Biodiversity & Conservation

CR.MCR.As.MolPol.Sab

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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The key structural species (Sabellaria spinulosa), important functional and characterizing species (such as Ophiothrix fragilis and Urticina felina) and other species (Alcyonium digitatum) in the biotope are all benthic, some of them permanently attached. Substratum loss would cause destruction of the biotope. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily although this can be affected by environmental conditions. Other species that may occur in the biotope (e.g. Urticina felina) might take longer to return due to poor dispersal (Solé-Cava et al., 1994) and slow growth (Chia & Spaulding, 1972).
Smothering
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The key structural species in the biotope (Sabellaria spinulosa), although a suspension feeder and permanently attached to the substratum has only low intolerance to smothering. The similar Sabellaria alveolata can tolerate several weeks of smothering by sand (Wilson, 1971). Feeding and breeding will be curtailed. Of the other species in the biotope, few are sufficiently mobile or powerful enough diggers to be able to escape from smothering sediment. Other species in the biotope such as Ophiothrix fragilis and Alcyonium digitatum are likely to be killed by smothering. Therefore an overall intolerance of intermediate has been recorded. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily although this can be affected by environmental conditions.
Increase in suspended sediment
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The biotope occurs in silty turbid conditions so must tolerate or require some degree of suspended sediment. Sabellaria spinulosa, the key structural species in the biotope requires suspended sediment in order to construct the tubes in which it lives. Increases in suspended sediment may benefit this species (Hughes, 1998). (NB Sabellaria spinulosa requires quite coarse grains for tube construction). Urticina felina (a passive carnivore) and Ophiothrix fragilis, species selected as representative of the biotope as well as other species such as Alcyonium digitatum (both suspension feeders) are likely to suffer 'clogging' or interference with feeding mechanisms following large increases in siltation and in extreme cases even suffocation (Aronson, 1992). However, as suspension feeders, these species have a requirement for some suspended particles. It may take some while for the species affected by changes in suspended particle availability to regain condition or for growth rates to return to normal.
Decrease in suspended sediment
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The biotope occurs in silty turbid conditions so must tolerate or require some degree of suspended sediment. Sabellaria spinulosa, the key structural species in the biotope requires suspended sediment in order to construct the tubes in which it lives. Decreases in the amount of suspended sediment may limit growth rates of the worm and reduce the carrying capacity of this biotope for this species. (NB Sabellaria spinulosa requires quite coarse grains for tube construction). However, as suspension feeders, these species have a requirement for some suspended particles. It may take some while for the species affected by changes in suspended particle availability to regain condition or for growth rates to return to normal.
Desiccation
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Although the biotope itself is circalittoral, the key structural species (Sabellaria spinulosa) is occasionally found in the intertidal (as individuals rather than dense crusts). Other species often in the biotope, Ophiothrix fragilis and Urticina felina, can also be found intertidally, typically on the lower shore. These 3 species, as well as other species that may be in the biotope (e.g. Pagurus bernhardus, Gibbula cineraria, Mytilus edulis) may be tolerant of some degree of desiccation. However, other species such as Alcyonium digitatum are entirely subtidal and would be highly intolerant of desiccation. Exposure of the biotope to an hour of air and sunshine may cause the loss of a few species but the biotope as a whole would probably remain physically and functionally intact. As a circalittoral biotope, it is unlikely to be exposed to desiccating influences. It could potentially take several years for those species affected by desiccation to recolonize and return to their former status. During this time the biotope will probably continue to exist albeit with slightly fewer species.
Increase in emergence regime
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Emergence is relevant in the case of this biotope as, because of the silty conditions in which it is found, circalittoral habitats may occur in the intertidal. Several of the other species in the biotope are found intertidally (e.g. Urticina felina, Ophiothrix fragilis, Mytilus edulis) and can tolerate some level of emergence. However, the key structural species in this biotope (Sabellaria spinulosa) (although occasionally found intertidally as individuals rather than dense crusts) is typically subtidal. It can probably tolerate a small level of emergence but may die if regularly exposed to the air for an hour. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily although this can be affected by environmental conditions. Other species that may occur in the biotope (e.g. Urticina felina) might take longer to return due to poor dispersal (Solé-Cava et al., 1994) and slow growth (Chia & Spaulding, 1972).
Decrease in emergence regime
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Emergence is relevant in the case of this biotope as, because of the turbid conditions in which it is found, circalittoral habitats may occur in the intertidal. The biotope is circalittoral and is likely to benefit from decrease in emergence.
Increase in water flow rate
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Sabellaria spinulosa is dependent on water movement for a supply of suspended particles which it uses to construct its tube. Increased water flow rate may enhance the supply of suspended particles and therefore favour the most structurally important species in this biotope. Other species that may be found in the biotope such as Urticina felina are found in a variety of water flow regimes and are unlikely to be greatly affected by changes in this factor. However, Ophiothrix fragilis may be swept away by increased flow rates (Hiscock, 1983). Overall, the biotope would be expected to persist with some changes in the composition of ancillary species.
Decrease in water flow rate
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Sabellaria spinulosa is dependent on water movement for a supply of suspended particles which it uses to construct its tube. Reductions in water flow rate may reduce the amount of suspended sand grains available. This may limit growth of the worms or reduce the density of worms that can be supported in a particular area. Other species that may be found in the biotope such as Urticina felina are found in a variety of water flow regimes and are unlikely to be greatly affected by changes in this factor. However, species in the community benefit from water flow which brings them suspended food and removes silt. It seems likely that some loss of species may occur. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily (see additional information). Recruitment may be aided by the presence of adults and/or empty tubes which form a preferred substratum (Wilson, 1929). Recovery is therefore likely to be rapid.
Increase in temperature
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Sabellaria spinulosa is distributed south of Britain and Ireland and it would therefore be expected to be unaffected by moderate warming. The geographical distributions of the selected important or characterizing species extend both north and south of the British Isles into warmer and colder waters. However, Ophiothrix fragilis has intermediate intolerance to thermal shocks (short acute changes in temperature). Stress can cause a reduction in the loading of symbiotic subcutaneous bacteria and this can be followed by death (Newton & McKenzie, 1995). However, mild winters have been noted to result in highly successful recruitments of Ophiothrix fragilis (Smaal, 1994). It should take only a short time for Sabellaria spinulosa growth rates to return to normal following periods of time below 5 °C. It may take longer for species such as Urticina felina to regain condition and full reproductive function.
Decrease in temperature
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Growth of the key structural species in this biotope (Sabellaria spinulosa) is inhibited below 5 °C (Wilson, 1971) although the species is distributed north of the British Isles into the Arctic. Crisp (1964) did not record any mortality of Sabellaria spinulosa during the cold 1962/63 winter. The geographical distributions of the selected important or characterizing species extend both north and south of the British Isles into warmer and colder waters. No adverse effect of decreased temperature is expected.
Increase in turbidity
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The biotope occurs in silty turbid conditions so the component species must be able to tolerate or require some degree of light attenuation in comparison with clear water. Few of the species are likely to be highly intolerant of changes in turbidity. Some species (Sabellaria spinulosa and Ophiothrix fragilis) feed primarily on phytoplankton. Phytoplankton require light for photosynthesis. Decreases in light availability may limit phytoplankton abundance and reduce food available for suspension feeders. It may take a while for 'normal' levels of phytoplankton to return and for the suspension feeders to regain condition.
Decrease in turbidity
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Decrease in turbidity may be sufficient to reduce availability of suspended particles, hindering growth, repair and feeding of the key structural species in the biotope Sabellaria spinulosa. Effects are likely to be sublethal in the short-term but may reduce viability of populations and result in decline if the turbidity decrease is chronic. Decrease in turbidity may also reduce supply of suspended food to ancillary species. Light levels will also increase and the biotope may become dominated by algae. For a short-term decrease in turbidity, effects are likely to be minor but for more chronic decrease some species might be lost. Recovery is likely to be rapid (see additional information).
Increase in wave exposure
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The key structural species (Sabellaria spinulosa), in addition to several other species that may be found in the biotope (Ophiothrix fragilis, Urticina felina, Mytilus edulis), inhabit a wide range of wave exposures (from sheltered to very exposed). Increases in wave exposure of the biotope are unlikely to have a great effect where it occurs on bedrock or other stable hard substrata. However, where it occurs on consolidated cobbles and pebbles may disturb the substratum and destroy beds. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily so that recovery is likely to be rapid (see additional information). Recruitment may be aided by the presence of adults and/or empty tubes which form a preferred substratum (Wilson, 1929).
Decrease in wave exposure
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Wave action may have an important role in suspending the sediment that is required by Sabellaria spinulosa to build its tubes. Decreases in wave exposure may reduce the amount of available sand grains suspended in the water column, potentially limiting growth of the worm tubes and restricting abundance. Decrease in wave exposure may also allow siltation to occur adversely affecting some species in the biotope. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily so that recovery is likely to be rapid (see additional information). Recruitment may be aided by the presence of adults and/or empty tubes which form a preferred substratum (Wilson, 1929).
Noise
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Sabellaria spinulosa, the key structural species in the biotope is considered not sensitive to noise disturbance. It is possible that predator avoidance behaviour in Ophiothrix fragilis may be triggered by noise vibrations although this has not been recorded.
Visual Presence
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The key structural species (Sabellaria spinulosa) and other selected important or characterizing species (Urticina felina, Ophiothrix fragilis, Alcyonium digitatum, Mytilus edulis) that may be found in the biotope are not sensitive to visual disturbance.
Abrasion & physical disturbance
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Physical disturbance may cause damage to or loss of some of the Sabellaria spinulosa crust and organisms that live on or in it. However, the key structural species (Sabellaria spinulosa) is likely to be resilient to some physical abrasion. The ability of the structurally similar Sabellaria alveolata to repair tubes is well developed (Cunningham et al., 1984; Vorberg, 2000). Other selected important or characterizing species (Urticina felina, Ophiothrix fragilis, Mytilus edulis), sponges and tunicates may be more susceptible and the species richness of the biotope reduced so that the biotope is identified as having intermediate intolerance to abrasion and physical disturbance. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily although this can be affected by environmental conditions (see additional information). Recruitment may be aided by the presence of adults and/or empty tubes which form a preferred substratum (Wilson, 1929).
Displacement
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Although displacement may not affect some of the species that may live in the biotope (e.g. Urticina felina, Ophiothrix fragilis), the key structural species (Sabellaria spinulosa) is permanently attached to the substratum. Displacement would result in death of this species and loss of the main structure of the biotope. The biotope may also contain other permanently attached species (e.g. Alcyonium digitatum) which are likely to be highly intolerant of displacement. Mobile species in the biotope are unlikely to be affected. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily although this can be affected by environmental conditions (see additional information). Other permanently attached species may take longer to recover but these are unlikely to have a great effect on the biotope.

Chemical Factors

Synthetic compound contamination
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Sabellaria spinulosa, the key structural species in this biotope has been recorded as thriving in an area affected by an acidified halogenated effluent (Hoare & Hiscock, 1974). The biotope may therefore replace other biotopes in pollution stressed situations or be an initial colonizing biotope. However, echinoderms such as Ophiothrix fragilis and Ophiopholis aculeata, which may be found in this biotope, are generally considered to be very sensitive to marine pollution (Newton & McKenzie, 1995) and any examples of the biotope present in locations affected by synthetic chemicals may be impoverished. On the other hand, Sabellaria spinulosa colonized the wreck of the MV Robert at Lundy possibly blocking the effect of antifouling chemicals and allowing a rich community to develop. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily although this can be affected by environmental conditions (see additional information). Other species may take longer to recover but these are unlikely to have a large role in the biotope.
Heavy metal contamination
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Insufficient information is available to make an assessment. One of the species characteristic of this biotope, Ophiothrix fragilis, is noted as being an efficient bioaccumulator of heavy metals (Hutchins et al., 1996).
Hydrocarbon contamination
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It is not known how the key structural species in this biotope (Sabellaria spinulosa) reacts to hydrocarbon contamination although it is recorded as thriving in some rather extremely polluted conditions (Hoare & Hiscock, 1974). Echinoderms such as Ophiothrix fragilis and Ophiopholis aculeata which may be found in this biotope are generally considered to be very sensitive to marine pollution. Some laboratory experiments have shown Ophiothrix fragilis to be intolerant of hydrocarbon pollution (Newton & McKenzie, 1995).
Radionuclide contamination
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Insufficient information is available to make an assessment. Ophiothrix fragilis is noted as being an efficient bioaccumulator of radionuclides (Hutchins et al., 1996).
Changes in nutrient levels
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It is not known whether changes in nutrient concentration will have any direct effect on the key or important species in this biotope. However, several species within the biotope are suspension feeders, trapping mainly phytoplankton. Reductions in nutrient concentration may reduce the abundance of phytoplankton and consequently the amount of food available. Nutrient limitation has been noted to cause stress and potentially mortality in Ophiothrix fragilis (Newton & McKenzie, 1995). When food supplies return to normal it may take some while for suspension feeders to regain body condition.
Increase in salinity
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Decrease in salinity
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Sabellaria spinulosa is found primarily in fully marine (saline) conditions. However, dense populations do occur in the Solway Firth and Bristol Channel, both areas at the entrance to estuaries. There are occasional records from the intertidal where some reduced salinity must be experienced from precipitation run-off. Reductions in salinity in the circalittoral are likely to have detrimental effects for this key structural species. Urticina felina, a characterizing species in this biotope is likely to be highly intolerant of reductions in salinity. Ophiothrix fragilis is recorded from salinities as low as 10 psu (Wolff, (1968) so it is unlikely that this species would be affected. Sabellaria spinulosa has a long lived larva with good dispersive ability and can recruit readily although this can be affected by environmental conditions (see additional information). Other species may take longer to recover but these are unlikely to have a great effect on the biotope.
Changes in oxygenation
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Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2 mg/l. Insufficient information is available regarding the key structural species (Sabellaria spinulosa) tolerance to decreases in oxygenation. Although another species in the biotope, Ophiothrix fragilis, is known to have a low respiration rate (Migné & Davoult, 1997(b)), particularly during colder winter temperatures, extreme hypoxia is known to cause mass mortality (Stachowitsch, 1984).

Biological Factors

Introduction of microbial pathogens/parasites
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Insufficient information
Introduction of non-native species
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Insufficient information
Extraction
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Extraction of Sabellaria spinulosa, the key structural species in this biotope is highly unlikely and the species is the subject of a UK Biodiversity Action Plan. If there is a continued increase in the marine aquarium trade for cold water species then Urticina felina, a component species of this biotope, could be a potential target species for extraction. Urticina felina is a slow growing anemone with poor dispersive abilities. It may take several years for recovery to occur but removal and recovery of this species may not have an important role in the viability and functioning of the biotope. Therefore a low intolerance with very high recovery has been suggested.

Additional information icon Additional information

Recoverability
Sabellaria spinulosa is the most important species in this biotope. There are few frequent characterizing species although more studies of the biotope MCR.Csab.Sspi although it is replaced by CR.MCR.CSAB.Sspi in the 2003 version of the biotopes classification which has more species listed as characterizing. The species present in this biotope probably reflect the species composition of nearby biotopes. Because characterization of this biotope relies predominantly on the presence of a crust of Sabellaria spinulosa, intolerance or recoverability of species other than Sabellaria spinulosa may not have a great bearing on that of the biotope as a whole. Sabellaria spinulosa is most frequently found in disturbed and polluted conditions and is a ‘r-strategist’ (a life strategy which allows a species to deal with the vicissitudes of climate and food supply by responding to suitable conditions with a high rate of reproduction. R-strategists are continually colonizing habitats of a temporary nature (from Baretta-Bekker et al., 1992)). Areas where Sabellaria spinulosa had been lost due to winter storms appeared to recolonize up to a maximum thickness of 2.4 cm during the following summer (R. Holt, pers. comm. in Jones 1998). The rich community described from the MV Robert (Hiscock, 1981) identified as this biotope was surveyed five years after the vessel sank suggesting rapid development of the biotope. Recoverability is therefore expected to be high for the biotope.

This review can be cited as follows:

Jackson, A. & Hiscock, K. 2006. Sabellaria spinulosa crusts on silty turbid circalittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 03/09/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=348&code=1997>