as vivid red as this one. The comments below your link also suggest photo enhancements. I really don't know but there are some news sites linking this to the earthquakes and who knows what those can dredge up. I mentioned cinnabar as I know it's an ore of mercury. If that is what it was, the net fisherman standing in the water might have made a poor choice. Cinnabar would probably be too heavy to be held in suspension by a lazy river so that wouldn't be probable. That guy didn't seem to be bothered so I'd suspect this isn't a new occurrence there.
say about rivers bursting into flames. The Cuyahoga River which runs through Cleveland did that more than once. That was one of the reasons for the creation of the Environmental Protection Agency.
Fire seems a bit more spectacular, and counter-intuitive as in fire and water than turning orange in an unregulated industrial area.
They were first reported back in the days of the industrial revolution. I don't know if an exact cause was ever determined. We have oil and natural gas wells in Ohio and a fair concentration in the eastern and north-eastern areas such as where that river flows. I suppose stuff can percolate up from below and not just be produced by man.