The Marine Life Information Network

Global warming (extreme)

Extreme emission scenario (by the end of this century 2081-2100) benchmark of:

• A 5°C rise in SST and NBT (coastal to the shelf seas),

• A 6°C rise in surface air temperature (in eulittoral and supralittoral habitats).

• A 1°C rise in Deep-sea habitats (>200 m) off the continental shelf, and

• A 5°C rise in surface air temperature in intertidal habitats exclusive to Scotland. Further detail.

Evidence

Deep waters off the continental shelf (200 – 2500 m) are expected to see a lower temperature rise (≈ 1^oC) by the end of this century than shallow water habitats, regardless of scenario (FAO (Fisheries and Aquaculture Organisation), 2019). Leptometra celtica is thought to be found from 46 m to more than 1279 m (Koukouras et al., 2007), although it has also been recorded at 20 m in sheltered conditions in Scottish Sea lochs. It can be found from Scotland, down to the western Mediterranean, and as far south as the Moroccan coast (Fonseca et al., 2014). Clark & Clark (1967) indicate that Leptometra celtica has been found associated with bottom water temperatures of 9.6-14.7°C, and its depth distribution appears to be dependent on temperature. It appears in shallow waters in the northern part of its distribution (i.e. north-west UK, where surface temperatures in the Atlantic Ocean vary between 9-14°C; Huthnance, 2010), and deeper waters in more southerly areas (i.e. south-west UK, Iberian Peninsula, western Mediterranean). NE Atlantic upper bathyal temperatures generally range between 7-10°C (Parry et al., 2015), suggesting that deep-water populations of Leptometra celtica are at the tip of their northern distribution

Sensitivity Assessment.Upper bathyal water temperatures are generally quite stable (Parry et al., 2015), although the fact that Leptometra celtica is distributed from the Faroe Islands to the coast of Morocco, and ranges from a depth of 20 m in sea lochs in Scotland to over 1000 m depth, highlights that this species is tolerant to a range of temperatures. Hiscock et al. (2004) suggest that shallow water Leptometra celtica populations are at the southern limit of their distribution and may be lost as a result of ocean warming. In contrast to shallow water populations, UK deep-water populations of Leptometra celtica are at the northern edge of their distribution, and a 1°C rise in temperature is likely to be beneficial to this species and may even lead to a northward expansion of its upper bathyal population range. Therefore, under all three scenarios (the middle and high emission and extreme scenarios), where temperature is expected to increase by 1°C by the end of the century, resistance of this biotope has been assessed as ‘High’ and resilience is assessed as ‘High’ so that the biotope is considered ‘Not sensitive’ to ocean warming at the benchmark level.

Global warming (high)

High emission scenario (by the end of this century 2081-2100) benchmark of:

• A 4°C rise in SST, NBT (coastal to the shelf seas) and surface air temperature (in eulittoral and supralittoral habitats).

• A 1°C rise in Deep-sea habitats (>200 m) off the continental shelf, and

• A 3°C rise in surface air temperature in intertidal habitats exclusive to Scotland. Further detail.

Evidence

Deep waters off the continental shelf (200 – 2500 m) are expected to see a lower temperature rise (≈ 1^oC) by the end of this century than shallow water habitats, regardless of scenario (FAO (Fisheries and Aquaculture Organisation), 2019). Leptometra celtica is thought to be found from 46 m to more than 1279 m (Koukouras et al., 2007), although it has also been recorded at 20 m in sheltered conditions in Scottish Sea lochs. It can be found from Scotland, down to the western Mediterranean, and as far south as the Moroccan coast (Fonseca et al., 2014). Clark & Clark (1967) indicate that Leptometra celtica has been found associated with bottom water temperatures of 9.6-14.7°C, and its depth distribution appears to be dependent on temperature. It appears in shallow waters in the northern part of its distribution (i.e. north-west UK, where surface temperatures in the Atlantic Ocean vary between 9-14°C; Huthnance, 2010), and deeper waters in more southerly areas (i.e. south-west UK, Iberian Peninsula, western Mediterranean). NE Atlantic upper bathyal temperatures generally range between 7-10°C (Parry et al., 2015), suggesting that deep-water populations of Leptometra celtica are at the tip of their northern distribution

Sensitivity Assessment.Upper bathyal water temperatures are generally quite stable (Parry et al., 2015), although the fact that Leptometra celtica is distributed from the Faroe Islands to the coast of Morocco, and ranges from a depth of 20 m in sea lochs in Scotland to over 1000 m depth, highlights that this species is tolerant to a range of temperatures. Hiscock et al. (2004) suggest that shallow water Leptometra celtica populations are at the southern limit of their distribution and may be lost as a result of ocean warming. In contrast to shallow water populations, UK deep-water populations of Leptometra celtica are at the northern edge of their distribution, and a 1°C rise in temperature is likely to be beneficial to this species and may even lead to a northward expansion of its upper bathyal population range. Therefore, under all three scenarios (the middle and high emission and extreme scenarios), where temperature is expected to increase by 1°C by the end of the century, resistance of this biotope has been assessed as ‘High’ and resilience is assessed as ‘High’ so that the biotope is considered ‘Not sensitive’ to ocean warming at the benchmark level.

Global warming (middle)

Middle emission scenario (by the end of this century 2081-2100) benchmark of:

• A 3°C rise in SST, NBT (coastal to the shelf seas) and surface air temperature (in eulittoral and supralittoral habitats).

• A 1°C rise in Deep-sea habitats (>200 m) off the continental shelf.

• A 2°C rise in surface air temperature in intertidal habitats exclusive to Scotland. Further detail.

Evidence

Deep waters off the continental shelf (200 – 2500 m) are expected to see a lower temperature rise (≈ 1^oC) by the end of this century than shallow water habitats, regardless of scenario (FAO (Fisheries and Aquaculture Organisation), 2019). Leptometra celtica is thought to be found from 46 m to more than 1279 m (Koukouras et al., 2007), although it has also been recorded at 20 m in sheltered conditions in Scottish Sea lochs. It can be found from Scotland, down to the western Mediterranean, and as far south as the Moroccan coast (Fonseca et al., 2014). Clark & Clark (1967) indicate that Leptometra celtica has been found associated with bottom water temperatures of 9.6-14.7°C, and its depth distribution appears to be dependent on temperature. It appears in shallow waters in the northern part of its distribution (i.e. north-west UK, where surface temperatures in the Atlantic Ocean vary between 9-14°C; Huthnance, 2010), and deeper waters in more southerly areas (i.e. south-west UK, Iberian Peninsula, western Mediterranean). NE Atlantic upper bathyal temperatures generally range between 7-10°C (Parry et al., 2015), suggesting that deep-water populations of Leptometra celtica are at the tip of their northern distribution

Sensitivity Assessment.Upper bathyal water temperatures are generally quite stable (Parry et al., 2015), although the fact that Leptometra celtica is distributed from the Faroe Islands to the coast of Morocco, and ranges from a depth of 20 m in sea lochs in Scotland to over 1000 m depth, highlights that this species is tolerant to a range of temperatures. Hiscock et al. (2004) suggest that shallow water Leptometra celtica populations are at the southern limit of their distribution and may be lost as a result of ocean warming. In contrast to shallow water populations, UK deep-water populations of Leptometra celtica are at the northern edge of their distribution, and a 1°C rise in temperature is likely to be beneficial to this species and may even lead to a northward expansion of its upper bathyal population range. Therefore, under all three scenarios (the middle and high emission and extreme scenarios), where temperature is expected to increase by 1°C by the end of the century, resistance of this biotope has been assessed as ‘High’ and resilience is assessed as ‘High’ so that the biotope is considered ‘Not sensitive’ to ocean warming at the benchmark level.

Marine heatwaves (high)

High emission scenario benchmark: A marine heatwave occurring every two years, with a mean duration of 120 days, and a maximum intensity of 3.5°C. Further detail.

Evidence

Marine heatwaves caused by increased air-sea flux of heat are only expected to penetrate surface waters (≤ 50 m) (Cerrano et al., 2000, Garrabou et al., 2009; Dan Smale, pers. comm.). Therefore, sensitivity to marine heatwaves is probably ‘Not relevant’ in this bathyal habitat.

Marine heatwaves (middle)

Middle emission scenario benchmark:  A marine heatwave occurring every three years, with a mean duration of 80 days, with a maximum intensity of 2°C. Further detail.

Evidence

Marine heatwaves caused by increased air-sea flux of heat are only expected to penetrate surface waters (≤ 50 m) (Cerrano et al., 2000, Garrabou et al., 2009; Dan Smale, pers. comm.). Therefore, sensitivity to marine heatwaves is probably ‘Not relevant’ in this bathyal habitat.

Ocean acidification (high)

High emission scenario benchmark: a further decrease in pH of 0.35 (annual mean) and corresponding 120% increase in H+ ions , seasonal aragonite saturation of 20% of UK coastal waters and North Sea bottom waters, and the aragonite saturation horizon in the NE Atlantic, off the continental shelf, occurring at a depth of 400 m by the end of this century 2081-2100. Further detail 

Evidence

Increasing levels of CO₂ in the atmosphere have led to the average pH of surface waters dropping from 8.25 in the 1700s to 8.14 in the 1990s (Jacobson, 2005). By the end of this century, pH is predicted to decrease by a further 0.15 – 0.35 units depending on the emission scenario used. Crinoids represent the most ancient class of living echinoderms (Smith, 1997), dating back 500 million years ago when atmospheric CO₂ levels were much higher than levels predicted for the end of this century (Guensburg & Sprinkle, 2001). In general, it is thought that calcifying invertebrates will be more sensitive to ocean acidification than non-calcifying invertebrates, which appear to have a more mixed response (Hofmann et al., 2010), although echinoderms on the whole generally appear to be tolerant to a 0.4 unit decrease in pH (Dupont et al., 2010). Widdicombe & Spicer (2008) suggested that the effects of pCO₂ and hypercapnia was likely be species specific rather than predictable by phylogeny or habitat, although early life history stages in invertebrates are known to be more susceptible to ocean acidification than adult stages (Hofmann et al., 2010), and this has been shown to be the case for echinoderms (Dupont et al., 2010).

Sensitivity Assessment. Echinoderms, in general, appear to be robust to a pH decrease of up to 0.4 units, and Leptometra celtica can be found at depths of up to 1279 m, where pH can be up to 0.2 pH units lower than surface waters (Convention of Biological Diversity 2014), which suggests that this species has some tolerance to a decrease in pH.  Hence, for both the middle and high emission scenarios, the resistance of this biotope has been assessed as ‘High’ and resilience is assessed as ‘High’ so that the biotope is considered ‘Not sensitive’ to ocean acidification at the benchmark level. Confidence is ‘medium’ for the middle emission scenario, as its large bathymetric range suggests that this species will be likely to tolerate a 0.2 unit pH decrease, but confidence in the assessment for the high emission scenario is ‘low’ due to lack of evidence.

Ocean acidification (middle)

Middle emission scenario benchmark: a further decrease in pH of 0.15 (annual mean) and corresponding 35% increase in H+ ions with no coastal aragonite undersaturation and the aragonite saturation horizon in the NE Atlantic, off the continental shelf, at a depth of 800 m by the end of this century 2081-2100. Further detail.

Evidence

Increasing levels of CO₂ in the atmosphere have led to the average pH of surface waters dropping from 8.25 in the 1700s to 8.14 in the 1990s (Jacobson, 2005). By the end of this century, pH is predicted to decrease by a further 0.15 – 0.35 units depending on the emission scenario used. Crinoids represent the most ancient class of living echinoderms (Smith, 1997), dating back 500 million years ago when atmospheric CO₂ levels were much higher than levels predicted for the end of this century (Guensburg & Sprinkle, 2001). In general, it is thought that calcifying invertebrates will be more sensitive to ocean acidification than non-calcifying invertebrates, which appear to have a more mixed response (Hofmann et al., 2010), although echinoderms on the whole generally appear to be tolerant to a 0.4 unit decrease in pH (Dupont et al., 2010). Widdicombe & Spicer (2008) suggested that the effects of pCO₂ and hypercapnia was likely be species specific rather than predictable by phylogeny or habitat, although early life history stages in invertebrates are known to be more susceptible to ocean acidification than adult stages (Hofmann et al., 2010), and this has been shown to be the case for echinoderms (Dupont et al., 2010).

Sensitivity Assessment. Echinoderms, in general, appear to be robust to a pH decrease of up to 0.4 units, and Leptometra celtica can be found at depths of up to 1279 m, where pH can be up to 0.2 pH units lower than surface waters (Convention of Biological Diversity 2014), which suggests that this species has some tolerance to a decrease in pH.  Hence, for both the middle and high emission scenarios, the resistance of this biotope has been assessed as ‘High’ and resilience is assessed as ‘High’ so that the biotope is considered ‘Not sensitive’ to ocean acidification at the benchmark level. Confidence is ‘medium’ for the middle emission scenario, as its large bathymetric range suggests that this species will be likely to tolerate a 0.2 unit pH decrease, but confidence in the assessment for the high emission scenario is ‘low’ due to lack of evidence.

Sea level rise (extreme)

Extreme scenario benchmark: a 107 cm rise in average UK by the end of this century (2018-2100). Further detail.

Evidence

At a depth of 200 – 600 m, these biotopes will not be affected by sea-level rise.  Therefore sensitivity to this climate change pressure is probably ‘Not relevant’ in this bathyal habitat.

Sea level rise (high)

High emission scenario benchmark: a 70 cm rise in average UK by the end of this century (2018-2100). Further detail.

Evidence

At a depth of 200 – 600 m, these biotopes will not be affected by sea-level rise.  Therefore sensitivity to this climate change pressure is probably ‘Not relevant’ in this bathyal habitat.

Sea level rise (middle)

Middle emission scenario benchmark: a 50 cm rise in average UK sea-level rise by the end of this century (2081-2100). Further detail.

Evidence

At a depth of 200 – 600 m, these biotopes will not be affected by sea-level rise.  Therefore sensitivity to this climate change pressure is probably ‘Not relevant’ in this bathyal habitat.

Temperature increase (local)

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

Evidence

Changes in abiotic variables such as temperature can affect echinoderms in a range of ways, from decreased production to complete mortality (Tokioka, 1963,1966 in Lawrence, 1995). Abrupt temperature changes are thought to induce spawning in laboratory specimens of Antedon bifida (Dimelow, 1958, in Holland, 1991). Leptometra celtica is found at depths from 40 m to more than 200 m on the edge of the continental shelf to the west of the British Isles, at 20 m in Scottish sea lochs (Southward & Campbell, 2006) and as far south as the Moroccan coast (Fonseca et al., 2013). The species, therefore, appears to occur in shallower waters in the northern part of its distribution (i.e. north-west UK, where surface temperatures in the Atlantic Ocean vary between 9-14°C; Huthnance, 2010), and deeper in more southerly areas (i.e. south-west UK where surface temperatures in the Atlantic Ocean vary between 10-18°C; Huthnance, 2010). Clark & Clark (1967) further indicate that Leptometra celtica has been found associated with bottom water temperatures of 9.61 – 14.70°C.

Therefore, if the biotope occurs in an area corresponding to the lower limit or middle of its temperature range, as given by Clark and Clark (1967), then it is probably able to tolerate a long-term increase in temperature of 2°C.  However, if the biotope occurs at the upper limit of its temperature range, then it probably won’t be able to tolerate an increase in temperature of 2°C. Even at the lowest limit of its temperature range, Leptometra celtica is unlikely to tolerate a short-term increase in temperature of 5°C.

Sensitivity assessment. Due to the range of bottom water temperatures that Leptometra celtica is associated with, resistance is assessed as ‘Medium’, resilience is assessed as ‘Medium’, and overall sensitivity is assessed as ‘Medium’.

Temperature decrease (local)

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

Evidence

Changes in abiotic variables such as temperature can affect echinoderms in a range of ways, from decreased production to complete mortality (Tokioka, 1963 and 1966, in Lawrence, 1995). Abrupt temperature changes are thought to induce spawning in laboratory specimens of Antedon bifida (Dimelow, 1958, in Holland, 1991). Leptometra celtica is found at depths of 40 m to more than 200 m on the edge of the continental shelf to the west of the British Isles, at 20 m in Scottish sea lochs (Southward & Campbell, 2006) and as far south as the Moroccan coast (Fonseca et al., 2013). The species, therefore, appears to occur in shallower waters in the northern part of its distribution (i.e. north-west UK, where surface temperatures in the Atlantic Ocean vary between 9-14°C; Huthnance, 2010), and deeper in more southerly areas (i.e. south-west UK where surface temperatures in the Atlantic Ocean vary between 10-18°C; Huthnance, 2010). Clark & Clark (1967) further indicate that Leptometra celtica has been found associated with bottom water temperatures of 9.61 – 14.70°C.

Therefore, if the biotope occurs in an area corresponding to the upper limit or middle of its temperature range, as given by Clark and Clark (1967), then it is probably able to tolerate a long-term decrease in temperature of 2°C.  However, if the biotope occurs at the lower limit of its temperature range, then it probably won’t be able to tolerate a decrease in temperature of 2°C. Even at the upper limit of its temperature range, Leptometra celtica is unlikely to tolerate a short-term decrease in temperature of 5°C.

Sensitivity assessment. Due to the range of bottom water temperatures that Leptometra celtica is associated with, resistance is assessed as ‘Medium’, resilience is assessed as ‘Medium’, and overall sensitivity is assessed as ‘Medium’.

Salinity increase (local)

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

Evidence

The depth at which Leptometra celtica assemblages are found, combined with the distance from shore and the low potential for brine or freshwater discharge, means changes in salinity are unlikely.  However, Fonseca et al. (2011) reported an assemblage of Leptometra celtica in 500 m off the southern coast of Portugal, where it is exposed to a westward-flowing vein of higher-salinity Mediterranean water. However, the authors did not give salinity values or state how much they varied. Bozec et al. (2011) discussed variability in Mediterranean outflow water over decades and mentioned multi-decadal variations in the flow pathway. This combination of location and variability suggest that Leptometra celtica might be subjected to variations in salinity in some areas but it is not clear how much variation is involved and over what lengths of time (e.g. within vs. over several generations). Therefore, as specific evidence is limited on its effect, this pressure is assessed as ‘No Evidence’.    

Salinity decrease (local)

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

Evidence

The depth at which Leptometra celtica assemblages are found, combined with the distance from shore and the low potential for brine or freshwater discharge, means changes in salinity are unlikely.  However, Fonseca et al. (2013) reported an assemblage of Leptometra celtica in 500 m off the southern coast of Portugal, where it is exposed to a westward-flowing vein of higher-salinity Mediterranean water. However, the authors did not give salinity values or state how much they varied. Bozec et al. (2011) discussed variability in Mediterranean outflow water over decades and mentioned multi-decadal variations in the flow pathway. This combination of location and variability suggest that Leptometra celtica might be subjected to variations in salinity in some areas, but it is not clear how much variation is involved and over what lengths of time (e.g. within vs. over several generations). Therefore, as specific evidence is limited on its effect, this pressure is assessed as ‘No Evidence’.    

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

Crinoids are dependent on water movement to allow them to feed via suspension feeding (Birkeland, 1988). Although semi-cryptic (rheophobic) species orient their arms in postures that take advantage of multi-directional water movement, those that live completely exposed (rheophilic), such as Leptometra celtica, arrange their arms in various planar, conical, or parabolic postures in response to laminar, near-bottom flow (e.g. La Touche, 1978; Macurda and Meyer, 1974; Meyer & Macurda Jr, 1980). Figure 3 in Fonseca et al. (2013) shows a group of Leptometra celtica with arms arranged in a monoplanar fan in response to likely unidirectional near-bottom flow. Crinoids modify arm postures in response to flow that is either too weak or too strong for feeding. It is unclear whether Leptometra celtica can rely on gravitational settling of particles for feeding, however.

The settlement of Leptometra celtica individuals is also facilitated by specific hydrodynamics, i.e., bottom currents that create a turbulent environment (Fonseca et al., 2013). Barbaglio et al. (2012) reported that pre-settlement larvae of Antedon mediterranea slowed and moved to the bottom, indicating the importance of these specific hydrodynamics.

Leptometra celtica assemblages occur at the shelf edge and in the heads of canyons, as these are areas associated with fast currents, providing a favourable habitat for suspension feeding organisms (Parry et al., 2015). Flow within canyons can be caused by wind-driven shelf-break or slope currents, leading to upwelling or downwelling flows within the canyon, with the strongest effects at the canyon rim (Allen and Durrieu de Madron, 2009). The specific velocity limits for Leptometra celtica are unknown, however.

Modifications in the intensity of currents (e.g., those caused by climate change) could seriously impact the structure and functioning of canyon communities (Fernadez-Arcaya et al., 2017). It could also have important implications for nutrient supply to the deep-ocean ecosystem (Fernadez-Arcaya et al., 2017). However, changes in water flow at the pressure benchmark are unlikely to result in such major implications to Leptometra celtica assemblages. It may be worth noting though, that for the shallow, reef-dwelling, 10-armed feather star Oligometra serripinna, particle capture rate peaked at a current speed of 6.4 cm sec^-1 (close to the mean ambient speed) and declined at higher tested velocities (9.5 and 13.3 cm/sec) (Leonard et al., 1988).

Sensitivity assessment. Leptometra celtica assemblages occur at the shelf edge and in the heads of canyons with fast currents (JNCC, 2015) and the species appears to have developed behaviours (e.g., crouching) adapted to a change in the current regime. Therefore, resistance is assessed as ‘High’.  Although it has not been observed, Leptometra celtica is probably able to recolonise after an episode of larval recruitment, or through adult immigration, however, the habitat preference for larvae and adults are likely to be different. This mobility of Leptometra celtica, therefore, acts as a means of colonization of optimal habitats for post-larvae, so resilience is assessed as ‘High’. The biotopes are therefore considered ‘Not sensitive’ at the benchmark level.

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

Leptometra celtica assemblages are deep-sea biotopes, relevant to the Atlantic upper-bathyal or mid-bathyal zones, at depths of 200 –600 m or 600 –1300 m, respectively. Therefore, the biotopes will not be affected by changes in the emergence regime, and the assessment at the pressure benchmark is ‘Not relevant’.

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

Leptometra celtica assemblages are deep-sea biotopes, relevant to the Atlantic upper-bathyal or mid-bathyal zones, at depths of 200 –600 m or 600 –1300 m, respectively. As such, they occur at depths at which even the wave action generated by storm conditions is unlikely to penetrate. Therefore, the assessment for the biotopes at the pressure benchmark is ‘Not relevant’.

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 effects of heavy metals on Leptometra celtica was found, and little is known about the effects of heavy metals on echinoderms in general. Bryan (1984) reported that early work had shown that echinoderm larvae were sensitive to heavy metals contamination. Migliaccio et al. (2014) reported that exposure of larvae from the Mediterranean shallow-water sea urchin Paracentrotus lividis to increased levels of cadmium and manganese caused abnormal larval development and skeletal malformations.

Potential impacts from the disposal of waste from the oil and gas sector (including drill cuttings, drilling mud and produced water) can include increased metal abundance (Cordes et al., 2016). Increased concentrations of harmful metals (e.g., barium) have been identified as causing community-level changes in megafaunal assemblages (Cordes et al., 2016). However, no specific evidence was recorded for Leptometra celtica or echinoderms. 

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.

Although there is no information available on the effect of hydrocarbons on Leptometra celtica, mass mortality of echinoderms has followed oil spills. Organisms must be exposed to the oil for an effect to occur, so exposure will have an influence (Lawrence, 1995). Crude oil from the Torrey Canyon in 1967 off Land’s End, Cornwall, and the detergent used to disperse it, caused mass mortality of echinoderms. Repopulation of one species, the sea potato Echinocardium cordatum, did not occur until two years later. The high sensitivity of Echinocardium cordatum was also seen in another soil off Brittany in 1978 and the discharge of oil-contaminated drill cuttings in the Dutch sector of the North Sea (Lawrence, 1995).

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. Certain anthropogenic chemicals are known as endocrine disrupter (ED) contaminants. These can cause dysfunctions in steroid hormone production/metabolism and activities, as well as inducing significant effects on reproductive competence, development and growth (Carnevali, 2005). These compounds can be bioaccumulated by organisms and include polychlorinated biphenyls (PCBs), nonylphenols and organotins (Barbaglio et al., 2006; Carnevali, 2005). Echinoderms are susceptible to bioaccumulation of such dissolved aquatic pollutants through primary uptake across external epithelia or secondary update from food (Smith et al. 1981, Tremolada et al. 2004 in Barbaglio, et al., 2006).

Sugni et al. (2010) exposed Antedon mediterranea to five different endocrine disrupters: triphenyltin (TPT), fenarimol (FEN), methyltestosterone (MET), p,p′-DDE (DDE), and cyproterone acetate (CPA), and found that TPT was the most effective in altering both reproductive and regenerative parameters, even at very low concentrations.

For Antedon mediterranea, Barbaglio et al. (2006) tested the effects of Fenarimol, a halogenated pesticide, particularly a fungicide, as well as TPT-Cl, an organotin compound used extensively in agriculture and in antifouling paints. This study showed that both compounds strongly affect skeletal development, as shown by both external and internal anatomical malformations, as well as regenerative potential. 

Some experiments have reproduced common conditions of exposure to environmental contaminants, with concentrations comparable to those of moderately polluted coastal zones. These showed that prolonged exposure to such compounds significantly affects the regenerative mechanisms (regeneration times, overall growth, general morphology and histological and cellular patterns; Barbaglio et al., 2006; Carnevali, 2005). If Leptometra celtica is exposed to these compounds, it is likely to be similarly affected through their interference with fundamental physiological processes, including growth, development and reproductive competence (Sugni et al., 2007).

Radionuclide contamination

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

Evidence

Tierney et al. (2017) found that radiocarbon (¹⁴C) was transported from the Sellafield nuclear site as far as the Firth of Lorn, Scotland (~260 km from Sellafield), and recorded ecosystem uptake via ¹⁴C enrichment in marine organisms. Although ¹⁴C activity did diminish with distance from Sellafield following dilution in Atlantic water, ¹⁴C enrichment was a result of uptake by phytoplankton during photosynthesis, which was transferred through the benthic food web as enriched particulate organic material. The Firth of Lorn mud basins support dense beds of Leptometra celtica (Tierney et al., 2017). Although this species was not sampled in the study, other suspension feeders (sea pens) were found to be enriched with ¹⁴C (Tierney et al., 2017). However, the study was undertaken in a different region and depth than the deep-sea Leptometra celtica assemblage biotopes, notably with different currents. As such, the evidence is considered insufficient for an assessment of the effects of radionuclide contamination on the biotopes. This pressure-feature combination is assessed as ‘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’, and no evidence was available on the effects of 'introduction of other substances' on Leptometra celtica.

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

Leptometra celtica assemblages occur in deep-water and the cold, open ocean waters that bathe the shelf margin and slope are typically well oxygenated (Hill, 2008). This may indicate that the species prefers such conditions. However, echinoderm oxygen consumption rates are typically lower than those found in representatives of other marine invertebrate phyla, such as crustaceans (Lawrence & Lane, 1982, in Hughes et al., 2011; Webster, 1975). Leptometra celtica may thus survive exposure to lower dissolved oxygen concentrations than other invertebrates, especially more active forms. Oxygen consumption varies depending on other environmental conditions influencing the metabolic rate. However, Hughes et al. (2011) found no change in echinoderm respiration rate with depth.

Sensitivity assessment. Leptometra celtica assemblages occur in well-oxygenated areas and are likely to have low oxygen consumption rates. Resistance is assessed as ‘High’ and resilience is assessed as ‘High’, therefore Leptometra celtica assemblage biotopes are considered to be ‘Not sensitive’ at the benchmark level.

Nutrient enrichment

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

Evidence

Intermittent mixing events may generate increased ammonium and nitrate concentrations at shelf break areas (Colloca et al., 2004), where the biotopes are known to occur. Colloca et al. (2004) stated that nutrient input at the shelf break due to water turbulence and shelf-break upwelling (Pinazo et al., 1996, in Colloca et al., 2004) could be involved in structuring the benthic and demersal assemblages, including high concentrations of crinoids. Nutrient enrichment is also associated with upwelled water and results in high pelagic productivity (Joint et al., 2002; Serrano et al., 2008; Tenore et al., 1995).  It is likely that Leptometra celtica would benefit from the additional detritus for filter-feeding due to this productivity increase.  

Nevertheless, by definition, the biotopes are considered 'Not sensitive' at the pressure benchmark, which assumes compliance with good status as defined by the WFD.

Organic enrichment

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

Evidence

Colloca et al. (2004) stated that an increase in organic matter transportation at the shelf break due to water turbulence and shelf break upwelling (Pinazo et al., 1996, in Colloca et al., 2004) could be involved in structuring the benthic and demersal assemblages, including high concentrations of crinoids. Organic enrichment is positively correlated with mud (Serrano et al., 2008), so a change in substratum may occur over time.  There are records of Leptometra celtica living deep sandy-muds in Scotland (SNH, 2013).  Leptometra celtica has been reported as occurring on sediment at depths of 40-200 m (Baxter et al., 2011).  However, abundant Leptometra celtica was recorded on ‘mixed muddy sediments with a surface scatter of stones and shells’, and Ferguson et al. (2018) (see also associated images of these biotopes) include a photograph of Leptometra celtica apparently clinging to dead shells or pebbles on an unconsolidated sediment substratum, at 265 m depth (Davies et al., 2008). The other images associated with these biotopes (from MESH cruise 01-07-01; Davies et al., 2008) show Leptometra celtica clinging to the seabed, which either consists of a sediment or a hard-bottom with a thin sediment veneer. Serrano et al. (2008) found Leptometra celtica associated with fine and very fine sands that were poorer in organic matter. Muddy substrata may, therefore, be suitable for Leptometra celtica, however, it may benefit from the presence of stones or shells.

Bo et al. (2010) concluded that upwelling conditions re-suspend organic particles but can also increase phytoplankton biomass in the euphotic layer, which subsequently sinks to the seafloor as organic detritus, favouring suspension-feeding organisms such as crinoids.  This depends on the amount and rate of sinking however, as phytodetritus may blanket the seafloor (see ‘smothering and siltation changes’ pressure).

Sensitivity assessment.  Leptometra celtica requires organic matter in suspension to filter feed (Fonseca et al., 2013). Therefore, the species would likely benefit from any organic enrichment. Please note that although Leptometra celtica is unlikely to be affected if the organic matter causes a change to mud substratum, the biotope would be lost and/or reclassified. Resistance for the organic enrichment pressure is assessed as ‘High’, resilience as ‘High’, and the Leptometra celtica assemblages are considered ‘Not sensitive’ at the benchmark level.

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 no resistance to this pressure and to be unable to recover from a permanent loss of available habitat.

Sensitivity assessment. Resistance is assessed as ‘None’, resilience is assessed as ‘Very low’ and sensitivity is considered to be ‘High’.

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

Crinoids are suspension feeders and can be found on a wide variety of substrata, depending on their attachment strategy. Some deep-sea stalked crinoids root in sediment (e.g., Bathycrinus species; Eléaume et al., 2012), and some deep-sea feather stars with long, slender cirri that are not distally hooked or prehensile (e.g., Atelecrinus species; Messing, 2013) can rest on hard or sediment substrata. Leptometra celtica has been reported as occurring on bedrock, gravel, shell, or sediment at depths of 40-200 m (Baxter et al., 2011). Ferguson et al. (2018) (see also associated images of these biotopes) include a photograph of Leptometra celtica apparently clinging to dead shells or pebbles on an unconsolidated sediment substratum, at 265 m depth (Davies et al., 2008). The other images associated with these biotopes (from MESH cruise 01-07-01; Davies et al., 2008) show Leptometra celtica clinging to the seabed, which either consists of sediment or a hard-bottom with a thin sediment veneer.  Howson et al. (2006) reported Leptometra celtica on hard substrata such as bedrock in shallow waters. No information is available to suggest that Leptometra celtica attaches to artificial hard substrata such as oil rigs. Oliveira et al. (2015) observed that a discarded fishing net stretched over soft bottom provided a fixation point for a large concentration of Leptometra cf. celtica. However, for the 'physical change (to another seabed type)' pressure to occur), the original substratum would be lost/removed, which would result in the removal of living species and likely lead to a change in biotope (i.e. loss of the biotope in that area).

Sensitivity assessment. If the sediment that characterizes the biotopes was replaced with rock substratum, this would represent a fundamental change to the physical character of the biotopes. Although evidence shows that Leptometra celtica can occur on a range of substrata, this change in biotope would cause a reclassification of the biotope (i.e., loss of the biotope). Resistance is, therefore, assessed as ‘None’, resilience as ‘Very low’, and sensitivity is 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

Sediment type is a key factor structuring the biological assemblage present in a biotope. A change in one Folk class for Leptometra celtica assemblages on coarse sediment could mean a change to ‘mixed’ or ‘sand and muddy sand’ substratum. For assemblages on sand, a change on one Folk class could mean a change to ‘mixed’, ‘coarse’ or ‘mud and sandy mud’. There are records of abundant Leptometra celtica living on ‘mixed muddy sediments with a surface scatter of stones and shells’, and on deep sandy-muds in Scotland (SNH, 2013).  Leptometra celtica has been reported as occurring on bedrock, gravel, shell, or sediment at depths of 40-200 m (Baxter et al., 2011). Ferguson et al. (2018) (see also associated images of these biotopes) include a photograph of Leptometra celtica apparently clinging to dead shells or pebbles on an unconsolidated sediment substratum, at 265 m depth (Davies et al., 2008). The other images associated with these biotopes (from MESH cruise 01-07-01; Davies et al., 2008) show Leptometra celtica clinging to the seabed, which either consists of sediment or a hard-bottom with a thin sediment veneer. The substrata ‘mixed’, ‘coarse’, ‘sand and muddy sand’ or ‘mud and sandy mud’ would, therefore, all be suitable for Leptometra celtica, but any associated species are likely to differ. As such, and due to the change in sediment type, it would likely result in a change to a different biotope.

Sensitivity assessment. A change in Folk class from ‘coarse’ sediment to ‘mixed’ or ‘sand and muddy sand’ would probably not affect the characterizing species (Leptometra celtica) which appears to have habitat preferences that would fall within this range. Equally, a change in Folk class from ‘sand’ to ‘mixed’, ‘coarse’ or ‘mud and sandy mud’ is unlikely to affect the characterizing species. However, this change in substratum may represent a fundamental change in the character of the biotopes and a change in the abundance of the associated species. This would result in the loss and/or reclassification of the biotopes. Resistance is, therefore, assessed as ‘None’, resilience as ‘Very low’ and the biotopes are considered to have ‘High’ sensitivity to a change in seabed type (by one Folk class).

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

As Leptometra celtica assemblages are characterized by species with very limited mobility, removal of the substratum at the benchmark pressure would cause destruction of the biotope within the affected area. Assuming adequate fixation substratum remains (Fonseca et al., 2013), recovery could occur from the regeneration of surviving individuals (Przibram, 1901, cited in Holland, 1991), new individuals moving into the area, and through larval recruitment. However, Leptometra celtica is likely to have low fecundity and low connectivity (Gallego et al., 2013), meaning the recruitment of new individuals following disturbance is likely to be more limited.

Sensitivity assessment. The resistance of Leptometra celtica assemblages to the removal of substratum is assessed as ‘None’, resilience as ‘Medium’ and overall sensitivity to the pressure is assessed as ‘Medium’.

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

Studies within La Fonera Canyon in the NW Mediterranean Sea showed that trawling gear passing near and along the canyon flanks down to 800 m depth significantly impacted the seafloor (Puig et al., 2012 in Fernadez-Arcaya et al., 2017). This could, therefore, have an impact on the associated communities.

Cranmer et al. (1984) found that specimens of crinoids (identified either as Leptometra celtica or Antedon bifida) were badly damaged when collected in trawl samples, with their cirri often missing. Despite crinoids being able to regenerate lost or damaged arms, or a new animal from the larger part if bisected (Przibram, 1901, cited in Holland, 1991), the cirri are used to attach to substratum (Rowley, 2007). Therefore, without these, the individuals will have reduced survival potential. Cook et al. (2013) noted a significant decline in abundance of Antedon bifida one year after a trawling event on a protected reef.  During trawl surveys, Colloca et al. (2004) observed that about 300 kg of crinoids, or about 200,000 individuals, could easily be collected in one hour of trawling. Clark & Clark (1967) noted that arm length in this species reaches at least 16.5 cm, which creates a span of over 30 cm, so it is unlikely that adult individuals could pass through the mesh of a fishing net.

The impact of otter trawling on beds of the congeneric species Leptometra phalangium has been documented for the eastern Mediterranean. Smith et al. (2000) examined an area affected by trawling on the north coast of Greece at approx. 200 m depth.  Aggregations of Leptometra phalangium, a dominant species in the control area, were observed on either side of the trawling lane. However, the rare individuals seen in the trawl lane were solitary and found raised on the bank of trawl-door plough marks. Leptometra phalangium and other echinoderms were strongly reduced in numbers in trawled areas, along with a decrease in the richness, abundance and biomass of benthic species (Smith et al., 2000). Similarly, Smith et al. (2007) found that the distribution of Leptometra phalangium was significantly negatively correlated with trawling impact. Mangano et al. (2013) examined trawling impacts in the southern Tyrrhenian Sea and showed that Leptometra phalangium was only found in areas where fishing activity was the least intensive. Furthermore, the crinoid bed of Leptometra celtica found by Fonseca et al. (2013) at around 500 m depth on the Portuguese south coast corresponded to an area thought not to be trawled by crustacean trawlers due to the substratum. Surrounding trawled areas displayed far fewer epibenthic taxa in comparison with the non-towed areas where crinoids occurred (Fonseca et al., 2013). They also noted that the crinoid bed was located in an “enclave of gravelly sand surrounded by muddy sediments” (p. 223), which were the habitat of the commercially trawled lobster, Nephrops norvegicus.

Removal of significant numbers of crinoid specimens is likely to have a large impact on the biotope’s structure and function. Leptometra celtica is able to crawl or swim (SNH pers. comm., in Mazik et al., 2015; M. Eleaume, 2019, pers. comm., 5 May 2019) and may exhibit this behaviour if subject to disturbance. However, it is unknown how far or quickly they move. This behaviour may allow them to repopulate damaged areas, if a viable population exists nearby, through either larval settlement or swimming adults. Clark et al. (2019) speculated that feather stars might be early re-colonizers on seamounts following abatement of long-term bottom trawling but also noted that such individuals might be remnants missed by trawling rather than (or as well as) recruits. Unstalked crinoids have also been observed recolonizing scours left behind by drifting icebergs in Antarctica (Gutt et al., 1996).

Sensitivity assessment. Surface abrasion would remove, damage or kill most of the population of Leptometra celtica, so resistance is assessed as ‘None’. Recovery could occur through larval settlement or adult immigrants, so resilience is assessed as ‘Medium’. Overall sensitivity to the pressure is assessed as ‘Medium’.

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, if not identical effects as the 'abrasion' pressure (see above).

Sensitivity assessment. Leptometra celtica lives on the surface of the seabed. However, any impacts to the sub-surface would inevitably affect the seabed surface. Most of the population, therefore, would likely be killed, damaged or removed by the pressure, causing loss of the biotope, and recovery would be reliant upon larval settlement or adult immigration. Resistance is assessed as ‘None’, resilience as ‘Medium’ and overall sensitivity to the pressure is assessed as ‘Medium’.

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

Leptometra celtica is a suspension feeder (Flammang, 1995) and requires suspended particles carried by near-bottom currents to feed.  The species occurs on the edge of the continental shelf (e.g. at 200 m depth; Howell, 2010). These environments are characterized by high concentrations of suspended material rising from the shelf-break (Lavaleye et al., 2002), indicating a preference for a certain level of suspended material. As with Leptometra phalangium, Leptometra celtica lives in direct contact with mobile sandy-gravel substrata in turbid areas where strong currents deliver particles for suspension feeding (Colloca et al., 2004; Davies et al., 2014).

La Touche & West (1980) found that 17% of the gut contents of Antedon bifida were inorganic particles, which was consistent throughout the year and for all locations studied.  An increase in turbidity, reducing light availability, may reduce primary production by phytoplankton in the water column and thus influence food availability. However, particulate food supplies are also likely to be derived from distant sources, so the long-term impact is not likely to be significant. A large fraction of Antedon bifida stomach contents (ca. 65%) may consist of detritus, which is considered an important source of nutrition (La Touche & West, 1980). This indicates that the species isn’t solely reliant upon suspended particles. However, Meyer (1982) reported large variations in faecal composition among different individuals of a single reef-dwelling crinoid, Anneissia (formerly Comanthus) bennetti sampled at the same place during a single dive (e.g., 9-57% for sediment grains; 5.5-17% for diatoms).

Several groups of shallow-water feather stars include light-sensitive species that are cryptic during the day and crawl to feeding perches at dusk (e.g., Meyer & Macurda Jr, 1980). Antedon mediterranea is one of these shade-loving (sciaphilic) species, which means it may be positively impacted by light reduction in its environment. Antedon bifida is found in shallow areas, under floating pontoons in ports for example (i.e., protected from direct light). From observations of Antedon bifida individuals maintained in tanks, individuals will move during night time rather than day time (M. Eleaume, pers. comm., 5 May 2019). Therefore, Antedon bifida may also be shade-loving (sciaphilic) as well. Antedon petasus is mostly found in waters deeper than 90 m (below the euphotic zone) and sometimes co-occurs with Leptometra celtica in the Bay of Biscay (M. Eleaume, pers. comm. 5 May 2019), suggesting a shade-loving (sciaphilic) behaviour as well.

Sensitivity assessment.  Leptometra celtica assemblages occur around shelf edges areas characterised by high concentrations of suspended material (Lavaleye et al., 2002). The characterizing species requires suspended material for feeding but is likely to be shade-loving (sciaphilic), which means it may be positively impacted by light reduction in its environment. As such, Leptometra celtica can probably tolerate an increase in suspended sediment at the benchmark level of change in one rank on the WFD scale for one year (i.e., from 10 to 100 mg/l). Resistance is, therefore, assessed as ‘High’, resilience as ‘High’ and the biotopes are considered ‘Not sensitive’ at the benchmark level.

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

Burial by sediment is the main cause of mass mortality reported for fossil echinoderms. This can be caused in modern seas by events ranging from tectonically related turbidity flows (Garfield et al., 1994), to severe storms (Sanchez-Vidal et al., 2012), or to siltation from dredging or ocean mining (Lawrence, 1995). In addition, increases in oil and gas exploration to deeper offshore waters (including in the UK) could lead to a discharge of drilling waste, which consists primarily of dense particulate solids that settle rapidly and accumulate in sediments down-current from the platform (Fernadez-Arcaya et al., 2017).

Blanchard (2004) examined trawling impacts on the Bay of Biscay coast of France at around 100 m depth and noted that suspension feeders such as Leptometra celtica are sensitive to particles resuspended by the passage of the trawl. Hill (2008) noted that most of the feeding and respiratory structures of feather stars will become clogged if subjected to smothering by sediment. However, as the arms of Leptometra celtica can be up to 16.5 cm in length (Clark & Clark, 1967), the tops of the arms could extend above the sediment (Hill, 2008). Furthermore, adult Leptometra celtica has long cirri, typically 3.5-4 cm in length that may be used to raise themselves up above the substratum (M. Eleaume, pers. comm., 5 May 2019).  Some comatulid species have also developed behaviours that seem to be directed to compensating for feeding structure clogging. Pentametrocrinus atlanticus, a deep-sea solitary and probably gravitational settling feeder, has been observed in Whittard Canyon shaking their arms after an ROV had disturbed the surrounding substratum (M. Eleaume, 2019, pers. comm., 5 May). Similar behaviour (shaking of arms) has been observed from Antedon bifida kept in tanks (M. Eleaume, 2019, pers. comm., 5 May).

Sensitivity assessment. Although smothering may cause the feeding and respiratory structures of Leptometra celtica to become clogged (Hill, 2008), the species may be able to compensate for clogging by shaking their arms. Leptometra celtica can also raise up and extend their arms above a 5 cm deposit of fine material, and/or use their cirri to raise themselves up above the substratum, allowing them to filter feed.  As such, resistance is assessed as ‘High’, resilience as ‘High’ and the biotopes are considered ‘Not sensitive’ at the benchmark level. Any abrasion effects associated with the removal of this pressure are covered under the specific abrasion pressure.

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

Burial by sediment is the main cause of mass mortality reported for fossil echinoderms. This can be caused in modern seas by events ranging from tectonically generated turbidity flows (Garfield et al., 1994), to severe storms (Sanchez-Vidal et al., 2012), or to siltation from dredging or ocean mining (Lawrence, 1995). In addition, increases in oil and gas exploration to deeper offshore waters (including in the UK) could lead to a discharge of drilling waste, which consists primarily of dense particulate solids that settle rapidly and accumulate in sediments down-current from the platform (Fernadez-Arcaya et al., 2017).

Blanchard (2004) examined trawling impacts on the Bay of Biscay coast of France at around 100 m depth and noted that suspension feeders such as Leptometra celtica are sensitive to particles resuspended by the passage of the trawl. Hill (2008) noted that the feeding and respiratory structures of feather stars will become clogged if subjected to smothering by sediment. The slender arms of Leptometra celtica are only up to 16.5 cm

Around a drill site in the Faroe-Shetland Channel, Jones et al. (2006) reported a ca 87% reduction in density of another crinoid species, Heliometra glacialis, in an area affected by 1.5 m of sediment smothering, compared to an undisturbed reference area.  Heliometra glacialis and Leptometra celtica have a similar physiology and ecology, so a similar sensitivity is assumed. Furthermore, the reduction in suspension feeders in disturbed areas may have also promoted the preferential recolonization by epibenthic deposit feeders. This changes the overall species composition (Jones et al., 2006), resulting in loss of the existing biotope.

Survival of filter/suspension feeders was directly linked to motility in the Faroe-Shetland Channel (Jones et al., 2006), and they were found to increase in abundance with a reduction in smothering disturbance. The impact of disturbance on sessile forms was thought to be directly related to levels of suspended solids and to their ability to clear particles from their feeding and respiratory surfaces (Rogers, 1990, in Jones et al., 2006). Although the mobility of Leptometra celtica is limited, their crawling/swimming behaviour (SNH pers. comm., in Mazik et al., 2015; M. Eleaume, pers. comm., 5 May 2019) might, therefore, allow rapid re-colonization of disturbed areas if the pressure is removed.

Sensitivity assessment. Deposition of 30 cm of fines may completely smother Leptometra celtica assemblages, particularly as their arms (16.5 cm in length; Clark & Clark, 1967) and long cirri (3.5-4 cm) will not be able to extend above the sediment. Resistance is therefore assessed as ‘None’.  Recovery could occur from adults moving into the area and from larval recruitment. Therefore, resilience is assessed as ‘Medium’, and overall sensitivity is assessed as ‘Medium’. Any abrasion effects associated with the removal of this pressure are covered under the specific abrasion pressure.

Litter

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

Evidence

In UK waters, the Leptometra celtica assemblage biotopes have only been found to date at the SW Canyons (Howell et al., 2010). Canyons act as natural traps, deposits and transport pathways of particles from the shelf to the abyssal plains (Granata et al., 1999; Oliveira et al., 2007; Turchetto et al., 2007 in Oliveira et al., 2015), and the hydrodynamic processes of canyons also enhance the transport of litter (Fernadez-Arcaya et al., 2017). A study comparing the accumulation of marine litter in different deep-sea habitats across Europe showed that litter densities in canyons were higher than in other physiographic settings, such as continental shelves, seamounts, banks, and mounds (Pham et al., 2014 in Fernadez-Arcaya et al., 2017).

The effects of litter on the benthic fauna are little understood. However, impacts such as suffocation and physical damage of sessile fauna (e.g., corals, sponges, crinoids) have been observed (Ramirez-Llodra et al., 2013; Pham et al., 2014; Bergmann et al., 2015 in Fernadez-Arcaya et al., 2017). Oliveira et al. (2015) studied marine litter in a submarine canyon off SW Portugal and found that coiled up fishing lines were a primary source of entanglements for tridimensional complex or branching fauna, including Leptometra celtica. Echinodermata may become entangled on their own while moving on the seafloor or scavenging for food, but since they are mobile it is plausible that they might be able to escape with only minor distress (Oliveira et al., 2015). In addition, some types of litter may provide suitable substratum for some species. Oliveira et al. (2015) observed a net stretched over a soft bottom that provided a fixation point for a large concentration of Leptometra cf. celtica. Slightly above the seafloor, these filter feeder organisms were apparently in an advantageous position to gather food from the bottom currents.

Sensitivity assessment. Marine litter is likely to cause some entanglement of Leptometra celtica assemblages, however, the species can utilise litter as a fixation substratum (Oliveira et al., 2015). Resistance is assessed as ‘Medium’, resilience as ‘Medium’ and overall sensitivity is considered to be ‘Medium’.

Electromagnetic changes

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

Evidence

No evidence could be found for the effects of electromagnetic changes on Leptometra celtica. Therefore, this pressure benchmark is assessed as ‘No evidence’.

Underwater noise changes

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

Evidence

Leptometra celtica has no means to detect noise, however, crinoids do respond to changes in water pressure and movement (i.e. vibrations). For example, Morais et al. (2007) noted that Leptometra celtica displayed a ‘crouching’ behaviour as a reaction to an approaching ROV and Promachocrinus kerguelensis in the Antarctic has been observed reacting to an approaching ROV by ‘flying’ (M. Eleaume, pers. comm., 5 May 2019). The ‘flying’ or ‘crouching’ behaviour they display may be a consequence of vibration (bow waves generated by the approaching ROVs or submersible) or the light associated with the video camera. In other species, such as Atelecrinus helgae or some Democrinus from Whittard Canyon, touching the individuals using the arm of an ROV also induces a ‘flying’ or ‘crouching’ reaction (M. Eleaume, pers. comm., 5 May 2019). It is unknown what sort of receptors crinoids have, and whether these receptors are sensitive to vibrations but this cannot be ruled out. 

Sensitivity assessment. Observations by Morais et al. (2007) suggest that Leptometra celtica displays a likely avoidance response (i.e. ‘crouching’ behaviour) to approaching ROVs (vibration), in a similar way to other crinoid species (M. Eleaume, pers. comm., 5 May 2019). As there is no evidence of mortality, and effects are limited to behavioural responses, resistance is assessed as ‘High’, resilience as ‘High’ and overall the biotopes are considered to be ‘Not sensitive’ at the benchmark level.

Introduction of light or shading

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

Evidence

Several groups of shallow-water feather stars include light-sensitive species that are cryptic during the day and crawl to feeding perches at dusk (e.g., Meyer & Macurda Jr, 1980).  Antedon mediterranea is one of these shade-loving (sciaphilic) species, which means it may be negatively impacted by the introduction of light. Antedon bifida is found in shallow areas, under floating pontoons in ports for example (i.e., protected from direct light). From observations of Antedon bifida individuals maintained in tanks, individuals will move during night time rather than day time (M. Eleaume, pers. comm., 5 May 2019). Therefore, Antedon bifida may also be shade-loving (sciaphilic) as well. Antedon petasus is mostly found in waters deeper than 90 m (below the euphotic zone) and sometimes co-occurs with Leptometra celtica in the Bay of Biscay (M. Eleaume, 2019, pers. comm., 5 May), suggesting a shade-loving (sciaphilic) behaviour as well.

Leptometra celtica, and other crinoids have also been shown to respond to changes in anthropogenic light. Messing (2019, pers. comms., 30 April) observed strong responses (crown rotation, arm waving) in two species of stalked crinoids in response to bright submersible lights at a depth of ~400 m in the Bahamas. Furthermore, Morais et al. (2007) noted that Leptometra celtica displayed a ‘crouching’ behaviour as a reaction to an approaching ROV and Promachocrinus kerguelensis in the Antarctic has been observed reacting to an approaching ROV by ‘flying’ (M. Eleaume, 2019, pers. comm., 5 May). The ‘flying’ or ‘crouching’ behaviour they display may be a consequence of the light associated with the video camera (or vibration from bow waves generated by the approaching ROVs or submersible). In other species, such as Atelecrinus helgae or some Democrinus from Whittard Canyon, touching the individuals using the arm of an ROV also induces a ‘flying’ or ‘crouching’ reaction (M. Eleaume, pers. comm., 5 May 2019). It is unknown what sort of receptors crinoids have, and whether these receptors are sensitive to light, but this cannot be ruled out. 

Sensitivity assessment. Although Leptometra celtica assemblages occur at considerable depths where little or no incident light penetrates from the surface, and where the movement of surface vessels is not likely to affect the species, evidence shows that they respond to changes in anthropogenic light.  Observations by Messing (2019, pers. comms., 30 April), Eleaume (2019, pers. comm., 5 May) and Morais et al. (2007) suggest that Leptometra celtica and other crinoids display a likely avoidance response (i.e. crown rotation, arm waving, ‘crouching’ or ‘flying’ behaviour) to approaching ROVs or submersible (bright lights).  As there is no evidence of mortality, and effects are limited to behavioural responses, resistance is assessed as ‘High’, resilience as ‘High’ and overall the biotopes are considered to be ‘Not sensitive’ at the benchmark level.

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

Leptometra celtica is thought to have a short pelagic larval duration, and therefore low connectivity (Gallego et al., 2013). As such, the biotopes will not be affected by barriers to species movement. This pressure benchmark is assessed as ‘Not relevant’.

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

Leptometra celtica is mainly sessile, despite exhibiting some crawling and swimming behaviour of limited unknown distance (Rowley, 2007; SNH, pers. comm., in Mazik et al., 2015; M. Eleaume, 2019, pers. comm., 5 May). Its larvae are thought to have a short pelagic larval duration, and therefore low connectivity (Gallego et al., 2013). As such, Leptometra celtica will not be affected by an increased risk of collision. This pressure benchmark is assessed as ‘Not relevant’.

Visual disturbance

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

Evidence

Leptometra celtica, and other crinoids do respond to changes in movement and light. Messing (2019, pers. comms., 30 April) observed strong responses (crown rotation, arm waving) in two species of stalked crinoids in response to bright submersible lights at a depth of ~400 m in the Bahamas. Furthermore, Morais et al. (2007) noted that Leptometra celtica displayed a ‘crouching’ behaviour as a reaction to an approaching ROV and Promachocrinus kerguelensis in the Antarctic has been observed reacting to an approaching ROV by ‘flying’ (M. Eleaume, 2019, pers. comm., 5 May). The ‘flying’ or ‘crouching’ behaviour they display may be a consequence of the light associated with the video camera or vibration (bow waves generated by the approaching ROVs or submersible). In other species, such as Atelecrinus helgae or some Democrinus from Whittard Canyon, touching the individuals using the arm of an ROV also induces a ‘flying’ or ‘crouching’ reaction (M. Eleaume, 2019, pers. comm., 5 May). It is unknown what sort of receptors crinoids have, and whether these receptors are sensitive to light, but this cannot be ruled out. 

Sensitivity assessment. Observations by Messing (2019, pers. comms., 30 April), Eleaume (2019, pers. comm., 5 May) and Morais et al. (2007) suggest that Leptometra celtica and other crinoids display a likely avoidance response (i.e. crown rotation, arm waving, ‘crouching’ or ‘flying’ behaviour) to approaching ROVs or submersible (bright lights).  As there is no evidence of mortality, and effects are limited to behavioural responses, resistance is assessed as ‘High’, resilience as ‘High’ and overall the biotopes are considered to be ‘Not sensitive’ at the benchmark level.

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

Leptometra celtica is not subject to cultivation or translocation so this pressure is considered ‘Not relevant’.

Introduction or spread of invasive non-indigenous species

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

Evidence

No evidence could be found for the effects of 'introduction or spread of non-indigenous' species on Leptometra celtica. This pressure benchmark is assessed as ‘No evidence’.

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

Myzostomida are the most abundant agents to infect Crinoidea (Jangoux, 1987a). Leptometra celtica is affected by two myzostome worms: the semi-parasitic Pulvinomyzostomum pulvinar, which lives within the digestive tract of its crinoid host (Jangoux, 1987b), and the epibiont Myzostoma alatum. Graff (1884) originally identified the host of both as Leptometra phalangium, but his specimens were collected off NW Scotland, outside the range of this species. Clark (1921) listed both species as occurring on both Leptometra species, with specimens of Pulvinomyzostomum pulvinar from NW Scotland and off Italy, and Myzostoma alatum from NW Scotland, Portugal, and the Mediterranean coast of Spain. Jangoux (1987b) also listed Roscoff for the former and noted that its infestation level can reach 10-20%. Pulvinomyzostomum pulvinar does not injure its host, but, being located at the anterior part of the digestive tract, it instead diverts the flow of food particles entering the crinoid’s mouth (Prenant, 1959, West & West, 1976 in Jangoux, 1987b).  Crinoids are noted to be sensitive to external agents (those that attach themselves to the host’s external body surface, such as Myzostoma alatum), possibly resulting from a weak defensive capacity of their epidermal barrier (Jangoux, 1987a).

Although no diseases associated with crinoids have been reported, echinoderms in other parts of the world have been severely affected by epidemic type diseases, so there is the potential for this to occur. Nevertheless, this pressure only considers microbial pathogens which are spread/introduced by human activities/humans, or are controllable by management, or reported to cause a decline in the affected species population.  Myzostomes are therefore not deemed relevant to the pressure, so this pressure is assessed as ‘No evidence’.

Removal of target species

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

Evidence

Leptometra celtica is not a commercially or recreationally targeted species so this pressure is ‘Not relevant’.

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

This pressure only assesses the biological effects of the removal of species. For evidence on the effects of the removal itself, please see the physical damage pressures.

Leptometra celtica is a small crinoid (a feather star) that lives on the surface of the seabed, and it raises its arms to feed on suspended particles carried by near-bottom currents. The species is therefore at risk of being removed as by-catch. This is supported by evidence showing that, during trawl surveys, about 300 kg of crinoids, or about 200,000 individuals, could easily be collected in one hour of trawling (Colloca et al., 2004). If a significant proportion of Leptometra celtica are removed, the biotope structure (species richness and diversity) will be altered. Evidence for this loss of structure has been recorded by Smith et al. (2000), who noted a strong reduction in Leptometra phalangium and other echinoderms in trawled areas of the eastern Mediterranean, along with a decrease in the richness, abundance and biomass of benthic species.

The degree of recovery would depend on the ability of Leptometra celtica to survive damage (Przibram, 1901, cited in Holland, 1991), immigrate into an area via swimming (Scottish Natural Heritage pers. comm., in Mazik et al., 2015; M. Eleaume, 2019, pers. comm., 5 May), or recolonise through larval recruitment. However, Leptometra celtica is likely to have low fecundity, typical of most crinoids (McEdward et al., 1988, in Holland, 1991), and Gallego et al. (2013) suggest the species has low connectivity, resulting from a short pelagic larval duration. Although Leptometra celtica occurs inshore as well as in the deep-sea offshore, any significant exchange of organisms between these areas is unlikely, meaning that the populations are likely to be distinct (Gallego et al., 2013). Recruitment of new individuals following disturbance will, therefore, be limited to any viable populations nearby.

Sensitivity assessment. Trawl surveys have shown that large quantities of crinoids can be collected during one hour of trawling (Colloca et al., 2004). The removal of a significant proportion of Leptometra celtica would alter the biotope structure (species richness and diversity), so resistance is assessed as ‘Low’.  Resilience is assessed as ‘Medium’, as recovery could occur through larval recruitment and individuals moving into the area. Sensitivity is therefore assessed as ‘Medium’.