MarLIN

information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Atlantic upper bathyal live Lophelia pertusa reef (biogenic structure)

17-09-2018

Summary

UK and Ireland classification

UK and Ireland classification

Description

Scleractinian coral reefs formed predominantly by Lophelia pertusa in the upper bathyal zone. Lophelia attaches to any hard substratum present and then grows outwards forming a hard reef structure. Lophelia reef is often associated with a range of coral species and a high diversity of other fauna. This biotope refers only to reef framework summits with live Lophelia. Further research is required to identify associated species on Lophelia reef that distinguish between reefs occuring in different vertical zones. Lophelia reef can be found in a mosaic with all substrata types. (Information from JNCC, 2015).

Depth range

200-600 m

Additional information

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Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

The M.AtUB.Bi.CorRee.LopPer biotope is characterised by Lophelia pertusa, Sabellidae, Actiniaria, encrusting sponges, Ascidiacea, Munida and Echinus. Lophelia pertusa is the most common reef forming scleractinian cold-water coral.  Lophelia pertusa colonies can grow to several metres, and branches of separate colonies can anatomise, strengthening the structure of the reef (Roberts et al., 2009).  The complex reef formations that are created by Lophelia pertusa provide a range of niches, which host a wide number of species (Buhl & Mortensen et al., 2005; Mortensen et al., 2010; Freiwald et al., 2004; Muller et al., 2013).  A total of 1317 species have been listed associated with Lophelia pertusa reefs within the North East Atlantic (Roberts et al., 2006).  Therefore, although there is not a full species list associated with this biotope, it is likely that it will have high species diversity.  Henry & Roberts (2007) found that the biodiversity of cold-water coral mounds containing Lophelia pertusa in the North East Atlantic was typically greater than that of the off-mound habitats.  Jonsson et al. (2004) also found that there was a decrease in the biodiversity and the abundance of individuals the further from a Lophelia pertusa reef within a Swedish fjord.  The increase in biodiversity around Lophelia pertusa reefs shows that they are important ecosystem engineers.  Therefore, while Lophelia pertusa is not the only coral species found in the cold-water coral reefs of the North East Atlantic, it is the major reef forming species and, hence the focus for sensitivity assessment.  

Resilience and recovery rates of habitat

Lophelia pertusa has a worldwide distribution. However, records show it to be most abundant in deep waters, at high latitudes in the North East Atlantic (Davies et al., 2008). Global oceanographic data show that Lophelia pertusa is found at a mean depth of 480 m (Davies et al., 2008). Most records were found where current speeds (mean of 0.07 m/s) and productivity (mean of 0.9 mg/m3) are higher than the regional mean, at full salinity (35), and where mean temperatures were 6.2-6.7°C and mean dissolved oxygen levels were 6.0-6.2 ml/l (Davies et al., 2008). Until the 1990’s little scientific information was available on Lophelia pertusa (Wilson, 1979a,b; Rogers, 1999).  However, the rapid growth in commercial deep-water activities such as bottom trawling and offshore hydrocarbon exploration meant that greater understanding of deep-water ecosystems was needed. Although there is extensive literature on the destruction of cold-water coral reefs through anthropogenic pressures, there is almost no information regarding the recovery of these habitats.

The oldest radiocarbon dated Lophelia pertusa colony was found off the coast of Norway and was between 7800 – 8800 years old (Mikkelson et al., 1982; Hovland et al., 1998; Hovland & Mortensen, 1999).  Lophelia pertusa caught as by-catch from the west coast of Ireland was found to be at least 4550 years old (Hall-Spencer et al., 2002).  In the high latitudes in the North East Atlantic, the growth of Lophelia pertusa reefs is unlikely before 10,000 years ago, due to the extent of ice during the last ice age (Schröder-Ritzrau, 2005).  The growth of Lophelia pertusa varies.  The lowest recorded growth rate was 5 mm / annum (Roberts, 2002a) with the highest being 34 mm/ annum (Gass & Roberts, 2006).

Lophelia pertusa is gonochoristic and is thought to spawn annually (Waller, 2005).  Evidence from the North East Atlantic Lophelia pertusa supports this supposition, and samples collected within this area showed a seasonal reproductive cycle with a single cohort per year, with a spawning event around February (Waller & Tyler 2005).  Asexual replication of Lophelia pertusa polyps occurs by unequal intratentacular budding (Cairns 1979, 1994; Roberts et al., 2009; Brooke & Jarnegren, 2013). Larsson et al. (2014) examined embryogenesis and larval development in the laboratory in fragments of live Lophelia pertusa colonies from the Tisler reef and Trondheim Fjord, Norway. Spawning occurred in Jan to March, although spawning was asynchronous depending on site of origin, over a period of two months. They observed that multiple male polyps spawned simultaneously, resulting in a high fertilization efficiency. Spawned oocytes were 160 µm in diameter and resultant embryos were neutral or negatively buoyant and developed into 120-270 µm long ciliated planulae. The planulae were active swimmers (0.5 mm/s) and actively swam upwards into the upper water column. Larsson et al. (2014) estimated that larvae could vertically migrate ca 50 m/day, which would bring them out of the benthic boundary layer in reef conditions. The planulae spent three to five weeks in the water column before the onset of bottom-probing behaviour. Larsson et al. (2014) concluded that the larvae were probably planktotrophic rather than lecithotrophic suggested by Waller (2005). Bottom-probing behaviour became common amongst the larvae studied four to five weeks after fertilization and coincided with the development of nematocysts, which suggested that had become competent, although settlement was not observed.  The planula larvae of Lophelia pertusa require hard substrata for settlement, including rock surfaces, artificial substrata, coral fragments or hydrocarbon seep associated carbonates. In sedimentary areas, Lophelia pertusa may settle on hard substrata as small as a shell, pebble, or worm tube (Rogers, 1999). However, a hard substratum is a pre-requisite for settlement and a layer of sediment may interfere with settlement and hence recruitment.

The ability of Lophelia pertusa to colonize isolated hard substrata and artificial substrata such as submarine cables, the Brent Spar storage buoy and oil rigs suggests that it has a pelagic larval phase (Rogers, 1999; Roberts, 2002a). Roberts (2002a) concluded that the occurrence of Lophelia on structures in the Beryl and Brent oil fields in the North Sea was good evidence for a dispersive planula larva. Roberts (2002a) suggested that the colonies in the North Sea oil fields originated as larvae from the offshore banks of the Atlantic margin, and were carried into the North Sea in cooled Atlantic water, possibly via the east Shetland Atlantic Inflow current. Transport of larvae in the water mass of prevailing water currents probably provides the opportunity for long-distance dispersal. Larsson et al.'s (2014) study corroborates these assumptions. Larsson et al. (2014) noted that the ability of the larvae to swim upwards would put them into the tidal currents flowing over reefs (ca 0.1-0.4 m/s) so that they were likely to be swept away and unlikely to settle in their native reef, although they cite a genetic study that indicated that larval retention occurred in reefs in the NE Skagerrak (Dahl et al., 2012; cited in Larsson et al., 2014). Larsson et al. (2014) also recorded a larval lifespan of eight weeks (but noted it might be longer in the wild), which when combined with the late onset of competency, suggested a high dispersal potential.

Evidence suggests that larvae are dispersive but that migration is not sufficient to counteract reproductive isolation of populations (Dr Alex Rogers, 2005 pers comm.). Molecular genetic data indicates that Beryl oil fields samples of Lophelia are closely related to northern Rockall Trough populations but that there is strong genetic differentiation (population sub-division), with very low gene flow between areas (Le Goff-Vitry & Rogers, 2002; Dr Alex Rogers, 2005 pers comm.). Molecular genetic studies of the population of Lophelia pertusa in the North East Atlantic showed that it was not a panmictic population but composed of genetically distinct offshore and fjordic subpopulations from the Iberian margin to the Scandinavian fjords (Le Goff-Vitry & Rogers, 2005). Also, inbreeding was also observed in some subpopulations that indicated self-recruitment in those sites. In addition, there was high variation in the degree of genetic variation between subpopulations, for example in the Darwin mounds that exhibited a high proportion of clones and low genetic diversity.  In particular, the fjordic populations were highly differentiated genetically, for example, the Osterfjord subpopulation showed very low genetic diversity.  Morrison et al. (2011; summary only) also found genetic differentiation between populations of Lophelia pertusa in the Gulf of Mexico, coastal southeast United States, New England seamounts and the eastern North Atlantic. They concluded that while some larvae were dispersed over large geographic distances gene flow between the ocean regions was restricted. The evidence suggests that asexual reproduction predominates in reef growth and that the contribution from larvae may be limited (Dr Alex Rogers, 2005 pers comm.). Le Goff-Vitry & Rogers (2002, 2005) concluded that gene flow along the continental margin was sporadic and that recolonization of disturbed coral reefs through larval dispersal is likely to take long periods of time.

Fragmentation of the coral skeleton is part of the process of reef growth and development (Wilson, 1979b; Rogers, 1999).  Therefore, minor damage to colonies is probably a natural process within reef formation.  Lophelia pertusa larvae have to settle onto hard substrata, yet the reefs can spread out over soft sediment.  The reef structure its self can also engineer the physical environment around it (Roberts et al., 2009).  The reef structure created by Lophelia pertusa modifies the water flow regime within the reef (Mullins et al., 1981).  The complex structure of the reef slows down water flow and this can cause sediments to fall out of suspension. The reef also provides a wide range of niches for other species, and the increase in biological activity within the reef can also increase sedimentation (Roberts et al., 2009).   In addition, the interaction of tidal currents and the mounds and reefs created by cold-water corals can induce the downwelling of surface waters (Robert et al., 2009), which in turn provides a pathway for organic matter to reach 600 metre deep cold-water corals along the Rockall Bank (Soetaert et al., 2016).

Maier (2008) found that, in aquaria, severely fragmented pieces of Lophelia pertusa collected during survey work showed considerable recovery potential.  Damaged Lophelia pertusa were maintained in aquaria for a number of months, during which time they were fed regularly.  During the time of experiment corallite pieces as small as 3 mm showed regeneration (Maier, 2008).  Maier (2008) noted that although this regeneration was possible within aquaria, corals are not guaranteed to survive damage in the field due to the destruction of the coral framework, sedimentation and other factors not present in the aquaria experiment.  However, it does show that cold-water coral propagation within aquaria is possible.  

Gass & Roberts (2006) examined 14 oil and gas platforms within the North Sea and found Lophelia pertusa to be growing on 13 of them.  Two of the platforms were examined more closely and 947 individual colonies were found, the largest of which was 132 cm in diameter (Gass & Roberts, 2006). Prior to the oil and gas platforms in the North Sea, there were no known records of live Lophelia pertusa.  Larvae recruited to these North Sea platforms were probably transported in the North Atlantic water mass entering the North Sea.  The nearest known Lophelia pertusa colonies to the North Sea are from the west coast of Scotland.  Lophelia pertusa larvae are most likely to have reached the North Sea via the substantial inflow of Atlantic water flowing southwards east of Shetland from the Atlantic shelf edge current and the Fair Isle Current (Roberts, 2002; taken from Gass & Roberts, 2006).

Evidence of reef recovery within the field is severely lacking.  Roberts et al. (2006) stated that cold-water coral reefs have been severely damaged by trawling for deep-water fish, causing severe physical damage from which recovery to former reef status will take several hundred or thousands of years, if at all (Freiwald et al., 2004; Fosså et al., 2002; Hall-Spencer, 2002).  Growth rates are slow, the age of the reefs which have been carbon dated show that they have been undisturbed for long periods of time.  For a single Lophelia pertusa colony to grow to 1.5 m high could take 200 -366 years depending on growth rate (Rogers, 1999).  Colonies of Lophelia pertusa growing in close proximity merge to create a reef structure.  Old reefs can create mounds tens of metres high, and hundreds of metres wide.  The period of time for which Lophelia pertusa reefs to return to full ecosystem function is unclear but an estimate of hundreds of years is not unrealistic.  If a reef thousands of years old has been damaged then the time for the reef to return to its previous state would take an equal length of time if conditions for recruitment were still favourable.  The formation of cold-water coral reefs is complex and fully explained by Roberts et al. (2009).

Resilience assessment.  The ability of Lophelia pertusa to recover from natural or anthropogenic damage is poorly understood (Brooke & Jarnegren, 2013).  There is extensive evidence for the damage of Lophelia pertusa, yet there is no evidence for the natural recovery of any of these damaged reefs.  From experiments within controlled aquaria, there is evidence that Lophelia pertusa can recover from very small fragments (Maier, 2008).  However, there is no evidence of this occurring in the field.  Oil and gas platforms provide evidence that the larvae of Lophelia pertusa have the potential to travel extensive distances and can grow to considerable sizes within 20 – 30 years.  Although this evidence suggests that Lophelia pertusa has the potential to recover relatively quickly within certain controlled aquaria conditions, it does not take into consideration the age of the Lophelia pertusa reefs that are the basis of this biotope.  The oldest Lophelia pertusa reefs in the North East Atlantic were found to be between 7800 – 8800 (Mikkelson et al., 1982; Hovland et al., 1998; Hovland & Mortensen, 1999).  It is now widely accepted that anthropogenic pressures are having a negative effect on cold-water coral reefs, including those containing Lophelia pertusa (Roberts & Cairns 2014).  However, the limited knowledge regarding the worldwide distribution of the cold-water coral reef habitats makes it very difficult to determine how much habitat has been lost to anthropogenic pressures.  There are, however, a number of recorded cases of Lophelia pertusa reefs being lost from the North East Atlantic.  Fosså et al. (2002) documented and photographed the damage caused to west Norwegian Lophelia pertusa reefs by trawling activity (see Fosså, 2003 for photographs).  They reported that four, out of five sites studied, contained damaged corals. In the shallow regions of Sørmannsneset, only fragments of dead Lophelia pertusa were seen, spread around the site with no evidence of living colonies in the surrounding area, and Fosså et al. (2002) concluded that the colonies had been "wiped out".  Overall, they estimated that between 30 and 50% of Lophelia pertusa reefs are either impacted or destroyed by bottom trawling in western Norway.  From the west coast of Ireland, widespread bottom trawling damage of Lophelia pertusa reefs has been found between 840-1300 m (Hall-Spencer et al., 2002).  Lophelia pertusa has also been identified within the by-catch of deep-water fishing vessels trawling off the west coast of Ireland (Hall-Spencer et al., 2002).  Other papers that provide evidence for the damage of cold-water coral reefs through bottom trawling include Hall-Spencer et al. (2002), Grehan et al. (2003), Wheeler et al. (2005), Roberts et al. (2006), Alhaus et al. (2009), Roberts & Cairns (2014).  In addition to deep water fisheries, the hydrocarbon industry, mining, and ocean acidification have all been found to degrade the health of cold-water coral reefs (Roberts et al., 2009). 

Therefore, where resistance is ‘None’, ‘Low’, or ‘Medium’, resilience is assessed ‘Very low’.  There is no evidence from case studies that show Lophelia pertusa reefs recover from damage, so it is unclear if a Lophelia pertusa reef will ever recover.  In addition, for permanent or ongoing (long-term) pressures where recovery is not possible as the pressure is irreversible, resilience is assessed as ‘Very low’ by default. 

Climate Change Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
High High Not sensitive
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: High
C: Medium

Deep waters off the continental shelf (200 – 2500 m) are predicted to see a lower temperature rise (≈ 1°C) than shallow-water habitats by the end of this century, regardless of the climate change scenario modelled (FAO (Fisheries and Aquaculture Organisation), 2019). Lophelia pertusa is typically found in areas where temperatures range from 4 to 12°C (Davies et al., 2008, Lunden et al., 2014), with UK reefs and colonies generally in water temperatures of 6-10°C (Frederiksen et al., 1992, Duineveld et al., 2007, Roberts et al., 2009).  The upper lethal limit for this species is thought to be 15°C (Brooke et al., 2013).

Temperatures are generally thought to stable in Lophelia pertusa habitats (Dullo et al., 2008).  However, substantial increases in temperature have been observed. For example on the Tisler Reef, in Norway, in 2006 and 2008 the temperature rose by approximately 4°C in 24 hours, spiked at 12°C and remained above 10°C for approximately 30 days (Guihen et al., 2012). No Lophelia pertusa mortality was observed during this time, although mass mortality of the deep-water sponge, Geodia baretti, occurred (Guihen et al., 2012). Furthermore, over coral mounds off the coast of North Carolina, US, the incursion of the Gulf stream can lead to temperatures fluctuating greatly, and reaching 15°C on a regular basis, with a mean bottom water temperature of 9.9°C (Brooke et al., 2013). In the Gulf of Mexico, Lophelia pertusa occurred in areas where temperatures were 8.5-10.6°C (Davies et al., 2010). Temperature variations of 0.8°C were observed over 5-11 hr periods, associated with internal waves. Furthermore, high-frequency temperature variability over 20-30-minute periods was also recorded at one of the coral sites (476m depth), where a temperature rise of 0.5°C occurred, followed by a slower temperature decline. These fluctuations exhibit 5-11 hour cycles. These observations suggest that this species can tolerate increases in temperature.  

Results of the effect of short-term (≤6 months) experimental increases in temperature on Lophelia pertusa have been mixed, with some finding this species sensitive to increased temperatures (Dodds et al., 2007, Lunden et al., 2014), and others showing positive effects of increases in temperature (Büscher et al., 2017). Buscher et al. (2017) found an increase in growth rates in Norwegian populations in response to a six month increase in temperature from 8-12°C. In the study by Lunden et al. (2013), a 2°C increase in temperature (from 8 to 10°C) saw a 10% decrease in survivorship, although some genotypes were more sensitive than others to the increase in temperature. Naumann et al. (2014) examined the respiration rate and calcification rates of Lophelia pertusa collected from the Mediterranean at 12, 9 and 6°C after acclimation for one month. Lophelia pertusa was found to acclimate to lower temperatures (9 and 6°C) and maintained a constant respiration rate although calcification rates were reduced by 58% at 12°C.

Sensitivity assessment. Under all scenarios (middle and high emission scenarios and extreme scenario), waters off the continental shelf are expected to increase marginally by approximately 1°C, increasing the temperature at which Lophelia pertusa reefs are found to between 6 and 11°C, which is not outside their current temperature distribution.  Whereas an increase of 1°C is not expected to cause catastrophic effects, laboratory experiments suggest an increase in temperature may lead to some stress on Lophelia pertusa, potentially leading to changes in feeding and respiration rates. It must be noted that any negative impacts observed in laboratory experiments, were observed when temperatures were increased suddenly by 2°C or more, and experiments were run over short timescales (< 6 months). Under future projections for all scenarios, the temperature increase in deep waters is expected to rise by only 1°C, over the next 50-80 years, giving North-East Atlantic populations of Lophelia pertusa the chance to acclimate, as it has to warmer water temperatures in the Gulf of Mexico and the Mediterranean. Therefore, resistance has been assessed as ‘High’, whilst resilience has been assessed as ‘High’. This leads to an overall sensitivity score of ‘Not sensitive’ at the 1°C temperature rise benchmark for all three scenarios.

High High Not sensitive
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: High
C: Medium

Deep waters off the continental shelf (200 – 2500 m) are predicted to see a lower temperature rise (≈ 1°C) than shallow-water habitats by the end of this century, regardless of the climate change scenario modelled (FAO (Fisheries and Aquaculture Organisation), 2019). Lophelia pertusa is typically found in areas where temperatures range from 4 to 12°C (Davies et al., 2008, Lunden et al., 2014), with UK reefs and colonies generally in water temperatures of 6-10°C (Frederiksen et al., 1992, Duineveld et al., 2007, Roberts et al., 2009).  The upper lethal limit for this species is thought to be 15°C (Brooke et al., 2013).

Temperatures are generally thought to stable in Lophelia pertusa habitats (Dullo et al., 2008).  However, substantial increases in temperature have been observed. For example on the Tisler Reef, in Norway, in 2006 and 2008 the temperature rose by approximately 4°C in 24 hours, spiked at 12°C and remained above 10°C for approximately 30 days (Guihen et al., 2012). No Lophelia pertusa mortality was observed during this time, although mass mortality of the deep-water sponge, Geodia baretti, occurred (Guihen et al., 2012). Furthermore, over coral mounds off the coast of North Carolina, US, the incursion of the Gulf stream can lead to temperatures fluctuating greatly, and reaching 15°C on a regular basis, with a mean bottom water temperature of 9.9°C (Brooke et al., 2013). In the Gulf of Mexico, Lophelia pertusa occurred in areas where temperatures were 8.5-10.6°C (Davies et al., 2010). Temperature variations of 0.8°C were observed over 5-11 hr periods, associated with internal waves. Furthermore, high-frequency temperature variability over 20-30-minute periods was also recorded at one of the coral sites (476m depth), where a temperature rise of 0.5°C occurred, followed by a slower temperature decline. These fluctuations exhibit 5-11 hour cycles. These observations suggest that this species can tolerate increases in temperature.  

Results of the effect of short-term (≤6 months) experimental increases in temperature on Lophelia pertusa have been mixed, with some finding this species sensitive to increased temperatures (Dodds et al., 2007, Lunden et al., 2014), and others showing positive effects of increases in temperature (Büscher et al., 2017). Buscher et al. (2017) found an increase in growth rates in Norwegian populations in response to a six month increase in temperature from 8-12°C. In the study by Lunden et al. (2013), a 2°C increase in temperature (from 8 to 10°C) saw a 10% decrease in survivorship, although some genotypes were more sensitive than others to the increase in temperature. Naumann et al. (2014) examined the respiration rate and calcification rates of Lophelia pertusa collected from the Mediterranean at 12, 9 and 6°C after acclimation for one month. Lophelia pertusa was found to acclimate to lower temperatures (9 and 6°C) and maintained a constant respiration rate although calcification rates were reduced by 58% at 12°C.

Sensitivity assessment. Under all scenarios (middle and high emission scenarios and extreme scenario), waters off the continental shelf are expected to increase marginally by approximately 1°C, increasing the temperature at which Lophelia pertusa reefs are found to between 6 and 11°C, which is not outside their current temperature distribution.  Whereas an increase of 1°C is not expected to cause catastrophic effects, laboratory experiments suggest an increase in temperature may lead to some stress on Lophelia pertusa, potentially leading to changes in feeding and respiration rates. It must be noted that any negative impacts observed in laboratory experiments, were observed when temperatures were increased suddenly by 2°C or more, and experiments were run over short timescales (< 6 months). Under future projections for all scenarios, the temperature increase in deep waters is expected to rise by only 1°C, over the next 50-80 years, giving North-East Atlantic populations of Lophelia pertusa the chance to acclimate, as it has to warmer water temperatures in the Gulf of Mexico and the Mediterranean. Therefore, resistance has been assessed as ‘High’, whilst resilience has been assessed as ‘High’. This leads to an overall sensitivity score of ‘Not sensitive’ at the 1°C temperature rise benchmark for all three scenarios.

High High Not sensitive
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: High
C: Medium

Deep waters off the continental shelf (200 – 2500 m) are predicted to see a lower temperature rise (≈ 1°C) than shallow-water habitats by the end of this century, regardless of the climate change scenario modelled (FAO (Fisheries and Aquaculture Organisation), 2019). Lophelia pertusa is typically found in areas where temperatures range from 4 to 12°C (Davies et al., 2008, Lunden et al., 2014), with UK reefs and colonies generally in water temperatures of 6-10°C (Frederiksen et al., 1992, Duineveld et al., 2007, Roberts et al., 2009).  The upper lethal limit for this species is thought to be 15°C (Brooke et al., 2013).

Temperatures are generally thought to stable in Lophelia pertusa habitats (Dullo et al., 2008).  However, substantial increases in temperature have been observed. For example on the Tisler Reef, in Norway, in 2006 and 2008 the temperature rose by approximately 4°C in 24 hours, spiked at 12°C and remained above 10°C for approximately 30 days (Guihen et al., 2012). No Lophelia pertusa mortality was observed during this time, although mass mortality of the deep-water sponge, Geodia baretti, occurred (Guihen et al., 2012). Furthermore, over coral mounds off the coast of North Carolina, US, the incursion of the Gulf stream can lead to temperatures fluctuating greatly, and reaching 15°C on a regular basis, with a mean bottom water temperature of 9.9°C (Brooke et al., 2013). In the Gulf of Mexico, Lophelia pertusa occurred in areas where temperatures were 8.5-10.6°C (Davies et al., 2010). Temperature variations of 0.8°C were observed over 5-11 hr periods, associated with internal waves. Furthermore, high-frequency temperature variability over 20-30-minute periods was also recorded at one of the coral sites (476m depth), where a temperature rise of 0.5°C occurred, followed by a slower temperature decline. These fluctuations exhibit 5-11 hour cycles. These observations suggest that this species can tolerate increases in temperature.  

Results of the effect of short-term (≤6 months) experimental increases in temperature on Lophelia pertusa have been mixed, with some finding this species sensitive to increased temperatures (Dodds et al., 2007, Lunden et al., 2014), and others showing positive effects of increases in temperature (Büscher et al., 2017). Buscher et al. (2017) found an increase in growth rates in Norwegian populations in response to a six month increase in temperature from 8-12°C. In the study by Lunden et al. (2013), a 2°C increase in temperature (from 8 to 10°C) saw a 10% decrease in survivorship, although some genotypes were more sensitive than others to the increase in temperature. Naumann et al. (2014) examined the respiration rate and calcification rates of Lophelia pertusa collected from the Mediterranean at 12, 9 and 6°C after acclimation for one month. Lophelia pertusa was found to acclimate to lower temperatures (9 and 6°C) and maintained a constant respiration rate although calcification rates were reduced by 58% at 12°C.

Sensitivity assessment. Under all scenarios (middle and high emission scenarios and extreme scenario), waters off the continental shelf are expected to increase marginally by approximately 1°C, increasing the temperature at which Lophelia pertusa reefs are found to between 6 and 11°C, which is not outside their current temperature distribution.  Whereas an increase of 1°C is not expected to cause catastrophic effects, laboratory experiments suggest an increase in temperature may lead to some stress on Lophelia pertusa, potentially leading to changes in feeding and respiration rates. It must be noted that any negative impacts observed in laboratory experiments, were observed when temperatures were increased suddenly by 2°C or more, and experiments were run over short timescales (< 6 months). Under future projections for all scenarios, the temperature increase in deep waters is expected to rise by only 1°C, over the next 50-80 years, giving North-East Atlantic populations of Lophelia pertusa the chance to acclimate, as it has to warmer water temperatures in the Gulf of Mexico and the Mediterranean. Therefore, resistance has been assessed as ‘High’, whilst resilience has been assessed as ‘High’. This leads to an overall sensitivity score of ‘Not sensitive’ at the 1°C temperature rise benchmark for all three scenarios.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

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.) Therefore, sensitivity to marine heatwaves is probably ‘Not relevant’ in this bathyal habitat.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

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.) Therefore, sensitivity to marine heatwaves is probably ‘Not relevant’ in this bathyal habitat.

Low Very Low High
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: High
C: High

Increasing levels of CO2 in the atmosphere have led to the average pH of sea surface waters dropping from 8.25 in the 1700s to 8.14 in the 1990s (Jacobson, 2005). By the end of this century, pH is predicted to decrease by a further 0.15 – 0.35 units depending on the emission scenario used. Due to their calcified nature, both deep and shallow water scleractinian coral reefs are generally thought to be highly sensitive to ocean acidification (Hall-Spencer & Harvey, 2019). The deep-water species, Lophelia pertusa is a plastic species that has a wide bathymetric range (30-3000 m), lives in several different temperate habitats, and can thrive in the Mingulay Reef complex, where tidal downwelling can cause daily variations in pH equivalent to a 25-year jump in atmospheric CO2 (Hennige et al., 2015). This suggests that it may have some tolerance to changes in pH.

Results of short-term experimental acidification (≤3 months) on Lophelia pertusa show negative effects such as a decrease in respiration rates (Hennige et al., 2014; 0.3 unit pH decrease), and calcification rates (Maier et al., 2009; both at 0.15 and 0.3 unit pH decrease), or no observable effects (Maier et al., 2013b). Georgian et al. (2016) found variation in response between populations. Decreasing pH (from ambient pH of 7.9 to 7.75 and 7.6) led to a decrease in respiration, prey capture rates and net calcification in specimens from the Gulf of Mexico, whereas specimens from Norway responded to a decrease in pH by increasing respiration and prey capture rates, leading to increased calcification (Georgian et al., 2016). Longer-term studies (≥ 6 months) showed a potential for acclimation. Results suggested that Lophelia pertusa was able to maintain calcification at levels of ocean acidification expected for the end of this century in both the middle and high emission scenario (Form & Riebesell, 2012, Maier et al., 2013a, Movilla et al., 2014, Hennige et al., 2015).

However, the absorption of carbon dioxide from the atmosphere and the resultant decrease in pH and increase in acidity also changes the carbonate chemistry of the ocean.  This results in 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 falls below 1, and dissolution of calcified structures that are not protected by living tissue (e.g. coral reef and fragments) may occur. Currently, the depth of the ASH in the North Atlantic has already risen by 80 - 150 m in the past two centuries (Chung et al., 2003, Feely et al., 2004), and is found at approximately 2000 m (Jiang et al., 2015). By the end of this century, the depth of the ASH is expected to rise to approximately 400 m under the high emission scenario and 800 m for the middle emission scenario in the NE Atlantic (Zheng & Long, 2014).

In long term laboratory experiments on Lophelia pertusa, where the aragonite saturation state fell below 1, net calcification became close to zero, and in some cases fell below zero as rates of dissolution overtook calcification rates (Form & Riebesell, 2012, Hennige et al., 2015, Büscher et al., 2017, Kurman et al., 2017), except when temperature was raised from 8°C to 12°C, when calcification remained positive (Büscher et al., 2017). Experimental evidence suggests that some Lophelia genotypes may be more resilient than others to ocean acidification (Kurman et al., 2017). It was thought that Lophelia pertusa populations can only occur above the aragonite saturation horizon, but Lophelia pertusa was reported to persist at aragonite saturation  <1 along the Californian margin (Gomez et al., 2018). However, this was the first observation of Lophelia pertusa below the ASH 

(Gomez et al., 2018), and Lophelia was not found at an aragonite saturation state < 1.25 in the Gulf of Mexico (Lunden et al., 2013). Under experimental conditions, coral fragments maintained a slight net positive calcification under low pH (7.66) and an aragonite saturation state of 0.76 (±0.10) for 12 months (Hennige et al., 2015), which suggests some tolerance to future conditions.  Lophelia pertusa can up-regulate its internal pH and, therefore, the saturation state at the site of calcification (McCulloch et al., 2012), although up-regulation is energetically costly (McCulloch et al., 2012). The persistence of Lophelia pertusa along the California margin may be due to extremely high productivity of the area (Gomez et al., 2018), and maintenance of net calcification under experimental conditions (Hennige et al., 2015) may be due to an abundant food source.

Lophelia pertusa is an important species of ecosystem engineer, with its reef structure providing a variety of niches for both coral-dependent and habitat-generalist fauna (Lessard-Pilon et al., 2010). As the ASH shoals, dissolution of the exposed coral skeleton may lead to loss of the reef framework, (Jackson et al., 2014). Loss of framework may be compounded by the observation that, under high CO2 conditions, Lophelia pertusa branches grew longer and thinner and there was a noticeable change in biomineralisation processes, leading to branches becoming 20-30% weaker than those in control conditions (Hennige et al., 2015). Results from the field suggest that Lophelia pertusa branches found in aragonite undersaturated waters have a lower skeletal density than populations found in saturated waters (Gomez et al., 2018). Dissolution of the reef framework and a weakening of the integrity of live coral branches will lead to a loss of structural complexity, and make corals more susceptible to mechanical damage and bioerosion (Hennige et al., 2015). Extensive coral graveyards have been observed below the aragonite saturation horizon in Australia. These coral graveyards are thought to have flourished during the last ice age 18 – 33 thousand years ago (Trotter et al., 2019), suggesting that aragonite undersaturation will not cause complete dissolution and total loss of the reef framework.

Sensitivity Assessment. There is evidence that some populations of Lophelia pertusa can survive at an aragonite saturation state of <1 (Gomez et al., 2018) but this is the only record of this species being found in undersaturated waters, in an area of extreme productivity. While this offers some hope for future Lophelia pertusa reefs, evidence suggests that aragonite undersaturation is likely to lead to extensive losses of these reefs and, even if net calcification can be maintained, the coral framework will likely weaken, or large portions of it be lost, leading to a decrease in structural complexity and simplification of the habitat.

For the middle emission scenario (0.15 unit decrease in pH), the aragonite saturation horizon (ASH) is not expected to reach the upper bathyal (200-600 m) or shelf seas (<200 m), and hence Lophelia pertusa colonies are not expected to suffer dissolution, and are expected to be able to maintain growth rates. Therefore, resistance is probably ‘High’, and resilience is assessed as ‘High’ and sensitivity as ‘Not sensitive’ under the mid-emission scenario benchmark. 
But, under the high-emission scenario (0.35 unit decrease in pH), ca 50% of upper-bathyal Lophelia pertusa reefs may be predicted to fall below the ASH saturation state and suffer dissolution, leading to a reduction in reef structure, whilst net calcification will decrease.  Therefore, resistance has been assessed as ‘Low’.  Cold-water corals are slow-growing, and the undersaturation of waters will continue, leading to a lack of recovery potential, so that resilience has been assessed as ‘Very low’. Hence, sensitivity is assessed as ‘High’.

High High Not sensitive
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: High
C: High

Increasing levels of CO2 in the atmosphere have led to the average pH of sea surface waters dropping from 8.25 in the 1700s to 8.14 in the 1990s (Jacobson, 2005). By the end of this century, pH is predicted to decrease by a further 0.15 – 0.35 units depending on the emission scenario used. Due to their calcified nature, both deep and shallow water scleractinian coral reefs are generally thought to be highly sensitive to ocean acidification (Hall-Spencer & Harvey, 2019). The deep-water species, Lophelia pertusa is a plastic species that has a wide bathymetric range (30-3000 m), lives in several different temperate habitats, and can thrive in the Mingulay Reef complex, where tidal downwelling can cause daily variations in pH equivalent to a 25-year jump in atmospheric CO2 (Hennige et al., 2015). This suggests that it may have some tolerance to changes in pH.

Results of short-term experimental acidification (≤3 months) on Lophelia pertusa show negative effects such as a decrease in respiration rates (Hennige et al., 2014; 0.3 unit pH decrease), and calcification rates (Maier et al., 2009; both at 0.15 and 0.3 unit pH decrease), or no observable effects (Maier et al., 2013b). Georgian et al. (2016) found variation in response between populations. Decreasing pH (from ambient pH of 7.9 to 7.75 and 7.6) led to a decrease in respiration, prey capture rates and net calcification in specimens from the Gulf of Mexico, whereas specimens from Norway responded to a decrease in pH by increasing respiration and prey capture rates, leading to increased calcification (Georgian et al., 2016). Longer-term studies (≥ 6 months) showed a potential for acclimation. Results suggested that Lophelia pertusa was able to maintain calcification at levels of ocean acidification expected for the end of this century in both the middle and high emission scenario (Form & Riebesell, 2012, Maier et al., 2013a, Movilla et al., 2014, Hennige et al., 2015).

However, the absorption of carbon dioxide from the atmosphere and the resultant decrease in pH and increase in acidity also changes the carbonate chemistry of the ocean.  This results in 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 falls below 1, and dissolution of calcified structures that are not protected by living tissue (e.g. coral reef and fragments) may occur. Currently, the depth of the ASH in the North Atlantic has already risen by 80 - 150 m in the past two centuries (Chung et al., 2003, Feely et al., 2004), and is found at approximately 2000 m (Jiang et al., 2015). By the end of this century, the depth of the ASH is expected to rise to approximately 400 m under the high emission scenario and 800 m for the middle emission scenario in the NE Atlantic (Zheng & Long, 2014).

In long term laboratory experiments on Lophelia pertusa, where the aragonite saturation state fell below 1, net calcification became close to zero, and in some cases fell below zero as rates of dissolution overtook calcification rates (Form & Riebesell, 2012, Hennige et al., 2015, Büscher et al., 2017, Kurman et al., 2017), except when temperature was raised from 8°C to 12°C, when calcification remained positive (Büscher et al., 2017). Experimental evidence suggests that some Lophelia genotypes may be more resilient than others to ocean acidification (Kurman et al., 2017). It was thought that Lophelia pertusa populations can only occur above the aragonite saturation horizon, but Lophelia pertusa was reported to persist at aragonite saturation  <1 along the Californian margin (Gomez et al., 2018). However, this was the first observation of Lophelia pertusa below the ASH 

(Gomez et al., 2018), and Lophelia was not found at an aragonite saturation state < 1.25 in the Gulf of Mexico (Lunden et al., 2013). Under experimental conditions, coral fragments maintained a slight net positive calcification under low pH (7.66) and an aragonite saturation state of 0.76 (±0.10) for 12 months (Hennige et al., 2015), which suggests some tolerance to future conditions.  Lophelia pertusa can up-regulate its internal pH and, therefore, the saturation state at the site of calcification (McCulloch et al., 2012), although up-regulation is energetically costly (McCulloch et al., 2012). The persistence of Lophelia pertusa along the California margin may be due to extremely high productivity of the area (Gomez et al., 2018), and maintenance of net calcification under experimental conditions (Hennige et al., 2015) may be due to an abundant food source.

Lophelia pertusa is an important species of ecosystem engineer, with its reef structure providing a variety of niches for both coral-dependent and habitat-generalist fauna (Lessard-Pilon et al., 2010). As the ASH shoals, dissolution of the exposed coral skeleton may lead to loss of the reef framework, (Jackson et al., 2014). Loss of framework may be compounded by the observation that, under high CO2 conditions, Lophelia pertusa branches grew longer and thinner and there was a noticeable change in biomineralisation processes, leading to branches becoming 20-30% weaker than those in control conditions (Hennige et al., 2015). Results from the field suggest that Lophelia pertusa branches found in aragonite undersaturated waters have a lower skeletal density than populations found in saturated waters (Gomez et al., 2018). Dissolution of the reef framework and a weakening of the integrity of live coral branches will lead to a loss of structural complexity, and make corals more susceptible to mechanical damage and bioerosion (Hennige et al., 2015). Extensive coral graveyards have been observed below the aragonite saturation horizon in Australia. These coral graveyards are thought to have flourished during the last ice age 18 – 33 thousand years ago (Trotter et al., 2019), suggesting that aragonite undersaturation will not cause complete dissolution and total loss of the reef framework.

Sensitivity Assessment. There is evidence that some populations of Lophelia pertusa can survive at an aragonite saturation state of <1 (Gomez et al., 2018) but this is the only record of this species being found in undersaturated waters, in an area of extreme productivity. While this offers some hope for future Lophelia pertusa reefs, evidence suggests that aragonite undersaturation is likely to lead to extensive losses of these reefs and, even if net calcification can be maintained, the coral framework will likely weaken, or large portions of it be lost, leading to a decrease in structural complexity and simplification of the habitat.

For the middle emission scenario (0.15 unit decrease in pH), the aragonite saturation horizon (ASH) is not expected to reach the upper bathyal (200-600 m) or shelf seas (<200 m), and hence Lophelia pertusa colonies are not expected to suffer dissolution, and are expected to be able to maintain growth rates. Therefore, resistance is probably ‘High’, and resilience is assessed as ‘High’ and sensitivity as ‘Not sensitive’ under the mid-emission scenario benchmark. 
But, under the high-emission scenario (0.35 unit decrease in pH), ca 50% of upper-bathyal Lophelia pertusa reefs may be predicted to fall below the ASH saturation state and suffer dissolution, leading to a reduction in reef structure, whilst net calcification will decrease.  Therefore, resistance has been assessed as ‘Low’.  Cold-water corals are slow-growing, and the undersaturation of waters will continue, leading to a lack of recovery potential, so that resilience has been assessed as ‘Very low’. Hence, sensitivity is assessed as ‘High’.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

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

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

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

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

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

Hydrological Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
Medium Very Low Medium
Q: High
A: High
C: Low
Q: High
A: High
C: High
Q: High
A: High
C: Low

Lophelia pertusa distribution is controlled by a number of environmental factors, including; temperature, oxygen saturation, food supply, availability of suitable substratum, and carbonate chemistry (Davies et al., 2008; Roberts et al., 2009; Georgian et al., 2014).  The distribution of Lophelia pertusa in the North Atlantic appears to correlate with water masses within certain temperature ranges rather than other environmental factors (Frederiksen et al., 1992; Freiwald,1998).  Lophelia pertusa is typically found in areas where temperatures range from 4 to 12°C (Davies et al., 2008; Robert et al., 2006; Lunden et al., 2014).  Lophelia pertusa around the UK, Ireland, Norway are found in water temperatures 6 to 8°C (Zibrowius, 1980; Frederiksen et al., 1992; Freiwald et al., 2004), while Tursi et al. (2004) recorded Lophelia pertusa living within areas with sea temperatures between 12.5 to 14°C in the Mediterranean.

A single Lophelia pertusa was reported on the Beryl Alpha platform between depths of 75 and 114 m (Roberts, 2002a).  The water column around the platform was stratified; the salinity varied from 34.8 ppt at the surface to just over 35 ppt at 50 m, while the surface temperature remained fairly constant at 11.5°C to a depth of 50 m before dropping rapidly to 8°C between 70 and 110 m (Roberts, 2002a).  Roberts (2002a) noted that the depth of Lophelia pertusa corresponded with 8°C and a salinity of 35 ppt.  He suggested that Lophelia pertusa was restricted to depths of greater than 70 m by the temperature and salinity, competition from other epifauna (e.g. sponges and sea anemones) and possibly by wave action during storms (Roberts, 2002a).

Temperature fluctuations measured within Lophelia pertusa reefs typically range between 1 and 2°C (Schroeder, 2002; Wisshak et al., 2005; Davies et al., 2009; cited by Form & Riebesell, 2012).  Rogers (1999) suggested that the death of coral on the upper reaches of a reef may reflect changes in the depth of the thermocline.  But the upper limit of the Lophelia pertusa reefs may be attributed to other factors, e.g. the origin of the water masses, salinity, wave action, or competition with other species e.g. sponges (Frederiksen et al., 1992; Rogers, 1999; Mortensen et al., 2001; Dr Alex Rogers, 2005 pers comm.).

Dodds et al. (2007) found that the metabolic rates of Lophelia pertusa increased dramatically when specimens collected from the Mingulay Reef complex were exposed to temperatures greater than those experienced within the reef.  An increase in temperature from 6.5 to 9°C and 9°C to 11°C (ca 2°C) resulted in a doubling in oxygen consumption (Dodds et al., 2007).  Dodds et al. (2007) suggested that the physiological response observed indicated a sensitivity to even this small a temperature change. Naumann et al. (2014) examined the respiration rate and calcification rates of Lophelia pertusa collected from the Mediterranean at 12, 9 and 6°C after acclimation for one month. Lophelia pertusa was found to acclimate to lower temperatures (9 and 6°C) and maintained a constant respiration rate although calcification rates were reduced by 58% at 6°C.  Lunden et al. (2014) found that when Lophelia pertusa, collected from the Gulf of Mexico, were exposed to temperatures of 14°C in the laboratory experienced 47% mortality within seven days and 100% mortality in the subsequent three week recovery period; at 16°C mortality was 100% after seven days.

Brooke et al. (2013) examined the thermal tolerance of Lophelia pertusa fragments from the Gulf of Mexico to a range of temperatures (5, 8, 15, 20 and 25°C) for periods of 24 hrs and seven days. Survival was ca 60% after 24 hrs at 20°C but only ca 20% after seven days.  Survival was relatively high (ca 80%) after seven days at 15°C, although there was variation in survival between replicates.  Survival was also high (a mean of ca 90% but a range of 55-100%) after six months in fragments transplanted (on benthic landers to 418 or 450 m) to the waters of North Carolina, which experienced a wider range of temperatures than the Gulf of Mexico. Brooke et al. (2013) noted that deep coral reefs of the southeastern United States experience temperature fluctuations from a mean of ca 8.5°C to a spike of 15°C for hours to days. Guihen et al. (2012)  also reported marked temperature fluctuations on the Tisler Reef, Norway in 2006 and 2008 where the temperature rose by ca 4°C in 24 hrs, spiked at 12°C and remained above 10°C for ca 30 days. No mortality of Lophelia was observed, although the periods of warm water coincided with the mass mortality of the resident population of the deep-water sponge Geodia baretti (Guihen et al., 2012). Brooke et al. (2013) concluded that Lophelia pertusa had a high tolerance to temperature fluctuations, as it was exposed to rapid and frequent changes to 15°C (possibly higher) and that these exposures were too brief to adversely affect the survival of the coral colonies.

Sensitivity assessment.  Lophelia pertusa is an extremely long-lived species and is found in deep water where short-term temperature fluctuations found are typically 1-2°C. It was thought to be stenothermal; adapted to relatively stable thermal conditions in deep water (see Rogers, 1999). However, exceptional short-term and rapid temperature changes have been recorded in the Tisler Reef, Norway and may be routine in the Gulf of Mexico or off the coast of North Carolina (Guihen et al., 2012; Brooke et al., 2013). An upper temperature limit of 14°C is suggested for Lophelia pertusa by the observations of Lunden et al. (2014) while the observations of Brook et al. (2003) suggest it may be higher. It is probable that local populations can adapt to local conditions. Nevertheless, the evidence suggests (Guihen et al., 2012; Brooke et al., 2013) that Lophelia reefs in the North East Atlantic could probably survive a localised short-term increase in temperature of 5°C for a month, as long as the temperature did not exceed 14-15°C. A prolonged increase of 2°C for a year would probably result in an increase in metabolic rate (Dodds et al., 2007) with a resultant increase in food demand. However, Roberts et al. (2009) noted that downwelling of warmer (by 0.75°C) water within the Mingulay Reef (in response to the tidal cycle) would increase the corals' metabolic rate at the same time as supplying increased food. The effects of a prolonged chronic increase in temperature (e.g. 2°C for a year, the benchmark) could probably depend on location of the reef and other factors such as food supply but there is no empirical evidence of the effect of temperature changes at the level of the benchmark. It is also noted that while Brooke et al. (2013) recorded a high survivorship (a mean of ca 90%) in transplanted fragments after six months, the range of mortality was 0-45%.  Therefore, resistance is assessed as ‘Medium’ as a precaution based on possible long-term effects of increased temperature or exposure to localised thermal effluent. Hence, resilience is assessed as ‘Very Low’ and sensitivity as ‘Medium’.  

Medium Very Low Medium
Q: High
A: Low
C: Low
Q: High
A: High
C: High
Q: High
A: Low
C: Low

Lophelia pertusa distribution is controlled by a number of environmental factors, including; temperature, oxygen saturation, food supply, availability of suitable substratum, and carbonate chemistry (Davies et al., 2008; Roberts et al., 2009; Georgian et al., 2014).  The distribution of Lophelia pertusa in the North Atlantic appears to correlate with water masses within certain temperature ranges rather than other environmental factors (Frederiksen et al., 1992; Freiwald,1998).  Lophelia pertusa is typically found in areas where temperatures range from 4 to 12°C (Davies et al., 2008; Robert et al., 2006; Lunden et al., 2014).  Lophelia pertusa around the UK, Ireland, Norway are found in water temperatures 6 to 8°C (Zibrowius, 1980; Frederiksen et al., 1992; Freiwald et al., 2004), while Tursi et al. (2004) recorded Lophelia pertusa living within areas with sea temperatures between 12.5 to 14°C in the Mediterranean.

A single Lophelia pertusa was reported on the Beryl Alpha platform between depths of 75 and 114 m (Roberts, 2002a).  The water column around the platform was stratified; the salinity varied from 34.8 ppt at the surface to just over 35 ppt at 50 m, while the surface temperature remained fairly constant at 11.5°C to a depth of 50 m before dropping rapidly to 8°C between 70 and 110 m (Roberts, 2002a).  Roberts (2002a) noted that the depth of Lophelia pertusa corresponded with 8°C and a salinity of 35 ppt.  He suggested that Lophelia pertusa was restricted to depths of greater than 70 m by the temperature and salinity, competition from other epifauna (e.g. sponges and sea anemones) and possibly by wave action during storms (Roberts, 2002a).

Temperature fluctuations measured within Lophelia pertusa reefs typically range between 1 and 2°C (Schroeder, 2002; Wisshak et al., 2005; Davies et al., 2009; cited by Form & Riebesell, 2012).  Rogers (1999) suggested that the death of coral on the upper reaches of a reef may reflect changes in the depth of the thermocline.  But the upper limit of the Lophelia pertusa reefs may be attributed to other factors, e.g. the origin of the water masses, salinity, wave action, or competition with other species e.g. sponges (Frederiksen et al., 1992; Rogers, 1999; Mortensen et al., 2001; Dr Alex Rogers, 2005 pers comm.).

Dodds et al. (2007) found that the metabolic rates of Lophelia pertusa increased dramatically when specimens collected from the Mingulay Reef complex were exposed to temperatures greater than those experienced within the reef.  An increase in temperature from 6.5 to 9°C and 9°C to 11°C (ca 2°C) resulted in a doubling in oxygen consumption (Dodds et al., 2007).  Dodds et al. (2007) suggested that the physiological response observed indicated a sensitivity to even this small a temperature change. Naumann et al. (2014) examined the respiration rate and calcification rates of Lophelia pertusa collected from the Mediterranean at 12, 9 and 6°C after acclimation for one month. Lophelia pertusa was found to acclimate to lower temperatures (9 and 6°C) and maintained a constant respiration rate although calcification rates were reduced by 58% at 6°C.  Lunden et al. (2014) found that when Lophelia pertusa, collected from the Gulf of Mexico, were exposed to temperatures of 14°C in the laboratory experienced 47% mortality within seven days and 100% mortality in the subsequent three week recovery period; at 16°C mortality was 100% after seven days.

Brooke et al. (2013) examined the thermal tolerance of Lophelia pertusa fragments from the Gulf of Mexico to a range of temperatures (5, 8, 15, 20 and 25°C) for periods of 24 hrs and seven days. Survival was ca 60% after 24 hrs at 20°C but only ca 20% after seven days. Survival was relatively high (ca 80%) after seven days at 15°C, although there was variation in survival between replicates.  Survival was also high (a mean of ca 90% but a range of 55-100%) after six months in fragments transplanted (on benthic landers to 418 or 450 m) to the waters of North Carolina, which experienced a wider range of temperatures than the Gulf of Mexico. Brooke et al. (2013) noted that deep coral reefs of the southeastern United States experience temperature fluctuations from a mean of ca 8.5°C to a spike of 15°C for hours to days. Guihen et al. (2012)  also reported marked temperature fluctuations on the Tisler Reef, Norway in 2006 and 2008 where the temperature rose by ca 4°C in 24 hrs, spiked at 12°C and remained above 10°C for ca 30 days. No mortality of Lophelia was observed, although the periods of warm water coincided with the mass mortality of the resident population of the deep-water sponge Geodia baretti (Guihen et al., 2012). Brooke et al. (2013) concluded that Lophelia pertusa had a high tolerance to temperature fluctuations, as it was exposed to rapid and frequent changes to 15°C (possibly higher) and that these exposures were too brief to adversely affect the survival of the coral colonies.

Sensitivity assessment.  Lophelia pertusa is an extremely long-lived species and is found in deep water where short-term temperature fluctuations found are typically 1-2°C. It was thought to be stenothermal; adapted to relatively stable thermal conditions in deep water (see Rogers, 1999). However, exceptional short-term and rapid temperature changes have been recorded in the Tisler Reef, Norway and may be routine in the Gulf of Mexico or off the coast of North Carolina (Guihen et al., 2012; Brooke et al., 2013).  Although no evidence of exposure to temperature decreases was found, its ability to survive in variable temperature regimes suggests that Lophelia, and hence the reef, is probably more tolerant of temperature change than originally thought. The effects of a prolonged chronic decrease in temperature (e.g. 2°C for a year, the benchmark) could probably depend on location of the reef and other factors such as food supply but there is no empirical evidence of the effect of temperature changes at the level of the benchmark, especially a decrease in temperature. It is also noted that while Brooke et al. (2013) recorded a mean survivorship of ca 90% in transplanted fragments after six months, the range of mortality was 0-45%.  Therefore, resistance is assessed as ‘Medium’ as a precaution based on possible long-term effects of changes in temperature. Hence, resilience is assessed as ‘Very Low’ and sensitivity as ‘Medium’.  

Low Very Low High
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

Lophelia pertusa occurs in waters of 35 -37 psu but in fjords tolerates salinities as low as 32 psu (Rogers, 1999; Mortensen et al., 2001).  However, Rogers (1999) regarded Lophelia pertusa to be stenohaline.  The Lophelia pertusa reef and its associated fauna occur in relatively stable waters, which are not subject to fluctuations in salinity.  While Lophelia pertusa is probably highly intolerant of changes in salinity at the benchmark level, it is unlikely to experience an increase in salinity except in rare cases such as the unlikely production of hypersaline effluents by offshore installations. 

Sensitivity assessment.  Due to the highly stable conditions in which Lophelia pertusa is usually found a change in salinity is likely to cause mortality of the coral polyps.  Consequently, resistance has been assessed as ‘Low’, resilience as ‘Very low’, and sensitivity assessed as ‘High’.

Low Very Low High
Q: High
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

Lophelia pertusa occurs in waters of 35 - 37 psu but in fjords tolerates salinities as low as 32 psu (Rogers, 1999; Mortensen et al., 2001).  However, Rogers (1999) regarded Lophelia pertusa to be stenohaline.  The Lophelia pertusa reef and its associated fauna occur in relatively stable waters, which are not subject to fluctuations in salinity.  While Lophelia pertusa is probably highly intolerant of changes in salinity at the benchmark level, it is unlikely to experience a decrease in salinity except in rare cases.  However, in shallow fjordic water Lophelia pertusa is restricted to the deeper, stable oceanic water below the relatively reduced salinity coastal waters at the surface.  An increase in freshwater runoff may increase the depth of the pycnocline and would probably result in the death of the upper extent of the reef.

Sensitivity assessment.  Resistance has been assessed as ‘Low’ and resistance as ‘Very Low’ so that overall sensitivity is assessed as of ‘High’ at the level of the benchmark.

High High Not sensitive
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: High
C: Medium

Early records of cold-water coral reefs are associated with strong water flows (Roberts et al., 2009).  Further investigation found that Lophelia pertusa reefs occur where the topography causes current acceleration, e.g. on raised seabed features (e.g. seamounts and banks) and where the channel narrows in Norwegian fjords (Rogers, 1999).  Higher water flow rates are thought to aid the two dominant food supply mechanisms to Lophelia pertusa (Roberts et al., 2009).  The two mechanisms are; the regular rapid downwelling of surface water delivering pulses of warm nutrient-rich surface water, and, the periodic advection of high turbidity bottom waters (Roberts et al., 2009).  Frederiksen et al. (1992) suggested that topographical highs create internal waves that re-suspended organic particulates from the seabed, and increase the flux of nutrient-rich waters to the surface waters increasing phytoplankton productivity; both effects resulting in increased food availability for Lophelia pertusa and other suspension feeders.

Frederiksen et al. (1992) suggested that Lophelia pertusa reefs around the Lousy and Hatton Banks would typically encounter currents speeds of 0.01-0.1 m/s.  Water flow rates >0.4 m/s were recorded by moored and landed deployed current meters close to deep-water coral mounds in the Porcupine Seabight (Grehan et al., 2003), while Masson et al. (2003) recorded a maximum residual bottom water flow of 0.35 m/s over a 20 day period in July 2000 over the Darwin Mounds.  Currents speeds of 0.01 -0.1 m/s, 0.35 or 0.4 m/s approximate to between weak and moderately strong water flow.  However, oceanic and tidal currents in the region of the Faroes were reported to be about 0.5 m/s (moderately strong) and in the region of west Shetland 0.5 to 0.7 m/s or more (moderately strong). Meinis et al. (2007) reported current speeds of up to 0.45 m/s, with a residual current of 0.1 m/s, along coral mounds on the southwest Rockall Trough.  Similarly, Davies et al. (2008) reviewed the environmental parameters for the occurrence of Lophelia pertusa. They concluded that it occupied a niche where the current speed (ranging from 0.004 to 0.51 m/s, with a mean of 0.07 m/s) and productivity (a mean of 0.9 mg/m3) were higher than average. They reported that globally Lophelia was associated with high productivity and irregular topography.

Mortensen (2001) investigated the growth and behaviour of Lophelia pertusa in an aquarium with flowing seawater.  No polyp mortality was observed in the vicinity of his aquaria inlets but high mortality at the opposite end.  Similarly, the death of coral polyps within a coral coppice was thought to be due to reduced water flow within the colony (Wilson, 1979b).  Mortensen (2001) also noted that high current flow (greater than ca 0.05 m/s) was detrimental to growth, presumably due to reduced food capture rates.  Purser et al. (2010) collected samples of Lophelia pertusa from the Tisler reef off Norway.  They then kept them in controlled laboratory aquaria and tested the effect of flow velocity on food capture rates.  Flow rates were kept at 0.025 m/s and 0.05 m/s, and the reduction in Artemia salina nauplii concentrations was recorded.  Maximum net capture rates were found at the 0.025 m/s (Purser et al., 2010). Orejas et al. (2016) also concluded from flume studies that water flow rates impacted food capture efficiency in Lophelia pertusa. It mostly captured zooplankton at low flow speeds of 0.02 m/s and phytoplankton at 0.05 m/s and that polyp expansion was greatest at low flow speeds of 0.005 and 0.67 m/s rather than at 0.15 and 0.27 m/s. Although, cold-water coral reefs are associated with areas of high bottom currents velocities (as above), Orejas et al. (2016) noted that strong currents were often short-lived and driven by tidal events and that currents were slow for several hours between tidal cycles, for example in the Mingulay Reef velocity could decrease to less than 0.02 m/s during each tidal cycle. In addition, the structure of the coral matrix also slows the currents locally within the coral matrix itself and the reef colonies probably dissipate higher current velocities with increasing size (Orejas et al., 2016). 

Sensitivity assessment.  Lophelia pertusa reefs probably rely on constant, mass water flow to supply food and nutrients and prevent the build-up of sediment, interspersed with slack periods or lower flow to allow optimal feeding, although the coral matrix itself probably slows water flow within the reef.  A decrease in water flow across the reef would reduce the availability of food, which may decrease the health of the Lophelia pertusa colony.  If it were reduced below a certain level, mortality could occur.  Although Lophelia pertusa relies on water flow, Mortensen's data (2001) suggests a sustained water flow over 0.05 m/s may reduce growth.  Areas in which Lophelia pertusa reefs are found experience great changes in water flow rates throughout the tidal cycle.  As long as the increase in water flow rate did not mean that water flow rates were permanently above 0.05 m/s, the pressure at the benchmark is unlikely to have a negative impact on the biotope.  Therefore, both resistance and resilience have been assessed as ‘High’, and sensitivity assessed as ‘Not sensitive’ at the benchmark level.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Lophelia pertusa do not occur in the intertidal, they occur in oceanic waters, at depths of over 200 m, except in Norwegian fjords where it upper depth limit may be 50 m, below the influence of coastal waters.  Therefore, it is unlikely to be affected by changes in the emergence regime and 'Not relevant' has been recorded. 

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Offshore Lophelia pertusa reefs occur, by definition, in extremely wave exposed conditions, although wave action is ameliorated by depth.  Draper (1967) noted that wave periods in offshore areas are generally of longer than in enclosed seas and therefore penetrates to greater depths.  However, Draper (1967) estimated that as far out as the continental shelf, for one day a year, storm conditions could generate an oscillatory water movement on the seabed of only ca 0.4 m/s at 180 m.  In Norwegian fjords where Lophelia pertusa reefs occur as shallow as 50 m, wave action is slight at the surface and most likely does not penetrate more than a few tens of metres.  Inner fjords have limited fetch so that wave action is unlikely to penetrate to more than a few tens of metres even in storm conditions (Dr Keith Hiscock pers. comm.).

The oscillatory water movement generated by wave action could potentially result in fragmentation of branching coral skeletons at the upper limit of their depth distribution, although their skeletons are fairly robust.  Occasional fragmentation may not unduly affect the reef but allow it to spread in the long-term as the fragments continue to grow, or provide a substratum for colonization by Lophelia pertusa larvae.  However, Lophelia pertusa occurs at depths at which even the wave action generated by storm conditions is unlikely to penetrate.  Therefore, ‘Not relevant’ has been recorded.

Chemical Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is Not assessed but evidence is presented where available.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is Not assessed but evidence is presented where available.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is Not assessed but evidence is presented where available.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No evidence.

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is Not assessed.

Low Very Low High
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: Medium
C: Medium

It has been suggested that the lower limit of Lophelia pertusa's bathymetric distribution is partially determined by the oxygen minimum zone (Freiwald, 1998; Rogers, 1999).  Roberts et al. (2003) suggested the lower depth limit of Lophelia pertusa's distribution in the North East Atlantic was related to temperature.  It is likely to be a combination of factors which determine the distribution of Lophelia pertusa (Davies et al., 2008; Roberts et al., 2009). 

Dodds et al. (2007) investigated the metabolic tolerance of Lophelia pertusa to temperature and dissolved oxygen change in the laboratory.  They found that Lophelia pertusa could survive anoxia for 1 hour, and hypoxia (2-3 kPa; 0.88-1.32 mg/l) for 96 hours (4 days).  Lophelia pertusa was able to increase its uptake of oxygen by the expansion of the surface area of its polyp in response to low oxygen concentrations (Dodds et al., 2007). Lophelia pertusa was able to regulate its oxygen consumption until the oxygen concentration fell below 98-10 kPA at 9°C. Dodds et al. (2007) suggested that the critical oxygen concentration for this species, below which it would not be able to carry out normal aerobic function was ca 9.5 kPa (ca 3.26 ml/l; ca 4.56 mg/l).  Davies et al. (2008) mapped the suitable habitat for Lophelia pertusa and found that Lophelia pertusa records were associated with areas of water with an ambient oxygen concentration between 4.3 – 7.2 ml/l (6.47-10.35 mg/l), with a mean of 6-6.2 ml/l, and that the species was not found in areas where the oxygen concentration was less than 2.37 ml/l (3.32 mg/l).  Lunden et al. (2014) studied, among other things, the effect of decreasing oxygen concentration of Lophelia pertusa collected from the Gulf of Mexico.  Oxygen concentrations within the Gulf of Mexico are lower than those recorded in the North East Atlantic, with records ranging from 1.5 – 3.2 ml/l (Lunden et al., 2014).  Laboratory experiments exposed Lophelia pertusa to different oxygen concentrations for 7 days.  The Lophelia pertusa samples survived (100%) exposure to 5.3 and 2.9 ml/l but 100% mortality at ca 1.57 ml/l (ca 2.2 mg/l) after 7 days. 

Sensitivity assessment.   A change in oxygen concentration at the benchmark (2 mg/l or less for a week) has the potential to cause significant mortality in cold-water reefs in North East Atlantic.  The evidence suggests that if the mean oxygen concentration fell below 3.26 ml/l, (ca 4.56 mg/l) then mortality could occur within the area and if the oxygen concentration fell below 2.2 mg/l for a week (see Lunden et al., 2014), 100% mortality is possible. Therefore, resistance is assessed as ‘Low’, and resilience is assessed as ‘Very low, so that sensitivity assessment is probably ‘High’.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

The physical structure and position of cold-water coral structures (reefs and mounds) have been shown to induce up-welling and down-welling events, determined by the tidal currents and the tidal cycles, that provide food to the reef and link surface water productivity with deep waters (Roberts et al., 2009; Soetaert et al., 2016; Kazanditis & Witte, 2016). The nutrient levels (e.g. nitrates, phosphates, and ammonia) and inorganic carbon in the vicinity of cold-water coral reefs in the North East Atlantic vary with the tidal cycle and with depth (Findlay et al., 2014). For example, Findlay et al. (2014) reported a range of inorganic carbon of 2088 to 2186 µmol/kg and nitrate (NO3) or 4.1-18.8 µmol/l in the sites they examined in the North East Atlantic. Davies et al. (2008) also report a range of nitrate levels of 8 - 23.4 µM (mean of 13.8 µM)  for sites where Lophliea pertusa was recorded in the North East Atlantic. Davies et al. (2008) noted a negative correlation between high nutrient concentrations (nitrate, phosphate and silicate) with Lophelia pertusa distribution. They also noted that the species was also not found in the lowest nutrient concentrations and that while high nutrient levels limited distribution, the species probably required intermediate levels (Davies et al., 2008).

The evidence suggests that high or low nutrient levels, when compared across the North East Atlantic (Davies et al., 2008) may be detrimental. Nevertheless, no information on the effect of nutrient enrichment on cold-water coral reefs or mounds was found.  Therefore, 'No evidence' is recorded. 

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

The physical structure and position of cold-water coral structures (reefs and mounds) have been shown to induce up-welling and down-welling events, determined by the tidal currents and the tidal cycles, that provide food to the reef and link surface water productivity with deep waters (Roberts et al., 2009; Duineveld et al., 2012; Soetaert et al., 2016; Kazanidis & Witte, 2016). Kazanidis & Witte (2016) note that the supply of organic matter to the cold-water corals also benefits other suspension feeders in the community. For example, the Mingulay area had a higher biomass of suspension or filter feeders than the Logachev area. Kazanidis & Witte (2016) suggested that this was due to the benthopelagic coupling of highly productive surface waters with the reef and higher velocity of bottom currents in the Migulary area compared to the Logachev area.

Nevertheless, no information on the effect of organic enrichment (at the level of the benchmark) on cold-water coral reefs or mounds was found.  Therefore, 'No evidence' is recorded.

Physical Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

All marine habitats and benthic species are considered to have a resistance of ‘None’ to this pressure and to be unable to recover from a permanent loss of habitat (resilience is ‘Very Low’).  Sensitivity within the direct spatial footprint of this pressure is, therefore ‘High’.  Although no specific evidence is described confidence in this assessment is ‘High’, due to the incontrovertible nature of this pressure.

None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

Lophelia pertusa larvae must settle onto hard substrata (Roberts et al., 2009) to enable them to find a solid anchor point, from which the hard skeleton of the coral can attach.  The presence of Lophelia pertusa on oil and gas platforms (Gass & Roberts, 2006), suggests that their larvae are able to settle onto artificial substrata.  There is no information available on the preference of Lophelia pertusa larvae for certain types of hard substrata.  However, for a change in substrata to occur, the original substratum would need to be removed first, which would result in removal of living coral and dead coral debris, resulting in the destruction of the reef and loss of the biotope. 

Sensitivity assessment.  Therefore, a resistance of ‘None’ and a resilience of ‘Very Low’ have been recorded, resulting in a sensitivity of ‘High’.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Lophelia pertusa larvae have to settle onto a hard substratum.  The branching nature of this reef forming species means that their structures can extend out over soft substratum.  However, as this species requires a hard substratum onto which to anchor, a change in soft sediment type is Not relevant to this biotope.  Hence, the pressure is assessed as ‘Not relevant’. 

None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

Lophelia pertusa larvae have to settle onto hard substrata.  However, a large reef may grow out over soft sediment, from which sediment may be extracted.  The reef structure can also significantly change the water flow rates, which can mean that sediment being carried in suspension, is deposited in the reef.  Extraction of substratum to 30 cm within this biotope would mean that all of the reef forming, characterizing species, Lophelia pertusa, would be removed.  This would entirely destroy the habitat and would result in the loss of the biotope.

Sensitivity assessment.  Lophelia pertusa and the biotope have no resistance the removal of substratum to 30 cm, therefore, the resistance is assessed as ‘None’.  The extremely long lived nature and slow growth rate of the characterizing species Lophelia pertusa means that resilience is ‘Very Low’, giving this biotope an overall sensitivity assessment of ‘High’.

None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

Although Lophelia pertusa reefs occur at great depths, they are likely to be subject to physical disturbance due to anchorage or positioning of offshore structures on the seabed but especially due to deep-sea trawling.  Rogers (1999) suggested that trawling gear would break up the structure of the reef, fragment the reefs, and potentially result in the complete disintegration of the coral matrix, and loss of the associated species.

Fosså et al. (2002) documented and photographed the damage caused to west Norwegian Lophelia pertusa reefs by trawling activity (see Fosså, 2003 for photographs).  They reported that four, out of five sites studied, contained damaged corals. In the shallow regions of Sørmannsneset, only fragments of dead Lophelia pertusa were seen, spread around the site with no evidence of living colonies in the surrounding area, and Fosså et al. (2002) concluded that the colonies had been "wiped out".  Overall, they estimated that between 30 and 50% of Lophelia pertusa reefs were either impacted or destroyed by bottom trawling in western Norway.  Mechanical damage by fishing gear would also damage or kill the associated epifaunal species, some of which are slow-growing e.g. sponges, potentially turn over the coral rubble field, and modify the substratum (Rogers, 1999; Fosså et al., 2002).  Fosså et al. (2002) demonstrated that gorgonian (horny) corals were also torn apart by bottom trawling.  Fosså (2003) also note that fixed fishing nets, e.g. gill nets, and long-line fisheries and their associated anchors could potentially result in damage to the reefs such as breakage of the coral colonies.  However, damage by long-line or gill net fisheries is probably of limited extent compared to bottom trawling (Fosså, 2003).  Hall-Spencer et al. (2002) also provided photographic evidence of an area of reef impacted by bottom trawling, with a clearly visible trench (5 -10 cm deep) made by otter boards surrounded by smashed coral fragments in west Norway.  Hall-Spencer et al. (2002) also noted that otter trawling with rockhopper gear damaged coral habitats in west Ireland, based on analysis of by-catch but also noted that fishing vessels actively avoided rough ground and that the majority of trawls did not result in Lophelia pertusa by-catch.  Koslow et al. (2001) reported that on shallow, heavily fished seamounts off Tasmania, trawling had effectively removed the dominant cold-water coral and its associated fauna.  The substratum of heavily fished seamounts was primarily bare rock or coral rubble and sand, features not seen on any lightly fished or un-fished seamount.  The abundance and richness of benthic fauna were also "markedly reduced" on heavily fished seamounts (Koslow et al. (2001).

Sensitivity assessment.  Overall, there is significant evidence of damage to Lophelia pertusa and other cold-water coral reefs due to deep-sea trawling.  Resistance is assessed as ‘None’, and resilience is ‘Very Low’, giving the biotope a sensitivity of ‘High’.

None Very Low High
Q: High
A: High
C: High
Q: High
A: High
C: High
Q: High
A: High
C: High

Penetration and or disturbance of the substratum would result in similar, if not identical results as Abrasion or removal of a Lophelia pertusa reef and its associated community (see abrasion/disturbance).

Sensitivity assessment.  A resistance of ‘None’ has been given.  If the substratum is either penetrated or disturbed, then the overlying reef would also be affected.  The extremely long lived and slow growing nature of Lophelia pertusa, the characterizing species within this biotopes, means that damage incurred would take an extremely long time to recover.  Therefore, resilience has been assessed as ‘Very Low’ resulting in sensitivity being ‘High’.

Low Very Low High
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: Medium
C: Medium

A change in suspended solids can have two major effects on a biotope.  The firstly being that a change in suspended solids can change the levels of light attenuation, and therefore the amount of light which will reach the biotope.  However, this biotope is found outside of the photic zone within the North East Atlantic and therefore this is not a consideration.  The second effect of a change in suspended solids is the supply of food to the biotope.  The characterizing species, Lophelia pertusa, is a filter feeding organism and relies on the supply of suspended organic matter for sustenance.  The location of Lophelia pertusa reefs is determined by a multitude of factors, however, a combination of water flow and seafloor relief are important in regards to the supply of food particles and larvae (Flach & Thomsen 1998; Gage et al. 2000; Hughes & Gage, 2004).  Reefs are found in areas where the topography works to accelerate near-bed currents, which enhance food supply (Mortensen et al., 2001; Thiem et al., 2006; Kiriakoulakis et al., 2007; Robert et al., 2009; Davies et al., 2009; Soetaert et al., 2016; Kazanditis & Witte, 2016).  

Davies et al., (2009) measured the turbidity of the water along a transect within the Mingulay reef complex off the west coast of Scotland.  Turbidity levels varied along the transect. However, on the sections of the transect that were closer to the top of the reef, lower turbidity levels appeared to be during the onset of an ebb tide (Davies et al., 2009).  Increased turbidity was found to correlate with an increase in the speed of water flow, therefore, throughout the space of one tide, there was considerable variation in the levels of suspended solids within the water column.  This information suggests that over a short time period Lophelia pertusa and their associated species can tolerate changes in suspended solids. 

Brooke et al. (2009) compared the tolerance of two morphotypes of Lophelia pertusa (gracilis, fragile; brachcephala, heavily calcified) to different levels of turbidity.  The fragments collected from the Gulf of Mexico were kept in aquaria, at five different turbidity levels, for 14 days.  Both morphotypes of Lophelia pertusa found in clear conditions (<10 mg/l) had 100% survival rates.  Over 80% of Lophelia pertusa kept at intermediate turbidity conditions (10 –100 mg/l) survived.  Two of the experimental turbidity’s fell within the medium turbidity water frame directive (WFD) ranking system, these were 103 mg/l and 245 mg/l.  In the former, both morphotypes had a survival rate of >50%, and the later had a survival rate of >30%.  Within the very turbid category (ca 362 mg/l) the more fragile morphotype, gracilis, experienced 100% mortality, and brachycephala had an extremely low survival rate (Brooke et al., 2009).  From the results of this laboratory experiment, Brooke et al. (2009) summarized that Lophelia pertusa survival decreased in steps, rather than a continuous linear decline; suggesting that the corals have physiological thresholds beyond which they unable to cope with turbidity levels, at which point mortality can occur.

Mortensen (2001) found that when both food and sediment were presented to Lophelia pertusa at the same time sediment was ingested, however, the process of feeding and polyp cleaning do not occur at the same time (Brooke et al., 2009).  An increase in turbidity with the Lophelia pertusa environment would lead to more settlement of sediment onto the coral polyps.  This would lead to an increase in the amount of time required to remove the sediment from the polyp, which could restrict the amount of time available for feeding.  Brooke et al. (2009) suggested that this could lead to the starvation of the coral polyp even though food may be available.

However, Larsson et al. (2013b) reported that suspended sediment exposure has no significant effect on respiration or fatty acid composition in Lophelia pertusa and that the amount of additional mucus produced to clean its polyps was low and di not significantly affect energy expenditure. Larsson et al. (2013) exposed Lophelia pertusa fragments to fine (<63 µm) natural sediment and drill cuttings at 5 mg/l and 25 mg/l for 12 weeks in the laboratory. After 12 weeks, mortality was low with only 0.3% (1 polyp) dying after exposure to 25 mg/l natural sediment and 2.2% (8 polyps) dying after exposure to 12 weeks but zero in controls. They attributed the mortality to the build-up of sediment on the fragments and potential resultant smothering (see below) (Larsson & Purser, 2011; Larsson et al., 2013b).  At the low concentration of sediments, the polyps were fully extended but only half extended at the high concentration and there was a trend towards lower growth rates when exposed to drill cuttings rather than natural sediment Larsson et al. (2013b).  In addition, in a pilot experiment, Larsson et al. (2013a) reported significant mortality (67%) planulae exposed to 25 mg/l of drilling cuttings after 4 days, while mortality at 5 mg/l was low and not significantly different from controls. Larssson et al. (2013) also reported that Gilmour (1999; cited in Larsson et al., 2013a) that larval mortality was an average of 98% after 2 days exposure to 50 and 100 mg/l of natural sediment. Nevertheless, Larsson et al. (2013a) concluded that Lophelia pertusa polyps coped reasonably well with increased suspended sediment and deposition rates. In comparison, information on natural rates of sedimentation experienced in reef habitats is limited. Brooke et al. (2009) reported suspended sediment levels of 9-10 mg/l  and sedimentation rates of 31 and 47 g/m2/d at two sites in the Gulf of Mexico. But Larson et al. (2013a) noted that these rates were probably high compared to typical 0.5 -3.7 g/m2/d reported in the North East Atlantic cold-water coral habitats, which in turn suggested that Lophelia pertusa was capable of tolerating naturally occurring suspended sediment levels. 

A decrease in the levels of suspended material at the level of the benchmark could lead to a reduction in the availability of food to Lophelia pertusa, and other filter feeding organisms within the biotope. However, Larsson et al. (2013b) reported that Lophelia pertusa was highly tolerant of living on minimal resources (food) for several months. In their experiments, Lophelia survived (100%) starvation for 28 weeks (Larsson et al., 2013b).

Sensitivity assessment.  The evidence suggests that a change in turbidity from clear to intermediate (10m/l to 10-100 mg/l) for a year could result in limited or some mortality but that a change for intermediate to medium turbidity (100-300 mg/) for a year could result in significant mortality depending on duration and local hydrography. For example, Brooke et al., (2009) demonstrated significant mortality after only 14 days at 103 and 245 mg/l.  Therefore, resistance is assessed as ‘Low’, resilience as ‘Very low’, and sensitivity is assessed as ‘High’ at the benchmark level.

Medium Very Low Medium
Q: High
A: High
C: Medium
Q: High
A: High
C: High
Q: High
A: Medium
C: Medium

Rogers (1999) suggested that Lophelia pertusa would be intolerant of increased rates of sedimentation, caused by decreased water flow, or the resuspension and subsequent sedimentation of sediment by marine activities, such as offshore construction or mobile fishing gear (e.g. beam or otter trawls), or the discharge of drill cuttings An increase in sedimentation is thought to be one of largest sources of degradation of coral reefs (Norse, 1993) and may suppress the growth rates of Lophelia colonies (Fosså et al., 2002).  Information on natural rates of sedimentation experienced in reef habitats is limited. Rogers (1999) suggested that sedimentation rates of >10 mg/cm²/day in shallow water coral reefs were high. Brooke et al. (2009) reported suspended sediment levels of 9-10 mg/l  and sedimentation rates of 31 and 47 g/m2/d at two sites in the Gulf of Mexico. But Larson et al. (2013a) noted that these rates were probably high compared to typical 0.5 -3.7 g/m2/d reported in the North East Atlantic cold-water coral habitats, which in turn suggested that Lophelia pertusa was capable of tolerating naturally occurring suspended sediment levels and sedimentation rates. 

Mortensen (2001) reported that 25-100% of polyps died after being starved for 3 months or more but in some cases, polyps survived starvation for 16 and 20 months. However, Larsson et al. (2013b) reported that Lophelia pertusa was highly tolerant of living on minimal resources (food) for several months. In their experiments, Lophelia survived (100%) starvation for 28 weeks (ca six months) (Larsson et al., 2013b).

Preliminary results suggested that sand deposition rates of 0.1 mg/cm²/min significantly reduced polyp expansion in Lophelia pertusa (Roberts & Anderson, 2002b), which would reduce feeding and hence growth rates.  Mortensen (2001) demonstrated that Lophelia pertusa was able to remove sediment particles <3 mm within 3-5 min and 3-5 mm particles within ca 15 min due to the beating of cilia towards the tips of the tentacles, and reported that the living coenosarc (coral tissue) was always clean of sediment.  Earlier studies by Shelton (1980), showed that Lophelia pertusa could remove graphite particles within ca 30 sec.  Similarly, Reigl (1995) demonstrated that scleractinian corals were able to clean sand from their surface actively.  When exposed to 200 mg of sand per cm² in a single application, scleractinian corals cleared 50% of the sand within 1000 min, and all the species studied survived for 6 weeks continuous exposure to 200 mg of sand per cm².  Reigl (1995) concluded that corals could cope with considerable amounts of sand deposition.  Nevertheless, Rogers (1999) suggested that an increase in sedimentation was likely to interfere with feeding and hence growth, which would alter the balance between growth and bioerosion, potentially resulting in degradation of the reef.  In addition, smothering could prevent settlement of larvae and hence recruitment.

In burial experiments, Larsson & Purser (2011) exposed Lophelia fragments to regular depositions of sediment (<63 µm ) over 3 weeks resulting in a covering of the polyps by 6.5 mm or 19.0 mm of sediment. Mortality was low for the duration of the experiment with only 3.7% (seven polyps) dying under 19 mm and 0.5% (one polyp) dying under 6.5 mm of sediment (Larsson & Purser, 2011). Allers et al. (2013) investigated the resilience of Lophelia pertusa taken off Norway to sedimentation in laboratory-based experiments. They found that both the mucus production and branching morphology of Lophelia pertusa meant that accumulation of sediment was relatively slow.  Even high sediment deposition (462 mg/cm2) did not result in complete coverage of the fragments skeleton by sediment. Short-term (<24 hours) exposure to sedimentation reduced the availability of oxygen to Lophelia pertusa.  However, the organism could tolerate both low-oxygen and anoxic conditions without suffering visible, short-term effects (Allers et al., 2013).  As little as 3 mm of sediment covering a Lophelia pertusa polyp led to complete anoxia within six days, and the thicker the covering of sediment the faster anoxia occurred (Allers et al., 2013).  But complete burial for >24 hours caused suffocation and 100% mortality (Allers et al., 2013). Brooke et al. (2009) reported different tolerance of Lophelia pertusa to total burial. Samples of Lophelia pertusa were collected from the Gulf of Mexico and tested for their tolerance to complete burial in sediment to a depth of over 1 cm.  It was found that a significant tolerance threshold was reached between 2 – 4 days, after which time very low survival rates were recorded and 100% mortality occurred after 7 days (Brooke et al., 2009). In burial experiments, Larsson & Purser (2011) exposed Lophelia fragments to regular depositions of sediment (<63 µm ) over 3 weeks resulting in a covering of the polyps by 6.5 mm or 19.0 mm of sediment. Mortality was low for the duration of the experiment with only 3.7% (seven polyps) dying under 19 mm and 0.5% (one polyp) dying under 6.5 mm of sediment (Larsson & Purser, 2011).

Sensitivity assessment.  At the benchmark level, the majority of the Lophelia pertusa polyps would probably be unaffected due to the size of the colony, which is raised above the seabed.  The levels of water flow within this environment are recorded as significant, therefore, it is likely that the sediment would be re-suspended, and removed relatively quickly.  However, if the sediment were to remain for more than two days then it is likely that any polyps which were buried would suffer mortality.  The resistance of this biotope to the pressure at the benchmark is assessed as ‘Medium’, resilience as ‘Very low’, and sensitivity is assessed as ‘Medium’. 

Low Very Low High
Q: High
A: Medium
C: Medium
Q: High
A: High
C: High
Q: High
A: Medium
C: Medium

Using the information within provided for the ‘light’ smothering and siltation pressure, it can be assumed that the burial of Lophelia pertusa in 30 cm of sediment would cause considerable damage to the health of this reef forming species.  If the sediment were to remain in place for more than two days, any buried polyps are likely to have suffered mortality.

Sensitivity assessment.  At the pressure benchmark, resitstance is assessed as ‘Low’, resilience as ‘Very low’, and sensitivity as ‘High’. 

Not Assessed (NA) Not assessed (NA) Not assessed (NA)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not assessed.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No evidence.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Species characterizing this habitat do not have hearing perception but vibrations may cause an impact, however, no studies exist to support an assessment.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Natural light rarely penetrates to the depth this biotope is found in the North East Atlantic.  Therefore, an increase in the amount of natural light is ‘Not relevant’ to this biotope.  However, due to the oil and gas platforms and other forms of exploration or removal of resources, it is possible that un-natural light could be introduced to this biotope.  There is no evidence to support an assessment at this pressure benchmark though, and consequently, an assessment of ‘No evidence’ has been given.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

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

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not relevant – this pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats.

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not relevant.

Biological Pressures

Use / to open/close text displayedResistanceResilienceSensitivity
Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

This pressure is not relevant to the characterizing species within this biotope.  Therefore, an assessment of ‘Not relevant’ has been given. 

Not relevant (NR) Not relevant (NR) Not relevant (NR)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No alien or non-native species are known to compete with Lophelia pertusa or other cold-water corals.  As a result, a sensitivity assessment of ‘No relevant’ has been recorded.

No evidence (NEv) Not relevant (NR) No evidence (NEv)
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

No information on diseases was found.  However, the parasitic foraminiferan Hyrrokkin sarcophaga was reported growing on polyps of Lophelia pertusa in aquaria (Mortensen, 2001).  The foraminiferan dissolves a hole in the coral skeleton and invades the polyp.  In his aquaria, two Lophelia pertusa polyps became infested but did not seem to be influenced by the infestation (Mortensen, 2001).  Any parasitic infestation is likely to reduce the viability of the host, even if only a few or possibly hundreds of polyps were affected but in the absence of additional evidence, an assessment of ‘No evidence’ has been given. 

High High Not sensitive
Q: Medium
A: Medium
C: Medium
Q: High
A: High
C: High
Q: Medium
A: Medium
C: Medium

Lophelia pertusa is not directly targeted by a commercial fishery.  However, with the advent of deep-water fisheries, the habitats within which Lophelia pertusa is found have been heavily targeted by deep-water fishing trawlers because of their high biodiversity. None of the species that are targeted by the commercial fishery have known symbiotic relationships.  The only known species with which Lophelia pertusa has a symbiotic relationship with is the polychaete Eunice norvegica (Mueller et al., 2013).

Sensitivity assessment.  The biological impact of the removal of species associated with Lophelia pertusa is not thought to have a negative impact on this biotope.  Consequently, resistance and resilience are assessed as ‘High’, resulting in a sensitivity assessment of ‘Not sensitive’. The potential physical effects of commercial fisheries are addressed under the 'abrasion' and 'penetration' pressures above. 

None Very Low High
Q: High
A: High
C: Medium
Q: High
A: Medium
C: High
Q: High
A: Medium
C: Medium

Extraction of Lophelia pertusa colonies from the reef would result in fragmentation of the coral, and destruction of the reef structure.  The development of larger vessels and more powerful trawls, e.g. rockhopper gear designed to operate on rough stony bottoms, has probably exposed the reefs to increased impacts from fishing (Fosså et al., 2002; Fosså, 2003).  For example, the fishery of the continental break targeted Greenland halibut, redfish, and saithe.  The orange-roughy is another valuable deep-sea species associated with offshore banks, pinnacles and canyons with strong currents, which are favoured by Lophelia pertusa (Rogers, 1999).  In the UK, monkfish is a major fishery in the vicinity of the Lophelia pertusa reefs around Rockall (Dr Jason Hall-Spencer, pers comm.). 

Demersal fishing operations have been shown to have a significant negative impact on Lophelia pertusa reefs within the North-east Atlantic.  Unequivocal evidence for the physical damage of bottom trawling in cold-water habitats has been presented for many areas around the world (Roberts et al., 2009), including areas within the North East Atlantic.  Fosså et al. (2002) used remotely operated vehicles to survey areas of cold-water coral reefs off the west coast of Norway.  They described areas historically known cold-water coral reefs, containing Lophelia pertusa, to show only scattered coral fragments or crushed and broken coral skeletons.  When their findings were extrapolated it was estimated that between 30 – 50% of Lophelia pertusa reefs from Norway had been damaged by trawling (Fosså et al., 2002).  Hall-Spencer et al. (2002) found that cold-water coral reefs containing Lophelia pertusa off the West Ireland continental shelf break were being damaged by commercial trawls for deep-water fish.  Coral aged to be at least 4500 years old, was being removed from reefs as by-catch.  Grehan et al. (2004) collected imagery data from cold-water coral reefs containing Lophelia pertusa off the West Ireland continental shelf break and West Norway.  They found widespread damage caused by trawling to cold-water coral reefs within these geographical areas.

Trawling can also re-suspend seabed sediments and cause further damage to the habitat through smothering (see smothering pressure).  Trawling experiments in the Mediterranean found that water-column turbidity increased by as much as three times for five days after a trawling event (Palanques et al., 2001; taken from Roberts et al., 2009).  No evidence was available on the impact of re-suspended sediment caused by trawling, the radius of its effects on Lophelia pertusa, or the effects on the associated species. 

Sensitivity assessment. Removal of a large percentage of the characterizing species would alter the character of the biotope. The resistance to removal is ‘None’  due to the easy accessibility of the biotopes location and the inability of these species to evade collection. The resilience is ‘Very low’, with recovery only being able to begin when the harvesting pressure is removed altogether. This gives an overall sensitivity score of ‘High’.

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Citation

This review can be cited as:

Garrard, S.M., Perry, F. & Tyler-Walters, H., 2019. Atlantic upper bathyal live [Lophelia pertusa] reef (biogenic structure). In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-10-2020]. Available from: https://www.marlin.ac.uk/habitat/detail/1142

Last Updated: 21/11/2019

Tags: Cold-water coral Deep-sea