Browsing by Author "Kalkan, Evrim."

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    Investigating the role of the Turkish straits system as a phylogeographical break in the mediterranean - black sea transition
    (Thesis (Ph.D.) - Bogazici University. Institute of Environmental Sciences, 2013., 2013.) Kalkan, Evrim.; Bilgin, İbrahim Raşit.; Bekbölet, Miray.
    Understanding the allopatric isolation and evolutionary processes in the marine realm can be difficult due to high dispersal potential of pelagic larvae. In addition, the role of barriers in shaping gene flow patterns between the populations of marine species can be less pronounced than their terrestrial counterparts. Straits are such potential barriers to gene flow in the marine environment, resulting in the isolation of populations on either side. The Turkish Straits System, comprising two straits (the Dardanelles and the Bosphorus Strait) and the Sea of Marmara forms the only connection between the Black Sea and the Mediterranean, and is a unique ecosystem with a well-defined two-layered stratification and current regime. The role of Turkish Straits System on gene flow, as a barrier and/or corridor has been proposed, but not extensively tested using genetics. Here, using three regions of mitochondrial DNA (CO1, COIII and 16S) and five microsatellite markers I tried to understand the effect of the system on gene flow in populations of the Mediterranean Mussel, Mytilus galloprovincialis (Lamarck, 1819), the common European prawn, Palaemon elegans Rathke, 1837 and the marbled crab, Pachygrapsus marmoratus (Fabricius, 1787). With this study, individuals belonging to three species were collected from 42 sampling sites, encompassing the Black Sea, the Turkish Straits System and the Mediterranean Sea. The results of the mtDNA analyses of Mytilus galloprovincialis showed that the Black Sea populations were isolated and differentiated from those in the Aegean during the last ice age and subsequently were able to colonize the Sea of Marmara and Aegean twice, with larval transport via the surface currents of the Turkish Straits System. However, individuals from the Aegean population were not able to migrate into the Turkish Straits System and the Black Sea in the reverse direction due to the lower-layer currents of the system. Microsatellite analyses did not support the mtDNA differentiation observed among the Black Sea and the Aegean mussel populations, suggesting that they did not correspond to different species. Two different haplogroups were detected in Palaemon elegans as a result of the mtDNA analyses, though with a lower degree of differentiation than previously recorded in the literature. The results of CO1 analysis for Pachygrapsus marmoratus also indicated a weak restriction of gene flow from the Mediterranean to the Black Sea. For all three species, the Turkish Straits System played semi-permeable barrier role to gene flow and dispersal. This semi-permeable characteristic of the Turkish Straits System, simultaneously acting as a barrier and corridor to gene flow is relatively uncommon, and has been documented in the Turkish Straits System for the first time, using genetics methods.
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    The effects of sewage discharges on shallow hard substrate macrozoobenthic communities in the Bosphorus
    (Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2006., 2006.) Kalkan, Evrim.; Bekbölet, Miray.; Mutlu, Erhan.
    In order to determine the pollution effects of sewage discharges on the benthic communities, shallow water hard bottom macrozoobenthic communities were examined along the coasts of the Bosphorus Strait. Samples were collected at 15 stations and environmental parameters measured at 3-month intervals from May 2004 to February 2005. While 9 stations were selected as discharge stations, 6 stations were selected as control stations. A total of 180 samples were collected in May, August and November 2004 and February 2005. Samples were collected from the upper infralittoral zone at dept range 0.5-1m. The analysis of 180 quadrate samples yielded a total of 167537 individuals belonging to 85 taxa. These are distributed qualitatively among the taxonomic groups as follows: Crustacea 50.59% (43 taxa); Polychaeta 21.18% (18 taxa); Mollusca 14.12% (12 taxa); Nemertea 3.53% (3 taxa); Turbellaria 3.53% (3 taxa) and other groups Cnidaria (2 taxa), Oligochaeta (2 taxa), Pycnogonida (1 taxa) and Echinodermata (1 taxa). Individuals, on the other hand, these are distributed among the taxonomic groups quantitatively as follows: Crustacea 43.99% (73919 ind.); Mollusca 37.25% (62258 ind.); Polychaeta 11.06% (18490 ind.); Oligochaeta 5.79% (9681 ind.) and other groups Turbellaria (1899 ind.), Nemertea (799 ind.), Cnidaria (385 ind.), Pycnogonida (121 ind.) and Echinodermata (5 ind.). With regard to qualitative and quantitative dominance, Crustacea was the most important taxonomic group in the area investigated. Various univariate, graphical/distributional, multivariate statistical methods and BENTIX index were employed to analyze the data collected from the study area. Analysis of the data revealed clear differences between the sampling sites subjected to sewage discharge and the others. The results suggested that the benthic ecosystem was more or less disturbed in stations subjected to sewage. The typical characteristics of the benthic communities exposed to pollutants such as the prevalence and high dominance of the opportunistic species, low number of species, low diversity and multi-metric benthic index scores and low total faunal abundance were encountered in most of these stations. On the contrary, it could be said that benthic communities was appeared to be healthier in stations non exposed to sewage, characterized by the high number of species, high total faunal abundance, high diversity and multi-metric benthic index scores. It can be construed that the effects of pollution on these communities was quite low. There is now almost adequate information about the effects of sewage discharges on shallow water hard substratum macrozoobenthic communities, although open questions. The present work has also provided a base for further biomonitoring studies.