BIOTIC Species Information for Lithothamnion glaciale
Researched byAngus Jackson Data supplied byMarLIN
Refereed byThis information is not refereed.
Scientific nameLithothamnion glaciale Common nameMaerl
MCS CodeZM237 Recent SynonymsNone

PhylumRhodophycota Subphylum
Superclass ClassRhodophyceae
SubclassFlorideophycidae OrderCorallinales
Suborder FamilyCorallinaceae
GenusLithothamnion Speciesglaciale

Additional InformationThis genus was previously called Lithothamnium but now Lithothamnion is the preferred name. Previous classifications included two varieties (sometimes formerly given species status): Lithothamnium granii (Foslie); and Lithothamnium colliculosum. It is quite difficult to differentiate between Lithothamnion glaciale and Lithothamnion corallioides. The hard surface and the absence of numerous surface mounds on Lithothamnion glaciale may help separate them although for greater accuracy the cortical cell structure should be used.
Taxonomy References Suneson, 1943, Rosenvinge, 1917, Adey & Adey, 1973, Adey, 1970, Irvine & Chamberlain, 1994, Howson & Picton, 1997,
General Biology
Growth formAlgal gravel
Crustose hard
Feeding methodPhotoautotroph
Mobility/MovementNot relevant
Environmental positionEpifloral
Typical food typesNot relevant HabitBed forming
BioturbatorNot relevant FlexibilityNone (< 10 degrees)
FragilityFragile SizeMedium(11-20 cm)
Height Growth Rate13 µm/day
Adult dispersal potential10-100m DependencyIndependent
General Biology Additional Information
  • Maerl has been found in densities of up to 22,000 thalli per square metre. The proportion of live to dead nodules varies considerably (Birkett et al., 1998). In the British Isles, Lithothamnion glaciale is found in relative abundances of up to 36 % of coralline red algae and up to 80 % further north (Adey & Adey, 1973)
  • Individual thalli of this species may occur as male female, asexual or non-breeding plants depending on the development of the various types of reproductive conceptacles.
  • Crustose plants adhere strongly to the substratum and reach 20 cm in diameter at least (Suneson, 1943; Irvine & Chamberlain, 1994). Unattached plants probably reach 4-5 cm in diameter.
  • Little is known about growth rates of this species. Maerl is amongst the slowest growing species in the North Atlantic (Birkett et al., 1998). Adey, (1970) recorded rates of up to 13 microns per day in the lab. This is fast in comparison to other sub-arctic maerl species which may explain why Lithothamnion glaciale is often the most abundant North Atlantic crustose coralline alga.
  • Mobility and sociability is not applicable to algal species.
  • Maerl beds in general are known as a particularly diverse habitat with over 150 macro algal species and 500 benthic faunal species recorded (Birkett et al., 1998(a)). The loose structure of these beds permits water circulation and oxygenation to considerable depth. As a consequence of this loose structure, maerl provides shelter for an astonishing variety of fauna e.g. molluscs (Hall-Spencer, 1998) and amphipods (Grave De, 1999).
Biology References Adey et al., 1976, Suneson, 1943, Rosenvinge, 1917, Adey & Adey, 1973, Cardinal et al., 1979, Adey, 1966, Adey, 1970, Irvine & Chamberlain, 1994, Birkett et al., 1998(a), Hall-Spencer, 1998, Grave De, 1999,
Distribution and Habitat
Distribution in Britain & IrelandMost abundant in the sea lochs of western Scotland, Orkney and Shetland. Recorded along the east coast south to Flamborough. Occasional on the south coast, Wales, Isle of Man and Lundy. Sparse records from north and south-western Ireland.
Global distributionIn the NE Atlantic from the British Isles north to Arctic Russia including the Faeroe Isles, Iceland and western Baltic. In the NW Atlantic from Cape Cod north to Arctic Canada and Greenland. Also northern Japan and China in the western Pacific.
Biogeographic rangeNot researched Depth range0-70 m
MigratoryNon-migratory / Resident   
Distribution Additional Information
  • Information on distribution of Lithothamnion glaciale in Fair Isle is available at
  • Detail about British Isles distribution is found in Hall-Spencer (1985).
  • Most abundant from 6-30 metres (Suneson, 1943). In the clear waters around northern Japan it may be found as deep as 60-70 m. Depth range is highly dependent on turbidity although temperature plays a role. Below 4-6 °C growth rate has little dependence on light availability (Adey, 1970).
  • Occasionally found in shallow waters and even in large tide pools on the shore (Adey, 1970).
  • Deposits from maerl beds can sometimes form quite extensive white 'coral sand' beaches, such as those in the Western Isles and Orkney.

Substratum preferencesBedrock
Large to very large boulders
Small boulders
Gravel / shingle
Physiographic preferencesOpen coast
Strait / sound
Ria / Voe
Biological zoneUpper Infralittoral
Lower Infralittoral
Upper Circalittoral
Lower Circalittoral
Wave exposureExposed
Moderately Exposed
Very Sheltered
Tidal stream strength/Water flowStrong (3-6 kn)
Moderately Strong (1-3 kn)
Weak (<1 kn)
SalinityFull (30-40 psu)
Variable (18-40 psu)
Habitat Preferences Additional Information
Distribution References Adey et al., 1976, Suneson, 1943, Rosenvinge, 1917, Adey & Adey, 1973, Adey, 1966, Adey, 1970, Irvine & Chamberlain, 1994, Birkett et al., 1998(a), Hall-Spencer, 1995, JNCC, 1999, Hardy & Guiry, 2003,
Reproduction/Life History
Reproductive typeGonochoristic
Developmental mechanismSpores (sexual / asexual)
Reproductive SeasonInsufficient information Reproductive LocationInsufficient information
Reproductive frequencyAnnual protracted Regeneration potential No
Life span21-50 years Age at reproductive maturityInsufficient information
Generation timeInsufficient information FecundityInsufficient information
Egg/propagule sizeInsufficient information Fertilization typeInsufficient information
Larval/Juvenile dispersal potentialInsufficient information Larval settlement periodInsufficient information
Duration of larval stageNot relevant   
Reproduction Preferences Additional Information
  • Adey, (1970) estimates the life-span of individual plants to be from 10-50 years.
  • Little is known about the reproductive mechanisms of this species. However, sexual reproduction can occur between gonochoristic plants. Asexual reproduction occurs through the formation of spores. In some populations sexual individuals are rare (e.g. in the Gulf of Maine, (Adey, 1966)) and reproduction is mediated mainly if not entirely by the production of asexual conceptacles.
  • Reproduction is probably mainly controlled by temperature (Adey, 1970). In Greenland and Sweden, Lithothamnion glaciale has reproductive conceptacles all year round whereas in Scotland, although conceptacles are common in winter, the plants are sterile in summer (Hall-Spencer, 1994 cited in Birkett et al., 1998)
  • A further form of propagation is by vegetative growth and division of a single thallus into two or more competent individuals that continue to grow. In the other main maerl species that occur round the British Isles (Phymatolithon calcareum and Lithothamnion corallioides), this vegetative growth is the main form of propagation (Irvine & Chamberlain, 1994). Spores can potentially disperse long distances although if dispersal is dependent on vegetative propagation, then distances will be extremely limited.
Reproduction References Adey & Adey, 1973, Adey, 1966, Adey, 1970, Irvine & Chamberlain, 1994, Birkett et al., 1998(a),
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