The Marine Life Information Network

Temperature increase (local)

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

Evidence

CR.MCR.EcCr.CarSp is distributed across the west coast of Scotland and south west coast of Ireland. Sea surface temperature across this distribution ranges from northern to southern Sea Surface Temperature (SST) of 8-16°C in summer and 6-13°C in winter (Beszczynska-Möller & Dye, 2013). 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). Spirobranchus triqueter is recorded as abundant in sub-tidal habitats of Trondheimsfjord (63°N) (Kukliński & Barnes, 2008), no survey reports could be found further north. The most southerly records are from the Iberian peninsula, Spain (Ramos, 2010) as well from the Alexandria coast of Egypt, Mediterranean Sea (Sarah, 2010). Across this latitudinal gradient Spirobranchus triqueter is likely to experience a range of temperatures from approximately 5-28°C (Seatemperature, 2015), and is therefore unlikely to be affected at the pressure benchmark. Bishop (1985) suggested that Echinus esculentus cannot tolerate high temperatures for prolonged periods due to increased respiration rate and resultant metabolic stress. Ursin (1960) reported Echinus esculentus occurred at temperatures between 0-18°C in Limfjord, Denmark. Bishop (1985) noted that gametogenesis occurred at 11-19°C however, continued exposure to 19°C disrupted gametogenesis. Embryos and larvae developed abnormally after 24hr exposure to 15°C but normally at 4, 7 and 11°C (Tyler & Young 1998). Mature examples of Caryophyllia smithii are recorded in Greece (Koukouras, 2010), and are therefore unlikely to be physically affected at the benchmark. However, Tranter et al. (1982) suggested Caryophyllia smithii reproduction was cued by seasonal increases in seawater temperature. Therefore unseasonal increases in temperature may disrupt natural reproductive processes and negatively influence recruitment patterns.

Seawater temperature is positively correlated to sponge growth (Duckworth & Peters, 2013). Duckworth & Peters (2013) demonstrated that an increase in water temperature to 26 and 31°C had no detectable effect on boring activity of Cliona celata. Whereas as cold winter temperatures (<5°C) can cause boring activity to cease, the incurrent papillae to withdraw and the excurrent papillae constrict (Fell et al., 1984; Carver et al., 2010). Indicating cold temperatures are more limiting to Cliona celata than hot. Piscitelli et al. (2011) observed an annual peak in reproductive activity in April-May from individuals in the Mediterranean, and suggested this was a result of a sharp seasonal increase in water temperature. Which suggests variable temperatures could affect larval recruitment processes, but otherwise not otherwise negatively affect Cliona celata.

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

Temperature decrease (local)

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

Evidence

CR.MCR.EcCr.CarSp is distributed across the west coast of Scotland and south west coast of Ireland. Sea surface temperature across this distribution ranges from northern to southern Sea Surface Temperature (SST) of 8-16°C in summer and 6-13°C in winter (Beszczynska-Möller & Dye, 2013). 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). Across this latitudinal gradient both species are likely to experience a range of temperatures from approximately 5-18°C. 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). Echinus esculentus has been recorded from the Murmansk Coast, Russia. Due to the high latitude at which Echinus esculentus can occur it is unlikely to be affected at the pressure benchmark. 

Spirobranchus triqueter is described as a temperate species by Kupriyanova & Badyaev (1998). Spirobranchus triqueter is recorded as abundant in sub-tidal habitats of Trondheimsfjord (63°N) (Kukliński & Barnes, 2008), no survey reports could be found further north. Averaged across several years the lowest winter temperature within Trondheimsfjord is 4.9°C (Seatemperature, 2015). Below 7°C Spirobranchus triqueter is unable to build calcareous tubes (Thomas, 1940). Mature adults may survive a decrease at the pressure benchmark however larvae may not be able to attach to the substate (Riley & Ballerstedt, 2005) if a temperature decrease co-occurred with cold winter temperatures in the UK. However, settlement is reportedly low within winter (see resilience section) and, therefore, the effects on recruitment are likely to be minor. However, Caryophyllia smithii has a northern range limit in the Shetland isles and Southern Norway (NBN, 2015) and may, therefore, be negatively affected by cold temperatures in Northern examples of this biotope.

Seawater temperature is positively correlated to sponge growth (Duckworth & Peters, 2013). Duckworth & Peters (2013) demonstrated that an increase in water temperature to 26 and 31°C had no detectable effect on boring activity. Whereas as cold winter temperatures (<5°C) can cause boring activity to cease, the incurrent papillae to withdraw and the excurrent papillae constrict (Fell et al., 1984; Carver et al., 2010). Indicating cold temperatures are more limiting to Cliona celata than hot. Piscitelli et al. (2011) observed an annual peak in reproductive activity in April-May from individuals in the Mediterranean, and suggested this was a result of a sharp seasonal increase in water temperature. Which suggests variable temperatures could affect larval recruitment processes, but not otherwise affect Cliona celata negatively.

Sensitivity assessment. Alcyonium digitatum, Echinus esculentus have northern/boreal distributions and are unlikely to be affected at the benchmark level. Spirobranchus triqueter is unable to build calcareous tubes at low temperatures, however, during winter, this is unlikely to have any significant effects on recruitment. In addition, the depth of the biotope probably protects it from short-term acute decreases in temperature. The important characterizing Caryophyllia smithii is close to its northern distribution limit within the British Isles and a decrease at the benchmark level may result in some mortality in northern examples of the biotope.  Therefore, resistance is therefore ‘Medium’, resilience is ‘High’ and sensitivity is ‘Low’.

Salinity increase (local)

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

Evidence

Lyster (1965) tested the tolerance of Spirobranchus triqueter larvae to various hyper and hypo salinity treatments. Larvae were placed in cultures ranging from 0-90‰ and notes were made on the time taken for larvae to die or begin displaying abnormal behaviour. Spirobranchus triqueter larvae were tolerant of salinities ranging from 20-50‰, above 50‰ caused high mortality. Spirobranchus triqueter is therefore unlikely to be affected at the pressure benchmark.

Echinoderms are generally stenohaline and possess no osmoregulatory organ (Boolootian, 1966). Therefore an increase in salinity may cause Echinus esculentus mortality. 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.

CR.MCR.EcCr.CarSp is restricted to full salinity (Connor et al., 2004), it therefore seems likely that an increase in salinity to >40‰ may cause a decline in the abundance of characterizing species. Furthermore a reduction in Echinus esculentus may cause an increase in red algae growth, which would change the character of the biotope.

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

Salinity decrease (local)

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

Evidence

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 23^rd 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).

Echinoderms are generally unable to tolerate low salinity (stenohaline) and possess no osmoregulatory organ (Boolootian, 1966). At low salinity urchins gain weight, and the epidermis loses its pigment as patches are destroyed; prolonged exposure is fatal. However, within Echinus esculentus there is some evidence to suggest intracellular regulation of osmotic pressure due to increased amino acid concentrations. Furthermore as highlighted the Marine Nature Conservation Review (MNCR) records of 23^rd Oct 2014 show Echinus esculentus is found within a number of variable and reduced salinity biotopes, e.g. IR.LIR.KVS.SlatPsaVS.

Lyster (1965) tested the tolerance of Spirobranchus triqueter larvae to various hyper and hypo salinity treatments. Larvae were placed in cultures ranging from 0-90‰ and notes were made on the time taken for larvae to die or begin displaying abnormal behaviour. Spirobranchus triqueter larvae can survive very well in salinities down to 20‰, and can tolerate salinities down to 10‰. Adults are tolerant of salinities as low as 3‰, and can be found in areas were salinity ranges from 18-23‰ (Alexander et al., 1935).

Carver et al. (2010) suggested Cliona celata can function efficiently in salinities as low as 20‰, and can withstand exposure to 15‰ for brief periods, but prevailing salinities less than 10–15‰ are likely to be lethal (Hartman 1958, Hopkins 1962).

Sensitivity review. CR.MCR.EcCr.CarSp are recorded exclusively in full marine conditions (30-40 ‰) (Connor et al., 2004). The lack of records within “Reduced” salinity (18-30‰) suggests the community would not persist/be recognisable if salinity was reduced. Spirobranchus triqueter is likely to be able to tolerate reduced salinity, Records from the MNCR suggest Alcyonium digitatum, Caryophyllia smithii & Echinus esculentus can occur in reduced salinity habitats, however the general evidence suggests that these species would decrease in abundance. Resistance has been assessed as ‘Low’, Resilience as ‘Medium’. Sensitivity has been assessed as ‘Medium’.

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

Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueter and sponges are suspension feeders, relying on water currents to supply food (Hiscock, 1983). These taxa therefore thrive in conditions of vigorous water flow e.g. around Orkney and St Abbs, Scotland, where Alcyonium digitatum dominated biotopes may experience tidal currents of 3 and 4 knots (approximately 1.5 m/sec) during spring tides (Kluijver, 1993). Caryophyllia smithii in particular is described as favouring sites with high tidal flow (Bell & Turner, 2000; Wood, 2005).

Bell (2002) documented Cliona celata regeneration, following artificial damage, at two sites within Lough Hyne, Ireland. The study demonstrated 80% of Cliona celata were fully regenerated at the site which received high water flow (2m/sec) within 100 days, whereas no Cliona celata found in slower water velocities (0.1 m/sec) had fully regenerated. The author suggested an increase in water flow may increase food availability and therefore be of benefit to Cliona celata, whereas slow water flow (0.1 m/sec) may limit food supply and therefore slow regeneration if damaged.

Spirobranchus triqueter has been recorded in areas with very sheltered to exposed water flow rates (Price et al., 1980). Wood (1988) observed Spirobranchus sp. in strong tidal streams and Hiscock (1983) found that in strong tidal streams or strong wave action where abrasion occurs, fast growing species such as Spirobranchus triqueter occur.

Echinus esculentus occurred in kelp beds on the west coast of Scotland in currents of about 0.5 m/sec. Outside the beds specimens were occasionally seen being rolled by the current (Comely & Ansell, 1988), which may have been up to 1.4 m/sec. Urchins are removed from the stipe of kelps by wave and current action. Echinus esculentus are also displaced by storm action. After disturbance Echinus esculentus migrates up the shore, an adaptation to being washed to deeper water by wave action (Lewis & Nichols, 1979). Therefore, increased water flow may remove the population from the affected area; probably to deeper water although individuals would probably not be killed in the process and could recolonize the area quickly.

Sensitivity assessment. CR.MCR.EcCr.CarSp is recorded from moderately strong to negligible tidal currents (<1.5m/sec) (Connor et al., 2004). The abundance of the characterizing species may be affected by a large scale increase/decrease in water flow (e.g. >1m/sec), however a change in tidal velocity of 0.1-0.2 m/s is not likely to have a significant effect. Resistance has been assessed as ‘High’, resilience has been assessed as ‘High’. Sensitivity has been assessed as ‘Not sensitive’.

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.MCR.EcCr.FaAlCr.Adig, CR.MCR.EcCr.FaAlCr.Pom & CR.MCR.EcCr.FaAlCr.Sec, which are restricted to fully subtidal/circalittoral conditions-The pressure benchmark is relevant only to littoral and shallow sublittoral fringe biotopes.

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.MCR.EcCr.CarSp is recorded from extremely wave exposed-moderately wave exposed sites (Connor et al., 2004). Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueteri and sponges are suspension feeders relying on water currents to supply food. These taxa therefore thrive in conditions of vigorous water flow.

Echinus esculentus occurred in kelp beds on the west coast of Scotland in currents of about 0.5 m/sec. Outside the beds specimens were occasionally seen being rolled by the current (Comely & Ansell, 1988), which may have been up to 1.4 m/sec. Urchins are removed from the stipe of kelps by wave and current action. Echinus esculentus are also displaced by storm action. After disturbance Echinus esculentus migrates up the shore, an adaptation to being washed to deeper water by wave action (Lewis & Nichols, 1979). Keith Hiscock (pers. comm.) reported Echinus esculentus occurred in significant numbers as shallow as 15m below low water at the extremely wave exposed site of Rockall, Scotland. Therefore, localised increases in wave height may remove the population from the affected area; probably to deeper water although individuals would probably not be killed in the process and could recolonize the area quickly.

Sensitivity assessment. Wave action is a fundamental environmental variable controlling the biological community of sublittoral biotopes. A large and significant change in wave height may fundamentally alter the character of CR.MCR.EcCr.CarSp. However a change in near shore significant wave height of 3-5% is not likely to have a significant effect on the biological community. Resistance has been assessed as ‘High’, resilience has been assessed as ‘High’. Sensitivity has been assessed as ‘Not sensitive’.

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.

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.

Based on the available evidence for several species Bryan (1984) suggested that polychaetes are fairly resistant to heavy metals.

Little is known about the effects of heavy metals on echinoderms. Bryan (1984) reported that early work had shown that echinoderm larvae were sensitive to heavy metals contamination, for example Migliaccio et al. (2014) reported exposure of Paracentrotus lividis larvae to increased levels of cadmium and manganese caused abnormal larval development and skeletal malformations. Kinne (1984) reported developmental disturbances in Echinus esculentus exposed to waters containing 25 µg / l of copper (Cu).

At the time of writing no information could be found relating to the sensitivity of Caryophyllia smithii to heavy metal contamination.

Cliona celata is known to be a hardy sponge, tolerant to a number of abiotic stressors (Duckworth & Peters, 2013), however at the time of writing no information could be gathered concerning the effects of heavy metal contamination of Cliona celata.

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.MCR.EcCr.CarSp 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).

Large numbers of dead polychaetes and other fauna were washed up at Rulosquet marsh near Isle de Grand following the Amoco Cadiz oil spill in 1978 (Cross et al., 1978). However, no information was found relating to Spirobranchus triqueter in particular.

Echinus esculentus is subtidal and unlikely to be directly exposed to oil spills. However, as with the ‘Prestige’ oil spill rough seas can cause mixing with the oil and the seawater, and therefore sub-tidal habitats can be affected by the oil spill. Castège et al., (2014) recorded the recovery of rocky shore communities following the Prestige oil spill which impacted the French Atlantic coast. Rough weather at the time of the spill increased mixing between the oil and seawater, causing sub-tidal communities/habitats to be affected. The urchin Echinus esculentus was reported absent after the oil spill however returned after 2-5 years. Large numbers of dead Echinus esculentus were found between 5.5 and 14.5 m in the vicinity of Sennen cove, presumably due to a combination of wave exposure and heavy spraying of dispersants following the ‘Torrey canyon’ oil spill (Smith 1968). Smith (1968) also demonstrated that 0.5 -1ppm of the detergent BP1002 resulted in developmental abnormalities in its echinopluteus larvae. Echinus esculentus populations in the vicinity of an oil terminal in A Coruna Bay, Spain, showed developmental abnormalities in the skeleton. The tissues contained high levels of aliphatic hydrocarbons, naphthalenes, pesticides and heavy metals (Zn, Hg, Cd, Pb, and Cu) (Gomez & Miguez-Rodriguez 1999).

Cliona celata is known to be a hardy sponge, tolerant to a number of abiotic stressors (Duckworth & Peters, 2013). Bustamante et al. (2010) suggested intertidal Cliona celata were negatively affected by the Prestige’ oil spill. However at the time of writing no other information could be gathered on the effects of oil contamination on Cliona celata.

At the time of writing no information could be found relating to the sensitivity of Caryophyllia smithii to hydrocarbon contamination.

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 presented where available.

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).

Large numbers of dead Echinus esculentus were found between 5.5 and 14.5 m in the vicinity of Sennen, presumably due to a combination of wave exposure and heavy spraying of dispersants in that area following the Torrey Canyon oil spill (Smith 1968). Smith (1968) also demonstrated that 0.5 -1ppm of the detergent BP1002 resulted in developmental abnormalities in echinopluteus larvae of Echinus esculentus. Echinus esculentus populations in the vicinity of an oil terminal in A Coruna Bay, Spain, showed developmental abnormalities in the skeleton. The tissues contained high levels of aliphatic hydrocarbons, naphthalenes, pesticides and heavy metals (Zn, Hg, Cd, Pb, and Cu) (Gomez & Miguez-Rodriguez 1999).

At the time of writing no information could be found relating to the sensitivity of Caryophyllia smithii to heavy metal contamination.

Cliona celata is known to be a hardy sponge, tolerant to a number of abiotic stressors (Duckworth & Peters, 2013), however at the time of writing no information could be gathered concerning the effects of synthetic compound contamination of Cliona celata.

Radionuclide contamination

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

Evidence

'No Evidence'.

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.

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

There is anecdotal evidence to suggest that Alcyonium digitatum, Caryophyllia smithii and Echinus esculentus are sensitive to hypoxic events.

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^-1, or even less (Herreid, 1980; Rosenberg et al., 1991; Diaz & Rosenberg, 1995).

Alcyonium digitatum mainly inhabits environments in which the oxygen concentration usually exceeds 5 ml l-1 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. Alcyonium sp. and Bryozoans were also in an impoverished state. Caryophyllia smithii were also in a contracted state, apparently dead, and with Echinus esculentus were the worst affected species during the bloom. 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 (Dennis, 1979).

CR.MCR.EcCr.CarSp is recorded from negligible-weak tidal streams (<0.5 m/sec) but can occur at wave exposed sites (Connor et al., 2004). Therefore, water movement (through wave action and/or tidal flow) could potentially cause mixing with surrounding oxygenated water (Dennis, 1979) and may therefore decrease the effects of de-oxygenation rapidly.

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

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.

Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueter and sponges are suspension feeders. Nutrient enrichment of coastal waters that enhances the population of phytoplankton may be beneficial to Alcyonium digitatum, Caryophyllia smithii and Spirobranchus triqueter in terms of an increased food supply but the effects are uncertain (Hartnoll, 1998). The survival of Alcyonium digitatum, Caryophyllia smithii and Spirobranchus triqueter 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).

Cliona celata is considered a hardy sponge, tolerant of environmental stressors such as high nutrient loads, low salinity, and large temperature variation (Duckworth & Peters, 2013). Carballo et al. (1994) suggested Cliona celata was a good indicator species of pollution, and noted it’s abundance at polluted sites which receive sewage discharge within Algeciras Bay, Spain.

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.

Organic enrichment

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

Evidence

Alcyonium digitatum, Caryophyllia smithii and Spirobranchus triqueter are suspension feeders of phytoplankton and zooplankton. Organic enrichment of coastal waters that enhances the population of phytoplankton may be beneficial to Alcyonium digitatum, Caryophyllia smithii and Spirobranchus triqueter in terms of an increased food supply but the effects are uncertain (Hartnoll, 1998). The survival of Alcyonium digitatum, Caryophyllia smithii and Spirobranchus triqueter 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).

Cliona celata is considered a hardy sponge, tolerant of environmental stressors such as high nutrient loads, low salinity, and large temperature variation (Duckworth & Peters, 2013). Carballo et al. (1994) suggested Cliona celata was a good indicator species of pollution, and noted it’s abundance at polluted sites which receive sewage discharge within Algeciras Bay, Spain.

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. Organic 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.

Sensitivity assessment. Organic enrichment is not likely to directly negatively affect the characterizing species within this biotope, however chronic organic enrichment may cause secondary effects such as hypoxia (refer to de-oxygenation pressure). Resistance has been assessed as ‘Low’, Resilience as ‘Medium’. Sensitivity as ‘Medium’.

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.

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’.

Physical change (to another sediment type)

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

Evidence

Not relevant

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.

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.MCR.EcCr.CarSp is a subtidal 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.

Alcyonium digitatum, Caryophyllia smithii, Echinus esculentus and Spirobranchus triqueter are sedentary or slow moving species that might be expected to suffer from the effects of dredging. 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.

Species with fragile tests, such as Echinus esculentus were reported to suffer badly as a result of scallop or queen scallop dredging (Bradshaw et al., 2000; Hall-Spencer & Moore, 2000). Kaiser et al. (2000) reported that Echinus esculentus were less abundant in areas subject to high trawling disturbance in the Irish Sea. Jenkins et al. (2001) conducted experimental scallop trawling in the North Irish sea and recorded the damage caused to several conspicuous megafauna species, both when caught as bi-catch and when left on the seabed. The authors predicted 16.4% of Echinus esculentus were crushed/dead, 29.3% would have >50% spine loss/minor cracks, 1.1% would have <50% spine loss and the remaining 53.3% would be in good condition. Sea urchins can rapidly regenerate spines, e.g. Psammechinus miliaris were found to re-grow all spines within a period of 2 months (Hobson, 1930).  The trawling examples mentioned above were conducted on sedimentary habitats and thus the evidence is not directly relevant to the rock based biotopes- CR.MCR.EcCr.CarSp however does indicate the likely effects of abrasion on Echinus esculentus.

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.

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.

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

Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueter and sponges 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. 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.

Moore (1977) suggested that Echinus esculentus was unaffected by turbid conditions. Echinus esculentus is an important grazer of red macro-algae within CR.MCR.EcCr. Increased turbidity and resultant reduced light penetration is likely to negatively affect algal growth. However, Echinus esculentus can feed on alternative prey, detritus or dissolved organic material (Lawrence, 1975, Comely & Ansell, 1988).

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.

According to Bacescu (1972), sabellids are accustomed to turbidity and silt. Spirobranchus triqueter has also recently been recorded by De Kluijver (1993) from Scotland in the aphotic zone, indicating that the species would not be sensitive to an increase in turbidity.

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

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

Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueter and sponges are sessile and thus would be unable to avoid the deposition of a smothering layer of sediment. Some Alcyonium digitatum colonies can attain a height of up to 20 cm (Edwards, 2008), so would still be able to feed in the event of sediment deposition. However, Spirobranchus triqueter is an encrusting species and would thus likely be smothered, and depending on sediment retention could block larval settlement. Cliona celata can either have a boring life form (it bores into rock) or a massive form (grows ontop of rock). With the boring form only inhalant and exhalent papillae are visible just above the rock surface (Wood, 2007). The massive form has raised, rounded ridges with large specimens growing up to 1 m across and 50 cm high (Snowden, 2007). Haliclona viscosa is described as a cushion forming species, which forms a thick crust which may reach a diameter of 30-40 cm and a height of 1.5-5cm (Topsent, 1888). Pachymatisma johnstonia can reach up to 15 cm in diameter and height up to 10 cm (Neish, 2007).

Comely & Ansell (1988) recorded large Echinus esculentus from kelp beds on the west coast of Scotland in which the substratum was seasonally covered with "high levels" of silt. This suggests that Echinus esculentus is unlikely to be killed by smothering, however, smaller specimens and juveniles may be less resistant. A layer of sediment may interfere with larval settlement.  If retained within the host biotope for extended periods a layer of 5cm of the sediment may negatively affect successive recruitment events.

Caryophyllia smithii is small (approx. <3 cm height from the seabed) and would therefore likely be inundated in a “light” sedimentation event. However Bell & Turner (2000) reported Caryophyllia smithii was abundant at sites of “moderate” sedimentation (7mm ± 0.5mm) in Lough Hyne. It is therefore likely that Caryophyllia smithii would be resistant to periodic sedimentation. If 5cm of sediment were removed rapidly, via tidal currents, Caryophyllia smithii would likely remain within the biotope.

It is likely that 5cm of deposited sediment may inundate a significant proportion of the encrusting community within CR.MCR.EcCr.CarSp. However, CR.MCR.EcCr.CarSp is recorded from moderately strong to negligible tidal currents (<1.5m/sec) (Connor et al., 2004). Therefore, water movement (through wave action and/or tidal flow) would be expected to clear 5 cm of deposited sediment within a few tidal cycles.

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

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

Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueter and sponges are sessile and thus would be unable to avoid the deposition of a smothering layer of sediment. Some Alcyonium digitatum colonies can attain a height of up to 20 cm (Edwards, 2008), so would still be able to feed in the event of sediment deposition. However, Spirobranchus triqueter is an encrusting species and would thus likely be smothered, and depending on sediment retention could block larval settlement. Cliona celata can either have a boring life form (it bores into rock) or a massive form (grows ontop of rock). With the boring form only inhalant and exhalent papillae are visible just above the rock surface (Wood, 2007). The massive form has raised, rounded ridges with large specimens growing up to 1 m across and 50 cm high (Snowden, 2007). Haliclona viscosa is described as a cushion forming species, which forms a thick crust which may reach a diameter of 30-40 cm and a height of 1.5-5cm (Topsent, 1888). Pachymatisma johnstonia can reach up to 15 cm in diameter and height up to 10 cm (Neish, 2007).

Comely & Ansell (1988) recorded large Echinus esculentus from kelp beds on the west coast of Scotland in which the substratum was seasonally covered with "high levels" of silt. This suggests that Echinus esculentus is unlikely to be killed by smothering, however, smaller specimens and juveniles may be less resistant. A layer of sediment may interfere with larval settlement.  If retained within the host biotope for extended periods a layer of 5cm of the sediment may negatively affect successive recruitment events.

Caryophyllia smithii is small (approx. <3 cm height from the seabed) and would therefore likely be inundated in a “light” sedimentation event. However Bell & Turner (2000) reported Caryophyllia smithii was abundant at sites of “moderate” sedimentation (7mm ± 0.5mm) in Lough Hyne. It is therefore likely that Caryophyllia smithii would be resistant to periodic sedimentation. If 5cm of sediment were removed rapidly, via tidal currents, Caryophyllia smithii would likely remain within the biotope.

It is likely that 30cm of deposited sediment may inundate a significant proportion of the encrusting community within CR.MCR.EcCr.CarSp. However, CR.MCR.EcCr.CarSp is recorded from moderately strong to negligible tidal currents (<1.5m/sec) (Connor et al., 2004). Therefore, water movement (through wave action and/or tidal flow) would be expected to clear deposited sediment.

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

Litter

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

Evidence

Not assessed.

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.

Underwater noise changes

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

Evidence

Alcyonium digitatum, Caryophyllia smithii, Echinus esculentus, Spirobranchus triqueter and sponges have no hearing perception but vibrations may cause an impact, however no studies exist to support an assessment (where relevant).

Introduction of light or shading

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

Evidence

There was no evidence to suggest that If exposed to anthropogenic light sources algal species would benefit. CR.MCR.EcCr.CarSp is also a circalittoral biotope and are thus by definition 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'.

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.

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’.

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'

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

Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueter and sponges are not commercially cultivated within the UK or likely to be translocated. Xavier et al. (2010) suggested Cliona celtata was in fact a species complex of potentially four morphologically indistinct species. Cliona celata is also a “pest” species within scallop mariculture (Carver et al., 2010), where Cliona celata bores into reared scallop shells. It is therefore conceivable that separate species within the Cliona celata species complex could be transported outside of it’s traditional range, however at the time of writing there is no evidence to suggest translocation would negatively affect CR.MCR.EcCr.CarSp. Echinus esculentus was identified by Kelly & Pantazis (2001) as a species suitable for culture for the urchin Roe industry. However, at the time of writing no evidence could be found to suggest that significant Echinus esculentus mariculture was present in the UK. If industrially cultivated it is feasible that Echinus esculentus individuals could be translocated. This pressure is therefore considered ‘Not relevant’ at the time of writing.

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’.

Introduction or spread of invasive non-indigenous species

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

Evidence

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 mats 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. 

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.MCR.EcCr.CarSp.

Sensitivity assessment. The circalittoral rock characterizing this biotope is likely to be unsuitable for the colonization by Crepidula fornicata due to the extremely wave exposed to 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). Crepidula has been recorded from the lower intertidal to ca 160 m in depth but is most common in the shallow subtidal above 50 m (Blanchard, 1997; Thieltges et al., 2003; Bohn et al., 2012, 2015; Hinz et al., 2011; OBIS, 2023; Tillin et al., 2020), therefore, colonization of Crepidula would be limited to low densities in deeper examples of the biotope. 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. 

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

‘No evidence’ was found to suggest that any of the characterizing species within CR.MCR.EcCr.CarSp are sensitive to current/known microbial pathogens.

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. Thomas (1940) recorded parasites of Spirobranchus triqueter. Trichodina pediculus (a ciliate) was observed in high numbers moving over the branchial crown. However, this relationship is symbiotic, not parasitic. Parasites found in the worm include gregarines & ciliated protozoa and parasites that had the appearance of sporozoan cysts. However, no information was found about the effects of microbial pathogens on Spirobranchus triqueter. Echinus esculentus is susceptible to 'Bald-sea-urchin disease', which causes lesions, loss of spines, tube feet, pedicellariae, destruction of the upper layer of skeletal tissue and death. It is thought to be caused by the bacteria Vibrio anguillarum and Aeromonas salmonicida. Bald sea-urchin disease was recorded from Echinus esculentus on the Brittany Coast. Although associated with mass mortalities of Strongylocentrotus franciscanus in California and Paracentrotus lividus in the French Mediterranean it is not known if the disease induces mass mortality (Bower, 1996). At the time of writing, there was no evidence concerning microbial pathogens that may affect Cliona celata.

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.MCR.EcCr.CarSp are commercially exploited. This pressure is considered ‘Not Relevant’.

Echinus esculentus was identified by Kelly & Pantazis (2001) as a species suitable for culture for the urchin Roe industry. However, at the time of writing no evidence could be found to suggest that significant Echinus esculentus mariculture was present in the UK. Removal of Echinus esculentus from CR.MCR.EcCr.CarSp could cause an increase in algal growth which may limit the growth of faunal species (Bell & Turner, 2000; Connor et al., 2004).

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

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.MCR.EcCr.CarSp Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueter and sponges 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. Spirobranchus triqueter). Echinus esculentus is an important red algae grazer within CR.MCR.EcCr (Connor et al., 2004), without which the abundance of red algae may increase and possibly displace some of the faunal turf species. If Alcyonium digitatum, Caryophyllia smithii, Spirobranchus triqueter and sponges were removed this would alter the character of the biotope.

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