Monthly pic April 2014

Iron bacteria film. Canon 5D MKIII, Canon EF 100mm f/2.8 USM Macro, 1/30, f/7.1, iso 3200, tripod.
That’s right: ground breaking technology enabled me to capture LSD induced psychedelic effects as experienced by local renegade hippies. Really? No… but I dare you to find a more colourful scene in nature.

You are looking at an iridescent film on the water surface of a wet dune slack. What you might easily mistake for a fuel spill is actually a biofilm formed by iron bacteria (like Leptothrix discophora). You can tell the difference by breaking up the surface of the film: where a fuel film immediately sticks together again, a biofilm actually fractures into smaller pieces. Such iridescent films are often an indicator for a seepage zone, where groundwater reaches the surface. The bacteria oxidise the dissolved iron (or manganese) from the groundwater, sometimes resulting in a brown ferric oxide covering the soil.

While certainly not ideal when found inside a well, I have not observed these biofilms getting dominant in wet dune slacks. In fact they probably are an important link in the aquatic ecosystem, hosting a multitude of other species, including phytoplankton. Looking at my camera's magnified live view I could see tiny (1mm) creatures moving on top of the film, probably living a psychedelic lifestyle ;)

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