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

  • EC_Habitats
  • UK_BAP

Recorded distribution in Britain and Ireland

The distribution of %Lithothamnion glaciale% extends to the southern British Isles and is most abundant off the western coast of Scotland, Orkney and the Shetland Isles. This biotope has been recorded in only a few locations on the west coast of Scotland and in the Shetland Isles.

Habitat preferences

Temperature range preferences - See additional information.

Water clarity preferences - Very high clarity / Very low turbidity
High clarity / Low turbidity
Medium clarity / Medium turbidity

Limiting Nutrients - Calcium

Other preferences -

Additional information

Growth of Lithothamnion glaciale is maximal at 10-12 °C (Adey, 1970). Growth of Lithothamnion glaciale is impaired at reduced salinities (Adey, 1970). Distribution of maerl is dependent on several factors. Living maerl has poor tolerance of desiccation and so is typically found subtidally (Hall-Spencer, 1998). As a photosynthetic organism there is a requirement for light which restricts the species to depths shallower than 32 m in the relatively turbid waters of northern Europe (Hall-Spencer, 1998). Some shelter from wave action is required to prevent physical damage, dispersal or burial although some degree of water movement is important to ensure that silt does not smother the maerl bed.
King & Schramm (1982) report that ionic calcium concentration is the main factor affecting growth of maerl in culture experiments rather than salinity per se (although this has not been shown in the field). Uptake of calcium carbonate occurs optimally at 30 psu.

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 29/11/2015]. Available from: <>