Errr.....no? Human waste in water is a major cause of disease. Sure, a turd or two won't be a problem. And sure, it'll decompose. But all kinds of pathogens remain. There are billions of people, and as the eponymous book says: everyone poops.
People have been pooping for millions of years without filling our oceans with poop. We have been creating new chemicals for a hundred years and have created a huge waste problem. The last time pooping had a big impact on the global ecosystem was during the Great Oxygenation Event, afaik.
