AYBE- İklim ve Deniz Bilimleri Lisansüstü Programı - Yüksek Lisans
Bu koleksiyon için kalıcı URI
Gözat
Son Başvurular
1 - 5 / 48
-
ÖgeComplete mitochondrial phylogeny of palaearctic serotine bats (Genus eptesicus, vespertilionidae, chiroptera)(Graduate School, 2024-07-01)Investigating speciation mechanisms is essential in evolutionary biology studies to understand biodiversity on Earth. As bats are one of the least studied groups of mammals, understanding their taxonomy for designing effective conservation strategies is important. The Serotine bats, which have over 30 species, provide a rich study group due to their wide distribution in various habitats such as forests, urban areas, deserts, and caves. With their insectivorous diet, they play an important role in the population control of insects and thus maintaining ecological balance. The complex evolution of Serotine bats is shaped by geography, environmental changes, and gene flow, providing further research opportunities. Phylogenetic studies conducted on mitochondrial and nuclear genes showed discordance between mitochondrial and nuclear phylogenies. Species identification among Serotine bats is often challenged by introgression events. This study aims to assemble and analyze complete mitochondrial genomes of Palaearctic Serotine bats to understand their phylogenetic relationships and detect possible selection signatures within their mitochondrial genomes. Thirteen samples representing seven species and nine subspecies were assembled, and all 37 mitochondrial genes are annotated. The phylogenetic relationships are inferred using Bayesian and Maximum Likelihood methods. The selection pressure on thirteen protein genes is investigated by calculating DNA polymorphism for each gene and constructing a Bayesian phylogenetic tree. The resulting tree topologies are compared with whole mitochondrial genome phylogeny topologies. On the assembled mitogenomes, all 37 mitochondrial genes, including thirteen protein-coding genes, twenty-two transfer RNAs, two ribosomal RNAs, and one non-coding displacement loop (D-loop), were identified. The resulting analysis shows two main mitochondrial phylogenetic groups: Eastern serotinus-bottae and Western serotinus-nilssonii in the Palaearctic Serotine bats. This result validates previously determined species groups. The selection analysis shows differences in topologies in ND2, ND4L, ND6, and COX3 trees; however, DNA polymorphism statistics fail to validate the analyzed pattern which indicates that the mitochondrial genes might not have a selection among Palaearctic Serotine bat species.
-
ÖgeInvestigation of paleoclimatic and geochemical changes in lake Akgöl(Terme,Samsun)during the late holocene(Graduate School, 2023)In this study Lake Akgöl (Terme, Samsun, Türkiye) sediments are investigated for paleoenvironmental changes during the Late Holocene (<1500 years before present). The lake is located in the Black Sea and is declared a ''Wildlife Protection Area''.The purpose of this thesis is to examine paleoenvironmental changes that impacted the southern Black Sea margin based on a multi-proxy analysis of a 193-cm-long sediment core from Lake Akgöl (Terme, Samsun, Türkiye). Sediment description and analysis were performed in the East Mediterranean Centre for Oceanography and Limnology (EMCOL) Applied Research Center at ITU. Sediment properties that have been measured for a subsequent paleoenvironmental reconstruction include gamma ray density, magnetic susceptibility (MS), grain size composition, total organic carbon (TOC)/total inorganic carbon (TIC), X-ray fluorescence (XRF), and X-ray diffractometry (XRD). The chronology is based on sediment dating using AMS radiocarbon ages.From bottom to top the core indicates following changes based on XRF counting.Between 190-175 cm (~1350-1300 cal. yr BP) high XRF counts of in K, Fe, Si, Mn, and Ti are linked to a high abundance of detrital input. This is also supported by the high presence of fine-to-coarse silt, and fine to medium sandy layers in this interval.Between 175-160 cm (~1300-1200 cal. yr BP) XRF counts of the same elements have low counts.Between 160-140 cm (~1200-800 cal. yr BP) detritus- related XRF counts increase again and are paralleled by low TOC values.Above 130 cm (<800 cal. yr BP) TOC values increase reflecting a higher organic productivity at the site towards modern time. High Ca values in this core part are related to microfossil contents (e.g. ostracods, molluscs) instead of authigenic origin.The XRD analysis of the record shows that the lower core part is dominated by Quartz and Feldspars among others, whereas in the more fine-grained upper part Gypsum and Illite are prominent (among others).
-
ÖgeIdentification Of Antarctic Freshwater Diatom Species Using Microscopic And Molecular Techniques(Avrasya Yer Bilimleri Enstitüsü, 2020-07-22)Because of the great morphological similarity of some diatom species, eDNA method has been the method that was particularly intended to be used in this study. DNAs were successfully isolated from all of the samples. However, the RuBisCO large subunit (rbcL) gene part that is specific to diatoms could be reproduced in polymerase chain reacton (PCR) only in 2020 Horseshoe Island samples. The DNA damage in 2017 and 2019 samples pointed out rapid damage of diatom DNA and highligths the importance of addition of nuclease blockers for right storage conditions of the samples. However, the amount of diatom DNA in the 2020 samples were not in the required amounts necessary for the new generation sequencing (NGS) method. Between the two microscope methods, SEM gave more successful results for morphological species determination compared to light microscope since it allowed higher resolution images that was necessary for detailed viewing of diatom structures. On the other hand, the light microscope offered a longer time and detailed study on the samples. All the images were then combined with SEM images and a common species designation was made. In conclusion, freshwater diatom species in fourteen Antarctic lakes in King George and Horseshoe Island were determined. This study also provided a basis for new studies in the future, and by knowing the diatom species distributions in Antarctic lakes, metabolic models can be used to understand the possible species-specific response to climate change in Antarctica.
-
ÖgeRelation of STT-Based Enso Indices With The Euro-Mediterranean Temperature Variability(Avrasya Yer Bilimleri Enstitüsü, 2020-07-21)El Niño-Southern Oscillation (ENSO) is a climate phenomenon that causes large scaleclimate variability. It is a coupled mode of ocean-atmosphere interaction between sealevel pressure and sea surface temperature fluctuations in the equatorial Pacific. Typically, in order to observe the phenomena, an ENSO index is used, which is formed with sea surface temperature anomalies. Positive (El Niño phase) and negative (La Niña phase) temperature anomaly have different effects on a global scale. SST-based indexes are created by taking the average of four different regions. These regions, fromthe Peruvian shores to the center of equatorial Pacific, are listed as follows: NINO1+2, NINO3, NINO3.4 and NINO4. Indexes can create different oscillations during thesame period. In addition, even they differ in some regions the effect of each index issimilar. According to some studies (e.g. Ziv et al., 2006; Lolis & Türkeş, 2016) negative phase Arctic Oscillation affects temperature, sea level pressure and 500 hPa geopotential height anomalies (z500) of the Euro-Mediterranean region. Sen et al. (2019) mentioned that, in negative phases of AO and ENSO, strengthening East Asian trough pushes the Mediterranean trough towards west. Consequently, a dipole pattern forms over Euro-Mediterranean region. Sen et al. (2019) study suggested that, NINO1+2 index is more effective on dipole pattern, although NINO3.4 is commonly used. In this study, we investigated which ENSO index is more related to the dipole pattern in the Euro-Mediterranean region. Analyses were conducted for boreal winters (December-January-February) of 70 years between 1950-2019. Correlation analysis indicated that NINO1+2 index is better correlated with z500, sea level pressure and surface temperature than the other indices over the Euro- Mediterranean region. In addition, in the La Niña phase, it has a significant relationship with the omega blocking system formed over Europe. According to some studies (Pozo-Vazquez et al., 2001, 2005), the negative (cold) phase of ENSO is compared with positive North Atlantic Oscillation pattern which means that the low pressure on Iceland deepens while the Azores high becomes stronger. As a result of composite analysis, NINO3.4 has been found to form a low pressure center over Iceland and a high pressure center over Azores. The NINO1+2 deepens the East Asian and Mediterranean troughs in the La Niña phase. Moreover, these troughs move westward in the cold phase. Shift of the Mediterranean trough to the west is also associated with negative phases of Arctic Oscillation and NINO1+2. In addition, the strength of the East Asian trough is positively associated with the displacement of the Mediterranean trough. Z500 composite analysis between NINO1+2 and NINO3.4 shows that NINO1+2 is more related with the dipole pattern over Euro-Mediterranean region. Therefore, we recommend use of the NINO12 index in Euro-Mediterranean climate variability studies.
-
ÖgeSebs Modeli Kullanarak Harran Ovası Üzerinde Buharlaşma –Terleme Tahmini(Eurasia Institute of Earth Sciences, 2019-10-01)In recent years, human activity and climate change greatly threaten water resources. Evapotranspiration (ET) is one of the most important components in the water cycle. Estimation of evapotranspiration has always been faced with many uncertainties. Estimating evaporation based on physical and experimental equations is very common. These methods are based on meteorological data whose shortcomings limit the use of these relations. For instance, this information is point-specific and related to meteorological stations. Another uncertainty problem is regional estimation by using statistical methods. Over the past few decades, many studies have been carried out on estimating evapotranspiration using remote sensing technology. One of the methods which are widely used for estimating ET is SEBS algorithm. The SEBS was proposed for estimating fluxes of heat or energy and estimating evaporation fraction [24]. This study aims to estimate ET over the Harran Plain that has the largest agricultural irrigation systems in the Southern Anatolian Project. Evapotranspiration is estimated for 2015. Cloud-free days in each season of 2015 are selected. Results compared with data obtained from TARBIL and evapotranspiration extracted from GLDAS products. TARBIL project gives reference evapotranspiration. For calculating the actual ET from the TARBIL data crop coefficient (Kc) was required. The assumption for estimating Kc is based on cotton plants. Kc for this study considered from 0.35 to 1.3. SEBS shows very good compatibility results with TARBIL data with a 10% error but ET extracted from GLDAS was not in the expected range (0 to 2.7 mm/day). GLDAS generates ET in 0.25-degree (27.5×27.5 km) resolution that it is not enough for relatively small areas like Harran plain while SEBS estimates ET in high resolution (1×1 km). For studies of water management, water budget, land surface fluxes in the area with low vegetation cover and also in large scales GLDAS can be used but in case of our target that it is the estimation of ET in agricultural lands especially in a relatively small area SEBS gives us more accurate and more trustworthy ET.