The Seamap Australia Substratum Component describes to the surface of any non-living material upon or within which biota can attach and grow. This typically consists of natural rock or mineral sediment, but also organic debris, man-made surfaces, and non-living biota (e.g. shells). In some cases, e.g. soft sediments or veneers, habitats may extend below the surface. In these situations Seamap Australia considers the uppermost 15 centimetres of the substratum
The Substratum Component can be paired with the Substratum Origin to give 8 total levels describing the non-living component of the seabed habitat. The Substratum Component describes the hardness and grainsize of the substratum, while the Substratum Origin describes the geologic of the substratum.
Level 4 subgroups
Level 4 subgroups further break down the Level 3 substratum classification into mineral grainsize. Descriptions and images of Level 4 classifications are embedded within Level 3 items in the Substratum Component Visual Classification Guide.
Unknown, or Not Assessed
An Unknown, or Not Assessed classification can be applied at any level within the hierarchy.