The Marine Life Information Network

Substratum loss

Benchmark. All of the substratum occupied by the species or biotope under consideration is removed. A single event is assumed for sensitivity assessment. Once the activity or event has stopped (or between regular events) suitable substratum remains or is deposited. Species or community recovery assumes that the substratum within the habitat preferences of the original species or community is present. Further details

Evidence

Amphiura filiformis is an infaunal species and therefore substratum loss would result in mortality. Recoverability is considered to be moderate - see additional information for rationale.

Smothering

Benchmark. All of the population of a species or an area of a biotope is smothered by sediment to a depth of 5 cm above the substratum for one month. Impermeable materials, such as concrete, oil, or tar, are likely to have a greater effect. Further details.

Evidence

Amphiura filiformis is an infaunal species which can burrow and lives up to a depth of 4cm within the sediment. Therefore, smothering by sediment of 5 cm is unlikely to have great effect although feeding and hence viability of the population may be reduced if the sediment is particularly fine and mobile. Since only sub-lethal effects are likely intolerance is considered to be low. Smothering by impermeable materials, such as oil, is likely to result in death. Recovery is likely to be rapid as individuals move up through the sediment to resume their position for feeding and any fine particles are removed.

Increase in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Amphiura filiformis is a passive suspension feeder. Increases in siltation of inorganic particles may interfere with the feeding of this species. However, the species live in burrows maintained by mucus so Amphiura filiformis can tolerate slight increases in siltation by removing an excess of particles with mucus production. On the Northumberland coast Amphiura filiformis is abundant in an area close to a rich supply of fine sediment from coastal erosion and run-off (Buchanan, 1964). The supply is sufficient enough to produce a covering of fine silty sediment. Intolerance to siltation is therefore low. On return to normal conditions recovery is likely to be rapid.

Decrease in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

A decrease in the siltation of inorganic food particles may be of benefit to Amphiura filiformis. It would mean that the relative concentrations of organic material in suspension would be higher, possibly resulting in more efficient feeding. Not sensitive has been suggested.

Desiccation

1. A normally subtidal, demersal or pelagic species including intertidal migratory or under-boulder species is continuously exposed to air and sunshine for one hour.
2. A normally intertidal species or community is exposed to a change in desiccation equivalent to a change in position of one vertical biological zone on the shore, e.g., from upper eulittoral to the mid eulittoral or from sublittoral fringe to lower eulittoral for a period of one year. Further details.

Evidence

Amphiura filiformis occurs at the infralittoral fringe and in the circalittoral zone (below 15 m) and so is not normally subject to desiccation stress which suggests the species would be intolerant of the factor. However, if desiccation were to increase the species is a mobile infaunal crawler and should be able to move to avoid the factor so intolerance is reported to be low.

Increase in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Amphiura filiformis occurs at the infralittoral fringe and in the circalittoral zone (below 15 m) and so is not normally subject to emergence. However, if the emergence regime were to change the species is a mobile infaunal crawler and should be able to move to avoid the factor so intolerance is reported to be low.

Decrease in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

Amphiura filiformis occurs at the infralittoral fringe and in the circalittoral zone (below 15 m). Therefore it will be tolerant of a decrease in emergence.

Increase in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

As a suspension feeder without any self-produced feeding current, water flow rate will be of primary importance. Individuals respond rapidly to currents by extending their arms vertically to feed. Under laboratory conditions individuals would be unlikely to maintain this position if water movement were to increase to strong (3-6 knots) and so would retract their arms (Buchanan, 1964). A long term increase in water flow rate is also likely to change the nature of the sediment removing finer particles. High density aggregations of Amphiura filiformis seem to be characteristic of fine sediments with silt/clay values of 10 to 20% (O'Conner et al., 1983) so removal of the finer matter is likely to reduce abundance. 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 some circumstances some animals may be able to move to unaffected areas. On return to normal conditions immigration of adults may occur but recovery through re-colonization by pelagic larvae is highly variable and may take several years and so recoverability is set at moderate. See additional information for full rationale.

Decrease in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

As a suspension feeder without any self-produced feeding current, water flow rate will be of primary importance. 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). 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). Sediments may become muddier due to increased settlement of silt if current strength declines. However, at the level of the benchmark it is not expected that populations will be affected and Amphiura filiformis has been assessed to tolerate a decrease in water flow rate.

Increase in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

The species is distributed in waters to the north and south of the Britain and Ireland and so is probably able to tolerate a long term change in temperature of 2 °C. 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. Juvenile disk diameter increased from 0.5 to 3.0mm in 28 weeks under these conditions compared to over 2 years in the North Sea (Duineveld & Noort van, 1986). As the species appears to be killed only by extreme increases in temperature, an intolerance of low has been suggested. Recovery of normal growth rates and fecundity will be rapid on return to pre-impact temperatures and so recoverability is set to high.

Decrease in temperature

1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

The species is distributed in waters to the north and south of the Britain and Ireland and so is probably able to tolerate a long term change in temperature of 2 °C. 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). 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) suggests that Amphiura filiformis does not occur in areas with winter temperatures below 4 °C although in Helgoland waters can tolerate temperatures as low as 3.5 °C. Low temperatures are a limiting factor for breeding which takes place during the warmest months in the UK. As the species appears to be killed only be extreme temperatures, intolerance is recorded as low. Recovery of normal growth rates and fecundity will be rapid on return to pre-impact temperatures and so recoverability is set to high.

Increase in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Amphiura filiformis is likely to have poor facility for perception of irradiance and consequently is probably not sensitive to changes in turbidity. However, one of the main food source of this species is phytoplankton that does have a requirement for light. Increases in turbidity may limit the amount of phytoplankton available to the brittlestars. In the very long term this would probably reduce growth and fecundity and hence the viability of the population. However, Amphiura filiformis can go for periods without food and at the benchmark level of turbidity effects should not be significant. Also food supplies are also likely to come from distant sources unaffected by local changes in turbidity. Intolerance is therefore, considered to be 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.

Decrease in turbidity

1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

Amphiura filiformis is likely to have poor facility for perception of irradiance and consequently is probably not sensitive to changes in turbidity. However, one of the main food source of this species is phytoplankton that does have a requirement for light. Decreased turbidity may enhance phytoplankton production which may result in an enhances food supply. Tolerant has been suggested with moderate confidence.

Increase in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Amphiura filiformis is found in sheltered habitats characterised by fine muddy sandy sediments and low wave exposure. The species is likely to be intolerant of increases in wave exposure because strong wave action can resuspend the sediment and break up and scatter Amphiura filiformis. However, 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. Recovery within five years may be possible as recolonization can take place from recruitment of larvae and juveniles and also immigration of adults from unaffected areas however recruitment is very sporadic and so recoverability is set to moderate - see additional information for full rationale.

Decrease in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

Amphiura filiformis is found in sheltered habitats characterised by fine muddy sandy sediments and low wave exposure. Thus an assessment for a decrease in wave exposure was not considered relevant.

Noise

1. Underwater noise levels e.g., the regular passing of a 30-metre trawler at 100 metres or a working cutter-suction transfer dredge at 100 metres for one month during important feeding or breeding periods.
2. Atmospheric noise levels e.g., the regular passing of a Boeing 737 passenger jet 300 metres overhead for one month during important feeding or breeding periods. Further details

Evidence

Amphiura filiformis can withdraw its arms into its burrow when disturbed by noise vibrations in the surrounding water. At the benchmark level effects are likely to be minimal and so intolerance is recorded as low. If disturbed feeding would resume as soon as conditions were favourable and so recovery would be immediate.

Visual presence

Benchmark. The continuous presence for one month of moving objects not naturally found in the marine environment (e.g., boats, machinery, and humans) within the visual envelope of the species or community under consideration. Further details

Evidence

Amphiura filiformis is likely to have poor facility for visual perception and consequently is probably not sensitive to visual disturbance.

Abrasion & physical disturbance

Benchmark. Force equivalent to a standard scallop dredge landing on or being dragged across the organism. A single event is assumed for assessment. This factor includes mechanical interference, crushing, physical blows against, or rubbing and erosion of the organism or habitat of interest. Where trampling is relevant, the evidence and trampling intensity will be reported in the rationale. Further details.

Evidence

Brittlestars have fragile arms which are likely to be damaged by abrasion or physical disturbance. Amphiura filiformis burrows in the sediment and extends only its arms when feeding. 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. For example, Bergman & Hup (1992) 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. Intolerance to abrasion and disturbance is therefore recorded as low. Individuals can still function whilst regenerating a limb so recovery will be rapid.

Displacement

Benchmark. Removal of the organism from the substratum and displacement from its original position onto a suitable substratum. A single event is assumed for assessment. Further details

Evidence

Although not highly active, Amphiura filiformis is a crawling, burrowing, infaunal species. Following displacement individuals could crawl or burrow through sediment (Rosenberg et al., 1997) until a suitable site is found. Burrowing through sediment may take more time and energy but predation risks are decreased. Individuals can right themselves if displacement caused them to be inverted and they can rapidly burrow into the sediment. Therefore, intolerance to displacement is low and recovery is immediate.

Synthetic compound contamination

Sensitivity is assessed against the available evidence for the effects of contaminants on the species (or closely related species at low confidence) or community of interest. For example:

• evidence of mass mortality of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as high sensitivity;
• evidence of reduced abundance, or extent of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as intermediate sensitivity;
• evidence of sub-lethal effects or reduced reproductive potential of a population of the species or community of interest will be assessed as low sensitivity.

The evidence used is stated in the rationale. Where the assessment can be based on a known activity then this is stated. The tolerance to contaminants of species of interest will be included in the rationale when available; together with relevant supporting material. Further details.

Evidence

Echinoderms tend to be very sensitive to various types of marine pollution (Newton & McKenzie, 1995) and so an intolerance assessment of high is reported. A study of the influence of TBT on arm regeneration in another brittle star Ophioderma brevispina, revealed some evidence of inhibition at 10ng/l and significant inhibition at 100 ng/l. It is suggested that TBT acts via the nervous system, although direct action on the tissues at the point of breakage could not be excluded. If populations are lost recovery is moderate - see additional information.

Heavy metal contamination

Evidence

Information about the effects of heavy metals on echinoderms is limited and no details specific to Amphiura filiformis, or any other brittlestars, were 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 Paracentrotus lividus to copper (Cu) had been used to develop a water quality assessment. LC₅₀ concentrations exceeding 0.1 mg Cu L^-1, 1 mg Zn L^-1 and 10 mg Cr L^-1 for a duration between 4 -14 days of exposure have been reported for echinoderm species (Table 5.12, Crompton, 1997). As some mortality is reported, intolerance is assessed as intermediate. Adult echinoderms such as Ophiothrix fragilis 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.

Hydrocarbon contamination

Evidence

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) suggest 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. Although acute toxicity test showed that drill cuttings containing oil based muds had a very low toxicity (LC₅₀ 52,800 ppm total hydrocarbons in test sediment) Newton & McKenzie (1998) suggest these toxicity tests are a poor predictor of chronic response. Chronic sub-lethal effects were detected around the Beryl oil platform in the North Sea where the levels of oil in the sediment were very low (3ppm) and Amphiura filiformis was excluded from areas nearer the platform with higher sediment oil content. However, the authors do suggest that effects may also be related to the non-hydrocarbon element of the cuttings such as metals, physical disturbance or organic enrichment. Amphiura filiformis is a host for symbiotic sub-cuticular bacteria. After exposure to hydrocarbons loadings of this bacteria were reduced indicating a possible sub-lethal stress to the host (Newton & McKenzie, 1995). However, since field evidence suggests reduced abundance some distance away from oil pollution, intolerance to hydrocarbons is assessed as high. Recovery to original numbers and population structure is likely to take longer than five years (see additional information) and so recovery is assessed as moderate. In addition, oil contamination is likely to remain in the sediment for a long time after the pollution source is removed.

Radionuclide contamination

Evidence

There is insufficient information on the intolerance of Amphiura filiformis to radionuclides although adult echinoderms, such as Ophiothrix fragilis, are known to be efficient concentrators of radionuclides (Hutchins et al., 1996). There is no information available regarding the effects of such bioaccumulation.

Changes in nutrient levels

Evidence

Amphiura filiformis responds positively to increased organic enrichment (Nilsson, 1999). In the Skagerrak in the North Sea, a massive increase in abundance and biomass of the species between 1972 and 1988 is attributed to organic enrichment (Josefson, 1990). 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. Individuals from the more densely populated offshore sediment did not experience enhanced somatic growth (unlike those from the less populated coastal site) indicating a negatively density-dependent relationship. Therefore, it appears that Amphiura filiformis can be tolerant* of increases in nutrients. However when increased organic input results in almost complete oxygen depletion, mortality of individuals will occur although this is dealt with in "oxygenation" (see below). For the most part it would appear that Amphiura filiformis may benefit from an increase in nutrients and tolerant* has been suggested.

Increase in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Amphiura filiformis is a subtidal species generally occurring in areas of full salinity. An increase in salinity would be most unlikely and sensitivity to this factor has not been assessed.

Decrease in salinity

1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Amphiura filiformis is a subtidal species generally occurring in areas of full salinity although the species has been recorded from the Sado estuary in Portugal (Monteiro Marques, 1982 cited in Stickle & Diehl, 1987; Table 1) where the salinity is 26psu. However, echinoderms are generally regarded to be stenohaline organisms and a salinity change at the benchmark level is expected to kill individuals of Amphiura filiformis. Intolerance is therefore recorded as high. See additional information for recovery.

Changes in oxygenation

Benchmark.  Exposure to a dissolved oxygen concentration of 2 mg/l for one week. Further details.

Evidence

In experiments exposing benthic invertebrates to decreasing oxygen levels Amphiura filiformis only left its protected position in the sediment when oxygen levels fell below 0.85mg/l (Rosenberg et al., 1991). This escape response increases predation risk. Mass mortality of Amphiura filiformis has been 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). Also associated with eutrophic related oxygen depletion is an increase in sulphide concentration in the sediment, which is very toxic to most aerobic organisms. Decreases in sub-cuticular bacteria have also been recorded following nutrient limitation. Reductions in these bacteria are probably indicative of levels of stress and may lead to mortality (Newton & McKenzie, 1995). However, at oxygen concentrations between 0.85mg/l and 1.0mg/l, Rosenberg et al. (1991) observed the species was able to survive for several weeks. Therefore, the intolerance of Amphiura filiformis to the benchmark oxygen level of 2mg/l for one week is low. There are some effects of decreased oxygenation on the species 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). Therefore at the benchmark level growth rate and regeneration rate are decreased reducing the viability of the population. On return to normal oxygenation levels recovery will be very rapid.

Introduction of microbial pathogens/parasites

Benchmark. Sensitivity can only be assessed relative to a known, named disease, likely to cause partial loss of a species population or community. Further details.

Evidence

No information concerning infestation or disease related mortalities was found.

Introduction of non-native species

Sensitivity assessed against the likely effect of the introduction of alien or non-native species in Britain or Ireland. Further details.

Evidence

No non-native species are known to compete with Amphiura filiformis.

Extraction of this species

Benchmark. Extraction removes 50% of the species or community from the area under consideration. Sensitivity will be assessed as 'intermediate'. The habitat remains intact or recovers rapidly. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

It is extremely unlikely that this species would be subject to extraction as it has no commercial and limited research value although dredging operations may remove populations in some habitats.

Extraction of other species

Benchmark. A species that is a required host or prey for the species under consideration (and assuming that no alternative host exists) or a keystone species in a biotope is removed. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Amphiura filiformis has no known obligate relationships so is not sensitive to the removal of any other species.