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

Lophelia reefs

08-11-2016
Researched byFrances Perry & Dr Harvey Tyler-Walters Refereed byDr Jason Hall-Spencer, Dr Alex Rogers, Prof. Paul Tyler & Dr Murray Roberts

Summary

UK and Ireland classification

EUNIS 2008A5.631Circalittoral Lophelia pertusa reefs
JNCC 2015SS.SBR.Crl.LopLophelia reefs
JNCC 2004SS.SBR.Crl.LopLophelia reefs
1997 BiotopeCOR.COR.LopLophelia reefs

Description

The cold-water coral Lophelia pertusa forms patches of bushy growths composed of a network of anastomosing branches that grow into thickets, coppices and eventually reefs under favourable conditions. The morphology and size of reefs are highly variable but reefs may be circular, dome-shaped or elongate, forming distinct patches or arranged in lines of 'islands' along the edges of the continental shelf, sea mounts, offshore banks and other raised sea bed features. Reefs may be composed of coral thickets 10 -50 m across and several metres high, mounds of 50 -500 m in diameter and 2 -33 m high, or through growth and/or fusion of nearby patches, form large elongate coral banks of up to 5 km in length and I km wide, reaching heights of ca 200 m and cover several square kilometres, depending on local conditions. Reefs of the coral Lophelia pertusa, typically support a range of other biota. Lophelia reefs are generally found in areas of elevated current. The coral provides a 3 dimensional structure and a variety of microhabitats that provide shelter and a surface of attachment for other species. In the Sula Ridge Norway, the coral grows in an iceberg furrow forming a coral bank 13 km in length, 300 m wide and 45 m high. Although Lophelia pertusa dominates, other cold-water corals may also occur, e.g. Madrepora oculata, Desmophyllum cristagalli, Dendrophyllia cornigera, Enallopsammia rostata and Solensmilia variabilis. The reef supports a species rich assemblage of invertebrates, especially suspension feeders such as foraminiferans, sponges, hydroids, gorgonians  (Paragorgia arborea, Paramuricea placomus, Primnoa resedaeformis). Lophelia pertusa may also support other corals (Madrepora oculata and Solenosmilia variabilis), polychaetes, bryozoans, brachiopods, asteroids, ophiuroids, holothurians, ascidians, squat lobsters (Munida sarsi) and bivalves may also be present. These organisms have all been recorded within and among the corals (Wilson, 1979; Mortensen et al., 1995). Mobile species present include the redfish (Sebastes viviparous and Sebastes marinus), Ling (Molva molva) and tusk (Brosme brosme) (Husebo et al., 2002). Relatively few species have so far been shown to be closely associated with Lophelia pertusa, for example, eunicid polychaetes, especially Eunice norvegica, and brittlestars, especially Ophiocantha species. The associated community requires further study. The xenophyophore Syringammina fragilissima (a giant protozoan growing up to 20 cm in diameter) occurs at markedly increased densities in downstream 'tails' of the some Lophelia mounds. [NB biotope description composed by author.]

Depth range

50-100 m

Additional information

The review of the ecology is based primarily on the detailed review of Lophelia pertusa by Rogers (1999). The author is grateful to the referees for their helpful comments and for highlighting additional information and recent findings. The sensitivity review uses information collated since 2005.  The ecology review will be updated in due course.

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Further information sources

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JNCC

Sensitivity reviewHow is sensitivity assessed?

Sensitivity characteristics of the habitat and relevant characteristic species

Lophelia pertusa is the only characterizing species within SS.SBR.Crl.Lop this reef forming scleractinian coral is the most common reef framework forming, 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 reefs containing Lophelia pertusa in the North East Atlantic was typically greater than that in neighbouring 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, and where current speeds and productivity are higher than average (Davies et al., 2008). Until the 1990’s little scientific information was available on Lophelia pertusa.  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 5mm / 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).  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, the increase in biological activity within the reef can also increase sedimentation (Roberts et al., 2009).

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) found Lophelia pertusa 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).  The North Alywn Alpha and Healther Alpha platforms provide a 20 to 30 year settlement experiment within the North Sea 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 have probably been 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 hundreds 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.  These reef formations grow up into the water column, which elevates the organisms and allows them to protrude further out into the fast moving water flows.  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).

Sensitivity 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 which are the basis of this biotope.  The oldest Lophelia pertusa reefs in the North East Atlantic have been 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 lack of knowledge regarding the worldwide distribution of the cold-water 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., 2004).  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). 

Pressures will affect Lophelia pertusa in two ways.  Firstly, a pressure could cause mortality of the coral polyps.  This would leave the reef structure intact, however, the loss of the polyps will mean that the reef will no longer be maintained and it will stop growing.  If all of the polyps are killed then the reef structure will degrade and be lost over time.  Secondly, a mechanical pressure could destroy the reef structure.  This would lead to the immediate loss of the reef structure, which would remove the polyps from their optimum conditions.  The polyps may not die immediately, however, they are likely to die within weeks of the pressure event through stress and the effect of secondary pressure caused by the reef destruction.  Eventually, both of these effects will cause the same effects and therefore, they are assessed to have the same resilience.  Where resistance is ‘None’, ‘Low’, ‘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 Lophelia pertusa will ever recover.

Hydrological Pressures

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

Lophelia pertusa distribution is controlled by a number of environmental factors, including; temperature, oxygen saturation, food supply, and carbonate chemistry (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 (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).  Within the Mediterranean, Tursi et al. (2004) recorded Lophelia pertusa living within areas with sea temperatures between 12.5 to 14°C; the upper limit of the species' tolerance.  Temperature fluctuations measured within Lophelia pertusa reefs range between 1 and 2°C (Schroeder, 2002; Wisshak et al., 2005; Davies et al., 2009; cited by Form & Riebesell, 2012).  The small temperature fluctuations recorded within Lophelia pertusa and the extremely long lived nature of the reefs suggests that the species is not tolerant of large fluctuations in temperature for extended periods of time.  Dodds et al. (2007) found that when Lophelia pertusa collected from the Mingulay reef complex were exposed to temperatures greater than those experienced within the reef, metabolic rates of Lophelia pertusa increased dramatically.  For a 2 °C increase in temperature (from 9°C to 11°C) oxygen consumption doubled (Dodds et al., 2007).  This, in turn, increased the higher energetic demands and led to greater food requirements (Dodds et al., 2007).  Lunden et al. (2014) found that when Lophelia pertusa, collected within the Gulf of Mexico, were exposed to temperatures >14°C there was 100% mortality within their sample.  Rogers (1999) suggested that 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, pers comm.). 

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).

Sensitivity assessment.  Lophelia pertusa is an extremely long lived species and is found in deep water where it is isolated from rapid acute changes in temperature.  Short term temperature fluctuations found within Lophelia pertusa reefs have been recorded at 1 -2°C.  An increase in temperature to the level of the benchmark is likely to stress the organisms.  Experiments have shown that an increase in temperature to increase metabolic rate, and consequently the organism’s food requirement.  There is no empirical evidence of the effect of temperature changes at the level of the benchmark.  However, our knowledge of the conditions within which Lophelia pertusa are found suggests that it would be removed from optimum conditions and thus may suffer negative impacts.  Death of the coral polyps themselves would not immediately result in loss of the reef and the associated species.  The associated species, especially epifauna would be lost over a period of years as the coral matrix was slowly eroded to coral rubble and eventually sediment.  Although Lophelia pertusa may be able to colonize the substratum in the meantime, it would still take many years to replace the original reef.  A resistance of ‘Low’ has been given with a resilience of ‘Very Low’, which consequently gives a sensitivity of ‘High’.  

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

Lophelia pertusa distribution is controlled by a number of environmental factors, including; temperature, oxygen saturation, food supply, and carbonate chemistry (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 (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).  Within the Mediterranean, Tursi et al. (2004) recorded Lophelia pertusa living within areas with sea temperatures between 12.5 to 14°C; the upper limit of the species' tolerance.  Temperature fluctuations measured within Lophelia pertusa reefs range between 1 and 2°C (Schroeder, 2002; Wisshak et al., 2005; Davies et al., 2009; cited by Form & Riebesell, 2012).  The small temperature fluctuations recorded within Lophelia pertusa and the extremely long lived nature of the reefs suggests that the species is not tolerant of large fluctuations in temperature for extended periods of time.  Rogers (1999) suggested that 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, pers comm.). 

A single Lophelia pertusa was reported on the Beryl Alpha platform between depths of 75 and114 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).

Sensitivity assessment.  Lophelia pertusa is an extremely long lived species and is found in deep water where it is isolated from naturally occurring rapid acute changes in temperature.  Short term temperature fluctuations found within Lophelia pertusa reefs have been recorded at 1 -2 °C.  A decrease in temperature to the level of the benchmark is likely to stress the organisms.  There is no empirical evidence of the effect of temperature changes at the level of the benchmark.  However, our knowledge of the conditions within which Lophelia pertusa are found suggests that it would be removed from optimum conditions and thus may suffer negative impacts.  The death of the coral polyps themselves would not immediately result in loss of the reef and the associated species.  The associated species, especially epifauna would be lost over a period of years as the coral matrix was slowly eroded to coral rubble and eventually sediment.  Although Lophelia pertusa may be able to colonize the substratum in the meantime, it would still take many years to replace the original reef (see additional information below).  A resilience of ‘Low’ has been given with a resistance of ‘Very Low’ so that sensitivity is ‘High’.  

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, a resistance has been assessed as ‘Low’, giving a resilience of ‘Very low’, which gives the biotope a sensitivity of ‘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 an increase in salinity except in rare cases such as the unlikely production of hyposaline effluents by offshore installations.  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’, which results in an overall sensitivity at the level of the bench of ‘High’ intermediate has been recorded. 

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 down welling 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.

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.  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.  The mass movement of water and food availability may be of greater importance than current speed alone.  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 -0.7 m/s or more (moderately strong).  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.  It was found that maximum net capture rates were found at the 0.025 m / s rate (Purser et al., 2010).

Sensitivity assessment.  Lophelia pertusa relies on constant, mass water flow to supply food and nutrients.  A decrease in water flow would reduce the availability of food to the reef, which may decrease the health of the Lophelia pertusa colony.  If it were reduced below a certain level, mortality would 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’, which results in a sensitivity assessment of ‘Low’.  Any further increase in water flow above the benchmark is likely to cause an impact to the Lophelia pertusa. 

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.  The assessment for this biotope at the pressure benchmark is ‘Not relevant’.

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

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

Not sensitive at the pressure benchmark of compliance with all relevant environmental protection standards.

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

Not sensitive at the pressure benchmark of compliance with all relevant environmental protection standards.

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

Not sensitive at the pressure benchmark of compliance with all relevant environmental protection standards.

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 sensitive
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR
Q: NR
A: NR
C: NR

Not sensitive at the pressure benchmark that assumes compliance with all relevant environmental protection standards.

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 northeast 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.  They found that Lophelia pertusa could survive anoxia for 1 hour, and hypoxia for 96 hours.  The critical oxygen concentration for Lophelia pertusa within its environment was reported as 3.26 ml/l below which concentration the organism wouldn’t be able to carry out normal aerobic function (Dodds et al., 2007).  Davies et al. (2008) mapped the suitable habitat for Lophelia pertusa and found that in the North East Atlantic this organism is associated with areas with an ambient oxygen concentration between 4.62 – 7.39 ml/l.  Both Dodds et al. (2007) and Davies et al. (2008) studied the effects of oxygen concentration on Lophelia pertusa from the North East Atlantic, where the mean oxygen concentration is 6.1 ml/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 were used to expose Lophelia pertusa to different oxygen concentrations for 7 days.  Oxygen concentrations below 1.5 ml/l were found to cause 100% mortality within their sample.  In response to low oxygen concentrations, Lophelia pertusa is able to increase its uptake of oxygen by the expansion of the surface area of its polyp (Dodds et al., 2007).

Sensitivity assessment.  The information used to assess this pressure is given in ml / l, but the benchmark level is given in mg / l.  The conversion of dissolved oxygen from mg to ml in fresh water is 10 ml / l to 13.3 ml / l.  At the level of the benchmark, it is unlikely the conversion rate will change the outcome of the assessment.  This biotope is found in the North East Atlantic, and therefore the evidence provided by those studies which have used samples collected within this area is most relevant.  A change in oxygen concentration at the benchmark has the potential to cause significant mortality within certain areas of the North East Atlantic.  Although the mean oxygen concentration within this area is 6.1 ml/l, if the mean oxygen concentration fell below 3.26 ml/l, then 100% mortality could occur within the area. 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

Information concerning the effects of nutrient levels on Lophelia pertusa and its associated community could not be found.  As a result, a sensitivity assessment of ‘No evidence’ has been given. 

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

Information concerning the effects of nutrient levels on Lophelia pertusa and its associated community could not be found.  As a result, a sensitivity assessment of ‘No evidence’ has been given. 

Physical Pressures

 ResistanceResilienceSensitivity
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,  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; Davies et al., 2009).  

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 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.  It must also be determined from this experiment that exposure to an increase in turbidity for over a year would be a long time for Lophelia pertusa.

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.

A decrease in the levels of suspended material at the level of the benchmark would lead to a reduction in the availability of food to Lophelia pertusa, and other filter feeding organisms within the biotope.  Empirical evidence on the amount of food required by Lophelia pertusa is not available, and information from JNCC core records are lacking on the levels of suspended sediment normally experienced within this biotope.  Therefore, it is not possible to determine if there would be any effect at the level of the benchmark.

Sensitivity assessment.  There is no information regarding the level of turbidity normally found within this biotope From the information available an increase in turbidity from clear to intermediate, or intermediate too high for a year could cause significant mortality of Lophelia pertusa.  It is unclear how a decrease in turbidity may affect Lophelia pertusa.  Resistance is assessed as ‘Low’, and resilience is assessed as ‘Very low’, giving a sensitivity of ‘High’.

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).  Rogers (1999) suggested that sedimentation rates of >10 mg/cm²/day in shallow water coral reefs were high.  Smothered polyps would be expected to starve.

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.  Preliminary results suggest 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 is 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 would prevent settlement of larvae and hence recruitment.

Dodds et al. (2007) found that Lophelia pertusa can change its metabolic rate in accordance with oxygen availability.  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 accumulation of sediment is relatively slow.  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).  But complete burial for >24 hours caused suffocation and mortality (Allers et al., 2013).  As little as 3 mm of sediment covering a Lophelia pertusa can lead to complete anoxia within six days, and the thicker the covering of sediment the faster anoxia occurs (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.  It was found that a significant tolerance threshold was reached between 2 – 4 days, after which time very low survival rates were recorded (Brooke et al., 2009).

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’ and resilience is assessed as ‘Very low’, giving the biotope a sensitivity of ‘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, this biotope is assessed to have a ‘Low’ resistance, the resilience is assessed as ‘Very low’, giving an overall sensitivity of ‘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 propagule 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. Physical and hydrographic barriers may limit propagule dispersal.  But propagule 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.

Biological Pressures

 ResistanceResilienceSensitivity
Not relevant (NR) Not relevant (NR) Not sensitive
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 sensitive
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: Medium
A: Medium
C: Medium
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 ‘High’.

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:

Perry, F. & Tyler-Walters, H., 2016. [Lophelia] reefs. 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. Available from: http://www.marlin.ac.uk/habitat/detail/294

Last Updated: 18/03/2016