Akademik Veri Yönetim Sistemi
Tezin Türü: Doktora
Tezin Yürütüldüğü Kurum: Dokuz Eylül Üniversitesi, Fen Bilimleri Enstitüsü, Türkiye
Tezin Onay Tarihi: 2024
Tezin Dili: İngilizce
Öğrenci: BETÜL BARDAKCI ŞENER
Asıl Danışman (Eş Danışmanlı Tezler İçin): Güzel Yücel Gier
Eş Danışman: Eyüp Mümtaz Tıraşın
Özet:
Fish is considered a very healthy food for human consumption. There has, however, been a concern that the fish farms themselves may pose a threat to human health in the sense that they may affect the environment adversely. The benthic region and the water column next to fish farms have been investigated in order to determine any such effect. There was no significant difference in nutrients found between samples taken from fish farms or the water column next to the cages compared to samples taken from more distant reference points. However, because of irregular feeding regimes and currents, those measurements may be inaccurate. In addition to nutrient analysis, phytoplankton was used as a bio-indicator to determine the effects of fish farms on the environment. However, since phytoplankton moves with currents and also gets consumed by predators, the differences in the amounts of phytoplankton near and further away from farms cannot simply be explained as resulting only from nutrient levels released from farms. The aim of this project is to monitor nutrients released from fish farms into the environment by employing bioassays within fish cages and at points positioned gradually away from the cages. 4 bioassays were established after incubation periods. The measured concentrations of nitrite+nitrate, orthophosphate, and silicate in the ambient seawater compared with those inside the bags showed no significant temporal variation and were all within the range typically found in oligotrophic waters. Chlorophyll a concentrations measured in the ambient water were low as in the oligotrophic seas. The estimated growth rates of chlorophyll a concentrations and phytoplankton cell numbers inside the filtered and unfiltered bags were not statistically different. Species richness decreased dramatically after the incubation period in all the bags. Three diatom species, Leptocylindrus danicus, Nitzschia longissimi, and Cylindrotheca closterium, proliferated exponentially inside all bags, exceeding the overall average growth rate. According to results obtained from experiment 3, under continuous nutrient releases from fish farms, high population growth rates can be achieved in oligotrophic environments when phytoplankton losses due to grazing, advection, and sinking are eliminated. According to experiments 2 and 4, with increasing distance from the farm (250m), growth rates decreased due to the decrease in nutrient concentration, and growth was almost not observed at 1000 m.