If you’re out exploring nature and you find water with an oily sheen on it, the Michigan Department of Natural Resources wants you to poke it with a stick.
How it reacts when you poke it can let you know if it formed because of a natural bacterial process or not. If it shatters, it’s likely natural. If it clings together, take a picture, note your location and report it.
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If you can’t find a stick, you can drop a rock into the water. A bacterial sheen will break into small platelets when disturbed and a petroleum sheen will reform. Another way to tell is by smell. Natural sheens won’t smell like petroleum.
Some bacteria that live in waterlogged places get energy from iron and manganese. The bacteria are harmless. As the bacteria grow and decompose, the iron may appear oily or form red or orange films, fluffs and coatings, according to the Huron River Watershed Council. The bacteria can also excrete manganese, which looks like black slime.
The breakdown of organic matter can also create an oily sheen on the water surface. In the spring and summer, a dark cloud in the water accompanied by an oily sheen could be the outer skeletons of insect cases. As the skins decompose, an oily film sometimes forms on the surface of the water. A diatom bloom can also leave oil behind as the algal cells die.
Click here to learn more about identifying oil sheens from the Department of Environmental Protection.
How to make a report to EGLE
To report spills, releases or other environmental emergencies involving air, land, water, groundwater, wetlands, dams, landfills, hazardous or radioactive materials, mines, public drinking water, oil and gas wells, nuclear power plants: Call the EGLE (PEAS) hotline at 800-292-4706.
Many incidents that are reportable to EGLE should also be reported to the federal National Response Center by calling 800-424-8802.
If your situation is not an emergency, but you have a question you can call the Environmental Assistance Center here 800-662-9278.