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information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Toothed wrack (Fucus serratus)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.

Summary

Description

Fucus serratus, the toothed wrack, is a robust, olive-brown shrubby seaweed that grows in high densities low on the seashore. The fronds are about 2 cm wide, splitting in two repeatedly. The fronds bear no air bladders. The whole plant typically grows to about 60 cm long. The fronds have a serrated edge and grow from a short stalk.

Recorded distribution in Britain and 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.

Habitat

Fucus serratus is found on hard substrata on the lower shore in more sheltered areas of coastline.

Depth range

Not relevant

Identifying features

  • Fronds are flat and straplike with a well developed mid-rib.
  • Fronds edged with sharp, forward-pointing serrations.
  • The frond bears no air bladders.
  • The frond surface has numerous pin-pricks with clusters of tiny white hairs.
  • Receptacles form slightly thickened patches about 4 cm long surrounded by a sterile border at the terminal end of the frond.

Additional information

Also known as serrated or saw wrack. Ripe male plants can be distinguished by their orange colour.

Listed by

- none -

Further information sources

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Biology review

Taxonomy

PhylumOchrophyta
ClassPhaeophyceae
OrderFucales
FamilyFucaceae
GenusFucus
AuthorityLinnaeus, 1753
Recent Synonyms

Biology

Typical abundanceHigh density
Male size range50-70cm
Male size at maturity
Female size rangeLarge(>50cm)
Female size at maturity
Growth formShrub
Growth rate0.2-0.1cm/day
Body flexibility
MobilityNot relevant
Characteristic feeding methodAutotroph
Diet/food source
Typically feeds onNot relevant
SociabilityNo information
Environmental positionEpifloral
DependencyIndependent.
SupportsSubstratum

the hydroid, Dynamena pumila, the bryozoans Flustrellidra hispida, Alcyonidium hirsutum, Alcyonidium polyoum, Electra pilosa, and the polychaete Spirorbis spirorbis.

Is the species harmful?No

Biology 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.

Habitat preferences

Physiographic preferencesOpen coast, Sea loch / Sea lough, Ria / Voe, Estuary
Biological zone preferences
Substratum / habitat preferencesBedrock, Cobbles, Large to very large boulders, Small boulders
Tidal strength preferencesModerately Strong 1 to 3 knots (0.5-1.5 m/sec.), Strong 3 to 6 knots (1.5-3 m/sec.), Very Weak (negligible), Weak < 1 knot (<0.5 m/sec.)
Wave exposure preferencesExtremely sheltered, Moderately exposed, Sheltered, Very sheltered
Salinity preferencesFull (30-40 psu), Reduced (18-30 psu), Variable (18-40 psu)
Depth rangeNot relevant
Other preferencesNo text entered
Migration PatternNot relevant

Habitat 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.

Life history

Adult characteristics

Reproductive typeGonochoristic (dioecious)
Reproductive frequency Annual protracted
Fecundity (number of eggs)>1,000,000
Generation timeInsufficient information
Age at maturityInsufficient information
SeasonMay - November
Life span2-5 years

Larval characteristics

Larval/propagule type-
Larval/juvenile development Not relevant
Duration of larval stageNo information
Larval dispersal potential Greater than 10 km
Larval settlement period

Life history 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.

Sensitivity reviewHow is sensitivity assessed?

Physical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
High High Moderate High
Fucus serratus is permanently attached to the substratum. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. If the entire population of Fucus serratus is removed, other species may come to dominate. Re-establishment of the seaweed may depend on the ability to out-compete other species and this may be dependent on suitable environmental conditions.
High High Moderate Low
Intolerance to smothering will depend on the state of the tide. If the factor occurs when the tide is out and the alga is lying flat on the substratum then all the frond will be covered and photosynthesis prevented. If smothering occurs whilst the alga is underwater and upright then not all the photosynthetic surfaces of adult plants will be covered. Germlings are likely to be smothered and killed and will be the most intolerant stage of Fucus serratus life history. A further form of smothering can occur through heavy growth of epibionts such as Flustrellidra hispida on the frond surfaces. This growth may reduce photosynthesis and increase anoxia at the frond surface. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. If the entire population of Fucus serratus is removed, other species may come to dominate. Re-establishment of the seaweed may depend on the ability to outcompete other species and this may be dependent on suitable environmental conditions.
Low Very high Very Low Low
Siltation will only have an effect during the time that the seaweed is covered with water. Increased siltation may cover the frond surface with a layer of sediment reducing photosynthesis and growth rate. Once conditions return to 'normal' then it probably won't take long for the population to resume a normal size and growth rate.
No information
Intermediate High Low High
Seaweeds cannot prevent desiccation, they can only tolerate it. Seaweeds have a critical water content. Desiccation past this point causes irreversible damage. The critical point for Fucus serratus is 40 percent water content. A reduction in water content to 40 percent can occur after 2 hours exposure to sunshine. Fucus spiralis, a similar species to Fucus serratus, transplanted further up the shore to the Pelvetia canaliculata zone (greater desiccation) die within 4-8 weeks (Schonbeck & Norton, 1978). Other species better able to tolerate desiccation will competitively displace Fucus serratus following increases in desiccation. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. If the entire population of Fucus serratus is removed, other species may come to dominate. Re-establishment of the seaweed may depend on the ability to outcompete other species and this may be dependent on suitable environmental conditions.
Intermediate High Low Moderate
Fucus spiralis, a similar species to Fucus serratus, transplanted further up the shore to the Pelvetia canaliculata zone (longer emergence) die within 4-8 weeks. Other species better able to tolerate desiccation will competitively displace Fucus serratus following increases in emergence. Decreases in emergence will put the species in competition with species that typically remain submerged (e.g. laminarians) although in some locations of reduced salinity (the Belt Sea) the Fucus serratus population remains continually submerged. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. If the entire population of Fucus serratus is removed, other species may come to dominate. Re-establishment of the seaweed may depend on the ability to outcompete other species and this may be dependent on suitable environmental conditions.
No information
Intermediate High Low Moderate
Increases in water flow rate may cause some of the population to be torn off the substratum. Decreases in water flow rate are unlikely to have any effect. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. Recruitment may occur through reproduction of the remaining population or from other populations. As some of the population remains it is unlikely that other species will come to dominate. Removal of some of the adult canopy will allow the understorey germling back to grow faster. Recovery will probably have occurred after a year.
No information
Tolerant Not relevant Not sensitive High
Decreases in temperature are unlikely to have any effect. The species distribution extends north to Novaya Zemlya where water temperatures are much colder. Fucus distichus, a similar species can survive for several months at -40 °C. The species distribution also extends further south than the British Isles into warmer waters. Increases of up to 5°C above British and Irish temperatures is not likely to have a detrimental effect. Growth of Fucus serratus is optimal at 20 °C so British and Irish populations are more likely to benefit from increases in temperature. Fucus serratus cannot survive continual exposure to temperatures above 28°C for a week.
No information
Low Very high Very Low Moderate
Turbidity is only relevant when Fucus serratus is covered with water. Seaweed photosynthesis declines on emersion and recommences when recovered with water. Once conditions return to 'normal' then it will probably not take long for the population to resume a normal size and growth rate.
No information
High High Moderate Moderate
Fucus serratus only occurs on coasts with moderate exposure or less. Increases above this level of wave action will cause damage to individual plants, breaking fronds and removing entire plants from the substratum. Fucus serratus is more intolerant of wave exposure than Fucus vesiculosus. On more exposed coasts there are fewer adult individuals in the population. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. If the entire population of Fucus serratus is removed, other species may come to dominate. Re-establishment of the seaweed may depend on the ability to outcompete other species and this may be dependent on suitable environmental conditions.
No information
Tolerant Not relevant Not sensitive High
Seaweeds have no known mechanism for detection of noise vibrations.
Tolerant Not relevant Not sensitive High
Seaweeds have no known mechanism for visual perception.
Intermediate High Low High
Although the species is highly flexible, abrasion is likely to cause damage to and removal of fronds and even removal of entire plants from the substratum. Human trampling has been shown to significantly reduce the cover of fucoids on a shore (Holt et al., 1997) Cracks and crevices are ideal places for germlings to develop and these sites may be protected from abrasion. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. Recruitment may occur through reproduction of the remaining population of from other populations. As some of the population remains it is unlikely that other species will come to dominate. Removal of some of the adult canopy will allow the understorey germling back to grow faster. Recovery will probably have occurred after a year.
High High Moderate High
Fucus serratus is permanently attached to the substratum. If removed, the attachment cannot be reformed. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. If the entire population of Fucus serratus is removed, other species may come to dominate. Re-establishment of the seaweed may depend on the ability to out-compete other species and this may be dependent on suitable environmental conditions.

Chemical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
High High Moderate Not relevant
Different life stages of Fucus serratus differ in their intolerance to synthetic chemicals. Scalan & Wilkinson (1987) found that spematozoa and newly fertilized eggs of Fucus serratus were the most intolerant of biocides, while adult plants were only just significantly affected at 5 ml/l of the biocides Dodigen v181-1, Dodigen v 2861-1 and ML-910. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. If the entire population of Fucus serratus is removed, other species may come to dominate. Re-establishment of the seaweed may depend on the ability to outcompete other species and this may be dependent on suitable environmental conditions.
Heavy metal contamination
Low High Low Not relevant
Fucoid algae readily accumulate heavy metals within their tissues. The effect of heavy metals on the growth rate of adult Fucus serratus plants has been studied by Stromgren (1979b;1980a & b). Copper significantly reduces the growth rate of vegetative apices at 25 µg/l over 10 days (Stromgren, 1979b). Zinc, lead, cadmium & mercury significantly reduce growth rate at 1400 µg/l , 810ug/l, 450ug/l and 5ug/l respectively (Stromgren, 1980a & b). The benchmark concentrations of heavy metals may therefore reduce growth rate, so intolerance is reported as low, although early life stages of the species may be more intolerant.
Hydrocarbon contamination
Intermediate High Low High
Adult plants are tolerant of exposure to spills of crude oil although very young germlings are intolerant of relatively low concentrations of 'water soluble' extractions of crude oils. Exposure of eggs to these extractions (at 1.5 micrograms/ml for 96 hours) interferes with adhesion during settling) and (at 0.1micrograms/ml) prevents further development (Johnston, 1977). Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. Recruitment may occur through reproduction of the remaining population or from other populations. As some of the population remains it is unlikely that other species will come to dominate. Removal of some of the adult canopy will allow the understorey germling back to grow faster. Recovery will probably have occurred after a year.
Radionuclide contamination
No information No information No information Not relevant
Insufficient
information
Changes in nutrient levels
Intermediate High Low Moderate
When in high densities, the seaweed competes for space light and nutrients. Nutrient availability is the most important factor controlling germling growth. Plants under low nutrient regimes achieve smaller sizes and may be out competed. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. Recruitment may occur through reproduction of the remaining population of from other populations. As some of the population remains it is unlikely that other species will come to dominate. Removal of some of the adult canopy will allow the understorey germling back to grow faster. Recovery will probably have occurred after a year.
Low Very high Very Low High
Being intertidal and subject to precipitation, Fucus serratus is exposed to a range of salinities. The species is able to compensate for these changes in salinity by adjusting internal ion concentrations. Salinity affects the photosynthetic rate and hence growth rate of seaweed. For Fucus serratus, growth rate is maximal at a salinity of 20 psu. Above and below this growth rate declines. If salinity is suddenly increased for brief periods then the rate of net photosynthesis increases before decreasing. Salinity can also affect respiration rates. Once conditions return to 'normal' then it probably won't take long for the population to resume a normal size and growth rate.
No information
Low Very high Very Low Low
Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. There is no information about Fucus serratus tolerance to changes in oxygenation. Once conditions return to 'normal' then it probably won't take long for the population to resume a normal size and growth rate.

Biological pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
No information No information No information Not relevant
Insufficient
information
No information No information No information Not relevant
Insufficient
information
Intermediate High Low High
Fucus serratus is one of several harvested and exploited algal species. Fucus serratus is highly fecund, is iteroparous, surviving and breeding for protracted periods over 3-4 years. The eggs are broadcast into the water column allowing a potentially large dispersal distance. The species is found on all British and Irish coasts so there are few mechanisms isolating populations. Recruitment may occur through reproduction of the remaining population of from other populations. As some of the population remains it is unlikely that other species will come to dominate. Removal of some of the adult canopy will allow the understorey germling back to grow faster. Recovery will probably have occurred after a year.
Tolerant Not relevant Not sensitive Low
Fucus serratus has no known obligate relationships.

Additional information

Importance review

Policy/legislation

- no data -

Status

Non-native

Importance information

The seaweed is collected, dried and used as a soil additive. Various fucalean algae are used in the production of alginates. These are used widely in the pharmaceutical and cosmetics industries. The dense beds of Fucus serratus provide shelter for a very wide variety of species and also provide considerable substratum for epiphytic species. National status for Fucus serratus is not available but is almost certainly widespread.

Bibliography

  1. Brenchley, J.L., Rava, J.A. & Johnston, A.M., 1997. Resource acquisition in two intertidal fucoid seaweeds, Fucus serratus and Himanthalia elongata: seasonal variation and effects of reproductive development. Marine Biology, 129, 367-375.

  2. Creed, J.C., Norton, T.A. & Kain, J.M., 1997. Intraspecific competition in Fucus serratus germlings: The interaction of light, nutrients and density. Journal of Experimental Marine Biology and Ecology, 212, 211-223.

  3. Dickinson, C.I., 1963. British seaweeds. London & Frome: Butler & Tanner Ltd.

  4. Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins.

  5. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  6. Johnston, C.S., 1977. The sub-lethal effects of water-soluble extracts of oil on the fertilisation and development of Fucus serratus L. (Serrated wrack). Rapports et Proces Verbaux des Reunions. Conseil International pour l'Exploration de la Mer, 171, 184-185.

  7. Knight, M. & Parke, M., 1950. A biological study of Fucus vesiculosus L. and Fucus serratus L. Journal of the Marine Biological Association of the United Kingdom, 29, 439-514.

  8. Lobban, C.S. & Harrison, P.J., 1997. Seaweed ecology and physiology. Cambridge: Cambridge University Press.

  9. Scanlan, C.M. & Wilkinson, M., 1987. The use of seaweeds in biocide toxicity testing. Part 1. The sensitivity of different stages in the life-history of Fucus and of other algae, to certain biocides. Marine Environmental Research, 21, 11-29.

  10. Schonbeck, M.W. & Norton, T.A., 1978. Factors controlling the upper limits of fucoid algae on the shore. Journal of Experimental Marine Biology and Ecology, 31, 303-313.

  11. Seed, R. & O'Connor, R.J., 1981. Epifaunal associates of Fucus serratus at Dale, south-west Wales. Holarctic Ecology, 4, 1-11.

  12. Strömgren, T., 1979b. The effect of zinc on the increase in length of five species of intertidal Fucales. Journal of Experimental Marine Biology and Ecology, 40, 95-102.

  13. Strömgren, T., 1980a. The effect of dissolved copper on the increase in length of four species of intertidal fucoid algae. Marine Environmental Research, 3, 5-13.

  14. Strömgren, T., 1980b. The effect of lead, cadmium and mercury on the increase in length of five intertidal Fucales. Journal of Experimental Marine Biology and Ecology, 43, 107-119.

  15. Williams, G.A., 1996. Seasonal variation in a low shore Fucus serratus (Fucales, Phaeophyta) population and its epiphytic fauna. Hydrobiologia, 326/327, 191-197.

Citation

This review can be cited as:

Jackson, A. 2008. Fucus serratus Toothed wrack. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/species/detail/1326

Last Updated: 29/05/2008