Paleoclimatological and paleoecological interpretations of Nacella concinna species through stable isotope analysis, Horseshoe Island, Antarctica
Simsek, S. (2026). Paleoclimatological and paleoecological interpretations of Nacella concinna species through stable isotope analysis, Horseshoe Island, Antarctica. MSc Thesis. Middle East Technical University: Ankara. 151 pp.
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Document type: Dissertation
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| Keyword |
Nacella concinna (Strebel, 1908) [WoRMS]
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| Author keywords |
Sclerochronology, Paleotemperature, Paleoecology, Horseshoe Island, Antarctica |
| Abstract |
This thesis presents the first sclerochronological and stable isotope (δ¹⁸O and δ¹³C) study of the patelloid gastropod Nacella concinna within the framework of Turkish academic literature. Eight samples collected from Horseshoe Island (northwest of the Antarctic Peninsula) during the Second National Antarctic Scientific Expedition (TAE-II) were analyzed to assess the species' potential as a high-resolution proxy for local paleoclimatic and paleoecological conditions. A two-step methodological approach consisting of the microscopic analysis of growth dynamics and macroscopic sampling for isotope profiling was employed in the study. Sclerochronological results confirmed the presence of annual growth rings, with dark (brown) bands corresponding to rapid summer growth and light (cream) bands reflecting slower winter accumulation. Individual anomalies, band thinning in the late life stage, and pearly-grey zones indicated the ecological stress on the life cycle of organisms. Age determination was made based on growth bands and constrained using the known collection dates of the specimens, allowing backward age estimation from the time of sampling. These age estimates were further supported by growth parameters derived from the Von Bertalanffy Growth Function (VBGF). Two different paleotemperature equations and four different δ¹⁸Ow scenarios were used to reconstruct paleotemperatures. Shell δ¹⁸O and δ¹³C values were compared with sea surface temperatures (SST) at Rothera and Palmer stations. Furthermore, temperatures calculated using δ¹⁸Ow values from Zachos showed similar trends to global SST trends. This study confirms that Nacella concinna shells are a reliable biological archive for the Antarctic Peninsula. In addition, this study establishes a fundamental methodology for future sclerochronological studies in Turkey and provides preliminary evidence for the applicability of instrumental analysis for element mapping on the shell in future studies. |
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