Cerianthus lloydii with Nemertesia spp. and other hydroids in circalittoral muddy mixed sediment

Summary

UK and Ireland classification

Description

In sheltered muddy sandy gravel with appreciable quantities of surficial cobbles, pebbles and shells a community similar to ClloMx may develop with frequent Cerianthus lloydii and other burrowing anemones. However, the pebbles and cobbles embedded in the sediment are colonised by hydroids and in particular Nemertesia antennina and Nemertesia ramosa. Other hydroids may include Kirchenpaueria pinnata and Halecium halecinum whilst ascidians such as Ascidiella aspersaor, Corella parallelogramma may also be present locally. Pecten maximus and Spirobranchus triqueter may also be frequent in certain areas. (Information from Connor et al., 2004; JNCC, 2015).

Depth range

10-20 m, 20-30 m

Additional information

-

Listed By

Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

The plains of sandy muddy gravel within SS.SMx.CMx.ClloMx are characterized by burrowing anemones of which Cerianthus lloydii is the most abundant species.  Other conspicuous species found in this biotope are mobile scavengers and predators including Callionymus lyra, Pagurus bernhardus and Asterias rubens.  In the sub-biotope SS.SMx.CMx.ClloMx.Nem, the substratum includes more cobbles and pebbles, and the hydroids Nemertesia spp. have a high abundance and are characterizing species in addition to Cerianthus lloydiiNemertesia spp. as well as some of the other hydroids can only attach themselves to a solid substratum, which is why they are missing from SS.SMx.CMx.ClloMx.  SS.SMx.CMx.ClloMx.Nem has greater species diversity than SS.SMx.CMx.ClloMx.  Therefore, the sensitivity of this biotope is based on the important characterizing species Cerianthus lloydii and Nemertesia spp.  The mobile scavengers probably forage over a greater range than this biotope and are not assessed specifically.  The sensitivity of other hydroids is mentioned where relevant.

Resilience and recovery rates of habitat

Little evidence was found to support this resilience assessment for Cerianthus lloydii.  MES (2010) suggested that the genus Cerianthus would be likely to have a low recovery rate following physical disturbance based on long-lifespan and slow growth rate.  No specific evidence was cited to support this conclusion.  The MES (2010) review also highlighted that there were gaps in information for this species and that age at sexual maturity and fecundity is unknown although the larvae are pelagic (MES 2010).  No empirical evidence was found for recovery rates following perturbations for Cerianthus lloydii.  This species has limited horizontal mobility and re-colonization via adults is unlikely (Tillin & Tyler-Walters, 2014).

Hydroids exhibit rapid rates of recovery from disturbance through repair, asexual reproduction, and larval colonization.  Sparks (1972) reviewed the regeneration abilities and rapid repair of injuries.  Fragmentation of the hydroid provides a route for short distance dispersal, for example, each fragmented part of Sertularia cupressina can regenerate itself following damage (Berghahn & Offermann, 1999). New colonies of the same genotype may, therefore, arise from damage to existing colonies (Gili & Hughes, 1995).  Many hydroid species also produce dormant, resting stages that are very resistant of environmental perturbation (Gili & Hughes 1995).  Colonies can be removed or destroyed; however, the resting stages may survive attached to the substratum and provide a mechanism for rapid recovery (Kosevich & Marfenin, 1986; Cornelius, 1995a).  The lifecycle of hydroids typically alternates between an attached solitary or colonial polyp generation and a free-swimming medusa generation.  Planulae larvae produced by hydroids typically metamorphose within 24 hours and crawl only a short distance away from the parent plant (Sommer, 1992).  Gametes liberated from the medusae (or vestigial sessile medusae) produce gametes that fuse to form zygotes and develop into free-swimming planula larvae (Hayward & Ryland, 1994) and are present in the water column between 2-20 days (Sommer, 1992).  Rafting on floating debris as dormant stages or reproductive adults (or on ships hulls or in ship ballast water), together with their potentially long lifespan, may have allowed hydroids to disperse over a wide area in the long-term and explain the near cosmopolitan distributions of many hydroid species (Cornelius, 1992; Boero & Bouillon 1993).  Hydroids are potential fouling organisms; rapidly colonizing a range of substrata placed in marine environments and are often the first organisms to colonize available space in settlement experiments (Gili & Hughes, 1995).  For example, hydroids were reported to colonize an experimental artificial reef within less than 6 months, becoming abundant in the following year (Jensen et al., 1994).  In similar studies, Obelia spp. recruited to the bases of reef slabs within three months and the slab surfaces within six months of the slabs being placed in the marine environment (Hatcher, 1998).  Cornelius (1992) stated that Obelia spp. could form large colonies within a matter of weeks. In a study of the long-term effects of scallop dredging in the Irish Sea, Bradshaw et al. (2002) noted that hydroids increased in abundance, presumably because of their regeneration potential, good local recruitment and ability to colonize newly exposed substratum quickly.  Cantero et al. (2002) describe fertility of Obelia dichotoma, Kirchenpaureria pinnata, Nemertesia ramosa in the Mediterranean as being year-round, whilst it should be noted that higher temperatures may play a factor in this year round fecundity.  Bradshaw et al. (2002) observed that reproduction in Nemertesia antennina occurred regularly, with three generations per year.  In addition, the presence of adults stimulated larval settlement, so that where adults remained, reproduction was likely to result in local recruitment.  Hayward & Ryland (1994) stated that medusae release in Obelia dichotoma occurred in summer.

The hydroids that are present within SS.SMx.CMx.ClloMx.Nem include Halecium halecinum, Nemertesia antennina, and Nemertesia ramosa.  Halecium halecinum is an erect hydroid growing up to 25 cm and is found on stones and shells in coastal areas.  It is widely distributed in the Atlantic and is present from Svalbard to the Mediterranean (Hayward & Ryland, 1994; Palerud et al., 2004; Medel et al., 1998).  Nemertesia anteninna grows up to 25 cm is found attached to shells and stones on sandy bottoms from the shallow sublittoral into deeper waters offshore, and is recorded in the northeast Atlantic, from at least the Faroes, the Barents Sea and Iceland south through Mauritania to southern Africa, including the Mediterranean, Azores and Madeira.  Nemertesia ramosa grows up to 15 cm, is found inshore to deeper water and is common throughout the British Isles, and is distributed from Iceland to north-west Africa (Hayward & Ryland, 1994).

Resilience assessment.  The characterizing species of interest are the burrowing anemone Cerianthus lloydii and the hydroid, Nemertesia antennina.  However, their presence strongly affects the designation of the biotope.  Hydroids, including Nemertesia antennina, are likely to recover from damage very quickly. Based on the available evidence, resilience for the hydroid species assessed is ‘High’ (recovery within two years) for any level of perturbation (where resistance is ‘None’, ‘Low’, ‘Medium’ or ‘High’). Therefore, the ability of both SS.SMx.CMx.ClloMx and SS.SMx.CMx.ClloMx.Nem to recover will depend on the ability of Cerianthus lloydii to recover.  However, there is very little information regarding the resilience of Cerianthus lloydii.  A resilience of ‘Medium’ (2 – 10 years) is suggested for all resistance levels (where resistance is ‘None’, ‘Low’, ‘Medium’) based on expert judgement.  Confidence in this assessment is 'Low', due to the lack of direct evidence for the characterizing species.

Note. The resilience and the ability to recover from human-induced pressures is a combination of the environmental conditions of the site, the frequency (repeated disturbances versus a one-off event) and the intensity of the disturbance.  Recovery of impacted populations will always be mediated by stochastic events and processes acting over different scales including, but not limited to, local habitat conditions, further impacts and processes such as larval-supply and recruitment between populations. Full recovery is defined as the return to the state of the habitat that existed prior to impact.  This does not necessarily mean that every component species has returned to its prior condition, abundance or extent but that the relevant functional components are present and the habitat is structurally and functionally recognizable as the initial habitat of interest. It should be noted that the recovery rates are only indicative of the recovery potential.

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

Cerianthus lloydii adults are locally abundant in many localities on all coasts of the British Isles and in some areas are common on the shore.  This species occurs on all western coasts of Europe from Greenland and Spitzbergen south to Biscay.  Larvae, but not adults, have been recorded from the Mediterranean.  There is no further information available on the temperature tolerance of Cerianthus lloydii.

In a review of the ecology of hydroids, Gili & Hughes, (1995) report that temperature is a critical factor stimulating or preventing reproduction and that most species have an optimal temperature for reproduction.  However, limited evidence for thermal thresholds and thermal ranges were available for the characterizing species recorded in this biotope.  Berrill (1949) reported that growth in Obelia commissularis (syn. dichotoma) was temperature dependant but ceased at 27°C.  Hydranths did not start to develop unless the temperature was less than 20°C and any hydranths under development would complete their development and rapidly regress at ca 25°C. Berrill (1948) reported that Obelia species were absent from a buoy in July and August during excessively high summer temperatures in Booth Bay Harbour, Maine, USA.  Berrill (1948) reported that the abundance of Obelia species and other hydroids fluctuated greatly, disappearing and reappearing as temperatures rose and fell markedly above and below 20°C during this period.  The upwelling of cold water (8-10°C colder than surface water) allowed colonies of Obelia sp. to form in large numbers.  Cantero et al. (2002) describe the presence and year-round fertility of Obelia dichotoma, Kirchenpaureria pinnata, Nemertesia ramosa and Halecium spp.in the Mediterranean, indicating probable tolerance to temperature increases at the benchmark level.

Sensitivity assessment.  At the level of the benchmark, a change in temperature is unlikely to have a negative impact on the biotope. Therefore, both the resistance and resilience are assessed as ‘High’, and sensitivity is assessed as ‘Not sensitive’ at the benchmark level.

High
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High
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Not sensitive
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Medium
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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

Cerianthus lloydii adults are locally abundant in many localities on all coasts of the British Isles and in some areas are common on the shore. This species occurs on all western coasts of Europe from Greenland and Spitzbergen south to Biscay.  No further information is available on the temperature tolerance of Cerianthus lloydii.

Orejas et al. (2012) describe the feeding ecology of Obelia dichotoma in an Arctic environment (Kongsfjorden, Svalbard) which experiences temperatures of 1-5°C (Beszczynska-Möller & Dye, 2013).  Palerud et al. (2004) also describe the presence of Obelia dichotoma, Halecium Halecinum and Nemertesia sp. in Svalbard.  This suggests that the characterizing hydroids are probably tolerant of the lowest temperatures they are likely to encounter in Britain and Ireland of ca 4°C (Beszczynska-Möller & Dye, 2013).  It should be noted that growth rates are reduced at low temperatures.  Berrill (1949) reported that for Obelia, stolons grew, under optimal nutritive conditions, at less than 1 mm in 24 hrs at 10-12°C, 10 mm in 24 hrs at 16-17°C, and as much as 15-20 mm in 24 hrs at 20°C.

Sensitivity assessment. All species assessed are present in northern/boreal habitats and are unlikely to be affected at the benchmark level.  Resistance has been assessed as ‘High’, and resilience as ‘High’.  Therefore, sensitivity has been assessed as ‘Not sensitive’ at the benchmark level.

High
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Medium
Medium
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High
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High
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Not sensitive
Low
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Medium
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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

No evidence was found for osmoregulation by Cerianthus lloydiiCerianthus lloydii is recorded in biotopes with variable salinity regimes (18-40 psu) such as SS.SMx.CMx.ClloModHo but most records occur in full salinity. Studies on hydroids, in general, have found that prey capture rates may be affected by salinity and temperature (Gili & Hughes, 1995) although no evidence was found for Nemertesia antennina. However, due to the lack of evidence for the characterizing species within this biotope an assessment of ‘No evidence’ has been given. 

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

No evidence was found for osmoregulation by Cerianthus lloydiiCerianthus lloydii is recorded in biotopes with variable salinity regimes (18-40 psu) such as SS.SMx.CMx.ClloModHo but most records occur in full salinity. Due to the lack of evidence for the characterizing species within this biotope an assessment of ‘No evidence’ has been given.

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

Evidence for the effect of changes in water flow on Cerianthus lloydii is unavailable.  This species is recorded from biotopes with a wide range of water flow regimes, from very weak to strong flow (Connor et al., 1997b).  Therefore, it is likely to have a high tolerance to changes in water flow regimes.

The characteristic hydroids are typically found in places of low to moderate water movement, although Hayward & Ryland (1995a) note that the abundant communities occur in narrow straits and headlands that may experience high levels of water flow. Hydroids can bend passively with water flow to reduce drag forces to prevent detachment and enhance feeding (Gili & Hughes, 1995). Hydroid growth form also varies to adapt to prevailing conditions, allowing species to occur in a variety of habitats (Gili & Hughes, 1995).  Flow rates are an important factor for feeding in hydroids, and prey capture rates are higher in areas of greater turbulence (Gili & Hughes, 1995).  The capture rate of zooplankton by hydroids is correlated with prey abundance (Gili & Hughes, 1995), thus prey availability can compensate for sub-optimal flow rates. Water movements are also important to hydroids to prevent siltation, which can cause death (Round et al., 1961). Tillin & Tyler-Walters (2014) suggest that the range of flow speeds experienced by biotopes in which hydroids are found indicate that a change (increase or decrease) in the maximum water flow experienced by mid-range populations for the short periods of peak spring tide flow would not have negative effects on this ecological group.

Sensitivity assessment. This biotope is recorded from moderately strong to very weak flow and wave exposed to very wave sheltered conditions from 5 m to 30 m depth.  The biotope probably experiences wave mediated flow in its more shallow examples while tidal flow is more important in its deeper examples.  The biotope probably would not occur in areas subject to both strong flow and wave action, nor in areas subject to very weak flow and shelter from wave action. Therefore, the biotope probably experiences a range of water flow and/or wave mediated flow between the extremes cited above.  Therefore, a change in the flow of 01.-0.2 m/s is probably not significant and a resistance and resilience are assessed as ‘High’ so that sensitivity is assessed as ‘Not sensitive’.

High
Low
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High
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High
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Not sensitive
Low
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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

This biotope does not occur in the intertidal, and consequently an increase in emergence is considered 'Not relevant' to this biotope.

Not relevant (NR)
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Not relevant (NR)
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Not relevant (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

No evidence for the effect of changes in wave exposure on Cerianthus lloydii was available.  However, it is recorded from extremely wave sheltered to wave exposed sites (Connor et al., 1997b). Jackson (2004) reported that Nemertesia ramosa was intolerant of high wave exposure and only found in sheltered areas.  Faucci & Boero (2000) recorded hydroid communities at two sites of different wave exposure and recorded the presence of Obelia dichotoma and Halecium spp. in both the exposed and sheltered sites, but only found Kirchenpaueria sp. in the sheltered site.

Sensitivity assessment.  This biotope is recorded from moderately strong to very weak flow and wave exposed to very wave sheltered conditions from 5 m to 30 m depth.  The biotope probably experiences wave mediated flow in its more shallow examples while tidal flow is more important in its deeper examples.  The biotope probably would not occur in areas suggest to both strong flow and wave action, nor in areas subject to very weak flow and shelter from wave action. Therefore, the biotope probably experiences a range of water flow and/or wave mediated flow between the extremes cited above. Storms may mobilise the surface of the substratum and may explain the sparse fauna.  Nevertheless, 3-5% change in significant wave height is unlikely to be significant within this biotope.  Therefore, resistance has been assessed as ‘High’, resilience as ‘High’ and the biotope is probably ‘Not sensitive’ at the benchmark level.

High
Low
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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.

Not Assessed (NA)
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Not assessed (NA)
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Not assessed (NA)
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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.

Not Assessed (NA)
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Not assessed (NA)
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Not assessed (NA)
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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 presented where available.

Not Assessed (NA)
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Not assessed (NA)
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Not assessed (NA)
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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)
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Not relevant (NR)
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No evidence (NEv)
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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)
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Not assessed (NA)
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Not assessed (NA)
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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 does not appear to be significantly affected until extremely low concentrations are reached. For many benthic invertebrates, this concentration is about 2 ml/l (Herreid, 1980; Rosenberg et al., 1991; Diaz & Rosenberg, 1995).  Cole et al. (1999) suggest possible adverse effects on marine species below 4 mg/l and probable adverse effects below 2mg/l.

Hydroids mainly inhabit environments in which the oxygen concentration exceeds 5 ml/l (Gili & Hughes, 1995).  Diaz & Rosenberg (1995) noted that anemones include species that were reported to be particularly tolerant of hypoxia (e.g. Cerianthus sp and Epizoanthus erinaceus). A major hypoxic event due a pyncocline in the Gulf of Trieste resulted in a mass mortality of benthos between 12 and 26th September 1983 (Stachowitsch, 1992), during which the oxygen levels fell below 4.2 mg/l, became anoxic, and hydrogen sulphide and ammonia were released (Faganeli et al., 1985). Amongst the epifauna, the even hypoxia resistant polychaetes and bivalves died after 4-5 days and the only organism to survive after one week were the anemones Cerianthus sp and Epizoanthus erinaceus, the gastropods Aporrhais pespelecani and Trunculariopsis trunculus and the sphinuculid Sipunculus nudis (Stachowitsch, 1992).

Sensitivity assessment.  The above evidence suggests that Cerianthus lloydii would probably survive for a week at or below 2 mg O2/l while the hydroids would probably be reduced to just resting stages. Therefore, a resistance of 'Low' is recorded to represent the probable significant mortality of hydroids in the community. However, the hydroids would recover rapidly, so that resilience is likely to be 'High' and sensitivity 'Low'.

Low
High
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Medium
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High
High
High
High
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Low
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Medium
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Nutrient enrichment [Show more]

Nutrient enrichment

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

Evidence

No information was available on the effect of nutrient enrichment on Cerianthus lloydii. Witt et al. (2004) found that the hydroid Obelia sp. was more abundant in a sewage disposal area in the Weser estuary (Germany), which experienced sedimentation of 1 cm for more than 25 days.  It should be noted that another hydroid (Sertularia cupressina) was reduced in abundance when compared with unimpacted reference areas.  As suspension feeders, an increase in organic content at the benchmark is likely to be of benefit to the characterizing hydroids.  However, there is no direct evidence for the characterizing hydroid species Nemertesia anteninna.

Sensitivity assessment.  Little evidence was found on which to base an assessment.  However, the biotope is assessed as ‘Not sensitive' at the pressure benchmark of compliance with good status as defined by the WFD. 

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

Organic enrichment

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

Evidence

Borja et al., (2000) and Gittenberger & van Loon (2011) in the development of the AZTI Marine Biotic Index (AMBI) index to assess disturbance (including organic enrichment) both assigned Cerianthus lloydii to their Ecological Group I, ‘species very sensitive to organic enrichment and present under unpolluted conditions (initial state)’.  The basis for their assessment and relation to the pressure benchmark is not clear (Tillin & Tyler-Walters, 2014).

Witt et al. (2004) found that the hydroid Obelia spp. was more abundant in a sewage disposal area in the Weser estuary (Germany) which experienced sedimentation of 1 cm for more than 25 days.  It should be noted that another hydroid (Sertularia cupressina) was reduced in abundance when compared with unimpacted reference areas.  As suspension feeders, an increase in organic content at the benchmark is likely to be of benefit to the characterizing hydroids.

Sensitivity assessment.  At the pressure benchmark, which refers to enrichment rather than gross organic pollution, this biotope is considered to have a 'Low' resistance and hence, 'Medium' resilience. Therefore, sensitivity is assessed as 'Medium'.

Low
High
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Medium
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Medium
Low
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Medium
Low
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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
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High
High
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Very Low
High
High
High
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High
High
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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 was 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.  The resistance to this change is ‘None’, and the resilience is assessed as ‘Very low’ due to the permanent nature of a change in the substratum.  The biotope is assessed to have a ‘High’ sensitivity to this pressure at the benchmark.

None
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Very Low
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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

Cerianthus lloydii is found in a very wide range of substrata (Tillin & Tyler-Walters, 2014), but only dominates the fauna in the mixed substrata biotope described in this biotope  A change in Folk class from mixed to coarse or sandy mud substrata would result in loss of the biotope, even though population of Cerianthus lloydii could remain. Nemertesia antennina and other hydroids are only found attached to large pebbles and cobbles within SS.SMx.CMx.ClloMx.Nem. A reduction in the presence of cobbles and pebbles due to a change in sediment type would also reduce the abundance of the characteristic hydroids.

Sensitivity assessment.  A change in the substratum by one Folk class would result in the loss of the biotope. Therefore, a resistance of ‘None’ is recorded.  As resilience is 'Very low' (the pressure is a permanent change), sensitivity is, therefore, 'High'

None
Low
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Very Low
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High
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High
Low
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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

Resistance is assessed as ‘None’ based on expert judgment but supported by the literature relating to the position of these species on or within the seabed.  At the pressure benchmark, the exposed sediments are considered suitable for recolonization almost immediately following extraction.  Recovery will be mediated by the scale of the disturbance and the suitability of the sedimentary habitat.  Recovery is most likely to occur via larval recolonization.  Resilience is probably ‘Low’, so that sensitivity is assessed as ‘High’.

None
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Low
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High
Low
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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

No direct evidence was found to assess the sensitivity Cerianthus lloydii to surface abrasion.  The burrowing life habit of the species specifically assessed would confer some protection from surface disturbance although individuals would be more exposed when close to the surface feeding. Cerianthus lloydii inhabits a soft tube, which can be up to 40 cm long and is permanently buried. The anemone can move freely within the tube and can retract swiftly if required (Tillin & Tyler-Walters, 2014).

The available evidence indicates that hydroids can be entangled and removed by abrasion.  Drop down video surveys of Scottish reefs exposed to trawling showed that visual evidence of damage to bryozoans and hydroids on rock surfaces was generally limited and restricted to scrape scars on boulders (Boulcott & Howell, 2011).  The study showed that damage is incremental with damage increasing with the frequency of trawls rather than a blanket effect occurring on the pass of the first trawls.

Re-sampling of grounds that were historically studied (from the 1930s) indicates that some species have increased in areas subject to scallop fishing (Bradshaw et al., 2002).  This study also found (unquantified) increase in abundance of tough stemmed hydroids including Nemertesia spp.; its morphology may have prevented excessive damage. Bradshaw et al. (2002) suggested that as well as having high resistance to abrasion pressures, Nemertesia spp. have benthic larvae that could rapidly colonize disturbed areas with newly exposed substrata close to the adult.  Hydroids may also recover rapidly as the surface covering of hydrorhizae may remain largely intact, from which new uprights are likely to grow. In addition, the resultant fragments of colonies may be able to develop into new colonies.

Hydroid colonies were still present in the heavily fished area, albeit at lower densities than in the closed area. This may largely be because the Isle of Man scallop fishery is closed from 1st June to 31st October (Andrews et al., 2011), so at the time the samples were taken for the study in question, the seabed had been undredged for at least 3.5 months. The summer period is also the peak growing/breeding season for many marine species. (Bradshaw, 2003)

Sensitivity assessment.  Abrasion at the surface only is considered likely to damage and remove epiphytic species.  Cerianthus lloydii has the ability to retract into its tube.  However, there is the possibility of the tube being damaged, which could affect the health of the organism.  The resistance of the biotope is assessed as ‘Medium’, although the significance of the impact for the bed will depend on the spatial scale of the pressure footprint.  Resilience is assessed as ‘Medium’ (2-10 years), and sensitivity is assessed as ‘Medium’.

Medium
Low
Medium
Medium
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Medium
Low
Medium
Medium
Help
Medium
Low
Medium
Medium
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

Penetration and or disturbance of the substratum would result in similar results as abrasion or removal of this biotope.  Damage to Cerianthus lloydii would be greater within this pressure, as their ability to retract within their tubes would be limited.

Sensitivity assessment.  The resistance of the biotope is assessed as ‘Low’, although the significance of the impact for the bed will depend on the spatial scale of the pressure footprint.  Resilience is assessed as ‘Medium’, and sensitivity is assessed as ‘Medium’.

Low
Low
Medium
Medium
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Medium
Low
Medium
Medium
Help
Medium
Low
Medium
Medium
Help
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

An increase in suspended sediment may have a deleterious effect on the suspension feeding community.  It is likely to clog their feeding apparatus to some degree, resulting in a reduced ingestion over the benchmark period and, subsequently, a decrease in growth rate (Jackson, 2004).  As the hydroids capture small prey in suspension (Gili & Hughes, 1995), a reduction in feeding efficiency could potentially lead to a reduction in overall biomass.

No evidence on the effect of a change in turbidity on Cerianthus lloydii could be found. Nemertesia ramosa is a passive suspension feeder, extracting seston from the water column. Increased siltation may clog up the feeding apparatus, requiring energetic expenditure to clear.  Recovery is likely to take only a few days. (Jackson, 2004).  A decrease in suspended sediment is likely to benefit the community associated with this biotope. The suspension feeders may be able to feed more efficiently due to a reduction in time and energy spent cleaning feeding apparatus. Over the course of the benchmark, the hydroids may increase in abundance.

Sensitivity assessment.  No directly relevant evidence was found to assess the effect of pressure.  Resistance to this pressure is assessed as 'High' as an increase in turbidity may influence feeding and growth rates but not result in mortality of adults.  Resilience is assessed as 'High' (by default) and the biotope is assessed as 'Not sensitive' to changes in turbidity at the benchmark level.

High
Low
NR
NR
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High
High
High
High
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Not sensitive
Low
Low
Low
Help
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

In normal accretion, Cerianthus lloydii keeps pace with the accretion and, as a result, develops burrows much larger than the animal itself (Schäfer, 1972; Bromley, 2012). Schäfer (1972) reported that an increase in depositional rate led to an avoidance behaviour in Cerianthus lloydii.  The organism ceases tube building activity and instead the animal bunches its tentacles and intrudes its way up to the new surface, where it establishes a new burrow. However, no information on the depth of material through which is can burrow was given.

In general, it appears that hydroids are sensitive to silting (Boero, 1984; Gili & Hughes, 1995) and the decline of beds in the Wadden Sea have been linked to environmental changes including siltation.  Round et al., 1961 reported that the hydroid Sertularia (now Amphisbetia) operculata died when covered with a layer of silt after being transplanted to sheltered conditions.  Boero (1984) suggested that deepwater hydroid species develop upright, thin colonies that accumulate little sediment, while species in turbulent water movement were adequately cleaned of silt by water movement.  Hughes (1977) found that maturing hydroids that had been smothered with detritus and silt lost most of the hydrocladia and hydranths. After one month, the hydroids were seen to have recovered but although neither the growth rate nor the reproductive potential appeared to have been affected, the viability of the planulae may have been affected.  Nemertesia ramosa is an upright hydroid with a height of up to 15 cm. The colony structure is fairly tough and flexible. Smothering with 5 cm of sediment may cover over some individuals; others may just have the lower section of the main stem covered (Hayward & Ryland, 1994).

Sensitivity assessment. Cerianthus lloydii will actively burrow up through sediment that has smothered the entrance to its burrow.  The thickness of sediment through which Cerianthus lloydii is able to burrow is not known.  Smothering by 5 cm of sediment is likely to cause some mortality of Cerianthus lloydii.  It may be possible for fully grown adults to burrow through the sediment, however, the confidence in this assessment is low.  This pressure will also influence the hydroid species within SS.SMx.CMx.ClloMx.Nem.  Given the information available, the resistance to this pressure is considered to be ‘Medium’, as is the resilience, and sensitivity is assessed as ‘Medium’ at the benchmark.

Medium
Medium
Low
Low
Help
Medium
Low
Medium
Medium
Help
Medium
Low
Low
Low
Help
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

In normal accretion, Cerianthus lloydii keeps pace with the accretion and, as a result, develops burrows much larger than the animal itself (Schäfer, 1972; Bromley, 2012). Schäfer (1972) reported that an increase in depositional rate led to an avoidance behaviour in Cerianthus lloydii.  The organism ceases tube building activity and instead the animal bunches its tentacles and intrudes its way up to the new surface, where it establishes a new burrow. However, no information on the depth of material through which it can burrow was given.

In general, it appears that hydroids are sensitive to silting (Boero, 1984; Gili & Hughes, 1995) and the decline of beds in the Wadden Sea have been linked to environmental changes including siltation.  Round et al. (1961) reported that the hydroid Sertularia (now Amphisbetia) operculata died when covered with a layer of silt after being transplanted to sheltered conditions.  Boero (1984) suggested that deepwater hydroid species develop upright, thin colonies that accumulate little sediment, while species in turbulent water movement were adequately cleaned of silt by water movement.  Hughes (1977) found that maturing hydroids that had been smothered with detritus and silt lost most of the hydrocladia and hydranths. After one month, the hydroids were seen to have recovered but although neither the growth rate nor the reproductive potential appeared to have been affected, the viability of the planulae may have been affected.  Nemertesia ramosa is an upright hydroid with a height of up to 15 cm and Nemertesia antennina grows up to 25 cm (Hayward & Ryland, 1994). The colony structure is fairly tough and flexible. Smothering with 30 cm of sediment will completely cover all individuals.

Sensitivity assessment. Cerianthus lloydii will actively burrow up through sediment that has smothered the entrance to its burrow.  The thickness of sediment through which Cerianthus lloydii is able to burrow is not known.  However, at a maximum body length of 15 cm, a deposit of 30 cm is a considerable amount of sediment to burrow through.  The level of energy expenditure needed to burrow through this amount of sediment may be too much for some individuals, and there will be a higher change of asphyxia due to the amount of time the organisms are buried. For these reasons smothering by 30 cm of sediment is likely to cause mortality of a large proportion of Cerianthus lloydii.  At this pressure benchmark, the hydroid species within SS.SMx.CMx.ClloMx.Nem will all be totally smothered, which will result in their death.  Given the information available, the resistance to this pressure is considered to be ‘Low’, the resilience is probably 'Medium', and sensitivity is assessed as ‘Medium’ at the benchmark.

Low
Low
NR
NR
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Medium
Low
Medium
Medium
Help
Medium
Low
NR
NR
Help
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)
NR
NR
NR
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Not assessed (NA)
NR
NR
NR
Help
Not assessed (NA)
NR
NR
NR
Help
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.

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
Help
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

Species characterizing this habitat do not have hearing perception but vibrations may cause a response. However, noise, as defined by the pressure, is probably 'Not relevant'.

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

Introduction of light or shading

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

Evidence

No evidence.

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
Help
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

Not relevant – this pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats. Physical and hydrographic barriers may limit propagule dispersal.  But propagule dispersal is not considered under the pressure definition and benchmark.

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
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 – this pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats. Physical and hydrographic barriers may limit propagule dispersal.  But propagule dispersal is not considered under the pressure definition and benchmark.

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
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
Help
Not relevant (NR)
NR
NR
NR
Help

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

Habitat restoration projects may translocate stock to re-populate areas of suitable habitat (Elsäßer et al., 2013).  No evidence was found for detrimental effects arising from this practice in this habitat, although there is potential for the movement of pathogens and non-indigenous, invasive species.

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
Help
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

The American slipper limpet Crepidula fornicata was introduced to the UK and Europe in the 1870s from the Atlantic coasts of North America with imports of the eastern oyster Crassostrea virginica. It was recorded in Liverpool in 1870 and the Essex coast in 1887-1890. It has spread through expansion and introductions along the full extent of the English Channel and into the European mainland (Blanchard, 1997, 2009; Bohn et al., 2012, 2013a, 2013b, 2015; De Montaudouin et al., 2018; Helmer et al., 2019; Hinz et al., 2011; McNeill et al., 2010; Powell-Jennings & Calloway, 2018; Preston et al., 2020; Stiger-Pouvreau & Thouzeau, 2015).

Crepidula fornicata is recorded from shallow, sheltered bays, lagoons and estuaries or the sheltered sides of islands, in variable salinity (18 to 40) although it prefers ca 30 (Tillin et al., 2020). 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 in a wide variety of habitats including clean sands, artificial substrata, Sabellaria alveolata reefs and areas subject to moderately strong tidal streams (Blanchard, 1997, 2009; Bohn et al., 2012, 2013a, 2013b, 2015; De Montaudouin et al., 2018; Hinz et al., 2011; Powell-Jennings & Calloway, 2018; Preston et al., 2020; Stiger-Pouvreau & Thouzeau, 2015; Tillin et al., 2020). 

High densities of Crepidula fornicata cause ecological impacts on sedimentary habitats. The species can form dense carpets that can smother the seabed in shallow bays, changing and modifying the habitat structure. At high densities, the species physically smothers the sediment, and the resultant build-up of silt, pseudofaeces, and faeces is deposited and trapped within the bed (Tillin et al., 2020, Fitzgerald, 2007, Blanchard, 2009, Stiger-Pouvreau & Thouzeau, 2015). The biodeposition rates of Crepidula are extremely high and once deposited, form an anoxic mud, making the environment suitable for other species, including most infauna (Stiger-Pouvreau & Thouzeau, 2015, Blanchard, 2009). For example, in fine sands, the community is replaced by a reef of slipper limpets, that provide hard substrata for sessile suspension-feeders (e.g., sea squirts, tube worms and fixed shellfish), while mobile carnivorous microfauna occupy species between or within shells, resulting in a homogeneous Crepidula dominated habitat (Blanchard, 2009). Blanchard (2009) suggested the transition occurred and became irreversible at 50% cover of the limpet. De Montaudouin et al. (2018) suggested that homogenization occurred above a threshold of 20-50 Crepidula /m2

Impacts on the structure of benthic communities will depend on the type of habitat that Crepidula colonizes. De Montaudouin & Sauriau (1999) reported that in muddy sediment dominated by deposit-feeders, species richness, abundance and biomass increased in the presence of high densities of Crepidula (ca 562 to 4772 ind./m2), in the Bay of Marennes-Oléron, presumably because the Crepidula bed provided hard substrata in an otherwise sedimentary habitat. In medium sands, Crepidula density was moderate (330-1300 ind./m2) but there was no significant difference between communities in the presence of Crepidula. Intertidal coarse sediment was less suitable for Crepidula with only moderate or low abundances (11 ind./m2) and its presence did not affect the abundance or diversity of macrofauna. However, there was a higher abundance of suspension–feeders and mobile Crustacea in the absence of Crepidula (De Montaudouin & Sauriau, 1999). The presence of Crepidula as an ecosystem engineer has created a range of new niche habitats, reducing biodiversity as it modifies habitats (Fitzgerald, 2007). De Montaudouin et al. (1999) concluded that Crepidula did not influence macroinvertebrate diversity or density significantly under experimental conditions, on fine sands in Arcachon Bay, France. De Montaudouin et al. (2018) noted that the limpet reef increased the species diversity in the bed, but homogenised diversity compared to areas where the limpets were absent. In the Milford Haven Waterway (MHW), the highest densities of Crepidula were found in areas of sediment with hard substrata, e.g., mixed fine sediment with shell or gravel or both (grain sizes 16-256 mm) but, while Crepidula density increased as gravel cover increased in the subtidal, the reverse was found in the intertidal (Bohn et al., 2015). Bohn et al. (2015) suggested that high densities of Crepidula in high-energy environments were possible in the subtidal but not the intertidal, suggesting the availability of this substratum type is beneficial for its establishment. Hinz et al. (2011) reported a substantial increase in the occurrence of Crepidula off the Isle of Wight, between 1958 and 2006, at a depth of ca 60 m, on hard substrata (gravel, cobbles, and boulders), swept by strong tidal streams. Presumably, Crepidula is more tolerant of tidal flow than the oscillatory flow caused by wave action which may be less suitable (Tillin et al., 2020). 

King scallop (Pecten maximus) and Queen scallop (Aequipecten opercularis) in the Bay of Brest, have been reported to decrease in the presence of Crepidula, largely due to silting and biodeposition that changes the habitat (Stiger Pouvreau & Thouzeau, 2015; Thouzeau et al., 2000). The scallop post larvae are unable to settle and survive on muddy Crepidula substrata. Crepidula could potentially be the main competitor for Pecten maximus, especially creating competition for space (Menesguen & Gregoris, 2018; Ragueneau et al., 2018). However, no direct competition for food was observed between Crepidula and the scallops (Thouzeau et al., 2000, Chauvaud et al. 2000) and scallop shell growth rates did not decrease with increasing Crepidula populations. Therefore, although Crepidula populations will likely impact scallop post-larvae settlement, it does not affect shell growth rates or adult survivorship (Thouzeau et al., 2000). Models show that competition for space between the species does not impact the abundance of Crepidula, but does lower the abundance of Pecten sp. (Menesguen & Gregoris, 2018). 

Sensitivity assessment. The sediments characterizing this biotope are likely to be too mobile and unsuitable for most of the invasive non-indigenous species currently recorded in the UK. However, the above evidence suggests that Crepidula could colonize mixed sediment habitats in the subtidal, typical of this biotope, due to the presence of gravel, shells, cobbles, or any other hard substrata embedded in the substratum that can be used for larvae settlement (Tillin et al., 2020). Bohn et al. (2015) demonstrated that Crepidula had a preference for gravelly habitats, while De Montaudouin & Sauriau (1999) and Bohn et al. (2015) noted that Crepidula densities were low in intertidal coarse sediments. Therefore, Crepidula has the potential to colonize, and modify the habitat and its associated community due to the introduction of Crepidula shell biomass, silt, pseudofaeces and faeces (Blanchard, 2009; Tillin et al., 2020), as occurs in maerl gravels (Grall & Hall-Spencer, 2003), resulting in the loss of the biotope. This is a moderately exposed to very sheltered habitat, so storms may mobilise the sediment (JNCC, 2022), which may also mitigate or prevent colonization by Crepidula at high densities, although it has been recorded from areas of strong tidal streams (Hinz et al., 2011). Therefore, the habitat may be more suitable for Crepidula in wave sheltered areas of the biotope and where water movement is mediated by tidal flow rather than wave action, e.g., the deeper examples of the biotope. 

Therefore, resistance is assessed as 'Medium' in examples where wave action is high and subject to storms but 'Low' in wave sheltered areas dominated by tidal flow. Resilience is assessed as 'Very low' as it would require the removal of Crepidula, probably by artificial means. Hence, sensitivity is assessed as 'High' based on the worst-case scenario. Crepidula has not yet been reported to occur in this biotope so the confidence in the assessment is 'Low' and further evidence is required.

Low
Low
NR
NR
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Very Low
High
High
High
Help
High
Low
NR
NR
Help
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

No evidence was available on the effect of microbial pathogens on Cerianthus lloydii.  Hydroids exhibit astonishing regeneration and rapid recovery from injury (Sparks, 1972) and the only inflammatory response is active phagocytosis (Tokin & Yaricheva, 1959; 1961, as cited in Sparks, 1972).  No record of diseases in the characterizing hydroids could be found.

Sensitivity assessment.  There was insufficient information to assess the effect of this pressure on the biotope.  Therefore, an assessment of ‘No evidence’ has been given. 

No evidence (NEv)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
No evidence (NEv)
NR
NR
NR
Help
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

Sensitivity assessment.  None of the characterizing species within this biotope are currently directly targeted in the UK and hence this pressure is considered to be ‘Not relevant’.

Not relevant (NR)
NR
NR
NR
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Not relevant (NR)
NR
NR
NR
Help
Not relevant (NR)
NR
NR
NR
Help
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

Direct, physical impacts from harvesting are assessed through the abrasion and penetration of the seabed pressures.  The characterizing species within this biotope could easily be incidentally removed from this biotope as by-catch when other species are being targeted.  The loss of these species and other associated species would decrease species richness and negatively impact on the ecosystem function.

Sensitivity assessment. Removal of a large percentage of the characterizing species would alter the character of the biotope.  The resistance to removal is ‘Low’ due to the easy accessibility of the biotopes location and the inability of these species to evade collection. The resilience is ‘Medium’ with recovery only being able to begin when the harvesting pressure is removed altogether. This gives an overall sensitivity score of ‘Medium’.

Medium
Low
Medium
Medium
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Medium
Low
Medium
Medium
Help
Medium
Low
Medium
Medium
Help

Bibliography

  1. Andrews, J.W., Brand, A.R. & Holt, T.J., 2011. Isle of Man Queen Scallop Trawl and Dredge Fishery. MSC assessment report. pp. 203.

  2. Berghahn, R. & Offermann, U. 1999. Laboratory investigations on larval development, motility and settlement of white weed (Sertularia cupressina L.) - in view of its assumed decrease in the Wadden Sea. Hydrobiogia, 392(2), 233–239.

  3. Berrill, N.J., 1948. A new method of reproduction in Obelia. Biological Bulletin, 95, 94-99.

  4. Berrill, N.J., 1949. The polymorphic transformation of Obelia. Quarterly Journal of Microscopical Science, 90, 235-264.

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

  6. 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

  7. 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/

  8. Boero, F. & Bouillon, J., 1993. Zoogeography and life cycle patterns of Mediterranean hydromedusae (Cnidaria). Biological Journal of the Linnean Society, 48, 239-266.

  9. Boero, F., 1984. The ecology of marine hydroids and effects of environmental factors: a review. Marine Ecology, 5, 93-118.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. Borja, A., Franco, J. & Perez, V., 2000. A marine biotic index to establish the ecological quality of soft-bottom benthos within European estuarine and coastal environments. Marine Pollution Bulletin, 40 (12), 1100-1114.

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

  16. Bradshaw, C., Collins, P. & Brand, A., 2003. To what extent does upright sessile epifauna affect benthic biodiversity and community composition? Marine Biology, 143 (4), 783-791.

  17. Bradshaw, C., Veale, L.O., Hill, A.S. & Brand, A.R., 2002. The role of scallop-dredge disturbance in long-term changes in Irish Sea benthic communities: a re-analysis of an historical dataset. Journal of Sea Research, 47, 161-184. DOI https://doi.org/10.1016/S1385-1101(02)00096-5

  18. Bromley, R.G., 2012. Trace Fossils: Biology, Taxonomy and Applications: Routledge.

  19. Cantero, Á.L.P., Carrascosa, A.M.G. & Vervoort, W., 2002. The benthic hydroid fauna of the Chafarinas Islands (Alborán Sea, western Mediterranean): Nationaal Natuurhistorisch Museum.

  20. Chauvaud, L., Jean, F., Ragueneau, O. & Thouzeau, G., 2000. Long-term variation of the Bay of Brest ecosystem: benthic-pelagic coupling revisited. Marine Ecology Progress Series, 200, 35-48. DOI https://doi.org/10.3354/meps200035

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Citation

This review can be cited as:

Perry, F., & Watson, A., 2023. Cerianthus lloydii with Nemertesia spp. and other hydroids in circalittoral muddy mixed sediment. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 28-05-2024]. Available from: https://marlin.ac.uk/habitat/detail/1092

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