Fucus serratus

Researched By	Angus Jackson	Data Supplied By	MarLIN
Refereed by	Dr Graham Scott
Taxonomy
Scientific name	Fucus serratus	Common name	Toothed wrack
MCS Code	ZR382	Recent Synonyms	None
Phylum	Chromophycota	Subphylum
Superclass		Class	Phaeophyceae
Subclass		Order	Fucales
Suborder		Family	Fucaceae
Genus	Fucus	Species	serratus
Subspecies
Additional Information	Also known as serrated or saw wrack. Ripe male plants can be distinguished by their orange colour.
Taxonomy References	Howson & Picton, 1997, Hayward et al., 1996, Dickinson, 1963, Williams, 1996, Knight & Parke, 1950
General Biology
Growth form	Shrub, 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	Large(>50cm)
Height	Usually up to 70 cm	Growth Rate	0.2-0.1 cm / day
Adult dispersal potential	None	Dependency	Independent
Sociability	Solitary
Toxic/Poisonous?	No
Additional Information	During most of the year plant densities range between 10-14/0.25 square metres. When recruitment is occurring then densities may rise to 18-22/0.25 square metres. Surface cover by this species may reach over 95 percent during the summer. This decreases and becomes more patchy during winter and autumn. Fucus serratus typically grows up to 70 cm but has been recorded at over 2 m in length in very sheltered environments. Growth rate refers to maximal growth rate under optimal conditions. Growth rate varies considerably depending on environmental conditions. Growth rate ranges from 4-12 cm per annum. There are two size classes: germlings less than 10 cm (30-40 percent of the population); and adult plants greater than 40 cm. The germlings developing from eggs are initially microscopic and become visible to the naked eye after about two weeks. There is no clear mode in between but individuals of intermediate size are always present. Fucus serratus supports a wide variety of epiphytes with over 90 species having been recorded. Growth of microalgae on the frond surface can cause shading and reduced photosynthesis, anoxia at the frond surface and may interfere with reproduction. Mobile herbivores may benefit Fucus serratus through removal of this algal film. Other dominant macrofaunal species found on Fucus serratus include Lacuna pallidula, Littorina mariae, Amphithoe rubricata, Idotea granulosa and epiflora include Rhydomenia palmata and Elachista fucicola.
Biology References	Creed et al., 1997, Brenchley et al., 1997, Seed & O'Connor, 1981, Lüning, 1990, Williams, 1996, Knight & Parke, 1950
Distribution and Habitat
Distribution in Britain & Ireland	All British and Irish coasts.
Global distribution	Northern Portugal and the Atlantic coast of France; British Isles, North Sea coasts and into the western Baltic; Scandinavia up to Novaya Zemlya; Iceland and the Gulf of St. Lawrence in the western north Atlantic.
Biogeographic range	Not researched	Depth range	Not relevant
Migratory	Non-migratory / Resident
Distribution Additional Information	Depth in metres is considered not relevant because the species is intertidal. More exposed coasts have a lower proportion of adult individuals in the population. In more sheltered areas Fucus serratus may grow on substrata such as cobbles.
Substratum preferences	Bedrock, Large to very large boulders, Small boulders, Cobbles	Physiographic preferences	Open coast, Sealoch, Ria / Voe, Estuary
Biological zone		Wave exposure	Moderately Exposed, Sheltered, Very Sheltered, Extremely Sheltered
Tidal stream strength/Water flow	Strong (3-6 kn), Moderately Strong (1-3 kn), Weak (<1 kn), Very Weak (negligible)	Salinity	Reduced (18-30 psu), Full (30-40 psu), Variable (18-40 psu)
Habitat Additional Information
Distribution References	Hayward et al., 1996, Williams, 1996, Knight & Parke, 1950
Reproduction/Life History
Reproductive type	Gonochoristic	Developmental mechanism	Insufficient information
Reproductive Season	May to November	Reproductive Location	Water column
Reproductive frequency	Annual protracted	Regeneration potential	No
Life span	3-5 years	Age at reproductive maturity	Insufficient information
Generation time	Insufficient information	Fecundity	See additional information
Egg/propagule size	Insufficient information	Fertilization type	External
Larvae/Juveniles Larval/Juvenile dispersal potential >10km Larval settlement period Duration of larval stage Insufficient information
Additional Information	Dickinson, (1963) notes that fruiting fronds can be found almost throughout the year with fertile plants most in evidence during the winter months. However, most other work suggests that reproduction commences in late spring/early summer and continues through summer and autumn, peaking in August - October. Eggs and sperm are released into the water and fertilisation occurs in the water column. The eggs produce a sperm attractant called fucoserratin that is active within 0.5mm. The zygote then develops into a minute plant that can then settle onto the substratum. Post reproductive fronds are shed contributing to loss of surface cover. Many plants may be lost during winter due to storms and heavy wave action. Germlings have a high mortality, up to 83 % being recorded lost in 77 days on the Isle of Man. Reproduction occurs earlier and growth is faster on sheltered shores. Egg release is protracted. The largest number of receptacles recorded from a single plant is over 4,600. Eggs are broadcast into the water column to be carried by the current to settle and develop wherever they fall. Eggs attach firmly to the substratum within a few hours. Many eggs are eaten by browsing molluscs.
Reproduction References	Dickinson, 1963, Brenchley et al., 1997, Johnston, 1977, Williams, 1996, Knight & Parke, 1950