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1
Kubin, Elisabeth, Pierre-Marie Poulain, Elena Mauri, Milena Menna, and Giulio Notarstefano. "Levantine Intermediate and Levantine Deep Water Formation: An Argo Float Study from 2001 to 2017." Water 11, no. 9 (August 27, 2019): 1781. http://dx.doi.org/10.3390/w11091781.
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Levantine intermediate water (LIW) is formed in the Levantine Sea (Eastern Mediterranean) and spreads throughout the Mediterranean at intermediate depths, following the general circulation. The LIW, characterized by high salinity and relatively high temperatures, is one of the main contributors of the Mediterranean Overturning Circulation and influences the mechanisms of deep water formation in the Western and Eastern Mediterranean sub-basins. In this study, the LIW and Levantine deep water (LDW) formation processes are investigated using Argo float data from 2001 to 2017 in the Northwestern Levantine Sea (NWLS), the larger area around Rhodes Gyre (RG). To find pronounced events of LIW and LDW formation, more than 800 Argo profiles were analyzed visually. Events of LIW and LDW formation captured by the Argo float data are compared to buoyancy, heat and freshwater fluxes, sea surface height (SSH), and sea surface temperature (SST). All pronounced events (with a mixed layer depth (MLD) deeper than 250 m) of dense water formation were characterized by low surface temperatures and strongly negative SSH. The formation of intermediate water with typical LIW characteristics (potential temperature > 15 °C, salinity > 39 psu) occurred mainly along the Northern coastline, while LDW formation (13.7 °C < potential temperature < 14.5 °C, 38.8 psu < salinity < 38.9 psu) occurred during strong convection events within temporary and strongly depressed mesoscale eddies in the center of RG. This study reveals and confirms the important contribution of boundary currents in ventilating the interior ocean and therefore underlines the need to rethink the drivers and contributors of the thermohaline circulation of the Mediterranean Sea.
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Gačić, M., K. Schroeder, G. Civitarese, S. Cosoli, A. Vetrano, and G. L. Eusebi Borzelli. "Salinity in the Sicily Channel corroborates the role of the Adriatic–Ionian Bimodal Oscillating System (BiOS) in shaping the decadal variability of the Mediterranean overturning circulation." Ocean Science 9, no. 1 (January 29, 2013): 83–90. http://dx.doi.org/10.5194/os-9-83-2013.
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Abstract. Previous studies have demonstrated that the salinity in the Levantine basin depends on the intensity of the Atlantic water (AW) inflow. Moreover, its spreading eastward (to the Levantine basin) or northward (to the Ionian Sea) is determined by the Ionian circulation pattern, i.e. by the Adriatic–Ionian Bimodal Oscillating System (BiOS) mechanism. The aim of this paper is to relate salinity variations in the Levantine basin to the salt content variability in the core of the Levantine Intermediate Water (LIW) passing through the Sicily Channel (SC) and its possible impact on the Western Mediterranean Transition – WMT (i.e. the sudden salinity and temperature increase in the deep layer of the Algero-Provençal subbasin occurring since 2004). From the historical data set MEDAR/MEDATLAS in the Levantine and northern Ionian, we present evidence of decadal occurrences of extreme salinities associated with the varying influx of AW over the last 60 yr. Furthermore, we show that the salinity variations in the two subbasins are out of phase. High-salinity episodes in the Levantine are a pre-conditioning for the potential occurrence of the events like the Eastern Mediterranean Transient (EMT). Cross-correlation between the salinity time series in the Levantine basin and in the SC suggests that the travel time of the LIW is between 10 and 13 yr. Comparing the timing of the salinity increase associated with the WMT and the salinity in the LIW core in the SC, we estimate that the total time interval needed for the signal propagating from the Levantine to reach the deep mixed layers of the Algero-Provençal subbasin is about 25 yr. We also showed that the extra salt input from the eastern Mediterranean contribute up to about 60% to the salt content increase in the bottom layer of the western Mediterranean.
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Cardin, V., G. Civitarese, D. Hainbucher, M. Bensi, and A. Rubino. "Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?" Ocean Science Discussions 11, no. 1 (February 3, 2014): 391–423. http://dx.doi.org/10.5194/osd-11-391-2014.
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Abstract. We present temperature, salinity and oxygen data collected during the M84/3 and P414 cruises in April and June 2011 on a basin-wide scale to determine the ongoing oceanographic characteristics in the Eastern Mediterranean (EM). The east–west transect through the EM sampled during the M84/3 cruise together with data gained on previous cruises over the period 1987–2011 are analysed in terms of regional aspects of the evolution of water mass properties and heat and salt content variation. The present state of the EM basin is also evaluated in the context of the evolution of the Eastern Mediterranean Transient (EMT). From this analysis we can infer that the state of the basin is still far from achieving the pre-EMT conditions. Indeed, the 2011 oceanographic conditions of the deep layer of the central Ionian lie between the thermohaline characteristics of the EMT and the pre-EMT phase, indicating a possible slow return towards the latter. In addition, the thermohaline properties of the Adriatic Deep Water are still in line (warmer and saltier) as when it restarted to produce dense waters after the EMT. Special attention is given to the variability of thermohaline properties of the Levantine Intermediate Water and Adriatic Deep Water in three main areas: the Cretan, the central Levantine and the central Ionian Seas. Finally, this study evidences the relationships among the hydrological property distributions of the upper-layer in the Levantine basin and the circulation regime in the Ionian.
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Stöven, T., and T. Tanhua. "Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements." Ocean Science 10, no. 3 (June 5, 2014): 439–57. http://dx.doi.org/10.5194/os-10-439-2014.
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Abstract. Ventilation is the primary pathway for atmosphere–ocean boundary perturbations, such as temperature anomalies, to be relayed to the ocean interior. It is also a conduit for gas exchange between the interface of atmosphere and ocean. Thus it is a mechanism whereby, for instance, the ocean interior is oxygenated and enriched in anthropogenic carbon. The ventilation of the Mediterranean Sea is fast in comparison to the world ocean and has large temporal variability. Here we present transient tracer data from a field campaign in April 2011 that sampled a unique suite of transient tracers (SF6, CFC-12, 3H and 3He) in all major basins of the Mediterranean. We apply the transit time distribution (TTD) model to the data in order to constrain the mean age, the ratio of the advective / diffusive transport and the number of water masses significant for ventilation. We found that the eastern part of the eastern Mediterranean can be reasonably described with a one-dimensional inverse Gaussian TTD (IG-TTD), and thus constrained with two independent tracers. The ventilation of the Ionian Sea and the western Mediterranean can only be constrained by a linear combination of IG-TTDs. We approximate the ventilation with a one-dimensional, two inverse Gaussian TTD (2IG-TTD) for these areas and demonstrate a possibility of constraining a 2IG-TTD from the available transient tracer data. The deep water in the Ionian Sea has a mean age between 120 and 160 years and is therefore substantially older than the mean age of the Levantine Basin deep water (60–80 years). These results are in contrast to those expected by the higher transient tracer concentrations in the Ionian Sea deep water. This is partly due to deep water of Adriatic origin having more diffusive properties in transport and formation (i.e., a high ratio of diffusion over advection), compared to the deep water of Aegean Sea origin that still dominates the deep Levantine Basin deep water after the Eastern Mediterranean Transient (EMT) in the early 1990s. The tracer minimum zone (TMZ) in the intermediate of the Levantine Basin is the oldest water mass with a mean age up to 290 years. We also show that the deep western Mediterranean has contributed approximately 40% of recently ventilated deep water from the Western Mediterranean Transition (WMT) event of the mid-2000s. The deep water has higher transient tracer concentrations than the mid-depth water, but the mean age is similar with values between 180 and 220 years.
5
Borghini, M., H. Bryden, K. Schroeder, S. Sparnocchia, and A. Vetrano. "The Mediterranean is becoming saltier." Ocean Science 10, no. 4 (August 7, 2014): 693–700. http://dx.doi.org/10.5194/os-10-693-2014.
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Abstract. The deep waters of the western Mediterranean Sea have become saltier and warmer for at least the past 40 years at rates of about 0.015 and 0.04 °C per decade. Here we show that two processes contribute to these increases in temperature and salinity. On interannual timescales, deep water formation events in severe winters transmit increasingly salty intermediate waters into the deep water. The second process is a steady downward flux of heat and salt associated with salt finger mixing down through the halocline–thermocline that connects the Levantine Intermediate Water with the deep water. We illustrate these two processes with observations from repeat surveys of the western Mediterranean basin we have made over the past 10 years.
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Borghini, M., H. Bryden, K. Schroeder, S. Sparnocchia, and A. Vetrano. "The Mediterranean is getting saltier." Ocean Science Discussions 11, no. 1 (February 26, 2014): 735–52. http://dx.doi.org/10.5194/osd-11-735-2014.
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Abstract. The deep waters of the Mediterranean Sea have been getting saltier and warmer for at least the past 40 yr at rates of about 0.015 and 0.04 °C per decade. Here we show that two processes contribute to these increases in temperature and salinity. On interannual time scales, deep water formation events in severe winters transmit increasingly salty intermediate waters into the deep water. The second process is a steady downward flux of heat and salt through the halocline-thermocline that connects the Levantine Intermediate Water with the deep water. We illustrate these two processes with observations from repeat surveys of the western Mediterranean basin we have made over the past 10 yr.
7
Wu, Peili, and Keith Haines. "Modeling the dispersal of Levantine Intermediate Water and its role in Mediterranean deep water formation." Journal of Geophysical Research: Oceans 101, no. C3 (March 15, 1996): 6591–607. http://dx.doi.org/10.1029/95jc03555.
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Stöven, T., and T. Tanhua. "Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements." Ocean Science Discussions 10, no. 5 (October 10, 2013): 1647–705. http://dx.doi.org/10.5194/osd-10-1647-2013.
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Abstract. Ventilation is the prime pathway for ocean surface perturbations, such as temperature anomalies, to be relayed to the ocean interior. It is also the conduit for gas exchange between atmosphere and ocean and thus the mechanism whereby, for instance, the interior ocean is oxygenated and enriched in anthropogenic carbon. The ventilation of the Mediterranean Sea is fast in comparison to the world ocean and has large temporal variability, so that quantification of Mediterranean Sea ventilation rates is challenging and very relevant for Mediterranean oceanography and biogeochemistry. Here we present transient tracer data from a field-campaign in April 2011 that sampled a unique suite of transient tracers (SF6, CFC-12, tritium and 3He) in all major basins of the Mediterranean. We apply the Transit Time Distribution (TTD) model to the data which then constrain the mean age, the ratio of the advective/diffusive transport mechanism, and the presence, or not, of more than one significant (for ventilation) water mass. We find that the eastern part of the Eastern Mediterranean can be reasonable described with a one dimensional Inverse Gaussian (1IG) TTD, and thus constrained with two independent tracers. The ventilation of the Ionian Sea and the Western Mediterranean can only be constrained by a multidimensional TTD. We approximate the ventilation with a two-dimensional Inverse Gaussian (2IG) TTD for these areas and demonstrate one way of constraining a 2IG-TTD from the available transient tracer data. The deep water in the Ionian Sea has higher mean ages than the deep water of the Levantine Basin despite higher transient tracer concentrations. This is partly due to the deep water of Adriatic origin having more diffusive properties in the transport and formation, i.e. a high ratio of diffusion over advection, compared to the deep water of Aegean Sea origin that still dominates the deep Levantine Basin deep water after the Eastern Mediterranean Transient (EMT) in the early 1990s. We also show that the deep Western Mediterranean has approximately 40% contribution of recently ventilated deep water from the Western Mediterranean Transition (WMT) event of the mid-2000s. The deep water has higher transient tracer concentrations than the mid-depth water, but the mean age is similar.
9
OZCAN, T., E. IRMAK, A. S. ATES, and T. KATAGAN. "First record of the red shrimp, Aristeus antennatus (Risso, 1816) (Decapoda: Aristeidae) from the Aegean Sea coast of Turkey." Mediterranean Marine Science 10, no. 1 (June 1, 2009): 121. http://dx.doi.org/10.12681/mms.125.
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A female specimen of the deep-water red shrimp, Aristeus antennatus(Risso, 1816) was caught at depths of between 550 m and 670 m during 2005 by trawling off the Marmaris coast. A. antennatus is a species known to inhabit only the Levantine Sea coast of Turkey. This paper is on the first record of the species along the southern Aegean Sea coast of Turkey
10
Gertman, I., N. Pinardi, Y. Popov, and A. Hecht. "Aegean Sea Water Masses during the Early Stages of the Eastern Mediterranean Climatic Transient (1988–90)." Journal of Physical Oceanography 36, no. 9 (September 1, 2006): 1841–59. http://dx.doi.org/10.1175/jpo2940.1.
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Abstract The Aegean water masses and circulation structure are studied via two large-scale surveys performed during the late winters of 1988 and 1990 by the R/V Yakov Gakkel of the former Soviet Union. The analysis of these data sheds light on the mechanisms of water mass formation in the Aegean Sea that triggered the outflow of Cretan Deep Water (CDW) from the Cretan Sea into the abyssal basins of the eastern Mediterranean Sea (the so-called Eastern Mediterranean Transient). It is found that the central Aegean Basin is the site of the formation of Aegean Intermediate Water, which slides southward and, depending on their density, renews either the intermediate or the deep water of the Cretan Sea. During the winter of 1988, the Cretan Sea waters were renewed mainly at intermediate levels, while during the winter of 1990 it was mainly the volume of CDW that increased. This Aegean water mass redistribution and formation process in 1990 differed from that in 1988 in two major aspects: (i) during the winter of 1990 the position of the front between the Black Sea Water and the Levantine Surface Water was displaced farther north than during the winter of 1988 and (ii) heavier waters were formed in 1990 as a result of enhanced lateral advection of salty Levantine Surface Water that enriched the intermediate waters with salt. In 1990 the 29.2 isopycnal rose to the surface of the central basin and a large volume of CDW filled the Cretan Basin. It is found that, already in 1988, the 29.2 isopycnal surface, which we assume is the lowest density of the CDW, was shallower than the Kassos Strait sill and thus CDW egressed into the Eastern Mediterranean.
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ACHILLEOS, KATERINA, CARLOS JIMENEZ, BJÖRN BERNING, and ANTONIS PETROU. "Bryozoan diversity of Cyprus (eastern Mediterranean Sea): first results from census surveys (2011–2018)." Mediterranean Marine Science 21, no. 1 (April 20, 2020): 228. http://dx.doi.org/10.12681/mms.21201.
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The Mediterranean bryozoan fauna is considered to be well studied compared to other marine areas of the world. However, in the Levantine Basin, bryozoan diversity has not yet been adequately documented. This report presents the first systematic and most comprehensive study of bryozoans sampled in Cyprus during census surveys from 2011 to 2018. The specimens were collected between 9 and ~620 m depth from several habitat types (mainly soft-bottom environments but also hard natural/artificial substrata, ancient shipwrecks, a marine cave, and deep-water coral habitats) around the island by means of bottom trawls, remotely operated vehicles, and scuba diving. The surveys produced a total of 91 species, 26 of which (=28%) are new records for the Levantine Basin, and 10 (=11%) are probably new to science. Our results thus show that the diversity of bryozoans in the eastern Mediterranean Sea is still significantly underestimated.
12
Bowman, Steven A. "Regional seismic interpretation of the hydrocarbon prospectivity of offshore Syria." GeoArabia 16, no. 3 (July 1, 2011): 95–124. http://dx.doi.org/10.2113/geoarabia160395.
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ABSTRACT Analysis of 5,000 km of multi-client long-offset 2-D seismic data has led to the identification of three sedimentary basins, Levantine, Cyprus, and Latakia, located in offshore Syria. Each basin has a unique structural and stratigraphic history. They are separated from each other by the middle to Late Cretaceous aged Latakia Ridge System that initiated as a compressional fold-thrust belt and was re-activated under a sinistral strike-slip regime that developed during the Early Pliocene in response to a re-organisation of the plate-tectonic stresses. There is significant evidence for a working petroleum system in offshore Syria with numerous onshore oil and gas shows, DHIs (direct hydrocarbon indicators) observed on seismic, and oil seeps identified from satellite imagery. Prospective reservoirs range in age from Triassic to Pliocene – Quaternary and include Lower Miocene deep-water turbidite sands as encountered in recent discoveries in the offshore southern Levantine Basin. The complex structural evolution of each of the three sedimentary basins has produced an array of potential structural and stratigraphic trapping mechanisms.
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Schneider, A., T. Tanhua, W. Roether, and R. Steinfeldt. "Changes in ventilation of the Mediterranean Sea during the past 25 year." Ocean Science 10, no. 1 (January 27, 2014): 1–16. http://dx.doi.org/10.5194/os-10-1-2014.
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Abstract. Significant changes in the overturning circulation of the Mediterranean Sea has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transition (WMT) during the mid-2000s. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of low ventilation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.
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SOUVERMEZOGLOU, Ε., Ε. KRASAKOPOULOU, and A. PAVLIDOU. "Temporal and spatial variability of nutrients and oxygen in the North Aegean Sea during the last thirty years." Mediterranean Marine Science 15, no. 4 (December 31, 2014): 805. http://dx.doi.org/10.12681/mms.1017.
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Inorganic nutrient and dissolved oxygen data collected in the North Aegean Sea during 1986 - 2008 were analyzed in order to evaluate the role of the inflowing Black Sea originated surface water (BSW) in the nutrient regime of the area. In periods of high buoyancy inflow from Dardanelles strait, a reduction of inorganic nutrients in the surface layer is observed along the north-west route of the BSW; in parallel, the underlying layer of Levantine intermediate water revealed an increase of inorganic nutrients, receiving the degradation material from the surface layer. The above spatial patterns suggest a contribution of the BSW to the observed enhanced production of the North Aegean Sea. Anomalously low buoyancy inflow of BSW combined with severe winter meteorological conditions promote deep water formation events. The physical and chemical characteristics of the deep waters found in the different basins of the North Aegean Sea in 1997 (following the deep water formation in winters of 1992-1993) differed from those observed after the formation in winter 1987. These differences were probably related to the drastic changes occurred in the deep waters of the Eastern Mediterranean in the early 1990, by the Eastern Mediterranean Transient. Considering that deep water formation processes provide occasionally inorganic nutrients to the euphotic layer, it seems that BSW through its uninterrupted supply of small quantities of nutrients should play an additional role in the production in the North Aegean Sea.
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Ayache, M., J. C. Dutay, P. Jean-Baptiste, K. Beranger, T. Arsouze, J. Beuvier, J. Palmieri, B. Le-vu, and W. Roether. "Modelling of the anthropogenic tritium transient and its decay product helium-3 in the Mediterranean Sea using a high-resolution regional model." Ocean Science Discussions 11, no. 6 (December 5, 2014): 2691–732. http://dx.doi.org/10.5194/osd-11-2691-2014.
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Abstract. This numerical study provides the first simulation of the anthropogenic tritium invasion and its decay product helium-3 (3He) in the Mediterranean Sea. The simulation covers the entire tritium (3H) transient generated by the atmospheric nuclear-weapon tests performed in the 1950s and early 1960s and run till 2011. Tritium, helium-3 and their derived age estimates are particularly suitable for studying intermediate and deep-water ventilation and spreading of water masses at intermediate/deep levels. The simulation is made using a high resolution regional model NEMO-MED12 forced at the surface with prescribed tritium evolution derived from observations. The simulation is compared to measurements of tritium and helium-3 performed along large-scale transects in the Mediterranean Sea during the last few decades on cruises of Meteor M5/6, M31/1, M44/4, M51/2, M84/3, and Poseidon 234. The results show that the input function used for the tritium, generates a realistic distribution of the main hydrographic features of the Mediterranean Sea circulation. In the eastern basin, the results highlight the weak formation of Adriatic Deep Water in the model, which explains its weak contribution to the Eastern Mediterranean Deep Water in the Ionian sub-basin. It produces a realistic representation of the Eastern Mediterranean Transient signal, simulating a deep-water formation in the Aegean sub-basin at the beginning of the 1993, with a realistic timing of deep-water renewal in the eastern basin. In the western basin, the unusual intense deep convection event of winter 2005 in the Gulf of Lions during the Western Mediterranean Transition is simulated. However the spreading of the recently ventilated deep water toward the South is too weak. The ventilation and spreading of the Levantine Intermediate Water from the eastern basin toward the western basin is simulated with realistic tracer-age distribution compared to observation-based estimates.
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Pappa, F. K., G. A. Kyriakidis, C. Tsabaris, D. L. Patiris, E. G. Androulakaki, H. Kaberi, V. Zervakis, M. Kokkoris, R. Vlastou, and E. Krasakopoulou. "Temporal variation of 137Cs profiles in Lemnos deep basin, North Aegean Sea, Greece." HNPS Proceedings 23 (March 8, 2019): 79. http://dx.doi.org/10.12681/hnps.1910.
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137Cs activity concentration in seawater is an efficient radio-tracing technique to separate and identify the origin of different water masses along with depth. This technique has been applied for the study of deep basins at the North Aegean Sea [1], a marine region which is continuously enriched with 137Cs originated from the Black Sea, through the Dardanelles Straits. In this work, a second sampling campaign (from 2008 to 2013) was carried out in Lemnos’s deep basin and water quantities were collected from different depths. These quantities were chemically treated at HCMR to pre-concentrate 137Cs by using the AMP precipitation method [2]. The produced samples were measured by means of γ- ray spectroscopy. The 137Cs data profile in combination with other oceanographic data (salinity and temperature), provides significant information for the water masses origin with respect to depth. More specifically, at the surface layer, Black Sea water masses (characterized by enriched concentrations of 137Cs) are observed, with 137Cs concentrations about 4 Bq/m3. At the intermediate layers, Levantine water masses (characterized by low concentrations of 137Cs) appear with 137Cs activity reduced to 2 Bq/m3, while the deep layer dense water masses exhibit intermediate 137Cs concentrations of 3 Bq/m3. The 137Cs concentration results are compared with previous measurements performed in the same basin from 1999 to 2013, where the decline of 137Cs concentrations in the surface layer is observed and similar concentrations about 3 Bq/m3(within uncertainties) in the deep layer are obtained.
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Bonanno, A., F. Placenti, G. Basilone, R. Mifsud, S. Genovese, B. Patti, M. Di Bitetto, et al. "Variability of water mass properties in the Strait of Sicily in summer period of 1998–2013." Ocean Science 10, no. 5 (October 2, 2014): 759–70. http://dx.doi.org/10.5194/os-10-759-2014.
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Abstract. The Strait of Sicily plays a crucial role in determining the water-mass exchanges and related properties between the western and eastern Mediterranean. Hydrographic measurements carried out from 1998 to 2013 allowed the identification of the main water masses present in the Strait of Sicily: a surface layer composed of Atlantic water (AW) flowing eastward, intermediate and deep layers mainly composed of Levantine intermediate water (LIW), and transitional eastern Mediterranean deep water (tEMDW) flowing in the opposite direction. Furthermore, for the first time, the signature of intermittent presence of western intermediate water (WIW) is also highlighted in the northwestern part of the study area (12.235° E, 37.705° N). The excellent area coverage allowed to highlight the high horizontal and vertical inter-annual variability affecting the study area and also to recognize the permanent character of the main mesoscale phenomena present in the surface water layer. Moreover, strong temperature-salinity correlations in the intermediate layer, for specific time intervals, seem to be linked to the reversal of surface circulation in the central Ionian Sea. The analysis of CTD data in deeper water layer indicates the presence of a large volume of tEMDW in the Strait of Sicily during the summers of 2006 and 2009.
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Dubois-Dauphin, Quentin, Paolo Montagna, Giuseppe Siani, Eric Douville, Claudia Wienberg, Dierk Hebbeln, Zhifei Liu, et al. "Hydrological variations of the intermediate water masses of the western Mediterranean Sea during the past 20 ka inferred from neodymium isotopic composition in foraminifera and cold-water corals." Climate of the Past 13, no. 1 (January 10, 2017): 17–37. http://dx.doi.org/10.5194/cp-13-17-2017.
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Abstract. We present the neodymium isotopic composition (εNd) of mixed planktonic foraminifera species from a sediment core collected at 622 m water depth in the Balearic Sea, as well as εNd of scleractinian cold-water corals (CWC; Madrepora oculata, Lophelia pertusa) retrieved between 280 and 442 m water depth in the Alboran Sea and at 414 m depth in the southern Sardinian continental margin. The aim is to constrain hydrological variations at intermediate depths in the western Mediterranean Sea during the last 20 kyr. Planktonic (Globigerina bulloides) and benthic (Cibicidoides pachyderma) foraminifera from the Balearic Sea were also analyzed for stable oxygen (δ18O) and carbon (δ13C) isotopes. The foraminiferal and coral εNd values from the Balearic and Alboran seas are comparable over the last ∼ 13 kyr, with mean values of −8.94 ± 0.26 (1σ; n = 24) and −8.91 ± 0.18 (1σ; n = 25), respectively. Before 13 ka BP, the foraminiferal εNd values are slightly lower (−9.28 ± 0.15) and tend to reflect higher mixing between intermediate and deep waters, which are characterized by more unradiogenic εNd values. The slight εNd increase after 13 ka BP is associated with a decoupling in the benthic foraminiferal δ13C composition between intermediate and deeper depths, which started at ∼ 16 ka BP. This suggests an earlier stratification of the water masses and a subsequent reduced contribution of unradiogenic εNd from deep waters. The CWC from the Sardinia Channel show a much larger scatter of εNd values, from −8.66 ± 0.30 to −5.99 ± 0.50, and a lower average (−7.31 ± 0.73; n = 19) compared to the CWC and foraminifera from the Alboran and Balearic seas, indicative of intermediate waters sourced from the Levantine basin. At the time of sapropel S1 deposition (10.2 to 6.4 ka), the εNd values of the Sardinian CWC become more unradiogenic (−8.38 ± 0.47; n = 3 at ∼ 8.7 ka BP), suggesting a significant contribution of intermediate waters originated from the western basin. We propose that western Mediterranean intermediate waters replaced the Levantine Intermediate Water (LIW), and thus there was a strong reduction of the LIW during the mid-sapropel ( ∼ 8.7 ka BP). This observation supports a notable change of Mediterranean circulation pattern centered on sapropel S1 that needs further investigation to be confirmed.
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Schneider, A., T. Tanhua, W. Roether, and R. Steinfeldt. "Changes in ventilation of the Mediterranean Sea during the past 25 yr." Ocean Science Discussions 10, no. 4 (August 20, 2013): 1405–45. http://dx.doi.org/10.5194/osd-10-1405-2013.
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Abstract. The Mediterranean Sea has a fast overturning circulation and the deep water masses are well ventilated in comparison to the deep waters of the world ocean. Significant changes in the overturning circulation has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transit (WMT) near the mid of the decade following. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. This variability is important to understand and to monitor, because ventilation is the main process to propagate surface perturbations, such as uptake of anthropogenic CO2, into the ocean interior. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of stagnation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.
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BAYHAN, K. Y., J. E. CARTES, and E. FANELLI. "Biological condition and trophic ecology of the deep-water shrimp Aristaeomorpha foliacea in the Levantine Sea (SW Turkey)." Mediterranean Marine Science 16, no. 1 (September 14, 2014): 103. http://dx.doi.org/10.12681/mms.867.
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The trophic ecology (diets, stable isotope composition) and life cycle (gonado-somatic, GSI, and hepato-somatic, HSI, indices) of Aristaeomorpha foliacea were analysed seasonally (in May, June, and November 2012 and January 2013) off southeast Turkey (Levantine Basin), over the slope at 442-600 m depth. A. foliacea females were mature in June, suggesting gonad maturity was somewhat delayed off southeast Turkey compared to other areas in the Eastern Mediterranean. The HSI of A. foliacea was highest in May and June (8.2% of body weight) for males and both immature and mature females, sharply lower in November (3.5%) and then increasing again in winter (7.1%). Stomach fullness (F) showed a tendency similar to HSI in both females and males, increasing from May to June. A. foliacea had rather low d15N (6.68‰ to 8.26‰) off southeast Turkey, with females having higher d15N with increasing size. The δ13C signal (-14.85 to -14.68‰) indicated that diet was mainly though not exclusively based on zooplankton (pelagic shrimps and small myctophids of 1.3-4.5 mm TL, cnidarians, hyperiids and pteropods). The increase of A. foliacea remains in A. foliacea guts and of some benthic prey (polychaetes, bivalves, gastropods) after the reproductive period would explain the moderate depletion of δ13C in spring-summer. The greatest changes in the diet occurred between periods of water mass stratification (June and November) and periods of water mass homogeneity (May and January), with greater consumption of zooplankton in the latter season. A. foliacea seems to have lower reproductive capacity (GSI 5.6%) than other deep-water species of penaeidae that live shallower (Parapenaues longirostris) and deeper (Aristeus antennatus) than it does. The species has a more specialized zooplankton diet, exploiting short, more efficient trophic chains, which could be an advantage explaining its dominance in oligotrophic areas of the Central-Eastern Mediterranean, including the Turkish slope.
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Astrahan, P., J. Silverman, Y. Gertner, and B. Herut. "Spatial distribution and sources of organic matter and pollutants in the SE Mediterranean (Levantine basin) deep water sediments." Marine Pollution Bulletin 116, no. 1-2 (March 2017): 521–27. http://dx.doi.org/10.1016/j.marpolbul.2017.01.006.
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Ozer, Tal, Isaac Gertman, Hezi Gildor, Ron Goldman, and Barak Herut. "Evidence for recent thermohaline variability and processes in the deep water of the Southeastern Levantine Basin, Mediterranean Sea." Deep Sea Research Part II: Topical Studies in Oceanography 171 (January 2020): 104651. http://dx.doi.org/10.1016/j.dsr2.2019.104651.
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Sbrana, Mario, Walter Zupa, Alessandro Ligas, Francesca Capezzuto, Archontia Chatzispyrou, Maria Cristina Follesa, Vita Gancitano, et al. "Spatiotemporal abundance pattern of deep-water rose shrimp, Parapenaeus longirostris, and Norway lobster, Nephrops norvegicus, in European Mediterranean waters." Scientia Marina 83, S1 (January 9, 2020): 71. http://dx.doi.org/10.3989/scimar.04858.27a.
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The main characteristics concerning the distribution of two of the most important decapod crustaceans of commercial interest in the Mediterranean Sea, the deep-water rose shrimp, Parapenaeus longirostris, and the Norway lobster, Nephrops norvegicus, are studied in the European Mediterranean waters. The study is based on data collected under the MEDITS trawl surveys from 1994 to 2015 from the Gibraltar Straits to the northeastern Levantine Basin (Cyprus waters). The observed differences can be interpreted as different responses to environmental drivers related to the differing life history traits of the two species. In fact, N. norvegicus is a long-living, benthic burrowing species with low growth and mortality rates, while P. longirostris is an epibenthic, short-living species characterized by higher rates of growth and mortality.
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Njire, Jakica, Mirna Batistić, Vedrana Kovačević, Rade Garić, and Manuel Bensi. "Tintinnid Ciliate Communities in Pre- and Post-Winter Conditions in the Southern Adriatic Sea (NE Mediterranean)." Water 11, no. 11 (November 7, 2019): 2329. http://dx.doi.org/10.3390/w11112329.
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The Southern Adriatic Sea is a dynamic region under the influence of diverse physical forces that modify sea water properties as well as plankton dynamics, abundance, and distribution in an intricate way. The most pronounced being: winter vertical convection, lateral exchanges between coastal and open sea waters, and the ingression of water masses of different properties into the Adriatic. We investigated the distribution and abundance of tintinnid species in this dynamic environment in pre- and post-winter conditions in 2015/2016. A strong ingression of the saline Levantine Intermediate Water, supported by the cyclonic mode of the North Ionian Gyre in 2015 and 2016, in December was associated with a high diversity of oceanic species. An unusual spatial distribution of neritic-estuarine species Codonellopsis schabi was observed in deeper layers along the analyzed transect, which emphasizes the strong influence of physical processes on deep water biology in the South Adriatic. A shift of population toward greater depths (mesopelagic) and modification of deep sea community structure was recorded in April as a consequence of the winter convection-driven sinking of tintinnids. Our findings indicate that tintinnid abundance and composition is heavily influenced by physical conditions and they are good indicators of the impact of physical forces, including climate changes, on marine environment.
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Fedele, Giusy, Elena Mauri, Giulio Notarstefano, and Pierre Marie Poulain. "Characterization of the Atlantic Water and Levantine Intermediate Water in the Mediterranean Sea using 20 years of Argo data." Ocean Science 18, no. 1 (January 26, 2022): 129–42. http://dx.doi.org/10.5194/os-18-129-2022.
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Abstract. Atlantic Water (AW) and Levantine Intermediate Water (LIW) are important water masses that play a crucial role in the internal variability of the Mediterranean thermohaline circulation. To be more specific, their variability and interaction, along with other water masses that characterize the Mediterranean basin, such as the Western Mediterranean Deep Water (WMDW), contribute to modify the Mediterranean Outflow through the Strait of Gibraltar, and hence they may influence the stability of the global thermohaline circulation. This work aims to characterize AW and LIW in the Mediterranean Sea, taking advantage of the large observational dataset (freely available on https://argo.ucsd.edu, https://www.ocean-ops.org, last access: 17 January 2022; Wong et al., 2020) provided by Argo floats from 2001 to 2019. AW and LIW were identified using different diagnostic methods, highlighting the inter-basin variability and the strong zonal gradient that both denote the two water masses in this marginal sea. Their temporal variability was also investigated over the last 2 decades, providing a more robust view of AW and LIW characteristics, which have only been investigated using very short periods in previous studies due to a lack of data. A clear salinification and warming trend characterize AW and LIW over the last 2 decades (∼ 0.007 ± 0.140 and 0.006 ± 0.038 yr−1; 0.026 ± 0.715 and 0.022 ± 0.232 ∘C yr−1, respectively). The salinity and temperature trends found at sub-basin scale are in good agreement with previous results. The strongest trends are found in the Adriatic basin in the properties of both AW and LIW.
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Santi, I., P. Kasapidis, S. Psarra, G. Assimakopoulou, A. Pavlidou, M. Protopapa, A. Tsiola, C. Zeri, and P. Pitta. "Composition and distribution patterns of eukaryotic microbial plankton in the ultra-oligotrophic Eastern Mediterranean Sea." Aquatic Microbial Ecology 84 (June 4, 2020): 155–73. http://dx.doi.org/10.3354/ame01933.
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Marine microbial eukaryotes play crucial roles in water-column ecosystems; however, there are regional gaps in the investigation of natural microbial eukaryote communities, and uncertainties concerning their distribution persevere. This study combined 18S rRNA metabarcoding, biomass measurements and statistical analyses of multiple environmental variables to examine the distribution of planktonic microbial eukaryotes at different sites and water layers in the ultra-oligotrophic Eastern Mediterranean Sea (Western Levantine Basin). Our results showed that microbial eukaryotic communities were structured by depth. In surface waters, different sites shared high percentages of molecular operational taxonomic units (MOTUs), but this was not the case for deep-sea communities (≥1000 m). Plankton biomass was significantly different among sites, implying that communities of a similar composition may not support the same activity or population size. The deep-sea communities showed high percentages of unassigned MOTUs, highlighting the sparsity of the existing information on deep-sea plankton eukaryotes. Water temperature and dissolved organic matter significantly affected community distribution. Micro-eukaryotic distribution was additionally affected by the nitrogen to phosphorus ratio and viral abundance, while nano- and pico-communities were affected by zooplankton. The present study explores microbial plankton eukaryotes in their natural oligotrophic environment and highlights that, even within restricted oceanic areas, marine plankton may follow distribution patterns that are largely controlled by environmental variables.
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Papadopoulos, Vassilis P., Simon A. Josey, Aristides Bartzokas, Samuel Somot, Simon Ruiz, and Paraskevi Drakopoulou. "Large-Scale Atmospheric Circulation Favoring Deep- and Intermediate-Water Formation in the Mediterranean Sea." Journal of Climate 25, no. 18 (March 23, 2012): 6079–91. http://dx.doi.org/10.1175/jcli-d-11-00657.1.
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Abstract Atmospheric circulation patterns that are conducive to extreme ocean heat loss are investigated at four sites of special interest in the Mediterranean Sea. The Gulf of Lions, the South Adriatic Sea, the Cretan Sea, and the Levantine Sea are areas where anomalously high winter heat loss may lead to deep- or intermediate-water formation. At each of the above sites, the atmospheric circulation during such events is derived by averaging the sea level pressure (SLP) fields during the lower decile of the wintertime series of the net heat exchange. A relatively simple SLP pattern dominated by an anticyclone over northwestern Europe with a weaker cyclone to the southeast is found to be associated with strong heat loss in the selected sites with minor variations in pattern structure depending on the site. The SLP composite pattern reflects the combined effect of different atmospheric modes of variability and the authors consider the impacts on heat loss of a number of these modes (North Atlantic Oscillation, east Atlantic pattern, east Atlantic–west Russia pattern, and Scandinavian pattern), together with the North Sea–Caspian pattern and the Mediterranean index. The extremes in heat loss are strongly connected with the intensity and the positions of the poles of these patterns that modulate, through the necessary SLP gradient and associated northerlies, the transfer of cold and dry air over the areas of dense-water formation. Analysis of air–sea temperature difference, specific humidity, and evaporation anomalies indicates that the extremes of the net heat fluxes are primarily due to the latent and sensible heat flux components.
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Hainbucher, D., V. Cardin, G. Siena, U. Hübner, M. Moritz, U. Drübbisch, and F. Basan. "Hydrography in the Mediterranean Sea during a cruise with RV <i>POSEIDON</i> in April 2014." Earth System Science Data Discussions 8, no. 1 (May 13, 2015): 427–46. http://dx.doi.org/10.5194/essdd-8-427-2015.
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Abstract. We report on data from an oceanographic cruise in the Mediterranean Sea on the German research vessel POSEIDON in April 2014. Data were taken on a west–east section starting at the Strait of Gibraltar and ending south-east of Crete as well on sections in the Ionian and Adriatic Sea. The objectives of the cruise were twofold; long-term variations of the Levantine Intermediate Water (LIW) and the deep water masses of the Eastern Mediterranean Sea were investigated. The measurements include salinity, temperature, oxygen and currents and were conducted with a CTD/rosette system, an underway CTD and an ADCP. The sections are on tracks which have been sampled during several other cruises, thus supporting the opportunity to investigate the long term temporal development of the different variables. The use of an underway CTD made it possible to conduct measurements of temperature and salinity with a high resolution of 6 nm and a vertical resolution of 1 dbar for the upper 800 m of the water column.
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Hainbucher, D., V. Cardin, G. Siena, U. Hübner, M. Moritz, U. Drübbisch, and F. Basan. "Hydrography in the Mediterranean Sea during a cruise with RV <i>Poseidon</i> in April 2014." Earth System Science Data 7, no. 2 (September 3, 2015): 231–37. http://dx.doi.org/10.5194/essd-7-231-2015.
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Abstract. We report on data from an oceanographic cruise in the Mediterranean Sea on the German research vessel Poseidon in April 2014. Data were taken on a west–east section, starting at the Strait of Gibraltar and ending south-east of Crete, as well on sections in the Ionian and Adriatic Sea. The objectives of the cruise were threefold: to contribute to the investigation of the spatial evolution of the Levantine Intermediate Water (LIW) properties and of the deep water masses in the eastern Mediterranean Sea, and to investigate the mesoscale variability of the upper water column. The measurements include salinity, temperature, oxygen and currents and were conducted with a conductivity, temperature and depth(CTD)/rosette system, an underway CTD and an acoustic Doppler current profiler (ADCP). The sections are on tracks which have been sampled during several other cruises, thus supporting the opportunity to investigate the long-term temporal development of the different variables. The use of an underway CTD made it possible to conduct measurements of temperature and salinity with a high horizontal spacing of 6 nm between stations and a vertical spacing of 1 dbar for the upper 800 m of the water column.
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Ahumada, M. A., and A. Cruzado. "Modeling of the circulation in the Northwestern Mediterranean Sea with the Princeton Ocean Model." Ocean Science 3, no. 1 (February 9, 2007): 77–89. http://dx.doi.org/10.5194/os-3-77-2007.
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Abstract. The Princeton Ocean Model – POM (Blumberg and Mellor, 1987) has been implemented in the Northwestern Mediterranean nested (in one-way off-line mode) to a general circulation model of the Mediterranean Sea – OGCM (Pinardi and Masetti, 2000; Demirov and Pinardi, 2002) in order to investigate if this model configuration is capable of reproducing the major features of the circulation as known from observations and to improve what has been made by previous numerical modeling works. According to the model results, the large-scale cyclonic circulation in the northern part of the Northwestern Mediterranean is, at least in the upper layers, less coherent in winter and spring than in summer and autumn. Furthermore, there is evidence that the mesoscale structure (eddies and meanders) is, during all year, a significant dynamic characteristic in this region of the Mediterranean Sea. Finally, concerning the circulation in the lower layers, the model results have confirmed that Levantine Intermediate Water (LIW) and Western Mediterranean Deep Water (WMDW) follow essentially a cyclonic path during all year.
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Ahumada, M. A., and A. Cruzado. "Modelling of the circulation in the Northwestern Mediterranean Sea with the Princeton Ocean Model." Ocean Science Discussions 3, no. 4 (August 9, 2006): 1255–92. http://dx.doi.org/10.5194/osd-3-1255-2006.
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Abstract. The Princeton Ocean Model – POM (Blumberg and Mellor, 1987) has been implemented in the Northwestern Mediterranean nested (in one-way off-line mode) to a general circulation model of the Mediterranean Sea – OGCM (Pinardi and Masetti, 2000; Demirov and Pinardi, 2002) in order to investigate if this model configuration is capable of reproducing the major features of the circulation as known from observations and to improve what has been made by previous numerical modeling works. According to the model results, the large-scale cyclonic circulation in the northern part of the Northwestern Mediterranean is, at least in the upper layers, less coherent in winter and spring than in summer and autumn. Furthermore, there is evidence that the mesoscale structure (eddies and meanders) is, during all year, a significant dynamic characteristic in this region of the Mediterranean Sea. Finally, concerning the circulation in the lower layers has been confirmed that the Levantine Intermediate Water and the Western Mediterranean Deep Water follow essentially a cyclonic path during all year.
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Beccari, Valentina, Ahuva Almogi-Labin, Daniela Basso, Giuliana Panieri, Yizhaq Makovsky, Irka Hajdas, and Silvia Spezzaferri. "Late Holocene pteropod distribution across the base of the south-eastern Mediterranean margin: the importance of the > 63 µm fraction." Journal of Micropalaeontology 42, no. 1 (March 17, 2023): 13–29. http://dx.doi.org/10.5194/jm-42-13-2023.
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Abstract. Euthecosomata pteropods were analysed in core sediments collected in the framework of the 2016 EUROFLEETS2 SEMSEEP cruise, offshore of Israel, in the eastern Mediterranean Sea. The investigated cores were retrieved in a deep-sea coral area at 690 m depth, an actively methane-seeping pockmark area at 1038 m depth, and a deep-sea channel area at 1310 m water depth. We identified and documented the pteropod species belonging to the families Heliconoididae, Limacinidae, Creseidae, Cavoliniidae, Cliidae, and Hyalocylidae and to some heteropods. Our study highlights the importance of investigating pteropods in the size fractions > 63 µm instead of the > 125 µm only. In particular, neglecting the small size fraction may result in a remarkable (up to 50 %–60 %) underestimation of the relative abundance of the epipelagic species Creseis acicula and Creseis conica and the mesopelagic species Heliconoides inflatus. This may significantly affect palaeoenvironmental reconstructions. The observed presence of tropical species supports the suggestion that the eastern Mediterranean is a refugium for these species. This study provides a basic benchmark for the late Holocene evolution of pteropod and heteropod distribution over 5800–5300 cal BP across the base of the south-eastern Levantine margin.
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Parinos, C., A. Gogou, I. Bouloubassi, R. Pedrosa-Pàmies, I. Hatzianestis, A. Sanchez-Vidal, G. Rousakis, D. Velaoras, G. Krokos, and V. Lykousis. "Occurrence, sources and transport pathways of natural and anthropogenic hydrocarbons in deep-sea sediments of the eastern Mediterranean Sea." Biogeosciences 10, no. 9 (September 24, 2013): 6069–89. http://dx.doi.org/10.5194/bg-10-6069-2013.
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Abstract. 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.
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Leivadaros, Petros, Christos Tsabaris, Dionisis L. Patiris, Georgios Eleftheriou, Filothei K. Pappa, Efrossyni Androulakaki, Manos Dasenakis, Evangelia Krasakopoulou, and Vassilis Zervakis. "Recent 137Cs Distribution in the Aegean Sea, Greece." Journal of Marine Science and Engineering 10, no. 11 (November 10, 2022): 1719. http://dx.doi.org/10.3390/jmse10111719.
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Recent spatial and vertical distributions of 137Cs activity concentration in the Aegean Sea are presented almost 30 years after the Chernobyl accident. The study aims to provide the current radioactivity levels of 137Cs in the Aegean Sea and to combine the 137Cs activity concentration with typical oceanographic parameters (T, S) in order to utilize them as tracers to identify/validate the different water masses that are present in the Aegean Sea. This work was performed in the frame of the “KRIPIS” project in 2017 for continuous investigations of the deep basins from all over the Aegean Sea and includes samplings from the water column layers of seven stations. The 137Cs activity concentrations were determined via lab-based gamma ray spectroscopy after appropriate chemical pre-concentration of 137Cs, while the salinity and temperature of the water column were obtained by in-situ measurements. The activity concentration values of 137Cs varied from 1.6 to 5.5 Bq m−3. Clear distinction of the Black Sea and Levantine Waters was obtained based on the combination of temperature and salinity values with 137Cs activity concentration. Furthermore, including 137Cs as a supplementary tracer, the Transitional Subsurface Aegean Waters were identified at the Myrtoan and Antikythera Straits, combining the salinity, temperature and 137Cs activity concentration.
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Marty, J. C., and J. Chiavérini. "Hydrological changes in the Ligurian Sea (NW Mediterranean, DYFAMED site) during 1995–2007 and biogeochemical consequences." Biogeosciences Discussions 7, no. 1 (February 22, 2010): 1377–406. http://dx.doi.org/10.5194/bgd-7-1377-2010.
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Abstract. Data obtained during the monthly cruises of the DYFAMED time-series study (northwestern Mediterranean Sea) in the period 1995–2007 were compiled to examine the hydrological changes and the linked evolution of some biogeochemical characteristics. A regular increase of temperature and salinity (0.005 °C y−1, 0.0022 psu y−1) was recorded in deep waters of the NW Mediterranean Sea (2000 m depth) during 1995–2005. In February 2006 an abrupt increase in T (+0.1 °C) and S (+0.03 psu) was measured as the result of successive intense winter mixing events during the 3 previous years. The February 2006 event led to the mixing of the whole water column (0 to > 2000 m) and increased salt and heat content of the Western Mediterranean Deep Water by mixing with saltier and warmer Levantine Intermediate Water. The deficit in fresh water inputs to the western Mediterranean basin in three successive years (2003–2005) was suspected to be the major cause of this event since an increase of salinity in surface waters was monitored during these years. The measured phytoplankton biomass was specifically high after the periods of intense mixing. Chlorophyll a integrated biomass reached 230 mg m−2 in 1999, 175 mg m−2 in 2003, and 206 mg m−2 in 2006. The high levels of biomass were related to the particularly high increases in nutrients content in surface layers following the intense water column mixing and the subsequent development of a diatom bloom (as seen by fucoxanthin content). The frequency of extreme events (high mixing, high nutrients, and high biomass) increased in recent years. Our results suggested that the NW Mediterranean Sea could have an increased productivity and was not deriving towards the decreased productivity predicted by models.
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Marty, J. C., and J. Chiavérini. "Hydrological changes in the Ligurian Sea (NW Mediterranean, DYFAMED site) during 1995–2007 and biogeochemical consequences." Biogeosciences 7, no. 7 (July 7, 2010): 2117–28. http://dx.doi.org/10.5194/bg-7-2117-2010.
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Abstract. Data obtained during the monthly cruises of the DYFAMED time-series study (northwestern Mediterranean Sea) in the period 1995–2007 were compiled to examine the hydrological changes and the linked variation of some biogeochemical characteristics (nutrients and pigments). A regular increase of temperature and salinity (0.005 °C y−1, 0.0022 psu y−1) was recorded in deep waters of the NW Mediterranean Sea (2000 m depth) during 1995–2005. In February 2006 an abrupt increase in T (+0.1 °C) and S (+0.03 psu) was measured at 2000 m depth as the result of successive intense winter mixing events during the 3 previous years. The February 2006 event led to the mixing of the whole water column (0 to >2000 m) and increased salt and heat content of the Western Mediterranean Deep Water by mixing with saltier and warmer Levantine Intermediate Water. The deficit in fresh water inputs to the western Mediterranean basin in three successive years (2003–2005) was suspected to be the major cause of this event since an increase of salinity in surface waters was monitored during these years. The measured phytoplankton biomass was specifically high after the periods of intense mixing. Chlorophyll a integrated biomass reached 230 mg m−2 in 1999, 175 mg m−2 in 2003, and 206 mg m−2 in 2006. The high levels of biomass were related to the particularly high increases in nutrients content in surface layers following the intense water column mixing and the subsequent development of a diatom bloom (as seen by fucoxanthin content). The occurrence of extreme events (high mixing, high nutrients, and high biomass) increased in recent drought years (2003 to 2006). Our results indicated that the NW Mediterranean Sea productivity is increasing.
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Cascella, Antonio, Sergio Bonomo, Bassem Jalali, Marie-Alexandrine Sicre, Nicola Pelosi, Sabine Schmidt, and Fabrizio Lirer. "Climate variability of the last ~2700 years in the Southern Adriatic Sea: Coccolithophore evidences." Holocene 30, no. 1 (July 31, 2019): 53–64. http://dx.doi.org/10.1177/0959683619865600.
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New information on palaeoenvironmental conditions over the past ~2700 years in the Central Mediterranean Sea have been acquired through the high-resolution study of calcareous nannofossils preserved in the sediment core SW104-ND14Q recovered in the Southern Adriatic Sea (SAS) at 1013-m water depth. The surface water properties at this open SAS site are sensitive to atmospheric forcing (acting both at local and regional scale) and the North Ionian Sea driven inflowing waters. Our data show a relationship between reworked coccolith abundances, flood frequency across the Southern Alps and the North Atlantic Oscillation (NAO) confirming their value as indicator of runoff/precipitation. Changes in the abundance of the opportunistic (r-strategist) species Emiliania huxleyi and deep dweller taxa Florisphaera profunda were used to reconstruct the upper water column stratification and associated changes in coccolithophorid productivity. The negative correlation between reworked coccoliths and the N-Ratio ( r = −0.44; p = 6−7) suggest that fresh water induced stratification is a controlling factor of the SAS coccolithophorid production. High coccolithophorid productivity levels occurred during dry periods and/or time intervals of inflowing salty and nutrient-rich Levantine Intermediate Waters favouring convection while lower levels took place during high freshwater discharge, mainly during the ‘Little Ice Age’ and two centennial scale intervals of weakest NAO around 200 BCE and 500 CE.
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Malanotte-Rizzoli, P., V. Artale, G. L. Borzelli-Eusebi, S. Brenner, G. Civitarese, A. Crise, J. Font, et al. "Physical forcing and physical/biochemical variability of the Mediterranean Sea: a review of unresolved issues and directions for future research." Ocean Science Discussions 10, no. 4 (July 24, 2013): 1205–80. http://dx.doi.org/10.5194/osd-10-1205-2013.
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Abstract. The importance of the Mediterranean Sea for the world ocean has long been recognized. First, the Mediterranean sea has a profound impact on the Atlantic ocean circulation and, consequently, on the global thermohaline conveyor belt. Maps of the Mediterranean salty water tongue exiting from the Gibraltar strait at intermediate depths and spreading throughout the Atlantic interior are well known since the 1950s. Through direct pathways to the Atlantic polar regions or through indirect mixing processes, the salty Mediterranean water preconditions the deep convection cells of the polar Atlantic. There the North Atlantic Deep Water is formed which successively spreads throughout the world ocean constituting the core of the global thermohaline circulation. Even more importantly, the Mediterranean Sea is a laboratory basin for the investigation of processes of global importance, being much more amenable to observational surveys because of its location in mid-latitude and its dimensions. Both the western and eastern basins in fact possess closed thermohaline circulations analogous to the global conveyor belt. A unique upper layer open thermohaline cell connects the eastern to the western basin and, successively, to the north Atlantic through the Gibraltar strait. In it, the Atlantic water entering into Gibraltar in the surface layer, after travelling to the easternmost Levantine basin, is transformed into one of the saltiest water masses through air–sea heat and moisture fluxes. This is the salty water which, crossing the entire basin in the opposite direction below the surface Atlantic water, finally exits from the Gibraltar strait at mid-depths. Both the western and eastern basins are endowed with deep/intermediate convection cells analogous to the polar Atlantic deep convection cells or to the intermediate mode water ones. Deep and intermediate water masses are therefore formed in different sites of the entire basin. Because of their easily accessible locations, these convection cells are much more amenable to direct observational surveys and mooring arrays. An ubiquitous, energetic mesoscale and sub-mesoscale eddy field is superimposed to and interacts with the sub-basin scale, wind-driven gyres that characterize the upper thermocline circulation. Three different scales of motion are therefore superimposed producing a richness of interaction processes which typify similar interactions in unexplored ocean regions. Both wide and narrow shelves are present separated by steep continental slopes from the deep interiors. Cross-shelf fluxes of physical as well biogeochemical parameters are crucial in determining the properties of the shallow versus deep local ecosystems and their trophic chain. Most importantly, the Mediterranean Sea is a basin of contrasting ecosystems, from the strongly oligotrophic deep interiors to the fully eutrophic northern Adriatic characterized by recurrent, anomalous algal blooms and related anoxia events. This review focuses on the identification of the major unresolved scientific issues and wants also to provide directions for future research which may lead to the formulation of interdisciplinary, collaborative implementation plans to address these issues both theoretically and observationally.
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Cardin, V., G. Civitarese, D. Hainbucher, M. Bensi, and A. Rubino. "Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?" Ocean Science 11, no. 1 (January 9, 2015): 53–66. http://dx.doi.org/10.5194/os-11-53-2015.
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Abstract. Temperature, salinity and oxygen data collected during April and June 2011 (M84/3 and P414 cruises respectively) are analysed to derive the oceanographic characteristics of the Eastern Mediterranean (EM) basin. These observed characteristics are compared with those from previous cruises over the period 1987–2011. As a result, the interannual and decadal variability of the EM thermohaline properties are discussed in the context of the evolution of the Eastern Mediterranean Transient (EMT) and of the general circulation of the basin. We found that the state of the EM is still far from the pre-EMT conditions, though the 2011 results possibly indicate a slow return to this status. In particular, a comparison between thermohaline property evolution deriving from interannual variability of the preconditioning and air–sea interaction (heat fluxes) in the South Adriatic and the Cretan Seas reveals aspects of the alternation of the two dense water sources (Adriatic and Aegean) during the last three decades, which have strong implications for the hydrographic characteristics of the intermediate and deep layers of the Ionian and Levantine basins.
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García-Lafuente, Jesús, Cristina Naranjo, Simone Sammartino, José C. Sánchez-Garrido, and Javier Delgado. "The Mediterranean outflow in the Strait of Gibraltar and its connection with upstream conditions in the Alborán Sea." Ocean Science 13, no. 2 (March 24, 2017): 195–207. http://dx.doi.org/10.5194/os-13-195-2017.
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Abstract. The present study addresses the hypothesis that the Western Alborán Gyre in the Alborán Sea (the westernmost Mediterranean basin adjacent to the Strait of Gibraltar) influences the composition of the outflow through the Strait of Gibraltar. The process invoked is that strong and well-developed gyres help to evacuate the Western Mediterranean Deep Water from the Alborán basin, thus increasing its presence in the outflow, whereas weak gyres facilitate the outflow of Levantine and other intermediate waters. To this aim, in situ observations collected at the Camarinal (the main) and Espartel (the westernmost) sills of the strait have been analysed along with altimetry data, which were employed to obtain a proxy of the strength of the gyre. An encouraging correlation of the expected sign was observed between the time series of potential temperature at the Espartel Sill, which is shown to keep information on the outflow composition, and the proxy of the Western Alborán Gyre, suggesting the correctness of the hypothesis, although the weakness of the involved signals does not allow for drawing definitive conclusions.
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Blanchet, Cécile L., Rik Tjallingii, Anja M. Schleicher, Stefan Schouten, Martin Frank, and Achim Brauer. "Deoxygenation dynamics on the western Nile deep-sea fan during sapropel S1 from seasonal to millennial timescales." Climate of the Past 17, no. 3 (May 12, 2021): 1025–50. http://dx.doi.org/10.5194/cp-17-1025-2021.
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Abstract. Ocean deoxygenation is a rising threat to marine ecosystems and food resources under present climate warming conditions. Organic-rich sapropel layers deposited in the Mediterranean Sea provide a natural laboratory to study the processes that have controlled changes in seawater oxygen levels in the recent geological past. Our study is based on three sediment cores spanning the last 10 000 years and located on a bathymetric transect offshore from the western distributaries of the Nile delta. These cores are partly to continuously laminated in the sections recording sapropel S1, which is indicative of bottom-water anoxia above the western Nile deep-sea fan. We used a combination of microfacies analyses and inorganic and organic geochemical measurements to reconstruct changes in oxygenation conditions at seasonal to millennial timescales. Millimetre-thick laminations are composed of detrital, biogenic and chemogenic sublayers reflecting seasonal successions of sedimentation. Dark layers reflect the deposition of summer floods and two types of light layers correspond to autumn plankton blooms and authigenic carbonates formed in the water column during spring–early summer, respectively. The isotopic signature of the authigenic carbonates suggests permanent anoxic to euxinic bottom waters resulting in high levels of anaerobic remineralization of organic matter and highlights their potential to reconstruct seawater chemistry at times when benthic fauna was absent. Ratios of major elements combined with biomarkers of terrestrial and marine organic matter and redox-sensitive compounds allow changes in terrigenous input, primary productivity and past deoxygenation dynamics on millennial timescales to be tracked. Rapid fluctuations of oxygenation conditions in the upper 700 m water depth occurred above the Nile deep-sea fan between 10 and 6.5 ka BP, while deeper cores recorded more stable anoxic conditions. Synchronous changes in terrigenous input, primary productivity and past oxygenation dynamics after 6.5 ka BP show that runoff-driven eutrophication played a central role in rapid oxygenation changes in the south-eastern Levantine Basin. These findings are further supported by other regional records and reveal time-transgressive changes in oxygenation state driven by rapid changes in primary productivity during a period of long-term deep-water stagnation.
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Tachikawa, K., L. Vidal, M. Cornuault, M. Garcia, A. Pothin, C. Sonzogni, E. Bard, G. Menot, and M. Revel. "Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition." Climate of the Past 11, no. 6 (June 11, 2015): 855–67. http://dx.doi.org/10.5194/cp-11-855-2015.
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Abstract. 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 anoxic below a depth of 1800 m. However, whether this boundary permanently existed from the early to the mid-Holocene has not been examined yet. To answer this question, 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 and pore water oxygen depletion occurred prior to S1 deposition inferred from barium enrichment. In the middle of the S1 deposition period, reduced authigenic V, Fe and As contents and the 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 within the upper 1780 m of the eastern Mediterranean Sea was preconditioned by reduced ventilation, resulting from excess freshwater inputs due to insolation changes under deglacial conditions that initiated between 15 and 12 cal ka BP within the upper 1780 m. Short-term re-oxygenation in the Levantine Basin is estimated to have affected bottom water at least as deep as 1780 m in response to cooling and/or the reduction of freshwater inputs. We tentatively propose that complete ventilation recovery at the S1 termination was depth-dependent, with earlier oxygenation within the upper 1780 m. Our results provide new constraints on vertical water column structure in the eastern Mediterranean Sea since the last deglaciation.
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Tachikawa, K., L. Vidal, M. Cornuault, M. Garcia, A. Pothin, C. Sonzogni, E. Bard, G. Menot, and M. Revel. "Eastern Mediterranean Sea circulation inferred from the conditions of S1 sapropel deposition." Climate of the Past Discussions 10, no. 6 (December 20, 2014): 4647–81. http://dx.doi.org/10.5194/cpd-10-4647-2014.
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Abstract. 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.
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Dimiza, Margarita D., Maria V. Triantaphyllou, Elisa Malinverno, Stella Psarra, Boris-Theofanis Karatsolis, Paraskevi Mara, Anna Lagaria, and Alexandra Gogou. "The composition and distribution of living coccolithophores in the Aegean Sea (NE Mediterranean)." Micropaleontology 61, no. 6 (2016): 521–40. http://dx.doi.org/10.47894/mpal.61.6.09.
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This study presents the species composition of living coccolithophore communities in the Aegean Sea (northeastern Mediterranean), investigating their spatial and temporal variations in various environmental conditions from mesotrophic to ultra- oligotrophic regions. Coccolithophores of the photic zone in the Aegean Sea are relatively diverse (65 heterococcolithophores and 34 holococcolithophores) and dominated mostly by Emiliania huxleyi, Syracosphaera spp., Rhabdosphaeraceae and holococcolithophores. Hierarchical classification using R-mode cluster analysis distinguished five coccolithophore groups: Group Ia (Emiliania huxleyi, Syracosphaera molischii and Syracosphaera ossa) prevails in the high cell density and low diversity assemblages during the winter and early spring, when low temperatures and high nutrient concentrations are prevailing. Particularly in the north Aegean, E. huxleyi is dominating the upper photic zone being affected by the Black Sea Water inflow and the associated control on the water column stratification. Group Ib (Florisphaera profunda, Algirosphaera robusta, Syracosphaera anthos and Syracosphaera lamina) becomes important in the lower photic zone, making up the typical deep assemblages, whereas Group Ic (mainly Helicosphaera carteri and Gephyrocapsa oceanica) implies an opportunistic behavior in distinctly polluted neritic regions. Group IIa (Rhabdosphaera clavigera, Syracosphaera protrudens, Syracosphaera halldalii and numerous holococcolithophores) dominates the late spring-early autumn low cell density and high diversity assemblages, mainly in the thermally-stratified south Aegean and/or shallow, coastal environments with normal/ oligotrophic conditions, while Group IIb (Umbellosphaera tenuis and Syracosphaera pulchra) dominates the coccolithophore assemblages mainly during the early autumn in the north Aegean, thus reflecting the influence of Levantine Intermediate Water masses in the middle-lower photic zone. Our results suggest that abundance and variability in Aegean Sea coccolithophore assemblages are primarily controlled by surface water circulation and the associated water column stratification,with the sea temperature gradient affecting species composition.
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Denda, Anneke, and Bernd Christiansen. "Zooplankton at a seamount in the eastern Mediterranean: distribution and trophic interactions." Journal of the Marine Biological Association of the United Kingdom 91, no. 1 (August 31, 2010): 33–49. http://dx.doi.org/10.1017/s0025315410001153.
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The study focuses on the question, how a seamount in the oligotrophic eastern Mediterranean affects the zooplankton community, as compared to the open water. Zooplankton samples were taken with 333 µm nets at two sites, the Rhodes Basin and the Anaximenes Mountain, in December 2006. The samples were sieved into size fractions, and the composition, biomass, abundance and stable isotope signatures were analysed. In general, biomass and abundance of zooplankton were low, reflecting the oligotrophic character of the eastern Mediterranean, but zooplankton standing stocks were higher at the Rhodes Basin than at the Anaximenes Mountain. Stable isotope signatures showed, at a generally low level, enrichment in zooplankton taxa along the food chain within the different pelagic zones and from the surface to the deep-sea, but no significant differences between Rhodes Basin and the seamount were evident in the food web structure. The zooplankton community in the Anaximenes Mountain region in the northern Levantine Basin seems not to be influenced by a local seamount effect, despite the difference in standing stocks between the seamount and the Rhodes Basin. This seems to be driven by larger-scale upwelling and downwelling structures of cyclones and anticyclones, dominating the circulation in the area.
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Cartes, J. E., F. Maynou, P. Abelló, M. Emelianov, L. Gil de Sola, and M. Solé. "Long-term changes in the abundance and deepening of the deep-sea shrimp Aristaeomorpha foliacea in the Balearic Basin: Relationships with hydrographic changes at the Levantine Intermediate Water." Journal of Marine Systems 88, no. 4 (December 2011): 516–25. http://dx.doi.org/10.1016/j.jmarsys.2011.07.001.
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Konyukhov, Aleksandr I., Vadim F. Sharafutdinov, and Vasiliy V. Kalabin. "Geological structure, sedimentary environments and oil and gas potential of Oligocene-Miocene and Pliocene-Pleistocene deposits in the Levant basin." Georesursy 21, no. 2 (May 2019): 80–93. http://dx.doi.org/10.18599/grs.2019.2.80-93.
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An extensive sedimentary-rock basin is located within the continental margin of the Levant, where, since 2008, numerous natural gas fields have been discovered, including Tamar, Tannin, Dalit and Leviathan in the offshore zone of Israel, and Aphrodite in the zone of economic interests of Cyprus. Deposits of biogenic methane, located in the deep-water Levantine depression, are confined to terrigenous sandstones of late Oligocene-Early Miocene age. The discovery of another gas field Zohr in 2015 in the area of the underwater uplift of Eratosthenes caused a real boom among petroleum geologists. The fact is that natural gas deposit with reserves of about 30 trillion cubic feet is not in the terrigenous, but carbonate reservoir of the reef genesis, which opens significant prospects for the discovery of new large gas accumulations in the area of this major uplift. All the above-mentioned deposits are located in the same range of sea depths (1600-2000 m) in the propagation zone of the Messinian evaporites, that serves as a regional screen. An analysis of the materials currently published suggests that in the epochs of the sediments formation in which gas deposits are located, the depths of the seabed in the southern regions of the Levant depression were significantly lower compared to modern ones. Currently, there is no doubt that in the Levant region there is the largest gas-bearing basin in the Mediterranean region, with gas reserves of several hundred trillion cubic feet.
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Bonomo, Sergio, Michael Grelaud, Allesandro Incarbona, Elisa Malinverno, Francesco Placenti, Angelo Bonanno, Enrico Di Stefano, et al. "Living Coccolithophores from the Gulf of Sirte (Southern Mediterranean Sea) during the summer of 2008." Micropaleontology 58, no. 6 (2012): 487–503. http://dx.doi.org/10.47894/mpal.58.6.02.
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The Gulf of Sirte is a largely unexplored area in the southernmost Mediterranean Sea.We are presenting here 2008 summer data on the distribution pattern of living coccolithophores, a main phytoplankton calcifying group, in 105 samples from 20 stations. The survey includes coastal and offshore stations, enabling us to provide indications on the dynamics of phytoplankton productivity in relation to oceanographic processes. The total coccosphere concentrations show higher values in the offshore stations and lower ones for coastal sites. Umbellosphaera tenuis, Emiliania huxleyi, Florisphaera profunda, Syracosphaera pulchra HOL (Calyptrosphaera oblonga) and Rhabdosphaera spp. dominate the assemblages. The coccolithophore community shows the typical vertical zonation, with K-strategist taxa (among others U. tenuis, Rhabdosphaera spp. and Discosphaera tubifera) in the upper 75 meters depth and Lower Photic Zone taxa, dominated by F. profunda, below. The latter species shows its maximum development in the Deep Chlorophyll Maximum layer, which occurs in the upper part of the Levantine Intermediate Water, where the nutrient content is higher than in the overlying layers. The mesoscale oceanographic circulation significantly affects the spatial and vertical distribution of coccolithophores, with the thermocline and halocline depth shaping the vertical zonation of coccolithophore taxa and resulting in a strong lateral gradient within the gulf: in the eastern sector, under the influence of the Gulf of Sirte anticyclone, the DCM is deeper and so is the occurrence of K-strategist taxa and F. profunda.
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BRONSTEIN, OMRI, and ANDREAS KROH. "Needle in a haystack—genetic evidence confirms the expansion of the alien echinoid Diadema setosum (Echinoidea: Diadematidae) to the Mediterranean coast of Israel." Zootaxa 4497, no. 4 (October 11, 2018): 593. http://dx.doi.org/10.11646/zootaxa.4497.4.9.
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Diadema setosum (Leske, 1778), a widespread tropical echinoid and key herbivore in shallow water environments is currently expanding in the Mediterranean Sea. It was introduced by unknown means and first observed in southern Turkey in 2006. From there it spread eastwards to Lebanon (2009) and westwards to the Aegean Sea (2014). Since late 2016 sporadic sightings of black, long-spined sea urchins were reported by recreational divers from rock reefs off the Israeli coast. Numerous attempts to verify these records failed; neither did the BioBlitz Israel task force encounter any D. setosum in their campaigns. Finally, a single adult specimen was observed on June 17, 2017 in a deep rock crevice at 3.5 m depth at Gordon Beach, Tel Aviv. Although the specimen could not be recovered, spine fragments sampled were enough to genetically verify the visual underwater identification based on morphology. Sequences of COI, ATP8-Lysine, and the mitochondrial Control Region of the Israel specimen are identical to those of the specimen collected in 2006 in Turkey, unambiguously assigning the specimen to D. setosum clade b. This lends support to the hypothesis of a single introduction event and fits well with the habitat suitability and distribution model for D. setosum published recently. The more rapid and larger range extension along a south-eastern, counter-current trajectory may reflect a strong habitat preference for D. setosum in this area of the Levantine Basin as predicted by the model.
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Ayache, Mohamed, Jean-Claude Dutay, Thomas Arsouze, Sidonie Révillon, Jonathan Beuvier, and Catherine Jeandel. "High-resolution neodymium characterization along the Mediterranean margins and modelling of <i>ε</i><sub>Nd</sub> distribution in the Mediterranean basins." Biogeosciences 13, no. 18 (September 22, 2016): 5259–76. http://dx.doi.org/10.5194/bg-13-5259-2016.
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Abstract. An extensive compilation of published neodymium (Nd) concentrations and isotopic compositions (Nd IC) was realized in order to establish a new database and a map (using a high-resolution geological map of the area) of the distribution of these parameters for all the Mediterranean margins. Data were extracted from different kinds of samples: river solid discharge deposited on the shelf, sedimentary material collected on the margin or geological material outcropping above or close to a margin. Additional analyses of surface sediments were done in order to improve this data set in key areas (e.g. Sicilian strait). The Mediterranean margin Nd isotopic signatures vary from non-radiogenic values around the Gulf of Lion, (εNd values ∼ −11) to radiogenic values around the Aegean and the Levantine sub-basins up to +6. Using a high-resolution regional oceanic model (1/12° of horizontal-resolution), εNd distribution was simulated for the first time in the Mediterranean Sea. The high resolution of the model provides a unique opportunity to represent a realistic thermohaline circulation in the basin and thus apprehend the processes governing the Nd isotope distribution in the marine environment. Results are consistent with the preceding conclusions on boundary exchange (BE) as an important process in the Nd oceanic cycle. Nevertheless this approach simulates a too-radiogenic value in the Mediterranean Sea; this bias will likely be corrected once the dust and river inputs will be included in the model. This work highlights that a significant interannual variability of εNd distribution in seawater could occur. In particular, important hydrological events such as the Eastern Mediterranean Transient (EMT), associated with deep water formed in the Aegean sub-basin, could induce a shift in εNd at deep/intermediate depths that could be noticeable in the eastern part of the basin. This underlines that the temporal and geographical variations of εNd could represent an interesting insight of Nd as tracer of the Mediterranean Sea circulation, in particular in the context of palaeo-oceanographic applications.