One of the most important indicators of environmental status is the amount of dissolved oxygen. In terms of ecosystem health, it is known that the dissolved oxygen levels in the intermediate and bottom layers is about 4-5 mg/L. The gradual decrease of oxygen in the bottom waters (in deep bottom waters and in the bottom/soil waters of the gulfs) increases the risk of the extinction of life and the formation of hydrogen sulfide.
The Ministry of Environment, Urbanization and Climate Change, Department of Laboratory Measurement and Monitoring, carries out the “Integrated Marine Pollution Monitoring
Program” in cooperation with TUBITAK Marmara Research Center. Under the program, studies are conducted to monitor pollution and marine quality using various indicators in allTurkish seas—the Black Sea, the Sea of Marmara and the straits, the Mediterranean Sea, and the Aegean Sea.
In the Mediterranean Sea, the oxygen saturation of the surface water in summer is percent 97–112, and the concentration values ranged between 4.20 and 8.33 mg/L(Graph 70).
The dissolved oxygen values measured in coastal and open surface waters of the Aegean Sea were generally in the range of percent 95-115 in both sampling periods. DO values changed in the range of 5.5-9.88 mg/L in the winter period and between 4.1-8.0 mg/L in the summer period, with an average value of 6.9 mg/L. Values at depths >200 m varied between 4.6 and 8.3 mg/L (Graph 71).
Saturated dissolved oxygen (DO) values in the Black Sea were generally measured in the range of percent 95-percent 115 between 2014 and 2019 (Graph 72).
Due to the bi-layered structure constantly present in the Sea of Marmara, the oxygen- saturated upper layer waters cannot reach the lower layer due to the interlayer barrier so that a lowoxygen content is observed in the lowerwater. However, the living and non- living organic matter that increases in surface waters with the increase of terrestrial input collapses over time and becomes trapped in the intermediate layer, and when it is degraded by heterotrophs, the oxygen in the environment is consumed and hypoxic conditions are formed. In all time periods, the dissolved oxygen saturation levels in
One of the most important indicators of environmental status is the amount of dissolved oxygen. In terms of ecosystem health, it is known that the dissolved oxygen levels in the intermediate and bottom layers is about 4-5 mg/L. The gradual decrease of oxygen in the bottom waters (in deep bottom waters and in the bottom/soil waters of the gulfs) increases the risk of the extinction of life and the formation of hydrogen sulfide.
The Ministry of Environment, Urbanization and Climate Change, Department of Laboratory Measurement and Monitoring, carries out the “Integrated Marine Pollution Monitoring
Program” in cooperation with TUBITAK Marmara Research Center. Under the program, studies are conducted to monitor pollution and marine quality using various indicators in allTurkish seas—the Black Sea, the Sea of Marmara and the straits, the Mediterranean Sea, and the Aegean Sea.
In the Mediterranean Sea, the oxygen saturation of the surface water in summer is percent 97– percent 112, and the concentration values ranged between 4.20 and 8.33 mg/L(Graph 70).
The dissolved oxygen values measured in coastal and open surface waters of the Aegean Sea were generally in the range of percent 95- percent 115 in both sampling periods. DO values changed in the range of 5.5-9.88 mg/L in the winter period and between 4.1-8.0 mg/L in the summer period, with an average value of 6.9 mg/L. Values at depths >200 m varied between 4.6 and 8.3 mg/L (Graph 71).
Saturated dissolved oxygen (DO) values in the Black Sea were generally measured in the range of percent 95- percent 115 between 2014 and 2019 (Graph 72).
Due to the bi-layered structure constantly present in the Sea of Marmara, the oxygen- saturated upper layer waters cannot reach the lower layer due to the interlayer barrier so that a lowoxygen content is observed in the lowerwater. However, the living and non- living organic matter that increases in surface waters with the increase of terrestrial input collapses over time and becomes trapped in the intermediate layer, and when it is degraded by heterotrophs, the oxygen in the environment is consumed and hypoxic conditions are formed. In all time periods, the dissolved oxygen saturation levels in surface waters of the WMUs in the Sea of Marmara (0-10 m average) were generally varied between percent 90 and percent 110 (Graph 73).
GRAPH 70- DISSOLVED OXYGEN VALUES AND PERCENTAGE VALUES IN THE MEDITERRANEAN SEA BETWEEN 2014-2019
GRAPH 71- DISSOLVED OXGYEN VALUES AND PERCENTAGES IN THE EAGEAN SEA BETWEEN 2014-2019
GRAPH 72- PERCENTAGE OF DISSOLVED OXYGEN IN THE BLACK SEA BETWEEN 2014-2019
GRAPH 73- PERCENTAGE OF DISSOLVED OXYGEN IN THE SEA OF MARMARA BETWEEN 2014- 2019
Source: MOEUCC-DG for EIA, Permitting and Inspection and TÜBİTAK-MAM (2019). Integrated Pollution Monitoring Project (2017-2019). ÇTÜE 5178702, Report No. ÇTÜE.17.2116 (Marmara Sea Final Report, 2019), February 2019, Gebze-Kocaeli.
