Effects of post-event event effluent on sea fishing

[Scythe13]

I've been thinking of this recently, possibly to the point where it's an unhealthy level of consideration.

There are a few things I'd like to put out and get feedback on.

1. Fish poo, and it's a natural part of the sea cycle. What's to say our poo will be that different?
2. What breaks down fish poo at the moment? Bottom feeders (pardon the pun). Won't they become more plentiful with the increase of effluence? Thus the breakdown of the matter should increase in speed, due to more bottom feeders present. More food means more bottom feeders, means more fish that prey on them, etc.
3. How will the effluent get into the sea? Treatment plants shut down, so are people going to be pooing in rivers or directly into the sea? For me this makes the idea of canals more dangerous than the sea. Not many major cities will be hosting beach poo parties. More likely people will be pooing in the city rivers etc.
4. No running water, so no toilets will be flushing, so why would a shutdown sanitation centre be an issue? No running water means there will be no waste getting to the sewers anyway, so no crap at the sewer centre.
5. People will be more likely to poo in woods, fields etc, than into a stretch of running water, or in the sea. This is a bigger issue in my opinion.
6. Bodies...these will be the bigger problem if there's a major die off. Bodies will be put into stretches of running water and disposed of that way. Many will be burned and buried, but some will be 'flushed' down a river and into the sea. But these bodies will end up no different from the carcass of a whale. Only thing that would concern me then would be AID and HIV in the fish swimming around in the water.

These are my thoughts. I'd love a bit of feedback on this.