Leyla Tolun

Submarine fault scarps in the Sea of Marmara pull-apart (North Anatolian Fault): Implications for seismic hazard in Istanbul

Earthquake scarps associated with recent historical events have been found on the floor of the Sea of Marmara, along the North Anatolian Fault (NAF). The MARMARASCARPS cruise using an unmanned submersible (ROV) provides direct observations to study the fine-scale morphology and geology of those scarps, their distribution, and geometry. The observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north Marmara extensional step-over, between the strike-slip Ganos and Izmit faults. Smaller strike-slip segments and pull-apart basins alternate within the main step-over, commonly combining strike-slip and extension. Rapid sedimentation rates of 1?3 mm/yr appear to compete with normal faulting components of up to 6 mm/yr at the pull-apart margins. In spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief. Sets of youthful earthquake scarps extend offshore from the Ganos and Izmit faults on land into the Sea of Marmara. Our observations suggest that they correspond to the submarine ruptures of the 1999 Izmit (Mw 7.4) and the 1912 Ganos (Ms 7.4) earthquakes. While the 1999 rupture ends at the immediate eastern entrance of the extensional Cinarcik Basin, the 1912 rupture appears to have crossed the Ganos restraining bend into the Sea of Marmara floor for 60 km with a right-lateral slip of 5 m, ending in the Central Basin step-over. From the Gulf of Saros to Marmara the total 1912 rupture length is probably about 140 km, not 50 km as previously thought. The direct observations of submarine scarps in Marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading. Incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the NAF next to Istanbul. Coulomb stress modeling shows a zone of maximum loading with at least 4?5 m of slip deficit encompassing the strike-slip segment 70 km long between the Cinarcik and Central Basins. That segment alone would be capable of generating a large-magnitude earthquake (Mw 7.2). Other segments in Marmara appear less loaded.

The pollution status and the toxicity of surface sediments in İzmit Bay (Marmara Sea), Turkey

Izmit Bay is one of the most polluted and populated enclosed sea in Turkey. It has been the centre of industrial activities for the last 30 years. Seven major sources enter the bay waters along the north coastline of the bay. This investigation forms part of continuing ecotoxicology studies in the Izmit Bay designed to constrain and minimise the pollution caused by flourishing industry and a growing population. Sediments sampled from the mouths of the major discharges of Izmit Bay were analysed for their organic carbon, total polycyclic aromatic hydrocarbon (t-PAH) and trace inorganic element (Cd, Al, As, Pb, Hg and Cu) contents and compared with those found in the sediments from the reference station in the outer bay (in the Marmara Sea). The toxicity of sediments was determined in the bulk and elutriate samples by using algal (Phaeodactylum tricornutum) batch bioassays. Chemical data showed that the sediments collected from the inner sites of the bay have been contaminated with Cd, Hg, As and PAHs. Organic carbon contents were also found higher. All the major industrial discharges into the bay are now biologically treated but bioassays performed with bulk sediments revealed that the recent sediments are toxic to the microalgae throughout the bay. The results are consistent with the previous toxicity studies performed with the industrial discharges.

Towards a clean Izmit Bay.

The elongated semi-enclosed Bay of Izmit, which receives both domestic and industrial wastes, has been monitored by measuring its physical and biochemical parameters for 2 years, 1994-1995. It is clear that there are two distinct water masses. The upper layer has been occupied by the less saline (22-26 ppt) waters of the Black Sea origin; whereas the lower layer contains saline (38.5 ppt) Mediterranean waters. The seasonal variations in the biochemical characteristics were dependent on the bays two-layer flow system. If one considers the distribution of transparency in the upper bay waters, it has been observed that the Secchi disk depth (SDD) decreases from west to east. Furthermore, these depths are limited by the high primary productivity associated with the low concentrations of nutrients observed during the spring. Discharges of wastes into the surface waters significantly affect the biological production and oxygen consumption in the lower layer. Within the last 10 years, 80% of organic matter has been removed from industrial wastewater. However, organic loads from the domestic wastewaters have doubled because of the growth in the surrounding population. Fortunately, as a result, the total organic loads in the bay have not changed significantly within the last 10 years.

The changes of T-PAH levels and health status of mussels in Izmit bay (Turkey) after Marmara earthquake and subsequent refinery fire

As is well known, a powerful earthquake along the North Anatolian Fault struck the eastern part of the Marmara region on August 17, 1999. Izmit Bay, which is known as one of the most polluted sites of Turkey, was also affected by the quake and the subsequent refinery fire. The measurements performed just before and after the earthquake showed that T-PAH levels increased significantly after the event [Okay OS, Tolun L, Telli-Karakoç F, Tüfekçi V, Tüfekçi H, Morkoç E. Izmit Bay (Turkey) ecosystem after Marmara earthquake and subsequent refinery fire: the long-term data. Marine Pollution Bulletin 2001;42:361-9]. In the framework of ecotoxicological studies, the Bay ecosystem was continuously monitored for T-PAH levels in seawater, sediments and mussels (Mytilus galloprovincialis) to find out whether change occurred during the 2-year period following the earthquake. For that purpose, after the earthquake, the samples were collected six times between the period of September 1999 and March 2001 at coastal stations of the Bay situated away from the mouth of main discharges. The responses of the mussels were also measured by means of the lysosomal stability of the blood cells and feeding rate biomarker techniques at two different sites of the bay. Although the T-PAH levels in all matrices generally showed a decreasing trend, they were found to be still high especially at stations near the refinery. Both biomarker results showed that the health status of the mussels is very poor in the Bay ecosystem, based on the results obtained from the two sites monitored.

Comparison of several toxicity tests applied to complex wastewaters and mussel biomarkers in receiving waters

In this study, the complex wastewaters/effluents discharged to coastal regions of Turkey and Greece were sampled, and various toxicity tests were applied. The bioassays used included the assessment of the luminescence inhibition of the bacterium Vibrio fisheri, the photosynthesis inhibition (14C uptake rate) and growth inhibition of the algal species Phaeodactylum tricornutum, and the mortality of the crustacean Artemia franciscana and rotifer Brachionus plicatilis. Additionally, “neutral red retention” and “filtration rate” sublethal biomarker techniques were performed by utilizing the mussel species Mytilus galloproviancialis, inhabiting the points of discharges in Turkey. All discharges tested were found to be acutely toxic to P. tricornutum and slightly toxic to V. fisheri, A. franciscana, and B. plicatilis. Test results showed that the 14C uptake rate toxicity test was the most sensitive one among the other bioassays. The biomarker results showed that the health status of mussels in the coastal areas decreased significantly, indicating the pollution of the receiving waters in Turkey. The conclusions drawn highlight the necessity for an intesive ecotoxicological monitoring scheme that will incorporate the most suitable bioassays and biomarkers to adequately contribute to the upgrading and maintenance of the ecological quality of the coastal waters in Greece and in Turkey. *Presented as an invited plenary lecture at “The 2nd Asian International Conference on Ecotoxicology and Environmental Safety” (SECOTOX 2004), Songkla, Thailand, 26–29 September 2004.

Development of National Action Plan to Address Pollution from Land Based Activities in Turkey

Countries surrounding the Mediterranean Sea and Black Sea signed the Barcelona Convention (1976) and Bucharest Convention (1992) respectively and Turkey is the one of the contracting parties for both of them. In this content, they formed the “Mediterranean Action Plan (MAP)” and “Black Sea Environment Programme” to control water pollution in the Mediterranean and Black Sea, respectively. To achieve this goal, each region formed their Land Based Sources Strategic Action Programme (LBS SAP) in the second part of the 1990s within the framework of the Land Based Sources Protocols (LBS Protocol) which are sub protocols of the Barcelona Convention and Bucharest Convention. These programmes define the major land based environmental problems and proposed solutions to the problems and set the deadlines to perform the necessary tasks. In the line with LBS SAP’s, Mediterranean countries have been already developed their “National Action Plan’s for Land Based Sources (LBS NAP) in 2005.

Potential risk assessment of metals in edible fish species for human consumption from the Eastern Aegean Sea

The levels of Hg, Cd, Pb, Cr, Cu and Zn were measured in the tissues of four edible fish species namely: Diplodus annularis, Pagellus erythrinus, Merluccius merluccius and Mullus barbatus, collected from the Turkish Coast of the Aegean Sea. Except for D. annularis, the levels of Cd and Pb in all fish tissues sampled in Aliaga Bay in 2009 were above the tolerable limits according to the Food and Agriculture Organization of the United Nations (FAO). Hg in P. erythrinus and M. barbatus were higher than the maximum permitted limits (FAO), while D. annularis and M. merluccius were lower than the limit for biota in the district of Aliaga. Although the Target Hazard Quotient (THQ) values for Cd, Pb, Cu, Cr, Zn in all fish samples were lower than 1.0, the THQ for Hg levels were higher than 1.0 for most of the samples. According to the THQ values, M. merluccius may be consumed in moderation from Aliaga Bay, while the consumption of M. barbatus and P. erythrinus collected from Aliaga Bay are potentially hazardous to human health due to the Hg concentrations. Fish collected from Izmir Bay can be consumed safely.