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Globally, all marine ecosystems are under pressure by anthropogenic stressors. However, semi-enclosed seas are at a greater risk of degradation due to their limited connectivity to open seas. This leads to a greater accumulation of pollutants and abrupt regime shifts triggered by unsustainable exploitation of living resources, as ecosystems exhibit low degrees of redundancy and more frequent large-scale episodic events such as harmful algal blooms. The Sea of Marmara is a semi-enclosed marine region that has been subjected to various anthropogenic stressors since the 1990s. Recently, local and governmental authorities have employed basin-wide ecosystem management plans to control and manage point and nonpoint (diffuse) sources of pollutants. However, the management of fisheries in relation to the dynamics of the Sea of Marmara food web has attracted less attention from policymakers, even though fisheries exploitation is one of the most significant anthropogenic pressures. In this study, we capitalized on a previous static ecosystem model of the Sea of Marmara by revising and extending it to simulate the changes between 1990 and 2020. We delineated the temporal dynamics and regime shifts in the food web in terms of ecosystem structure and function by using ecological indicators and developed quantitative management advice for its fisheries. The results showed that the ecosystem has experienced three regimes since 1990, with regime shifts occurring with the onset of the 2000s and the mid 2010s. The first regime exhibited high diversity and material cycling, the second regime was characterized by low diversity and increased impact of fisheries, and the third regime culminated in a fished-down food web state. The analysis of fishery dynamics showed that the majority of harvested species were overexploited. We suggest that the implementation of quotas for exploited species should be considered an immediate solution to the unsustainable exploitation of fish stocks and can help restore ecosystem conditions.

This study reports our observation of the large sea slug Tethys fimbria Linnaeus, 1767 in the northern-eastern Sea of Marmara (the Princes’ Islands). We observed T. fimbria on the detrital bottom of the sea at a depth of 35 m in June 2022. This species had previously been reported during spawning in a recent study conducted in the southern part of the Çanakkale Strait (the Dardanelles Strait that connects the Marmara Sea with the Aegean Sea). Prior to 2022 there had been no reports of this conspicuous species from the Marmara Sea in the scientific literature or in photo-records among divers. Following our observation of the species in the sea around the Princes’ Islands, underwater photographers reported pictures of T. fimbria from different locations in the Marmara Sea on social media platforms. The sea slug seems to extend its distribution northwards. The potentially new arrival of the large sea slug in the Sea of Marmara, rather than a distribution shift from deoxygenated deep Marmara basins or a climate-related northwards expansion, is discussed.

The Sea of Marmara, located in Northwestern Türkiye, is under multiple stressors, including climate change and industrial, agricultural, and domestic pollution, that cause deoxygenation in coastal waters, with multiregional consequences affecting the surface and deep-water masses transported to the Mediterranean and Black Seas, respectively, via its straits. With climate-change driven changes in the intensity of extreme precipitation events, the marine environment becomes more vulnerable to increasing terrestrial pollutants. Evaluating the spatial and temporal variation of river runoff is crucial to understanding the interaction between the geophysical and hydrogeochemical processes that affects the nutrient balance of the sea. This study aims to (i) explore the historical (for the period 1960-2021) and spatial changes of monthly-averaged coastal discharges along the coastline of the Sea of Marmara for the first time, based on observations from the national hydrological service; (ii) analyze the change in long-term and seasonal trends of runoff and net-precipitation rate and derive a regional relation between the two parameters. Single Spectrum Analysis (SSA) is used to obtain the trends. Gaps in the time series are filled in using a non-parametric spectral estimation method. Discharges from the northern, eastern, and southern basins are, respectively, 3%, 17%, and 80% of the total discharge, which has varied between 1.5 and 15 km3 per year in the last decade, with short-lived extremes occurring in early spring. Total runoff rate shows a declining long-term trend that is accelerating with increasing evaporation. The intensity of the terrestrial precipitation extremes shows a temporal increase; there is a quadratic relation between the long-term trends of net precipitation and total runoff. Quantification of nutrient load distribution along the coastline associated with the spatial-temporal changes in coastal fluxes is urgent because the cumulative stressors (warming, nutrient overenrichment, pollutants) pose a threat of triggering extreme events and eutrophication in the Sea of Marmara with multiregional impact.

The North Anatolian Fault Zone (NAFZ) is the most prominent active fault system in Northwestern Turkey. It is a major fracture that traverses the Northern part of Asia Minor and marks the boundary between the Anatolian tectonic plate and the larger Eurasian continental block, and has been the source of numerous large earthquakes throughout history. The NAFZ splits into three strands at the eastern part of the Marmara Sea. The northern strand passes through Izmit Bay, traverses the Marmara Sea and reaches to the Saros Gulf. The central fault zone passes through Izmit Bay, traverses the Sea of Marmara and reaches the Saros Gulf to the southeast. Earthquakes on this zone involve primarily horizontal ground motions (strike-slip type of faulting). Because of this unstable tectonic system, the area is considered to be as one of the most seismically active zones of the world. In the last hundred years, numerous large earthquakes have also occurred along the NAFZ, in the western part of Turkey. Beginning with an earthquake in 1939, several more quakes - with Richter magnitudes greater than 6.7 - struck in progression along adjacent segments of the great fault. The August 17, 1999 Izmit earthquake was the eleventh of such a series that have broken segments of the NAFZ, in both eastward and westward direction. The epicenter of the 1999 earthquake was near Izmit, as well as the location of previous events. The sequence of historic events indicates that the next destructive tsunamigenic earthquake could occur west of the 1999 event in the Sea of Marmara. The present study incorporates the results of a subsequent 2001 study which uses standardized remote sensing techniques and GIS-methods – based on Digital Elevation Model (DEM) data, and on geo- morph metric parameters that influenced local site conditions in the Sea of Marmara, as determined with Digital elevation data of the Shuttle Radar Topography Mission (SRTM), and with high resolution ASTER-data. With such remote sensing methods, areas that are potentially vulnerable areas in the Sea of Marmara were detected, so that disaster mitigation strategies can be implemented more effectively in the future. Based on such technology, local site conditions, which exacerbated earthquake intensities and collateral disaster destruction in the Marmara Sea region, were identified. Also reviewed by the present study are the similarities of NAFZ with the San Andreas fault in California in the USA, for the formation of an active transform boundary of the strike-slip type, with the two sides moving horizontally and continuously past each other. Finally examined is the tectonic and continuing geodynamic evolution and collision between the Arabian Plate and Eurasia, which places in danger many cities in southeastern Turkey and NorthWest Syria - which is are located on the boundary with the Arabian tectonic plate, as evidenced by the recent disastrous earthquake of 8 February 2023 along the Eastern Anatolian Fault Zone (EAFZ).

Abnormalities of shape, color or body deformities such as lack of swim bladders or any parts of the body are an unexplained issue for many fish species. There is a gap of knowledge regarding their causes. Generally, it is an important problem in the rearing technique in aquaculture management due to the high economic consequences. The morphological abnormalities occur in marine fishes as well. Missing dorsal spines or rays, scale disorientation, jaw deformities, eye deformations and the lack of some parts of the body are within the context of abnormality. In the present study, the bodyabnormalityobservedinaspecimenofEuropeanhake(MerlucciusmerlucciusLinnaeus,1758)missingitsrighteyewhichwascaughtbyafishermanintheMarmaraSeaon13October2020, and its causes are reported and discussed. Further studies are needed to correlate the wild fish anomalies caused by pollution.

The Marmara is the most highly trafficked region in Turkey in terms of seaway and highway transport congestion. The transport mode-based CO2 emissions budget for the region needs to take more environmentally friendly measures. In this study, 13 ro-ro and ferry lines (RFLs) are evaluated in the Sea of Marmara to compare ship-generated CO2 emissions with road transport as if the carried vehicles had used the highway instead of transport by RFL. Additionally, this study revealed the management strategies for CO2 emissions reduction for both transport modes under current conditions. The total CO2 emissions budget of 13 RFLs in the Sea of Marmara is higher than the potential CO2 emissions of their carried vehicles. Using the methods of Entec UK Ltd and Trozzi and Vaccaro, the amount of CO2 emissions generated by the RFLs is 204,470.99 and 170,459.85 t/year, respectively. The potential CO2 emissions of road vehicles carried in 2017, 2018 and 2019 are computed by applying Tier 1 methods as 121,690.54, 106,844.89, and 100,921.95 t/year, respectively. It is observed that shifting trucks from the highway to the seaway contributes to a reduction of the yearly CO2 emissions budget generated from the transport sector to provide sustainable transportation management in the region.

The present research study investigated the catch-per-unit-effort (CPUE, kg/h) and biomass of Par-apenaeus longirostris in consideration of three parameters, i.e. seasons, regions, and depth levels. Beam trawls were used to collect the specimens at a total of 229 sampling stations in the Sea of Marmara between September 2011 and July 2014. In the Sea of Marmara, the mean CPUE of P. longirostris was calculated to be 8.4±0.5 kg h-1 , and the mean biomass to be 354 kg/km-2. The mean CPUE value was at its highest in summer and autumn, and the lowest was observed in winter and spring. The by-region mean CPUE value of P. longirostris was the highest in the northern Sea of Marmara (14.3±1.9 kg h-1), and the lowest was detected in the south (3.6±1.0 kg h-1). The highest biomass value was found at a depth of 50-100 m, in the northern Sea of Marmara, while the lowest was calculated in the southeastern Sea of Marmara.

Jellyfishes, which are one of the most important consumers in marine ecosystems, may have detri-mental effects on fish stocks that have economic value. Therefore, identifying and monitoring jelly-fish presence is important. We observed four individuals of symbiotic rhizostome scyphozoan Cot-ylorhiza tuberculata in the vicinity of the Princes’ Islands Archipelago, in the Northeast Sea of Marmara, Turkey in September 2020. Although this species is a common member of gelatinous plankton in the Mediterranean Sea, the present study is the first record from the Sea of Marmara.

Within the scope of this paper, seismic reflection and bathymetry studies were carried out in the shallow marine area forming the westernmost part of the Tekirdağ Basin using the R/V Selen Research Vessel within the MTA Marine Research Department. In the study area, ~ 500 km length bathymetry data and ~191 km shallow seismic profiles ( 41 lines) were collected. By means of the data, tectonic structures and deformation textures of the North Anatolian Fault System (NAFS) in the marine area of Gaziköy were examined. As a result of the processing and interpretation of the seismic sections, compression structures occurring due to the SW rotation of the NAFS in the study area, the morphology of the Ganos depression that formed as a result of faulting and also three different stratigraphic units were distinguished. These units are separated from each other by distinct unconformity surfaces and each unit presents different deformation structures. One of the most significant results obtained from the seismic data is that the unconformity surface that separates the current sediments of the seafloor from the older units is represented by the overlapping structures indicate sea level changes. It has been assessed that this situation occurred as a result of the erosional process developed during sea level fall.

Excluding the jellyfish from the bunt-end is a common slipping process used in the Sea of Marmara purse seine fishery. For this aim, a sheet of netting piece, larger mesh size and thicker diameter, is rigged on the bunt-end of the purse seine net. The jellyfish mass on the netting piece are slipped by rolling over the headline (floating line) after partially hauling or drying-up the net while it is still in the water. In this study, the catch amount of this slipping was roughly estimated with the introduction of the slipping process only used by the purse seiners in the Sea of Marmara. There were eight successful purse seine operations conducted between 8 and 11 September 2018 in depth ranged 77 to 677 m. The percentage of landed species versus to jellyfish varied between 23% and 85%. The mean landed anchovy amount is 4379 (3756.6) kg for per operation. The mean slipped amount of jellyfish is 3812.5 (2404.4) kg. However, both anchovy (99.8%) and jellyfish (96.3%) are the vast majority species that landed and slipped, respectively. In the operations totally 100 boxes of anchovy (1180 kg) unintentionally was slipped with the jellyfish. In addition, two sharks with larger size were slipped to the sea as alive over the floating line of the net. Although slipping practised rarely in Turkey, all the purse seiner in the Sea of Marmara have to use the adapted slipped process to get rid of jellyfish. However, there are no records and scientific findings regarding slipped amount of the jellyfish. For this reason, this study is important to presented preliminary results regarding amount of the jellyfish. In conclusion, this study is extended completely the Sea of Marmara practised to understand the dimensions of jellyfish amount and slipping process.

The article is devoted to the early phase of the career of Martin Eric Nasmith (1883–1965) and is an attempt to summarise his achievements during three underwater patrols in the Dardanelles and the Sea of Marmara in 1915. Those missions brought him the appellation of the most effective British submariner of WW1. In Anglophone historiography, all the books and articles related to this subject constitute a one-sided narrative based solely on British sources. Thus, the author has made the first attempt in western historiography to compare the British and Turkish points of view. Although a few such efforts have been made in Tur- key, their results are not widely known to western historians, and in some cases, they raise objections. The decision to take up this challenge came from an awareness that Nasmith’s view of the situation at the moment when he was personally observing the effects of his attacks could not be complete and entirely objective. He could not have known that some of the vessels he had sunk in shallow coastal waters were salvaged by the Turks and restored to service. The article gives detailed coverage of the attacks conducted by Nasmith on Ottoman warships, steam-powered merchant ships and land targets, during all three patrols of the “E11” submarine. As a result of his research, the author was able to draw attention to the fact that the results of “E11”’s second patrol were incomparably more favourable than those of the first one (for which Nasmith was awarded the Victoria Cross), both in terms of losses inflicted on the Ottoman Navy and on the transport fleet. In the case of the latter, the total tonnage of definitively sunken steam-powered vessels was more than 470 percent higher. While Nasmith claimed that he had sunk at least 122 Ottoman vessels during all three patrols, Turkish sources indicate that the total number of warships and steam-powered transport ships definitively destroyed by him did not exceed fifteen.

In this study, length distribution, length-weight relationship, age, growth parameters, and reproduction of 331 Gobius niger collected monthly by trawling in the Sea of Marmara between October 2011-July 2014 were determined. The total length and weight distributions of the population varied from 6.2-14.2 cm and 2.85–36.25 g, respectively. The average length was found 10.28 cm and average weight was found 13.71 g. Black goby was distributed between 0-4 age groups. Otolith length-total length relationship was calculated as OL= 2.337*TL+0.143 (R2=0.76). Length-weight relationship were determined total, female, and male as W = 0.096*L3.084 (R²=0.89); females W= 0.010*L3.042 (R2=0.88); males W=0.005*L3.33 (R²=0.94) respectively. The growth parameters were calculated for the whole populations as L∞=15.31 cm K= 0.36 y-1 t0=-1.77 year, L∞=14.89 cm, K=0.35 y-1, t0=-1.97 year for females and L∞=1 4.65 cm, K=0.45 y-1, t0=-1.39 year for males. The natural mortality rate (M) was calculated as 0.82 year-1, total mortality rate (Z) was 1.33 year-1, and fishing mortality rate (F) was 0.51 year-1. The exploitation rate (E) of population was determined as 0.38 year-1. The first sexual maturity length of G. niger was found L50=9.58 cm. The reproduction period was indicated between March to July.

In this study, length–weight relationships and the catch per unit effort-relative abundance (CPUE kg/h, N/h) of the three-gurnard species Chelidonichthys lucerna (Linnaeus, 1758), Lepidotrigla cavillone (Lacepède, 1801), Eutrigla gurnardus (Linnaeus, 1758) were determined according to season, area and depth in the Sea of Marmara. Samples were obtained by beam trawl monthly between October 2011-July 2014. Total of 229 station were sampled. Totally six fishing area distributed as 1. area: Erdek, 2. area: Tekirdağ, 3. area: Marmara Island, 4. area: Kapıdağ, 5. area: Yalova and 6. area: Silivri. The parameter b for 3 triglidae species ranged from 2.66 to 2.85. The exponent b typically indicated C. lucerna and L. cavillone negative allometric growth, E.gurnardus isometric growth. The relative abundance of all species caught by beam trawl, bony fishes and triglidae species were determined as 63.6 kg/h, 4.7 kg/h and 0.422 kg/h (9%), respectively. The highest abundance (CPUE) in triglidae family was determined as 0.305 kg/h (2.5 N/h) in C. lucerna species and followed by L. cavillone 0.066 kg/h (1.9 N/h and E. gurnardus 0.051 kg/h (0.96 N/h) species. According to the seasons, the highest abundance of C. lucerna and L. cavillone species was found in the summer, spring for E. gurnardus species. According to the region, the highest abundance was found in Tekirdağ for C. lucerna species, Kapıdağ Peninsula for L. cavillone species and Marmara Island for E. gurnardus species. According to the depth, the abundance (CPUE) of the gurnard species has changed. It was found that C. lucerna and L. cavillone were more abundant at depths of 50-100 m, deeper than 100 m for E. gurnardus.

The Turkish Strait System, which is the only connection between the Black Sea and the Mediterranean Sea, is a challenging region for ocean circulation models due to topographic constraints and water mass structure. We present a newly developed high resolution unstructured finite element grid model to simulate the Turkish Strait System using realistic atmospheric forcing and lateral open boundary conditions. We find that the jet flowing from the Bosphorus Strait into the Marmara creates an anticyclonic circulation. The eddy kinetic energy field is high around the jets exiting from the Bosphorus Strait, Dardanelles Strait, and also the leeward side of the islands in the Marmara Sea. The model successfully captures the two-layer structure of the Sea of Marmara. The volume transport at the Bosphorus is around 120 km3/year which is consistent with the recent observations. The largest bias in the model is at the interface depth due to the shallower mixed layer.

This investigation focused on weekly variations in cell density and volume of the dinoflagellateNoctiluca scintillans between March 2001 and January 2004 in the Dardanelles. March-June andOctober-December periods were excessive bloom periods. During the bloomperiods the density of N. scintillans reached 2.20 × 105 cells L-1 witha volume of 1.32 × 1012 µm3 L-1. In addition tothe high surface density, there was an increase in subsurface waters duringthe blooms. The bloom of N. scintillans, like that of diatom and otherdinoflagellate blooms, was associated not only with eutrophication, but alsowith stable temperatures and salinities.

The destructive earthquake that struck near the Gulf of Izmit along the North Anatolian fault in Northwest Turkey on August 17, 1999, not only generated a local tsunami that was destructive at Golcuk and other coastal cities in the eastern portion of the enclosed Sea of Marmara, but was also responsible for extensive damage from collateral hazards such as subsidence, landslides, ground liquefaction, soil amplifications, compaction and underwater slumping of unconsolidated sediments. This disaster brought attention in the need to identify in this highly populated region, local conditions that enhance earthquake intensities, tsunami run-up and other collateral disaster impacts. The focus of the present study is to illustrate briefly how standardized remote sensing techniques and GIS-methods can help detect areas that are potentially vulnerable, so that disaster mitigation strategies can be implemented more effectively. Apparently, local site conditions exacerbate earthquake intensities and collateral disaster destruction in the Marmara Sea region. However, using remote sensing data, the causal factors can be determined systematically. With proper evaluation of satellite imageries and digital topographic data, specific geomorphologic/topographic settings that enhance disaster impacts can be identified. With a systematic GIS approach - based on Digital Elevation Model (DEM) data - geomorphometric parameters that influence the local site conditions can be determined. Digital elevation data, such as SRTM (Shuttle Radar Topography Mission, with 90m spatial resolution) and ASTER-data with 30m resolution, interpolated up to 15 m) is readily available. Areas with the steepest slopes can be identified from slope gradient maps. Areas with highest curvatures susceptible to landslides can be identified from curvature maps. Coastal areas below the 10 m elevation susceptible to tsunami inundation can be clearly delineated. Height level maps can also help locate topographic depressions, filled with recently formed sediments, which are often linked with higher groundwater tables. Such areas are particularly susceptible to higher earthquake intensities and damage. The sum of risk GIS factors increases the susceptibility of local soils in amplifying seismic ground motions. Areas most susceptible to higher earthquake impacts can be identified using a systematic GIS approach, the weighted–overlay-method implemented in ArcGIS. Finally, the data obtained by remote sensing can be converted into Google Earth-kml-format and become available at no cost, to raise public disaster awareness and preparedness in the Sea of Marmara region.

Marmara Denizi doğusunda Kuzey Anadolu Fay zonu (KAFZ) üzerinde bulunan BUC-10A ve İZ-30 sediment karotları, sırasıyla Büyükçekmece'nin 12 km açığından ve Izmit Körfezi'nden alınmıştır. Bu karotların çökel istifi tektonik ve paleo-oşinografik süreçleri araştırmak amacıyla sedimentolojik ve jeokimyasal yöntemlerle incelenmiştir. BUC-10A sediment karotunda toplam inorganik karbonat (TIK, toplam kalsiyum karbonat olarak) miktarı ve toplam organik karbon (TOK) içeriği sırasıyla %12.1-34.3 ve %0.5-4.1 aralığında değişir. Söz konusu sediment karotun da 1.60-2.43 m arasında organik maddece zengin sapropel tabakası ayırt edilmiştir. Aynı karotun metal konsantrasyonlarının değişim aralıkları Cr: 55-96, Cu: 21-37, Ni: 63 39-74, Mn: 345-693, Pb: 19-34, Zn: 79-143 ppm, Fe: % 2.30-3.15'dir. IZ-30 karotunda TOK , TIK, Cr, Cu, Fe, Ni, Mn, Pb ve Zn değerlerinin değişim aralıkları sırasıyla % 0.40-1.70, %0.25-31.1, 39-87 ppm, 13-32 ppm, % 2.10-4.80, 18-41 ppm, 315-528 ppm, 7-21 ppm ve 78-185 ppm'dir. Alınan karotlarda yapılan kalkofil metal (Fe, Mn, Cu, Pb, ve Zn) analizleri hidrotermal etkinliğe bağlı herhangi bir zenginleşmeyi göstermemektedir. Sedimentolojik çalışmalarla IZ 30 karotunda günümüzden önce (GÖ) 3276±48 takvim yılı yaşında, muhtemelen tektonik aktivite ile tetiklenmiş bir kütle akması saptanmıştır. Bu karotun tabanına yakın bir bölümünde günümüz su seviyesine göre -49,5 m derinlikte GÖ 9364±64 yıl olarak yaşlandırılan eski bir kıyı çizgisi bulunmuştur

Paracanthocephaloides kostylewi (Meyer, 1932), a rare parasite of the common sole Solea solea, previously placed in the Arhythmacanthidae, is transfered to the genus Solearhynchus de Buron & Maillard, 1985 of the family Echinorhynchidae as Solearhynchus kostylewi (Meyer, 1932) new comb., because its proboscis is armed by a single type of hooks, the posterior hook in each row is pinlike and with feebly developed root. The species is redescribed on the basis of newly collected material from the Gemlik Bay, Sea of Marmara. A key to the species of Solearhynchus is provided.

This study on the species composition and distribution of tintinnids, which form one of the most abundant ciliate groups in the seas, was carried out in Büyükçekmece Bay in 1998-1999. Plankton samples were collected horizontally from the subsurface (0.5 m) with a 55 µm plankton net at five stations and a 3 l water sampler was used for their quantitative analysis. All tintinnid species were identified according to their lorica shape as the usual important criterion. A total of 14 species were identified. Primary hydrographic conditions such as salinity, temperature and dissolved oxygen were recorded on each sampling occasion. The genera Favella and Eutintinnus were dominant in terms of species and individual numbers. Eutintinnus fraknoi was the most abundant species, with a mean abundance of 0.4x103 ind. l-1. The study shows that the species and individual numbers of tintinnids decreased in winter and early spring when phytoplankton increases. The abundance of tintinnids in Büyükçekmece Bay appears to be correlated with the decrease in abundance of total phytoplankton (rs= -0.57, p= 0.05) and diatoms (rs= -0.65, p< 0.05) and the increase in temperature (rs= 0.61, p< 0.05). Furthermore, phytoplankton abundance was positively correlated to dissolved oxygen (rs= 0.64, p< 0.05). In particular, Favella serrata was more affected by temperature and Eutintinnus lusus-undae by salinity compared to other species.