Investigation of suboxic and anoxic levels in different regions of the Sea of Marmara

The Sea of Marmara is an important basin that is a part of the Turkish Straits System and remains within the borders of Turkey. It is exposed to terrestrial inputs and pollution due to its location, which is the only sea route connecting the Black Sea to other seas, and being located in a densely populated and highly developed industry. Problems such as deoxygenation caused by this situation lead to the formation of suboxic and anoxic conditions, especially in deep pits and in gulfs where circulation is low. Investigation of these conditions is important in terms of sustainability of marine environments and taking necessary precautions. Therefore, there are critical parameters (pH, dissolved oxygen, total dissolved sulfur, sulfate, redox potential, etc.) that should be monitored and evaluated primarily in the marine environment. The most important of these is the detection of sulfate-reducing bacteria, which will also shed light on the presence of bisulfide and hydrogen sulfide. In this study, suboxic and anoxic levels observed in the Çınarcık Basin (45C) and İzmit Bay (İZ17) regions, which have been followed for many years in the Marmara Sea, were investigated, and at the same time, sulfate-reducing bacteria were detected for the first time in the water column. Suboxic conditions were detected at 45C and İZ17 stations, and it was also determined that anoxic conditions started at the bottom depths at İZ17 station. In these regions, at 45C and İZ17 stations, the highest amount of sulfate-reducing bacteria was determined as 85000 cell/ml and 13300 cell/ml, and the lowest amount was determined as 3000 cell/ml and 20 cell/ml.