BIOTIC

BIOTIC Species Information for Phymatolithon calcareum

Researched by

Angus Jackson

Data supplied by

MarLIN

Refereed by

Dr Christine Maggs

Taxonomy

Scientific name

Phymatolithon calcareum

Common name

Maerl

MCS Code

ZM255

Recent Synonyms

None

Phylum

Rhodophycota

Subphylum

Superclass

Class

Rhodophyceae

Subclass

Florideophycidae

Order

Corallinales

Suborder

Family

Corallinaceae

Genus

Phymatolithon

Species

calcareum

Subspecies

Additional Information

Maerl is a generic name for certain coralline algae that grow unattached on the sea bed. No crustose plants of Phymatolithon calcareum have been recorded from the British Isles.

Taxonomy References

Howson & Picton, 1997, Campbell, 1994, Irvine & Chamberlain, 1994, Adey & McKibbin, 1970, Birkett et al., 1998(a),

General Biology

Growth form

Algal gravel

Feeding method

Photoautotroph

Mobility/Movement

See additional information

Environmental position

Epifloral

Typical food types

Not relevant

Habit

Bed forming

Bioturbator

Not relevant

Flexibility

None (< 10 degrees)

Fragility

Fragile

Size

Small-medium(3-10cm)

Height

Insufficient information

Growth Rate

1-2 mm/year

Adult dispersal potential

10-100m

Dependency

Independent

Sociability

Gregarious

Toxic/Poisonous?

General Biology Additional Information

Mobility is recorded as not relevant here since Phymatolithon calcareum does not fall into the available categories. It does have a crustose permanently attached form but this has not been recorded in the British Isles. It is typically found as an unattached plant. Coralline algal thalli that form maerl beds have 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. There are no sexes and 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

Adey & McKibbin, 1970, Donnan & Davies, 1996, Birkett et al., 1998(a), Potin et al., 1990, Grall & Glémarec, 1997, Hall-Spencer & Moore, 2000a,

Distribution and Habitat

Distribution in Britain & Ireland

Recorded around the Shetland Orkney Islands and along the east coast of Scotland, south coast of England with isolated records at Bideford Bay, Pembrokeshire and Caernarfon Bay. Abundant around the west coasts of Ireland and Scotland

Global distribution

From Norway down to northern Spain. Includes the western Baltic and the Mediterranean

Biogeographic range

Not researched

Depth range

1-30m

Migratory

Not relevant

Distribution Additional Information

Most frequent at depths between 1-10 m. May be found deeper in clear waters, e.g. found at depths of up to 30 m in outer Galway Bay.
%Phymatolithon calcareum% has been reported recently from 13-20m off Swange to Old Harry and off Bembridge, the Isle of Wight (Collins pers. comm.; Collins et al., 1990).

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

Tidal stream strength/Water flow

Strong (3-6 kn)
Moderately Strong (1-3 kn)

Salinity

Full (30-40 psu)

Habitat Preferences Additional Information

Distribution References

Campbell, 1994, Irvine & Chamberlain, 1994, Donnan & Davies, 1996, Birkett et al., 1998(a), Grall & Glémarec, 1997, Hall-Spencer & Moore, 2000a, Veale et al., 1999, Collins et al., 1990, 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

Life span

51-100 years

Age at reproductive maturity

Not relevant

Generation time

Insufficient information

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	Insufficient information

Reproduction Preferences Additional Information

Recruitment in France is believed to be primarily through fragmentation from crustose forms. No crustose forms are known from the British Isles so propagation must be virtually entirely vegetative. Maerl beds in the Sound of Iona are recorded as containing dead nodules up to 4,000 years old (Farrow, 1983, cited in Maggs et al., 1998). Insufficient information is available on reproductive frequency, fecundity and developmental mechanism. In the British Isles there are a few records of fertile plants but no records of the crustose forms that this reproduction would produce. Plants may be fertile and develop conceptacles throughout the year. Plants from Brittany are mostly fertile in winter. Cabioch (1969) suggested that Phymatolithon calcareum 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. Adey & McKibbon (1970) undertook growth studies of Phymatolithon calcareum in the field and under laboratory conditions. Their results for field studies in the Ria de Vigo, expressed as µ/day, show that growth occurs predominantly in the summer and suggests an annual growth of about 0.55 mm/year for branch tips of Phymatolithon calcareum according to Maggs et al. (1998).

Reproduction References

Irvine & Chamberlain, 1994, Birkett et al., 1998(a), Cabioch, 1969, Franz et al. 2000, Halfar et al., 2000, Farrow (1983),