Amphiura filiformis, Mysella bidentata and Abra nitida in circalittoral sandy mud

10-11-2004
Researched byJacqueline Hill Refereed byDr David Hughes
EUNIS CodeA5.351 EUNIS NameAmphiura filiformis, Mysella bidentata and Abra nitida in circalittoral sandy mud

Summary

UK and Ireland classification

EUNIS 2008A5.351Amphiura filiformis, Mysella bidentata and Abra nitida in circalittoral sandy mud
EUNIS 2006A5.351Amphiura filiformis, Mysella bidentata and Abra nitida in circalittoral sandy mud
JNCC 2004SS.SMu.CSaMu.AfilMysAnitAmphiura filiformis, Mysella bidentata and Abra nitida in circalittoral sandy mud
1997 BiotopeSS.CMS._.AfilEcorAmphiura filiformis and Echinocardium cordatum in circalittoral clean or slightly muddy sand

Description

Medium to fine clean / muddy (clayey) sand off shallow wave- exposed coasts can be characterized by Amphiura filiformis and Echinocardium cordatum. This community occurs in muddy sands and deeper water (Hiscock, 1984; Picton et al., 1994) and may be related to the 'off-shore muddy sand association' described by other workers (Jones, 1951; Mackie, 1990). This community is also characterized by Pholoe sp., Nephtys hombergii, Nucula nitidosa, Callianassa subterranea and Eudorella truncatula (e.g. Kunitzer et al., 1992). Virgularia mirabilis, Cerianthus lloydii and Chaetopterus variopedatus may be other conspicuous surface features but they do not occur in high numbers in this biotope. Deeper, more muddy sediments may give rise to CMS.AbrNucCor. In areas subject to benthic fisheries disturbance, Arctica islandica (if present) may show scars on their shells (Klein & Witbaard, 1993). (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

The biotope is widespread around the British Isles, having been recorded from a number of Scottish sea lochs, the northern Irish Sea, the central and southern North Sea and the Isles of Scilly.

Depth range

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Additional information

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Further information sources

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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. Amphiura filiformis and Echinocardium cordatum are functionally dissimilar and are not always / 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 Amphiura filiformis and Echinocardium cordatum the biotope supports a fauna of burrowing species such as Callianassa subterranea and smaller less conspicuous species, such as polychaetes, nematodes and bivalves, living within the sediment.
  • There are however, some interspecific relationships within the biotope. The bivalve Tellimya (=Montacuta) ferruginosa is a commensal of Echinocardium cordatum, and as many as 14 or more of this bivalve have been recorded with a single echinoderm. Adult specimens live freely in the burrow of Echinocardium cordatum, while the young are attached to the spines of the echinoderm by byssus threads (Fish & Fish, 1996). The amphipod crustacean Urothe marina (Bate) is another common commensal (Hayward & Ryland, 1995).
  • Most of the species living in deep mud biotopes are generally cryptic in nature and not usually subject to predation. However, the arms of Amphiura filiformis are an important food source for demersal fish and Nephrops norvegicus providing significant energy transfer to higher trophic levels. Increased nutrients leading to eutrophication processes (increased primary production) may contribute to increase the accumulation of hydrophobic contaminants in Amphiura filiformis and their transfer to higher trophic levels (Gunnarsson & Skold, 1999). 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. Observations by Hoare & Wilson (1977) suggest however, that predation pressure on this species is low. Many specimens of Virgularia mirabilis lack the uppermost part of the colony which has been attributed to nibbling by fish. The sea slug Armina loveni is a specialist predator of Virgularia mirabilis.
  • In their investigation of density dependent migration in Amphiura filiformis Rosenberg et al. (1997) calculated in areas of high density of the species (3000 individuals per m2), the area of sediment at about 3 to 4cm depth covered by disks of Amphiura filiformis can be estimated as 22%. The capacity of such a density of brittle stars to displace sediment can be calculated at 0.18 m2 per hour. Thus, movement of Amphiura filiformis should generate a more or less continuous displacement of sediment and be of great significance to the biogeochemical processes in the sediment.
  • The burrowing and feeding activities of Amphiura filiformis 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 destabilization of the seabed can affect rates of particle resuspension. At a permanent monitoring station in Galway Bay, the brittle star Amphiura filiformis consistently ranks third among the numerically dominant species. On this basis and due to its effect on the sediment (Ocklemann & Muus, 1978), it is tentatively given 'keystone' status within the community in question (O'Conner et al., 1983).
  • The openings of the burrows of Callianassa subterranea provide temporary refuge for fish such as the black goby Gobius niger and the sand goby Pomatoschistus minutus. Occasional errant polychaetes, particularly polynoid worms, inhabit the burrows (Nickell & Atkinson, 1995).
  • The bioturbatory activities of thalassinidean mud-shrimps such as Callianassa subterranea have important consequences for the structural characteristics of the sediment they inhabit.
  • The hydrodynamic regime, which in turn controls sediment type, is the primary physical environmental factor structuring benthic communities such as CMS.AfilEcor. 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 Amphiura filiformis and Echinocardium cordatum are long-lived and are unlikely to show any significant seasonal changes in abundance or biomass. 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.
  • Burrowing activity of the mud shrimp Callianassa subterranea in the North Sea appears to be seasonal (Rowden & Jones, 1997). Relatively little activity was observed in the period January - April, before a steady increase through spring and early summer, reaching a maximum at the end of the summer and a decline in autumn and winter. In January, when bioturbatory activity was low the seabed appeared essentially flat and smooth , whilst in September the bed was littered with numerous mounds and depressions.
  • One of the key factors affecting benthic habitats is disturbance, which in shallow subtidal habitats will increase in winter due to weather conditions. Storms may cause dramatic changes in distribution of macro-infauna by washing out dominant species, opening the sediment to recolonization by adults and/or available spat/larvae (Eagle, 1975; Rees et al., 1977; Hall, 1994) and by reducing success of recruitment by newly settled spat or larvae (see Hall, 1994 for review). For example, during winter gales along the North Wales coast (Rees et al., 1976) northerly gales threw piles of Echinocardium cordatum on to the strand line and the author suggests these events are not uncommon. Lawrence (1989) also reports that Echinocardium cordatum and other organisms such as bivalves and brittlestars can be washed out of the sediment by water currents generated by gales.

Habitat structure and complexity

  • The biotope has very little structural complexity with most species living in or on the sediment. The sediment expelled by Callianassa subterranea forms unconsolidated volcano-like mounds, which can significantly modify the seabed surface topography (Rowden et al., 1998). The sea pen, Virgularia mirabilis, and the anemone Cerianthus lloydii extend above the sediment surface although these do not occur in high numbers and apart from a couple of species of nudibranch living on the sea pens these species do not provide significant habitat for other fauna.
  • Some structural complexity is provided by animal burrows although these are generally simple. The burrows of Echinocardium cordatum, for example, provide a habitat for other species such as the small bivalve Tellimya (=Montacuta) ferruginosa. Most species living within the sediment are limited to the area above the anoxic layer, the depth of which will vary depending on sediment particle size and organic content. The mud shrimp Callianassa subterranea creates complex burrow systems consisting of a multi-branched network of tunnels connected to several inhalant shafts, each terminating in a funnel shaped opening to the surface. The presence of burrows of species such as Echinocardium cordatum and Callianassa subterranea allows a much larger surface area of sediment to become oxygenated, and thus enhance the survival of a considerable variety of small species (Pearson & Rosenberg, 1978). Burrows also create habitats for other animals such as clams and polychaetes.
  • Deposit feeders manipulate, sort and process sediment particles which may result in destabilization and bioturbation of the sediment which inhibits survival of suspension feeders. This can result in a change in the vertical distribution of particles in the sediment that may facilitate vertical stratification of some species with particle size preferences. Vertical stratification of species according to sediment particle size has been observed in some soft-sediment habitats (Peterson, 1977).

Productivity

Productivity in subtidal sediments is often quite low. Macroalgae are absent from CMS.AfilEcor 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. However, the arms of Amphiura filiformis are an important food source for demersal fish and Nephrops norvegicus providing significant energy transfer to higher trophic levels.

Recruitment processes

  • Studies of Amphiura filiformis suggest autumn recruitment (Buchanan, 1964) and spring and autumn (Glmarec, 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.
  • In Echinocardium cordatum the sexes are separate and fertilization is external, with the development of a pelagic larva (Fish & Fish, 1996). The fact that Echinocardium cordatum is to be found associated with several different bottom communities would indicate that the larvae are not highly selective and discriminatory and it is probable that the degree of discrimination in 'larval choice' becomes diminished with the age of the larvae (Buchanan, 1966). Metamorphosis of larvae takes place within 39 days after fertilization (Kashenko, 1994). On the north-east coast of England a littoral population bred for the first time when three years old. In the warmer waters of the west of Scotland breeding has been recorded at the end of the second year (Fish & Fish, 1996). Buchanan (1967) observed that offshore populations were very slow growing and did not appear to reach sexual maturity so recruitment may be sporadic in places. However, since Buchanan (1967) also found that intertidal populations bred every year, recruitment should take place on an annual basis.
  • Many of the other species in the biotope, including Callianassa subterranea and Virgularia mirabilis appear to have planktonic larvae so much recruitment to the biotope may be from distant sources.

Time for community to reach maturity

No evidence on community development was found. However, the two key species Amphiura filiformis and Echinocardium cordatum are 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. In Galway Bay (O'Connor et al., 1983) 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. Echinocardium cordatum breed for the first time when two to three years old. Recruitment of Echinocardium cordatum is often sporadic with reports of recruiting in only 3 years over a 10 year period (Buchanan, 1966) although this relates to subtidal populations. Intertidal individuals reproduce more frequently. Many of the other species in the biotope, such as polychaetes and bivalves, are likely to reproduce annually. However, because the key species in the biotope, Amphiura filiformis and Echinocardium cordatum, 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.

Additional information

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Preferences & Distribution

Recorded distribution in Britain and IrelandThe biotope is widespread around the British Isles, having been recorded from a number of Scottish sea lochs, the northern Irish Sea, the central and southern North Sea and the Isles of Scilly.

Habitat preferences

Depth Range
Water clarity preferences
Limiting Nutrients Not relevant
Salinity
Physiographic
Biological Zone
Substratum Sand, Muddy sand
Tidal
Wave
Other preferences

Additional Information

Species composition

Species found especially in this biotope

    Rare or scarce species associated with this biotope

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    Additional information

    Sensitivity reviewHow is sensitivity assessed?

    Explanation

    The sensitivity of the biotope is based on the sensitivity of the key species after which the biotope is named, Amphiura filiformis and Echinocardium cordatum. The burrowing mud-shrimp Callianassa subterranea is also an important species within the biotope because its burrowing activities can alter the nature of the sediment through bioturbation and burrows allow a much larger surface area of sediment to become oxygenated, and thus enhance the survival of a considerable variety of small species (Pearson & Rosenberg, 1978).

    Species indicative of sensitivity

    Community ImportanceSpecies nameCommon Name
    Important characterizingAmphiura filiformisA brittlestar
    Important structuralCallianassa subterraneaA burrowing mud shrimp
    Key functionalEchinocardium cordatumSea potato

    Physical Pressures

     IntoleranceRecoverabilitySensitivitySpecies RichnessEvidence/Confidence
    High Moderate Moderate Major decline High
    Most species in the CMS.AfilEcor biotope are infaunal or epifaunal and will be lost if the substratum is removed so the overall intolerance of the biotope is high. Although there are some mobile species in the biotope, such as the polychaete Nephtys hombergii, they are not very fast moving and so are also likely to be removed. The key species do not reach sexual maturity for several years. For example, it takes approximately 5-6 years for Amphiura filiformis to grow to maturity and about 3 years for Echinocardium cordatum. However, it has been observed that subtidal populations of Echinocardium cordatum appear never to reach sexual maturity (Buchanan, 1967) and recruitment is often sporadic, with reports of the species recruiting in only 3 years over a 10 year period (Buchanan, 1966). Intertidal individuals reproduce more frequently so recruitment may be dependent on intertidal populations. The burrowing mud shrimp reaches sexual maturity within the first year, possibly breeding twice a year and producing planktonic larvae so recovery is expected to be rapid. Immigration of adult mud shrimps can also aid recovery. The remaining megafauna in the biotope vary in their longevity and reproductive strategies and some species will reach sexual maturity very rapidly. However, as the key species take a long time to reach sexual maturity it seems likely that a community of Amphiura filiformis and Echinocardium cordatum may take longer than five years to recover and so a rank of moderate is reported.
    Low Immediate Not sensitive No change High
    The biotope will have low intolerance to smothering by 5 cm of sediment because most species are burrowing and live within the sediment anyway. Amphiura filiformis lives within the top 3-4 cm of sediment and Echinocardium cordatum and Callianassa subterranea create burrows in the sediment and many other species in the biotope are also infaunal. There may be an energetic cost expended to either re-establish burrow openings, to self-clean feeding apparatus or to move up through the sediment though this is not likely to be significant. Most animals will be able to reburrow or move up through the sediment within hours or days so recovery is set at immediate. Intolerance to smothering by other factors such as oil may be higher.
    Low Immediate Not sensitive No change High
    Most species in the biotope are burrowing infauna so will not be affected by an increase in suspended sediment. There may be possible clogging of the feeding organs of the suspension feeding sea pens although 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. However, since most species in the biotope have low intolerance to an increase in suspended sediment at the benchmark level an overall rank of low is also reported for the biotope. 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 High Moderate Major decline Moderate
    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 would probably also be reduced. However, the benchmark is a reduction in suspended sediment of 100mg/l for a month which 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 High
    The biotope only occurs in the circalittoral zone (below 10 m) and is not subject to desiccation.
    Not relevant Not relevant Not relevant Not relevant High
    The biotope only occurs in the circalittoral zone (below 10 m) and is not subject to a change in emergence regime.
    Not sensitive* High
    The biotope only occurs in the circalittoral zone (below 10 m) and is not subject to a change in emergence regime.
    High Moderate Moderate Minor decline High
    The biotope is generally found in areas of weak or very weak tidal streams and so is likely to be intolerant of increases in water flow. However, in Scottish sea lochs, Howson et al. (1994) also found the biotope in areas of moderately strong tidal streams. Tidal currents keep most of the organic particles in the sediment in suspension which can support suspension feeders such as Amphiura filiformis even in low organic content sediments. The horizontal supply of small and light nutritious particles by resuspension and advective transport has been shown to influence the growth rate of suspension-feeding benthos (Dauwe, 1998). As a suspension feeder without any self-produced feeding current water flow rate will be of primary importance to Amphiura filiformis. Individuals 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). The sea pen Virgularia mirabilis, for example, would be unable to feed in water flow increased by the benchmark level. A long term increase (i.e. the benchmark level of one year) 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. High density aggregations of Amphiura filiformis seem to be characteristic of fine sediments with silt/clay values of 10 to 20% (O'Connor et al., 1983) so removal of the finer matter is likely to reduce abundance. In more exposed and coarser sediments Amphiura filiformis may be replaced by Amphiura brachiata that may change the nature of the biotope because A. brachiata is a suspension, rather than deposit feeder. Deeper burrowing species such as the thalassinidean crustaceans Callianassa subterranea are not likely to be affected by sediment changes at the surface. The overall impact of an increase in water flow rate on the biotope may be the loss of some key species, such as Amphiura filiformis, which changes the biotope, and some other species such as sea pens so intolerance is assessed as high. Recovery is moderate - see additional information.
    Low High Low No change Moderate
    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. Over the period of a year many individuals would be likely to die so intolerance is assessed as high. In slightly less energetic conditions and finer sediment, the biotope CMU.SpMeg, which includes high abundance of sea pens and burrowing megafauna such as Callianassa subterranea, is more likely to be present. For recovery see additional information.
    Intermediate High Low Minor decline Moderate
    The key species Amphiura filiformis and Echinocardium cordatum have a relatively wide degree of tolerance to temperature in accordance with their cosmopolitan distribution. Both species are distributed in warmer waters to the south of Britain and Ireland and most sediment species will be subject to annual variations in temperature of about 10 °C. Therefore, CMS.AfilEcor may be tolerant of long term increases although growth and fecundity of some species may be affected. In Echinocardium cordatum for example, there is rapid growth in the summer and no growth in the winter (Ridder de et al., 1991) and generally higher growth rates in warmer waters (Duineveld & Jenness, 1984). Muus (1981) showed that juvenile Amphiura filiformis are capable of much higher growth rates in experiments with temperatures between 12 and 17 °C. However, Amphiura filiformis and other animals live subtidally where wide and rapid variations in temperature, such as experienced in the intertidal do not occur. Therefore the biotope may be more intolerant of a short term increase of 5 °C and so a rank of intermediate is recorded. For most deep burrowing species like Callianassa subterranea temperature changes in the water column are likely to be buffered to some extent by the sediment and so many individuals will not be affected.
    Intermediate High Low Minor decline Moderate
    The key species Amphiura filiformis and Echinocardium cordatum have a relatively wide degree of tolerance to temperature in accordance with their cosmopolitan distribution. Both species are distributed in waters to the north of Britain and Ireland and so are probably able to tolerate long term decreases in temperature. In British waters most sediment species will be subject to annual variations in temperature of about 10 °C. Therefore, CMS.AfilEcor may be tolerant of long term increases although growth and fecundity of some species may be affected. However species may be less tolerant of short term decreases. Echinoderms, including Amphiura filiformis, of the North Sea seem periodically affected by winter cold with mortalities during cold waters. Low temperatures are a limiting factor for breeding which takes place during the warmest months in the UK. Very low water temperature can also cause mass mortalities of Echinocardium cordatum. During the severe winter of 1963 the species was almost completely eliminated from the German Bight to a depth of about 20 m (Lawrence, 1996) and very heavy mortality was observed in the English Channel and North Sea (Crisp (ed.), 1964). The intolerance of the biotope is set at intermediate as some individuals of the key species may be lost during short term decreases in extreme cold weather.
    Low Very high Very Low No change Moderate
    An increase in turbidity, reducing light availability may reduce primary production by phytoplankton in the water column. However, productivity in the CMS.AfilEcor biotope is secondary (detritus) and although an increase in turbidity may reduce phytoplankton contribution to detritus any effects, at the level of the benchmark, are not likely to be significant and so intolerance is assessed as low. On return to normal conditions recovery is likely to be very high as increased light results in more photosynthetic productivity and improved food supply.
    Low Very high Moderate No change Moderate
    A decrease in turbidity, increasing light availability may improve primary production by phytoplankton in the water column. However, productivity in the CMS.AfilEcor biotope is secondary (detritus) and although a decrease in turbidity may raise phytoplankton contribution to detritus any effects, at the level of the benchmark, are not likely to be significant and so intolerance is assessed as low. On return to normal conditions recovery is likely to be very high.
    High Moderate Moderate Decline Moderate
    The key species, Amphiura filiformis and Echinocardium cordatum are found in sheltered habitats characterized by fine muddy sandy sediments and low wave exposure. Both species are likely to be intolerant of increases in wave exposure. Strong wave action can re-suspend the sediment and break up and scatter Amphiura filiformis although the species is able to burrow further into the sediment and if displaced is able to reburrow. Nevertheless, intolerance to wave exposure at the benchmark level is likely to be high because the species would probably not survive the disturbance for a period of a year. Echinocardium cordatum is typically a sheltered shore species although in coastal waters of the Netherlands the species occurs in the tidal zone on some sandflats exposed to wave-action, at the entrances of the Oosterschelde and the Westerschelde (Wolff, 1968). In the bay of Douarnenez, Brittany Echinocardium cordatum was only found in areas of fine sand dominated by high sediment instability, due to marked exposure to westerly swells (Guillou, 1985). However, the species is unlikely to survive in areas of extreme wave exposure and is recorded as having intermediate intolerance. The intolerance of the biotope is assessed as high because of the probable loss of the key structuring species, Amphiura filiformis. Recolonization within five years should be possible as recolonization can take place from recruitment of larvae and juveniles and also immigration of adults from unaffected areas but the community is not likely to return to the original profile within five years because Amphiura filiformis does not reach sexual maturity until 5-6 years. Recovery has therefore, been assessed as moderate.
    Low High Low No change Moderate
    The biotope occurs in areas of very low or no wave exposure such as sea lochs so a reduction in wave exposure is not likely to have a significant impact on the biotope and so intolerance is assessed as low. If a decrease in wave exposure were also combined with a decrease in water flow rate deoxygenation may occur to which some species in the biotope would be intolerant.
    Tolerant Not relevant Not relevant Not relevant High
    Some of the important characterizing species associated with this biotope, such as Amphiura filiformis, may respond to sound vibrations and will retract their arms into the sediment. Feeding will resume once the disturbing factor has passed. However, none of the characterizing species are especially intolerant of noise disturbance at the level of the benchmark such as boats etc. passing overhead and so the biotope is recorded as being not sensitive.
    Tolerant Not relevant Not relevant Not relevant High
    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 reported as not sensitive to the factor.
    Intermediate High Low Minor decline Moderate
    The biotope is not generally subject to anthropogenic physical disturbance because it does not support any commercial species. Consequently, there is little information on effects of physical disturbance on the CMS.AfilEcor community. However, there is information on individual species. Echinocardium cordatum, for example, has a fragile test that is likely to be damaged by an abrasive force such as movement of trawling gear over the seabed. A substantial reduction in the numbers of the species due to physical damage from scallop dredging has been observed (Eleftheriou & Robertson, 1992). Echinocardium cordatum was reported to suffer between 10 and 40% mortality due to fishing gear, depending on the type of gear and sediment after a single trawl event (Bergman & van Santbrink, 2000). They suggested that mortality may increase to 90% in summer when individuals migrate to the surface of the sediment during their short reproductive season. Bergman & van Santbrink (2000) suggested that Echinocardium cordatum was one of the most vulnerable species to trawling.

    Bergman & Hup (1992) for example, found that beam trawling in the North Sea had no significant direct effect on small brittle stars. Brittlestars can tolerate considerable damage to arms and even the disk without suffering mortality and are capable of arm and even some disk regeneration. The intolerance of Amphiura filiformis to abrasion and physical disturbance is recorded as low. Individuals can still function whilst regenerating a limb so recovery will be rapid. In an analysis of long-term effects of scallop dredging on benthic communities in the Irish Sea, Bradshaw et al. (2002) noted a decline in the sedentary, filter feeding brittlestars Ophiothrix fragilis and Ophiopholis aculeata but an increase in surface detritivores or scavenging brittlestars such as Amphiura filiformis, Ophiocomina nigra and Ophiura albida. 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.

    The factor is not relevant to Callianassa subterranea because the species rarely leaves its burrows under normal circumstances and burrows are deep enough, sometimes up to 80 cm, to avoid trawls and dredges. Thus physical disturbance like trawling is unlikely to affect Callianassa subterranea to any great extent. Other species, also found in this biotope, that were observed to be sensitive include the bivalves Nucula nitidosa and Corbula gibba and the polychaetes Nephtys sp. and Terebellides stroemi. For epifaunal species, no long-term effects on the total number of species or individuals were detected, but individual species did show effects, notably an increase in the density of Ophiura sp. and a decrease in numbers of the fish Hippoglossoides platessoides and the whelk Buccinum undatum. Other authors have also suggested that increases in echinoderm populations in the North Sea are associated with fishing disturbance (Aronson, 1990; Lindley et al., 1995). Therefore, the overall effect on the biotope would be a reduction in species diversity and the loss of a number of individuals of the key species Echinocardium cordatum so the intolerance of the biotope is reported to be intermediate. Recovery of Echinocardium cordatum should be possible within five years so a rank of high is reported.

    Low Immediate Not sensitive No change High
    Most species in the biotope are burrowing and have low intolerance to displacement, such as that caused by a passing trawl that does not kill species but throws them into suspension, because animals can reburrow into suitable substrata. 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 as can Echinocardium cordatum. Sea pens such as Virgularia mirabilis will re-burrow (Jones et al., 2000) and recover completely within 72 hours after displacement, provided the basal peduncle remains in contact with the sediment surface. Burrowing crustaceans such as Callianassa subterranea can reburrow immediately although full burrow construction may take longer. Infaunal organisms that move through the sediment but do not construct permanent burrows, like errant polychaetes will return to the sediment after displacement. Therefore, provided individuals are not damaged most species within the biotope are able to rapidly re-burrow after displacement so intolerance is assessed as low and recovery will be immediate.

    Chemical Pressures

     IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
    High Moderate Moderate Decline Low
    There was no information found on the effect of chemical pollutants on the biotope. However, effects on some of the individual species in the biotope have been reported from which impacts on the biotope can be extrapolated. Dahllöf et al. (1999) studied the long term effects of tri-butyl-tin (TBT) on the function of a marine sediment system. TBT spiked sediment was added to sediment that already had a TBT background level of approximately 27ng g-1 (83 pmol TBT /g) and contained the following fauna: Amphiura spp., Brissopsis lyrifera 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. Echinocardium cordatum was also found to be highly intolerant of detergents used to disperse oil from the Torrey Canyon oil spill which caused mass mortalities of the species (Smith, 1968). Thus, the key species seem to be highly intolerant of some chemical pollutants and may be lost from the biotope. Loss of the key species means loss of the biotope so intolerance is assessed as high. On return to normal conditions recovery may take many years and recovery is reported to be moderate - see additional information.
    Heavy metal contamination
    Intermediate High Low Minor decline Moderate
    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. Cu 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 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. Some burrowing crustaceans, brittle stars and bivalves may disappear from the biotope and lead to an increasing dominance of polychaetes.
    Hydrocarbon contamination
    High Moderate Moderate Major decline Moderate
    There was no information found on the effect of hydrocarbon pollution on the biotope. The best documented oil spill for protected habitats with soft mud/sand substrates is the West Falmouth, Florida spill of 1969. Immediately after the spill virtually the entire benthic fauna was eradicated immediately following the incident and populations of the opportunistic polychaete Capitella capitata increased to abundances of over 200,000/m² (Sanders, 1978). The key species in the biotope, Amphiura filiformis and Echinocardium cordatum and also Callianassa subterranea are very intolerant of hydrocarbon pollution and so the intolerance of the biotope is recorded as high. Mass mortality of Echinocardium cordatum, down to about 20m, was observed shortly after the Amoco Cadiz oil spill (Cabioch et al., 1978). However, oil from spills would have to be dispersed deep into the water column to affect the biotope and since the biotope occurs in very sheltered conditions this is unlikely to occur. However, the key species in the biotope have been observed to be intolerant of chronic oil pollution. For example, reduced abundance of Echinocardium cordatum was detectable up to > 1000m away one year after the discharge of oil-contaminated drill cuttings in the North Sea (Daan & Mulder, 1996). Callianassa subterranea also appears to be highly intolerant of sediment contaminated by oil-based drilling muds (Daan et al., 1992) and 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. Oil polluted sediments may remain so for many years so recovery may be protracted. For example, persistent toxicity of Amoco Cadiz oil in sediment prevented the start of the recovery period (Clark, 1997). On return to normal conditions recovery may take many years because of the life-history of the key species. Recovery is recorded to be moderate - see additional information for rationale.
    Radionuclide contamination
    No information No information No information Insufficient
    information
    Not relevant
    Investigations of bioturbation in radionuclide contaminated sediments close to the Sellafield nuclear processing plant in the Irish Sea indicate that the burrowing mud shrimp Callianassa subterranea has some tolerance to radionuclide pollution (Hughes & Atkinson, 1997). However, the impact on the key species in the biotope, Amphiura filiformis and Echinocardium cordatum, is unknown and the sensitivity of the biotope cannot be assessed.
    Changes in nutrient levels
    Intermediate High Low Minor decline High
    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). Callianassa subterranea also has low intolerance to increases in the organic content of the sediment However, Echinocardium cordatum has higher intolerance to increased nutrients where the effect is a reduced mean individual weight (Josefson, 1990). Pearson & Rosenberg (1976) describe the changes in fauna along a gradient of increasing organic enrichment by pulp fibre where Echinocardium cordatum is absent from all but distant sediments with low organic input. 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, so other species are also likely to disappear in increasing nutrients. Therefore, an increase in nutrients at the benchmark level of a 50% increase is likely to result in reduced viability and abundance of Echinocardium cordatum and the possible loss of the less tolerant species so intolerance is assessed as intermediate. Echinocardium cordatum reaches sexual maturity within 3 years. It has been observed that subtidal populations of Echinocardium cordatum appear never to reach sexual maturity (Buchanan, 1967) and recruitment is often sporadic, with reports of the species recruiting in only 3 years over a 10 year period (Buchanan, 1966). However, intertidal individuals reproduce more frequently and the settling larva is not thought to be very substratum selective so recruitment should be possible within five years. The burrowing mud shrimp reaches sexual maturity within the first year, possibly breeding twice a year and producing planktonic larvae so recovery is expected to be rapid. Immigration of adult mud shrimps can also aid recovery. The remaining megafauna in the biotope vary in their longevity and reproductive strategies and some species will reach sexual maturity very rapidly. Thus, recovery of the biotope should be possible within five years and so a rank of high is reported.
    High Moderate Moderate Major decline Moderate
    The biotope is found in fully marine sublittoral conditions that do not experience water evaporation such as seen in rock pools in the intertidal or in lagoons. Therefore, it seems likely that the biotope will be intolerant of increases in salinity. The overall effect on the biotope of a chronic increase in salinity for a period of a year is likely to be the loss of most species and so intolerance is reported as high. On return to normal conditions recovery to previous community profile is likely to take several years - see additional information.
    High High Intermediate Major decline Moderate
    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 in the biotope are highly intolerant of salinity changes and although Echinocardium cordatum has been observed in brackish conditions marine populations 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.
    High High Moderate Decline High
    Amphiura filiformis and Callianassa subterranea are tolerant of reduced oxygen concentrations and would not be significantly affected by the benchmark level of 2 mg/l for a week. However, the spatangoid urchin Echinocardium cordatum is highly intolerant of a fall in oxygenation. In the south-eastern North Sea a period of reduced oxygen resulted in the death of many individuals of Echinocardium cordatum (Niermann, 1997) and in laboratory experiments many individuals were dead at a concentration of 2.4mg/l (Nilsson & Rosenberg, 1994). Other species in the biotope will have varying responses to deoxygenation. 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. However, with a loss of the key species Echinocardium cordatum the biotope will also be lost so intolerance is assessed as high. Echinocardium cordatum reaches sexual maturity within three years, reproduces every year and has pelagic larvae so recovery should be possible within five years and a rank of high is reported. Individuals can also migrate from unaffected areas. The time for re-establishment of faunal biomass after a period of anoxia related mortality in the south-eastern North Sea was 2 years (Niermann, 1997).

    Biological Pressures

     IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
    Low High Low No change Moderate
    There is little information on microbial pathogen effects on the characterizing species in this biotope. The occurrence of several parasitic gregarine protozoans, such as Urospora neapolitana, have been observed in the body cavity of Echinocardium cordatum (Coulon & Jangoux, 1987). However, no information concerning infestation or disease related mortalities was found. No evidence of losses of this biotope due to disease were found and a rank of low has been reported. However, other species have been affected by disease so there is always the potential for this to occur.
    Tolerant Not relevant Not relevant Not relevant Moderate
    There are no records of any non-native species invading the biotope and so is assessed as not sensitive. However, as several species have become established in British waters there is always the potential for this to occur.
    Intermediate High Low Minor decline Moderate
    It is unlikely that the biotope would be subject to extraction as it has no commercial and limited research value although dredging operations may remove populations in some habitats if the burrowing crustacean Nephrops norvegicus is present. There is not a great deal of dependency in the species present and therefore extraction of one would not radically change the function of the biotope. However, with the loss of a key species, after which the biotope is named, the species composition of the biotope would be significantly different. An important functional species in the biotope, Callianassa subterranea, would probably not be extracted even if dredging, or similar, operations were to take place because it lives within burrow systems that may extend up to 80 cm or more. However, the species has important consequences for sedimentary characteristics such as bioturbation and oxygenation as well as creating habitats for other species to colonize so its removal may affect the overall species composition of the biotope. Nevertheless, the species is not present in very high abundance so a significant impact on the biotope. Intolerance is assessed as intermediate although recovery is expected to be high (see additional information).
    Low High Low Minor decline Moderate

    Additional information

    Recoverability
    They key species do not reach sexual maturity for several years. For example, it takes approximately 5-6 years for Amphiura filiformis to grow to maturity and about 3 years for Echinocardium cordatum. However, it has been observed that subtidal populations of Echinocardium cordatum appear never to reach sexual maturity (Buchanan, 1967) and recruitment is often sporadic, with reports of the species recruiting in only 3 years over a 10 year period (Buchanan, 1966). Intertidal individuals reproduce more frequently so recruitment may be dependent on intertidal populations. The burrowing mud shrimp reaches sexual maturity within the first year, possibly breeding twice a year and producing planktonic larvae so recovery is expected to be rapid. Immigration of adult mud shrimps can also aid recovery. The remaining megafauna in the biotope vary in their longevity and reproductive strategies and some species will reach sexual maturity very rapidly. However, as the key species take a long time to reach sexual maturity it seems likely that a community of Amphiura filiformis and Echinocardium cordatum may take longer than five years to recover and so a rank of moderate is reported.

    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

    The biotope does not contain any commercially important species such as Nephrops norvegicus and so is not likely to be subject to exploitation.

    Additional information

    -

    Bibliography

    1. Aronson, R.B., 1990. Onshore-offshore patterns of human fishing activity. Palaios, 5, 88-93.
    2. 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.
    3. 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.
    4. Bergman, M.J.N. & van Santbrink, J.W., 2000. Fishing mortality of populations of megafauna in sandy sediments. In The effects of fishing on non-target species and habitats (ed. M.J. Kaiser & S.J de Groot), 49-68. Oxford: Blackwell Science.
    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. 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.
    7. Buchanan, J.B., 1966. The biology of Echinocardium cordatum (Echinodermata: Spatangoidea) from different habitats. Journal of the Marine Biological Association of the United Kingdom, 46, 97-114.
    8. Buchanan, J.B., 1967. Dispersion and demography of some infaunal echinoderm populations. Symposia of the Zoological Society of London, 20, 1-11.
    9. Cabioch, L., Dauvin, J.C. & Gentil, F., 1978. Preliminary observations on pollution of the sea bed and disturbance of sub-littoral communities in northern Brittany by oil from the Amoco Cadiz. Marine Pollution Bulletin, 9, 303-307.
    10. Clark, R.B., 1997. Marine Pollution, 4th ed. Oxford: Carendon Press.
    11. 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.
    12. Coulon, P. & Jangoux, M., 1987. Gregarine species (Apicomplexa) parasitic in the burrowing echinoid Echinocardium cordatum: occurrence and host reaction. Diseases of Aquatic Organisms, 2, 135-145.
    13. Crisp, D.J. (ed.), 1964. The effects of the severe winter of 1962-63 on marine life in Britain. Journal of Animal Ecology, 33, 165-210.
    14. Daan, R. & Mulder, M., 1996. On the short-term and long-term impact of drilling activities in the Dutch sector of the North Sea ICES Journal of Marine Science, 53, 1036-1044.
    15. Daan, R., Groenewould van het, H., Jong de, S.A. & Mulder, M., 1992. Physico-chemical and biological features of a drilling site in the North Sea, 1 year after discharges of oil-contaminated drill cuttings. Marine Ecology Progress Series, 91, 37-45.
    16. 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.
    17. 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.
    18. 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.
    19. Duineveld, G.C.A. & Jenness, M.I., 1984. Differences in growth rates of the sea urchin Echinocardium cordatum as estimated by the parameters of the von Bertalanffy equation applied to skeletal rings. Marine Ecology Progress Series, 19, 64-72.
    20. Eagle, R.A., 1975. Natural fluctuations in a soft bottom benthic community. Journal of the Marine Biological Association of the United Kingdom, 55, 865-878.
    21. Eleftheriou, A. & Robertson, M.R., 1992. The effects of experimental scallop dredging on the fauna and physical environment of a shallow sandy community. Netherlands Journal of Sea Research, 30, 289-299.
    22. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

    23. Glémarec, M., 1979. Problemes d'ecologie dynamique et de succession en baie de Concarneau. Vie et Milieu, 28-29, 1-20.
    24. Guillou, J., 1985. Population dynamics of Echinocardium cordatum (Pennant) in the bay of Douarnenez (Brittany). In Proceedings of the Fifth International Echinocardium Conference / Galway / 24-29 September 1984 (ed. B.F. Keegan & B.D.S. O'Conner), 275-280. Rotterdam: Balkema.
    25. Gunnarsson, J.S. & Skold, M., 1999. Accumulation of polychlorinated biphenyls by the infaunal brittle stars Amphiura filiformis and A. chiajei: effects of eutrophication and selective feeding. Marine Ecology Progress Series, 186, 173-185.
    26. Hall, S.J., 1994. Physical disturbance and marine benthic communities: life in unconsolidated sediments. Oceanography and Marine Biology: an Annual Review, 32, 179-239.
    27. Hiscock, K., 1984. Rocky shore surveys of the Isles of Scilly. March 27th to April 1st and July 7th to 15th 1983. Peterborough: Nature Conservancy Council, CSD Report, No. 509.
    28. 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.
    29. Howson, C.M., Connor, D.W. & Holt, R.H.F., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. Joint Nature Conservation Committee Report, No. 164 (Marine Nature Conservation Review Report MNCR/SR/27)., Joint Nature Conservation Committee Report, No. 164 (Marine Nature Conservation Review Report MNCR/SR/27).
    30. 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.
    31. 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,
    32. 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
    33. Jones, N.S., 1951. The bottom fauna of the south of the Isle of Man. Journal of Animal Ecology, 20, 132-144.
    34. 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.
    35. Josefson, A.B., 1990. Increase in the benthic biomass in the Skagerrak-Kattegat during the 1970s and 1980s - effects of organic enrichment? Marine Ecology Progress Series, 66, 117-130.
    36. Künitzer, A., Basford, D., Craeymeersch, J.A., Dewarumez, J.M., Derjes, J., Duinevald, G.C.A., Eleftheriou, A., Heip, C, Herman, P., Kingston, P., Neirmann, U., Rachor, E., Rumohr, H. & Wilde, P.A.J. de, 1992. The benthic infauna of the North Sea: species distribution and assemblages. ICES Journal of Marine Science, 49, 127-143.

    37. Kashenko, S.D., 1994. Larval development of the heart urchin Echinocardium cordatum feeding on different macroalgae. Biologiya Morya, 20, 385-389.
    38. Klein, R. & Witbaard, R., 1993. The appearance of scars on the shell of Arctica islandica L. (Mollusca, Bivalvia) and their relation to bottom trawl fishery. NIOZ - Rapport, 12., Unpublished, Nederlands Instituut voor Onderzoek der Zee.
    39. Lawrence, J.M., 1996. Mass mortality of echinoderms from abiotic factors. In Echinoderm Studies Vol. 5 (ed. M. Jangoux & J.M. Lawrence), pp. 103-137. Rotterdam: A.A. Balkema.
    40. Lindley, J.A., Gamble, J.C. & Hunt, H.G., 1995. A change in the zooplankton of the central North Sea (55° to 58° N): a possible consequence of changes in the benthos. Marine Ecology Progress Series, 119, 299-303.
    41. Mackie, A.S.Y., 1990. Offshore benthic communities of the Irish Sea. In The Irish Sea: an environmental review. Part 1: nature conservation, ed. Irish Sea Study Group, pp. 169-218. Liverpool, Liverpool University Press for Irish Sea Study Group.
    42. Muus, K., 1981. Density and growth of juvenile Amphiura filiformis (Ophiuroidea) in the Oresund. Ophelia, 20, 153-168.
    43. Nickell, L.A. & Atkinson, R.J.A., 1995. Functional morphology of burrows and trophic modes of three thalassinidean shrimp species, and a new approach to the classification of thalassinidean burrow morphology. Marine Ecology Progress Series, 128, 181-197.
    44. Niermann, U., 1997. Macrobenthos of the south-eastern North Sea during 1983-1988. Berichte der Biologischen Anstalt Helgoland, 13, 144pp.
    45. Nilsson, H.C. & Rosenberg, R., 1994. Hypoxic response of two marine benthic communities. Marine Ecology Progress Series, 115, 209-217.
    46. 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.
    47. 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.
    48. Ockelmann, K.W. & Muus, K., 1978. The biology, ecology and behaviour of the bivalve Mysella bidentata (Montagu). Ophelia, 17, 1-93.
    49. 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.
    50. Pearson, T.H. & Rosenberg, R., 1976. A comparative study of the effects on the marine environment of wastes from cellulose industries in Scotland and Sweden. Ambio, 5, 77-79.
    51. 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.
    52. Peterson, C.H., 1977. Competitive organisation of the soft bottom macrobenthic communities of southern California lagoons. Marine Biology, 43, 343-359.
    53. 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/
    54. Picton, B.E., Emblow, C.S., Morrow, C.C., Sides, E.M. & Costello, M.J., 1994b. Marine communities of the Mulroy Bay and Lough Swill area, north-west Ireland, with an assessment of their nature conservation importance. , Unpublished, Environmental Sciences Unit, Trinity College. (Field Survey Report).
    55. 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.
    56. Rees, E.I.S., Nicholaidou, A. & Laskaridou, P., 1977. The effects of storms on the dynamics of shallow water benthic associations. In Proceedings of the 11th European Symposium on Marine Biology, Galway, Ireland, October 5-11, 1976. Biology of Benthic Organisms, (ed. B.F. Keegan, P.O Ceidigh & P.J.S. Boaden), pp. 465-474.
    57. Ridder de, C., David, B., Laurin, B. & Gall le, P., 1991. Population dynamics of the spatangoid echinoid Echinocardium cordatum (Pennant) in the Bay of Seine, Normandy. In Proceedings of the Seventh International Echinoderm Conference Atami, 9 - 14 September 1991: Biology of Echinodermata, (ed. Yanagisawa, T., Yasumasu, I., Oguro, C., Suzuki, N. & Motokawa, T.), 153-158. Balkema, Rotterdam.
    58. Rosenberg, R., 1995. Benthic marine fauna structured by hydrodynamic processes and food availability. Netherlands Journal of Sea Research, 34, 303-317.
    59. 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.
    60. Rosenberg, R., Hellman, B. & Johansson, B., 1991. Hypoxic tolerance of marine benthic fauna. Marine Ecology Progress Series, 79, 127-131.
    61. Rosenberg, R., Nilsson, H.C., Hollertz, K. & Hellman, B., 1997. Density-dependent migration in an Amphiura filiformis (Amphiuridae, Echinodermata) infaunal population. Marine Ecology Progress Series, 159, 121-131.
    62. Rowden, A.A. & Jones, M.B., 1997. Recent mud shrimp burrows and bioturbation. Porcupine Newsletter, 6, 153-158.
    63. 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.
    64. Rygg, B., 1985. Effect of sediment copper on benthic fauna. Marine Ecology Progress Series, 25, 83-89.
    65. Sanders, H.L., 1978. Florida oil spill impact on the Buzzards Bay benthic fauna: West Falmouth. Journal of the Fisheries Board of Canada, 35, 717-730.
    66. Smith, J.E. (ed.), 1968. 'Torrey Canyon'. Pollution and marine life. Cambridge: Cambridge University Press.
    67. Wolff, W.J., 1968. The Echinodermata of the estuarine region of the rivers Rhine, Meuse and Scheldt, with a list of species occurring in the coastal waters of the Netherlands. The Netherlands Journal of Sea Research, 4, 59-85.

    Citation

    This review can be cited as:

    Hill, J.M. 2004. Amphiura filiformis, Mysella bidentata and Abra nitida in circalittoral sandy 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/368

    Last Updated: 10/11/2004