Fixing eutrophication!!! What inspired you to want to do this, it sounds so very interesting ! I've read that in some places, eutrophication is a natural process, but it has been amplified by human interference
Very simple answer: I love the ocean and rivers and the deadzone needs to be fixed. The places I visited and had so much joy in as a child are changing very quickly. The rivers I swam and fished in now have algae problems and are warmer, the lakes I swam in are almost completely unsafe for human swimming, and the ocean, my beloved... I can feel it on my skin and in the stones when I visit. There is less there, when diving and fishing and even in the tide pools out west. There is less life in her and it genuinely fucks me up. I wanna have kids, and I wanna share these things with them. As it is now, they won't know because of what is being done.
And yes, absolutely eutriphication is a natural process. But it usually it takes hundreds of year or longer, as it happens on a geological time scale. It's not supposed to happen within half a human life span. Not at all this quick. I know people say oh but the rivers used to be on fire and there was x pollution. Like bruh it ain't on fire but man this invisible slow shit is way more insidious.