Lake Iznik Research Articles

Invasive-Weed-Optimization-Based Extreme Learning Machine for Prediction of Lake Water Level Using Major Atmospheric–Oceanic Climate Scenarios

Fresh water lakes are vulnerable assets that need to be protected against manmade/natural challenges like climate change and anthropogenesis activities. This study addresses the predictability of the lake water level changes based on the knowledge acquired directly from the climate data. Two fresh water lakes named Lake Iznik and Uluabat, located in Turkey, are addressed. Time series of the lake water levels during October 1990–September 2019 at a monthly scale, along with the corresponding anomalies of 24 Large-Scale Atmospheric–Oceanic Oscillations (LSAOOs) from around the globe, are used in the analysis. The relationship between variables and the structure of the models are initially acquired based on the significance of the dependence between climate indices and lake water levels with consideration of the significance of the Spearman rank-order coefficient. Then, the time series are divided into training (80%) and testing (20%) sets. The Extreme Learning Method (ELM), enhanced with the genetic algorithm (ELM-GA) and Invasive Weed Optimization (ELM-IWO), is then used in the predictive models. Based on the results, Lake Uluabat showed a stronger teleconnection with LSAOOs, while the ELM-GA for Lake Iznik and ELM-IWA for Lake Uluabat depicted the best performance in the prediction of lake water levels. Comparison of the enhanced ELM-IWO to the corresponding ELM-GA illustrates that the ELM-IWO reveals more acceptable results owing to its flexible nature.

A case study of using artificial neural networks to predict heavy metal pollution in Lake Iznik.

Artificial neural networks offer a viable route in assessing and understanding the presence and concentration of heavy metals that can cause dangerous complications in the wider context of water quality prediction for the sustainability of the ecosystem. In order to estimate the heavy metal concentrations in Iznik Lake, which is an important water source for the surrounding communities, characterization data were taken from five different water sources flowing into the lake between 2015 and 2021. These characterization results were evaluated with IBM SPSS Statistics 23 software, with the addition of the lake water quality system. For this purpose, seven distinct physicochemical parameters were measured and monitored in Karasu, Kırandere, Olukdere and Sölöz water sources flowing into the lake, to serve as input data. Concentration levels of 15 distinct heavy metals in Karsak Stream originating from the lake were as the output. Specifically, Sn for Karasu (0.999), Sb for Kırandere (1.000), Cr for Olukdere (1.000) and Pb and Se for Sölöz (0.995) indicate parameter estimation R2 coefficients close to 1.000. Sn stands out as the common heavy metal parameter with best estimation prospects. Given the importance of the independent variable in estimating heavy metal pollution, conductivity, COD, COD and temperature stood out as the most effective parameters for Karasu, Olukdere, Kırandere and Sölöz, respectively. The ANN model emerges as a good prediction tool that can be used effectively in determining the heavy metal pollution in the lake as part of the efforts to protect the water budget of Lake Iznik and to eliminate the existing pollution.

Remote sensing and monitoring of water resources: A comparative study of different indices and thresholding methods

Water resources are essential for the ecological system and the development of civilization. Water is imperative factor for health preservation and sustaining various human activities, including industrial production, agriculture, and daily life. Remote sensing provides a cost-effective and practical means to detect and monitor water bodies, offers valuable insights into the impact of climatic events on water structures, especially in coastal lake regions. The research primarily utilizes Landsat-9 OLI-2 satellite images to evaluate the effectiveness of various water indices (WRI, NWI, MNDWI, NDWI) in combination with global automatic thresholding methods (K-Means, Zhenzhou's, Adaptive, Intermodes, Prewitt and Mendelsohn's Minimum, Maximum Entropy, Median, Concavity, Percentile, Intermeans, Kittler and Illingworth's Minimum Error, Tsai's Moments, Otsu's, Huang's fuzzy, Triangle, Mean, IsoData, Li’s). The study was carried out on Lake Nazik, Lake Iznik, and Lake Beyşehir, which have unique geographical characteristics, and examined the adaptability and robustness of the selected indices and thresholding methods. MNDWI consistently stands out as a robust index for water extraction, delivering accurate results across different thresholding methods in regions all three lakes. As a result of quite extensive analysis, it is obtained that MNDWI and NDWI are reliable choices for water feature extraction in various lake environments, but the specific index should consider the thresholding method and unique lake characteristics. The Minimum thresholding method stands out as the most effective thresholding technique, demonstrating impressive results across different lakes. Specifically, it achieved an average Peak Signal-to-Noise Ratio (PSNR) of 78.97 and Structural Similarity Index (SSIM) of 99.37 for Lake Nazik, 74.08 PSNR and 98.34 SSIM for Lake Iznik, and 63.96 PSNR and 93.61 SSIM for Lake Beyşehir.

Seismic stratigraphy and sediment cores reveal lake-level fluctuations in Lake Iznik (NW Turkey) over the past ∼70 ka

Our study aims to understand the palaeohydrological history of Lake Iznik and unravel the complex interplay between climatic, tectonic, and environmental factors that have shaped this Turkish basin. Through the analysis of seismic stratigraphy and sediment cores, we reveal a significant lowstand, indicating a lake level 60 m lower than today at ∼70 ka BP. Subsequently, a major phase of stepwise transgression is evidenced by 13 buried palaeoshorelines between ∼70 and 45 ka BP. From 45 to ∼10 ka cal BP, strong currents controlled the sedimentation in the lake, as evidenced by the occurrence of contourite drifts. Between ∼14 and 10 ka cal. BP, a major lowstand indicating a drier climate interrupted the current-controlled sedimentation regime. From ∼10 ka cal. BP, the subsequent increase in lake level occurred at the same time as the reconnection between the Mediterranean and Black seas. Archaeological evidence, including submerged structures of a basilica, establishes a link between lake-level changes and human settlement during the last millennium. The level of Lake Iznik has since continued to fluctuate due to climate change, tectonic events, and human activity.

Heavy Metal Accumulation in Aquatic Macrophytes and Plankton, Water-Sediment in Lake Iznik

This study aims to investigate heavy metal accumulation in water-sediment, plankton, and macrophyte samples of Lake Iznik, one of the important lakes of Turkey. In 2016, water-sediment and plankton samples were taken from 19 and 10 stations respectively. In addition, heavy metal analyzes were performed on samples taken from Potamogeton pectinatus, Najas marina, Myriophyllum spicatum, Typha latifolia, Schoenoplectus litoralis, Phragmites australis, which are the most abundant macrophytes in the lake. The data of water and sediment samples were spatially analyzed in GIS and mapped with ArcGIS. In the water samples of Lake Iznik, arsenic (As), mercury (Hg) and in sediment samples, arsenic (As), chromium (Cr), copper (Cu) and nickel (Ni) were detected at remarkable levels. The results revealed that Iznik Lake was under pressure in terms of heavy metals and their effects should be reduced.

Spatial distribution, source identification, and risk assessment of polychlorinated organic pollutants (PCDD/Fs and DL-PCBs) in the sediments of the largest urban water supply area (Iznik lake) in the Marmara region, Bursa, Türkiye

Iznik lake is the biggest lake in the Marmara region, which is the most industrialized and populated area of Türkiye. The lake is one of Türkiye's most important water supply areas and is located nearby the Iznik district of Bursa, with a population of about 45,000. It is being used for irrigation and fishery production, but not for drinking water. In this paper, the distribution, pollution source, and risk assessment of polychlorinated dibenzodioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in the surface sediments of Iznik lake and streams (both flowing to and flowing from the lake) were investigated. Six surface sediments collected from the lake and four surface sediments collected from the streams were analyzed in high-resolution gas chromatography-mass spectrometry (HR/GC–MS) system in accordance with EPA 1613 and EPA 1668 methods. The concentration ranges of the ∑PCDD/Fs is 21.4 pg/g d.w. (inside the lake (IZ-6)) – 54.5 pg/g d.w. (Gülayağı stream (IZ-8)) and ∑DL-PCBs is 13.5 pg/g d.w. (inside the lake (IZ-3)) – 46.3 pg/g d.w. (Olukdere (IZ-7)) respectively, with 2.68 pg TEQ/g d.w. on average. The results showed that the high chlorinated (Hepta – Octa CDD/Fs) dioxins/furans and pentachlorinated PCBs (PCB 118 and 105) are dominant in the sediments. A detailed assessment of PCDD/F congener profiles observed in the lake sediments speculated that the wastewater discharges to the lake could be the main pollution source, while other sources such as open burning activities, runoff of pesticide residues from agricultural areas and atmospheric deposition may have some contribution also. The health risk assessment performed for polluted sediment demonstrated that, in the worst case, dioxin-like (PCDD/Fs and DL-PCBs) concentration was a total intake of 0.37 pg TEQ/kg body weight/day, no exceeds the tolerable daily intake amount, where fish consumption accounts for nearly all of the total intake.

Lateral variations in the signature of earthquake‐generated deposits in Lake Iznik,NWTurkey

AbstractUsing lake‐sediment cores to document past seismicity requires a comprehensive understanding of possible lateral variations in depositional processes. This study aims to reveal the lateral variations in earthquake‐induced event deposits throughout Lake Iznik, a large lake located on the middle strand of the North Anatolian Fault. Based on stratigraphic, sedimentological and geochemical analyses of 14 sediment cores from two subbasins across the lake, five different types of event deposits (T1–T5) were identified and characterised. One event deposit type (T5) is restricted to a delta mouth, characterised by the occurrence of authigenic Fe‐Mn carbonates and interpreted to result from flood events. The four other types of event deposits are characterised by their synchronicity between cores and their age consistency with historical earthquakes and are interpreted to be likely generated by earthquakes. The locally prominent 1065 CE historical earthquake that ruptured the sub‐lacustrine Iznik Fault produced at least three different types of event deposits. One deposit type (T2) is only observed for this very local earthquake, implying that the type of event deposit might also depend on ground‐motion parameters. At the lake scale, the occurrence of various event deposits depends on the flow distance from the source of sediment destabilisations to the coring site.

Detection of beta-lactam antibiotic resistance in aquatic Enterobacteriaceae isolates

Abstract Production of the beta-lactamase enzymes is the primary resistance mechanism caused by unconcious consumption of the beta-lactam group of antibiotics in Enterobacteriaceae. Combined disc tests were performed for extended-spectrum beta-lactamase (ESBL) confirmation (n = 15) and class C beta-lactamase (AmpC) confirmation (n = 6) after the disc diffusion test was applied in a total of 27 Enterobacteriaceae strains from Western Black Sea, Lake Manyas and Lake Iznik. Plasmid-mediated blaTEM, blaSHV, blaCTX-M , blaIMP genes, CIT, MOX, FOX gene groups and chromosomal blaAmpc gene of E. cloacae were investigated using the polymerase chain reaction (PCR). Three E. coli strains were shown to produce ESBL, while one E.coli and three E. cloacae strains were confirmed for AmpC production by disc tests. blaTEM (n = 2), blaSHV (n = 4), blaCTX-M (n = 2), blaTEM + blaSHV (n = 1), blaCTX-M + CIT (n = 1), blaSHV + CIT (n = 1) genes and/or gene groups were detected in 11 E. coli isolates; while blaSHV (n = 3) was observed in three Klebsiella strains (two K. oxytoca and one K. pneumoniae). With this study, the aquatic environments of Turkey were proved to be the reservoirs of antibiotic-resistance determinants of plasmid-mediated beta-lactamases in environmental wild-type bacteria transmitted by horizontal gene transfer.

Spatial Variations of the Bacterial Diversity in an Alkaline Lake

Lake Iznik is one of the largest lake of Turkey covering 308 km2 surface area with 65 m max. depth. The lake has alkaline characteristics (Akcaalan et al. 2014). It is a mesotrophic lake that becomes stratified between June-September and well mixed between October-April. Although there are almost 200 lakes in Turkey, there is very little published research focused on the bacterial diversity structures (Ozbayram et al. 2020.) The specific objective of this study was to evaluate the bacterial community profile in the surface water and sediment of the alkaline lake during the winter turnover. For this purpose, the samples were collected from 6 stations (5 on the shore and 1 in the middle of the lake) in February 2020 when the lake was completely mixed. In addition to the surface water and sediment samples, a sample was also collected from the depth of 40 m from the station located in the mid-lake. The water samples were filtered from a 0.22 µm filter and the sediment samples were taken into sterile plastic containers. The total DNAs were extracted using the NucleoSpin® Soil Kit (Macherey-Nagel, Germany) following the manufacturer’s instructions. Bacterial community profiles of the samples were analyzed by 16S rRNA gene-targeted sequencing using Illumina® MiSeq™. Physicochemical parameters were measured as explained by Ozbayram et al. 2020. The pH was between 8.29-8.67 and the Electrical Conductivity (EC) was in the range of 734-996 µS/cm (Suppl. material 1 -Table S1). Whereas the Dissolved Oxygen (DO) levels were measured as 10.12-11.65 mg/L in the surface waters, it was 9.72 mg/L in the 40 m. Among all samples, the highest value of the Shannon and Pielou's evenness indices were calculated for the surface water sample collected from station 2 indicated a more evenly distributed and diverse bacterial community (Suppl. material 1-Table S2). Bacterial diversity patterns of the samples were presented at the phylum level in Figure 1. In compliance with the literature on freshwaters (Zhang et al. 2014), the community was dominated by Proteobacteria species, and higher abundances were determined in the sediment samples (ranged 40.4-50.0 %). Especially, Gammaproteobacteria, Deltaproteobacteria were the major classes of this phylum in the sediment. On the other hand, the composition of bacterial communities in water samples showed a difference in which Actinobacteria and Bacteroidetes (in particular, the order: Flavobacteriales) were also predominated the communities. However, the community profile slightly differed with depth (station 6). At the genus level, most of the reads were not assigned any genera. Ilumatobacter, Fluviicola, and Flavobacterium were represented 3.4-7.1% of the bacterial community of water samples. Fig. 1 Overall, due to the complete mixing conditions in the lake, there was a homogenization of the bacterial communities and the diversity patterns were quite similar in the water samples. In further studies, samples will be collected during the stratification and the community structures will be compared.

Active Subaquatic Fault Segments in Lake Iznik Along the Middle Strand of the North Anatolian Fault, NW Turkey

AbstractThe seismic activity of the middle strand of the North Anatolian Fault (MNAF), Northwestern Turkey, is debated because of its quiescence during the instrumental period, in contrast to a significant historical activity documented by several chronicles over the last two millennia. Here, we focus on Lake Iznik, bordered by the MNAF, to get a new insight into its long‐term seismicity and its tectonic setting. The study of lacustrine sediment cores reveals 14 earthquake‐induced turbidites since their ages correspond to seismic events during the past two millennia. Bathymetry and high‐resolution seismic reflection data allow to describe two hitherto unknown subaquatic active fault structures (the South Boyalica and Iznik faults) that belong to the MNAF system. Sediment cores sampled on both sides of the Iznik Fault document an event deposit and a sedimentary unit vertically offset of ~40 cm interpreted as the last rupture during the 1065 CE destructive earthquake. Older events are supposed on this fault more than thousand years ago. Further studies will help to estimate the horizontal co‐seismic offset of this oblique‐slip fault and the calendar of older ruptures. The current seismic gap of thousand years on this segment greatly increases the seismic hazard in this region and must be considered in the seismic risk assessment of the NAF system.

Co-seismic beachrock deformation of 8th century AD Earthquake in Middle Strand of North Anatolian Fault, Lake Iznik, NW Turkey

A historical earthquake-related co-seismic deformation observed on beachrock beds along the southern shoreline of Lake Iznik is discussed as a new paleoseismic record for an 8th century AD earthquake in the Middle Strand of the North Anatolian Fault, NW Turkey. Electrical Resistivity Tomography (ERT) images beneath the beachrock surface allowed monitoring of the subsurface trace of a normal fault dipping north along a 100 m surface rupture. No strike-slip deformation exists along the rupture, suggesting that the deformation in the beachrock is connected with a secondary structure, and that the main surface rupture was under the lake waters. The deformed beds of the beachrock, dated using Optically Stimulated Luminescence (OSL) to 1.3 ± 0.15 ka, are overlain by an undeformed secondary deposition of beds dated to 1.2 ± 0.09 ka. This allows us to narrow down the time of the faulting and implying that it was most likely a result of the AD 715 earthquake.

Contrasting the Water Quality and Bacterial Community Patterns in Shallow and Deep Lakes: Manyas vs. Iznik.

The objectives of this study are to monitor the physicochemical properties of two freshwater lakes with different chemical characteristics and trophic status over a year (2019) and assess the bacterial diversity by a high-throughput sequencing method for a certain time. Carlson Trophic Index analysis revealed that, whereas the deep lake, Iznik Lake, (TSImean = 48.9) has mesotrophic characteristics, the shallow lake Manyas Lake (TSImean = 74.2) was found at a hypertrophic status. The most important parameters controlling water qualities in the lakes were temperature, alkalinity, and phosphate levels. Although the bacterial communities were dominated by the same phyla (Cyanobacteria, Bacteroidetes, Actinomicrobia, Proteobacteria, and Verrucomicrobia) in both lakes, the communities differed distinctly at the lower levels. Whereas Sporichthyaceae in Manyas Lake accounted for 10% of the total reads, the major share of the sequences was assigned to Cyanobacteria Family I (8%) in Iznik Lake. The hypertrophic Manyas Lake had a more diverse bacterial community rather than Iznik Lake and contained higher numbers of unique Operational Taxonomic Units.

Comparison of otolith morphology of invasive big-scale sand smelt (Atherina boyeri) from natural and artificial lakes in Turkey.

In this study, otolith morphology and otolith contour from big-scale sand smelt, Atherina boyeri were analyzed in Lake Egirdir and Lake Iznik (natural lakes), and Hirfanli Dam Lake (artificial lake). The otolith contour and sixteen otolith morphological characters such as width, depth, shape, sulcus acusticus shape, ostium, cauda, rostrum size-shape, and thickness, antirostrum size-shape, and thickness, anterior and posterior regions, mesial and lateral surfaces were successfully investigated for three total length groups of A. boyeri inhabiting the lakes. Intraspecific variation in rostrum shape, rostrum size, rostrum thickness, antirostrum, anterior region, mesial and lateral surfaces were observed for the three total length groups of three A. boyeri populations. In the three different lakes, saccular otoliths surface morphology of A. boyeri were detected such as flatten surface for Lake Egirdir, rough surface for Lake Iznik, and relatively smooth surface for Hirfanli Dam Lake using the Scanning Electron Microscope. The otolith contours were noticeable difference in the three total length groups of A. boyeri from the different lakes. Intraspecific variability of the otolith characters and morphology consist of the otolith surface morphology and otolith contour were presented and compared for the three total length groups of the A. boyeri from the different lakes.

Ecological analysis of heavy metal and radioactivity potential of Holocene sediments in Iznik Lake

Abstract In this study, the heavy metal and radioactive properties of Iznik Lake were investigated. Concentration values of the first (Ag, Bi, Mo, Sn, Se, Zn, As, B, Cd, Co, Cr, Cu, Ni, Pb, Pt and Sb) and second (Na, Mg, K, Ca, P, S, Fe, Al and Mn) group of elements in borehole 1 (BH-1) drilling did not show much variation from the top to the bottom of the drilling. Concentration values of the first group of elements in borehole 2 (BH-2) drill samples decreased at higher levels of drilling. In addition, natural and anthropogenic radionuclides were measured by gamma spectrometry, and the results of environmental natural radioactivity of Iznik Lake and its surroundings were determined. In the measurement results, Ra-226 was found to be below the world average value at all locations. It is assumed that the determination of K-40 values above the average values was due to agricultural activities carried out intensively in the study area. Th-232 values were found to be below the world average value in drilling samples; Cs-137 values were below the background level in all samples. According to these results, the study area does not contain any unnatural radioactivity.

Cross- Cultural Exchange Between the Islamic World and Europe (Iznik ceramic and Italian maiolica as a case study)

The word ceramic is a term taken directly from the western world. It had been used to define the pots crafted in tile technique. In the Ottoman records “Evani” was used instead of ceramics and “Kasi” for tiles. This paper deals with the history of pottery in the Islamic world and in Europe. Islamic world is represented by Iznik. Iznik, historically Nicaea, town in the northwestern of Turkey. It lies on the eastern shore of Lake Iznik. In 1331 A.D, Nicaea was besieged and conquered by the Ottoman Turks, who renamed it Iznik. On the other hand, European pottery is represented by Italian maiolica. Such wares were produced in both the northern and the southern parts of Italy, but the wares were distinctly different. A distinctive point of this research is the political and economic relations between the Ottoman Empire and Europe, and their influence on pottery production.The main objective of this paper is dealing with themes of exchange in pottery production, between Iznik in Turkey, and Italy in Europe. This exchange took shape in the emergence of a special form of ceramic plates of Italian tradition in Iznik. This type of ceramic plates known as “Tondino” dishes. These plates had a characteristic form, they are composed of broad flattened rim with a deep well. This form of plates was fashionable in Italy around 1500-1530. Iznik workshops had produced identical samples of tondino plates in the contemporary period as well. On the other hand, decorative elements of Iznik had greatly influenced Italian maiolica production. Of these spiral scrolls of the “Golden Horn”. ‘Golden Horn’ style is one of shapes of Chinese influence in the Near East. This style was imitated on Italian maiolica Albarello vessels. However, such influence did not come directly from china, but Iznik was a mediator. Furthermore, decorative elements of Rhodian style with their characterized polychrome design are imitated in Paduan workshops of Italy. This style showed a sudden change in the color scheme of Iznik pottery. Pale turquoise is applied for details, cobalt blue for the ground, however, green is lacking. Paduan imitation of Rhodian style was a clear form of adulation to the Ottoman Empire in the 17th century A.D In addition, various plates of Iznik production had combined between traditional decorative elements together with European heraldry of famous Italian families such as Venetian family of Morosini or the Dalmatian family Spingarolli de Dessa. Thus, such samples specifying a true image of the cross- cultural exchange between the Near East and the West.This paper aims at:II. Shed light on the role of Muslim artisan in ceramic industry and their effect on the Western civilization, Italy in particular.IV. Emphasizing that Muslim artisan had been influenced by the civilization of the West and adapted what suits their tradition and religion as well.V. Illuminates on the influence of political and economic status of the Ottoman Empire and Italy on all industries; and ceramics in particular. يتناول هذا البحث اشکال التبادل الحضاري في صناعة الخزف ما بين العالم الإسلامي متمثلا في خزف ازنيک الترکي، والخزف الأوروبي والذي يمثله الموليق الإيطالي. أحد اشکال هذا التبادل هو ظهور شکل مميز من الأواني الخزفية إيطالية المنشأ ضمن خزف ازنيک. هذا الشکل عرف باسم اطباق التوندينو والتي کان لها شهرة في إيطاليا في الفترة ما بين ١٥٠٠- ١٥٣٠م. اشکال مماثلة لهذه الاطباق إيطالية المنشأ تم انتاجها في ورش ازنيک في نفس الفترة الزمنية. وعلى الجانب الآخر، العناصر الزخرفية التقليدية التي شاع استخدامها في خزف ازنيک کان لها تأثير في زخارف الموليق الإيطالي. ومن هذه التأثيرات زخارف القرن الذهبي التي اتخذت الاشکال الحلزونية أحادية اللون (الأزرق). مثل هذه الاشکال الحلزونية تم تطبيقها على اواني الالبريلو من الموليق الإيطالي. شکل آخر من التأثيرات الترکية على الموليق الإيطالي هو زخارف رودس متعددة الألوان والتي تم تطبيقها في ورش تصنيع الخزف في بادو. شکل آخر من التبادل او ربما الاندماج الفني هو الجمع ما بين الزخارف الترکية التقليدية جنبا الى جنب مع بعض شعارات النبالة الخاصة ببعض الأسر الإيطالية. مثل هذه النماذج تسهم في تقديم صورة جلية عن التبادل الحضاري ما بين الأمم. يهدف هذا البحث إلى: إلقاء الضوء على دور الفنان المسلم في صناعة الخزف، وأثره على الحضارات الغربية، وبالأخص الحضارة الإيطالية. التأکيد على تأثر الفنان المسلم بالحضارات الغربية، حيث نهل منها ما يتناسب مع تقاليده ومعتقداته الدينية. إلقاء الضوء على الحالة الاقتصادية والسياسية لکل من الإمبراطورية العثمانية وإيطاليا وتأثيرهم على مختلف الصناعات، وبالأخص صناعة الخزف.

Spatial distribution and sources of BTEX and TPH contamination in freshwater sediments from Lake Iznik, NW Turkey

Iznik Lake is an important water supply deteriorating gradually due to anthropogenic pollution. Concentration and distribution of monoaromatic hydrocarbons (benzene, toluene, ethylbenzene and three xylene isomers; BTEX) were detected in the lake sediments using a static headspace GC-MS. ∑BTEX concentrations varied between 10.6 and 272.3 µg kg-1 dry weight (dw), with an average of 88.3 µg kg-1 dw. The light aromatic fraction of m-,p-Xylene was the most abundant compound (50.0% in average), followed by toluene (31.2%), o-xylene (12.2%), ethylbenzene (5.3%) and benzene (1.3%). Multivariate statistical analyses indicated that the BTEX levels and their distributions were controlled mainly by morphological and textural features of the sediment; anthropogenic inputs transported by the surrounding rivers, mainly influenced by agricultural facilities; absorbance of BTEX compounds in sediment; and biodegradation processes. Due to lack of any national sediment quality guideline regarding BTEX, the results will establish a significant baseline that will shed light on the administrative authorities for formulating their rational environmental strategies.

Paralytic shellfish toxin producing Aphanizomenon gracile strains isolated from Lake Iznik, Turkey

Aphanizomenon gracile is one of the most widespread Paralytic Shellfish Toxin (PST) producing cyanobacteria in freshwater bodies in the Northern Hemisphere. It has been shown to produce various PST congeners, including saxitoxin (STX), neosaxitoxin (NEO), decarbamoylsaxitoxin (dcSTX) and gonyautoxin 5 (GTX5) in Europe, North America and Asia. Three cyanobacteria strains were isolated in Lake Iznik in northwestern Turkey. Morphological characterization of these strains suggested all three strains conformed to classical taxonomic identification of A. gracile with some differences such as clumping of filaments, partially hyaline cells in some filaments and longer than usual vegetative cells. Sequences of 16S rRNA gene of these strains were placed within an A. gracile cluster including the majority of PST producing strains, confirming the identification of these strains as A. gracile. These new strains possessed saxitoxin biosynthesis genes sxtA, sxtG and their sequences clustered with those of other A. gracile. Liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis demonstrated the presence of NEO, STX, dcSTX and decarbamoylneosaxitoxin (dcNEO) in all strains. This is the first report of a PST producer in any water body in Turkey and first observation of dcNEO in an A. gracile culture.

Erosion Surfaces of the Land Between Iznik-Mekece (Turkey)

The study area begins from the eastern part of the Lake Iznik which is in the southeast of Marmara Region in Northwest Turkey, and extends to Mekece. The area is part of the North Anatolian Fault Line, which has been operating since Miocene. Gemlik Gulf-Iznik Depression-Karadin Trough, and Pamuk Plain are the depression series from west to the east which developed due to the fault. During the cool and rainy periods of the Pleistocene, a part of the depression filled with water and became the Lake Iznik. In this period, there have been level changes on the lake due to the climate oscillations and some lacustrine terraces formed. Main geomorphological units in the study area are; high mountain ranges, high and low plateaus, plains and flat fields. Erosion surfaces, which spread widely in the study area, have been handled and evaluated according to Prof. Dr. Oğuz Erol’s method. Erosion surfaces were dated as Lower-Middle Miocene surfaces, Upper Miocene surfaces and Pliocene surfaces by applying Erol’s ‘Relation Method Between Slopes and Contour Lines’. Some of these surfaces are valuable for the settlement and agriculture because of the small amount of the slopes. It can be said that the research area has a polycyclic feature, and it is in the late youth stage of geomorphologic development.

Contribution of natural and anthropogenic effects in the Iznik Lake bottom sediment: Geochemical and microfauna assemblages evidence

The relationship between the distribution of benthic foraminifera with ostracoda and sediment type and geochemical environment in the Iznik Lake is discussed. The microfauna (benthic foraminifer and ostracod) were sampled in seven recent bottom sediment samples, and geochemical variables of the sediment of the same samples were measured. This study is aimed at investigating the geochemical properties of 7 bottom sediment samples analysed in 5 lines in Iznik Lake. The depths for the samples varies from 1 to 68 m. The microfauna individuals were found in very low quantity, a total of 5 species foraminifera and 11 species 10 genus ostracod were identified. The geochemical properties were found to correspond well to the sediment type and depositional environment and five different sediment/depositional environment types could be distinguished. The individuals of microfauna reveals specific faunal assemblages that are closely related to these sediment and geochemical environment types. According to the survey, sediments encountered in the formation of gypsum crystals feature when considered together with the magnetism of Iznik Lake and the surrounding area suggest that are affected by new tectonics. Again this geochemical study the magnetic properties of the heavy-mineral contents, the entire amount of magnetite and hematite and heavy-mineral content has appeared to be affected by changes in the process. The purpose of this work is to distinguish the natural (geogenic) component, originated by techtonical origin this lake, from anthropogenic contamination owing to human activity. There were relationship between microfauna assemblages and heavy metals, trace element pollutant in the bottom lake sediments. Additionally, less individuals are found in most of the sediment samples in observed (in this 7 samples), this coincidence suggests that the heavy metals within the environment can also be a cause. The reason that of heavy metals, trace element pollutants are a factor in the distribution of microfaunal assemblages of genera and species were observed.

Fauna and flora of drilling and core data from the İznik Lake: The Marmara and the Black Sea connection

The study deals with on the Quaternary connection of the Iznik Lake between the Gemlik Gulf and the Black Sea located in the Marmara Region. The core and drilling data were evaluated. They were collected at two locations and depths from drilling cores and at the three deepest locations of the lake. A total of 510 samples were examined from the lake-bottom cores. Ostracod, mollusc, nannoplankton, ascidian spicule, and diatom assemblages observed at different levels of the drillings were studied. No foraminiferal data were recorded. Molluscan association such as Dreissena bugensis, D. caspia, Monodacna pontica, Clathrocaspia makarovi, Euxinipyrgula milachevitchi, Euxinipyrgula lincta indicate Neoeuxinian age. Amnicythere olivia, A. stepanaitysae, A. striatocostata, Tyrrhenocythere amnicola and Loxoconcha immodulata of the ostracod assemblage, exhibiting Ponto-Caspian origin, were found. In addition, fossil ascidian spicules comprising various species of Bonetia, Micrascidites, Monniotia, and Rigaudia genera were encountered, probably representing Late Pleistocene to Holocene ages. Campylodiscus echeneis, Cocconeis placentula var. lineata Epithemia turgida var. granulata, Epithemia adnata, Nitzschia commutate and N. vermicularis, from the diatom assemblage are genera and species also found in the İznik Lake and in the Black Sea. Mollusc and ostracod fauna, the Ponto-Caspian origin indicates that the İznik Lake was connected with the Black Sea and the Marmara Sea in the recent period. Thus, the Ponto-Caspian assemblages indicate the early Neoeuxinian (Surozhian) brackish water inundated the study area.Geochronological ages determined by the 14C method from the deposits occurring at 53–54 m above present sea level in the İznik Lake indicate the periods of connection via Iznik Lake during 33,630 to 32,920 cal BP (SK-1) and BP 27,335 to 27,070 cal BP (SK-2). When the position of the deposits is compared with the previously available Late Pleistocene 14C data obtained from the molluscs identified in the nearby Gemlik Gulf at −76 m present water depth and also with the early Khazarian (Middle Pleistocene) age data on the molusc fauna at 130–150 m heights of uppermost terraces above present sea level to NW of the lake, we suggest the influence of a neo-tectonic regime for the occurrence of comparable age deposits at different levels in the region. It may be proposed that a vertical displacement in the order of a 100 m occurred since the late Pleistocene in the İznik Lake area and the lake acquired its present features as a result of the tectonic movements.