Substrate (aquatic environment)

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Substrate is the earthy material that forms or collects at the bottom of an aquatic habitat. It is made of sediments that may consist of:

  • Silt – A loose, granular material with mineral particles 0.5 mm or less in diameter.[1]
  • Clay – A smooth, fine-grained material made of fine particles of hydrous aluminium phyllosilicate minerals (such as kaolinite).[2][3]
  • Mud – A mixture of water with silt, clay, or loam.
  • Sand – Mineral particles between 0.06 and 2 mm in diameter.
  • Granule – Between 2 and 4 mm in diameter.
  • Pebble – Between 4 – 64 mm in diameter.
  • Cobble – between 6.4 and 25.6 cm in diameter
  • Boulder – more than 25.6 cm in diameter.
  • Other, assorted organic matter, detritus.

Stream substrate can affect the life found within the stream habitat. Muddy streams generally have more sediment in the water, reducing clarity. Clarity is one guide to stream health.

Marine substrate can be classified geologically as well. See Green et al., 1999 for a reference.

Mollusks and clams that live in areas with substrate, and need them to survive, use their silky byssal threads to cling to it. See Cteniodes Ales for reference.

See also[edit]


  1. ^ "Definition of SILT". 28 April 2024. Retrieved 1 May 2024.
  2. ^ "Definition of CLAY". 27 April 2024. Retrieved 1 May 2024.
  3. ^ Bergaya, Faïza; Theng, B. K. G.; Lagaly, Gerhard (2006). Handbook of clay science (PDF). Amsterdam: Elsevier. p. 5. ISBN 0080441831. Retrieved 1 May 2024.


  • Gordon, McMahon, Finlayson, Gippel and Nathan. "Substrate". Stream Hydrology: An Introduction for Ecologists. 2nd Ed. John Wiley and Sons. 2004. pp 13 & 14.
  • Baker, Ffolliott, DeBano and Neary (eds). "Stream Substrate". Riparian Areas of the Southwestern United States: Hydrology, Ecology, and Management. Lewis Publishers. 2004. Taylor and Francis e-Library. 2005. pp 285 & 286.
  • "Stream Substrate Particle Size". Eldorado and Tahoe National Forests (N.F.), Range Standards & Guidelines to Amend the Land & Resource Management Plans of the Eldorado and Tahoe National Forests. Draft Environmental Impact Statement. July 1999. Page A-6