Dardanelles Strait Research Articles

Seasonal variations in dissolved organic matter composition using absorbance and fluorescence spectroscopy in the Dardanelles Straits – North Aegean Sea mixing zone

The Dardanelles Straits – North Aegean Sea mixing zone is the area where the less saline waters of Black Sea origin supply organic material to the oligotrophic Mediterranean Sea. The objective of this work was to assess the seasonal dynamics of dissolved organic matter (DOM) in this region based on the optical properties (absorbance and fluorescence). By combining excitation-emission fluorescence with parallel factor analysis (EEM-PARAFAC), four fluorescent components were identified corresponding to three humic – like components and one amino acid – like. The latter was dominant during all seasons. Chromophoric DOM (CDOM) and dissolved organic carbon (DOC) were found to be strongly coupled only in early spring when conservative conditions prevailed and the two water masses present (Black Sea Waters – BSW and Levantine Waters – LW) could be identified by their absorption coefficients (a300) and spectral slopes S275–295. In summer and autumn the relationships collapsed. During summer two features appear to dominate the dynamics of CDOM: i) photodegradation that acts as an important sink for both the absorbing DOM and the terrestrially derived fluorescent humic substances and ii) the release of marine humic like fluorescent substances from bacterial transformation of DOM. Autumn results revealed a source of fluorescent CDOM of high molecular weight, which was independent of water mass sources and related to particle and sedimentary processes. The removal of the amino acid-like fluorescence during autumn provided evidence that although DOC was found to accumulate under low inorganic nutrient conditions, dissolved organic nitrogenous compounds could serve as bacterial substrate.

Phytoplankton variability and community structure in relation to hydrographic features in the NE Aegean frontal area (NE Mediterranean Sea)

The structure of phytoplankton community in the salinity-stratified Northeastern Aegean frontal area adjacent to the Dardanelles Straits was investigated on a seasonal basis (autumn, spring and summer) and in relation to circulating water masses: the modified Black Sea Water (BSW) and the Levantine Water (LW). By employing High Performance Liquid Chromatography (HPLC) for the analysis of phytoplankton pigments in conjunction with conventional cell counting methodologies (i.e. inverted light microscopy, flow cytometry) and primary production measurements, a comprehensive qualitative and quantitative characterization of phytoplankton community composition and its activity was conducted. Chlorophyll-a normalized production and estimated growth rates presented the highest values within the ‘fresh’ BSW mass during summer, though generally growth rates were low (<0.4 d−1) at all seasons. The spatiotemporal variation of BSW outflow was found to greatly affect the relative contribution of pico-, nano- and micro-phytoplankton to total phytoplankton biomass and production. Large cell organisms, and in particular diatoms, were closely associated with the surface BSW masses outflowing from the Straits. Our results showed that all phytoplankton size components were significant over time and space suggesting a rather multivorous food web functioning of the system.

Extant silicoflagellates from the Northeast Aegean (eastern Mediterranean Sea): Morphologies and double skeletons

Silicoflagellate abundance, vertical distribution and morphology were studied during spring (March 2014) at three sampling stations located in the Northeast Aegean Sea adjacent to the Dardanelles Strait and characterized by a variable influx of cold, low-salinity Black Sea water. The silicoflagellate assemblage was dominated by Dictyocha stapedia and Stephanocha speculum with minor contribution of D. aculeata and Octactis pulchra. While specimens of D. stapedia were represented by the typical morphologies described in other areas of the Mediterranean Sea, populations of S. speculum displayed peculiar characters: they were large, predominantly 7-sided, with a small apical ring as well as apical ring spines, concave basal ring sides and non-rotated apical structure. Some of these features have been described for S. speculum at high latitudes, but the combined characters make these specimens slightly different from the high latitude populations. Similar morphologies have been observed in the western Black Sea, thus we can infer that the peculiar specimens detected in the Northeast Aegean are associated with the influx of Black Sea water masses.

Evolutionary mechanisms of the Paratethys Sea and its separation into the Black Sea and Caspian Sea

A possible mechanism leading to the transformation of the Paratethys seas (i.e., the Sarmatian Sea-Lake, Meotian Sea, Pontian Sea-Lake, etc.) is here proposed. The time period from the formation of the closed Sarmatian Sea-Lake to the present is also considered. It will be shown that the main reason for the collapse of the Sarmatian Sea-Lake into the Black and Caspian seas was development of a canyon that cut through the mountains separating the Black and Mediterranean seas. Later, this canyon was transformed into the Bosporus and the Dardanelles straits. The canyon was formed mainly by erosive activity of a river that had periodically emerged from the Paratethys. Abrasion of the canyon bottom and the related erosional lowering of its level led to gradual drainage of the Paratethys basins. The consequences of the Messinian Salinity Crisis in the Mediterranean Sea contributed to the penetration of salt water into the Paratethys and then to its temporary isolation and transformation into a closed sea-lake. Later, its level rose, and the river was formed again. That river flowed into the Mediterranean Sea, in the process eroding its own bed. During low levels of the World Ocean, the riverbed experienced increased erosion, eventually dropping below high ocean level, at which time the river was flooded by Mediterranean water. This process led to the formation of a corridor linking the seas together; this corridor developed over the course of many glacioeustatic fluctuations in the World Ocean.

Assessment of trace metal contamination in the sea cucumber (Holothuria tubulosa) and sediments from the Dardanelles Strait (Turkey).

This study was performed to determine the concentrations of some trace metals (Cd, Cu, Pb, Ni, Zn, and Fe) in Holothuria tubuosa (Gmelin, 1788) belonging to Echinoderm species and in sediments that they live at three different stations (Gelibolu, Umur Bey/Lapseki, and Dardanos) on Dardanelles Strait between April 2013 and March 2014. The mean trace metal concentrations determined in H. tubulosa and sediment were as follows: Cd 0.18mg/kg, Cu 2.43mg/kg, Pb 2.09mg/kg, Ni 14.58mg/kg, Zn 16.86mg/kg, and Fe 73.46mg/kg and Cd 0.70mg/kg, Cu 5.03mg/kg, Pb 14.57mg/kg, Ni 27.15mg/kg, Zn 54.52mg/kg, and Fe 3779.9mg/kg, respectively. It was detected that the statistical difference between trace metals determined seasonally in muscle tissue of H. tubulosa was significant (p > 0.05). As a result of the study, it was detected that H. tubulosa is a bioindicator species in determining Ni trace metal in sediment. The results were compared to the limit values of National and International Food Safety, and it was detected that Cd and Ni concentrations measured in sediment were above LEL of Ni and Cd concentrations according to Sediment Quality Guidelines.

Possible recovery site of four non-recovered bodies lost in the Marmara Sea by using an ocean circulation model

Five men in a paddle boat were lost in the northern Marmara Sea, Turkey, on 17 August 2014. One of the bodies and some parts of the paddle boat were recovered 100 km south of the incident after seven days. The other four bodies were never recovered. An ocean circulation and a Lagrangian drift model were used together to predict the possible recovery site of the four bodies after they were lost in the Marmara Sea. Based on the circulation model output and atmospheric conditions at the time of the incident, it is concluded that there are two possible fates for the missing bodies. They either travelled west and reached the western coast of the Marmara Sea or, most probably, they drifted further to the south and left the Marmara Sea by passing through the Dardanelles Strait.

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

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

Seasonal and interannual variability of the water exchange in the Turkish Straits System estimated by modelling

A chain of simple linked models is used to simulate the seasonal and interannual variability of the Turkish Straits System. This chain includes two-layer hydraulic models of the Bosphorus and Dardanelles straits simulating the exchange in terms of level and density difference along each strait, and a one-dimensional area averaged layered model of the Marmara Sea. The chain of models is complemented also by the similar layered model of the Black Sea proper and by a one-layer Azov Sea model with the Kerch Strait. This linked chain of models is used to study the seasonal and interannual variability of the system in the period 1970-2009. The salinity of the Black Sea water flowing into the Aegean Sea increases by approximately 1.7 times through entrainment from the lower layer. The flow entering into the lower layer of the Dardanelles Strait from the Aegean Sea is reduced by nearly 80% when it reaches the Black Sea. In the seasonal scale, a maximal transport in the upper layer and minimal transport in the bottom layer are during winter/spring for the Bosphorus and in spring for the Dardanelles Strait, whereas minimal transport in upper layer and maximal undercurrent are during the summer for the Bosphorus Strait and autumn for the Dardanelles Strait. The increase of freshwater flux into the Black Sea in interannual time scales (41 m3s-1 per year) is accompanied by a more than twofold growth of the Dardanelles outflow to the North Aegean (102 m3s-1 per year).

New records of anthozoan species (Cnidaria, Octocorallia, Hexacorallia) for the Turkish Straits System

Abstract This study includes new records of soft corals found in the Turkish Straits System (Dardanelles) between 2013-2014. In the above-mentioned area, 50 stations were searched by scientific divers from the intertidal zone to a depth of over 45 m and the ecological characteristics with substrate differences were also recorded. A total of 47 cnidarians were examined during the surveys. Eleven anthozoan species (Aiptasia mutabilis, Alcyonium acaule, Andresia parthenopea, Calliactis parasitica, Cereus pedunculatus, Condylactis aurantiaca, Epizoanthus couchii, Maasella edwardsi, Pteroeides spinosum, Sarcodictyon roseum, Veretillum cynomorium) belonging to 4 orders are new to the Dardanelles strait, one of which is reported from the Marmara Sea. The current data contributed to the advancement of the knowledge about anthozoan species in the Turkish Seas.

Reproduction and population structure of the sea cucumber Holothuria tubulosa in the Dardanelles Strait, Turkey

In this study, Holothuria tubulosa Gmelin 1791 was investigated from April 2013 to March 2014 in the Dardanelles Strait, to outline the morphological characteristics, reproductive patterns and the relationship between population characteristics and environmental parameters. Between 15 and 30 individuals of this species were sampled monthly from three stations. There was a negative allometry between length and weight, being gutted weight the most reliable measurement for this species. Reproductive patterns of the species were identified the first time for Turkish coasts. By macroscopic examination of the gonads, smallest sizes (gutted length) were measured as 8.4 and 8.1 cm for female and male, respectively. Sex ratio was calculated as 1: 1.1 with differences between seasons. The reproduction of sea cucumbers occurred between August and September after Gonadosomatic Index (GSI) values reached their maximum in July. The species was found down to 10 m depth with a population density of 0.21 / m2, which was rather low compared to previously reported values for Mediterranean populations of this species. There was a high positive correlation between population density and GSI of the species. The highest population density was observed where the largest sea grass meadows are found.

Seasonal and Spatial Variability of SST Using MODIS Data: the Case Study of Aegean Sea

This paper focuses on the analysis of spatial and temporal variability of Sea Surface Temperature (SST) derived from Aqua Moderate Imaging Spectrometer (MODIS) infrared imagery in the Aegean Sea. Data were organized to examine both seasonal and monthly variation of SST during 2005 - 2008. The four year period was chosen as a first approach to address and describe this phenomenon. A descriptive statistical analysis was performed, while hot spots and SST anomalies for each month and season were identified. The results show a smooth monthly variation of SST with February to be the coldest month while July the hottest as expected. The year with the higher average SST value was 2007 with 25.1 o C while 2006 presents the minimum average value. In addition, the high resolution maps of 1 km that extracted from the analysis with a wide spatial coverage, allows to the detail representation of SST in the region. This helps to produce a rich eddy field and it allows monitoring the outflow of Black Sea Waters through the Dardanelles Strait.

Temporal and spatial variability of nutrients and oxygen in the North Aegean Sea during the last thirty years

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.

HF Radar observations of the Dardanelles outflow current in North Eastern Aegean using validated WERA HF radar data

A two-site WERA HF radar station was installed in November 2009 at the eastern coast of Lemnos Island in North Aegean Sea, aiming to monitor the surface inflow of Black Sea waters exiting from the Dardanelles Strait, as well as to constitute a coastal management tool for incidents of oil-pollution or save-and-rescue operations. Strong interference by foreign transmissions is a source of noise deteriorating the quality of the backscattered signal, thus significantly reducing the HF radar’s effective data return rate. In order to ameliorate this problem, further quality-control and data gap interpolating procedures have been developed and applied, to be used in addition to the procedures incorporated and used by the manufacturer’s signal processing software. The second-level processing involves traditional despiking in the temporal domain, preceding Empirical Orthogonal Function analysis. The latter is used not only to filter high-frequency noise but also to fill data gaps in time and space. The data reconstruction procedure has been assessed via comparison of (a) HF radial with CODE-type drifter radial velocities as well as (b) HF-derived virtual drifter tracks with actual drifter tracks. The main circulation features and their variability, as revealed by the reconstructed fields, are presented.

Danish Straits versus Turkish Straits: The Potential Impact of Prospective Russian Oil Exports

The Danish Straits, which connect Baltic Sea to North Sea as an oil transit choke point, are becoming vastly important as a gateway to Europe for Russian oil exports. In terms of the future source of Russian oil, the country is estimated to hold half of the total Arctic resources. This indicates the forthcoming increase in the importance of Danish Straits in the global energy security. Besides, two additional alternative and important choke points are located in Turkey, which are the Straits of Bosporus and Dardanelles, known as Turkish Straits. These straits are also one of the significant exit points of Russian oil exports but as Russia shifted its direction of oil exports toward Baltic ports, the strategic position of Turkish Straits have been affected from this transition as well. It is an open question whether the Turkish Straits will continue to be the outlet of Russian oil exports or the Danish Straits will take over that position in line with the oil resources development in the Arctic Region. This study aims to analyse the Turkish and Danish Straits and establish their significance in terms of energy security. The current and future oil export strategies of Russia on the existing chokepoints are also discussed, with special emphasis on the potential impacts of Arctic development as Russia continues with the exploration and extraction of Arctic oil resources.

The oceanic response of the Turkish Straits System to an extreme drop in atmospheric pressure

AbstractMoorings across all four entry/exit sections of the Dardanelles Strait and the Bosphorus Strait simultaneously measured the response of the Turkish Straits System to the passage of a severe cyclonic storm that included an atmospheric pressure drop of more than 30 mbar in less than 48 h. The bottom pressure response at the Aegean Sea side of the Dardanelles Strait was consistent with an inverted barometer response, but the response at the other sections did not follow an inverted barometer, leading to a large bottom pressure gradient through the Turkish Straits System. Upper‐layer flow toward the Aegean Sea was reversed by the storm and flow toward the Black Sea was greatly enhanced. Bottom pressure across the Sea of Marmara peaked 6 h after the passage of the storm's minimum pressure. The response on the Dardanelles side was a combination of sea elevation and pycnocline depth rise, and the response on the Bosphorus side was an even greater sea elevation rise and a drop in pycnocline depth. The peak in bottom pressure in the Sea of Marmara was followed by another reverse in the flow through the Dardanelles Strait as flow was then directed away from the Sea of Marmara in both straits. A simple conceptual model without wind is able to explain fluctuations in bottom pressure in the Sea of Marmara to a 0.89–0.96 level of correlation. This stresses the importance of atmospheric pressure dynamics in driving the mass flux of the Turkish Strait System for extreme storms.

Ağır Metallerin Ekosistem Tepkilerini Anlamaya Yönelik Karadeniz’in Gösterge Organizmaları Kullanılarak Yapılmış Çalışmalar

Studies to understand Ecosystem Responses of Heavy Metals using indicator organisms of the Black SeaThe European Parliament published in the field of Marine Environment Policy Marine Strategy Framework Directive (MSFD), ecological quality and integrity in estuarine, the coastal and open ocean systems, has been developed to protect and restore. MSFD is based on the principle of ecosystem-based management takes into account all pressures of the seas and approaches to the sea regionally. The purpose of the directive in the EU by 2020 is to ensure Good Environmental Status of the seas (GES). In particular Bulgaria and Romania after they join the European Union countries, the Black Sea has become important for Europe. The Black Sea is one of the unique in the world an inland sea connected to the small Sea of Marmara by the narrow Bosporus Strait; Strait of Dardanelles further connects to the Aegean Sea. For this reason, there is very little natural circulation is self-cleaning ability remains limited. Turkey poured into the Black Sea off the coast of the Sakarya, Kýzýlýrmak, Yeþilýrmak, from the West, the Danube, from the North Dnieper and Dniester Rivers with a million tons of organic waste into the Black Sea basin are carrying the item and other terrestrial origin. One of the important pollutants due to heavy metals toxic property of natural concentrations of negatively affecting the ecosystem when they take on the biological activities of the organisms that make up the food chain, the balance between biota and the environment corruption and adversely affects the people at the top of the food chain. This review covers the studies of heavy metals has been using the indicator organisms of the Black Sea to understand the ecosystem response. The results of the studies discussed and made suggestions

Influence of Dardanelles outflow induced thermal fronts and winds on drifter trajectories in the Aegean Sea

The data provided by 12 drifters deployed in the Northern Aegean Sea in the vicinity of the Dardanelles Strait in August 2008 and February 2009 are used to explore the surface circulation of the basin and the connectivity to the Black Sea. The drifters were deployed within the Dardanelles outflow of waters of Black Sea origin in the Northeastern Aegean. Thanks to the particular choice of the drifter deployment positions, the data set provides a unique opportunity to observe the branching behaviour of the surface currents around Lemnos Island. Such pathways were notpossible to study with previous drifter deployments that were far from the Dardanelles Strait. In addition, the drifter tracks covered the Aegean basin quite thoroughly, mapping major circulation features and supporting the overall general circulation patterns described by previous observational and modelling studies. The collected data display cases in which drifters are driven by winds and thermal fronts. Wind products were used to estimate the influence of the atmospheric forcing on the drifter trajectories. Satellite sea surface temperature images were connected to the drifter tracks, demonstrating a high correlation between the remote and in situ observations. The waters of Black Sea origin were traced all the way to the Southern Aegean, establishing a strong connectivity link between the Aegean and Black Sea basins.

Chemical properties and fluorescence of DOM in relation to biodegradation in the interconnected Marmara–North Aegean Seas during August 2008

The dynamics of dissolved organic matter (DOM) in the Marmara Sea–Dardanelles Straits–North Aegean Sea were investigated using measurements of dissolved organic carbon and nitrogen (DOC, DON), PARAFAC modeling of 3-D excitation–emission fluorescence spectra and bacterial production (BP) and respiration (BR) rates. In the surface brackish waters, chemical parameters showed an increase from the Aegean to the Marmara (DOC: 65–217μmolL−1; DON: 3.08–9.34μmolL−1; Dissolved Inorganic Nitrogen (DIN): 0.044–1.38), followed by an increase in BP rates (7.2–195nmolL−1d−1). In the subsurface waters, DIN also showed an increase in the Marmara basin (0.085–9.79μmolL−1) followed by an increase in BP rates (3.3–17.4nmolL−1d−1). PARAFAC modeling revealed three fluorescent components: λex/λem: <260(330)/464nm, humic-like; λex/λem: <(260) 285/364nm, quinone-like; λex/λem: 270/308nm, tyrosine-like. DOC:DON ratios were found similar for the Marmara (21±3) and the N. Aegean Sea (19±2). The slopes ΔDOC:ΔDON suggested that in the Marmara Sea mineralization processes require more carbon relative to nitrogen (22.3), whereas in the N. Aegean there is preferential removal of nitrogen over carbon (5.66). The lack of significant correlation between DOC and AOU (apparent oxygen utilization) in the deep Marmara waters indicates that particulate organic matter is important in deep mineralization processes.

Observed volume fluxes and mixing in the Dardanelles Strait

[1] Pairs of moorings equipped with current profilers were deployed at each end of the Dardanelles Strait and remained in place for over 13 months. Current observations were able to resolve well the exchange flow and volume fluxes. Volume fluxes showed distinct temporal variability in upper and lower layers, especially evident on synoptic time scales. The synoptic flux variability in the upper layer was coherent with the local atmospheric forcing and the bottom pressure anomaly gradient, while the flux variations in the lower layer were related to the bottom pressure anomaly gradient. Estimated volume flux values were often two or more times larger than their respective annual means. Annual upper-layer flux means were 25.66 × 10−3 and 36.68 × 10−3 Sv, whereas the lower-layer averages were 14.02 × 10−3 and 31.67 × 10−3 Sv for the Marmara and Aegean sections, respectively. The fluxes also showed that there was a net low-salinity water outflow to the Aegean Sea, and that they varied weakly on longer time scales (monthly to seasonal). High-salinity water fluxes (≥ 39 psu) were used to calculate strait-averaged vertical eddy diffusivities which ranged between 10−4 and 10−2 m2 s−1. Additionally, microstructure observations were used to evaluate vertical eddy diffusivities. These estimates indicated that mixing in the strait varied spatially and temporarily, and it was dependent on complex strait geometry, exchange flow status, and partially on meteorological conditions. Large values of eddy diffusivities, with a depth-averaged mean of 1.3 × 10−2 m2 s−1, and vigorous mixing were found in the Nara Pass, the narrowest section in the Dardanelles Strait.

The South Marmara Fault

We use about 800 km of multichannel exploration seismic reflection profiles of the seventies as well as the results of three drill holes that penetrated the sedimentary cover down to the Upper Cretaceous basement to describe a continuous gently curvilinear, south-concave zone of deformation about 10 km wide that extended over the whole southern shelf of the Sea of Marmara from the Gulf of Gemlik to the Dardanelles Straits in Lower Pliocene time, about 4 Ma. We call this zone of deformation the South Marmara Fault (SMF) system and propose that the SMF was then a branch of the dextral North Anatolian Fault. This branch passed to the north of the Marmara Island Eocene block and thus had a south-facing concavity. This curvature resulted in a significant component of shortening in the western part of the fault. The SMF was deactivated at the end of Lower Pliocene, about 3.5 Ma, except for its easternmost branch between the Gulf of Gemlik and Imrali Island where about 5 mm/year of dextral motion is still occurring today.