Fucus distichus

Researched By	Nicola White	Data Supplied By	MarLIN
Refereed by	Dr Graham Scott
Taxonomy
Scientific name	Fucus distichus	Common name	A brown seaweed
MCS Code	ZR380	Recent Synonyms	Fucus distichus distichus, Powell, 1957a; Fucus distichus anceps, Powell, 1957a.
Phylum	Chromophycota	Subphylum
Superclass		Class	Phaeophyceae
Subclass		Order	Fucales
Suborder		Family	Fucaceae
Genus	Fucus	Species	distichus
Subspecies
Additional Information	No text entered
Taxonomy References	Rice & Chapman, 1985, Fish & Fish, 1996, Howson & Picton, 1997
General Biology
Growth form	Foliose	Feeding method	Photoautotroph
Mobility/Movement	Permanent attachment	Environmental position	Epifloral
Typical food types	Not relevant	Habit	Attached
Bioturbator	Not relevant	Flexibility	High (>45 degrees)
Fragility	Intermediate	Size	Medium-large(21-50cm)
Height	Up to 30 cm	Growth Rate	10 cm / year
Adult dispersal potential	Not researched	Dependency	Independent
Sociability	Solitary
Toxic/Poisonous?	No
Additional Information	The morphology of Fucus distichus is remarkably varied. Powell (1957a) recognised four subspecies, which were later separated into two distinct species (Fucus distichus and Fucus evanescens) by Rice and Chapman (1985). In its rock pool habit on the east coast of North America Fucus distichus is considered by Pearson & Davison (1994) to be slow growing, a poor competitor and stress intolerant. Adults of Fucus distichus are very tolerant of grazing due to a high content of phlorotannin, but germlings do not have any protection and are susceptible to grazing by littorinids.
Biology References	Rice & Chapman, 1985, Powell, 1957, Pearson & Davison, 1994, Ang, 1991
Distribution and Habitat
Distribution in Britain & Ireland	Restricted to northern shores of Scotland and north and west Ireland.
Global distribution	Norway, northern Scotland, Iceland, Greenland, eastern North America from Labrador to Maine and the Pacific coast of America discontinuously from Alaska to California
Biogeographic range	Not researched	Depth range	Upper eulittoral
Migratory	Non-migratory / Resident
Distribution Additional Information	In Britain and Ireland, Fucus distichus has only been recorded attached to bedrock in the mid to upper eulittoral zone on exposed rocky shores in northern Scotland and Ireland. It is thought to be prevented from growing further south due to its poor tolerance of desiccation and inability to compete with plants growing further down the shore. However, on the east coast of North America, Fucus distichus is only found in rock pools and is incapable of growing on emergent rock surfaces in the mid to upper eulittoral.
Substratum preferences	Bedrock, Large to very large boulders	Physiographic preferences	Open coast
Biological zone	Upper Eulittoral	Wave exposure	Extremely Exposed, Very Exposed
Tidal stream strength/Water flow	Strong (3-6 kn), Moderately Strong (1-3 kn), Weak (<1 kn), Very Weak (negligible)	Salinity	Full (30-40 psu), Variable (18-40 psu)
Habitat Additional Information
Distribution References	Rice & Chapman, 1985, Ang, 1991, JNCC, 1999, Norton, 1985, Hardy & Guiry, 2003
Reproduction/Life History
Reproductive type	Permanent hermaphrodite	Developmental mechanism	Not relevant
Reproductive Season	April to August	Reproductive Location	Insufficient information
Reproductive frequency	Annual protracted	Regeneration potential	No
Life span	3-5 years	Age at reproductive maturity	1-2 years
Generation time	1-2 years	Fecundity	Insufficient information
Egg/propagule size	Insufficient information	Fertilization type	Insufficient information
Larvae/Juveniles Larval/Juvenile dispersal potential Insufficient information Larval settlement period Not relevant Duration of larval stage Insufficient information
Additional Information	Receptacles of Fucus distichus are initiated in December, they become ripe in April and gametes are released from April to August. Plants usually become mature when 100mm long. The whole plant dies back after reproducing and is removed from the rock by wave action during its third winter. Most plants live for 2 to 3 years (Powell, 1957b). Fucus distichus produces gametes of both sexes within each conceptacle. When released, ova can survive and disperse for several days. Antherozoids can only live for several hours. Self-fertilisation is thought to be high in the species and once a zygote is formed it can only be dispersed over limited distances (Rice et al., 1985).
Reproduction References	Powell, 1957(b), Rice et al., 1985, Ang, 1991