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

Aphelochaeta marioni lives infaunally in soft sediments. The physical removal of its substratum, e.g. as a result of channel dredging activities, would also remove the entire population of Aphelochaeta marioni and hence, intolerance is recorded as high. Aphelochaeta marioni has no pelagic phase in its lifecycle, and dispersal is limited to lateral movement by the slow burrowing of the adults and juveniles (Farke, 1979). 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

Aphelochaeta marioni lives infaunally in soft sediments 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, Aphelochaeta marioni 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

Aphelochaeta marioni is not likely to be perturbed by an increase in suspended sediment because it lives infaunally in soft sediment (Brenchley, 1981). It is a surface deposit feeder. While feeding, the animal remains in its burrow and the two palps roam at the surface transporting sand, debris and diatoms to the mouth along a tentacle canal crenulated with cilia (Farke, 1979). An increased rate of siltation may result in an increase in food availability and therefore growth and reproduction of Aphelochaeta marioni may be enhanced. However, food availability would only increase if the additional suspended sediment contained a significant proportion of organic matter and the population would only be enhanced 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

Aphelochaeta marioni is a surface deposit feeder and therefore relies on a supply of nutrients at the sediment surface. A decrease in the suspended sediment would result in a decreased rate of deposition on the substratum surface and therefore a reduction in food availability for Aphelochaeta marioni. This would be likely to impair growth and reproduction. The benchmark states that this change would occur for one month and therefore would be unlikely to cause mortality. An intolerance of low is therefore 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

Aphelochaeta marioni lives infaunally in sediment that has a high silt content and retains a large amount of water. It is therefore protected from desiccation stress.

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

Aphelochaeta marioni lives in the intertidal zone in significant numbers (Gibbs, 1969; Farke, 1979). The species lives infaunally and hence is not likely to suffer from desiccation stress. However, Aphelochaeta marioni can only feed when immersed and therefore will experience reduced feeding opportunities. Over the course of a year the resultant energetic cost is likely to cause some mortality. In addition, increased emergence will increase the vulnerability to predation from shore birds. 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

Aphelochaeta marioni thrives in the subtidal zone 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

An increase in water flow rate is not likely to affect Aphelochaeta marioni directly as it lives infaunally. However, increased water flow rate will change the sediment characteristics in which the species lives, primarily by re-suspending and preventing deposition of finer particles (Hiscock, 1983). The preferred habitat of Aphelochaeta marioni has a high silt content (Gibbs, 1969), a substratum which would not occur in very strong tidal streams. Therefore, the species would be outside its habitat preference and some mortality would be likely to occur. 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 also 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

Aphelochaeta marioni thrives in areas with low water flow, including the lowest category on the water flow scale (Connor et al., 1997), and is tolerant of hypoxia (Broom et al., 1991). Hence, the species is likely to tolerate a reduction in water flow. However, decreased water movement would result in increased deposition of suspended sediment (Hiscock, 1983). An increased rate of siltation may result in an increase in food availability for Aphelochaeta marioni and therefore growth and reproduction may be enhanced, but only if food was previously limiting.

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

Aphelochaeta marioni is distributed over a wide temperature range. It has been recorded from the Mediterranean Sea and Indian Ocean (Hartmann-Schröder, 1974; Rogall, 1977; both cited in Farke, 1979) and therefore the species must be capable of tolerating higher temperatures than it experiences in Northern Europe. Furthermore, Aphelochaeta marioni lives infaunally and so is likely to be insulated from rapid temperature change. An increase in temperature would be expected to cause some physiological stress but no mortality and therefore an intolerance of low is recorded. Metabolic activity should quickly return to normal when temperatures decrease and so a recoverability of very high is recorded.

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

Aphelochaeta marioni is distributed over a wide temperature range. It has been recorded from the Western Baltic Sea, South Atlantic Ocean and North Sea (Hartmann-Schröder, 1974; Rogall, 1977: both cited in Farke, 1979) and therefore the species must be capable of tolerating low temperatures. Aphelochaeta marioni lives buried in sediment and is therefore well insulated from decreases in temperature. In the Wadden Sea, the population was apparently unaffected by a short period of severe frost in I973 (Farke, 1979). A decrease in temperature would be likely to cause some physiological stress but no mortality and therefore an intolerance of low is recorded. Metabolic activity should quickly return to normal when temperatures increase and so a recoverability of very high is recorded.

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

Aphelochaeta marioni typically inhabits turbid waters such as estuaries. It does not require light and therefore is not directly affected by an increase in turbidity for the purposes of light attenuation. An increase in turbidity may affect primary production in the water column and therefore reduce the availability of diatom food sinking to the sediment surface. In addition, primary production by the micro-phyto benthos on the sediment surface may be reduced, further decreasing food availability. However, phytoplankton will also immigrate from distant areas and so the effect may be decreased. As the turbidity increase only persists for a year, decreased food availability would probably only affect growth and fecundity and an intolerance of low is recorded. 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

Aphelochaeta marioni does not require light and therefore would not be affected by a decrease in turbidity for light attenuation purposes.

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

Aphelochaeta marioni characteristically inhabits soft sediments in sheltered areas. This suggests that it would be intolerant of wave exposure to some degree. An increase in wave exposure by two categories for one year would be likely to affect the species in several ways. Fine sediments would be eroded (Hiscock, 1983) resulting in the likely reduction of the habitat of Aphelochaeta marioni and a decrease in food availability. Strong wave action is also likely to cause damage or withdrawal of delicate feeding and respiration structures resulting in loss of feeding opportunities and compromised growth. Furthermore, individuals may be damaged or dislodged by scouring from sand and gravel mobilized by increased wave action. It is likely that high mortality would result from the considerations discussed above and therefore an intolerance of high 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

Aphelochaeta marioni characteristically inhabits soft sediments in sheltered areas and is tolerant of hypoxia (Broom et al., 1991). It is therefore likely to tolerate a decrease in wave exposure.

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

No information was found concerning the intolerance of Aphelochaeta marioni to noise. 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

Aphelochaeta marioni is only active at night (Farke, 1979). Farke (1979) noted their intolerance to visual disturbance in a microsystem in the laboratory. In order to observe feeding and breeding in the microsystem, the animals had to be gradually acclimated to lamp light. Even then, additional disturbance, such as an electronic flash, caused the retraction of palps and cirri and cessation of all activity for some minutes. Visual disturbance, in the form of direct illumination during the species' active period at night, may therefore result in loss of feeding opportunities, which may compromise growth and reproduction. Hence, an intolerance of low is recorded. When the visual disturbance is removed feeding activity should return to normal immediately.

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

Aphelochaeta marioni is a soft bodied organism which exposes its palps and cirri at the surface while feeding. The species lives infaunally in soft 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 Aphelochaeta marioni. 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

Farke (1979) noted the effects of displacement on Aphelochaeta marioni (studied as Tharyx marioni) while performing experiments on intolerance to salinity changes. It was observed that when an individual was removed from its habitat and displaced to a similar habitat, it took approximately one minute to dig itself into the sediment. Aphelochaeta marioni is therefore recorded as not sensitive to displacement.

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 directly relating to the effects of synthetic chemicals on Aphelochaeta marioni. However, there is evidence from other polychaete species. Collier & Pinn (1998) investigated the effect on the benthos of ivermectin, a feed additive treatment for infestations of sea-lice on farmed salmonids. The polychaete Hediste diversicolor was particularly susceptible, exhibiting 100% mortality within 14 days when exposed to 8 mg/m² of ivermectin in a microcosm. Arenicola marina was also intolerant of ivermectin through the ingestion of contaminated sediment (Thain et al., 1998; cited in Collier & Pinn, 1998) and it was suggested that deposit feeding was an important route for exposure to toxins. Beaumont et al. (1989) investigated the effects of tri-butyl tin (TBT) on benthic organisms. At concentrations of 1-3 µg/l there was no significant effect on the abundance of Hediste diversicolor or Cirratulus cirratus (family Cirratulidae) after 9 weeks in a microcosm. However, no juvenile polychaetes were retrieved from the substratum and hence there is some evidence that TBT had an effect on the larval and/or juvenile stages of these polychaetes. The high mortality of polychaetes due to exposure to ivermectin suggests a high intolerance to synthetic chemicals, but this decision is made with very low confidence. Recoverability is recorded as high (see additional information below).

Heavy metal contamination

Evidence

Bryan (1984) suggested that polychaetes are rather tolerant of heavy metals. In Restronguet Creek, the sediments contained levels of arsenic, copper and tin two orders of magnitude higher than in unpolluted estuaries, while levels of silver and zinc were approximately forty times higher (Bryan & Gibbs, 1983). The presence of Aphelochaeta marioni in this area (Bryan & Gibbs, 1983) suggests that the species is tolerant of heavy metal contamination. Furthermore, Aphelochaeta marioni was shown to accumulate arsenic (Gibbs et al., 1983). Aphelochaeta marioni (studied as Tharyx marioni) was found to have whole body concentrations of arsenic greater than 2000 µg/g dry weight (even when living under low ambient arsenic conditions). For reference, other Cirratulids, e.g. Cirriformia tentaculata, from the same habitat contained arsenic at concentrations lower than 100 µg/g dry weight. The purpose of the arsenic accumulation is unclear. Trials with gobies failed to confirm that it was a predator deterrent mechanism and it is probably not a detoxification mechanism as arsenic accumulations were similar for worms living in widely varying arsenic concentrations. Hence, there is no evidence to suggest that Aphelochaeta marioni is intolerant of heavy metal contamination. However, other annelids have been shown to be intolerant of heavy metal contamination (e.g. see review by Crompton, 1997) and therefore an intolerance of low is recorded. Due to their tolerance, a recoverability of very high is recorded.

Hydrocarbon contamination

Evidence

Cirratulids seem to be mostly immune to oil spills, probably because their feeding tentacles are protected by a heavy secretion of mucus (Suchanek, 1993). This is supported by observations of Aphelochaeta marioni following the Amoco Cadiz oil spill in March, 1978 (Dauvin, 1982, 2000). Prior to the spill, Aphelochaeta marioni (studied as Tharyx marioni) was present in very low numbers in the Bay of Morlaix, western English Channel. Following the spill, the level of hydrocarbons in the sediment increased from 10 mg/kg dry sediment to 1443 mg/kg dry sediment 6 months afterwards. In the same period, Aphelochaeta marioni increased in abundance to a mean of 76 individuals/m², which placed it among the top five dominant species in the faunal assemblage. It was suggested that the population explosion occurred due to the increased food availability because of accumulation of organic matter resulting from high mortality of browsers. Six years later, abundance of Aphelochaeta marioni began to fall away again, accompanied by gradual decontamination of the sediments. Aphelochaeta marioni is therefore recorded as not sensitive, with a potential to benefit from hydrocarbon contamination.

Radionuclide contamination

Evidence

No evidence was found concerning the intolerance of Aphelochaeta marioni to radionuclide contamination.

Changes in nutrient levels

Evidence

Raman & Ganapati (1983) studied the distribution of Aphelochaeta marioni (studied as Tharyx marioni) in relation to a sewage outfall in Visakhaptnam Harbour, Bay of Bengal. Aphelochaeta marioni was found to be dominant in the 'semi-healthy zone' characterized by high dissolved oxygen (median 7.2 mg/l), low biological oxygen demand (9.6 mg/l) and low nutrients (nitrate 0.02 mg/l, phosphate 0.88 mg/l). Aphelochaeta marioni was not found in high numbers in the polluted zone close to the sewage outfall, characterized by low dissolved oxygen (median 6.0 mg/l), high biological oxygen demand (14-60 mg/l) and high nutrients (nitrate 0.042-0.105 mg/l, phosphate 2.35-3.76 mg/l). This would suggest that Aphelochaeta marioni is intolerant of eutrophication. However, it would be expected that an increase in organic nutrients would lead to increased food availability for the deposit feeding Aphelochaeta marioni and that the species would thrive provided it could tolerate the increase in biological oxygen demand. Broom et al. (1991) stated that Aphelochaeta marioni was characteristic of faunal assemblages in the Severn Estuary with very poorly oxygenated mud and Thierman et al. (1996) noted that Aphelochaeta marioni "does not have a massively adverse reaction to sulphidic conditions". Furthermore, Dauvin (1982, 2000) recorded an increase in abundance of Aphelochaeta marioni following an oil spill which resulted in an explosion of plant growth due to high mortality of grazers. Therefore, the available evidence on intolerance of Aphelochaeta marioni to nutrient changes does not allow consistent conclusions to be drawn. The worst case scenario is that nutrient enrichment will lead to reduced abundance of Aphelochaeta marioni so an intolerance of intermediate is recorded, with very low confidence. Recoverability 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

Populations of Aphelochaeta marioni inhabit the open coast where sea water is at full salinity. They are clearly capable of thriving in fully saline conditions and hence probably relatively tolerant of increases in salinity. No information was found concerning the reaction to hypersaline conditions (>40psu). Farke (1979) studied the effects of changing salinity on Aphelochaeta marioni (studied as Tharyx marioni) in a microsystem in the laboratory. Over several weeks, the salinity in the microsystem was increased from 25-40 psu and no adverse reaction was noted. However, when individuals were removed from the sediment and displaced to a new habitat, they only dug into their new substratum if the salinities in the two habitats were similar. If the salinities differed by 3-5 psu, the worms carried out random digging movements, failed to penetrate the sediment and died at the substratum surface after a few hours. This would suggest that Aphelochaeta marioni can tolerate salinity changes when living infaunally but is far more intolerant when removed from its habitat.

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

Aphelochaeta marioni thrives in estuaries and is therefore likely to be tolerant of decreases in salinity. It has been recorded from brackish inland waters in the Southern Netherlands with a salinity of 16 psu, but not in areas permanently exposed to lower salinities (Wolff, 1973). However, it also penetrates into areas exposed to salinities as low as 4 psu for short periods at low tide when fresh water discharge from rivers is high (Farke, 1979). The distribution of Aphelochaeta marioni, therefore, suggests that it is very tolerant of low salinity conditions.

Changes in oxygenation

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

Evidence

Connor et al. (1997) described sediments in which Aphelochaeta marioni is commonly found as usually with a "black anoxic layer close to the sediment surface." Broom et al. (1991) recorded that Aphelochaeta marioni (studied as Tharyx marioni) characterized the faunal assemblage of very poorly oxygenated mud in the Severn Estuary. They found Aphelochaeta marioni to be dominant where the redox potential at 4 cm sediment depth was 56 mV and, therefore, concluded that the species was tolerant of very low oxygen tensions. Thierman et al. (1996) studied the distribution of Aphelochaeta marioni in relation to hydrogen sulphide concentrations. The species was found to be abundant at low sulphide concentrations (<50 µM) but only occasional at concentrations from 75-125 µM. They concluded that Aphelochaeta marioni does not display a massively adverse reaction to sulphidic conditions and is able to tolerate a low amount of sulphide. The evidence suggests that Aphelochaeta marioni is capable of tolerating hypoxia but it is difficult to determine to what degree. It is likely that feeding, growth and reproduction would be impaired under sustained low oxygen conditions and therefore an intolerance of low is recorded. Activity should return to normal when oxygen tensions increase and therefore a recoverability of very high is recorded.

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

Gibbs (1971) recorded that nearly all of the population of Aphelochaeta marioni in Stonehouse Pool, Plymouth Sound, was infected with a sporozoan parasite belonging to the acephaline gregarine genus Gonospora, which inhabits the coelom of the host. No evidence was found to suggest that gametogenesis was affected by Gonospora infection and there was no apparent reduction in fecundity. However, any parasitic infection is likely to impair the host in some way and an intolerance of low is recorded. If the parasite were to be removed, the host would be likely to return to normal health quickly so a recoverability of very high is recorded. No other information was found concerning infection of Aphelochaeta marioni 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

No information was found concerning non-native species which would be likely to compete with Aphelochaeta marioni.

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 Aphelochaeta marioni 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

Commercial extraction of other infaunal species is likely to have an effect on Aphelochaeta marioni where their distributions overlap. Hall & Harding (1997) demonstrated that commercial cockle harvesting by suction dredging had significant effects on soft-sediment infaunal communities. Following dredging, species numbers were reduced by up to 30% and abundances by up to 50%. In Maine, USA, commercial digging for worms and clams was studied by Brown & Wilson (1997). Following experimental digging for two and a half months, the densities of three polychaete species, including Tharyx acutus, were significantly reduced, as was the total number of taxa present. It should be noted that Tharyx acutus is a surface dweller and therefore has a different lifestyle to Aphelochaeta marioni. Hence, the inferences that can be drawn are limited. However, it seems likely that the disruption of the infaunal community caused by commercial harvesting would result in mortality of Aphelochaeta marioni and therefore an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below).