Organic Oil
Indigenous
Microbial process
Surface sheen
Certain anaerobic bacteria derive their energy by oxidizing dissolved ferrous iron, producing thin-film interference color patterns on still swamp water.
“The rainbow sheens found as a thin film on top of pooled water in swamps and marshes are the result of natural oils released by decaying vegetation or the biological processes of anaerobic bacteria reducing iron in soil.” – Jeff Ripple