On January 30, 2016, I attended a seminar where Mr Seppo Knuuttila gave a presentation on the state of the the Baltic Sea. He is a Senior Research Scientist at SYKE, the Finnish Environment Institute. His presentation was very clear and I now know (a.o.!) what a pulse of saltwater is and why it is so rare and important for the Gulf of Finland.
The situation is not altogether hopeless: the situation in the Gulf of Finland HAS improved during the last few years. The cities of Helsinki and Espoo are reaching their targets on reducing emission.
Here is an interesting report