|Biotic Setting||Benthic/Attached Biota
|Biotic Class||Microbial Communities
|Biotic Subclass||Structure Forming Microbes
Mat/Film Forming Microbes
|Definition||Areas dominated by colonies of microscopic or single-celled organisms that form a
hard structure, visible film, layer, or mat on or near the surface of the substrate.
Colonies may be composed of benthic microalgae (e.g., diatoms), photosynthetic bacteria
(e.g., cyanobacteria), archaea, saprotrophic bacteria (e.g., decomposers or decay
organisms), chemoautotrophic bacteria, or other microbial groups. These features may
exist on or near the surface of the sediment either subtidally or subaerially (Figure
8.12), or they may exist as extensive areas of decay associated with dead organisms
that have fallen to the seafloor (Figure 8.13).
Note: There may be high levels of biotic diversity within microbial mats. Microbial mats are often encountered in extreme environments where grazing pressure from multi-cellular organisms is reduced; for example, they can be observed in the high intertidal zone, in areas of low dissolved oxygen, and in deep-sea areas around thermal vents.