prey items. By season, the DR of species feeding mainly on mesopelagic prey ( Hoplostethus mediterraneus and Helicolenus dactylopterus) were higher in summer, while DR for benthos/suprabenthos feeders (i.e. C. coelorhynchus and Nezumia sclerorhynchus) were higher in spring. Higher food consumption coincides with maximum food availability, both among mesopelagic feeders (higher availability of euphausiids, Pasiphaea sivado and Sergestes arcticus in summer) and among Macrouridae (higher suprabenthos densities in spring). In a tentative estimate the energy intake deduced from diet (i.e. mean energy value of food ingested) was constant in all seasons for each species studied. Results for the energy intake also indicate higher energy intake in the diet of mesopelagic feeders than in the diet of benthic feeders. Overall results are discussed in relation to the deep-sea ecosystem structure and functioning.

  3. Pass over Eastern Asia to Philippine Sea and Guam

    NASA Video Gallery

    This pass begins over Mongolia, looking towards the Pacific Ocean, China, and Japan. As the video progresses, you can see major cities along the coast and the Japanese islands on the Philippine Sea...

  4. Composition and sources of sedimentary organic matter in the deep Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Pedrosa-Pàmies, R.; Parinos, C.; Sanchez-Vidal, A.; Gogou, A.; Calafat, A.; Canals, M.; Bouloubassi, I.; Lampadariou, N.

    2015-07-01

    Surface sediments collected from deep slopes and basins (1018-4087 m depth) of the oligotrophic Eastern Mediterranean Sea have been analysed for bulk elemental and isotopic composition of organic carbon, total nitrogen and selected lipid biomarkers, jointly with grain size distribution and other geochemical proxies. The distribution and sources of sedimentary organic matter (OM) have been subsequently assessed and general environmental variables, such as water depth and currents, have been examined as causative factors of deep-sea sediment characteristics. Lithogenic and biogenic carbonates are the dominant sedimentary fractions, while both bulk and molecular organic tracers reflect a mixed contribution from autochthonous and allochthonous sources for the sedimentary OM, as indicated by relatively degraded marine OM, terrestrial plant waxes and anthropogenic OM including degraded petroleum by-products, respectively. Wide regional variations have been observed amongst the studied proxies, which reflect the multiple factors controlling sedimentation in the deep Eastern Mediterranean Sea. Our findings highlight the role of deep Eastern Mediterranean basins as depocentres of organic-rich fine-grained sediments (mean 5.4 ± 2.4 μm), with OM accumulation and burial due to aggregation mechanisms and hydrodynamic sorting. A multi-proxy approach is hired to investigate the biogeochemical composition of sediment samples, which sheds new light on the sources and transport mechanisms along with the impact of preservation vs. diagenetic processes on the composition of sedimentary OM in the deep basins of the oligotrophic Eastern Mediterranean Sea.

  5. 77 FR 23209 - Endangered and Threatened Species; Proposed Delisting of Eastern DPS of Steller Sea Lions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-18

    ... National Oceanic and Atmospheric Administration 50 CFR Parts 223 and 224 RIN 0648-BB41 Endangered and Threatened Species; Proposed Delisting of Eastern DPS of Steller Sea Lions AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce. ACTION: Proposed...

  6. Composition and sources of sedimentary organic matter in the deep eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Pedrosa-Pàmies, R.; Parinos, C.; Sanchez-Vidal, A.; Gogou, A.; Calafat, A.; Canals, M.; Bouloubassi, I.; Lampadariou, N.

    2015-12-01

    Surface sediments collected from deep slopes and basins (1018-4087 m depth) of the oligotrophic eastern Mediterranean Sea have been analysed for bulk elemental and isotopic composition of organic carbon, total nitrogen and selected lipid biomarkers, jointly with grain size distribution and other geochemical proxies. The distribution and sources of sedimentary organic matter (OM) have been subsequently assessed and general environmental variables, such as water column depth and physical circulation patterns, have been examined as causative factors of deep-sea sediment characteristics. Lithogenic and biogenic carbonates are the dominant sedimentary fractions, accounting for up to 85.4 and 66.5 % of the total weight respectively. The low OC and TN contents in the surface sediments of the study area, which ranged from 0.15 to 1.15 % and 0.06 to 0.11 % respectively, reflect the oligotrophic character of the eastern Mediterranean Sea. Both bulk and molecular organic tracers reflect a mixed contribution from autochthonous and allochthonous sources for the sedimentary OM, as indicated by relatively degraded marine OM, terrestrial plant waxes and anthropogenic OM (e.g. degraded petroleum by-products) respectively. Wide regional variations have been observed amongst the studied proxies, which reflect the multiple factors controlling sedimentation in the deep eastern Mediterranean Sea. Our findings highlight the role of deep eastern Mediterranean basins as depocentres of organic-rich fine-grained sediments (mean 5.4 ± 2.4 μm), with OM accumulation and burial being attributed to aggregation mechanisms and hydrodynamic sorting. A multi-proxy approach is applied aiming to investigate the biogeochemical composition of sediment samples, which sheds new light on the sources and transport mechanisms along with the impact of preservation vs. diagenetic processes on the composition of sedimentary OM in the deep basins of the oligotrophic eastern Mediterranean Sea.

  7. Modes of sedimentary basin formation in the north-eastern Black Sea

    NASA Astrophysics Data System (ADS)

    Stephenson, Randell; Starostenko, Vitaly; Sydorenko, Grygoriy; Yegorova, Tamara

    2016-04-01

    The Greater Caucasus and Black Sea sedimentary basins developed in a Mesozoic back-arc setting, the former older than the latter (Jurassic v. Cretaceous). Compressional shortening of the former and accompanying ongoing development of marginal basin depocentres in the north-eastern Black Sea - which is closely tied to the formation of the Crimea-Greater Caucasus orogen - is a Cenozoic phenomenon, starting in the Eocene and proceeding until the present day. Recently, the sedimentary basin/crust/lithosphere geometry of the study area has been characterised across a range of scales using regional seismic reflection profiling, long-offset refraction/wide-angle reflection profiling and local earthquake tomography. These provide a new integrated image of the present-day crustal structure and sedimentary basin architecture of the northern margin of the eastern Black Sea, north across the Azov Sea and provide evidence of the deeper expression of sedimentary basins and the processes controlling the geometry of their inversion during the Cenozoic. It is inferred that the Greater Caucasus paleo-Basin, lying stratigraphically below the Black Sea and younger sedimentary successions, extends further to the west than previously known. This basin has significant thickness in the area between the Azov and Black seas and probably forms the deeper core of the Crimea-Caucasus inversion zone. The Crimea-Greater Caucasus orogenic belt is the expression of "basin inversion" of the Jurassic Greater Caucasus paleo-Basin, the degree of inversion of which varies along strike. The Greater Caucasus foredeep basins - Indolo-Kuban and Sorokin-Tuapse troughs -represent syn-inversional marginal troughs to the main inversion zone. The Shatsky Ridge - the northern flank of the main East Black Sea Basin - may also be mainly a syn-inversional structure, underlain by a blind thrust zone expressed as a northward dipping zone of seismicity on the northern margin of the eastern Black Sea.

  8. New constraints on the active tectonic deformation of the Aegean

    USGS Publications Warehouse

    Nyst, M.; Thatcher, W.

    2004-01-01

    Site velocities from six separate Global Positioning System (GPS) networks comprising 374 stations have been referred to a single common Eurasia-fixed reference frame to map the velocity distribution over the entire Aegean. We use the GPS velocity field to identify deforming regions, rigid elements, and potential microplate boundaries, and build upon previous work by others to initially specify rigid elements in central Greece, the South Aegean, Anatolia, and the Sea of Marmara. We apply an iterative approach, tentatively defining microplate boundaries, determining best fit rigid rotations, examining misfit patterns, and revising the boundaries to achieve a better match between model and data. Short-term seismic cycle effects are minor contaminants of the data that we remove when necessary to isolate the long-term kinematics. We find that present day Aegean deformation is due to the relative motions of four microplates and straining in several isolated zones internal to them. The RMS misfit of model to data is about 2-sigma, very good when compared to the typical match between coseismic fault models and GPS data. The simplicity of the microplate description of the deformation and its good fit to the GPS data are surprising and were not anticipated by previous work, which had suggested either many rigid elements or broad deforming zones that comprise much of the Aegean region. The isolated deforming zones are also unexpected and cannot be explained by the kinematics of the microplate motions. Strain rates within internally deforming zones are extensional and range from 30 to 50 nanostrain/year (nstrain/year, 10-9/year), 1 to 2 orders of magnitude lower than rates observed across the major microplate boundaries. Lower strain rates may exist elsewhere withi the microplates but are only resolved in Anatolia, where extension of 13 ?? 4 nstrain/ year is required by the data. Our results suggest that despite the detailed complexity of active continental deformation

  9. ORGANOCHLORINE CONTAMINANTS IN SEA TURTLES FROM THE EASTERN PACIFIC

    EPA Science Inventory

    We measured organochlorine residues in three species of sea turtles from the Baja California peninsula, Mexico. Seventeen of 21 organochlorine pesticides analyzed were detected, with heptachlor epoxide and y-hexachlorocyclohexane the most prevalent in 14 (40%) and 11 (31%) of th...

  10. Evaluation of model simulated and MODIS-Aqua retrieved sea surface chlorophyll in the eastern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Chakraborty, Kunal; Gupta, Anubhav; Lotliker, Aneesh A.; Tilstone, Gavin

    2016-11-01

    In this study we assess the accuracy of sea surface Chlorophyll-a (Chla) retrieved from satellite (MODIS-Aqua), using standard OC3M algorithm, and from a Regional Ocean Modelling System (ROMS) biophysical model against in situ data, measured in surface waters of the eastern Arabian Sea, from April 2009 to December 2012. MODIS-Aqua OC3M Chla concentrations showed a high correlation with the in situ data with slope close to unity and low root mean square error. In comparison, the ROMS model underestimated Chla, though the correlation was significant indicating that the model is capable of reproducing the trend in in situ Chla. Time Series trends in Chla were examined against wind driven Upwelling Indices (UIW) from April 2009 to December 2012 in north-eastern (Gujarat) and south-eastern (Kochi) coastal waters of the Arabian Sea. The annual peak in Chla along the Kochi coast during the summer monsoon was adequately captured by the model. It is well known that the peak in surface Chla along the Kochi and Gujarat coasts during the summer monsoon is the result of coastal upwelling, which the ROMS model was able to reproduce accurately. The maximum surface Chla along the Gujarat coast during the winter monsoon is due to convective mixing, which was also significantly captured by ROMS biophysical model. There was a lag of approximately one week between the maximum surface Chla and the peak in the Upwelling Index.

  11. Late Quaternary sea-level highstands in the central and eastern Indian Ocean: A review

    NASA Astrophysics Data System (ADS)

    Woodroffe, Colin D.

    2005-11-01

    The relative sea-level history of several atolls in the central and eastern Indian Ocean, including the Cocos (Keeling) Islands, Chagos Archipelago, and the Maldives-Laccadive Archipelagoes, has been debated for over a century but takes on a particular significance in the face of anticipated climate change. For each of these central and eastern Indian Ocean atolls Pleistocene limestone is encountered at depths of 6-20 m below sea level. On the Cocos (Keeling) Islands this has been dated to Last Interglacial age. Conglomerate platform underlies the reef islands on Cocos within which a sequence of fossil microatolls of massive and branching Porites records a gradual fall of sea level relative to the atoll. In the Maldives, the significance of outcrops of 'reef rock' has been vigorously debated without resolving sea-level history. Although in situ Heliopora occurs on the reef flat of Addu Atoll, dated at around 2700 radiocarbon yrs BP, other evidence for higher sea level remains poorly constrained. Conglomerates of a similar age have been described from the Chagos Archipelago, but it has not been unequivocally demonstrated that they formed under conditions of relatively higher sea level. In contrast to reefs further west in the Indian Ocean, each of these atolls has living microatolls of massive Porites that have been constrained in their upward growth by sea level. Interpretation of the upper surface of two such specimens from the Cocos (Keeling) Islands indicates broad fluctuations in the sea surface over the past century; similar microatolls are described from the Maldives implying little change in sea level over recent years. Regardless of minor past fluctuations, most reef islands in the Maldives are particularly low-lying and appear vulnerable to inundation, and extracting a more detailed sea-level history remains an important challenge.

  12. Changes in Nitrogen to Phosphorus ratio in the Inner Saronikos Gulf (West Aegean Sea) in relation to the operation of the Sewage Treatment Plant of Athens, Greece

    NASA Astrophysics Data System (ADS)

    Psyllidou-Giouranovits, Rosa

    2013-04-01

    In this work we provide an overview of nitrogen (N) to phosphorus (P) ratio in the inner Saronikos gulf as it has changed over the last twenty five (25) years in relation to the sewage discharges from the Sewage Treatment Plant of Athens in Psittalia Island. Saronikos gulf receives effluents from Athens Metropolitan area (population over 5 million). Until 1994, domestic and industrial sewage of Athens was discharged untreated into the surface water layer of Keratsini and Elefsis bay, whereas, after 1994, the sewage of the Athens Metropolitan area were primarily treated in Psitallia Sewage Treatment Plant and discharged in the inner Saronikos Gulf. Additionally, the secondary stage of the Psittalia Sewage Plant operated in the end of 2004 affecting the nitrogen to phosphorus (DIN:P) ratio (DIN stands for nitrate+nitrite+ammonium). The treated effluent plume frorm Psittalia Sewage Treatment Plant is trapped within the seasonal pycnocline developed during May-November, whereas, during the mixing period (December-April) it reaches the sea-surface. During the last 25 years, significant temporal variation of nutrient concentrations has been observed which has revealed an increase of the DIN:P ratio near the Psittalia Sewage Treatment Plant. In the vicinity of the sewage outfall in Psittalia, DIN:P ratio in the deep layer (30m-bottom) did not show significant variation between the two periods: before and after the operation of the Sewage Treatment Plant (12.9 before the operation of the sewage treatment and 13.3 after the operation of the sewage treatment) showing that inorganic nitrogen and phosphate changed almost with the same rate. However, the limiting factor for phytoplankton growth remains nitrogen. On the contrary, significant increase of DIN:P ratio was observed in the surface layer between the two periods, during summer (stratified period). DIN:P increased from 5.9 for the period 1987-1995 (before the Sewage Treatment Plant operation) to 19.6 for the period 1995

  13. Distribution of drifting seaweeds in eastern East China Sea

    NASA Astrophysics Data System (ADS)

    Komatsu, Teruhisa; Tatsukawa, Kenichi; Filippi, Jean B.; Sagawa, Tatsuyuki; Matsunaga, Daisuke; Mikami, Atsuko; Ishida, Kenichi; Ajisaka, Tetsuro; Tanaka, Katsuhiko; Aoki, Masakazu; Wang, Wei-Ding; Liu, Hui-Fei; Zhang, Shou-Du; Zhou, Min-Dong; Sugimoto, Takashige

    2007-09-01

    In offshore waters with relatively low primary production, drifting seaweeds composed of Sargassum species form an identical ecosystem such as an oasis in desert. Commercially important pelagic fishes such as jack mackerel ( Trachurus japonicus) and yellow tail ( Seriola quinqueradiata) spawn in East China Sea pass their juvenile period accompanying drifting seaweeds. Therefore drifting seaweeds are very important not only in offshore ecosystem but also fishery resources. However the distribution of drifting seaweeds in East China Sea has scarcely known. Then we conducted two research cruises of R/V Hakuho-Maru in May 2002 and in March 2004. During the cruises, drifting seaweeds were visually observed from the bridge and sampled with a towing net. The observation revealed that the drifting seaweeds were distributed along the front between the Kuroshio Current and coastal waters and mainly composed of one seaweed species, Sargassum horneri (Turner) C. Agardh from spring to early summer. There are no reports on geographical distribution of this species in the coasts south of southern Kyushu Island in Japan. Kuroshio Current flows northeastward there. Buoys with GPS attached to drifting seaweeds released off Zhejiang Province, China, in March 2005 to track their transport. Their positions monitored by ORBCOM satellite showed that they were transported to the area in East China Sea, where the drifting seaweeds were observed during the cruises, in 2 months. These facts suggest that S. horneri detached from Chinese coast in March or months earlier than March could be transported to fringe area of continental shelf and waters influenced by Kuroshio Current from March to May. Therefore the Sargassum forests, especially S. horneri, along the Chinese coast play a very important role in the ecosystem of the East China Sea as a source of drifting seaweeds.

  14. Geostrophic transport variability along the Aves Ridge in the eastern Caribbean Sea during 1985-1986

    NASA Astrophysics Data System (ADS)

    Morrison, John M.; Smith, Orson P.

    1990-01-01

    Data from five cruises during 1985-1986 along 63.55°W, across the eastern Caribbean Sea, are examined for seasonal variability of gcostrophic transport. A biannual maximum transport signal appears to correspond to that measured in the Florida Straits as well as to variations in the regional wind stress curl. Similar seasonal variations in the properties of water masses, entering the eastern margin of the basin and concentrated through the passages of the Lesser Antilles, are also indicated. A permanent system of strong westward flowing streams, interspersed by weaker eastward flowing streams, is shown to exist.

  15. Seismicity of the eastern Hellenic Subduction Zone

    NASA Astrophysics Data System (ADS)

    Bruestle, A.; Kueperkoch, L.; Rische, M.; Meier, T.; Friederich, W.; Egelados Working Group

    2012-04-01

    The Hellenic Subduction Zone (HSZ) is the seismically most active region of Europe. The African plate is subducting beneath the Aegean lithosphere with a relative velocity of 4 cm per year. A detailed picture of the microseismicity of the eastern HSZ was obtained by the recordings of the temporary networks CYCNET (September 2002 - September 2005) and EGELADOS (October 2005 - March 2007). In total, nearly 7000 earthquakes were located with a location uncertainty of less than 20 km. The SE Aegean is dominated by (1) shallow intraplate seismicity within the Aegean plate, by (2) interplate seismicity at the plate contact and by (3) intermediate deep seismicity along the subducting African slab. Strong shallow seismicity in the upper plate is observed along the Ptolemy graben south of Crete extending towards the Karpathos Basin, indicating intense recent deformation of the forearc. In contrary, low shallow seismicity around Rhodes indicates only minor seismic crustal deformation of the upper plate. An almost NS-striking zone of microseismicity has been located, running from the Karpathos basin via the Nisyros volcanic complex towards the EW striking Gökova graben. In the SE Aegean the geometry of the Wadati-Benioff-Zone (WBZ) within the subducting African plate is revealed in detail by the observed microseismicity. Between about 50 to 100 km depth a continuous band of intermediate deep seismicity describes the strongly curved geometry of the slab. From the central to the eastern margin of the HSZ, the dip direction of the WBZ changes from N to NW with a strong increase of the dip angle beneath the eastern Cretan Sea. The margin of the dipping African slab is marked by an abrupt end of the observed WBZ beneath SW Anatolia. Below 100 km depth, the WBZ of the eastern HSZ is dominated by an isolated cluster of intense intermediate deep seismicity (at 100-180 km depth) beneath the Nisyros volcanic complex. It has an extension of about 100x80 km and is build up of 3 parallel

  16. Chronology for the Aegean Late Bronze Age 1700-1400 B.C.

    PubMed

    Manning, Sturt W; Ramsey, Christopher Bronk; Kutschera, Walter; Higham, Thomas; Kromer, Bernd; Steier, Peter; Wild, Eva M

    2006-04-28

    Radiocarbon (carbon-14) data from the Aegean Bronze Age 1700-1400 B.C. show that the Santorini (Thera) eruption must have occurred in the late 17th century B.C. By using carbon-14 dates from the surrounding region, cultural phases, and Bayesian statistical analysis, we established a chronology for the initial Aegean Late Bronze Age cultural phases (Late Minoan IA, IB, and II). This chronology contrasts with conventional archaeological dates and cultural synthesis: stretching out the Late Minoan IA, IB, and II phases by approximately 100 years and requiring reassessment of standard interpretations of associations between the Egyptian and Near Eastern historical dates and phases and those in the Aegean and Cyprus in the mid-second millennium B.C. PMID:16645092

  17. Ocean drilling program for Georges Bank, Eastern Pacific Rise, Mid American Trench, and Antarctica (Weddell sea)

    SciTech Connect

    Not Available

    1985-06-01

    The draft form of an environmental impact statement (EPA No. 850262D) on a proposed 10-year international ocean drilling program describes plans for drilling in the Georges Bank, Eastern Pacific Rise, Mid-American Trench, and Weddell Sea areas. Core samples from the ocean floor in the four study areas will examine oceanic crust, active and passive margins, and ocean paleoenvironment. The program would generate information on sea floor spreading, plate tectonics, the structure of the earth's interior, evolution of ocean life, climatic changes through time, and the structure of the planet. Negative impacts would be damage to the sea floor, drilling muds, possible gas or brine blowouts, and a possible effect on the sonar or hearing of marine mammals. Legal mandates for the impact statement are laws addressing water pollution, international conventions of the sea, and protection for marine life.

  18. Low-frequency Pliocene climate variability in the eastern Nordic Seas

    NASA Astrophysics Data System (ADS)

    Risebrobakken, Bjørg; Andersson, Carin; De Schepper, Stijn; McClymont, Erin L.

    2016-09-01

    The Pliocene (5.3-2.6 Ma) is often described as a relatively stable climatic period, with warm temperatures characterizing high latitudes. New suborbital resolved stable isotope records from Ocean Drilling Program Hole 642B in the eastern Nordic Seas document that the Pliocene was not a stable period characterized by one climate. Rather, seven distinct climate phases, each lasting between 150,000 and 400,000 years, are identified and characterized in the time interval 5.1-3.1 Ma. Four of the transitions between the defined climate phases occurred close to an eccentricity minimum and a minimum in amplitude of change for Northern Hemisphere summer insolation, while two occurred around an eccentricity maximum and a maximum in amplitude in insolation change. Hence, a low-frequency response of the Nordic Seas to insolation forcing is indicated. In addition, paleogeographic and related paleoceanographic changes, expansion of the Arctic sea ice cover, and onset of Northern Hemisphere glaciation were important factors behind the evolving Pliocene low-frequency variability in the eastern Nordic Seas. It is likely that the identified climate phases and transitions are important beyond the Nordic Seas, due to their association with changes to both insolation and paleogeography. However, a strong and variable degree of diagenetic calcite overgrowth is documented for the planktic foraminifera, especially influencing the planktic δ18O results; the absolute values and amplitude of change cannot be taken at face value.

  19. Variation in sand body types on the eastern Bering Sea epicontinental shelf.

    USGS Publications Warehouse

    Nelson, C.H.; Dupre, W.R.; Field, M.E.; Howard, J.D.

    1982-01-01

    The eastern epicontinental shelf of the Bering Sea is characterized by variations in river and glacial sediment supply, wave energy, tidal range (microtidal to mesotidal), and tidal, geostrophic, and storm-induced currents. These factors, combined with the effect of the Holocene rise in sea level, have resulted in the formation of a complex assemblage of generally linear sand bodies of similar morphology anad lithology, but different origins. The sand bodies are large features found from the present shoreline to tens of kilometers offshore, in water depths up to 50m. -from Authors

  20. Eastern-western Arctic sea ice analysis, 1993

    SciTech Connect

    1993-12-31

    This publication is the 20th edition of the annual Arctic sea-ice atlases prepared by the JIC. The atlas contains weekly charts depicting Northern Hemisphere ice conditions and extent. The significant use of high resolution satellite imagery, combined with valuable ice reconnaissance data from various sources, has greatly improved the accuracy of these analyses. The purpose of this atlas is to provide the user with reliable weekly hemispheric ice analyses. These charts are prepared by experienced Navy and NOAA ice analysts who plot and evaluate numerous data sources: (a) Conventional shore station, ship, and aerial reconnaissance observations; and (b) Satellite data from various sensors. Table I, located on the inside back cover, lists these sensors and their availability. A final product is synthesized from the inputs described above. When insufficient data is available, estimated boundaries are plotted, using meteorological data and computer generated ice drift vectors to determine estimated ice position.

  1. Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events.

    PubMed

    Incarbona, Alessandro; Martrat, Belen; Mortyn, P Graham; Sprovieri, Mario; Ziveri, Patrizia; Gogou, Alexandra; Jordà, Gabriel; Xoplaki, Elena; Luterbacher, Juerg; Langone, Leonardo; Marino, Gianluca; Rodríguez-Sanz, Laura; Triantaphyllou, Maria; Di Stefano, Enrico; Grimalt, Joan O; Tranchida, Giorgio; Sprovieri, Rodolfo; Mazzola, Salvatore

    2016-07-14

    The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales.

  2. Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events

    NASA Astrophysics Data System (ADS)

    Incarbona, Alessandro; Martrat, Belen; Mortyn, P. Graham; Sprovieri, Mario; Ziveri, Patrizia; Gogou, Alexandra; Jordà, Gabriel; Xoplaki, Elena; Luterbacher, Juerg; Langone, Leonardo; Marino, Gianluca; Rodríguez-Sanz, Laura; Triantaphyllou, Maria; di Stefano, Enrico; Grimalt, Joan O.; Tranchida, Giorgio; Sprovieri, Rodolfo; Mazzola, Salvatore

    2016-07-01

    The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales.

  3. Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events

    PubMed Central

    Incarbona, Alessandro; Martrat, Belen; Mortyn, P. Graham; Sprovieri, Mario; Ziveri, Patrizia; Gogou, Alexandra; Jordà, Gabriel; Xoplaki, Elena; Luterbacher, Juerg; Langone, Leonardo; Marino, Gianluca; Rodríguez-Sanz, Laura; Triantaphyllou, Maria; Di Stefano, Enrico; Grimalt, Joan O.; Tranchida, Giorgio; Sprovieri, Rodolfo; Mazzola, Salvatore

    2016-01-01

    The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales. PMID:27412622

  4. Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events.

    PubMed

    Incarbona, Alessandro; Martrat, Belen; Mortyn, P Graham; Sprovieri, Mario; Ziveri, Patrizia; Gogou, Alexandra; Jordà, Gabriel; Xoplaki, Elena; Luterbacher, Juerg; Langone, Leonardo; Marino, Gianluca; Rodríguez-Sanz, Laura; Triantaphyllou, Maria; Di Stefano, Enrico; Grimalt, Joan O; Tranchida, Giorgio; Sprovieri, Rodolfo; Mazzola, Salvatore

    2016-01-01

    The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales. PMID:27412622

  5. Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition

    NASA Astrophysics Data System (ADS)

    Tachikawa, K.; Vidal, L.; Cornuault, M.; Garcia, M.; Pothin, A.; Sonzogni, C.; Bard, E.; Menot, G.; Revel, M.

    2014-12-01

    Holocene Eastern Mediterranean Sea sediments contain an organic-rich sapropel S1 layer that was formed in oxygen-depleted waters. The spatial distribution of this layer revealed that during S1 deposition deep waters were permanently anoxic below 1800 m in water depth. To provide further insight into past Eastern Mediterranean Sea circulation, a multi-proxy approach was applied to a core retrieved close to the 1800 m boundary (at 1780 m). We measured the bulk sediment elemental composition, the stable isotopic composition of the planktonic foraminifer Globigerinoides ruber, and the abundance of benthic foraminifera since the last deglaciation. The result indicates that authigenic U and Mo accumulation began around 13-12 cal ka BP, in concert with surface water freshening estimated from the G. ruber δ18O record. The onset of bottom/pore water oxygen depletion occurred prior to S1 deposition inferred from barium enrichment. In the middle of the S1 deposition period, between 9 and 8 cal ka BP, reduced authigenic V, Fe and As contents and Br / Cl ratio indicated short-term bottom water re-oxygenation. A sharp Mn peak and maximal abundance for benthic foraminifera marked a total recovery for circulation at approximately 7 cal ka BP. Based on our results and existing data, we suggest that S1 formation withinthe upper 1780 m of the Eastern Mediterranean Sea was preconditioned by reduced ventilation, resulting from excess fresh water inputs due to insolation changes under deglacial conditions, that initiated between 15 and 12 ka. Short-term re-oxygenation in the Levantine Basin is estimated to have affected bottom water below and above the anoxic boundary. We tentatively propose that complete ventilation recovery at the S1 termination was attained earlier within the upper 1780 m than at deeper water depths. Our results provided new constraints for eastern Mediterranean Sea thermohaline circulation.

  6. South Aegean Geodynamic And Tsunami Monitoring Platform

    NASA Astrophysics Data System (ADS)

    Paradissis, Demitris; Drakatos, George; Marinou, Aggeliki; Anastasiou, Demitris; Alatza, Stauroula; Zacharis, Vangelis; Papanikolaou, Xanthos; Melis, Nicolaos; Kalogeras, Ioannis; Chouliaras, Gerasimos; Evangelidis, Christos; Makropoulos, Konstantinos

    2015-04-01

    The Aegean Sea is one of the most tectonically and seismically active areas in the world, thus constituting a Natural Laboratory. For the first time, a permanent multiparametric platform of networks that combine different (both terrestrial and space oriented) techniques, is established, in order to monitor the tectonic and volcanic activity in the area and produce an on-line database available both to the scientific community and the public. This platform includes continuous GNSS networks, tide-gauge sensors, accelerometers and seismographs. All the available existing infrastructure has been upgraded, enlarged and modernized resulting in a collaborative operation. New instrumentation has been installed in carefully selected sites. All the available data are analysed using state of the art processing software. Raw data and products will be available through a project dedicated portal. The multiparametric data and results gathered will be integrated and combined with the existing archive owned by the participating institutes to produce a thoroughgoing view of the underlying geophysical processes. The island of Santorini will serve as a focused study case for the project, due to the special tectono-volcanic interest and because of the already existing dense multiparametric network. Our goal is to provide permanent infrastructure and knowledge both to enlighten ambiguous scientific hypothesis and serve as a focal point for further scientific research.

  7. Long-lead predictions of eastern United States hot days from Pacific sea surface temperatures

    NASA Astrophysics Data System (ADS)

    McKinnon, K. A.; Rhines, A.; Tingley, M. P.; Huybers, P.

    2016-05-01

    Seasonal forecast models exhibit only modest skill in predicting extreme summer temperatures across the eastern US. Anomalies in sea surface temperature and monthly-resolution rainfall have, however, been correlated with hot days in the US, and seasonal persistence of these anomalies suggests potential for long-lead predictability. Here we present a clustering analysis of daily maximum summer temperatures from US weather stations between 1982-2015 and identify a region spanning most of the eastern US where hot weather events tend to occur synchronously. We then show that an evolving pattern of sea surface temperature anomalies, termed the Pacific Extreme Pattern, provides for skillful prediction of hot weather within this region as much as 50 days in advance. Skill is demonstrated using out-of-sample predictions between 1950 and 2015. Rainfall deficits over the eastern US are also associated with the occurrence of the Pacific Extreme Pattern and are demonstrated to offer complementary skill in predicting high temperatures. The Pacific Extreme Pattern appears to provide a cohesive framework for improving seasonal prediction of summer precipitation deficits and high temperature anomalies in the eastern US.

  8. Identification of multiple nursery habitats of skates in the eastern Bering Sea.

    PubMed

    Hoff, G R

    2016-05-01

    The use of more than a single nursery habitat type is examined for oviparous elasmobranchs using data summarized from studies conducted on the Alaska skate Bathyraja parmifera and the Aleutian skate Bathyraja aleutica in the eastern Bering Sea. The eastern Bering Sea skate species use two discrete areas as nurseries, one for egg deposition and a second for newly emergent juveniles. Egg deposition sites were located along the outer shelf and upper slope near canyons in the eastern Bering Sea. Newly emergent juveniles were found along the outer and middle shelf for B. parmifera and deep-slope for B. aleutica, suggesting that habitat used by newly emergent juvenile skates is distinct from habitat used for egg deposition and embryo development. In reviewing many studies on oviparous elasmobranchs, similar patterns emerge of habitat use during their early life history. To distinguish these distinct habitats, appropriate terminology is proposed. Egg case nursery is suggested for areas of egg deposition and juvenile nursery is suggested for areas where juveniles aggregate after emergence. Criteria to describe each habitat type are outlined. PMID:27062636

  9. Radionuclides and trace metals in eastern Mediterranean Sea algae.

    PubMed

    Al-Masri, M S; Mamish, S; Budier, Y

    2003-01-01

    Three types of sea alga distributed along the Syrian coast have been collected and analyzed for radioactivity and trace elements. Results have shown that (137)Cs concentrations in all the analyzed sample were relatively low (less than 1.2 Bq kg(-1) dry weight) while the levels of naturally occurring radionuclides, such as (210)Po and (210)Pb, were found to be high in most samples; the highest observed value (27.43 Bq kg(-1) dry weight) for (210)Po being in the red Jania longifurca alga. In addition, most brown alga species were also found to accumulate (210)Po, which indicates their selectivity to this isotope. On the other hand, brown alga (Cystoseira and Sargassum Vulgare) have shown a clear selectivity for some trace metals such as Cr, As, Cu and Co, this selectivity may encourage their use as biomonitor for pollution by trace metals. Moreover, the red alga species were found to contain the highest levels of Mg while the brown alga species were found to concentrate Fe, Mn, Na and K and nonmetals such as Cl, I and Br. PMID:12660047

  10. Radium isotopes in the Orinoco estuary and Eastern Caribbean Sea

    SciTech Connect

    Moore, W.S.; Todd, J.F. )

    1993-02-15

    Radium isotopes provide a means of identifying the source of freshened waters in the ocean and determining the time elapsed since these waters were in the estuary. The authors present evidence that during April, waters from the Amazon mixing zone pass within 50 km of the mouth of the Orinoco River. These Amazon waters are characterized by a lower [sup 228]Ra/[sup 226]Ra activity ratio (AR) than are waters from the Orinoco at similar salinities. During autumn, the increased discharge of the Orinoco displaces the freshened Amazon waters seaward, yet the two can be distinguished clearly. Within the Caribbean Sea, waters of Orinoco origin carry a characteristic radium signature including excess activities of [sup 224]Ra. This isotope may be used to estimate the time elapsed since the waters were removed from contact with sediments. Current speeds based on [sup 224]Ra dating ranged from 15 to 33 cm/s during April. The radium isotopes also provide an assessment of sediment mixing in the estuary. During low discharge (April), considerable mixing of older sediment by physical or biological processes or dredging maintained high activities of [sup 228]Ra in the estuary and produced the highest [sup 228]Ra/[sup 226]Ra AR's yet measured in any estuary. During high discharge (September), a large fraction of the [sup 228]Ra was derived from desorption from fresh sediment rather than mixing of older sediments. Activities of [sup 224]Ra were high in the estuary during both high and low discharge, indicating that considerable mixing of recently introduced sediment must occur during each period. During April, [sup 224]Ra and [sup 228]Ra activities in the water were about equal, indicating that most of the sediment being resuspended had been stored in the estuary long enough to reestablish radioactive equilibrium in the [sup 232]Th decay series (i.e., 20 years). 19 refs., 11 figs., 3 tabs.

  11. Contemplating autoimmunity in the Aegean islands.

    PubMed

    Walker, Lucy S K; Ziegler, Steven; Becher, Burkhard

    2016-03-01

    The Greek island of Crete became host to lively discussions on immunoregulation as experts from around the world gathered for the 7th Aegean Conference on Autoimmunity in September 2015. PMID:26882250

  12. Climate-mediated changes in zooplankton community structure for the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Eisner, Lisa B.; Napp, Jeffrey M.; Mier, Kathryn L.; Pinchuk, Alexei I.; Andrews, Alexander G.

    2014-11-01

    Zooplankton are critical to energy transfer between higher and lower trophic levels in the eastern Bering Sea ecosystem. Previous studies from the southeastern Bering Sea shelf documented substantial differences in zooplankton taxa in the Middle and Inner Shelf Domains between warm and cold years. Our investigation expands this analysis into the northern Bering Sea and the south Outer Domain, looking at zooplankton community structure during a period of climate-mediated, large-scale change. Elevated air temperatures in the early 2000s resulted in regional warming and low sea-ice extent in the southern shelf whereas the late 2000s were characterized by cold winters, extensive spring sea ice, and a well-developed pool of cold water over the entire Middle Domain. The abundance of large zooplankton taxa such as Calanus spp. (C. marshallae and C. glacialis), and Parasagitta elegans, increased from warm to cold periods, while the abundance of gelatinous zooplankton (Cnidaria) and small taxa decreased. Biomass followed the same trends as abundance, except that the biomass of small taxa in the southeastern Bering Sea remained constant due to changes in abundance of small copepod taxa (increases in Acartia spp. and Pseudocalanus spp. and decreases in Oithona spp.). Statistically significant changes in zooplankton community structure and individual species were greatest in the Middle Domain, but were evident in all shelf domains, and in both the northern and southern portions of the eastern shelf. Changes in community structure did not occur abruptly during the transition from warm to cold, but seemed to begin gradually and build as the influence of the sea ice and cold water temperatures persisted. The change occurred one year earlier in the northern than the southern Middle Shelf. These and previous observations demonstrate that lower trophic levels within the eastern Bering Sea respond to climate-mediated changes on a variety of time scales, including those shorter than

  13. Iceberg ploughmark features on bottom surface of the South-Eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Dorokhov, Dmitry; Sivkov, Vadim; Dorokhova, Evgenia; Krechik, Viktor

    2016-04-01

    A detail swath bathymetry, side-scan sonar and acoustic profiling combined with sediment sampling during the 64th cruise of RV "Academic Mstislav Keldysh" (October 2015) allowed to identify new geomorphological features of the South-Eastern Baltic Sea bottom surface. The extended chaotic ploughmarks (furrows) in most cases filled with thin layer of mud were discovered on surface of the Gdansk-Gotland sill glacial deposits. They are observed on the depth of more than 70 m and have depth and width from 1 to 10 m. Most of them are v- or u-shaped stepped depressions. The side-scan records of similar geomorpholoical features are extensively reported from Northern Hemisphere and Antarctica (Goodwin et al., 1985; Dowdeswell et al., 1993). Ploughmarks are attributed to the action of icebergs scouring into the sediment as they touch bottom. We are suggest that furrows discovered in the South-Eastern Baltic Sea are also the result of iceberg scouring during the Baltic Ice Lake stage (more than 11 600 cal yr BP (Bjorck, 2008)). This assumption confirmed by occurrence of fragmental stones and boulders on the sea bottom surface which are good indicators of iceberg rafting (Lisitzin, 2003). Ice ploughmarks at sea bottom surface were not occurred before in the South-Eastern Baltic Sea. The study was financed by Russian Scientific Fund, grant number 14-37-00047. References Bjorck S. The late Quaternary development of the Baltic Sea Basin. In: The BACC Author Team (eds) Assessment of climate change for the Baltic Sea Basin. Springer, Berlin, Heidelberg. 2008. Dowdeswell J. A., Villinger H., Whittington R. J., Marienfeld P. Iceberg scouring in Scoresby Sund and on the East Greenland continental shelf // Marine Geology. V. 111. N. 1-2. 1993. P. 37-53. Goodwin C. R., Finley J. C., Howard L. M. Ice scour bibliography. Environmental Studies Revolving Funds Report No. 010. Ottawa. 1985. 99 pp. Lisitzin A. P. Sea-Ice and Iceberg Sedimentation in the Ocean: Recent and Past. Springer

  14. Behavior, disturbance responses and distribution of bowhead whales Balaena mysticetus in the eastern Beaufort Sea, 1980-84: a summary

    SciTech Connect

    Richardson, W.J.; Greene, C.R.; Wuersig, B.

    1985-06-01

    The behavior of bowhead whales summering in the eastern (Canadian) Beaufort Sea, and their reactions to industrial activities, were studied during five summers in the report. The objective was to provide data needed to assess the possible effects of offshore oil exploration and development in the Alaskan Beaufort Sea on this endangered species.

  15. 33 CFR 334.1470 - Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques; bombing and gunnery target area.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Caribbean Sea and Vieques Sound... RESTRICTED AREA REGULATIONS § 334.1470 Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques... Caribbean, U.S. Naval Station, Roosevelt Roads, Puerto Rico, and such agencies and subordinate commands...

  16. 33 CFR 334.1470 - Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques; bombing and gunnery target area.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Caribbean Sea and Vieques Sound... RESTRICTED AREA REGULATIONS § 334.1470 Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques... Caribbean, U.S. Naval Station, Roosevelt Roads, Puerto Rico, and such agencies and subordinate commands...

  17. 33 CFR 334.1470 - Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques; bombing and gunnery target area.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Caribbean Sea and Vieques Sound... RESTRICTED AREA REGULATIONS § 334.1470 Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques... Caribbean, U.S. Naval Station, Roosevelt Roads, Puerto Rico, and such agencies and subordinate commands...

  18. 33 CFR 334.1470 - Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques; bombing and gunnery target area.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Caribbean Sea and Vieques Sound... RESTRICTED AREA REGULATIONS § 334.1470 Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques... Caribbean, U.S. Naval Station, Roosevelt Roads, Puerto Rico, and such agencies and subordinate commands...

  19. 33 CFR 334.1470 - Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques; bombing and gunnery target area.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Caribbean Sea and Vieques Sound... RESTRICTED AREA REGULATIONS § 334.1470 Caribbean Sea and Vieques Sound, in vicinity of Eastern Vieques... Caribbean, U.S. Naval Station, Roosevelt Roads, Puerto Rico, and such agencies and subordinate commands...

  20. Indo-Pacific sea surface temperature influences on failed consecutive rainy seasons over eastern Africa

    USGS Publications Warehouse

    Hoell, Andrew; Funk, Christopher C.

    2014-01-01

    Rainfall over eastern Africa (10°S–10°N; 35°E–50°E) is bimodal, with seasonal maxima during the "long rains" of March–April–May (MAM) and the "short rains" of October–November–December (OND). Below average precipitation during consecutive long and short rains seasons over eastern Africa can have devastating long-term impacts on water availability and agriculture. Here, we examine the forcing of drought during consecutive long and short rains seasons over eastern Africa by Indo-Pacific sea surface temperatures (SSTs). The forcing of eastern Africa precipitation and circulation by SSTs is tested using ten ensemble simulations of a global weather forecast model forced by 1950–2010 observed global SSTs. Since the 1980s, Indo-Pacific SSTs have forced more frequent droughts spanning consecutive long and short rains seasons over eastern Africa. The increased frequency of dry conditions is linked to warming SSTs over the Indo-west Pacific and to a lesser degree to Pacific Decadal Variability. During MAM, long-term warming of tropical west Pacific SSTs from 1950–2010 has forced statistically significant precipitation reductions over eastern Africa. The warming west Pacific SSTs have forced changes in the regional lower tropospheric circulation by weakening the Somali Jet, which has reduced moisture and rainfall over the Horn of Africa. During OND, reductions in precipitation over recent decades are oftentimes overshadowed by strong year-to-year precipitation variability forced by the Indian Ocean Dipole and the El Niño–Southern Oscillation.

  1. The Hillary Canyon and the Iselin Bank (Eastern Ross Sea, Antarctica): Alongslope and Downslope Route For Ross Sea Bottom Water

    NASA Astrophysics Data System (ADS)

    De Santis, L.; Bergamasco, A.; Colizza, E.; Geletti, R.; Accaino, F.; Wardell, N.; Olivo, E.; Petronio, L.; Henrys, S. A.; Black, J.; Mckay, R. M.; Bohm, G.

    2015-12-01

    The modern seabed of the Antarctic continental slope generally does not show a rugged geomorphology. Channel systems incise the lower continental rise, but in most cases they are inherited features formed as channel-levee turbiditic systems during past, more temperate times. The Hillary Canyon cuts the eastern Ross Sea continental slope and rise, to the Southeast of the Iselin Bank, and is directly connected to the Glomar Challenger Trough on the continental shelf. Cold dense salty water forms today in the Ross Sea polynya, spreads below the Ross Ice Shelf, becomes supercooled, fills up the landward deepening Glomar Challenger Trough and then spills over the sill of the shelf edge and flows downslope, often along the Hillary Canyon, in a geostrophic way, deviated westwards by the Coriolis Force, but sometimes also with a cascading a-geostrophic behaviour. This supercold water signal was found on the continental slope down to 1200 m depth. The shape of this tongue of modified ISW, whose thickness reaches up to 100 m, is very narrow, suggesting that the overflow occurs in very localized areas along the slope. Here we combine seismic stratigraphy analysis of multichannel seismic reflection profiles, box and gravity cores in the Hillary Canyon and along the eastern flank of the Iselin Bank, with seabed bathymetry and numerical modelling of thevertical and spatial distribution of the water masses, in order to identify modern and past pathways of the Ross Sea Bottom Water current. The results of this work show that the Hillary Canyon and the sediment mounds that formed along its flanks have been active since early Miocene times. Sediment drift-moat features and sediment waves are indicative of strong Northwest bottom currents reworking the seabed sediments at different water depths along the slope, possibly since the late Miocene. These sediment drifts are some of the targets of the IODP proposal 751-full.

  2. Sea Level, Antecedent Topography and Holocene Coral Reef of Maydolong, Eastern Samar, Philippines

    NASA Astrophysics Data System (ADS)

    Gong, S.; Sun, H.; Albert-Delmoro, C.; Azura-Cafe, L.; Shen, C.

    2013-12-01

    Holocene coral reefs are well developed along the coasts of Eastern Samar, Philippines, a cyclone-prone area. Three cores were recovered from Holocene coral reef at Maydolong, Eastern Samar, two at reef margin and one in the backreef zone, ranging from 12.4 to 19.6 m in length. Lithofacies and 230Th ages of 15 fossil corals and 3 travertine samples of the 3 cores show that the reef development was controlled by degalcial sea-level rise, and Pleistocene karst that is underlying the Holocene coral reef. The reef margin is dated to start from 8,296×19 yr BP (before 1950 AD) at 7.1 m below mean sea level (MSL) and ended about 5,710×13 yr BP when reached the paleosea level. Only 120 m landward, the backreef deposition occurred during 8,181×20 to 6,664×18 yr BP, comparable to the reef margin but start from a much lower depth, 17.7 m below MSL. Travertine occurs in the limestone underlying the Holocene reef and is dated to range from 35 to 55 kyr BP. The evidences suggest that antecedent karst topography decided the locations of Holocene reef. The backreef deposition started in a karst depression but was able to catch up the sea-level rise at a sedimentation rate of 9.6 m/kyr before the paleosea level slowed down in the middle Holocene.

  3. Early winter mesozooplankton of the coastal south-eastern Barents Sea

    NASA Astrophysics Data System (ADS)

    Dvoretsky, Vladimir G.; Dvoretsky, Alexander G.

    2015-01-01

    The south-eastern Barents Sea (Pechora Sea) is a little studied region of the Russian Arctic. We investigated mesozooplankton community of this area in early winter period for the first time. The study was based on collections performed with a Juday net (168 μm) in November 2010. Three types of stations differing in mesozooplankton composition and abundance were revealed by non-metric multidimensional scaling analyses. Taxa richness and diversity of the mesozooplankton were high. The total abundance and biomass varied from 931 to 4360 individuals m-3 and from 4.0 to 64.2 mg dry mass m-3, respectively. Maximum density of mesozooplankton was located in the hydrographical frontal zone where cold and warm waters interacted. Copepods dominated in terms of the total abundance. Abundances of major taxa were strongly correlated with environmental variables, of which temperature, salinity and depth were the most important. Previous studies showed that many mesozooplankton are in a dormant state during the Arctic winter from October to April. However, our investigation found young copepodites to be present for many of the common copepod species, which suggests successful reproduction of some opportunistic taxa (Pseudocalanus, Acartia, Temora, Oithona) and that the small copepod community was in an active phase. The main factor influencing possible development of the copepods in the south-eastern Barents Sea was river run-off which supplied plankton with detritus and suspended organic matter.

  4. Neogene Tectonics of Part of the Junction of Cyprus and Hellenic Arcs in the Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Küçük, H. M.; Dondurur, D.; ćifçi, G.; Gürçay, S.; Hall, J.; Yaltırak, C.; Aksu, A. E.

    2012-04-01

    The junction between the Hellenic and Cyprus Arcs is one of the tectonically most active regions of the eastern Mediterranean. This junction developed in association with convergence between the African and Eurasian Plates, and the re-organization of the smaller Aegean-Anatolian and Arabian Microplates. Recent studies have shown that the predominant Miocene deformation process in the eastern Mediterranean is compressional tectonism. However, many studies have also shown that the strain is partitioned in the Pliocene-Quaternary and the area displays regions dominated by compression, strike slip and extensional tectonism. The junction between the Hellenic and Cyprus Arcs exhibits complex morphological features including submarine mountains, rises, ridges and trenches. Approximately 600 km of high resolution 72-channel seismic profiles were collected from the junction of Cyprus and Hellenic Arcs using a 450 m long 6.25 m hydrophone spacing streamer and a seven gun array with a 200 cubic inch total volume. This project was part of the joint scientific venture between Dokuz Eylül University (Turkey) and Memorial University of Newfoundland (Canada), and was funded by TÜBITAK and NSERC. The study area includes the southwestern Antalya Basin and the Anaxagoras Mountain of the larger Anaximander Mountains. The multichannel data were processed both at Dokuz Eylül and Memorial University of Newfoundland, using the Landmark Graphics ProMAX software, with automatic gain control, short-gap deconvolution, velocity analysis, normal move-out correction, stack, filter (typically 50-200 Hz bandpass), f-k time migration, and adjacent trace sum. Despite the fact that the source volume was modest, reflections are imaged to 2-3 s two-way time below seabed, even in 2 km water depth. The processed seismic reflection profiles show that there are three distinct sedimentary units, separated by two prominent markers: the M-reflector separates the Pliocene-Quaternary from the underlying

  5. Identification of new deep sea sinuous channels in the eastern Arabian Sea.

    PubMed

    Mishra, Ravi; Pandey, D K; Ramesh, Prerna; Clift, Peter D

    2016-01-01

    Deep sea channel systems are recognized in most submarine fans worldwide as well as in the geological record. The Indus Fan is the second largest modern submarine fan, having a well-developed active canyon and deep sea channel system. Previous studies from the upper Indus Fan have reported several active channel systems. In the present study, deep sea channel systems were identified within the middle Indus Fan using high resolution multibeam bathymetric data. Prominent morphological features within the survey block include the Raman Seamount and Laxmi Ridge. The origin of the newly discovered channels in the middle fan has been inferred using medium resolution satellite bathymetry data. Interpretation of new data shows that the highly sinuous deep sea channel systems also extend to the east of Laxmi Ridge, as well as to the west of Laxmi Ridge, as previously reported. A decrease in sinuosity southward can be attributed to the morphological constraints imposed by the elevated features. These findings have significance in determining the pathways for active sediment transport systems, as well as their source characterization. The geometry suggests a series of punctuated avulsion events leading to the present array of disconnected channels. Such channels have affected the Laxmi Basin since the Pliocene and are responsible for reworking older fan sediments, resulting in loss of the original erosional signature supplied from the river mouth. This implies that distal fan sediments have experienced significant signal shredding and may not represent the erosion and weathering conditions within the onshore basin at the time of sedimentation.

  6. Identification of new deep sea sinuous channels in the eastern Arabian Sea.

    PubMed

    Mishra, Ravi; Pandey, D K; Ramesh, Prerna; Clift, Peter D

    2016-01-01

    Deep sea channel systems are recognized in most submarine fans worldwide as well as in the geological record. The Indus Fan is the second largest modern submarine fan, having a well-developed active canyon and deep sea channel system. Previous studies from the upper Indus Fan have reported several active channel systems. In the present study, deep sea channel systems were identified within the middle Indus Fan using high resolution multibeam bathymetric data. Prominent morphological features within the survey block include the Raman Seamount and Laxmi Ridge. The origin of the newly discovered channels in the middle fan has been inferred using medium resolution satellite bathymetry data. Interpretation of new data shows that the highly sinuous deep sea channel systems also extend to the east of Laxmi Ridge, as well as to the west of Laxmi Ridge, as previously reported. A decrease in sinuosity southward can be attributed to the morphological constraints imposed by the elevated features. These findings have significance in determining the pathways for active sediment transport systems, as well as their source characterization. The geometry suggests a series of punctuated avulsion events leading to the present array of disconnected channels. Such channels have affected the Laxmi Basin since the Pliocene and are responsible for reworking older fan sediments, resulting in loss of the original erosional signature supplied from the river mouth. This implies that distal fan sediments have experienced significant signal shredding and may not represent the erosion and weathering conditions within the onshore basin at the time of sedimentation. PMID:27386293

  7. Hydrodynamic and Thermohaline Seasonal Structures of Peninsular Malaysia's eastern continental shelf sea

    NASA Astrophysics Data System (ADS)

    Daryabor, Farshid; Tangang, Fredolin; Juneng, Liew

    2010-05-01

    The seasonal ocean circulation and the seasonal thermal structure in Peninsular Malaysia's eastern continental shelf sea were studied numerically using the Regional Ocean Model System (ROMS) with 18-km horizontal resolution and 50 sigma levels conforming to a realistic bottom topography. A 10-year control run was performed using climatological monthly mean wind stresses, restoring-type surface salt, temp and heat, and observational oceanic inflow/outflow at the open boundaries. The seasonally averaged effects of isolated forcing terms are presented and analyzed from the following experiments: 1) heat fluxes effects removed and 2) wind effects removed. This procedure allowed analysis of the contribution of individual parameters to the general hydrology and specific features of the Peninsular Malaysia's eastern continental shelf sea: for example, coastal jets, mesoscale topographic gyres, and countercurrents. The results show that the ROMS model has the capability of simulating seasonal variations of the Peninsular Malaysia's eastern continental shelf sea circulation and thermohaline structure. The simulated Peninsular Malaysia's eastern continental shelf sea surface circulation is generally anticyclonic (cyclonic) during the summer (winter) monsoon period with a strong western boundary current, a mean maximum speed of 0.8 m s-1 (0.5 m s-1), and extending to a depth of around 30 m (40 m). During summer, the western boundary current splits and partially leaves the coast; the bifurcation point is at 40°N in Jun and shifts north to 70°N in July. A mesoscale eddy on the Sunda shelf, the southwest of Natuna Island at (2.50°N, 1060°E) and extending to two mesoscale eddy at (20°N, 1070°E) and (2.50°N, 1090°E) also on the Gulf of Thailand (7.50°N, 1040°E), was also simulated. These eddies are cyclonic (anticyclonic) with maximum swirl velocity of 0.3 m s-1 at the peak of the summer (winter) monsoon. The simulated thermohaline structure for summer and winter are

  8. Sedimentology and geochemistry of mud volcanoes in the Anaximander Mountain Region from the Eastern Mediterranean Sea.

    PubMed

    Talas, Ezgi; Duman, Muhammet; Küçüksezgin, Filiz; Brennan, Michael L; Raineault, Nicole A

    2015-06-15

    Investigations carried out on surface sediments collected from the Anaximander mud volcanoes in the Eastern Mediterranean Sea to determine sedimentary and geochemical properties. The sediment grain size distribution and geochemical contents were determined by grain size analysis, organic carbon, carbonate contents and element analysis. The results of element contents were compared to background levels of Earth's crust. The factors that affect element distribution in sediments were calculated by the nine push core samples taken from the surface of mud volcanoes by the E/V Nautilus. The grain size of the samples varies from sand to sandy silt. Enrichment and Contamination factor analysis showed that these analyses can also be used to evaluate of deep sea environmental and source parameters. It is concluded that the biological and cold seep effects are the main drivers of surface sediment characteristics from the Anaximander mud volcanoes.

  9. Sedimentology and geochemistry of mud volcanoes in the Anaximander Mountain Region from the Eastern Mediterranean Sea.

    PubMed

    Talas, Ezgi; Duman, Muhammet; Küçüksezgin, Filiz; Brennan, Michael L; Raineault, Nicole A

    2015-06-15

    Investigations carried out on surface sediments collected from the Anaximander mud volcanoes in the Eastern Mediterranean Sea to determine sedimentary and geochemical properties. The sediment grain size distribution and geochemical contents were determined by grain size analysis, organic carbon, carbonate contents and element analysis. The results of element contents were compared to background levels of Earth's crust. The factors that affect element distribution in sediments were calculated by the nine push core samples taken from the surface of mud volcanoes by the E/V Nautilus. The grain size of the samples varies from sand to sandy silt. Enrichment and Contamination factor analysis showed that these analyses can also be used to evaluate of deep sea environmental and source parameters. It is concluded that the biological and cold seep effects are the main drivers of surface sediment characteristics from the Anaximander mud volcanoes. PMID:25935808

  10. Holocene development of the eastern Gulf of Finland coastal zone (Baltic Sea)

    NASA Astrophysics Data System (ADS)

    Ryabchuk, Daria; Sergeev, Alexander; Gusentsova, Tatiana; Gerasimov, Dmitry; Zhamoida, Vladimir; Amantov, Aleksey; Kulkova, Marianna; Sorokin, Peter

    2014-05-01

    In 2011-2013 geoarcheological and marine geological research of the eastern Gulf of Finland coasts and near-shore bottom were undertaken. Researches were concentrated within several key-areas (Sestroretskaya Lowland, Narva-Luga Klint Bay and southern coastal zone of the Gulf (near Bolshaya Izhora village). Study areas can provide important information about Gulf of Finland Holocene coastal development as since Ancylus time (about 10000 cal.BP). Development of numerous sand accretion forms (spits, bars, dunes) of different shape, age and genesis caused formation of lagoon systems, situated now on-land due to land uplift. Coasts of lagoons in Sestroretskaya Lowland and Narva-Luga Klint Bay were inhabited by Neolithic and Early Metal people. Analysis of coastal morphology and results of geological research (GIS relief analyses, ground penetrating radar, drilling, grain-size analyses, radiocarbon dating) and geoarcheological studies allowed to reconstruct the mechanism of large accretion bodies (bars and spits) and lagoon systems formation during last 8000 years. Geoarcheological studies carried out within eastern Gulf of Finland coasts permitted to find some features of the Neolithic - Early Metal settlements distribution. Another important features of the eastern Gulf of Finland coastal zone relief are the series of submarine terraces found in the Gulf bottom (sea water depths 10 to 2 m). Analyses of the submarine terraces morphology and geology (e.g. grain-size distribution, pollen analyses and organic matter dating) allow to suppose that several times during Holocene (including preAncylus (11000 cal.BP) and preLittorina (8500 cal.BP) regressions) the sea-water level was lower than nowadays. During the maximal stage of the Littorina transgression (7600-7200 cal. BP) several open bays connected with the Littorina Sea appeared in this area. The lagoon systems and sand accretion bodies (spits and bars) were formed during the following decreasing of the sea level. Late

  11. Nd isotopes in deep-sea corals in the North-eastern Atlantic

    NASA Astrophysics Data System (ADS)

    Copard, Kevin; Colin, Christophe; Douville, Eric; Freiwald, Andre; Gudmundsson, Gudmundur; De Mol, Ben; Frank, Norbert

    2010-09-01

    Neodymium (Nd) concentrations and isotopic signatures of living and fossil deep-sea coral species Lophelia pertusa, Desmophyllum dianthus and Madrepora oculata from the northeast Atlantic Ocean have been investigated in order to test the ability of deep-sea corals to reconstruct the seawater Nd isotopic signature and past changes of ocean circulation in the eastern North Atlantic. Small quantities of Nd—less than 45 ng/g—are incorporated into the aragonite skeleton of living deep-sea corals that dwell at upper intermediate depths throughout the Northeast Atlantic. Rigorous cleaning techniques are needed in order to avoid Nd contamination from manganese-oxide and iron hydroxide coatings. Moreover, Nd isotopic compositions have been measured using thermal ionization mass spectrometry (TIMS) by Nd-oxide method. Our data indicate that the isotopic signatures of modern corals are similar to those of adjacent water masses, implying that deep-sea corals can serve as an archive of the seawater Nd isotopic compositions in the past. The first results from few fully-cleaned fossils corals collected within the Porcupine Seabight and the southwest Rockall Bank reveal significantly higher ɛNd for corals dated between 150 ± 40 and 3060 ± 90 yrs than those of the living corals located in similar areas. This suggests rapid hydrological variations along the eastern margin of the North Atlantic Ocean at intermediate water depth with higher contribution of the Mediterranean Overflow Waters (MOW) or other temperate Atlantic mid-depth water masses (ENACW or NAC) in the past.

  12. A new morpho-bathymetric map of the Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Mascle, Jean; Brosolo, Laetitia

    2016-04-01

    A new morpho-bathymetric synthesis of the Eastern Mediterranean Sea has been compiled using a digital terrain model (DTM) based on a 100-meter grid. This DTM has been constructed using data provided by several peri-mediterranean Institutes, and collected using various swath bathymetry systems operated by different research vessels. One may estimate that 90% of the seabed extending by water depths higher than 2000m have been mapped using swath systems. The aim of this synthesis is chiefly to illustrate, in detail, the morphological features resulting from the various (sedimentary, tectonic, geochemical, magmatic, etc.) active geological processes operating on the four main physiographic domains, which characterize the Eastern Mediterranean Sea: the Calabria outer arc (Ionian Sea), the Mediterranean Ridge (most of the central basin), the Nile sedimentary cone (off Egypt) and the Eratosthenes seamount (south of Cyprus). For areas not yet covered by swath bathymetric systems the map has been completed by digital data extracted either from GEBCO or from EMODNET DTM files (http://www.gebco.net/data_and_products/gebco_digital_atlas/) (http://www.emodnet-hydrography.eu/). Several artifacts introduced by the use of these files, for example theoccurrences of their grids, can be detected along most of the steep continental slopes not yet mapped in detail, as well as in the southern domain of the Adriatic Sea. Similarly it has not been possible to systematically correct a few, but non-linear, discrepancies in Z values between various DTM files. Such discrepancies result either from the use of data collected by swath systems operating at different frequencies and/or from minor differences in seawater sound velocity corrections.

  13. Spatial scales of bacterial community diversity at cold seeps (Eastern Mediterranean Sea)

    PubMed Central

    Pop Ristova, Petra; Wenzhöfer, Frank; Ramette, Alban; Felden, Janine; Boetius, Antje

    2015-01-01

    Cold seeps are highly productive, fragmented marine ecosystems that form at the seafloor around hydrocarbon emission pathways. The products of microbial utilization of methane and other hydrocarbons fuel rich chemosynthetic communities at these sites, with much higher respiration rates compared with the surrounding deep-sea floor. Yet little is known as to the richness, composition and spatial scaling of bacterial communities of cold seeps compared with non-seep communities. Here we assessed the bacterial diversity across nine different cold seeps in the Eastern Mediterranean deep-sea and surrounding seafloor areas. Community similarity analyses were carried out based on automated ribosomal intergenic spacer analysis (ARISA) fingerprinting and high-throughput 454 tag sequencing and were combined with in situ and ex situ geochemical analyses across spatial scales of a few tens of meters to hundreds of kilometers. Seep communities were dominated by Deltaproteobacteria, Epsilonproteobacteria and Gammaproteobacteria and shared, on average, 36% of bacterial types (ARISA OTUs (operational taxonomic units)) with communities from nearby non-seep deep-sea sediments. Bacterial communities of seeps were significantly different from those of non-seep sediments. Within cold seep regions on spatial scales of only tens to hundreds of meters, the bacterial communities differed considerably, sharing <50% of types at the ARISA OTU level. Their variations reflected differences in porewater sulfide concentrations from anaerobic degradation of hydrocarbons. This study shows that cold seep ecosystems contribute substantially to the microbial diversity of the deep-sea. PMID:25500510

  14. Trophic ecology of deep-sea Asteroidea (Echinodermata) from eastern Canada

    NASA Astrophysics Data System (ADS)

    Gale, Katie S. P.; Hamel, Jean-François; Mercier, Annie

    2013-10-01

    Asteroids (sea stars) can be important predators in benthic communities and are often present in ecologically important and vulnerable deep-sea coral and sponge habitats. However, explicit studies on the trophic ecology of deep-sea asteroids are rare. We investigated the diets of seven species of deep-sea asteroid from the bathyal zone of Newfoundland and Labrador, eastern Canada. A multifaceted approach including live animal observations, stomach content analysis, and stable isotope analysis revealed the asteroids to be either top predators of megafauna or secondary consumers (mud ingesters, infaunal predators, and suspension feeders). The stable isotope signatures of Ceramaster granularis, Hippasteria phrygiana, and Mediaster bairdi are characteristic of high-level predators, having δ15N values 4.4‰ (more than one trophic level) above Ctenodiscus crispatus, Leptychaster arcticus, Novodinia americana, and Zoroaster fulgens. We present strong evidence that corals and sponges are common food items for two of the predatory species, C. granularis and H. phrygiana. During laboratory feeding trials, live H. phrygiana fed on several species of soft coral and C. granularis fed on sponges. Stomach content analysis of wild-caught individuals revealed sclerites from sea pens (e.g. Pennatula sp.) in the stomachs of both asteroid species; H. phrygiana also contained sclerites from at least two other species of octocoral and siliceous sponge spicules were present in the stomachs of C. granularis. The stomach contents of the secondary consumers contained a range of invertebrate material. Leptychaster arcticus and Ctenodiscus crispatus feed infaunally on bulk sediment and molluscs, Zoroaster fulgens is a generalist infaunal predator, and the brisingid Novodinia americana is a specialist suspension feeder on benthopelagic crustaceans. This study provides a foundation for understanding the ecological roles of bathyal asteroids, and suggests that some species may have the

  15. Uncoupling between dinitrogen fixation and primary productivity in the eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Rahav, Eyal; Herut, Barak; Stambler, Noga; Bar-Zeev, Edo; Mulholland, Margaret R.; Berman-Frank, Ilana

    2013-03-01

    In the nitrogen (N)-impoverished photic zones of many oceanic regions, prokaryotic organisms fixing atmospheric dinitrogen (N2; diazotrophs) supply an essential source of new nitrogen and fuel primary production. We measured dinitrogen fixation and primary productivity (PP) during the thermally stratified summer period in different water regimes of the oligotrophic eastern Mediterranean Sea, including the Cyprus Eddy and the Rhodes Gyre. Low N2 fixation rates were measured (0.8-3.2 µmol N m-2 d-1) excluding 10-fold higher rates in the Rhodes Gyre and Cyprus Eddy (~20 µmol N m-2 d-1). The corresponding PP increased from east to west (200-2500 µmol C m-2 d-1), with relatively higher productivity recorded in the Rhodes Gyre and Cyprus Eddy (2150 and 2300 µmol C m-2 d-1, respectively). These measurements demonstrate that N2 fixation in the photic zone of the eastern Mediterranean Sea contributes only negligibly by direct inputs to PP (i.e., cyanobacterial diazotrophs) and is in fact uncoupled from PP. By contrast, N2 fixation is significantly coupled to bacterial productivity and to net heterotrophic areas, suggesting that heterotrophic N2 fixation may in fact be significant in this ultraoligotrophic system. This is further substantiated by the high N2 fixation rates we measured from aphotic depths and by the results of phylogenetic analysis in other studies showing an abundance of heterotrophic diazotrophs.

  16. Sea-floor geology and topography offshore in Eastern Long Island Sound

    USGS Publications Warehouse

    Poppe, L.J.; McMullen, K.Y.; Ackerman, S.D.; Blackwood, D.S.; Schaer, J.D.; Forrest, M.R.; Ostapenko, A.J.; Doran, E.F.

    2011-01-01

    A gridded multibeam bathymetric dataset covers approximately 133.7 square kilometers of sea floor offshore in eastern Long Island Sound. Although originally collected for charting purposes during National Oceanic and Atmospheric Administration hydrographic survey H11997, these acoustic data, and the sea-floor sampling and photography stations subsequently occupied to verify them during USGS cruise 2010-015-FA, are part of an expanding series of studies that provide a fundamental framework for research and resource management (for example, cables, pipelines, and dredging) activities in this major East Coast estuary. Results show the composition and terrain of the seabed and provide information on sediment transport and benthic habitat. Bedrock outcrops, erosional outliers, lag deposits of boulders, scour depressions, and extensive gravel pavements are common in the eastern part of the study area. These features, which result from the near-constant exposure to strong tidal currents, indicate sedimentary environments dominated by processes associated with erosion. Large fields of transverse and barchanoid sand waves in the western part of the study area reflect slightly lower energy levels and sedimentary environments where processes associated with coarse bedload transport prevail.

  17. Beluga whale (Delphinapterus leucas) vocalizations and call classification from the eastern Beaufort Sea population.

    PubMed

    Garland, Ellen C; Castellote, Manuel; Berchok, Catherine L

    2015-06-01

    Beluga whales, Delphinapterus leucas, have a graded call system; call types exist on a continuum making classification challenging. A description of vocalizations from the eastern Beaufort Sea beluga population during its spring migration are presented here, using both a non-parametric classification tree analysis (CART), and a Random Forest analysis. Twelve frequency and duration measurements were made on 1019 calls recorded over 14 days off Icy Cape, Alaska, resulting in 34 identifiable call types with 83% agreement in classification for both CART and Random Forest analyses. This high level of agreement in classification, with an initial subjective classification of calls into 36 categories, demonstrates that the methods applied here provide a quantitative analysis of a graded call dataset. Further, as calls cannot be attributed to individuals using single sensor passive acoustic monitoring efforts, these methods provide a comprehensive analysis of data where the influence of pseudo-replication of calls from individuals is unknown. This study is the first to describe the vocal repertoire of a beluga population using a robust and repeatable methodology. A baseline eastern Beaufort Sea beluga population repertoire is presented here, against which the call repertoire of other seasonally sympatric Alaskan beluga populations can be compared.

  18. Beluga whale (Delphinapterus leucas) vocalizations and call classification from the eastern Beaufort Sea population.

    PubMed

    Garland, Ellen C; Castellote, Manuel; Berchok, Catherine L

    2015-06-01

    Beluga whales, Delphinapterus leucas, have a graded call system; call types exist on a continuum making classification challenging. A description of vocalizations from the eastern Beaufort Sea beluga population during its spring migration are presented here, using both a non-parametric classification tree analysis (CART), and a Random Forest analysis. Twelve frequency and duration measurements were made on 1019 calls recorded over 14 days off Icy Cape, Alaska, resulting in 34 identifiable call types with 83% agreement in classification for both CART and Random Forest analyses. This high level of agreement in classification, with an initial subjective classification of calls into 36 categories, demonstrates that the methods applied here provide a quantitative analysis of a graded call dataset. Further, as calls cannot be attributed to individuals using single sensor passive acoustic monitoring efforts, these methods provide a comprehensive analysis of data where the influence of pseudo-replication of calls from individuals is unknown. This study is the first to describe the vocal repertoire of a beluga population using a robust and repeatable methodology. A baseline eastern Beaufort Sea beluga population repertoire is presented here, against which the call repertoire of other seasonally sympatric Alaskan beluga populations can be compared. PMID:26093397

  19. Multidisciplinary tephrochronological correlation of marker events in the eastern Tyrrhenian Sea between 48 and 105 ka

    NASA Astrophysics Data System (ADS)

    Petrosino, Paola; Morabito, Simona; Jicha, Brian R.; Milia, Alfonsa; Sprovieri, Mario; Tamburrino, Stella

    2016-04-01

    The basal portion (2.92-5.08 m from core top) of the CET1 core located in a bathyal area of the eastern Tyrrhenian Sea is the subject of a multidisciplinary investigation, encompassing tephrostratigraphy, quantitative analyses of planktonic foraminifera and calcareous nannofossil assemblages, and δ18O measurements, supported by a 40Ar/39Ar age determination. Calcareous nannofossil assemblages allowed the attribution of the analyzed sediments to the biozone MMN21a, and the succession spans from more than 48 to ca. 105 ka, although there are at least two stratigraphic gaps and minor resedimentation episodes. A paleoclimatic reconstruction obtained via δ18O and planktonic foraminifera data identifies several of the major climatic events that occurred in the investigated time span. A total of 13 visible tephra layers and cryptotephras are recognized and correlated with their volcanic sources (Campanian Volcanic Zone and Pantelleria volcano) and, when possible, with well-known and dated events or with widespread marker tephras. Using a combination of biostratigraphic, oxygen isotope, and tephrostratigraphic correlations, we develop a chronostratigraphy for the main climatic events and tephra layers in the core and pinpoint tephra markers for the climatic events comprised between GS 22 and GI 24 in the eastern Tyrrhenian Sea.

  20. Ice-gouged microrelief on the floor of the eastern Chukchi Sea, Alaska: a reconnaissance survey

    USGS Publications Warehouse

    Toimil, Lawrence J.

    1978-01-01

    Side-scan sonar and bathymetric records obtained from 1,800 km of trackline from the eastern Chukchi Sea continental shelf, between water depths of 20 and 70 m show the ubiquitous presence of furrow-like linear depressions produced by gouging of the sea bed by ice keels. These sea bed micro-features are regionally widespread but are not uniformly distributed. Furthermore, the microrelief, texture, and lithologic structure of sea bed sediments have been significantly modified by the disruptive processes associated with ice gouge formation. An analysis of some 10,.200 individual gouges shows that the density of ice gouges increases with increasing latitude, increasing slope gradients, and decreasing water depth. Across the northern half of the shelf few trackline segments are free of ice gouges; in the southern portion numerous segments contain no ice gouges. However, ice gouges extend at least as far south as Cape Prince of Wales Shoal. Densities of over 200 gouges per km of trackline are not uncommon in water depths less than 30 m ,but no values higher than 50 km are encountered in water deeper than 50 m. No ice gouges have been observed in water depths exceeding 58 m. Saturation ice gouge densities (greater than 300/Pan) occur along the eastern side 6f Barrow Sea Valley and the northeast flank of Hanna Shoal. Maximum gouge incision depths per km of trackline are greatest in water 36 to 50 m deep . A maximum incision depth of 4.5 m occurs in the 35-40 m water depth interval. Individual ice gouge events wider than 100 m, most produced by multi-keeled ice fragments, are found between 31 and 45 m depths. The dominant azimuth of gouge furrows shows no preferred orientation on the Chukchi Sea shelf; only locally does bathmetric control of the trend of gouges appear. The occurrence of current-produced bedforms within individual ice gouges suggests an interaction between slow-moving grounded or gouging ice keels and swift currents. In other cases, current

  1. Multiple Distant Origins for Green Sea Turtles Aggregating off Gorgona Island in the Colombian Eastern Pacific

    PubMed Central

    Amorocho, Diego F.; Abreu-Grobois, F. Alberto; Dutton, Peter H.; Reina, Richard D.

    2012-01-01

    Mitochondrial DNA analyses have been useful for resolving maternal lineages and migratory behavior to foraging grounds (FG) in sea turtles. However, little is known about source rookeries and haplotype composition of foraging green turtle aggregations in the southeastern Pacific. We used mitochondrial DNA control region sequences to identify the haplotype composition of 55 green turtles, Chelonia mydas, captured in foraging grounds of Gorgona National Park in the Colombian Pacific. Amplified fragments of the control region (457 bp) revealed the presence of seven haplotypes, with haplotype (h) and nucleotide (π) diversities of h = 0.300±0.080 and π = 0.009±0.005 respectively. The most common haplotype was CMP4 observed in 83% of individuals, followed by CMP22 (5%). The genetic composition of the Gorgona foraging population primarily comprised haplotypes that have been found at eastern Pacific rookeries including Mexico and the Galapagos, as well as haplotypes of unknown stock origin that likely originated from more distant western Pacific rookeries. Mixed stock analysis suggests that the Gorgona FG population is comprised mostly of animals from the Galapagos rookery (80%). Lagrangian drifter data showed that movement of turtles along the eastern Pacific coast and eastward from distant western and central Pacific sites was possible through passive drift. Our results highlight the importance of this protected area for conservation management of green turtles recruited from distant sites along the eastern Pacific Ocean. PMID:22319635

  2. Multiple distant origins for green sea turtles aggregating off Gorgona Island in the Colombian eastern Pacific.

    PubMed

    Amorocho, Diego F; Abreu-Grobois, F Alberto; Dutton, Peter H; Reina, Richard D

    2012-01-01

    Mitochondrial DNA analyses have been useful for resolving maternal lineages and migratory behavior to foraging grounds (FG) in sea turtles. However, little is known about source rookeries and haplotype composition of foraging green turtle aggregations in the southeastern Pacific. We used mitochondrial DNA control region sequences to identify the haplotype composition of 55 green turtles, Chelonia mydas, captured in foraging grounds of Gorgona National Park in the Colombian Pacific. Amplified fragments of the control region (457 bp) revealed the presence of seven haplotypes, with haplotype (h) and nucleotide (π) diversities of h = 0.300±0.080 and π = 0.009±0.005 respectively. The most common haplotype was CMP4 observed in 83% of individuals, followed by CMP22 (5%). The genetic composition of the Gorgona foraging population primarily comprised haplotypes that have been found at eastern Pacific rookeries including Mexico and the Galapagos, as well as haplotypes of unknown stock origin that likely originated from more distant western Pacific rookeries. Mixed stock analysis suggests that the Gorgona FG population is comprised mostly of animals from the Galapagos rookery (80%). Lagrangian drifter data showed that movement of turtles along the eastern Pacific coast and eastward from distant western and central Pacific sites was possible through passive drift. Our results highlight the importance of this protected area for conservation management of green turtles recruited from distant sites along the eastern Pacific Ocean.

  3. Crustal architecture of the eastern margin of Japan Sea: back-arc basin opening and contraction

    NASA Astrophysics Data System (ADS)

    No, T.; Sato, T.; Takahashi, N.; Kodaira, S.; Kaneda, Y.; Ishiyama, T.; Sato, H.

    2012-12-01

    Although large earthquakes such as the 1964 Niigata earthquake (M 7.5), 1983 Nihonkai-Chubu earthquake (M 7.8), and 1993 Hokkaido Nansei-Oki earthquake (M 7.8) have caused large amounts of damage to the eastern margin of the Japan Sea, a substantial number of seismic studies have been conducted for the seismogenic zone on the Pacific Ocean side of Japan. In addition, the detail of the source fault model for the eastern margin of the Japan Sea is not well defined for all cases. This highlights the need for further studies to investigate seismic imaging. Therefore, we have collaborated with other Japanese research institutions for a project titled "Priority Investigations of Strain Concentration Areas" (which is funded by Special Coordination Funds for Promoting Science and Technology, Japan). This project has conducted seismic surveys from 2009 to 2012 using the deep-sea research vessel, Kairei, from the Japan Agency for Marine-Earth Science and Technology. There is a strain concentration area in the eastern part of the survey area (Okamura et al., 1995). The western part of the survey area includes the Yamato Basin and Japan Basin. It is very important to study the crustal structure in the seismotectonic studies of the eastern margin of the Japan Sea. We conducted a marine seismic survey by using a multichannel seismic (MCS) system and ocean bottom seismographs (OBSs) along the eastern margin of the Japan Sea. Seismic data were acquired along 42 lines with a total length of approximately 9,000 km. The following results were obtained from seismic imaging. On the basis of the results of the MCS imaging, active reverse faults and folds were observed in the margin of the Toyama Trough; however, the sedimentary layers in the trough were flat. In the sedimentary layers and crusts of the Sado Ridge, Mogami Trough, and source area of the 1964 Niigata earthquake located north of the Sado Island, greater deformation was observed. The deformation weakened toward the Yamato

  4. Assessment of microphysical and chemical factors of aerosols over seas of the Russian Artic Eastern Section

    NASA Astrophysics Data System (ADS)

    Golobokova, Liudmila; Polkin, Victor

    2014-05-01

    The newly observed kickoff of the Northern Route development drew serious attention to state of the Arctic Resource environment. Occurring climatic and environmental changes are more sensitively seen in polar areas in particular. Air environment control allows for making prognostic assessments which are required for planning hazardous environmental impacts preventive actions. In August - September 2013, RV «Professor Khlustin» Northern Sea Route expeditionary voyage took place. En-route aerosol sampling was done over the surface of the Beringov, Chukotka and Eastern-Siberia seas (till the town of Pevek). The purpose of sampling was to assess spatio-temporal variability of optic, microphysical and chemical characteristics of aerosol particles of the surface layer within different areas adjacent to the Northern Sea Route. Aerosol test made use of automated mobile unit consisting of photoelectric particles counter AZ-10, aetalometr MDA-02, aspirator on NBM-1.2 pump chassis, and the impactor. This set of equipment allows for doing measurements of number concentration, dispersed composition of aerosols within sizes d=0.3-10 mkm, mass concentration of submicron sized aerosol, and filter-conveyed aerosols sampling. Filter-conveyed aerosols sampling was done using method accepted by EMEP and EANET monitoring networks. The impactor channel was upgraded to separate particles bigger than 1 mkm in size, and the fine grain fraction settled down on it. Reverse 5-day and 10-day trajectories of air mass transfer executed at heights of 10, 1500 and 3500 m were analyzed. The heights were selected by considerations that 3000 m is the height which characterizes air mass trend in the lower troposphere. 1500 m is the upper border of the atmospheric boundary layer, and the sampling was done in the Earth's surface layer at less than 10 m. Minimum values of the bespoken microphysical characteristics are better characteristic of higher latitudes where there are no man induced sources of

  5. Labrador Sea surface temperature control on the summer weather in the Eastern Europe

    NASA Astrophysics Data System (ADS)

    Gnatiuk, Natalia; Vihma, Timo; Bobylev, Leonid

    2016-04-01

    Many studies have addressed the linkages between the Arctic Amplification and mid-latitude weather patterns. Most of them have focused on the effects of changes in sea ice, terrestrial snow or open ocean SST on the air temperature in selected mid-latitude areas. However, when analysing such potential linkages, one should be aware that from the point of view of the atmosphere it is almost the same whether the thermal forcing originates from the sea ice melt, snowmelt, or changes in SST. Most important is to quantify how the atmosphere responds to anomalies in the surface temperature and then affects weather patterns in remote areas. For this purpose, we studied the hemispheric-scale relationships between anomalies in the Northern Hemisphere Earth surface temperature (Ts) and 2-m air temperature (T2m) in mid-latitudes (Central and Eastern Europe). Using regression analyses based on the ERA-Interim reanalysis data, we assessed the said temperature relationships with focus on the lagged monthly and inter-seasonal linkages. Technically we divided the Northern Hemisphere in equal areas with a size of 15x10 degrees and calculated correlation coefficients for the monthly mean temperatures between all defined regions from one side and the Central/East European study regions from another side over the period 1979-2014. Using this approach, we found that the strongest links in the considered kind of relationships take place between spring sea surface temperature in the Labrador Sea and summer air (T2m) temperature in the Eastern Europe. In order to confirm the correlation results obtained, to identify thermal forcing factors and to assess their relative importance, we analysed the multiyear averages and anomalies of various meteorological parameters for 10 coldest and 10 warmest springs and summers in the period 1979-2014: surface pressure, total precipitation, sea-ice and total cloud cover, wind components, surface solar radiation downwards, surface heat fluxes and air

  6. Sedimentary history of the eastern Bohai Sea, China since the deglacial and implications for paleo-tidal current

    NASA Astrophysics Data System (ADS)

    Yao, Zhengquan; Shi, Xuefa

    2016-04-01

    Numerical simulation suggests that the Holocene sediments re-suspension and distribution in the Bohai Sea was mainly controlled by tidal current regime, which was closely related with sea-level change. Study on sediments in the Bohai Sea thus can provide insights into the evolution of tidal-influenced sedimentary environment and its links with sea-level change. Our understanding of this issue remains incomplete, however, owing to the lack of comprehensive study on sediment core with high-resolution proxies to test such inference. In this study, analyses of sedimentary facies, proxies (grain size, total organic carbon and total nitrogen, X-ray fluorescence scanning Sulfur and Chlorine ratio) and accelerator mass spectrometry 14C dates of a sediment core recovered from the eastern Bohai Sea were carried out to clarify the Holocene sedimentary environment, tidal current change and its relation to the sea-level. The results indicate that the eastern Bohai Sea was dominated by fluvial-coastal environment prior to 12400 cal. a BP due to the sea-level lowstand and changed to tidal-influenced environment from 12400 to 6700 cal. a BP following the rapid sea-level rising. Thereafter shelf environment with minor tidal influence dominated the eastern Bohai Sea under the condition of a deceleration of sea-level rise. The significant change at ~6700 cal. a BP both in sedimentary environment and sediment proxies, indicating an environmental transition from strong tidal-influenced to less tidal-influenced setting. With the sea-level rising from the early Holocene to the mid-Holocene, tidal-current was much strong due to the low sea-level stand and became weak after the maximum transgression at ~6700 cal. a BP. These results are consistent with the numerical simulation, which suggested that less strong tidal current were the consequence of the most highstand sea-level since the mid-Holocene. Our study thus provides a sedimentary record to support the interpretation of numerical

  7. Plant speciation in continental island floras as exemplified by Nigella in the Aegean Archipelago.

    PubMed

    Comes, Hans Peter; Tribsch, Andreas; Bittkau, Christiane

    2008-09-27

    Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of geographical isolation on non-adaptive radiation and allopatric speciation brought about by genetic drift. The Aegean Archipelago forms a highly fragmented complex of mostly continental shelf islands that have become disconnected from each other and the mainland in relatively recent geological times (ca <5.2 Ma). These ecologically fairly homogenous islands thus provide a suitable biogeographic context for assessing the relative influences of past range fragmentation, colonization, gene flow and drift on taxon diversification. Indeed, recent molecular biogeographic studies on the Aegean Nigella arvensis complex, combining phylogenetic, phylogeographic and population level approaches, exemplify the importance of allopatry and genetic drift coupled with restricted gene flow in driving plant speciation in this continental archipelago at different temporal and spatial scales. While the recent (Late Pleistocene) radiation of Aegean Nigella, as well as possible instances of incipient speciation (in the Cyclades), is shown to be strongly conditioned by (palaeo)geographic factors (including changes in sea level), shifts in breeding system (selfing) and associated isolating mechanisms have also contributed to this radiation. By contrast, founder event speciation has probably played only a minor role, perhaps reflecting a migratory situation typical for continental archipelagos characterized by niche pre-emption because of a long established resident flora. Overall, surveys of neutral molecular markers in Aegean Nigella have so far revealed population genetic processes that conform remarkably well to predictions raised by genetic drift theory. The challenge is now to gain more direct insights into the relative importance of the role of genetic drift, as opposed to natural selection, in the phenotypic and reproductive divergence among these Aegean plant

  8. Coastal sea level variability in the eastern English Channel: Potentialities for future SWOT applicability

    NASA Astrophysics Data System (ADS)

    Turki, Imen; Laignel, Benoit; Chevalier, Laetitia; Costa, Stephane

    2014-05-01

    Scientists and engineers need to understand the sea level variability in order to provide better estimates of the sea level rise for coastal defense using tide gauges and radar altimetry missions. The natural limitation of the tide gauge records is their geographical sparsity and confinement to coastlines. The future Surface Water and Ocean Topography (SWOT) mission will be launched in 2015 over a period of 5 years and will be designated to address this issue. This research was carried out in the framework of the program Surface Water and Ocean Topography (SWOT) which is a partnership between NASA and CNES. Using a series of statistical analyses, we point to characterize the sea level variability in the eastern English Channel (western France) from four tide gauges in Dunkirk, Dieppe, Le Havre and Cherbourg for the period 1964-2012. To assess the extent to which tide gauge point observations represent tide gauge data, we compare tide gauge records to SWOT measurements in their vicinity. Results have shown that the bimodality of the sea level, provided by the distribution analysis, can be reproduced by SWOT measurements with an overestimation of both modes and also the extreme values. The rate of the linear regression was also overestimated from 1.7-4 mm/yr to 2.6-5.4 mm/yr. The continuous wavelet transform of sea level records has shown the large-scale variability of annual (1-year band) and interannual cycles (2-6- and 6-12-year bands) in sea level, which can be explained by oceanographic and hydrological factors. High frequency dynamics of the sea level variability at short time-scales were extracted from SWOT measurements. They provide a good survey of the surge events (band of 3-4 months) and the spring-neap tidal cycle (band of 28 days). Then, tide gauges should be used in conjunction with satellite data to infer the full time-scale variability. Further studies are needed to refine the SWOT applicability in coastal areas. Key words: coastal zone, sea level

  9. Dust and polluted aerosol impacts on diazotrophy during a mesocosm experiment in the Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Rahav, Eyal; Herut, Barak; Liu, Hongbin; Guo, Cui; Cheung, Isaac; Psarra, Stella; Lagaria, Anna; Tsiola, Anastasia; Tsagaraki, Tanya; Pitta, Paraskevi; Mulholland, Margaret; Berman-Frank, Ilana

    2014-05-01

    Atmospheric inputs of nutrients via dust and aerosols to the surface ocean layer are considered to contribute greatly to dinitrogen (N2) fixation and to primary productivity. N2 fixation rates in the Mediterranean Sea are typically low and the parameters limiting this process are still unclear. Addition of dust analogs to a mesocosm experiment in the Western Mediterranean Sea (DUNE) enhanced N2 fixation by 3 to 5 fold. However, in the Eastern Mediterranean Sea, an area highly exposed to Saharan dust and aerosol, the impact of these inputs on N2 fixation from onboard microcosm experiment are unclear and inconclusive. We examined the influence of Saharan dust (1.6 mg L-1) and polluted aerosol (1 mg L-1) additions on diazotroph populations and N2 fixation rates in nine 3 m3 mesocosms (MESOAQUA project) using the enriched seawater method of 15N uptake. The enrichments induced an immediate 2-4 fold increase in N2 fixation (measured from 6 to 48 h after enrichments). After 4 days, N2 fixation rates returned to their background level and no significant change was observed relative to the control mesocosms. The increase in N2 fixation rates were reflected in the differential composition of diazotrophs. Dust enrichment enhanced the abundance of the filamentous cyanobacterium Trichodesmium spp., while aerosol addition predominantly enhanced the presence of heterotrophic diazotrophs including Pseudomonas and Desulfovibrio. Our results indicate that sources of nutrients supplied via Saharan dust and polluted aerosol pulses to the stratified surface Eastern Mediterranean waters could increase the contribution of diazotrophs and N2 fixation in these ultraoligotrophic waters and impact productivity and biogeochemical cycling.

  10. Late quaternary sea bottom conditions in the southern Panama basin, Eastern Equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Patarroyo, German D.; Martínez, José I.

    2015-11-01

    A paleoceanographic reconstruction of the southern Panama Basin for the last 23.000 years, based on the benthic foraminiferal analysis from the deep sea core ME0005A-24JC (0.01°N, 86.28°W, water depth 2941) is presented. Cluster and SHEBI (SHE Analysis for Biozone Identification) analyses performed on the benthic foraminiferal assemblages, evidence a faunal turnover in the early Holocene at 14 ky BP. Between 23 and 14 ky BP, Fursenkoina rotundata, Hoeglundina elegans, Globobulimina affinis, Globobulimina pacifica, Cibicidoides wuellerstorfi and Uvigerina hispidocostata were common. Conversely, from 14 ky to the present, the assemblage is represented by Chilostomella oolina, Laticarinina pauperata, and Uvigerina proboscidea. This faunal turnover suggests significant fluctuations in oxygen content at the sea floor and the organic matter (OM) influx, which could reflect: (1) fluctuations in the surface productivity related to the equatorial divergence and, (2) OM advection caused by the dynamic of the deep sea currents. Paleoproductivity estimates and benthic foraminiferal rates depict a general trend towards lower values since the Last Glacial Maximum (LGM) with a conspicuous change at 14 ky BP. Therefore, the paleoceanographic reconstructions of the ME0005A-24JC core suggest a transition from La Niña-like conditions during the LGM to El Niño-like conditions in the recent, as previously proposed for the Eastern Equatorial Pacific. Estimates of the paleo-intensity of deep sea currents based on the relative percentage abundance of the epifaunal foraminifera Cibicidoides wuellerstorfi suggest stronger deep sea currents on the Carnegie Ridge before 14 ky BP.

  11. Response of benthic foraminifera to phytodetritus in the eastern Arabian Sea under low oxygen conditions

    NASA Astrophysics Data System (ADS)

    Enge, Annekatrin; Wukovits, Julia; Wanek, Wolfgang; Watzka, Margarete; Witte, Ursula; Hunter, William; Heinz, Petra

    2016-04-01

    At water depths between 100 and 1500 m a permanent Oxygen Minimum Zone (OMZ) impinges on the sea floor in the eastern Arabian Sea, exposing benthic organisms to anoxic to suboxic conditions. The flux of organic matter to the sea floor is relatively high at these depths but displays seasonal variation. Deposition of relatively fresh phytodetrital material (phytoplankton remains) can occur within a short period of time after monsoon periods. Several organism groups including foraminifera are involved to different extent in the processing of phytodetritus in the OMZs of the northern Arabian Sea. A series of in situ feeding experiments were performed to study the short-term processing (< 11 days) of organic carbon, nitrogen and nutritional demands of foraminifera at different oxygen concentrations on the continental margin in the eastern Arabian Sea. For the experiments, a single pulse of isotopically labeled phytodetritus was added to the sediment along a depth transect (540-1100 m) on the Indian Margin, covering the OMZ core and the lower OMZ boundary region. Uptake of phytodetritus within 4 days shows the relevance of phytodetritus as food source for foraminifera. Lower content of phytodetrital carbon recorded in foraminifera from more oxygenated depths shows greater food uptake by foraminifera in the OMZ core than in the OMZ boundary region. The foraminiferal assemblage living under almost anoxic conditions in the OMZ core is dominated by species typically found in eutroph environments (such as Uvigerinids) that are adapted to high flux of organic matter. The elevated carbon uptake can also result from missing food competition by macrofauna or from greater energy demand in foraminifera to sustain metabolic processes under hypoxic stress. Variable levels and ratios of phytodetrital carbon and nitrogen indicate specific nutritional demands and storage of food-derived nitrogen in some foraminifera species under near anoxia where the mean phytodetrital nitrogen content

  12. Iceberg severity off eastern North America: Its relationship to sea ice variability and climate change

    SciTech Connect

    Marko, J.R.; Fissel, D.B. ); Wadhams, P. ); Kelly, P.M. ); Brown, R.D. )

    1994-09-01

    Iceberg trajectory, deterioration (mass loss), and sea ice data are reviewed to identify the sources of observed interannual and seasonal variations in the numbers of icebergs passing south of 48[degrees]N off eastern North America. The results show the dominant role of sea ice in the observed variations. Important mechanisms involved include both seasonal modulation of the southerly iceberg flow by ice cover control of probabilities for entrapment and decay in shallow water, and the suppression of iceberg melt/deterioration rates by high concentrations of sea ice. The Labrador spring ice extent, shown to be the critical parameter in interannual iceberg number variability, was found to be either determined by or closely correlated with midwinter Davis Strait ice extents. Agreement obtained between observed year-to-year and seasonal number variations with computations based upon a simple iceberg dissipation model suggests that downstream iceberg numbers are relatively insensitive to iceberg production rates and to fluctuations in southerly iceberg fluxes in areas north of Baffin Island. Past variations in the Davis Strait ice index and annual ice extents are studied to identify trends and relationships between regional and larger-scale global climate parameters. It was found that, on decadal timescales in the post-1960 period of reasonable data quality, regional climate parameters have varied, roughly, out of phase with corresponding global and hemispheric changes. These observations are compared with expectations in terms of model results to evaluate current GCM-based capabilities for simulating recent regional behavior. 64 refs., 11 figs., 3 tabs.

  13. Paleodepth variations on the Eratosthenes Seamount (Eastern Mediterranean): sea-level changes or subsidence?

    NASA Astrophysics Data System (ADS)

    Spezzaferri, S.; Tamburini, F.

    2007-09-01

    The Eratosthenes Seamount (Eastern Mediterranean) is interpreted as a crustal block in process of break up in response to subduction and incipient collision of the African and Eurasian Plates. Subsidence is considered to be the mechanism triggering the Messinian to Pleistocene water deepening above this unique structure. However, the application of a recently developed transfer equation of depth range distribution of benthic foraminifera indicates that sea-level changes may also have played a role, although it was generally minor. In particular, we suggest that across the Miocene/Pliocene boundary and during the Pliocene-Pleistocene, the eustatic signal is frequently coupled with uplifts and subsidence. The uplift of Cyprus across the Pliocene-Pleistocene transition is clearly recorded in the paleodepth curve. Micropaleontological studies and the use of this transfer equation based on the distribution of benthic foraminifera proves to be useful when studying the paleodepth history of complex sites, where tectonic and eustatic signals combine. We also show that marginal seas record global sea-level changes that can be identified even in tectonically active settings.

  14. Three Anisakis spp. isolated from toothed whales stranded along the eastern Adriatic Sea coast.

    PubMed

    Blažeković, Kristina; Pleić, Ivana Lepen; Đuras, Martina; Gomerčić, Tomislav; Mladineo, Ivona

    2015-01-01

    Knowledge concerning cetacean ecology in the Mediterranean is limited but important for sustainable planning and enforcement of appropriate conservation measures. Any information that might help to elucidate their ecology is essential. We explored the population and genetic structures of Anisakis spp. nematodes isolated from four toothed whale species - bottlenose dolphins (Tursiops truncatus), striped dolphins (Stenella coeruleoalba), Risso's dolphins (Grampus griseus) and Cuvier's beaked whales (Ziphius cavirostris) - stranded along the eastern Adriatic Sea coast (1990-2012) to reveal more information on host ecological patterns. Lower parasite prevalence was observed in resident dolphin species compared with occasionally occurring species, as well as in young compared with adult dolphins, indicating different feeding habits related to age. No unequivocal relationship between the biological traits of a host (age, body length, body mass and blubber depth) and Anisakis population parameters was observed. Phylogenetic analysis revealed a new geographical record of Anisakis simplex sensu stricto (1.96%) and Anisakis physeteris (1.31%) in the Adriatic Sea in addition to resident Anisakis pegreffii (96.73%). In an assessment of the Adriatic Sea and oceans worldwide, the genetic structure of Anisakis revealed that A. pegreffii populations do not differ among various final host species but do differ with respect to geographical location in contrast to previously accepted Anisakis panmixia.

  15. Distribution and sources of organic matter in sediments of the south-eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Remeikaitė-Nikienė, Nijolė; Lujanienė, Galina; Malejevas, Vitalijus; Barisevičiūtė, Rūta; Žilius, Mindaugas; Garnaga-Budrė, Galina; Stankevičius, Algirdas

    2016-05-01

    Temporal and spatial distribution of sedimentary organic matter (SOM) as well as its sources in the south-eastern Baltic Sea were investigated. Organic matter was characterized by the organic carbon content, δ13C and δ15N signatures and C/N ratios. The sampling was performed in the coastal, offshore areas and in the Curonian Lagoon in the period from May 2012 to September 2014. The average elemental (C/N ~ 6.4) and isotopic composition (δ13C from - 29.6‰ to - 24.9‰) of SOM suggested that during most of the year it was composed of both freshwater and marine phytoplanktonic material. Elevated δ15N values (average ranging from 5.6‰ to 6.7‰) were detected in SOM from the Curonian Lagoon. This most likely reflected the increased isotopic signal of the Nemunas River (δ15N ~ 8‰) derived from the anthropogenic input in the basin area. At the Baltic Sea offshore sites, SOM had lower δ15N values (δ15N ~ 3.5‰ on average), indicating phytoplankton blooms. A two-end member mixing model based on the carbon stable isotopic composition showed that a large proportion (~ 90%) of SOM in the northern part of the Curonian Lagoon was of the freshwater origin. The allochthonous organic matter accounted for about 47% of SOM in the studied Baltic Sea area with the highest contribution (about 75%) within the Curonian Lagoon plume zone in the coastal waters.

  16. Corrigendum to ''Climate-mediated changes in zooplankton community structure for the eastern Bering Sea'' [Deep-Sea Res. II 109 (2014) 157-171

    NASA Astrophysics Data System (ADS)

    Eisner, L. B.; Napp, J. M.; Mier, K. L.; Pinchuk, A. I.; Andrews, A. G.

    2016-10-01

    The authors regret that the panels are mislabelled in the caption for Fig. 7. The caption should read, "Untransformed mean zooplankton abundances in the eastern Bering Sea for large taxa in the (A) north (~60-63°N) and (B) south (<~60°N) and for small taxa in the (C) north and (D) south. Bar indicates warm and cold regimes".

  17. The interaction between Aegean back-arc extension and Anatolia escape since Late Miocene

    NASA Astrophysics Data System (ADS)

    Philippon, M. M.; Brun, J. P.; Gueydan, F.; Sokoutis, D.

    2015-12-01

    The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Using laboratory experiments designed to study lithosphere-scale deformation, we show that the overall pattern of Aegean extension requires not only the combination of trench retreat and Anatolia escape since 15 Ma but also the presence of an inherited lithosphere-scale mechanical discontinuity: the Vardar Suture Zone (VSZ). The reactivation in dextral shear of the eastern branch of the VSZ accommodates both the trench retreat (NS stretching) and the westward escape of Anatolia (EW shortening) in the Cyclades area since 15 Ma. Additionally, our model shows that the North Anatolian Fault (NAF) is a late structure in the evolution of the Aegean, initiated 10 Ma after the onset of Anatolia escape. The model displays displacement sub-domains, which result from strain partitioning instead of being "rigid microplates", directly comparable to the present-day displacement field (GPS) of the Aegean and western Anatolia. Our modelling provides a simple way to look at the dynamics of Aegean extension in two main stages. From middle Eocene to middle Miocene, extension was only driven by the southward retreat of the Hellenic trench at a rate lower than 1 cm.y-1. Since middle Miocene, the combination of slab rollback with Anatolia westward escape, resulted in a southwest direction of trench retreat, with an accelerating rate of up to 3 cm.y-1.

  18. Distribution of atmospheric CH4 concentration in eastern margin of Japan Sea from 7K14 cruises

    NASA Astrophysics Data System (ADS)

    Aoki, S.; Komiya, S.; Noborio, K.; Matsumoto, R.

    2015-12-01

    Hydrate of natural gas is widely distributed in marine sediments in the eastern margin of Japan Sea. Active gas vents from the seafloor have previously been reported worldwide at gas hydrate fields. Atmospheric methane (CH4), a major component of seep gases, is an important short-lived climate pollutant. Gas seeps may contribute to increase atmospheric gas concentration above the sea surface. Our objectives were to continuously measure and investigate the distribution of the atmospheric CH4 concentration over the sea surface at the gas hydrate fields along the eastern margin of Japan Sea. We used the R/V Kaiyo-Maru No.7 (Kaiyo Engineering Co., Ltd., Japan) for the survey in Japan Sea from mid April to early June 2014. Continuous measurement of atmospheric CH4 was performed on the ship using a wave-length-scanned cavity ring-down spectrometer (WS-CRDS) (model G2201-i, Picarro Inc., USA). Air sample was collected from an air intake at the top deck (approximately 8 m above sea level) of the ship using an air pump placed in the observation room. To our experience, the ship sailed at approximately 6 knot. Location data were obtained with the nautical GPS. Observed atmospheric CH4 concentration over the sea surface was approximately between 1.8-1.9 ppm in most sea areas, but exceeds 2.0 ppm in some areas. This study was conducted as a part of the METI's shallow gas hydrate exploration project.

  19. Earthquakes increase hydrothermal venting and nutrient inputs into the Aegean

    NASA Astrophysics Data System (ADS)

    Dando, P. R.; Hughes, J. A.; Leahy, Y.; Taylor, L. J.; Zivanovic, S.

    1995-05-01

    Areas of submarine gas and water venting around the island of Milos, in the Hellenic volcanic island arc, were mapped. Water samples were collected from five stations in the geothermally active Paleohori Bay on 15 March 1992. Seismic events, of M s 5.0 and 4.4, occurred south of the Bay on 20 March and the sampling was repeated after these. Phosphate and manganese in the water column increased by 360% after the seismic activity. Analysis of water samples collected from gas and water seeps and of interstitial water from sediment cores showed that the hot sediment in the Bay was enriched in phosphate, to a mean concentration of 65 μmol l -1 in the interstitial water. The number of geothermally active areas in the Aegean, together with the extent of venting and the frequency of earthquakes suggests that the hydrothermal areas may be an important source of phosphate in this oligotrophic Sea.

  20. Annual Acoustic Presence of Fin Whale (Balaenoptera physalus) Offshore Eastern Sicily, Central Mediterranean Sea.

    PubMed

    Sciacca, Virginia; Caruso, Francesco; Beranzoli, Laura; Chierici, Francesco; De Domenico, Emilio; Embriaco, Davide; Favali, Paolo; Giovanetti, Gabriele; Larosa, Giuseppina; Marinaro, Giuditta; Papale, Elena; Pavan, Gianni; Pellegrino, Carmelo; Pulvirenti, Sara; Simeone, Francesco; Viola, Salvatore; Riccobene, Giorgio

    2015-01-01

    In recent years, an increasing number of surveys have definitively confirmed the seasonal presence of fin whales (Balaenoptera physalus) in highly productive regions of the Mediterranean Sea. Despite this, very little is yet known about the routes that the species seasonally follows within the Mediterranean basin and, particularly, in the Ionian area. The present study assesses for the first time fin whale acoustic presence offshore Eastern Sicily (Ionian Sea), throughout the processing of about 10 months of continuous acoustic monitoring. The recording of fin whale vocalizations was made possible by the cabled deep-sea multidisciplinary observatory, "NEMO-SN1", deployed 25 km off the Catania harbor at a depth of about 2,100 meters. NEMO-SN1 is an operational node of the European Multidisciplinary Seafloor and water-column Observatory (EMSO) Research Infrastructure. The observatory was equipped with a low-frequency hydrophone (bandwidth: 0.05 Hz-1 kHz, sampling rate: 2 kHz) which continuously acquired data from July 2012 to May 2013. About 7,200 hours of acoustic data were analyzed by means of spectrogram display. Calls with the typical structure and patterns associated to the Mediterranean fin whale population were identified and monitored in the area for the first time. Furthermore, a background noise analysis within the fin whale communication frequency band (17.9-22.5 Hz) was conducted to investigate possible detection-masking effects. The study confirms the hypothesis that fin whales are present in the Ionian Sea throughout all seasons, with peaks in call detection rate during spring and summer months. The analysis also demonstrates that calls were more frequently detected in low background noise conditions. Further analysis will be performed to understand whether observed levels of noise limit the acoustic detection of the fin whales vocalizations, or whether the animals vocalize less in the presence of high background noise.

  1. Sea-Floor geology and character of Eastern Rhode Island Sound West of Gay Head, Massachusetts

    USGS Publications Warehouse

    Poppe, L.J.; McMullen, K.Y.; Ackerman, S.D.; Blackwood, D.S.; Irwin, B.J.; Schaer, J.D.; Forrest, M.R.

    2011-01-01

    Gridded multibeam bathymetry covers approximately 102 square kilometers of sea floor in eastern Rhode Island Sound west of Gay Head, Massachusetts. Although originally collected for charting purposes during National Oceanic and Atmospheric Administration hydrographic survey H11922, these acoustic data and the sea-floor stations subsequently occupied to verify them (1) show the composition and terrain of the seabed, (2) provide information on sediment transport and benthic habitat, and (3) are part of an expanding series of studies that provide a fundamental framework for research and management activities (for example, windfarms and fisheries) along the Massachusetts inner continental shelf. Most of the sea floor in the study area has an undulating to faintly rippled appearance and is composed of bioturbated muddy sand, reflecting processes associated with sediment sorting and reworking. Shallower areas are composed of rippled sand and, where small fields of megaripples are present, indicate sedimentary environments characterized by processes associated with coarse bedload transport. Boulders and gravel were found on the floors of scour depressions and on top of an isolated bathymetric high where erosion has removed the Holocene marine sediments and exposed the underlying relict lag deposits of Pleistocene drift. The numerous scour depressions, which formed during storm-driven events, result in the juxtaposition of sea-floor areas with contrasting sedimentary environments and distinct gravel, sand, and muddy sand textures. This textural heterogeneity in turn creates a complex patchwork of habitats. Our observations of local variations in community structure suggest that this small-scale textural heterogeneity adds dramatically to the sound-wide benthic biological diversity.

  2. Annual Acoustic Presence of Fin Whale (Balaenoptera physalus) Offshore Eastern Sicily, Central Mediterranean Sea

    PubMed Central

    Sciacca, Virginia; Caruso, Francesco; Beranzoli, Laura; Chierici, Francesco; De Domenico, Emilio; Embriaco, Davide; Favali, Paolo; Giovanetti, Gabriele; Larosa, Giuseppina; Marinaro, Giuditta; Papale, Elena; Pavan, Gianni; Pellegrino, Carmelo; Pulvirenti, Sara; Simeone, Francesco; Viola, Salvatore; Riccobene, Giorgio

    2015-01-01

    In recent years, an increasing number of surveys have definitively confirmed the seasonal presence of fin whales (Balaenoptera physalus) in highly productive regions of the Mediterranean Sea. Despite this, very little is yet known about the routes that the species seasonally follows within the Mediterranean basin and, particularly, in the Ionian area. The present study assesses for the first time fin whale acoustic presence offshore Eastern Sicily (Ionian Sea), throughout the processing of about 10 months of continuous acoustic monitoring. The recording of fin whale vocalizations was made possible by the cabled deep-sea multidisciplinary observatory, “NEMO-SN1”, deployed 25 km off the Catania harbor at a depth of about 2,100 meters. NEMO-SN1 is an operational node of the European Multidisciplinary Seafloor and water-column Observatory (EMSO) Research Infrastructure. The observatory was equipped with a low-frequency hydrophone (bandwidth: 0.05 Hz–1 kHz, sampling rate: 2 kHz) which continuously acquired data from July 2012 to May 2013. About 7,200 hours of acoustic data were analyzed by means of spectrogram display. Calls with the typical structure and patterns associated to the Mediterranean fin whale population were identified and monitored in the area for the first time. Furthermore, a background noise analysis within the fin whale communication frequency band (17.9–22.5 Hz) was conducted to investigate possible detection-masking effects. The study confirms the hypothesis that fin whales are present in the Ionian Sea throughout all seasons, with peaks in call detection rate during spring and summer months. The analysis also demonstrates that calls were more frequently detected in low background noise conditions. Further analysis will be performed to understand whether observed levels of noise limit the acoustic detection of the fin whales vocalizations, or whether the animals vocalize less in the presence of high background noise. PMID:26581104

  3. Condition of South-Eastern Baltic Sea Shores and Methods of Protecting Them

    NASA Astrophysics Data System (ADS)

    Ostrowski, Rafał; Pruszak, Zbigniew; Babakov, Alexander

    2014-06-01

    The paper describes lithodynamic and morphodynamic processes occurring in the main part of the south-eastern Baltic coastal area, namely on the sea shores from the Vistula mouth in the Gulf of Gdansk to the Lithuanian-Latvian border. The study area is subject to intensive natural coastal changes, as well as shore evolution caused by anthropogenic impacts at several locations. Methods of coastal protection against erosion and shore stabilization systems applied in the past and currently are described. The paper deals with the causes of the dynamics of beach/dune shores and cliffs. It presents the authors' field observations of 2010-2013, as well as previously gained knowledge and the results of Polish, Russian and joint Polish-Russian field surveys.

  4. Plastic debris ingested by deep-water fish of the Ionian Sea (Eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Anastasopoulou, Aikaterini; Mytilineou, Chryssi; Smith, Christopher J.; Papadopoulou, Konstantia N.

    2013-04-01

    Debris has been recognized as a global environmental problem including within deep habitats. From 26 fish species (1504 specimens) caught in the Eastern Ionian Sea during deep-water long-line surveys, plastic debris was found in 24 individuals of Galeus melastomus (3.2%) and single individuals of Pteroplatytrygon violacea, Squalus blainville, Etmopterus spinax, and Pagellus bogaraveo. The occurrence of debris among their food was infrequent. Ingested debris included primarily plastics (86.5%) and to a lesser extent pieces of metal and wood. Among ingested plastics, fragments of hard plastic material constituted the highest proportion (56.0%), followed by plastic bag fragments (22.0%), fragments of fishing gears (19.0%) and textile fibers (3.0%). Among the species with ingested debris, G. melastomus swallowed all debris categories; P. violacea and S. blainville ingested plastic bag fragments, whereas pieces of hard plastics were found in E. spinax and P. bogaraveo.

  5. Radioactivity and heavy metal levels in hazelnut growing in the Eastern Black Sea Region of Turkey.

    PubMed

    Cevik, U; Celik, N; Celik, A; Damla, N; Coskuncelebi, K

    2009-09-01

    The Eastern Black Sea Region of Turkey is one of the main hazelnut producers in Turkey and in the world. Since this region was contaminated by the Chernobyl accident in 1986, a comprehensive study was planned and carried out to determine the radioactivity level in hazelnut growing region. The dose due to consumption of hazelnut by the public was estimated and it was shown that this dose imposes no threat to human health. In addition, heavy metal analysis was performed in the samples and the amount of Cr, Mn, Fe, Ni, Cu, Zn, and Pb were also detected. The results showed that the concentrations of heavy metal are below the daily intake recommended by the international organizations.

  6. Relationship between macrobenthos and physical habitat characters in tidal flat in eastern Seto Inland Sea, Japan.

    PubMed

    Otani, Sosuke; Kozuki, Yasunori; Kurata, Kengo; Ueda, Kaori; Nakai, Shigefumi; Murakami, Hitoshi

    2008-01-01

    The investigations were carried out at 6 tidal flats located on the eastern part of the Seto Inland Sea, Japan. This study was focused on physical characteristics of sediments, namely as particle size of sediment and difference in elevation, and generalizes the relationship between sediments and macrobenthos. A total of 192 species were collected at 187 stations at 6 tidal flats. Physical characteristics of sediment were classified into 9 groups by cluster analysis in relation to sediment particle size and difference in elevation. Those groups had also significant difference in physical characteristics of sediments, and were characterized by some specific macrobenthos species. Distribution of macrobenthos can be explained by the classification of physical characteristics of sediment. These findings show the possibility to predict the variety of macrobenthos community using the physical characteristics of sediment.

  7. Nutrient Limitation in Surface Waters of the Oligotrophic Eastern Mediterranean Sea: an Enrichment Microcosm Experiment.

    PubMed

    Tsiola, A; Pitta, P; Fodelianakis, S; Pete, R; Magiopoulos, I; Mara, P; Psarra, S; Tanaka, T; Mostajir, B

    2016-04-01

    The growth rates of planktonic microbes in the pelagic zone of the Eastern Mediterranean Sea are nutrient limited, but the type of limitation is still uncertain. During this study, we investigated the occurrence of N and P limitation among different groups of the prokaryotic and eukaryotic (pico-, nano-, and micro-) plankton using a microcosm experiment during stratified water column conditions in the Cretan Sea (Eastern Mediterranean). Microcosms were enriched with N and P (either solely or simultaneously), and the PO4 turnover time, prokaryotic heterotrophic activity, primary production, and the abundance of the different microbial components were measured. Flow cytometric and molecular fingerprint analyses showed that different heterotrophic prokaryotic groups were limited by different nutrients; total heterotrophic prokaryotic growth was limited by P, but only when both N and P were added, changes in community structure and cell size were detected. Phytoplankton were N and P co-limited, with autotrophic pico-eukaryotes being the exception as they increased even when only P was added after a 2-day time lag. The populations of Synechococcus and Prochlorococcus were highly competitive with each other; Prochlorococcus abundance increased during the first 2 days of P addition but kept increasing only when both N and P were added, whereas Synechococcus exhibited higher pigment content and increased in abundance 3 days after simultaneous N and P additions. Dinoflagellates also showed opportunistic behavior at simultaneous N and P additions, in contrast to diatoms and coccolithophores, which diminished in all incubations. High DNA content viruses, selective grazing, and the exhaustion of N sources probably controlled the populations of diatoms and coccolithophores. PMID:26626911

  8. Marine heat flow measurements across subsea permafrost limit in the eastern Mackenzie Trough, Canadian Beaufort Sea

    NASA Astrophysics Data System (ADS)

    Kim, Y. G.; Hong, J. K.; Jin, Y. K.; Riedel, M.; Melling, H.; Kang, S. G.; Dallimore, S.

    2015-12-01

    Marine heat flow measurements using a 5 m-long Ewing-type heat probe were made during Korean icebreaker R/V Araon's Arctic expeditions (ARA04C in 2013 and ARA05B in 2014) to better know the shallow subsurface thermal structure in the eastern slope of Mackenzie Trough, the Canadian Beaufort Sea, in which associative geological processes of permafrost degradation and gas hydrate dissociation occur because of long-term warming since the Last Glacial Maximum. Heat flow in the continental slope was collected for the first time and is rather higher than those from deep boreholes (up to a few km below the seafloor) in the continental shelf. However, the smaller geothermal gradient and thermal conductivity were observed from sites along a transect line across permafrost limit on the eastern slope of the trough. It is noted that geothermal gradients are relatively constant in the vicinity of permafrost limit but are much smaller (even minus) only at deeper depths with positive bottom water temperature. Reason for such distribution is unclear yet. Based on observed geothermal gradient and bottom water temperature, permafrost table shown in subbottom profile seems to be controlled not by temperature. On the other hand, our finding of permafrost evidence on the other subbottom profile located landward may support that permafrost limit in the trough is along with ~100 m isobath.

  9. Spatial variation of statistical properties of extreme water levels along the eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Pindsoo, Katri; Soomere, Tarmo; Rocha, Eugénio

    2016-04-01

    Most of existing projections of future extreme water levels rely on the use of classic generalised extreme value distributions. The choice to use a particular distribution is often made based on the absolute value of the shape parameter of the Generalise Extreme Value distribution. If this parameter is small, the Gumbel distribution is most appropriate while in the opposite case the Weibull or Frechet distribution could be used. We demonstrate that the alongshore variation in the statistical properties of numerically simulated high water levels along the eastern coast of the Baltic Sea is so large that the use of a single distribution for projections of extreme water levels is highly questionable. The analysis is based on two simulated data sets produced in the Swedish Meteorological and Hydrological Institute. The output of the Rossby Centre Ocean model is sampled with a resolution of 6 h and the output of the circulation model NEMO with a resolution of 1 h. As the maxima of water levels of subsequent years may be correlated in the Baltic Sea, we also employ maxima for stormy seasons. We provide a detailed analysis of spatial variation of the parameters of the family of extreme value distributions along an approximately 600 km long coastal section from the north-western shore of Latvia in the Baltic Proper until the eastern Gulf of Finland. The parameters are evaluated using maximum likelihood method and method of moments. The analysis also covers the entire Gulf of Riga. The core parameter of this family of distributions, the shape parameter of the Generalised Extreme Value distribution, exhibits extensive variation in the study area. Its values evaluated using the Hydrognomon software and maximum likelihood method, vary from about -0.1 near the north-western coast of Latvia in the Baltic Proper up to about 0.05 in the eastern Gulf of Finland. This parameter is very close to zero near Tallinn in the western Gulf of Finland. Thus, it is natural that the Gumbel

  10. Occurrence, sources and transport pathways of natural and anthropogenic hydrocarbons in deep-sea sediments of the Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Parinos, C.; Gogou, A.; Bouloubassi, I.; Pedrosa-Pàmies, R.; Hatzianestis, I.; Sànchez-Vidal, A.; Rousakis, G.; Velaoras, D.; Krokos, G.; Lykousis, V.

    2012-12-01

    Surface sediments collected from deep basins (22 stations, 1018-4087 m depth) of the Eastern Mediterranean Sea (EMS) were analyzed for aliphatic, triterpenoid and polycyclic aromatic hydrocarbons (PAHs) as tracers of natural and anthropogenic inputs. Concentrations of total aliphatic hydrocarbons (TAHC), n-alkanes (NA) and the Unresolved Complex Mixture (UCM) of aliphatic hydrocarbons ranged from 1.34 to 49.2 µg g-1, 145 to 4810 ng g-1 and 0.73 to 36.7 µg g-1, respectively, while total PAHs (TPAH25) concentrations ranged from 11.6 to 223 ng g-1. Molecular profiles of aliphatic hydrocarbons and PAHs reflect the contribution of both natural (epicuticular plant waxes) and anthropogenic (degraded petroleum products, unburned fossil fuels and combustion of petroleum, grass, wood and coal) compounds in deep EMS sediments, with hydrocarbon mixtures displaying significant regional variability. Hydrocarbon concentrations correlated significantly with the Total Organic Carbon (TOC) content of sediments, indicating that organic carbon exerts an important control on their transport and fate in the study area, while strong sub-basin and mesoscale variability of water masses also impact their regional characteristics. Major findings of this study support that deep basins/canyons of the EMS could act as traps of both natural and anthropogenic hydrocarbons.

  11. Distinct microbial communities thriving in gas hydrate-associated sediments from the eastern Japan Sea

    NASA Astrophysics Data System (ADS)

    Yanagawa, Katsunori; Kouduka, Mariko; Nakamura, Yuri; Hachikubo, Akihiro; Tomaru, Hitoshi; Suzuki, Yohey

    2014-08-01

    Marine gas hydrate and cold-seep systems, which maintain a large amount of methane in the seabed, may critically impact the geochemical and ecological characteristics of the deep-sea sedimentary environment. However, it remains unclear whether marine sediments associated with gas hydrate harbor novel microbial communities that are distinct from those from typical marine sediments. In this study, microbial community structures thriving in sediments associated with and without gas hydrate in the eastern Japan Sea were characterized by 16S rRNA gene-based phylogenetic analyses. Uncultivated bacterial lineages of candidate division JS1 and a novel group NT-B2 were dominant in the sediments from gas hydrate-associated sites. Whereas, microbial populations from sites not associated with gas hydrate were mainly composed of Bacteroidetes, Nitrospirales, Chlamydiales, Chlorobiales, and yet-uncultured bacterial lineages of OD1 and TM06. The good correlation between the dominance of JS1 and NT-B2 and the association of gas hydrate could be attributed to the supply of more energetically favorable energy sources in gas-rich fluids from the deep subsurface than refractory organic matter of terrigenous and diatomaceous origin.

  12. Geological Interpretation of Bathymetric and Backscatter Imagery of the Sea Floor off Eastern Cape Cod, Massachusetts

    USGS Publications Warehouse

    Poppe, Larry J.; Paskevich, Valerie F.; Butman, Bradford; Ackerman, Seth D.; Danforth, William W.; Foster, Dave S.; Blackwood, Dann S.

    2006-01-01

    The imagery, interpretive data layers, and data presented herein were derived from multibeam echo-sounder data collected off Eastern Cape Cod, Massachusetts, and from the stations occupied to verify these acoustic data. The basic data layers show sea-floor topography, sun-illuminated shaded relief, and backscatter intensity; interpretive layers show the distributions of surficial sediment and sedimentary environments. Presented verification data include new and historical sediment grain-size analyses and a gallery of still photographs of the seabed. The multibeam data, which cover a narrow band of the sea floor extending from Provincetown around the northern tip of Cape Cod and south southeastward to off Monomoy Island, were collected during transits between concurrent mapping projects in the Stellwagen Bank National Marine Sanctuary (Valentine and others, 2001; Butman and others, 2004; and Valentine, 2005) and Great South Channel (Valentine and others, 2003a, b, c, d). Although originally collected to maximize the use of time aboard ship, these data provide a fundamental framework for research and management activities in this part of the Gulf of Maine (Noji and others, 2004), show the composition and terrain of the seabed, and provide information on sediment transport and benthic habitat. These data and interpretations also support ongoing modeling studies of the lower Cape's aquifer system (Masterson, 2004) and of erosional hotspots along the Cape Cod National Seashore (List and others, 2006).

  13. From Space to Seafloor - Investigating Oil and Gas Seepage in the Eastern Black Sea

    NASA Astrophysics Data System (ADS)

    Körber, J.; Sahling, H.; Pape, T.; Heygster, G.; Bohrmann, G.

    2011-12-01

    Emissions of gases from the seafloor are of interest due to their relevance for the global climate, their potential as energy source, and impact on geochemical and biogeochemical cycles. Gas seepage has previously been reported to occur along the continental margin, on the shelf, and at some locations in the central deep Black Sea. These discoveries led to the assumption that seepage of light hydrocarbons from the seafloor is one of the major sources feeding the high methane concentrations of the Black Sea water body. It is commonly accepted that the proportion of pure bubble-forming methane released from deep-sea seeps reaching the hydrosphere/atmosphere interface is negligible since it is nearly entirely dissolved during its ascent through the water column or it is replaced by other gases diffusing from the water column into the bubbles. However, there is first evidence from recent studies at seeps showing intimate seepage of oil and gas that oil coatings around gas bubbles might protect the methane from complete dissolution. A set of Advanced Synthetic Aperture Radar (ASAR) satellite images has been analysed in order to detect oil slicks as sea surface expressions of natural seepage in the deep eastern Black Sea off Georgia. Eight oil seep sites located between 450 and 1200 m water depth have been identified. Intensive hydroacoustic seafloor and water column investigations during two ship expeditions in 2010 and 2011 in combination with shallow sediment sampling and evaluation of hydroacoustic data from earlier cruises confirmed seepage of oil and gas. Ratios of thermogenic and biogenic gas vary significantly between the oil and gas seeps (e.g. Pechori Mound) and pure gas seeps (e.g. Batumi seep). Oil seeps seem to be related to ridge structures and underlying shale diapirs originating from the hydrocarbon rich Oligocene-Miocene Maikop formation. High resolution mapping of the Colkheti Seep (1125 mbsl), one of the most prominent oil seeps off Georgia, using an

  14. Source, composition and reactivity of sedimentary organic carbon in the river-dominated marginal seas: A study of the eastern Yellow Sea (the northwestern Pacific)

    NASA Astrophysics Data System (ADS)

    Yoon, Suk-Hee; Kim, Jung-Hyun; Yi, Hi-Il; Yamamoto, Masanobu; Gal, Jong-Ku; Kang, Sujin; Shin, Kyung-Hoon

    2016-08-01

    We investigated the source, composition and reactivity of sedimentary organic carbon (OC) in a river-dominated continental marginal sea, the eastern Yellow Sea. A multi-proxy approach was applied to 9 riverbank sediments and 69 marine surface sediments, combining bulk and molecular organic parameters. The riverbank sediments (n=9) have on average low C/N ratio (4.8±0.5) and enriched δ13CTOC values (-21.5±0.6%) while the BIT index is on average 0.27. The sedimentary OC in the marine surface sediments appears to have a predominantly marine origin (on average C/N ratio=7.0±0.6 and δ13CTOC=-21.9±0.5%, n=69) with minor contribution of continental (i.e. soil- and lake/river-derived) OC (on average BIT index=0.00±0.01, n=69). However, the Δ14C values were depleted (on average -227±53%, n=8). Accordingly, our results highlight that fossil OC, potentially derived from erosion of sedimentary bedrocks in the catchment areas and/or human activities is being contributed to the sedimentary OC pool in the eastern Yellow Sea. More work is needed to better constrain the source, composition, and age of the organic material supplied to the eastern Yellow Sea, given the lack of biogeochemical data from the Korean rivers.

  15. The Norwegian Danish Basin: A key to understanding the Cenozoic in the eastern North Sea

    NASA Astrophysics Data System (ADS)

    Rasmussen, Thomas L.; Clausen, Ole R.; Andresen, Katrine J.; Goledowski, Bartosz

    2015-04-01

    The Danish part of Norwegian-Danish Basin, which constitutes the eastern part of the North Sea Basin, has been the key area for sequence stratigraphic subdivision and analysis of the Cenozoic succession since the mid 1990's. Widespread 3D seismic data, in the central parts of the North Sea Basin, as well as more scattered 3D seismic data in the Danish part of the Norwegian-Danish Basin, have given a more detailed understanding of the sequences and indicate that climate is tenable for the origin of Cenozoic sequence boundaries. The previous sequence stratigraphic interpretations have been an integrated part of an ongoing debate concerning vertical movements of the Fennoscandian shield versus the impact of climate and erosion. A newly accessed coherent regional 2D and reprocessed 3D seismic data set, in the Norwegian part of the Norwegian-Danish Basin, constitute the database for a new sequence stratigraphic analysis of the entire area. The objective of the new study is to test previous subdivisions and introduce a coherent 3D sequence stratigraphic analysis and depositional model for the entire Norwegian-Danish Basin. This analysis is necessary to get out of the stalemate with the uplift discussion. The study shows that the original subdivision by Michelsen et al. (1995, 1998) stands. However, revision of few a sequence boundaries may have to be adjusted due to new biostratigraphic information published. Furthermore, high-angle clinoforms and geomorphological transport complexes observed in the Danish North Sea Basin can be traced into the Norwegian sector. This together with the recognition of several other high-angle clinoform complexes, and their associated seismic facies distribution maps and thickness-maps, enhances the level of detail and constrains the previous published paleogeographic reconstructions of the Cenozoic. The geometry of the Cenozoic infill, in the Norwegian part of the Norwegian-Danish Basin, is here interpreted to be controlled by relative sea

  16. Assessment of Eutrophication Quality in Greek Coastal Ecosystem (Eastern Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Pavlidou, Alexandra; Rousselaki, Eleni; Assimakopoulou, Georgia; Tsapakis, Manolis; Simboura, Nomiki

    2014-05-01

    The Mediterranean Sea has always been considered as one of the most oligotrophic areas in the world, especially in the Eastern part of the Sea. However, eutrophication problems occur in some coastal areas of the Mediterranean (e.g. eastern coasts of Spain, Gulf of Lions, northern Adriatic Sea, Apulian coasts, Saronikos Gulf, Thessaloniki Bay, northern coasts of Greece, etc.). This work is focused on the assessment of the Eutrophication Quality in different coastal areas of Greece affected by various anthropogenic and natural pressures and was performed under the Water Framework Directive. A network of 28 sampling stations was used during two relevant sampling periods, April - May 2012 and March - April 2013, in the framework of the National Monitoring Project of Greece. The Eutrophication assessment method integrates chemical and biological parameters of the water column. A synthetic Eutrophication Index (E.I.) was produced for the greek coastal areas by Primpas et al. quality classification scheme, combining the concentrations of nutrients (phosphate, nitrate, nitrite, ammonia) and chlorophyll-α biomass into a single formula. The E.I. assesses the eutrophication status using a five scale scheme according to the requirements of WFD: (High) less than 0.04; (Good) 0.04-0.38; (moderate) 0.38-0.85; (poor) 0.85-1.51; (bad) >1.51. Nutrient and chlorophyll-a concentrations revealed significant spatial variation among the various coastal areas of Greece influenced by different point and/or diffuse anthropogenic pressures (related to nutrient enrichment), reflecting the level of human-induced impairment where an increase in nutrient loads leads to increased water quality problems. The assessment of E.I showed that during 2012, 32% of the selected coastal areas were characterized as Good, 54% as Moderate and 14% of the selected greek coastal areas were characterized as Poor. During 2012, none of the study areas corresponded to High or Bad eutrophication status. During 2013

  17. Offshore evidence of postglacial relative sea-level change from eastern Ireland.

    NASA Astrophysics Data System (ADS)

    Callard, S. Louise; Long, Antony J.; Plets, Ruth M.; Cooper, J. Andrew; Belknap, Daniel F.; Edwards, Robin J.; Jackson, Derek W. T.; Kelley, Joseph T.; Long, David; Milne, Glenn A.; Monteys, Xavier; Quinn, Rory

    2014-05-01

    Field evidence and Glacial Isostatic Adjustment (GIA) models help constrain the extent of the British Irish Ice Sheet (BIIS) during and since the Last Glacial Maximum (LGM). Because of differential ice loading histories, relative sea-level (RSL) changes at sites from around the Irish Sea basin are complex. Existing GIA models are constrained using sea-level observations and some poorly dated and unevenly distributed ice margin data, but there is a paucity of RSL observations below -10 m OD that spans the Late Glacial, a period of abrupt RSL change that includes at least one meltwater pulse. Addressing this interval of time requires the collection of new field data from offshore regions around Ireland, taking advantage of recent advances in remote sensing techniques. This paper presents results from offshore eastern Ireland, one of seven areas targeted as part of a larger NERC funded project 'Late Glacial sea-level minima in the Irish Sea'. Previous research in this region has focused on dating raised marine sediments from exposed onshore coastal sections that represent periods of RSL highstands during the early deglaciation. However, the significance of these data for RSL reconstruction and hence their constraints on GIA models is debated. Here we use a combination of marine geophysics (multibeam bathymetry and backscatter, pinger sub-bottom profiler) vibro-coring and laboratory analyses to reconstruct Late Glacial RSL change from this region. The area's bathymetry demonstrate a strong glacial imprint on the northern side of the study area, with a large arcuate fan extending from Dundalk Bay to -18m, perhaps formed during a period of ice readvance, most likely during the Killard Point Stadial (c. 16.5 k cal a BP). Pinger seismic data allow the identification of six seismo-stratigraphic units, of which the most notable is a chaotic unit sitting on a prominent reflector that can be traced between -22 m to -50 m. The unit is interpreted as a gravel lag overlying

  18. An inverse modeling study of circulation in the Eastern Bering Sea during 2007-2010

    NASA Astrophysics Data System (ADS)

    Panteleev, Gleb; Yaremchuk, Max; Francis, Oceana; Stabeno, Phyllis J.; Weingartner, T.; Zhang, J.

    2016-06-01

    A two-way nested 4d-variational data assimilation system is implemented in the Eastern Bering Sea (EBS) to investigate changes in circulation and thermodynamic state for a 3.8 year period. Assimilated observations include data from 19 moorings deployed on the shelf and in the Bering Strait, 1705 hydrographic stations occupied during eight surveys, and remotely sensed sea surface temperature and sea surface height (SSH) data. Validation of the presented 4dVar reanalysis against the output of two sequential data-assimilative systems (the Bering Ecosystem Study ice-ocean Modeling and Assimilation System (BESTMAS) and the Arctic Cap Nowcast-Forecast System (ACNFS)) has shown that the product is more consistent with the observed transports in the Bering Strait and in the EBS interior both in terms of their magnitude and time variability. Analysis of the data-optimized solution quantifies a sequence of wind-forced events that resulted in the anomalous heat and freshwater transports through the Bering Strait, including a 28 day long flow reversal that occurred in November 2009 and carried Siberian Coastal Current water down to the Gulf of Anadyr. Lagrangian study of the Arctic-bound Pacific waters indicates the extreme importance of the cross-shelf exchange along the path of the Bering Slope Current and quantifies the spectrum of residence times for the waters entering EBS through Unimak Pass and through Aleutian passages. Residence times in the EBS cold pool are diagnosed to be 2-3 times longer than those in the surrounding waters.

  19. Important aspects of Eastern Mediterranean large-scale variability revealed from data of three fixed observatories

    NASA Astrophysics Data System (ADS)

    Bensi, Manuel; Velaoras, Dimitris; Cardin, Vanessa; Perivoliotis, Leonidas; Pethiakis, George

    2015-04-01

    Long-term variations of temperature and salinity observed in the Adriatic and Aegean Seas seem to be regulated by larger-scale circulation modes of the Eastern Mediterranean (EMed) Sea, such as the recently discovered feedback mechanisms, namely the BiOS (Bimodal Oscillating System) and the internal thermohaline pump theories. These theories are the results of interpretation of many years' observations, highlighting possible interactions between two key regions of the EMed. Although repeated oceanographic cruises carried out in the past or planned for the future are a very useful tool for understanding the interaction between the two basins (e.g. alternating dense water formation, salt ingressions), recent long time-series of high frequency (up to 1h) sampling have added valuable information to the interpretation of internal mechanisms for both areas (i.e. mesoscale eddies, evolution of fast internal processes, etc.). During the last 10 years, three deep observatories were deployed and maintained in the Adriatic, Ionian, and Aegean Seas: they are respectively, the E2-M3A, the Pylos, and the E1-M3A. All are part of the largest European network of Fixed Point Open Ocean Observatories (FixO3, http://www.fixo3.eu/). Herein, from the analysis of temperature and salinity, and potential density time series collected at the three sites from the surface down to the intermediate and deep layers, we will discuss the almost perfect anti-correlated behavior between the Adriatic and the Aegean Seas. Our data, collected almost continuously since 2006, reveal that these observatories well represent the thermohaline variability of their own areas. Interestingly, temperature and salinity in the intermediate layer suddenly increased in the South Adriatic from the end of 2011, exactly when they started decreasing in the Aegean Sea. Moreover, Pylos data used together with additional ones (e.g. Absolute dynamic topography, temperature and salinity data from other platforms) collected

  20. Kolumbo active seamount (Greece): A window into the Aegean mantle

    NASA Astrophysics Data System (ADS)

    Rizzo, A. L.; Caracausi, A.; Chavagnac, V.; Nomikou, P.; Polymenakou, P.; Magoulas, A.; Mandalakis, M.; Kotoulas, G.

    2015-12-01

    Submarine volcanism is ubiquitous in active tectonic settings of the earth, but due to depth and hazardousness of these environments the study is a challenge. In May 2014, we performed a cruise in the Aegean Sea aimed to investigate the high-temperature (>200°C) hydrothermal system of Kolumbo active underwater volcano, 7 km northeast off Santorini. Last explosive eruption occurred in 1650 A.D. and killed ~70 people, so plainly the eruptive potential is real. We sampled gases discharged from seven chimneys located at ~500 m b.s.l. and we investigated their composition. The chemistry indicates that these consist of almost pure CO2 with a small atmospheric contamination. The δ13C-CO2 varies from 0 to 1.5‰ and shows a positive correlation with the concentration of He, H2, CO and CH4 as the result of chemical and isotope fractionation due to variable extents of gas-water interaction. The 3He/4He varies from 7.0 to 7.1 Ra, coherently with the fact that this ratio does not suffer any fractionation due to gas-water interaction. These values are surprisingly higher (more than 3 units Ra) than the measurements performed in gases and rocks from Santorini (Rizzo et al., 2015). They are in the typical range of arc volcanoes worldwide (7-9 Ra; Hilton et al., 2002; Di Piazza et al., 2015), indicating that the 3He/4He ratios measured at Kolumbo are likely the result of direct mantle degassing in a general extensive regime. More importantly, these ratios are the highest in all the South Aegean volcanism, which leads to consider homogeneous (and MORB-like) the He isotope composition of the mantle below the central part of the Hellenic Volcanic Arc and eastward up to Nisyros, which until this study showed the highest ratios (6.2Ra; Shimizu et al., 2005). Our results strongly emphasize the role of tectonics in the transfer of fluids from the mantle toward the surface. The complicated geodynamics status of the Aegean-Anatolian region, plays a key role in generating crustal

  1. Crustal structure of the Aegean area obtained by traveltime tomography

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Brüstle, A.; Küperkoch, L.; Friederich, W.

    2012-04-01

    The Hellenic arc and Aegean sea area are of locus of high seismicity and intense tectonic activity. Previous studies using either traveltimes of body waves or dispersion curves of surface waves show strong lateral heterogeneity of velocity structure of the crust and upper mantle under the Aegean area. Especially crustal thicknesses vary from about 20 km to 45 km. The complexity of crustal structure often requires the use of a number of one-dimensional layered models, in the calculation of synthetic seismograms for different ray traversing paths, to determine moment tensor of small-to-moderate earthquakes in this area. Using travel times from the EHB catalog data between 1980 and 1997 from International Seismological Center (Engdahl et al. 1998), Euro-Mediterranean Bulletin data between 1998 and 2008 from the Euro-Mediterranean Seismological Center (Godey et al. 2006), and additional local earthquakes recorded by the temporary stations deployed in the EGELADOS project, we derive a new three-dimensional velocity model of the crust in the Aegean area using the traveltime tomographic inversion code FMTOMO developed by Rawlinson et al. (2006). The events falling into the research area defined by 34°-40°N and 20°-29°E are firstly relocated using HypoDD (Waldhauser & Ellsworth 2000) before tomographic inversion is performed. Since the number of earthquakes is much greater than the number of stations, the source and receiver roles are interchanged to accelerate the forward calculation of traveltimes which is done by tracking the wavefront propagation with the fast marching method. The initial one-dimensional model was obtained by simultaneously inverting the data both for hypocenter locations and velocity using VELEST (Kissling et al. 1994). Checkboard resolution tests for the P waves show that anomalies of size of half a degree could be correctly recovered down to depth of 50 km. One notable feature from the preliminary inversion results for the P velocity is that the

  2. Moment tensor inversion of the January 8, 2013 (Mw=5.7) and May 24, 2014 (Mw 6.8) North Aegean Earthquakes: seismicity and active tectonics of the North Aegean Region

    NASA Astrophysics Data System (ADS)

    Kalafat, Dogan; Kekovali, Kivanc; Pinar, Ali

    2015-04-01

    The North Aegean Sea is one of the most seismically active and deforming region between the Eurasia and Anatolia tectonic plates. On 8th January 2013 at 14:16 UTC (16:16 local time) a moderate earthquake (Mw= 5.7) occurred between the south of Gökçeada and southwest of Bozcaada Islands. The earthquake was felt at a wide area. Especially felt in the NE Greece south of Lemnos Island and NW Turkey surrounding areas, such as Çanakkale, Marmara Region and Northern Aegean coast as well as to Athens. The area is defined as the continuation of the branch of North Anatolian Fault (NAF) inside the Aegean Sea. Fault plane solution determined by this study shows that the earthquake occurred on NE-SW oriented strike slip fault segment. The aftershocks distribution also supported the rupture of the NE-SW oriented fault. Approximately 17 months later, another big earthquake occurred in the same area. On 24th May 2014, at 09:25 UTC (12:25 local time), a powerful Ml=6.7 (Mw=6.8) earthquake hit Greece and Turkey, 87 km west of Çanakkale, and totally 350 people injured in Greece and Turkey. This earthquake has been strongly felt in Greece, Turkey, Bulgaria, Romania. The main-shock occurred on a fault with a NE-SW strike, where the largest portion of the energy was released towards these directions. Therefore the earthquake was felt strongly in Çanakkale, Istanbul and Marmara region. In this study we calculated CMT solutions for main-shock and important aftershocks (M>4.0). CMT analyses were done for 50 important earthquakes. Moment tensor solutions show generally strike-slip faulting. The fault which caused earthquake, is thought to be a branch of North Anatolian Fault Zone in the North Aegean Sea. Generally, the location of the earthquakes and orientation of the NE-SW nodal planes are consistent with right-lateral faulting within the North Aegean Trough (NAT). The Aegean Sea is characterized by dextral strike-slip faulting along NE-SW striking faults, along fault zones formed

  3. Total Mercury in Surface and Deep Waters in the Western and Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Varde', M.; Cofone, F.; Servidio, A.; Rosselli, A.; Hedgecock, I. M.; Ammoscato, I.; Mannarino, V.; Sprovieri, F.; Gensini, M.; Pirrone, N.

    2014-12-01

    In the framework of the Italian National Research Council (CNR) Med-Oceanor measurement program and as part of the Global Mercury Observation System (GMOS) objectives, we performed two cruise campaigns with the CNR's Research Vessel (RV) Urania, in the western and eastern Mediterranean Basin, in the summers of 2012 and 2013. Total Mercury (THg) concentration in seawater was systematically measured at different depths from the sea bottom to the surface. A total of 155 surface and deep seawater samples at 25 selected stations were collected during the cruise campaigns using a stainless-steel rosette system on which 24 Niskin bottles (10L) were mounted. Continuous monitoring of temperature, conductivity, salinity and oxygen with depth were obtained by CTD measurements. All fluorinated containers were cleaned prior to use following GMOS SOPs. The chemical reagents used were suitable for ultra-trace Hg analysis. After sampling, samples were preserved by adding HCl solution to the sample bottles, which were refrigerated during transportation and analyzed within four weeks of the end of the oceanographic campaign. Sea water samples were analyzed in the laboratory following the US-EPA 1631 method revision E (US-EPA, 2002). To assess the critical issues related to mercury (Hg) contamination and to prevent leakage of Hg through volatilization we used all necessary precautions for sampling, sample stabilization, preservation and subsequent analysis in the laboratory. Quality assurance and quality control were performed using transport blanks, laboratory blanks and use of seawater certified reference materials. The accuracy of the analytical procedures for the determination of THg in sea water was corroborated by participation in a global inter-laboratory comparison study for THg in natural waters. THg concentrations in surface and deep waters found in the Mediterranean basin during the last two cruise campaigns Med-Oceanor as well as the THg measurements in sea water

  4. Evidence for eddy formation in the eastern Arabian Sea during the northeast monsoon

    NASA Technical Reports Server (NTRS)

    Bruce, John G.; Johnson, Donald R.; Kindle, John C.

    1994-01-01

    The seasonal formation of a large (500-800 km diameter) anticyclonic eddy in the upper 300-400 m of the eastern Arabian Sea during the northest monsoon period (December-April) is indicated fom hydrographic and satellite altimetry sea level observations, as well as from numerical model experiments. The center of the eddy circulation is approximately 10 deg N, 70 deg E, just to the west of the north-south Laccadive Island chain. In this paper the eddy is called the Laccadive High (LH). In some ways it is like a mirrorlike counterpart to the Great Whirl that develops during the southwest monsoon of the Somali coast (western Arabian Sea). The LH occurs at the same latitude but on the opposite side of the basin during the reversed monsoon. It is different from the Great Whirl, however, in its formation process, its intensity, and its decay. The hydrographic data obtained from surveys all during a single season give sufficiently close station spacing to allow reasonable contouring of the geopotential surfaces and of the properties within and around the LH region with minimum time aliasing. The Geostat altimeter record extends over 4 years, during which the seasonal variability of the LH indicates a dynamic relief of approximately 15-20 cm, which is in good agreement with the hydrographics observations. The altimetry time series also suggests a westward translation of the LH by January with a subsequent dissipation in midbasin. The model used is a wind-forced three-layer primitive equation model which depicts a LH agreement with the timing, position, and amplitude of both the hydrographic and altimetric measurements. The numerical simulation includes a passive tracer located in the Western Bay of Bengal; the western advection of the tracer around the south coasts of Sri Lanka and India in December and January is consistent with the appearance of low-salinity water observed to extend into the Arabian Sea during this period. The modeling studies suggest that both local and

  5. Luminescence Dating of Marine Terrace Sediments Between Trabzon and Rize, Eastern Black Sea Basin: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Softa, Mustafa; Spencer, Joel Q. G.; Emre, Tahir; Sözbilir, Hasan; Turan, Mehmet

    2016-04-01

    Quaternary marine terraces in the coastal region of Pontides in Northeastern Turkey are valuable archives of past sea level change. Until recently, dates of raised marine terraces undeciphered in the coastal region between Trabzon and Rize because of chronologic limitations. In this paper was to determine ages of the terrace deposits by applying optically stimulated luminescence (OSL) dating methods using single aliquot regenerative dose (SAR) techniques on quartz minerals from extracted marine terraces. Several samples were collected from three orders of Quaternary marine terraces which are reproducible at all sampling location in between cities of Trabzon and Rize, Turkey, coastal of Eastern Pontides, at the front of the thrust system. The terrace deposits mainly consist of clays, silts, sands and gravels. The sediments in these deposits are mainly derived from basaltic, andesitic, and limestone geology, and have elipsoid, square and flat shapes. The terrace deposits have heights ranging from 1 to 17 meters and increases in height and thickness from west to east. Initial OSL results from 1 mm and 3 mm quartz aliquots demonstrate good luminescence characteristics. Preliminary equivalent dose analysis results ranging from 17.6 Gy to 79.6 Gy have been calculated using the Central Age Model (CAM) and Minimum Age Model (MAM). According to ages obtained from three separate terrace is ~8 ka, ~42 ka and ~78 ka, respectively. Results of marine terrace sediments indicate this region has three sedimentation periods and coastal region of Pontides has been remarkably tectonically active since latest Pleistocene to earlier Holocene. This study will present preliminary OSL dating results obtained from samples of Quaternary marine terrace formation. Keywords: optically stimulated luminescence (OSL) dating, single grain, marine terraces, Eastern Pontides.

  6. Nutrient dynamics in tropical rivers, lagoons, and coastal ecosystems of eastern Hainan Island, South China Sea

    NASA Astrophysics Data System (ADS)

    Li, R. H.; Liu, S. M.; Li, Y. W.; Zhang, G. L.; Ren, J. L.; Zhang, J.

    2014-01-01

    Nutrient dynamics based on field observations made along the eastern Hainan Island during the period 2006-2009 were investigated to understand nutrient biogeochemical processes, and to provide an overview of human perturbations of coastal ecosystems in this tropical region. The rivers showed seasonal variations in nutrient concentrations, with enrichment of dissolved inorganic nitrogen and dissolved silicate, and depletion of PO43-. High riverine concentrations of nitrate mainly originated from agricultural fertilizer inputs. The DIN : PO43- ratios ranged from 37 to 1063, suggesting preferential depletion of PO43- relative to nitrogen in rivers. Chemical weathering in the drainage area might explain the high levels of dissolved silicate. Aquaculture ponds contained high concentrations of NH4+ and dissolved organic nitrogen. The particulate phosphorus concentrations in the study area were lower than those reported for estuaries worldwide. The particulate silicate levels in rivers and lagoons were lower than the global average level. Nutrient biogeochemistry in coastal areas was affected by human activities (e.g., aquaculture, agriculture), and by natural phenomena including typhoons. The nutrient concentrations in coastal waters were low because of dispersion of land-derived nutrients in the sea. Nutrient budgets were built based on a steady-state box model, which showed that riverine fluxes are magnified by estuarine processes (e.g., regeneration, desorption) in estuaries and Laoyehai Lagoon, but not in Xiaohai Lagoon. Riverine and groundwater inputs were the major sources of nutrients to Xiaohai and Laoyehai lagoons, respectively, and riverine inputs and aquaculture effluents were the major sources for the eastern coast of Hainan Island. Nutrient inputs to the coastal ecosystem increased with typhoon-induced runoff of rainwater, elucidating the important influence of typhoons on small tropical rivers.

  7. High-resolution Holocene paleoclimatic events from the Southern-eastern Tyrrhenian Sea (Salerno Gulf)

    NASA Astrophysics Data System (ADS)

    Lirer, F.; Sprovieri, M.; Ferraro, L.; Vallefuoco, M.; Cascella, A.; Pelosi, N.; Capotondi, L.

    2012-12-01

    A high-resolution paleoclimatic study is here presented for the Holocene in the southern-eastern Tyrrhenian Sea, based on calcareous plankton taxa (planktonic foraminifera and calcareous nannofossils) distribution, δ18OG.ruber record, tephrostratigraphy and various dating methods (210Pb and 137Cs, AMS 14C) for a composite sediment core (from the top to the bottom, C90_1m, C90 and C836, water depth 103 mbsl) from the continental shelf of the Salerno Gulf. High sedimentation rates of ca. 1cm/100 yr (base Holocene) to ca 20cm/100 yr (present day), make this area an ideal marine archive of millennial/secular paleoclimate changes. In the early Holocene the study marine sedimentary archive recorded the climatic phases (S1a, S1i and S1b) associated to the deposition of the anoxic event Sapropel S1 in the eastern Mediterranean Sea (4.7 kyr long). In particular, the cold global event reported at 8.2 ka BP by Rohling and Pälike (2005), correlable to the Sapropel S1 interruption (S1i), in here recorded by strong increase in abundances of planktonic foraminifera N. pachyderma right coiled and of calcareous nannofossils B. bigelowii. This event is strongly supported by positive δ18O G.ruber excursion (~0.6 ‰). Upwards to ca 2000 yrs BP (Eneolithic to Golden age), δ18O G.ruber signal combined with calcareous plankton data suggest the occurrence of three Rapid Climatic Chance (RCC), superimposed to short-tern oscillations, those correspond to main changes in geochemical and biological proxies. During the last 2000 yrs BP (Roman period to present day), the planktonic foraminifera show two main turnovers in abundance: from herbivore-opportunistic species to carnivore species at ca 79AD and a progressive turnover between carnivore species and herbivore-opportunistic species at 1462 AD (Medieval Warm Period-Little Ice Age transition). Finally, the onset of a new important cool climatic phase (between 1462 AD and 1940 AD), the so-called Little Ice Age (LIA), expressed in the

  8. Geological and geomechanical properties of the carbonate rocks at the eastern Black Sea Region (NE Turkey)

    NASA Astrophysics Data System (ADS)

    Ersoy, Hakan; Yalçinalp, Bülent; Arslan, Mehmet; Babacan, Ali Erden; Çetiner, Gözde

    2016-11-01

    Turkey located in the Alpine-Himalayan Mountain Belt has 35% of the natural stone reserves of the world and has good quality marble, limestone, travertine and onyx reserves especially in the western regions of the country. The eastern Black Sea Region with a 1.4 million meters cubes reserve has a little role on the natural stone production in the country. For this reason, this paper deals with investigation on the potential of carbonate stone in the region and determination of the geological and geo-mechanical properties of these rocks in order to provide economic contribution to the national economy. While the study sites are selected among the all carbonate rock sites, the importance as well as the representative of the sites were carefully considered for the region. After representative samples were analyzed for major oxide and trace element compositions to find out petrochemical variations, the experimental program conducted on rock samples for determination of both physical and strength properties of the carbonate rocks. The results of the tests showed that there are significant variations in the geo-mechanical properties of the studied rock groups. The density values vary from 2.48 to 2.70 gr/cm3, water absorption by weight values range from 0.07 to 1.15% and the apparent porosity of the carbonate rocks are between 0.19 and 3.29%. However, the values of the UCS shows variation from 36 to 80 MPa. Tensile and bending strength values range from 3.2 to 7.5 MPa and 6.0-9.2 MPa respectively. Although the onyx samples have the lowest values of apparent porosity and water absorption by weight, these samples do not have the highest values of UCS values owing to occurrence of the micro-cracks. The UCS values of the rock samples were also found after cycling tests However, the limestone samples have less than 5% deterioration after freezing-thawing and wetting-drying tests, but travertine and onyx samples have more than 15% deterioration. Exception of the apparent

  9. Evidence of methane venting and geochemistry of brines on mud volcanoes of the eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Charlou, J. L.; Donval, J. P.; Zitter, T.; Roy, N.; Jean-Baptiste, P.; Foucher, J. P.; Woodside, J.; Medinaut Scientific Party

    2003-08-01

    As a part of the Dutch-French MEDINAUT diving expedition in 1998, cold seeps and mud volcanoes were studied and sampled in two distinctive tectonic settings in the eastern Mediterranean Sea. The first setting was the Olimpi Mud Volcano field (OMV area), including Napoli, Milano, Maidstone and Moscow mud volcanoes, south of Crete on the Mediterranean ridge. The second setting was the Anaximander Mountains (AM area), southwestern Turkey, where Amsterdam, Kazan and Kula mud volcanoes were explored. Large methane concentrations (45-892 nmol/kg) were measured in the water column not only above mud volcanoes but also in seeps and vents along related fault systems, indicating intense degassing related to fluid circulation in sediments. The tracer results show that there is considerable variability in terms of gas seepage and matter flux between these mud volcanoes. Brine accumulations found as shallow pools on Napoli or associated with deep faults (Nadir Lake) outside mud volcanoes exhibit variable chlorinity, mineral and gas composition. The brines are significantly enriched in δ18O relative to ambient seawater and are consistent with evaporated seawater. In the Nadir Brine Lake, the level of methane is as high as 5.93 mmol/kg, lower than the methane saturation level of 120 mmol/kg theoretically found at the salinity (120), pressure (200 bar), and temperature (13.6°C) conditions of Nadir lake. In contrast, the shallow brine pools on Napoli mud volcano (also OMV area) have methane levels of only 4.45 μmol/kg. In all brines, helium data show a clear radiogenic isotopic ratio ( R=0.06× Ra), in excellent agreement with recently published data for the Urania basin. Methane to ethane ratios (>1000) and δ13C(CH 4) values (-65.6‰PDB) indicate that the CH 4 is microbially produced. Unlike mid-ocean ridges, where abiogenic methane and helium have a common origin in the brines, the large variation in the CH 4/He ratio indicates that CH 4 and helium sources are unrelated, a

  10. Deep-sea fan deposition of the lower Tertiary Orca Group, eastern Prince William Sound, Alaska

    USGS Publications Warehouse

    Winkler, Gary R.

    1976-01-01

    textural changes probably indicate shallower water to the east. A radial distribution of paleocurrents and distinctive associations of turbidite facies within the sedimentary rocks suggest that the Orca Group in eastern Prince William Sound was deposited on a westward-sloping, complex deep-sea fan. Detritus was derived primarily from 'tectonized' sedimentary, volcanic, and plutonic rocks. Coeval submarine volcanism resulted in intercalation of basalt within prisms of terrigenous sediment.

  11. Expelled subsalt fluids form a pockmark field in the eastern Red Sea

    NASA Astrophysics Data System (ADS)

    Feldens, P.; Schmidt, M.; Mücke, I.; Augustin, N.; Al-Farawati, R.; Orif, M.; Faber, E.

    2016-10-01

    This study aimed to constrain the source area of fluids responsible for the formation of a pockmark field in the eastern Red Sea. The newly discovered field extends over an area of at least 1,000 km2 at a water depth of ~400 m. The pockmarks have modal diameters of 140-150 m and are either randomly distributed on the seafloor or aligned within valleys approximately 25 m deep and several kilometres in length. Seismic data show that chimneys and/or regions of acoustic turbidity prevail beneath the pockmark field down to the top of Miocene evaporites, which are widespread in the Red Sea. Four gravity cores were taken from the pockmark field. For most of the cores, geochemical analyses show that porewater has a higher Cl concentration than the local seawater and increased Cl/Br ratios, which indicate an origin from evaporites. The adsorbed hydrocarbons are of thermal origin, with C1/(C2+C3) ratios between 4 and 23 and stable carbon isotope data for methane varying from δ13C of -34 to -36.4‰ with respect to Vienna Pee Dee Belemnite. On the basis of the calculated maturity of the source rock of 1.2-1.4 Ro, local thermal gradients and sedimentation rates, its deeper depth boundary is approximated at 2,000 to 2,200 m. The results indicate that the adsorbed hydrocarbons sampled at the seafloor had to pass through an evaporite sequence of potentially several hundred metres to a few km in thickness. The most likely explanation for the increased permeability of the evaporite sequence is brittle deformation triggered by extensive local tectonic movements and supported by high fluid overpressure within the evaporite sequence.

  12. Composition and dynamics of the phytoplankton of the Ionian Sea (eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Casotti, R.; Landolfi, A.; Brunet, C.; D'Ortenzio, F.; Mangoni, O.; Ribera D'Alcalã, M.; Denis, M.

    2003-09-01

    The relationship between phytoplankton distribution and dynamics, and the resident water masses in the Ionian Sea was investigated in the spring of 1999 by flow cytometry, HPLC, microscopy, 14C incorporation, and serial dilutions. More than 50% of total biomass was represented by ultraphytoplankton, with proportions increasing with depth (up to 80%) and eastward (up to 60%). Synechococcus sp. cyanobacteria dominated ultraphytoplankton numbers and biomass. Hydrological stability explained the relative vertical distribution of Synechococcus sp. and Prochlorococcus sp. cyanobacteria and their degree of photoacclimation. The northwestern area ("Italian Side") was in a transition from bloom to oligotrophic conditions, reflected in high biological instability in terms of phytoplankton composition, photoacclimative properties, and photosynthetic efficiency (P/B of 11.40 mg C mg chl-1 h-1). The influence of the Adriatic Surface Water, carrying a trace of the spring bloom was visible from satellite imagery (SeaWiFS). The eastern part of the sampled area ("Greek Side," GS) was hydrologically more stable (low estimated vertical velocities), resulting in higher photosynthetic efficiency (P/B of 20.47 mg C mg chl-1 h-1) and phytoplankton photoacclimative properties. The Atlantic Water (AW) was the most oligotrophic in terms of nutrient concentration, chla, and productivity (208.0 mg C m-2 d-1), but also the most variable in terms of mesoscale features. Growth of Synechococcus sp. and Prochlorococcus sp. was slow (0.36 d-1 at max), while picoeukaryotes grew well in the deep chlorophyll maximum (DCM) of the GS (0.67 d-1) Picoeukaryote growth was tightly coupled with grazing (0.80 d-1), indicating efficient biomass recycling. Biological characterization and DCM dynamics in the three areas are discussed in relation to physical features present at the time of sampling.

  13. Response of subsurface waters in the eastern Arabian Sea to tropical cyclones

    NASA Astrophysics Data System (ADS)

    Rao, A. D.; Joshi, Madhu; Jain, Indu; Ravichandran, M.

    2010-11-01

    Thermister chain data at different depths for June 1998 cyclone in the Arabian Sea at a location (69.2 E,15.5 N) which is about 60 km to the left of the cyclone track indicates subsurface warming below 60 m and inertial oscillations of temperature with a periodicity of about 2 days. The oscillations continued for ˜15 days even after the cyclone crossed the coast. The analysis of the buoy, DS1 located at the same position also suggests a stabilized southward flow after about two weeks of the cyclone crossed the coast. Analysis of the buoy data for May 1999 cyclone in the same region also indicates similar pattern. In order to investigate the effect of cyclone-ocean interaction and primarily to understand the process for the subsurface warming, 3-dimensional Princeton Ocean Model is configured for the eastern part of the Arabian Sea. The model uses high horizontal resolution of about 6 km near the coast and a terrain following sigma coordinate in the vertical with 26 levels. The study focuses on surface cooling and temperature rise in the underlying waters and explains its mechanism through upwelling and downwelling respectively. The simulations in concurrence with the observations suggest that the occurrence of subsurface warming precedes the surface cooling with a lag of ˜a day as the cyclone advances DS1. The simulations also demonstrate local temperature stratification plays an important role for cooling of the upper ocean and warming of the subsurface waters and extent of warming is directly related to the depth of the thermocline.

  14. Expelled subsalt fluids form a pockmark field in the eastern Red Sea

    NASA Astrophysics Data System (ADS)

    Feldens, P.; Schmidt, M.; Mücke, I.; Augustin, N.; Al-Farawati, R.; Orif, M.; Faber, E.

    2016-05-01

    This study aimed to constrain the source area of fluids responsible for the formation of a pockmark field in the eastern Red Sea. The newly discovered field extends over an area of at least 1,000 km2 at a water depth of ~400 m. The pockmarks have modal diameters of 140-150 m and are either randomly distributed on the seafloor or aligned within valleys approximately 25 m deep and several kilometres in length. Seismic data show that chimneys and/or regions of acoustic turbidity prevail beneath the pockmark field down to the top of Miocene evaporites, which are widespread in the Red Sea. Four gravity cores were taken from the pockmark field. For most of the cores, geochemical analyses show that porewater has a higher Cl concentration than the local seawater and increased Cl/Br ratios, which indicate an origin from evaporites. The adsorbed hydrocarbons are of thermal origin, with C1/(C2+C3) ratios between 4 and 23 and stable carbon isotope data for methane varying from δ13C of -34 to -36.4‰ with respect to Vienna Pee Dee Belemnite. On the basis of the calculated maturity of the source rock of 1.2-1.4 Ro, local thermal gradients and sedimentation rates, its deeper depth boundary is approximated at 2,000 to 2,200 m. The results indicate that the adsorbed hydrocarbons sampled at the seafloor had to pass through an evaporite sequence of potentially several hundred metres to a few km in thickness. The most likely explanation for the increased permeability of the evaporite sequence is brittle deformation triggered by extensive local tectonic movements and supported by high fluid overpressure within the evaporite sequence.

  15. Influence of chemosynthetic ecosystems on nematode community structure and biomass in the deep eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Lampadariou, N.; Kalogeropoulou, V.; Sevastou, K.; Keklikoglou, K.; Sarrazin, J.

    2013-08-01

    Mud volcanoes are a~special type of cold seeps where life is based on chemoautotrophic processes. They are considered to be extreme environments and are characterized by unique megafaunal and macrofaunal communities. However, very few studies on mud volcanoes taking into account the smaller meiobenthic communities have been carried out. Two mud volcanoes were explored during the MEDECO (MEditerranean Deep-sea ECOsystems) cruise (2007) with the remotely operated vehicle (ROV) Victor-6000: Amsterdam, located south of Turkey between 1700 and 2000 m depth (Anaximander mud field); and Napoli, south of Crete, located along the Mediterranean Ridge at about 2000 m depth (Olimpi mud field). The major aim of this study was to describe distributional patterns of meiofaunal communities and nematode assemblages from different seep microhabitats. Meiofaunal taxa and nematode assemblages at both mud volcanoes differed significantly from other Mediterranean sites in terms of standing stocks, dominance and species diversity. Density and biomass values were significantly higher at the seep sites, particularly at Amsterdam. Patterns of nematode diversity, the dominant meiofaunal taxon, varied, displaying both very high or very low species richness and dominance, depending on the microhabitat studied. The periphery of the Lamellibrachia and bivalve shell microhabitats of Napoli exhibited the highest species richness, while the reduced sediments of Amsterdam yielded a species-poor nematode community dominated by two successful species, one belonging to the genus Aponema and the other to the genus Sabatieria. Analysis of β-diversity showed that microhabitat heterogeneity of mud volcanoes contributed substantially to the total nematode species richness in the eastern Mediterranean Sea. These observations indicate a strong influence of mud volcanoes and cold-seep ecosystems on the meiofaunal communities and nematode assemblages.

  16. Spring and fall phytoplankton blooms in a productive subarctic ecosystem, the eastern Bering Sea, during 1995-2011

    NASA Astrophysics Data System (ADS)

    Sigler, Michael F.; Stabeno, Phyllis J.; Eisner, Lisa B.; Napp, Jeffrey M.; Mueter, Franz J.

    2014-11-01

    The timing and magnitude of phytoplankton blooms in subarctic ecosystems often strongly influence the amount of energy that is transferred through subsequent trophic pathways. In the eastern Bering Sea, spring bloom timing has been linked to ice retreat timing and production of zooplankton and fish. A large part of the eastern Bering Sea shelf (~500 km wide) is ice-covered during winter and spring. Four oceanographic moorings have been deployed along the 70-m depth contour of the eastern Bering Sea shelf with the southern location occupied annually since 1995, the two northern locations since 2004 and the remaining location since 2001. Chlorophyll a fluorescence data from the four moorings provide 37 realizations of a spring bloom and 33 realizations of a fall bloom. We found that in the eastern Bering Sea: if ice was present after mid-March, spring bloom timing was related to ice retreat timing (p<0.001, df=1, 24); if ice was absent or retreated before mid-March, a spring bloom usually occurred in May or early June (average day 148, SE=3.5, n=11). A fall bloom also commonly occurred, usually in late September (average day 274, SE=4.2, n=33), and its timing was not significantly related to the timing of storms (p=0.88, df=1, 27) or fall water column overturn (p=0.49, df=1, 27). The magnitudes of the spring and fall blooms were correlated (p=0.011, df=28). The interval between the spring and fall blooms varied between four to six months depending on year and location. We present a hypothesis to explain how the large crustacean zooplankton taxa Calanus spp. likely respond to variation in the interval between blooms (spring to fall and fall to spring).

  17. Granulomatous lesions in a wild mullet population from the eastern Ligurian Sea (Italy): mycobacteriosis vs. pseudotuberculosis.

    PubMed

    Varello, K; Prearo, M; Serracca, L; Meloni, D; Rossini, I; Righetti, M; Pezzolato, M; Fioravanti, M L; Ercolini, C; Bozzetta, E

    2014-06-01

    Mycobacterium spp. and Photobacterium damselae subsp. piscicida are recognized as the most frequent causative agents of granulomatous lesions in fish. Although frequent episodes of mycobacterial infections have been reported in wild fish worldwide, only sporadic cases have been documented to date in Italy. To investigate for the presence of lesions referable to mycobacteriosis and to identify the mycobacterial species involved, a total of 159 wild mullets were fished from the eastern coast of the Ligurian Sea, killed and necropsied. Liver and spleen samples were collected from all fish for histopathological and microbiological analyses. Molecular investigations for identification of Photobacterium damselae subsp. piscicida were performed. Gross examination revealed granulomatous lesions in one animal; microscopically, 42.14% of fish displayed granulomas with various histological features, 19.50% resulted positive at Ziehl-Neelsen staining, and were confirmed as mycobacterial lesions by culture. The identified colonies were characterized as M. fortuitum, M. abscessus, M. flavescens, M. chelonae, M. septicum and M. nonchromogenicum. In all, 35% of animals resulted positive for Photobacterium damselae subsp. piscicida. These data suggest widespread mycobacterial infection also by Photobacterium damselae subsp. piscicida infections in wild fish. Moreover, the pathogenicity of some mycobacterial species, previously considered as saprophytic, was demonstrated. PMID:23944162

  18. Interannual variability of winter eddy patterns in the eastern South China Sea

    NASA Astrophysics Data System (ADS)

    He, Yinghui; Xie, Jieshuo; Cai, Shuqun

    2016-05-01

    Merged altimetry data collected over 21 years are analyzed to study the interannual variability of winter eddy activities in the eastern South China Sea (SCS) associated with the El Niño-Southern Oscillation. Composite analyses of eddy probability reveal that a Luzon cold eddy (LCE) northwest of the Luzon Island, an anticyclonic eddy northwest of the Mindoro Island (referred as MAE) and a cyclonic eddy west of the Mindoro Island (referred as MCE) are common for winter. Further studies indicate that LCE and MAE weaken and MCE strengthens in El Niño winters, whereas data show the opposite behavior for La Niña winters. In addition, the geographical pattern of MAE and MCE in an El Niño winter is different from that in a La Niña winter. The interannual wind curl anomalies west of the Luzon and Mindoro Islands and the outflow from the SCS via the Mindoro Strait may be responsible for the interannual eddy variability.

  19. Assessment of big floods in the Eastern Black Sea Basin of Turkey.

    PubMed

    Yüksek, Ömer; Kankal, Murat; Üçüncü, Osman

    2013-01-01

    In this study, general knowledge and some details of the floods in Eastern Black Sea Basin of Turkey are presented. Brief hydro-meteorological analysis of selected nine floods and detailed analysis of the greatest flood are given. In the studied area, 51 big floods have taken place between 1955-2005 years, causing 258 deaths and nearly US $500,000,000 of damage. Most of the floods have occurred in June, July and August. It is concluded that especially for the rainstorms that have caused significantly damages, the return periods of the rainfall heights and resultant flood discharges have gone up to 250 and 500 years, respectively. A general agreement is observed between the return periods of rains and resultant floods. It is concluded that there has been no significant climate change to cause increases in flood harms. The most important human factors to increase the damage are determined as wrong and illegal land use, deforestation and wrong urbanization and settlement, psychological and technical factors. Some structural and non-structural measures to mitigate flood damages are also included in the paper. Structural measures include dykes and flood levees. Main non-structural measures include flood warning system, modification of land use, watershed management and improvement, flood insurance, organization of flood management studies, coordination between related institutions and education of the people and informing of the stakeholders.

  20. Fatal poisoning of chilhood in the Eastern Black Sea region of Turkey (2009-2013).

    PubMed

    Karadeniz, Hulya; Birincioglu, Ismail; Turna, Ozgur; Ketenci, Huseyin Cetin; Beyhun, Nazım Ercument

    2015-08-01

    Poisoning is a major problem worldwide among children. Nonetheless, the offending agent, the associated morbidity and mortality vary from place to place and show changes over a period of time. The aim of this study was to investigate the medico-legal paediatric autopsies of childhood poisonings in the Eastern Black Sea Region of Turkey. Reports of autopsies performed between 2009 and 2013 in the Morgue Department of the Council of Forensic Medicine. All medico-legal paediatric autopsies in Trabzon (n:1049) were retrospectively examined. The study comprised an investigation into 62 deaths from poisoning in children aged 0-18 years. The parameters of age, sex, toxic substance category and origin were evaluated. Poisoning accounted for 5.9% of the deaths of children aged 0-18 years. Of the 62 cases, 32 (51.6%) were male and 30 (48.4%) were female, giving a female to male ratio of 1/1.1. The primary causes of fatal poisoning in children were carbon monoxide (64.5%, n = 40), followed by drugs (16.1%, n = 10), insecticides (9.7%, n = 6), mushrooms (6.5%, n = 4), and snake venom (3.2%, n = 2). The results of this study implicated carbon monoxide poisoning as a serious risk factor for mortality in our region. Childhood poisoning may be prevented by public education and simple precautions in general.

  1. Geological structure of the deep eastern Mediterranean Sea (east of 25 Degrees E)

    SciTech Connect

    Montadert, L.; Sage, L.; Letouzey, J. )

    1988-08-01

    The deformation fronts of the Cyprus arc and the Mediterranean ridge, extending from the Turkey-Syria boundary to north Cyrenacia, are the southernmost superficial expression of the convergence between the Eurasian and African plates. They separate the Eastern Mediterranean deep basin into two different structural units: (1) A thrust belt, northward, with the presence of Cenozoic sedimentary basins which could be considered piggy-back basins (Iskenderun, Adana, Cilicia, and Antalya basins). These basins, filled by 4,000 to 6,000 m of Cenozoic sediments, lie on a substratum composed of south-vergent nappes emplaced between the Late Cretaceous and the late Miocene. (2) A foreland area, southward, where the thick Herodotus and Levantine sedimentary basins, relatively undeformed, lie on the passive and subsident African continental margin initiated during Late Triassic or early Liassic time. Due to the still-active collision between the thrust belt and the Erathosthenes seamount, Cyprus was uplifted and today represents the emerged part of the deformation front. During the Messinian, with the isolation of the Mediterranean Sea, evaporitic deposits including a salt layer (sometimes more than 2,000 m thick) were widely distributed into the Iskenderun, Cilicia, Antalya, Levantine, and Herodotus basins. In these basins, the Messinian sedimentation was directly controlled by basin topography.

  2. Anomalous distribution of fluoride and phosphorus forms in surface sediments along eastern Egyptian Mediterranean Sea coast.

    PubMed

    El-Said, Ghada F; Khalil, Mona Kh; Draz, Suzanne E O

    2016-07-01

    The study focused on the distribution of fluoride, total phosphorus, and four phosphorus fractions in some sites along the Egyptian Mediterranean Sea coast. The geochemical parameters and textures of 30 surficial sediment samples from six sectors were determined. The sediment's geochemical parameters (total carbonates (TCO3) and total organic carbon (TOC), exchangeable and carbonate-associated phosphorus (Pex), iron- and aluminum-associated phosphorus (POH), calcium-associated phosphate/apatite (PHCl), residual phosphorus (PR), total phosphorus (TP), calcium (Cas), magnesium (Mgs), and fluoride (Fs)) showed variable values. The rank of phosphorus fractions in the sediments PHCl > PR > POH > Pex reflected that the eastern Egyptian coast was still uncontaminated. Generally, Pex levels gave a gradual increase in the offshore direction, while POH values varied along the stations of each sector. Also, the presented data indicated that the apatite-P fraction was the main storage of the phosphate in the sediments with a contribution to TP ranging from 58 to 87 %. The highest and lowest average fluoride contents (0.49 ± 0.10 and 0.25 ± 0.31 mg/g) were determined in the Port Said and Damietta sectors, respectively. Interestingly, the variability of both phosphorus and fluoride levels in the investigated area seemed to be accompanied with the sediment's character beside the proximity to potential effluent sources. PMID:27053053

  3. Recruitment variation of eastern Bering Sea crabs: Climate-forcing or top-down effects?

    NASA Astrophysics Data System (ADS)

    Zheng, Jie; Kruse, Gordon H.

    2006-02-01

    During the last three decades, population abundances of eastern Bering Sea (EBS) crab stocks fluctuated greatly, driven by highly variable recruitment. In recent years, abundances of these stocks have been very low compared to historical levels. This study aims to understand recruitment variation of six stocks of red king ( Paralithodes camtschaticus), blue king ( P. platypus), Tanner ( Chionoecetes bairdi), and snow ( C. opilio) crabs in the EBS. Most crab recruitment time series are not significantly correlated with each other. Spatial distributions of three broadly distributed crab stocks (EBS snow and Tanner crabs and Bristol Bay red king crab) have changed considerably over time, possibly related in part to the regime shift in climate and physical oceanography in 1976-1977. Three climate-forcing hypotheses on larval survival have been proposed to explain crab recruitment variation of Bristol Bay red king crab and EBS Tanner and snow crabs. Some empirical evidence supports speculation that groundfish predation may play an important role in crab recruitment success in the EBS. However, spatial dynamics in the geographic distributions of groundfish and crabs over time make it difficult to relate crab recruitment strength to groundfish biomass. Comprehensive field and spatially explicit modeling studies are needed to test the hypotheses and better understand the relative importance and compound effects of bottom-up and top-down controls on crab recruitment.

  4. Anomalous distribution of fluoride and phosphorus forms in surface sediments along eastern Egyptian Mediterranean Sea coast.

    PubMed

    El-Said, Ghada F; Khalil, Mona Kh; Draz, Suzanne E O

    2016-07-01

    The study focused on the distribution of fluoride, total phosphorus, and four phosphorus fractions in some sites along the Egyptian Mediterranean Sea coast. The geochemical parameters and textures of 30 surficial sediment samples from six sectors were determined. The sediment's geochemical parameters (total carbonates (TCO3) and total organic carbon (TOC), exchangeable and carbonate-associated phosphorus (Pex), iron- and aluminum-associated phosphorus (POH), calcium-associated phosphate/apatite (PHCl), residual phosphorus (PR), total phosphorus (TP), calcium (Cas), magnesium (Mgs), and fluoride (Fs)) showed variable values. The rank of phosphorus fractions in the sediments PHCl > PR > POH > Pex reflected that the eastern Egyptian coast was still uncontaminated. Generally, Pex levels gave a gradual increase in the offshore direction, while POH values varied along the stations of each sector. Also, the presented data indicated that the apatite-P fraction was the main storage of the phosphate in the sediments with a contribution to TP ranging from 58 to 87 %. The highest and lowest average fluoride contents (0.49 ± 0.10 and 0.25 ± 0.31 mg/g) were determined in the Port Said and Damietta sectors, respectively. Interestingly, the variability of both phosphorus and fluoride levels in the investigated area seemed to be accompanied with the sediment's character beside the proximity to potential effluent sources.

  5. Comparative study of organohalogen contamination between two populations of Eastern Atlantic loggerhead sea turtles (Caretta caretta).

    PubMed

    Camacho, María; Boada, Luis D; Orós, Jorge; López, Pedro; Zumbado, Manuel; Almeida-González, Maira; Luzardo, Octavio P

    2013-12-01

    We evaluated the presence of 37 organohalogen contaminants in plasma samples from 162 juvenile and 197 adult loggerhead turtles (Caretta caretta) from the archipelagos of the Canary Islands and Cape Verde, respectively, and compared the contamination profiles found. We detected five organochlorine pesticides (OCP) and 16 polychlorinated biphenyls (PCBs). The concentrations of the two groups of contaminants were higher in turtles from the Canary Islands (OCPs, 1.04 vs. 0.37 ng/mL; PCBs, 1.92 vs. 0.08 ng/mL). We also observed a different profile of PCB contamination between the two populations. In addition, there was a negative correlation between body size and the total concentration of PCBs in the Canary Islands turtles, but not in turtles from Cape Verde. The present study presents the first data on the organochlorine contaminants (OCs) of live turtles from Canary Islands. In addition, we perform a comparison of the levels and profiles of OCs between these two different groups of loggerhead sea turtles from the Eastern Atlantic. PMID:24114274

  6. Multichannel seismic-reflection data collected in 1980 in the eastern Chukchi Sea

    USGS Publications Warehouse

    Grantz, Arthur; Mann, Dennis M.; May, Steven D.

    1986-01-01

    The U.S. Geological Survey (USGS) collected approximately 2,652 km of 24-channel seismic-reflection data in early September, 1980, over the continental shelf in the eastern Chukchi Sea (Fig. 1). The profiles were collected on the USGS Research Vessel S.P. Lee. The seismic energy source consisted of a tuned array of five airguns with a total volume of 1213 cubic inches of air compressed to approximately 1900 psi. The recording system consisted of a 24-channel, 2400 meter long streamer with a group interval of 100 m, and a GUS (Global Universal Science) model 4200 digital recording instrument. Shots were fired every 50 meters. Navigational control for the survey was provided by a Magnavox integrated navigation system using transit satellites and doppler-sonar augmented by Loran C (Rho-Rho). A 2-millisecond sampling rate was used in the field; the data were later desampled to 4-milliseconds during the demultiplexing process. 8 seconds data length was recorded. Processing was done at the USGS Pacific Marine Geology Multichannel Processing Center in Menlo Park, California, in the sequence: editing-demultiplexing, velocity analysis, CDP stacking, deconvolution-filtering, and plotting on an electrostatic plotter. Plate 1 is a trackline chart showing shotpoint navigation.

  7. The Boundary Layer Character of Tidal Currents in the Eastern Irish Sea

    NASA Astrophysics Data System (ADS)

    Elliott, A. J.

    2002-09-01

    The vertical profile of the tidal currents observed by a ship borne ADCP at a site in the eastern Irish Sea where the water depth is 50 m was logarithmic with height above the bed in the lower 50-60% of the water column except for periods of about 1 h either side of slack water. The maximum height of the boundary layer reached 40 m during the flood tide. The shearing stress, determined by the method of Bowden et al. (1959), showed a tendency to be uniform with height in the lower half of the water column while the eddy viscosity increased linearly away from the bed, scaling on κu*z where u* is the friction velocity. Both of these features are characteristic of the logarithmic profile region of a boundary layer flow. Estimates of zo, the roughness length, and CD, the bottom drag coefficient, were around 10-3 m and 2·4×10-3, consistent with the known character of the bed. The scatter in the derived boundary layer parameters was reduced significantly by averaging the data within 30-min intervals which suggests the presence of tidal eddies having periods comparable to the 5-min sampling period of the ADCP. Short period fluctuations in the flow were coherent over the lower 20 m of the water column and propagated vertically away from the bed.

  8. Chelidoperca stella, a new species of perchlet (Perciformes: Serranidae) from the Andaman Sea, eastern Indian Ocean.

    PubMed

    Matsunuma, Mizuki; Motomura, Hiroyuki

    2016-01-01

    A new species of serranid fish, Chelidoperca stella, is described on the basis of five specimens from the Andaman Sea in the eastern Indian Ocean. The species can be readily distinguished from all valid congeners by having fewer pored lateral-line scales (34 or 35 vs. 40-45 in the latter) and the pelvic fin white with several small yellow spots (vs. spots absent). The species is also characterized by having relatively high counts of small serrae on the posterior margins of the preopercle (33-43 serrae), interopercle (7-10) and subopercle (18-28), despite the small body size (51.7-61.8 mm SL). Although Chelidoperca stella resembles C. margaritifera in having 2.5 scale rows between lateral line and the sixth dorsal-fin spine base, a relatively wider interorbital region, and the interorbital scales not reaching a vertical through the orbit anterior margin, but differs by having the above-mentioned diagnostic characters plus a slightly shorter longest anal-fin soft ray [17.4-18.7 (mean 18.1) % SL vs. 22.6-26.4 (24.4) % SL in C. margaritifera]. PMID:27394461

  9. Phylogeographic patterns of Merodon hoverflies in the Eastern Mediterranean region: revealing connections and barriers.

    PubMed

    Ståhls, Gunilla; Vujić, Ante; Petanidou, Theodora; Cardoso, Pedro; Radenković, Snezana; Ačanski, Jelena; Pérez Bañón, Celeste; Rojo, Santos

    2016-04-01

    We investigated the phylogeographic patterns of Merodon species (Diptera, Syrphidae) in the Eastern Mediterranean. Ten species were sampled on five different islands and mainland sites as a minimum. All samples were screened for their mtDNA COI barcode haplotype diversity, and for some samples, we additionally generated genomic fingerprints. The recently established zoogeographic distribution categories classify these species as having (1) Balkan distribution; (2) Anatolian distribution; (3) continental areas and large islands distribution; and (4) with wide distribution. The ancestral haplotypes and their geographical localities were estimated with statistical parsimony (TCS). TCS networks identified as the ancestral haplotype samples that originated from localities situated within the distributional category of the species in question. Strong geographical haplotype structuring was detected for many Merodon species. We were particularly interested to test the relative importance of current (Aegean Sea) and past Mid-Aegean Trench) barriers to dispersal for Merodon flies in the Aegean. We employed phylogenetic β-diversity (Pβ total) and its partition in replacement (Pβ repl) and richness difference (Pβ rich) to test the importance of each explanatory variable (interisland distance, MAT, and island area) in interisland differences using partial Mantel tests and hierarchical partitioning of variation. β-Analyses confirmed the importance of both current and past barriers to dispersal on the evolution of group. Current interisland distance was particularly important to explain the replacement of haplotypes, while the MAT was driving differences in richness of haplotypes, revealing the MAT as a strong past barrier whose effects are still visible today in the phylogenetic history of the clade in the Aegean. These results support the hypothesis of a highly restricted dispersal and gene flow among Merodon populations between islands since late Pleistocene. Additionally

  10. Phylogeographic patterns of Merodon hoverflies in the Eastern Mediterranean region: revealing connections and barriers.

    PubMed

    Ståhls, Gunilla; Vujić, Ante; Petanidou, Theodora; Cardoso, Pedro; Radenković, Snezana; Ačanski, Jelena; Pérez Bañón, Celeste; Rojo, Santos

    2016-04-01

    We investigated the phylogeographic patterns of Merodon species (Diptera, Syrphidae) in the Eastern Mediterranean. Ten species were sampled on five different islands and mainland sites as a minimum. All samples were screened for their mtDNA COI barcode haplotype diversity, and for some samples, we additionally generated genomic fingerprints. The recently established zoogeographic distribution categories classify these species as having (1) Balkan distribution; (2) Anatolian distribution; (3) continental areas and large islands distribution; and (4) with wide distribution. The ancestral haplotypes and their geographical localities were estimated with statistical parsimony (TCS). TCS networks identified as the ancestral haplotype samples that originated from localities situated within the distributional category of the species in question. Strong geographical haplotype structuring was detected for many Merodon species. We were particularly interested to test the relative importance of current (Aegean Sea) and past Mid-Aegean Trench) barriers to dispersal for Merodon flies in the Aegean. We employed phylogenetic β-diversity (Pβ total) and its partition in replacement (Pβ repl) and richness difference (Pβ rich) to test the importance of each explanatory variable (interisland distance, MAT, and island area) in interisland differences using partial Mantel tests and hierarchical partitioning of variation. β-Analyses confirmed the importance of both current and past barriers to dispersal on the evolution of group. Current interisland distance was particularly important to explain the replacement of haplotypes, while the MAT was driving differences in richness of haplotypes, revealing the MAT as a strong past barrier whose effects are still visible today in the phylogenetic history of the clade in the Aegean. These results support the hypothesis of a highly restricted dispersal and gene flow among Merodon populations between islands since late Pleistocene. Additionally

  11. Methodology for filling gaps and forecast in sea level: Applications to the eastern English Channel and the North Atlantic Sea (western France)

    NASA Astrophysics Data System (ADS)

    Turki, Imen; Laignel, Benoit; Kakeh, Nabil; Chevalier, Laetitia; Costa, Stephane

    2014-05-01

    This research was carried out in the framework of the program Surface Water and Ocean Topography (SWOT) which is a partnership between NASA and CNES. Sea level is a key variable in marine, climate, and coastal process studies. In this research, a new methodology was implemented for filling gaps and forecasting the sea level by combining classical harmonic models to high statistical methods. In agreement with previous studies, this work indicates that sea level heights are correlated to climate conditions of sea level pressures (SLP). After averaging out surface waves from the mean sea level, the deterministic tides and the stochastic processes of residual surges were investigated using classical harmonic analyses and a statistical model of autoregressive moving average (ARMA), respectively. The estimation of the residual surges was also investigated together with the SLP. This new methodology was applied to the Atlantic sea and the eastern English Channel (western France). Results have shown that the developed model reproduces the observations with RMSE of 4.5 cm and 7 cm for 12 days and 30 days of gaps, respectively. For medium scales of 6 months, the RMSE reaches 9,2 cm. Larger scales more than 10 months were also statistically reproduced. Accordingly, the proposed model seems to be more promising for filling gaps and estimating the sea level at short- to large- time scales. This new methodology presents a coherent, simple, and easy tool to estimate the deterministic nature of tidal processes and the stochastic framework of residual surges. Key words: sea level forecast, astronomical tides, residual surges, ARMA, sea level pressure.

  12. Buried paleo-sedimentary basins in the north-eastern Black Sea-Azov Sea area and tectonic implications (DOBRE-2)

    NASA Astrophysics Data System (ADS)

    Starostenko, Vitaly; Stephenson, Randell; Janik, Tomasz; Tolkunov, Anatoly

    2014-05-01

    A number of independent but inter-related projects carried out under the auspices of various national and international programmes in Ukraine including DARIUS were aimed at imaging the upper lithosphere, crustal and sedimentary basin architecture in the north-eastern Black Sea, southern Crimea and Kerch peninsulas and the Azov Sea. This region marks the transition from relatively undisturbed Precambrian European cratonic crust and lithosphere north of the Azov Sea to areas of significant Phanerozoic tectonics and basin development, in both extensional as well as compressional environments, to the south, including the eastern Black Sea rift, which is the main sedimentary basin of the study area. The wide-angle reflection and refraction (WARR) profile DOBRE-2, a Ukrainian national project with international participation (see below), overlapping some 115 km of the southern end of the DOBREfraction'99 profile (that crosses the intracratonic Donbas Foldbelt) in the north and running to the eastern Black Sea basin in the south, utilised on- and offshore recording and energy sources. It maps crustal velocity structure across the craton margin and documents, among other things, that the Moho deepens from 40 km to ~47 km to the southwest below the Azov Sea and Crimean-Caucasus deformed zone. A regional CDP seismic profile coincident with DOBRE-2, crossing the Azov Sea, Kerch Peninsula and the north-eastern Black Sea southwest to the Ukraine-Turkey border, acquired by Ukrgeofisika (the Ukrainian national geophysical company) reveals in its inferred structural relationships the ages of Cretaceous and younger extensional and subsequent basin inversion tectonic events as well as the 2D geometry of basement displacement associated with post mid-Eocene inversion. A direct comparison of the results of the WARR velocity model and the near-vertical reflection structural image has been made by converting the former into the time domain. The results dramatically demonstrate that

  13. Integrated survey of elemental stoichiometry (C, N, P) from the Western to Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Pujo-Pay, M.; Conan, P.; Oriol, L.; Cornet-Barthaux, V.; Falco, C.; Ghiglione, J.-F.; Goyet, C.; Moutin, T.; Prieur, L.

    2010-10-01

    This paper provides an extensive vertical and longitudinal description of the biogeochemistry in the whole Mediterranean Sea during the summer 2008. During this strong stratified period, the distribution of nutrients, particulate and dissolved organic carbon (DOC), nitrogen (DON) and phosphorus (DOP) were investigated along a 3000 km transect (BOUM cruise) crossing the Western and Eastern Mediterranean basins. The partitioning of chemical C, N and P species among all these mineral and organic pools has been analysed to produce a detailed spatial and vertical extended examination of the elemental stoichiometry. Surface Mediterranean waters were depleted in nutrients and the thickness of this depleted layer increased towards the East from about 10 m in the Gulf of Lion to more than 100 m in the Levantine basin, concomitantly to the gradual deepening of the thermocline and nutriclines. We used threshold in oxygen concentration to discriminate the water column in three layers; surface (Biogenic Layer BL), intermediate (Mineralization Layer ML), and deep layer (DL) and to propose a schematic representation of biogeochemical fluxes between the different compartments and to compare the functioning of the two basins. The stoichiometry revealed a clear longitudinal and vertical gradient in the mineral fraction with a P-depletion evidenced on both dimension. As a consequence of the severe deficiency in phosphorus, the C:N:P ratios in all pools within the BL largely exceed the Redfield ratios. Despite these gradients, the deep estimated fluxes in the mineral compartment tend towards the canonical Redfield values in both basins. A change in particulate matter composition has been evidenced by a C increase relative to N and P along the whole water column in the western basin and between BL and ML in the eastern one. More surprisingly, a decrease in N relative to P with depth was encountered in the whole Mediterranean Sea. We suggest that there was a more rapid recycling of N

  14. A three-step model to assess shoreline and offshore susceptibility to oil spills: the South Aegean (Crete) as an analogue for confined marine basins.

    PubMed

    Alves, Tiago M; Kokinou, Eleni; Zodiatis, George

    2014-09-15

    This study combines bathymetric, geomorphological, geological data and oil spill predictions to model the impact of oil spills in two accident scenarios from offshore Crete, Eastern Mediterranean. The aim is to present a new three-step method of use by emergency teams and local authorities in the assessment of shoreline and offshore susceptibility to oil spills. The three-step method comprises: (1) real-time analyses of bathymetric, geomorphological, geological and oceanographic data; (2) oil dispersion simulations under known wind and sea current conditions; and (3) the compilation of final hazard maps based on information from (1) and (2) and on shoreline susceptibility data. The results in this paper show that zones of high to very-high susceptibility around the island of Crete are related to: (a) offshore bathymetric features, including the presence of offshore scarps and seamounts; (b) shoreline geology, and (c) the presence near the shore of sedimentary basins filled with unconsolidated deposits of high permeability. Oil spills, under particular weather and oceanographic conditions, may quickly spread and reach the shoreline 5-96 h after the initial accident. As a corollary of this work, we present the South Aegean region around Crete as a valid case-study for confined marine basins, narrow seaways, or interior seas around island groups. PMID:25113103

  15. A three-step model to assess shoreline and offshore susceptibility to oil spills: the South Aegean (Crete) as an analogue for confined marine basins.

    PubMed

    Alves, Tiago M; Kokinou, Eleni; Zodiatis, George

    2014-09-15

    This study combines bathymetric, geomorphological, geological data and oil spill predictions to model the impact of oil spills in two accident scenarios from offshore Crete, Eastern Mediterranean. The aim is to present a new three-step method of use by emergency teams and local authorities in the assessment of shoreline and offshore susceptibility to oil spills. The three-step method comprises: (1) real-time analyses of bathymetric, geomorphological, geological and oceanographic data; (2) oil dispersion simulations under known wind and sea current conditions; and (3) the compilation of final hazard maps based on information from (1) and (2) and on shoreline susceptibility data. The results in this paper show that zones of high to very-high susceptibility around the island of Crete are related to: (a) offshore bathymetric features, including the presence of offshore scarps and seamounts; (b) shoreline geology, and (c) the presence near the shore of sedimentary basins filled with unconsolidated deposits of high permeability. Oil spills, under particular weather and oceanographic conditions, may quickly spread and reach the shoreline 5-96 h after the initial accident. As a corollary of this work, we present the South Aegean region around Crete as a valid case-study for confined marine basins, narrow seaways, or interior seas around island groups.

  16. Increased sea level promotes coral cover on shallow reef flats in the Andaman Sea, eastern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Brown, B. E.; Dunne, R. P.; Phongsuwan, N.; Somerfield, P. J.

    2011-12-01

    Sea level in the Indian Ocean is subject to considerable temporal and spatial variabilities. During the period 1960-2009 at Phuket, Thailand, in the NE Indian Ocean, mean sea level increased by 2.7 mm y-1. Regular monitoring of coral cover on fringing reef flats at Phuket since 1979 revealed a sensitive response of this habitat to both transient sea-level depressions and sea-level elevation. Since 1987 when more frequent sampling began, coral cover was positively correlated with the mean sea level experienced over the preceding months. Changing mean sea level explained a high proportion of the observed variation in cover, with overall increasing sea levels and a lack of negative sea-level anomalies promoting cover on the outer reef flats. Concomitantly, there have been no changes in reef community structure or any apparent shifts in zonation patterns across the reef. While future benefits of continued increases in mean sea level on reef flats in the region will be constrained by the frequency and intensity of sea-level depressions associated with the Indian Ocean Dipole, and bleaching events, the overall picture for these shallow reefs is a positive one as they respond to increasing sea level and show rapid recovery from environmental disturbances.

  17. Changing Trends and Variance in Eastern Equatorial Pacific Sea Surface Temperatures over the Twentieth Century

    NASA Astrophysics Data System (ADS)

    Jimenez, G.; Cole, J. E.; Thompson, D. M.; Tudhope, A. W.

    2015-12-01

    Global climate models and instrumental datasets often disagree regarding sea surface temperature (SST) trends in the tropical Pacific. Coral Sr/Ca records with sub-seasonal resolution provide SST proxies that complement and extend limited instrumental records. We present a new partially replicated Sr/Ca-SST record from two Galápagos corals (Isla Wolf, at 1°24'N, 91°48'W), that spans 1937-2010. The record shows high SST variance in the region, which increases nearly twofold after the late 1970s. Similarly, there is little trend in the mean until 1976, after which SSTs warm during all seasons. Both the increase in variance and the trend are strongest during the warm season, leading to progressively more anomalous conditions during El Niño events. To investigate recent changes in the eastern equatorial Pacific since the 1976/1977 climate transition, we compare the Galápagos record to a published coral Sr/Ca-SST record from Clipperton Atoll (10°18'N, 109°13'W, spanning 1874-1993; Wu et al., 2014, Palaeogeogr. Palaeoclimatol. Palaeoecol.). As in the Galápagos, Clipperton corals show increasing SSTs in all seasons after 1976. The trend at Clipperton is greater than in the Galápagos, though the variance is smaller and does not change significantly throughout the record. Finally, the north-south temperature gradient between Clipperton and Galápagos has increased slightly over the interval in which the two records overlap (1937-1993). Gridded instrumental SST data generally agree with the coral Sr/Ca-SST results, though the gridded data suggest lower variance at both sites. In sum, we show that an increase in the mean and variance of SSTs in the eastern equatorial Pacific is associated with an enhanced meridional SST gradient over the twentieth century, and especially since 1976. These results contrast with recent suggestions that a weakened meridional SST gradient in the equatorial Pacific may be leading to stronger El Niño events. Our results support the

  18. Phylogenetic identification of marine bacteria isolated from deep-sea sediments of the eastern South Atlantic Ocean.

    PubMed

    da Silva, Marcus Adonai Castro; Cavalett, Angélica; Spinner, Ananda; Rosa, Daniele Cristina; Jasper, Regina Beltrame; Quecine, Maria Carolina; Bonatelli, Maria Letícia; Pizzirani-Kleiner, Aline; Corção, Gertrudes; Lima, André Oliveira de Souza

    2013-12-01

    The deep-sea environments of the South Atlantic Ocean are less studied in comparison to the North Atlantic and Pacific Oceans. With the aim of identifying the deep-sea bacteria in this less known ocean, 70 strains were isolated from eight sediment samples (depth range between 1905 to 5560 m) collected in the eastern part of the South Atlantic, from the equatorial region to the Cape Abyssal Plain, using three different culture media. The strains were classified into three phylogenetic groups, Gammaproteobacteria, Firmicutes and Actinobacteria, by the analysis of 16s rRNA gene sequences. Gammaproteobacteria and Firmicutes were the most frequently identified groups, with Halomonas the most frequent genus among the strains. Microorganisms belonging to Firmicutes were the only ones observed in all samples. Sixteen of the 41 identified operational taxonomic units probably represent new species. The presence of potentially new species reinforces the need for new studies in the deep-sea environments of the South Atlantic.

  19. A new hybrid model for filling gaps and forecast in sea level: application to the eastern English Channel and the North Atlantic Sea (western France)

    NASA Astrophysics Data System (ADS)

    Turki, Imen; Laignel, Benoit; Kakeh, Nabil; Chevalier, Laetitia; Costa, Stephane

    2015-04-01

    This research is carried out in the framework of the program Surface Water and Ocean Topography (SWOT) which is a partnership between NASA and CNES. Here, a new hybrid model is implemented for filling gaps and forecasting the hourly sea level variability by combining classical harmonic analyses to high statistical methods to reproduce the deterministic and stochastic processes, respectively. After simulating the mean trend sea level and astronomical tides, the nontidal residual surges are investigated using an autoregressive moving average (ARMA) methods by two ways: (1) applying a purely statistical approach and (2) introducing the SLP in ARMA as a main physical process driving the residual sea level. The new hybrid model is applied to the western Atlantic sea and the eastern English Channel. Using ARMA model and considering the SLP, results show that the hourly sea level observations of gauges with are well reproduced with a root mean square error (RMSE) ranging between 4.5 and 7 cm for 1 to 30 days of gaps and an explained variance more than 80 %. For larger gaps of months, the RMSE reaches 9 cm. The negative and the positive extreme values of sea levels are also well reproduced with a mean explained variance between 70 and 85 %. The statistical behavior of 1-year modeled residual components shows good agreements with observations. The frequency analysis using the discrete wavelet transform illustrate strong correlations between observed and modeled energy spectrum and the bands of variability. Accordingly, the proposed model presents a coherent, simple, and easy tool to estimate the total sea level at timescales from days to months. The ARMA model seems to be more promising for filling gaps and estimating the sea level at larger scales of years by introducing more physical processes driving its stochastic variability.

  20. Eastern margin of the Ross Sea Rift in western Marie Byrd Land, Antarctica: Crustal structure and tectonic development

    NASA Astrophysics Data System (ADS)

    Luyendyk, Bruce P.; Wilson, Douglas S.; Siddoway, Christine S.

    2003-10-01

    The basement rock and structures of the Ross Sea rift are exposed in coastal western Marie Byrd Land (wMBL), West Antarctica. Thinned, extended continental crust forms wMBL and the eastern Ross Sea continental shelf, where faults control the regional basin-and range-type topography at ˜20 km spacing. Onshore in the Ford Ranges and Rockefeller Mountains of wMBL, basement rocks consist of Early Paleozoic metagreywacke and migmatized equivalents, intruded by Devonian-Carboniferous and Cretaceous granitoids. Marine geophysical profiles suggest that these geological formations continue offshore to the west beneath the eastern Ross Sea, and are covered by glacial and glacial marine sediments. Airborne gravity and radar soundings over wMBL indicate a thicker crust and smoother basement inland to the north and east of the northern Ford Ranges. A migmatite complex near this transition, exhumed from mid crustal depths between 100-94 Ma, suggests a profound crustal discontinuity near the inboard limit of extended crust, ˜300 km northeast of the eastern Ross Sea margin. Near this limit, aeromagnetic mapping reveals an extensive region of high amplitude anomalies east of the Ford ranges that can be interpreted as a sub ice volcanic province. Modeling of gravity data suggests that extended crust in the eastern Ross Sea and wMBL is 8-9 km thinner than interior MBL (β = 1.35). Gravity modeling also outlines extensive regions of low-density (2300-2500 kg m-3) buried basement rock that is lighter than rock exposed at the surface. These regions are interpreted as bounded by throughgoing east-west faults with vertical separation. These buried low-density rocks are possibly a low-density facies of Early Paleozoic metagreywacke, or the low-density epizonal facies of Cretaceous granites, or felsic volcanic rocks known from moraines. These geophysical features and structures on land in the wMBL region preserve the record of middle and Late Cretaceous development of the Ross Sea rift

  1. Ensemble-based evaluation of extreme water levels for the eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Eelsalu, Maris; Soomere, Tarmo

    2016-04-01

    The risks and damages associated with coastal flooding that are naturally associated with an increase in the magnitude of extreme storm surges are one of the largest concerns of countries with extensive low-lying nearshore areas. The relevant risks are even more contrast for semi-enclosed water bodies such as the Baltic Sea where subtidal (weekly-scale) variations in the water volume of the sea substantially contribute to the water level and lead to large spreading of projections of future extreme water levels. We explore the options for using large ensembles of projections to more reliably evaluate return periods of extreme water levels. Single projections of the ensemble are constructed by means of fitting several sets of block maxima with various extreme value distributions. The ensemble is based on two simulated data sets produced in the Swedish Meteorological and Hydrological Institute. A hindcast by the Rossby Centre Ocean model is sampled with a resolution of 6 h and a similar hindcast by the circulation model NEMO with a resolution of 1 h. As the annual maxima of water levels in the Baltic Sea are not always uncorrelated, we employ maxima for calendar years and for stormy seasons. As the shape parameter of the Generalised Extreme Value distribution changes its sign and substantially varies in magnitude along the eastern coast of the Baltic Sea, the use of a single distribution for the entire coast is inappropriate. The ensemble involves projections based on the Generalised Extreme Value, Gumbel and Weibull distributions. The parameters of these distributions are evaluated using three different ways: maximum likelihood method and method of moments based on both biased and unbiased estimates. The total number of projections in the ensemble is 40. As some of the resulting estimates contain limited additional information, the members of pairs of projections that are highly correlated are assigned weights 0.6. A comparison of the ensemble-based projection of

  2. Petrophysical Properties Of Sandy Sediments Possibly Hosting Gas Hydrate In The Eastern Margin Of Japan Sea

    NASA Astrophysics Data System (ADS)

    Uchida, T.; Takashima, I.; Sunaga, H.; Sasaki, S.; Matsumoto, R.

    2011-12-01

    In 2010 the MD179 project was undertaken by the Marion Dufresne aiming at recovery of deep seated gas and gas hydrate, methane induced carbonate, and deep sediments older than 300 ka in order to develop geologic model of gas hydrate accumulation and evaluate the possible environmental impact of gas hydrate for the last glacial-interglacial cycles. Sediment samples below the seafloor were obtained in the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas by the MD179 cruise. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene silty layers, where trace fossils and strong bioturbations are commonly observed. Those sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these arenite sands were undertaken, which indicatesd that porosities of muddy sediments are around 50 % but those of arenites range from 42 to 52 %, of which mean pore sizes and permeabilities are larger than those of siltstones and mudstones. These coarser sediments might have been transported approximately around 3 to 30 ka, where supplying sediments may not be abundant due to sea level fluctuation during the Pleistocene ice age. While the presence of gas hydrate in intergranular pores of arenite sands has not been confirmed, the soupy occurrence in recovered sediments may strongly indicate the presence of gas hydrate filling the intergranular pore system of arenite sands that is called pore-space hydrates. They have been recognized till now in the Mallik as well as in the Nankai Trough areas, which are considered to be very common even in the subsurface sandy sediments at the eastern margin of Japan Sea. Concentration of gas hydrate may need primary intergranular pores large enough to occur within a host sediment that may be arenite sand without matrix grains deposited in the sedimentary

  3. Estimates of Eastern Equatorial Pacific Sea Surface Temperatures During the Pliocene From Carbonate 'Clumped Isotope' Thermometry

    NASA Astrophysics Data System (ADS)

    Thiagarajan, N.; Tripati, A.; Eiler, J.

    2007-12-01

    The early Pliocene (5 to 3 Ma) was an interval in Earth history that was globally warmer than the present; thus, study of the details of Pliocene climate can provide insights into the dynamics of warm climates. There are two competing models of the temperature structure of the tropical Pacific upper-ocean during the early Pliocene: the dynamical 'ocean thermostat' model [1,2] and the 'El Padre' (or permanent 'El Nino') model [3], each of which predict zonal temperature gradients and mean conditions in the Eastern Equatorial Pacific (EEP), and which differ markedly from one another in these predictions. The dynamical 'ocean thermostat' model predicts an increased temperature contrast between the Western Equatorial Pacific (WEP) and EEP, enhanced thermocline tilt and intensified upwelling under warmer conditions. In contrast, the 'El Padre' model postulates a collapse of the zonal temperature gradient, reduced thermocline tilt and a reduction in upwelling and/or warmer temperatures of upwelled waters. Existing reconstructions of tropical temperatures produce WEP sea surface temperatures which agree with each other, but yield very different results in the EEP [4,5]. We have reconstructed EEP sea surface temperatures at Ocean Drilling Program (ODP) Site 847 using a few samples spanning key intervals of the last 6 million years using carbonate clumped isotope thermometer [6,7,8]. This technique is based on the temperature dependence of the abundances of 13C-18O bonds in carbonate minerals. Initial measurements of planktonic foraminifera and coccoliths from ODP Site 847 indicate cool EEP sea surface temperatures, supporting models of Pliocene climate that have enhanced zonal temperature gradients, relative to modern. Analyses of Globigerinoides sacculifer (with sac) from sediments indicate calcification temperatures of 20.3°C ± 0.1°C and seawater δ18O values of -0.8‰ ± 0.1‰ from ~6.1 to 5.1 million years ago. Measurements of a mixed coccolith assemblage from the

  4. Hydrography and biogeochemistry of the north western Bay of Bengal and the north eastern Arabian Sea during winter monsoon

    NASA Astrophysics Data System (ADS)

    Balachandran, K. K.; Laluraj, C. M.; Jyothibabu, R.; Madhu, N. V.; Muraleedharan, K. R.; Vijay, J. G.; Maheswaran, P. A.; Ashraff, T. T. M.; Nair, K. K. C.; Achuthankutty, C. T.

    2008-09-01

    The north eastern Arabian Sea and the north western Bay of Bengal within the Indian exclusive economic zone were explored for their environmental characteristics during the winter monsoons of 2000 and 2001 respectively. The two regions were found to respond paradoxically to comparable intensities of the atmospheric forcing. There is an asymmetry in the net heat exchange of these two basins with atmosphere because of the varying thickness of barrier layer. During winter, the convective mixing in the Arabian Sea is driven by net heat loss from the ocean, whereas the Bay of Bengal does not contribute to such large heat loss to the atmosphere. It appears that the subduction of high saline Arabian Sea water mass is the mechanism behind the formation of a barrier layer in the northeast Arabian Sea; whereas that in the Bay of Bengal and the southeast Arabian Sea are already established as due to low saline water mass. The weak barrier layer in the Arabian Sea yields to the predominance of convective mixing to bring in nitrate-rich waters from the deeper layers to the surface, thereby supporting enhanced biological production. On the other hand, the river discharge into the Bay of Bengal during this period results in the formation of a thick and stable barrier layer, which insulates vertical mixing and provide oligotrophic condition in the Bay.

  5. New techniques on oil spill modelling applied in the Eastern Mediterranean sea

    NASA Astrophysics Data System (ADS)

    Zodiatis, George; Kokinou, Eleni; Alves, Tiago; Lardner, Robin

    2016-04-01

    Small or large oil spills resulting from accidents on oil and gas platforms or due to the maritime traffic comprise a major environmental threat for all marine and coastal systems, and they are responsible for huge economic losses concerning the human infrastructures and the tourism. This work aims at presenting the integration of oil-spill model, bathymetric, meteorological, oceanographic, geomorphological and geological data to assess the impact of oil spills in maritime regions such as bays, as well as in the open sea, carried out in the Eastern Mediterranean Sea within the frame of NEREIDs, MEDESS-4MS and RAOP-Med EU projects. The MEDSLIK oil spill predictions are successfully combined with bathymetric analyses, the shoreline susceptibility and hazard mapping to predict the oil slick trajectories and the extend of the coastal areas affected. Based on MEDSLIK results, oil spill spreading and dispersion scenarios are produced both for non-mitigated and mitigated oil spills. MEDSLIK model considers three response combating methods of floating oil spills: a) mechanical recovery using skimmers or similar mechanisms; b) destruction by fire, c) use of dispersants or other bio-chemical means and deployment of booms. Shoreline susceptibility map can be compiled for the study areas based on the Environmental Susceptibility Index. The ESI classification considers a range of values between 1 and 9, with level 1 (ESI 1) representing areas of low susceptibility, impermeable to oil spilt during accidents, such as linear shorelines with rocky cliffs. In contrast, ESI 9 shores are highly vulnerable, and often coincide with natural reserves and special protected areas. Additionally, hazard maps of the maritime and coastal areas, possibly exposed to the danger on an oil spill, evaluate and categorize the hazard in levels from low to very high. This is important because a) Prior to an oil spill accident, hazard and shoreline susceptibility maps are made available to design

  6. Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea

    PubMed Central

    Pilfold, Nicholas W.; Derocher, Andrew E.; Stirling, Ian; Richardson, Evan; Andriashek, Dennis

    2012-01-01

    Background Polar bears (Ursus maritimus) of the Beaufort Sea enter hyperphagia in spring and gain fat reserves to survive periods of low prey availability. We collected information on seals killed by polar bears (n = 650) and hunting attempts on ringed seal (Pusa hispida) lairs (n = 1396) observed from a helicopter during polar bear mark-recapture studies in the eastern Beaufort Sea in spring in 1985–2011. We investigated how temporal shifts in ringed seal reproduction affect kill composition and the intraspecific vulnerabilities of ringed seals to polar bear predation. Principal Findings Polar bears primarily preyed on ringed seals (90.2%) while bearded seals (Erignathus barbatus) only comprised 9.8% of the kills, but 33% of the biomass. Adults comprised 43.6% (150/344) of the ringed seals killed, while their pups comprised 38.4% (132/344). Juvenile ringed seals were killed at the lowest proportion, comprising 18.0% (62/344) of the ringed seal kills. The proportion of ringed seal pups was highest between 2007–2011, in association with high ringed seal productivity. Half of the adult ringed seal kills were ≥21 years (60/121), and kill rates of adults increased following the peak of parturition. Determination of sex from DNA revealed that polar bears killed adult male and adult female ringed seals equally (0.50, n = 78). The number of hunting attempts at ringed seal subnivean lair sites was positively correlated with the number of pup kills (r2 = 0.30, P = 0.04), but was not correlated with the number of adult kills (P = 0.37). Conclusions/Significance Results are consistent with decadal trends in ringed seal productivity, with low numbers of pups killed by polar bears in spring in years of low pup productivity, and conversely when pup productivity was high. Vulnerability of adult ringed seals to predation increased in relation to reproductive activities and age, but not gender. PMID:22829949

  7. Maturity data record inversion of the Sorgenfrei-Tornquist Zone of the eastern North Sea

    NASA Astrophysics Data System (ADS)

    Nielsen, Søren B.; Clausen, Ole R.

    2015-04-01

    The dynamic analysis of major tectonic inversion structures is generally founded on structural and stratigraphic observations and may be predicted by numerical models of compressional basin inversion. Here we show that the dynamics of an inversion zone can be constrained by using thermal maturity data such as present day borehole temperature, vitrinite reflectance, AFT and general stratigraphic information in deep boreholes in combination with basin modelling software. Basin formation in the eastern North Sea was initiated during the Paleozoic and ensuing episodic rifting took place during the Mesozoic followed by thermal subsidence and localized inversion during the late Mesozoic and early Cenozoic. The Sorgenfrei-Tornquist Zone (STZ) is a very prominent structural feature (strike slip zone) roughly separating the Fennoscandian area from the North Sea Basin. Change of regional trans-tension to trans-pression caused extensive inversion in Europe and along the STZ during the late Cretaceous, producing deep erosion in places along the inversion axes and simultaneous formation of loading-induced marginal troughs. Also predicted is a different style of inversion - relaxation inversion - which occurs once compression ceases. The relaxation inversion mode involves no shortening and is characterised by gentle low-amplitude doming of a wider area with only little erosion of the inversion ridge and formation of shallow and more distal marginal troughs. It has been argued from a range of evidences that relaxation inversion provides the best explanation for the mid Paleocene inversion phase in Europe. In the present study we have analysed and modelled wells on the inversion axis of the STZ and in the marginal troughs and the results show that wells influenced by the STZ inversion axis was subject to deep erosion during the late Cretaceous, and that no Cenozoic erosion is required. Furthermore, two deep geothermal test wells with excellent temperature and maturity data located

  8. Mitochondrial DNA Reveals Genetic Structuring of Pinna nobilis across the Mediterranean Sea

    PubMed Central

    Sanna, Daria; Cossu, Piero; Dedola, Gian Luca; Scarpa, Fabio; Maltagliati, Ferruccio; Castelli, Alberto; Franzoi, Piero; Lai, Tiziana; Cristo, Benedetto; Curini-Galletti, Marco; Francalacci, Paolo; Casu, Marco

    2013-01-01

    Pinna nobilis is the largest endemic Mediterranean marine bivalve. During past centuries, various human activities have promoted the regression of its populations. As a consequence of stringent standards of protection, demographic expansions are currently reported in many sites. The aim of this study was to provide the first large broad-scale insight into the genetic variability of P. nobilis in the area that encompasses the western Mediterranean, Ionian Sea, and Adriatic Sea marine ecoregions. To accomplish this objective twenty-five populations from this area were surveyed using two mitochondrial DNA markers (COI and 16S). Our dataset was then merged with those obtained in other studies for the Aegean and Tunisian populations (eastern Mediterranean), and statistical analyses (Bayesian model-based clustering, median-joining network, AMOVA, mismatch distribution, Tajima’s and Fu’s neutrality tests and Bayesian skyline plots) were performed. The results revealed genetic divergence among three distinguishable areas: (1) western Mediterranean and Ionian Sea; (2) Adriatic Sea; and (3) Aegean Sea and Tunisian coastal areas. From a conservational point of view, populations from the three genetically divergent groups found may be considered as different management units. PMID:23840684

  9. Phosphorus speciation and availability in sediments off the eastern coast of Hainan Island, South China Sea

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Liu, Su-Mei; Wu, Ying; Zhang, Jing

    2016-04-01

    Surface and core sediments were collected off the eastern coast of Hainan Island (South China Sea), and a sequential extraction method (SEDEX) was used to separate and quantify five sedimentary phosphorus (P) reservoirs: exchangeable or loosely sorbed P (Ex-P), iron-bound P (Fe-P), authigenic P (Ca-P), detrital P (De-P) and organic P (OP). Total P (TP) in the surface and core sediments ranged from 7.96 to 22.34 μmol g-1, and was dominated by inorganic P (IP). De-P and Ca-P were the main chemical species of P in surface and core sediments. The distribution of the P species in surface and core sediments was governed by various factors, including terrigenous input, biological processes, Fe oxides/hydroxides, organic matter degradation, and sediment grain size. The organic carbon (OC)/OP ratio ranged from 37 to 293 (average, 107±58) in surface sediments, suggesting that the organic matter in sediments had been subject to degradation and comprised mostly refractory compounds. The OC/Preactive ratio (37-69) was relatively low in the core sediments, suggesting an excess of sedimentary reactive P compared with OC. The Fe/P ratio ranged from 2 to 19 in surface and core sediments, which indicates that the higher proportions of the crystalline phases occurred in estuarine areas relative to the offshore areas. The potential bioavailable P accounted for 20.3-54.2% of TP in the surface and core sediments.

  10. Late Holocene Sea Surface Temperature Trends in the Eastern Tropical Pacific

    NASA Astrophysics Data System (ADS)

    Rustic, G. T.; Koutavas, A.; Marchitto, T. M., Jr.

    2015-12-01

    The Eastern Tropical Pacific (ETP) is a highly dynamic ocean region capable of exerting influencing on global climate as illustrated by the El Niño-Southern Oscillation (ENSO). The sea surface temperature (SST) history of this region in past millennia is poorly constrained due to the lack of in situ records with appropriate resolution. Here we present a ~2700 year sub-centennially resolved SST reconstruction from Mg/Ca ratios of the planktonic foraminifer Globigerinoides ruber from Galápagos sediments. The ETP SST record exhibits a long-term cooling trend of over 0.2°C/ky that is similar to Northern Hemisphere multi-proxy temperature trends suggesting a common origin, likely due to insolation forcing. The ETP remains in-phase with Northern Hemisphere climate records through the warm Roman Climate Optimum (~0-400CE), cooler Dark Ages Cold Period (~450-850CE), and through the peak warming of the Medieval Climate Anomaly (900-1150 CE) when SST is within error of modern. Following peak MCA, the ETP cooled rapidly and then rebounded at ~1500 CE during the coldest portion of the Little Ice Age. Overall the data suggest an out-of-phase relationship during much of the last millennium, which we attribute to dynamical adjustments consistent with the "dynamical ocean thermostat" mechanism. Further evidence for these dynamical adjustments comes from reconstructions of the east-west zonal SST gradient using existing Mg/Ca SST reconstructions from the western Pacific warm pool. The last millennium has been the most dynamic period over the past 2700 years, with significant (~1 °C) SST variability in the ETP and modulation of the zonal gradient. A combination of dynamical and thermodynamic mechanisms are invoked to explain the region's complex SST history.

  11. Variation of total organic carbon content along the stream Harsit, Eastern Black Sea Basin, Turkey.

    PubMed

    Bayram, Adem; Önsoy, Hizir; Akinci, Görkem; Bulut, Volkan Numan

    2011-11-01

    The TOC in surface waters and wastewater is an important analytical parameter describing the total content of all organic substances containing carbon. In practice, the TOC originated from natural and anthropogenic sources, and even if it is not directly responsible for dangers on human health, its determination is important for any kind of water that is used by public. The aim of this study was to determine variation of total organic carbon (TOC) and total carbon (TC) content in the stream Harsit, which courses in Eastern Black Sea Region, Turkey. Sampling was fortnightly conducted in each of the four seasons between March 2009 and February 2010. A total of 230 water samples were collected from ten sampling stations along the main branch of the stream Harsit with 143 km of length. Obtained TOC values were evaluated and used to classify the water quality of stream Harsit, according to the Turkish Water Pollution Control Regulation (TWPCR). The annual average TOC content values for the stations were found between 2.33 and 6.97 mg/L. It was seen that the TOC content have increased along the streamcourse of Harsit until the fourth station, where reaches its maximum value. The TOC content, then, has decreased and the minimum value was observed in the eighth station. The results showed that, except in winter season, maximum TOC content observed in many of the water samples were above Class I water standard indicated in TWPCR, which classifies the water resources according to the different area of uses. It was also found that TOC has a small contribution to TC and the highest TOC content in stream waters were measured in Gumushane station where direct discharge of city wastewaters and solid waste dumping to the stream were observed.

  12. Late Quaternary sapropel sediments in the eastern Mediterranean Sea: Faunal variations and chronology

    NASA Astrophysics Data System (ADS)

    Muerdter, David R.; Kennett, James P.; Thunell, Robert C.

    1984-05-01

    Distinctive planktonic foraminiferal assemblages which characterize particular late Quaternary sapropel layers in deep basin sediments from the eastern Mediterranean Sea have been identified using cluster analysis. Three distinct clusters allow for identification and intercore correlation of the nine sapropels deposited during the last 250,000 yr. Cluster 1, representing sapropel layers S1 and S9, exhibits low abundances of Neogloboquadrina dutertrei and high abundances of Globigerinoides ruber; Cluster 2, which groups S3, S5, and S7, contains high abundances of G. ruber, N. dutertrei, and Globigerina bulloides, and Cluster 3, which includes samples from S4, S6, and S8, is marked by extremely abundant N. dutertrei and G. bulloides, and rare G. ruber. Analysis of sedimentation rates in 14 cores reveals the following approximate ages for the sapropel layers: S2 = 52,000 yr B.P.; S3 = 81,000-78,000 yr B.P.; S4 = 100,000-98,000 yr B.P.; and S5 = 125,000-116,000 yr B.P. As previously suggested, sedimentation rates on the Mediterranean Ridge were determined to be relatively constant during the last 127,000 yr. In contrast, basin sedimentation rates have fluctuated markedly from lower rates during interglacial stage 5 to higher rates during the last glacial episode. These glacial/interglacial differences are most pronounced in the northern Ionian Basin, because of increased terrigenous sediment deposition during glacial episodes. Unusually high biogenic sedimentation rates occurred in an arc south of Crete during the deposition of sapropel S5, probably due to higher productivity in this region.

  13. Looking for evidence of climate change impacts in the eastern Irish Sea

    NASA Astrophysics Data System (ADS)

    Esteves, L. S.; Williams, J. J.; Brown, J. M.

    2011-06-01

    Although storminess is often cited as a driver of long-term coastal erosion, a lack of suitable datasets has only allowed objective assessment of this claim in a handful of case studies. This reduces our ability to understand and predict how the coastline may respond to an increase in "storminess" as suggested by global and regional climate models. With focus on 16 km of the Sefton coastline bordering the eastern Irish Sea (UK), this paper analyses available measured datasets of water level, surge level, wave height, wind speed and barometric pressure with the objective of finding trends in metocean climate that are consistent with predictions. The paper then examines rates of change in shoreline position over the period 1894 to 2005 with the aim of establishing relationships with climatic variability using a range of measured and modelled metocean parameters (with time spans varying from two to eight decades). With the exception of the mean monthly wind speed, available metocean data do not indicate any statistically significant changes outside seasonal and decadal cycles. No clear relationship was found between changes in metocean conditions and rates of shoreline change along the Sefton coast. High interannual variability and the lack of long-term measurements make unambiguous correlations between climate change and shoreline evolution problematic. However, comparison between the North Atlantic Oscillation winter index (NAOw) and coastline changes suggest increased erosion at times of decreasing NAOw values and reduced erosion at times of increasing NAOw values. Erosion tends to be more pronounced when decreasing NAOw values lead to a strong negative NAO phase. At present, anthropogenic changes in the local sediment budget and the short-term impact of extreme events are still the largest threat likely to affect coastal flooding and erosion risk in the short- and medium-term. Nevertheless, the potential impacts of climate change in the long-term should not be

  14. Eddy overturning of the Antarctic Slope Front controls glacial melting in the Eastern Weddell Sea

    NASA Astrophysics Data System (ADS)

    NøSt, O. A.; Biuw, M.; Tverberg, V.; Lydersen, C.; Hattermann, T.; Zhou, Q.; Smedsrud, L. H.; Kovacs, K. M.

    2011-11-01

    The Eastern Weddell Sea is characterized by narrow continental shelves and Warm Deep Water (WDW) is located in close proximity to the ice shelves in this region. The exchange of WDW across the Antarctic Slope Front (ASF) determines the rate of basal ice shelf melting. Here, we present a unique data set consisting of 2351 vertical profiles of temperature and salinity collected by southern elephant seals (Mirounga leonina) and a profile beneath the Fimbul Ice Shelf (FIS), obtained via drilling through 395 m of ice. This data set reveals variations in salinity and temperature through winter, and using a conceptual model of the coastal salt budget we quantify the main exchange processes. Our data show that modified WDW, with temperatures below -1.5°C, is advected onto the shelf and into the ice shelf cavities by an eddy overturning of the ASF. The onshore Ekman flux of surface waters during summer is the main source of freshwater that leads to the formation of low salinity shelf waters in the region. The modified WDW that reaches beneath the ice shelves is too cold for basal ice shelf melting to create such low salinity water. A high-resolution model of an idealized ASF-continental shelf-ice shelf system supports the conclusions from the data analysis. The inflow of WDW onto the continental shelf and into the ice shelf cavity occurs within a bottom boundary layer where the eddy advection in the model is particularly strong, in close agreement with the observed vertical profile of temperature beneath the FIS.

  15. Influence of chemosynthetic ecosystems on nematode community structure and biomass in the deep eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Lampadariou, N.; Kalogeropoulou, V.; Sevastou, K.; Keklikoglou, K.; Sarrazin, J.

    2012-12-01

    Mud volcanoes are a special type of cold seeps where life is based on chemoautotrophic processes. They are considered as extreme environments and are characterised by unique megafaunal and macrofaunal communities. However, very few studies on mud volcanoes taking into account the smaller meiobenthic communities have been carried out. Two mud volcanoes were explored during the MEDECO cruise (2007) with the Remotely Operated Vehicle (ROV) Victor-6000; Amsterdam, located south of Turkey between 1700 and 2000 m depth (Anaximander mud field) and Napoli, south of Crete, located along the Mediterranean Ridge at about 2000 m depth (Olimpi mud field). The major aim of this study was to describe distributional patterns of meiofaunal communities and nematode assemblages from different seep microhabitats. Meiofaunal taxa and nematode assemblages at both mud volcanoes differed significantly from other Mediterranean sites in terms of standing stocks, dominance and species diversity. Density and biomass values were significantly higher at the seep sites, particularly at Amsterdam. Nematodes, the dominant meiofaunal taxon, displayed deeper penetration vertically into the sediment at the seep areas, indicating that biological rather than physicochemical factors are responsible for their vertical distribution. Patterns of nematode diversity varied, displaying both very high or very low species richness and dominance, depending on the habitat studied. The Lamellibrachia periphery and mussel bed of Napoli exhibited the highest species richness while the reduced sediments of Amsterdam yielded a species-poor nematode community, dominated by two successful species; one belonging to the genus Aponema and the other to the genus Sabatieria. Analysis of β-diversity showed that habitat heterogeneity of mud volcanoes contributed substantially to the total nematode species richness in the eastern Mediterranean Sea. These observations indicate a strong influence of mud volcanoes and cold

  16. Neogene crustal extension in Aegean, revisited

    SciTech Connect

    Stiros, S.C. )

    1988-08-01

    The Neogene evolution of the Aegean and adjacent areas has been described as the result of homogeneous, subduction-associated lithosphere stretching by a factor near two, interrupted or not by short regional compressional intervals. However, reconsideration of some of the existing data (structural, volcanological, heat flow) and new or unpublished information from Greece, southern Bulgaria, and Yugoslavia concerning different scales, structural (tectonics of lignite and other basins), morpholtectonic (describing bulges, differential coastal movements, rotations of blocks around vertical axes, etc.), some seismic lines offshore, and aeromagnetic data suggest the following. (1) The patterns of Neogene volcanism, heat flow, and vertical motions are inconsistent with the idea of homogeneous stretching. (2) There is no evidence of features that should have accommodated the postulated level of regional extension. (3) The evolution of most Neogene basins, compressional features, and bulges in normal faulting environments most likely does not reflect cycles of regional extension-compression but of transtension-transpression associated with Mesozoic and still active shear zones and deeper processes. These data suggest that for the Aegean the uniform extension model is unsatisfactory in both large and local scale; small amounts of probably secondary extension are likely; and processes other than subduction must be anticipated.

  17. A misleading(?) similarity of indentor corners; Aegean-Anatolia versus the Himalaya syntaxes

    NASA Astrophysics Data System (ADS)

    Edwards, M.; Schneider, D.; Grasemann, B.; Accel, T.

    2006-12-01

    An appealing similarity of indentor corner-type geodynamic features in diffuse plate boundaries can be seen in the comparison of eastern Tibet/Namcha Barwa syntaxis (the termination of the main Himalaya) with the Aegean/Anatolian region (the termination of the easternmost Alpine Belt). Short-timescale measurements (seismological, GPS) show both regions are dynamic tectonic features that punctuate the ends of collisional orogens. Both regions are foci of elevated seismicity and, most strikingly, involve dramatic continental "escape tectonics" that boast some of the globe's highest angular velocities (surface vorticity) for continents that, moreover, have almost mirror-image symmetry. Finally, both regions are the progeny of protracted Tertiary orogenesis and exhume world-class high pressure deep crustal rocks. Beyond here, however, the appealing similarity of these apparent indentor corners ends; the Aegean/Anatolian region owes its exciting modern geodynamics to accelerated subducting slab retreat and, in stark contrast to the India-Asia collision, has limited net plate convergence. Furthermore, the renowned Aegean exhumation owes little to erosion and evacuation of material by intense surface processes, and extreme relief since the Miocene has been largely absent. Our data from Project ACCEL (this meeting) and many other studies highlight that the retreating slab governs displacement velocities for collisional plate boundaries whose lengths are short; most of the presently observed Aegean angular velocity enabled Anatolian escape and is certainly due to rapid slab retreat since at least the Miocene. The orogen preserves other equivalent, now diminished or terminated, examples of accelerated slab retreat such as the Appenines/Calabrian Arc and the Eastern Alps/Carpathians, indicative of the spatial and temporal transience of these slab retreat sites. These features would appear to be short term indentor corners. The indentor corners of the eastern and western

  18. Ultraphytoplankton basin-scale distribution in the eastern Mediterranean Sea in winter: link to hydrodynamism and nutrients

    NASA Astrophysics Data System (ADS)

    Denis, M.; Thyssen, M.; Martin, V.; Manca, B.; Vidussi, F.

    2010-07-01

    The basin-scale distribution of ultraphytoplankton (<10 μm) was determined in the upper 200 m of the eastern Mediterranean Sea during the winter season. Four clusters were resolved by flow cytometry on the basis of their optical properties and identified as Synechococcus, Prochlorococcus, pico- (<3 μm) and nanoeukaryotes (3-10 μm). Synechococcus was the most abundant population (maximum abundance of about 37 000 cells cm-3) and contributed up to 67.7% to the overall ultraphytoplanktonic carbon biomass, whereas the contribution of Prochlorococcus never exceeded 6.5%. The maximum integrated carbon biomass was 1763, 453, 58 and 571 mg C m-2 for nanoeukaryotes, picoeukaryotes, Prochlorococcus and Synechococcus respectively. Water mass properties were analyzed on the basis of temperature and salinity distributions in order to account for the general circulation and locate the main hydrodynamic structures (fronts, gyres, transition between western and eastern basins). The effect of the main hydrodynamic structures and nutrients on the ultraphytoplankton distribution was investigated. No positive correlation between nutrients and phytoplankton could be established when considering large scales. However, below 50 m depth, nutrient ratios between particular stations were correlated to corresponding density ratios. In contrast, significant relationships were found between Synechococcus abundance and density, resulting from the impact of a gyre in southern Adriatic basin and a thermohaline front in the Ionian basin. A significant relationship was also found between picoeukaryotes and salinity in the comparison of western and eastern Mediterranean Sea.

  19. Seasonality of sea ice controls interannual variability of summertime ΩA at the ice shelf in the Eastern Weddell Sea - an ocean acidification sensitivity study

    NASA Astrophysics Data System (ADS)

    Weeber, A.; Swart, S.; Monteiro, P. M. S.

    2015-01-01

    Increasing anthropogenic CO2 is decreasing surface water aragonite saturation state (ΩA), a growing concern for calcifying Euthecosome pteropods and its wider impact on Antarctic ecosystems. However, our understanding of the seasonal cycle and interannual variability of this vulnerable ecosystem remains limited. This study examines surface water ΩA from four consecutive summers in the Eastern Weddell Gyre (EWG) ice shelf region, and investigates the drivers and the role played by the seasonal cycle in the interannual variability of ΩA. Interannual variability in the seasonal phasing and the rate of summer sea ice thaw was found to be the primary factor explaining interannual variability in surface water ΩA. In "optimal" summers when summer sea ice thaw began in late November/early December (2008/2009 and 2010/2011), the summertime increase in ΩA was found to be 1.02, approximately double that from summers when sea ice thaw was delayed to late December (2009/2010 and 2011/2012). We propose that the two critical climate (physical-biogeochemical) sensitivities for ΩA are the timing and the rate of sea ice thaw, which has a direct impact on the mixed layer and the resulting onset and persistence of phytoplankton blooms. The strength of summertime carbonate saturation depends on seasonal changes of sea ice, stratification and primary production. The sensitivity of surface water biogeochemistry in this region to interannual changes in mixed layer - sea ice processes, suggests that future trends in climate and the seasonal cycle of sea ice, combined with rapidly increasing anthropogenic CO2 will likely be a concern for the Antarctic ice shelf ecosystem within the next few decades. If in the future, primary production is reduced and CO2 increased, our results suggest that in the EWG summertime surface water aragonite undersaturation will emerge by the middle of this century.

  20. Acoustic insights into the zooplankton dynamics of the eastern Weddell Sea

    NASA Astrophysics Data System (ADS)

    Cisewski, Boris; Strass, Volker H.

    2016-05-01

    The success of any efforts to determine the effects of climate change on marine ecosystems depends on understanding in the first instance the natural variations, which contemporarily occur on the interannual and shorter time scales. Here we present results on the environmental controls of zooplankton distribution patterns and behaviour in the eastern Weddell Sea, Southern Ocean. Zooplankton abundance and vertical migration are derived from the mean volume backscattering strength (MVBS) and the vertical velocity measured by moored acoustic Doppler current profilers (ADCPs), which were deployed simultaneously at 64°S, 66.5°S and 69°S along the Greenwich Meridian from February, 2005, until March, 2008. While these time series span a period of full three years they resolve hourly changes. A highly persistent behavioural pattern found at all three mooring locations is the synchronous diel vertical migration (DVM) of two distinct groups of zooplankton that migrate between a deep residence depth during daytime and a shallow depth during nighttime. The DVM was closely coupled to the astronomical daylight cycles. However, while the DVM was symmetric around local noon, the annual modulation of the DVM was clearly asymmetric around winter solstice or summer solstice, respectively, at all three mooring sites. DVM at our observation sites persisted throughout winter, even at the highest latitude exposed to the polar night. Since the magnitude as well as the relative rate of change of illumination is minimal at this time, we propose that the ultimate causes of DVM separated from the light-mediated proximal cue that coordinates it. In all three years, a marked change in the migration behaviour occurred in late spring (late October/early November), when DVM ceased. The complete suspension of DVM after early November is possibly caused by the combination of two factors: (1) increased availability of food in the surface mixed layer provided by the phytoplankton spring bloom, and

  1. Focal Mechanisms at the convergent plate boundary in Southern Aegean, Greece.

    NASA Astrophysics Data System (ADS)

    Moshou, Alexandra; Papadimitriou, Eleftheria; Drakatos, George; Evangelidis, Christos; Karakostas, Vasilios; Vallianatos, Filippos; Makropoulos, Konstantinos

    2014-05-01

    Greece is characterized by high seismicity, mainly due to the collision between the European and the African lithospheric plates and the dextral strike slip motion along the North Anatolia Fault zone and North Aegean Trough. The subduction of the Eastern Mediterranean oceanic plate along the Hellenic Arc under the Aegean microplate along with the accompanied roll back of the descending slab is considered the main tectonic feature of the region (Papazachos and Comninakis 1971; Makropoulos and Burton 1984; Papazachos et al. 2000a, b). The divergent motion between the Aegean block and mainland Europe is indicated by an extension zone in the northern Aegean, with Crete and Aegean diverging from mainland Europe at a rate of about 3.5 cm yr-1 with Africa moving northward relative to Europe at a rate of about 1 cm yr-1 (Dewey et al., 1989; Papazachos et al., 1998; Mc-Clusky et al., 2000; Reilinger et al., 2006). In this tectonically complicated area diverge types of deformation are manifested, in addition to the dominant subduction processes. Aiming to shed more light in the seismotectonic properties and faulting seismological data from the Hellenic Unified Seismological Network (HUSN) were selected and analyzed for determining focal mechanisms using the method of moment tensor inversion, additional to the ones being available from the routine moment tensor solutions and several publications. Thus, 31 new fault plane solutions for events with magnitude M>4.0, are presented in this study, by using the software of Ammon (Randall et al., 1995). For this scope the data from at least 4 stations were used with an adequate azimuthal coverage and with an epicentral distance not more than 350 km. The preparation of the data includes the deconvolution of instruments response, then the velocity was integrated to displacement and finally the horizontal components were rotated to radial and transverse. Following, the signal was inverted using the reflectivity method of Kennett (1983

  2. Modelling of oil spills in confined maritime basins: The case for early response in the Eastern Mediterranean Sea.

    PubMed

    Alves, Tiago M; Kokinou, Eleni; Zodiatis, George; Lardner, Robin; Panagiotakis, Costas; Radhakrishnan, Hari

    2015-11-01

    Oil spill models are combined with bathymetric, meteorological, oceanographic, and geomorphological data to model a series of oil spill accidents in the Eastern Mediterranean Sea. A total of 104 oil spill simulations, computed for 11 different locations in the Levantine Basin, show that oil slicks will reach the coast of Cyprus in four (4) to seven (7) days in summer conditions. Oil slick trajectories are controlled by prevailing winds and current eddies. Based on these results, we support the use of chemical dispersants in the very few hours after large accidental oil spills. As a corollary, we show shoreline susceptibility to vary depending on: a) differences in coastline morphology and exposure to wave action, b) the existence of uplifted wave-cut platforms, coastal lagoons and pools, and c) the presence of tourist and protected environmental areas. Mitigation work should take into account the relatively high susceptibility of parts of the Eastern Mediterranean. PMID:26253313

  3. Modelling of oil spills in confined maritime basins: The case for early response in the Eastern Mediterranean Sea.

    PubMed

    Alves, Tiago M; Kokinou, Eleni; Zodiatis, George; Lardner, Robin; Panagiotakis, Costas; Radhakrishnan, Hari

    2015-11-01

    Oil spill models are combined with bathymetric, meteorological, oceanographic, and geomorphological data to model a series of oil spill accidents in the Eastern Mediterranean Sea. A total of 104 oil spill simulations, computed for 11 different locations in the Levantine Basin, show that oil slicks will reach the coast of Cyprus in four (4) to seven (7) days in summer conditions. Oil slick trajectories are controlled by prevailing winds and current eddies. Based on these results, we support the use of chemical dispersants in the very few hours after large accidental oil spills. As a corollary, we show shoreline susceptibility to vary depending on: a) differences in coastline morphology and exposure to wave action, b) the existence of uplifted wave-cut platforms, coastal lagoons and pools, and c) the presence of tourist and protected environmental areas. Mitigation work should take into account the relatively high susceptibility of parts of the Eastern Mediterranean.

  4. Evidence for post last-glacial-maximum punctuated sea level rise found on the eastern Mediterranean coast of Israel

    NASA Astrophysics Data System (ADS)

    Katz, Oded; Goodman-Tchernov, Beverly

    2015-04-01

    The eustatic sea level curve for the eastern Mediterranean presents a general trend characterized by rapid post last-glacial-maximum rise (20,000 years ago), slowing approximately 6000 years ago and stabilizing at current sea-level 4000 years ago. Sea level evidence from portions of the Israeli coastline, suggest minimal to no hydro-glacio-isostatic influence on the local relative sea level curve, and no tectonic offsets for at least the past two thousand years. Recently, a submerged series of relict wave cut notches and erosional pits were identified along a sequence of coastal sites located approximately 20 km from one another (Michmoret, Olga, Caesarea, Dor) at 3 m and 6 m water depths. The features were carved into an upper-Pleistocene to Holocene eolianite sandstone, the age of which was previously constrained by OSL measurements to MIS 1-3. Elsewhere, similar features are widely used as sea-level markers. In this study, at some of the sites, we found a coinciding 3 m to 6 m submerged cliff with overhanging upper part, morphology that is comparable to the morphology of the modern coastal cliff. These submerged features should either suggest a tectonic offset, which is not favorable for the study area, or they might suggest that sea level rise has not been gradual, but rather punctuated, exhibiting pulses of sea level rise followed by periods of sea level stagnation. For the study site, the last stagnation took place at a few meters below current sea-level and enabled the development of the observed wave induced morphology within the eolianite. At present sea level, similar features exist and are being actively formed within the same host rock. At some of the sites, artificially-cut archaeological features from about the last 2000 years present with notches or erosional pits thereby providing insight into the period of time required for their creation due to their archaeological associations. Sea level rise might impacts the coastline significantly, with

  5. Towards an absolute chronology for the Aegean iron age: new radiocarbon dates from Lefkandi, Kalapodi and Corinth.

    PubMed

    Toffolo, Michael B; Fantalkin, Alexander; Lemos, Irene S; Felsch, Rainer C S; Niemeier, Wolf-Dietrich; Sanders, Guy D R; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8(th) century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11(th) century BCE according to the Conventional Aegean Chronology and in the late 12(th) century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11(th) century BCE. PMID:24386150

  6. Towards an Absolute Chronology for the Aegean Iron Age: New Radiocarbon Dates from Lefkandi, Kalapodi and Corinth

    PubMed Central

    Toffolo, Michael B.; Fantalkin, Alexander; Lemos, Irene S.; Felsch, Rainer C. S.; Niemeier, Wolf-Dietrich; Sanders, Guy D. R.; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8th century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11th century BCE according to the Conventional Aegean Chronology and in the late 12th century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11th century BCE. PMID:24386150

  7. Towards an absolute chronology for the Aegean iron age: new radiocarbon dates from Lefkandi, Kalapodi and Corinth.

    PubMed

    Toffolo, Michael B; Fantalkin, Alexander; Lemos, Irene S; Felsch, Rainer C S; Niemeier, Wolf-Dietrich; Sanders, Guy D R; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8(th) century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11(th) century BCE according to the Conventional Aegean Chronology and in the late 12(th) century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11(th) century BCE.

  8. Dispersal barriers in tropical oceans and speciation in Atlantic and eastern Pacific sea urchins of the genus Echinometra.

    PubMed

    McCartney, M A; Keller, G; Lessios, H A

    2000-09-01

    Echinometra is a pantropical sea urchin made famous through studies of phylogeny, speciation, and genetic structure of the Indo-West Pacific (IWP) species. We sequenced 630 bp of the cytochrome oxidase I (COI) mitochondrial gene to provide comparable information on the eastern Pacific and Atlantic species, using divergence between those separated by closure of the Isthmus of Panama 3.1 million years ago (Ma) to estimate dates for cladogenic events. Most recently (1.27-1. 62 Ma), the Atlantic species E. lucunter and E. viridis diverged from each other, at a time in the Pleistocene that sea levels fell and Caribbean coral speciation and extinction rates were high. An earlier split, assumed to have been coincident with the completion of the Isthmus of Panama, separated the eastern Pacific E. vanbrunti from the Atlantic common ancestor. Transisthmian COI divergence similar to that in the sea urchin genus Eucidaris supports this assumption. The most ancient split in Echinometra occurred between the IWP and the neotropical clades, due to cessation of larval exchange around South Africa or across the Eastern Pacific Barrier. Gene flow within species is generally high; however, there are restrictions to genetic exchange between E. lucunter populations from the Caribbean and those from the rest of the Atlantic. Correlation between cladogenic and vicariant events supports E. Mayr's contention that marine species, despite their high dispersal potential, form by means of geographical separation. That sympatric, nonhybridizing E. lucunter and E. viridis were split so recently suggests, however, that perfection of reproductive barriers between marine species with large populations can occur in less than 1.6 million years (Myr).

  9. Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985. Final report, June 1985-May 1986

    SciTech Connect

    Richardson, W.J.

    1986-05-01

    The two-year project is designed to quantify what proportion of the energy requirements of Western Arctic bowheads is provided by food acquired in the Eastern part of the Alaskan Beaufort Sea. The report describes results from Year 1 fieldwork in September and early October 1985. Water masses were studied by boat-based sampling and by airborne and satellite remote sensing. Zooplankton composition, biomass, distribution, patchiness, and energy content were documented by boat-based sampling. The distribution, numbers and activities of bowheads were determined by aerial surveys and behavioral observations. Bowheads probably consume several times more food there in some other years.

  10. Inter-cohort growth patterns of pharaoh cuttlefish Sepia pharaonis (Sepioidea: Sepiidae) in Eastern Arabian Sea.

    PubMed

    Sasikumarl, Geetha; Mohamed, K S; Bhat, U S

    2013-03-01

    Sepia pharaonis is an important commercial species endemic to the tropical Indo-Pacific region. Despite its commercial significance, only few information on natural populations is available. This study was aimed to describe the aspects of size-composition, length-weight relationship, catch rates, seasonal recruitment and inter-cohort growth patterns of S. pharaonis population (Clade C), distributed along the Eastern Arabian Sea (South-West coast of India). For this, the Dorsal Mantle Length (DML) and weight of cuttlefishes was obtained from commercial trawl catches, from April 2002 to October 2006. Data was analyzed by normal length-weight methods such as von Bertalanffy. A total of 12454 cuttlefishes, ranging in length from four to 41cm were analyzed. Size-composition patterns discriminated two pulses in recruitment to the fishery, discernible by a decrease in the monthly mean size of the population. The DMLs of the two seasonal cohorts were subjected to modal-progression analysis using the Bhattacharya's method for the estimation of growth. The estimated parameters Linfinity and K in von Bertalanffy Growth Function (VBGF) were used to model growth curves in length for the cohorts. The first cohort, (post-monsoon cohort) which supports the major fishery, was composed of medium-sized, fast growing individuals, whereas the second cohort (pre-monsoon cohort), comprised of slow growing and large-sized individuals. There were differential growth characteristics between the sexes and the life span was estimated at less than 2.3 years for males and 2.1 years for females. Negative allometric growth in weight (W) with length (L) was observed for males (W=0.33069.L2.5389) and females (W=0.32542.L26057). The females were heavier compared to males at any given mantle length, and the males were found to attain larger ultimate lengths. The major fishing season for cuttlefish was from May to November, when higher monthly catch rates of 1.67-13.02kg/h were observed in comparison

  11. Particulate PAHs and n-alkanes in the air over Southern and Eastern Mediterranean Sea.

    PubMed

    Romagnoli, Paola; Balducci, Catia; Perilli, Mattia; Perreca, Erica; Cecinato, Angelo

    2016-09-01

    Particulate polycyclic aromatic hydrocarbons, n-alkanes and polar organic compounds were investigated in the marine atmosphere of Southern and Eastern Mediterranean Sea, in the frame of the scientific cruise of Urania ship between 27 July and 11 August 2013. The PM10 fraction of aerosol to which most organic substances are associated, were collected daily; contemporarily, gaseous regulated toxicants (ozone, nitrogen oxides and carbon oxide) and carbonyls were recorded. Samplings were carried out in front of Palermo and Messina, respectively the start and end harbors, and along the cruise, both in movement (transects, N = 14) and at stops (N = 11). Total PAHs ranged from 0.06 ng/m(3) up to 1.8 ng/m(3), with the maximums observed close to harbors. Unlike total concentrations that were in general comparable, the percent composition of PAHs was distinct for harbors, transects and stops, which allowed to draw insights about the pollution sources impact. Concentrations of n-alkanes (C18-C35) ranging from 6.7 to 43 ng/m(3) were quantified. The carbonyls evaluation revealed relatively high concentrations of formaldehyde (∼4-24 μg/m(3)) and acetone (∼5-35 μg/m(3)) near harbors, and of acrolein (up to 12 μg/m(3)) offshore, while benzaldehyde was quite independent of the site type (≈0.5 μg/m(3)). Nicotine and caffeine were detected, at different extents (0.0-2.2 ng/m(3) and 0.01-0.17 ng/m(3), respectively), in ca. 70% and 100% of samples. Alkyl phthalates ranged from 2.7 to 67 ng/m(3) and showed variable percentages in the samples. Finally, traces of N,N-diethyl-meta-toluene amide (up to 0.4 ng/m(3)) were found at all sites. PMID:27341155

  12. Seismic characteristics and accretion history of Halimeda bioherms on Kalukalukuang Bank, eastern Java Sea (Indonesia)

    NASA Astrophysics Data System (ADS)

    Phipps, C. V. G.; Roberts, H. H.

    1988-03-01

    Extensive areas of Halimeda bioherms similar to those described by Orme et al. (1978), Orme (1985), Davies and Marshall (1985), and Phipps et al. (1985) from Australia's Great Barrier Reef have formed on Kalukalukuang Bank (K-Bank) 50 km east of the Sunda Shelf margin in the easter Java Sea. K-Bank is an isolated limestone platform whose top slopes southward from a water depth of about 20 m at the north to about 100 m at the south (≈30 km). It occurs in a bidirectional monsoonal wind regime and a predominantly southerly flowing current from Makassar Strait. The water column around K-Bank has a well developed shallow thermocline (50 m to 150 m). K-Bank has a relatively flat top with marginal banks of suspected Pleistocene origin as interpreted from seismic relationships. A reconnaissancelevel survey grid of high-resolution seismic profiles indicates that Halimeda bioherms are restricted to the bank margins with the exception of the eastern margin. Bioherms either extend to the steep margin of the platforms or are separated from the platform edge by banks of coral and coralline algae. The morphology of the Halimeda bioherms varies from steep-sided, elongate ridges in the northern bank area, through coalescing symmetrical mounds with partly infilled valleys, to broad undulating areas similar to those described by Orme (1985) from the Great Barrier Reef. High-resolution seismic records indicate erosional episodes in the high-relief areas, an interpretation that seems to be supported by accumulation rates calculated from C14 dates of cores. Thicknesses of Halimeda accumulation above a prominent reflector considered as Pleitocene, vary from around 20 m in the north to a maximum of over 50 m in the southwest. Accumulation rates obtained from dating of two cores to-ward the north of K-Bank, average 0.294 m/100 yr for core VC4 and a maximum of 0.59 m/100 yr in a part of core PC12. Dating of material from the top 30 cm of a deep bioherm (≈100 m) in the southwest of K

  13. Climate variability and socio-environmental changes in the northern Aegean (NE Mediterranean) during the last 1500 years

    NASA Astrophysics Data System (ADS)

    Gogou, Alexandra; Triantaphyllou, Maria; Xoplaki, Elena; Izdebski, Adam; Parinos, Constantine; Dimiza, Margarita; Bouloubassi, Ioanna; Luterbacher, Juerg; Kouli, Katerina; Martrat, Belen; Toreti, Andrea; Fleitmann, Dominik; Rousakis, Gregory; Kaberi, Helen; Athanasiou, Maria; Lykousis, Vasilios

    2016-04-01

    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 ± 2 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 palaeoclimatic evidence derived from 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

  14. Climate variability and socio-environmental changes in the northern Aegean (NE Mediterranean) during the last 1500 years

    NASA Astrophysics Data System (ADS)

    Gogou, Alexandra; Triantaphyllou, Maria; Xoplaki, Elena; Izdebski, Adam; Parinos, Constantine; Dimiza, Margarita; Bouloubassi, Ioanna; Luterbacher, Juerg; Kouli, Katerina; Martrat, Belen; Toreti, Andrea; Fleitmann, Dominik; Rousakis, Gregory; Kaberi, Helen; Athanasiou, Maria; Lykousis, Vasilios

    2016-03-01

    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

  15. Spatio-temporal analysis of the sea level in the Eastern Mediterranean Sea and Black Sea using Jason-1, Jason-2, Topex/Poseidon and Envisat satellite altimetry data from 2002 - 2012

    NASA Astrophysics Data System (ADS)

    Aghakarimi, Armin; Demir, Coşkun; Onur Karslıoǧlu, Mahmut; Kılıçoǧlu, Ali

    2013-04-01

    Altimetry satellites basically determine the distance from the satellite to a target surface by measuring the satellite-to-surface round-trip time of a radar pulse, and thus the sea surface height from the reference ellipsoid. Satellite altimetry, supplying continuous long term observations, has been contributing to understanding the sea surface height variations. Spatial and temporal variability of the Eastern Mediterranean Sea and Black Sea have been investigated in this work using 10 years data of four satellite altimetry missions; Jason-1, Jason-2 , Topex/Poseidon and Envisat. In order to perform time series analysis, altimetry data points along each pass are clustered in a way that each cluster contains only one observation of a cycle. The method of clustering is referred to a pattern of the altimetry data along the geodetic latitude. Sea Surface Height (SSH) of all data points of the clusters have been projected to the center of the clusters using the geoidal trend which is calculated on the basis of a global gravitational model, namely EGM08. Harmonic analysis has been performed for time series of all clusters and then trends of them have been computed. Also in this step Pope Test has been used for outlier detection. The significance of the calculated trends has been investigated using t-test. For analyzing the spatial variability of the sea level through the seas, Principal Component Analysis (PCA) has been used. Spline interpolation is applied to fill the possible data gaps in time series. PCA is also used for investigating the dominant variability of the sea level. For this purpose the sea level variation signal has been reconstructed by using the first three principal components. Results show that there is a general decreasing but very small tendencies in the most of clusters for all altimetry missions in both seas. Keywords: satellite altimetry, sea level change, time series, PCA

  16. Coupling primary production and terrestrial runoff to ocean acidification and carbonate mineral suppression in the eastern Bering Sea

    NASA Astrophysics Data System (ADS)

    Mathis, Jeremy T.; Cross, Jessica N.; Bates, Nicholas R.

    2011-02-01

    Water column pH and carbonate mineral saturation states were calculated from dissolved inorganic carbon (DIC) and total alkalinity data collected over the eastern Bering Sea shelf in the spring and summer of 2008. The saturation states (Ω) of the two most important carbonate minerals, calcite (Ωcalcite) and aragonite (Ωaragonite) were strongly coupled to terrestrial runoff from the Yukon and Kuskokwim rivers, primary production in the surface waters, and remineralization of organic matter at depth over the shelf. In spring, before ice melt occurred, pH over the shelf was largely confined to a range of 7.9-8.1 and Ωcalcite and Ωaragonite ranged from 1.5 to 3.0 and 0.8 to 2.0, respectively. At the stations closest to river outflows, aragonite was undersaturated in the water column from the surface to the bottom. During the summer sea ice retreat, high rates of primary production consumed DIC in the mixed layer, which increased pH and Ωcalcite and Ωaragonite. However, Ωcalcite and Ωaragonite decreased by ˜0.3 in the bottom waters over the middle and outer shelf. Over the northern shelf, where export production is highest, Ωaragonite decreased by ˜0.35 and became highly undersaturated. The observed suppression and undersaturation of Ωcalcite and Ωaragonite in the eastern Bering Sea are correlated with anthropogenic carbon dioxide uptake into the ocean and will likely be exacerbated under business-as-usual emission scenarios. Therefore, ocean acidification could threaten some benthic and pelagic calcifying organisms across the Bering Sea shelf in the coming decades.

  17. Assessing different turbulence close schemes in the North Aegean: Preliminary results

    NASA Astrophysics Data System (ADS)

    Mamoutos, Ioannis; Zervakis, Vassilis; Tragou, Elina

    2015-04-01

    The North Aegean Sea potentially constitutes one of the deep-water formation sites of the Mediterranean Sea. The production of deep water however is highly controlled by the inflow of Black Sea waters forming a thin insulating surface layer over a large part of the region. For this reason, extensive replenishment of the deeper-than-400 m basins takes place infrequently, at intervals several years long. After the recorded major deep water formation events of 1987, 1992 and 1993, several smaller magnitude formation events have been observed in the 2000s. Long stagnation periods separate successive formation events, during which turbulent exchange through the interface between the deep, secluded locally-formed water mass and the overlaid, laterally flowing water masses is the major factor determining the evolution of the deep-layer properties. In this work we test different diapycnal mixing schemes via comparing the results of long-term hindcasts of the evolution of the deep-layer properties to successive observations in three deep basins of the North Aegean. The Regional Ocean Model System (ROMS) was used for the hindcasts. All the available turbulence closure schemes - KPP, GLS and Mellor - Yamada 2.5 - were used for the experiments. A rectangular grid covering the Aegean sea was developed (longitudinal range: 22.50 E - 28.37 E, latitudinal range: 36.43 N - 41.12 N) with a 1/40 degree ( ~ 2.5 km ) resolution in both directions and 30 vertical sigma layers. The initial and boundary conditions used refer to the 1985 - 2013 period, and have been provided by GNOO. Atmospheric forcing fields from ERA - interim data set were used with spatial resolution 0.5 × 0.5 degrees and three-hour time step. The Black-sea water inflow is temporally variable and has been provided by Vladimir Maderich based on Black and Marmara Sea budgets and hydraulic control at Bosphorus and Dardanelles Straits. The preliminary results of the numerical experiments are hereby presented and discussed

  18. DUPAL anomaly in the Sea of Japan: Pb, Nd, and Sr isotopic variations at the eastern Eurasian continental margin

    USGS Publications Warehouse

    Tatsumoto, M.; Nakamura, Y.

    1991-01-01

    Volcanic rocks from the eastern Eurasian plate margin (southwestern Japan, the Sea of Japan, and northeastern China) show enriched (EMI) component signatures. Volcanic rocks from the Ulreung and Dog Islands in the Sea of Japan show typical DUPAL anomaly characteristics with extremely high ??208/204 Pb (up to 143) and enriched Nd and Sr isotopic compositions (??{lunate}Nd = -3 to -5, 87Sr 86Sr = ~0.705). The ??208/204 Pb values are similar to those associated with the DUPAL anomaly (up to 140) in the southern hemisphere. Because the EMI characteristics of basalts from the Sea of Japan are more extreme than those of southwestern Japan and inland China basalts, we propose that old mantle lithosphere was metasomatized early (prior to the Proterozoic) with subduction-related fluids (not present subduction system) so that it has been slightly enriched in incompatible elements and has had a high Th/U for a long time. The results of this study support the idea that the old subcontinental mantle lithosphere is the source for EMI of oceanic basalts, and that EMI does not need to be stored at the core/ mantle boundary layer for a long time. Dredged samples from seamounts and knolls from the Yamato Basin Ridge in the Sea of Japan show similar isotopic characteristics to basalts from the Mariana arc, supporting the idea that the Yamato Basin Ridge is a spreading center causing separation of the northeast Japan Arc from Eurasia. ?? 1991.

  19. Size frequency distributions of key epibenthic organisms in the eastern Chukchi Sea and their correlations with environmental parameters

    NASA Astrophysics Data System (ADS)

    Konar, B.; Ravelo, A.; Grebmeier, J.; Trefry, J. H.

    2014-04-01

    Epibenthic communities play a key role in ecosystem functioning in Arctic shelf Seas, such as in the Chukchi Sea in the Pacific Arctic. These communities, however, are patchily distributed and are influenced by various environmental parameters. Along with taxonomic composition, another community aspect that may vary spatially and be influenced by the environment is the distribution of organism sizes. This study presents the first size frequency distributions of nine epifaunal taxa that were determined to be dominant in the eastern Chukchi Sea in July/August 2009 and 2010, including male, female and gravid Chionoecetes opilio and Hyas coarctatus crabs, the gastropods Neptunea spp., Plicifusus spp., Colus spp., and Cryptonatica spp., and the echinoderms Gorgonocephalus spp., Leptasterias spp., and Echinarachnius parma. Some abundant taxa exhibited a wide range of sizes (i.e. C. opilio, Neptunea spp., and Leptasterias spp.), while others had a much smaller size range (i.e. Cryptonatica spp. and E. parma). We also found that size distributions of these taxa correlated with various combinations of the environmental parameters that have been shown to be important in structuring the general distribution patterns for the epibenthic invertebrate communities in the study area, including percent total sediment organic carbon, sediment chlorophyll a, temperature, latitude, sediment grain size 2 and 4 phi, pH, and dissolved oxygen. Our findings present benchmark information that is needed to detect future alterations in body-size frequency distributions that are likely to happen in response to the predicted climate and environmental changes in the Chukchi Sea region.

  20. Functional diversity patterns of abyssal nematodes in the Eastern Mediterranean: A comparison between cold seeps and typical deep sea sediments

    NASA Astrophysics Data System (ADS)

    Kalogeropoulou, V.; Keklikoglou, K.; Lampadariou, N.

    2015-04-01

    Spatial patterns in deep sea nematode biological trait composition and functional diversity were investigated between chemosynthetic and typical deep sea ecosystems as well as between different microhabitats within the chemosynthetic ecosystems, in the Eastern Mediterranean. The chemosynthetic ecosystems chosen were two mud volcanoes, Napoli at 1950 m depth and Amsterdam at 2040 m depth which are cold seeps characterized by high chemosynthetic activity and spatial heterogeneity. Typical deep sea ecosystems consisted of fine-grained silt-clay sediments which were collected from three areas located in the south Ionian Sea at 2765 to 2840 m depth, the southern Cretan margin at 1089 to 1998 m depth and the Levantine Sea at 3055 to 3870 m depth. A range of biological traits (9 traits; 31 categories) related to buccal morphology, tail shape, body size, body shape, life history strategy, sediment position, cuticle morphology, amphid shape and presence of somatic setae were combined to identify patterns in the functional composition of nematode assemblages between the two habitats, the two mud volcanoes (macroscale) and between the microhabitats within the mud volcanoes (microscale). Data on trait correspondence was provided by biological information on species and genera. A total of 170 nematode species were allocated in 67 different trait combinations, i.e. functional groups, based on taxonomic, morphological and behavioral characteristics. The Biological Trait Analysis (BTA) revealed significant differences between the mud volcanoes and the typical deep sea sediments indicating the presence of different biological functions in ecologically very different environments. Moreover, chemosynthetic activity and habitat heterogeneity within mud volcanoes enhance the presence of different biological and ecological functions in nematode assemblages of different microhabitats. Functional diversity and species richness patterns varied significantly across the different

  1. Effects of the Eastern Mediterranean Sea circulation on the thermohaline properties as recorded by fixed deep-ocean observatories

    NASA Astrophysics Data System (ADS)

    Bensi, Manuel; Velaoras, Dimitris; Meccia, Virna L.; Cardin, Vanessa

    2016-06-01

    Temperature and salinity time-series from three fixed observatories in the Eastern Mediterranean Sea (EMed) are investigated using multi-annual (2006-2014), high-frequency (up to 3 h sampling rate) data. Two observatories are deployed in the two dense water formation (DWF) areas of the EMed (Southern Adriatic Sea, E2-M3A; Cretan Sea, E1-M3A) and the third one (Southeast Ionian Sea, PYLOS) lays directly on the intermediate water masses pathway that connects the DWF sources. The long-term variations of the hydrological characteristics at the observatories reflect the oscillating large-scale circulation modes of the basin (i.e. BiOS-Bimodal Oscillating System and internal thermohaline pump theories). In particular, between 2006 and 2014 an anti-correlated behaviour of the intermediate layer (200-600 m) salinity between the Adriatic and Cretan Sea observatories is verified. This behaviour is directly linked to reversals of the North Ionian Gyre, which appeared cyclonic during 2006-2011 and turned anticyclonic after 2011. Statistical analysis suggests that the travel time of the intermediate salinity maximum signal between the Cretan and Adriatic Sea is roughly 1.5 years, in good agreement with the analysis of additionally presented ARGO data as well as previous literature references. We argue that the understanding of such oscillations provides important foresight on future DWF events, as increased salinity may act as a crucial preconditioning factor for DWF processes. Additionally, energy spectrum analysis of the time-series revealed interesting short-term variability connected to mesoscale activity at the observatories. Hence, the sustain of permanent observatories able to monitor oceanic parameters at high sampling rates may play a key role in understanding both climatic and oceanic processes and trends.

  2. Carbonate assimilation during magma evolution at Nisyros (Greece), South Aegean Arc: Evidence from clinopyroxenite xenoliths

    NASA Astrophysics Data System (ADS)

    Spandler, Carl; Martin, Lukas H. J.; Pettke, Thomas

    2012-08-01

    To contribute to the understanding of magma evolution in arc settings we investigate the oldest volcanic unit (Kanafià Synthem) of Nisyros volcano, located in the eastern Aegean Sea (Greece). The unit consists of porphyritic pillow lavas of basaltic andesite composition with trace element signatures that are characteristic of island-arc magmas. Two lava types are distinguished on the basis of geochemistry and the presence or absence of xenoliths, with the xenolith-bearing lavas having distinctly elevated Sr, MREE/HREE and MgO/Fe2O3 compared to the xenolith-free lavas. Xenoliths include relatively rare quartzo-feldspathic fragments that represent continental-type material, and coarse clinopyroxenite xenoliths that consist largely of aluminous and calcic clinopyroxene, and accessory aluminous spinel. Anorthite-diopside reaction selvages preserved around the clinopyroxenite xenoliths demonstrate disequilibrium between the xenoliths and the host magma. The xenolith clinopyroxene is distinctly enriched in most lithophile trace elements compared to clinopyroxene phenocrysts in the host magmas. A notable exception is the Sr concentration, which is similar in both clinopyroxene types. The high Al and low Na contents of the clinopyroxenites preclude a cumulate, deep metamorphic, or mantle origin for these xenoliths. Instead, their composition and mineralogy are diagnostic of skarn rocks formed by magma-carbonate interaction in the mid/upper crust. The Kanafià lavas are interpreted to have undergone crystal fractionation, magma mixing/mingling and crustal assimilation while resident in the upper crust. We show that magma-carbonate reaction and associated skarn formation does not necessarily result in easily recognised modification of the melt composition, with the exception of increasing Sr contents. Carbonate assimilation also releases significant CO2, which will likely form a free vapour phase due to the low CO2 solubility of arc magmas. In the broader context, we stress

  3. Microfossils, a Key to Unravel Cold-Water Carbonate Mound Evolution through Time: Evidence from the Eastern Alboran Sea

    PubMed Central

    Stalder, Claudio; Vertino, Agostina; Rosso, Antonietta; Rüggeberg, Andres; Pirkenseer, Claudius; Spangenberg, Jorge E.; Spezzaferri, Silvia; Camozzi, Osvaldo; Rappo, Sacha; Hajdas, Irka

    2015-01-01

    Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the ocean's carbonate budget and atmospheric CO2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madrepora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geochemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents PMID:26447699

  4. Microfossils, a Key to Unravel Cold-Water Carbonate Mound Evolution through Time: Evidence from the Eastern Alboran Sea.

    PubMed

    Stalder, Claudio; Vertino, Agostina; Rosso, Antonietta; Rüggeberg, Andres; Pirkenseer, Claudius; Spangenberg, Jorge E; Spezzaferri, Silvia; Camozzi, Osvaldo; Rappo, Sacha; Hajdas, Irka

    2015-01-01

    Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the ocean's carbonate budget and atmospheric CO2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madrepora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geochemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents.

  5. Microfossils, a Key to Unravel Cold-Water Carbonate Mound Evolution through Time: Evidence from the Eastern Alboran Sea.

    PubMed

    Stalder, Claudio; Vertino, Agostina; Rosso, Antonietta; Rüggeberg, Andres; Pirkenseer, Claudius; Spangenberg, Jorge E; Spezzaferri, Silvia; Camozzi, Osvaldo; Rappo, Sacha; Hajdas, Irka

    2015-01-01

    Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the ocean's carbonate budget and atmospheric CO2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madrepora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geochemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents. PMID:26447699

  6. Direct ageing of Thunnus thynnus from the eastern Atlantic Ocean and western Mediterranean Sea using dorsal fin spines.

    PubMed

    Luque, P L; Rodriguez-Marin, E; Landa, J; Ruiz, M; Quelle, P; Macias, D; Ortiz De Urbina, J M

    2014-06-01

    This study deals with important methodology issues that affect age estimates of eastern Atlantic bluefin tuna Thunnus thynnus using dorsal fin spines. Nearly 3800 spine sections were used from fish caught in the north-east Atlantic Ocean and western Mediterranean Sea over a 21 year period. Edge type and marginal increment analyses indicated a yearly periodicity of annulus formation with the translucent bands (50% of occurrence) appearing from October to May. Nucleus vascularization seriously affected specimens older than 6 years, with the disappearance of 40-50% of the presumed annuli by that age. An alternate sectioning location was a clear improvement and this finding is an important contribution to the methodology of using this structure for ageing the full-length range of eastern T. thynnus. Finally, there were no significant differences between the coefficients of von Bertalanffy growth model estimated from mean length at age data (L∞  = 327.4; k = 0.097; t0  = -0.838) and those estimated from the growth curves accepted for the eastern and western T. thynnus management units. PMID:24890407

  7. Water masses, ocean fronts, and the structure of Antarctic seabird communities: putting the eastern Bellingshausen Sea in perspective

    USGS Publications Warehouse

    Ribic, Christine A.; Ainley, David G.; Ford, R. Glenn; Fraser, William R.; Tynan, Cynthia T.; Woehler, Eric J.

    2015-01-01

    Waters off the western Antarctic Peninsula (i.e., the eastern Bellingshausen Sea) are unusually complex owing to the convergence of several major fronts. Determining the relative influence of fronts on occurrence patterns of top-trophic species in that area, therefore, has been challenging. In one of the few ocean-wide seabird data syntheses, in this case for the Southern Ocean, we analyzed ample, previously collected cruise data, Antarctic-wide, to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer LTER and the winter Southern Ocean GLOBEC studies in the eastern Bellingshausen Sea. Fronts investigated during both winter (April–September) and summer (October–March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. We used clustering to determine species' groupings with water masses, and generalized additive models to relate species' densities, biomass and diversity to distance to respective fronts. Antarctic-wide, in both periods, highest seabird densities and lowest species diversity were found in the High Antarctic water mass. In the eastern Bellingshausen, seabird density in the High Antarctic water mass was lower (as low as half that of winter) than found in other Antarctic regions. During winter, Antarctic-wide, two significant species groups were evident: one dominated by Adélie penguins (Pygoscelis adeliae) (High Antarctic water mass) and the other by petrels and prions (no differentiation among water masses); in eastern Bellingshausen waters during winter, the one significant species group was composed of species from both Antarctic-wide groups. In summer, Antarctic-wide, a High Antarctic group

  8. Water masses, ocean fronts, and the structure of Antarctic seabird communities: Putting the eastern Bellingshausen Sea in perspective

    NASA Astrophysics Data System (ADS)

    Ribic, Christine A.; Ainley, David G.; Glenn Ford, R.; Fraser, William R.; Tynan, Cynthia T.; Woehler, Eric J.

    2011-07-01

    Waters off the western Antarctic Peninsula (i.e., the eastern Bellingshausen Sea) are unusually complex owing to the convergence of several major fronts. Determining the relative influence of fronts on occurrence patterns of top-trophic species in that area, therefore, has been challenging. In one of the few ocean-wide seabird data syntheses, in this case for the Southern Ocean, we analyzed ample, previously collected cruise data, Antarctic-wide, to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer LTER and the winter Southern Ocean GLOBEC studies in the eastern Bellingshausen Sea. Fronts investigated during both winter (April-September) and summer (October-March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. We used clustering to determine species' groupings with water masses, and generalized additive models to relate species' densities, biomass and diversity to distance to respective fronts. Antarctic-wide, in both periods, highest seabird densities and lowest species diversity were found in the High Antarctic water mass. In the eastern Bellingshausen, seabird density in the High Antarctic water mass was lower (as low as half that of winter) than found in other Antarctic regions. During winter, Antarctic-wide, two significant species groups were evident: one dominated by Adélie penguins ( Pygoscelis adeliae) (High Antarctic water mass) and the other by petrels and prions (no differentiation among water masses); in eastern Bellingshausen waters during winter, the one significant species group was composed of species from both Antarctic-wide groups. In summer, Antarctic-wide, a High Antarctic group dominated

  9. Water masses, ocean fronts, and the structure of Antarctic seabird communities: putting the eastern Bellingshausen Sea in perspective

    USGS Publications Warehouse

    Ribic, Christine A.; Ainley, David G.; Ford, R. Glenn; Fraser, William R.; Tynan, Cynthia T.; Woehler, Eric J.

    2011-01-01

    Waters off the western Antarctic Peninsula (i.e., the eastern Bellingshausen Sea) are unusually complex owing to the convergence of several major fronts. Determining the relative influence of fronts on occurrence patterns of top-trophic species in that area, therefore, has been challenging. In one of the few ocean-wide seabird data syntheses, in this case for the Southern Ocean, we analyzed ample, previously collected cruise data, Antarctic-wide, to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer LTER and the winter Southern Ocean GLOBEC studies in the eastern Bellingshausen Sea. Fronts investigated during both winter (April–September) and summer (October–March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. We used clustering to determine species' groupings with water masses, and generalized additive models to relate species' densities, biomass and diversity to distance to respective fronts. Antarctic-wide, in both periods, highest seabird densities and lowest species diversity were found in the High Antarctic water mass. In the eastern Bellingshausen, seabird density in the High Antarctic water mass was lower (as low as half that of winter) than found in other Antarctic regions. During winter, Antarctic-wide, two significant species groups were evident: one dominated by Adélie penguins (Pygoscelis adeliae) (High Antarctic water mass) and the other by petrels and prions (no differentiation among water masses); in eastern Bellingshausen waters during winter, the one significant species group was composed of species from both Antarctic-wide groups. In summer, Antarctic-wide, a High Antarctic group

  10. Crustal S-wave structure beneath Eastern Black Sea Region revealed by Rayleigh-wave group velocities

    NASA Astrophysics Data System (ADS)

    Çınar, Hakan; Alkan, Hamdi

    2016-01-01

    In this study, the crustal S-wave structure beneath the Eastern Black Sea Region (including the Eastern Black Sea Basin (EBSB) and Eastern Pontides (EP)) has been revealed using inversion of single-station, fundamental-mode Rayleigh-wave group velocities in the period range of 4-40 seconds. We used digital broadband recordings of 13 regional earthquakes that recently occurred in the easternmost EBSB recorded at stations of the Kandilli Observatory and Earthquake Research Institute (KOERI). The average group-velocity-dispersion curves were generated from 26 paths for the EBSB, and 16 paths for the EP, and they were inverted to determine the average 1-D shear-wave structure of the region. We have created a pseudo-section, roughly depicting the crustal structure of the region based on the group velocity inversion results of all station-earthquake paths. The thickness of the sedimentary layer reaches 12 km in the center of EBSB (Vs = 2.5-3.1 km/s) and decreases 4 km in the EP. There is a thin sedimentary layer in the EP (Vs = 2.7 km/s). A consolidated thin crust that exists in the EBSB possesses a high seismic velocity (Vs = 3.8 km/s). While a thin (∼26 km) and transitional crust exists beneath the EBSB, a thick (about 42 km) continental crust exists beneath the EP where the Conrad is clearly seen at about a 24 km depth. Thick continental crust in the EP region is clearly distinguished from a gradational velocity change (Vs = 3.4-3.8 km/s). The Moho dips approximately southwards, and the Vs velocity (4.25-4.15 km/s) beneath the Moho discontinuity decreases from the EBSB to the EP in the N-S direction. This may be an indication of a southward subduction.

  11. Climate change induced decadal variations in hydrodynamic conditions in the Eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Suursaar, U.; Kullas, T.

    2010-12-01

    Climate change manifests in the Baltic Sea region as increasing air and water temperatures, decrease in salinity and in shortening of the ice period. In addition, atmospheric westflow and storminess has intensified, which should also lead to changes in hydrodynamic regime of the sea. The objective of the paper is to study these changes in the practically tideless, fetch-limited nearshore region of West Estonia. The study is based on meteorological and sea level data from the Estonian weather and tide gauge stations, as well as on hydrodynamic modelling experiments with the shallow sea 2D model and wave hindcast for the period 1966-2008. Corrected with locally varying postglacial land uplift rates, the sea level rise according to the Estonian data was 1.5-2.7 mm/year over the period 1842-2009. Steeper than the lobal sea level rise, the rise in winter sea level, and particularly in annual maxima (3.5-11.2 mm/year), could be explained by the local sea level response to the changing regional wind climate. There are site-dependent changes in current patterns and upwelling occurrences. The significant wave heights exhibited some quasiperiodic cycles with the last high stage in 1980-95 and a slightly decreasing overall trend. As a result of northward shifts in cyclone trajectories, annual maximum waves have increased along the windward coasts of West Estonia, but decreased on the northern coast.

  12. Middle and Late Weichselian (Devensian) glaciation history of south-western Norway, North Sea and eastern UK

    NASA Astrophysics Data System (ADS)

    Sejrup, H. P.; Nygård, A.; Hall, A. M.; Haflidason, H.

    2009-02-01

    Data from eastern England, Scotland, the northern North Sea and western Norway have been compiled in order to outline our current knowledge of the Middle and Late Weichselian glacial history of this region. Radiometric dates and their geological context from key sites in the region are presented and discussed. Based on the available information the following conclusions can be made: (i) Prior to 39 cal ka and most likely after ca 50 cal ka Scotland and southern Norway were extensively glaciated. Most likely the central North Sea was not glaciated at this time and grounded ice did not reach the shelf edge. (ii) During the time interval between 29 and 39 ka periods with ameliorated climate (including the Ålesund, Sandnes and Tolsta Interstadials) alternated with periods of restricted glaciation in Scotland and western Norway. (iii) Between 29 and 25 ka maximum Weichselian glaciation of the region occurred, with the Fennoscandian and British ice sheets coalescing in the central North Sea. (iv) Decoupling of the ice sheets had occurred at 25 ka, with development of a marine embayment in the northern North Sea (v) Between 22 and 19 ka glacial ice expanded westwards from Scandinavia onto the North Sea Plateau in the Tampen readvance. (vi) The last major expansion of glacial ice in the offshore areas was between 17.5 and 15.5 ka. At this time ice expanded in the north-western part of the region onto the Måløy Plateau from Norway and across Caithness and Orkney and to east of Shetland from the Moray Firth. The Norwegian Channel Ice Stream (NCIS), which drained major parts of the south-western Fennoscandian Ice Sheet, was active at several occasions between 29 and 18 ka.

  13. Diversity, Abundance, and Niche Differentiation of Ammonia-Oxidizing Prokaryotes in Mud Deposits of the Eastern China Marginal Seas

    PubMed Central

    Yu, Shaolan; Yao, Peng; Liu, Jiwen; Zhao, Bin; Zhang, Guiling; Zhao, Meixun; Yu, Zhigang; Zhang, Xiao-Hua

    2016-01-01

    The eastern China marginal seas (ECMS) are prominent examples of river-dominated ocean margins, whose most characteristic feature is the existence of isolated mud patches on sandy sediments. Ammonia-oxidizing prokaryotes play a crucial role in the nitrogen cycles of many marine environments, including marginal seas. However, few studies have attempted to address the distribution patterns of ammonia-oxidizing prokaryotes in mud deposits of these seas. The horizontal and vertical community composition and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were investigated in mud deposits of the South Yellow Sea (SYS) and the East China Sea (ECS) by using amoA clone libraries and quantitative PCR. The diversity of AOB was comparable or higher in the mud zone of SYS and lower in ECS when compared with AOA. Vertically, surface sediments had generally higher diversity of AOA and AOB than middle and bottom layers. Diversity of AOA and AOB showed significant correlation with latitude. Nitrosopumilus and Nitrosospira lineages dominated AOA and AOB communities, respectively. Both AOA and AOB assemblages exhibited greater variations across different sites than those among various depths at one site. The abundance of bacterial amoA was generally higher than that of archaeal amoA, and both of them decreased with depth. Niche differentiation, which was affected by dissolved oxygen, salinity, ammonia, and silicate (SiO32-), was observed between AOA and AOB and among different groups of them. The spatial distribution of AOA and AOB was significantly correlated with δ15NTN and SiO32-, and nitrate and δ13C, respectively. Both archaeal and bacterial amoA abundance correlated strongly with SiO32-. This study improves our understanding of spatial distribution of AOA and AOB in ecosystems featuring oceanic mud deposits. PMID:26904010

  14. Diversity, Abundance, and Niche Differentiation of Ammonia-Oxidizing Prokaryotes in Mud Deposits of the Eastern China Marginal Seas.

    PubMed

    Yu, Shaolan; Yao, Peng; Liu, Jiwen; Zhao, Bin; Zhang, Guiling; Zhao, Meixun; Yu, Zhigang; Zhang, Xiao-Hua

    2016-01-01

    The eastern China marginal seas (ECMS) are prominent examples of river-dominated ocean margins, whose most characteristic feature is the existence of isolated mud patches on sandy sediments. Ammonia-oxidizing prokaryotes play a crucial role in the nitrogen cycles of many marine environments, including marginal seas. However, few studies have attempted to address the distribution patterns of ammonia-oxidizing prokaryotes in mud deposits of these seas. The horizontal and vertical community composition and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were investigated in mud deposits of the South Yellow Sea (SYS) and the East China Sea (ECS) by using amoA clone libraries and quantitative PCR. The diversity of AOB was comparable or higher in the mud zone of SYS and lower in ECS when compared with AOA. Vertically, surface sediments had generally higher diversity of AOA and AOB than middle and bottom layers. Diversity of AOA and AOB showed significant correlation with latitude. Nitrosopumilus and Nitrosospira lineages dominated AOA and AOB communities, respectively. Both AOA and AOB assemblages exhibited greater variations across different sites than those among various depths at one site. The abundance of bacterial amoA was generally higher than that of archaeal amoA, and both of them decreased with depth. Niche differentiation, which was affected by dissolved oxygen, salinity, ammonia, and silicate (SiO[Formula: see text]), was observed between AOA and AOB and among different groups of them. The spatial distribution of AOA and AOB was significantly correlated with δ(15)NTN and SiO[Formula: see text], and nitrate and δ(13)C, respectively. Both archaeal and bacterial amoA abundance correlated strongly with SiO[Formula: see text]. This study improves our understanding of spatial distribution of AOA and AOB in ecosystems featuring oceanic mud deposits.

  15. Qualitative and quantitative composition of microplastics particles during the expeditionary measurement program in the South-Eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Esiukova, Elena; Bagaeva, Margarita; Chubarenko, Natalia

    2016-04-01

    According to the tasks of the Russian Science Foundation project "Physical and dynamical properties of marine microplastics particles and their transport in a basin with vertical and horizontal salinity gradient on the example of the Baltic Sea" number 15-17-10020, a comprehensive expeditionary program of measurements in the South-Eastern Baltic started. The project is aimed at finding solutions for a number of problems caused by superfluous plastic pollution in the World Ocean and, in particular, in the Baltic Sea. This pollution has been accumulating for years and just recently it has become obvious that only multidisciplinary approach (geographical, biological, chemical, etc.) to the issues related to the processes of transformation of properties and propagation of plastic particles will allow the study of physical aspects of the problem. During the first stage of the study samples should be selected from the water surface, water column at various horizons, bottom sediments in the Baltic Sea, from different areas at the beaches - in order to further examine the qualitative and quantitative composition of microplastic particles in different seasons for different hydrophysical situations. Reconnaissance survey was begun to choose the fields for research close to point and distributed sources of microplastics. Preference is given to those beaches that are exposed to maximum anthropogenic pollution: areas around the town of Baltiysk, the northern part of the Vistula Spit (near the settlement of Kosa), and the Sambia peninsula coast (settlements of Yantarny, Donskoye, Primorye, Kulikovo, towns of Svetlogorsk, Pionersky, Zelenogradsk). Locations for experimental sites were found in order to assess time for formation of microplastics (Vistula Spit, Kosa settlement). In June-November, 2015 there were 5 expeditions in the waters of the South-Eastern Baltic, 7 expeditions along the coast line of the Baltic Sea (in Kaliningrad Oblast), and 5 expeditions to the Vistula

  16. Geologic interpretation and multibeam bathymetry of the sea floor in the vicinity of the Race, eastern Long Island Sound

    USGS Publications Warehouse

    Poppe, L.J.; DiGiacomo-Cohen, M. L.; Doran, E.F.; Smith, S.M.; Stewart, H.F.; Forfinski, N.A.

    2007-01-01

    Digital terrain models (DTMs) produced from multibeam bathymetric data provide valuable base maps for marine geological interpretations (Todd and others, 1999; Mosher and Thomson, 2002; ten Brink and others, 2004; Poppe and others, 2006a, b, c, d). These maps help define the geological variability of the sea floor (one of the primary controls of benthic habitat diversity), improve our understanding of the processes that control the distribution and transport of bottom sediments and the distribution of benthic habitats and associated infaunal community structures, and provide a detailed framework for future research, monitoring, and management activities. The bathymetric survey interpreted herein (National Oceanic and Atmospheric Administration (NOAA) survey H11250) covers roughly 94 km² of sea floor in an area where a depression along the Orient Point-Fishers Island segment of the Harbor Hill-Roanoke Point-Charlestown Moraine forms the Race, the eastern opening to Long Island Sound. The Race also divides easternmost Long Island Sound from northwestern Block Island Sound (fig. 1). This bathymetry has been examined in relation to seismic reflection data collected concurrently, as well as archived seismic profiles acquired as part of a long-standing geologic mapping partnership between the State of Connecticut and the U.S. Geological Survey (USGS). The objective of this work was to use these acoustic data sets to interpret geomorphological attributes of the sea floor, and to use these interpretations to better understand the Quaternary geologic history and modern sedimentary processes.

  17. Primary production, carbon export and nutrients availability in western and eastern Mediterranean Sea in early summer 1996 (MINOS cruise)

    NASA Astrophysics Data System (ADS)

    Moutin, T.; Raimbault, P.

    2002-06-01

    The distribution of primary production (PP), particulate carbon export from the photic zone to deeper layer, and nutrient concentrations are investigated in the Mediterranean Sea (MS) during May-June 1996. A decrease in integrated primary production, particulate carbon export and nutrient availability towards the eastern part of the Mediterranean sea was observed while integrated chlorophyll a remains rather constant. This pattern may be explained both by the adaptation of phytoplanktonic organisms to low light conditions and by a more efficient nutrient diffusion from the deeper layer in the east related to the position of the nutricline and density gradient. Integrated primary production ranging from 350 to 450 mgC m -2 day -1 in the west decreases toward the east to a value of about 150 mgC m -2 day -1. The latter value may appear as a limit for primary production rates under strong oligotrophic conditions. Particulate carbon export represents 4.0+2.9% of integrated primary production. Up to 90-95% of primary production is then sustained by internal recycling of organic matter. Evidence of a limitation of production by phosphate was obtained from differences between depth of nitracline and phosphacline and by enrichment experiments. The wide range of oligotrophic conditions in the Mediterranean Sea provides a case study for links between C, N and P-cycles.

  18. The geochemistry characteristic and dating of cold seepage carbonates of the Pearl River Mouth Basin, eastern of South China Sea

    NASA Astrophysics Data System (ADS)

    Fang, Yunxin; Fu, Shaoying

    2015-04-01

    Cold seepage carbonates are usually formed by the interaction of methane oxidizing archaea, sulfate reducing bacteria and cold seepage which contain abundant venting hydrocarbon gases. The presence of cold seepage carbonates on the seabed is one of the evidences that the area exist venting hydrocarbon gases, which are usually result by the dissociation of gas hydrate. The cold seepage property and fluid flow rate can influence the oxidation-deoxidation environment of the bottom water and sediment. Many previous studies focused on the mineral composition, microstructure, elemental composition, isotope composition of the cold seepage carbonates and isotopic dating for the cold seepage carbonates. The isotopic dating for the cold seepage carbonates can provide the information of the gas hydrate formation and dissociation in some area of the South China Sea. High precision TIMS-U dating and 14C dating are used as routine method for the dating of the Quaternary carbonates and fossils. The cold seepage carbonates in the study include the samples collected by ROV on the seabed and the drilling for gas hydrate in the Pearl River Mouth Basin, eastern of the South China Sea. The authigenic carbonate occurred in different depth in the A, B and C drilling site. They may be represent different events of gas hydrate formation and dissociation in the Quaternary. The dating study for all the cold seepage carbonates can provide the relative accurate eras of the gas hydrate dissociation events in certain area of the South China Sea.

  19. Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea

    PubMed Central

    Kousteni, V; Kasapidis, P; Kotoulas, G; Megalofonou, P

    2015-01-01

    Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species' distribution, most notably a population growth trend in the western Mediterranean/Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the small-spotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed. PMID:25469687

  20. Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea.

    PubMed

    Kousteni, V; Kasapidis, P; Kotoulas, G; Megalofonou, P

    2015-03-01

    Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species' distribution, most notably a population growth trend in the western Mediterranean/Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the small-spotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed. PMID:25469687

  1. Mud Volcanism and Fluid Venting In The Eastern Mediterranean Sea: Observations From Sidescan Sonar and Submersible Surveys

    NASA Astrophysics Data System (ADS)

    Zitter, T. A. C.; Huguen, C.; Woodside, J. M.; Mascle, J.; Scientific Party, Medineth/Medinaut

    Mud volcanoes in the eastern Mediterranean Sea have been identified by their distinctive acoustic signature as well as their morphology and sedimentology. They appear as circular regions of high backscatter believed to be caused principally by the clast content of the mud flows forming the mud volcano. Both the MEDINAUT and MEDINETH expeditions, conducted in 1998 and 1999 over two mud fields, the Olimpi field and the Anaximander Mountains area, in Eastern Mediterranean Sea, studied mud volcanism using a multidisciplinary approach in order to determine the relationships between the activity of the mud volcanoes (importance of degassing, associated fauna) and their geophysical signature. Mud volcanoes in Eastern Mediterranean Sea vary from conical and dome-shaped reliefs from 500m to 2km wide and 100 to 200m high to large "mud pie" types up to 6km wide. Sidescan sonar records give a very high resolution of the acoustic response, enabling to distinguish several mud flows, often flowing along tectonic lineations. A clear relationship between the occurrence of mud volcanism and cold seeps and both thrust and transcurrent faulting has been observed in both mud fields, although the tectonic settings vary from purely compressional to a more transpressional stress field. The faults are inferred to provide pathways for over- pressured fluids, and secondary faulting (transcurrent and extensional faults) may facilitate mud ascension. On the basis of sidescan sonar interpretation, other typical features have been inferred such as main feeder channels, eruptive cone centers, or brine pools. The in situ observations have been used to characterize the seafloor over numerous mud volcanoes and ground-truth the sonar data. They reveal an abundance of fluid seeps, mainly methane and methane-rich brines, as well as associated specific fauna such as tube worms, clams and chemosynthetic bacteria, and specific diagenetic phenomenon i.e. carbonate crusts. Video observations proved that

  2. Three-dimensional instantaneous dynamics modeling of present-day Aegean subduction

    NASA Astrophysics Data System (ADS)

    Glerum, Anne; Thieulot, Cedric; Pranger, Casper; van Hinsbergen, Douwe; Fraters, Menno; Spakman, Wim

    2015-04-01

    The Aegean region (Eastern Mediterranean) is exemplary of the interaction between crustal tectonics, plate motion, subduction and mantle flow: African subduction underneath the region has been continuous for at least the last 100 My, leading to about 2100-2500 km of subducted lithosphere residing in the mantle (van Hinsbergen et al., 2005). During this subduction, decoupled upper continental and oceanic crust accreted into a wedge of stacked nappes. In turn, these nappes have been significantly extended, predominantly during the last 25 My, due to the retreat of the African slab relative to Eurasia (van Hinsbergen and Schmid, 2012). As a first step to better understanding the coupling of the tectonic evolution of the crust and the underlying mantle dynamics, we are developing 3-D numerical models of the instantaneous dynamics of the present-day Aegean subduction system using the finite element code ASPECT (Kronbichler et al., 2012). The instantaneous models are set up with initial slab geometries derived from tomography and realistic plate boundary configurations and incorporate the major crustal weak zones of the overriding plate. Our modeling results in predictions of flow fields and stress, strain rate and rotation rate fields for the present-day tectonic setting of the Aegean region. By comparing our various model predictions to the widely available observations, such as focal mechanisms, GPS velocities and seismic anisotropy, we aim at an improved understanding of how mantle flow, subduction morphology and possibly slab segmentation, as well as the rheological behavior of the overriding plate, control present-day tectonic deformation. We expect to show preliminary results of this comparison. Kronbichler, M., Heister, T. and Bangerth, W. (2012), High Accuracy Mantle Convection Simulation through Modern Numerical Methods, Geophysical Journal International, 191, 12-29. Van Hinsbergen, D. J. J., Hafkenscheid, E., Spakman, W., Meulenkamp, J. E. and Wortel, R. (2005

  3. Sequence stratigraphy and a revised sea-level curve for the Middle Devonian of eastern North America

    USGS Publications Warehouse

    Brett, Carlton E.; Baird, G.C.; Bartholomew, A.J.; DeSantis, M.K.; Ver Straeten, C.A.

    2011-01-01

    The well-exposed Middle Devonian rocks of the Appalachian foreland basin (Onondaga Formation; Hamilton Group, Tully Formation, and the Genesee Group of New York State) preserve one of the most detailed records of high-order sea-level oscillation cycles for this time period in the world. Detailed examination of coeval units in distal areas of the Appalachian Basin, as well as portions of the Michigan and Illinois basins, has revealed that the pattern of high-order sea-level oscillations documented in the New York-Pennsylvania section can be positively identified in all areas of eastern North America where coeval units are preserved. The persistence of the pattern of high-order sea-level cycles across such a wide geographic area suggests that these cycles are allocyclic in nature with primary control on deposition being eustatic sea-level oscillation, as opposed to autocylic controls, such as sediment supply, which would be more local in their manifestation. There is strong evidence from studies of cyclicity and spectral analysis that these cycles are also related to Milankovitch orbital variations, with the short and long-term eccentricity cycles (100. kyr and 405. kyr) being the dominant oscillations in many settings. Relative sea-level oscillations of tens of meters are likely and raise considerable issues about the driving mechanism, given that the Middle Devonian appears to record a greenhouse phase of Phanerozoic history. These new correlations lend strong support to a revised high-resolution sea-level oscillation curve for the Middle Devonian for the eastern portion of North America. Recognized third-order sequences are: Eif-1 lower Onondaga Formation, Eif-2: upper Onondaga and Union Springs formations; Eif-Giv: Oatka Creek Formation; Giv-1: Skaneateles, Giv-2: Ludlowville, Giv-3: lower Moscow, Giv-4: upper Moscow-lower Tully, and Giv-5: middle Tully-Geneseo formations. Thus, in contrast with the widely cited eustatic curve of Johnson et al. (1985), which

  4. Uplift and denudation history of the eastern Dead Sea rift flank, SW Jordan: Evidence from apatite fission track thermochronometry

    NASA Astrophysics Data System (ADS)

    Feinstein, S.; Eyal, M.; Kohn, B. P.; Steckler, M. S.; Ibrahim, K. M.; Moh'd, B. K.; Tian, Y.

    2013-09-01

    Dead Sea rift (DSR), developed along the Dead Sea transform plate boundary, is characterized by salient flanks and morphotectonic asymmetry. Apatite fission track thermochronology (AFT) along ~1200 m high vertical profiles in Neoproterozoic basement and overlying Cambrian sandstone in southwestern Jordan is used to reconstruct timing, magnitude, and rate of uplift and denudation of the eastern DSR flank and examine its relationship to rift development and its flank landscape. Time-temperature models based on AFT data suggest three major Phanerozoic heating and cooling episodes, Late Paleozoic, Early Cretaceous, and Oligocene. The latest episode, on which this study focuses, indicates uplift of ~3.8±0.3 km under a moderate paleogeothermal gradient. About 40% of the uplift was tectonically driven with the remainder attributed to isostatic rebound in response to denudation and erosion. Models suggest that uplift commenced in the Oligocene with a considerable part occurring prior to development of the DSR, despite being ~200 km from the Red Sea-Gulf of Suez rift margin. Uplift is probably part of a regional rearrangement along the western Arabian platform margin occurring at the time of Red Sea rift initiation. Transition from primarily sedimentary layer stripping, most likely by scarp retreat, to one of dominantly incision of the underlying crystalline basement occurred in Late Miocene-Pliocene time following enhanced subsidence and development of a low base level in the DSR. Consequently, the magnitude of uplift by isostatic rebound due to incision exceeded lowering by surface truncation and increased summit elevation and riftward flexing of the flank.

  5. Draft Genome Sequence of Thalassotalea sp. Strain ND16A Isolated from Eastern Mediterranean Sea Water Collected from a Depth of 1,055 Meters

    PubMed Central

    Stelling, Savannah C.; Utturkar, Sagar M.; Alshibli, Noor K.; Brown, Steven D.

    2014-01-01

    Thalassotalea sp. strain ND16A belongs to the family Colwelliaceae and was isolated from eastern Mediterranean Sea water at a depth of 1,055 m. Members of Colwelliaceae are ubiquitous marine heterotrophs. Here, we report the draft genome sequence of Thalassotalea sp. strain ND16A, a member of the newly described genus Thalassotalea. PMID:25428976

  6. Draft Genome Sequence of Thalassotalea sp. Strain ND16A Isolated from Eastern Mediterranean Sea Water Collected from a Depth of 1,055 Meters

    SciTech Connect

    Stelling, Savannah C.; Techtmann, Stephen M.; Utturkar, Sagar M.; Alshibli, Noor K.; Brown, Steven D.; Hazen, Terry C.

    2014-11-26

    Thalassotalea sp. strain ND16A belongs to the family Colwelliaceae and was isolated from eastern Mediterranean Sea water at a depth of 1,055 m. Members of Colwelliaceae are ubiquitous marine heterotrophs. Lastly, here we report the draft genome sequence of Thalassotalea sp. strain ND16A, a member of the newly described genus Thalassotalea.

  7. Inshore capture-based tuna aquaculture impact on Posidonia oceanica meadows in the eastern part of the Adriatic Sea.

    PubMed

    Kružić, Petar; Vojvodić, Vjeročka; Bura-Nakić, Elvira

    2014-09-15

    Mapping and monitoring of the seagrass Posidonia oceanica in the eastern (Croatian) part of the Adriatic Sea since 2004 indicates a significant decline in meadow density in an area impacted by inshore capture-based tuna aquaculture. The density and overall condition of P. oceanica meadows impacted by tuna farms near Fulija Islet was compared to two reference sites (Iž Island and Mrtovnjak Islet). The factors with the most significant influence on P. oceanica meadows were found to be the input of organic matter originating from the cages, as well as high epiphyte biomass caused by nutrient enrichment. Significant differences in nutrient concentrations were found between the sites impacted by tuna farms (Fulija Islet) and the control stations. Shoot density of the P. oceanica meadows decreased at the stations in close vicinity to the tuna farm, which suggests that the tuna farm activity strongly affected the surrounding meadows.

  8. Importance of the eastern Alaskan Beaufort Sea to feeding bowhead whales, 1985-86. Final report, June 1985-August 1987

    SciTech Connect

    Richardson, W.J.

    1987-08-01

    The 2-year project was designed to quantify what proportion of the energy requirements of Western Arctic bowheads is provided by food acquired in the eastern part of the Alaskan Beaufort Sea. This final report presents the results from fieldwork in September - early October of 1985 and 1986. Water masses were studied by boat-based sampling and remote sensing. Zooplankton composition, biomass, distribution, patchiness and energy content were documented with nets and echosounders (a) over the continental shelf generally, and (b) near feeding bowheads. Whale distribution, numbers and activities were determined by aerial surveys and behavioral observations. Size segregation and residence times were studied by photogrammetry; five bowheads were radio tagged. Analyses of carbon-isotope ratios helped in tracing energy sources for bowheads.

  9. Gouge marks on deep-sea mud volcanoes in the eastern Mediterranean: Caused by Cuvier's beaked whales?

    NASA Astrophysics Data System (ADS)

    Woodside, J. M.; David, L.; Frantzis, A.; Hooker, S. K.

    2006-11-01

    Enigmatic seafloor gouge marks at depths of 1700-2100 m have been observed from submersible during geological survey work studying mud volcanoes in the eastern Mediterranean Sea. The marks consist of a central groove (about 10 cm deep and 1-2 m long), superimposed on a broader bowl-shaped depression (1-2 m long by about 50 cm wide) with raised rims (up to 10 cm high) to either side of the central groove. We discuss the potential biological causes of these marks, and conclude that they are probably created by Cuvier's beaked whales ( Ziphius cavirostris) during foraging dives to these depths. The mud volcanoes have a comparatively rich and diverse benthic ecology associated with methane-rich fluid seeps and thus could be the base of food chains that reach top predators like the deep-diving whales. The characteristic high acoustic backscatter of the mud volcanoes would facilitate their detection by the echolocation system of these whales.

  10. Quantifying the air-sea CO2 flux at a time-series in the Eastern Tropical Atlantic

    NASA Astrophysics Data System (ADS)

    Lefevre, Nathalie; Veleda, Doris; Araujo, Moacyr; Caniaux, Guy

    2016-04-01

    Hourly fCO2 is recorded at a time-series at the PIRATA buoy located at 6oS 10oW in the eastern tropical Atlantic since June 2006. This site is located south and west of the seasonal Atlantic cold tongue and is affected by its propagation from June to September. Using an alkalinity-salinity relationship determined for the eastern tropical Atlantic and the observed fCO2, pH and the inorganic carbon concentration are calculated. The time-series of fCO2 exhibits strong intraseasonal, seasonal and interannual variability. On seasonal timescales, the variations of fCO2 and pH are mostly controlled by sea surface salinity. At interannual timescales, some important differences appear in 2011-2012: lower fCO2 and fluxes are observed from September to December 2011 and are explained by higher advection of salty waters at the mooring. In early 2012, the anomaly is still present and is associated with lower sea surface temperatures. No significant long-term trend is detected over the period 2006-2013 on CO2 and any other physical parameter. However, as atmospheric fCO2 is increasing over time, the outgassing of CO2 is reduced over the period 2006-2013 as the flux is mainly controlled by the difference of fCO2 between the ocean and the atmosphere. A longer time-series is required to determine if any significant trend exists in this region.

  11. A GIS Approach for Reconstructing the Litorina Sea Lagoon in Tolkuse-Rannametsa Area, Eastern Gulf of Riga.

    NASA Astrophysics Data System (ADS)

    Habicht, Hando-Laur; Rosentau, Alar; Jõeleht, Argo; Hang, Tiit; Kohv, Marko

    2015-04-01

    The eastern coast of the Gulf of Riga in the NE Baltic Sea is characterized by slow post-glacial isostatic uplift (about 1mm/yr) and slowly undulating low topography. Therefore even small increases in sea-level can easily lead to the flooding of considerable areas. The complex deglaciation history of the Baltic Sea area left, at times, south western Estonia submerged, while at other times, it emerged as terrestrial land. Different transgressive and regressive development stages of the Baltic Sea did not only shape the landscape, but also influenced the locations of the Stone Age settlements which were closely bound to the coastal areas which also include estuaries and lagoonal systems. The coastal region of the Gulf of Riga is abundant in Meso- and Neolithic settlement sites. The present study combines LiDAR, ground-penetrating radar (GPR) and geological data to reconstruct development of the Litorina Sea lagoon in Tolkuse-Rannametsa area and to create prognostic palaeogeographic maps in order to search for Meso- and Neolithic coastal settlement sites. Over 47 km of GPR profiling was done; sediments were described and dated in 37 cores two riverbank outcrops. Diatoms were analysed in the master core. A semi-automatic method for the removal of modern anthropogenic features from LiDAR derived digital elevation model (DEM) was developed, tested and used. In modelling process the impact of sedimentary processes subsequent to the time being modelled was taken into account by employing a backstripping methodology. The differential glacio-isostatic uplift within the study area was taken into account by using interpolated water-level surfaces. Palaeogeographic reconstructions shed new light into region's post-glacial coastal evolution and enabled us to suggest the possible locations of the Stone Age settlements with some of the proposed areas buried under up to 3 m thick peat layer. The results of the current study provide new chronological and shore displacement data

  12. Sub-seasonally resolved coral records of northern Red Sea - eastern Mediterranean climate during the Holocene and the last interglacial

    NASA Astrophysics Data System (ADS)

    Felis, T.; Rimbu, N.; Al-Rousan, S.; Kuhnert, H.; Lohmann, G.; Kölling, M.; Pätzold, J.

    2012-04-01

    The northern Red Sea represents a unique location where ocean currents transport warm tropical waters northward, enabling coral reef growth at unusually high latitudes of up to 29 °N. Moreover, one of the world's northernmost complexes of uplifted Pleistocene reef terraces can be found here at Aqaba (Jordan). We present sub-seasonally resolved reconstructions of surface ocean conditions in the northern Red Sea derived from annually banded Porites corals. The Sr/Ca and δ18O variations in the aragonitic skeletons of our modern and fossil coral colonies provide proxy records of temperature, salinity and hydrologic balance at the sea surface during the last centuries and during time windows (40 to 100 years length) of the Holocene and the last interglacial period. Previous work has shown that seasonality and interannual to decadal climate variability in the northern Red Sea as documented in our coral records is strongly coupled to climate variations in the eastern Mediterranean, Middle East and Europe, reflecting the prominent role of atmospheric teleconnections of the Arctic Oscillation (AO)/North Atlantic Oscillation (NAO) in controlling regional climate on these timescales. New coral Sr/Ca data, in combination with δ18O, reveal an abrupt regime shift toward fresher surface ocean conditions in northern Red Sea surface waters at the end of the Little Ice Age. Possible mechanisms include a re-organization of the Northern Hemisphere atmospheric circulation. Sr/Ca records from a large number of fossil corals indicate a trend of decreasing temperature seasonality over the last 6000 years toward present-day. Such a trend is expected in the higher latitudes of the Northern Hemisphere from insolation changes on orbital timescales. Coral δ18O and Sr/Ca records suggest an increased seasonality in the hydrologic balance during time intervals around 4400, 4600 and 6000 years ago, which could result from both enhanced winter evaporation or increased summer precipitation

  13. Vertical distribution of mesozooplankton and its δ15N signature at a deep-sea site in the Levantine Sea (eastern Mediterranean) in April 1999

    NASA Astrophysics Data System (ADS)

    Koppelmann, Rolf; Weikert, Horst; Lahajnar, Niko

    2003-09-01

    Mesozooplankton samples were collected throughout the water column in the 4270 m deep Ierapetra basin, 30 nm SE off Crete, in April 1999. Information on trophic relationships within mesozooplankton size classes (<0.5, 0.5-1, 1-2, and 2-5 mm) and the sources of diet were obtained by measuring the composition of stable nitrogen isotopes of size-fractionated zooplankton and particles collected by sediment traps. Compared to data from the Arabian Sea, the δ15N values of zooplankton were markedly lower in the Levantine Sea. Data from the upper 250 m (2-3‰) suggest that N2 from the atmosphere was used by diazotroph cyanophycea as a nitrogen source for primary production. A loop system is hypothesized by which isotopically light NH4+ is recycled and used by phytoplankton. In the deep mesopelagic zone, an increase in δ15N with increasing depth was observed. In the deep bathypelagic zone, the δ15N values were more or less stable and indicate a trophic level of ˜2.5. A first zooplankton analysis revealed that juveniles of the calanoid copepod Lucicutia longiserrata, one of the rare true deep-sea species in the Levantine basin, were predominant in this zone. The taxonomic composition as well as the vertical distribution of zooplankton in the large habitat zones resembled that in January 1987, before the onset of a hydrological shift in the eastern Mediterranean. We therefore suggest that the situation in April 1999 does not characterize the mode of nitrogen transfer during the EMT.

  14. Space and time variability of satellite-derived sea surface temperatures and phytoplankton pigment concentrations in the eastern North Atlantic

    SciTech Connect

    Oliveira, P.B.; Peliz, A.R.; Fiuza, A.F.G.

    1994-12-31

    An analysis of NOAA/AVHRR II sea surface temperatures (SST) and NIMBUS-7/CZCS phytoplankton pigment concentrations was conducted in order to characterize their mean distributions and their space-time variability in the eastern North Atlantic, particularly in the vicinity of the western Iberian Peninsula. A 9-year long (1982--1990) SST set relative to a large part of the North Atlantic was extensively processed and analyzed to obtain the highest space-time resolution possible using only measured values. A good compromise led to a 9-year sequence of weekly averages of SST at 90 km x 90 km resolution. The first applications of these data were the preparation of yearly, seasonal and monthly mean surface temperature distributions with unprecedented resolution, as well as the construction of sequences of weekly SST charts for the whole 9-year period. The latter were used to construct a color video-loop which clearly shows the seasonal and interannual evolution of SST in a large region of the North Atlantic, in particular the meridional migration of the isotherms, the variability of large-scale thermal features associated with the Gulf Stream, the Labrador Current, the Azores Current, and the coastal upwelling along the North Atlantic eastern boundary.

  15. Drought reconstruction in eastern Hulun Buir steppe, China and its linkages to the sea surface temperatures in the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Liu, Na; Liu, Yu; Bao, Guang; Bao, Ming; Wang, Yanchao; Zhang, Lizhi; Ge, Yuxiang; Bao, Wurigen; Tian, Heng

    2016-01-01

    A tree-ring width chronology covering the period 1780-2013 AD was developed from Pinus sylvestris var. mongolica for the eastern Hulun Buir steppe, a region located on the edge of the eastern Mongolian Plateau, China. Climate-growth response analysis revealed drought stress to be the primary limiting factor for tree growth. Therefore, the mean February-July standardized precipitation evapotranspiration index (SPEI) was reconstructed over the period 1819-2013, where the reconstruction could account for 32.8% of the variance in the instrumental record over the calibration period 1953-2011. Comparison with other tree-ring-based moisture sequences from nearby areas confirmed a high degree of confidence in our reconstruction. Severe drought intervals since the late 1970s in our study area consisted with the weakening East Asian summer monsoon, which modulating regional moisture conditions in semi-arid zone over northern China. Drought variations in the study area significantly correlated with sea surface temperatures (SSTs) in North Pacific Ocean, suggesting a possible connection of regional hydroclimatic variations to the Pacific Decadal Oscillation (PDO). The potential influence associated with El Niño-Southern Oscillation (ENSO) was primarily analyzed.

  16. Structural and tectonic evolution of the eastern Cayman Trough (Caribbean Sea) from seismic reflection data

    SciTech Connect

    Leroy, S.; Mauffret, A.; Pubellier, M.

    1996-02-01

    The eastern Cayman Trough preserves a record of the Late Cretaceous to Paleogene Caribbean history that is largely affected by Neogene strike-slip tectonics of the current plate boundary. We conducted an analysis of seismic data within the eastern Cayman Trough, based upon single and multi-channel seismic reflection profiles collected during the Seacarib II cruise in 1987 and the Casis cruise in 1992. These data show that the basement of the eastern Cayman Trough can be divided into four domains from east to west, with distinct morphologic and sedimentary character and inferred older to younger ages: (1) a province of rifted Mesozoic continental crust exhibiting seven parallel horst blocks striking northeast-southwest; (2) a continent-ocean transition between provinces 1 and 3 that exhibits seamounts, small hills, and sedimentary basins; (3) an Eocene oceanic crust with rough basement but smoother relief than the rifted crust; basement trends are roughly north-south and oblique to the northwest trend in domain 1, and (4) the northern Jamaica slope, which forms an east-west-trending slope, with northward-dipping strata that flank the three deeper water domains of the Cayman Trough. The domains are interpreted to be the product of the Eocene east-west opening of the Cayman Trough as a pull-apart basin in a left-lateral strike-slip setting. Closure of the 1100 km of Eocene and younger oceanic crust of the Cayman Trough places the fault-block province adjacent to the Belize margin of Central America. A Neogene phase of transpression has reactivated structures in the four domains, along with on-land structures described by previous authors in Jamaica. The proximity of the eastern margin of the Cayman Trough to petroliferous, continental rocks in Central America suggests an improved possibility of hydrocarbon potential. Unfortunately, sediment thicknesses of less than 1 km probably are not conducive to hydrocarbon formation.

  17. Eastern Ionian Sea paleoceanographic conditions during the Plio - Pleistocene as revealed through the study of fish otoliths

    NASA Astrophysics Data System (ADS)

    Agiadi, K.; Triantaphyllou, M. V.; Girone, A.; Karakitsios, V.; Dermitzakis, M. D.

    2009-04-01

    Fish otoliths from the SE Zakynthos and SW Kephallonia islands (Eastern Ionian Sea) provide new evidence for the reconstruction of the paleoceanographic conditions during the Late Pliocene - Early Pleistocene interval. The forty - six fish taxa identified in the sediments of the study areas are separated in tropical, subtropical, temperate and subpolar ecological groups occupying surface, intermediate and deep water layers, based on their modern geographic and bathymetric distributions. During the Late Pliocene, the presence of Chlorophthalmus agassizi in the Eastern Ionian Sea probably denotes temperate oligotrophic conditions. At about 1.96 Ma B.P the high contribution of the bathypelagic Electrona risso, whose modern contribution is limited by the 10-15° C isotherms and productivity greater than 50gC/m2y (Whitehead et al., 1984), is combined with the increased presence of the deeper water species Maurolicus muelleri and Benthosema glaciale, which are mostly known from the high temperate - subpolar zones of today's oceans (Whitehead et al., 1984; Mytilineou et al., 2005). The nutrient-rich intermediate water layers at this time thus overlie colder deep waters, much like today (Malanotte-Rizzoli et al., 1997). In addition, the high abundance of representatives of the genus Diaphus could imply warmer surface conditions (Whitehead et al., 1984). The situation around 1.93 Ma, throughout the water column, is much more homogenous, signified by the introduction of Hygophum hygomii in the deeper water layers, as well as the decrease in relative abundance of Benthosema glaciale, perhaps due to a certain increase in deep water temperate. However, the most dominant species by far in the assemblage remains Ceratoscopelus maderensis, a purely temperate meso-bahtypelagic species (D'Onghia et al., 2004). At around 1.9Ma, there is a marked increase in the relative abundance of tropical taxa, namely Diaphus taaningi and Bregmaceros sp., which occupy the upper 500 meters of the

  18. Monitoring seismic velocity changes caused by the 2014 Northern Aegean earthquake using continuous ambient noise records

    NASA Astrophysics Data System (ADS)

    Evangelidis, Christos; Daskalakis, Emmanouil; Tsogka, Chrysoula

    2016-04-01

    The 24 May 2014 Northern Aegean earthquake (6.9 Mw), an event on the Northern Aegean Trough (NAT), ruptured on two different fault segments with a total ruptured length of ~100 km. For the second delayed segment, rupture propagated eastward from the hypocenter for ˜65 km with a supershear velocity (5.5 km/s). Low-aftershock seismicity on the supershear segment implies a simple and linear fault geometry there. An effort to monitor temporal seismic velocity changes across the ruptured area of the Northern Aegean earthquake is underway. In recent years, neighboring seismic broadband stations near active faults have been successfully used to detect such changes. The crosscorrelation functions (CCF) of ambient noise records between stations yields the corresponding traveltimes for those inter-station paths. Moreover, the auto-correlation functions (ACF) at each station produce the seismic responce for a coincident source and receiver position. Possible temporal changes of the measured traveltimes from CCFs and ACFs correspond to seismic velocity changes. Initially, we investigate the characteristics and sources of the ambient seismic noise as recorded at permanent seismic stations installed around NAT at the surrounding islands and in mainland Greece and Turkey. The microseismic noise levels show a clear seasonal variation at all stations. The noise levels across the double frequency band (DF; period range 4-8 s) reflect the local sea-weather conditions within a range of a few hundred kilometers. Three years of continuous seismic records framing the main shock have been analysed from ~15 stations within a radius of 100 km from the epicentre. We observe a clear decrease of seismic velocities most likely corresponding to the co-seismic shaking. The spatial variation of this velocity drop is imaged from all inter-station paths that correspond to CCF measurements and for station sites that correspond to ACF measurements. Thus, we explore a possible correlation between co

  19. Mesoscale changes in the water column in response to fish farming zones in three coastal areas in the Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Pitta, P.; Apostolaki, E. T.; Giannoulaki, M.; Karakassis, I.

    2005-11-01

    The hypothesis that the presence of fish farming zones affects the water quality and plankton communities at large spatial scales was investigated through sampling carried out in three regions of the Aegean Sea during May and September. In each region, two sub-areas were sampled: one with fish farming zones (within 2-3 nm) and one without fish farms ('reference site', more than 20 nm). Replicated water samples at different depths were taken in each sub-area for each of the investigated regions. Samples were analysed for nutrients, chlorophyll a, phaeopigments, POC and PON as well as for heterotrophic bacteria, cyanobacteria, flagellates and ciliates. Statistically significant changes in some nutrient species were found during September, which is in the period of maximal supply of feed to caged fish and nutrient loss to a highly stratified oligotrophic environment. Most of the significant changes of nutrients as well as chlorophyll a or PON were found at the deepest layer of the water column below the thermocline, indicating that it is related to the remineralization of benthic organic material. The data support previously published results in this area indicating that there is a rapid transfer of nutrients up the food web. This study also showed the need for studying the effects of fish farms on water quality at larger spatial scales.

  20. Nestedness in centipede (Chilopoda) assemblages on continental islands (Aegean, Greece)

    NASA Astrophysics Data System (ADS)

    Simaiakis, Stylianos Michail; Martínez-Morales, Miguel Angel

    2010-05-01

    In natural ecosystems, species assemblages among isolated ecological communities such as continental islands often show a nested pattern in which biotas of sites with low species richness are non-random subsets of biotas of richer sites. The distribution of centipede (Chilopoda) species in the central and south Aegean archipelago was tested for nestedness. To achieve this aim we used distribution data for 53 species collected on 24 continental Aegean islands (Kyklades and Dodekanisa). Based on the first-order jackknife estimator, most of islands were comprehensively surveyed. In order to quantify nestedness, we used the nestedness temperature calculator (NTC) as well as the nestedness metric based on overlap and decreasing Fill (NODF). NTC indicated that data exhibited a high degree of nestedness in the central and south Aegean island complexes. As far as the Kyklades and Dodekanisa are concerned, NTC showed less nested centipede structures than the 24 islands. Likewise, NODF revealed a significant degree of nestedness in central and south Aegean islands. It also showed that biotas matrices without singletons were more nested than the complete ones (Aegean, Kyklades and Dodekanisa). The two commonest centipede taxa (lithobiomorphs and geophilomorphs) contributed differently to centipede assemblages. In the Kyklades and Dodekanisa, geophilomorphs did not show a reliable nested arrangement unlike lithobiomorphs. In relation to the entire data set, nestedness was positively associated with the degree of isolation. In the Kyklades altitudinal range best explained nestedness patterns, while in Dodekanisa habitat heterogeneity proved to be more important for the centipede communities. Island area does not seem to be a significant explanatory variable. Some of our results from the Kyklades were critically compared with those for terrestrial isopod and land snail nested assemblages from the same geographical area. The complex geological and palaeogeographical history of

  1. Sedimentation studies relevant to low level radioactive effluent dispersal in the Irish Sea. Part 2. Sea bed morphology, sediments and shallow sub-bottom stratigraphy of the eastern Irish Sea

    SciTech Connect

    Williams, S.J.; Kirby, R.; Smith, T.J.; Parker, W.R.

    1981-01-01

    A detailed survey of the Eastern Irish Sea between the Isle of Man and the Cumbrian coast was carried out during 1979-80 using sidescan sonar, pinger and echo sounder seismic equipment supplemented by box cores, gravity cores and grab samples. The objective of the study was to provide a firm sedimentological basis for any further work concerning the horizontal and vertical distributions of radionuclides discharged from the Windscale nuclear fuel reprocessing plant within the sea bed sediments. The sidescan data were used to map the distribution of surface sediments and infer net sand transport paths, whilst the continous seismic profile records were used to study the sub-bottom stratigraphy and geological structures. The sediment samples were analyzed for faunal content and evidence of animal-sediment interaction.

  2. Responses of eastern Chinese coastal salt marshes to sea-level rise combined with vegetative and sedimentary processes

    NASA Astrophysics Data System (ADS)

    Ge, Zhen-Ming; Wang, Heng; Cao, Hao-Bin; Zhao, Bin; Zhou, Xiao; Peltola, Heli; Cui, Li-Fang; Li, Xiu-Zhen; Zhang, Li-Quan

    2016-06-01

    The impacts of sea-level rise (SLR) on coastal ecosystems have attracted worldwide attention in relation to global change. In this study, the salt marsh model for the Yangtze Estuary (SMM-YE, developed in China) and the Sea Level Affecting Marshes Model (SLAMM, developed in the U.S.) were used to simulate the effects of SLR on the coastal salt marshes in eastern China. The changes in the dominant species in the plant community were also considered. Predictions based on the SLAMM indicated a trend of habitat degradation up to 2100; total salt marsh habitat area continued to decline (4–16%) based on the low-level scenario, with greater losses (6–25%) predicted under the high-level scenario. The SMM-YE showed that the salt marshes could be resilient to threats of SLR through the processes of accretion of mudflats, vegetation expansion and sediment trapping by plants. This model predicted that salt marsh areas increased (3–6%) under the low-level scenario. The decrease in the total habitat area with the SMM-YE under the high-level scenario was much lower than the SLAMM prediction. Nevertheless, SLR might negatively affect the salt marsh species that are not adapted to prolonged inundation. An adaptive strategy for responding to changes in sediment resources is necessary in the Yangtze Estuary.

  3. Responses of eastern Chinese coastal salt marshes to sea-level rise combined with vegetative and sedimentary processes.

    PubMed

    Ge, Zhen-Ming; Wang, Heng; Cao, Hao-Bin; Zhao, Bin; Zhou, Xiao; Peltola, Heli; Cui, Li-Fang; Li, Xiu-Zhen; Zhang, Li-Quan

    2016-06-23

    The impacts of sea-level rise (SLR) on coastal ecosystems have attracted worldwide attention in relation to global change. In this study, the salt marsh model for the Yangtze Estuary (SMM-YE, developed in China) and the Sea Level Affecting Marshes Model (SLAMM, developed in the U.S.) were used to simulate the effects of SLR on the coastal salt marshes in eastern China. The changes in the dominant species in the plant community were also considered. Predictions based on the SLAMM indicated a trend of habitat degradation up to 2100; total salt marsh habitat area continued to decline (4-16%) based on the low-level scenario, with greater losses (6-25%) predicted under the high-level scenario. The SMM-YE showed that the salt marshes could be resilient to threats of SLR through the processes of accretion of mudflats, vegetation expansion and sediment trapping by plants. This model predicted that salt marsh areas increased (3-6%) under the low-level scenario. The decrease in the total habitat area with the SMM-YE under the high-level scenario was much lower than the SLAMM prediction. Nevertheless, SLR might negatively affect the salt marsh species that are not adapted to prolonged inundation. An adaptive strategy for responding to changes in sediment resources is necessary in the Yangtze Estuary.

  4. Spatial variability in phytoplankton community structure along the eastern Arabian Sea during the onset of south-west monsoon

    NASA Astrophysics Data System (ADS)

    Ahmed, Ayaz; Kurian, Siby; Gauns, Mangesh; Chndrasekhararao, A. V.; Mulla, Amara; Naik, Bhagyashri; Naik, Hema; Naqvi, S. W. A.

    2016-05-01

    The Arabian Sea experiences moderate to weak upwelling along the south-west coast of India, which subsequently propagates towards the north. This causes variation in plankton community composition, which is addressed in the present study. Here we report the spatial variations in distribution of phytoplankton groups along the north-south transect in the eastern Arabian Sea based on marker pigments supported with flow-cytometric and microscopic analyses. 15 phytoplankton pigments were identified using High-performance liquid chromatography (HPLC) and the chemotaxonomic software (CHEMTAX) analysis associated these to seven major group of phytoplankton. The phytoplankton biomass, chlorophyll a (Chl a) was higher in southern stations with dominance of fucoxanthin whereas, divinyl chlorophyll a (divinyl Chl a), marker pigment of Prochlorococcus was present only in the northern region. Microscopic observation revealed the dominance of larger forms; diatoms (Chaetoceros coarctatum and Nitzschia sp.) and dinoflagellates (Scrippsiella sp., Oxytoxum nanum and Oxytoxum sp.) in the southern region. Furthermore, a study of plankton size distribution showed dominance of picoplankton (fpico) followed by nanoplankton (fnano) along the northern stations with comparatively higher microplankton (fmicro) in the south. This study clearly showed the influence of different environmental conditions on the phytoplankton community as reflected in dominance of diatoms in the southern (south of 12 °N) and that of picoplankton in the northern (north of 12 °N) region.

  5. Responses of eastern Chinese coastal salt marshes to sea-level rise combined with vegetative and sedimentary processes.

    PubMed

    Ge, Zhen-Ming; Wang, Heng; Cao, Hao-Bin; Zhao, Bin; Zhou, Xiao; Peltola, Heli; Cui, Li-Fang; Li, Xiu-Zhen; Zhang, Li-Quan

    2016-01-01

    The impacts of sea-level rise (SLR) on coastal ecosystems have attracted worldwide attention in relation to global change. In this study, the salt marsh model for the Yangtze Estuary (SMM-YE, developed in China) and the Sea Level Affecting Marshes Model (SLAMM, developed in the U.S.) were used to simulate the effects of SLR on the coastal salt marshes in eastern China. The changes in the dominant species in the plant community were also considered. Predictions based on the SLAMM indicated a trend of habitat degradation up to 2100; total salt marsh habitat area continued to decline (4-16%) based on the low-level scenario, with greater losses (6-25%) predicted under the high-level scenario. The SMM-YE showed that the salt marshes could be resilient to threats of SLR through the processes of accretion of mudflats, vegetation expansion and sediment trapping by plants. This model predicted that salt marsh areas increased (3-6%) under the low-level scenario. The decrease in the total habitat area with the SMM-YE under the high-level scenario was much lower than the SLAMM prediction. Nevertheless, SLR might negatively affect the salt marsh species that are not adapted to prolonged inundation. An adaptive strategy for responding to changes in sediment resources is necessary in the Yangtze Estuary. PMID:27334452

  6. New cold-water coral occurrences in the Eastern Ionian Sea: Results from experimental long line fishing

    NASA Astrophysics Data System (ADS)

    Mytilineou, Ch.; Smith, C. J.; Anastasopoulou, A.; Papadopoulou, K. N.; Christidis, G.; Bekas, P.; Kavadas, S.; Dokos, J.

    2014-01-01

    Our knowledge on the cold-water corals (CWCs) occurring in the deep waters of Eastern Ionian Sea (E. Mediterranean) has improved with new species records and information related to their occurrence, abundance, distribution, morphological and other characteristics. Data were collected from accidental coral catches during experimental long-line fishing using two different hook sizes (No. 7 targeting hake and No. 9 targeting blackspot seabream). Eight coral taxa were identified, with new records for the E. Ionian Sea for Antipathes dichotoma, Desmophyllum dianthus, Swiftia pallida and Pennatula phosphorea. CWCs occurred in 72% of the long lines and most of them were entire and live (except Leiopathes glaberrima). The most frequently caught coral group was Antipatharia. Isidella elongata and A. dichotoma presented the highest abundance. The main bulk of the corals was caught between 500 and 600 m depth. Some of the identified corals (L. glaberrima and I. elongata) seemed to have more close relationships with some species of the fish assemblage (Galeus melastomus, Helicolenus dactylopterus) inhabiting the study area. Species richness and coral catch in numbers were higher for the smaller hook size (No. 9), which caught the larger entire living colonies of A. dichotoma, L. glaberrima and I. elongata. As a result, the corals collected during the present study, characterized by slow growth rates and high longevities, could be considered vulnerable to the gear used in blackspot seabream fishery; this implies the need for more research, monitoring, protection and sustainable management.

  7. Seabird sockeye salmon co-variation in the eastern Bering Sea: Phenology as an ecosystem indicator and salmonid predictor?

    NASA Astrophysics Data System (ADS)

    Sydeman, William J.; Abraham, Christine L.; Vernon Byrd, G.

    2008-08-01

    Seabirds ( Rissa spp. and Uria spp.) and sockeye salmon ( Onchorhynchus nerka) of the eastern Bering Sea share similarities in their trophic ecology. We tested the role of seabirds as indicators of food web conditions that affect sockeye salmon at sea survival by investigating co-variation between seabirds breeding on the Pribilof Islands and returns of Bristol Bay sockeyes. We examined seabird phenology (hatching dates of eggs) against sockeye returns based on the year of ocean entry. Annual seabird hatching date was inversely related to sockeye returns, with the strongest co-variation found for sockeye which entered the ocean at 2 years of age (age 2 x smolts). The mechanism supporting this co-variation is unknown, but both birds and salmon may be responding to changes in prey availability (a "bottom-up" effect). The co-variation between seabird hatching date and sockeye returns supports the idea that variation in seabird breeding parameters indicates food web conditions that also affect other upper trophic level predators in marine systems. Coupling seabird phenology with existing annual predictions for Bristol Bay salmon may improve forecasts and fishery management.

  8. Enhanced salinities, as a proxy of seawater desalination discharges, impact coastal microbial communities of the eastern Mediterranean Sea.

    PubMed

    Belkin, Natalia; Rahav, Eyal; Elifantz, Hila; Kress, Nurit; Berman-Frank, Ilana

    2015-10-01

    Seawater desalination plants increase local coastal salinities by discharging concentrated brine back to the sea with ∼ 50% higher than ambient salinities. The impacts of high salinities on microbial coastal populations of the eastern Mediterranean Sea (EMS) were examined in two mesocosm experiments; first, during the mixed-spring and second, during the stratified-summer periods with average salinity of ∼ 39. Ambient salinities were increased by 5% and 15%. Higher salinity (15%) mesocosms induced rapid (within 2 h) declines in both primary productivity (PP) and algal biomass parallel to an increase in bacterial productivity. Subsequently, for the duration of the experiments (11-12 days), both Chlorophyll a and PP rates increased (2 to 5 and 1.5 to 2.5-fold, respectively) relative to unamended controls. The initial assemblages of the ambient microbial populations and intensity of salinity enrichments influenced the community responses. During the mixed-spring experiment, the composition of prokaryotic and eukaryotic populations shifted only slightly, suggesting high functional plasticity of the initial populations. While during the stratified-summer experiment, high salinity changed the composition and reduced the biodiversity of the microbial communities. In an ultra-oligotrophic environment such as the EMS, salinity induced declines in microbial diversity may provide a tipping point destabilizing the local aquatic food web. PMID:26178627

  9. Enhanced salinities, as a proxy of seawater desalination discharges, impact coastal microbial communities of the eastern Mediterranean Sea.

    PubMed

    Belkin, Natalia; Rahav, Eyal; Elifantz, Hila; Kress, Nurit; Berman-Frank, Ilana

    2015-10-01

    Seawater desalination plants increase local coastal salinities by discharging concentrated brine back to the sea with ∼ 50% higher than ambient salinities. The impacts of high salinities on microbial coastal populations of the eastern Mediterranean Sea (EMS) were examined in two mesocosm experiments; first, during the mixed-spring and second, during the stratified-summer periods with average salinity of ∼ 39. Ambient salinities were increased by 5% and 15%. Higher salinity (15%) mesocosms induced rapid (within 2 h) declines in both primary productivity (PP) and algal biomass parallel to an increase in bacterial productivity. Subsequently, for the duration of the experiments (11-12 days), both Chlorophyll a and PP rates increased (2 to 5 and 1.5 to 2.5-fold, respectively) relative to unamended controls. The initial assemblages of the ambient microbial populations and intensity of salinity enrichments influenced the community responses. During the mixed-spring experiment, the composition of prokaryotic and eukaryotic populations shifted only slightly, suggesting high functional plasticity of the initial populations. While during the stratified-summer experiment, high salinity changed the composition and reduced the biodiversity of the microbial communities. In an ultra-oligotrophic environment such as the EMS, salinity induced declines in microbial diversity may provide a tipping point destabilizing the local aquatic food web.

  10. Distribution of low-level natural radioactivity in a populated marine region of the Eastern Mediterranean Sea.

    PubMed

    Evangeliou, Nikolaos; Florou, Heleny; Kritidis, Panayotis

    2012-12-01

    The levels of natural radioactivity have been evaluated in the water column of an eastern Mediterranean region (Saronikos Gulf), with respect to the relevant environmental parameters. A novel methodology was used for the determination of natural radionuclides, which substitutes the time-consuming radiochemical analysis, based on an in situ sample preconcentration using ion-selective manganese fibres placed on pumping systems. With regard to the results obtained, (238)U-series radionuclides were found at the same level or lower than those observed previously in Mediterranean regions indicating the absence of technologically enhanced naturally occurring radioactive material (TENORM) activities in the area. Similar results were observed for the (232)Th-series radionuclides and (40)K in the water column in comparison with the relevant literature on the Mediterranean Sea. The calculated ratios of (238)U-(232)Th and (40)K-(232)Th verified the lack of TENORM contribution in the Saronikos Gulf. Finally, a rough estimation was attempted concerning the residence times of fresh water inputs from a treatment plant of domestic wastes (Waste Water Treatment Plant of Psitalia) showing that fresh waters need a maximum of 15.7±7.6 d to be mixed with the open sea water.

  11. Spatial patterns of Aquificales in deep-sea vents along the Eastern Lau Spreading Center (SW Pacific).

    PubMed

    Ferrera, Isabel; Banta, Amy B; Reysenbach, Anna-Louise

    2014-09-01

    The microbial diversity associated with actively venting deep-sea hydrothermal deposits is tightly connected to the geochemistry of the hydrothermal fluids. Although the dominant members of these deposits drive the structure of the microbial communities, it is less well understood whether the lower abundance groups are as closely connected to the geochemical milieu, or driven perhaps by biotic factors such as microbial community interactions. We used the natural geochemical gradients that exist in the back-arc basin, Eastern Lau Spreading Center and Valu-Fa Ridge (ELSC/VFR) in the Southwestern Pacific, to explore whether the chemolithotrophic Aquificales are influenced by geographical location, host-rock of the vent field or deposit type. Using a combination of cloning, DNA fingerprinting (DGGE) and enrichment culturing approaches, all genera of this order previously described at marine vents were detected, i.e., Desulfurobacterium, Thermovibrio, Aquifex, Hydrogenivirga, Persephonella and Hydrogenothermus. The comparison between clone libraries and DGGE showed similar patterns of distribution of different Aquificales whereas results differed for the enrichment cultures that were retrieved. However, the use of cultivation-based and -independent methods did provide complementary phylogenetic diversity overview of the Aquificales in these systems. Together, this survey revealed that the ELSC/VFR contains some of the largest diversity of Aquificales ever reported at a deep-sea vent area, that the diversity patterns are tied to the geography and geochemistry of the system, and that this geochemical diverse back-arc basin may harbor new members of the Aquificales.

  12. Responses of eastern Chinese coastal salt marshes to sea-level rise combined with vegetative and sedimentary processes

    PubMed Central

    Ge, Zhen-Ming; Wang, Heng; Cao, Hao-Bin; Zhao, Bin; Zhou, Xiao; Peltola, Heli; Cui, Li-Fang; Li, Xiu-Zhen; Zhang, Li-Quan

    2016-01-01

    The impacts of sea-level rise (SLR) on coastal ecosystems have attracted worldwide attention in relation to global change. In this study, the salt marsh model for the Yangtze Estuary (SMM-YE, developed in China) and the Sea Level Affecting Marshes Model (SLAMM, developed in the U.S.) were used to simulate the effects of SLR on the coastal salt marshes in eastern China. The changes in the dominant species in the plant community were also considered. Predictions based on the SLAMM indicated a trend of habitat degradation up to 2100; total salt marsh habitat area continued to decline (4–16%) based on the low-level scenario, with greater losses (6–25%) predicted under the high-level scenario. The SMM-YE showed that the salt marshes could be resilient to threats of SLR through the processes of accretion of mudflats, vegetation expansion and sediment trapping by plants. This model predicted that salt marsh areas increased (3–6%) under the low-level scenario. The decrease in the total habitat area with the SMM-YE under the high-level scenario was much lower than the SLAMM prediction. Nevertheless, SLR might negatively affect the salt marsh species that are not adapted to prolonged inundation. An adaptive strategy for responding to changes in sediment resources is necessary in the Yangtze Estuary. PMID:27334452

  13. Monsoon driven changes in phytoplankton populations in the eastern Arabian Sea as revealed by microscopy and HPLC pigment analysis

    NASA Astrophysics Data System (ADS)

    Parab, Sushma G.; Prabhu Matondkar, S. G.; Gomes, H. do R.; Goes, J. I.

    2006-12-01

    miliaris with higher amounts of zeaxanthin, β-carotene, Chl b and prasinoxanthin. Trichodesmium trichomes were noticed in the water column as early as December when nitrate concentrations became limiting. The low phytoplankton biomass and high ammonium concentrations argue that active grazing populations may be responsible for preventing diatom-dinoflagellate populations from establishing themselves to bloom proportions in the eastern Arabian Sea during the early NE monsoon. Trichodesmium continued its dominance well into May, when nutrient enrichment associated with its death and decay helped simulate the growth of both diatoms and dinoflagellates. Given that anoxic conditions are becoming more pervasive in the eastern Arabian Sea, our observations in particular, those of a shift towards dinoflagellate dominance during the development of anoxia assume particular importance.

  14. Eastern Mediterranean sea levels through the last interglacial from a coastal-marine sequence in northern Israel

    NASA Astrophysics Data System (ADS)

    Sivan, D.; Sisma-Ventura, G.; Greenbaum, N.; Bialik, O. M.; Williams, F. H.; Tamisiea, M. E.; Rohling, E. J.; Frumkin, A.; Avnaim-Katav, S.; Shtienberg, G.; Stein, M.

    2016-08-01

    A last interglacial (Marine Isotope Stage, MIS5e) marine-coastal sequence has been identified along the Galilee coast of Israel, with the type section located at Rosh Hanikra (RH). The microtidal regime and tectonic stability, along with the detailed stratigraphy of the RH shore, make the study region ideally suited for determining relative sea level (RSL) through the MIS5e interval in the eastern Mediterranean. The sequence contains fossilized microtidal subunits at a few meters above the current sea level. Unfortunately, all fossils were found to be altered, so that U-Th datings cannot be considered to represent initial deposition. We contend that U-Th dating of Strombus bubonius shells (recrystallized to calcite) suffices to indicate a lower limit of ∼110 ± 8 ka for the time sea level dropped below the RH sedimentary sequence. The RH-section comprises three main subunits of a previously determined member (the Yasaf Member): (a) a gravelly unit containing the diagnostic gastropod Strombus bubonius Lamarck (Persististrombus latus), which was deposited in the intertidal to super-tidal stormy zone; (b) Vermetidae reef domes indicating a shallow-water depositional environment; and (c) coarse to medium-sized, bioclastic sandstone, probably deposited in the shallow sub-tidal zone. The sequence overlies three abrasion platforms that are cut by tidal channels at elevations of +0.8 m, +2.6 m and +3.4 m, and which are filled with MIS5e sediments. We present a detailed study of the sequence, with emphasis on stratigraphic, sedimentological, and palaeontological characteristics that indicate sea-level changes. Although without precise absolute dating, the stratigraphic sequence of RH through MIS5e allows us to identify a time-series of RSL positions, using the elevations of three stratigraphic subunits. Reconstructed RSL values range from +1.0 m to +7 m (with uncertainly < 1 m), and most fall within a narrow range of +1.0 to +3.3 m. Toward the end of MIS5e, RSL exceeded

  15. Collapse and flow of lowstand shelf-margin deposits: An example from the eastern Tyrrhenian Sea, Italy

    USGS Publications Warehouse

    Trincardi, F.; Field, M.E.

    1992-01-01

    The upper slope of the eastern Tyrrhenian Sea margin has a complex morphology shaped by Quaternary tectonism and by sedimentation phases controlled by changing sea levels. Sediment slides of widely varying size and shape are common in Quaternary deposits of the upper slope, particularly where gradients are steep. Our study of a large sediment failure in lowstand prograded coastal deposits west of Cape Licosa indicates that the nature of shelf-margin deposition is an additional important control on failure. The failure zone has a mobilization surface showing in-situ deformation in the sediment above it; an upper failure surface; a head scarp; and a zone of ponded sediment debris downslope from the exposed surface of failure. The basal mobilization surface is roughly parallel to the seafloor and coincident with a major downlap surface. The failed section is less that 20 m thick and local in extent, but deformation on the basal mobilization surface extends outside the immediate area of the failure. Directly downslope of the slide scarp are internally stratified mounds that show no evidence of deformation or movement. Most of the prograded deposit experienced in-situ deformation that evolved into the collapse of part of the sediment pile above the mobilization surface. A portion of the mobilized sediment flowed a few kilometers basinward and accumulated at the base of a slope-parallel ridge. Sediment failure occurred on the Licosa shelf margin following a major pulse of coastal sedimentation along the lowstand shoreline. On many continental margins, sea-level lowering is thought to be an important cause of failure unconsolidated sediment deposited during previous high-stand conditions. The Licosa slide demonstrates that sea-level fall has another, equally important but indirect, role in sediment failure. As sea level falls and reaches its lowstand position, streams are at their peak efficiency and a coarsening-upward clastic coastal wedge is rapidly emplaced at

  16. Multiscale wind cycles and current pulses at the Black Sea eastern boundary

    NASA Astrophysics Data System (ADS)

    Melnikov, Vasiliy; Moskalenko, Lidija; Piotoukh, Vladimir; Zatsepin, Andrey

    2015-04-01

    The goal of the research is to examine meteorological descriptive elements, sea-water properties, regional hydrodynamics and energy conversion fluxes in order to study sea responses to the local and far-field weather system. The Black Sea is situated in the chain of internal basins between the North Atlantic and Central Asia deserts in the marginal interaction zone and, accordingly, is under the influence of the Azores and Siberian anticyclones, Arctic cold-air surges and subtropical desert belt to the south. The analysis is based on the data of modern oceanographic measuring network "Hydro-physical Polygon" of the Institute of oceanology, using contact and remote sensing methods, weather stations around the Black Sea coasts, including long-term (1938-2014) measurements at the Gelendzhik weather station. Various satellite and Reanalysis databases are used. Currently, there are three long-time measuring moored stations (each contains ADCP and thermistor chain) and scanning profiling system "Akvalog". Hydrological sections and field surveys using towed ADCP and CTD are performed on a regular basis. The data are accumulated in the coastal archive which allows calibration of satellite measurements and testing results of numerical modeling. Data processing includes data sets preparation, editing, time series statistical calculations using histograms, progressive vector diagrams, traditional Fourier spectral analysis including auto- and cross spectra, auto and mutual wavelet diagrams, moving spectrograms, vector data methods using rotary components, spectral invariants, empirical modes, hodograph and pre-specified spectrum representations on the basis of stochastic models with imposed dynamical assumptions. Due to the intermittent nature of the time rows, spectral representation is misleading, often. In order to identify the individual evolving dynamical phenomenon, typical background (seasonal) three-dimensional structures of the hydrological field, as well as

  17. Controls of bioclastic turbidite deposition in eastern Muertos Trough northeast Caribbean Sea

    SciTech Connect

    Forsthoff, G.M.; Holcombe, T.L.

    1985-02-01

    A study of seismic-reflection profiles and sediment cores establishes regional bathymetric and source area control over the composition, transport, and distribution of turbidites in the eastern Muertos Trough, Bioclastic (carbonate) turbidites dominate the eastern portion of the trough. Analyses of carbon content and sand-sized components suggest that the bioclastic turbidites (characterized by planktonic foraminifera, pteropods, and sponge spicules) are reworked pelagic oozes originally deposited on the outer-shelf and upper-slope areas south of St. Croix and eastern Puerto Rico. The presence of several intrashelf and upper-slope basins prohibits shallow-water carbonate sediments from entering the Muertos Trough. Volcanic rock fragments derived from Puerto Rico are transported to the trough via the Guayanilla Canyon system. Mixing of the volcanic fragments with outer-shelf and upper-slope lutites results in mixed bioclastic-terrigenous turbidites south of central and western Puerto Rico. The paucity of shallow-water carbonate sediments in the trough suggests that the submarine canyons are effective conduits for the rapid transport of volcaniclastic sands across the shelf and thereby prevent extensive mixing with inner- and middle-shelf carbonate sediments. Sediment transport within the trough is primarily axial in an east-west direction. Outer trench-wall fault scarps, south of Guayanilla Canyon, limit the southerly progradation of the trench-wedge facies and deflect incoming gravity flows in a down-axis (westward) direction. Where no faults exist, the trench wedge progrades southward and interfingers with the pelagic sediments of the northern Venezuelan basin.

  18. Spring plankton dynamics in the Eastern Bering Sea, 1971-2050: Mechanisms of interannual variability diagnosed with a numerical model

    NASA Astrophysics Data System (ADS)

    Banas, Neil S.; Zhang, Jinlun; Campbell, Robert G.; Sambrotto, Raymond N.; Lomas, Michael W.; Sherr, Evelyn; Sherr, Barry; Ashjian, Carin; Stoecker, Diane; Lessard, Evelyn J.

    2016-02-01

    A new planktonic ecosystem model was constructed for the Eastern Bering Sea based on observations from the 2007-2010 BEST/BSIERP (Bering Ecosystem Study/Bering Sea Integrated Ecosystem Research Program) field program. When run with forcing from a data-assimilative ice-ocean hindcast of 1971-2012, the model performs well against observations of spring bloom time evolution (phytoplankton and microzooplankton biomass, growth and grazing rates, and ratios among new, regenerated, and export production). On the southern middle shelf (57°N, station M2), the model replicates the generally inverse relationship between ice-retreat timing and spring bloom timing known from observations, and the simpler direct relationship between the two that has been observed on the northern middle shelf (62°N, station M8). The relationship between simulated mean primary production and mean temperature in spring (15 February to 15 July) is generally positive, although this was found to be an indirect relationship which does not continue to apply across a future projection of temperature and ice cover in the 2040s. At M2, the leading direct controls on total spring primary production are found to be advective and turbulent nutrient supply, suggesting that mesoscale, wind-driven processes—advective transport and storminess—may be crucial to long-term trends in spring primary production in the southeastern Bering Sea, with temperature and ice cover playing only indirect roles. Sensitivity experiments suggest that direct dependence of planktonic growth and metabolic rates on temperature is less significant overall than the other drivers correlated with temperature described above.

  19. Timing of active methane seep events in the eastern margin of the Japan Sea based on benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Oi, T.

    2015-12-01

    We study the late Quaternary assemblages and stable isotope analyses of benthic foraminifera from the marine core sediments around three methane seep area in the eastern margin of the Japan Sea. Study samples are collected on the Umitaka Spur (MD179-3304), a west part of the Oki Trough (UT14-PC1303&PC1305), and a north part of the Mogami Trough (HR14-RC1408). Each sedimentation rate is calculated by the ages of 14C, tephra, oxygen isotope events, and bottoms of the thin laminated layer.Obvious occurrences of the methane related foraminifera, Rutherfordoides sp., are found from three all core sediments, and these sedimentation ages range to 28-25ka, early part of the MIS 2. However, we never find the unique occurrences from RC1408 sections except of MIS 2 even if another low stand stage of MIS 6. Above Rutherfordoides distributions, rare benthic foraminiferal number shows an anoxic bottom condition where most benthic foraminifera couldn't live during the LGM (Oba et al., 1991), nonetheless, Rutherfordoides sp. lived continuously until the LGM. From the surface sediments, Rutherfordoides cornuta, lives on plural area from the northwest Pacific but not from the Japan Sea (Matoba and Nakagawa, 2009) is related to high methane gas content of the sediments in the Sagami Bay (Akimoto et al., 1996). Nakagawa et al. (2009) reported that distributions of Rutherfordoides rotundata (closely related R. cornuta) indicate that an expulsion of a large amount of methane occurred on the Umitaka Spur during the LGM due to a massive dissociation of subsurface methane hydrate. And, the negative carbon isotope peak signal of Rutherfordoides sp. from RC1408 in the Mogami Trough, also indicate to dissociations of methane hydrate and active methane seeps by the lowest sea level same as Umitaka Spur (Takeuchi et al., 2007). Acknowledgement This research was a part of METI's project entitled "FY2014 Promoting research and development on methane hydrate" .

  20. Combined analysis of seismotectonics of the southern Dead Sea Fault (Eastern Mediterranean) using GPS measurements and seismicity

    NASA Astrophysics Data System (ADS)

    Cochran, W. J.; Gomez, F. G.; Abu Rajab, J.; Al Tarazi, E.

    2010-12-01

    Owing to its relative structural simplicity, the Dead Sea Fault (DSF) is an ideal subject to study active kinematics associated with slow continental transforms. The DSF constitutes the boundary between the Arabian and Sinai plates in the eastern Mediterranean region. The southern DSF’s seismic activity has relatively quiescent over the last 4 centuries, despite historical documentation of large (Mw ≥ 7) earthquakes. This study incorporates high precision Global Positioning System (GPS) measurements and seismicity along the southern DSF to assess kinematics of the transform and the Dead Sea pull-apart basin. In addition to other regional continuous GPS data, this study presents new results from a network of 38 survey-mode GPS sites and 4 continuous GPS stations in Jordan. Survey-mode GPS data were acquired through multiple campaigns between 2005 and 2010. Raw GPS data were processed using Gamit/Globk, and transformed into an Arabia-fixed reference frame. Application of elastic dislocation models suggests a left-lateral slip rate of 4.0-4.7 mm/yr, and a locking depth of 10-18 km, respectively. This range of slip-rates is consistent with previous geologic interpretations along the southern DSF, and the lower end of the locking depth range is generally consistent with the seismogenic crustal depth. Slip rates for the Wadi Araba and Jordan Valley fault segments provide boundary constraints for assessing kinematics of the large step-over basin at the Dead Sea. Comparison of geodetic moment accumulation rates with seismic moment release permits quantifying a possible deficit in the rates of seismicity that can contribute to the understanding of the regional earthquake hazard.

  1. New insights and questions about the Meso-Cenozoic Tectonic evolution of Eastern Black Sea and Caucasus.

    NASA Astrophysics Data System (ADS)

    Sosson, Marc; Rolland, Yann; Hässig, Marc; Meijers, Maud; Smith, Brigitte; Muller, Carla; Adamia, Shota; Melkonian, Rafael; Kangarli, Talat; Sahakyan, Lilit; Sadradze, Nino; Avagyan, Ara; Galoyan, Ghazar; Alania, Victor; Enukidze, Onice; Sheremet-Korniyenko, Yevgeniya; Yegorova, Tamara

    2014-05-01

    Since last decade a lot of new field researches (supported by MEBE and DARIUS programmes) were carried out in order to clarify the tectonic evolution of the South Caucasus and Eastern Black Sea regions. A summary of these improvements are as following: 1. Evidence of only one suture zone in the Lesser Caucasus: the Sevan-Akera suture zone as the eastward continuity of the Izmir-Ankara-Erzincan one. 2. Timing and modalities of the Upper Cretaceous obduction process of the Sevan-Akera back-arc basin. 3. Paleolatitude reconstruction of the Taurides-Anatolides-South Armenia microplate (TASAM) since the Late Cretaceous 4. Paleocene to Miocene tectonic evolution of the collision zone between Eurasia and the TASAM. 5. Structures and propagation of the Lesser Caucasus and Greater Causasus foreland basins from Paleocene to Miocene. 6. Structures of the inverted Paleocene-Eocene Adjara-Trialeti basin of the Eurasian margin and timing of deformations from Lesser Caucasus to Greater Caucasus. 7. New stratigraphic data from the Crimea Mountain which argues for a Lower Cretaceous rifting of the Eastern Black Sea. According to aforementioned results and previous studies, this widespread zone (from the Eastern Black Sea to the Lesser Caucasus) appears act as a large puzzle of heterogeneous lithospheres (continental, oceanic, arc, back-arc basins) since the Early Cretaceous. This is probably why this area has differently reacted in time and space to the northward collision of the TASAM with Eurasia since the Late Cretaceous and then of Arabian plate since the Oligo-Miocene. It seems that some lithospheres which have cold mantellic behavior (especially the Black Sea) react as rigid blocks, while others with a continental origin, reheated by magmatism, (as the Taurides-Anatolides) were extruded to the west or bended as an orocline (as the Lesser Caucasus, the Pontides). This is why some main questions remain, are not solved and are still debated. 1. The continuity of main structures

  2. Adaptation and spectral tuning in divergent marine proteorhodopsins from the eastern Mediterranean and the Sargasso Seas.

    PubMed

    Sabehi, Gazalah; Kirkup, Benjamin C; Rozenberg, Mira; Stambler, Noga; Polz, Martin F; Béjà, Oded

    2007-05-01

    Proteorhodopsins (PRs) phototrophy was recently discovered in oceanic surface waters. PRs have been observed in different marine environments and in diverse taxa, including the ubiquitous marine alphaproteobacterial SAR11 group and the uncultured gammaproteobacterial SAR86 group. Previously, two SAR86 PR subgroups, discovered in the Pacific Ocean, were shown to absorb light with different maxima, lambda max 527 nm (green) and lambda max 490 nm (blue) and their distribution was explained by prevailing light conditions - green pigments at the surface and blue in deeper waters. Here, we show that PRs display high diversity in geographically distinct patterns despite similar physical water column properties such as mixing and light penetration. We compared summer and winter samples representing stratified and mixed conditions from both the Mediterranean and Sargasso Sea. As expected, in the Mediterranean Sea, green pigments were mainly confined to the surface and the percentage of blue pigments increased toward deeper samples; in the Sargasso Sea, unexpectedly, all PRs were of the blue type. As an additional result, both locations show seasonal dependence in the distribution of different PR families. Finally, spectral tuning was not restricted to a single PR family as previously reported but occurs across the sampled PR families from various microbial taxa. The distribution of tunable PRs across the PR tree suggests that ready adaptability has been distributed widely among microorganisms, and may be a reason that PRs are abundant and taxonomically widely dispersed.

  3. Spawning phenology and geography of Aleutian Islands and eastern Bering Sea Pacific cod (Gadus macrocephalus)

    NASA Astrophysics Data System (ADS)

    Neidetcher, Sandra K.; Hurst, Thomas P.; Ciannelli, Lorenzo; Logerwell, Elizabeth A.

    2014-11-01

    Pacific cod (Gadus macrocephalus) is an economically and ecologically important species in the southeastern Bering Sea and Aleutian Islands, yet little is known about the spawning dynamics of Pacific cod in these regions. To address this knowledge gap, we applied a gross anatomical maturity key for Pacific cod to describe temporal and spatial patterns of reproductive status over three winter spawning seasons: 2005, 2006, and 2007. Maturity status of female Pacific cod was assessed by fishery observers during sampling of commercial catches and used to construct maps showing spawning activity in the Bering Sea and Aleutian Islands. Most spawning activity was observed on the Bering Sea shelf and Aleutian Island plateaus between 100 and 200 m depth. Data for those days when a high percentage of spawning stage fish were observed were used to identify areas with concentrations of spawning fish. Spawning concentrations were identified north of Unimak Island, in the vicinity of the Pribilof Islands, at the shelf break near Zhemchug Canyon, and adjacent to islands in the central and western Aleutian Islands along the continental shelf. The spawning season was found to begin in the last days of February or early March and extend through early to mid-April. Variation in spawning time (averaging ~10 days between years) may have been associated with a change from warm (2005) to cold (2007) climate conditions during the study period. Our information on Pacific cod spawning patterns will help inform fishery management decisions, models of spawning and larval dispersal and the spatial structure of the stock.

  4. Deep water circulation in the eastern Mediterranean Sea for the last 95 kyr: new insights from stable isotopes and benthic foraminiferal assemblages

    NASA Astrophysics Data System (ADS)

    Cornuault, Marine; Vidal, Laurence; Tachikawa, Kazuyo; Licari, Laetitia; Rouaud, Guillaume; Sonzogni, Corinne; Revel, Marie

    2016-04-01

    The response of the Eastern Mediterranean Sea circulation to climate forcing over the last 95 kyr BP was studied using core MD04-2722 collected at 1780m water depth in the Levantine Sea. Foraminiferal stable isotopes and benthic foraminiferal assemblages were combined to reconstruct deep water ventilation and oxygenation in relation to surface water freshening. Over the last deglaciation, benthic foraminiferal δ13C values and benthic foraminiferal oxygen index decreased while δ18O gradient between benthic and planktonic foraminifera increased. These results testify respectively of slower ventilation, bottom water oxygen depletion and stronger stratification prior to S1 sapropel deposition. Similar conditions were deduced for S3 sapropel. Combination of deglacial sea level rise and fresher North Atlantic surface water contribution were evaluated to be a precondition of S1 formation in the Levantine Sea. Local Nile freshwater supply during the African Humid Period further strengthened the water column stratification. For the last glacial period, three events at around 53, 46 and 37 ka BP were marked by benthic δ13C decrease demonstrating deep water circulation reduction at the core location. Bottom water oxygenation was only slightly lowered. Considering the effect of North Atlantic surface water salinity to the Mediterranean Sea circulation, we propose the 46 and 37 ka BP events as responses to the Heinrich Events 4 and 5 that supplied fresher surface water to the Mediterranean Sea. Since the '53 ka event' is characterized by the appearance of an anoxic benthic foraminiferal species observed for S1 and S3 layers, we tentatively attributed it to the 'missing' sapropel S2. Our results indicate that intense stagnation in the Eastern Mediterranean Sea could occur when both local freshwater supply and fresher North Atlantic surface water contributed. The influence of North Atlantic condition was significant on the eastern Mediterranean circulation under warm and cold

  5. Environmental policy in the north-eastern sector of the Black sea coast

    NASA Astrophysics Data System (ADS)

    Kosyan, Ruben; Godin, Evgenii; Kosyan, Alisa

    2015-04-01

    Active economic development of the Black Sea East coastal zone has started in the beginning of 20-th century. Those days the pebble taken from beaches was used for construction of buildings, rail and motor roads. Active consumption of pebble from the beaches and river banks had caused a sharp increase of sea shores abrasion and washout rate, number of landslides had also increased. Contemporary Caucasian shores of Black Sea are being developed under increasing man-caused load. Favorable natural conditions, their variety and uniqueness determine the exceptional role of these shores as very important recreational zone of Russian South. Waste urbanized areas, agricultural territories and National Parks are located in immediate neighborhood with the sea. Important industrial facilities and federal and international communi- cations, including major seaports are located in the shore zone. At present time major gas and oil transportation facilities are commissioned and being constructed in the area. Due to the change of geopolitical situation the Russian shoreline had significantly reduced in comparison with Soviet period, especially in most developed regions. Large resort complexes in Georgia, Crimea and Baltic area were lost. Russia had also lost many major seaports that, under conditions of structural change of economy and export growth, had caused the necessity of building new industrial facilities in the Black Sea coastal zone, and, consequently, had stimulated active human invasion into natural coastal processes. At the time being, a major part (three hundred nine kilometers) of Black Sea coast within Russian sector is subject to abrasion and landslide processes. Abrasion process and beaches wash-out, landslides cause destruction of industrial and transport facilities, living and public buildings, resort complexes and valuable agricultural areas. In this light, the challenge of estimation of effective methods of shores protection against wave-induced erosion

  6. A multiproxy approach to constrain the source, composition and reactivity of sedimentary organic carbon in the eastern Yellow Sea (the northwestern Pacific)

    NASA Astrophysics Data System (ADS)

    Yoon, SukHee; Kim, JunHyun; Lee, DongHun; Yi, HiiIl; Yamamoto, Masanobu; Gal, JonKu; Choi, BoHyung; Kang, Sujin; Shin, KyungHoon

    2016-04-01

    We investigated the source, composition and reactivity of sedimentary organic carbon (OC) in a river-dominated continental marginal sea, the eastern Yellow Sea. A multi-proxy approach was applied to 9 riverbank sediments and 69 marine surface sediments, combining bulk and molecular organic parameters. The sedimentary OC in the marine surface sediments appears to have a predominantly marine origin (on average C/N ratio=7.0±0.6 and δ13CTOC=-21.9±0.5‰, n=69) with minor contribution of continental (i.e. soil- and lake/river-derived) OC (on average BIT index=0.00±0.01, n=69). However, the 14C values were depleted (on average -227±53‰, n=8), indicating that about 18-33% of ancient OC, potentially derived from erosion of sedimentary bedrocks or from fossil fuels such as petroleum might be added to the sedimentary OC pool. The possible contribution of petroleum-derived OC was confirmed by Carbon preference indices (CPI) of n-alkanes (<1). Accordingly, our results highlight an important contribution of ancient OC in the eastern Yellow Sea. Nonetheless, more work is needed to better constrain the source, composition, and age of the organic material supplied to the eastern Yellow Sea, given the lack of biogeochemical data from the Korean rivers.

  7. Phylogeography of the Atlanto-Mediterranean sea cucumber Holothuria (Holothuria) mammata: the combined effects of historical processes and current oceanographical pattern.

    PubMed

    Borrero-Pérez, G H; González-Wangüemert, M; Marcos, C; Pérez-Ruzafa, A

    2011-05-01

    We assessed the genetic structure of populations of the widely distributed sea cucumber Holothuria (Holothuria) mammata Grube, 1840, and investigated the effects of marine barriers to gene flow and historical processes. Several potential genetic breaks were considered, which would separate the Atlantic and Mediterranean basins, the isolated Macaronesian Islands from the other locations analysed, and the Western Mediterranean and Aegean Sea (Eastern Mediterranean). We analysed mitochondrial 16S and COI gene sequences from 177 individuals from four Atlantic locations and four Mediterranean locations. Haplotype diversity was high (H=0.9307 for 16S and 0.9203 for COI), and the haplotypes were closely related (π=0.0058 for 16S and 0.0071 for COI). The lowest genetic diversities were found in the Aegean Sea population. Our results showed that the COI gene was more variable and more useful for the detection of population structure than the 16S gene. The distribution of mtDNA haplotypes, the pairwise F(ST) values and the results of exact tests and amova revealed: (i) a significant genetic break between the population in the Aegean Sea and those in the other locations, as supported by both mitochondrial genes, and (ii) weak differentiation of the Canary and Azores Islands from the other populations; however, the populations from the Macaronesian Islands, Algarve and West Mediterranean could be considered to be a panmictic metapopulation. Isolation by distance was not identified in H. (H.) mammata. Historical events behind the observed findings, together with the current oceanographic patterns, were proposed and discussed as the main factors that determine the population structure and genetic signature of H. (H.) mammata.

  8. Sea turtle distribution along the boundary of the Gulf Stream current off eastern Florida

    USGS Publications Warehouse

    Hoffman, W.; Fritts, T.H.

    1982-01-01

    Aerial surveys, out to 222 km off the east coast of central Florida during August 1980, revealed that marine turtles were distributed in a narrow zone west of the Gulf Stream. Of 255 loggerhead turtles, Caretta caretta, only three were observed east of the western boundary of the Gulf Stream. Radiometric thermometry revealed that the waters occupied by most Caretta were markedly cooler than the nearby waters of the Gulf Stream. Of 18 leatherback turtles, Dermochelys coriacea, all were seen west of the Gulf Stream in waters less than 70 m in depth. Marine turtles off eastern Florida are confined seasonally to nearshore waters west of the Gulf Stream. The records of Dermochelys in nearshore waters are in contrast with a deep water oceanic ecology often hypothesized for this species.

  9. Computation of a precise mean sea surface in the eastern north Pacific using SEASAT altimetry

    NASA Astrophysics Data System (ADS)

    Marsh, James G.; Cheney, Robert E.; Martin, Thomas V.; McCarthy, John J.

    Satellite altimetry has application to both solid earth and ocean dynamics research. Because the mean surface of the ocean coincides with the geoid to within about 1 m, three-dimensional maps constructed from grids of altimeter measurements yield information about the gravity field and processes taking place in and beneath the earth's crust. At the same time, statistical analyses of the altimeter data used to construct the surface can provide a survey of the mesoscale eddy field [Cheney and Marsh, 1981].This short report presents results obtained by using SEASAT altimetry in a 5000×5000 km area of the eastern North Pacific. We hope to illustrate several points: the precision of the SEASAT data, the power of the crossing-arc technique employed in the data reduction, and the geodetic/oceanographic implications of precise altimetric maps.

  10. Speciation of phosphorus in the continental shelf sediments in the Eastern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Acharya, Shiba Shankar; Panigrahi, Mruganka Kumar; Kurian, John; Gupta, Anil Kumar; Tripathy, Subhasish

    2016-03-01

    The distributions of various forms of phosphorus (P) and their relation with sediment geochemistry in two core sediments near Karwar and Mangalore offshore have been studied through the modified SEDEX procedure (Ruttenberg et al., 2009) and bulk chemical analysis. The present study provides the first quantitative analysis of complete phosphorus speciation in the core sediments of the Eastern Arabian shelf. The chemical index of alteration (CIA), chemical Index of Weathering (CIW) and Al-Ti-Zr ternary diagram suggest low to moderate source area weathering of granodioritic to tonalitic source rock composition, despite the intense orographic rainfall in the source area. Due to the presence of same source rock and identical oxic depositional environment, the studied sediments show the same range of variation of total phosphorus (24 to 83 μmol/g) with a down-depth depleting trend. Organic bound P and detrital P are the two major chemical forms followed by iron-bound P, exchangeable/loosely bound P and authigenic P. The authigenic P content in the sediments near Mangalore coast varies linearly with calcium (r=0.88) unlike that of Karwar coast. The different reactive-phosphorus pools exhibit identical depleting trend with depth. This indicates that the phosphorus released from the organic matter and Fe bound fractions are prevented from precipitating as authigenic phosphates in the deeper parts of the sediment column. The low concentration of total P, dominance of detrital non-reactive fraction of P and inhibition of formation of authigenic phosphate result in the absence of active phosphatization in the Eastern Arabian Shelf in the studied region. High sedimentation rate (35-58 cm/kyr) and absence of winnowing effect appear to be the dominant factor controlling the P-speciation in the studied sediments.

  11. Genetic identification of a rare record of Ommastrephes Bartramii (Cephalopoda: Ommastrephidae) from the Eastern Adriatic Sea.

    PubMed

    Franjević, Damjan; Skaramuca, Daria; Katavić, Vedran; Rajević, Nives; Skaramuca, Boško

    2015-01-01

    The neon flying squid Ommastrephes bartramii Lesueur, 1821 belongs to the Ommastrephidae, Cephalopoda family. The family Ommastrephidae (Mollusca: Cephalopoda) includes many commercially important species, dispersed around the world. The Ommastrephidae family is conventionally divided into three subfamilies (Illicinae, Todarodinae, and Ommastrephinae). We report a specimen of neon flying squid caught in the winter 2013 at Luka Šipanska, Island of Šipan, Croatia and identified at the genetic level using the standard mitochondrial COI barcode region. This record represents the first genetic identification of a neon flying squid from the Adriatic Sea.

  12. Genetic identification of a rare record of Ommastrephes Bartramii (Cephalopoda: Ommastrephidae) from the Eastern Adriatic Sea.

    PubMed

    Franjević, Damjan; Skaramuca, Daria; Katavić, Vedran; Rajević, Nives; Skaramuca, Boško

    2015-01-01

    The neon flying squid Ommastrephes bartramii Lesueur, 1821 belongs to the Ommastrephidae, Cephalopoda family. The family Ommastrephidae (Mollusca: Cephalopoda) includes many commercially important species, dispersed around the world. The Ommastrephidae family is conventionally divided into three subfamilies (Illicinae, Todarodinae, and Ommastrephinae). We report a specimen of neon flying squid caught in the winter 2013 at Luka Šipanska, Island of Šipan, Croatia and identified at the genetic level using the standard mitochondrial COI barcode region. This record represents the first genetic identification of a neon flying squid from the Adriatic Sea. PMID:26103681

  13. Sedimentological conditions and sediment transport pathways in the nearshore zone of the Russian part of South-Eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Dorokhova, Evgenia

    2016-04-01

    The sediment transport pathways and sedimentological conditions are identified on the South-Eastern Baltic Sea coastal zone (Russian part) up to the depth of 30 m on the base of grain size analysis of recent marine sediments. The interrelations between grain size statistical parameters of 971 sediment samples are used. The two independent approaches that discussed in the literature are applied: 1) the sediment trend analysis, based on spatial variations of sediment grain size parameters from sample to sample (McLaren, 1981) and 2) the population anomalies method, which allows to determine the sedimentation conditions (erosion, transit or accumulation) from the deviations of sediments grain size parameters in each sampling place from the average values in investigation area (Baraniecki and Racinowski, 1996). Taking into account that the sediment grain size composition achieve its constant in calm period of reduced storm influence and that the all samples were taking during summer season, the obtained sedimentation pattern present the long-time annual average of sediment transport pathways in the investigated area. The results show that the sediment accumulation under the wave influence prevails up to the depth of 5 m. The continuous accumulation zone breaks in erosion where the shore line changes its direction. Seaward of the accumulation zone the sediment transit area extends and interrupts by zones of erosion and accumulation up to the depth of 20 m. Sediment transport here occurs in hydrodynamic circulation cells within bays along the Sambian peninsula north coast. The erosion zones serves as sediment source on the underwater shore slope. The north-eastern direction of sediment transport exist along the straightened coast of Curonian spit according to prevail west winds. Deeper there are zones of transit and "slowly" sediment accumulation up to the depth of 30 m. The seaward and isobaths parallel sediment transport pathways are obtained in these zones. The work

  14. The Temporal Dynamics of Coastal Phytoplankton and Bacterioplankton in the Eastern Mediterranean Sea

    PubMed Central

    Raveh, Ofrat; David, Niv; Rilov, Gil; Rahav, Eyal

    2015-01-01

    This study considers variability in phytoplankton and heterotrophic bacterial abundances and production rates, in one of the most oligotrophic marine regions in the world–the Levantine Basin. The temporal dynamics of these planktonic groups were studied in the coastal waters of the southeastern Mediterranean Sea approximately every two weeks for a total of two years. Heterotrophic bacteria were abundant mostly during late summer and midwinter, and were positively correlated with bacterial production and with N2 fixation. Based on size fractionating, picophytoplankton was abundant during the summer, whereas nano-microphytoplankton predominated during the winter and early spring, which were also evident in the size-fractionated primary production rates. Autotrophic abundance and production correlated negatively with temperature, but did not correlate with inorganic nutrients. Furthermore, a comparison of our results with results from the open Levantine Basin demonstrates that autotrophic and heterotrophic production, as well as N2 fixation rates, are considerably higher in the coastal habitat than in the open sea, while nutrient levels or cell abundance are not different. These findings have important ecological implications for food web dynamics and for biological carbon sequestration in this understudied region. PMID:26474399

  15. Zooplankton community and hydrographical properties of the Neretva Channel (eastern Adriatic Sea)

    NASA Astrophysics Data System (ADS)

    Vidjak, Olja; Bojanić, Natalia; Kušpilić, Grozdan; Ninčević Gladan, Živana; Tičina, Vjekoslav

    2007-12-01

    Temporal and spatial variability of micro and mesozooplankton was studied in 1998 and 1999 at four stations in the Neretva Channel area influenced by the Neretva river and the open waters of the south Adriatic Sea. The area is orthophosphate limited, but an excessive accumulation of land derived nitrogen is prevented by phytoplankton uptake and the general circulation pattern. Microzooplankton was dominated by ciliates, with average abundances comparable to other Adriatic channel areas (122 543 ind. l-1). Non-loricate ciliates (NLC) generally peaked in the warmer periods, but a winter increase was evident towards the inner part of the channel. Tintinnid abundances generally increased in autumn. A significant relationship with temperature was not recorded for either protozoan group. An inverse relationship between NLC and salinity might be indirectly caused by their preference for the food abundant surface layer. Mesozooplankton was dominated by copepods, with distinct summer maxima throughout the area and pronounced winter maxima of >10,000 ind. m-3 at the inner stations. The community was predominantly neritic but the open sea waters were important in structuring the mesozooplankton assemblage at all stations during the autumn winter period. Although temperature regulated the seasonal dynamics of most metazoans and the species succession in the copepod community, small omnivorous copepods ( Oncaea media complex, Oithona nana and Euterpina acutifrons) dominated regardless of the season. A trophic link between copepods and ciliates was evident in winter during low phytoplankton biomass.

  16. Characteristics of sea-cliff erosion induced by a strong winter storm in the eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Katz, Oded; Mushkin, Amit

    2013-07-01

    Changes in sea-cliff morphologies along the 30-km-long Sharon Escarpment segment of Israel's weakly cemented Mediterranean eolianite cliff line were analyzed to gain quantitative insights into erosion characteristics associated with a high-energy winter storm (10-20 year return interval). Ground-based repeat LiDAR measurements at five sites along the cliff line captured perturbations of cliff stability by basal wave scouring during the storm, subsequent post-storm gravity-driven slope failures in the cliff face above, and return of the system to transient stability within several months. Post-storm erosion, which amounted to 70% of the total volume of cliff erosion documented, resulted in dramatic local effects of up to 8 m of cliff-top retreat. And yet, at the larger scale of the 30-km cliff line examined, erosion during the storm and the year that followed affected less than 4% of the cliff length and does not appear to be above the average cliff-length annual erosion implied by previously published decadal-scale retreat rates along this sea cliff. Our results do not support a direct association between strong storm events and elevated erosion and retreat at the cliff-line scale.

  17. Post-Rift Compressional Deformation on the Passive Margin of a young Mediterranean Backarc Basin (Eastern Sardinian Margin, Tyrrhenian Sea)

    NASA Astrophysics Data System (ADS)

    Chanier, F.; Gaullier, V.; Maillard, A.; Thinon, I.; Sage, F.; Lymer, G.; Vendeville, B.; Giresse, P.; Bassetti, M. A.; Lofi, J.

    2014-12-01

    Compressional deformation has been reported on many passive margins, mostly attributed to thin-skinned tectonics in response to gravity gliding or spreading from viscous layers (overpressured shales, salt décollement). However some of the reported structures are obviously related to regional stress and also affect the basement, not only the upper sedimentary cover. Such deformation has been documented and discussed in the last decade mainly from the northern Atlantic margins (Doré et al., 2008 ; Pereira et al., 2011, & ref. herein). The compressional structures on passive margins have been notably considered as linked to tectonomagmatic and active asthenospheric upwelling, post-breakup compression and compactional stresses. The western margin of the Tyrrhenian Sea (Central Mediterranean) is a passive margin formed during the late Miocene opening of a back-arc basin in relation with the roll-back and retreat of the Ionian subducting lithosphere (African Plate). From our new data, we can show evidence for compressional features that developed in the Pliocene, shortly after the main rifting period on the western Tyrrhenian Sea (Middle to Late Miocene) and beginning of oceanic spreading (Earliest Pliocene). We could describe such structures across the inner margin onshore, from field analysis, as well as offshore, from newly acquired seismic data (METYSS 1 & 3; Gaullier et al. 2014). The characters and distribution of such compressional deformation, occurring very shortly after the onset of oceanic spreading in the deep basin (earliest Pliocene), allow us to discuss the possible interactions between breakup processes and inversion episodes on passive margins. Doré A.G., Lundin E.R., Kusznir N.J., & Pascal C., 2008. Potential mechanisms for the genesis of Cenozoic domal structures on the NE Atlantic margin: Pros and cons and some new ideas. Geol. Soc. London Spec. Pub., 306, 1-26. Gaullier V., Chanier F., et al., 2014. Salt tectonics and crustal tectonics along the

  18. The Bulgheria canyon-fan: a small-scale proximal system in the eastern Tyrrhenian Sea (Italy)

    NASA Astrophysics Data System (ADS)

    Budillon, Francesca; Conforti, Alessandro; Tonielli, Renato; de Falco, Giovanni; di Martino, Gabriella; Innangi, Sara; Marsella, Ennio

    2011-03-01

    The Bulgheria canyon-fan system in the eastern Tyrrhenian Sea displays well-developed, small-scale, fluvial-like features and has formed alongside the northern slope of the Sapri peri-Tyrrhenian basin. This study reveals, for the first time, the morphology and course of the present-day system as well as the buried elements based on a Digital Terrain Model and high-resolution seismic profiles interpretation. Two adjacent canyons (Infreschi and Luna) originate in the Cilento outer shelf at a short distance from each other and feed an intraslope basin fan through two main sub-parallel channels that run about 12 and 8 km, respectively. Channel and levee development seems to be controlled primarily by the local slope gradient and by Coriolis forces that induce a faster vertical growth of the right-side features, as is often observed in the Northern Hemisphere. Centrifugal forces, on the other hand, have induced episodic flow-stripping at the meander loops and bends, causing local destruction of the main channel levees rather than new levee growth at the outer bends. Overbank deposits are associated with overspill turbidite deposition in the mid fan where a topographic constraint occurs, whereas large-sediment, low-angle wave fields are mainly developed on the outer fan. Buried features and relict morphologies suggest that the Infreschi channel experienced at least two phases of re-incision since the final stages of the middle Pleistocene. Local re-adjustment of outer lobe growth due to channel avulsion and meander abandonment is possibly a consequence of relative base-level fluctuations. The sedimentary record of the mid and outer fan includes outrun mass wasting deposits from extensive failures of the Sapri slope. Indeed, a marked scar is present on the eastern side of the modern outer lobe that indicates the persistency of mass flow passages up to recent times. In addition to the environmental factors that are currently considered to cause canyon formation on the

  19. Atlantic Water advection versus sea-ice advances in the eastern Fram Strait during the last 9 ka: Multiproxy evidence for a two-phase Holocene

    NASA Astrophysics Data System (ADS)

    Werner, Kirstin; Spielhagen, Robert F.; Bauch, Dorothea; Hass, H. Christian; Kandiano, Evgeniya

    2013-06-01

    A sediment core from the West Spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last ~9 ka in the eastern Fram Strait (FS). Our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern FS occurred stepwise, in response to the postglacial sea-level rise and the related onset of modern sea-ice production on the shallow Siberian shelves. The late Early and Mid-Holocene interval (9 to 5 ka) was generally characterized by relatively unstable conditions. High abundance of the subpolar planktic foraminifer species Turborotalita quinqueloba implies strong intensity of Atlantic Water (AW) inflow with high productivity and/or high AW temperatures, resulting in a strong heat flux to the Arctic. A series of short-lived cooling events (8.2, 6.9, and 6.1 ka) occurred superimposed on the warm late Early to Mid-Holocene conditions. Our proxy data imply that simultaneous to the complete postglacial flooding of Arctic shallow shelves and the initiation of modern sea-ice production, strong advance of polar waters initiated modern oceanographic conditions in the eastern FS at ~5.2 ka. The Late Holocene was marked by the dominance of the polar planktic foraminifer species Neogloboquadrina pachyderma, a significant expansion of sea ice/icebergs, and strong stratification of the water column. Although planktic foraminiferal assemblages as well as sea subsurface temperatures suggest a return of slightly strengthened advection of subsurface AW after 3 ka, a relatively stable cold-water layer prevailed at the sea surface, and the study site was probably located within the seasonally fluctuating marginal ice zone during the Neoglacial period.

  20. What triggered the early-to-mid Pleistocene tectonic transition across the entire eastern Mediterranean?

    NASA Astrophysics Data System (ADS)

    Schattner, Uri

    2010-01-01

    Subduction plays a fundamental role in plate tectonics and when interrupted it may trigger a series of geodynamic and sedimentary responses. Synchronous structural modifications recorded across the entire eastern Mediterranean region are dated to a relatively short period — early-to-mid Pleistocene. These deformations are documented within plates (e.g., Arabian, Sinai and African plates), along plate boundaries (e.g., Dead Sea and North Anatolian faults and Cyprus Arc), and in the Mediterranean basin. During the same period the northward subduction of the Sinai plate was interrupted when the Eratosthenes Seamount-Cyprus Arc collision initiated. Subduction-collision processes of the eastern Mediterranean serve as a unique modern analogue for similar settings worldwide. Understanding their association with accompanying neo-tectonic processes is therefore predominantly important. By fostering a detailed and comprehensive approach this research provides a coherent tectonic picture for the eastern Mediterranean early-to-mid Pleistocene tectonic transition in order to explore its triggering mechanisms. Since the Neogene convergence across the eastern Mediterranean was accompanied by Eurasian indentation by Arabia northward motion, westwards Anatolia escape and southwards Aegean propagation. This semi counterclockwise plate motion was temporarily interrupted by the incipient Seamount-Arc collision which is suggested here as a trigger of the early-to-mid Pleistocene tectonic transition.

  1. Pleistocene sand ramp deposits in the Aegean (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Draganits, E.; Zuschin, M.; Gier, S.; Bickel, L.

    2010-05-01

    Yellowish calcarenite is found abundantly on Despotiko, a small, unpopulated island in the central Aegean. Up to several meters thick layers of this sandstone is found as discordant cover above greenschist to amphibolite grade metamorphic rocks of the Attic-Cycladic Crystalline of the Central Hellenides. In some cases reddish soil is found below the sandstone. The calcarenite preferably fills preexisting relief of the underlying crystalline, therefore the thickest occurrences are found in the intermittent creeks. The sandstone can be traced from below sea-level up to around 90 m altitudes with abundant occurrences, but is most common at the north and northwest coast of the island. Generally, the sandstone layers and the internal lamination are parallel or at shallow angles to the slopes of the underlying crystalline without forming any morphological terraces. In some cases continuous layers of the sandstone can be traced for more than 20 m altitude. Cross-bedding has been observed in very rare cases and dips steeply towards the SE. The calcarenite (locally called "lithos poros") is strongly dominated by marine bioclasts (Corallinaceae, foraminifera, gastropod and bivalve fragments, etc.) with only minor siliciclastic components hardly exceeding 20%. The grains well-rounded and well-sorted with rain sizes range between medium sand to granule sizes. Based on the sandstone distribution in a high range of altitudes, sedimentary structures (e.g. pin-stripe lamination, high-angle cross bedding, rhizoliths, occurrence of terrestrial gastropod shells and correlation with almost identical sandstones in the Mediterranean) we conclude an aeolian origin and probably Pleistocene age of this sandstone. Horizons containing dm-sized, angular metamorphic clasts within well-rounded and well-sorted aeolian layers point to interaction of wind-blown and talus processes. Therefore these sediments are interpreted as sand ramps that formed during increased aeolian activity during the

  2. Downward fluxes of elemental carbon, metals and polycyclic aromatic hydrocarbons in settling particles from the deep Ionian Sea (NESTOR site), Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Theodosi, C.; Parinos, C.; Gogou, A.; Kokotos, A.; Stavrakakis, S.; Lykousis, V.; Hatzianestis, J.; Mihalopoulos, N.

    2013-07-01