This. Inflows of saline water from the North Sea are important for the ecology of the Baltic Sea. The sea is naturally low in salinity due to its shallowness and the relatively large influx of fresh water from rivers. More saline water only gets into the sea via the straits from the Atlantic.

Apparently, the pulses that bring in saline water (along with more oxygen-rich water) into the Baltic Sea have been getting less frequent in recent decades. They still happen, though.

It seems outlandish that anybody would write about such an idea (or the damming of the Baltic Sea part of it) without even mentioning that. It sounds like a crazy engineering idea with no real regard for side effects.

Particularly, it hinders the migration of pipeline hungry diver populations!

I mean do we care about the ecology now?