Neslihan Balkis

Role of single-celled organisms in mucilage formation on the shores of Büyükada Island (the Marmara Sea)

This study was implemented to determine the environmental factors and causative organisms of the recent mucilage formation in the Marmara Sea. Samples were taken during the study from 7 different depths (0.5―30 m) of one sampling point of the Buyukada Island shore between January and June 2008. As a result, 6 2 phytoplankton species belonging to 5 different groups were identified. Dinofiagellates were dominant in terms of species number, and diatoms in terms of cell number. In January and February, mucilage formation was very dense, where 5 phytoplankton species (Clindrotheca closterium, Pseudo-nitzschia sp., Skeletonema costatum, Thalassiosira rotula (Bacillariophyceae) and Gonyaulax fragilis (Dinophyceae)) were reported as dominant organisms. Among them, Gonyaulax fragilis has never been reported in the Marmara Sea previously, thus that organism appeared firstly with the formation of dense mucilage and then when the mucilage decayed in May and June 2008, G. fragilis disappeared. Autofluorescent single-celled organisms were classified in three groups depending on their cell sizes (>20 μm, >2 μm, >o.2 μm) by membrane filtration and total count of bacteria were determined by epifluorescence microscope after dying with DAPI. The highest total bacteria was recorded in April at 25 m depth (66 55 ± 44 . 4 cells ml ―1 ) while the lowest count was in June at 0 . 5 m depth ( 1077 ± 2 6. 1 cells ml ―1 ). The seawater temperature ranged between 7.0 and 21.5°C, salinity between 20 . 9 and 37 . 4 ppt and dissolved oxygen amount between 2 . 75 and 12 . 75 mg l ―1 . The chlorophyll-a amount ranged between 0.10 and 6. 35 μg l ―2 , the higher values were recorded in January at 15 m depth (6.35 μg l ―1 ) and in April at 10 m depth ( 4 .8 9 μg l ―1 ). Among the nutrients, the amounts of nitrite + nitrate-N varied between 0 . 02 and 7 .6 7 μg-at N l ―1 , phosphate-P between 0.11 and 0.96 μg-at P l ―1 and silicate-Si between 0.37 and 8. 93 μg-at Si l ―1 . The highest values were determined at a deeper layer where nutrients are accumulated. On the other hand, the N:P ratio interval was found as 0.1―11.3, Si:P ratio as 2.92―52.33 and N:Si ratio as 0.01―1.10 during the sampling period. Nitrogen was the limiting nutrient and the silica amount was enough to enable the development of diatoms.

The crab species found on the coasts of Gökçeada (Imbroz) Island in the Aegean Sea

In this study, 32 crab species belonging to 13 families are recorded from Gökçeada Island, based on bottom material collected at 39 stations around the island at depths between 0 and 70 m, using dredges, drift nets and scoop nets. Ecological properties of the species are provided.

Evaluation of Ecological Quality Status with the Trophic Index (TRIX) Values in the Coastal Waters of the Gulfs of Erdek and Bandırma in the Marmara Sea

In developing countries, more than 90 percent of wastewater and 70 percent of industrial wastes are discharged into coastal waters without being treated (Creel, 2003). The entry of wastes into marine environment not only changes water quality parameters but also affects benthic organisms, causes habitat change and increases the risk of eutrophication and, thereby, causes the area to become susceptible. The Urban Wastewater Treatment Directive (UWTD; EC, 1991) defines eutrophication as the “enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus, causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned”. Karydis (2009) characterized “oligotrophic” waters as nutrient poor with low productivity, “eutrophic” waters as nutrient rich with high algal biomass and “mesotrophic” waters as moderate conditions. Hypoxia or even anoxia is the last stage of eutrophication (Gray, 1992) and this phase is often characterized as “dystrophic” (Karydis, 2009). In addition, eutrophication of coastal waters has been considered as one of the major threats to the health of marine ecosystems in the last few decades (Andersen et al., 2004; Yang et al., 2008). The risk of eutrophication may increase or decrease depending on the speed and direction of flow and wind. It can occur as a result of natural processes, for example, where there is upwelling of nutrient rich deep water to nutrient poor but light rich surface water of the photic zone of the water column (Jorgensen & Richardson, 1996). Cultural eutrophication arising from anthropogenic activities is particularly evident in marine areas with limited water exchange, and in lagoons, bays and harbours (Crouzet et al., 1999).

Dinoflagellate resting cysts in recent marine sediments from the Gulf of Gemlik (Marmara Sea, Turkey) and seasonal harmful algal blooms

Abstract: Thirty-four dinoflagellate cyst taxa were found in surface sediment (0–2 cm) at five stations (60–100-m water depth) in the Gulf of Gemlik, Marmara Sea, during four seasons from August 2011 to May 2012. Lingulodinium machaerophorum, Operculodinium centrocarpum and Selenopemphix quanta dominated cyst assemblages in the polluted gulf, where nutrient-rich surface water was stratified during most seasons and bottom water was hypoxic. Twelve cyst taxa were incubated and produced motile cells that reproduced and survived 14–15 days. Highest cyst species number (33) occurred in summer; maximum number of cysts (living and empty) per cm3 wet sediment was in spring, with the annual range from 1520 (fall) to 108,000 (spring). Nine taxa (Brigantedinium simplex, L. machaerophorum, O. centrocarpum, S. quanta, Spiniferites mirabilis, Spiniferites ramosus, cysts of Alexandrium sp., Scrippsiella trifida and S. trochoidea) were found in all seasons at all stations. The harmful dinoflagellates L. machaerophorum and cysts of S. trochoidea and Alexandrium sp. were the most abundant species. The cyst of the toxic species, Cochlodinium sp., is reported for the first time from Turkey. Other HAB species included A. tamarense, Protoceratium reticulatum, Heterocapsa triquetra and Gymnodinium catenatum/nolleri. Relative abundance of potentially toxic dinoflagellates (74%–92% of total cysts cm−3) was always higher than nontoxic species, and percentage abundance of cysts cm−3 produced by autotrophs (19/34 total species) almost always exceeded those of heterotrophs. Although distributions of the resting cyst taxa were significantly influenced by surface temperature, dissolved oxygen and total water depth, surface salinity was the strongest predictor for cyst occurrences.

Toxic metal (Pb, Cd and Hg) levels in the nearshore surface sediments from the European and Anotolian Shores of Bosphorus, Turkey.

In this study, some toxic metal such as Pb, Cd and Hg analyzes have been done in the nearshore surface sediments. Sediment samples have been collected from five parts from the European and Anotolian Shores of the Bosphorus during 2003-2004. Total Pb, Cd and Hg contents vary between <0.01 μg g(-1) and 238 μg g(-1); <0.01 μg g(-1) and 0.92 μg g(-1); 0.001 μg g(-1) and 0.45 μg g(-1), respectively. Contamination Factor (CF) values of Pb and Cd range between 1 and 3 whilst CF values of Hg are lower than 1 in all the stations. It means that there are no Hg metal enrichment by natural or anthropogenic inputs contrary to moderately contamination for Pb and Cd metals throughout the Bosphorus sediments.

Assessment of phytoplankton and environmental variables for water quality and trophic state classification in the Gemlik Gulf, Marmara Sea (Turkey)

Phytoplankton assemblages related to environmental factors and ecological status of the Gemlik Gulf were investigated between June 2010 and May 2011. A total 155 phytoplankton species were detected and 6 taxa (Amphisolenia laticincta, Archaeperidinium minutum, Cochlodinium sp., Gynogonadinium aequatoriale, Heterocapsa rotundata and Metaphalacroma sp.) were new records for the Turkish Seas. The lowest and highest total phytoplankton abundance among the sampling units (depths) was recorded in April 2011 (7.4×103cellsL-1) and July 2010 (251.8×103cellsL-1). Local small patches of visible red tide events were detected especially in the gulf, although a phytoplankton bloom was not observed. The water column was well stratified in the early autumn and well mixed in the early spring according to stratification index values. Surface nutrient concentrations increased especially at stations located inside of the gulf. The limiting effect of silicate was observed in early, mid-summer and early winter periods while the nitrogen was the limiting nutrient in the gulf during the whole sampling period. In the Gulf, low water quality-high mesotrophic and bad water quality-eutrophic status, high quality and low trophic level were generally detected according to Chl a, dissolved oxygen and trophic index. However, indices developed to determine the trophic level and water quality of the Mediterranean Sea can give unexpected results about the current environmental quality status when it is applied to the Marmara Sea which has limited photic zone by the halocline-pycnocline and thermocline.