Effects of physico-chemical properties of Çanakkale strait, Gemlik bay and İzmit bay on biochemical properties and aquaculture potential of Ulva rigida C. Agardh, 1823

This research project was supported by the Yalova University Scientific Research Projects (BAP) Coordination Unit with the project budget numbered 2021/YL/0012. Ulva rigida, one of the green macroalgae, is a species classified in the Ulvaceae family, which includes nearly 100 algae species. It spreads in sublittoral regions rich in phosphate and nitrogen in the marine ecosystem. In this study, physico-chemical analyzes of marine water required for cultivation of Ulva rigida and changes in nutrient composition of macroalgae samples were investigated seasonally. The protein content of Ulva rigida collected from the three designated stations was found to be between 15.01% and 25.97% in winter. Ulva, which is collected from the sea water temperatures of 22 °C and 23 °C from the Gulf of Izmit and the Gulf of Gemlik in summer, contains 8.61% and 8.77% dry matter, respectively, and is 9.3 °C and 9 °C in winter. The effect of temperature on dry matter was determined by the fact that approximately 2 times more dry matter was obtained with 18.33% and 15.47%, respectively. While the amount of chlorophyll-a in the Çanakkale Strait and Gemlik Bay stations was 0.8% in the winter season, it was determined that the amount decreased by 88% in the summer season. According to the correlation analyses, it was concluded that the nitrate amount in seawater has a high negative effect on the chlorophyll-a amount of Ulva and that nitrate between 0.7 mg/L and 1.4 mg/L is sufficient for synthesizing a high amount of chlorophyll-a. In this thesis study, when dry matter, protein, oil, ash and chlorophyll -a values were evaluated together, it was concluded that the most ideal station is the Gulf of Izmit and yields can be obtained in winter. While it was concluded that nitrate deficiency increased the amount of oil, it was found that the nitrate detected in the winter season at the stations determined for dry matter, chlorophyll-a and protein values was sufficient. The excessive amount of compounds such as nitrate and phosphate mixed with the seas with anthropological effects is an indicator of pollution. It has been concluded that if Ulva rigida, which uses phosphate and nitrate as nutrients, is grown at sampling stations, it is possible to reduce the negative effects of these polluting factors and to convert them into organic and inorganic compounds that will contribute to industrial efficiency. In this thesis, seasonal nutrient composition of Ulva rigida, seasonal physico-chemical structure of sea water, protein, oil, ash, chlorophyll and dry matter content were revealed. Ulva rigida has a potential to be used in the food and feed sector with the protein and oil it contains, in the agriculture sector as a natural fertilizer enrichment considering the ash values, and in the food, cosmetics, medicine and pharmacy sectors with its chlorophyll content, and the development of research and applications is recommended for a sustainable ecosystem. Keywords: Ulva rigida, Aquaculture, Macroalgae, Biochemical Composition, Marmara Sea