We recently received two separate questions from a couple of members about conditions they saw recently in Middle River. One was about river foam and the other was about white- coated rocks. Read the explanations made by Karen Andersen, Laboratory and Program Director for Friends of the Shenandoah River.

River Foam

"The foam...is most likely naturally occurring, the result of the decay of organic matter that allows air to get trapped in the water column. After undergoing turbulence, water bubbles form creating natural foam and subsequent release of surfactants. Naturally occurring foam won't feel slippery when you rub it between your fingers, and it'll have more of an earthy smell. Natural foam shows up pretty often this time of year, especially when we get a little warm spell and some rain. The foam could also be the result of discharge from a point source such as a wastewater treatment plant or another source of discharge or runoff. Typically, if it's a detergent issue, the foam will feel slippery and likely have an odor.  Brown discoloration is sometimes caused by sediment and/or pollutants mixing in with the foam."

White Rocks

"This could be mineral deposits such as calcium (calcium carbonate) and magnesium.  Another thought is it could be diatoms, a unicellular eukaryotic alga characterized by having a siliceous skeleton. "Frustule" is the hard and porous cell wall or external layer of diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance. Also, it is called 'algae that live in houses made of glass'. When there is a die-off of diatoms, sometimes that silica from their skeleton covers rocks and other materials in the water body."

Thanks, Karen, for the science behind what we see!