Patches of sunlight, green leaves, and blue sky were reflected on the shallow milky water of the pond. Bare branches and twigs draped over and into the pool. A few pine needles and autumn leaves lay motionless on the meniscus. A delicate matrix of dying Mud Water Starwort stems could be seen making abstract patterns just below the shaded surfaces while swathes of something russet and mysterious cloaked the mud.
Jessica's Nature Blog 
Your “something russet and mysterious” is indeed iron that has been oxidized and precipitated out of the water by the iron bacteria. The patches of pale blue film on top of the water—shown in the first and last photograph—are created by Leptothrix discophora, one of the iron-oxidizing bacteria. Other iron bacteria also oxidize iron in the water and are probably present along with the L. discophora on the edges of this pond. The L. discophora bacteria live at the air/water interface, with one end of their rod-shaped bodies in the air and the other end in the water. My guess is that the film keeps the tiny bodies oriented. As the microbes reproduce, they shove parts of the film over and under other parts, so that the film becomes thicker. Various film thicknesses produce various colors by light-wave interference, often resulting in the appearance of an oil slick. I know I’m repeating myself; I hope this isn’t also TMI.
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That is fascinating information, Linda. I agree that the orange coloured material could well be the result of iron oxidising bacteria. I wish I could have had a closer look but the area was fenced off and I had to view from a bridge. I do however have some photographs of something comparable from a freshwater stream on the Oregon coast. I will post them later.
I am not so convinced about the blue areas being a thin surface layer from the bacterial activity. I am familiar with that; and although it cannot be ruled out as a possibility, without a closer examination, I would have to say that the pale blue patches were entirely consistent with patchy reflection of blue sky on the cloudy water. I do have some lovely shots of the iridescent films including pale blue patches from the Yachats beach stream site which I will also post in due course.
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