Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand

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Map Key

Orange points: Core Records
Pale Blue points: Non-core, certain determination
Black points: Non-core, uncertain determination
Yellow areas: Predicted habitat extent

Biotope distribution data provided by the JNCC (mhc.jncc.gov.uk)

Researched by

Eliane De-Bastos

Refereed by

Admin

Researched by
Eliane De-Bastos

Refereed by
Admin

Summary

UK and Ireland classification

Standard	Classification	Description
EUNIS 2008	A5.272	Owenia fusiformis and Amphiura filiformis in deep circalittoral sand or muddy sand
JNCC 2022	SS.SSa.OSa.OfusAfil	Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand
JNCC 2015	SS.SSa.OSa.OfusAfil	Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand
JNCC 2004	SS.SSa.OSa.OfusAfil	Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand
1997 Biotope

EUNIS 2008 A5.272 - Owenia fusiformis and Amphiura filiformis in deep circalittoral sand or muddy sand
JNCC 2015 SS.SSa.OSa.OfusAfil - Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand
JNCC 2004 SS.SSa.OSa.OfusAfil - Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand
1997 Biotope -

Description

Areas of slightly muddy sand (generally <20% mud) in offshore waters may be characterized by high numbers of the tube-building oweniid polychaete Owenia fusiformis and Galathowenia sp., often with the brittlestar Amphiura filiformis. Whilst Owenia fusiformis is also found in other circalittoral or offshore biotopes it usually occurs in lower abundances than in SS.SSa.OSa.OfusAfil. Other species found in this community are the polychaetes Goniada maculata, Pholoe inornata, Diplocirrus glaucus, Chaetozone setosa and Spiophanes kroyeri with occasional bivalves such as Timoclea ovata and Thyasira equalis. The sea cucumber Labidoplax buski and the cumacean Eudorella truncatula are also commonly often found in this biotope. This biotope along with SS.SMu.CSaMu.ThyEten, SS.SMu.CSaMu.AfilKurAnit, SS.SMu.CSaMu.AfilEten and SS.SMu.OMu.PjefThyAfil, may comprise the Amphiura-dominated components of the 'offshore muddy sand association' (Jones 1951; Mackie 1990) and the infralittoral etage described by Glemarec (1973). Variants of the biotope may contain the characteristic high numbers of Owenia fusiformis and Amphiura filiformis, but may also include Arctica islandica and Ennucula tenuis. Where these occur, the biotope may be considered a transitionary variant between SS.SSa.OSa.OfusAfil and SS.SMu.CSaMu.AfilKurAnit. (Information from JNCC, 2022).

Depth range

No information

Additional information

Listed By

Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

SS.SSa.OSa.OfusAfil here is considered to represent an offshore example of SS.SSa.CMuSa.AbraAirr. However, no records have been found and this sensitivity assessment is based upon the description of the biotope given by Connor et al. (2004). SS.SSa.OSa.OfusAfil occurs in areas of slightly muddy sand (generally <20% mud) in offshore waters and may be characterized by high numbers of the tube building polychaete Owenia fusiformis often with the brittlestar Amphiura filiformis, both of which are associated with and live buried in muddy sands. Whilst Owenia fusiformis is also found in other circalittoral or offshore biotopes, such as SS.SSa.OSa.MalEdef, it usually occurs in lower abundances than in SS.SSa.OSa.OfusAfil. This suggests that the occurrence of Owenia fusiformis and Amphiura filiformis in offshore muddy substrata define this biotope. For this reason, these are considered the characterizing species of this biotope and will be the focus of this sensitivity assessment. Furthermore, as an infaunal tube building polychaete, Owenia fusiformis are known to be good ecosystem engineers as a result of building their tubes for protection from hydrodynamics and predators, which in turn provide stability to the benthic soft sediment, and influence the structure of the benthic community with regard to diversity, abundances and spatial distribution (Dauer et al., 1982; Zuhlke, 2001, cited in Noffke et al., 2009). Other species found in this community are the polychaetes Goniada maculata, Pholoe inornata, Diplocirrus glaucus, Chaetozone setosa and Spiophanes kroyeri with occasional bivalves such as Timoclea ovata and Thyasira equalis. The sea cucumber Labidoplax buskii (syn. Labidoplax buski) and the cumacean Eudorella truncatula are also commonly often found in this biotope.

Resilience and recovery rates of habitat

The fauna characterizing these biotopes occur buried in muddy sands. Brittlestar Acrocnida brachiata displays the characteristic brittlestar body plan with a flat central disc (up to 12 mm diameter) and five very long, slender arms, up to 15 times the diameter of the disc (Fish & Fish, 1996). Acrocnida brachiata is known to spawn during summer and it has been suggested that it has a brief pelagic phase (Fish & Fish, 1996). Zakadjian (1990) studied the reproductive strategy of Acrocnida brachiata from the Bay of Seine and suggested a well-defined annual reproductive cycle, with gonad development beginning in late summer to autumn and spawning occurring in May and June. The authors also suggested that individuals did not reach sexual maturity until the second or third year of life with most individuals spawning at least two or three times in their lifetimes of up to 4-5 years (Zakadjian, 1990). Reproduction did not seem to coincide with annual temperature peak. Acrocnida brachiata, like other brittlestars, has been reported to be able to tolerate a significant level of sub-lethal predation, with large portions of populations having been observed to be regenerating arms (Bourgoin & Guillou, 1994). Acrocnida brachiata may benefit from the buried position it occupies in the sediment to strategically rotate arms between suspension feeding and burial in the sediment to allow arm regeneration (Makra & Keegan, 1999).

Astropecten irregularis has a stiff flattened body and can grow up to 20 cm in diameter. The sexes are separate and breeding apparently takes place during the summer months. It has a bipinnaria larva but no brachiolaria in the life-cycle (Fish & Fish, 1996). Freeman et al. (2001) studied the seasonal trends in abundance, spatial distribution, spawning and growth of a population of Astropecten irregularis of the coast of North Wales. The authors observed that Astropecten irregularis population varied seasonally, with maximum and minimum abundances in summer and winter respectively, suggesting that the starfish might migrate offshore to deeper, more stable waters during winter. The higher densities in the summer may coincide with spawning aggregations, which on the study site occur during late spring, early summer. In north-eastern Europe, Astropecten irregularis displays a marked annual reproductive cycle, with frequent spawning episodes throughout the summer months. Like most starfish, fertilization takes places externally, which is likely to benefit from population aggregations and synchronized spawning (Freeman et al., 2001). The authors suggested a lifespan of approx. 3.5 years, although under laboratory conditions Astropecten irregularis have been reported to live for up to about 10 years (Christensen, 1970, cited in Freeman et al., 2001).

Owenia fusiformis lives in a tough, flexible tube, which it builds by selectively collecting grain particles from its environment (Noffke et al., 2009). The sexes are separate and the larvae have a planktonic life of about four weeks. On the south coast of England, breeding occurs during June and July. Length of life is four years, with breeding occurring every year (Fish & Fish, 1996; Rouse & Pleijel, 2001). Owenia fusiformis has a polymodal population structure of three to five year classes (Menard et al., 1990). The mortality rate increases gradually with age but suddenly increases in the fourth year of life (Menard et al., 1990). Growth is rapid in summer, slows in the autumn and is negligible in winter, resuming in April each year. The maximum recorded density was 4660 individuals/m² but this fluctuated over each year with mortality and massive larval settlement (Menard et al., 1990). Maturity is size-dependent and all worms 6 cm long or more are mature but some individuals reach maturity at 2.4 cm. Some individuals may breed in their first year if they can grow fast enough (Gentil et al., 1990). In the southern North Sea, spatfall occurs from spring to early summer (Hartmann-Schöder, 1996, cited in Noffke et al., 2009) and in the English Channel the maximum of spat is in mid-May (Thiebaut et al., 1992). Larval settlement depends on the portion of fine sediment (mud) in the sediment (Wilson, 1932), with juvenile settlement strongly decreasing where mud portion was <5%. Furthermore, if the fine fraction is missing in the sediment, initial tube building is strongly restricted and the survival of the juveniles is thus negatively influenced (Pinedo et al., 2000; Noffke et al., 2009). These post-settlement processes are thought to have more influence on the macrobenthic community than processes in the pelagic phase.

Amphiura filiformis is a small brittlestar, disc up to 10 mm in diameter, with very long arms (10x disc diameter) which lives buried in muddy sand. Muus (1981) showed the mortality of new settling Amphiura filiformis to be extremely high with less than 5% contributing to the adult population in any given year. Sköld et al. (1994) also commented on the high mortality and low rates of recruitment in this species. In Galway Bay populations (O'Connor et al., 1983), 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. Muus (1981) estimated the lifespan of Amphiura filiformis to be 25 years based on oral width (which does not change with gonadal growth) with recruitment taking place at the 0.3 mm disc size. In very long-term studies of Amphiura filiformis populations in Galway Bay, a lifespan of some 20 years is possible (O'Connor et al., 1983). Amphiura filiformis reaches sexual maturity after 2 years, breeds annually and, in the UK, one period of recruitment occurs in the autumn (Pedrotti, 1993). The species is thought to have a long pelagic life. Sköld et al. (1994) estimated the time lag between full gonads and settlement to be 88 days. This duration is comparable to the time period when pelagic larvae have been recorded in the plankton from July to November in one prior study and August to December in another prior study (Fosshagen, 1965; Thorson, 1946, respectively, cited in Sköld et al., 1994). A long planktonic life stage means this species is predicted to disperse over considerable distances.

Resilience assessment: Minor damage to individual brittlestars, such as Acrocnida brachiata and Amphiura filiformis, and starfish Astropecten irregularis is likely to be repaired, and recovery from impacts with a small spatial footprint may occur through migration of adults. Where the majority of the population remain (resistance is High or Medium), and/or recruitment by adult mobility is possible recovery (resilience) is likely to be High. Where populations are removed or significantly reduced over large areas then recovery will be through recruitment of juveniles and will depend on the supply of new larvae. The characterizing species in these biotopes reproduce annually, so recovery through juvenile recruitment may occur within two years. However, recruitment rates may be low in places and are dependent on favourable hydrodynamic conditions that allow settlement of new recruits. So where impacts remove a significant proportion of the population (resistance is Low or None), recovery is likely to be Medium (2-10 years). Within this time period it is likely that most species could have re-established biomass and age structured populations.

NB: The resilience and the ability to recover from human induced pressures is a combination of the environmental conditions of the site, the frequency (repeated disturbances versus a one-off event) and the intensity of the disturbance. Recovery of impacted populations will always be mediated by stochastic events and processes acting over different scales including, but not limited to, local habitat conditions, further impacts and processes such as larval-supply and recruitment between populations. Full recovery is defined as the return to the state of the habitat that existed prior to impact. This does not necessarily mean that every component species has returned to its prior condition, abundance or extent but that the relevant functional components are present and the habitat is structurally and functionally recognizable as the initial habitat of interest. It should be noted that the recovery rates are only indicative of the recovery potential.

Hydrological Pressures

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	Resistance	Resilience	Sensitivity
Temperature increase (local) [Show more] Temperature increase (local) Benchmark. A 5°C increase in temperature for one month, or 2°C for one year. Further detail Evidence The characterizing species in these biotopes are widely distributed, from Norway to Morocco and the Mediterranean (Fish & Fish, 1996; Sabatini, 2008; Neil & Avant, 2008; Hill & Wilson, 2008). Kröncke et al. (2011) reported the increase in abundance and regional changes in the distribution of various species with a southern distribution in the North Sea in 2000, suggesting the changes were largely associated with an increase in sea surface temperature, primary production and, thus, food supply. The authors suggested that the increase of annual average was of about 1.1°C. Brittlestar Acrocnida brachiata was reported to be amongst these species, suggesting the brittlestar may benefit from warmer sea temperatures. On the other hand, Amphiura filiformis was among the species observed to have decreased. Zakadjian (1990) studied the reproductive strategy of Acrocnida brachiata from the Bay of Seine, where the annual temperature variations in the study site were from 6 to 22°C, with no link suggested between reproduction and temperature. Freeman et al. (2001) observed that spawning in Astropecten irregularis in theirs studies coincided with an increase in seawater temperature from approx. 8°C to 15°C. Furthermore, the authors noted that, in the laboratory, the shallow burrowing species adjusted the depth at which they burrowed into the sediment to seawater temperature, burrowing deeper at lower temperatures. In Galway Bay, long-term recordings of water temperature at a site of high density aggregations of Amphiura filiformis showed the species is subject to annual variations in temperature of about 10°C (O'Connor et al., 1983). Increases in temperature may affect growth and fecundity. Muus (1981) showed that juvenile Amphiura filiformis are capable of much higher growth rates in experiments with temperatures between 12 and 17°C. Owenia fusiformis is found in waters from -1 to 30°C (Dauvin & Thiebaut, 1994) globally. In the Bay of Seine, where there is a large population of Owenia fusiformis, the temperature varies between 5 and 20°C (Gentil et al., 1990). Sensitivity assessment: The characterizing species of these biotopes are widely distributed and likely to occur both north and south of the British Isles. Furthermore, the evidence presented suggests that these species are likely to potentially benefit from an increase in temperature at the pressure benchmark level, with increased distribution range, growth and fecundity. Resistance and resilience are therefore assessed as High and the biotopes considered Not Sensitive to an increase in temperature at the benchmark level.	High Medium Medium High Help	High High High High Help	Not sensitive Medium Medium High Help
Temperature decrease (local) [Show more] Temperature decrease (local) Benchmark. A 5°C decrease in temperature for one month, or 2°C for one year. Further detail Evidence The characterizing species in these biotopes are widely distributed, from Norway to Morocco and the Mediterranean (Fish & Fish, 1996; Sabatini, 2008; Neil & Avant, 2008; Hill & Wilson, 2008). Zakadjian (1990) studied the reproductive strategy of Acrocnida brachiata from the Bay of Seine, where the annual temperature variations in the study site were from 6 to 22°C, with no link suggested between reproduction and temperature. Holme (1967) reported the absence of Acrocnida brachiata from samples taken from Weymouth Bay and Poole Bay, England, after severe winter temperatures (4 and 5°C, respectively, below the mean for about a month). The abundance of Amphiura filiformis was also reported to have decreased. Freeman et al. (2001) observed that, in the laboratory, Astropecten irregularis adjusted the depth at which it burrowed into the sediment to seawater temperature, burrowing deeper at lower temperatures. Furthermore, the authors noted that locomotory activity in Astropecten irregularis was inhibited at low seawater temperatures (<6°C), and that temperature is likely to be an important factor influencing the abundance and distribution of the species in coastal waters, as it has been suggested that individuals migrate offshore during the winter (Freeman et al., 2001) In Galway Bay, long-term recordings of water temperature at a site of high density aggregations of Amphiura filiformis showed the species is subject to annual variations in temperature of about 10°C (O'Connor et al., 1983). Increases in temperature may affect growth and fecundity. Muus (1981) showed that juvenile Amphiura filiformis are capable of much higher growth rates in experiments with temperatures between 12 and 17°C. However, echinoderms, including Amphiura filiformis, of the North Sea seem periodically affected by winter cold. A population at 27 m depth off the Danish coast was killed by the winter of 1962-63 (Muus, 1981) and a population at 35-50 m depth in the inner German Bight was killed in the winter of 1969-1970 and a new population not re-established until 1974 (Gerdes, 1977). Ursin (1960, cited in Gerdes, 1977) suggested that Amphiura filiformis does not occur in areas with winter temperatures below 4°C although in Helgoland waters it could tolerate temperatures as low as 3.5°C. Owenia fusiformis is found in waters from -1 to 30°C (Dauvin & Thiebaut, 1994) globally. In the Bay of Seine, where there is a large population of Owenia fusiformis, the temperature varies between 5 and 20°C (Gentil et al., 1990). Sensitivity assessment: The characterizing species of these biotopes are widely distributed and likely to occur both north and south of the British Isles. However, the evidence presented suggests that low temperatures are likely to be a limiting factor for activity and breeding of the characterizing species. Furthermore, the species seem to be affected by extreme low temperatures and some mortality in shallower examples of the biotopes may occur as a result of a temperature change in winter at the benchmark level. Resistance is therefore assessed a Low and resilience as Medium and the biotopes considered to have a Medium sensitivity to a decrease in temperature at the benchmark level.	Low Medium Medium High Help	Medium High Medium Medium Help	Medium Medium Medium Medium Help
Salinity increase (local) [Show more] Salinity increase (local) Benchmark. A increase in one MNCR salinity category above the usual range of the biotope or habitat. Further detail Evidence Echinoderms are stenohaline owing to the lack of an excretory organ and a poor ability to osmo- and ion-regulate (Stickle & Diehl, 1987; Russell, 2013). A review by Russell (2013) confirmed that none of the echinoderm species relevant in this assessment occur in hypersaline conditions. Pagett (1981) suggested that localised physiological adaption to reduced or variable salinities may occur in nearshore areas subject to freshwater runoffs. Records indicate that SS.SSa.CMuSa.AbraAirr mainly occurs in full (30-35 ppt) salinity, but that it may also be found in variable (18-35 ppt) salinity (Connor et al., 2004). This suggests that the species in this biotope may experience variable salinities, and resident species perhaps may be adapted to variation in salinity, as suggested by the results given by Pagett (1981). On the other hand, records indicate that SS.SSa.OSa.OfusAfil only occurs in full salinity and is a circalittoral habitat, so is less likely to experience variable salinities, and resident species, therefore, less likely to be adapted to variation in salinity, as suggested by the results given by Pagett (1981). Sensitivity assessment: There is little direct evidence of the effects of hypersaline conditions on the characterizing species of these biotopes. However, echinoderms are generally considered to be stenohaline (Stickle & Diehl, 1987; Russell, 2013). The biotopes mainly experience full salinity conditions (Connor et al., 2004) and the species found are unlike to be adapted to increases in salinity. Therefore, an increase in salinity to >40 psu is likely to result in mortality of the characterizing species. Resistance is assessed as Low but with low confidence. Resilience is probably Medium so that sensitivity is therefore assessed as Medium.	Low Low Low Low Help	Medium High Medium Medium Help	Medium Low Low Low Help
Salinity decrease (local) [Show more] Salinity decrease (local) Benchmark. A decrease in one MNCR salinity category above the usual range of the biotope or habitat. Further detail Evidence Echinoderms are stenohaline owing to the lack of an excretory organ and a poor ability to osmo- and ion-regulate (Stickle & Diehl, 1987; Russell, 2013). However, there are examples where characterizing species in these biotopes have been recorded in hyposaline conditions. For example, Amphiura filiformis was recorded in the Sado estuary in Portugal (Monteiro-Marques, 1982 cited in Russell, 2013) where the salinity is 25.5‰, and in the Black Sea where it tolerated 8.9‰ (Russell, 2013). Furthermore, adult and juvenile Astropecten irregularis were exposed to varying salinities of 16-32‰ and mortality was observed to have occurred at 26‰ (Russell, 2013). Pagett (1981) suggested that localised physiological adaption to reduced or variable salinities may occur in nearshore areas subject to freshwater runoffs. Records indicate that SS.SSa.CMuSa.AbraAirr mainly occurs in full (30-35 ppt) salinity, but that it may also be found in variable (18-35 ppt) salinity (Connor et al., 2004). This suggests that the species in this biotope may experience variable salinities, and resident species perhaps may be adapted to variation in salinity, as suggested by the results given by Pagett (1981). On the other hand, records indicate that SS.SSa.OSa.OfusAfil only occurs in full salinity and is a circalittoral habitat, so is less likely to experience variable salinities, and resident species, therefore, less likely to be adapted to variation in salinity, as suggested by the results given by Pagett (1981). Owenia fusiformis is found in front of river outlets in the Mediterranean (Somaschini, 1993) and English Channel (Gentil et al., 1990) so is, therefore, likely to experience variable salinities. Sensitivity assessment: Echinoderms are generally considered to be stenohaline (Stickle & Diehl, 1987; Russell, 2013). However, the evidence suggests that the characterizing species in these biotopes are likely to resist a decrease in salinity to 18-30 psu. Astropecten irregularis is the only characterizing species that may suffer some mortality so resistance is therefore assessed as Medium and resilience as High. Sensitivity is therefore assessed as Low.	Medium Medium Medium High Help	High High Medium Medium Help	Low Medium Medium Medium Help
Water flow (tidal current) changes (local) [Show more] Water flow (tidal current) changes (local) Benchmark. A change in peak mean spring bed flow velocity of between 0.1 m/s to 0.2 m/s for more than one year. Further detail Evidence Tyler & Banner (1977) studied coastal hydrodynamics and echinoderm distributions in Oxwich Bay in the Bristol Channel. The authors suggested a positive correlation between the distribution of Acrocnida brachiata and the percentage of fine sediments, and that wave and tidal-current energy played a major role in determining the distribution of echinoderms on the seabed by influencing the composition of the sediment. Acrocnida brachiata occurred mainly in the muddier areas of the bay, where maximum bottom spring-tidal flood currents of 0.41 m/s were recorded. Owenia fusiformis was also common in the study site. Amphiura filiformis respond rapidly to currents by extending their arms into the water column to feed. Under laboratory conditions, they were shown to maintain this vertical position at currents of 0.3 m/s (Buchanan, 1964). Amphiura filiformis feed on suspended material in flowing water but will change to deposit feeding in stagnant water or areas of very low water flow (Ockelmann & Muus, 1978). Acrocnida brachiata and Amphiura filiformis have been recorded in biotopes experiencing moderately strong (<0.5 -1.5 m/s), and very weak to moderately strong (negligible - 1.5m/s) water flow strengths, respectively (Connor et al., 1997a&b, 2004). Food requirements probably set a lower limit on the current regime of areas able to support brittlestars. Astropecten irregularis has been reported to migrate offshore during winter, probably to avoid being displaced during storm surges, which has been observed, suggesting that Astropecten irregularis is probably likely to be displaced by increased tidal streams (Freeman et al., 2001). Noffke et al. (2009) reported that Owenia fusiformis occurred in abundance in a study site characterized by highly variable flow velocity and direction due to tides. It was reported to have adapted feeding strategies depending on the flow conditions (Dales, 1957, cited in Noffke et al., 2009) and sediment dynamics. Owenia fusiformis is found in front of river outlets in the Mediterranean and can be subject to a wide range of water velocities. Increase in water flow rate will most likely cause winnowing of the sediment, but the tubes of Owenia fusiformis can stabilize the sediment and reduce water movement related stresses on the benthos (Somaschini, 1993). Both Amphiura filiformis and Owenia fusiformis have been reported in the Northumberland coast, the UK, where tidal currents ranged between surface speeds of 0.65 m/s at springs to 0.4 m/s at neaps, on a flood tide. Bottom residual currents were much weaker than near-surface, reaching a maximum of 0.7 m/s (Jones, 1979, cited in Birchenough & Frid, 2009) Sensitivity assessment: The biotopes are found in weak to very weak tidal streams (Connor et al., 2004). The evidence presented suggests the characterizing species of these biotopes appear to have behavioural adaptations to changes in water flow. An increase in water flow rate may inhibit suspension feeding in the biotopes and alter the character of the soft-sediment but species may be able to switch to deposit feeding. A decrease in water flow may result in increased siltation, which could be associated with deposition of organic particles. The characterizing species are likely to be able to utilize the additional deposits and burrow up through the deposited sediment. A change in water flow rate at the pressure benchmark level is considered to fall within the range of flow speeds experienced by mid-range populations. Resistance and resilience are therefore assessed as High and the biotope considered Not Sensitive to a change in water flow at the pressure benchmark level.	High High High High Help	High High High High Help	Not sensitive High High High Help
Emergence regime changes [Show more] Emergence regime changes Benchmark. 1) A change in the time covered or not covered by the sea for a period of ≥1 year or 2) an increase in relative sea level or decrease in high water level for ≥1 year. Further detail Evidence Changes in emergence are Not Relevant to the biotopes, which are restricted to fully subtidal/circalittoral conditions. The pressure benchmark is relevant only to littoral and shallow sublittoral fringe biotopes.	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help
Wave exposure changes (local) [Show more] Wave exposure changes (local) Benchmark. A change in near shore significant wave height of >3% but <5% for more than one year. Further detail Evidence The brittlestar species that characterize these biotopes, Acrocnida brachiata and Amphiura filiformis, occur in a range of wave exposures from very sheltered to extremely exposed, and extremely sheltered to moderately exposed, respectively (Tillin & Tyler-Walters, 2014). Tyler & Banner (1977) studied coastal hydrodynamics and echinoderm distributions in Oxwich Bay in the Bristol Channel. The authors suggested a positive correlation between the distribution of Acrocnida brachiata and the percentage of fine sediments, and that wave and tidal-current energy played a major role in determining the distribution of echinoderms on the seabed by influencing the composition of the sediment. Acrocnida brachiata occurred mainly in the muddier areas of the bay. Owenia fusiformis was also common in the study site. Astropecten irregularis have been suggested to migrate offshore in the winter to avoid storms, and have been reported being washed ashore during strong wave surges (Rees et al., 1977, cited in Freeman et al., 2001). The communities described by Jones (1951) which are thought to represent SS.SSa.CMuSa.AbraAirr (Connor et al., 2004), occurred in fairly exposed conditions, with the author suggesting the wave action was felt at the depth of 45 m (25 fm), depth at which the community was reported to occur. Wells et al. (1981) reported that Owenia fusiformis in the intertidal and shallow subtidal are likely to be buried as a result of wave action but can survive this by working its way up through the sediment in its flexible tube. However, the effect of being washed out of the sediment by wave action was not commented on. In this situation, Owenia fusiformis would probably have to rebury in the sediment and construct a new tube. However, Owenia fusiformis only builds one tube in its lifespan (Noffke et al., 2009). Although tube building by polychaetes is normally a relatively fast process of a few hours (Ziegelmeier, 1952; Hempel, 1957; Myers, 1972), this is unlikely to occur quickly enough to avoid predation by flatfish and opportunistic predators. A decrease in wave exposure is likely to cause increased siltation which adult Owenia fusiformis can probably survive (Dauvin & Gillet, 1991; Wells et al., 1981). However, juveniles cannot construct tubes in sediments with a grain size <63 µm (mud). Therefore if there is a lot of clay and silt deposited around a population of Owenia fusiformis recruits will not be able to construct tubes, and juvenile mortality is likely to be high. Amphiura filiformis is found in sheltered habitats characterized by fine muddy sandy sediments and low wave exposure. The species is unlikely to be resistant of increases in wave exposure because strong wave action can re-suspend the sediment and break up and scatter Amphiura filiformis. However, the species is able to burrow further into the sediment and is able to re-burrow if displaced. Sensitivity assessment: SS.SSa.CMuSa.AbraAirr occurs at shallower depths than SS.SSa.OSa.OfusAfil (Connor et al., 2004) hence it is more likely to experience variable wave exposure. However, the ranges of wave exposures at which the biotopes occur are unlikely to be severe enough as to compromise the maintenance of the sediment composition of less than 20% silt/clay (Connor et al., 2004). The benchmark refers to a change in nearshore significant wave height. Assuming an offshore representation of SS.SSa.OSa.OfusAfil, it is likely this biotope will be less affected than SS.SSa.CMuSa.AbraAirr. Nevertheless, a change in nearshore significant wave height >3% but <5% is likely to fall within the range of wave exposures in which the biotopes occur. Resistance and resilience are therefore assessed as High and the biotopes considered Not Sensitive at the pressure benchmark level.	High High Medium Medium Help	High High High High Help	Not sensitive High Medium Medium Help

Chemical Pressures

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	Resistance	Resilience	Sensitivity
Transition elements & organo-metal contamination [Show more] Transition elements & organo-metal contamination Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail Evidence This pressure is Not assessed but evidence is presented where available. Information about the effects of heavy metals on echinoderms is limited and no details specific to any brittlestars was found. However, Bryan (1984) reports that early work has shown that echinoderm larvae are intolerant of heavy metals, e.g. the intolerance of larvae of sea urchin Paracentrotus lividus to copper (Cu) had been used to develop a water quality assessment. LC50 concentrations exceeding 0.1 mg copper per litre, 1 mg zinc per litre and 10 mg chromium per litre for a duration between 4 -14 days of exposure have been reported for echinoderm species (Crompton, 1997). Adult echinoderms are known to be efficient concentrators of heavy metals including those that are biologically active and toxic (Hutchins et al., 1996). However, there is no information available regarding the effects of this bioaccumulation. More recent studies by Deheyn & Latz (2006) at the Bay of San Diego found that heavy metal accumulation in brittlestars occurs both through dissolved metals as well as through diet, to the arms and disc, respectively. Similarly, Sbaihat et al. (2013) measured concentrations of heavy metals (Cu, Ni, Cd, Co, Cr and Pb) in the body of Ophiocoma scolopendrina collected from the Gulf of Aqaba, and found that most concentration was found in the central disc rather than arms and no simple correlations could be found between contaminant and body length. Owenia fusiformis from the south coast of England were found to have loadings of 1335 µg copper per gram bodyweight and 784 µg zinc per gram bodyweight. The metals were bound in spherules within the cells of the gut (Gibbs et al., 2000). No mention was made of any ill effects of these concentrations of metal within the body and it is presumed that Owenia fusiformis is resistant of heavy metal contamination.	Not Assessed (NA) NR NR NR Help	Not assessed (NA) NR NR NR Help	Not assessed (NA) NR NR NR Help
Hydrocarbon & PAH contamination [Show more] Hydrocarbon & PAH contamination Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail Evidence This pressure is Not assessed but evidence is presented where available. Oil spills resulting from tanker accidents can cause large-scale deterioration of communities in intertidal and shallow subtidal sedimentary systems. The key species and many other species in the biotopes are likely to be affected. For example, after the West Falmouth, Florida spill of 1969 the entire benthic fauna was eradicated immediately following the spill and populations of the opportunistic polychaete Capitella capitata increased to abundances of over 200,000/m² (Sanders, 1978). Echinoderms have not been found to be resistant to the toxic effects of oil, likely because of the large amount of exposed epidermis (Suchanek, 1993), and tend to be very sensitive to various types of marine pollution (Newton & McKenzie, 1995). Exposure to 30,000 ppm oil reduces the bacterial load by 50% and brittlestars begin to die (Newton & McKenzie, 1995). 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. During monitoring of sediments in the Ekofisk oilfield Addy et al. (1978) suggested that reduced abundance of Amphiura filiformis within 2-3 km of the site was related to discharges of oil from the platforms and to physical disturbance of the sediment. Brittlestars host symbiotic sub-cuticular bacteria (Kelly & McKenzie, 1995). After exposure to hydrocarbons, loadings of such bacteria were reduced indicating a possible sub-lethal stress to the host (Newton & McKenzie, 1995). A few Owenia fusiformis were recorded in the subtidal sediments of the Pembrokeshire coast after the Sea Empress oil spill but whether densities had increased, decreased or remained the same was not recorded (Rutt et al., 1998). Different polychaetes have the reported as having varying levels of resistance to oil pollution (Kingston et al., 1997). Invertebrate communities respond to severe chronic oil pollution in much the same way. Initial massive mortality and lowered community diversity is followed by extreme fluctuations in populations of opportunistic mobile and sessile fauna (Suchanek, 1993). Infaunal communities, such as those characterizing these biotopes are highly likely to be adversely affected by an event of oil pollution, but the biological effects of accumulation of PAHs are likely to depend on the length of time exposed (Viñas et al., 2009). Oil contamination is likely to remain in the sediment for a long time after the pollution source is removed. Ingestion of contaminated sediments is likely to be a more important route of exposure for deposit feeders such as the characterizing species of these biotopes. Untreated oil (e.g. from oil spills) is not a risk, since it is concentrated mainly at the surface, and circalittoral biotopes are likely to be protected by their depth. If oil is treated by dispersant, the resulting emulsion will penetrate down the water column, especially under the influence of turbulence (Hartnoll, 1998).	Not Assessed (NA) NR NR NR Help	Not assessed (NA) NR NR NR Help	Not assessed (NA) NR NR NR Help
Synthetic compound contamination [Show more] Synthetic compound contamination Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail Evidence This pressure is Not assessed but evidence is presented where available. Echinoderms tend to be very sensitive to various types of marine pollution (Newton & McKenzie, 1995) but there is no more detailed information than this broad statement. In laboratory experiments Smith (1968) found the concentration of BP1002 (the detergent used in the Torrey Canyon oil spill clean-up) needed to kill the majority of brittlestar Ophiocomina nigra was 5 ppm. 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 27 ng/g (83 pmol TBT per g) and contained Amphiura spp., 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, contamination from TBT is likely to result in the death of some not-resistant species such as brittlestars. However, Walsh et al. (1986) observed inhibition of arm regeneration in another brittlestar, Ophioderma brevispina, following exposure to TBT at levels between 10 ng/l and 100 ng/l. Loizeau & Menesguen (1993), found that 8-15% of the PCB burden in dab, Limanda limanda, from the Bay of Seine could be explained by ophiuroid consumption. Thus, Amphiura communities may play an important role in the accumulation, remobilization and transfer of PCBs and other sediment associated contamination to higher trophic levels. Other species in the biotopes, in particular polychaete worms, are generally more resistant of a range of marine pollutants so a change in the faunal composition may be expected if chemical pollution increases. Polluted areas would be characterized by biotopes with lower species diversity and a higher abundance and density of pollution resistant species such as polychaetes.	Not Assessed (NA) NR NR NR Help	Not assessed (NA) NR NR NR Help	Not assessed (NA) NR NR NR Help
Radionuclide contamination [Show more] Radionuclide contamination Benchmark. An increase in 10µGy/h above background levels. Further detail Evidence Adult echinoderms are known to be efficient concentrators of radionuclides (Hutchins et al., 1996). However, no information concerning the effects of such bioaccumulation was found. Carvalho (2011) determined the concentrations of ²¹⁰Po and ²¹⁰Pb in marine organisms from the seashore to abyssal depths, as these two radioactive elements tend to be higher in the marine environment. The author’s results showed that concentrations varied greatly, even between organisms of the same biota, mainly related with the trophic levels occupied by the species, suggesting that the more levels between a species and the bottom of the food chain, the more likely that the concentrations of radioactive elements were likely to be diluted. This may have great implications for the deposit feeders that characterize these biotopes. There was no information available about the effect of this bioaccumulation. Sensitivity assessment: Although species in these biotopes are likely to bio-accumulate radionuclides with potential impacts on the biological community, no information concerning the effects of such bioaccumulation was found. Therefore, there is insufficient evidence to assess this pressure against the benchmark.	No evidence (NEv) NR NR NR Help	Not relevant (NR) NR NR NR Help	No evidence (NEv) NR NR NR Help
Introduction of other substances [Show more] Introduction of other substances Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail Evidence This pressure is Not assessed.	Not Assessed (NA) NR NR NR Help	Not assessed (NA) NR NR NR Help	Not assessed (NA) NR NR NR Help
De-oxygenation [Show more] De-oxygenation Benchmark. Exposure to dissolved oxygen concentration of less than or equal to 2 mg/l for one week (a change from WFD poor status to bad status). Further detail Evidence Oxygen-deficient marine areas are characterized by a decline in the number and diversity of species. Cole et al. (1999) suggested possible adverse effects on marine species exposed to dissolved oxygen concentrations below 4 mg/l and probable adverse effects below 2 mg/l. A decrease in oxygenation is likely to see the loss of the key species in the biotopes. During periods of hypoxia infaunal species migrate to the surface of the sediment (Diaz & Rosenberg, 1995). Stachowitsch (1984) observed a mass mortality of benthic organisms in the Gulf of Trieste, northern Adriatic Sea, caused by the onset of severe hypoxia in the near-bottom water. A wide variety of organisms were affected, including burrowing invertebrates, sponges, and the brittlestar Ophiothrix quinquemaculata. Amphiura filiformis has been reported as a species resistant to moderate hypoxia (Diaz & Rosenberg, 1995). In experiments exposing benthic invertebrates to decreasing oxygen levels, Amphiura filiformis only left its protected position in the sediment when oxygen levels fell below 0.85 mg/l (Rosenberg et al., 1991). This escape response increases predation risk. Mass mortality of Amphiura filiformis was observed during severely low oxygen events (<0.7 mg/l) (Nilsson, 1999). Mass mortality has also been observed following large increases in eutrophication and subsequent reductions in oxygen (Vistisen & Vismann, 1997). At oxygen concentrations between 0.85 mg/l and 1.0 mg/l, Rosenberg et al. (1991) observed the species was able to survive for several weeks. However, the regeneration rate of arms is significantly decreased at low oxygen concentrations (1.8-2.2 mg/l) (Nilsson, 1999), growth rate is decreased in oxygen concentrations of <2.7 mg/l and spawning is restricted (Nilsson & Sköld, 1996). Infaunal burrowers in the community live in close association with hypoxic and even anoxic muddy substrata. Owenia fusiformis is very resistant of anoxia and can resist anaerobic conditions for up to 21 days by becoming quiescent (Dales, 1958). In the Gullmarsfjord a hypoxia event in 1980/1981, of ca 0.3 mg/l eliminated all the macrobenthic fauna below 115 m depth. The recovery sequence was slow and communities were not re-established eighteen months after the collapse (Josefson & Widbom, 1988). No specific information the resistance of Acrocnida brachiata and Astropecten irregularis to decreased oxygen was found. Sensitivity assessment: A decrease in oxygenation at the pressure benchmark level is likely to result in significant (25-75%) mortality of the characterizing species of these biotopes. With the loss of these species, the biotopes would likely be lost. Community composition would likely become dominated by fewer species that are resistant of hypoxic conditions, such as some polychaete worms, so that the overall species richness would decline significantly. Resistance is therefore assessed as Low and resilience as Medium, and the biotopes are judged as having Medium sensitivity to de-oxygenation at the pressure benchmark level.	Low High Medium High Help	Medium High Medium Medium Help	Medium High Medium Medium Help
Nutrient enrichment [Show more] Nutrient enrichment Benchmark. Compliance with WFD criteria for good status. Further detail Evidence Increased nutrients are most likely to affect abundance of phytoplankton which may include toxic algae (OSPAR, 2009). This primary effect resulting from elevated nutrients will impact upon other biological elements or features (e.g. toxins produced by phytoplankton blooms or de-oxygenation of sediments) and may lead to ‘undesirable disturbance’ to the structure and functioning of the ecosystem. With enhanced primary productivity in the water column, organic detritus that falls to the sea bed may also be enhanced. Owenia fusiformis has been reported as not resistant of changes in nutrients, and Amphiura spp. as probably favoured by Hiscock et al. (2005a). However, interface feeders such as Owenia fusiformis and Amphiura filiformis that occur in these biotopes, have been reported to respond rapidly to increased primary production that may result from increased nutrient availability (Pearson & Mannvik, 1998, cited in Schückel et al., 2010). Furthermore, Noffke et al. (2009) suggested that the data reported by Reiss et al. (2006) of a mass occurrence of Owenia fusiformis (>11,000 ind./m²) could be associated to the close proximity of an estuary with a zone of permanent haline stratification, concluding that the increased abundance was directly linked to the nutrient supply in the estuary, resulting in higher productivity and consequent food available to the polychaetes. Quillien et al. (2015) investigated the effects of green tides on macrotidal exposed and semi-exposed sandy beaches and found that mean abundance and species richness of macrozoobenthic invertebrates were higher where green tides occurred and that the communities in the two types of beach analysed responded differently to eutrophication seen as green tides. In terms of mean abundance and species richness, Owenia fusiformis and Acrocnida cf. spatulispina were amongst the species positively affected by the presence of green tides in exposed sandy beaches. Nutrient enrichment that leads to eutrophication is recognised as a major and worldwide pollution threat, and a direct symptom is mass development of opportunistic macroalgae, which can have negative impacts of sediment and water quality, hence of benthic community, particularly in low energy environments (Quillien et al., 2015). Sensitivity assessment: The overall species diversity in these biotopes is likely to decline given the varying responses of the species occurring here to nutrient enrichment (Hiscock et al., 2005a). The community, and hence the biotopes, may change to one dominated by nutrient enrichment resistant species, in particular polychaete worms. However, these changes generally refer to gross nutrient enrichment. A decrease in nutrient availability may result in impaired growth and fecundity although species diversity is not likely to be affected significantly. Nevertheless, the biotopes are considered to be Not Sensitive at the pressure benchmark that assumes compliance with good status as defined by the WFD.	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help	Not sensitive NR NR NR Help
Organic enrichment [Show more] Organic enrichment Benchmark. A deposit of 100 gC/m²/yr. Further detail Evidence Organic enrichment is likely to promote pelagic productivity and increase the amount of organic matter reaching the sea bed, which may be beneficial to deposit feeders as a direct source of food. Nilsson (1999) investigated the effects of organic enrichment (control 0 gC/m², medium 27 gC/m² and high 55 gC/m²) on arm regeneration of Amphiura filiformis over a two month period. Amphiura filiformis responded positively to increased organic enrichment (Nilsson, 1999). In the Skagerrak in the North Sea, a massive increase in abundance and biomass of the brittlestar between 1972 and 1988 was attributed to organic enrichment (Josefson, 1990; Hernroth et al., 2012). Rosenberg et al. (1997) also reported that Amphiura filiformis appeared to be more densely packed in the sediment when food occurred superabundantly compared to when food was less common. Sköld & Gunnarsson (1996) reported enhanced growth and gonad development in response to short-term enrichment of sediment cores containing Amphiura filiformis maintained in laboratory mesocosms. However, if increased organic input resulted in almost complete oxygen depletion, mortality of individuals was likely to occur (see de-oxygenation pressure). Mcleod et al. (2008) investigated the recovery of soft sediment benthic invertebrate community following removal of high levels of organic enrichment from fish farming in Tasmania. The authors observed that Amphiura species were associated with areas least impacted by organic enrichment. Al-Farraj et al. (2012) analysed polychaete community structures within important sewage treatment stations in Saudi Arabia and found that the control stations, situated farther from the stations had the highest species diversity, richness and evenness, dominated by polychaetes Owenia fusiformis and Lumbrineris garcilis. These species were not dominant in sites within close proximity of the sewage treatment stations. Birchenough & Frid (2009) analysed the succession of the macrobenthic community in the three years following cessation of sewage sludge disposal of the Northumberland coast, UK after 18 years of dumping. The authors reported a continued localized increase on individuals and species in the disposal area that was followed by a decline, in the two sites close to the disposal site (less than 1 km). The control stations did not show this fluctuation in species abundance other than what expected as a result of seasonal variations. Owenia fusiformis was one of the most abundant species three months after cessation close to the disposal site, but its abundance became stable thereafter, suggesting the opportunistic polychaete may benefit from organic enrichment by taking advantage of the of the diminished competition in the early stages of community succession. Borja et al. (2000) and Gittenberger & van Loon (2011) in the development of an AMBI index to assess disturbance (including organic enrichment) both assigned Amphiura filiformis and Owenia fusiformis to their Ecological Group II species indifferent to enrichment, always present in low densities with non-significant variations with time (from initial state, to slight unbalance)’. However, for Acrocnida brachiata, while Borja et al. (2000) assigned the species to Ecological Group I ‘species very sensitive to organic enrichment and present under unpolluted conditions’, Gittenberger & van Loon (2011) assigned the species to Ecological Group II ‘species indifferent to enrichment, always present in low densities with non-significant variations with time (from initial state, to slight unbalance)’. Astropecten irregularis has not been assigned an AMBI category. Although the Gittenberger & van Loon (2011) report is an update on Borja et al. (2000), the former is a peer reviewed publication. Given that the evidence used in both cases is unclear, confidence in the evidence is assessed as medium. Sensitivity assessment: The evidence presented based on the AMBI scores conflicts and is considered with caution. 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), which could result in significant change in the community composition of sedimentary habitats. Forrest et al. (2009) identified that the recovery of muddy sediments beneath fish farms from enrichment can be highly variable and may be many years at poorly flushed sites, such as those where these biotopes tend to occur. In summary, some mortality of the characterizing species of these biotopes is likely to occur, either as a direct result of a deposit of 100 gC/m² over the period of one year, or indirect result of hypoxia. Resistance is therefore assessed as Low (loss of 25-75%) and resilience as Medium. Thus, the biotopes are considered to have Medium sensitivity to organic enrichment at the pressure benchmark level.	Low High Medium Low Help	Medium High Medium Medium Help	Medium High Medium Low Help

Physical Pressures

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Biological Pressures

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	Resistance	Resilience	Sensitivity
Genetic modification & translocation of indigenous species [Show more] Genetic modification & translocation of indigenous species Benchmark. Translocation of indigenous species or the introduction of genetically modified or genetically different populations of indigenous species that may result in changes in the genetic structure of local populations, hybridization, or change in community structure. Further detail Evidence The key characterizing species in the biotopes are not cultivated or likely to be translocated. This pressure is therefore considered Not Relevant.	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help
Introduction or spread of invasive non-indigenous species [Show more] Introduction or spread of invasive non-indigenous species Benchmark. The introduction of one or more invasive non-indigenous species (INIS). Further detail Evidence There are no records of the introduction or spread of non-indigenous species in these biotopes. This pressure is therefore considered Not relevant.	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help
Introduction of microbial pathogens [Show more] Introduction of microbial pathogens Benchmark. The introduction of relevant microbial pathogens or metazoan disease vectors to an area where they are currently not present (e.g. Martelia refringens and Bonamia, Avian influenza virus, viral Haemorrhagic Septicaemia virus). Further detail Evidence Introduced organisms (especially parasites or pathogens) are a potential threat in all coastal ecosystems. Several examples are known of echinoderm populations that have been massively reduced by sudden outbreaks of epidemic disease. Cases include the mass mortality of the sea urchin Diadema antillarum throughout the Caribbean as a result of infection by a water-borne pathogen (Lessios, 1988), and the decimation of urchin populations in the North Atlantic by parasitic amoebae and nematodes (Hagen, 1997). So far, no information of SS.SSa.CMuSa.AbraAirr and SS.SSa.OSa.OfusAfil been affected was found, but epidemic disease should be considered as having the potential to significantly affect echinoderm dominated populations, such as these biotopes. Brittlestars have symbiotic sub-cuticular bacteria. The host-bacteria association can be perturbed by acute stress and changes in bacterial loading may be used as an indicator of sub-lethal stress (Newton & McKenzie, 1995). No information was found on microbial pathogens affecting Owenia fusiformis. Sensitivity assessment. No direct evidence of the biotopes being affected by the introduction of microbial pathogens was found as with which to assess this pressure.	No evidence (NEv) NR NR NR Help	Not relevant (NR) NR NR NR Help	No evidence (NEv) NR NR NR Help
Removal of target species [Show more] Removal of target species Benchmark. Removal of species targeted by fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail Evidence SS.SSa.CMuSa.AbraAirr and SS.SSa.OSa.OfusAfil are currently not targeted by commercial fisheries and hence not directly affected by this pressure. This pressure is therefore considered Not Relevant.	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help	Not relevant (NR) NR NR NR Help
Removal of non-target species [Show more] Removal of non-target species Benchmark. Removal of features or incidental non-targeted catch (by-catch) through targeted fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail Evidence Direct, physical impacts are assessed through the abrasion and penetration of the seabed pressures, while this pressure considers the ecological or biological effects of by-catch. Species in these biotopes, including the characterizing species, Acrocnida brachiata, Astropecten irregularis, Owenia fusiformis and Amphiura filiformis, may be damaged or directly removed by static or mobile gears that are targeting other species (see abrasion and penetration pressures). Commercial fisheries may discard damaged or dead non-target species, which could result in increased available food supply to deposit feeding characterizing species that may have survived in the area targeted by fisheries, but may also attract mobile predators and scavengers including fish and crustaceans which may alter predation rates in the biotopes. Sensitivity assessment. The evidence suggests that some loss of the characterizing species is likely to occur as a result of unintentional removal. Removal of the characterizing species would result in the biotopes being lost. Thus, the biotopes are considered to have Low resistance to this pressure and to have Medium resilience, resulting in the sensitivity being judged as Medium.	Low High High High Help	Medium High Medium Medium Help	Medium High Medium Medium Help

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De-Bastos, E.S.R. 2023. Owenia fusiformis and Amphiura filiformis in offshore circalittoral sand or muddy sand. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25-11-2024]. Available from: https://marlin.ac.uk/habitat/detail/381

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