Lithothamnion glaciale

Researched By	Angus Jackson	Data Supplied By	MarLIN
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Lithothamnion glaciale	Common name	Maerl
MCS Code	ZM237	Recent Synonyms	None
Phylum	Rhodophycota	Subphylum
Superclass		Class	Rhodophyceae
Subclass	Florideophycidae	Order	Corallinales
Suborder		Family	Corallinaceae
Genus	Lithothamnion	Species	glaciale
Subspecies
Additional Information	This 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 form	Algal gravel, Crustose hard	Feeding method	Photoautotroph
Mobility/Movement	Not relevant	Environmental position	Epifloral, Epilithic
Typical food types	Not relevant	Habit	Bed forming
Bioturbator	Not relevant	Flexibility	None (< 10 degrees)
Fragility	Fragile	Size	Medium(11-20 cm)
Height		Growth Rate	13 µm/day
Adult dispersal potential	10-100m	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
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 & Ireland	Most 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 distribution	In 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 range	Not researched	Depth range	0-70 m
Migratory	Non-migratory / Resident
Distribution Additional Information	Information on distribution of Lithothamnion glaciale in Fair Isle is available at http://www.fairisle.org.uk/FIMETI/Reports/Safeguarding_Our_Heritage/appendix5.htm 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 preferences	Bedrock, Large to very large boulders, Small boulders, Cobbles, Pebbles, Gravel / shingle, Maerl	Physiographic preferences	Open coast, Strait / sound, Sealoch, Ria / Voe, Estuary
Biological zone	Upper Infralittoral, Lower Infralittoral, Upper Circalittoral, Lower Circalittoral	Wave exposure	Exposed, Moderately Exposed, Sheltered, Very Sheltered
Tidal stream strength/Water flow	Strong (3-6 kn), Moderately Strong (1-3 kn), Weak (<1 kn)	Salinity	Full (30-40 psu), Variable (18-40 psu)
Habitat 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 type	Gonochoristic, Vegetative	Developmental mechanism	Spores (sexual / asexual)
Reproductive Season	Insufficient information	Reproductive Location	Insufficient information
Reproductive frequency	Annual protracted	Regeneration potential	No
Life span	21-50 years	Age at reproductive maturity	Insufficient information
Generation time	Insufficient information	Fecundity	Insufficient information
Egg/propagule size	Insufficient information	Fertilization type	Insufficient information
Larvae/Juveniles Larval/Juvenile dispersal potential Insufficient information Larval settlement period Insufficient information Duration of larval stage Not relevant
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)