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

Although Antedon bifida is free living and can swim and crawl short distances the species will be lost along with substratum removal so intolerance is assessed as high. See additional information for recovery.

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

Smothering by 5 cm of sediment is likely to result in the death of feather-stars. Although the tops of arms can probably extend above the sediment most of the feeding and respiratory structures will become clogged. Animals are also unlikely to be able to move above the sediment as they require a hard substratum for attachment. Intolerance is therefore reported to be high. If sediment were then removed recolonization could take place and recovery should be possible within five years - see additional information.

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

Antedon bifida is often found in turbid areas where strong water currents deliver particles for suspension feeding. Therefore, the species can probably tolerate an increase in suspended sediment at the benchmark level although cleaning costs may increase. Intolerance is recorded as low. On return to normal conditions recovery will be immediate.

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 supply of suspended particles is required for feeding as Antedon bifida is a suspension feeder so a decrease may reduce food supplies. Therefore, a decrease in suspended sediment may impair growth rates. However, the benchmark reduction is for a month only so the impact will be minimal and intolerance is assessed as low. On return to normal suspended particle levels growth will soon return to normal.

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

The species is subtidal, only occurring very rarely at extreme low water springs, so is likely to be intolerant of desiccation. Therefore, an intolerance of high is reported. See additional information for recovery.

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

The species is subtidal, although some populations are found at very low water springs, so an increase in emergence is likely to result in desiccation to which the species is highly intolerant. Therefore, an intolerance of high is reported. For recovery see additional information.

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

The species is subtidal and so is tolerant to a decrease in emergence. However, there are some individuals found at very low water springs so a decrease in emergence will enable them to move up the shore. However, the overall intolerance of the species is reported to be tolerant.

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

The species occurs in areas where there is fast current flow suitable for passive suspension feeding. In a series of unpublished experiments by Mr M. Hannan (cited in Hiscock, 1983) Antedon bifida was able to maintain its grip on a concrete substratum in currents up to 90cm/s in a flume. Thus, the claw-like cirri enable the species to survive in moderately strong currents and dense populations are found in areas where water flow is likely to be between 1 and 3 knots during maximal tidal flow. However, if water currents increased to very strong (>6 knots) from moderately strong for a period of a year it is likely that populations would not survive. La Touche (1978) observed that Antedon bifida was unable to maintain its arms in a vertical feeding position in all but the weakest of currents. However, the extremely flexible and opportunistic nature of the species arms and pinnules to adapt in other ways and in several types of water movement. Although dense beds of feather-stars are likely to buffer water currents to some degree feeding is likely to be difficult and many individuals are likely to be washed away. Intolerance is therefore recorded as high. For recovery see additional information.

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

The species occurs in areas where there is fast current flow suitable for passive suspension feeding so a decrease in water flow is likely to reduce food supplies. Thus, growth and fecundity will be impaired and over the period of the year individuals are likely to die or move away to higher flow areas. Thus, intolerance of the species is considered to be high. For recovery see additional information.

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 from Scotland to Portugal so is probably able to tolerate a long term increase in temperature of 2°C. However, as a subtidal species Antedon bifida is less likely to be able to tolerate a short term increase in temperature of 5°C. Intolerance is set to intermediate. For recovery see additional information.

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

Insufficient
information.

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

Antedon bifida is not sensitive directly to increases in turbidity because light attenuation does not impact upon suspension feeding. However, an increase in turbidity, reducing light availability may reduce primary production by phytoplankton in the water column and thus influence food availability. However, particulate food supplies are also likely to be derived from distant sources so the impact of a change for a period of a year is not likely to be significant, maybe a reduction in growth and fecundity, and an intolerance of low is reported. Recovery is likely to be very high as photosynthetic levels and local phytoplankton production will rapidly return to normal.

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

Antedon bifida is not sensitive directly to decreases in turbidity because light attenuation does not impact upon suspension feeding. However, a decrease in turbidity, improving light availability may improve primary production by phytoplankton in the water column and thus increase food availability. Food supplies are also likely to be derived from distant sources so the impact of a change for a period of a year is not likely to be significant, maybe a slight increase in growth and fecundity, and so an intolerance of low is reported. Recovery is likely to be very high as photosynthetic levels and local phytoplankton production will rapidly return to normal.

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

Antedon bifida is not found in areas subject to wave exposure and so is likely to be intolerant. If subjected to wave exposure, the species will probably be unable to feed and may be damaged by wave action. Populations are unlikely to survive such a increase for a period of a year so intolerance is reported to be high. On return to normal conditions recovery should be possible within five years - see additional information.

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

Antedon bifida is found in areas of extremely low wave exposure such as Scottish sea lochs so is likely to tolerate a decrease.

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

Antedon bifida may respond to vibrations by curling up their arms, maybe to avoid predation for example. However, the species is unlikely to sensitive to noise and so the biotope is assessed as tolerant.

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

Some response to visual disturbance has been detected in echinoderms. There is some evidence that the basiepithelial nerve plexus below the entire outer skins is sensitive to light (D. Nichols pers. comm.). However, movement of boats etc. in the marine environment is not likely to affect the species so a rank of not sensitive is reported.

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

Antedon bifida is likely to be intolerant of abrasion as individuals would probably be killed or damaged by a force equivalent to a scallop dredge dragged across them. The species can regenerate body parts even when most arms and part of the disc have been lost so most damaged individuals are likely to recover. For recovery see additional information below.

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

If moved to another suitable substratum Antedon bifida is able to attach itself by means of the cirri which grasp the substratum. Therefore, intolerance to displacement is low. If inverted the species is able to right itself very rapidly so recovery is recorded as 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

Prolonged exposure to low concentrations of polychlorinated biphenyls (PCB's) have been shown to result in growth and regenerative abnormalities in the feather-star Antedon mediterranea (Carnevali et al., 2001). Therefore, it seems likely that the congeneric Antedon bifida would also be intolerant of PCBs. However, no reports of the death of individuals was found. Hoare & Hiscock (1974) reported that Antedon bifida appeared to be completely intolerant of conditions within the vicinity of an acidified, halogenated effluent discharge. Intolerance is therefore reported to be high. See additional information for recovery.

Heavy metal contamination

Evidence

Information about the effects of heavy metals on echinoderms is limited and no details specific to Antedon bifida 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. Kinne (1984) reported developmental disturbances in Echinus esculentus exposed to waters containing 25 µg / l of copper (Cu). Therefore, it is likely that adult Antedon bifida is intolerant of heavy metal contamination and so intolerance is assessed as intermediate. See additional information for recovery.

Hydrocarbon contamination

Evidence

Although there is no information available on the effect of hydrocarbons on Antedon bifida although echinoderms in general appear to be highly intolerant. For example, long term chronic pollution is thought to be responsible for reduced abundance of Asterias rubens (Bokn et al., 1993) and Echinocardium cordatum (Daan & Mulder, 1996). Crude oil from the Torrey Canyon in 1967 off Land's End of Cornwall, and the detergent used to disperse it caused mass mortalities of echinoderms; Asterias rubens, Echinocardium cordatum, Psammechinus miliaris, Echinus esculentus, Marthasterias glacialis and Acrocnida brachiata (Smith, 1968). Therefore, an intolerance of high is reported. See additional information for recovery.

Radionuclide contamination

Evidence

Insufficient
information.

Changes in nutrient levels

Evidence

Insufficient
information.

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

Echinoderms are considered to be stenohaline animals that lack the ability to osmo- and ion-regulate (Stickle & Diehl, 1987). The inability of echinoderms to osmoregulate extracellularly causes body fluid volume to decrease when individuals are transferred to higher external salinity. Over the period of a year, populations are unlikely to survive increased salinity. Echinoderm larvae have a narrow range of salinity tolerance and will develop abnormally and die if exposed to increased salinity. The species is therefore likely to be intolerant of an increase in salinity for a period of a year and an intolerance of high is reported. See additional information for recovery.

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

Echinoderms are considered to be stenohaline animals that lack the ability to osmo- and ion-regulate (Stickle & Diehl, 1987). The inability of echinoderms to osmoregulate extracellularly causes body fluid volume to increase when individuals are transferred to lower external salinity probably resulting in the death of animals. Echinoderm larvae have a narrow range of salinity tolerance and will develop abnormally and die if exposed to reduced salinity. The species is therefore likely to be intolerant of a decrease in salinity for a period of a year and an intolerance of high is reported. 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

Antedon bifida is an aerobic organism and oxygen uptake is by the tube feet and across the body wall. It is typically found in areas of fast tidal flow where water will be oxygenated. Although there is no evidence regarding the effect of low oxygen conditions on Antedon bifida, Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2 mg/l. Therefore, an intolerance of intermediate has been reported.

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

Like most echinoderms Antedon bifida is host to symbiotic organisms. The annelid myzostome Myzostoma cirriferum is an obligate associate of echinoderms and live mainly with crinoids including Antedon bifida (Eeckhaut & Jangoux, 1997). Infestation levels seem to vary between sites (Leonard & Jeal, 1984). Although no diseases associated with these organisms have been reported echinoderms in other parts of the world have been severely affected by epidemic type diseases so there is the potential for this to occur.

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 known non-native species compete with or prey upon Antedon bifida and so the species is assessed as not sensitive. However, as several species have become established in British waters there may be future introductions that compete or prey upon species in the biotope.

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

Extraction of Antedon bifida is unlikely because it has no commercial value and often occurs in areas where no other commercial species exist and where dredging would be difficult such as on rocky reefs. However, if 50% of the population were removed recovery should be high. See additional information.

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

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