Pink sea fan (Eunicella verrucosa)

NBN Interactive08-06-2007

Map accurate at time of writing. Visit NBN or OBIS to view current distribution

Researched byDr Keith Hiscock Refereed byThis information is not refereed.
Authority(Pallas, 1766)
Other common names- Synonyms-

Summary

Description

The "pink" sea fan may be white to deep pink in colour. Colonies branch profusely and the branches are covered in warty protuberences from which the small anemone-like polyps emerge. Colonies may be up to 50 cm high but more often up to 25 cm and are usually oriented in one plane (at right angles to the prevailing water currents).

Recorded distribution in Britain and Ireland

Recorded northwards to north Pembrokeshire and eastwards to Portland Bill in Britain. Common in parts of south Devon and Cornwall and at Lundy. Present on the south and west coasts of Ireland but common only in Galway and Donegal Bays.

Global distribution

South and west coasts of Britain and Ireland south to north-west Africa and present in the western Mediterranean (Carpine, 1975; Manual, 1988).

Habitat

Found mainly on upward facing bedrock in areas where water movement (wave action or tidal streams) is moderately strong.

Depth range

4->50 m

Identifying features

  • Profusely branching fan-shaped colonies with close-set polyps on warty protuberences (calyces).
  • Sclerites are warty spindles in the inner coenenchyme and balloon-club in the outer.
  • Height up to 30 cm.
  • Colour of flesh varies from white to deep orange-pink.

Additional information

May be confused with Swiftia pallida, which occurs in Scotland northwards to Scandinavia but is much less branched, has generally thinner branches and may be white or rose coloured.

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Biology review

Taxonomy

PhylumCnidariaSea anemones, corals, sea firs & jellyfish
ClassAnthozoaSea anemones, soft & cup corals, sea pens & sea pansies
OrderAlcyonacea
FamilyGorgoniidae
GenusEunicella
Authority(Pallas, 1766)
Recent Synonyms

Biology

Typical abundanceModerate density
Male size rangeMale size at maturity
Female size rangeMedium-large(21-50cm)Female size at maturity
Growth formArborescent / ArbuscularGrowth rate10mm/year
Body flexibilityMobility
Characteristic feeding methodNot relevant, Passive suspension feeder
Diet/food source
Typically feeds onSuspended matter including plankton
Sociability Environmental positionEpibenthic
DependencyIndependent.
SupportsSubstratum

Tritonia nilsohdneri, Amphianthus dohrnii, Simnia patula

Is the species harmful?No

Biology information

The sea fan anemone Amphianthus dohrnii specifically lives on sea fans. The sea slug Tritonia nilsohdneri feeds on sea fans and is camouflaged to look like the sea fan. The 'poached egg shell' Simnia patula feeds on sea fans and observations at Lundy (K. Hiscock, R. Irving pers. comm.) suggest that their egg laying might cause mortality (see 'Additional Information' in Adult Sensitivity). Other species colonize damaged or partially dead sea fans where the coenenchyme has been lost, especially barnacles, bryozoans and ascidians.

Habitat preferences

Physiographic preferencesOpen coast, Offshore seabed, Strait / sound
Biological zone preferencesLower circalittoral, Upper circalittoral
Substratum / habitat preferencesArtificial (man-made), Bedrock, Large to very large boulders
Tidal strength preferencesModerately Strong 1 to 3 knots (0.5-1.5 m/sec.)
Wave exposure preferencesExposed, Moderately exposed, Sheltered, Very exposed
Salinity preferencesFull (30-40 psu)
Depth range4->50 m
Other preferencesMainly on upward facing rock but occasionally on vertical surfaces.
Migration PatternNon-migratory / resident, Not relevant

Habital Information

Older records suggest that the species occurred in the English Channel almost to the Thames Estuary (Margate). May occur in south-west Scotland but records needed (Manual, 1988)

Life history

Adult characteristics

Reproductive type No information Reproductive frequency Annual episodic
Fecundity (number of eggs) No information Generation time Insufficient information
Age at maturity Insufficient information Season Insufficient information
Life span 20-100 years

Larval characteristics

Larval/propagule type - Larval/juvenile development Lecithotrophic
Duration of larval stage Not relevant Larval dispersal potential 100 -1000 m
Larval settlement period Insufficient information

Life history information

The age of Eunicella verrucosa colonies can be determined (destructively) from growth rings in the axis. There is one growth ring per annum as evidenced by studies that measured growth rate in marked fans and then harvested the sea fans to count growth rings (Keith Hiscock, unpublished studies). Growth rate can be highly variable with an increase in branch length of up to 6 cm in some branches in one year and virtually none in others in Lyme Bay populations (C. Munro, pers. comm.) in one year. About 1 cm per annum increase in branch length was recorded in marked colonies at Lundy corresponding to measures of branch length correlated with number of annual growth rings (Keith Hiscock, unpublished studies, see above). There is no specific information on reproduction in Eunicella verrucosa but observation of the occurrence of small colonies suggests that production and settlement of larvae is successful in occasional years in south-west Britain. The larvae are most likely lecithotrophic and have a short life. Colonies seem to take some time if ever to colonize wrecks that are distant (>1 km) from existing populations. For the morphologically similar Paramuricea clavata in the Mediterranean, Coma et al. (1995) described reproduction and the cycle of gonadial development with spawning occurring 3-6 days after full or new moon in summer. Spawned eggs adhered to a mucus coating to female colonies: a feature that would be expected to have been readily observed if it occurred in Eunicella verrucosa. Maturation of planulae took place among the polyps of the parent colony and, on leaving the colony, planulae immediately settled on surrounding substrata. It seems more likely that planulae of Eunicella verrucosa are released immediately from the polyps and are likely to drift.

Sensitivity reviewHow is sensitivity assessed?

Physical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
High Very low / none Very High Moderate
Sea fans are attached to the substratum and would not survive substratum loss. Therefore, intolerance is high. Recruitment would have to occur from nearby populations as larval dispersal is likely to be poor. Settlement appears to be sporadic and may not occur for several years. Growth to large colonies will take in excess of 10 years and replacement of very large colonies in excess of 25 years.
Intermediate Moderate Moderate Moderate
Colonies of Eunicella verrucosa extend above the substratum and therefore above the smothering. Some small individuals might be killed but the majority of individuals will survive. Settlement appears to be sporadic and may not occur for several years. However, since only small colonies would expected to be killed and, with large colonies nearby, they will be replaced, recoverability is moderate.
Low Very high Very Low Moderate
Colonies produce mucus to clear themselves of silt and therefore, although siltation might occur and inhibit feeding for a while, the silt will be removed by water movement or mucus.
Not relevant Not relevant Not relevant High
Sea fans thrive in clear water conditions and, since silt is unlikely to be used as part of the diet, a decrease in siltation is believed to be not relevant.
Not relevant Not relevant Not relevant Not relevant
Sea fans are found only in the circalittoral and so desiccation will not occur.
Not relevant Not relevant Not relevant Not relevant
Sea fans are found only in the circalittoral and so changes in emergence are not relevant.
Not relevant Not relevant Not relevant Not relevant
Sea fans are found only in the circalittoral and so changes in emergence are not relevant.
Intermediate Moderate Moderate Moderate
Sea fans are found in strong tidal streams but most likely retract their polyps when current velocity gets too high for the polyps to retain food. Tidal streams exert a steady pull on the colonies and are therefore likely to detach only very weakly attached colonies. 'Moderate' recoverability reflects the infrequency of recruitment and slow growth rate for replacement colonies to reach a significant size.
Intermediate Moderate Moderate Moderate
Colonies rely on high water flow rates to bring food and to remove silt. Colonies deprived of food may be adversely affected and, without significant water flow to remove silt, silt may kill tissue leaving areas bare of coenenchyme to be colonized by encrusting organisms. 'Moderate' recoverability reflects the infrequency of recruitment and slow growth rate for replacement colonies to reach a significant size.
Tolerant* Not relevant Not sensitive* Moderate
Eunicella verrucosa extends from south-west Britain to the Mediterranean (Manual, 1988). Therefore, it is a warmer water species and will most likely grow faster and reproduce more frequently in warmer conditions. In the case off an acute rise in temperature at the warmest time of year, it is not expected that temperature will be harmful.
Low High Low Moderate
Long-term decrease in temperature is likely to lead to a poor year for recruitment but is unlikely to lead to mortality. A live specimen collected from shallow depths off North Devon in 1973 exhibited growth rings that demonstrated that the colony had survived the 1962/63 cold winter. Also, large colonies were being collected from Lundy in the late 1960's suggesting no significant loss in 1962/63. (K. Hiscock, own observations.) Assuming that temperature decrease reduces recruitment, the population size might decline for a year but recovery will occur following a successful recruitment.
Tolerant Not relevant Not sensitive Moderate
Eunicella verrucosa occurs in the turbid waters of North Devon and, in its usual locations in clearer water. It seems, therefore, that it will survive short-term increases in turbidity. Increased turbidity will also lead to a reduction in the abundance of algae which can smother sea fans.
Intermediate Moderate Moderate Low
Whilst Eunicella verrucosa most likely relies on plankton rather than suspended organic matter for food, decreases in turbidity can have a significant adverse impact on shallow water populations because of increased amounts of summer ephemeral seaweeds growing and smothering colonies. Not all colonies are likely to be killed and recovery to a population structure similar to before mortality is likely to be a few years. However, because of sporadic recruitment, it may take more than five years for the population structure to regain a similar size.
Intermediate Moderate Moderate High
Sea fans will be detached from the substratum by storms. Detached colonies are frequently seen on the seabed and after severe storms may be washed-up on the strandline. Not all colonies are likely to be killed and, whilst density of colonies might be back to pre-event levels within a few years, recovery to a population structure similar to before mortality is likely to be in excess of five years.
Intermediate Moderate Moderate Moderate
Sea fans live in conditions where either wave action or tidal flow bring food and keep colonies clear of silt. If tidal streams are weak, then wave action may be important and a decrease in wave exposure may result in some mortality. Not all colonies are likely to be killed and recovery to a population structure similar to before mortality is likely to be a few years.
Not relevant Not relevant Not relevant High
Anthozoans are not known to be able to detect noise.
Not relevant Not relevant Not relevant High
Anthozoans are not known to be able to detect visual presence.
Intermediate Moderate Moderate Moderate
Physical disturbance and abrasion is likely to damage the coenenchyme, although sea fans are firmly attached and very flexible so are unlikely to be detached unless 'hooked' by the abrasive object. The report by Eno et al. (1996) suggested that Eunicella verrucosa was "remarkably resilient" to impact from lobster pots. However, abrasion that removes the coenenchyme may allow the settlement of epibiota that will increase drag and may include species that bore into the skeleton and weaken the colony (impacts observed on the structurally similar sea fan Paramuricea clavata described by Bavestrello et al., 1997). Since some individuals in a population may be killed or viability reduced, intolerance is recorded as intermediate. The coenenchyme covering the axial skeleton will re-grow over scrapes of one side of the skeleton in about one week (Keith Hiscock, pers comm.). However, where whole individuals are killed recoverability is likely to be low as many individual colonies will be 20 or more years old and recruitment is likely to be sporadic.
High Moderate Moderate Moderate
Colonies that are detached are likely to survive for some time lying on the seabed but will be little able to feed and will most likely be smothered. Colonies cannot re-attach and are therefore doomed. Not all colonies are likely to be killed in a displacement event and recovery to a population structure similar to before mortality is likely to be a few years.

Chemical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
No information Not relevant No information Not relevant
No information found.
Heavy metal contamination
No information Not relevant No information Not relevant
No information found.
Hydrocarbon contamination
No information Not relevant No information Not relevant
No information found.
Radionuclide contamination
No information Not relevant No information Not relevant
No information found.
Changes in nutrient levels
Tolerant Not relevant Not sensitive Moderate
It is not expected that a change in nutrients will have a significant effect on Eunicella verrucosa abundance and survival. Sea fans feed on planktonic organisms and, although abundance of those organisms might change as nutrient concentrations vary, the long term effects on food sources are not likely to be significant. However, algae colonize and may smother sea fans and may increase in abundance as a result of increase in nutrient concentrations.
Not relevant Not relevant Not relevant Moderate
Sea fans live in fully saline conditions in the open sea. Increase in salinity may only occur marginally to levels more typical of the Mediterranean where sea fans thrive.
High Very High Moderate
Sea fans live in fully saline conditions in the open sea. It seems likely that lowered salinity will kill colonies. Recovery will depend on recruitment which is likely to be very slow if surviving colonies are distant and even partial recovery may take more than ten years. Also, colonies grow slowly and the establishment of populations with large individuals will take many years.
High Very High Moderate
There was no information available concerning the effects of hypoxia for Eunicella verrucosa. However, as a species that lives in fully oxygenated waters in conditions of flowing waters, it is expected that they might have a high intolerance to decreased oxygen levels. Recovery will depend on recruitment which is likely to be very slow if surviving colonies are distant and even partial recovery may take more than ten years. Also, colonies grow slowly and the establishment of populations with large individuals will take many years.

Biological pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
No information Not relevant No information Not relevant
Insufficient
information.
Not relevant Not relevant Not relevant Not relevant
No non-native species are known to be associated with or adversely affect Eunicella verrucosa.
Intermediate Moderate Moderate Moderate
Extraction for the souvenir trade occurred in localised areas in the late 1960's. Large colonies were selected and so some of the population remained to grow and reproduce locally. Recovery of populations would be likely to be more rapid than if all had been removed. However, although settlement of replacement individuals might occur rapidly, colonies grow slowly and the establishment of populations with large individuals will take many years.
Not relevant Not relevant Not relevant Moderate
Species associated with Eunicella verrucosa are not extracted and the populations occur on rock where destructive activities such as dredging and trawling are unlikely to occur.

Additional information

Eunicella verrucosa may be damaged or destroyed by the ovalid snail %Simnia patula%. The snails feed on (Lebour, 1932) and are expected to lay their eggs on Eunicella verrucosa. Theodor (1967) describes how the snail %Simnia spelta% causes denudation of branches of %Eunicella stricta%, rarely destroying the colony but causing bare skeleton to attract fouling organisms. The mechanism of destruction might be that described by Main (1982) for %Simnia barbarensis% which strips the soft tissues of the host and lays its egg capsules on the internal skeleton. In late July 2001, a high proportion of Eunicella verrucosa on the north coast of Lundy, England were observed to be dead or part dead with only the external skin of the coenenchyme remaining (K. Hiscock, own observations). Simnia patula were later found on colonies (R. Irving, pers. comm.).

Importance review

Policy/legislation

Wildlife & Countryside ActSchedule 5, section 9
UK Biodiversity Action Plan Priority
Species of principal importance (England)
Species of principal importance (Wales)
IUCN Red ListVulnerable (VU)
Features of Conservation Importance (England & Wales)

Status

National (GB) importanceNot rare/scarceGlobal red list (IUCN) categoryVulnerable (VU)

Non-native

Native-
Origin- Date ArrivedNot relevant

Importance information

Eunicella verrucosa provides an important habitat for two associated species: the sea slug Tritonia nilsohdneri and the sea fan anemone Amphianthus dohrnii. The 'poached egg shell' Simnia patula also occurs on Eunicella but Alcyonium spp. are a more favoured habitat. The pink sea fan is a charismatic species and one that illustrates slow growth and poor recovery potential if lost. Whilst listed as nationally scarce (Sanderson, 1996), the species is most likely more widespread than recorded. Also, there may be very large populations in some areas; for instance a population of half a million colonies is suggested for Lyme Bay (Anonymous, 2001)

Bibliography

  1. Anonymous, 1999l. Pink sea-fan (Eunicella verrucosa). Species Action Plan. In UK Biodiversity Group. Tranche 2 Action Plans. English Nature for the UK Biodiversity Group, Peterborough., English Nature for the UK Biodiversity Group, Peterborough.

  2. Anonymous, 2001. East Tennants Seafan Research Study [on-line] http//:www.reef-research.org, 2001-07-10

  3. Bavestrello, G., Cerrano, C., Zanzi, D. & Cattaneo Vietti, R. 1997. Damage by fishing activities in the gorgonian coral Paramuricea clavata in the Ligurian Sea. Aquatic Conservation: Marine and Freshwater Ecosystems, 7, 253-262.

  4. Bunker, F., 1986. Survey of the Broad sea fan Eunicella verrucosa around Skomer Marine Reserve in 1985 and a review of its importance (together with notes on some other species of interest and data concerning previously unsurveyed or poorly documented areas). Volume I. Report to the NCC by the Field Studies Council.

  5. Carpine, C. & Grasshoff, M. 1975. Les gorgonaires de la Méditerranée. Bulletin Océanographique de Monaco, 71, 1-140.

  6. Cerrano, C., Bavestrello, G., Bianchi, C., Cattaneo-Vietti, R., Bava, S., Morganti, C., Morri, C., Picco, P., Sara, G., Schiaparelli, S., Siccardi, A. & Sponga, F., 2000. A catastrophic mass-mortality episode of gorgonians and other organisms in the Ligurian Sea (North-western Mediterranean), summer 1999. Ecology Letters, 3 (4), 284-293.

  7. Coma, R., Linares, C., Ribes, M., Diaz, D., Garrabou, J. & Ballesteros, E., 2006. Consequences of a mass mortality in populations of Eunicella singularis (Cnidaria: Octorallia) in Menorca (NW Mediterranean). Marine Ecology Progress Series, 331, 51-60.

  8. Coma, R., Ribes, M., Zabela, M. & Gili, J.-M. 1995. Reproduction and cycle of gonadial development in the Mediterranean gorgonian Paramuricea clavata. Marine Ecology Progress Series, 117, 173-183.

  9. Coma, R., Ribes, M., Zabela, M. & Gili, J.-M. 1995. Reproduction and cycle of gonadial development in the Mediterranean gorgonian Paramuricea clavata. Marine Ecology Progress Series, 117, 173-183.

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  23. Sheehan, E.V., Stevens, T.F., Gall, S.C., Cousens, S.L. & Attrill, M.J., 2013. Recovery of a temperate reef assemblage in a marine protected area following the exclusion of towed demersal fishing. Plos One, 8 (12), e83883.

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Citation

This review can be cited as:

Hiscock, K. 2007. Eunicella verrucosa Pink sea fan. 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/1121

Last Updated: 08/06/2007