Görüneni̇n Ötesi̇nde: Mi̇kroplasti̇k, Çözünmüş Organi̇k Karbon Ve Sicakliğin Bakteri̇ Ve Si̇li̇yatlar Üzeri̇ne Etki̇si̇ni̇n İncelenmesi̇

Shallow lake ecosystems face multiple stressors, including microplastic (MP) pollution, allochthonous dissolved organic matter (allo-DOM or tDOM) inputs, and the impact of climate change on water temperature. With the aim of investigating these human-induced and climate-driven impacts, this thesis discusses the indirect effects of microplastics on ciliates within a trophic cascade, the influence of pulsed allo-DOM with varying qualities on planktonic communities, and the combined effects of warming and terrestrial dissolved organic carbon (tDOC) on bacteria and ciliate dynamics. Through the use of mesocosm experiments, following conclusions were reached. For MP, larger particles were found to influence ciliate biomass and diversity by releasing them from crustacean zooplankton grazing. The allo-DOM experiment revealed that the quality of allo-DOM significantly regulated microbial community biomass and composition, with nonlinear responses (biomass increase followed by a decrease) in bacteria and ciliate dynamics. Lastly, the combined warming and tDOC experiment exhibited complex, non-linear responses in bacteria and ciliate communities where the impacts of tDOC dominated warming impacts on the overall response. Findings of this thesis contribute to a more comprehensive understanding of the complex interplay between anthropogenic influences and natural stressors in aquatic environments to which bacteria and ciliates were quite responsive, informing future research directions and management strategies.