Evaluation of Marmara Sea Bays in terms of Pressure-Impact Status and Eutrophication

Abstract

Closed or semi-enclosed bays in the Marmara Sea, which have long residence time, can be exposed to eutrophication as a result of organic matter enrichment from land-based pollutants. The Pressure Index method was tested for the first time in this study in order to reveal the pressure exerted by land-based sources on Izmit, Gemlik, Bandırma and Erdek Bays. As a result of the evaluation of the pressures, it was determined that the pressures on Izmit, Gemlik inner and Bandırma Bay were high, whereas Erdek and Gemlik Outer Bays were under moderate pressure. In terms of eutrophication, the nutrient, chlorophyll-a and secchi disk data of the monitoring studies carried out in the bays were compared with the limit values of the “Urban Wastewater Treatment Regulation Sensitive” and “Less Sensitive Areas Declaration and the Surface Water Quality Regulation”. Although there are differences according to the regulations, it has been determined that Izmit, Gemlik (Inner) and Bandırma Bays have eutrophic-hypertrophic conditions, Erdek and Gemlik (Outer) Bays have mesotrophic conditions. There are differences in the results due to the use of different variables and limit values in the evaluation of coastal waters by regulations. In addition to collecting regulations under a single heading, it is recommended to include biological quality elements in the eutrophication assessment.