Styela gelatinosa, Pseudamussium septemradiatum and solitary ascidians on sheltered deep circalittoral muddy sediment

27-11-2002
Researched byDr Keith Hiscock Refereed byThis information is not refereed.
EUNIS CodeA5.373 EUNIS NameStyela gelatinosa, Pseudamussium septemradiatum and solitary ascidians on sheltered deep circalittoral muddy sediment

Summary

UK and Ireland classification

EUNIS 2008A5.373Styela gelatinosa, Pseudamussium septemradiatum and solitary ascidians on sheltered deep circalittoral muddy sediment
EUNIS 2006A5.373Styela gelatinosa, Pseudamussium septemradiatum and solitary ascidians on sheltered deep circalittoral muddy sediment
JNCC 2004SS.SMu.OMu.StyPseStyela gelatinosa, Pseudamussium septemradiatum and solitary ascidians on sheltered deep circalittoral muddy sediment
1997 BiotopeCOS.COS.StyStyela gelatinosa and other solitary ascidians on sheltered deep circalittoral muddy sediment

Description

This biotope is known only from deep water in Loch Goil (Clyde sea lochs) in fine mud at 65 m with terrigenous debris. Large numbers of solitary ascidians, including Styela gelatinosa, Ascidia conchilega, Corella parallelogramma and Ascidiella spp., occur together with terebellid worms and the bivalve Pseudamussium septemradiatum. It is possibly an ice age relict biotope. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Recorded distribution in Britain and Ireland

Recorded only in the deep water of Loch Goil, west coast of Scotland.

Depth range

-

Additional information

There appear to be no closely similar biotopes.

Listed By

Further information sources

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JNCC

Habitat review

Ecology

Ecological and functional relationships

  • The characterizing and other species in this biotope occupy space in the habitat but their presence is most likely primarily determined by the occurrence of a suitable substratum rather than by interspecific interactions.
  • Various species including the ascidian species characteristic of this biotope may attach to the clam Pseudamussium septemradiatum. Fourteen species are listed by Allen (1953a) as attached to live individuals of Pseudamussium septemradiatum from the Clyde Sea area including five foramaniferans, one sponge, two polychaetes, one bryozoan, two barnacles, two small bivalves but only one ascidian, Styela clava. Allen (1953a) notes that dead shells had very little attached and suggested that movement of the scallop was important in retaining surfaces clear of silt for settlement of attached fauna.
  • The biotope supports some burrowing bivalve species and the sea cucumber Paracucumaria hyndmani.

Seasonal and longer term change

One of the key factors affecting benthic habitats is disturbance which in deep sediment habitats such as COS.Sty is minimal and so communities may be relatively stable. However, there may be some seasonal changes in the biotope including recruitment of young, growth rates and abundance of adults. Also, species in the biotope may be attached to terrigenous debris that may degenerate and many of the species in the biotope are short-lived (see 'Recruitment Processes') so that their abundance from year-to-year may vary depending on success of breeding and recruitment.

Habitat structure and complexity

The biotope most likely has very little structural complexity. However, terrigenous debris, especially if that includes twigs and branches, may create some complexity. There is no evidence from the very limited survey data available of burrowing activity that might create complexity in the sediment habitat or burrows that cryptic species can use.

Productivity

Productivity in subtidal sediments is often quite low. Macroalgae and, most likely, microalgae are absent from COS.Sty and so productivity is secondary, derived from detritus and organic material. Organic material is derived from terregenous debris (vegetation) and water column sources (e.g. plankton, detritus). Organic material is degraded by micro-organisms and the nutrients are recycled.

Recruitment processes

The species in this biotope predominantly have planktotrophic larvae and are potentially able to recruit from fairly distant sources (>10 km). Critically, no information has been found on recruitment processes of Styela gelatinosa although (Millar, 1963b) Styela coriacea produces tadpole larvae that can swim but appear to settle rapidly as do Ascidiella scabrawhere settlement time is estimated to be 2-10 days (see Berill, 1950). No information was found for reproduction in Pseudamussium septemradiatum but scallops generally have a long planktonic stage (for instance 28 days+ for Pecten maximus: Beaumont & Barnes, 1992). In an enclosed sea loch such as Loch Goil, there is most likely some retention of larvae, local recruitment of species with short-lived larvae such as some ascidians and possibly little recruitment from open coast populations.

Time for community to reach maturity

The community probably has a high turnover rate within individuals of the component species reflecting the likely transitory nature of the biogenic hard substrata available for settlement. For instance, Ascidiella scabra has a high fecundity and settles readily, probably for an extended period from spring to autumn. Svane (1988) describes it as "an annual ascidian" and demonstrated recruitment onto artificial and scraped natural substrata. The occurrence and longevity of most large solitary ascidians appears similar to that of Ascidiella scabra. Allen (1953a) demonstrated that Pseudamussium septemradiatum has a life span of about 3.5 years in populations sampled in the Firth of Clyde. Other species that are recorded as rare or occasional in the biotope (Abra alba, Ciona intestinalis, Metridium senile, Protanthea simplex, Sabella pavonina) are all known to settle onto new surfaces within a year or a very few years. Unfortunately, no information has been found for Styela gelatinosa that can be used to estimate longevity or settlement frequency. Nevertheless, it appears that the community would reach maturity rapidly (possibly within a year or a very few years) after new substrata became available.

Additional information

Very little information is available on the biology of Styela gelatinosa has been found and inferences have to be drawn from knowledge of the biology of other ascidians.

Preferences & Distribution

Recorded distribution in Britain and IrelandRecorded only in the deep water of Loch Goil, west coast of Scotland.

Habitat preferences

Depth Range
Water clarity preferences
Limiting Nutrients No information found
Salinity
Physiographic Enclosed coast / Embayment
Biological Zone
Substratum
Tidal
Wave Very sheltered
Other preferences See additional information.

Additional Information

The biotope occurs in an area with terrigenous debris that most likely provide a hard substratum on which large solitary sea squirts can settle and grow in conditions that experience no wave action and only weak tidal flows. The presence of suitable settlement surfaces may be essential to the development of the community which has not been recorded in other areas of the Clyde sea lochs despite extensive sampling from studies undertaken by the Scottish Marine Biological Association and now the University Marine Biology Station based on Cumbrae (for instance, Allen, 1953a).

Species composition

Species found especially in this biotope

Rare or scarce species associated with this biotope

Additional information

The MNCR recorded 17 species in the single record of this biotope (JNCC, 1999).

Sensitivity reviewHow is sensitivity assessed?

Explanation

The biotope is visually dominated by large solitary ascidians of which Ascidiella scabra is the most abundant and represents sensitivity of that group as an important characterizing species. However, the extent to which sensitivity of Styela gelatinosa is represented by Ascidiella scabra is uncertain and no relevant information has been found on Styela gelatinosa. Pseudamussium septemradiatum is a small scallop that has limited information available to assess sensitivity but probably shares characteristics of reproduction and larval biology with other more researched scallops (Pecten maximus, Aequipecten opercularis) used in assessing likely sensitivity. Pseudamussium septemradiatum shells provide an important hard substratum for other species to settle and so is key structural. Abra alba, although only recorded as occasional, is used to represent burrowing bivalve species. Because of the low number of species (17) recorded in the biotope, information on species recorded as rare is also taken account of especially for Asterias rubens, Ciona intestinalis, Metridium senile and Sabella pavonina. The community was sampled remotely so that the abundance of large organisms (which occur in lower densities than smaller ones) such as Asterias rubens and Metridium senile may be higher than suggested.

Species indicative of sensitivity

Community ImportanceSpecies nameCommon Name
Important otherAbra albaA bivalve mollusc
Important otherAscidiella scabraA sea squirt
Important otherMetridium senilePlumose anemone
Key structuralPseudamussium septemradiatumA scallop
Important characterizingStyela gelatinosaA sea squirt

Physical Pressures

 IntoleranceRecoverabilitySensitivitySpecies RichnessEvidence/Confidence
High Moderate Moderate Major decline Very low
Most species are infaunal or epifaunal and will be lost if the substratum is removed so the overall intolerance of the biotope is high. Epifaunal species (that constitute a significant part of the biotope) depend on the presence of hard substratum including terrigenous debris and the shells of Pseudamussium septemratiatum. Although recruitment of species can be rapid (see additional information below), the need for hard substratum to re-occur means that recovery might be slow and a recoverability of moderate is suggested .
Intermediate Very high Low Minor decline Low
Smothering by 5 cm of sediment is likely to lead to the death of some of the organisms in the biotope. However, many species such as large solitary ascidians including Styela gelatinosa will most like protrude sufficiently above the sediment to escape mortality. Abra alba and Terebellidae will be able to burrow upwards through silt. Overall, it is expected that some species might be killed but for most there will be expenditure of energy to clear silt or burrow up through silt and intolerance is considered intermediate with recoverability very high. However, impermeable materials would have a more severe effect.
Low Very high Very Low No change Low
Some species may benefit from increased food supply if suspended sediment has a high organic content. There may be additional cleaning costs for suspension feeders but this will not affect survival of animals. The intolerance of the biotope is therefore reported to be low. Recovery is likely to be very rapid as affected animals clean away sediment particles.
Low High Moderate Minor decline Low
Food availability for some suspension feeding species may decline but this will not affect survival of animals. The intolerance of the biotope is therefore reported to be low.
Not relevant Not relevant Not relevant Not relevant High
The biotope only occurs in deep water and so desiccation is not relevant.
Not relevant Not relevant Not relevant Not relevant High
The biotope only occurs in deep water and so emergence is not relevant.
Not sensitive* Not relevant High
The biotope only occurs in deep water and so desiccation is not relevant.
Intermediate High Low Minor decline Moderate
The biotope habitat is fine sediment that only develops in areas of weak tidal streams and, because of the presence of terrigenous debris, the biotope most likely is in an area where currents slacken allowing material to fall to the seabed. A long term increase in water flow rate is likely to affect the nature of the substratum as fine particles and semi-buoyant terrigenous debris are washed away (together with attached fauna) and a coarser sediment type including shell debris remains. Since the majority of characterizing species are epifaunal, the community might benefit from increase in hard substratum. As a general rule, ascidians require a reasonable water flow rate in order to ensure sufficient food availability. High water flow rates may also be detrimental to feeding ability and posture. Hiscock (1983) found that, for the solitary ascidian Ascidia mentula, siphons closed when the current velocity rose above about 15 cm/sec. It seems likely therefore that some reduction in feeding would occur with increased water flow rate although that would result in slower growth and loss of condition but not mortality. The intolerance of the biotope is reported to be intermediate because some species may be swept away with their substratum. However, once loss has occurred, increased water flow might be beneficial by creating more hard substratum. Recovery will occur within a year or slightly longer depending on the time of year an impact occurs.
Not sensitive* Not relevant High
The biotope occurs in weak tidal streams. A decrease may reduce the supply of particles to the suspension feeders in the biotope. However, effects are only expected to be sub-lethal so intolerance is reported to be low. Normal feeding will resume on return to normal conditions.
High None Very High Rise Moderate
There is no information on the response of the biotope to an increase in temperature. The biotope is found in relatively deep sublittoral habitats where the temperature may fluctuate by a maximum of about 10°C over the period of a year. Whilst most species are widely distributed in the north east Atlantic, the important characterizing species Styela gelatinosa is only elsewhere recorded much further north than Loch Goil. Therefore, Styela gelatinosa may be lost and the biotope would no longer be COS.Sty. In the case a catastrophic event that destroyed the entire population of the characteristic species Styela gelatinosa, the biotope would be unlikely to ever recover as the nearest recorded populations of Styela gelatinosa are in deep water off the Faroes and in Norway. However, there are no other biotopes that are very similar (the closest possibly being SCR.Aasp Ascidiella aspersa on sheltered circalittoral rocks on muddy sediment) and a new biotope without Styela gelatinosa would need to be described. An increase in temperature may allow the establishment of some warm waters species and species richness may increase.
Tolerant* Not sensitive No change Moderate
There is no information on the response of the biotope to a decrease in temperature. The biotope is found in relatively deep sublittoral habitats where the temperature may fluctuate by a maximum of about 10°C over the period of a year because of seasonal changes. Species are widely distributed in the north east Atlantic. Therefore, the biotope is likely to be able to tolerate a long term decrease in temperature. Furthermore, the sea squirt Styela gelatinosa is a northern species and its survival prospects would most likely be enhanced by a decrease in temperature ensuring that the biotope survives and possibly thrives. Therefore 'not sensitive*' is suggested.
Tolerant Not relevant Not relevant No change Moderate
An increase in turbidity, reducing light availability may reduce primary production by phytoplankton in the water column and reduce the food available to suspension feeders. However,, if organic material is included in the material increasing turbidity, suspension feeders may benefit. Overall, no net benefit or disbenefit is likely and 'not sensitive' is suggested..
Tolerant Not sensitive* No change Moderate
An decrease in turbidity, increasing light availability may increase primary production by phytoplankton in the water column and increase the food available to suspension feeders. However, if organic material is part of the material causing turbidity, suspension feeders may have a reduced food supply. Overall, no net benefit or disbenefit is likely and 'not sensitive' is suggested..
Tolerant Not relevant Not relevant Not relevant High
The biotope occurs in a sea loch where even strong gales cause only limited wave action that, because of its short fetch, does not penetrate to anywhere near the depth of this biotope (see Hiscock, 1983 for details). Therefore, even a significant increase in wave exposure will not result in disturbance to the depths at which the biotope occurs and an assessment of not sensitive is made.
Not sensitive* Not relevant High
The biotope occurs in depths where wave action has no effect so decrease in wave action is irrelevant.
Tolerant Not relevant Not relevant Not relevant High
Tunicates are not known to have organs sensitive to noise and most species in the biotope are unlikely to be sensitive to noise and so the biotope is assessed as not sensitive.
Tolerant Not relevant Not relevant Not relevant High
Tunicates are not known to have organs sensitive to visual presence. Sabella pavonina, recorded as rare in the biotope, reacts to shadows and may be briefly unable to feed as a result of retracting. However, overall not sensitive is suggested.
Intermediate High Low Minor decline Moderate
On a sedimentary seabed, physical disturbance may crush a minority of species but is most likely to displace substrata including burying individual in a population. Some species, the burrowing infauna, may recover but damaged or buried sessile fauna may be killed. Intolerance is assessed as intermediate and recovery high (see additional information below).
Intermediate High Low Minor decline Low
Epifaunal species are most likely to be displaced together with the substratum to which they are attached and, unless buried, are likely to survive. Infaunal species are likely to be able to re-burrow. Some mortality may occur in species that become buried so intolerance is suggested as intermediate. For recoverability, see additional information below.

Chemical Pressures

 IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
High High Moderate Decline Low
Ascidians may be intolerant of synthetic chemicals such as tri-butyl-tin anti-foulants. Rees et al. (2001), working in the Crouch estuary, observed that six ascidian species were recorded at one station in 1997 compared with only two at the same station in 1987, shortly following the banning of TBT in antifouling paints. Also, there was a marked increase in the abundance of ascidians especially Ascidiella aspersa and Ascidia conchilega in the estuary after the ban on TBT was introduced. Although there is no direct evidence for effects of synthetic chemicals on Pseudamussium septemradiatum, TBT-based antifouling paint was shown to be detrimental to growth and survival of juvenile Pecten maximus scallops (Paul & Davies, 1986) and there is some evidence that recruitment to inshore scallop beds may have been affected by TBT used in anti-fouling paints (Minchin et al., 1987). Since solitary ascidians and small scallops are the main characterizing component species, an intolerant of high is suggested but with low confidence. Recoverability of high is according to additional information below but assumes that the population of Styela gelatinosa is not annihilated.
Heavy metal contamination
No information Not relevant No information Insufficient
information
Not relevant
No information has been found for effects of heavy metals on ascidian species that characterize the biotope. Although there is no direct evidence for effects of synthetic chemicals on Pseudamussium septemradiatum, Pecten maximus scallops concentrate metals in their tissues with an efficiency greater than that of other bivalves (Gould & Fowler, 1991). When Pecten maximus is grown in close proximity to copper-oxide based antifouling paint high levels of copper may be accumulated in the tissues (Davies & Paul, 1986), growth is also inhibited and mortality increased. Experimental studies with various species suggests that polychaete worms are quite tolerant of heavy metals (Bryan, 1984). However, there is insufficient information on the species present in the biotope to assess the intolerance of the biotope.
Hydrocarbon contamination
No information Not relevant No information Insufficient
information
Moderate
No information has been found.
Radionuclide contamination
No information Not relevant No information Insufficient
information
Moderate
No information has been found.
Changes in nutrient levels
Low Immediate Not sensitive No change Low
The biotope is found in areas of fine sediment with significant input of terrigenous debris, mainly organic material. An increase in nutrients in subtidal habitats of this depth will not cause the biotope to become overgrown with ephemeral algae so the smothering effects often associated with eutrophication will not occur. The intolerance of the biotope to a 50% increase in nutrients is expected to be low and recovery will be rapid on return to normal conditions.
Not relevant Not relevant Not relevant Not relevant Moderate
Although the biotopes classification suggests that COS.Sty occurs in full salinity, it seems likely that, even at the depth this biotope occurs, some dilution may occur especially during periods of heavy rain and freshwater flow. Since increase in salinity would be unlikely to above full salinity conditions, 'not relevant' is indicated.
Intermediate High Low Minor decline Low
Although the biotopes classification suggests that COS.Sty occurs in full salinity, it seems likely that, even at the depth this biotope occurs, some dilution may occur especially during periods of heavy rain and freshwater flow. A fall in salinity from full to reduced would be unlikely to affect Ascidiella scabra which occurs in reduced salinity conditions. Other ascidian species (with the exception of Styela gelatinosa for which there is no information found) are found in variable salinity as are species such as Sabella pavonina, Asterias rubens and Metridium senile. Overall, the biotope is likely to be tolerant of some lowering of salinity. However, in situations where salinity is already variable, a further lowering is likely to result in mortality. Intolerance is indicated as intermediate but may be high. For recoverability, see additional information.
Intermediate High Low Decline Low
There is no information regarding the effect of deoxygenation on the key species in the biotope or the biotope as a whole. Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l. Different species in the biotope will have varying responses to deoxygenation. Ascidians are active suspension feeders that pump water. It seems likely that the effects of lowered oxygenation will be reduced as stagnation can be avoided. Other species such as the scallop Pseudamussium septemradiatum and species burrowing in the sediment are more likely to be adversely affected especially in the still conditions that the biotope lives in. Also, the presence of large amounts of rotting organic debris (terrigenous detritus) in the biotope may increase demand for scant oxygen resources and exacerbate de-oxygenation so that some species perish. An intolerance of intermediate is therefore suggested but with very low confidence. Recovery is likely to be high (see additional information below).

Biological Pressures

 IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
No information Not relevant No information Not relevant Moderate
There were no records found of any diseases or parasites affecting the species or the biotope.
Tolerant Not relevant Not relevant Not relevant Moderate
Of the non-native species known from British waters, the sea squirt Styela clava and the slipper limpet Crepidula fornicata are the only ones thought likely to thrive in this biotope. However, at present, no non-native species are known from the biotope and not sensitive is suggested.
Not relevant Not relevant Not relevant Not relevant Not relevant
It is extremely unlikely that any of the species indicative of sensitivity would be targeted for extraction and we have no evidence for the indirect effects of extraction of other species on this biotope.
Not relevant Not relevant Not relevant Not relevant Moderate

Additional information

Recoverability
The biotope is dominated by species, especially the large solitary ascidians, that have mobile larvae and are known to settle readily onto new surfaces. The community probably has a high turnover rate within individuals of the component species reflecting the likely transitory nature of the biogenic hard substrata available for settlement. For instance, Ascidiella scabra has a high fecundity and settles readily, probably for an extended period from spring to autumn. Svane (1988) describes it as "an annual ascidian" and demonstrated recruitment onto artificial and scraped natural substrata. The occurrence and longevity of most large solitary ascidians appears similar to that of Ascidiella scabra although no information has been found of Styela gelatinosa. Allen (1953a) demonstrated that Pseudamussium septemradiatum has a life span of about 3.5 years in populations sampled in the Firth of Clyde and, based on information from other scallops, recruitment is likely to occur readily from long-lived larvae. Other species that are recorded as rare or occasional in the biotope (Abra alba, Ciona intestinalis, Metridium senile, Protanthea simplex, Sabella pavonina) are all known to settle onto new surfaces within a year or a very few years. No information has been found for Styela gelatinosa that can be used to estimate longevity or settlement frequency. Nevertheless, it appears that the community would reach maturity rapidly (possibly within a year or a very few years) after new substrata became available and providing that sources of larvae existed nearby. In the case a catastrophic event that destroyed the entire population of the characteristic species Styela gelatinosa, the biotope would be unlikely to ever recover as the nearest recorded populations of Styela gelatinosa are in deep water off the Faroes and in Norway. However, there are no other biotopes that are very similar (the closest possibly being SCR.Aasp Ascidiella aspersa on sheltered circalittoral rocks on muddy sediment) and a new biotope without Styela gelatinosa would need to be described.

Importance review

Policy/Legislation

Habitats of Principal ImportanceMud habitats in deep water
Habitats of Conservation ImportanceMud habitats in deep water
UK Biodiversity Action Plan PriorityMud habitats in deep water

Exploitation

None

Additional information

This biotope is only known from one location and from one survey station. It is distinctly different from other biotopes and includes one species (Styela gelatinosa) that is unique to it. It is therefore important as a nationally rare biotope.

Bibliography

  1. Allen, J.A. 1953a. Observations on the epifauna of the deep-water muds of the Clyde Sea area, with special reference to Chlamys septemradiata (Müller). Journal of Animal Ecology, 22, 240-260.
  2. Beaumont, A.R. & Barnes, D.A. 1992. Aspects of the veliger larval growth and byssus drifting of the spat of Pecten maximus and Aequipecten (Chlamys) opercularis. ICES Journal of Marine Science, 49, 417-423.
  3. Berril, N.J., 1950. The Tunicata with an account of the British species. London: Ray Society.
  4. Bryan, G.W., 1984. Pollution due to heavy metals and their compounds. In Marine Ecology: A Comprehensive, Integrated Treatise on Life in the Oceans and Coastal Waters, vol. 5. Ocean Management, part 3, (ed. O. Kinne), pp.1289-1431. New York: John Wiley & Sons.
  5. Cole, S., Codling, I.D., Parr, W. & Zabel, T., 1999. Guidelines for managing water quality impacts within UK European Marine sites. Natura 2000 report prepared for the UK Marine SACs Project. 441 pp., Swindon: Water Research Council on behalf of EN, SNH, CCW, JNCC, SAMS and EHS. [UK Marine SACs Project.], http://www.ukmarinesac.org.uk/
  6. Connor, D.W., Dalkin, M.J., Hill, T.O., Holt, R.H.F. & Sanderson, W.G., 1997a. Marine biotope classification for Britain and Ireland. Vol. 2. Sublittoral biotopes. Joint Nature Conservation Committee, Peterborough, JNCC Report no. 230, Version 97.06., Joint Nature Conservation Committee, Peterborough, JNCC Report no. 230, Version 97.06.
  7. Davies, C.E. & Moss, D., 1998. European Union Nature Information System (EUNIS) Habitat Classification. Report to European Topic Centre on Nature Conservation from the Institute of Terrestrial Ecology, Monks Wood, Cambridgeshire. [Final draft with further revisions to marine habitats.], Brussels: European Environment Agency.
  8. Gould, E. & Fowler, B.A., 1991. Scallops and pollution. In Scallops: biology, ecology and aquaculture (ed. S.E.Shumway), pp. 495-515. Amsterdam: Elsevier. [Developments in Aquaculture and Fisheries Science, no.21.]
  9. Hiscock, K., 1983. Water movement. In Sublittoral ecology. The ecology of shallow sublittoral benthos (ed. R. Earll & D.G. Erwin), pp. 58-96. Oxford: Clarendon Press.
  10. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line] http://www.jncc.gov.uk/mermaid,
  11. Millar, R.H., 1963b. The development and larvae of Styela coriacea. Journal of the Marine Biological Association of the United Kingdom, 43, 71-74.
  12. Minchin, D., Duggan, C.B. & King, W., 1987. Possible effects of organotins on scallop recruitment. Marine Pollution Bulletin, 18, 604-608.
  13. Paul, J.D. & Davies, I.M., 1986. Effects of copper-and tin-based anti-fouling compounds on the growth of scallops (Pecten maximus) and oysters (Crassostrea gigas). Aquaculture, 54, 191-203.
  14. Rees, H.L., Waldock, R., Matthiessen, P. & Pendle, M.A., 2001. Improvements in the epifauna of the Crouch estuary (United Kingdom) following a decline in TBT concentrations. Marine Pollution Bulletin, 42, 137-144.
  15. Svane, I., 1988. Recruitment and development of epibioses on artificial and cleared substrata at two site in Gullmarsfjorden on the Swedish west coast. Ophelia, 29, 25-41.

Citation

This review can be cited as:

Hiscock, K. 2002. Styela gelatinosa, Pseudamussium septemradiatum and solitary ascidians on sheltered deep circalittoral muddy sediment. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/habitat/detail/274

Last Updated: 27/11/2002