Molgula manhattensis with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock

Summary

UK and Ireland classification

Description

This biotope is typically found on slightly sand-scoured, tide-swept, moderately exposed circalittoral bedrock and cobbles. It is commonly recorded from the shallower reaches of the circalittoral around depths from 5 m to 15 m BCD, as it occurs mostly in very turbid waters. From afar, the physical characteristics are usually silted bedrock reefs and cobble, interspersed with patches of clean sand, causing a scour effect on the rock. Dense aggregations of the ascidianMolgula manhattensis form a silty mat on the rock and there is a sparse hydroid and bryozoan turf. A hydroid turf, composed of Nemertesia antenninaHalecium beaniiHydrallmania falcataSertularella gaudichaudiTubularia indivisaand Alcyonium digitatum, in varying amounts, occurs at most sites on the tops of boulders and ridges. A bryozoan turf is also present, but not usually dense and includes Flustra foliaceaAlcyonidium diaphanumElectra pilosa and the crust-forming bryozoan Conopeum reticulum. The polychaete Lanice conchilega thrives in the sandy patches which often occur between the rock ridges. The scour effect tends to reduce the diversity of sponges present with only Halichondria panicea occasionally present. Isolated clumps of the polychaete Sabellaria spinulosa may be present but they do not occur in dense aggregations as in the Sspi.ByB biotope. The anemones Urticina felina and Sagartia troglodytes may occur in cracks between cobbles or on stones buried in the sandy substratum. The anemone Cylista elegans is more commonly found attached to crevices in the bedrock. Other species such as the hermit crab Pagurus bernhardus, the barnacle Balanus crenatus, the polychaete Sabella pavonia and Spirobranchus triqueter may all be present whilst the crabPisidia longicornis may be found under cobbles and stones. Records of this biotope are distributed along the south coast of England and the north Wales coast as well as Pembrokeshire near the entrance to Milford Haven.

Depth range

0-5 m, 5-10 m, 10-20 m

Additional information

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Listed By

Habitat review

Ecology

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Ecological and functional relationships

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Seasonal and longer term change

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Habitat structure and complexity

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Productivity

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Recruitment processes

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Time for community to reach maturity

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Additional information

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Preferences & Distribution

Habitat preferences

Depth Range 0-5 m, 5-10 m, 10-20 m
Water clarity preferencesNo information
Limiting Nutrients No information
Salinity preferences Full (30-40 psu)
Physiographic preferences
Biological zone preferences Lower circalittoral, Upper circalittoral
Substratum/habitat preferences Bedrock, Cobbles, Sand
Tidal strength preferences Moderately strong 1 to 3 knots (0.5-1.5 m/sec.)
Wave exposure preferences Moderately exposed
Other preferences

Additional Information

Species composition

Species found especially in this biotope

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    Rare or scarce species associated with this biotope

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    Additional information

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    Sensitivity review

    Sensitivity characteristics of the habitat and relevant characteristic species

    CR.HCR.XFa.Mol occurs typically on slightly sand-scoured, tide-swept, moderately exposed circalittoral bedrock and cobbles, from around 5m to 15m BCD, in mostly very turbid waters. Dense aggregations of the ascidian Molgula manhattensis form a silty mat on the rock. A hydroid and faunal turf, composed of Nemertesia antennina, Halecium beanii, Hydrallmania falcata, Sertularella gaudichaudi, Tubularia indivisa and Alcyonium digitatum, in varying amounts, occurs at most sites on the tops of boulders and ridges. A bryozoan turf is also present, but not usually dense and includes Flustra foliacea, Alcyonidium diaphanum, Electra pilosa and the crust-forming bryozoan Conopeum reticulum.

    Of the species mentioned above, Molgula manhattensis has been identified as the primary focus of research, without which the biotope would be unrecognisable. It is however important to note the following species are also important to the character of the biotope character (in terms of abundance and % similarity); Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa, Urticina felina. Where appropriate, references to these species will be made throughout this review.

    Resilience and recovery rates of habitat

    Molgula manhattensis is a small solitary ascidian which can form dense aggregations (as in CR.HCR.XFa.Mol) (Connor et al., 2004). Molgula manhattensis has a rounded appearance and can grow up to 1-3 cm in diameter and up to 3cm height (Hiscock, 2008). Several species had, until recently, been included in Molgula manhattensis: Molgula simplex; Molgula siphonata; Molgula socialis, and Molgula tubifera (Connor & Picton in Howson & Picton, 1997). Separation for the purpose of this review has not been carried out as it is uncertain to what extent authors of papers have worked with Molgula manhattensis sensu stricto. It also seems (Kott 1976 quoted in Kott 1985) that the eastern Atlantic species may be Molgula tubifera and that Molgula manhattensis occurs on the Atlantic coast of North America from Maine to Lousiana. Nevertheless, the Species Directory (Howson & Picton, 1997) lists Molgula manhattensis for Britain and Ireland and so no change in name is suggested here. Molgula manhattensis has a wide distribution; recorded from the Coastal Waters of south-east Alaska and British Columbia (Molnar et al., 2008), Panama (National Museum of Natural History, 2013) and Argentina (Fofonoff, 2014), as well as from Bergen (Norway) to Galicia (northern Spain) (Claude, 1969). Berrill (1931) noted that Molgula tubifera (possibly a synonym of Molgula manhattensis) collected from the Salcombe Estuary and Millbay Docks in Plymouth were oviparous and had a tadpole larva that developed outside of the body. The tadpole developed and hatched in about 10 hours at a temperature of 18°C and the tadpole larva settled after a further one to 10 hours. Berrill (1931) further describes the larval biology of Molgula manhattensis from North America and notes much the same development as in Molgula tubulifera. Indicating Molgula manhattensis has a poor dispersal capacity. If populations were fully removed from a biotope, recolonization would have to be from existing individuals no more than a few kilometres away. Molgula manhattensis settles onto bare surfaces and grows rapidly (Otsuka & Dauer, 1982; Osman & Whitlatch, 1995) including in polluted or hypoxia-stressed situations (Weis & Weis, 1992; Sagasti et al., 2000). It is also likely that Molgula manhattensis larvae are attracted by existing populations and settle near to adults. Osman & Whitlatch (1995) found that settlement was significantly higher on panels adjacent to other Molgula manhattensis control panels. Molgula manhattensis is thought to have a lifespan of one year, during which time sexual maturity is thought to be reached rapidly and reproduction occur several times (Zvyagintsev et al., 2003). Fast growth means that a dense cover could be established within about 2 months of colonization.

    Hydroids as a general group are thought of as early colonizers of bare surfaces (Whomersley & Picken, 2003; Zintzen et al., 2008). Tubularia spp. Specifically are thought of as pioneer species because they are often the first to colonize virgin surfaces and have short life histories. In some habitats Tubularia spp, are transient, however in other tide swept or scoured habitats (e.g. CR.HCR.FaT.CTub.Adig) represent a permanent feature of an annual cycle and tend to dominate in specific seasons e.g. spring-Autumn (Zintzen et al., 2008; Hiscock pers comm). Tubularia indivisa is a common athecate hydroid distributed across the North East Atlantic from the Arctic Ocean to the Mediterranean (WORMS, 2015). Tubularia indivisa is a short-lived species, and recruitment is seasonally variable with settlement peaking in early spring (march) however other smaller recruitment events occur within summer and autumn (Hughes, 1983). The season in which settlement occurs has a direct relationship with life expectancy, high gastropod grazing pressure in spring and summer can cause a mortality rate of 70% (Hughes, 1983). Therefore, post settlement life expectancy can vary from 30 (spring recruitment) to 160 days (autumn recruitment). Observations of Tubularia indivisa from the spring settlement cohort indicate that reproduction can occur within 6-8 weeks, however, Autumn cohorts are likely to persist throughout the winter and begin reproduction the following spring. Tubularia indivisa has a large larval dispersal capacity, and larvae can potentially settle 1-10km from the parental source (Zintzen et al., 2008).

    Alcyonium digitatum is a colonial species of soft coral with a wide distribution in the North Atlantic, recorded from Portugal (41°N) to Northern Norway (70°N) as well as on the east coast of North America (Hartnoll, 1975; Budd, 2008). Colonies consist of stout “finger like” projections (Hartnoll, 1975) which can reach up to 20 cm tall (Budd, 2008) and can dominate circalittoral rock habitats (as in CR.HCR.FaT.CTub.Adig; Connor et al., 2004). Alcyonium digitatum colonies are likely to have a lifespan that exceeds 20 years as colonies have been followed for 28 years in marked plots (Lundälv, pers. comm., in Hartnoll, 1998). Those colonies which are 10-15 cm in height have been aged between 5 and 10 years old (Hartnoll, unpublished). Most colonies are unisexual, with the majority of individuals being female.  Sexual maturity is predicted to occur, at it’s earliest, when the colony reaches its second year of growth, however, the majority of colonies are not predicted to reach maturity until their third year (Hartnoll, 1975).

    Alcyonium digitatum spawns from December and January. Gametes are released into the water where fertilization occurs. The embryos are neutrally buoyant and float freely for 7 days, when they give rise to actively swimming lecithotrophic planulae which may have an extended pelagic life before they eventually settle (usually within 1 or 2 further days) and metamorphose to polyps (Matthews, 1917; Hartnoll, 1975; Budd, 2008). In laboratory experiments, several larvae of Alcyonium digitatum failed to settle within 10 days, presumably finding the conditions unsuitable. These larvae were able to survive 35 weeks as non-feeding planulae. After 14 weeks some were still swimming and after 24 weeks the surface ciliation was still active although they rested on the bottom of the tanks. By the end of the experiment, at 35 weeks the larvae had shrunk to a diameter of 0.3 mm. This ability to survive for long periods in the plankton may favour the dispersal and eventual discovery of a site suitable for settlement (Hartnoll, 1975). The combination of spawning in winter and the long pelagic lifespan may allow a considerable length of time for the planulae to disperse, settle and metamorphose ahead of the spring plankton bloom. Young Alcyonium digitatum will consequently be able to take advantage of an abundant food resource in spring and be well developed before the appearance of other organisms that may otherwise compete for the same substrata. In addition, because the planulae do not feed whilst in the pelagic zone they do not suffer by being released at the time of minimum plankton density. They may also benefit by the scarcity of predatory zooplankton which would otherwise feed upon them (Hartnoll, 1975).

    Flustra foliacea is a perennial species that broods its larvae (Eggleston, 1972; Dyrynda & Ryland, 1982). The brooded lecithotrophic larvae of bryozoans have a short pelagic lifetime of about 12 hours, and may therefore have poor dispersal capabilities (Ryland, 1976). Flustra foliacea colonies begin as encrusting sheets (Tyler-Walters & Ballerstedt, 2007). Colonies have a growth season from late April–October, however, new frond growth typically occurs in early Autumn. The first larvae can be released when fronds are approximately 1 year old (Eggleston, 1972). Once larval production has begun it can continue throughout the growth season however there is a major peak in Autumn and a minor peak in Spring (Dyrynda & Ryland, 1982). Larval settlement is probably related to surface contour, chemistry and the proximity of conspecific colonies (Tyler-Walters & Ballerstedt, 2007). Stebbing (1971) noted that Flustra foliacea colonies regularly reached 6 years of age, although 12-year-old specimens were reported, off the Gower peninsula, Wales.  Fariñas-Franco et al. (2014) recorded the colonization of an artificial reef constructed of 16 tonnes of king scallop shells (Pecten maximus) deployed in Strangford Loch in February 2010. The reef was then seeded with translocated Modiolus modiolus in March 2010. Among other species, Flustra foliacea had colonized the reef within 6 months of the reef construction. Flustra foliacea was also recorded locally prior to the construction of the reef, and therefore recruitment may have a local source.

    Whomersley & Picken (2003) documented epifauna colonization of offshore oil platforms in the North Sea from 1989-2000. On all platforms, Mytilus edulis dominated the near-surface community. For the first 3 years, hydroids and tubeworms dominated the community below the mussel band. However, the hydroid community were later out-competed by other more climax communities. Recruitment of Alcyonium digitatum and Metridium senile began at 2-5 years (dependent on the oil rig). The community structure and zonation differed between the 4 rigs, however generally after four years Metridium senile had become the dominant organism below the mussel zone to approximately 60-80 m Below Sea Level (BSL). Zonation differed between oil rigs however, from approximately 60-90 m BSL Alcyonium digitatum was the dominant organism.

    The Scylla was intentionally sunk on the 27th March 2004 in Whitsand Bay, Cornwall to act as an artificial reef. Hiscock et al. (2010) recorded the succession of the biological community on the wreck for 5 years following the sinking of the ship. Initially the wreck was colonized by opportunistic species /taxa; filamentous algae, hydroids, serpulid worms and barnacles. Tubularia sp. were early colonizers, appearing within a couple of months after the vessel was sunk. Metridium senile appeared late in the summer of the first year, but didn’t become visually dominant until 2007 (3 years after the vessel was sunk). Cylista elegans was recorded within the summer of 2005, and by the end of 2006 was well established. Corynactis viridis was first recorded in the summer of the first year and quickly formed colonies via asexual reproduction. Urticina felina was first recorded at the end of august 2006 (2 years after the vessel was sunk), and by summer 2008 had increased in abundance. Alcyonium digitatum was first recorded in early summer 2005, a year after the vessel was sunk. Within 1 year of growth colonies had grown to nearly full size, however, did not become a visually dominant component of the community until 2009 (5 years after the vessel had been sunk). The authors noted that erect branching Bryozoa are not a common part of rocky reef communities to the west of Plymouth and at the time of writing had not colonized to any great extent on ‘Scylla’ by the end of the study, although several species were recorded which included Chartella papyracea in 28/08/2006 (2 years after the vessel was sunk). Caryophyllia smithii was noted to colonize the wreck a year after the vessel was sunk (07/09/2005).

    The recolonization of epifauna on vertical rock walls was investigated by Sebens (1985, 1986). He reported that rapid colonizers such as encrusting corallines, encrusting bryozoans, amphipods and tubeworms recolonized within 1-4 months. Ascidians such as Dendrodoa carnea, Molgula manhattensis and Aplidium spp. achieved significant cover in less than a year, and, together with Halichondria panicea, reached pre-clearance levels of cover after 2 years. A few individuals of Alcyonium digitatum and Metridium senile colonized within 4 years (Sebens, 1986) and would probably take longer to reach pre-clearance levels.

    Resilience assessment. The available information suggests Molgula manhattensis and Tubularia indivisa are annual species with the potential to rapidly colonize suitable substrates. Alcyonium digtatum and Flustra foliacea are perennial species however can potentially re-colonize new substrates within two years. Urticina felina was also reported to colonize the “Scylla“within two years. Due to the poor dispersal capability of Molgula manhattensis, Tubularia indivisa and Flustra foliacea full removal of the community from the habitat is likely to extend recovery/resilience. If the community is completely removed from the habitat (resistance of none or low) resilience has been assessed as ‘Medium’, however, if resistance has been assessed as medium or high then resilience will be assessed as ‘High’.

    Hydrological Pressures

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    ResistanceResilienceSensitivity
    Temperature increase (local) [Show more]

    Temperature increase (local)

    Benchmark. A 5°C increase in temperature for one month, or 2°C for one year. Further detail

    Evidence

    Molgula manhattensis has a wide distribution; recorded from the Coastal Waters of southeast Alaska and British Columbia (Molnar et al., 2008), Panama (National Museum of Natural History, 2013) and Argentina (Fofonoff, 2014), as well as from Bergen (Norway) to Galicia (northern Spain) (Monniot, 1969). Across this latitudinal gradient Molgula manhattensis is unlikely to be affected by an increase in 2°C for one year. The effect of a 5°C increase in temp for one month is unknown.

    Alcyonium digitatum is described as a northern species by Hiscock et al. (2004), but is distributed from Northern Norway (70°N) to Portugal (41°N) (Hartnoll, 1975; Budd, 2008). Tubularia indivisa is recorded from the Arctic ocean to the Mediterranean (WORMS, 2015). Across this latitudinal gradient both species are likely to experience a range of temperatures from approximately 5-18°C (Seatemperature, 2015).

    Urticina felina is distributed from the Arctic Ocean (Ofwegen et al., 2001) to Portugal (Ramos, 2010). Gosse (1860) observed that Urticina felina (as Actinia crassicornis) was "one of the most difficult (anemones) to keep in an aquarium" and that "the heat of the summer is generally fatal to our captive specimens". It is therefore likely that local warming may adversely affect individuals, especially in southern examples of this biotope, and some mortality might occur.

     

    CR.HCR.XFa.Mol is recorded  from the south coast of Anglesey and the Linconshire coast to Sussex and North Cornwall (Connor et al., 2004). Across this distribution Sea Surface Temperature (SST) ranges from north to south 8-16°C in summer and 6-13°C in winter (Beszczynska-Möller & Dye, 2013).

    Sensitivity assessment. Due to it’s wide distribution, and being recorded within tropical locations, Molgula manhattensis is unlikely to be affected at the benchmark level. However, the effect of acute increases in temperature is unknown. A 2°C temperature increase may however approach the upper thermal tolerance of other important species within CR.HCR.XFa.Mol. Resistance has been assessed as ‘Medium’. Resilience as ‘High’. Sensitivity has been assessed as ‘Low’.  

    Medium
    Low
    NR
    NR
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    High
    High
    High
    High
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    Low
    Low
    Low
    Low
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    Temperature decrease (local) [Show more]

    Temperature decrease (local)

    Benchmark. A 5°C decrease in temperature for one month, or 2°C for one year. Further detail

    Evidence

    Molgula manhattensis has a wide distribution; recorded from the Coastal Waters of southeast Alaska and British Columbia (Molnar et al., 2008), Panama (National Museum of Natural History, 2013) and Argentina (Fofonoff, 2014), as well as from Bergen (Norway) to Galicia (northern Spain) (Claude, 1969). Across this latitudinal gradient Molgula manhattensis is unlikely to be affected at the benchmark.

    Alcyonium digitatum is described as a northern species by Hiscock et al. (2004), but is distributed from Northern Norway (70°N) to Portugal (41°N) (Hartnoll, 1975; Budd, 2008). Tubularia indivisa is recorded from the Arctic ocean to the Mediterranean (WORMS, 2015). Across this latitudinal gradient both species are likely to experience a range of temperatures from approximately 5-18°C (Seatemperature, 2015).

    Alcyonium digitatum was also reported to be apparently unaffected by the severe winter of 1962-1963 where air temperature reached -5.8°C (Crisp, 1964).

    Urticina felina is recorded within the Arctic circle (Stephenson, 1935; Walsh & Somero, 1981) and is therefore unlikely to be affected at the benchmark level.

    CR.HCR.XFa.Mol is recorded  from the south coast of Anglesey and the Linconshire coast to Sussex and North Cornwall (Connor et al., 2004). Across this distribution Sea Surface Temperature (SST) ranges from north to south 8-16°C in summer and 6-13°C in winter (Beszczynska-Möller & Dye, 2013).

    Sensitivity assessment. Resistance has been assessed as ‘High’, resilience as ‘High’. Sensitivity has been assessed as ‘Not sensitive’.

    High
    Low
    NR
    NR
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    High
    High
    High
    High
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    Not sensitive
    Low
    Low
    Low
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    Salinity increase (local) [Show more]

    Salinity increase (local)

    Benchmark. A increase in one MNCR salinity category above the usual range of the biotope or habitat. Further detail

    Evidence

    Little information was found for the hyper salinity effects on Molgula manhattensis. Zuo et al. (2009) demonstrated Molgula manhattensis ingestion rate was highest at 30-32 psu, and decreased at 40psu. Suggesting an increase in salinity to >40 psu may cause an eventual decline in abundance.

    Alcyonium digitatum’ distribution and the depth at which it occurs also suggest it would not likely experience regular salinity fluctuations and therefore tolerate significant increases in salinity.

    Ryland (1970) stated that, with a few exceptions, the Gymnolaemata (the class of Bryozoans which Flustra folicea is part of) were fairly stenohaline and restricted to full salinity (35 psu) and noted that reduced salinities result in an impoverished bryozoan fauna. Similarly, Dyrynda (1994) noted that Flustra foliacea were probably restricted to the vicinity of the Poole Harbour entrance by their intolerance to reduced salinity. Although, protected from extreme changes in salinity due to their subtidal habitat, the introduction of freshwater, or hyposaline effluents may adversely affect Flustra foliacea colonies.

    CR.HCR.XFa.Mol occurs exclusively in full salinity (Connor et al., 2004). An increase in salinity to >40‰ may cause a decline in the abundance of some of the characterizing species. However, the effect is largely unknown.

    Sensitivity assessment. Resistance has been assessed as ‘Medium’, resilience as ‘High’. Sensitivity has been assessed as ‘Low’.

    Medium
    Low
    NR
    NR
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    High
    High
    High
    High
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    Low
    Low
    Low
    Low
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    Salinity decrease (local) [Show more]

    Salinity decrease (local)

    Benchmark. A decrease in one MNCR salinity category above the usual range of the biotope or habitat. Further detail

    Evidence

    Molgula manhattensis is one of very few ascidian species that can tolerate low salinity, and it may occur in large numbers in closed basins of highly diluted seawater (Zvyagintsev et al., 2003). Van Name (1945; quoted in Kott, 1985), notes that Molgula manhattensis occurs in salinities equivalent to 20 to 36 psu whilst Hartmeyer (1923) quoted in Tokioka & Kado (1972) records Molgula manhattensis in brackish (16-30 psu) water of the Belt Sea, Denmark.

    Alcyonium digitatum does inhabit situations such as the entrances to sea lochs (Budd, 2008) or the entrances to estuaries (Braber & Borghouts, 1977) where salinity may vary occasionally. Furthermore as highlighted the Marine Nature Conservation Review (MNCR) records of 23rd Oct 2014 show Alcyonium digitatum is found within a number of variable salinity biotopes, e.g. MCR.BYH.Flu.Hocu,. However, its distribution and the depth at which it occurs suggest that Alcyonium digitatum would not likely often experience salinity fluctuations and therefore unlikely to survive significant reductions in salinity (Budd, 2008).

    Ryland (1970) stated that, with a few exceptions, the Gymnolaemata (the class of Bryozoans which Flustra folicea is part of) were fairly stenohaline and restricted to full salinity (35 psu) and noted that reduced salinities result in an impoverished bryozoan fauna. Similarly, Dyrynda (1994) noted that Flustra foliacea were probably restricted to the vicinity of the Poole Harbour entrance by their intolerance to reduced salinity. Although, protected from extreme changes in salinity due to their subtidal habitat, the introduction of freshwater, or hyposaline effluents may adversely affect Flustra foliacea colonies.

     

    The effects of deceases in salinity on Tubularia indivisa are unclear. Tubularia indivisa is recorded as abundant at a number of locations within the Mersey estuary (Bassindale, 1938). However, the majority of hydroids are subtidal and, although some brackish water species exist (Gili & Hughes, 1995) they are probably intolerant of prolonged decreases in salinity.

    Sensitivity review. CR.HCR.XFa.Mol occurs exclusively in full salinity (Connor et al., 2004). Molgula manhattensis can reportedly tolerate low salinities, however other species within the community may decrease in abundance. Resistance has been assessed as ‘Medium’, Resilience as ‘High’. Sensitivity has been assessed as ‘Low’.

    Medium
    Medium
    High
    High
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    High
    High
    High
    High
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    Low
    Medium
    High
    High
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    Water flow (tidal current) changes (local) [Show more]

    Water flow (tidal current) changes (local)

    Benchmark. A change in peak mean spring bed flow velocity of between 0.1 m/s to 0.2 m/s for more than one year. Further detail

    Evidence

    CR.HCR.XFa.Mol is recorded from moderate tidal streams (0.5-1.5m/sec) (Connor et al., 2004).

    Hiscock (1983) found that, for the solitary ascidian Ascidia mentula, siphons closed when the current velocity rose above about 0.15 m/s. Therefore, a dramatic increase in tidal velocity (>1 m/sec) may cause a decline in feeding time and Molgula manhattensis abundance

    Alcyonium digitatum is a suspension feeder relying on water currents to supply food. And may therefore thrive in conditions of vigorous water flow e.g. around Orkney and St Abbs, Scotland, where the community may experience tidal currents of 3 and 4 knots during spring tides (Kluijver, 1993).

    Flustra foliacea colonies are flexible, robust and reach high abundances in areas subject to strong currents and tidal streams (Stebbing, 1971; Eggleston, 1972; Knight-Jones & Nelson-Smith, 1977; Hiscock, 1983, 1985; Holme & Wilson, 1985). Dyrynda (1994) suggested that mature fronded colonies do not occur on unstable substratum due to the drag caused by their fronds, resulting in rafting of colonies on shells or the rolling of pebbles and cobbles, resulting in destruction of the colony. Dyrynda (1994) reported that the distribution of Flustra foliacea in the current swept entrance to Poole Harbour was restricted to circalittoral boulders, on which it dominated as nearly mono-specific stands.

    Sensitivity assessment. CR.HCR.XFa.Mol is recorded from moderate tidal streams (0.5-1.5m/sec) (Connor et al., 2004). A decrease in tidal velocity of 0.1-0.2 m/s is not likely to have a significant effect on the biological community within CR.HCR.XFa.Mol. Resistance has been assessed as ‘High’, resilience has been assessed as ‘High’. Sensitivity has been assessed as ‘Not sensitive’.

    High
    Medium
    High
    High
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    High
    High
    High
    High
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    Not sensitive
    Medium
    High
    High
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    Emergence regime changes [Show more]

    Emergence regime changes

    Benchmark.  1) A change in the time covered or not covered by the sea for a period of ≥1 year or 2) an increase in relative sea level or decrease in high water level for ≥1 year. Further detail

    Evidence

    Changes in emergence are 'Not relevant' to CR.HCR.XFa.Mol, which is restricted to fully subtidal/circalittoral conditions-The pressure benchmark is relevant only to littoral and shallow sublittoral fringe biotopes.

    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Wave exposure changes (local) [Show more]

    Wave exposure changes (local)

    Benchmark. A change in near shore significant wave height of >3% but <5% for more than one year. Further detail

    Evidence

    CR.HCR.XFa.Mol is recorded from moderately wave exposed sites. Alcyonium digitatum is a suspension feeder relying on water currents to supply food, and may therefore thrive in conditions of vigorous water flow.

    As a general rule, ascidians require a reasonable water flow rate in order to ensure sufficient food availability and oxygen supply. However, high water flow rates may be detrimental to feeding ability and posture. Hiscock (1983) found that, for the solitary ascidian Ascidia mentula, siphons closed when current velocity rose above about 0.15 m/s. A significant increase in near shore wave height may therefore cause a decline in feeding ability and therefore declines in Molgula manhattensis abundance.

     

    Flustra foliacea colonies are flexible, robust and reach high abundances in areas subject to strong currents and tidal streams (Stebbing, 1971; Eggleston, 1972; Knight-Jones & Nelson-Smith, 1977; Hiscock, 1983, 1985; Holme & Wilson, 1985). Dyrynda (1994) suggested that mature fronded colonies do not occur on unstable substratum due to the drag caused by their fronds, resulting in rafting of colonies on shells or the rolling of pebbles and cobbles, resulting in destruction of the colony. Dyrynda (1994) reported that the distribution of Flustra foliacea in the current swept entrance to Poole Harbour was restricted to circalittoral boulders, on which it dominated as nearly mono-specific stands.

    Urticina felina favours areas with strong wave action (Manuel, 1988) and strong tidal currents (Migné & Davoult, 1997).

    Sensitivity assessment. Resistance has been assessed as ‘High’, resilience has been assessed as ‘High’. Sensitivity has been assessed as ‘Not sensitive’.

    High
    Low
    NR
    NR
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    High
    High
    High
    High
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    Not sensitive
    Low
    Low
    Low
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    Chemical Pressures

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    ResistanceResilienceSensitivity
    Transition elements & organo-metal contamination [Show more]

    Transition elements & organo-metal contamination

    Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

    Evidence

    This pressure is Not assessed but evidence is presented where available.

    Ascidians as a group are known to accumulate heavy metals, such as Vanadium (Danskin, 1978). Molgula manhattensis commonly lives in the entrance to harbours and estuaries so that it might be expected to be tolerate heavy metals. Bryozoans are common members of the fouling community, and amongst those organisms most resistant to anti-fouling measures, such as copper containing anti-fouling paints (Soule & Soule, 1979; Holt et al, 1995). Bryozoans are common members of the fouling community, and amongst those organisms most resistant to antifouling measures, such as copper containing anti-fouling paints (Soule & Soule, 1979; Holt et al., 1995). Bryozoans were shown to bio accumulate heavy metals to a certain extent (Holt et al., 1995). For example, Bowerbankia gracialis and Nolella pusilla accumulated Cd, exhibiting sublethal effects (reduced sexual reproduction and inhibited resting spore formation) between 10-100 µg Cd /l and fatality above 500 µg Cd/l (Kayser, 1990).

    No information on the direct biological effects of heavy metal contamination on Alcyonium digitatum. Possible sub-lethal effects of exposure to heavy metals, may result in a change in morphology, growth rate or disruption of reproductive cycle. The vulnerability of this species to concentrations of pollutants may also depend on variations in other factors e.g. temperature and salinity conditions outside the normal range.

    French & Evans (1986) conducted a colonization experiment on panels coated in copper and zinc based anti-fouling paints and compared the community to panels which weren’t covered in anti-fouling paint. Tubularia indivisa was an abundant species on the panels not coated in anti-fouling paint, indicating Tubularia indivisa is highly sensitive to anti-fouling chemicals.

    Not Assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    Hydrocarbon & PAH contamination [Show more]

    Hydrocarbon & PAH contamination

    Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

    Evidence

    This pressure is Not assessed but evidence is presented where available.

    CR.HCR.XFa.Mol is a sub-tidal biotope (Connor et al., 2004). Oil pollution is mainly a surface phenomenon its impact upon circalittoral turf communities is likely to be limited. However, as in the case of the Prestige oil spill off the coast of France, high swell and winds can cause oil pollutants to mix with the seawater and potentially negatively affect sub-littoral habitats (Castège et al., 2014). Smith (1968) reported dead colonies of Alcyonium digitatum at a depth of 16m in the locality of Sennen Cove, Cornwall which was likely a result of toxic detergents sprayed along the shoreline to disperse oil from the Torrey Cannon tanker spill (Budd, 2008).

    At the time of writing there was no information available concerning the effects of oil contamination on Molgula manhattensis.

    At the time of writing little information on the effects of hydrocarbons on bryozoans was found. Ryland & Putron (1998) did not detect adverse effects of oil contamination on the bryozoan Alcyonidium spp. in Milford Haven or St. Catherine's Island, south Pembrokeshire although it did alter the breeding period.

    During the Torrey Canyon oil spill, Urticina felina were found to be alive even in intertidal areas (Smith, 1968).

    Not Assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    Synthetic compound contamination [Show more]

    Synthetic compound contamination

    Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

    Evidence

    This pressure is Not assessed but evidence is any presented where available.

    Hulathduwa & Brown (2006) studied the colonization of artificial oyster reefs that had been soaked in crude oil as well being sprayed with dispersant. The authors reported that Molgula manhattensis had a significantly higher abundance with joint application of oil and cleaner than when only oil was applied. Indicating Molgula manhattensis was potentially tolerant of synthetic oil dispersants. Weis & Weis (1992) found that the ascidian was commonly present, although in small numbers, on wood treated with chromated arsenate. In mesocosm experiments, Flemer et al. (1995) studied the effect of the pesticide endosulfan and found that the average abundance of Molgula manhattensis increased with increasing concentration of the pesticide possibly as a result of reduced competition with more susceptible organisms. The high abundance of the species in harbours where levels of tributyl tin are or were likely to be high also suggests tolerance. Molgula manhattensis may benefit from tolerance to synthetic pollutants by occupying space that would have been colonized by less tolerant species. On the other hand, Rees et al. (2001) reported that the abundance of epifauna (including bryozoans) had increased in the Crouch estuary in the five years since TBT was banned from use on small vessels. This last report suggests that bryozoans and ascidians may be at least inhibited by the presence of TBT.

     

    Smith (1968) reported dead colonies of Alcyonium digitatum at a depth of 16 m in the locality of Sennen Cove, Cornwall resulting from the offshore spread and toxic effect of detergents (a mixture of a surfactant and an organic solvent) e.g. BP 1002 sprayed along the shoreline to disperse oil from the Torrey Canyon tanker spill. Possible sub-lethal effects of exposure to synthetic chemicals, may result in a change in morphology, growth rate or disruption of reproductive cycle. The vulnerability of this species to concentrations of pollutants may also depend on variations in other factors e.g. temperature and salinity conditions outside the normal range (Budd, 2008).

     

    Bryozoans are common members of the fouling community, and amongst those organisms most resistant to antifouling measures, such as copper containing anti-fouling paints (Soule & Soule, 1979; Holt et al., 1995). Bryan & Gibbs (1991) reported that there was little evidence regarding TBT toxicity in bryozoa with the exception of the encrusting Schizoporella errata, which suffered 50% mortality when exposed for 63 days to 100ng/l TBT. Rees et al. (2001) reported that the abundance of epifauna (including bryozoans) had increased in the Crouch estuary in the 5 years since TBT was banned from use on small vessels. This last report suggests that bryozoans may be at least inhibited by the presence of TBT. Hoare & Hiscock (1974) suggested that polyzoa (bryozoa) were amongst the most intolerant species to acidified halogenated effluents in Amlwch Bay, Anglesey and reported that Flustra foliacea did not occur less than 165m from the effluent source.

    No additional information concerning the direct biological effects of synthetic compound contamination on Tubularia indivisa was found.

    Not Assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    Radionuclide contamination [Show more]

    Radionuclide contamination

    Benchmark. An increase in 10µGy/h above background levels. Further detail

    Evidence

    'No Evidence'.

    No evidence (NEv)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    No evidence (NEv)
    NR
    NR
    NR
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    Introduction of other substances [Show more]

    Introduction of other substances

    Benchmark. Exposure of marine species or habitat to one or more relevant contaminants via uncontrolled releases or incidental spills. Further detail

    Evidence

    This pressure is Not assessed.

    Not Assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    De-oxygenation [Show more]

    De-oxygenation

    Benchmark. Exposure to dissolved oxygen concentration of less than or equal to 2 mg/l for one week (a change from WFD poor status to bad status). Further detail

    Evidence

    In general, respiration in most marine invertebrates do not appear to be significantly affected until extremely low concentrations are reached. For many benthic invertebrates this concentration is about 2 ml/l, or even less (Herreid, 1980; Rosenberg et al., 1991; Diaz & Rosenberg, 1995).  There is anecdotal evidence to suggest that Alcyonium digitatum is sensitive to hypoxic events. However, because the degree of de-oxygenation wasn’t quantified the evidence cannot be compared to the pressure benchmark.  Alcyonium digitatum mainly inhabits environments in which the oxygen concentration usually exceeds 5 ml /l and respiration is aerobic (Budd, 2008). In August 1978, a dense bloom of a dinoflagellate, Gyrodinium aureolum occurred surrounding Geer reef in Penzance Bay, Cornwall and persisted until September that year. Observations by local divers indicated a decrease in underwater visibility (<1 m) from below 8 m Below Sea Level. It was also noted that many of the faunal species appeared to be affected, e.g. no live Echinus esculentus were observed whereas on surveys prior to August were abundant. Also, Alcyonium sp. and bryozoans were in an impoverished state. During follow up surveys conducted in early September Alcyonium sp. were noted to be much healthier and feeding. It was suggested the decay of Gyrodinium aureolum either reduced oxygen levels or physically clogged faunal feeding mechanisms. Adjacent reefs where also surveyed during the same time period and the effects of the Gyrodinium aureolum bloom were less apparent. It was suggested that higher water agitation in shallow water on reefs more exposed to wave action were less effected by the phytoplankton bloom (Griffiths et al., 1979). 

    Sagasti et al. (2000) demonstrated that Molgula manhattensis can withstand episodes of hypoxia and so intolerance is likely to be low amounting to some loss in condition. Some of the cushion sponges occur in Abereiddy Quarry in Pembrokeshire near to a zone affected by severe de-oxygenation (Hiscock & Hoare, 1973) and might be able to survive brief episodes of low oxygen conditions.

    Sensitivity assessment. CR.HCR.XFa.Mol occurs in high energy habitats (moderately strong tidal streams and moderatley strong wave expsoure). The high water movement that characterizes this biotope is likely to increase mixing with surrounding oxygenated water (Dennis, 1979) and may, therefore, decrease the effects of de-oxygenation. However, further evidence is required before an assessent can be made. 

    No evidence (NEv)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    No evidence (NEv)
    NR
    NR
    NR
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    Nutrient enrichment [Show more]

    Nutrient enrichment

    Benchmark. Compliance with WFD criteria for good status. Further detail

    Evidence

    This biotope is considered to be 'Not sensitive' at the pressure benchmark that assumes compliance with good status as defined by the WFD.

    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not sensitive
    NR
    NR
    NR
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    Organic enrichment [Show more]

    Organic enrichment

    Benchmark. A deposit of 100 gC/m2/yr. Further detail

    Evidence

    Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina felina.are suspension feeders of phytoplankton and zooplankton. Nutrient enrichment of coastal waters that enhances the population of phytoplankton may be beneficial to Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina felina in terms of an increased food supply but the effects are uncertain (Hartnoll, 1998). The survival of Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina feline may be influenced indirectly. High primary productivity in the water column combined with high summer temperature and the development of thermal stratification (which prevents mixing of the water column) can lead to hypoxia of the bottom waters which faunal species are likely to be highly intolerant of (see de-oxygenation pressure).

    Johnston & Roberts (2009) conducted a meta-analysis, which reviewed 216 papers to assess how a variety of contaminants (including sewage and nutrient loading) affected 6 marine habitats (including subtidal reefs). A 30-50% reduction in species diversity and richness was identified from all habitats exposed to the contaminant types. It was suggested by Comely & Ansell (1988) that Echinus esculentus could absorb dissolved organic material for the purposes of nutrition. Nutrient enrichment may encourage the growth of ephemeral and epiphytic algae and therefore increase sea-urchin food availability. Lawrence (1975) reported that sea urchins had persisted over 13 years on barren grounds near sewage outfalls, presumably feeding on dissolved organic material, detritus, plankton and microalgae, although individuals died at an early age.

    However, further evidence is required before an assessment can be made. 

    No evidence (NEv)
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    No evidence (NEv)
    NR
    NR
    NR
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    Physical Pressures

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    ResistanceResilienceSensitivity
    Physical loss (to land or freshwater habitat) [Show more]

    Physical loss (to land or freshwater habitat)

    Benchmark. A permanent loss of existing saline habitat within the site. Further detail

    Evidence

    All marine habitats and benthic species are considered to have a resistance of ‘None’ to this pressure and to be unable to recover from a permanent loss of habitat (resilience is ‘Very Low’). Sensitivity within the direct spatial footprint of this pressure is therefore ‘High’. Although no specific evidence is described confidence in this assessment is ‘High’, due to the incontrovertible nature of this pressure.

    None
    High
    High
    High
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    Very Low
    High
    High
    High
    Help
    High
    High
    High
    High
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    Physical change (to another seabed type) [Show more]

    Physical change (to another seabed type)

    Benchmark. Permanent change from sedimentary or soft rock substrata to hard rock or artificial substrata or vice-versa. Further detail

    Evidence

    If rock were replaced with sediment, this would represent a fundamental change to the physical character of the biotope and the species would be unlikely to recover. The biotope would be lost.

    Sensitivity assessment. Resistance to the pressure is considered ‘None’, and resilience ‘Very low’. Sensitivity has been assessed as ‘High’.

    None
    High
    High
    High
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    Very Low
    High
    High
    High
    Help
    High
    High
    High
    High
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    Physical change (to another sediment type) [Show more]

    Physical change (to another sediment type)

    Benchmark. Permanent change in one Folk class (based on UK SeaMap simplified classification). Further detail

    Evidence

    'Not relevant'.

    Not relevant (NR)
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    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Habitat structure changes - removal of substratum (extraction) [Show more]

    Habitat structure changes - removal of substratum (extraction)

    Benchmark. The extraction of substratum to 30 cm (where substratum includes sediments and soft rock but excludes hard bedrock). Further detail

    Evidence

    The species characterizing this biotope are epifauna or epiflora occurring on rock and would be sensitive to the removal of the habitat. However, extraction of rock substratum is considered unlikely and this pressure is considered to be ‘Not relevant’ to hard substratum habitats.

    Not relevant (NR)
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Abrasion / disturbance of the surface of the substratum or seabed [Show more]

    Abrasion / disturbance of the surface of the substratum or seabed

    Benchmark. Damage to surface features (e.g. species and physical structures within the habitat). Further detail

    Evidence

    CR.HCR.XFa.Mol is a sub tidal circa littoral biotope (Connor et al., 2004). Therefore abrasion is most likely to be a result of bottom or pot fishing gear, cable laying etc. which may cause localised mobility of the substrata and mortality of the resident community. The effect would be situation dependent however if bottom fishing gear were towed over a site it may mobilise a high proportion of the rock substrata and cause high mortality in the resident community.

    Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina feline are sedentary or slow moving species that might be expected to suffer from the effects of dredging. Colonies are flexible and soft providing a buffer against external abrasion from such factors as a fishing pot landing on a colony. However, individuals and colonies may be scraped off the rock by an anchor or passing dredge. Veale et al. (2000) reported that the abundance, biomass and production of epifaunal assemblages decreased with increasing fishing effort. Boulcott & Howell (2011) conducted experimental Newhaven scallop dredging over a circalittoral rock habitat in the sound of Jura, Scotland and recorded the damage to the resident community. The results indicated that the sponge Pachymatisma johnstoni was highly damaged by the experimental trawl. However, only 13% of photographic samples showed visible damage to Alcyonium digitatum. Where Alcyonium digitatum damage was evident it tended to be small colonies that were ripped off the rock. The authors highlight physical damage to faunal turfs (erect bryozoans and hydroids) was difficult to quantify in the study. However, the faunal turf communities did not show large signs of damage and were only damaged by the scallop dredge teeth which was often limited in extent (approximately. 2cm wide tracts). The authors indicated that species such as Alcyonium digitatum and faunal turf communities were not as vulnerable to damage through trawling as sedimentary fauna and whilst damage to circalittoral rock fauna did occur it was of an incremental nature, with loss of species such as Alcyonium digitatum and faunal turf communities increasing with repeated trawls.

    Sensitivity assessment. Resistance has been assessed ‘Medium’, resilience has been assessed as ‘High’. Sensitivity has been assessed as ‘Low

    Please note Boulcott & Howell (2011) did not mention the abrasion caused by fully loaded collection bags on the new haven dredges. A fully loaded Newhaven dredge may cause higher damage to community as indicated in their study.

    Medium
    High
    High
    High
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    High
    High
    High
    High
    Help
    Low
    High
    High
    High
    Help
    Penetration or disturbance of the substratum subsurface [Show more]

    Penetration or disturbance of the substratum subsurface

    Benchmark. Damage to sub-surface features (e.g. species and physical structures within the habitat). Further detail

    Evidence

    The species characterizing this biotope group are epifauna or epiflora occurring on rock which is resistant to subsurface penetration.  The assessment for abrasion at the surface only is therefore considered to equally represent sensitivity to this pressure. This pressure is 'Not relevant' to hard rock biotopes.

    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Changes in suspended solids (water clarity) [Show more]

    Changes in suspended solids (water clarity)

    Benchmark. A change in one rank on the WFD (Water Framework Directive) scale e.g. from clear to intermediate for one year. Further detail

    Evidence

    Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina felina.are not thought highly susceptible to changes in water clarity due to the fact they are suspension feeding organisms and are not directly dependent on sunlight for nutrition. Water turbidity does not matter much Molgula manhattensis occurs both in clean water and in water with a heavy load of suspended matter (Zvyagintsev et al., 2003). Alcyonium digitatum has been shown to be tolerant of high levels of suspended sediment. Hill et al. (1997) demonstrated that Alcyonium digitatum sloughed off settled particles with a large amount of mucous. Alcyonium digitatum is also known to inhabit the entrances to sea lochs (Budd, 2008) or the entrances to estuaries (Braber & Borghouts, 1977) where water clarity is likely to be highly variable.

    Increased turbidity will reduce light penetration and hence phytoplankton productivity. Small phytoplankton are probably an important food source in the shallow subtidal, although, Flustra foliacea is also found at greater depths, where organic particulates (detritus) are probably more important.

    Sparse information could be found for the tolerance of Tubularia indivisa to changes in water clarity, other than survey reports of abundant Tubularia indivisa in Isle of Thanet, which is well known as an area characterized by poor underwater visibility (Howson et al., 2005).

    Sensitivity assessment. Resistance has been assessed as ‘High’, Resilience as ‘High’. Sensitivity has been assessed as ‘Not Sensitive’.

    High
    High
    High
    High
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    High
    High
    High
    High
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    Not sensitive
    High
    High
    High
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    Smothering and siltation rate changes (light) [Show more]

    Smothering and siltation rate changes (light)

    Benchmark. ‘Light’ deposition of up to 5 cm of fine material added to the seabed in a single discrete event. Further detail

    Evidence

    Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina felina.are sessile and thus would be unable to avoid the deposition of a smothering layer of sediment. Molgula manhattensis is a small ascidian, which can gain a height of 3cm (Hiscock, 2008), and would therefore likely be smothered by 5cm of sediment. Alcyonium digitatum colonies can attain a height of up to 20 cm (Edwards, 2008), Flustra folicea colonies can attain a height of 20 cm (Porter, 2012) so would still be able to feed in the event of sediment deposition.

    Molgula manhattensis seems well able to cope with increased level of suspended sediment being ingested (Naranjo et al., 1996). Water turbidity does not matter much Molgula manhattensis occurs both in clean water and in water with a heavy load of suspended matter (Zvyagintsev et al., 2003).

    Holme & Wilson (1985) examined the bottom fauna in a tide-swept region of the central English Channel. Flustra foliacea dominated communities were reported to form in areas subject to sediment transport (mainly sand) and periodic, temporary, submergence by thin layers of sand (ca <5 cm).

    Mature Tubularia indivisa can attain a height of 10-15cm (Edwards, 2008) so would still be able to expand tentacles and columns of the polyps to filter feed in 5cm of sediment were deposited on the biotope.

    Urticina felina anemones adhere strongly to the substratum and would be entirely covered by smothering material. However, Urticina felina lives in situations where it may be covered from time-to-time by sediment, especially coarser substrata which suggests some ability to survive. For example, Holme & Wilson (1985) observed Urticina felina attached to pebbles, cobbles or rock subject to sand scour or periodic smothering by sand at 50-55m depth, offshore, in the western English Channel. The tidal streams in the central parts of the Channel may reach 125 cm/s during neaps and 166 cm/s on springs. Therefore, he suggested that Urticina felina was tolerant of sand scour or periodic smothering by < ca. 5cm of sand, being able to extend its column to maintain its disc above the sand surface (Holme & Wilson, 1985).

    Sensitivity assessment. Molgula manhattensis would be expected to be smothered, however the remaining community would likely extrude from the sediment. Furthermore CR.HCR.XFa.Mol is recorded from moderate tidal streams (0.5-1.5m/sec) (Connor et al., 2004). Due to the high tidal energy within CR.HCR.XFa.Mol 5 cm of deposited sediment is likely to be removed from the biotope within a few tidal cycles. Resistance has been assessed as ‘High’, resilience as ‘High’. Sensitivity has therefore been assessed as ‘Not Sensitive’.

    High
    Low
    NR
    NR
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    High
    High
    High
    High
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    Not sensitive
    Low
    Low
    Low
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    Smothering and siltation rate changes (heavy) [Show more]

    Smothering and siltation rate changes (heavy)

    Benchmark. ‘Heavy’ deposition of up to 30 cm of fine material added to the seabed in a single discrete event. Further detail

    Evidence

    Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina felina.are sessile and thus would be unable to avoid the deposition of a smothering layer of sediment. Due to the volume of sediment all the characterizing species would be inundated.

    Molgula manhattensis seems well able to cope with increased level of suspended sediment being ingested (Naranjo et al., 1996). Water turbidity does not matter much Molgula manhattensis occurs both in clean water and in water with a heavy load of suspended matter (Zvyagintsev et al., 2003).

    Holme & Wilson (1985) examined the bottom fauna in a tide-swept region of the central English Channel. Flustra foliacea dominated communities were reported to form in areas subject to sediment transport (mainly sand) and periodic, temporary, submergence by thin layers of sand (ca <5 cm).

    Mature Tubularia indivisa can attain a height of 10-15cm (Edwards, 2008) so would still be able to expand tentacles and columns of the polyps to filter feed in 5cm of sediment were deposited on the biotope.

    Urticina felina anemones adhere strongly to the substratum and would be entirely covered by smothering material. However, Urticina felina lives in situations where it may be covered from time-to-time by sediment, especially coarser substrata which suggests some ability to survive. For example, Holme & Wilson (1985) observed Urticina felina attached to pebbles, cobbles or rock subject to sand scour or periodic smothering by sand at 50-55m depth, offshore, in the western English Channel. The tidal streams in the central parts of the Channel may reach 125 cm/s during neaps and 166 cm/s on springs. Therefore, he suggested that Urticina felina was tolerant of sand scour or periodic smothering by < ca. 5cm of sand, being able to extend its column to maintain its disc above the sand surface (Holme & Wilson, 1985).

    Sensitivity assessment. All the community within CR.HCR.XFa.Mol would be expected to be inundated within this pressure. However, there is evidence that these species naturally experience periodic inundation. CR.HCR.XFa.Mol is recorded from moderate tidal streams (0.5-1.5m/sec) (Connor et al., 2004). Due to the high tidal energy within CR.HCR.XFa.Mol 30 cm of deposited sediment is likely to be removed from the biotope in less than a year.

    Resistance has been assessed as ‘Low’, resilience as ‘Medium’. Sensitivity has therefore been assessed as ‘Medium’.

    Medium
    Low
    NR
    NR
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    High
    High
    High
    High
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    Low
    Low
    Low
    Low
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    Litter [Show more]

    Litter

    Benchmark. The introduction of man-made objects able to cause physical harm (surface, water column, seafloor or strandline). Further detail

    Evidence

    Not assessed.

    Not Assessed (NA)
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    NR
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    Not assessed (NA)
    NR
    NR
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    Not assessed (NA)
    NR
    NR
    NR
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    Electromagnetic changes [Show more]

    Electromagnetic changes

    Benchmark. A local electric field of 1 V/m or a local magnetic field of 10 µT. Further detail

    Evidence

    'No evidence' was found.

    No evidence (NEv)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    No evidence (NEv)
    NR
    NR
    NR
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    Underwater noise changes [Show more]

    Underwater noise changes

    Benchmark. MSFD indicator levels (SEL or peak SPL) exceeded for 20% of days in a calendar year. Further detail

    Evidence

    Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina feline have no hearing perception but vibrations may cause an impact, however no studies exist to support an assessment (where relevant).

    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Introduction of light or shading [Show more]

    Introduction of light or shading

    Benchmark. A change in incident light via anthropogenic means. Further detail

    Evidence

    There is no evidence to suggest that If exposed to anthropogenic light sources algal species would benefit. CR.HCR.XFa.Mol is a circalittoral biotope and is thus by definition a naturally shaded environments with low light levels. Increased shading (e.g. by construction of a pontoon, pier etc) could be beneficial to the characterizing species within these biotopes.

    Sensitivity assessment. Resistance is probably 'High', with a 'High' resilience and a sensitivity of 'Not Sensitive'.

    High
    High
    High
    High
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    High
    High
    High
    High
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    Not sensitive
    High
    High
    High
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    Barrier to species movement [Show more]

    Barrier to species movement

    Benchmark. A permanent or temporary barrier to species movement over ≥50% of water body width or a 10% change in tidal excursion. Further detail

    Evidence

    Barriers and changes in tidal excursion are 'Not relevant' to biotopes restricted to open waters.

    Not relevant (NR)
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Death or injury by collision [Show more]

    Death or injury by collision

    Benchmark. Injury or mortality from collisions of biota with both static or moving structures due to 0.1% of tidal volume on an average tide, passing through an artificial structure. Further detail

    Evidence

    'Not relevant' to seabed habitats.  NB. Collision by grounding vessels is addressed under ‘surface abrasion’.

    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Visual disturbance [Show more]

    Visual disturbance

    Benchmark. The daily duration of transient visual cues exceeds 10% of the period of site occupancy by the feature. Further detail

    Evidence

    'Not relevant'.

    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Biological Pressures

    Use [show more] / [show less] to open/close text displayed

    ResistanceResilienceSensitivity
    Genetic modification & translocation of indigenous species [Show more]

    Genetic modification & translocation of indigenous species

    Benchmark. Translocation of indigenous species or the introduction of genetically modified or genetically different populations of indigenous species that may result in changes in the genetic structure of local populations, hybridization, or change in community structure. Further detail

    Evidence

    Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina feline are not cultivated or likely to be translocated on a significant scaled within the British Isles. This pressure is therefore considered ‘Not relevant’.

    Translocation also has the potential to transport pathogens to uninfected areas (see pressure ‘introduction of microbial pathogens’). The sensitivity of the ‘donor’ population to harvesting to supply stock for translocation is assessed for the pressure ‘removal of target species’.

    Not relevant (NR)
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
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    Introduction or spread of invasive non-indigenous species [Show more]

    Introduction or spread of invasive non-indigenous species

    Benchmark. The introduction of one or more invasive non-indigenous species (INIS). Further detail

    Evidence

    At the time of writing, there is no evidence regarding known invasive species which may pose a threat to CR.HCR.XFa.Mol. Crepidula fornicata larvae require hard substrata for settlement. It prefers muddy gravelly, shell-rich, substrata that include gravel, or shells of other Crepidula, or other species e.g., oysters, and mussels. It is highly gregarious and seeks out adult shells for settlement, forming characteristic ‘stacks’ of adults. But it also recorded from rock, artificial substrata, and Sabellaria alveolata reefs (Blanchard, 1997, 2009; Bohn et al., 2012, 2013a, 2013b, 2015; De Montaudouin et al., 2018; Hinz et al., 2011; Helmer et al., 2019; Powell-Jennings & Calloway, 2018; Preston et al., 2020; Tillin et al., 2020). Close examination of the literature (2023) shows that evidence of its colonization and density on bedrock in the infralittoral or circalittoral was lacking. Tillin et al. (2020) suggested that Crepidula could colonize circalittoral rock due to its presence on tide-swept rough grounds in the English Channel (Hinz et al., 2011). However, Hinz et al. (2011) reported that Crepidula fornicata only dominated one assemblage (with an average of 181 individuals per trawl) on gravel substratum with boulders. Bohn et al. (2015) noted that Crepidula occurred at low density or was absent in areas dominated by boulders, and Bohn et al. (2013a, 2013b, 2015) and Preston et al. (2020) showed that while Crepidula could settle on slate panels or ‘stone’ it preferred shell, especially that of conspecifics. In addition, no evidence was found of the effect of Crepidula populations on faunal turf-dominated habitats. It was only recorded at low density (0.1-0.9/m2) in one faunal turf biotope (CR.MCR.CFaVS.CuSpH.As) (JNCC, 2015). Faunal turfs are dominated by suspension feeders so larval predation is probably high, which may prevent colonization by Crepidula. Also, faunal turf species actively compete for space and many are fast growing and opportunistic, so may out-compete Crepidula for space even if it gained a foothold in the community. 

    Didemnum vexillum is an invasive colonial sea squirt native to Asia which was first recorded in the UK in Darthaven Marina, Dartmouth in 2005. Didemnum vexillum can form extensive matts over the substrata it colonizes; binding boulders and cobbles and altering the host habitat (Griffith et al., 2009). Didemnum vexillum can also grow over and smother the resident biological community. Recent surveys within Holyhead Marina, North Wales have found Didemnum vexillum growing on and smothering native tunicate communities (Griffith et al., 2009). Due to the rapid-re-colonization of Didemnum vexillum eradication attempts have to date failed.  Presently Didemnum vexillum is isolated to several sheltered locations in the UK (NBN, 2015), however, Didemnum vexillum has successfully colonized the offshore location of the Georges Bank, USA (Lengyel et al., 2009) which is more exposed than the locations which Didemnum vexillum have colonized in the UK. It is therefore possible that Didemnum vexillum could colonize more exposed locations within the UK and could therefore pose a threat to CR.HCR.XFa.Mol.

    Sensitivity assessment. The circalittoral rock characterizing this biotope is likely to be unsuitable for the colonization by Crepidula fornicata due to the moderately wave exposed conditions, in which wave action and storms may mitigate or prevent the colonization by Crepidula at high densities, although Crepidula has been recorded from areas of strong tidal streams (Hinz et al., 2011). The presence of cobble (JNCC, 2015), in some examples of the biotope, could provide suitable hard substrata for the colonization by Crepidula however, there is no evidence to suggest Crepidula would establish. In addition, no evidence was found of the effect of Crepidula populations on faunal turf-dominated habitats or infralittoral or circalittoral rock habitats. At present, there is 'Insufficient evidence' to suggest that the circalittoral rock biotopes are sensitive to colonization by Crepidula fornicata or other invasive species; further evidence is required. 

    Insufficient evidence (IEv)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
    Help
    Insufficient evidence (IEv)
    NR
    NR
    NR
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    Introduction of microbial pathogens [Show more]

    Introduction of microbial pathogens

    Benchmark. The introduction of relevant microbial pathogens or metazoan disease vectors to an area where they are currently not present (e.g. Martelia refringens and Bonamia, Avian influenza virus, viral Haemorrhagic Septicaemia virus). Further detail

    Evidence

    At the time of writing there is no evidence to suggest that any of the characterizing species within CR.HCR.XFa.Mol are sensitive to current/known microbial pathogens.

    Microbial pathogens are not known to have a severe adverse effect (causing extensive mortality) on Molgula manhattensis.

    Alcyonium digitatum acts as the host for the endoparasitic species Enalcyonium forbesiand and Enalcyonium rubicundum (Stock, 1988). Parasitisation may reduce the viability of a colony but not to the extent of killing them but no further evidence was found to substantiate this suggestion.

    Stebbing (1971) reported that encrusting epizoites reduced the growth rate of Flustra foliacea by ca 50%. The bryozoan Bugula flabellata produces stolons that grow in and through the zooids of Flustra foliacea, causing "irreversible degeneration of the enclosed polypide" (Stebbing, 1971). There is however no evidence of disease which can cause significant mortality at a population or biotope level within Flustra foliacea or Securiflustra securifrons.

    Tubularia indivisa can host an array of potentially pathogenic bacteria, however there is insufficient evidence to suggest significant population wide mortality (Schuett & Doepke, 2009).

    No evidence (NEv)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    No evidence (NEv)
    NR
    NR
    NR
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    Removal of target species [Show more]

    Removal of target species

    Benchmark. Removal of species targeted by fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

    Evidence

    At the time of writing none of the characterizing species within CR.HCR.XFa.Mol are commercially exploited. This pressure is considered ‘Not Relevant’.

    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Not relevant (NR)
    NR
    NR
    NR
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    Removal of non-target species [Show more]

    Removal of non-target species

    Benchmark. Removal of features or incidental non-targeted catch (by-catch) through targeted fishery, shellfishery or harvesting at a commercial or recreational scale. Further detail

    Evidence

    Alcyonium digitatum and faunal turf communities are probably resistant to abrasion through bottom fishing (see abrasion pressure).

    Alcyonium digitatum goes through an annual cycle, From Febuary to July all Alcyonium digitatum colonies are feeding, from July to November an increasing number of colonies stop feeding. During this period a large number of polyps can retracts and a variety of filamentous algae, hydroids and amphipods can colonize the surface of colonies epiphytically. From December-February the epiphytic community is however sloughed off (Hartnoll, 1975). If Alcyonium digitatum were removed the epiphytic species would likely colonize rock surfaces and are therefore not dependant on Alcyonium digitatum.

     

    Within CR.HCR.XFa.Mol Molgula manhattensis, Alcyonidium diaphanum, Alcyonium digitatum, Flustra foliacea, Tubularia indivisa and Urticina feline spatially compete, however at the time of writing there isn’t any evidence to suggest other interspecific relationships or dependencies between these species. Therefore removal of 1 or a number of these species would provide colonization space and most likely benefit the species with rapid colonization rates (e.g. Molgula manhattensis or Tubularia indivisa).

    Sensitivity assessment. Resistance has been assessed as ‘Low’, resilience has been assessed as ’Medium’. Sensitivity has been assessed as ‘Medium’.

    Low
    High
    High
    High
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    Medium
    High
    High
    High
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    Medium
    High
    High
    High
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    Bibliography

    1. Alexander, W., Southgate, B.A. & Bassindale, R., 1935. Survey of the River Tees: The Estuary, Chemical and Biological. HM Stationery Office.

    2. Antoniadou, C., Voultsiadou, E. & Chintiroglou, C., 2010. Benthic colonization and succession on temperate sublittoral rocky cliffs. Journal of Experimental Marine Biology and Ecology, 382 (2), 145-153.

    3. Ayling, A.L., 1983. Factors affecting the spatial distributions of thinly encrusting sponges from temperate waters. Oecologia, 60 (3), 412-418.

    4. Bacescu, M.C., 1972. Substratum: Animals. In: Marine Ecology: A Comprehensive Treatise on Life in Oceans and Coastal Waters. Volume 1 Environmental Factors Part 3. (ed. O. Kinne ). Chichester: John Wiley & Sons.

    5. Bell, J.J. & Turner, J.R., 2000. Factors influencing the density and morphometrics of the cup coral Caryophyllia smithii in Lough Hyne. Journal of the Marine Biological Association of the United Kingdom, 80, 437-441. DOI https://dx.doi.org/10.1017/S0025315400002137

    6. Bell, J.J., 2002. Morphological responses of a cup coral to environmental gradients. Sarsia, 87, 319-330. DOI https://doi.org/10.1080/00364820260400825

    7. Berril, N.J., 1931. Studies in tunicate development. Philosophical Transactions of the Royal Society of London (B), 219, 281-346.

    8. Beszczynska-Möller, A., & Dye, S.R., 2013. ICES Report on Ocean Climate 2012. In ICES Cooperative Research Report, vol. 321 pp. 73.

    9. Bishop, G.M. & Earll, R., 1984. Studies on the populations of Echinus esculentus at the St Abbs and Skomer voluntary Marine Nature Reserves. Progress in Underwater Science, 9, 53-66.

    10. Bishop, G.M., 1985. Aspects of the reproductive ecology of the sea urchin Echinus esculentus L. Ph.D. thesis, University of Exeter, UK.

    11. Blanchard, M., 2009. Recent expansion of the slipper limpet population (Crepidula fornicata) in the Bay of Mont-Saint-Michel (Western Channel, France). Aquatic Living Resources, 22 (1), 11-19. DOI https://doi.org/10.1051/alr/2009004

    12. Blanchard, M., 1997. Spread of the slipper limpet Crepidula fornicata (L.1758) in Europe. Current state and consequences. Scientia Marina, 61, Supplement 9, 109-118. Available from: http://scimar.icm.csic.es/scimar/index.php/secId/6/IdArt/290/

    13. Bohn, K., Richardson, C. & Jenkins, S., 2012. The invasive gastropod Crepidula fornicata: reproduction and recruitment in the intertidal at its northernmost range in Wales, UK, and implications for its secondary spread. Marine Biology, 159 (9), 2091-2103. DOI https://doi.org/10.1007/s00227-012-1997-3

    14. Bohn, K., Richardson, C.A. & Jenkins, S.R., 2015. The distribution of the invasive non-native gastropod Crepidula fornicata in the Milford Haven Waterway, its northernmost population along the west coast of Britain. Helgoland Marine Research, 69 (4), 313.

    15. Bohn, K., Richardson, C.A. & Jenkins, S.R., 2013a. Larval microhabitat associations of the non-native gastropod Crepidula fornicata and effects on recruitment success in the intertidal zone. Journal of Experimental Marine Biology and Ecology, 448, 289-297. DOI https://doi.org/10.1016/j.jembe.2013.07.020

    16. Bohn, K., Richardson, C.A. & Jenkins, S.R., 2013b. The importance of larval supply, larval habitat selection and post-settlement mortality in determining intertidal adult abundance of the invasive gastropod Crepidula fornicata. Journal of Experimental Marine Biology and Ecology, 440, 132-140. DOI https://doi.org/10.1016/j.jembe.2012.12.008

    17. Boolootian, R.A.,1966. Physiology of Echinodermata. (Ed. R.A. Boolootian), pp. 822-822. New York: John Wiley & Sons.

    18. Boulcott, P. & Howell, T.R.W., 2011. The impact of scallop dredging on rocky-reef substrata. Fisheries Research (Amsterdam), 110 (3), 415-420.

    19. Bower, S.M., 1996. Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Bald-sea-urchin Disease. [On-line]. Fisheries and Oceans Canada. [cited 26/01/16]. Available from: http://www.dfo-mpo.gc.ca/science/aah-saa/diseases-maladies/bsudsu-eng.html

    20. Braber, L. & Borghouts, C.H., 1977. Distribution and ecology of Anthozoa in the estuarine region of the rivers Rhine, Meuse and Scheldt. Hydrobiologia, 52, 15-21.

    21. Bradshaw, C., Veale, L.O., Hill, A.S. & Brand, A.R., 2000. The effects of scallop dredging on gravelly seabed communities. In: Effects of fishing on non-target species and habitats (ed. M.J. Kaiser & de S.J. Groot), pp. 83-104. Oxford: Blackwell Science.

    22. 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.

    23. Bucklin, A., 1987. Growth and asexual reproduction of the sea anemone Metridium: comparative laboratory studies of three species. Journal of Experimental Marine Biology and Ecology, 110, 41-52.

    24. Budd, G.C. 2008. Alcyonium digitatum Dead man's fingers. 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/species/detail/1187

    25. Bustamante, M., Tajadura-Martín, F.J. & Saiz-Salinas, J.I., 2010. Temporal and spatial variability on rocky intertidal macrofaunal assemblages affected by an oil spill (Basque coast, northern Spain). Journal of the Marine Biological Association of the United Kingdom, 90 (07), 1305-1317.

    26. Carballo, J., Naranjo, S. & García-Gómez, J., 1996. Use of marine sponges as stress indicators in marine ecosystems at Algeciras Bay(southern Iberian Peninsula). Marine Ecology Progress Series, 135 (1), 109-122.

    27. Carver, C.E., Thériault, I. & Mallet, A.L., 2010. Infection of cultured eastern oysters Crassostrea virginica by the boring sponge Cliona celata, with emphasis on sponge life history and mitigation strategies. Journal of Shellfish Research, 29 (4), 905-915.

    28. Castège, I., Milon, E. & Pautrizel, F., 2014. Response of benthic macrofauna to an oil pollution: Lessons from the “Prestige” oil spill on the rocky shore of Guéthary (south of the Bay of Biscay, France). Deep Sea Research Part II: Topical Studies in Oceanography, 106, 192-197.

    29. Castric-Fey, A., 1983. Recruitment, growth and longevity of Pomatoceros triqueter and Pomatoceros lamarckii (Polychaeta, Serpulidae) on experimental panels in the Concarneau area, South Brittany. Annales de l'Institut Oceanographique, Paris, 59, 69-91.

    30. Chomsky, O., Kamenir, Y., Hyams, M., Dubinsky, Z. & Chadwick-Furman, N., 2004. Effects of temperature on growth rate and body size in the Mediterranean Sea anemone Actinia equina. Journal of Experimental Marine Biology and Ecology, 313 (1), 63-73.

    31. Comely, C.A. & Ansell, A.D., 1988. Invertebrate associates of the sea urchin, Echinus esculentus L., from the Scottish west coast. Ophelia, 28, 111-137.

    32. Connor, D.W., Allen, J.H., Golding, N., Howell, K.L., Lieberknecht, L.M., Northen, K.O. & Reker, J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05. ISBN 1 861 07561 8. In JNCC (2015), The Marine Habitat Classification for Britain and Ireland Version 15.03. [2019-07-24]. Joint Nature Conservation Committee, Peterborough. Available from https://mhc.jncc.gov.uk/

    33. Costello, M., 2001. European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification: Paris: Muséum national d'histoire naturelle.

    34. Costello, M.J., Coll, M., Danovaro, R., Halpin, P., Ojaveer, H. & Miloslavich, P., 2010. A census of marine biodiversity knowledge, resources, and future challenges. Plos One, 5 (8), e12110.

    35. Cotter, E., O’Riordan, R.M. & Myers, A.A., 2003. Recruitment patterns of serpulids (Annelida: Polychaeta) in Bantry Bay, Ireland. Journal of the Marine Biological Association of the United Kingdom, 83 (1), 41- 48. DOI https://doi.org/10.1017/S0025315403006787h

    36. Crisp, D.J. (ed.), 1964. The effects of the severe winter of 1962-63 on marine life in Britain. Journal of Animal Ecology, 33, 165-210.

    37. Cross, F.A., Davis, W.P., Hoss, D.E. & Wolfe, D.A., 1978. Biological Observations, Part 5. In The Amoco Cadiz Oil Spill - a preliminary scientific report (ed. W.N.Ness). NOAA/EPA Special Report, US Department of Commerce and US Environmental Protection Agency, Washington.

    38. Danskin, G.P., 1978. Accumulation of heavy metals by some solitary tunicates. Canadian Journal of Zoology, 56 (4), 547-551.

    39. De Kluijver, M.J., 1993. Sublittoral hard-substratum communities off Orkney and St Abbs (Scotland). Journal of the Marine Biological Association of the United Kingdom, 73 (4), 733-754.

    40. De Montaudouin, X., Blanchet, H. & Hippert, B., 2018. Relationship between the invasive slipper limpet Crepidula fornicata and benthic megafauna structure and diversity, in Arcachon Bay. Journal of the Marine Biological Association of the United Kingdom, 98 (8), 2017-2028. DOI https://doi.org/10.1017/s0025315417001655

    41. Diaz, R.J. & Rosenberg, R., 1995. Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic macrofauna. Oceanography and Marine Biology: an Annual Review, 33, 245-303.

    42. Dons, C., 1927. Om Vest og voskmåte hos Pomatoceros triqueter. Nyt Magazin for Naturvidenskaberne, LXV, 111-126.

    43. Dorgham, M.M., Hamdy, R., El-Rashidy, H.H. & Atta, M.M., 2013. First records of polychaetes new to Egyptian Mediterranean waters. Oceanologia, 55 (1), 235-267.

    44. Duckworth, A.R. & Peterson, B.J., 2013. Effects of seawater temperature and pH on the boring rates of the sponge Cliona celata in scallop shells. Marine Biology, 160 (1), 27-35.

    45. Dyrynda, P.E.J. & Ryland, J.S., 1982. Reproductive strategies and life histories in the cheilostome marine bryozoans Chartella papyracea and Bugula flabellata. Marine Biology, 71, 241-256.

    46. Dyrynda, P.E.J., 1994. Hydrodynamic gradients and bryozoan distributions within an estuarine basin (Poole Harbour, UK). In Proceedings of the 9th International Bryozoology conference, Swansea, 1992. Biology and Palaeobiology of Bryozoans (ed. P.J. Hayward, J.S. Ryland & P.D. Taylor), pp.57-63. Fredensborg: Olsen & Olsen.

    47. Edwards, R.V. 2008. Tubularia indivisa Oaten pipes hydroid. 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/species/detail/1967

    48. Eggleston, D., 1972a. Patterns of reproduction in marine Ectoprocta off the Isle of Man. Journal of Natural History, 6, 31-38.

    49. Fariñas-Franco, J.M., Pearce, B., Porter, J., Harries, D., Mair, J.M. & Sanderson, W.G, 2014. Development and validation of indicators of Good Environmental Status for biogenic reefs formed by Modiolus modiolus, Mytilus edulis and Sabellaria spinulosa under the Marine Strategy Framework Directive. Joint Nature Conservation Committee,

    50. Fell, P.E., Parry, E.H. & Balsamo, A.M., 1984. The life histories of sponges in the Mystic and Thames estuaries (Connecticut), with emphasis on larval settlement and postlarval reproduction. Journal of Experimental Marine Biology and Ecology, 78 (1), 127-141.

    51. Flemer, D.A., Stanley, R.S., Ruth, B.F., Bundrick, C.M., Moody, P.H. & Moore, J.C. 1995. Recolonization of estuarine organisms - effects of microcosm size and pesticides. Hydrobiologia, 304, 85-101.

    52. Fowler, S. & Laffoley, D., 1993. Stability in Mediterranean-Atlantic sessile epifaunal communities at the northern limits of their range. Journal of Experimental Marine Biology and Ecology, 172 (1), 109-127. DOI https://doi.org/10.1016/0022-0981(93)90092-3

    53. Gage, J.D., 1992a. Growth bands in the sea urchin Echinus esculentus: results from tetracycline mark/recapture. Journal of the Marine Biological Association of the United Kingdom, 72, 257-260.

    54. Gommez, J.L.C. & Miguez-Rodriguez, L.J., 1999. Effects of oil pollution on skeleton and tissues of Echinus esculentus L. 1758 (Echinodermata, Echinoidea) in a population of A Coruna Bay, Galicia, Spain. In Echinoderm Research 1998. Proceedings of the Fifth European Conference on Echinoderms, Milan, 7-12 September 1998, (ed. M.D.C. Carnevali & F. Bonasoro) pp. 439-447. Rotterdam: A.A. Balkema.

    55. Gontar, V.I., Hop, H. & Voronkov, A.Y., 2001. Diversity and distribution of Bryozoa in Kongsfjorden, Svalbard. Polish Polar Research, 22 (3-4), 187-204.

    56. Griffith, K., Mowat, S., Holt, R.H., Ramsay, K., Bishop, J.D., Lambert, G. & Jenkins, S.R., 2009. First records in Great Britain of the invasive colonial ascidian Didemnum vexillum Kott, 2002. Aquatic Invasions, 4 (4), 581-590.

    57. Griffiths, A.B., Dennis, R. & Potts, G.W., 1979. Mortality associated with a phytoplankton bloom off Penzance in Mounts Bay. Journal of the Marine Biological Association of the United Kingdom, 59, 515-528.

    58. Hall-Spencer, J.M. & Moore, P.G., 2000a. Impact of scallop dredging on maerl grounds. In Effects of fishing on non-target species and habitats. (ed. M.J. Kaiser & S.J., de Groot) 105-117. Oxford: Blackwell Science.

    59. Hand, C.H., 1955. The sea anemones of central California: San Francisco University, Wasmann Biological Society.

    60. Hansson, H., 1998. NEAT (North East Atlantic Taxa): South Scandinavian marine Echinodermata Check-List. Tjärnö Marine Biological Assocation [On-line] [cited 26/01/16]. Available from: http://www.tmbl.gu.se/libdb/taxon/neat_pdf/NEAT*Echinodermata.pdf

    61. Hartman, W.D., 1958. Natural history of the marine sponges of southern New England. Peabody Museum of Natural History, Bulletin, 12 (12), 1-155.

    62. Hartnoll, R.G., 1975. The annual cycle of Alcyonium digitatum. Estuarine and Coastal Marine Science, 3, 71-78.

    63. Hartnoll, R.G., 1998. Circalittoral faunal turf biotopes: an overview of dynamics and sensitivity characteristics for conservation management of marine SACs, Volume VIII. Scottish Association of Marine Sciences, Oban, Scotland, 109 pp. [UK Marine SAC Project. Natura 2000 reports.] Available from: http://ukmpa.marinebiodiversity.org/uk_sacs/pdfs/circfaun.pdf

    64. Hayward, P.J. & Ryland, J.S. (ed.), 1995. The marine fauna of the British Isles and north-west Europe. Volume 2. Molluscs to Chordates. Oxford Science Publications. Oxford: Clarendon Press.

    65. Helmer, L., Farrell, P., Hendy, I., Harding, S., Robertson, M. & Preston, J., 2019. Active management is required to turn the tide for depleted Ostrea edulis stocks from the effects of overfishing, disease and invasive species. Peerj, 7 (2). DOI https://doi.org/10.7717/peerj.6431

    66. Herreid, C.F., 1980. Hypoxia in invertebrates. Comparative Biochemistry and Physiology Part A: Physiology, 67 (3), 311-320. DOI https://doi.org/10.1016/S0300-9629(80)80002-8

    67. Hill, A.S., Brand, A.R., Veale, L.O. & Hawkins, S.J., 1997. Assessment of the effects of scallop dredging on benthic communities. Final Report to MAFF, Contract CSA 2332, Liverpool: University of Liverpool

    68. Hinz, H., Capasso, E., Lilley, M., Frost, M. & Jenkins, S.R., 2011. Temporal differences across a bio-geographical boundary reveal slow response of sub-littoral benthos to climate change. Marine Ecology Progress Series, 423, 69-82. DOI https://doi.org/10.3354/meps08963

    69. Hiscock, K. 2000. Circalittoral caves and overhangs. 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/10

    70. Hiscock, K. & Wilson, E. 2007. Metridium senile Plumose anemone. 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/species/detail/1185

    71. 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.

    72. Hiscock, K., 1985. Littoral and sublittoral monitoring in the Isles of Scilly. September 22nd to 29th, 1984. Nature Conservancy Council, Peterborough, CSD Report, no. 562., Field Studies Council Oil Pollution Research Unit, Pembroke.

    73. Hiscock, K., Sharrock, S., Highfield, J. & Snelling, D., 2010. Colonization of an artificial reef in south-west England—ex-HMS ‘Scylla’. Journal of the Marine Biological Association of the United Kingdom, 90 (1), 69-94. DOI https://doi.org/10.1017/S0025315409991457

    74. Hiscock, K., Southward, A., Tittley, I. & Hawkins, S., 2004. Effects of changing temperature on benthic marine life in Britain and Ireland. Aquatic Conservation: Marine and Freshwater Ecosystems, 14 (4), 333-362.

    75. Hoare, R. & Hiscock, K., 1974. An ecological survey of the rocky coast adjacent to the effluent of a bromine extraction plant. Estuarine and Coastal Marine Science, 2 (4), 329-348.

    76. Holme, N.A. & Wilson, J.B., 1985. Faunas associated with longitudinal furrows and sand ribbons in a tide-swept area in the English Channel. Journal of the Marine Biological Association of the United Kingdom, 65, 1051-1072.

    77. Holt, T.J., Jones, D.R., Hawkins, S.J. & Hartnoll, R.G., 1995. The sensitivity of marine communities to man induced change - a scoping report. Countryside Council for Wales, Bangor, Contract Science Report, no. 65.

    78. Hopkins, S.H., 1962. Distribution of species of Cliona (boring sponge) on the Eastern Shore of Virginia in relation to salinity. Chesapeake Science, 3 (2), 121-124.

    79. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

    80. Hulathduwa, Y.D. & Brown, K.M., 2006. Relative importance of hydrocarbon pollutants, salinity and tidal height in colonization of oyster reefs. Marine Environmental Research, 62 (4), 301-314.

    81. Jenkins, S.R., Beukers-Stewart, B.D. & Brand, A.R., 2001. Impact of scallop dredging on benthic megafauna: a comparison of damage levels in captured and non-captured organisms. Marine Ecology Progress Series, 215, 297-301. DOI https://doi.org/10.3354/meps215297

    82. JNCC (Joint Nature Conservation Committee), 2022.  The Marine Habitat Classification for Britain and Ireland Version 22.04. [Date accessed]. Available from: https://mhc.jncc.gov.uk/

    83. Johnston, E.L. & Roberts, D.A., 2009. Contaminants reduce the richness and evenness of marine communities: a review and meta-analysis. Environmental Pollution, 157 (6), 1745-1752.

    84. Kaiser, M.J., Ramsay, K., Richardson, C.A., Spence, F.E. & Brand, A.R., 2000. Chronic fishing disturbance has changed shelf sea benthic community structure. Journal of Animal Ecology, 69, 494-503.

    85. Kayser, H., 1990. Bioaccumulation and transfer of cadmium in marine diatoms, Bryozoa, and Kamptozoa. In Oceanic processes in marine pollution, vol. 6. Physical and chemical processes: transport and transformation (ed. D.J. Baumgartner & I.W. Duedall), pp. 99-106. Florida: R.E. Krieger Publishing Co.

    86. Kelly, M., Owen, P. & Pantazis, P., 2001. The commercial potential of the common sea urchin Echinus esculentus from the west coast of Scotland. Hydrobiologia, 465 (1-3), 85-94.

    87. Kinne, O. (ed.), 1984. Marine Ecology: A Comprehensive, Integrated Treatise on Life in Oceans and Coastal Waters.Vol. V. Ocean Management Part 3: Pollution and Protection of the Seas - Radioactive Materials, Heavy Metals and Oil. Chichester: John Wiley & Sons.

    88. Knight-Jones, E.W. & Nelson-Smith, A., 1977. Sublittoral transects in the Menai Straits and Milford Haven. In Biology of benthic organisms (ed. B.F. Keegan, P. O Ceidigh & P.J.S. Broaden), pp. 379-390. Oxford: Pergamon Press.

    89. Kott, P., 1985. The Australian Ascidiacea. Part I, Phlebobranchia and Stolidobranchia. Memoirs of the Queensland Museum, 23, 1-440.

    90. Koukouras, A., 2010. Check-list of marine species from Greece. Aristotle University of Thessaloniki. Assembled in the framework of the EU FP7 PESI project

    91. Kukliński, P. & Barnes, D.K., 2008. Structure of intertidal and subtidal assemblages in Arctic vs temperate boulder shores. Polish Polar Research, 29 (3), 203-218. 

    92. Kupriyanova, E.K. & Badyaev, A.V., 1998. Ecological correlates of arctic Serpulidae (Annelida, Polychaeta) distributions. Ophelia, 49 (3), 181-193.

    93. Lawrence, J.M., 1975. On the relationships between marine plants and sea urchins. Oceanography and Marine Biology: An Annual Review, 13, 213-286.

    94. Lengyel, N.L., Collie, J.S. & Valentine, P.C., 2009. The invasive colonial ascidian Didemnum vexillum on Georges Bank - Ecological effects and genetic identification. Aquatic Invasions, 4(1), 143-152.

    95. Lewis, G.A. & Nichols, D., 1979a. Colonization of an artificial reef by the sea-urchin Echinus esculentus. Progress in Underwater Science, 4, 189-195.

    96. Lyster, I., 1965. The salinity tolerance of polychaete larvae. Journal of Animal Ecology, 34 (3), 517-527.

    97. MacBride, E.W., 1914. Textbook of Embryology, Vol. I, Invertebrata. London: MacMillan & Co.

    98. Martin, J.P., Garese, A., Sar, A. & Acuña, F.H., 2015. Fouling community dominated by Metridium senile (Cnidaria: Anthozoa: Actiniaria) in Bahía San Julián (southern Patagonia, Argentina). Scientia Marina, 79 (2), 211-221.

    99. Matthews, A., 1917. The development of Alcyonium digitatum with some notes on early colony formation. Quarterly Journal of Microscopial Science, 62, 43-94.

    100. Migliaccio, O., Castellano, I., Romano, G. & Palumbo, A., 2014. Stress response to cadmium and manganese in Paracentrotus lividus developing embryos is mediated by nitric oxide. Aquatic Toxicology, 156, 125-134. DOI https://doi.org/10.1016/j.aquatox.2014.08.007

    101. Molnar, J.L., Gamboa, R.L., Revenga, C. & Spalding, M.D., 2008. Assessing the global threat of invasive species to marine biodiversity. Frontiers in Ecology and the Environment, 6 (9), 485-492.

    102. Moore, H.B., 1937. Marine Fauna of the Isle of Man. Liverpool University Press.

    103. Moore, P.G., 1977a. Inorganic particulate suspensions in the sea and their effects on marine animals. Oceanography and Marine Biology: An Annual Review, 15, 225-363.

    104. NBN, 2015. National Biodiversity Network 2015(20/05/2015). https://data.nbn.org.uk/

    105. Neish, A.H. 2007. Pachymatisma johnstonia A sponge. 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/species/detail/1885

    106. Nelson, M.L. & Craig, S.F., 2011. Role of the sea anemone Metridium senile in structuring a developing subtidal fouling community. Marine Ecology Progress Series, 421, 139-149.

    107. Nichols, D., 1979. A nationwide survey of the British Sea Urchin Echinus esculentus. Progress in Underwater Science, 4, 161-187.

    108. Nichols, D., 1984. An investigation of the population dynamics of the common edible sea urchin (Echinus esculentus L.) in relation to species conservation management. Report to Department of the Environment and Nature Conservancy Council from the Department of Biological Sciences, University of Exeter.

    109. Piscitelli, M., Corriero, G., Gaino, E. & Uriz, M.J., 2011. Reproductive cycles of the sympatric excavating sponges Cliona celata and Cliona viridis in the Mediterranean Sea. Invertebrate Biology, 130 (1), 1-10.

    110. Porter, J., 2012. Seasearch Guide to Bryozoans and Hydroids of Britain and Ireland.   Ross-on-Wye: Marine Conservation Society.

    111. Powell, N., 1971. The marine bryozoa near the Panama Canal. Bulletin of Marine Science, 21 (3), 766-778.

    112. Powell-Jennings, C. & Callaway, R., 2018. The invasive, non-native slipper limpet Crepidula fornicata is poorly adapted to sediment burial. Marine Pollution Bulletin, 130, 95-104. DOI https://doi.org/10.1016/j.marpolbul.2018.03.006

    113. Preston, J., Fabra, M., Helmer, L., Johnson, E., Harris-Scott, E. & Hendy, I.W., 2020. Interactions of larval dynamics and substrate preference have ecological significance for benthic biodiversity and Ostrea edulis Linnaeus, 1758 in the presence of Crepidula fornicata. Aquatic Conservation: Marine and Freshwater Ecosystems, 30 (11), 2133-2149. DOI https://doi.org/10.1002/aqc.3446

    114. Price, J.H., Irvine, D.E. & Farnham, W.F., 1980. The shore environment. Volume 2: Ecosystems. London Academic Press.

    115. Ramos, M., 2010. IBERFAUNA. The Iberian Fauna Databank, 2015(2015/12/21). http://iberfauna.mncn.csic.es/

    116. 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. DOI https://doi.org/10.1016/S0025-326X(00)00119-3

    117. Rosenberg, R., Hellman, B. & Johansson, B., 1991. Hypoxic tolerance of marine benthic fauna. Marine Ecology Progress Series, 79, 127-131. DOI https://dx.doi.org/10.3354/meps079127

    118. Ryland, J.S. & De Putron, S., 1998. An appraisal of the effects of the Sea Empress oil spillage on sensitive invertebrate communities. Countryside Council for Wales Sea Empress Contract Report, no. 285, 97pp.

    119. Ryland, J.S., 1970. Bryozoans. London: Hutchinson University Library.

    120. Ryland, J.S., 1976. Physiology and ecology of marine bryozoans. Advances in Marine Biology, 14, 285-443.

    121. Sassaman, C. & Mangum, C., 1970. Patterns of temperature adaptation in North American Atlantic coastal actinians. Marine Biology, 7 (2), 123-130.

    122. SeaTemperature, 2015. World Sea Temperatures. (15/10/2015). http://www.seatemperature.org/

    123. Segrove, F., 1941. The development of the serpulid Pomatoceros triqueta L. Quarterly Journal of Microscopical Science, 82, 467-540.

    124. Shumway, S.E., 1978. Activity and respiration of the sea anemone, Metridium senile (L.) exposed to salinity fluctuations. Journal of Experimental Marine Biology and Ecology, 33, 85-92.

    125. Smith, J.E. (ed.), 1968. 'Torrey Canyon'. Pollution and marine life. Cambridge: Cambridge University Press.

    126. Snowden, E. 2007. Cliona celata A sponge. 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/species/detail/2188

    127. Soule, D.F. & Soule, J.D., 2002. The eastern Pacific Parasmittina trispinosa complex (Bryozoa, Cheilostomatida): new and previously described species. Hancock Institute for Marine Studies, University of Southern California.

    128. Soule, D.F. & Soule, J.D., 1979. Bryozoa (Ectoprocta). In Hart, C.W. & Fuller, S.L.H. (eds), Pollution ecology of estuarine invertebrates. New York: Academic Press, pp. 35-76.

    129. Stebbing, A.R.D., 1971a. Growth of Flustra foliacea (Bryozoa). Marine Biology, 9, 267-273.

    130. Stephenson, T.A., 1935. The British Sea Anemones, vol. 2. London: Ray Society.

    131. Stock, J.H., 1988. Lamippidae (Copepoda : Siphonostomatoida) parasitic in Alcyonium. Journal of the Marine Biological Association of the United Kingdom, 68 (2), 351-359.

    132. Svane, I. & Groendahl, F., 1988. Epibioses of Gullmarsfjorden: an underwater stereophotographical transect analysis in comparison with the investigations of Gislen in 1926-29. Ophelia, 28, 95-110.

    133. Thomas, J.G., 1940. Pomatoceros, Sabella and Amphitrite. LMBC Memoirs on typical British marine plants and animals no.33. University Press of Liverpool. Liverpool

    134. Tillin, H.M., Kessel, C., Sewell, J., Wood, C.A. & Bishop, J.D.D., 2020. Assessing the impact of key Marine Invasive Non-Native Species on Welsh MPA habitat features, fisheries and aquaculture. NRW Evidence Report. Report No: 454. Natural Resources Wales, Bangor, 260 pp. Available from https://naturalresourceswales.gov.uk/media/696519/assessing-the-impact-of-key-marine-invasive-non-native-species-on-welsh-mpa-habitat-features-fisheries-and-aquaculture.pdf

    135. Tranter, P.R.G., Nicholson, D.N. & Kinchington, D., 1982. A description of spawning and post-gastrula development of the cool temperate coral, Caryophyllia smithi. Journal of the Marine Biological Association of the United Kingdom, 62, 845-854. DOI https://doi.org/10.1017/s0025315400044106

    136. Tyler, P.A. & Young, C.M., 1998. Temperature and pressure tolerances in dispersal stages of the genus Echinus (Echinodermata: Echinoidea): prerequisites for deep sea invasion and speciation. Deep Sea Research II, 45 (1), 253-277. DOI https://doi.org/10.1016/S0967-0645(97)00091-X

    137. Tyler-Walters, H., 2008. Echinus esculentus. Edible sea urchin. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. [cited 26/01/16]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/species/detail/1311

    138. Tyler-Walters, H. & Ballerstedt, S., 2007. Flustra foliacea Hornwrack. 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/species/detail/1609

    139. Tyler-Walters, H., 2008b. Corallina officinalis Coral weed. 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/species/detail/1364

    140. Ursin, E., 1960. A quantitative investigation of the echinoderm fauna of the central North Sea. Meddelelser fra Danmark Fiskeri-og-Havundersogelser, 2 (24), pp. 204.

    141. Veale, L.O., Hill, A.S., Hawkins, S.J. & Brand, A.R., 2000. Effects of long term physical disturbance by scallop fishing on subtidal epifaunal assemblages and habitats. Marine Biology, 137, 325-337.

    142. Walsh, P. & Somero, G., 1981. Temperature adaptation in sea anemones: physiological and biochemical variability in geographically separate populations of Metridium senile. Marine Biology, 62 (1), 25-34.

    143. Warburton, F.E., 1966. The behavior of sponge larvae. Ecological Society of America, 47 (4), 672-674.

    144. Whomersley, P. & Picken, G., 2003. Long-term dynamics of fouling communities found on offshore installations in the North Sea. Journal of the Marine Biological Association of the UK, 83 (5), 897-901.

    145. Williams, R., 1997. Actinothoe sphyrodeta (Cnidaria, Actiniaria): the first records from Portugal and the Mediterranean Sea. Journal of the Marine Biological Association of the United Kingdom, 77 (1), 245-248.

    146. Wood, C., 2007. Seasearch Observer's Guide to Marine Life of Britain and Ireland,  Ross-on-Wye: Marine Conservation Society.

    147. Wood, E. (ed.), 1988. Sea Life of Britain and Ireland. Marine Conservation Society. IMMEL Publishing, London

    148. Wood. C., 2005. Seasearch guide to sea anemones and corals of Britain and Ireland. Ross-on-Wye: Marine Conservation Society.

    149. Zintzen, V., Norro, A., Massin, C. & Mallefet, J., 2008a. Temporal variation of Tubularia indivisa (Cnidaria, Tubulariidae) and associated epizoites on artificial habitat communities in the North Sea. Marine Biology, 153 (3), 405-420.

    Citation

    This review can be cited as:

    Stamp, T.E., Lloyd, K.A., & Watson, A., 2023. Molgula manhattensis with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock. 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. [cited 28-03-2024]. Available from: https://marlin.ac.uk/habitat/detail/1063

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    Last Updated: 04/12/2023