Virgularia mirabilis and Ophiura spp. with Pecten maximus on circalittoral sandy or shelly mud

10-11-2004
Researched byJacqueline Hill & Emily Wilson Refereed byDr David Hughes
EUNIS CodeA5.354 EUNIS NameVirgularia mirabilis and Ophiura spp. with Pecten maximus on circalittoral sandy or shelly mud

Summary

UK and Ireland classification

EUNIS 2008A5.354Virgularia mirabilis and Ophiura spp. with Pecten maximus on circalittoral sandy or shelly mud
EUNIS 2006A5.354Virgularia mirabilis and Ophiura spp. with Pecten maximus on circalittoral sandy or shelly mud
JNCC 2004SS.SMu.CSaMu.VirOphPmaxVirgularia mirabilis and Ophiura spp. with Pecten maximus on circalittoral sandy or shelly mud
1997 BiotopeSS.CMS._.VirOphVirgularia mirabilis and Ophiura spp. on circalittoral sandy or shelly mud

Description

Circalittoral fine sandy mud and shelly gravel may contain Virgularia mirabilis and Ophiura spp. Such sediments are very common in sea lochs, often occurring shallower than the finest mud or in somewhat more exposed parts of the lochs. A variety of species may occur, and species composition at a particular site may relate, to some extent, to the proportions of the major sediment size fractions. Greater quantities of stones and shells on the surface may give rise to more sessile epibenthic species (CMS.VirOph.HAs). Several species are common to most sites including Virgularia mirabilis which is present in moderate numbers, Ophiura albida and Ophiura ophiura which are often quite common, and Pecten maximus which is usually only present in low numbers. Inachus dorsettensis, Aporrhais pespelecani, Pagurus prideaux and Astropecten irregularis, although less widespread, are typical species of this sediment type. Virgularia mirabilis is usually accompanied by Cerianthus lloydii, Chaetopterus variopedatus, terebellids, including Lanice conchilega and, less commonly, Arenicola marina and Myxicola infundibulum in this biotope. Amphiura chiajei and Amphiura filiformis occur in high densities in the sandier examples of this biotope but are uncommon in the more gravelly muds. Polychaetes and bivalves are the main components of the infauna, although nemerteans, Edwardsia claparedii, Phoronis muelleri and Labidoplax buski are also widespread. Of the polychaetes Goniada maculata, Nephtys incisa, Minuspio cirrifera, Chaetozone setosa, Notomastus latericeus and Owenia fusiformis are the most widespread species. Myrtea spinifera, Lucinoma borealis, Mysella bidentata, Abra alba and Corbula gibba were common bivalves in this sediment type. Turritella communis may form dense aggregations at sandier sites. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Recorded distribution in Britain and Ireland

In Britain occurrence of this biotope is mainly restricted to sealochs on the west coast of Scotland. Also recorded from Orkney and Galway Bay, west Ireland.

Depth range

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Additional information

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Habitat review

Ecology

Ecological and functional relationships

  • The characterizing and other species in this biotope occupy space in the habitat but their presence is most likely primarily determined by the occurrence of a suitable substratum rather by interspecific interactions. Virgularia mirabilis and brittlestars are functionally dissimilar and are not necessarily associated with each other but occur in the same muddy sediment habitats. There is no information regarding possible interactions between these species. In addition to Virgularia mirabilis and brittlestars the biotope supports a fauna of smaller less conspicuous species, such as polychaetes and bivalves, living within the sediment.
  • Virgularia mirabilis might be adversely affected by high levels of megafaunal bioturbation, perhaps by preventing the survival of newly settled colonies. Seapens and various species of burrowing megafauna certainly coexist but no investigation of the interaction between them has been found. Burrowing species create tunnels in the sediment which themselves provide a habitat for other burrowing or inquilinistic species.
  • Many of the species living in deep mud biotopes are generally cryptic in nature and not usually subject to predation. Evidence of predation on Virgularia mirabilis by fish seems limited to a report by Marshall & Marshall (1882 in Hoare & Wilson, 1977) where the species was found in the stomach of haddock. Many specimens of Virgularia mirabilis lack the uppermost part of the colony which has been attributed to nibbling by fish. Observations by Hoare & Wilson (1977) suggest however, that predation pressure on this species is low. The sea slug Armina loveni is a specialist predator of Virgularia mirabilis. If present in high abundance, the arms of Amphiura filiformis are an important food source for demersal fish providing significant energy transfer to higher trophic levels. Brittlestars of the genus Ophiura are known to be a common prey for flatfish such as plaice (Downie, 1990 cited in Hughes, 1998b). There are also epibenthic predators/scavengers, such as Liocarcinus depurator and Pagurus prideaux, in the biotope. An increase in the numbers of predators can have an influence on the abundance and diversity of species in benthic habitats (Ambrose, 1993; Wilson, 1991). For example, enclosure experiments in a sea loch in Ireland have shown that high densities of swimming crabs such as Liocarcinus depurator, that feed on benthic polychaetes, molluscs, ophiuroids and small crustaceans, led to a significant decline in infaunal organisms (Thrush, 1986).
  • The majority of the species are suspension feeders so competition for food may occur.
  • When present in high abundance the burrowing and feeding activities of Amphiura filiformis can modify the fabric and increase the mean particle size of the upper layers of the substrata by aggregation of fine particles into faecal pellets. Such actions create a more open fabric with a higher water content which affects the rigidity of the seabed (Rowden et al., 1998). Such destabilisation of the seabed can affect rates of particle resuspension.
  • The hydrodynamic regime, which in turn controls sediment type, is the primary physical environmental factor structuring benthic communities such as CMS.VirOph. The hydrography also affects the water characteristics in terms of salinity, temperature and dissolved oxygen. It is also widely accepted that food availability (see Rosenberg, 1995) and disturbance, such as that created by storms, (see Hall, 1994) are also important factors determining the distribution of species in benthic habitats.

Seasonal and longer term change

  • Species such as the sea pen Virgularia mirabilis and Amphiura filiformis appear to be long-lived and are unlikely to show any significant seasonal changes in abundance or biomass. Seapen faunal communities appear to persist over long periods at the same location. Movement of the sea pen Virgularia mirabilis in and out of the sediment may be influenced by tidal conditions (Hoare & Wilson, 1977).
  • The numbers of some of the other species in the biotope may show peak abundances at certain times of the year due to seasonality of breeding and larval recruitment. Immature individuals of Liorcarcinus depurator, for example, are more frequent in the periods May - September.

Habitat structure and complexity

The biotope has very little structural complexity with most species living in or on the sediment. Several species, such as the sea pen Virgularia mirabilis and the anemone Cerianthus lloydii, extend above the sediment surface. However, apart from a couple of species of nudibranch living on the sea pens and the tubiculous amphipod Photis longicaudata associated with Cerianthus lloydii (Moore & Cameron, 1999) these species do not provide significant habitat for other fauna. Excavation of sediment by infaunal organisms, such as errant polychaetes, ensures that sediment is oxygenated to a greater depth allowing the development of a much richer and/or higher biomass community of species within the sediment.

Productivity

Productivity in subtidal sediments is often quite low. Macroalgae are absent from CMS.VirOph and so productivity is mostly secondary, derived from detritus and organic material. Allochthonous organic material is derived from anthropogenic activity (e.g. sewerage) and natural sources (e.g. plankton, detritus). Autochthonous organic material is formed by benthic microalgae (microphytobenthos e.g. diatoms and euglenoids) and heterotrophic micro-organism production. Organic material is degraded by micro-organisms and the nutrients are recycled. The high surface area of fine particles provides surface for microflora. If present in high abundance the arms of Amphiura filiformis can be an important food source for demersal fish and Nephrops norvegicus providing significant energy transfer to higher trophic levels.

Recruitment processes

  • Virgularia mirabilis and the other major component species in this biotopes appear to have a plankton stage within their life cycle, so colonization is likely to occur from distant sources.
  • The reproductive biology of British sea pens has not been studied, but in other species, for instance Ptilosarcus guerneyi from Washington State in the USA, the eggs and sperm are released from the polyps and fertilization takes place externally. The free-swimming larvae do not feed and settle within seven days if a suitable substratum is available (Chia & Crawford, 1973). The limited data available from other species would suggest a similar pattern of patchy recruitment, slow growth and long life-span for Virgularia mirabilis.
  • Tyler (1977) found that populations of Ophiura albida in the Bristol Channel had a well-marked annual reproductive cycle, with spawning taking place in May and early June. Spent adults and planktonic larvae were observed up to early October. In contrast the larger Ophiura ophiura had a more protracted breeding season.
  • Studies of Amphiura filiformis suggest autumn recruitment (Buchanan, 1964) and spring and autumn (Glémarec, 1979). Using a 265µm mesh size Muus (1981) identified a peak settlement period in the autumn with a maximum of 6800 recruits per m2. Muus (1981) shows the mortality of these settlers to be extremely high with less than 5% contributing to the adult population in any given year. In Galway Bay populations, small individuals make up ca. 5% of the population in any given month, which also suggests the actual level of input into the adult population is extremely low (O'Connor et al., 1983). The species is thought to have a long pelagic life so recruitment can come from distant sources.
  • The scallop Pecten maximus appears to have a long breeding period with peaks in spring and autumn (Fish & Fish, 1996). The veliger larvae are planktonic for about three to four weeks and settle on a wide range of algae, bryozoans and hydroids.

Time for community to reach maturity

No evidence on community development was found. Almost nothing is known about the life cycle and population dynamics of British sea pens, but data from other species suggest that they are likely to be long-lived and slow growing with patchy and intermittent recruitment. The other key species, Amphiura filiformis and Pecten maximus are also long lived and take a relatively long time to reach reproductive maturity. It takes approximately 5-6 years for Amphiura filiformis to grow to maturity so population structure will probably not reach maturity for at least this length of time. In addition, Muus (1981) shows the mortality of new settling Amphiura filiformis to be extremely high with less than 5% contributing to the adult population in any given year. Pecten maximus reaches sexual maturity within the first two to three years and has a life span of 10-20 years. The suggested life span for Ophiura ophiura in the west of Scotland was 5-6 years (Gage, 1990). Many of the other species in the biotope, such as polychaetes and bivalves, are likely to reproduce annually, be shorter lived and reach maturity much more rapidly. However, because the key species in the biotope, Virgularia mirabilis and Amphiura filiformis are long lived and take several years to reach maturity the time for the overall community to reach maturity is also likely to be several years, possibly in the region of 5-10 years.

Additional information

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Preferences & Distribution

Recorded distribution in Britain and IrelandIn Britain occurrence of this biotope is mainly restricted to sealochs on the west coast of Scotland. Also recorded from Orkney and Galway Bay, west Ireland.

Habitat preferences

Depth Range
Water clarity preferences
Limiting Nutrients Nitrogen (nitrates), Phosphorus (phosphates)
Salinity
Physiographic
Biological Zone
Substratum
Tidal
Wave
Other preferences

Additional Information

Seapen biotopes occur in wave sheltered sealochs and much deeper open sea suggesting that water movement, particularly being sheltered from wave action, is more important to their existence than light.

Species composition

Species found especially in this biotope

Rare or scarce species associated with this biotope

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Additional information

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Sensitivity reviewHow is sensitivity assessed?

Explanation

Virgularia mirabilis is the main important characterizing species, giving the name to the biotope. Amphiura filiformis is representative of brittlestars which are also important characterizing species associated with this biotope. Virgularia mirabilis and Amphiura filiformis are both burrowing species and can be important structurally. Pecten maximus is an important commercial species associated with this biotope.

Species indicative of sensitivity

Community ImportanceSpecies nameCommon Name
Important characterizingAmphiura filiformisA brittlestar
Important otherPecten maximusGreat scallop
Important characterizingVirgularia mirabilisA sea pen

Physical Pressures

 IntoleranceRecoverabilitySensitivitySpecies RichnessEvidence/Confidence
High Moderate Moderate Major decline Low
Most species are infaunal or epifaunal and will be lost if the substratum is removed so the overall intolerance of the biotope is high. Although some of the mobile species in the biotope may be able to escape, most, such as the harbour crab Liocarcinus depurator, the common starfish Asterias rubens and the brittlestars are not very fast moving and so are also likely to be removed. Recovery from complete loss of fauna in the sediment is likely to take a long time and so a rank of moderate has been reported - see additional information below for full recovery rationale.
Low Very high Very Low Minor decline Moderate
The biotope will have low intolerance to smothering by 5cm of sediment because many of the species are burrowing and live within the sediment anyway. The sea pen Virgularia mirabilis is able to withdraw rapidly into the sediment and appears to be able to recover from smothering (see species review). The brittlestar Amphiura filiformis, which inhabits the top 3-4 cm of sediment, is also not likely to be intolerant of smothering as it is able to move up through sediment. Many of the other infaunal organisms, such as the polychaetes and bivalves, should also survive smothering. However, some species may be unable to self-clean or dig out and so a small decline in species diversity may occur. However, as most species in the biotope are not especially intolerant of smothering by sediment the intolerance of the biotope is recorded as low. Intolerance to other smothering factors, oil for example, may be higher. Recovery should be rapid as species move through the sediment and self clean.
Low Immediate Not sensitive No change Moderate
The dominant trophic group associated with this biotope are suspension feeders and these species are likely to have self-cleaning mechanisms and so will be able to deal with certain levels of particulate material. However, suspension of large amounts of fine silt and clay fractions of sediment, resulting from activities such as dredging, may clog feeding structures. For example, there may be some clogging of the feeding organs of the suspension feeding sea pens. However, since these animals are able to self-clean this is not likely to be very energetically costly, particularly at the level of the benchmark. Some species may benefit from increased food supply if suspended sediment has a high organic content. Many species in the biotope are burrowing infauna so will not be affected by an increase in suspended sediment. Intolerance is therefore, assessed as low. Overall species composition and richness is not expected to be affected. On return to normal, suspended sediment levels recovery will be immediate as affected species will be able to self-clean within a few days.
Low Moderate Moderate Decline Low
A decrease in suspended sediment and siltation will reduce the flux of particulate material to the seabed. Since this includes organic matter the supply of food to the biotope may also be reduced. However, the benchmark reduction in suspended sediment of 100mg/l for a month is unlikely to have a significant effect on the biotope and would not alter species composition. Intolerance is therefore, assessed as low. On return to normal conditions, recovery will be rapid and a rank of very high is recorded.
Not relevant Not relevant Not relevant Not relevant Not relevant
This biotope is found in the circalittoral and so species are not likely to be affected by desiccation.
Not relevant Not relevant Not relevant Not relevant Not relevant
This biotope is found in the circalittoral, therefore the species in this biotope are not likely to be affected by an emergence regime.
Not sensitive*
This biotope is found in the circalittoral, therefore the species in this biotope are not likely to be affected by an emergence regime.
High Moderate Moderate Decline Low
The biotope is only found in areas of weak or very weak tidal streams and so is likely to be intolerant of increases in water flow. Some tidal flow is necessary for the horizontal supply of small and light nutritious particles by resuspension and advective transport, influencing the growth rate of suspension-feeding benthos (Dauwe, 1998). However, some suspension feeders in the biotope will be unable to feed if the water flow rate increases by two categories in the water flow scale (see benchmarks). The sea pen Virgularia mirabilis for example, will retract into the sediment at water currents speeds greater than 0.5m/s (i.e. 1 knot) (Hiscock, 1983). If water speeds remain at this level or above, sea-pens will be unable to extend above the sediment, will be unable to feed and will probably die. Suspension feeding brittlestars have no self-produced feeding currents and so water flow rate will be of primary importance. For example, individuals of Amphiura filiformis respond rapidly to currents by extending their arms vertically to feed. Under laboratory conditions they were shown to maintain this vertical position at currents of 30 cm/s (approx. 0.6 knots) (Buchanan, 1964). If water movement were to increase to strong (3-6 knots), individuals would be unlikely to maintain this position and so would retract their arms. Other suspension feeders in the biotope will also be unable to feed if the water flow rate increases by two categories in the water flow scale (see benchmarks). A long term increase (i.e. the benchmark level of one year) in water flow will change the nature of the top layers of sediment, becoming coarser and possibly unsuitable for some shallow burrowing species such as the brittle stars Amphiura. Therefore, a long term increase in water flow rates would probably result in the loss of many of the key species, and hence the biotope, so intolerance is reported to be high. Recovery would probably take a long time and is set at moderate - see additional information below.
Not sensitive* No change Moderate
The biotope exists in habitats such as sea lochs, where tidal streams are already very weak so a decrease in flow rate would result in almost non-moving water. In these enclosed or semi-enclosed water bodies, negligible water flow may result in some deoxygenation of the overlying water and the loss of some intolerant species. The sea pen Virgularia mirabilis for example, has high intolerance to deoxygenation and may die. Tidal currents keep most of the organic particles in the sediment in suspension which can support suspension feeders even in low organic content sediments. Therefore, if water movement becomes negligible suspended organic particles available to filter feeders such as the sea pens will decline. Growth and fecundity will be affected and over a period of a year may result in the death of sea pens. Amphiura filiformis shows a lack of activity in still water and low current speeds can impede feeding because it may reduce the transport of organic particles. Therefore, if water flow rate changes by the benchmark level of two categories for a year feeding would be significantly impaired and viability of the population reduced. The overall impact on the biotope is likely to be the loss of a few key species such as sea pens and so intolerance is assessed as high. Recovery would probably take longer than five years and so is assessed as moderate - see additional information below for rationale.
Intermediate High Low No change Low
In shallow sea lochs where the biotope CMS.VirOph is typically found, there are seasonal changes in temperature of about 10 °C. Therefore, the biotope may be tolerant of long term increases although growth and fecundity of some species could be affected. No information was found on the upper limit of sea pens tolerance to temperature increases. However, the distribution of Virgularia mirabilis extends south into the warmer waters of the Mediterranean suggesting they may be able to tolerate a long term increase in temperature of 2 °C. Muus (1981) showed that juvenile Amphiura filiformis are capable of much higher growth rates in experiments with temperatures between 12 and 17°C. However, most of the species in the biotope are subtidal animals where wide and rapid variations in temperature, such as experienced in the intertidal, are not likely to occur and so the biotope may be more intolerant of a rapid increase of 5 °C. The reported intolerance to changes in temperature for Virgularia mirabilis is intermediate (see species review). Since the loss of sea pens changes the biotope the intolerance of the biotope to increased temperature is also recorded as intermediate. Recovery of sea pens may take a long time so a rank of moderate is reported - see additional information below for full recovery rationale.
Intermediate High Low No change Low
In shallow sea lochs, sedimentary biotopes typically experience seasonal changes in temperature of about 10 °C and so CMS.VirOph may be tolerant of long term decreases although growth and fecundity of some species may be affected. No information was found on the lower limit of sea pens tolerance to temperature decreases. However, the distribution of Virgularia mirabilis extends into the northern North Atlantic where waters are colder than in the UK suggesting they may be able to tolerate a long term decrease in temperature of 2°C. However, sea pens and other species in the biotope are subtidal where wide and rapid variations in temperature, such as experienced in the intertidal, are not so common and so may be more intolerant of a short term decrease in temperature of 5°C. Echinoderms, including Amphiura filiformis, of the North Sea seem periodically affected by winter cold with mortalities during cold winters. Low temperatures are a limiting factor for breeding which takes place during the warmest months in the UK. Therefore, population viability of one of the key species may be reduced and so the intolerance of the biotope is reported to be intermediate. Recovery should be high - see additional information below.
Low Very high Very Low No change Low
This biotope is found in the circalittoral so light levels will be naturally low. Virgularia mirabilis is insensitive to light (Hoare & Wilson, 1977), therefore, an increase or decrease in light levels caused by changing turbidity levels will have little or no effect on the sea pen population. An increase in turbidity, reducing light availability may reduce primary production by phytoplankton in the water column. However, productivity in the CMU.SpMeg biotope is secondary (detritus) and is not likely to be significantly affected by changes in turbidity for a period of a month and so intolerance of the biotope is assessed as low. Recovery will be very rapid.
Low Very high Moderate No change Moderate
A decrease in turbidity, increasing light availability may increase primary production by phytoplankton in the water column. However, productivity in the CMS.VirOph biotope is secondary (detritus) and is not likely to be significantly affected by changes in turbidity and so intolerance is assessed as low. Nevertheless, primary production by pelagic phytoplankton and microphytobenthos do contribute to benthic communities and long term decreases in turbidity may increase the overall organic input to the detritus. Increased food supply may increase growth rates and fecundity of some species in the biotope.
High High Moderate Minor decline Low
The biotope exists in sheltered areas with low wave exposure and weak tidal currents. Sea pens, for example, may be unable to feed and may be damaged or broken by increased wave exposure. However, Virgularia mirabilis is able to withdraw into the sediment to avoid strong wave oscillations but if wave exposure increases are long term feeding will stop and individuals will be likely to die. If uprooted by wave exposure Virgularia mirabilis can reburrow provided it has not been damaged. Strong wave action can resuspend the sediment and break up and scatter Amphiura filiformis. An increase in wave exposure is likely to change the composition of species present in the biotope because it is likely to disrupt feeding and burrowing and may also have an impact on reproduction and recruitment. An increase in the factor can also change the sediment characteristics which may result in a change in the proportion of suspension to deposit feeders within it. Intolerance of the biotope to an increase in wave exposure is therefore reported to be high. See additional information below for recovery.
Not sensitive* No change Moderate
The biotope occurs in areas of very low or no wave exposure so a decrease is not relevant.
Tolerant Not relevant Not relevant No change Low
Some of the important characterizing species associated with this biotope, in particular the sea pens, may respond to sound vibrations and can withdraw into the sediment. Feeding will resume once the disturbing factor has passed. However, most of the species are infaunal and not likely to be sensitive to noise disturbance at the benchmark level. It is possible that predator avoidance behaviour in Liocarcinus depurator and other species may be triggered by noise vibrations although this has not been recorded. Therefore, unless predation pressure is reduced increased noise disturbance is not likely to have an impact on the nature and function of the biotope and a rank of not sensitive is recorded. Feeding will resume once the disturbing factor has passed.
Tolerant Not relevant Not relevant No change Low
Most species within the biotope are burrowing and have no or poor visual perception and are unlikely to be affected by visual disturbance such as shading. Epifauna such as crabs have well developed visual acuity and are likely to respond to movement in order to avoid predators. However, it is unlikely that the species will be affected by visual disturbance at the benchmark level. The biotope is therefore, not sensitive to the factor.
Low Very high Very Low Minor decline Moderate
Virgularia mirabilis is able to retract into the sediment and so some individuals may be able to avoid some forms of abrasion or physical disturbance. However, sea pens retract slowly and are likely to be sensitive to abrasion by trawling for instance, that is likely to break the rachis of Virgularia mirabilis. Species obtained by dredges were invariably damaged (Hoare & Wilson, 1977). Displaced individuals that are not damaged will reburrow but those that are damaged are likely to die. However, the densities of Virgularia mirabilis were similar in trawled and un-trawled sites in Loch Fyne and no changes in sea pen density was observed after experimental trawling over a 18 month period in another loch (Howson & Davies, 1991; Tuck et al. , 1998; Hughes, 1998b). Hughes (1998b) concluded that Virgularia mirabilis and Pennatula phosphorea, which can withdrawn into the sediment, were probably less susceptible to the effects of damage by fishing gear than Funiculina quadrangularis, which is unable to withdraw.

In an investigation into the effect of shellfish traps on benthic habitats (Eno et al. , 1996), creels were dropped on sea pens and left for extended periods to simulate the effects of smothering which could occur during commercial operations. The sea pens consistently righted themselves following removal of the pots.

Ramsay et al. (1998) suggest that Amphiura spp. may be less susceptible to beam trawl damage than other species like echinoids or tube dwelling amphipods and polychaetes. Bergman & Hup (1992) for example, found that beam trawling in the North Sea had no significant direct effect on small brittle stars. Bradshaw et al. (2002) noted that the brittlestars Ophiocomina nigra, Ophiura albida and Amphiura filiformis had increased in abundance in a long-term study of the effects of scallop dredging in the Irish Sea. Brittlestars can tolerate considerable damage to arms and even the disk without suffering mortality and are capable of arm and even some disk regeneration.

Overall, the dominant species are likely to be relatively tolerate of or avoid physical disturbance at the benchmark level and an intolerance of low has been recorded. Recoverability will be dependent on repair and regeneration of damage and is likely to be rapid.

Low Immediate Not sensitive Minor decline Low
Displaced individuals of Virgularia mirabilis, which are not damaged (see Abrasion above for damage), will re-burrow (Jones et al., 2000) and recover completely within 72 hours, provided the basal peduncle remains in contact with the sediment surface. The other important characterizing species associated with this biotope, such as brittlestars, also have the ability to reburrow, provided they have not been damaged. Displaced individuals of Amphiura filiformis that are not damaged (see Abrasion above) can right themselves if displacement caused them to be inverted and they can rapidly re-burrow into the sediment. Intolerance of the biotope to displacement is therefore low and recovery is likely to only take a short time and so recovery is recorded as immediate.

Chemical Pressures

 IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
High High Moderate Minor decline Low
There was no information found on the effect of chemical contaminants on the biotope. However, effects on some of the individual species in the biotope have been reported. Dahllöf et al. (1999) studied the long term effects of tri-n-butyl-tin (TBT) on the function of a marine sediment system. TBT spiked sediment was added to a sediment that already had a TBT background level of approximately 27ng g-1 (83 pmol TBT g-1) and contained the following fauna: Amphiura spp., the bivalve Abra alba and several species of polychaete. Within two days of treatment with a TBT concentration above 13.7 µmol / m² all species except the polychaetes had crept up to the surface and after six weeks these fauna had started to decay. Thus, increased contamination from TBT is likely to result in the death of some intolerant species such as brittle stars and heart urchins. Bryan & Gibbs (1991) report that crabs appear to be relatively resistant to TBT although some deformity of regenerated limbs has been observed. However, arthropods are very intolerant of the insecticide carbaryl (1-napthol n-methyl carbamate; sold under the trade name Sevin®) which has been used to control burrowing shrimp in oyster farms (Feldman et al., 2000). There is no information available on the possible consequences of chemicals to British sea pens. Different species will be affected by different chemicals but a general trend in areas of increasing pollution is a reduction in species diversity with habitats becoming dominated by pollution tolerant polychaete worms. However, Ivermectin, an anti-louse treatment coming into use in the salmon fish farming industry, has been shown to be highly toxic to sediment dwelling polychaetes (Hughes, 1998(b)). The dominant trophic group associated with this biotope are suspension feeders and therefore have the ability to accumulate pollutants although effects are uncertain. Growth and regeneration are decreased in species such as Pecten maximus and Amphiura filiformis. Intolerance of the biotope is reported to be high.
Heavy metal contamination
Intermediate High Low Minor decline Low
There was no information found on the effect of heavy metals on sea pens. In Norwegian fjords Rygg (1985) found a relationship between species diversity in benthic fauna communities and sediment concentrations of heavy metals Cu, Pb and Zn. Copper in particular showed a strong negative correlation and the author suggested a cause-effect relationship. Those species not present at sites where Cu concentrations were greater than ten times higher than the background level, such as Amphiura filiformis and several bivalves including Nucula sulcata and Thyasira equalis, were assessed as non-tolerant species. The tolerant species were all polychaete worms. Therefore, increased heavy metal contamination in sediments may change the faunal composition of the community and decrease overall species diversity. However, effects of heavy metals are generally sub-lethal so an intolerance rank of intermediate is recorded.
Hydrocarbon contamination
Intermediate High Low Minor decline Very low
There is very little information available on the impact of hydrocarbons on the species in the biotope. Nothing could be found for Virgularia mirabilis or other sea pens. In a study of the effects of oil exploration and production on benthic communities. Olsgard & Gray (1995) found Amphiura filiformis to be very intolerant of oil pollution. The overall impact of oil contamination on the biotope is likely to be a loss of species diversity as very intolerant species are lost and so intolerance of the biotope is reported to be intermediate but with a very low confidence. However, the biotope is found in the circalittoral and so any oil from spills would have to be dispersed deep into the water column to affect them. In addition the biotope occurs in sheltered locations and storms would be unlikely to disperse oils to these depths and so the biotope is not particularly vulnerable to this particular factor.
Radionuclide contamination
Low High Low Insufficient
information
Not relevant
In an investigation of bioturbation in the north-eastern Irish Sea Hughes & Atkinson (1997) surveyed several sites close to the Sellafield nuclear reprocessing plant. At a station immediately offshore from the Sellafield outfall pipeline a community similar to the CMS.VirOph biotope was present. Epifauna were abundant, particularly Ophiura ophiura and Asterias rubens. The sea pen Virgularia mirabilis occurred at high density. Dragonets and small gobies were also common. Thus, the key species in the biotope occur in bottom sediments that contain particles of long half-life radionuclides derived from the liquid effluent released from the reprocessing plant at Sellafield and so intolerance is assessed as low. However, species diversity may be slightly reduced compared to unpolluted sites.
Changes in nutrient levels
Low High Low Minor decline Low
Although absent from the most enriched areas the sea pen Virgularia mirabilis was present at organic contents of 4.5% (Atkinson, 1989). Very large increases in organic content can result in significant changes in community composition of sedimentary habitats. Typically an increasing gradient of organic enrichment results in a decline in the suspension feeding fauna and an increase in the number of deposit feeders, in particular polychaete worms (Pearson & Rosenberg, 1978). For example, in areas under fish farm cages gross organic pollution has been observed to result in the loss of megafaunal burrowers. However, these changes generally refer to gross nutrient enrichment. At the level of the benchmark, a 50% increase in nutrients is likely to impact only the most intolerant species and may result in a reduction in the number of sea pens. In places where oxygen concentrations are still sufficiently high, the suspension feeding Amphiura filiformis reacts positively to organic enrichment in terms of increasing abundance and biomass (Josefson & Smith, 1984; Rosenberg et al., 1987). Overall the intolerance of the biotope to a benchmark increase in nutrients is likely to be low.
Tolerant Not relevant Not relevant No change Low
The biotope is found in fully marine conditions so is likely to be intolerant of increases in salinity. The overall effect on the biotope of a chronic decrease in salinity for a period of a year is likely to be the loss of most species and so intolerance is reported as high.
High Moderate Intermediate Decline Low
The biotope is found in fully marine conditions and does not extend into estuaries so is likely to be intolerant of decreases in salinity. The key species are highly intolerant of salinity changes although Jones et al. (2000) suggest that Virgularia mirabilis appears to be somewhat tolerant of occasional lowering of salinity. Ophiura albida was found in the Baltic Sea at salinities of 8psu although circumstantial evidence suggests that adaptation is probably genetic in this species (Stickle & Diehl, 1987). In the laboratory Ophiura albida tolerated a salinity of 17psu for 22 days (Pagett, 1980). However, the species are likely to be intolerant of a long term, chronic decrease; e.g., a change of one category from the MNCR salinity scale for one year. The overall effect on the biotope of a chronic decrease in salinity for a period of a year is likely to be the loss of most species and so intolerance is reported as high. Recovery from loss of most species is likely to take many years and so is assessed as moderate - see additional information below for rationale.
Low Immediate Not sensitive No change Low
Virgularia mirabilis, the main important characterizing species in this biotope, is often found in sea lochs so may be able to tolerate some reduction in oxygenation. However, Jones et al., (2000) found sea pen communities to be absent from areas which are deoxygenated and characterized by a distinctive bacterial community. Hoare & Wilson (1977) reported Virgularia mirabilis absent from sewage related anoxic areas of Holyhead harbour. The brittlestars Ophiura albida and Amphiura filiformis are tolerant of low oxygen concentrations. Ophiura albida shows a definite resistance to low oxygen levels with 50% of individuals still surviving after 32 hours in seawater with an oxygen concentration of 0.21mg/l (Theede et al., 1969). Rosenberg et al. (1991) suggests that some part of the benthic community, including Amphiura filiformis, can withstand oxygen concentrations of around 1mg/l for several weeks. Therefore, the benchmark level of 2mg/l of oxygenation for one week will result in the death of only the most intolerant species and maybe some individual sea pens. The total loss of populations of the key species is not likely to occur at the benchmark level and since the faunal composition of the overall biotope is unlikely to change to any great extent intolerance is assessed as low. For most species on return to normal oxygenation recovery will be immediate as respiratory rates return to pre-impact levels.

Biological Pressures

 IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
No information No information No information Insufficient
information
Not relevant
Insufficient
information
Tolerant Not relevant Not relevant No change Moderate
There are no records of any non-native species invading the biotope (Eno et al., 1997) and so the biotope is assessed as not sensitive. However, as several species have become established in British waters there is always the potential for new introduced non-native species to have an effect on the biotope.
Not relevant Not relevant Not relevant Not relevant Low
The two important characterizing species are not subjected to targeted extraction. Pecten maximus, on the other hand, is a valuable commercial species. However, it is unlikely that they are collected from this biotope and not relevant has been suggested.
Not relevant Not relevant Not relevant Not relevant Low

Additional information

Recoverability
No evidence on community development was found. Very little is known about the population dynamics and longevity of Virgularia mirabilis in Britain. However, information from other species suggest that this species is likely to be slow growing with patchy and intermittent recruitment and so recovery from loss of this species is likely to take longer than five years. The other key species, Amphiura filiformis and Pecten maximums are also long lived and take a relatively long time to reach reproductive maturity. It takes approximately 5-6 years for Amphiura filiformis to grow to maturity so population structure will probably not reach maturity for at least this length of time. In addition, Muus (1981) shows the mortality of new settling Amphiura filiformis to be extremely high with less than 5% contributing to the adult population in any given year. Pecten maximums reaches sexual maturity within the first two to three years and has a life span of 10-20 years. The suggested life span for Ophiura ophiura in the west of Scotland was 5-6 years (Gage, 1990). Many of the other species in the biotope, such as polychaetes and bivalves, are likely to reproduce annually, be shorter lived and reach maturity much more rapidly. However, because the key species in the biotope, Virgularia mirabilis and Amphiura filiformis are long lived and take several years to reach maturity the time for the overall community to reach maturity is also likely to be several years, possibly in the region of 5-10 years. Thus, a rank of moderate is reported for recovery from loss of key species in the biotope.

Importance review

Policy/Legislation

Habitats of Principal ImportanceMud habitats in deep water
Habitats of Conservation ImportanceMud habitats in deep water
UK Biodiversity Action Plan PriorityMud habitats in deep water

Exploitation

  • Although scallops are exploited commercially, it is unlikely that they are collected from this biotope. However, if dredging for scallops did take place it would probably result in the destruction of sea pens and the loss of the biotope.
  • Due to the circalittoral nature of this biotope they are unlikely to be subject to coastal alteration, construction of tidal barrages or other large-scale environmental modifications. The fine sediments on which this biotope typically exists is not targeted for seabed extraction. Divers generally are not attracted to sedimentary habitats and so there is no likelihood of environmental damage by this means.

Additional information

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Bibliography

  1. Ambrose, W.G. Jr., 1993. Effects of predation and disturbance by ophiuroids on soft-bottom community structure in Oslofjord: results of a mesocosm study. Marine Ecology Progress Series, 97, 225-236.
  2. Atkinson, R.J.A., 1989. Baseline survey of the burrowing megafauna of Loch Sween, proposed Marine Nature Reserve, and an investigation of the effects of trawling on the benthic megafauna. Report to the Nature Conservancy Council, Peterborough, from the University Marine Biological Station, Millport, pp.1-59.
  3. Baden, S.P., Pihl, L. & Rosenberg, R., 1990. Effects of oxygen depletion on the ecology, blood physiology and fishery of the Norway lobster Nephrops norvegicus. Marine Ecology Progress Series, 67, 141-155.
  4. Bergman, M.J.N. & Hup, M., 1992. Direct effects of beam trawling on macro-fauna in a sandy sediment in the southern North Sea. ICES Journal of Marine Science, 49, 5-11.
  5. Bradshaw, C., Veale, L.O., Hill, A.S. & Brand, A.R., 2002. The role of scallop-dredge disturbance in long-term changes in Irish Sea benthic communities: a re-analysis of an historical dataset. Journal of Sea Research, 47, 161-184.
  6. Bryan, G.W. & Gibbs, P.E., 1991. Impact of low concentrations of tributyltin (TBT) on marine organisms: a review. In: Metal ecotoxicology: concepts and applications (ed. M.C. Newman & A.W. McIntosh), pp. 323-361. Boston: Lewis Publishers Inc.
  7. Buchanan, J.B., 1964. A comparative study of some of the features of the biology of Amphiura filiformis and Amphiura chiajei (Ophiuroidea) considered in relation to their distribution. Journal of the Marine Biological Association of the United Kingdom, 44, 565-576.
  8. Chia, F.S. & Crawford, B.J., 1973. Some observations on gametogenesis, larval development and substratum selection of the sea pen Ptilosarcus guerneyi. Marine Biology, 23, 73-82.
  9. Connor, D.W., Dalkin, M.J., Hill, T.O., Holt, R.H.F. & Sanderson, W.G., 1997a. Marine biotope classification for Britain and Ireland. Vol. 2. Sublittoral biotopes. Joint Nature Conservation Committee, Peterborough, JNCC Report no. 230, Version 97.06., Joint Nature Conservation Committee, Peterborough, JNCC Report no. 230, Version 97.06.
  10. Dahllöf, I., Blanck, H., Hall, P.O.J. & Molander, S., 1999. Long term effects of tri-n-butyl-tin on the function of a marine sediment system. Marine Ecology Progress Series, 188, 1-11.
  11. Dauwe, B., Herman, P.M.J. & Heip, C.H.R., 1998. Community structure and bioturbation potential of macrofauna at four North Sea stations with contrasting food supply. Marine Ecology Progress Series, 173, 67-83.
  12. Davies, C.E. & Moss, D., 1998. European Union Nature Information System (EUNIS) Habitat Classification. Report to European Topic Centre on Nature Conservation from the Institute of Terrestrial Ecology, Monks Wood, Cambridgeshire. [Final draft with further revisions to marine habitats.], Brussels: European Environment Agency.
  13. Eno, N.C., Clark, R.A. & Sanderson, W.G. (ed.) 1997. Non-native marine species in British waters: a review and directory. Peterborough: Joint Nature Conservation Committee.
  14. Eno, N.C., MacDonald, D. & Amos, S.C., 1996. A study on the effects of fish (Crustacea/Molluscs) traps on benthic habitats and species. Final report to the European Commission. Study Contract, no. 94/076.
  15. Feldman, K.L., Armstrong, D.A., Dumbauld, B.R., DeWitt, T.H. & Doty, D.C., 2000. Oysters, crabs, and burrowing shrimp: review of an environmental conflict over aquatic resources and pesticide use in Washington State's (USA) coastal estuaries. Estuaries, 23, 141-176.
  16. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

  17. Gage, J.D., 1990. Skeletal growth bands in brittle stars: Microstructure and significance as age markers. Journal of the Marine Biological Association of the United Kingdom, 70, 209-224.
  18. Glémarec, M., 1979. Problemes d'ecologie dynamique et de succession en baie de Concarneau. Vie et Milieu, 28-29, 1-20.
  19. Hall, S.J., 1994. Physical disturbance and marine benthic communities: life in unconsolidated sediments. Oceanography and Marine Biology: an Annual Review, 32, 179-239.
  20. Hiscock, K., 1983. Water movement. In Sublittoral ecology. The ecology of shallow sublittoral benthos (ed. R. Earll & D.G. Erwin), pp. 58-96. Oxford: Clarendon Press.
  21. Hoare, R. & Wilson, E.H., 1977. Observations on the behaviour and distribution of Virgularia mirabilis O.F. Müller (Coelenterata: Pennatulacea) in Holyhead harbour. In Proceedings of the Eleventh European Symposium on Marine Biology, University College, Galway, 5-11 October 1976. Biology of Benthic Organisms, (ed. B.F. Keegan, P.O. Ceidigh & P.J.S. Boaden, pp. 329-337. Oxford: Pergamon Press. Oxford: Pergamon Press.
  22. Howson, C.M. & Davies, L.M., 1991. Marine Nature Conservation Review, Surveys of Scottish Sea Lochs. A towed video survey of Loch Fyne. Vol. 1 - Report. Report to the Nature Conservancy Council from the University Marine Biological Station, Millport.
  23. Hughes, D.J. & Atkinson, R.J.A., 1997. A towed video survey of megafaunal bioturbation in the north-eastern Irish Sea. Journal of the Marine Biological Association of the United Kingdom, 77, 635-653.
  24. Hughes, D.J., 1998b. Subtidal brittlestar beds. An overview of dynamics and sensitivity characteristics for conservation management of marine SACs. Natura 2000 report prepared for Scottish Association of Marine Science (SAMS) for the UK Marine SACs Project., Scottish Association for Marine Science. (UK Marine SACs Project, Vol. 3). Available from:  http://www.ukmarinesac.org.uk/publications.htm

  25. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line] http://www.jncc.gov.uk/mermaid,
  26. Jones, L.A., Hiscock, K. & Connor, D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report.)., http://www.english-nature.org.uk/uk-marine
  27. Josefson, A.B. & Smith, S., 1984. Changes of benthos-biomass in the Skagerrak-Kattegat during the 70s: a result of chance events, climatic changes or eutrophication? Meddelande fran Havsfiskelaboratoriet. Lysekil, 292, 111-121.
  28. Moore, P.G. & Cameron, K.S., 1999. A note on a hitherto unreported association between Photis longicaudata (Crustacea: Amphipoda) and Cerianthus lloydii (Anthozoa: Hexacorallia). Journal of the Marine Biological Association of the United Kingdom, 79, 369-370.
  29. Muus, K., 1981. Density and growth of juvenile Amphiura filiformis (Ophiuroidea) in the Oresund. Ophelia, 20, 153-168.
  30. O'Connor, B., Bowmer, T. & Grehan, A., 1983. Long-term assessment of the population dynamics of Amphiura filiformis (Echinodermata: Ophiuroidea) in Galway Bay (west coast of Ireland). Marine Biology, 75, 279-286.
  31. O'Connor, B., Bowmer, T., McGrath, D. & Raine, R., 1986. Energy flow through an Amphiura filiformis (Ophiuroidea: Echinodermata) in Galway Bay, west coast of Ireland: a preliminary investigation. Ophelia, 26, 351-357.
  32. Olsgard, F. & Gray, J.S., 1995. A comprehensive analysis of the effects of offshore oil and gas exploration and production on the benthic communities of the Norwegian continental shelf. Marine Ecology Progress Series, 122, 277-306.
  33. Pagett, R.M., 1980. Tolerance to brackish water by ophiuroids with special reference to a Scottish sea loch, Loch Etive. In Echinoderms: Past and Present (ed. M. Jangoux), pp. 223-229. Rotterdam: Balkema.
  34. Pearson, T.H. & Rosenberg, R., 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanography and Marine Biology: an Annual Review, 16, 229-311.
  35. Picton, B.E. & Costello, M.J., 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. [CD-ROM] Environmental Sciences Unit, Trinity College, Dublin., http://www.itsligo.ie/biomar/
  36. Ramsay, K., Kaiser, M.J. & Hughes, R.N. 1998. The responses of benthic scavengers to fishing disturbance by towed gears in different habitats. Journal of Experimental Marine Biology and Ecology, 224, 73-89.
  37. Rosenberg, R., 1995. Benthic marine fauna structured by hydrodynamic processes and food availability. Netherlands Journal of Sea Research, 34, 303-317.
  38. Rosenberg, R., Gray, J.S., Josefson, A.B. & Pearson, T.H., 1987. Petersen's benthic stations revisited. II. Is the Oslofjord and eastern Skagerrak enriched? Journal of Experimental Marine Biology and Ecology, 105, 219-251.
  39. Rosenberg, R., Hellman, B. & Johansson, B., 1991. Hypoxic tolerance of marine benthic fauna. Marine Ecology Progress Series, 79, 127-131.
  40. Rowden, A.A., Jones, M.B. & Morris, A.W., 1998. The role of Callianassa subterranea (Montagu) (Thalassinidea) in sediment resuspension in the North Sea. Continental Shelf Research, 18, 1365-1380.
  41. Rygg, B., 1985. Effect of sediment copper on benthic fauna. Marine Ecology Progress Series, 25, 83-89.
  42. Stickle, W.B. & Diehl, W.J., 1987. Effects of salinity on echinoderms. In Echinoderm Studies, Vol. 2 (ed. M. Jangoux & J.M. Lawrence), pp. 235-285. A.A. Balkema: Rotterdam.

  43. Theede, H., Ponat, A., Hiroki, K. & Schlieper, C., 1969. Studies on the resistance of marine bottom invertebrates to oxygen-deficiency and hydrogen sulphide. Marine Biology, 2, 325-337.
  44. Thrush, S.F., 1986. Community structure on the floor of a sea-lough: are large epibenthic predators important? Journal of Experimental Marine Biology and Ecology, 104, 171-183.
  45. Tuck, I.D., Hall, S.J., Robertson, M.R., Armstrong, E. & Basford, D.J., 1998. Effects of physical trawling disturbance in a previously unfished sheltered Scottish sea loch. Marine Ecology Progress Series, 162, 227-242.
  46. Tyler, P.A., 1977. Seasonal variation and ecology of gametogenesis in the genus Ophiura (Ophiuroidea: Echinodermata) from the Bristol Channel. Journal of Experimental Marine Biology and Ecology, 30, 185-197.
  47. Wilson, W.H., 1991. Competition and predation in marine soft sediment communities. Annual Review of Ecology and Systematics, 21, 221-241.

Citation

This review can be cited as:

Hill, J.M. & Wilson, E. 2004. Virgularia mirabilis and Ophiura spp. with Pecten maximus on circalittoral sandy or shelly mud. 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/66

Last Updated: 10/11/2004