Not only Baltic Sea is really, really small and shallow sea with small circulation of water, but also it is one of the (or the most depending on source) dirties

Not only Baltic Sea is really, really small and shallow sea with small circulation of water, but also it is one of the (or the most depending on source) dirtiest one. There are huge projects to return sea life to it - and now with chemical waste leaking all this can be pointless. Also Baltic Sea is important for fishing industry for some countries - so there is huge danger of getting heavy metals etc getting in to food circulation and causing long term effects on whole populations.