Eunicella verrucosa and Pentapora foliacea on wave-exposed circalittoral rock

01-09-2000
Researched byJohn Readman, Angus Jackson & Dr. Keith Hiscock Refereed byThis information is not refereed.
EUNIS CodeA4.1311 EUNIS NameEunicella verrucosa and Pentapora foliacea on wave-exposed circalittoral rock

Summary

UK and Ireland classification

EUNIS 2008A4.1311Eunicella verrucosa and Pentapora foliacea on wave-exposed circalittoral rock
EUNIS 2006A4.1311Eunicella verrucosa and Pentapora foliacea on wave-exposed circalittoral rock
JNCC 2004CR.HCR.XFa.ByErSp.EunEunicella verrucosa and Pentapora foliacea on wave-exposed circalittoral rock
1997 BiotopeCR.MCR.XFa.ErSEunErect sponges, Eunicella verrucosa and Pentapora foliacea on slightly tide-swept moderately exposed circalittoral rock

Description

This variant typically occurs on wave-exposed, steep, circalittoral bedrock, boulder slopes and outcrops, subject to varying tidal streams. This silty variant contains a diverse faunal community, dominated by the seafan Eunicella verrucosa, the bryozoan Pentapora foliacea and the cup coral Caryophyllia smithii. There are frequently numerous Alcyonium digitatum, and these may become locally abundant under more tide-swept conditions. Alcyonium glomeratum may also be present. A diverse sponge community is usually present, including numerous erect sponges; species present include Cliona celata, Raspailia ramosa, Raspailia hispida, Axinella dissimilis, Stelligera stuposa, Dysidea fragilis and Polymastia boletiformisHomaxinella subdola may be present in the south west. A hydroid/bryozoan turf may develop in the understorey of this rich sponge assemblage, with species such as Nemertesia antennina, Nemertesia ramosa, crisiids, Alcyonidium diaphanum and Bugula plumosa. The sea cucumber Holothuria forskali may be locally abundant, feeding on the silty deposits on the rock surface. Other echinoderms encountered include the starfish Marthasterias glacialis and the urchin Echinus esculentus. Other fauna includes aggregations of colonial ascidians Clavelina lepadiformis and Stolonica socialis. Anemones such as Actinothoe sphyrodeta and Parazoanthus axinellae may be seen dotted across the rock surface. This biotope is present in south west England and Wales. (Information from Connor et al., 2004).

Recorded distribution in Britain and Ireland

Recorded in southern England from Dorset westwards, in the Isles of Scilly and on the north coasts of Devon and Cornwall, Lundy and Skomer. One record from Bardsey Island in north Wales (without Eunicella verrucosa) and also from several locations on the west coast of Ireland including Donegal and Bantry Bays.

Depth range

-

Additional information

-

Listed By

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JNCC

Habitat review

Ecology

Ecological and functional relationships

  • The biotopes represented by MCR.ErSEun are sponge and soft coral dominated. Sponges are noted as being inhabited by a wide diversity of invertebrates. Sponges can provide hard substrata for attachment, refugia and shelter, an enhanced food supply in feeding currents and a potential food source themselves (Klitgaard, 1995; Koukouras et al., 1996.)
  • The fauna associated with sponges in temperate to cold waters is considered to be facultative rather than obligate and reflects the fauna of the local geographic area (Klitgaard, 1995)
  • Predation levels of the characterizing species in the biotope are poorly understood. Eunicella verrucosa is preyed upon by the sea slug Tritonia nilsodhneri and Alcyonium digitatum by Tritonia plebeia. Alcyonium digitatum and Alcyonium glomeratum are preyed upon by the prosobranch Simnia patula Grazing by the sea urchin Echinus esculentus may modify faunal abundance and distribution. Some species of temperate sponge contain chemicals that can inhibit sea urchin feeding (Wright et al., 1997)
  • Large colonies of Pentapora foliacea with their complex laminar structure are noted as potentially sheltering thousands of other animals. Pentapora fascialis in the Mediterranean supports various epibiotic species, some of which may cause partial mortality of colonies (Cocito et al., 1998(a)).
  • The various mobile echinoderms characteristic of the biotope (e.g. Luidia ciliaris, Henricia oculata, Asterias rubens) may have a role in modifying other benthic populations through predation.
  • Eunicella verrucosa provides a habitat for the nationally rare sea anemone Amphianthus dohrnii.
  • Where the deposit feeding sea cucumber, the cotton spinner Holothuria forskali occurs, it may be important in removing silt and enabling settlement of other benthic species.

Seasonal and longer term change

Annual species in the biotope such as Nemertesia ramosa will increase and decrease through the seasons. Other species such as Alcyonium digitatum have seasonal stages, retracting their polyps and not feeding from about July to November, during which time the surface of the colony becomes covered with encrusting algae and hydroids (Fish & Fish, 1996). When the colony recommences feeding in December the surface film, together with the surface epithelium, is shed. The main species used to represent the biotope, Eunicella verrucosa, Axinella dissimilis, & Pentapora foliacea are typically long-lived perennials. Where the biotope occurs in the lower infralittoral or upper circalittoral, extensive growth of annual algae may occur, especially in years when the water is clear.

Habitat structure and complexity

Many of the species characteristic of this community add considerable physical complexity to the biotope. There are upright branching and cup sponges, sea fans, colonies of dead mans fingers and erect bryozoans. All of these species add depth and a three dimensional structure to the substratum. The biotope occurs on bedrock and boulders which may provide overhangs, crevices and shelter where crevice dwelling species such as sea cucumbers (Aslia lefevrei), squat lobsters and wrasse (mainly Centrolabrus exoletus) may live. Complex upright bryozoans as well as many sponges are recorded as providing substratum and shelter for other species . Sponge morphology is important in determining the number and abundance of inhabitant species. Sponges with a spicule 'fur' have more associated taxa than sponges without (Klitgaard, 1995). For example, Axinella species have a spicule 'fur' (Moss & Ackers, 1982). Hayward & Ryland, (1979) record large colonies of Pentapora foliacea as potentially sheltering thousands of other animals.
  • The biotope MCR.PhaAxi has a similar sponge component to MCR.ErSEun but has different associated fauna and occurs in deeper water with greater wave exposure.
  • MCR.ErSPbolSH is again a sponge dominated biotope with an understorey of hydroids and bryozoans. Although still on fairly stable substrata some of the species present are associated with more ephemeral or disturbed biotopes.

Productivity

No photosynthetic species are listed as characterizing species in MCR.ErSEun, a circalittoral biotope. Consequently, primary production is not regarded as a major component of productivity. Nevertheless, some characteristically deep water species of algae are often present and near to the infralittoral algae may sometimes be abundant. The biotopes MCR.ErSPbolSH and MCR.ErSSwi may have a small algal component. The biotopes are often species rich and may contain quite high animal densities and biomass. Specific information about the productivity of characterizing species or about the biotopes in general are not available.

Recruitment processes

Most of the characterizing species in the biotope are sessile suspension feeders. Recruitment of adults of these species to the biotope by immigration is unlikely. Consequently, recruitment must occur primarily through dispersive larval stages. Some species have larvae that can disperse widely and these may arrive from distant locations. Other species such as Pentapora foliacea have larvae that typically exist for only a short time and will settle in the proximity of the parent (Cocito et al., 1998b). Recruitment of the mobile predators and grazers may be through immigration of adults or via a larval dispersal phase.

Time for community to reach maturity

Some species within the biotope community are annuals and recruit each year (e.g. Nemertesia ramosa). Other species are potentially very slow growing and long lived such as Eunicella verrucosa which may live as long as 50 years (K. Hiscock pers. comm.).

Additional information

The main trophic group in the biotope is suspension feeders although there may be several species of fish and echinoderm predators or grazers present.

Preferences & Distribution

Recorded distribution in Britain and IrelandRecorded in southern England from Dorset westwards, in the Isles of Scilly and on the north coasts of Devon and Cornwall, Lundy and Skomer. One record from Bardsey Island in north Wales (without Eunicella verrucosa) and also from several locations on the west coast of Ireland including Donegal and Bantry Bays.

Habitat preferences

Depth Range
Water clarity preferences
Limiting Nutrients Data deficient
Salinity Full (30-40 psu)
Physiographic Open coast
Biological Zone Circalittoral
Substratum Bedrock, Large to very large boulders
Tidal Moderately Strong 1 to 3 knots (0.5-1.5 m/sec.), Weak < 1 knot (<0.5 m/sec.)
Wave Exposed, Moderately exposed, Very exposed
Other preferences

Additional Information

Recorded distribution is only for the representative biotope MCR.ErSEun. For recorded distributions of the other biotopes represented by this review see MERMAID. Apart from perhaps MCR.ErSSwi, the biotopes represented by this review have a silt component suggesting that localized shelter may be important in encouraging their development.

Species composition

Species found especially in this biotope

    Rare or scarce species associated with this biotope

    -

    Additional information

    Sensitivity reviewHow is sensitivity assessed?

    Sensitivity characteristics of the habitat and relevant characteristic species

    CR.HCR.XFa.ByErSp.Eun is dominated by the sea fan Eunicella verrucosa, the bryozoan Pentapora foliacea and the cup coral Caryophyllia smithii. It occurs in variable water movement on wave exposed steep circalittoral bedrock and boulders subject to silt as it is surrounded by coarse sediment.  The biotope contains a diverse range of fauna but other species that may be present are not considered characterizing. 

    There are a few similar biotopes that lack the characterizing Eunicella verrucosa and the biotope CR.HCR.XFa.ByErSp.Sag, which may also contain Eunicella verrucosa, is instead characterized by its fragile sponge component. Therefore, the sensitivity assessment is based on the sensitivity of the important characterizing species Eunicella verrucosa, Pentapora foliacea, and Caryophyllia smithii. The sensitivity of other members so the community is discussed where relevant.

    Resilience and recovery rates of habitat

    Eunicella verrucosa forms large colonies which branch profusely, mostly in one plane up to 30 cm tall and 40 cm wide and grows very slowly in British waters, approximately 1 cm per year (Bunker, 1984; Picton & Morrow, 2005).   There is no specific information on reproduction in Eunicella verrucosa but the larvae of Eunicella singularis are most likely lecithotrophic and have a short life (several hours to several days) (Weinberg & Weinberg, 1979). Recruitment in gorgonians is often reported to be sporadic and/or low (Yoshioka 1996; Lasker et al. 1998; Coma et al. 2006).   Eunicella verrucosa has been known to colonize wrecks at least several hundred metres from other hard substrata but is thought to have larvae that generally settle near the parent (Hiscock, 2007). Growth rate can be highly variable.  An increase in branch length of up to 6 cm was reported for some branches in one year but virtually none in others in Lyme Bay populations over a year (C. Munro, pers. comm. cited in Hiscock, 2007).  In the morphologically similar Paramuricea clavata in the Mediterranean, Coma et al. (1995) described reproduction and the cycle of gonad development.  Spawning occurred 3-6 days after the full or new moon in summer. Spawned eggs adhered to a mucus coating on 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 (Hiscock, 2007).  Coma et al. (2006) reported ongoing recovery in Eunicella singularis populations in the Mediterranean four years following a mass-mortality event (45%).  Although not recovered, Sheehan et al. (2013) noted that within three years of closing an area in Lyme Bay, UK to fishing, some recovery of Eunicella verrucosa had occurred, with a marked increase compared to areas that were still fished.

    Pentapora foliacea is an erect perennial bryozoan (Eggleston, 1972; Hayward & Ryland, 1995).  Whilst Hayward & Ryland (1999) conflated Pentapora foliacea and Pentapora fascialis, Lombardi et al. (2010) concluded that Pentapora foliacea and Pentpora fascialis were distinct species and that Pentapora foliacea was the resident species in the North East Atlantic while Pentaporafascialis was included in the Mediterranean clade.  Given taxonomic confusion in the literature, this assessment is based on information on both Pentapora foliacea and Pentapora fascialis.

    Pentapora fascialis has been recorded to recover in 3.5 years after almost total loss of a local population (Cocito et al., 1998).  The species was reported to repair damage to the colony through regrowth of new zooids and strengthening of the base by thickening of lower zooid walls (Hayward and Ryland, 1979).  Pentapora foliacea (as Pentapora fascialis)  grows initially as an encrusting sheet, which seems able to regenerate erect growths (P.J. Hayward pers. comm cited in Jackson, 2016). Colonies are typically 20 cm in diameter but can grow up to 2 m in diameter and reach a height of 30 cm in the British Isles (Hayward & Ryland, 1979).   The presence or absence of ovicells has been taken to be a reliable indicator of reproductive status and, therefore, of sexual maturity (Cocito et al., 1998). Ovicells were present in colonies in Skomer, Wales in September, indicating a reproduction event in September or late August (Lock et al., 2006). Colonies of Pentapora fascialis as small as 2.8 cm have been recorded as having ovicells, with reproduction possible from early stage of colony development (Cocito et al., 1998 cited in Jackson, 2016).

    Lock et al. (2006) describes growth of Pentapora foliacea in Skomer, Wales as highly variable, with some colonies growing 800 cm² in a year whilst other large colonies completely disappeared.  Recovery to pre-disturbance levels following a severe heat event, which resulted in decline of 86% in live colony portion of Pentapora fascialis in the Mediterranean, took four years Cocito & Sgorbini (2014).

    Caryophyllia smithii is a small (max 3 cm across) solitary coral, common within tide swept sites of the UK (Wood, 2005), distributed from Greece (Koukouras, 2010) to the Shetland Islands and southern Norway (Wilson, 1975; NBN, 2015). It was suggested by Fowler & Laffoley (1993) that Caryophyllia smithii was a slow growing species (0.5-1 mm in horizontal dimension of the corallum per year), which in turn suggested that inter-specific spatial competition with colonial faunal or algae species were important factors in determining local abundance of Caryophyllia smithii (Bell & Turner, 2000). Caryophyllia smithii reproduces sexually; sessile polyps discharge gametes typically from January-April. Gamete release is probably triggered by seasonal temperature increases.  Gametes are fertilized in the water column and develop into a swimming planula that then settles onto suitable substrata. The pelagic stage of the larvae may last up to 10 weeks, which provides this species with a good dispersal capability (Tranter et al., 1982). Caryophyllia smithii reproduces between January and March; spawning occurs from March to June (Tranter et al., 1982). However, asexual reproduction and division is commonly observed (Hiscock & Howlett, 1976).

    Hydroids are often the first organisms to colonize available space in settlement experiments (Gili & Hughes, 1995). Anthozoans, such as Alcyonium digitatum are long lived with potentially highly dispersive pelagic larvae and are relatively widespread. They are not restricted to this biotope and would probably be able to recruit within 2-5 years (Sebens, 1985; Jensen et al., 1994). Juvenile Alcyonium digitatum are highly susceptible to being smothered or eaten but can survive intense sea urchin predation when larger (Sebens, 1985; 1986).

    Bryozoans, hydroids, and ascidians are opportunistic, grow and colonize space rapidly and will probably develop a faunal turf within 1-2 years.

    Resilience assessment

    Bryozoans tend to be fast growing fauna that are capable of self-regeneration.  Dispersal of the larvae is limited and whilst it is likely that the bryozoan turfs would regenerate rapidly, probably within 2 years (resilience of ‘High’) for most levels of damage, in the case of removal of 75% or more of the bryozoans/habitat, recovery could take longer .

    Caryophyllia smithii colonized the wreck of the Scylla within a year, however this may be due to the time of the vessel sinking and if removed recovery may take longer.   Eunicella verrucosa has been described as slow growing in the British Isles (Picton & Morrow, 2005) and recovery is likely to be slow following population collapses.  Recent studies including a mass mortality event in the Mediterranean (Coma et al., 2006) and creation of a no take zone in Lyme Bay (Sheehan et al., 2013) have reported some recovery within the first few years.  For resistance of ‘None’, resilience has been assessed as ‘Low’ (recovery within 10-25 years).  Where resistance is Low or Medium, resilience has been assessed as ‘Medium’ (Recovery within 2-10 years).

    Hydrological Pressures

     ResistanceResilienceSensitivity
    High High Not sensitive
    Q: High
    A: Medium
    C: Medium
    Q: High
    A: High
    C: High
    Q: High
    A: Medium
    C: Medium

    Eunicella verrucosa has been recorded in the Western Mediterranean and off north west Africa (Wells et al., 1983 cited in Koomen & Helsdingen, 1996), and increase in temperature is not likely to negatively affect the species. However, during the last decades, mass mortality events related to high seawater temperature anomalies have been reported within the Western Mediterranean basin. A mass mortality event in 1999 affected many gorgonians, although Eunicella verrucosa near Gallinaria Island was ‘little affected’ (Cerrano et al. 2000).  ‘Occasional’ mortality was observed in the shallowest populations along the Provence coast (at 37-38 m) during a high temperature event in 1999 where sea temperature was 23-24 °C throughout the water column to 40m depth (Perez et al. 2000). In 2003, the pink sea fan populations were affected in the Gulf of Genoa but not along the Provence coast (Garrabou et al. 2009). Although total mortality was not explicitly reported for this species, a certain reduction in population size could be suspected, due to delayed mortality of colonies affected by high levels of injury, as observed in some other Mediterranean gorgonians (e.g. Linares et al.,2005; Coma et al., 2006).

    Cocito & Sgorbini (2014) studied spatial and temporal patterns of colonial bryozoans in the Ligurian Sea over nine years.  High temperature events causied mass mortality among a number of species.  The decline in Pentapora fascialis colony cover between 11 and 22 m depth followed the unusually warm summer in 1999 (temperature at 11 m of 23.87 ± 1.4 °C)  with a 86% reduction in live colony portion and the larger colonies were most affected.  Gradual recovery took place, with deeper communities recovering to pre-disturbance levels within four years.  Pentapora foliacea has been identified as

    Whilst Hayward & Ryland (1999) conflated Pentapora foliacea and Pentapora fascialis, Lombardi et al. (2010) concluded that Pentapora foliacea and Pentpora fascialis were distinct species and that P. foliacea was the resident species in the North East Atlantic while P.fascialis was included in the Mediterranean clade. 

    Caryophyllia smithii is found across the British Isles (NBN, 2015) and has been recorded in Greece (Koukouras, 2010).  It is therefore unlikely to be significantly affected at the benchmark. However, Tranter et al. (1982) suggested Caryophyllia smithii reproduction was cued by seasonal increases in sea water temperature. Therefore unseasonal increases in temperature may disrupt natural reproductive processes and negatively influence recruitment patterns.

    Sensitivity assessment

    Eunicella verrucosa, Pentapora foliaceas and Caryophyllia smithii are distributed throughout the UK, with distribution of some species as far south as the Mediterranean.   Resistance is therefore assessed as ‘High’, resilience as ‘High’ and the biotope assessed  as ‘Not sensitive’ at the benchmark level

    Medium Medium Medium
    Q: Medium
    A: Medium
    C: Medium
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low

    Eunicella verrucosa is a southern species, distribution is generally limited to the south west of the British Isles (Hayward & Ryland, 1990; NBN, 2015).  A decrease in temperature is likely to result in mortality. However, 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(Hiscock, pers comm.). Also, large colonies were collected from Lundy in the late 1960's suggesting no significant loss in 1962/63 (Hiscock, 2007). Assuming that temperature decrease reduces recruitment, the population size might decline for a year but recovery would occur following successful recruitment.

    Pentapora foliacea is found as far north the Minch off western Scotland (Lombardi et al., 2010). Patzold et al. (1987) recorded the formation of a growth bands in Pentapora foliacea during times of reduced reproduction, which appeared during periods of colder water temperatures.  Once established, colonies are most likely able to withstand occasional lower or higher than normal temperatures, but long term decreases in temperature may cause distribution range to shrink.

    Caryophyllia smithii is a southern species (Fish & Fish, 1996) with a northern range limit in the Shetland isles (NBN, 2015).  Therefore, it is likely to be negatively affected by cold temperatures in northern examples of this biotope.

    Sensitivity assessment

    Eunicella verrucosa, already close to its northern distribution limit, would likely suffer mortality in the event of a decrease in temperature, however, it appears to have survived the 1962/3 winter and may have some resistance to temporary changed. Resistance is therefore assessed as ‘Medium’, resilience as ‘Medium’ and sensitivity as ‘Medium’.

    Low Medium Medium
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low
    Q: Low
    A: NR
    C: Low

    CR.HCR.XFa.ByErSp.Eun is a circalittoral biotope and an increase at the benchmark would result in change from full to hypersalinity.  No records of the characterizing Caryophyllia smithii or Eunicella verrucosa in hypersaline conditions was found.  Chesher (1975) monitored the species surrounding a desalination outfall with brine effluent at 52‰ salinity, together with variable concentrations of copper and nickel.  As a group gorgonians were noted to survive brief exposure to 4-5% effluent, however long term survival decreased in relation to proximity to the outfall.  

    Whilst no evidence for the characterizing species was found, there is evidence of gorgonian mortality due to hypersaline effluent.  Resistance is therefore probably ‘Low’, resilience ‘Medium’ and sensitivity is ‘Medium’.

    Low Medium Medium
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low

    Ryland (1970) stated that, with a few exceptions, the Gymnolaemata were fairly stenohaline and restricted to full salinity (30-35 ppt), noting that reduced salinities result in an impoverished bryozoan fauna. For example, Flustra foliacea appears to be restricted to areas with high salinity (Tyler-Walters & Ballerstedt, 2007; Budd, 2008).

    Dyrynda (1994) noted that Flustra foliacea and Alcyonidium diaphanum were probably restricted to the vicinity of the Poole Harbour entrance by their intolerance to reduced salinity. Although, protected from extreme changes in salinity due to their subtidal habitat, severe hyposaline conditions could adversely affect  Flustra foliacea colonies.  However, Novosel et al. (2004) described large colonies of Pentapora fascialis growing inside the plumes of marine freshwater springs (3 psu lower than water outside of the channel).

    Eunicella varricosa has only been recorded in Full salinity biotopes while Caryophyllia smithii has been recorded in biotopes from Full to Low salinity (Connor et al., 2004) and would probably tolerate a change at the benchmark level.

    Sensitivity assessment

    Both Pentapora foliacea and Eunicella verrucosa would probably be affected adversely by a decrease in salinity at the benchmark level and resistance is assessed as ‘Low’, resilience as ‘Medium’ and sensitivity as ‘Medium’.

    High High Not sensitive
    Q: High
    A: Medium
    C: Medium
    Q: High
    A: High
    C: High
    Q: High
    A: Medium
    C: Medium

    CR.HCR.XFa.ByErSp.Eun consists mainly of species firmly attached to the substratum and which would be unlikely to be displaced by an increase in the strength of tidal streams at the benchmark level.

    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. Colonies rely on high water flow rates to bring food and to remove silt. (Hiscock, 2007).  Bunker (1986) reported that Eunicella verrucosa was present in areas subject to at least moderate tidal stream, but was most abundant in strong tidal streams.  There is a tendency for Eunicella verrucosa to align across the direction of the prevailing current (Bunker, 1986).

    Water flow has been shown to be important for the development of bryozoan communities and the provision of suitable hard substrata for colonization (Eggleston, 1972b; Ryland, 1976). In addition, areas subject to high mass transport of water such as the Menai Strait and tidal rapids generally support large numbers of bryozoan species (Moore, 1977a). Although bryozoans are active suspension feeders, feeding currents are probably fairly localized and they are dependent on water flow to bring adequate food supplies within reach (McKinney, 1986). A substantial decrease in water flow will probably result in impaired growth due to a reduction in food availability, and an increased risk of siltation (Tyler-Walters, 2005).

    Okamura (1984) reported that an increase in water flow from slow flow (1-2 cm/s) to fast flow (0.1 – 0.2 m/s) reduced feeding efficiency in small colonies but not in large colonies of Bugula stolonifera

    Caryophyllia smithii, is a suspension feeder, relying on water currents to supply food (Hiscock, 1983). These taxa therefore thrive in conditions of vigorous water flow e.g. around Orkney and St Abbs, Scotland, where Alcyonium digitatum dominated biotopes may experience tidal currents of 3 and 4 knots (approximately 1.5 m/sec) during spring tides (De Kluijver, 1993). Caryophyllia smithii in particular is described as favouring sites with high tidal flow (Bell & Turner, 2000; Wood, 2005). 

    Eunicella verrucosa, Caryophyllia smithii and Pentapora foliacea have been recorded in biotopes ranging from very weak to strong water flow (0-3 m/s) (Connor et al., 2004)

    Sensitivity assessment

    CR.HCR.XFa.ByErSp.Eun is found in moderately strong water flow (1-3 knots) and, whilst a significant decrease could result in less favourable conditions for Eunicella verrucosa,  a change at the benchmark level (0.1-0.2 m/s) is unlikely to affect the characterizing species, which are all found in biotopes that experience higher and lower water flow.  Resistance is therefore assessed as ‘High’, resilience as ‘High’ and the biotope is ‘Not Sensitive’.

    Not relevant (NR) Not relevant (NR) Not relevant (NR)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    Changes in emergence are Not Relevant to this biotope as it is restricted to fully subtidal/circalittoral conditions - the pressure benchmark is relevant only to littoral and shallow sublittoral fringe biotopes.

    High High Not sensitive
    Q: Low
    A: NR
    C: NR
    Q: High
    A: High
    C: High
    Q: Low
    A: Low
    C: Low

    Eunicella verrucosa occurs in biotopes that are extremely wave exposed (Connor et al., 2004).  Bunker (1986) reported that Eunicella verrucosa was most abundant in moderately exposed locations. However, dead sea fans have been recorded washed up along Chesil Beach (UK) following winter storms (Hatcher and Trewhella, 2006 cited in Wood, 2015b).

    Caryophyllia smithii has been recorded in very sheltered to extremely exposed biotopes (Connor et al., 2004).

    Pentapora foliacea is recorded as occurring in biotopes experiencing moderate to extreme wave exposure (Connor et al., 2004). However, extreme wave action (storms) has been noted to cause widespread destruction of colonies (Cocito et al. (1998a). Significant increases in wave exposure may therefore cause damage to colonies.

    Sensitivity assessment:

    CR.HCR.XFa.ByErSp.Eun occurs across a number of wave exposures, from moderate to extremely exposed.  A decrease in wave exposure, e.g. due to artificial barriers, may be detrimental as the biotope is dependent on strong water flow.  But whilst storms may cause mortality, a 3-5% change in significant wave height is unlikely to result in any impact in a wave exposed biotope. Resistance is assessed as ‘High’, resilience as ‘High’ and the biotope is ‘Not Sensitive’ at the benchmark level.

    Chemical Pressures

     ResistanceResilienceSensitivity
    Not relevant (NR) Not relevant (NR) Not sensitive
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    Chan et al. (2012) studied the response of the gorgonian Subergorgia suberosa to heavy metal-contaminated seawater from a former coastal mining site in Taiwan.  Cu, Zn, and Cd each showed characteristic bioaccumulation. Metallic Zn accumulated, but rapidly dissipated. In contrast, Cu easily accumulated, but was slow to dissipate, and Cd was only slowly absorbed and dissipated. Associated polyp necrosis, mucus secretion, tissue expansion, and increased mortality were reported in Subergorgia suberosa exposed to water polluted with heavy metals.

    However, this biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with all relevant environmental protection standards.

    Not relevant (NR) Not relevant (NR) Not sensitive
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    CR.HCR.XFa.ByErSp.Eun is a sub-tidal biotope complex  (Connor et al., 2004). Oil pollution is mainly a surface phenomenon and its impact upon circalittoral turf communities is likely to be limited. However, as in the case of the Prestige oil spill off the coast of France, high swell and winds can cause oil pollutants to mix with the seawater and potentially negatively affect sub-littoral habitats (Castège et al., 2014).

    Filter feeders are highly sensitive to oil pollution, particularly those inhabiting the tidal zones that experience high exposure and show correspondingly high mortality, as are bottom dwelling organisms in areas where oil components are deposited by sedimentation (Zahn et al., 1981). There is little information on the effects of hydrocarbons on bryozoans. Ryland & Putron (1998) did not detect adverse effects of oil contamination on the bryozoan Alcyonidium spp. in Milford Haven or St. Catherine's Island, south Pembrokeshire, although it did alter the breeding period.  Banks & Brown (2002) found that exposure to crude oil significantly impacted recruitment in the bryozoan Membranipora savartii.  No evidence for Eunicella verrucosa was found, although White et al. (2012) reported on deep water gorgonian communities, including Swiftia pallida six months after the Deep Water Horizon oil spill.  Stress in the gorgonians was observed including excessive mucous production, retracted polyps and smothering by brown flocculent material (floc).

    However, this biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with all relevant environmental protection standards.

    Not relevant (NR) Not relevant (NR) Not sensitive
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    Bryozoans are common members of the fouling community, and amongst those organisms most resistant to antifouling measures, such as copper containing anti-fouling paints (Soule & Soule, 1979; Holt et al., 1995). Hoare & Hiscock (1974) suggested that polyzoa (bryozoa) were amongst the most intolerant species to acidified halogenated effluents in Amlwch Bay, Anglesey and reported that Flustra foliacea did not occur less than 165m from the effluent source. The evidence therefore suggests that Securiflustra securifrons would be sensitive to synthetic compounds.

    This biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with all relevant environmental protection standards.

    No evidence (NEv) Not relevant (NR) No evidence (NEv)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    No evidence

    Not relevant (NR) Not relevant (NR) Not sensitive
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    No benchmark was proposed.  Therefore, sensitivity has been assessed as 'Not sensitive' at the pressure benchmark that assumes compliance with all relevant environmental protection standards.

    Low Medium Medium
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low

    In general, respiration in most marine invertebrates does not appear to be significantly affected until extremely low concentrations are reached. For many benthic invertebrates this concentration is about 2 ml/l (ca 2.66 mg/l) (Herreid, 1980; Rosenberg et al., 1991; Diaz & Rosenberg, 1995). Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2 mg/l.

    Little information on the effects of oxygenation on bryozoans was found. Sagasti et al. (2000) reported that epifaunal communities, including the dominant bryozoans, were unaffected by periods of moderate hypoxia (ca 0.35 -1.4 ml/l) and short periods of anoxia (<0.35 ml/l) in the York River, Chesapeake Bay, although bryozoans were more abundant in the area with generally higher oxygen. However, estuarine species are likely to be better adapted to periodic changes in oxygenation. 

    Bell (2002) reported that an oxycline at Lough Hyne (<5 % surface concentration) limited vertical colonization by Caryophillia smithii.

    No evidence was found 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 it would be intolerant to decreased oxygen levels.

    Sensitivity assessment

    Despite limited evidence, Eunicella verrucosa and Caryophyllia smithii are unlikely to tolerate hypoxic events given their preference for moderate water movement and based on general information for marine invertebrates. Resistance is ‘Low’, resilience is ‘Medium’ and sensitivity is ‘Medium’.

    Not relevant (NR) Not relevant (NR) Not sensitive
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    Whilst little information on Pentapora spp. was found, O’Dea & Okamura (2000) found that annual growth of the bryozoan Flustra foliacea in western Europe has substantially increased since 1970.  They suggest that this could be due to eutrophication in coastal regions due to organic pollution, leading to increased phytoplankton biomass (see Allen et al., 1998).    Echavarri-Erasun et al. (2007) described the effects of deep water sewage discharge on the relative abundance of rocky reef communities.  Species typical of hard substrata (including Caryophyllia smithii and bryozoans) increased in total richness and abundance near the outfall.  Whilst Eunicella verrucosa could be at risk of competition from algae in shallow waters due to nutrient enrichment, CR.HCR.XFa.ByErSp.Eun is a circalittoral biotope and flora are not considered in this review.

    This biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with good status as defined by the WFD.

    High High Not sensitive
    Q: Medium
    A: Medium
    C: Medium
    Q: High
    A: High
    C: High
    Q: Medium
    A: Medium
    C: Medium

    Cocito et al. (2013) demonstrated the ability of Eunicella verrucosa and other gorgonians to feed on both suspended organic matter and zooplankton. Whilst little information on Pentapora spp. was found, O’Dea & Okamura (2000) found that annual growth of the bryozoan Flustra foliacea in western Europe has substantially increased since 1970.  They suggest that this could be due to eutrophication in coastal regions due to organic pollution, leading to increased phytoplankton biomass (see Allen et al., 1998).   Novosel et al. (2004) described large colonies of Pentapora fascialis growing inside the plume of marine freshwater springs.  The plumes had significantly higher concentrations of NO3-, SiO4, NH4+, NO2- and PO43-.  Echavarri-Erasun et al. (2007) described the effects of deep water sewage discharge on the relative abundance of rocky reef communities.  Species typical of hard substrata (including Caryophyllia smithii and bryozoans) increased in total richness and abundance near the outfall.

    Sensitivity assessment

    All characterizing species are sessile filter feeders and the evidence suggests that all tolerate, or increase in abundance, when exposed to organic enrichment in the circalittoral.  Resistance is ‘High’ resilience is ‘High’ and the biotope is ‘Not sensitive’.

    Physical Pressures

     ResistanceResilienceSensitivity
    None Very Low High
    Q: High
    A: High
    C: High
    Q: High
    A: High
    C: High
    Q: High
    A: High
    C: High

    All marine habitats and benthic species are considered to have a resistance of ‘None’ to this pressure and to be unable to recover from a permanent loss of habitat (resilience is ‘Very low’). Sensitivity within the direct spatial footprint of this pressure is therefore ‘High’. Although no specific evidence is described, confidence in this assessment is ‘High’, due to the incontrovertible nature of this pressure.

    None Very Low High
    Q: High
    A: High
    C: High
    Q: High
    A: High
    C: High
    Q: High
    A: High
    C: High

    If rock were replaced with sediment, this would represent a fundamental change to the physical character of the biotope and the species would be unlikely to recover. The biotope would be lost.

    Sensitivity assessment

    Resistance to the pressure is considered ‘None’, and resilience ‘Very low’. Sensitivity has been assessed as ‘High’.

    Not relevant (NR) Not relevant (NR) Not relevant (NR)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    ‘Not relevant’ to biotopes occurring on bedrock.

    Not relevant (NR) Not relevant (NR) Not relevant (NR)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    The species characterizing this biotope are epifauna or epiflora occurring on rock and would be sensitive to the removal of the habitat. However, extraction of rock substratum is considered unlikely and this pressure is considered to be ‘Not relevant’ to hard substratum habitats.

    Low Medium Medium
    Q: High
    A: Low
    C: Low
    Q: High
    A: Low
    C: Low
    Q: High
    A: Low
    C: Low

    Physical disturbance by fishing gear has been shown to adversely affect emergent epifaunal communities with hydroid and bryozoan matrices reported to be greatly reduced in fished areas (Jennings & Kaiser, 1998 and references therein). Heavy mobile gears could also result in movement of boulders (Bullimore, 1985; Jennings & Kaiser, 1998) and sensitivity of Eunicella verrucosa to abrasion events has been assessed High in previous reviews (MacDonald, 1996; Hall et al., 2008; Tillin et al., 2010).

    Other studies suggest that Eunicella verrucosa may be more resistant to abrasion pressures.  Eno et al. (2001) conducted experimental potting on areas containing fragile epifaunal species in Lyme Bay, south west England. Divers observed that pink sea fan ‘flexed and bent before returning to an upright position under the weight of pots’. Although relatively resistant to a single event, long-term deteriation or the effects of repeated exposure were not clear (Eno et al., 2001). Observation of pots suggested that they were dragged along the bottom when wind and tidal streams were strong, however, little damage to epifauna was observed.  Eunicella verrucosa were patchily distributed in areas subject to potting damage, but the study could not determine whether this was due to damage from potting (Eno et al., 2001). A further four year study on potting in the Lundy Marine Protected Area detected no significant differences in Eunicella verrucosa between areas subject to commercial potting and those where this activity was excluded.   However Tinsley (2006) observed flattened sea fan that had continued growing, with new growth being aligned perpendicular to the current, so clearly even colonies of Eunicella verrucosa that  are damaged can survive. Healthy Eunicella verrucosa are able to recover from minor damage and scratches to the coenenchyme (Tinsley, 2006), and the coenenchyme covering the axial skeleton will re-grow over scrapes on one side of the skeleton in about one week (Hiscock, pers. comm, cited in Hiscock, 2007.)  Hinz et al. (2011) reported that abundance and average body size of Eunicella verrucosa were not significantly affected by scallop dredging intensity.  Some large Pentapora foliacea individuals were observed to be badly smashed by potting (Eno et al., 2001).

    Sensitivity assessment. Eunicella verrucosa is a sessile epifauna and is likely to be severely damaged by heavy gears, such as scallop dredging (MacDonald et al., 1996).  However,  some studies suggests that the species may be more resistant, particularly to low intensity lighter abrasion pressures, such as pots and associated anchor damage (Eno et al. 1996)  Taking all the evidence into account, a resistance of ‘Low’ is recorded, albeit with a low confidence value owing to the lack of consensus in the literature. Resilience is assessed as ‘Medium’ and sensitivity as ‘Medium’.

    Not relevant (NR) Not relevant (NR) Not relevant (NR)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    The species characterizing this biotope group are epifauna or epiflora occurring on rock which is resistant to subsurface penetration.  The assessment for abrasion at the surface only is therefore considered to equally represent sensitivity to this pressure. This pressure is thought ‘Not Relevant’ to hard rock biotopes.

    High High Not sensitive
    Q: Medium
    A: Medium
    C: Medium
    Q: High
    A: High
    C: High
    Q: Medium
    A: Medium
    C: Medium

    While high levels of suspended solids may inhibit feeding, colonies of the sea fan Eunicella verrucosa produce mucus to clear themselves of silt (Hiscock, 2007) and is probably tolerant of increases in suspended sediment (Hiscock et al., 2004b).  Bunker (1986) reported that Eunicella verrucosa were mostly observed on bedrock or boulders, but occurred at sites described as  ‘moderately silted’.

    Populations of Caryophyllia smithii were studied at three sites of differing sedimentation regimes in Lough Hyne, Ireland (Bell & Turner, 2000).  The height, length, width and density of individuals were measured along with the depth of accumulated sediment on the rock substratum at each site. Calyx size was largest at the site of least sedimentation and smallest at the site of most sedimentation. In contrast, height of individuals was greatest at the site of most sedimentation and smallest at the site of least sedimentation. The height of individuals correlated with the level of surrounding sediment. Caryophyllia smithii was more abundant in areas with higher sedimentation (Bell & Turner, 2000).

    Bryozoans are suspension feeders that may be adversely affected by increases in suspended sediment, due to clogging of their feeding apparatus. 

    Sensitivity assessment

    CR.HCR.XFa.ByErSp.Eun occurs on bedrock in moderate water flow in the circalittoral and is unlikely to experience highly turbid conditions.  From the evidence presented above, the characterizing species would probably tolerate some siltation and a change at the benchmark level is unlikely to cause mortality.  Resistance is recorded as ‘High’, resilience as ‘High’ and the biotope is ‘Not sensitive’ at the benchmark level.

    High High Not sensitive
    Q: Medium
    A: Low
    C: Medium
    Q: High
    A: High
    C: High
    Q: Medium
    A: Low
    C: Medium

    While high levels of suspended sediment may inhibit feeding, colonies of the sea fan Eunicella verrucosa produce mucus to clear themselves of silt (Hiscock, 2007). It is however thought that smothering causes mortality (Hiscock et al., 2004b). Bunker (1986) reported that Eunicella verrucosa were mostly observed on bedrock or boulders but occurred at sites up to ‘moderately silted’.  Eunicella verrucosa forms large colonies which branch profusely up to 30 cm in height (Picton & Morrow, 2005).

    Colonies of Pentapora fascialis can reach a height of 30 cm in the British Isles (Hayward & Ryland, 1979).  Partial mortality due to siltation has been recorded in the Mediterranean (Cocito et al., 1998a) although recovery was observed in all but one colony (which fragmented into two smaller colonies).

    Caryophyllia smithii is small (approx. <3 cm height from the seabed) and would therefore likely be inundated in a “light” sedimentation event. However Bell & Turner (2000) reported Caryophyllia smithii was abundant at sites of “moderate” sedimentation (7mm ± 0.5mm) in Lough Hyne. It is therefore likely that Caryophyllia smithii would be resistant to periodic sedimentation. If 5cm of sediment were removed rapidly, via tidal currents, Caryophyllia smithii would likely remain within the biotope.  Lock et al. (2006) partly attributed fluctuations in Caryophyllia smithii abundance at Skomer Island to surface sediment cover.

     

    Sensitivity assessment

    Smothering by 5 cm would cover the majority of Caryophyllia smithii and the smallest examples of the other characterizing species and could result in limited mortality.  Caryophyllia smithii has been reported as quite tolerant of temporary burial and the biotope occurs in moderate water flow and the sediment would likely be removed rapidly.  Resistance was assessed as ‘High’, resilience as ‘High’ and sensitivity as ‘Not sensitive’ at the benchmark level.

    Low Medium Medium
    Q: Medium
    A: Medium
    C: Medium
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low

    While siltation may inhibit feeding, colonies of the sea fan Eunicella verrucosa produce mucus to clear themselves of silt (Hiscock, 2007). It is however thought that smothering causes mortality (Hiscock et al., 2004b). Bunker (1986) reported that Eunicella verrucosa were mostly observed on bedrock or boulders but occurred at sites up to ‘moderately silted’.  Eunicella verrucosa forms large colonies which branch profusely up to 30 cm in height (Picton & Morrow, 2005).

    Colonies of Pentapora fascialis can reach a height of 30 cm in the British Isles (Hayward & Ryland, 1979).  Partial mortality due to siltation has been recorded in the Mediterranean (Cocito et al., 1998a) although recovery was observed in in all but one colony (which fragmented into two smaller colonies).

    Caryophyllia smithii is small (approx. <3 cm height from the seabed) and would therefore likely be inundated in a “heavy” sedimentation event. Whilst Bell & Turner (2000) reported Caryophyllia smithii was abundant at sites of “moderate” sedimentation (7mm ± 0.5mm) in Lough Hyne, it is unlikely that Caryophyllia smithii would survive.  Burton et al. (2005) partly attributed fluctuations in Caryophyllia smithii abundance at Skomer Island to surface sediment cover.

     

    Sensitivity assessment

    Smothering by 30 cm of sediment would likely bury the majority of characterizing species, with only those individuals on boulders and vertical surfaces escaping burial.  The biotope occurs in high energy environments and it is likely that the sediment would be removed.  However, the damage to the resident community would depend on the time taken for the deposited sediment to be removed. Therefore, resistance was assessed as ‘Low’ as the worst-case scenario. Hence, resilience is probably ‘Medium’ and sensitivity is assessed as ‘Medium’.

    Not Assessed (NA) Not Assessed (NA) Not assessed (NA)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    No evidence was found.  Ghost fishing by discarded fishing gear, lines and pots may cause some damage to the community, especially the tall erect epifauna, where discarded lines may catch the upright epifauna and increase drag, especially in stormy weather. Fishing lines can cause lesions to the gorgonian coenenchyme, leading to greater aggregates of epibionts which can eventually cause the branch to rupture (Bo et al., 2014).

    No evidence (NEv) Not relevant (NR) No evidence (NEv)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    No evidence

    High High Not sensitive
    Q: Low
    A: NR
    C: NR
    Q: High
    A: High
    C: High
    Q: Low
    A: Low
    C: Low

    Stanley et al. (2014) studied the effects of vessel noise on fouling communities and found that the bryozoans Bugula neritina, Watersipora arcuate and Watersipora subtorquata responded positively.  More than twice as many bryozoans settled and established on surfaces with vessel noise (128 dB in the 30–10,000 Hz range) compared to those in silent conditions.  Growth was also significantly higher in bryozoans exposed to noise, with 20% higher growth rate in encrusting and 35% higher growth rate in branching species.

    Whilst no evidence could be found on the effects of noise or vibrations on the characterizing species, it is unlikely that these species would be adversely affected by noise.

    Resistance to this pressure is assessed as 'High' and resilience as 'High'. This biotope is therefore considered to be 'Not sensitive'. 

    High High Not sensitive
    Q: Low
    A: NR
    C: NR
    Q: High
    A: High
    C: High
    Q: Low
    A: Low
    C: Low

    Whilst no evidence could be found for the effect of light on the characterising species of these biotopes, it is unlikely that these species would be impactedResistance to this pressure is assessed as 'High' and resilience as 'High'. This biotope is therefore considered to be 'Not sensitive'. 

    Not relevant (NR) Not relevant (NR) Not relevant (NR)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    Not relevant: barriers and changes in tidal excursion are not relevant to biotopes restricted to open waters.

    Not relevant (NR) Not relevant (NR) Not relevant (NR)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    Not relevant to seabed habitats.  NB. Collision by grounding vessels is addressed under ‘surface abrasion’.

    Not relevant (NR) Not relevant (NR) Not relevant (NR)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    Not relevant

    Biological Pressures

     ResistanceResilienceSensitivity
    Not relevant (NR) Not relevant (NR) No evidence (NEv)
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR
    Q: NR
    A: NR
    C: NR

    No evidence for the characterizing species could be found.

    Therefore, there is currently ‘No evidence’ on which to assess this pressure.

    Medium Medium Medium
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low

    This biotope is classified as circalittoral and therefore no algal species have been considered. 

    Solidobalanus fallax is an invasive southern species only recently recorded in south west England (Southward et al., 2004) and, along with hydroids and bryozoans, have been observed fouling (primarily damaged or diseased) gorgonians (Hall-Spencer et al., 2007).

    A number of invasive bryozoans are of concern including Schizoporella japonica (Ryland et al., 2014) and Tricellaria inopinata (Dyrynda et al., 2000; Cook et al., 2013), although no evidence of these affecting CR.HCR.XFa.ByErSp.Eun was found.

    Resistance is therefore assessed as ‘Medium’, resilience as ‘Medium’ and sensitivity as ‘Medium’.  Due to the constant risk of new invasive species, the literature for this pressure should be revisited.

    Medium Medium Medium
    Q: Medium
    A: Medium
    C: Low
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low

    The first recorded incidence of cold-water coral disease was noted in Eunicella verrucosa, in south west England in 2002 (Hall-Spencer et al., 2007).  Video surveys in south west England from 2003 to 2006 of 634 separate colonies at 13 sites revealed that disease outbreaks were widespread and 9% of colonies had tissue necrosis.  Coenenchyme became necrotic in diseased specimens, leading to tissue sloughing and exposing skeletal gorgonin to settlement by fouling organisms. Sites where necrosis was found had significantly higher incidences of fouling. No fungi were isolated from diseased or healthy tissue, but significantly higher concentrations of bacteria occurred in diseased specimens. Vibrio isolated from Eunicella verrucosa did not induce disease at 15°C, but, at 20°C, controls remained healthy and test gorgonians became diseased, regardless of whether Vibrio were isolated from diseased or healthy colonies. Bacteria associated with diseased tissue produced proteolytic and cytolytic enzymes that damaged Eunicella verrucosa tissue and may be responsible for the necrosis observed. Monitoring at the site where the disease was first noted showed new gorgonian recruitment from 2003 to 2006; 5 of the 18 necrotic colonies videoed in 2003 had died and become completely overgrown, whereas others had continued to grow around a dead central area (Hall-Spencer et al., 2007).  No evidence for disease in the characterizing bryozoans could be found.

    Sensitivity assessment

    Based on evidence of mortality linked to disease in Eunicella verrucosa, resistance is assessed as ‘Medium’, resilience as ‘Medium’ sensitivity as ‘Medium’.

    None Low High
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low

    Eunicella verrucosa has historically been harvested as a curio by divers and was collected until recently in the British Isles (Bunker, 1986; Wells et al., 1983 cited in Koomen & Helsdingen, 1996), however it is now protected under schedule 5 of the Wildlife and Countryside Act 1981 and harvesting is illegal.  No evidence of harvesting of the other characterizing species was found.

    Sensitivity assessment

    The characterizing Eunicella verrucosa is sessile, epifaunal and would have no resistance to harvesting.  Resistance has been assessed as ‘None’, resilience as ‘Low’ and sensitivity is therefore ‘High’.

    Low Medium Medium
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: NR
    C: NR
    Q: Low
    A: Low
    C: Low

    The characteristic species probably compete for space within the biotope, so that loss of one species would probably have little if any effect on the other members of the community. However, removal of the characteristic epifauna due to by-catch is likely to remove a proportion of the biotope and change the biological character of the biotope. For example, Eunicella verrucosa is sessile epifauna and is likely to be severely damaged by heavy gears, such as scallop dredging (MacDonald et al., 1996).  However,  some studies suggests that the species may be more resistant, particularly to low intensity lighter abrasion pressures, such as pots and associated anchor damage (Eno et al. 1996; Sheehan et al., 2013) 

    Therefore, a resistance of ‘Low’ is recorded, albeit with a low confidence value owing to the lack of consensus in the literature. Resilience is assessed as ‘Medium’ and sensitivity is ‘Medium’.

    Importance review

    Policy/Legislation

    Habitats of Principal ImportanceFragile sponge and anthozoan communities on subtidal rocky habitats
    Habitats of Conservation ImportanceFragile sponge and anthozoan communities
    Habitats Directive Annex 1Reefs
    UK Biodiversity Action Plan PriorityFragile sponge and anthozoan communities on subtidal rocky habitats

    Exploitation

    There is no known exploitation of the 3 selected key or important characterizing species in this biotope. Eunicella verrucosa is subject to a UK Biodiversity Action Plan (Anonymous, 1999l). The sea urchin Echinus esculentus is potentially subject to exploitation. The roe may be collected locally for eating but the main reason for extraction is for the curio trade. The possibility of a sea urchin fishery in Shetland for the Japanese market has been investigated recently (Penfold et al. 1996).

    Additional information

    The biotope as a whole is not subject to any management measures. However, one of the selected characterizing species, Eunicella verrucosa is the subject of a UK Biodiversity Action Plan (Anonymous, 1999(l)).

    Eunicella verrucosa is protected under schedule 5 of the Wildlife and Countryside Act 1981 against killing, injuring, taking possession and sale and is the subject of a UK Biodiversity Action Plan. Echinus esculentus, a characterizing species in the biotope, is listed under Schedule 7 of The Wildlife (NI) Order as an animal that must not be sold alive or dead at any time.)

    Bibliography

    1. Allen, J., Slinn, D., Shummon, T., Hurtnoll, R. & Hawkins, S., 1998. Evidence for eutrophication of the Irish Sea over four decades. Limnology and Oceanography, 43 (8), 1970-1974.
    2. 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.
    3. Banks, P.D. & Brown, K.M., 2002. Hydrocarbon effects on fouling assemblages: the importance of taxonomic differences, seasonal, and tidal variation. Marine Environmental Research, 53 (3), 311-326.
    4. Bell, J.J. & Turner, J.R., 2000. Factors influencing the density and morphometrics of the cup coral Caryophyllia smithii in Lough Hyne. Journal of the Marine Biological Association of the United Kingdom, 80, 437-441.
    5. Bell, J.J., 2002. Morphological responses of a cup coral to environmental gradients. Sarsia, 87, 319-330.
    6. Bo, M., Bava, S., Canese, S., Angiolillo, M., Cattaneo-Vietti, R. & Bavestrello, G., 2014. Fishing impact on deep Mediterranean rocky habitats as revealed by ROV investigation. Biological Conservation, 171, 167-176.

    7. Budd, G., 2008. Alcyonium digitatum. Dead man's fingers. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme, Plymouth: Marine Biological Association of the United Kingdom. 2015(19-11). www.marlin.ac.uk/speciesfullreview.php?speciesID=2442
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    Citation

    This review can be cited as:

    Readman, J.A.J. & Jackson, A. & Hiscock, K 2016. Eunicella verrucosa and Pentapora foliacea on wave-exposed circalittoral rock. 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/habitat/detail/77

    Last Updated: 31/05/2016