Okay notes that the Bosporus is significant both because it is an international waterway through which 50,000 vessels pass each year and because it is an important aquatic habitat that merges the Mediterranean and Black Sea ecosystems. Okay explains that the surface flow in the strait comes from the Black Sea, while water from the Mediterranean remains under the surface and says: "It is already known that the surface flow from the Black Sea is polluted by rivers that flow through the northwestern coastal area, particularly the Danube. The surface flow coming from the Black Sea is the most important potential pollutant of the strait ecosystem. The second source of pollution is vessel traffic through the strait. Annually, 50,000 vessels travel through the strait. Vessel-based pollution includes discharge of oil, wastewater, exhaust and contaminated waste.
The local ferries traveling within the strait and vehicle exhaust from cars on both sides of the strait, which is washed down into the strait by rain, are other major sources of pollution, according to Okay. The use of chemicals to prevent the growth of organisms on the underwater parts of ships has also been detrimental to water quality in the strait.
Okay took samples at 23 stations installed around the strait starting from the Black Sea inlet, relying on sediment and oysters for her measurements. Oysters are good indicators of the level of pollution in a certain area because they accumulate pollutants in their tissues. Okay summarizes her findings as follows: "There is extensive pollution starting in Büyükdere through Beşiktaş, particularly in İstinye. Likewise, the Kandilli-Kuzguncuk line on the Asian side suffers from growing chemical pollution because of heavy sea traffic. The İstinye area, which hosted a shipyard until 1991, particularly suffers from abject conditions under which even oysters, which have a high tolerance for pollution, cannot live. We considered the Büyükada stations reference points for our study of the strait, but we found extremely dangerous chemicals in the samples we picked from the beach."
In regards to measures that could be taken to deal with pollution, Okay suggests that vessels passing through the strait should be inspected. Okay also says warnings should be placed in conta-minated areas discouraging people from collecting oysters, which may be dangerous for human health.