Marmara Sea Research Articles

Coda-derived source properties estimated using local earthquakes in the Sea of Marmara, Türkiye

Abstract. Accurate estimates of the moment magnitude of earthquakes that physically measure the earthquake source energy are crucial for improving our understanding of seismic hazard in regions prone to tectonic activity. To address this demand, a method involving coda wave modelling was employed to estimate the moment magnitudes of earthquakes in the Sea of Marmara, northwestern Türkiye. This approach enabled us to model the source displacement spectrum of 303 local earthquakes efficiently recorded at 49 regional seismic stations between 2018 and 2020 in the region. The coda wave traces of individual events were inverted across 12 frequency ranges between 0.3 and 16 Hz. The resultant coda-derived moment magnitudes were found to be in good accordance with the conventional local magnitude estimates. However, the notable move-out between local magnitude and coda-derived moment magnitude estimates for smaller earthquakes less than a magnitude of 3.5 likely occurs due to potential biases arising from incorrect assumptions for anelastic attenuation and/or the finite sampling intervals of seismic recordings. Scaling relations between the total radiated energy and seismic moment imply a non-self-similar behaviour for the earthquakes in the Sea of Marmara. Our findings suggest that larger earthquakes in the study area exhibit distinct rupture dynamics compared to smaller ones, resulting in a more efficient release of seismic energy. Hence, we introduce an empirical relationship obtained from the scatter between local magnitude and coda-derived moment magnitude estimates.

A new technique mapping submerged beachrocks using low-altitude UAV photogrammetry, the Altınova region, northern coast of the Sea of Marmara (NW Türkiye)

High-resolution aerial imagery captured from low altitudes enables the detailed reconstruction of the geomorphological features of submerged beachrocks and the quantification of their topographic complexity. These coastal deposits serve as vital indicators for estimating past sea-level positions and deformation, contributing to our understanding of climate and tectonic processes across various temporal and spatial scales. This study focuses on submerged beachrocks identified in the nearshore coastal area of Tekirdağ city (Altınova), and the existing knowledge regarding such geological formations is limited.Situated in the tectonically active western Marmara region, the coastal zone of The Tekirdağ-Altınova is influenced by the North Anatolian Fault Zone (NAFZ), which has significantly shaped the coastline over time. Utilizing unmanned aerial vehicle (UAV) data, we successfully isolated submerged beachrocks from other coastal deposits, identifying them at depths of 2 m below current sea level and extending approximately 5 km along the coast. This identification was facilitated by integrating high-resolution aerial imagery with morphological analysis techniques, specifically employing structure-from-motion photogrammetry to generate a dense point cloud for bathymetric mapping.The utilization of cost-effective UAV imagery facilitated the efficient monitoring of beachrocks. Geographic information systems (GIS) and the TerraceM application were employed to analyze the high-resolution bathymetry data (with a 5 cm resolution), enabling the precise estimation of shoreline angles and associated errors. These shoreline angles, which correspond to the past sea levels high stand, were mapped using swath profiles oriented perpendicular to the isobaths. Our findings reveal that the majority of submerged beachrocks exhibit shoreline angles between ∼ −0.7 m and −1.1 m. This study presents innovative methodologies for mapping the height and spatial distribution of beachrocks, as well as for reliably estimating reliable uplift rates in the nearshore area of Tekirdağ-Altınova.

A Graphic Review of Studies on Ocean and Mediterranean Sea Environment Quality

With so many studies today on the water quality of the sea, one can hardly comprehend the multitude of topics that arise all over the world. This study provides a few graphic syntheses related to the most frequent words (including their clustering and links), trend topics, the spatial distribution of the researched areas, and the thematic evolution of the research directions over the decades. The most frequent authors’ keywords have a 50% similitude between the ocean studies and the studies related to the Mediterranean Sea; these keywords are part of a causal chain that dominates the marine studies on water quality: nutrients → eutrophication → phytoplankton → chlorophyll → seagrass. The most frequent words in the titles and abstracts of the selected papers from the Web of Science are “concentration” and “species”; in the Mediterranean studies, “chlorophyll” and “temperature” are the most frequent. In close connection with water quality, Zostera marina (eelgrass) and Crassotrea virginica (eastern oyster) prevail at the global scale, while Posidonia oceanica (Neptune grass) is relevant in the Mediterranean space. Some of the most studied water bodies are the South China Sea, San Francisco Bay, Chesapeake Bay, and, in the Mediterranean Sea, the Adriatic, Ionian, Aegean, and Marmara seas. “Climate change” and “remote sensing” are trend topics that shape the current studies on water quality; the increasing sea surface temperature enhances algal blooms—these need to be monitored using satellite imagery for the sustainable evolution of human activities, including aquaculture.

Evaluation of Some Aspects of the Growth Parameters and Exploitation Rates of Deep-Water Rose Shrimp (Parapenaeus longirostris) from the Sea of Marmara

Evaluation of Some Aspects of the Growth Parameters and Exploitation Rates of Deep-Water Rose Shrimp (Parapenaeus longirostris) from the Sea of Marmara

An Overview of Traditional and Next-Generation Earthquake Early Warning Systems

The Earthquake Early Warning System generates rapid and effective warnings after detecting an earthquake, before the arrival of destructive waves to the areas that may be affected. In this way, it is aimed to minimize the loss of life and property. In this study, traditional early warning systems that are frequently used in the world are discussed. The details of the next-generation early warning system, which has recently produced successful outputs, are discussed, and its advantages over traditional early warning systems are mentioned. The recent developments of this system are also analyzed. Next-generation early warning systems consist of a new array-based algorithm composed of two modules for real-time epicenter detection. The detection of an earthquake occurring in the Marmara Sea (Türkiye) with a next-generation early warning system using array-based location methodology is given as an example. Next-generation early warning systems have advantages over traditional ones, such as lower cost and time gains of up to minutes.

Evaluation of carbon dioxide partial pressure and air-sea fluxes in the Sea of Marmara

The increasing impact of global warming has made it crucial to monitor greenhouse gases (GHG). Carbon dioxide (CO2) is especially important due to its significant increase. Oceans and seas play a vital role in absorbing excess CO2 from the atmosphere, but they are facing challenges such as ocean acidification and damage to coral reefs. Therefore, it's essential to thoroughly understand climate change and its human-caused effects and to take necessary precautions or improve existing measures. In this direction, in seawater, determining alkalinity is crucial for monitoring CO2, along with other physical and chemical parameters, in order to help set carbon budgets and reduce environmental pressures. For this purpose, in this study in the Sea of Marmara, alkalinity and CO2 measurements were conducted for the first time at stations CG2, CG3, MD26, and MD24. The CO2 partial pressure (pCO2) values ranged from 95 to 165 µatm at the surface of all stations, and total alkalinity values ranged from 1.075 to 1.46 mmol kg-1 at specified depths. Based on these measurements, flux values were calculated between −1.10 and −5.39 mmol m2 day-1, indicating that the Sea of Marmara acted as a net CO2 sink.

Comparing microbial communities in mucilage and seawater samples: Metagenomic insights into mucilage formation in the Marmara Sea.

Marine environments are subject to various naturally occurring phenomena, including marine snow and mucilage. In 2021, the rapid emergence of mucilage in the Marmara Sea raised concerns about its environmental impact. This study investigates the microbial communities in mucilage and seawater samples from the Marmara Sea using metagenomic-scale comparative analyses. The results indicate significant differences in microbial composition and diversity, with mucilage samples showing higher levels of polysaccharide biosynthesis-related enzymes. Over 50% of reads in mucilage samples remained unclassified (dark matter), highlighting unknown microbial taxa. Clean seawater was characterized by a higher presence of Euryarchaeota, Proteobacteria, and Rhodothermaeota, while Chlamydiae and Fusobacteria were dominant in mucilage. The study underscores the necessity for comprehensive metagenomic analyses to understand microbial roles in mucilage formation and persistence. Early detection of microbial shifts could serve as a warning system for mucilage outbreaks, aiding in the development of management strategies.

Türkiye kıyılarındaki denizel dinoflagellatların kontrol listesi

Using the evaluations of 77 literature studies conducted along the Turkish coasts of the Black Sea, Marmara Sea, Aegean Sea, and the Mediterranean Sea, a checklist has been compiled. It has been observed that the dinoflagellate flora is represented by a total of 330 species belonging to 75 different genera. This literature study has determined that the number of dinoflagellate species reaches up to 181 in the Black Sea, 158 in the Marmara Sea, 206 in the Aegean Sea, and 192 in the Mediterranean Sea. This study has revealed that particularly in the case of new species records, the characteristic structural features, distributions, and photographs of the species are not provided. It has also been observed that many geographical points have not been investigated yet, and some species reported as new records have previously been reported in earlier studies. In future studies, updating the checklist becomes crucial in terms of forming a dataset.

What does external morphometry tell us about stock discrimination of Sardina pilchardus stocks from Türkiye?

The analysis of shape is a fundamental part of much biological research. Morphometrics, which incorporates concepts from biology, geometry, and statistics, is the study of the geometrical form of organisms. In addition, morphometric characteristics can be used to differentiate ‘phenotypic stocks’ as groups with similar growth, mortality, and reproductive rates. In this study, 25 morphometric characters were used to discriminate European pilchard (Sardina pilchardus) stocks from Türkiye. Intraspecific variation of the European pilchard was investigated based on morphometric characters. Samples were collected from the Aegean Sea (AS; N = 54), the Sea of Marmara (MS; N = 50) and the Mediterranean Sea (MEDS; N = 50) during the 2019 fishing season. Principal Component Analysis (PCA) and Canonical Discriminant Analysis (CDA) were used for stock discrimination of the European pilchard. Univariate statistics (ANOVA) showed that 24 of the 25 measurements differed significantly between samples to a varying degree (p < 0.001). According to CDA, an overall classification success rate of 87.7% was achieved using 12 morphometric parameters. All samples were clearly separated from each other in the discriminant space, suggesting that there was no strong intermingling between populations. In addition, we would like to conclude that the morphological difference is not at the genetic level, and would like to emphasize the need for additional stock discrimination methods.

Late Pleistocene–Holocene palynology and paleoceanography of İmralı Basin, Marmara Sea: Pollen-spore, dinoflagellate cyst and other NPP zonations

The Marmara Sea is the oceanographic gateway that links the hypersaline Eastern Mediterranean Sea with the hyposaline Black Sea via Straits of Dardanelles and Bosphorus, respectively, and also occupies a transitional vegetation and climatic regime between the Mediterranean and Euxinic phytogeographic ecosystems. Recent palynological studies of long cores from the shallow İmralı Basin perched on the southeastern slope of the Marmara Sea reveal that major paleoecological changes accompanied the isolation and reconnection of the Marmara Sea during the last two Pleistocene glacial–interglacial cycles. Here, we use data primarily from two İmralı Basin cores to determine new quantitative zonations for the pollen-spore, dinoflagellate cyst (dinocyst) and other non-pollen palynomorph (NPP) assemblages in sediments representing the last ∼30 cal ka. A gap in one core is closed using data from three short gravity cores. Twenty-four radiocarbon ages and 20 correlation-ties for sapropel and ash layers from these five cores provide an essentially complete record for the past 30 cal ka. Use of a full suite of palynomorph data (pollen and spores, fungal spores, dinocysts and other phytoplankton, aquatic parasites/saprophytes, zoo-planktonic and zoo-benthic NPPs) shows for the first time that fluctuations in aquatic palynoassemblages during the glacial periods are more complex than simple salinity or temperature responses. The changes involve food web-level turnovers in trait- and size-based food web components in which potential parasites/saprophytes appear critically important.Pollen stratigraphies reveal a significant loss of Euxinic tree taxa by MIS 3c, with only partial recovery in MIS 1. The Euxinic forest elements are replaced by cultivars and other indicators of anthropogenic influences during the MIS 1 that is also marked by a dry interval and corresponding in part with the 4.2 cal ka Eastern Mediterranean Drought Event. The dinocyst zones for the last ∼30 cal ka show a clear turnover from assemblages dominated by brackish Ponto–Caspian taxa to marine assemblages at ∼11.7 cal ka. This phytoplanktonic signal lags slightly behind (a) the vegetation and shift in the other NPP commencing ∼13.2 cal ka, the initial marine incursion at 13.8 cal ka, and the arrival of coccolithophores at ∼13 cal ka. Comparison to published MIS 6 and 5 data reveals higher MIS 2–1 species diversity, reappearance of the MIS 6 marker Impagidinium inaequalis, and the emergences of Pyxidinopsis psilata f. quadrata, cf. Boreadinium breve, and Peridinium spp. of Brenner 2005. The pre-reconnection microbiota is dominated by the unicellular alga Sigmopollis, spikes of colonial Pediastrum algae, the saprophytes/parasites cf. Multiplicisphaeridium and Chytridiomycota. This microbiota is displaced by the post-reconnection assemblage dominated by Botryococcus coenobia, various Platyhelminth egg capsules and ostracod lining-types that persist through the Holocene. A distinctive transitional microbiota with Discocotyle-type turbellarian egg capsules marks the Bølling–Allerød warming, followed at ∼13.3 ka by a marine assemblage with micro-foraminiferal linings and crustacean eggs. The interglacial marine phase of MIS 1 in İmralı Basin has much higher dinocyst species diversity than MIS 5e, reflecting Neolithic impacts (agriculture, land clearance) and expanded shipping trade. Initial marine flooding in the Marmara Sea during both interglacials are marked by sapropel deposition but variations of ravinement surface erosion, and marine deep water residence time in a stratified Marmara Sea are potentially important factors underlying hypoxia/anoxia and sapropel deposition.

Datum Alignment Between GNSS-IR Sea Level Estimations and Tide Gauges in Türkiye: A Vertical Local Tie Approach

Connecting Asia and Europe, Türkiye is vital for maritime transit, which requires continuous and precise sea level monitoring. Traditional tide gauges (TGs), while valuable, often have data gaps. GNSS-IR provides an alternative, though aligning it with TG measurements is challenging. This study introduces a method to estimate Vertical Local Tie (VLT) between the TG zero and the GNSS antenna phase centre, allowing GNSS-IR sea level estimates to be aligned with TG measurements. In disruptions, GNSS-IR can consistently supplement TG data. We validated this approach by evaluating a 1-year data from four GNSS stations namely, ARSZ, GADA, TRBZ, and YLVA involving in the Türkiye National Sea Level Monitoring System (TUDES) network. These stations are located on the coasts of the Mediterranean, Aegean, Black, and Marmara Seas, respectively. Compared with the TG measurements, ARSZ achieved the highest epoch-based correlation as 87.00%. For daily averages, the GADA and TRBZ showed a correlation of over 96% with TG data. Notably, TRBZ recorded the lowest daily average RMSE at 2.2 cm using the VLT-median approach. The results demonstrate that when VLT is utilized, well-configured GNSS stations, ensuring uninterrupted transmissions and appropriate data intervals, provide a reliable alternative or complement to TGs for sea level monitoring.

The marine cartilaginous fishes and sturgeons of the Sea of Marmara: an updated and annotated checklist

A revised checklist of sharks, batoids, and sturgeons in the Sea of Marmara, Turkey encompasses 41 species across 18 families. It provides a concise historical context and addresses issues related to problematic reports. Furthermore, the paper delves into the analysis of taxonomic changes in other literature reports, aiming to provide a framework for upcoming ichthyological surveys and ecological studies, while also presenting relevant data on the economic significance of select species.

A newly formed lagoon under eutrophication on the coast of Kumlubent-Gelibolu, Çanakkale Strait (Dardanelles), Sea of Marmara

Lagoons are semi-enclosed and dynamic water bodies that are highly vulnerable to coastal dynamics and environmental stressors associated with anthropogenic activities and climate change. We investigated a pristine lagoon, hereafter referred to as Kumlubent Lagoon, located on the coast of Gelibolu in the Çanakkale Strait in the Sea of Marmara. The evolution of coastal morphology and Kumlubent Lagoon’s formation was investigated by using satellite images collected between 2006 and 2020. In addition, water samples were collected from the lagoon and the shore on April 15 and 16, 2022 for nutrient (NO3, NO2, NH4, PO4, and Si), chlorophyll-a (chl-a) and total organic carbon (TOC) analyses in order to determine the trophic status of the lagoon. Our results showed that the nearshore deposition of coastal sediments gradually formed a sand barrier that isolated the lagoon from the sea in the year 2013. The nutrient analyses showed a clear indication of eutrophication of the lagoon. Accordingly, 29.784 µm/L of NH4, 1.168 µm/L of PO4, 34.15 (±1.54) µg/L of chl-a and 40.50 mg/L of TOC were measured in the water samples from the Kumlubent Lagoon. Our study suggests that the deposition of longshore drifted sediments in a southwesterly direction along the Çanakkale Strait plays a dramatic role in the development of coastal morphology in the Gelibolu-Kumlubent region. The rapid eutrophication of the Kumlubent Lagoon may be related to the high nutrient input from agricultural activities in the region.

Decadal changes in the Sea of Marmara indicate degraded ecosystem conditions and unsustainable fisheries

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.

Comparative analyses for determining shallow water bathymetry potential of multispectral UAVs: case study in Tavşan Island, Sea of Marmara

Comparative analyses for determining shallow water bathymetry potential of multispectral UAVs: case study in Tavşan Island, Sea of Marmara

Efficiency of different collectors for spat settlement of Mediterranean mussel (Mytilus galloprovincialis) in the southeastern Marmara Sea, Türkiye

ABSTRACT Mediterranean mussel have spread almost throughout Turkish seas. The objective of this study was to set up longline systems to determine spat efficiency by two different systems (buoy and pipe) consisting of three different materials, new rope, used rope and used net, in Erdek Bay. The second objective was to identify whether waste materials could be used in mussel culture. Sea water temperature, salinity, dissolved oxygen, chlorophyll-a, total suspended, inorganic and organic matter were measured at monthly intervals. Results revealed that the highest settlement (4196 spat) was observed in the collectors made of used nets in the pipe system (October 2016). In contrast, the lowest value (2 spat) was recorded from the collectors made of new ropes in the buoy system (August 2016). Waste materials presented relatively better results on settlement than the new ropes. The optimum production was observed in the mussel farm with 1239 spat in the buoy and 1607 spat in the pipe systems, which were commissioned in April 2016. It is concluded that the spat performance was affected by collectors and materials. Therefore, we propose the use of used ropes and used nets, which will allow more effective attachment surfaces to achieve higher spacing settlement.

Variations Observed in the Muscle Scars of Left Valve of Pododesmus patelliformis (Linnaeus, 1761) [Bivalvia: Anomiidae

This study investigates the unusual muscle scars observed in some specimens of Pododesmus patelliformis (Linnaeus, 1761). Materials were collected between 1964 and 1977 from 18 stations across the Sea of Marmara and the Aegean Sea. In only 49 out of the 85 specimens examined (57,7%), the muscle scars were distinctly separated from each other as described in the general literature. Thirty-six specimens (42,3%) exhibited muscle scars that differed from the known pattern. These atypical muscle scar types were categorized into five types, explained, photographed, and illustrated in this study.

No escape from the mucilage impact: Even opportunistic hydroids were affected in the catastrophic mucilage of 2021 in the Sea of Marmara

This study examines the effects of sedimentation and mucilage events on the hydroid communities of the Prince Islands, Sea of Marmara. Sampling in October 2021 and April 2022 revealed significant declines in hydroid abundance post the 2021 mucilage event, contrasting with increases observed in 2015 after excessive sedimentation in the area. Statistical analyses demonstrate temporal variations in hydroid assemblages, underscoring the ecological consequences of mucilage events on benthic communities. The unprecedented scale and prolonged duration of the 2021 mucilage event accentuate the magnitude of its impact on marine ecosystems. The decline in hydroid abundance following the mucilage event suggests a significant ecological impact, with implications for the recovery and resilience of benthic ecosystems. These findings contribute to our understanding of the complex interactions between environmental stressors and benthic communities, emphasizing the importance of proactive management strategies that preserve marine biodiversity in the face of anthropogenic pressures and climate change.

Effects of different culture methods on growth, meat yield, and nutritional composition of Mediterranean mussels (Mytilus galloprovincialis), south side of Marmara Sea, Türkiye

This study, conducted between February 2016 and October 2017 on the coast of Erdek in the Marmara Sea, established two longline systems (buoy and pipe). Monthly growth rates of juvenile mussels placed in polyethylene and polyamide nets within these systems were monitored. The monthly chemical composition and meat yield of mussels that reached harvest size were analyzed in both systems. Environmental parameters were measured monthly to assess environmental conditions. The highest meat yield of harvested mussels was recorded in January, with values of 36.99 ± 0.72% for mussels cultured in the pipe system and 31.43 ± 1.82% for those cultured in the buoy system. The highest growth in mussels was achieved in the group cultured in the pipe system within polyamide nets. The December sample showed the highest moisture content of 83.98% and the highest ash content of 2.34%. The highest crude fat content was found in the September sample. The June sample had the highest protein content. The Black Sea, Sea of Marmara, and Aegean Sea offer suitable areas for mussel cultivation. Currently, mussel farming is conducted in these areas, producing tens of thousands of tons annually. This publication contributes to the expansion of the production process.

Multi-scale superpixel-based nearest subspace classifier for mucilage detection from hyperspectral PRISMA data

Hyperspectral imaging has a critical role in observing the Earth's surface, providing images with rich spectral information. As a result, it has become an essential tool for monitoring and addressing environmental issues such as pollution, water balance, and climate change. Among these challenges, marine pollution poses a significant ecological threat, as evidenced by the recent mucilage incident in Turkey in April 2021. Mucilage, a dense mucus-like substance resulting from the overgrowth of marine plankton and microorganisms, detrimentally affects marine ecosystems when its levels surge. Traditional mucilage detection involves labour-intensive sampling and laboratory analysis, rendering it impractical for vast marine environments. Remote sensing techniques offer a promising alternative for automated mucilage detection from satellite imagery. In this study, we propose a multi-scale superpixel-based classification approach for mucilage detection, using the PRISMA satellite's hyperspectral mucilage datasets captured over the Sea of Marmara. Our method performs classification by analyzing the closeness between the subspace spanned by the samples in the superpixel and the subspace spanned by the within-class training samples. We formulate the solution to this approach via a Canonical Correlation Analysis framework and show that our proposed method outperforms its competitors, especially when the training data is limited. Our comprehensive experiments include assessing the transferability of classification methods on datasets collected from different locations and at different times. We compared the performance of our proposed method with state-of-the-art spectral-spatial classification methods, including deep learning-based random patches network (RPNet), structural-kernel collaborative representation (SKCR), and window based nearest subspace classifier (WBNSC). The results show that the proposed method outperforms existing techniques in most cases. The datasets and source code are publicly available on GitHub at https://github.com/kgtoker/MSBNSC, enabling more comprehensive access and collaboration in environmental monitoring efforts.