Marmara Denizi alt ve üst tabakalarında mesozooplankton dağılımının çevresel faktörlerle ilişkisi


Thesis Type: Postgraduate

Institution Of The Thesis: Istanbul University, Institute Of Graduate Studies In Sciences, Fen Fakültesi Bölümü, Turkey

Approval Date: 2024

Thesis Language: Turkish

Student: MELİSA BOZKURT

Supervisor: Benin Toklu Alıçlı

Abstract:

Zooplankton are an important organisms that are primary consumers in the pelagic ecosystem and provide the association between trophic levels. The distribution and abundance of zooplankters also affects the presence of other organisms in the marine ecosystem. For this reason, it is important to carry out monitoring studies and reveal the current situation. This thesis was conducted to reveal the relationship between the mesozooplankton community structure and environmental variables of the Sea of Marmara, which shows Black Sea and Mediterranean Sea characteristics through the Dardanelles and the Istanbul Strait. This study was conducted within the framework of the "Integrated Marine Pollution Monitoring Program", overseen by the Ministry of Environment, Urbanization, and Climate Change of the Republic of Türkiye and implemented through TÜBİTAK-MAM. The research took place aboard the TÜBİTAK Marmara research vessel during the winter, spring, and summer seasons of the year 2022 at six stations, representing both the upper and lower layers. The study involved plankton sampling with a mesh size of 200 µm using a plankton net at each station, and mesozooplankton samples were collected. Furthermore, measurements of temperature, salinity, dissolved oxygen, pH, Secchi disk depth, chlorophyll-a and photosynthetic active radiation values were determined. As a result of the study, 61 taxon/groups were identified, and the main groups representing the community throughout the sampling periods were Copepoda (35 taxa), Cladocera (5 taxa) and Appendicularia (3 taxa) and their dominance status changed according to the seasons. The total mesozooplankton abundance value was highest (5191 individuals/m3) in the upper layer in spring, and the lowest (56 individuals/m3) was observed in the lower layer in summer. During the study, the most dominant species are Acartia (Acartiura) clausi Giesbrecht, 1889, Centropages typicus Krøyer, 1849, Paracalanus parvus (Claus, 1863), Pleopis polyphemoides (Leuckart, 1859) and Oikopleura (Vexillaria) dioica Fol, 1872. In the study, the Shannon-Weaver diversity index was calculated to reveal the species diversity depending on seasons and stations. Values varied between 1.46–3.98 and higher values were detected in lower layer samples. As a result of the Bray-Curtis cluster analysis performed according to abundance values, it was revealed that the upper and lower layer community structure was differed from each other and it was determined that the summer season was separated from the winter and spring samplings. Redundancy analysis (RDA), one of the linear regression analyzes performed to investigate the association between environmental variables and mesozooplankton distribution, indicates that the most important factors affecting the distribution of mesozooplanktonic organisms are temperature and pH. In the study, one of the dominant species, A. clausi, exhibited a negative correlation with temperature and salinity. With this study, the current mesozooplankton composition in the Sea of Marmara was revealed and it was determined that the community returned to its former state after the intense mucilage event observed in the Sea of Marmara in 202