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Paardevlei Wetland Black, Smelly Mud

While netting for frog and insects, there was the BIG question – “Why black and why the smell?”


Wallowing in Paardevlei MUD

When dead organic material settles to the bottom and it loses the dissolved oxygen around it. It turns black and smelly (anoxic / anerobic). Marshes and mudflats are super-productive biomes, filled with plants and animals both aquatic and terrestrial.

Eventually, all those living things must die.


Handful of Paardevlei marsh MUD

This is when the decomposers come in to play. Tons of organic matter ends up buried in the mud, and the microorganisms go to town on it. Mud is a low-oxygen, or hypoxic, environment. These bacteria are called sulfate-reducing bacteria. Unlike most living things, they don’t use airborne oxygen (O2) for respiration. Instead, they use sulfate (SO4), which is a molecule made of sulfur bonded with oxygen. This makes them able to live where most bacteria can’t (in super low-oxygen environments like a mudflat like Paardevlei Wetland) and break down matter in the absence of oxygen.

Just like other organisms, these bacteria produce a waste product when they “breathe,” but it’s not carbon dioxide (CO2) it’s hydrogen sulfide (H2S). This produces that rotten egg smell.

So now you know a little more about the Paardevlei Wetland Black, Smelly Mud!

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