The marine environment of the Istanbul Strait and Marmara Sea is confronted by severe environmental degradation as a result of ship-originated pollution generated mainly by tankers and cargo vessels. Difficult natural conditions such as the intricate geometry of the Istanbul Strait, sharp turns on the navigation route, harsh meteorological conditions, and transient changes in the flow regime coupled with increasingly dense maritime traffic create a serious risk of accident. Significant amounts of crude oil spill have been the major cause of ecological damage experienced so far as a consequence of maritime accidents. The ecological hazard generated by oil spill has resulted in the decrease and/or extinction of surface and subsurface fish species and crustaceans. Furthermore, bilge, ballast, and wastewater release by vessels contributes to a great extent to marine pollution aggravated by the introduction of exotic species in different accidental ways as a result of heavy maritime traffic through the Istanbul Strait connecting two adjacent basins, namely the Mediterranean and Black Seas.

This review presents the ecological hazard experienced so far based on the results of the monitoring study carried out in the Istanbul Strait and Marmara Sea and highlights the need for the improvement of international regulations for specific waterways such as the Istanbul Strait.