Page 107 - Çevre Şehir İklim İngilizce - Sayı 3

Mustafa Yücel Evrim Kalkan Tezcan, et al.,

Recently, it has been observed that oxygen is depleted below 500 m in the
deep pit, denitrification (nitrogen respiration) increases, with the presence of
traces of hydrogen sulfide, at the level of 3-10 µM. This is quite clear from
the point of environmental sciences. Oxygen input was insufficient for aerobic
refining / oxidation for the degradation of organic matter in the lower waters,
which deposited down from the surface in the eastern part and in the gulf
(ODTÜ-DBE, 2021: 103; Yücel ve diğ., 2021: 268).

MARMOD PHASE I
Upon these assessments on the Marmara Sea The Ministry of Environment,
Urbanism and Climate Change of Türkiye initiated the Marmara Integrated
Modeling System (MARMOD) Project-Phase I studies in 2017 in order to determine
the urgent measures that need to be taken. The most important goal here was to
analyze the interactions of oxygenated waters from the Mediterranean Sea and
nutrient loads from Black Sea and the land at different depth layers by means of
1-dimensional models in Marmara (ÇŞB, ODTÜ-DBE, 2017: 136).
In the scope of MARMOD Project Phase I, historical data was collected as
a result of the cooperation among the institutions and the latest situation was
revealed with the actual data. Compared to the period before 2010, it was
observed that there has been a serious decrease in oxygen in the basins in
the last 15 years. Nutrient loads transported to and from Marmara through
Strait System was also calculated according to the current situation together
with the nutrients flowing into Marmara from the basins, and for the first time,
an integrated model was developed with the national sources, representing
the physical and biogeochemical properties specific to Marmara Sea (ÇŞB,
ODTÜ-DBE, 2017: 136).

MARMOD PHASE I Results

With the MARMOD Phase I results, it was revealed that a rehabilitation
plan covering the entire Marmara Basin is required for the rehabilitation of the
Marmara Sea (ÇŞB, ODTÜ-DBE, 2017: 136). The one-dimensional model was
operated for a period of 6 years for the average conditions of the Marmara
deep basin for the next periods, and it was found that the model simulates
today’s conditions quite well. Accordingly, the average oxygen concentration
under the mixture layer was found as 40 micromolar. Various scenario models
were run to support management plans to reveal that this value may rise
above the critical threshold of 80 µM which is defined as a reference condition
for Marmara deep basin on the basis of historical data and is also considered
to be the lower limit for hypoxia tolerance for high organisms (ÇŞB, ODTÜ-
DBE, 2017: 136).

92 Journal of Environment, Urbanization and Climate