Northeastern Marmara Sea Research Articles

Marmara Denizi’nde bentik deniz çöpü

This study presents the first data on benthic marine litter in the Marmara Sea, Turkey. To obtain the data, bottom trawl surveys were conducted at 34 sites between May 2017 and February 2018. The litter items were sampled and sorted following the MEDITS’ relevant instructions. 660 pieces of litter, weighing 434.9 kg, were sampled. The litter density was found to range between 27.5 n/km2 and 661.2 n/km2, averaging 73.9 n/km2, and the obtained items’ weights ranged between 0.03 kg/km2 and 1597.8 kg/km2, averaging 48.7 kg/km2. The plastic group L1 constituted 71.7% of the trawled litter. The highest mean litter density was detected in the Northeastern Marmara Sea in the spring and summer of 2018. The mean benthic litter density was found to be higher than the nearby areas. It was concluded that more effort should be invested in reducing marine pollution.

Temporal variations in phytoplankton composition in the northeastern Sea of Marmara: potentially toxic species and mucilage event

Temporal variations in phytoplankton composition in the northeastern Sea of Marmara was investigated associated with physico-chemical variables from January 2004 to December 2007. The occurrence of potentially toxic species and a mucilage event was also evaluated during this study period. The confined upper layer of the Sea of Marmara is mesotrophic to eutrophic and has higher productivity when compared to the neighbouring Black Sea and Aegean Sea. 132 taxa in the micro-phytoplankton community were identified, 11 of which are known to be potentially toxic. The most abundant species were Pseudo-nitzschia species from diatoms and Prorocentrum micans from dinoflagellates. Potentially toxic species were more common at the coastal stations. The onset of a mucilage formation was observed in October 2007, and well-known mucilage producers such as Gonyaulax hyalina (reported as G. fragilis) and Thalassiosira gravida (reported as T. rotula) dominated the phytoplankton community during this event. A marked decrease in the number of species and diversity index following June 2007 and reported shifts in the zooplankton community during the same period points to probable cascading effects in the pelagic ecosystem of the Sea of Marmara.

Impact of excessive sedimentation caused by anthropogenic activities on benthic suspension feeders in the Sea of Marmara

AbstractA massive die-off of benthic suspension feeders (BSF) covered by large amounts of sediments was observed along Prince Islands coasts (north-eastern Sea of Marmara) in August 2015. Alcyonarians, pennatulaceans, bivalves and sponges were severely affected. Many BSF probably died from burial and clogging of their feeding and respiratory apparatus. Of the gorgonian colonies, 66 ± 34% (mean ± SD) were dead, while 15 ± 16% (mean ± SD) displayed recent necrosis on the colony surface. In addition, histopathological and microbial examinations of the affected gorgonians and gold corals (Savalia savaglia) suggest that stress caused by sedimentation made them vulnerable to exploitation by consistently isolated opportunistic microorganisms. We isolatedVibrio splendidusandVibrio neptuniusfrom diseased gold coral colonies, but the bacterial isolates obtained from gorgonians could only be identified to genusVibriolevel. The presumably artificially introduced fungusMucor circinelloideswas common on both gold coral and gorgonians. This mould and opportunistic bacteria may have colonized BSF by taking advantage of low oxygen levels leading to impaired coral immune responses and thereby exacerbated the BSF mortality. Construction and landfill operations at Yassıada seem to be the greatest contributor to the observed sedimentation, as shown by silicate concentrations in nearby waters. These observations imply that preventive measures are necessary when construction operations take place in the vicinity of sensitive marine habitats.

Modelling the provenance of detritus flushed through the Strait of Bosphorus, Turkey, during early Holocene outflow from the Black Sea to the world ocean

Source-to-sink tracing of very fine sand supplied to a controversial lower Holocene deltaic lobe in the northeastern Marmara Sea was undertaken using SEM backscatter mapping and quantitative ‘mineral liberation analysis’ of very fine sand fractions. Forty-two samples from the Kurbağalıdere, Göksu, Golden Horn and Riva watersheds, and from Oligo-Miocene outcrops along the southwestern Black Sea coast, show that each of these potential sources has a distinct mineralogical fingerprint. Comparison with 11 samples from the lower Holocene delta and 19 samples from the overlying mud drape show that no single source can account for the mineral proportions in the sand fractions of these depositional sinks, but a mixed provenance provides good matches. For the deltaic lobe, quantitative mixing based on 250,000 Monte Carlo simulations suggests ~50% contribution from Oligo-Miocene successions of the southwestern Black Sea coast and inner shelf, ~20% contribution from the Göksu stream, and minor contributions from other sources including the Kurbağalıdere stream. This balance of source contributions continued to supply the Holocene mud drape until ~6calka, after which local sources became more important. It is hypothesized that unconsolidated sediment from a number of watersheds was parked along the coast of the Neoeuxine Lake and in the paleo-Bosphorus valley during the MIS 2 lowstand. A rising Neoeuxine Lake, possibly swollen by glacial outburst floods from the Altay region of Central Asia, flushed ~0.5km3 of this sediment through the Strait of Bosphorus to the deltaic lobe and permitted it to rapidly advance into the Marmara Sea, which at that time was rising ~1m each 100yr. Provenance of the lower portion of the Holocene mud drape is consistent with continued Black Sea outflow throughout the deposition of sapropel M1 in the Marmara Sea.

Reproduction in the Mediterranean endemic gorgonian Spinimuricea klavereni (Anthozoa, Octocorallia, Plexauridae)

AbstractSpinimuricea klavereni is a Mediterranean endemic gorgonian that is rarely encountered, probably because it typically occurs at depths below 50 m. It is exceptionally common in the northern Marmara Sea, with an unusually shallow upper depth limit of ~20 m. The reproductive biology of this species was studied during a one year period off Büyükada, in the northeastern Marmara Sea. Spinimuricea klavereni is a gonochoric broadcast spawner with an almost even sex ratio. Colonies were ~15 cm in height at first reproduction. Gametogenesis was continuous, characterized by high male and female fecundities year‐round. Oocytes and sperm sacs of all developmental stages were found throughout the year, with small‐sized oocytes and sperm sacs dominant throughout the year. The reproduction of S. klavereni did not seem to exhibit any marked seasonal pattern, unlike most other studied Mediterranean octocorals. Modest variation in gamete output was probably related to slight alterations in food availability and temperature. The non‐seasonal reproductive pattern we observed may be related to the low intra‐annual variation in temperature in the Marmara Sea, and the fact that the mesotrophic‐eutrophic level of productivity in the Marmara Sea can support the energetic requirements of continuous gametogenesis in this gorgonian. Whether these patterns are local adaptations or intrinsic characteristics for this Mediterranean endemic species remains to be studied.

Changes in abundance and community structure of the zooplankton population during the 2008 mucilage event in the northeastern Marmara Sea

The composition and abundance of zooplankton and the corresponding environmental conditions were investigated during the 2008 mucilage event (April-December 2008) in the Marmara Sea. As a result, 46 zooplanktonic taxa were identified. Copepods and cladocerans were generally the most abundant groups. Mnemiopsis leidyi had a significant seasonality, and abundance was related to fluctuations in temperature and salinity. The most important species were Acartia clausi and Penilia avirostris, but these species did not reach their usual autumn maximum. As a result, the mucilage event in 2008 caused significant shifts in zooplankton abundance and community structure in the Marmara Sea.

Wave dispersion study for tsunami propagation in the Sea of Marmara

In this paper the aim is to investigate whether there are differences between the dispersion and non-dispersion solutions on tsunami propagation. For this purpose, two numerical models of tsunami propagation are compared. One of these numerical models is a nondispersive model that uses Saint Venant equations and the other is a dispersive model that uses Boussinesq equations. The tsunamis resulting from a submarine mass failure (SMF) which is settled at the bottom of the north eastern Sea of Marmara are examined. An analytical solution considering wave dispersion is developed for obtaining near-field tsunami amplitudes above the submarine mass failure. Numerical modeling is used at the sea surface from the common boundary called as liquid boundary with incident waves up to the coastal regions to get the tsunami amplitudes. The output of the analytical model is taken as the disturbances for the numerical method. In the numerical solutions TELEMAC-2D software system is used for both dispersive and nondispersive modeling. The results of the dispersive and nondispersive models are compared to each other. Both temporal and spatial differences in the amplitudes and wave shapes are examined. The obtained results demonstrate that there are no noticeable differences between the dispersion and non-dispersion solutions except some special cases and some special landslide velocities.

Seasonal variations in the phytoplankton community in the north-eastern Sea of Marmara and a species list

This paper describes phytoplankton abundance data collected in the Sea of Marmara in 2000 and identifies new species to the region. The quantitative sampling was carried out monthly at 3 stations and seasonally at 6 stations at depths of 0.5, 5, 10 and 20 m. Additionally, vertical samplings by plankton net from 15–0 m were carried out in order to determine the species diversity. Simultaneously measured physical (salinity, temperature and Secchi disc) and chemical parameters (dissolved oxygen, nitrate + nitrite, chlorophyll-a, phosphate and silicate) were evaluated together with phytoplankton data. One hundred and fifteen species were recorded which are members of 55 dinoflagellates, 42 diatoms, 11 silicoflagellates and 7 other groups. Those species include toxic species with high reproduction rates and species that are accepted as carrying risk. Blooms ofAnabaenasp.,Nitzschia longissima(Brébisson in Kützing) Ralfs in Pritchard andProrocentrum triestinumSchiller species were observed during the study.Dictyocha antarcticaLohmann 1919,Dictyocha cruxEhrenberg 1840 andNitzschia rectilongaTakano 1983 species were recorded for the first time from the coastal waters of Turkey. The maximum phytoplankton abundance has been observed during the winter and autumn seasons in the 0.5 and 5 m depths; the concentration of the diatoms was higher during late winter and autumn, however, the concentration of the dinoflagellates was always high during the whole year and they did not show a seasonal variation. The phytoplankton density was lower at the 20 m depths because of the low light penetration property of the Sea of Marmara.

Annual crustacean zooplankton succession (Copepoda and Cladocera) in the upper layer of Ahirkapi coastal waters (northeastern Sea of Marmara)

The monthly abundance of crustacean zooplankton in Ahirkapi coastal waters (northeastern Sea of Marmara) was studied from July 2005 to July 2006. Copepods and cladocerans showed clear seasonal patterns. The crustacean zooplankton community was dominated by coastal and temperate water species, in particular by the calanoid copepods Acartia clausi, Paracalanus parvus, and Centropages ponticus, and the cladoceran, Penilia avirostris. L'abondance mensuelle des Crustaces zooplanctoniques des eaux cotieres d'Ahirkapi (nord-est de la mer de Marmara) a ete etudiee de juillet 2005 a juillet 2006. Les Copepodes et les Cladoceres ont montre des modeles saisonniers evidents. La communaute crustaceenne du zooplancton etait dominee par les especes d'eaux cotieres et temperees, particulierement par les Copepodes Calanoides Acartia clausi, Paracalanus parvus et Centropages ponticus et par le Cladocere Penilia avirostris.

Annual cycle of zooplankton abundance and species composition in Izmit Bay (the northeastern Marmara Sea)

The monthly abundance, biomass and taxonomic composition of zooplankton of Izmit Bay (the northeastern Marmara Sea) were studied from October 2001 to September 2002. Most species within the zooplankton community displayed a clear pattern of succession throughout the year. Generally copepods and cladocerans were the most abundant groups, while the contribution of meroplankton increased at inner-most stations and dominated the zooplankton. Both species number ( S) and diversity ( H′) were positively influenced by the increase in salinity of upper layers ( r = 0.30 and r = 0.31, p < 0.001, respectively), while chlorophyll a was negatively affected ( r = −0.36, p < 0.001). Even though Noctiluca scintillans had a significant seasonality ( F 11,120 = 8.45, p < 0.001, ANOVA), abundance was not related to fluctuations in temperature and only chlorophyll a was adversely correlated ( r = −0.35, p < 0.001). In general, there are some minor differences in zooplankton assemblages of upper and lower layers. A comparison of the species composition and abundance of Izmit Bay with other Black Sea bays reveals a high similarity between them.

Scenarios of tsunami amplitudes in the north eastern coast of Sea of Marmara generated by submarine mass failure

In this paper the tsunamis resulting from a submarine mass failure such as slides and slumps triggered by earthquakes or other environmental effects, which is settled at the bottom of the north eastern Sea of Marmara are examined in one sample region. As the solution method, one hybrid method is developed. The main objective of this method is to combine an analytical solution presenting near-field tsunami amplitudes above the submarine mass failure with a numerical solution indicating the tsunami amplitudes in the coastal regions. For this purpose, one common linear boundary between analytical and numerical solution domains is defined. Movements of Submarine Mass Failures (SMF) are modeled using one simple kinematics source model and the amplitudes of the tsunamis at the region that are closer to the landslide are computed by using the analytical method. SMF is modeled approximately from the bottom geometry, and an average depth is used. Scenarios of SMF are established depending on the velocities and thicknesses of the failure, and near-field tsunami amplitudes are obtained in the open sea during the source time. After the source times, the solutions are found in the numerical region using TELEMAC-2D software system with the mentioned boundary above. In this boundary, the output of the analytical solutions is taken as the boundary conditions or the disturbances for the numerical method. With these disturbances, the numerical method is performed and the amplitudes are calculated in the coastal area. The generation, propagation and coastal amplifications of the tsunamis are illustrated at some certain points and regions both in the open sea and near the coast line. The results have been visualized and discussed.

Atmospheric deposition of polycyclic aromatic hydrocarbons to Izmit Bay, Turkey

Wet deposition and dry deposition samples were collected in an urban/industrialized area of Izmit Bay, North-eastern Marmara Sea, Turkey, from September 2002 to July 2003. The samples were analyzed for sixteen polycyclic aromatic hydrocarbon (PAH) compounds by using HPLC-UV technique. Wet and dry deposition concentrations and fluxes of PAHs were determined. The results showed that PAH concentrations were high because of industrial processes, heavy traffic and residential areas next to the sampling site. Total dry deposition flux of the fifteen 3-6 ring PAHs was 8.30 microg m(-2)day(-1), with a range of 0.034-1.77 microg m(-2)day(-1). The total wet deposition flux of the fifteen 3-6 ring PAHs was 1716 microg m(-2) 11 month(-1), with a range of 10-440 microg m(-2) 11 month(-1). Significant seasonal differences were observed in both types of deposition samples. The winter fluxes of total PAHs were 1.5 and 2.5 times greater than those of the warm period for wet and dry deposition samples, respectively. Factor analysis of dry deposition samples and back trajectory analysis of wet deposition samples were also used to characterize and identify the PAH emission sources in this study.

Heavy Metal Pollution Assessment in Sediments of the Izmit Bay, Turkey

Surface sediments in the fraction < 63 microm collected from eight stations along the north coastline of Izmit Bay, north-eastern Marmara Sea, Turkey, were analyzed for major (organic carbon, Al, Ba, Fe and Mg) and trace (As, Cd, Co, Cr, Cu, Mo, Ni, Pb and Zn) elements by using inductively coupled plasma atomic emission spectrometry (ICP-AES). Sediments heavily contaminated are evaluated by the Sediment Quality Guidelines (SQG) of US EPA. The results were compared with the marine sediment quality standards (SQS), as well as literature values reported to assess the pollution status of the sediments. The enrichment factors (EFs) were calculated to evaluate actual level of contamination for all the elements using the earth crust as reference matrix, based on elemental values by Mason which show a normal pattern near to unity. The analysis revealed two groups of elements: (i) Arsenic, Cd, Pb, and Zn are the most enriched elements; (ii) Barium, Co, Cr, Cu, Fe, Mg, Mo and Ni are at background levels. The results show that road traffic run-offs, paint industries and coal combustion are among the most significant sources.

The distribution and sources of heavy metals in Izmit Bay surface sediments affected by a polluted stream

Dil Deresi stream is a highly contaminated stream passing through the most heavily industrialized area of Izmit Bay. In this research, surface sediments in the <63-μm fraction collected from 34 sites at western part of Izmit Bay, Northeastern Marmara Sea, Turkey were analyzed by ICP-AES for Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn and Zn. Metal concentrations were compared with the marine sediment quality standards (SQS) and literature data to assess the pollution status of the sediments. Enrichment factors (EFs) were calculated to assess whether the concentrations observed represent background or contaminated levels. The analysis revealed three groups of elements: (1) Sn is the most enriched element; (2) As, Cd, Pb and Zn are minor enriched elements; and (3) Co, Cr, Cu, Fe, Mg, Mn and Ni are at background concentrations. The distribution maps of the concentrations and enrichment factors for all heavy metals were also produced as a contour plot based on Geographic Information System (GIS) technology.

Pleistocene–Holocene calcareous nannofossil biostratigraphy of core samples from The Northeastern Sea of Marmara, Fenerbahçe–Pendik, NW Turkey

Pseudoemiliana lacunosa, Gephyrocapsa oceanica and Emiliania huxleyi (Ionian) (Pleistocene–Holocene) calcareous nannoplankton zones were identified from 82 samples of 14 cores taken from 8 locations in the northeastern Sea of Marmara. The investigation indicates that the identified biozones have been alternated by tectonic activity in the 1, 5 and 6 core locations. The study area has been affected three times by tectonic activity during the Pleistocene–Holocene time interval. The first activity occured during the Early Pleistocene and the others during Holocene.

Ecological risk assessment using trace elements from surface sediments of İzmit Bay (Northeastern Marmara Sea) Turkey

The aim of this study was to study ecological risk assessment of trace elements (As, Cd, Cr, Cu, Ni, Pb and Zn) in İzmit Bay surface sediments in the <63 μm fraction. Sediment samples were collected from 8 sites along the north coastline of the bay. Samples were subjected to a total digestion technique and analyzed for major (organic carbon) and minor (As, Cd, Cr, Cu, Ni, Pb and Zn) elements. Sediments heavily contaminated are evaluated by the Sediment Quality Guidelines (SQG) of US EPA. The degree of contamination ( C d) is estimated as very high at each site. Two sets of SQGs, effect range-low/effect range median values and TEL/probable effect level (PEL) values were used in our study. Sediments from the each site are judged toxic when two or more of the PEL values exceed EPA guidelines. Our results are in agreement with previously reported sediment toxicity test results.

Deltas south of the Bosphorus Strait record persistent Black Sea outflow to the Marmara Sea since ∼10 ka

At the southern exit of the Bosphorus Strait in the northeastern Marmara Sea, high-resolution seismic profiles reveal two lobate, progradational delta lobes in modern water depths of ∼40–65 m. The younger delta was active from ∼10 to 9 ka based on radiocarbon dates of equivalent prodelta deposits and the elevation of its topset-to-foreset transition. The topset-to-foreset transition climbs in the seaward direction because the delta prograded into a rising sea. Low abundances of marine fauna and flora in the 10–9-ka interval support a deltaic interpretation. There are no rivers in the area that could have fed the delta; instead, all evidence points to the strait itself as the source of sediment and water. When this outflow was strongest (∼10.6–6.0 ka), sapropels accumulated in basinal areas of both the Aegean and Marmara seas. Benthic foraminiferal and dinoflagellate cyst data from contemporary deposits elsewhere in the Marmara Sea point to the continual presence through the Holocene of a surface layer of brackish water that we ascribe to this same outflow from the Black Sea through the Bosphorus Strait. By ∼9.1–8.5 ka, two-layer flow developed in the Bosphorus Strait as global sea level continued to rise, and the sediment supply to the younger delta was cut off because the outflowing Black Sea water ceased to be in contact with the floor of the strait. The older delta lobe lies below a prominent lowstand unconformity and is tentatively interpreted to have formed from ∼29.5 to 23.5 ka (oxygen-isotopic stage 3) when the Marmara Sea stood at ∼−55 m and a second sapropel accumulated in deep basinal areas.

Spatial Distribution of Net Diatoms Along Adjacent Water Masses of Different Origin

Larger diatoms (>55 µm) were sampled using closing bottles from on board the R/V Bilim along adjacent water masses of different origin in order to observe patchy assemblages of net diatoms. MDS (Multi-Dimensional Scaling) plots of diatoms in adjacent water masses inhabiting the south-western Black Sea, Bosphorus, Golden Horn, the north-eastern Sea of Marmara and Izmit Bay have shown that patchy configurations of diatom were orientated along particular dominating environmental gradients, mainly temperature and salinity. A two-way evolution takes place in the Bosphorus as the Black Sea water flows towards the Sea of Marmara near the surface and under-neath the Mediterranean inflow, below the pycnocline towards the Black Sea. Considerable changes in salinity and temperature with depth in the region affected the drifting flora considerably, especially its diatom composition. Of all the regions, the south-western Black Sea was the most species diverse and abundant.

Geochemical characteristics of the recent sediments from the Sea of Marmara

Six box-cores, one boomerang core and one hundred sixty-six surface sediment samples recovered in the Sea of Marmara were analyzed in an attempt to establish the main controls on distribution and origin of trace metals within the oxic to suboxic basin of this sea. Surface and downcore data indicate that the abundance and distribution of the total metal concentrations for Fe, Ni, Zn, Cr, Co, Cu and Pb can largely be explained by the variable admixtures of terrigenous components in response to textural variations and biogenic calcareous components poor in metal contents. The distribution of Cr and Ni seems to be controlled, in part, by a contribution from the weathering of basic/ultrabasic sources on the coastal hinterland. A small but significant amount of Cu, Zn and Pb in sediments from the northeastern Sea of Marmara probably suggests a pollution effect from the northerly located Golden Horn Estuary that is known as one of the most polluted coastal regions of Turkey. Looking at the data, it seems that the Mn concentrations are unusually high in the deep-water sediments (4498–9127 ppm, carbonate free), along the east-west-trending Marmara Trough but low in sediments from the adjacent shallow waters (307–2059 ppm, carbonate free). The Mn enrichment in deep-water relative to shallow-water Marmara sediments is further indicated by the Fe/Mn ratios being, on average, 11–23 in deep waters and 34–69 in shallow waters. The contents of other metals (Fe, Ni, Zn, Cr, Co, Cu, Pb) in both shallow- and deep-water sediments fall nearly within the same range as those found in average crustal and sedimentary rocks, suggesting no significant enrichment of these metals in the deep Marmara basins. the downcore changes in the color, from reddish-brown at the surface (top 2–5 cm) to greenish-gray in the subsurface (5 cm), together with the occurrence of high Mn concentrations in the surface sediment layers in cores can be attributed, at least in part, to the diagenetic Mn enrichment within the sediment column. The usually low organic carbon contents and biogenic components present in sediments reflect that the well-known biogenic mechanism for the enrichment of Mn seems to be of minor importance in the deep Marmara waters. The generally low Mn concentrations contained in the surface (grab) and core sediments from the Black Sea and Aegean Sea approaching those of the Sea of Marmara do not provide any conclusion to support significant Mn contribution from these two adjacent seas, particularly from the so-called “manganese pump” zones in the shallow Black Sea waters. Comparison with other deep-sea sediments which have been deposited under the influences of hydrothermal activities, worldwide, suggests Mn enrichment in deep-water relative to shallow-water sediments of the Sea of Marmara, mainly as a result of hydrothermal contributions from this seismically active marine region. Based on the average Fe/Mn ratios obtained in cores, which tend to increase gradually from ∼11 in the deep Central Basin to ∼67–69 in the northeastern and southwestern shelves, the Central Basin of Marmara Trough can be considered as a possible, potential source for hydrothermal solutions leading to the enrichment of Mn in the deep Marmara waters. However, this remains to be further investigated.

Heavy metal concentrations in surface sediments from the two coastal inlets (Golden Horn Estuary and İzmit Bay) of the northeastern Sea of Marmara

A total of 57 surficial sediment samples collected in the Golden Horn Estuary and İzmit Bay (northeastern Marmara Sea) was analyzed for the heavy metals Fe, Mn, Cr, Ni, Co, Zn, Pb, and Cu and the results were compared with various natural and anthropogenic sources. It was observed that the concentrations of Zn, Cu, Pb, and, to some extent Cr, in the Golden Horn sediments are comparable with those in most other seas in the vicinity of highly industrialized and densely populated regions. Based on calculations from the metal: Al and metal: Fe ratios, the bottom sediments of Golden Horn were found to be enriched in Zn, Cu, Pb, and to a lesser extent Cr, by factors of up to 192 compared with the regional background levels of these metals. Fe, Mn, Co, and to some extent Ni, are mostly at natural levels. In contrast, the metal levels of the bottom sediments in İzmit Bay are significantly lower and they appear to be controlled by lithogenic rather than the anthropogenic influences. Highly significant correlation coefficients between the metals Zn, Cu, and Pb are widely attributed to the common sources of these metals, the metal smelters and shipyards in the vicinity of the areas studied. Based on the numerical value of the geoaccumulation index of heavy metals, it was found that the bottom sediments of İzmit Bay can be regarded as basically uncontaminated. Exceptionally high I geo values are found for the bottom sediments of the Golden Horn, indicating moderate to extreme contamination in this region by the metals Pb, Zn, Cu, and Cr. The presence of a large number of anthropogenic metal point sources, higher river run-off via the two major creeks, particularly coastal topography and hydrodynamic conditions, associated with the very high sedimentation rates, all strongly favour the accumulation of anomalously high metal concentrations in the Golden Horn Estuary, while the opposite is true for İzmit Bay.