Lithothamnion corallioides

Researched By	Angus Jackson	Data Supplied By	MarLIN
Refereed by	Dr Christine Maggs
Taxonomy
Scientific name	Lithothamnion corallioides	Common name	Maerl
MCS Code	ZM236	Recent Synonyms	None
Phylum	Rhodophycota	Subphylum
Superclass		Class	Rhodophyceae
Subclass	Florideophycidae	Order	Corallinales
Suborder		Family	Corallinaceae
Genus	Lithothamnion	Species	corallioides
Subspecies
Additional Information	Maerl is a generic name for certain coralline algae that grow unattached on the sea bed. Only two instances of the crustose form of Lithothamnion corallioides have been recorded from the British Isles; in Dorset and Devon.
Taxonomy References	Irvine & Chamberlain, 1994, Howson & Picton, 1997, Adey & McKibbin, 1970, Birkett et al., 1998
General Biology
Growth form	Algal gravel	Feeding method	Photoautotroph
Mobility/Movement	Not relevant, See additional information	Environmental position	Epilithic
Typical food types	Not relevant	Habit	Bed forming
Bioturbator	Not relevant	Flexibility	None (< 10 degrees)
Fragility	Intermediate	Size	Small-medium(3-10cm)
Height		Growth Rate	1-2 mm/year
Adult dispersal potential	10-100m	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
Additional Information	Mobility is recorded as not relevant here since maerl does not fall into the available categories. It does have a crustose permanently attached form but this has only been recorded at 2 sites in the British Isles. It is typically found as an unattached plant. Maerl has been found in densities of up to 22,000 thalli per square metre. The proportion of live to dead nodules varies considerably. As far as is known, maerl continues to grow throughout its life but fragmentation limits the size of the nodules. Individual plants may reach up to 5 cm across. Maerl beds are highly species rich with 150 macroalgal species and over five hundred faunal species (of which 120 are molluscs) recorded as living on or in maerl beds (Birkett et al., 1998(a)); see the maerl biotope £IGS.Phy.HEc£ for further information. As far as is known, the maerl does not host any commensal or parasitic species. However, a few algae are almost entirely restricted to maerl communities e.g. the red algae Gelidiella calcicola, Gelidium maggsiae and the crustose Cruoria cruoriaeformis (Birkett et al., 1998(a)).
Biology References	Irvine & Chamberlain, 1994, Adey & McKibbin, 1970, Donnan & Davies, 1996, Birkett et al., 1998, Potin et al., 1990, Grall & Glémarec, 1997, Birkett et al., 1998(a), Maggs & Guiry, 1987
Distribution and Habitat
Distribution in Britain & Ireland	Patchily distributed along the exposed western coasts of the southern British Isles. Locations include the west and south-west of Ireland, the south-west corner of Wales and a few sites off the south coast of England.
Global distribution	West and south-west British Isles south to the Canary Isles (unconfirmed records from Mauritania and Cape Verde). Also found in the Mediterranean.
Biogeographic range	Not researched	Depth range	1-30 m
Migratory	Non-migratory / Resident
Distribution Additional Information	Occurs most frequently at depths between 1-10 m. Occasionally found at depths of up to 30 m (for example Outer Galway Bay).
Substratum preferences	Pebbles, Gravel / shingle, Maerl, Muddy gravel, Coarse clean sand, Fine clean sand, Sandy mud, Muddy sand, Mud, Mixed	Physiographic preferences	Open coast, Strait / sound, Sealoch, Ria / Voe, Estuary
Biological zone	Sublittoral Fringe, Upper Infralittoral, Lower Infralittoral	Wave exposure	Moderately Exposed, Sheltered, Very Sheltered
Tidal stream strength/Water flow	Strong (3-6 kn), Moderately Strong (1-3 kn)	Salinity	Full (30-40 psu)
Habitat Additional Information
Distribution References	Donnan & Davies, 1996, Birkett et al., 1998, Grall & Glémarec, 1997, Birkett et al., 1998(a), Hardy & Guiry, 2003, Hardy & Guiry, 2003
Reproduction/Life History
Reproductive type	Vegetative	Developmental mechanism	Insufficient information
Reproductive Season	Insufficient information	Reproductive Location	Insufficient information
Reproductive frequency	Insufficient information	Regeneration potential	No
Life span	51-100 years	Age at reproductive maturity	Insufficient information
Generation time	Not relevant	Fecundity	Insufficient information
Egg/propagule size	Insufficient information	Fertilization type	Insufficient information
Larvae/Juveniles Larval/Juvenile dispersal potential <10m Larval settlement period Insufficient information Duration of larval stage Not relevant
Additional Information	Maerl beds in the Sound of Iona are recorded as containing dead nodules up to 4,000 years old. Insufficient information is available on reproductive frequency, fecundity and developmental mechanism. In Britain there is only one record of a fertile plant (found in July). Consequently virtually all propagation must be presumed to be vegetative and therefore dispersal potential is recorded as low. Plants from Brittany are mostly fertile in winter but Adey and McKibbin (1970) recorded a plant from Spain being fertile in August. Cabioch (1969) suggested Lithothamnion corallioides may have phasic reproduction with peaks every six years. This may account for observed changes in the relative proportions of live Lithothamnion corallioides and Phymatolithon calcareum nodules in maerl beds. Dominance cycles with periods of about thirty years have been recorded on some of the maerl beds of northern Brittany.
Reproduction References	Irvine & Chamberlain, 1994, Adey & McKibbin, 1970, Birkett et al., 1998, Cabioch, 1969, Birkett et al., 1998(a)