INVESTIGATION OF BACTERIAL COMMUNITY COMPOSITION IN OXIC AND ANOXIC SEDIMENT CORES ALONG REDOX GRADIENTS OF THE BLACK SEA

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2022-5-18

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Esti, Mertcan

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Biogeochemical cycles are essential for the maintenance of life on Earth. However, little is known about the underlying processes, which hinders the estimation of future states of cycles in a changing environment. Microorganisms are essential in biogeochemical cycles by controlling reactions, rates, and products. This study compared bacterial community compositions by amplicon sequencing of V3-V4 regions of the 16S rRNA genes in two sediment cores (oxic vs. anoxic) from the southwestern Black Sea. To understand the interactions between bacterial diversity and environmental parameters, nutrient, organic carbon, and major seawater ions analyses were performed and used in Non-Metric Multidimensional Scaling. Dissolved oxygen was found as the main driver of community composition. However, organic carbon became one of the main drivers of differentiating bacterial diversity after oxygen consumption. While the community composition in deeper sediments were correlated with the concentrations of H2S, NH4+, PO43+, and major ions; the microbial community in the middle and upper sediments were related to more energetic molecules such as NO3-, NO2-, and dFe, SO42-, and TOC. Results show that decreases in oxygen concentration in the water column would change the bacterial community composition through anaerobic metabolisms, producing greenhouse gases. This study suggests that climate change and anthropogenic effects related to the oxygen and carbon cycle will directly affect bacterial communities. The results suggest that sediment bacterial communities should be considered in the climate change models. The Black Sea is a suitable habitat for further analysis to study anaerobic microbial metabolisms. This is one of the first studies investigating the sediment bacteria in the Black Sea to predict the changes in bacterial communities under the redox shift from oxic to the anoxic water column. Also, whole bacterial diversity was analyzed by amplicon sequencing in the Black Sea sediments for the first time without targeting specific groups/metabolisms. This study is also a pioneer in its contribution to the overall biodiversity record in the Turkish seas.

Subject Keywords

black sea bacteria, 16S rRNA, microbial ecology, sediment biogeochemistry, bacterial community composition, microbial oceanography

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https://hdl.handle.net/11511/97404

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Graduate School of Marine Sciences, Thesis

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Citation Formats

M. Esti, “INVESTIGATION OF BACTERIAL COMMUNITY COMPOSITION IN OXIC AND ANOXIC SEDIMENT CORES ALONG REDOX GRADIENTS OF THE BLACK SEA,” M.S. - Master of Science, Middle East Technical University, 2022.