The nutrient indicator is a state indicator and is used to show geographic changes in current nutrient concentrations and trends over time. Widespread inputs of nitrogen and phosphorus from urban, industrial, and agricultural areas carried/discharged to the sea can cause eutrophication.
The Laboratory, Measurement and Monitoring Department of the Ministry of Environment and Urbanization, under the coordination of the TUBITAK-Marmara Research Center, has implemented the “Integrated Marine Pollution Monitoring Program.” Under this program, the quality and pollution status of our seas are determined based on various indicators through monitoring studies in the Mediterranean Sea, Aegean Sea, Sea of Marmara, and Black Sea.
The assessment of marine pollution and quality is based on water management units (WMUs). Water management units or coastal water bodies define a surface water section delineated by key surface water characteristics such as physical, hydromorphological, ecological, and pollution analyzes. They are the smallest management units covered by the Water Framework Directive. Concentrations of dissolved inorganic nitrogen (CHIN), silicate (Si), nitrite-nitrate-nitrogen (Nox), and total phosphorus (TP) were assessed in the surface nutrient distribution46.
PO4 and TP levels in Mediterranean coastal waters were relatively high in İskenderun and Mersin Bays, where terrestrial pressures were evident. The highest values were measured in the surface waters of WMU fed by the river discharges (Asi, Ceyhan, Seyhan, Göksu river waters) in winter. The average values of phosphate and TP in the surface waters of the WMU decreased with the seasonal decrease in stream flows in late summer (August), and similar average values were measured in marine areas where terrestrial pressure was weak. The areal distribution of total dissolved inorganic nitrogen (DIN) and the average values of WMUs showed a decreasing trend from İskenderun Bay Region to Marmaris Bay (east-west direction) in the Mediterranean Region, depending on the streamflow. The DIN concentration values in the coastal and open seawaters of Antalya Bay and the Finike region were in accordance with the general characteristics of the eastern Mediterranean in summer and winter. Nox concentrations increased significantly in winter in coastal marine areas affected by the discharges due to the seasonal increase in river discharge and precipitation in winter. This seasonal change is consistent with the high PO4, TP, and low SDD levels measured during the same periods in the WMUs of the eastern region where terrestrial pressures are evident ( Graph 66).
GRAPH 66- 2014-2019 COMPARISON OF MEDITERRANEAN SURFACE WATER NUTRIENT PARAMETERS
Source: MOEUCC-DG for EIA, Permitting and Inspection and TÜBİTAK-MAM (2019). Integrated Pollution Monitoring Project (2017-2019). ÇTÜE 5178702, Report No. ÇTÜE.17.2111 (Mediterranean Final Report, 2019), February 2019, Gebze-Kocaeli.
When the nutrient salt concentrations in the Aegean Sea were assessed seasonally, no significant difference between summer and winter values was observed. However, 2019 values were found to be low in all WMUs. Nox values were observed to be generally below 0.5 µM in both seasons, but concentrations were found to be 2-4 times higher (0.5-2 M), especially in EGE06 (Büyük Menderes River Estuary) and EGE10 (Inner Gulf of İzmir). This situation can be explained by the fact that both WMUs are under the influence of river inflow. In addition, it is assumed that the Inner Gulf of İzmir is under the influence of urban discharges. At the mouth of the Meriç River (EGE16), a strong river influence was observed during the sampling period. At the same time, the surface waters rich in nutrients from the Sea of Marmara were assumed to influence the Dardanelles Strait. All sampling events, including those of 2019, showed that nutrient concentrations in EGE10 were significantly higher than in the other WMUs (Graph 67).
GRAPH 67- 2014-2019 COMPARISON OF AEGEAN SURFACE WATER NUTRIENT PARAMETERS
Source: MOEUCC-DG for EIA, Permitting and Inspection and TÜBİTAK-MAM (2019). Integrated Pollution Monitoring Project (2017-2019). ÇTÜE 5178702, Report No. ÇTÜE.17.2113 (Aegean Sea Final Report, 2019), February 2019,
Gebze-Kocaeli
Although higher values are generally observed in the Black Sea during the winter months, the most striking feature is the high nitrogen and silicate values in the WMU (2,7,10) under the influence of the Sakarya, Kızılırmak, and Yeşilırmak rivers (Graph 68). In addition, high phosphorus values are recorded in KAR08, which is under the influence of Samsun city.
GRAPH 68- 2014-2019 COMPARISON OF BLACK SEA SURFACE WATER NUTRIENT PARAMETERS
Source: MOEUCC-DG for EIA, Permitting and Inspection and TÜBİTAK-MAM (2018). Integrated Pollution Moni- tor¬ing Project (2017-2019). ÇTÜE 5178702, Report No. ÇTÜE.17.2115 (Black Sea Final Report, 2019), February 2019, Gebze-Kocaeli.
It can be observed that nutrient levels in the Sea of Marmara are measured higher in winter than in spring and summer, but there are also differences between years ( Graph 69). All nutrients are at their lowest in spring, indicating that primary producers are consuming them. Phosphorus compounds were measured at the highest level in MAR04 (Gulf of Bandırma) at all seasons, indicating the permanent existence of industrial and domestic pressures. Apart from this, relatively high nitrogen compounds and silicates were detected in the WMUs (1-2-20-21) under the influence of Susurluk and in the Gulf of Izmit (16-17).
GRAPH 69- 2014-2019 COMPARISON OF MARMARA SEA SURFACE WATER NUTRIENT PARAMETERS
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.
