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

There is little direct evidence on the resistance of Kophobelemnon stelliferum to temperature changes. In the absence of this information, the temperature tolerances of Kophobelemnon stelliferum (based on their current geographical range and environmental preferences) have been used as a proxy.

Yesson et al. (2012) found that temperature was the most important factor in habitat suitability modelling for Pennatulacea, which included records of Kophobelemnidae, Protoptilidae and Pennatulidae. Similarly, Georgian et al. (2019) found temperature to be the most important for modelling Pennatulacea. However, they had one of the largest observed temperature ranges of all taxa studied. Modelling work was undertaken by Gormley et al. (2015) under an increased ocean temperature scenario of 4°C by 2100. The modelling suggested that sea pens would experience a significant loss of suitable habitat. In the UK, this is predicted to be a loss of 15,706 km². However, this value represents all sea pens and burrowing megafauna communities under the Priority Marine Habitats definition (i.e. water depths from 15-200 m), so is not specific to Kophobelemnon stelliferum.

The sea pen Virgularia mirabilis is known to experience annual temperature variations of 10°C in Scottish coastal waters (Hughes, 1998a), however, in the more stable mid to upper bathyal waters where Kophobelemnon stelliferum is found, temperature variation is likely to be narrower (Gage & Tyler, 1991, cited in Neves et al., 2015). The wide distribution of Kophobelemnon stelliferum (Mastrototaro et al., 2013; Rice et al., 1992) suggests it is eurythermal. Kophobelemnon stelliferum assemblages were reported by Howell et al. (2010) to occur within the temperature range of 7-12°C (average 9.78°C) in the North-east Atlantic. Kophobelemnon stelliferum also occurs off Newfoundland where average bottom temperatures are ~4.4°C (>1,100 m) and ~5°C (<1,100 m; Baker et al., 2012). Kophobelemnon spp. have also been recorded in the Venezuela Basin, where the bottom water temperature is relatively constant at 3.83 to 3.86°C (Briggs et al., 1996).

Sensitivity assessment. As Kophobelemnon stelliferum naturally occurs within a range of bottom water temperatures, it is not likely to be affected by a change in bottom temperature at the middle, high or extreme scenario pressure benchmarks (all relating to a 1°C rise in temperature in the deep-sea). Therefore, resistance is assessed as ‘High’, resistance as ‘High’ and the biotopes are considered to be ‘Not sensitive’ at the pressure benchmarks for extreme, high and middle scenarios.

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

There is little direct evidence on the resistance of Kophobelemnon stelliferum to temperature changes. In the absence of this information, the temperature tolerances of Kophobelemnon stelliferum (based on their current geographical range and environmental preferences) have been used as a proxy.

Yesson et al. (2012) found that temperature was the most important factor in habitat suitability modelling for Pennatulacea, which included records of Kophobelemnidae, Protoptilidae and Pennatulidae. Similarly, Georgian et al. (2019) found temperature to be the most important for modelling Pennatulacea. However, they had one of the largest observed temperature ranges of all taxa studied. Modelling work was undertaken by Gormley et al. (2015) under an increased ocean temperature scenario of 4°C by 2100. The modelling suggested that sea pens would experience a significant loss of suitable habitat. In the UK, this is predicted to be a loss of 15,706 km². However, this value represents all sea pens and burrowing megafauna communities under the Priority Marine Habitats definition (i.e. water depths from 15-200 m), so is not specific to Kophobelemnon stelliferum.

The sea pen Virgularia mirabilis is known to experience annual temperature variations of 10°C in Scottish coastal waters (Hughes, 1998a), however, in the more stable mid to upper bathyal waters where Kophobelemnon stelliferum is found, temperature variation is likely to be narrower (Gage & Tyler, 1991, cited in Neves et al., 2015). The wide distribution of Kophobelemnon stelliferum (Mastrototaro et al., 2013; Rice et al., 1992) suggests it is eurythermal. Kophobelemnon stelliferum assemblages were reported by Howell et al. (2010) to occur within the temperature range of 7-12°C (average 9.78°C) in the North-east Atlantic. Kophobelemnon stelliferum also occurs off Newfoundland where average bottom temperatures are ~4.4°C (>1,100 m) and ~5°C (<1,100 m; Baker et al., 2012). Kophobelemnon spp. have also been recorded in the Venezuela Basin, where the bottom water temperature is relatively constant at 3.83 to 3.86°C (Briggs et al., 1996).

Sensitivity assessment. As Kophobelemnon stelliferum naturally occurs within a range of bottom water temperatures, it is not likely to be affected by a change in bottom temperature at the middle, high or extreme scenario pressure benchmarks (all relating to a 1°C rise in temperature in the deep-sea). Therefore, resistance is assessed as ‘High’, resistance as ‘High’ and the biotopes are considered to be ‘Not sensitive’ at the pressure benchmarks for extreme, high and middle scenarios.

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

There is little direct evidence on the resistance of Kophobelemnon stelliferum to temperature changes. In the absence of this information, the temperature tolerances of Kophobelemnon stelliferum (based on their current geographical range and environmental preferences) have been used as a proxy.

Yesson et al. (2012) found that temperature was the most important factor in habitat suitability modelling for Pennatulacea, which included records of Kophobelemnidae, Protoptilidae and Pennatulidae. Similarly, Georgian et al. (2019) found temperature to be the most important for modelling Pennatulacea. However, they had one of the largest observed temperature ranges of all taxa studied. Modelling work was undertaken by Gormley et al. (2015) under an increased ocean temperature scenario of 4°C by 2100. The modelling suggested that sea pens would experience a significant loss of suitable habitat. In the UK, this is predicted to be a loss of 15,706 km². However, this value represents all sea pens and burrowing megafauna communities under the Priority Marine Habitats definition (i.e. water depths from 15-200 m), so is not specific to Kophobelemnon stelliferum.

The sea pen Virgularia mirabilis is known to experience annual temperature variations of 10°C in Scottish coastal waters (Hughes, 1998a), however, in the more stable mid to upper bathyal waters where Kophobelemnon stelliferum is found, temperature variation is likely to be narrower (Gage & Tyler, 1991, cited in Neves et al., 2015). The wide distribution of Kophobelemnon stelliferum (Mastrototaro et al., 2013; Rice et al., 1992) suggests it is eurythermal. Kophobelemnon stelliferum assemblages were reported by Howell et al. (2010) to occur within the temperature range of 7-12°C (average 9.78°C) in the North-east Atlantic. Kophobelemnon stelliferum also occurs off Newfoundland where average bottom temperatures are ~4.4°C (>1,100 m) and ~5°C (<1,100 m; Baker et al., 2012). Kophobelemnon spp. have also been recorded in the Venezuela Basin, where the bottom water temperature is relatively constant at 3.83 to 3.86°C (Briggs et al., 1996).

Sensitivity assessment. As Kophobelemnon stelliferum naturally occurs within a range of bottom water temperatures, it is not likely to be affected by a change in bottom temperature at the middle, high or extreme scenario pressure benchmarks (all relating to a 1°C rise in temperature in the deep-sea). Therefore, resistance is assessed as ‘High’, resistance as ‘High’ and the biotopes are considered to be ‘Not sensitive’ at the pressure benchmarks for extreme, high and middle scenarios.

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. comms.). The Kophobelemnon field biotopes occur in the Atlantic mid and upper bathyal zone, at depths of 200 – 1300 m. Therefore, the biotope will not be affected by changes arising from marine heatwaves, and the assessment at the pressure benchmark is ‘Not relevant’.

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. comms.). The Kophobelemnon field biotopes occur in the Atlantic mid and upper bathyal zone, at depths of 200 – 1300 m. Therefore, the biotope will not be affected by changes arising from marine heatwaves, and the assessment at the pressure benchmark is ‘Not relevant’.

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

Unlike scleractinians, octocorals do not have a rigid calcium carbonate exoskeleton, however, they do form discrete sclerites consisting of high magnesium calcite (Schubert et al., 2017). Kophobelemnon stelliferum, for example, has a calcified axis (López-González et al., 2009) and a high density of sclerites (López-González et al., 2001). This magnesium calcite is more soluble than the aragonite precipitated by scleractinians (Schubert et al., 2017), putting octocorals at risk from ocean acidification. However, the sclerites in octocorals are loosely dispersed in their fleshy tissue, so are not in direct contact with surrounding seawater. This tissue may, therefore, provide some protection against ocean acidification, as suggested in a study by Gabay et al. (2014), on a shallow-water zooxanthellate octocoral, Ovabunda macrospiculata. At a reduced pH of 7.6 and 7.3, when exposed for 31 - 42 days, no dissolution occurred to the sclerites that were protected by tissue. In comparison, isolated sclerites underwent microstructural changes indicating dissolution, which caused more than 60% damage over the exposure period (Gabay et al., 2014). Despite the results of this study, experiments on other octocorals showed differing effects of ocean acidification, ranging from no response to a decrease in calcification, varying by species (see Schubert et al., 2017; note that no Pennatulacea studies were included).

An ongoing study looking at the effects of ocean acidification on the shallow water Antarctic sea pen Malacobelemnon daytoni, which is in the same family as Kophobelemnon stelliferum (Kophobelemnidae), has indicated that several stress responses occur under RCP 8.5 scenario conditions (i.e. a decrease in pH of 0.33; Bopp et al., 2013) compared to natural conditions (pH 8.05; Natalia Servetto, 2019, pers. comm., 15^th October). Up-regulated genes were also observed. However, Kophobelemnon stelliferum is known to occur naturally in the slightly acidic waters around mud volcanoes (Rueda et al., 2016; Sitjà et al., 2019). For example, in the Spanish mud volcano fields, pH was measured by Rueda et al. (2012) to vary from 7.4 to 6.8.

Kita et al. (2015) studied the effects of CO₂ gas released from the seabed at a depth of 12 m in Scotland. The sea pen Virgularia mirabilis (which also occurs in the deep-sea) was frequently observed in the study area, however, no abnormal behaviour was observed in response to the CO₂, either during or after release. The authors noted that the elevated pCO₂ concentrations (<1599 µatm, at 30 cm above the seabed) returned to background levels (360-370 µatm) very quickly. Therefore, Virgularia mirabilis was not necessarily exposed to continuous low pH conditions.

As the oceans absorb carbon dioxide from the atmosphere, leading to a decrease in pH and an increase in acidity, there is a further concern; the shoaling of the aragonite saturation horizon (ASH). The ASH is defined as the depth in the oceans at which aragonite saturation equals 1. Below this depth, aragonite saturation will fall below 1, and dissolution of calcified structures may occur. Currently, the depth of the ASH in the north Atlantic is approximately 2000 m (Jiang et al., 2015). This depth has already become 80-150 m shallower over the past two centuries (Chung et al., 2003, Feely et al., 2004). By the end of this century, the depth of the ASH is expected to become shallower still, reaching depths of up to 400 m under the high emission scenario (RCP 8.5) and 600 m for the middle emission scenario (RCP 4.5) (Zheng & Long, 2014). Yesson et al. (2012) found that 12% of records of octocorals occurred in water undersaturated with aragonite (<1). For Sessiliflorae (sea pens), 15-20% of observations were below the aragonite saturation horizon.  For the Sessiliflorae, 6% were found in areas undersaturated for calcite, however, this was affected by a shallow water sampling bias.

Sensitivity assessment. Kophobelemnon stelliferum has a fleshy structure where its sclerites are protected by the surrounding tissue. Therefore, it is possible that existing colonies can survive a decrease in pH. However, it is not known whether new sclerites can be formed and new growth/sclerite formation achieved at a lower pH. It is worth noting though, that the species does occur in the acidic waters associated with mud volcanoes (pH 7.4 to 6.8; Rueda et al., 2016, 2012; Sitjà et al., 2019). However, there is some evidence that suggests that another (shallow-water) species in the Kophobelemnidae family shows stress responses and up-regulated genes in response to ocean acidification under an RCP 8.5 scenario (i.e. high emission scenario; Natalia Servetto, 2019, pers. comm., 15^th October). Under the mid and high emission scenarios, resistance is, therefore, assessed as ‘High’, as no mortality has been observed. Resilience is assessed as ‘High’ and overall the biotopes are assessed as ‘Not sensitive’ at the pressure benchmark.

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

Unlike scleractinians, octocorals do not have a rigid calcium carbonate exoskeleton, however, they do form discrete sclerites consisting of high magnesium calcite (Schubert et al., 2017). Kophobelemnon stelliferum, for example, has a calcified axis (López-González et al., 2009) and a high density of sclerites (López-González et al., 2001). This magnesium calcite is more soluble than the aragonite precipitated by scleractinians (Schubert et al., 2017), putting octocorals at risk from ocean acidification. However, the sclerites in octocorals are loosely dispersed in their fleshy tissue, so are not in direct contact with surrounding seawater. This tissue may, therefore, provide some protection against ocean acidification, as suggested in a study by Gabay et al. (2014), on a shallow-water zooxanthellate octocoral, Ovabunda macrospiculata. At a reduced pH of 7.6 and 7.3, when exposed for 31 - 42 days, no dissolution occurred to the sclerites that were protected by tissue. In comparison, isolated sclerites underwent microstructural changes indicating dissolution, which caused more than 60% damage over the exposure period (Gabay et al., 2014). Despite the results of this study, experiments on other octocorals showed differing effects of ocean acidification, ranging from no response to a decrease in calcification, varying by species (see Schubert et al., 2017; note that no Pennatulacea studies were included).

An ongoing study looking at the effects of ocean acidification on the shallow water Antarctic sea pen Malacobelemnon daytoni, which is in the same family as Kophobelemnon stelliferum (Kophobelemnidae), has indicated that several stress responses occur under RCP 8.5 scenario conditions (i.e. a decrease in pH of 0.33; Bopp et al., 2013) compared to natural conditions (pH 8.05; Natalia Servetto, 2019, pers. comm., 15^th October). Up-regulated genes were also observed. However, Kophobelemnon stelliferum is known to occur naturally in the slightly acidic waters around mud volcanoes (Rueda et al., 2016; Sitjà et al., 2019). For example, in the Spanish mud volcano fields, pH was measured by Rueda et al. (2012) to vary from 7.4 to 6.8.

Kita et al. (2015) studied the effects of CO₂ gas released from the seabed at a depth of 12 m in Scotland. The sea pen Virgularia mirabilis (which also occurs in the deep-sea) was frequently observed in the study area, however, no abnormal behaviour was observed in response to the CO₂, either during or after release. The authors noted that the elevated pCO₂ concentrations (<1599 µatm, at 30 cm above the seabed) returned to background levels (360-370 µatm) very quickly. Therefore, Virgularia mirabilis was not necessarily exposed to continuous low pH conditions.

As the oceans absorb carbon dioxide from the atmosphere, leading to a decrease in pH and an increase in acidity, there is a further concern; the shoaling of the aragonite saturation horizon (ASH). The ASH is defined as the depth in the oceans at which aragonite saturation equals 1. Below this depth, aragonite saturation will fall below 1, and dissolution of calcified structures may occur. Currently, the depth of the ASH in the north Atlantic is approximately 2000 m (Jiang et al., 2015). This depth has already become 80-150 m shallower over the past two centuries (Chung et al., 2003, Feely et al., 2004). By the end of this century, the depth of the ASH is expected to become shallower still, reaching depths of up to 400 m under the high emission scenario (RCP 8.5) and 600 m for the middle emission scenario (RCP 4.5) (Zheng & Long, 2014). Yesson et al. (2012) found that 12% of records of octocorals occurred in water undersaturated with aragonite (<1). For Sessiliflorae (sea pens), 15-20% of observations were below the aragonite saturation horizon.  For the Sessiliflorae, 6% were found in areas undersaturated for calcite, however, this was affected by a shallow water sampling bias.

Sensitivity assessment. Kophobelemnon stelliferum has a fleshy structure where its sclerites are protected by the surrounding tissue. Therefore, it is possible that existing colonies can survive a decrease in pH. However, it is not known whether new sclerites can be formed and new growth/sclerite formation achieved at a lower pH. It is worth noting though, that the species does occur in the acidic waters associated with mud volcanoes (pH 7.4 to 6.8; Rueda et al., 2016, 2012; Sitjà et al., 2019). However, there is some evidence that suggests that another (shallow-water) species in the Kophobelemnidae family shows stress responses and up-regulated genes in response to ocean acidification under an RCP 8.5 scenario (i.e. high emission scenario; Natalia Servetto, 2019, pers. comm., 15^th October). Under the mid and high emission scenarios, resistance is, therefore, assessed as ‘High’, as no mortality has been observed. Resilience is assessed as ‘High’ and overall the biotopes are assessed as ‘Not sensitive’ at the pressure benchmark.

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

The Kophobelemnon field biotopes occur in the Atlantic mid and upper bathyal zone, at depths of 200 – 1300 m. Therefore, the biotope will not be affected by changes arising from sea-level rise, and the assessment at the pressure benchmark is ‘Not relevant’.

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

The Kophobelemnon field biotopes occur in the Atlantic mid and upper bathyal zone, at depths of 200 – 1300 m. Therefore, the biotope will not be affected by changes arising from sea-level rise, and the assessment at the pressure benchmark is ‘Not relevant’.

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

The Kophobelemnon field biotopes occur in the Atlantic mid and upper bathyal zone, at depths of 200 – 1300 m. Therefore, the biotope will not be affected by changes arising from sea-level rise, and the assessment at the pressure benchmark is ‘Not relevant’.

Temperature increase (local)

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

Evidence

There is little direct evidence on the resistance of Kophobelemnon sp. to temperature changes. However, Yesson et al. (2012) found that temperature was the most important factor in habitat modelling for Pennatulacea, which included records of Kophobelemnidae, Protoptilidae and Pennatulidae. Georgian et al. (2019) similarly found temperature to be the most important for modelling Pennatulacea, however, they had one of the largest observed temperature ranges of all taxa studied. Murillo et al. (2018) also found that bottom temperature was positively correlated to the size of the sea pens Anthoptilum grandiflorum and Pennatula aculeata off Canada. For Pennatula grandis, bottom temperature was positively correlated with mean colony weight.

The sea pen Virgularia mirabilis is known to experience annual temperature variations of 10°C in Scottish coastal waters (Hughes, 1998a). However, in the more stable mid to upper bathyal waters where Kophobelemnon stelliferum is found, temperature variation is likely to be narrower (Gage & Tyler, 1991, cited in Neves et al., 2015). The wide distribution of Kophobelemnon stelliferum (Mastrototaro et al., 2013; Rice et al., 1992) suggests the species is eurythermal. Kophobelemnon stelliferum assemblages were reported by Howell et al. (2010) to occur within the temperature range of 7-12°C (average 9.78°C) in the north-east Atlantic. Kophobelemnon stelliferum also occurs off Newfoundland where average bottom temperatures are approx. 4.4°C (>1100 m) and approx. 5°C (<1100 m; Baker et al., 2012). Kophobelemnon sp. has also been recorded in the Venezuela Basin at depths of 3950 m, where the bottom water temperature is relatively constant at 3.83 to 3.86°C (Briggs et al., 1996).

Sensitivity assessment. The ability of Kophobelemnon stelliferum to retract into the sediment may avoid short-term temperature pressures, in addition to predator avoidance (De Clippele et al., 2015). However, at benchmark levels of one month, this method is not sustainable. If the biotope occurs in an area corresponding to the middle or upper limit of the temperature range of Kophobelemnon stelliferum (i.e. 4.4°C, as given by Baker et al., 2012), then it is probably able to tolerate a long-term increase in temperature of 2°C or a short-term increase of 5°C.  However, if the biotope occurs at the upper limit of the species' temperature range (i.e. 12°C, as given by Howell et al., 2010), then it is less likely to tolerate an increase in temperature of 2°C.  As Kophobelemnon stelliferum naturally occurs within a range of bottom water temperatures, resistance is assessed as ‘High’, resilience is assessed as ‘High’, and overall sensitivity is assessed as ‘Not sensitive’.

Temperature decrease (local)

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

Evidence

There is little direct evidence on the resistance of Kophobelemnon to temperature changes. However, Yesson et al. (2012) found that temperature was the most important factor in habitat modelling for Pennatulacea, which included records of Kophobelemnidae, Protoptilidae and Pennatulidae. Georgian et al. (2019) similarly found temperature to be the most important for modelling Pennatulacea. However, they had one of the largest observed temperature ranges of all taxa studied. Murillo et al. (2018) also found that bottom temperature was positively correlated to the size of the sea pens Anthoptilum grandiflorum and Pennatula aculeata off Canada. For Pennatula grandis, bottom temperature was positively correlated with mean colony weight.

The sea pen Virgularia mirabilis is known to experience annual temperature variations of 10°C in Scottish coastal waters (Hughes, 1998a). However, in the more stable mid to upper bathyal waters where Kophobelemnon stelliferum is found, temperature variation is likely to be narrower (Gage & Tyler, 1991, cited in Neves et al., 2015). The wide distribution of Kophobelemnon stelliferum (Mastrototaro et al., 2013; Rice et al., 1992) suggests the species is eurythermal. Kophobelemnon stelliferum assemblages were reported by Howell et al. (2010) to occur within the temperature range of 7-12°C (average 9.78°C) in the north-east Atlantic. Kophobelemnon stelliferum also occurs off Newfoundland where average bottom temperatures are approx. 4.4°C (>1100 m) and approx. 5°C (<1100 m; Baker et al., 2012). Kophobelemnon sp. has also been recorded in the Venezuela Basin at depths of 3950 m, where the bottom water temperature is relatively constant at 3.83 to 3.86°C (Briggs et al., 1996).

Sensitivity assessment. The ability of Kophobelemnon stelliferum to retract into the sediment may avoid short-term temperature pressures, in addition to predator avoidance (De Clippele et al., 2015). However, at benchmark levels of one month, this method is not sustainable. If the biotope occurs in an area corresponding to the middle or upper limit of the temperature range of Kophobelemnon stelliferum (i.e. 12°C, as given by Howell et al., 2010), then it is probably able to tolerate a long-term decrease in temperature of 2°C or a short-term decrease of 5°C.  However, if the biotope occurs at the lower limit of the species' temperature range (i.e. 4.4°C, as given by Baker et al., 2012), then it is less likely to tolerate a decrease in temperature of 2°C.  As Kophobelemnon stelliferum naturally occurs within a range of bottom water temperatures, resistance is assessed as ‘High’, resilience as ‘High’, and overall sensitivity is assessed as ‘Not sensitive’.

Salinity increase (local)

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

Evidence

No specific evidence was found on the effects of salinity changes on Kophobelemnon stelliferum. However, the depth at which Kophobelemnon stelliferum is found, combined with the distance from shore and the low potential for brine or freshwater discharge, means changes in salinity are unlikely. For example, Kophobelemnon sp. has been recorded in the Venezuela Basin at depths of 3950 m, where the bottom salinity is relatively constant at 34.976 to 34.986‰ (Briggs et al., 1996).

Yesson et al. (2012) found that salinity was one of the most important factors in determining the distribution of Pennatulacea, which included records of Kophobelemnidae, Protoptilidae and Pennatulidae. Salinity was also shown by Bastari et al. (2018) to be one of the key variables that influenced the presence or absence of Virgularia mirabilis in the Mediterranean, however, this did not explain distribution patterns for Pennatula spp. or Funiculina quadrangularis. Murillo et al. (2018) also found that salinity was positively correlated to the size of the sea pens Anthoptilum grandiflorum and Pennatula aculeata off Canada. For Pennatula grandis, salinity was positively correlated with mean colony weight.

Other sea pens that occur from shallow waters through to the deep-sea show some tolerance to small variations in salinity. For example, Troffe et al. (2005) noted that the sea pen Halipteris willemoesi occurred off British Colombia where salinity levels varied seasonally between 30.63-31.49 psu (depth range 25-74m).

Sensitivity assessment. Although changes in salinity are unlikely, the highly stable nature of water masses found at mid and upper bathyal depths and the salinity range that Kophobelemnon stelliferum is known to occur in suggests that the biotopes are likely to be intolerant of salinity changes. However, as specific evidence is limited, including on the salinity conditions where the species occurs naturally, 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

No specific evidence was found on the effects of salinity changes on Kophobelemnon stelliferum. However, the depth at which Kophobelemnon stelliferum is found, combined with the distance from shore and the low potential for brine or freshwater discharge, means changes in salinity are unlikely. For example, Kophobelemnon sp. has been recorded in the Venezuela Basin at depths of 3950 m, where the bottom salinity is relatively constant at 34.976 to 34.986‰ (Briggs et al., 1996).

Yesson et al. (2012) found that salinity was one of the most important factors in determining the distribution of Pennatulacea, which included records of Kophobelemnidae, Protoptilidae and Pennatulidae. Salinity was also shown by Bastari et al. (2018) to be one of the key variables that influenced the presence or absence of Virgularia mirabilis in the Mediterranean, however, this did not explain distribution patterns for Pennatula spp. or Funiculina quadrangularis. Murillo et al. (2018) also found that salinity was positively correlated to the size of the sea pens Anthoptilum grandiflorum and Pennatula aculeata off Canada. For Pennatula grandis, salinity was positively correlated with mean colony weight.

Other sea pens that occur from shallow waters through to the deep-sea show some tolerance to small variations in salinity. For example, Troffe et al. (2005) noted that the sea pen Halipteris willemoesi occurred off British Colombia where salinity levels varied seasonally between 30.63-31.49 psu (depth range 25-74 m).

Sensitivity assessment. Although changes in salinity are unlikely, the highly stable nature of water masses found at mid and upper bathyal depths and the salinity range that Kophobelemnon stelliferum is known to occur in suggests that the biotopes are likely to be intolerant of salinity changes. However, as specific evidence is limited, including on the salinity conditions where the species occurs naturally, 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

Sea pens are known to alter water current flow, thereby retaining nutrients and entraining plankton near the sediment (Tissot et al., 2006). Rice et al. (1992) also suggested that hydrodynamics may affect the depth range of Kophobelemnon stelliferum in submarine canyons. Flow rates are important for sea pens for passive suspension feeding. However, for Ptilosarcus gurneyi, volume flow rate and feeding rate were found to only increase initially with increasing ambient flow, before peaking at between 14 and 18 cm/s for larger specimens and lower for smaller specimens. Volume flow and feeding rates then decreased as the species deformed with the higher flow rates of up to 25 cm/s (Best, 1988). In the field, the mean flow conditions where Ptilosarcus gurneyi was found were noted to range naturally from 8 to 11 cm/s, with a maximum of up to 17 cm/s (at 18 cm above the substratum). Rice et al. (1992) noted that Kophobelemnon would experience increased drag with an increasing colony length, further exacerbated by the relative increase in the number of polyps. Drag may therefore affect larger colonies differently to smaller colonies, however, it is not known whether drag is a limiting factor.

Baker et al. (2012) found that colonies of Pennatula spp. within large sea pen meadows off Newfoundland were orientated in similar directions, presumably to maximize use of currents (Roberts et al., 2009).  Edwards et al. (2016) recorded the movement of the polyps of a solitary Kophobelemnon cf. stelliferum as a proxy of current direction in the deep-sea off Hawaii. They found that the individual pointed its polyps towards the current, and frequently moved the polyps in response to variations in current direction, maintaining orientations for 2 hrs or 3 hrs at a time. Experimentation on Virgularia mirabilis in the UK has further shown behavioural adaptations to modified flow. At 0.12m/s the polyps move to face away from the current, at 0.33 m/s the stalk is bent over and individual pinnae are pushed together, and at flows greater than 0.5 m/s the tentacles become retracted and the stalk retracts into the mud (Hiscock, 1983). However, if flow rates remain too high, sea pens will be unable to extend above the sediment, preventing feeding and potentially leading to mortality (Hill & Wilson, 2000). Kophobelemnon stelliferum is also able to retract into the sediment (De Clippele et al., 2015). There is contrasting evidence on the flexibility of Kophobelemnon stelliferum. López-González et al. (2001) observed that whole colonies were very rigid, whereas García-Alegre et al. (2018) stated a flexibility of >45°. Hill & Wilson (2000) suggested Virgularia mirabilis has a flexibility in the range of 10-45°, which may be similar to that of Kophobelemnon stelliferum. Hence, a similar response to increased flow rates is inferred.

Sensitivity assessment. Evidence suggests that sea pens, including Kophobelemnon stelliferum, exhibit behavioural responses to changes in water flow rates and current direction. At the benchmark level (a change in flow velocity of between 0.1m/s to 0.2m/s), evidence is only available for Virgularia mirabilis and Ptilosarcus gurneyi. For both species, a 0.2 m/s increase in flow rate caused the sea pens to deform, which can lead to a reduction in volume flow and feeding rate (Best, 1988; Hiscock, 1983).  There is conflicting evidence over the flexibility of Kophobelemnon stelliferum (López-González et al., 2001; García-Alegre et al., 2018), however, it may have a similar flexibility to that of Virgularia mirabilis (10-45°; Hill and Wilson, 2000). The ability of Kophobelemnon stelliferum to retract into the substratum may be used as an avoidance behaviour in the short-term, however, at the benchmark level of change for more than 1 year, this is not sustainable. If flow rates remain too high, the sea pens will be unable to extend above the sediment, inhibiting feeding and potentially leading to mortality (Hill & Wilson, 2000). Therefore, resistance is assessed as ‘Medium’ and resilience as ‘Low’, particularly as growth rates are associated with food availability (Neves et al., 2015).  Overall, the biotopes are assessed as ‘Medium’ sensitivity at the pressure benchmark.

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

The Kophobelemnon fields biotopes are found at mid and upper bathyal depths and as such will not be affected by changes in emergence regime. This pressure benchmark is assessed as ‘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

The Kophobelemnon fields biotopes are found at mid and upper bathyal depths and as such will not be affected by changes in nearshore wave exposure. This pressure benchmark 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

This pressure is ‘Not assessed’ but the evidence is presented where available.

Barite (BaSO₄), a solid primary particulate compound in water-based drilling muds, and can contain low concentrations of heavy metals and metalloid impurities such as arsenic, chromium, copper, lead, nickel and zinc (Neff, 2008, 2010). Gates & Jones (2012) studied the effects of drill cuttings at 380 m depth in the Norwegian Sea. Within the study area, Kophobelemnon stelliferum was the most commonly observed Pennatulid. The pre-drilling mean sediment concentration of barium at the well location was 150 mg/kg. This increased to 5450 mg/kg 27 days after drilling, 0-10 m away from the well. After three years, concentrations in the top 2 cm of the sediment remained high at 6133 and 6291 mg/kg at 25 and 50 m away from the well, respectively. The mean density of Kophobelemnon stelliferum 1 day before drilling was 5.12 per 100 /m². Twenty-seven days after drilling commenced, the density of Kophobelemnon stelliferum within the area disturbed by the drill cuttings showed only a slight reduction to 4.01 per 100 /m². However, 76 days after drilling, this had decreased to 1.93 per 100 /m². Three years after, densities had still not recovered and were 0.87 per 100 /m². It is important to note that it is not clear whether this pattern was caused by the barium or smothering effects of the drill cuttings. For more information on the smothering caused by the drill cuttings, please see the ‘Smothering and siltation changes’ 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

This pressure is ‘Not assessed’ but the evidence is presented where available.

Valentine & Benfield (2013) recorded the potential resistance and sensitivity of deep-sea epibenthic megafauna to hydrocarbons resulting from the Deepwater Horizon oil spill in the Gulf of Mexico. Their study was undertaken within a 2 km radius of the well blow out preventer, 1-2 months after the flow of oil had ended at depths between 1443 and 1591 m. Sea pens were only identifiable to class level (Anthozoa), however, live individuals were only present at two out of the four sites located 2 km away from the well. Dead sea pens were also found at one of these sites, as well as another site. These were also the sites with the highest organism abundances. No sea pens (either dead or alive) were present in the site closest to the well (500 m away), however, the lack of dead sea pens may be a result of consummation. This occurrence of dead sea pens and only live individuals at two out of the four sites suggests that sea pens may be sensitive to hydrocarbons. Although there is no evidence of sea pens occurring prior to the spill, and pre-spill surveys were very limited.

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 the evidence is presented where available. No evidence was found on the effect of synthetic compound contamination on Kophobelemnon stelliferum.

Radionuclide contamination

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

Evidence

No evidence was found on the effect of increased radionuclide contamination on Kophobelemnon stelliferum and, as such, this pressure 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’ but the evidence is presented where available.

Edwards et al. (2016) studied the effects of sea-disposed chemical munitions on benthic fauna in the deep-sea off Hawaii. The munitions showed evidence of implosion and exposure of the internal constituents and were likely to have contained chemical warfare agents when they were sea-disposed in 1944. During the study of the chemical munitions sites in 2012 by Edwards et al. (2016), a solitary Kophobelemnon stelliferum was observed in close proximity to a munitions casing over a three-day deployment of a time-lapse camera. The polyps of this solitary individual regularly changed orientation to face the current direction, therefore, no abnormal behaviour was noted. No information was provided on the size or age of the sea pen colony. Therefore, it is not possible to determine whether the sea pen was ever exposed to the original contaminant, which may have dispersed before the sea pen appeared.

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

Kophobelemnon spp. have been recorded in the Venezuela Basin, where the bottom water has a uniform dissolved oxygen concentration of 5.1 ml/L (Briggs et al., 1996). However, Kophobelemnon stelliferum is also found on anoxic mud breccia bottoms in the Gulf of Cadiz at around 460 m depth, where they occur at low densities (2-5 colonies per metre), in areas with bacterial mats (Rueda et al., 2016). This suggests the species can tolerate low oxygen conditions.  Another sea pen species, Halipteris willemoesi, also shows tolerance to variable dissolved oxygen levels. In two bays off British Colombia (depths of 25-74 m) dissolved oxygen varied seasonally between 2.76-5.97 mg/L (Troffe et al., 2005). However, Jones et al. (2000) found that Pennatula phosphorea, Virgularia mirabilis and Funiculina quadrangularis were absent from deoxygenated areas in Scottish sea lochs. Virgularia mirabilis was also found to be absent from sewage related anoxic areas in Holyhead harbour (Hoare & Wilson, 1976).

Sensitivity assessment. As Kophobelemnon stelliferum is known to occur in anoxic conditions in the deep-sea (Rueda et al., 2016), resistance is assessed as ‘High’, resilience as ‘High’ and the biotopes are assessed as ‘Not sensitive’ at the pressure benchmark.

Nutrient enrichment

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

Evidence

Dolan (2008) notes that the large autozooids of Kophobelemnon species, relative to their colony size, means they are adapted to low nutrient conditions. 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

Kophobelemnon stelliferum feeds on living planktonic material (García-Alegre et al., 2018), therefore requiring organic matter in suspension to feed (Musgrave, 1909; Wareham, 2009). Wareham (2009) found that Pennatulacea in the north-west Atlantic (including Kophobelemnon sp.) displayed high values of δ13C’ and δ15N, further suggesting that re-suspended particulate organic matter (POM) and benthic meiofauna make up a large proportion of their diet.  Although no significant relationships were found between the linear growth rates and environmental variables in Halipteris finmarchica, when data for both Halipteris finmarchica and Halipteris willemoesi was pooled, diametric growth rates were found to be statistically related to particulate organic carbon (POC), plus latitude, temperature and chlorophyll a concentration (Neves et al., 2015). Both POC and chlorophyll a relate to food availability (Neves et al., 2015).

In the deep-sea off northern California, where an undescribed species of Kophobelemnon was recorded in abundance, total organic carbon (TOC) data showed a heavy flux of carbon (Blake et al., 1994). The authors suggested that this was providing nutrition to the benthic organisms in the area.  In sea loch on Skye in Scotland, Pennatula phosphorea and Virgularia mirabilis were found in abundance, close to a distillery outfall that was discharging water enriched in malt and yeast residues and other soluble organic compounds (Nickell & Anderson, 1997, cited in Hughes, 1998a; Jones et al., 2000). Organic carbon content in sediment in the study area was <5% and macrofaunal analysis showed that the distillery effluent had very little effect on the benthic fauna.  In contrast, another study found that the sea pen Pennatula phosphorea was negatively correlated to the proximity to a fish farm, which exhibits a gradient of benthic carbon flux (Wilding, 2011; Wilding et al., 2012). However, these results should be interpreted with caution as this gradient may be related to other impacts from fish farming.

Sensitivity assessment. Kophobelemnon stelliferum feeds on living planktonic material (García-Alegre et al., 2018), thereby requiring organic matter in suspension to feed (Musgrave, 1909; Wareham, 2009). The species would likely benefit from organic enrichment, as evidenced by the high abundance of sea pens in areas exposed to organic effluents (Nickell & Anderson, 1997, cited in Hughes, 1998a). Therefore, resistance for the organic enrichment pressure is assessed as ‘High’, resilience as ‘High’, and the Kophobelemnon fields biotopes are assessed as ‘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. Resistance is assessed as ‘None’, resilience as ‘Very low’, and sensitivity is assessed as ‘High’. Although no specific evidence is described, confidence in this assessment is ‘High’ due to the incontrovertible nature of this pressure.

Physical change (to another seabed type)

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

Evidence

The deep-sea sea pen Umbellula encrinus has been shown by de Moura Neves et al. (2018) to live in both dominantly soft as well as dominantly hard bottom environments where the sea pens were living in-between areas of hard substratum. Sea pens are, therefore, not exclusive to entirely soft bottoms areas. Although some deep-sea sea pens have adaptations to allow them to attach to solid surfaces (Williams & Alderslade, 2011), this has not been observed in Kophobelemnon stelliferum. 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 and Kophobelemnon stelliferum would no longer be supported. This change in biotope would cause a reclassification of the biotope (i.e., loss of the biotope). Therefore, resistance is 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 the Kophobelemnon fields biotopes, which occur on mud, could mean a change to ‘mixed’ or ‘sand and muddy sand’ substratum.  Sea pens are adapted to live on soft-bottoms that are mainly muddy or sandy (Bastari et al., 2018). Buhl-Mortensen & Buhl-Mortensen (2014) recorded the presence of sea pens (including Kophobelemnon stelliferum and Pennatula phosphorea) on mud, gravelly sandy mud and sandy mud in the Hardangerfjord at depths between 158 m and 346 m. Baker et al. (2012) found that Kophobelemnon stelliferum occurred primarily in soft sediments, although all their studied sea pen species occurred in a range of seabed types. For example, Kophobelemnon stelliferum, Pennatula sp. and Protoptilum carpenteri were recorded in mud-sand, cobble, boulder and gravel habitats. However, the sea pens were almost always anchored in the mud/sand portions of the substratum and all were much more abundant in mud-sand habitats. One exception was Halipteris finmarchica, which was sometimes anchored in a gravelly habitat that had little sand or mud (Baker et al., 2012). Troffe et al. (2005) also found that fewer adult individuals of Halipteris willemoesi occurred where sediments were muddier (<0.25 mm grain size: 84.6-97.2%), with more sea pens present at a site with a lower percentage of mud (<0.25 mm grain size: 71.4-85.9%).

Virgularia mirabilis (which is found in shallow waters and the deep-sea) is known to occur on a range of muddy substratum including mud, sandy mud, gravelly mud or gravelly mud with shell fragments/stones (Connor et al., 2004). The large muscular peduncle of Virgularia mirabilis allows this species to colonize more unstable habitats, with a high content of gravel sediments (Greathead et al., 2007). Modelling work in shallow water predicted that mud content was the most important variable for three species of sea pen (Funiculina quadrangularis, Pennatula phosphorea and Virgularia mirabilis) (Greathead et al., 2015). Bastari et al. (2018) looked at the effect of sediment composition on modelled sea pen (Virgularia mirabilis, Funiculina quadrangularis and Pennatula phosphorea) distribution in the Mediterranean, including deep-sea areas. Less frequent records of Kophobelemnon stelliferum, Kophobelemnon leucharti and Protoptilum carpenteri were also found, but modelling was not undertaken for these species. For Pennatula sp., the ratio between gravel/sand content was found to affect the distribution, and it was found in sandy or muddy sediment (but only in depths between 15-100m, although the species does occur in the deep-sea).

Sensitivity assessment. A change in Folk class from mud to ‘mixed’ or ‘sand and muddy sand’ would probably not affect Kophobelemnon stelliferum, which appears to have habitat preferences that would fall within this range, as long as a degree of soft sediment is present. 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 re-classification of the biotopes. Therefore, resistance is 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 Kophobelemnon stelliferum is a sedentary, anchored into the sediment by its peduncle, removal of the substratum at the benchmark pressure would likely cause destruction of the biotope, within the affected area.  Kophobelemnon stelliferum does exhibit some limited self-defence behaviour, for example, it is able to burrow and retract into the sediment (De Clippele et al., 2015). It is possible that it can retract fully, similar to other sea pen species, however, this defensive behaviour is unlikely to prevent it from being impacted by extraction to 30 cm. Movement by detaching, drifting and re-attaching has also been recorded in other deep-water sea pens (e.g. Umbellula lindahli and Ptilosarcus gurneyi; Flores, 1999, cited in Wilson et al., 2002; Birkeland, 1974), as well as a number of shallow-water species, e.g., Renilla kollikeri (Kastendiek, 1976) and Pennatula rubra (Chimienti et al., 2018). Although, there is no evidence for this in Kophobelemnon stelliferum. Musgrave (1909) suggested that it is extremely probable that many deep-sea Pennatulids do have controlled locomotion abilities. Eno et al. (2001) noted that the sea pens Pennatula phosphorea and Funiculina quadrangularis were able to re-establish themselves within 144 hours after removal by divers.  Malecha & Stone (2009) similarly found that dislodged Halipteris willemoesi could re-bury in sediment after disturbance. However, most of the Halipteris willemoesi sea pens eventually became dislodged again, even without further disturbance (Malecha & Stone, 2009).

Sensitivity assessment. The resistance of the Kophobelemnon fields biotopes to the removal of substratum is assessed as ‘Low’ and despite limited self-defence behaviour, this pressure is likely to cause significant mortality. Resilience is assessed as ‘Low’ and overall sensitivity to the pressure is assessed as ‘High’.

Abrasion / disturbance of the surface of the substratum or seabed

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

Evidence

No specific evidence could be found on the effects of abrasion on Kophobelemnon stelliferum. However, sea pens do become snagged/tangled in fishing nets when subjected to trawling and are therefore impacted by abrasion pressure (Yesson, 2020, pers. comm., 27 January 2020).  Kophobelemnon stelliferum is anchored into the substratum by its peduncle but is able to retract into the sediment (De Clippele et al., 2015). Hence, Kenchington et al. (2011) suggested that the species had some resilience to abrasion, minimising chances of being caught in trawls. Kenchington et al. (2011) further suggested that the species had some resilience due to the positioning of the sea pen colony, whereby the majority of the rachis (stalk) is buried within the sediment and only the upper portion containing the polyps is exposed.

The flexibility of sea pens and their ability to bend may provide some resistance to trawling (Troffe et al., 2005). For example, evidence shows sea pens bending around underwater cameras (Halipteris willemoesi; Troffe et al., 2005) or as a result of the pressure wave generated by sinking creel pots (specifically Pennatula phosporea, Virgularia mirabilis and Pennatula phosphorea in Scottish sea lochs; Eno et al., 2001).  Eno et al. (2001) simulated the effects of creel pots being dragged over Pennatula phosphorea, Virgularia mirabilis and Funiculina quadrangularis in Scottish sea lochs. All but one specimen of Funiculina quadrangularis recovered from the abrasion effects in 24-72 hours. Those that had been uprooted had reinserted themselves, provided the peduncle gained contact with suitable substratum.

In a study by Malecha & Stone (2009) off Alaska (depth of 30 m), Halipteris willemoesi was dislodged and observed in situ to simulate trawling-related damage. Fifty per cent of dislodged Halipteris willemoesi had re-buried in sediment and positioned themselves upright within two weeks after the disturbance. Despite this initial recovery, after three months only 33% of dislodged Halipteris willemoesi remained upright. After one year, only 8.3% (one colony) remained erect. This may indicate delayed mortality or an increased likelihood of becoming dislodged again. However, as the sea pens were tethered to the seabed as part of the experiment, this may have contributed.  Malecha & Stone (2009) further assessed the impact of abrasion by subjecting Halipteris willemoesi to light tissue abrasion in situ to simulate the effect of trawling ground gear equipped with ‘cookies’ passing over sea pens. Minor damage to sea pens occurred, with up to 4% of tissue being removed in 50% of specimens. However, after three months, the abrasion showed no effect on survival and average tissue loss was <1%. In addition to light tissue abrasion, fractures of the axial rods of sea pens were also simulated. Although many of the Halipteris willemoesi individuals were able to maintain the broken part of their rachises off the seabed and polyps continued to actively feed, no signs of repair were observed within the one-year study period. After two weeks, 42% of these fractured sea whips were upright and after three months only 33% were upright. Only one was still erect after one year, with the specimen showing much tissue loss. When damaged sea pens were in contact with the seabed, however, predation by nudibranchs was observed and resulted in up to 80% of tissue loss. Trawl damage could, therefore, be exacerbated by predators (Malecha & Stone, 2009). No natural mortality or damage was seen in the control group after three months.

Lindholm et al. (2008) assessed the density and condition of the sea whip Halipteris willemoesi in areas of high trawling intensity at depths of 110-140 m off central California (note that the species also occurs in the deep sea). There was no difference in sediment particle size, sorting coefficient or moisture content between the study areas, indicating that sediment type was not a factor in any observed differences. Depth did vary between transects, however, and the shallowest areas contained the highest densities of upright sea whips. Although the fishing data showed that the areas had been actively trawled for the four years prior to sampling, the data suggested differently, likely explaining the density/abundance differences observed. The transects with the highest densities (average 92%) of upright sea whips (with none broken-but-erect) were unlikely to have been impacted by trawling for multiple years prior to sampling.  Although sea whips may be able to bend back following a single pass of a trawl, the other transects had few-to-no upright individuals and prostrate sea whips (those lying on the seabed) were present, of which the majority were broken fragments. This indicates that recovery is not possible when subject to more intense trawling pressure (i.e. multiple passes of a trawl). It is also worth noting that prostrate sea whips occurred most frequently in the transects with the highest densities of upright individuals (Lindholm et al., 2008), suggesting that some degree of natural mortality does occur.

Kenchington et al. (2011) reported that incidental mortality following bottom trawling can be high, for example, an additional 3.5 kg on top of 7 kg of sea pen bycatch. However, research on incidental mortality from the NE Pacific at depths of 700-1974 m found that in areas of long-term bottom trawling (>65 years), the incidence of disturbance to sea pens was limited (Yoklavich et al., 2018). Out of 32 observed Pennatulacea and 19 Funiculina spp., only one of each was disturbed (i.e. broken/lying flat), whilst the two Umbellula lindahli and seven Anthoptilum grandiflorum observed were not disturbed (Yoklavich et al., 2018). It is important to note that this study only accounts for the individuals remaining on the seafloor and does not consider how many are brought up as bycatch. Further information on bycatch can be found under the pressure ‘Removal of non-target species’.

Clark et al. (2019) studied the resilience of deep-sea benthic seamount communities, including Pennatulacea, in New Zealand. Four camera surveys were undertaken over 15 years on seamounts with a range of trawl histories. On the seamount that was closed to trawling when the surveys started, no Pennatulacea was present. However, follow-up surveys showed that Pennatulacea was present five years later. Fourteen years following the closure to trawling, Pennatulacea was then present in greater abundance. However, between these periods (i.e. nine years after trawling cessation), no Pennatulacea were observed, so these results can only be interpreted with low confidence.

Several studies indicate that the abundance of many sea pen species is negatively correlated with bottom trawling (Funiculina quadrangularis, Protoptilum carpenteri, Stylatula spp. and Ptilosarcus sp.; Buhl-Mortensen et al., 2016; Adey, 2007; Hixon & Tissot, 2007). For example, the density of Stylatula spp. at 183-361 m depth off the west coast of the USA, was four magnitudes higher in untrawled areas compared to in heavily trawled areas, where they had a mean of 4±3 individuals per hectare (Hixon & Tissot, 2007). Ptilosarcus sp. similarly had a mean density of 38 individuals per 500 m² in lightly trawled areas, compared to 2 individuals in heavily trawled areas at 180 m depth off central California (Engel & Kvitek, 1998).  

Studies by Bluhm (2001) and Simon-Lledó et al. (2019) looked at the effects of physical disturbance impacts (i.e. penetration, causing perturbation of sediments) from simulated deep-sea mining in the Peru Basin. Pre-impact mean densities of Pennatularia were recorded by Bluhm (2001) to be one individual per 10,000 m^-2. After intensive ploughing of the seabed (78 passes in 20% of the study area), no Pennatularia were recorded in the ploughed area after either 0, 0.5, 3 or 7 years (Bluhm, 2001). Twenty-six years after the disturbance, Simon-Lledó et al. (2019) found that Anthozoans (including two occurrences of one morphospecies from the order Pennatulacea) showed a declining density with increased distance to the plough tracks (i.e. greater disturbance intensity). Anthozoans exhibited the highest sensitivity to impacts out of all taxa studied, with substantial reductions in standing stock in both the short (0, 0.5, 3 and 7 years) and long term (26 years) after disturbance. The ploughing was also noted to cause sediment redeposition in unploughed areas (see Smothering and siltation changes pressure). Due to the low initial densities of Pennatularia recorded by Bluhm (2001) and the low taxonomic resolution of the Simon-Lledó et al. (2019) study, with only two Pennatulacea individuals present within the disturbance area, the evidence presented is only of limited use for this sensitivity assessment.

Sensitivity assessment. Although some studies have observed sea pens in trawled areas, the densities are much lower compared to untrawled areas. The positioning of Kophobelemnon stelliferum colonies within the sediment and their ability to retract increases their resistance to abrasion pressure (Kenchington et al., 2011), for example, in comparison to the sea whip Halipteris willemoesi which cannot retract (Malecha & Stone, 2009). Light simulated abrasion on another deep-sea sea pen (studied in shallow water) has been shown to cause only minor damage to tissues, from which they can recover. However, fractured axial rods and dislodgment caused eventual mortality after one year (Malecha & Stone, 2009). Incidental mortality is, therefore, a concern and recovery is likely reduced when sea pens are subjected to more intense trawling pressure (i.e. multiple passes of a trawl; Lindholm et al., 2008). Only a single study was available on the long-term recovery potential of Pennatulacea, that found that sea pens occurred in the greatest abundance 14 years post trawling cessation. Therefore, resistance is assessed as ‘Medium’ and resilience as ‘Low’. Overall sensitivity 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

The relevant evidence on the effects of fishing activities is present above under abrasion. Penetrative gear is likely to remove a greater proportion of the sea pen population, as it may remove them from their burrows, within the footprint of the activity.  Therefore, resistance is assessed as 'Low'. Resilience is probably 'Low' so that sensitivity is assessed as 'High'.

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

Kophobelemnon stelliferum feeds on living planktonic material (García-Alegre et al., 2018), therefore requiring organic matter in suspension to feed (Musgrave, 1909; Wareham Hayes, 2009). Wareham (2009) found that Pennatulacea in the north-west Atlantic (including Kophobelemnon sp.) displayed high values of δ13C’ and δ15N, further suggesting that re-suspended Particulate Organic Matter (POC) and benthic meiofauna make up a large proportion of their diet.

Torre et al. (2012) studied the effects of increased sediment load on the shallow water Antarctic Kophobelemnidae species Malacobelemnon daytoni, at concentrations of 0 (without sediment) to 5, 15, 50, 100, 200, 400 and 600 mg/l, for six hours. It is important to note that this sediment load did result in some sedimentation occurring (as would occur in reality). In the 18 hours following the sediment exposure, the change in oxygen concentration was measured. Malacobelemnon daytoni exhibited no significant difference in their relative oxygen consumption over the different exposures, with no maximal or critical threshold reached. Sediment exposure to the sea pen, therefore, had no significant effect on oxygen consumption, irrespective of the amount of sediment added. The oxygen consumption of the sea pen was found to decline slightly (approx. 20%) under sediment exposure compared to the sediment-free treatment, but this was not significant. Based on these results, Torre et al. (2012) stated that Malacobelemnon daytoni was tolerant to suspended sediment loads (and sedimentation). This was suggested to be due to a behavioural response (Torre et al., 2012).  For example, the sea pen Pteroides griseum, was observed to contract their filtering apparatus, in turn reducing ectodermic respiration (Brafield & Chapman, 1967).

Servetto & Sahade (2016) found that the spawning of Malacobelemnon daytoni could be linked with changes in suspended sediment load (i.e. resuspended organic material). This was noted to be beneficial to the species by allowing a second spawning each year. In the UK, Virgularia mirabilis has been shown to reject sediment particles from polyps (Hoare & Wilson, 1976) and produce mucus that is thought to keep the polyps clear of silt (Kinnear et al., 1996).

Sensitivity assessment. Kophobelemnon stelliferum requires suspended material for feeding and is likely to exhibit behavioural responses to tolerate exposure to increased sediment loads. As such, the Kophobelemnon field biotopes 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). Therefore, resistance is 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

Gates & Jones (2012, 2010) studied the effects of drill cuttings at 380 m depth in the Norwegian Sea. Kophobelemnon stelliferum was the most commonly observed Pennatulid within the study area. Twenty-seven days after drilling, some areas 10 m away from the well were covered by cuttings 40 cm deep. Other areas 50-100 m away were <0.5 cm. The area visually disturbed (i.e. partially/completely) by drill cuttings had reduced significantly after three years. The results from the area completely covered by the drill cuttings are detailed under the ‘Heavy’ deposition benchmark below. To address the benchmark in question (up to 5 cm of deposition), the results from the area partially covered by drill cuttings, within 100 m of the well are presented here. The mean density of Kophobelemnon stelliferum one day before drilling was 5.12 per 100 /m². This was not significantly different from the densities recorded in the partially covered areas 27 days, 76 days and three years’ post-drilling (6.91, 8.52 and 3.99 per 100 /m² respectively). Data was also collected from the areas 100-500 m away from the well after three years, which showed similar densities ranging from 3.85 to 2.90 per 100 /m² (with increased distance).

A study by Simon-Lledó et al. (2019) looked at the biological effects of simulated deep-sea mining in the Peru Basin. Physical disturbance impacts from intensive ploughing of the seabed (78 passes in 20% of the study area), caused sediment redeposition up to 3 cm thick in unploughed areas from 1-50 m away from the ploughed area (Schriever & Thiel, 1992, cited in Simon-Lledó et al., 2019). Twenty-six years after the simulated disturbance, Anthozoans (including two occurrences of one morphospecies from the order Pennatulacea) showed a decline in density with increased distance to the plough tracks (i.e. greater disturbance intensity). Anthozoans exhibited the highest sensitivity to impacts out of all taxa studied, with substantial reductions in standing stock in both the short (0, 0.5, 3 and 7 years) and long term (26 years) in all affected areas after disturbance. The ploughing was also noted to cause penetration in ploughed areas (see ‘Penetration and/or disturbance of the substratum below the surface of the seabed' above). It is important to note the low taxonomic resolution of the Simon-Lledó et al. (2019) study, however, with only two Pennatulacea individuals present within the disturbance area. Together with the potential effects from the abrasion pressure itself, the evidence presented is therefore of limited use for assessing the ‘Smothering and siltation changes’ pressure.

Torre et al. (2012) studied the effects of increased sediment load on the shallow water Antarctic Kophobelemnidae species Malacobelemnon daytoni, at concentrations of 0 (without sediment) to 5, 15, 50, 100, 200, 400 and 600 mg/L, for six hours. This sediment load resulted in some sedimentation occurring. For example, 18 hours after the chambers had been sealed following exposure to the 400 mg/L concentrations, the sediment load dropped to ca. 25 mg/L, meaning the rest had been deposited (no information available on the depth). This sedimentation was noted to occur more rapidly at the highest concentrations of sediment load. The change in oxygen concentration was measured 18-hours after sediment exposure. Malacobelemnon daytoni exhibited no significant difference in their relative oxygen consumption over the different exposures, with no maximal or critical threshold reached. Sediment exposure to the sea pen, therefore, had no significant effect on oxygen consumption, irrespective of the amount of sediment added. The oxygen consumption of the sea pen was found to decline slightly (approx. 20%) under sediment exposure compared to the sediment-free treatment, but this was not significant. Based on these results, Torre et al. (2012) stated that Malacobelemnon daytoni is tolerant to sedimentation (and suspended sediment loads). This was suggested to be due to a behavioural response (Torre et al., 2012). For example, the sea pen Pteroides griseum, was observed to contract their filtering apparatus, in turn reducing ectodermic respiration (Brafield & Chapman, 1967).  Eno et al. (2001) simulated the effects of 24 and 48 hours of smothering by creel pots on Pennatula phosphorea, Virgularia mirabilis and Funiculina quadrangularis in Scottish sea lochs. All species recovered to an upright position following the smothering within 72-96 and 96-144 hours.

Sensitivity assessment. Some sea pens were found to exhibit behavioural responses that can successfully mitigate the effects of sedimentation (Torre et al., 2012). The study by Gates & Jones (2012, 2010) showed that Kophobelemnon stelliferum was not negatively affected by the presence of drill cuttings at low levels (i.e. the area 100 m away from the well with partial coverage of cuttings). Therefore, resistance is assessed as ‘High’, resilience as ‘High’ and the biotopes are assessed as ‘Not sensitive’ at the pressure benchmark.

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

Gates & Jones (2012, 2010) studied the effects of drill cuttings at 380m depth in the Norwegian Sea. Kophobelemnon stelliferum was the most commonly observed Pennatulid, within the study area. Twenty-seven days after drilling, some areas 10 m away from the well were covered by cuttings 40 cm deep. Other areas 50-100 m away were only covered by <0.5 cm of cuttings. The area visually disturbed (i.e. partially/completely) by drill cuttings had reduced significantly after three years. The results from the area only partially covered by the drill cuttings are detailed under the ‘Light’ deposition benchmark above. To address the benchmark in question (up to 30 cm of deposition), the results from the area completely covered by drill cuttings, within 100 m of the well, are presented here. The mean density of Kophobelemnon stelliferum one day before drilling was 5.12 per 100 /m². Twenty-seven days after drilling commenced, the density of Kophobelemnon stelliferum within the area disturbed by the drill cuttings showed only a slight reduction to 4.01 per 100 /m². However, 76 days after drilling, this had decreased to 1.93 per 100 /m². Three years after, densities had still not recovered and were 0.87 per 100 /m². The drill cuttings also caused increased barium levels, so it is not clear whether this contributed to this observed pattern (see  ‘Transition elements & organo-metal contamination’).

A study by Simon-Lledó et al. (2019) looked at the biological effects of simulated deep-sea mining in the Peru Basin. Physical disturbance impacts from intensive ploughing of the seabed (78 passes in 20% of the study area), caused sediment redeposition up to 3 cm thick in unploughed areas from 1-50 m away from the ploughed area (Schriever & Thiel, 1992, cited in Simon-Lledó et al., 2019). Twenty-six years after the simulated disturbance, Anthozoans (including two occurrences of one morphospecies from the order Pennatulacea) showed a declining density with increased distance to the plough tracks (i.e. greater disturbance intensity). Anthozoans exhibited the highest sensitivity to impacts out of all taxa studied, with substantial reductions in standing stock in both the short (0, 0.5, 3 and 7 years) and long term (26 years) in all affected areas after disturbance. The ploughing was also noted to cause penetration in ploughed areas (see 'Penetration and/or disturbance of the substratum below the surface of the seabed' above). However, it is important to note the low taxonomic resolution of the Simon-Lledó et al. (2019) study with only two Pennatulacea individuals present within the disturbance area. Together with the potential effects from the abrasion pressure itself, the evidence presented is therefore of limited use for assessing the ‘Smothering and siltation changes’ pressure.

Torre et al. (2012) studied the effects of increased sediment load on the shallow water Antarctic Kophobelemnidae species Malacobelemnon daytoni, at concentrations of 0 (without sediment) to 5, 15, 50, 100, 200, 400 and 600 mg/L, for six hours. This sediment load resulted in some sedimentation. For example, 18 hours after the chambers had been sealed following exposure to the 400 mg/L concentration, the sediment load dropped to ca. 25 mg/L, because the rest had been deposited (no information available on the depth). This sedimentation was noted to occur more rapidly at the highest concentrations of sediment load. The change in oxygen concentration was measured after the 18-hour sediment exposure. Malacobelemnon daytoni exhibited no significant difference in their relative oxygen consumption over the different exposures, with no maximal or critical threshold reached. Sediment exposure to the sea pen, therefore, had no significant effect on oxygen consumption, irrespective of the amount of sediment added. The oxygen consumption of the sea pen was found to decline slightly (approx. 20%) under sediment exposure compared to the sediment-free treatment, but this was not significant. Based on these results, Torre et al. (2012) stated that Malacobelemnon daytoni was tolerant of sedimentation (and suspended sediment loads). This was suggested to be due to a behavioural response (Torre et al., 2012). For example, the sea pen Pteroides griseum was observed to contract their filtering apparatus, in turn reducing ectodermic respiration (Brafield & Chapman, 1967). However, there is no evidence for this behaviour in Kophobelemnon stelliferum.  Eno et al. (2001) simulated the effects of 24 and 48 hours of smothering by creel pots on Pennatula phosphorea, Virgularia mirabilis and Funiculina quadrangularis in Scottish sea lochs. All species recovered to an upright position following the smothering within 72-96 and 96-144 hours.

Sensitivity assessment. Despite some sea pens exhibiting behavioural responses to tolerate sedimentation (Brafield & Chapman, 1966 & Torre et al., 2012), Kophobelemnon stelliferum has been shown to decline in density in affected areas, with no recovery within three years (Gates & Jones, 2012, 2010), at the pressure benchmark (up to 30 cm),  Therefore, resistance is assessed as ‘None’, resilience as ‘Low’ and sensitivity is assessed as ‘High’. 

Litter

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

Evidence

No evidence could be found regarding the introduction of litter on Kophobelemnon stelliferum. This pressure is  ‘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 could be found regarding the effect of electromagnetic changes on Kophobelemnon stelliferum. This pressure 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

Some of the important characterizing species associated with this biotope, in particular, the sea pens, may respond to sound vibrations and can withdraw into the sediment. Feeding will resume once the disturbing factor has passed. However, most of the species are infaunal and unlikely to respond to a noise disturbance at the benchmark level. Therefore, this pressure is probably Not relevant in this biotope.

Introduction of light or shading

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

Evidence

No direct information exists on the effect of light on Kophobelemnon stelliferum. Hughes (1998a) found that Virgularia mirabilis was insensitive to light, however, some sea pen species exhibit luminescence (Davenport et al., 1956). This behaviour is thought to be a defensive strategy (Williams, 2011) and, therefore, may be affected by light pollution. However, in the absence of specific evidence on Kophobelemnon stelliferum, this pressure benchmark is assessed as ‘No evidence’.

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

Kophobelemnon stelliferum is sedentary, anchored into the sediment by its peduncle. Although the species does exhibit some limited movement behaviour (e.g. retracting into the sediment; De Clippele et al., 2015) and other sea pen species are known to detach, drift and re-attach (Birkeland, 1974; Kastendiek, 1976; Flores, 1999, cited in Wilson et al., 2002; Chimienti et al., 2018), the distance is likely to be limited. Furthermore, this behaviour is likely to only respond to predation or physical disturbance (Langton et al., 1990; Baker et al., 2012; De Clippele et al., 2015; Greathead et al., 2015; Chimienti et al., 2018). As such, the species will not be affected by barriers to species movement and this pressure 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

The Kophobelemnon fields biotopes occur in the mid and upper bathyal at depths of 200-1300 m and are characterized by sessile and sedentary invertebrates, which have limited mobility. The benchmark for this pressure is related to the passage through an artificial structure (e.g. barrage or turbine installations) and is, therefore, only relevant to mobile species and the mobile stages of benthic species (e.g. larvae) in shallow waters. As such, 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

No direct information on the effect of visual disturbance on Kophobelemnon stelliferum was found. However, the ability of the species to retract into the sediment as a response to disturbance (De Clippele et al., 2015), suggests that they can detect movement. Some sea pens species also exhibit luminescence (Davenport et al., 1956), which is thought to be a defensive strategy (Williams, 2011). This may be affected by light pollution. However, in the absence of specific evidence on the effects of visual disturbance, this pressure benchmark is assessed as ‘No evidence’

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

Kophobelemnon stelliferum 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 was found for the effects of Introduction or spread of non-indigenous species on Kophobelemnon stelliferum. This pressure 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

No evidence could be found for the effects of the Introduction of microbial pathogens on Kophobelemnon stelliferum. 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

Kophobelemnon stelliferum is not a commercially or recreationally targeted species. Therefore, this pressure is marked ‘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.

Kophobelemnon stelliferum colonies extend above the surface of the seabed and can reach 70 cm in length (Rice et al., 1992), and are at risk of being removed as by-catch. When sea pens are brought up as by-catch they are often snagged/tangled in the main net (Yesson, 2020, pers. comm., 27 January 2020). Trawls of 1 km in length have recorded over 100 kg of sea pen by-catch (Kenchington et al., 2016). Kenchington et al. (2011), however, reported that Kophobelemnon spp. are capable of retracting into the sediment, reducing the chances of being caught. In both the Canadian and Spanish/EU trawl survey data, very few records of Kophobelemnon spp. were present, despite there being hundreds of in situ observations from camera surveys in the area. The authors suggested that this may be due to the positioning of the sea pen colony, whereby the majority of the rachis (stalk) is buried within the sediment and only the upper portion containing the polyps is exposed.

Kenchington et al. (2011) also noted that fishing effort would impact long thin sea pens (i.e. sea whips, such as Halipteris finmarchica or Anthoptilum grandiflorum) more so that the short fleshy sea pens (e.g. Pennatula spp.). At a fishing sea pen by-catch threshold of 7 kg, they estimate that this would represent 198 and 583 individuals for short/fleshy and sea whips, respectively. Although this suggests that the impacts may differ depending on the sea pen morphology, these numbers both equate to population-level impacts, with potential recruitment implications.  Their study found low gear efficiency for sea pen by-catch (10%), however, incidental mortality can be high (additional 3.5 kg per bycatch of 7 kg). Further information on incidental mortality can be found under the pressure ‘Abrasion /disturbance of the substratum on the surface of the seabed’.

Gear type can also have a differing level of impact on the bycatch of sea pens. Troffe et al. (2005) conducted a study on the effects of shrimp beam trawls versus prawn traps on the sea pen Halipteris willemoesi off British Colombia, at depths down to 74 m (note that the species also occurs in the deep-sea). No adult sea pens were caught when a single pass of a beam trawl was undertaken at three of the transects where sea pens were known to be present in high densities. However, the 600 traps, which were set and retrieved from the same study area, entangled 30 sea pens, of which 50% were intact and the remaining fragmented. There was no statistical difference in the density of adult or juvenile sea pens before and after trawling, however (as shown by video data). Troffe et al. (2005) suggested that the sea pens may have been flexible enough to avoid entanglement in the trawl, as the rachis of the sea pens would bend around the video camera. However, the beam trawl gear was also designed to ‘fly’ roughly 0.3 m above the bottom, with skids on the net to slide over the substratum. This was likely to mean that the sea pens avoided contact with the trawl entirely. It is important to note that beam trawls do catch sea pens in other areas (C. Yesson, 2020, pers. comm., 27 January 2020), so the study by Troffe et al. (2005) should be interpreted with caution.  

Wareham & Edinger (2007) also recorded the by-catch frequencies of Pennatulacea (11 species, including Kophobelemnon stelliferum) for a range of gear types, based on fisheries observations in the north-west Atlantic deep-sea. Otter trawls caught the most sea pens (frequency 296), with other gear types being much lower (e.g. 48 for twin trawl, 41 for gillnet, 16 for longline, 12 for triple trawl, and 1 for each of crab pot and shrimp trawls). Pires et al. (2009) collected 24 specimens of the deep-sea sea pen Anthoptilum murrayi during their scientific sampling at depths of 1051-1799 m using otter trawls, further supporting this by-catch assessment. Of these, only a few colonies were undamaged and still bore intact polyps, indicating that sea pens are not viable after being caught. In a similar study, de Moura Neves et al. (2018) indicated that the deep-sea sea pen Umbellula encrinus was susceptible to being caught by a range of fishing gear types. However, this species is very tall (>2 m) in comparison to Kophobelemnon stelliferum (70 cm; Rice et al., 1992). Longline hooks of varied sizes caught colonies of all size ranges, but in comparison to shrimp traps and whelk pots, which caught mainly small-size colonies, longlines tended to catch large-sized specimens. Pires et al. (2009) also noted that previous studies have collected up to 52 colonies of Anthoptilum murrayi in a single scientific dredge. This suggests a low resistance to being bycaught in dredge fisheries.

Evidence of the effects of shallow water creel fishing in Scotland on Pennatulacea phosphorea and Virgularia mirabilis found that sea pens were resistant, primarily due to their flexibility and ability to retract (Eno et al., 2001). Although moderate quantities of Virgularia mirabilis and Pennatula phosphorea were bycaught in by creel fishery, high densities were still observed on the creel grounds (Adey, 2007).

Sensitivity assessment. Although large quantities or sea pens can be caught, with additional incidental mortality, Kophobelemnon stelliferum appears to show some resistance due to its ability to retract, its morphology and the specific positioning of the sea pen colony within the sediment (Kenchington et al., 2011). As only a minimal proportion of Kophobelemnon stelliferum are likely to be removed, the biotope structure (species richness and diversity) will remain similar. Therefore, the resistance of the Kophobelemnon fields biotopes is assessed as ‘Medium’. Resilience is assessed as ‘Low’, particularly as chances of fertilization will be reduced if sea pens are removed from the habitat (Pires et al., 2009). Sensitivity is, therefore, assessed as ‘Medium’.