The Marine Life Information Network

Temperature increase (local)

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

Evidence

The genus Heliometra is boreal and follows the appropriate isotherms as their distribution is plotted along the west American coast becoming more bathyal towards the equator (Fell, 1966). Clark & Clark (1967) suggested a thermal range of -1.9 to 5.8°C. Similarly, Dyer et al. (1984) recorded Heliometra glacialis in Arctic waters along the west coast of Svalbard, south to Bear Island in a temperature range of -1.5 to 4°C. They considered it to be an Arctic indicator species. Deja et al. (2023) also reported Heliometra glacialis at two locations in the Spitsbergen fjords, Svalbard, where the temperature and salinity -1.45°C and 34.3, and 2.7°C and 33.7 respectively. Fell (1966) suggested that Heliometra glacialis was eurybathic, as it is recorded from 10 to 1350 m noting that its distribution along the west American coasts followed their isotherms and became more bathyal towards the equator. 

Gersemia fruticosa colonies were kept at ambient temperatures from December 2006 to April 2007, which ranged from 0°C to 9°C, during aquaria-based studies by Sun et al. (2011). This suggested that Gersemia fruticosa could withstand large natural fluctuations in temperature. Furthermore, planulation occurred in Gersemia fruticosa when the temperature was at its annual minimum, suggesting that temperature is not the driving force. No information on the temperature range of Actinostola sp. was found but it is a noted deep-sea genus often associated with thermal vents.  

This biotope in UK and Irish waters is only known to occur at the Wyvile-Thompson Ridge, a bathymetric feature that separates deep Atlantic and Arctic water masses. This biotope is distributed on the northern (Arctic) side of the Wyvile-Thompson Ridge. Bett (2001) reported a difference between the benthic communities on the north and south sides of the Wyville-Thomson Ridge. The northern side was dominated by subzero arctic waters of the Norwegian Deep Water Current below 500 m (Bett, 2001; Sherwin & Turrell, 2005). 

Sensitivity assessment. No direct evidence was found on the effect of local temperature change on any of the characterizing species. This biotope likely occurs in the UK and Ireland at the most southern limit of its distribution. Despite some evidence for tolerance in temperature fluctuations, a biotope characterized by cold arctic waters, distributed at its most southerly limit would likely be adversely affected by increases in temperature at the benchmark level. Furthermore, the dominant characteristic species Heliometra glacialis is an Arctic species, restricted to circumpolar waters. However, the temperature range is controlled by the deep water currents and is likely to be stable. For example, Sherwin et al. (2012) reported that the seawater temperature of the upper 800 m of the Rockall Trough fluctuated between ca 9.0 and 10.5°C from 1948 to 2010. While pelagic larvae may tolerate a range of temperatures, adults may be more stenothermal, but no direct evidence was found. Hence, while natural temperature changes are unlikely, exposure to localised thermal effluents at the benchmark level (e.g. from deep-sea installations or operations, however unlikely) may be detrimental.  Therefore, resistance to a change in temperature is assessed as 'Medium' as a precaution, albeit with 'Low' confidence. Resilience is probably 'Medium' so sensitivity is assessed as 'Medium', again with 'Low' confidence. 

Temperature decrease (local)

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

Evidence

The genus Heliometra is boreal and follows the appropriate isotherms as their distribution is plotted along the west American coast becoming more bathyal towards the equator (Fell, 1966). Clark & Clark (1967) suggested a thermal range of -1.9 to 5.8°C. Similarly, Dyer et al. (1984) recorded Heliometra glacialis in Arctic waters along the west coast of Svalbard, south to Bear Island in a temperature range of -1.5 to 4°C. They considered it to be an Arctic indicator species. Deja et al. (2023) also reported Heliometra glacialis at two locations in the Spitsbergen fjords, Svalbard, where the temperature and salinity -1.45°C and 34.3, and 2.7°C and 33.7 respectively. Fell (1966) suggested that Heliometra glacialis was eurybathic, as it is recorded from 10 to 1350 m noting that its distribution along the west American coasts followed their isotherms and became more bathyal towards the equator. 

Gersemia fruticosa colonies were kept at ambient temperatures from December 2006 to April 2007, which ranged from 0°C to 9°C, during aquaria-based studies by Sun et al. (2011). This suggested that Gersemia fruticosa could withstand large natural fluctuations in temperature. Furthermore, planulation occurred in Gersemia fruticosa when the temperature was at its annual minimum, suggesting that temperature is not the driving force. No information on the temperature range of Actinostola sp. was found but it is a noted deep-sea genus often associated with thermal vents.  

This biotope in UK and Irish waters is only known to occur at the Wyvile-Thompson Ridge, a bathymetric feature that separates deep Atlantic and Arctic water masses. This biotope is distributed on the northern (Arctic) side of the Wyvile-Thompson Ridge. Bett (2001) reported a difference between the benthic communities on the north and south sides of the Wyville-Thomson Ridge. The northern side was dominated by subzero arctic waters of the Norwegian Sea Deep Water Current below 500 m (Bett, 2001; Sherwin & Turrell, 2005). 

Sensitivity assessment. No direct evidence was found on the effect of local temperature change on any of the characterizing species. This biotope likely occurs in the UK and Ireland at the most southern limit of its distribution. Despite some evidence for tolerance in temperature fluctuations, a biotope characterized by cold arctic waters, distributed at its most southerly limit would likely be adversely affected by increases in temperature at the benchmark level. Furthermore, the dominant characteristic species Heliometra glacialis is an Arctic species, restricted to circumpolar waters. However, the temperature range is controlled by the deep water currents and is likely to be stable. For example, Sherwin et al. (2012) reported that the seawater temperature of the upper 800 m of the Rockall Trough fluctuated between ca 9.0 and 10.5°C from 1948 to 2010. While pelagic larvae may tolerate a range of temperatures, adults may be more stenothermal, but no direct evidence was found. Hence, while natural temperature changes are unlikely, exposure to localised thermal effluents at the benchmark level (e.g. from deep-sea installations or operations, however unlikely) may be detrimental. Therefore, resistance to a change in temperature is assessed as 'Medium' as a precaution, albeit with 'Low' confidence. Resilience is probably 'Medium' so sensitivity is assessed as 'Medium', again with 'Low' confidence. 

Salinity increase (local)

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

Evidence

Echinoderms are osmoconformers and generally stenohaline due to their lack of an excretory organ, and their poor ability to osmoregulate (Binyon, 1966; Stickle & Diehl, 1987), while several species are recorded from extreme salinities (Stickle & Diehl, 1987; Russell, 2013). However, no information on the salinity tolerance of the characteristic species was found.  

Roberts et al. (2010b) suggested that hypersaline effluent dispersed quickly but was more of a concern at the seabed and in areas of low energy where widespread alternations in the community of soft sediments were observed. In several studies, echinoderms and ascidians were among the most sensitive groups examined (Roberts et al., 2010b). Fernández-Torquemada et al. (2013) suggested that echinoderms could be a useful early bioindicator for the effects of increased salinity.  In the Mediterranean, echinoderms were absent within one year in the areas affected by hypersaline effluent from a desalination plant but returned after dilution of the discharge with seawater (Fernández-Torquemada et al., 2013).

However, seawater salinity in the deep sea is more stable than inshore waters. For example, in the Rockall Trough, the deep water temperature and salinity are determined by ocean currents, such as the Eastern North Atlantic Water, Wyville Thompson Ridge Overflow Water, the Labrador Sea Water and the Antarctic Bottom Water (Gage, 1986; Sherwin et al., 2012). Sherwin et al. (2012) reported that the seawater salinity of the upper 800 m of the Rockall Trough had fluctuated between ca 35.25 and 35.45 from 1948 to 2010. Sherwin et al. (2012) reported that the salinity of the seawater in Rockall Trough was 35.4 at ca 500 m and dropped to 35.15 at ca 1,500 m (in October 2006). Ellett & Roberts (1973) recorded a salinity range of ca 35.05 to 35.25 over the Wyville-Thomson Ridge between 1949 and 1952. 

Sensitivity assessment. The species that dominate this biotope (e.g. Heliometra glacialis, Actinostola sp. and Gersemia sp.) are probably adapted to stable salinity conditions and have limited tolerance to salinity change. An increase in salinity from full to >40 psu is probably detrimental to the important characteristic species of the biotope. However, it is unlikely that this biotope would be exposed to hypersaline conditions (or effluent) unless from a newly opened brine seep or an unknown deep-sea operation. Although there is no direct evidence of the effects of hypersaline water on the characteristic species, the stenohaline nature of the echinoderms suggests that hypersaline conditions may cause mortality. Therefore, resistance is assessed as 'Low' but at Low confidence. Resilience would probably be 'Medium' so sensitivity is assessed as 'Medium'  but with 'Low' confidence.

Salinity decrease (local)

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

Evidence

Echinoderms are osmoconformers and generally stenohaline due to their lack of an excretory organ, and their poor ability to osmoregulate (Binyon, 1966; Stickle & Diehl, 1987), while several species are recorded from extreme salinities (Stickle & Diehl, 1987; Russell, 2013). However, no information on the salinity tolerance of the characteristic species was found.  

Roberts et al. (2010b) suggested that hypersaline effluent dispersed quickly but was more of a concern at the seabed and in areas of low energy where widespread alternations in the community of soft sediments were observed. In several studies, echinoderms and ascidians were among the most sensitive groups examined (Roberts et al., 2010b). Fernández-Torquemada et al. (2013) suggested that echinoderms could be a useful early bioindicator for the effects of increased salinity.  In the Mediterranean, echinoderms were absent within one year in the areas affected by hypersaline effluent from a desalination plant but returned after dilution of the discharge with seawater (Fernández-Torquemada et al., 2013).

However, seawater salinity in the deep sea is more stable than inshore waters. For example, in the Rockall Trough, the deep water temperature and salinity are determined by ocean currents, such as the Eastern North Atlantic Water, Wyville Thompson Ridge Overflow Water, the Labrador Sea Water and the Antarctic Bottom Water (Gage, 1986; Sherwin et al., 2012). Sherwin et al. (2012) reported that the seawater salinity of the upper 800 m of the Rockall Trough had fluctuated between ca 35.25 and 35.45 from 1948 to 2010. Sherwin et al. (2012) reported that the salinity of the seawater in Rockall Trough was 35.4 at ca 500 m and dropped to 35.15 at ca 1,500 m (in October 2006). Ellett & Roberts (1973) recorded a salinity range of ca 35.05 to 35.25 over the Wyville-Thomson Ridge between 1949 and 1952. 

Sensitivity assessment. The species that dominate this biotope (e.g. Heliometra glacialis, Actinostola sp. and Gersemia sp.) are probably adapted to stable salinity conditions and have limited tolerance to salinity change. An increase in salinity from full to reduced is probably detrimental to the important characteristic species of the biotope. However, it is unlikely that this biotope would be exposed to hyposaline conditions (or effluent) unless from a newly opened freshwater seep or an unknown deep-sea operation. Although there is no direct evidence of the effects of hyposaline water on the characteristic species, the stenohaline nature of the echinoderms suggests that hyposaline conditions may cause mortality. Therefore, resistance is assessed as 'Low' but at Low confidence. Resilience would probably be 'Medium' so sensitivity is assessed as 'Medium'  but with 'Low' confidence.

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

Deep sea habitats are probably dominated by mass water transport due to oceanic currents. For example, water flow in the Rockall Trough is dominated by the Eastern North Atlantic Water, Wyville Thompson Ridge Overflow Water, the Labrador Sea Water and the Antarctic Bottom Water (Gage, 1986; Sherwin et al., 2012), except near Feni Ridge or Anthon Dohrn seamount which are also influenced by tidal oscillation. Gage (1986) reported maximum flow rates of ca 0.5 m/s within 150 m of the bottom on the Feni Ridge west of the Anthon Dohrn seamount, mostly due to tidal oscillation, and associated with current-moulded bedforms (e.g. ripples). However, lower tidal currents <0.05 m/s with a maximum of ca 0.21 m/s were recorded within 400-500 m of the bottom elsewhere. Flow speeds in the Rockall Trough are typically 0.15 to 0.3 m/s (Wienberg et al., 2008) but localised flow over mounds, sea mount and other physical features probably affect local currents. 

This biotope occurs on cobble and pebble lag and occasional boulders under moderate to high energy currents from the lower reaches of the northern slope of the Wyville-Thomson Ridge in the Faeroe-Shetland Channel (JNCC, 2010; Scottish Government, 2024). The current speeds experienced in this biotope are unclear but the substratum suggests a minimum mean current speed of at least 1 m/s based on the sing the Hjulstrom-Sundborg diagram. 

Fell (1966) suggested that crinoids are moderately rheophilic, and avoid areas of low water flow and areas of excessive or strong water flow that would damage their delicate structures or resuspend sediment. Feather stars show plasticity in their feeding behaviour in response to changes in bottom-current flow, arranging their arms in various planar, conical, or parabolic postures in response to laminar, near-bottom flow (Hyman, 1955; La Touche, 1978; Macurda & Meyer, 1974; Meyer & Macurda Jr., 1980). The biotope is dominated by suspension feeders that require good water flow to provide food and oxygen. The abundance of Heliometra glacialis suggests the current regime is suitable for the species. 

Sensitivity assessment. A decrease in water flow could potentially facilitate the deposition of finer sediments (e.g. sands) and ultimately change the characteristic substrata and, therefore, the biotope. Similarly, an increase in water flow could result in the loss of the crinoids, at least. However, the biotope is characteristic of the high-energy environment of the Wyvile-Thompson Ridge and is probably exposed to tidal streams greater than 1 m/s, and considerable mass water transport.  Therefore, a change in the water flow of 0.1 – 0.2 m/s is probably not significant, and resistance is assessed as ‘High’. Hence, resilience is also ‘High’ and sensitivity is assessed as ‘Not sensitive’ at the benchmark level, albeit with 'Low' confidence. 

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 deep-sea biotope is not exposed to changes in emersion. 

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

This biotope occurs at mid-bathyal depths and will not be impacted by wave exposure. Hence, this pressure is assessed as ‘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

Bryan (1984) reported that early work had shown that echinoderm larvae were sensitive to heavy metals, e.g. the intolerance of larvae of Paracentrotus lividus to copper (Cu) had been used to develop a water quality assessment. Kinne (1984) reported developmental disturbances in Echinus esculentus exposed to waters containing 25 µg / l of copper (Cu) and heavy metals caused reproductive anomalies in the starfish Asterias rubens (Besten, et al., 1989, 1991). Sea urchins, especially the eggs and larvae, are used for toxicity testing and environmental monitoring (reviewed by Dinnel et al. 1988). Crompton (1997) reported that mortalities occurred in echinoderms after 4-14 day of exposure to above 10-100 µg/l Cu, 1-10 mg/l Zn and 10-100 mg/l Cr but that mortalities occurred in echinoderm larvae above10-100 µg/ l Ni.

Several species of Actinaria (Aiptasia sp. and Nematostella vectensis) were reported to suffer 'severe' or 'significant' mortality due to heavy metal exposure or organometals (depending on the species and metal) (see Watson & Tyler-Walters, 2023). 

Sensitivity assessment. No evidence of the effects of transitional metals or organometals on the characteristic species of this biotope was found. However, evidence from other echinoderms and anemones suggests that the dominant crinoid, anemone, and octocoral in this biotope might be adversely affected by exposure to transitional metals or organometals. Therefore, resistance is assessed as 'Low', so resilience is probably 'Medium' and sensitivity is assessed as 'Medium', albeit with 'Low' confidence due to lack of directly relevant evidence. Further evidence is required for this pressure.

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

Echinoderms seem especially intolerant of the toxic effects of oil, likely because of the large amount of exposed epidermis (Suchanek, 1993). Sea urchin eggs showed developmental abnormalities when exposed to 10-30 mg/l of hydrocarbons and crude oil: Corexit dispersant mixtures have been shown to cause functional loss of tube feet and spines in sea urchins (Suchanek, 1993). Olsgard & Gray (1995) found the brittlestar Amphiura filiformis very sensitive to oil pollution. During monitoring of sediments in the Ekofisk oilfield, Addy et al. (1978) suggest that reduced abundance of Amphiura filiformis within 2-3 km of the site was related to discharges of oil from the platforms and to physical disturbance of the sediment. Although acute toxicity tests showed that drill cuttings containing oil-based muds had very low toxicity (LC50 52,800 ppm total hydrocarbons in test sediment), Newton & McKenzie (1998) suggest these are poor predictors of chronic response. Chronic sub-lethal effects were detected around the Beryl oil platform in the North Sea where the levels of oil in the sediment were very low (3 ppm) and Amphiura filiformis was excluded from areas nearer the platform with higher sediment oil content. Similarly, in Ophiothrix fragilis, exposure to 30,000 ppm oil reduces its load of symbiotic bacteria by 50% and brittle stars begin to die (Newton & McKenzie, 1995).

Crude oil from the Torrey Canyon and the detergent used to disperse it caused mass mortalities of echinoderms; Asterias rubens, Echinocardium cordatum, Psammechinus miliaris, Echinus esculentus, Marthasterias glacialis and Acrocnida brachiata (Smith, 1968). Large numbers of dead Echinus esculentus were found between 5.5 and 14.5 m in the vicinity of Sennen after the Torrey Canyon oil spill, presumably due to a combination of wave exposure and heavy spraying of dispersants in that area (Smith 1968). Smith (1968) also demonstrated that 0.5 to 1 ppm of the detergent BP1002 resulted in developmental abnormalities in echinopluteus larvae of Echinus esculentus. Echinus esculentus populations in the vicinity of an oil terminal in A Coruna Bay, Spain, showed developmental abnormalities in the skeleton. The tissues contained high levels of aliphatic hydrocarbons, naphthalenes, pesticides and heavy metals (Zn, Hg, Cd, Pb, and Cu) (Gomez & Miguez-Rodriguez 1999). However, the observed effects may have been due to a single contaminant or synergistic effects of all present.

A study by Brils et al. (2002) into the toxicity of C10-19 hydrocarbons found that the shallow irregular echinoid Echinocardium cordatum was susceptible to oil-contaminated sediments at as low as 190 mg/kg dry weight of Echinocardium cordatum. The high intolerance of Echinocardium cordatum to hydrocarbons was seen by the mass mortality of animals, down to about 20 m, shortly after the Amoco Cadiz oil spill (Cabioch et al., 1978). Reduced abundance of the species was also detectable up to >1,000 m away one year after the discharge of oil-contaminated drill cuttings in the North Sea (Daan & Mulder, 1996).  The polyaromatic hydrocarbon (PAH) fluoranthene was shown to cause mortality in larvae of Arbacia punctulata (purple-spined sea urchin) with 48-hour LC50 of 3.9 µg/l in the presence of UV light (Spehar et al., 1999). 

TBT was shown to inhibit arm regeneration in the brittlestar Ophioderma brevispina, at 10 ng/l and produce significant inhibition at 100 ng/l. It was suggested that TBT acts via the nervous system, although direct action on the tissues at the point of breakage could not be excluded (Bryan & Gibbs, 1991).

Frometa et al. (2017) reported ‘no’ mortality in Swiftia exserta exposed to DWH WAF but ‘severe’ mortality after exposure to dispersant and oil mixtures (CEWAF). They concluded that combinations of dispersants and oils were more toxic to octocorals than oils alone. Smith (1968) reported that Actinia equina and Urticina (as Tealia) felina were the most common and the most resistant animals on the shore after the oil spill and clean up, while some specimens of Cereus pedunculatus, Sagartia elegans and Anemonia sulcata were found dead and few survived. Overall, in most of the studies reviewed by Watson & Tyler-Walters, (2023), the resistance of true corals (Scleractinia) and Octocorals to petroleum hydrocarbons, oils, and dispersed oils would be assessed as ‘Low’ or ‘None’ but with ‘Low’ confidence due to the limited number of studies examined. However, the resistance of Actinaria to petroleum hydrocarbons, oils, and dispersed oils was dependent on species.  

Sensitivity assessment. No evidence of the effects of hydrocarbon or PAH contamination on the characteristic species was found. However, evidence from other echinoderms, and Anthozoa, suggests that the dominant feather star, Actinostolidae and octocoral in this biotope might be adversely affected by hydrocarbon or PAH exposure. Therefore, resistance is assessed as 'Low'. Resilience is probably 'Medium' and sensitivity is assessed as 'Medium', albeit with 'Low' confidence due to the lack of directly relevant evidence. Further evidence is required for this pressure.

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

Little information on the toxicity of synthetic chemicals to holothurians was found. Newton & McKenzie (1995) suggested that echinoderms tend to be very intolerant of various types of marine pollution but gave no detailed information. Cole et al. (1999) reported that echinoderm larvae displayed adverse effects when exposed to 0.15 mg/l of the pesticide Dichlorobenzene (DCB). Smith (1968) demonstrated that 0.5 -1 ppm of the detergent BP1002 resulted in developmental abnormalities in echinopluteus larvae of Echinus esculentus. Therefore, crinoids and their larvae may also be intolerant of synthetic chemicals.

In Actinaria, Aiptasia spp. was reported to experience significant mortality after exposure to 19 mg/l Diuron (Bao et al., 2011) but only sublethal effects to paraformaldehyde or the bactericide Suflo-B33 (Tagatz et al., 1979), while Anthopleura spp. was reported to experience only sublethal effects after exposure to Chlordane (Pridmore et al., 1992) (see Watson & Tyler-Walters, (2023). No information on Octocorals was found. 

Sensitivity assessment. No evidence of the effects of synthetic chemical contamination on the characteristic species was found. However, evidence from other echinoderms, and Anthozoa, suggests that the dominant feather star, Actinostolidae and octocoral in this biotope might be adversely affected by some synthetic chemicals (listed above). Therefore, resistance is assessed as 'Low'. Resilience is probably 'Medium' and sensitivity is assessed as 'Medium', albeit with 'Low' confidence due to the lack of directly relevant evidence. Further evidence is required for this pressure.

Radionuclide contamination

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

Evidence

No evidence was found

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

Carrerio-Silva et al. (2022) examined the effects of elevated suspended polymetallic sulphide (PMS) particles and suspended quartz particles on the cold water octocoral Dentomuricea meteor. These particulates may be generated during deep-sea mining activities for PMS. They reported ‘severe’ mortality of the octocoral after exposure to PMS, together with an increase in the concentration of metals associated with the particulates in the water column and the tissue of the octocoral.  However, no information on the effect of 'other' substances on the characteristic echinoderms or Anthozoa was found. 

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

Lawrence (1996) reported mass mortality of echinoderms in the Gulf of Trieste due to hypoxia caused by a strong thermocline combined with high pelagic productivity and eutrophication. The brittlestar Ophiura quinquemaculata was killed within a few days, and holothurians including Ocnus planci (as Cucumaria planci), starfish Asteropecten sp. and the remaining brittlestars were killed within a week. In experiments, Amphiura filiformis only left its protected position in the sediment when oxygen levels fell below 0.85mg/l (Rosenberg et al., 1991). Mass mortality of Amphiura filiformis was observed during severely low oxygen events (<0.7 mg/l) (Nilsson, 1999). However, at oxygen concentrations between 0.85 mg/l and 1.0 mg/l Rosenberg et al. (1991) observed the species survived for several weeks. Echinoderms were shown to be intolerant of the effects of algal blooms, resulting in mortalities of the sea urchins Echinus esculentus and Paracentrotus lividus, and the holothurian Labidoplax digitata amongst other echinoderms, probably due to hypoxia caused by death of the algal bloom algae (Boalch, 1979; Forster, 1979; Griffiths et al., 1979; Lawrence, 1996). Vaquer-Sunyer & Duarte (2008) suggested a median sublethal oxygen concentration of 1.22 mg O₂/l (± 0.25) for a number of echinoderms reviewed in their study. Echinoderms were neither the most nor the least sensitive of the taxonomic groups examined.  Riedel et al. (2012) examined the effects of hypoxia and anoxia on macrofauna in the North Adriatic, using in situ experimental apparatus.  They concluded that decapods, echinoderms and polychaetes were among the most sensitive to hypoxia while ascidians and anthozoans were among the most resistant of the species encountered in their study. 

Vaquer-Sunyer & Duarte (2008) also suggested that cnidarians were amongst the most tolerant of hypoxia, together with molluscs and priapulids. Isabel et al. (2023) identified several communities in the Estuary and Gulf of St. Lawrence, Canada depending on depth and oxygen levels. They suggested that Actinostola callosa was one of four species indicative of low oxygen and hypoxic conditions. Its highest abundance occurred at 142 µmol /l oxygen (ca 0.004 mg/l). They predicted that its abundance would increase below 100 µmol/l, however, it was recorded between 92.9 and 300.9 µmol/l (Isabel et al., 2023).  

Sensitivity assessment. Overall, the above evidence suggests echinoderms are intolerant of hypoxic conditions, while cnidarians, and especially Actinostola callosa, are tolerant. However, in the deep sea, oxygen levels are probably determined by mass transport of water by deep currents. For example, Ellett & Martin (1973) reported that the dissolved oxygen levels in the Rockall Trough varied between ca 5 and 6 ml/l (ca 7 and 8.4 mg/l) between the surface and ca 2,000 m in depth. In addition, the short-term acute hypoxia, represented by the benchmark, may also be mitigated by the large water masses and strong currents typical of areas in which this biotope occurs. Therefore, resistance is assessed as ‘Medium’ to represent some mortality under the worst-case scenario. Hence, resilience is assessed as ‘Medium' and sensitivity as 'Medium' but with 'Low' confidence. 

Nutrient enrichment

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

Evidence

No evidence of the nutrient levels typical of these biotopes was found and no information on the effect of nutrient enrichment on the characteristic species was found. Therefore, 'No evidence' is recorded. 

Organic enrichment

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

Evidence

No evidence of the organic carbon levels typical of these biotopes was found and no information on the effect of organic enrichment on the characteristic species was found. Therefore, 'No evidence' is recorded. 

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 available habitat (resilience is ‘Very low’). Therefore, the biotopes are considered to have ‘High’ sensitivity to this pressure.

Physical change (to another seabed type)

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

Evidence

The loss of hard substrata and its replacement with sediment would cause the biotope to be lost. In addition, the mechanical removal of hard substratum would destroy any characterizing organisms present and ultimately result in the loss and reclassification of the biotope. Therefore, resistance is assessed as 'None'. As this pressure is considered a permanent change, resilience is assessed 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

This biotope is characterized by a hard rock (cobble matrix). A change in seabed type to anything but cobble and gravel-dominated coarse substrata at the benchmark level would result in the introduction of finer sediments. This would permanently change the characterizing substrata and, therefore, change the biotope. Hence, resistance is assessed as ‘None’, resilience as ‘Very low’ and overall sensitivity assessed as ‘High’. 

Habitat structure changes - removal of substratum (extraction)

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

Evidence

The only mobile characteristic species/taxa of this biotope is Heliometra glacialis. As this pressure is not permanent, Heliometra glacialis has the potential to move out of the area when disturbed but recolonize the area once the pressure has reversed, provided there is another suitable habitat available locally. However, Gersemia and Actinostolidae will likely be killed/crushed during the removal of the substrata (pebble, cobble matrix). As a result, the resistance of this biotope is assessed as ‘None’, resilience as ‘Medium’, with an overall sensitivity of ‘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

The main sources of potential abrasion and physical disturbance relevant to deep-sea biotopes are bottom fishing activities (e.g. beam trawls), deep-sea mining and drilling activities (e.g. mining vehicles; Miller et al., 2018), and anchoring and positioning of offshore structures (e.g. offshore wind turbines).

Erect epifaunal species are particularly vulnerable to physical disturbance (Jennings & Kaiser, 1998). Veale et al. (2000) reported that the abundance, biomass, and production of epifaunal assemblages decreased with increasing fishing effort. Mobile gears also result in modification of the substratum, including the removal of shell debris, cobbles and rocks, and the movement of boulders (Bullimore, 1985; Jennings & Kaiser, 1998) on which many of the species in this community depend. Picton & Goodwin (2007) noted that an area of boulders with a rich fauna of sponges and hydroids on the east coast of Rathlin Island, Northern Ireland was significantly altered since the 1980s.  Scallop dredging had begun in 1989 and boulders were observed to have been turned and the gravel harrowed. In addition, many of the boulders had disappeared and rare hydroid communities were greatly reduced (Picton & Goodwin, 2007). 

Direct evidence for Gersemia is limited. Henry et al. (2003) simulated disturbance caused by bottom fishing in aquaria, to test the resistance of Gersemia rubiformis. Four colonies were rolled and crushed once every two weeks over four months. Colony responses were recorded after four and seven days. Crushing immediately induced retraction in the colonies. Colonies exhibited the ability to regenerate well from acute localised injuries. The authors concluded that Gersemia rubiformis’ ability to regenerate, temporarily contract and survive crushing was beneficial in heavily disturbed habitats, i.e. bottom trawling areas where mechanical disturbance was high (Henry et al., 2003). Gilkinson et al. (2002) investigated the susceptibility of Gersemia rubiformis to capture by hydraulic clam dredges. Post-dredging, no changes in abundance were recorded. The capture rate was relatively low (2-19%), but 84% of Gersemia rubiformis were attached to discarded gastropod shells. Gilkinson et al. (2002) hypothesised that the pressure wave produced by the dredge, displaced corals, on their shells, out of the dredge pathways and resettled nearby. This would not occur in this biotope, as the underlying substrata are cobble matrix and will not be re-suspended, and would therefore be more likely to experience adverse effects. Prena et al. (1999) found that experimental otter trawls decreased biomass by 24% compared to reference areas, including a consistently significant decrease in Gersemia sp. Jørgensen et al. (2016) also found that Gersemia sp. biomass was also reduced in trawled areas and provided evidence of trawl-induced direct mortality of Gersemia sp.

Heliometra glacialis is a large epifaunal feather star that might be expected to be susceptible to capture by epibenthic trawls. Jørgensen et al. (2016) suggested it was highly vulnerable to trawling based on its size and height above the substratum. Jørgensen et al. (2016) reported that Heliometra glacialis had a higher abundance in untrawled rather than trawled areas of the Barents Sea, and that 'high vulnerability' species (that included Heliometra glacialis) had a significantly reduced abundance in trawled areas by an order of magnitude. In the northwestern Barents Sea, the body and fragments of the arms of Heliometra glacialis were frequently entangled in trawl netting or caught in the trawl (Jørgensen et al., 2016). Dyer et al. (1984) recorded over 100 Heliometra glacialis adult specimens (up to 20 cm arm length) in survey trawls over three stations in Svalbard waters. It was also recovered by trawling in the Beaufort Sea (Frost & Lowry, 1983).  No information on the effects of trawling or physical disturbance on Actinostolidae was found. 

Sensitivity assessment. This biotope was recorded on cobble and pebble lag and occasional boulders from the lower reaches of the northern slope of the Wyville-Thomson Ridge in the Faeroe-Shetland Channel (JNCC, 2010). The evidence suggests that abrasion or physical disturbance could cause a significant decline in the abundance of characterizing species/taxa in this biotope. Feather stars are mobile and swim in response to physical disturbance, but only slowly, and are captured in trawls (Jørgensen et al., 2016). In addition, fishing gear could remove, turn or otherwise mobilize the boulders, cobbles and pebbles to which most of the epifauna is attached, especially anemones and soft corals. Therefore, resistance is assessed as ‘Low’, resilience as ‘Medium’, and overall sensitivity 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, results as an abrasion and/or disturbance of the substratum on the surface of the seabed (see abrasion/disturbance above). Therefore, resistance is assessed as ‘Low’, resilience as ‘Medium’, and overall sensitivity as ‘Medium’ but with 'Low' confidence due to the lack of direct evidence. 

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

The stony reefs on the Wyville-Thomson Ridge consist of ridges of boulders, cobbles, and gravel left by the ploughing actions of icebergs at the end of the last ice age, under moderate to high energy currents that remove fine sediments (JNCC, 2010; Scottish Government, 2024). Suspension feeders (such as Heliometra glacialis and Gersemia sp.) rely on water movement to provide suspended particulates and plankton for feeding, oxygenate the water column and remove excess sediment that might otherwise clog their feeding apparatus (e.g. Fell, 1966).  Deja et al. (2023) reported small numbers of Heliometra glacialis on the backs of spider crabs (Hyas sp.) in the inner reaches of Spitsbergen fjords. The inner fjords were exposed to high suspended sediment loads due to glacial runoff; for example, the sedimentation rate reaches 20,000 g/m²/year in Kongsfjorden. They suggested that Heliometra glacialis used the spider crabs to keep above the unstable (silted) bottoms. They also noted that other suspension-feeding crinoids did occur in areas subject to periodic 'cloudy' environments. Heliometra glacialis is typically found on gravel mixed with mud and sand but is also found on sand, silt and loose stones (Clark & Clark, 1967; Deja et al., 2023).  

Sensitivity assessment. A decrease in suspended particulates may reduce the food available to the suspension-feeding community. Conversely, an increase may result in clogging of their feeding apparatus or scouring in the strong currents that characterize this habitat.  However, this biotope is characterized by moderate to high energy, where fine sediments are removed by current flow. It is directly affected by mass water movement due to the 'Norwegian Sea Deep Water' current and its suspended sediment load. Therefore, a change in suspended sediment is unlikely, and any sudden change in sediment load due to deposition from the water surface is probably short-lived. Hence, resistance is assessed as 'High', resilience as 'High', and sensitivity as 'Not sensitive', but with 'Low' confidence due to the lack of direct evidence. 

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

Jones et al. (2012) studied the recovery rate after drilling activity in the Faroe-Shetland Channel. Two former drilling sites were investigated; Site A (three years post drilling) and Site C (ten years post drilling), as well as representative background sites outside the influence of drilling activity. The main impact of the drilling activity was the deposition of ‘drill cuttings’ on the seabed in the surrounding area – primarily ‘downstream’. At Site A, soon after drilling, the area of seabed completely covered by cuttings totalled 30,700 m², the area of complete and partial cuttings 70,890 m², with an extended area of just partial cuttings. Three years later, the area affected by cuttings had reduced; the area of complete cuttings to 5,570 m²; and the area of complete and partial cuttings to 10,980 m². The effects reduced from an average of 90 m to 40 m from the drill site. After 10 years, at Site C, complete cuttings extended from the drill site on average18 m on average, the area of complete cuttings was 920 m² and the area of complete and partial cuttings was 2,700 m². Early signs of recovery were observed in Gersemia sp. after three years (abundance of <0.4 m²). More significant recovery was observed in Site C (after 10 years) with abundance counts over 50 per m². The results suggest that the effects of drilling (largely the deposition of drill cuttings) had negative impacts on the abundance and recovery of Gersemia sp. observed between three and ten years. Jones et al. (2012) noted that the impacts on benthic megafauna were most apparent within 100 m of the drill site but, although recovery was apparent after three and 10 years, it was still in process. They noted that the deposited cutting had winnowed away significantly after three years at their site where water flow was probably up to 1 m/s. 

Sensitivity assessment. This biotope is characterized by moderate to high energy, where fine sediments are removed by current flow. It is directly affected by mass water movement due to the 'Norwegian Sea Deep Water' current. The deposit of 5 cm of fine sediment (see benchmark) rather than drill cuttings is probably short-lived. Heliometra glacialis is large (up to 20 cm across), prefers raised areas, and is probably capable of avoiding the deposit. Therefore, resistance is assessed as 'High', resilience as 'High', and sensitivity as 'Not sensitive' at the benchmark level, but with 'Low' confidence due to the lack of direct evidence. However, the evidence (Jones et al., 2012) suggests the deposition of drill cuttings over an extensive area would be more detrimental. 

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

Jones et al. (2012) studied the recovery rate after drilling activity in the Faroe-Shetland Channel. Two former drilling sites were investigated; Site A (three years post drilling) and Site C (ten years post drilling), as well as representative background sites outside the influence of drilling activity. The main impact of the drilling activity was the deposition of ‘drill cuttings’ on the seabed in the surrounding area – primarily ‘downstream’. At Site A, soon after drilling, the area of seabed completely covered by cuttings totalled 30,700 m², the area of complete and partial cuttings 70,890 m², with an extended area of just partial cuttings. Three years later, the area affected by cuttings had reduced; the area of complete cuttings to 5,570 m²; and the area of complete and partial cuttings to 10,980 m². The effects reduced from an average of 90 m to 40 m from the drill site. After 10 years, at Site C, complete cuttings extended from the drill site on average18 m on average, the area of complete cuttings was 920 m² and the area of complete and partial cuttings was 2,700 m². Early signs of recovery were observed in Gersemia sp. after three years (abundance of <0.4 m²). More significant recovery was observed in Site C (after 10 years) with abundance counts over 50 per m². The results suggest that the effects of drilling (largely the deposition of drill cuttings) had negative impacts on the abundance and recovery of Gersemia sp. observed between three and ten years. Jones et al. (2012) noted that the impacts on benthic megafauna were most apparent within 100 m of the drill site but, although recovery was apparent after three and 10 years, it was still in process. They noted that the deposited cutting had winnowed away significantly after three years at their site where water flow was probably up to 1 m/s. 

Sensitivity assessment. This biotope is characterized by moderate to high energy, where fine sediments are removed by current flow. It is directly affected by mass water movement due to the 'Norwegian Sea Deep Water' current. The deposit of 30 cm of fine sediment (see benchmark) rather than drill cuttings is probably short-lived. Heliometra glacialis is large (up to 20 cm across), prefers raised areas, and is probably capable of avoiding the deposit. Therefore, resistance is assessed as 'High', resilience as 'High', and sensitivity as 'Not sensitive' at the benchmark level, but with 'Low' confidence due to the lack of direct evidence. However, the evidence (Jones et al., 2012) suggests the deposition of drill cuttings over an extensive area would be more detrimental. 

Litter

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

Evidence

Not assessed

Electromagnetic changes

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

Evidence

No evidence was found.

Underwater noise changes

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

Evidence

This biotope is characterized by invertebrates with no known means to detect noise that will not be affected by changes in underwater noise, as defined under this pressure.

Introduction of light or shading

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

Evidence

This biotope occurs at mid-bathyal depths at which no light penetrates from the surface. The assemblages of the feather star Leptometra celtica 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.  However, 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 submersibles (with bright lights). Similarly, Fell (1966) noted that most crinoids withdraw from intense illumination but may be attracted to weak light in darkness. 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 biotope is assessed as ‘Not sensitive’ at the benchmark level.  No evidence was found to suggest that the other characteristic species could be affected by artificial light.

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

The benthic lifestyle and widespread deep-sea habitat of the characteristic species mean they will not be affected by barriers as defined under this pressure. Physical and hydrographic barriers may limit the dispersal of larvae but larval dispersal is not considered under the pressure definition and benchmark.

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

This biotope is characterized by benthic invertebrates that are not at risk of collision with artificial structures. It might be affected adversely by falling marine debris such as barrels, containers, and even shipwrecks but the effects are probably addressed under 'abrasion' above. 

Visual disturbance

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

Evidence

This biotope is characterized by invertebrates that do not rely on visual cues and will not be affected by visual disturbance, as defined under this pressure.

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

No evidence was found to suggest that any of the characteristic species were subject to translocation or genetic modification, nor the introduction of genetically distinct organisms. 

Introduction or spread of invasive non-indigenous species

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

Evidence

No alien or non-native species are known to compete with the characteristic species or taxa of this biotope.  Hence, this pressure is recorded 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

Heliometra glacialis was reported to be parasitised by the specialized annelid Myzostoma sp. (e.g. Myzostoma gigas, Myzostoma fimbriatum) (Mortensen, 1927). Mortensen (1927) also reported the solitary entopoct Loxosomella antedonis growing on Heliometra glacialis. Fell (1966) also noted that crinoids are parasitised by a large number of organisms. 

Sensitivity assessment. Parasites do not kill their hosts unless the parasitic burden becomes too much for the host. However, parasitism is likely to be an energetic burden and reduce growth, reproduction and survivability. Therefore, resistance is assessed as 'Medium', resilience as 'Medium' and sensitivity as 'Medium', but with 'Low' confidence due to the lack of direct evidence of mortality. 

Removal of target species

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

Evidence

The characterizing species and taxa associated with the biotope are not commercially targeted. Therefore, this pressure is assessed as ‘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

The available evidence suggests that this biotope is sensitive to removal through bycatch. Experimental trawling by Prena et al. (1999) on the Grand Banks (Newfoundland) indicated that Gersemia sp. biomass was consistently lower (average 24%) than in reference areas. Jørgensen et al. (2016) also found that Gersemia sp. biomass was also reduced in trawled areas and provided evidence of trawl-induced direct mortality of Gersemia sp. Jørgensen et al. (2016) reported that Heliometra glacialis had a higher abundance in untrawled rather than trawled areas of the Barents Sea. Sanchez et al. (2008) recorded bycatch of Leptometra celtica in beam trawls off Le Danois Bank (southern Spain) and Heliometra glacialis has been removed by scientific trawls (Kolpakov et al., 2018). Dyer et al. (1984) caught over 100 specimens of Heliometra glacialis over three stations in Svalbard waters. 

Sensitivity assessment. The available evidence suggests that the characterizing species/taxa of this biotope are readily caught as bycatch by bottom fishing gear, i.e. trawls. However, there is evidence that suggests that some individuals may evade capture (Prena et al., 1999). Therefore, resistance is assessed as ‘Low’ (25-75% reduction in abundance/cover). As a result, resilience is assessed as ‘Medium’ and overall sensitivity as ‘Medium’.