İlkay Salihoğlu

MED POL survey of organotins in the Mediterranean

A pilot survey of tributyltin (TBT) and its derivatives in Mediterranean areas was undertaken in 1988 within the framework of the MED POL activities. The areas studied were the French Mediterranean coast, the Northern Tyrrhenian coast, the Southern coast of Turkey and the Alexandria (Egypt) coastal area. 113 water samples were analysed from the first three areas and 35 sediment samples from the fourth. Samples were collected at sites selected according to differing environmental conditions and potential inputs of TBT. Two shellfish-culture areas in the South of France located near marinas were included. The data reported represent the first coordinated survey of butyltin levels in seawater and sediments from Mediterranean areas. The concentrations generally exceed the no-observed effect level (NOEL) of 20 ng l−1 and are comparable to those previously reported for similar situations outside the Mediterranean area.

Vertical variations in the principle chemical properties of the Black Sea in the autumn of 1991

Abstract Basin-wide principal hydrochemical data for the upper 500 m of the Black Sea were obtained at a total of 197 stations during a multi-ship, multi-institutional, Hydroblack -91 cruise in September 1991. Only offshore stations, 38 from the 1991 joint cruise, 5 from R/V Knorr (1988), 16 from R/V Atlantis-II (1969), and 9 from R/V Bilim (1990) cruises, are considered in conjunction with the present and past data as a function of potential density rather than depth. The oxycline, coinciding with the upper boundary of the permanent pycnocline (σΘ = 14.2–14.3), extended down to the σΘ = 15.3–15.4 surfaces during warm periods (June–September) and to the σΘ = 15.75 surface during spring periods. The lower boundary of the oxycline (O2 ⩽ 20 μM) has remained constant within the last two decades when past and present spring data are considered, but has risen by 0.30 density units when late summer-autumn data are considered. Independent of the geographical location, the base of the transition layer was established at the σΘ = 16.15–16.20 surfaces where H2S ⩾ 5 μM. Nitrate and phosphate reached their maxima at σΘ = 15.3–15.4 surfaces and then decreased steadily with different slopes until the σΘ = 15.85 –15.95 surfaces. At the anoxic interface, phosphate concentration increases about 10 fold from ∼ 0.02 –0.5 μM at the σΘ = 15.85 –15.90 surface to 4 –6 μM at the σΘ = 16.15 –16.20 surface. Comparison with the data from the 1970s suggests that both the maximum values and the depth integrated mass of nitrate (g NO3—N/m2) between the σΘ = 14.2 and 16.0 surfaces have increased 2–3 fold, and the density surface where the NO3 maximum is established has shifted by 0.30 units in the late 1980s.

DDT, DDE, and PCB residues in fish, crustaceans and sediments from the eastern Mediterranean coast of Turkey☆

Abstract Residues of DDE, DDT and PCBs were determined in four different commercial bony fishes: grey mullet, red mullet, striped mullet and gold bandgoat fish, as well as in shrimps, limpets and sediments obtained from the eastern Mediterranean coast of Turkey. The PCB levels in living organisms and sediments were found to be very low, and in most cases below the detection limits. The DDE and DDT values were relatively high compared to PCBs and there was a linear correlation between the organochlorine residue concentrations and the extractable organic material of the analysed samples.

Elemental composition of seston and nutrient dynamics in the Sea of Marmara

The Sea of Marmara, an intercontinental basin with shallow and narrow straits, connects the Black and Mediterranean Seas. Data obtained during 1991–1996 have permitted the determination of the elemental composition of seston in the euphotic zone and the N: P ratio of the subhalocline waters of the Marmara Sea. Since primary production is always limited to the less saline upper layer (15–20 m), of the Marmara Sea, the subhalocline waters of Mediteranean origin are always rich in nutrients (NO3 + NO2 = 8–10 µm, PO4 = 0.8–1.2 µm) but depleted in dissolved oxygen (30–50 µm) throughout the basin, yielding an - 02: N: P ratio of 178: 9: 1. Pollution of the surface waters since the 60s has modified the subhalocline nutrient chemistry slightly. In the euphotic zone, the N: P ratio of the seston changes from 5.9 to 9.5 between the less and more productive periods. Though the biology of the Marmara has changed significantly during the previous two decades, the close relationship observed between the elemental composition of the surface seston and the NO3: PO4 ratio of the subhalocline waters strongly suggests that during the whole year primary production throughout the basin and POM export to the lower layer remain nitrogen-limited. This suggestion needs to be confirmed by bio-assays, biological studies and sediment trap data from the upper subhalocline depths. Nonetheless, the counterflows in the Marmara basin possess relatively low N: P ratios in both dissolved and particulate nutrients and extend as far as the adjacent seas.

Variations in the Vertical Structure of Water Chemistry within the Three Hydrodynamically Different Regions of the Black Sea

High-resolution, basin-wide chemical data reveal that the Black Sea upper layer possesses distinct chemical features at specific density surfaces, but with some noticeable regional differences in their positions and magnitudes. The nitracline, is consistently established at smaller density surface relative to the phosphocline over the basin; thus, N:P molar ratios appear to be unexpectedly high (40–80) within the upper nutricline, especially in the anticyclonic regions (ACR). The ratio drops to levels of 4–8 at the nitrate maxima formed within the base of the main oxycline. Phosphate profiles display a prominent minimum within the suboxic zone of the cyclonic regions (CR), which weakens markedly within the coastal regions and rim current. Vertical distributions of chemical ratios have led to valuable information on the relative fluxes in the oxic/anoxic transition zone as well as the quality of data sets from different years.

Abundance and Elemental Composition of Particulate Matter in the Upper Layer of Northeastern Mediterranean

Suspended particulate (POC PON, PP) profiles obtained in 1991-1994 indicate the existence of characteristic subsurface maxima near the base of the euphotic zone in the cyclonic Rhodes gyre and its peripheral waters in the Northeastern Mediterranean. Interestingly the N:P of the bulk seston was reasonable during stratification seasons when the surface water was relatively poor in phosphate; but the ratio was unexpectedly low (N:P=6-12) in the late winter of 1992 when the surface layer of Rhodes gyre was occupied with nutrient rich deep waters.

Spatial Isopycnal Analysis of the Main Pycnocline Chemistry of the Black Sea: seasonal and interannual variations

The results of 1991–1994 basin-wide investigations have been analysed using the method of spatial isopycnal analysis. Seasonal and interannual variations of phosphates, nitrates, dissolved oxygen and the suboxic zoneare revised. The range and possible reasons of spatial and temporal variations in the density-dependent vertical profiles of nutrients and oxygen in the layer of the main pycnocline, in the thickness and the position of suboxic zone of the Black Sea are discussed.

Pelagic tar in the Mediterranean Sea

Abstract Floating tar samples were collected, using neuston nets, in 101 stations in the Mediterranean Sea in August–September, 1987, by research vessels of Cyprus, Germany, Israel, and Turkey. The distribution of the tar content indicates that the most tar contaminated sea is in the northeast between Cyprus and Turkey and in the Gulf of Sirte off the coast of Libya, where the mean tar content was 1847 and 6859 μg m−2, respectively. The least polluted areas were the western Mediterranean, 236 μg m−2, and the northern Ionian Sea as far east as halfway between Crete and Cyprus with mean tar concentration of 150 μg m−2. Strongly heterogeneous but overall intermediate mean values of 1347 and 876 μg m−2 were found in the Levantine Basin west and south of Cyprus, respectively. A comparison between pelagic tar data collected in 1969, in 1974 and our data shows a sharp decline in tar concentration with time, from 37,000 μg m−2 in 1969 to 9700 μg m−2 in 1974 and to 1175 μg m−2 in 1987. The geographical distribution of tar may be explained by the severe reduction in the activity of oil terminals in Israel, Lebanon and Syria which causes a reduction in tar content in the southeastern Mediterranean. The increased activity of the oil terminal in Iskenderun Bay, Turkey, and the activity of oil loading at the terminals in Libya still leave a high level of tar pollution in the Mediterranean water off these coasts. However, recent technologies in the oil shipping industry, international conventions on oil pollution of the Mediterranean, and harsher steps to administer the anti pollution laws by various countries in the Mediterranean have caused a general decline of this problem.

Aerosol Nitrate and Non-Sea-Salt Sulfate Over the Eastern Mediterranean

Among the biogenic sources of sulfate aerosols, reduced sulfur gases such as DMS constitute and control a significant fraction of the atmospheric nss-sulfate budget (Charlson et al., 1987, e.g.). Certain species of phytoplankton; particularly the dinoflagellate Phaeocystis pouchetii and the coccolithophore Emiliana huxleyi are known to be important producers of dimethylsulfide (DMS) (Matrai and Keller, 1993, e.g.). Biogenic sulfur, created mainly by seasonal phytoplanktonic activity, could be particularly rich sources in certain regions and dominate the atmospheric sulfur cycle.

The distribution of man-made and naturally produced halocarbons in a double layer flow strait system

The Bosphorus Strait, which connects the Black Sea and Mediterranean Sea via the Marmara Sea, is characterised by two distinct water masses. The upper layer consists of low density Black Sea water (sigma-t 10-11) flowing southward, and it is underlain by high density water (sigma-t >28) of Mediterranean origin flowing northward. The sharp density gradient between the two layers is due to the difference in salinities. Here we report measurements on a suite of low molecular weight halocarbons together with basic hydrographic parameters in the strait. Concentrations of the transient tracers chloroftuorocarbons CFC-11 (CFC13), CFC-113 (CC12FCCIF2) and carbon tetrachloride (CCI4) were highest in the Cold Intermediate Black Sea Water (CIBSW), which is formed in the Black Sea during winter. This layer disappeared within the contraction region of the Bosphorus where a hydraulic jump occurs. The Marmara Sea deep water at the entrance to the Bosphorus Strait carried low amounts of CFCs indicating an equilibrium with the atmosphere 6-11 years earlier. Varying amounts of other halocarbons such as chloroform (CHCI3), dibromomethane (CH2Br2), methyl iodide (CH3I) and chloro-iodomethane (CH2CII) could be used for the identification of water masses of different origin. Around the Bosphorus- Marmara Junction (BMJ) in the Istanbul area, the upper water layer contained elevated levels of most of the halocarbons. This is attributed not only to contamination but also to natural production in the productive eutrophic waters of the region. Methyl iodide and chloro-iodomethane showed elevated concentrations of 0.7~).9 ng/l and 0.4-0.6 ng/l, respectively, in the upper water layer of the BMJ region, and also in near-bottom water at the northern exit of Bosphorus (0.2 and 0.1 ng/l, respectively). Chloroform (23 ng/l) and dibromomethane (10 ng/I) were also found within the pycnocline in the BMJ region and could be traced in a plume stretching northward along the pycnocline. Copyright