Biodiversity & Conservation

Lithothamnion glaciale maerl beds in tide-swept variable salinity infralittoral gravel



Image Christine Howson - Lithothamnion glaciale nodules amongst pebbles with the sunstar Crossaster papposus, Isle of Lewis. Image width ca 20 cm.
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Distribution map

SS.SMp.Mrl.Lgla recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats
  • UK_BAP

Marine natural heritage importance

Listed under EC Habitats Directive
UK Biodiversity Action Plan
National importance Scarce
Habitat Directive feature (Annex 1) Sandbanks which are slightly covered by sea water all the time
Large shallow inlets and bays

Biotope importance

The biotope is highly important for other species, with high structural complexity and biodiversity. Mobile grazers and foragers can move in and out of the biotope to feed.


Maerl is mainly sold dried as a soil additive but is also used in animal feed, water filtration systems, pharmaceuticals, cosmetics and bone surgery. Maerl beds are dredged for scallops (found in high densities compared with other scallop habitats) where extraction efficiency is very high. This harvesting has serious detrimental effects on the diversity, species richness and abundance of maerl beds (BIOMAERL team, 1999).

Additional information icon Additional information

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This review can be cited as follows:

Jackson, A. 2006. Lithothamnion glaciale maerl beds in tide-swept variable salinity infralittoral gravel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 26/11/2015]. Available from: <>