The Gulf of Finland is the easternmost part of the Baltic Sea. Great volumes of fresh water flow into the Gulf of Finland via various rivers. The largest of these rivers, i.e. the Neva, Kymijoki, Narva, and the Luga, flow to the eastern parts of the Gulf of Finland; towards the east, water in the Gulf of Finland is indeed very low in salt, and at the very end of the Gulf of Finland, in the vicinity of St. Petersburg, it is almost fresh.
For quite some time, the Gulf of Finland has suffered from eutrophication caused by excessive nutrient loads. Through the cooperation of the countries that surround the Gulf of Finland, efforts have been made to improve its water quality ever since the 1990s. From 2005 to 2011, in a joint project of the John Nurminen Foundation and the St. Petersburg water utility, phosphorus removal was made more efficient at the city’s largest wastewater treatment plants, which are also the largest in the entire Baltic Sea. Today, wastewaters from both the inhabitants of this metropolis and the industry are treated to a standard that actually exceeds what is required by the EU.
Reductions in the nutrient load of the Gulf of Finland are evidenced by e.g. clearer waters and reduced volumes of blue-green algae blooms, particularly in the eastern part of the Gulf of Finland. However, the work to reduce nutrient discharges even more must be continued. Marine traffic in the Gulf of Finland is amongst the busiest in the world: in addition to other traffic, as much as up to 25 oil tankers sail the Gulf of Finland daily.