Our local river has a small dam about 15 river miles upstream from the ocean. From time to time what looks like dirty detergent foam appears just downstream of the dam. I seem to recall a newspaper article that says its naturally occurring and protein based. What exactly is this stuff? Why isn’t it constant? Is it somehow connected to air/water temps? If its protein, where is it coming from?It happens in the dead of winter (New Jersey) as well as the summer. The water, while having four foot tide changes below the dam, is considered fresh water. FWIW, there are a lot of blueberry farms upstream but the river itself is supposed to be pretty clean (for NJ, that is).
I don’t recall, but there’s a diorama in the American Museum of Natural History that shows such foaming, and corroborates that it can happen naturally. IIRC, it was in the “Man and Nature” exhibit, the Warburg Memorial, which dates back to the 1950s. Unfortunately, I can’t recall what they said was responsible.
Of course, you can also get foaming from man-made pollutants as well. But there’s also a natural phenomenon.
Depends on the river, however:
Occurrence of Stable Foam in the Upper Rhine River Caused by Plant-Derived Surfactants
Even in winter, plant products get washed out of the soil and into the water.
Happens in the seas and oceans, too. I’ve often seen it in the North Sea.
I’ve seen this on the Tahquamenon River, in Michigan’s Upper Peninsula. The water has a lot of tannin in it, due to the types of trees that make up the local forest. Consequently, the water is distinctly brown and foams when it goes over the Tahquamenon Falls. It’s completely natural, albeit a little gross looking.
You know what else is natural and protein-based? Poop. Just sayin’.
There’s a great deal of this stuff featured in a wonderful old movie I used to show my classes, “The Rise And Fall of The Great Lakes,” which was shot on, yep, the Great Lakes. It was used as evidence of pollution, but as we’re learning here, it may not have been precisely that.
I saw a river once up in Canada, north of the Great Lakes, that was called “Root Beer River”, because the water itself was the exact same shade of brown as root beer (due to tannins), and it had foam on top of it that looked just like the foam from a root beer float.
This is what I came in to say as well. I think the turbulence of the water is a major factor. So maybe you see it in the river when they are letting the water out and currents are faster?