Strange Stream at Yachats – Part 1

Small stream with iron-oxidising bacteria

Following yesterday’s posting about a pond with a strange orange substance beneath shallow cloudy water, I received a most interesting comment suggesting that the orange colouring might not be decomposing algae as I had initially thought but the result of bacterial activity. Linda Grashoff has a special interest in iron-oxidising bacteria and has written many posts on the subject in her WordPress blog Romancing Reality, and she has written a beautiful and lavishly illustrated book about this fascinating topic. It is called “They Breathe Iron – Artistic and Scientific Encounters with an Ancient Life Form“. She said:

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.

This made me think about another occasion when I had encountered a strange little stream issuing from rocks at Yachats in Oregon on the west coast of America. It possessed a distinct iridescent film, and flowed across green photosynthesising organic matter that in places was coated orange. Bubbles of oxygen were trapped within the ?algae and beneath the film on the surface of the water. The rocks on the beach were rich in iron. The small stream must have been a good example of the activity of iron-oxidising bacteria in action.

This post shows a few photographs from that site – and more will follow tomorrow.

Iridescent film caused by iron-oxidising bacteria

Broken urface film caused by bacterial activity on the surface of a shallow stream

Oxygen bubbles from photosynthetic activity of green algae trapped below a broken surface film caused by bacteria

Oxygen bubbles from algae trapped below a bacterial film

Bubbles with orange iron deposit and bacterial film on the surface of a shallow beach stream

Bacterial film created by iron-oxidising bacterial with trapped oxygen bubbles from photosynthesising algae below.

Hint of Autumn 14

Shallow pond in autumn with dying vegetation and pine nedles

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.

Reflections on the surface of a shallow pond of cloudy water in autumn

View of a shallow murky pond in autumn

Vegetated margins of a shallow pond in autmn sunlight

Shallow murky pond in early autumn

The shallow margin of a pond with cloudy water and reflections on a sunny autumn morning

Decaying aquatic vegetation in a shallow water pond

Hint of Autumn 8

Brown and green acorns in the same cluster on the tree

Some acorns are turning brown as they ripen while most remain green even on the same cluster on this oak tree. Plenty of acorns have already fallen elsewhere despite the early stage of autumn. Many still remain on the woodland floor from last season.