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

Magelona mirabilis is an infaunal species which lives in the top few centimetres of fine sand substrata (Fiege et al., 2000). The majority of the population would be removed along with the substratum, e.g. as a result of channel dredging activities, and therefore intolerance is assessed as high. Recoverability is recorded as high (see additional information below).

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

Magelona mirabilis lives infaunally in fine sand and moves by burrowing. It deposit feeds at the surface by extending contractile palps from its burrow. An additional 5 cm layer of sediment would result in a temporary cessation of feeding activity, and therefore growth and reproduction are likely to be compromised. However, Magelona mirabilis would be expected to quickly relocate to its favoured depth, with no mortality, and hence an intolerance of low is recorded. Once the animals have relocated to the surface, feeding activity should return to normal and therefore a recoverability of immediate is recorded.

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

Magelona mirabilis is unlikely to be perturbed by an increase in suspended sediment as it lives infaunally. It is a deposit feeder, gathering organic particles from the sediment surface with its mobile palps. An increase in suspended sediment may result in greater food availability at the sediment surface, potentially enhancing growth and reproduction of Magelona mirabilis. However, the species would only benefit if there was a significant proportion of organic matter in the suspended sediment and if food was previously limiting.

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

Magelona mirabilis is a surface deposit feeder and therefore relies on a supply of nutrients at the sediment surface. A decrease in the suspended sediment may result in a decreased rate of deposition on the substratum surface and therefore a reduction in food availability. Magelona mirabilis is a short-lived species and a reduction in the amount of suspended sediment is likely to impair growth and may result in the death of some of the population (M. Kendall, pers. comm.). The benchmark states that this change would occur for one month and therefore an intolerance of intermediate has been recorded. As soon as suspended sediment levels increased, feeding activity would return to normal and hence recovery is recorded as immediate.

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

Magelona mirabilis lives infaunally and is therefore likely to be protected from desiccation stress. A proportion of the population lives in the intertidal (Fiege et al., 2000) suggesting the species is tolerant to emersion of its substratum. However, Mortimer & Mackie (2014) reported that once Magelona mirabilis specimens were removed from the sediment and exposed to air they struggled to penetrate the sediment once again. Intolerance is therefore assessed as intermediate. Recoverability is recorded as high (see additional information below).  

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

A proportion of the population of Magelona mirabilis lives in the intertidal zone (Fiege et al., 2000). The species lives infaunally and hence is not likely to suffer from desiccation stress unless displaced. However, Magelona mirabilis can only feed when immersed and therefore will experience reduced feeding opportunities. If it burrows to find immersed sediment, the digging will result in the palps being lost (M. Kendall, pers. comm.). Over the course of a year the resultant energetic cost is likely to cause some mortality. An intolerance of intermediate is therefore recorded. Recoverability is recorded as high (see additional information below).

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

Magelona mirabilis thrives in the subtidal zone (Fiege et al., 2000) and therefore could potentially benefit from a decreased emergence regime. It is possible that decreased emergence would allow the species to colonize further up the shore.

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

Magelona mirabilis is adapted to life in areas with strong currents, high wave exposure and unstable sediments (Lackshewitz & Reise, 1998). However, increased water flow rate may remove sediment or change the sediment characteristics in which the species lives, primarily by re-suspending and preventing deposition of finer particles (Hiscock, 1983). Magelona mirabilis typically occurs in sandy sediments (Fiege et al., 2000), a substratum which may be eroded by increases in water flow. Additionally, the consequent lack of deposition of particulate matter at the sediment surface would reduce food availability. The resultant energetic cost over one year would be likely to result in some mortality. An intolerance of intermediate is therefore recorded. Recoverability is recorded as high (see additional information below).

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

Magelona mirabilis is adapted to life in areas with strong currents, high wave exposure and unstable sediments (Lackshewitz & Reise, 1998). Decreased water movement would result in increased deposition of fine suspended sediment (Hiscock, 1983), changing the sediment characteristics of the habitat in which the species lives. Over the course of a year, it is likely that some mortality would occur and an intolerance of intermediate is recorded. Recoverability is assessed as high (see additional information below).

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

No information was found concerning the intolerance of Magelona mirabilis to an increase in temperature.

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 abundance of Magelona mirabilis experienced a sharp decline following the severe winter of 1995 / 1996 in the Wadden Sea, the Netherlands (Armonies et al., 2001). Between 1992 and 1995 the average abundance in an area 5 km west of Sylt was 2901 individuals per m²and by 1996 / 1997, abundance had fallen to 138 per m² (Armonies et al., 2001). The average water temperature in List Harbour, near Sylt, over the severe winter was 0.5 °C which was 2.7 °C and 3.7 °C below the mean water temperatures of the moderate and mild winters of 1996 / 1997 and 1997 / 1998 respectively (Strasser & Günther, 2001). This change in temperature is comparable to the chronic change in the benchmark and therefore an intolerance of intermediate has been recorded. Armonies et al. (2001) commented that, following the severe winter, recovery in this species was 'slow'. However, 'slow' was not quantified although the study suggests that the species had not yet recovered by the 1996 / 1997 sampling.

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

Magelona mirabilis does not require light and therefore is not directly affected by an increase in turbidity. However, increased turbidity may affect primary production in the water column and therefore reduce the availability of diatom food arriving at the sediment surface. In addition, primary production by the micro-phyto benthos on the sediment surface may be reduced, further decreasing food availability. However, Magelona mirabilis also feeds on detritus although it is not known what proportion of the diet is this represents (M. Kendall, pers. comm.). It is possible that, over the course of the year, growth and fecundity may be reduced and an intolerance of low is recorded. However, as soon as light levels return to normal, primary production will increase and hence recoverability is recorded as very high.

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

Magelona mirabilis does not require light and therefore would not be directly affected by a decrease in turbidity. However, decreased turbidity may increase primary production in the water column and by the micro-phyto benthos on the sediment surface. This could potentially increase the amount of food available to Magelona mirabilis although this species also feeds on detritus and it is not known what proportion of the diet diatoms represent (M. Kendall, pers. comm.), nor if it is limiting and therefore, tolerant has been recorded.

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

Magelona mirabilis is adapted to live in areas with strong currents, high wave exposure and unstable sediments (Lackshewitz & Reise, 1998). However, a further increase in wave action may affect the species in several ways (Hiscock, 1983). Strong wave action is likely to cause damage or withdrawal of delicate feeding structures resulting in loss of feeding opportunities and compromised growth. Individuals may be damaged or dislodged by scouring from sand and gravel mobilized by increased wave action. The sediment they live in may be eroded and burrowing would result in the loss of the delicate palps (M. Kendall, pers. comm.). However, Mortimer & Mackie (2014) observed that animals of Magelona johnstoni were able to continue feeding without palps, and that palp loss has no effect on magelonids' ability to continue to feed as they can regenerate two fully functioning palps within 30 days. However, it is likely that some mortality would result from the considerations discussed above. Therefore, an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below). 

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

Magelona mirabilis is adapted to life in areas with strong currents, high wave exposure and unstable sediments (Lackshewitz & Reise, 1998). Decreased wave exposure over the course of a year is likely to result in the establishment of a finer sediment habitat. It is expected that some mortality would occur and therefore intolerance is assessed as intermediate. Recoverability is recorded as high (see additional information below).

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

Jones (1968) reported that Magelona sp. was sensitive to vibrational stimuli both within the sand and the water column, stating that its lateral organs were similar to that of ctenophores and chaetognaths. Mortimer & Mackie (2014) observed that Magelona mirabilis was less responsive to vibrational stimuli than Magelona johnstoni, but therefore still responded to the slightest of knocks. However, it is unlikely to be affected by noise and vibration at the level of the benchmark.

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

No information was found concerning the intolerance of Magelona mirabilis to visual disturbance. The species has no eyes (Hayward & Ryland, 1995) and therefore would not be expected to respond to visual cues.

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

Magelona mirabilis is a soft bodied organism which exposes its palps at the surface while feeding. The species lives infaunally in sandy sediment, usually within a few centimetres of the sediment surface. Physical disturbance, such as dredging or dragging an anchor, would be likely to penetrate the upper few centimetres of the sediment and cause physical damage to Magelona mirabilis. An intolerance of intermediate is therefore recorded. Recoverability is recorded as high (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

Mortimer & Mackie (2014) and Mills & Mortimer (2019) observed burrowing in European magelonid species including Magelona mirabilis. They rapidly buried themselves following displacement to the sediment surface, but they exhibited difficulty in penetrating the sediment surface if disturbed. However, burrowing will result in damage to the palps (M. Kendall, pers. comm.). Furthermore, displacement to the sediment surface would increase the risk of predation by bottom-feeding fish, to which Magelona mirabilis is particularly vulnerable (Hunt, 1925; Hayward & Ryland, 1995). Some mortality may result and therefore intolerance is assessed as intermediate. Recoverability is recorded as high (see additional information below).

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

There is no evidence relating directly to the effects of synthetic chemicals on Magelona mirabilis. However, there is evidence from other polychaete species. Collier & Pinn (1998), for example, investigated the effect on the benthos of invermectin, a feed additive treatment for infestations of sea-lice on farmed salmonids. The polychaete Hediste diversicolor experienced 100% mortality within 14 days when exposed to 8 mg / m² of invermectin in a microcosm.
Polychaetes are, however, highly diverse and have different tolerances in different species (M. Kendall, pers. comm.). It is therefore not advisable to make assumptions about one particular polychaete species based on evidence relating to another.

Heavy metal contamination

Evidence

Little information was found concerning the intolerance of Magelona sp. to heavy metal contamination. However, Boilly & Richard (1978) stated that the presence of Magelona mirabilis is indicative of sediments which have been contaminated with iron. Studies on a dredge spoil disposal site in the harbours of Boulogne and Dunkerque in France (Bourgain et al., 1988) found higher densities of Magleona mirabilis three months after the dumping of dredge spoil than after five months, that is, when the metal contamination of the sediments was higher. No information regarding the effect of other metals on this species was found.

Hydrocarbon contamination

Evidence

Suchanek (1993) reviewed the effects of oil spills on marine invertebrates and concluded that, in general, on soft sediment habitats, infaunal polychaetes, bivalves and amphipods were particularly affected. However, no information was found concerning the intolerance of Magelona mirabilis to hydrocarbon contamination.
Evidence exists for other polychaete species. For example, Levell (1976) found that single spills of crude oil and oil / dispersant (BP 11 00X) mixtures caused a 25 - 50 % reduction in the abundance of Arenicola marina in addition to a reduction in feeding activity. Up to four repeated spillages (over a ten month period) resulted in complete eradication of the affected population either due to death or migration out of the sediment. It was also noted that recolonization was reduced although not completely prevented. In contrast, observations on Aphelochaeta marioni following the Amoco Cadiz oil spill in March, 1978 saw an increase in the abundance of this species after the spill (Dauvin, 1982, 2000).

Polychaetes are, however, highly diverse and have different tolerances in different species (M. Kendall, pers. comm.). It is therefore not advisable to make assumptions about one particular polychaete species based on evidence relating to another.

Radionuclide contamination

Evidence

No information was found concerning the intolerance of Magelona mirabilis to radionuclide contamination.

Changes in nutrient levels

Evidence

As a surface deposit feeder, Magelona mirabilis relies on a supply of organic matter at the sediment surface. Increased nutrient levels in the water column would be expected to result in increased deposition of organic matter at the sediment surface, and therefore moderate nutrient enrichment may be beneficial to Magelona mirabilis. Indeed, Kröncke (1990) postulated that the increase in certain species, including Magelona sp., on the Dogger Bank between 1951 and 1987 may be due to eutrophication. However, Niermann (1996) noted that Magelona sp. decreased in abundance following a nutrient enrichment event in the North Sea, probably because the species were adapted to living in sediments with low or moderate amounts of organic carbon. Intolerance is therefore assessed as intermediate. Recovery is recorded as high (see additional information below).

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

Magelona mirabilis occurs on the open coast where sea water is at full salinity (Fiege et al., 2000) and is therefore probably relatively tolerant of increases in salinity. No information was found concerning the intolerance of the species to hypersaline conditions.

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

Magelona mirabilis occurs in the Baltic Sea (Fiege et al., 2000), where salinity is typically lower than in the open ocean. It is likely that some populations of Magelona mirabilis are adapted to reduced salinity habitats however no information on the effects of an overall decrease in salinity were found.

Changes in oxygenation

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

Evidence

Niermann et al. (1990) reported the changes in a fine sand community from the German Bight in an area with regular seasonal hypoxia. In 1983, oxygen tension fell to exceptionally low levels; < 3 mg O₂/dm³ in large areas and < 1 mg O₂/dm³ in some places. Species richness was reduced by 30-50% following this event and overall biomass was reduced. Niermann et al. (1990) reported that Magelona sp. remained abundant during the period of hypoxia, and, in fact, decreased slightly in abundance on resumption of normoxia. The benchmark level of hypoxia is 2 mg O₂/l for one week. The evidence suggests that Magelona mirabilis would survive this and so is assessed as not sensitive.

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 was found concerning the infection of Magelona mirabilis by microbial pathogens.

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

There is no evidence to suggest that Magelona mirabilis is susceptible to displacement by non-native species.

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

There is no evidence that Magelona mirabilis is extracted deliberately.

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

Magelona mirabilis occurs on the shore alongside the lugworm Arenicola marina and could potentially be affected by bait digging activities given the fragile nature of their bodies (Mortimer, pers. comm.). This species is also potentially at risk from fishing activities on sandy substrata, e.g., beam trawling for flatfish, and extraction of sand by the aggregate industry (Eno, 1991).