What’s a microbial mat

 A microbial mat is a multi-layered sheet composed of different types of microbes, mainly bacteria and archaea, and sometimes also including eukaryotes like algae. These mats are often found in extreme environments like hot springs, hypersaline environments, and areas with low oxygen levels, but they can also be found in more common places like wetlands and at the bottom of shallow water bodies.

The layers within microbial mats are structured according to the different types of microorganisms and their functions. The top layer is typically populated by photosynthetic organisms, such as cyanobacteria (which are also called blue-green algae, although they are bacteria). Below this layer, there might be a layer of an oxygenic photosynthetic bacteria that do not produce oxygen, followed by a layer of microbes that consume organic compounds, and further down, other microbes that are involved in processes such as sulfate reduction or methanogenesis.