Biodiversity & Conservation

COR.COR.Lop

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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Removal of the substratum would result in removal of living coral and dead coral debris, resulting in destruction of the reef and loss of the biotope. Therefore an intolerance of high has been recorded. Recovery would probably take several hundreds to thousands of years (see additional information below).
Smothering
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Rogers (1999) suggested that Lophelia pertusa would be intolerant of increased rates of sedimentation (siltation), 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. Corals are generally thought to be intolerant of increases in sedimentation which is thought to be one of largest sources of degradation of coral reefs (Norse, 1993) and may suppress the growth rates of 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. However, 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 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 clearing 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.

At the benchmark level (smothering by 5 cm of sediment for a month) the majority of the Lophelia pertusa polyps would probably be unaffected due to the size of the colony, which is raised above the seabed. Similarly, most other suspension feeding invertebrates will probably survive for one month, suggesting an overall intolerance of low. Recovery would probably be rapid once the sediment was removed.

However, any activity that reduces growth may have detrimental effects on the survival of Lophelia colonies and the reef in the long term. Lophelia reefs are probably highly intolerant of prolonged or frequent smothering effects.
Increase in suspended sediment
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Increased suspended sediment levels may interfere with feeding in suspension feeders, including Lophelia pertusa, and hence growth (see above). Therefore an intolerance of low has been recorded at the benchmark level. Recovery would probably be rapid.
Decrease in suspended sediment
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Lophelia occurs in areas of strong currents, where internal waves and current acceleration provides adequate food supplies in the form of plankton and suspended organic particulates. Therefore, any activity that decreased the level of suspended particulates may reduce the food available to Lophelia and other suspension feeders. Rogers (1999) suggested that any interference with feeding and hence growth, may alter the balance between growth and bioerosion, potentially resulting in degradation of the reef. However, at the benchmark level duration of one month, decrease in food availability is likely to have only short term effects. Therefore, an intolerance of low has been recorded. Recovery would probably be rapid.
Desiccation
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Cold-water corals and other subtidal epifauna are most probably highly intolerant of desiccation and aerial exposure. However, deep-water corals are extremely unlikely to be exposed to the air and not relevant has been recorded.
Increase in emergence regime
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Lophelia reefs 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.
Decrease in emergence regime
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Lophelia reefs 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.
Increase in water flow rate
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Strong current flow appears to be required for growth in Lophelia, which occurs in areas of strong water flow. Lophelia 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). Frederiksen et al. (1992) suggested that topographical highs create internal waves, depending on slope, that resuspended 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 and other suspension feeders. Water flow is important for suspension feeders and passive carnivores, such as Lophelia, to provide adequate food, oxygen and nutrients, to remove waste products and prevent sedimentation but the optimum current speed varies with species (see Hiscock, 1983 for discussion). For example, Mortensen (2001) observed no polyp mortality in the vicinity of his aquaria inlets but high mortality at the opposite end. Similarly, the death of coral polyps within a coral coppice is 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 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 (White , 2001 cited in 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). Although this species occurs in areas subject to moderately strong current and mass water movement, Mortensen's data (2001) suggests that increased flow may reduce growth. Therefore, an increase in water flow from moderately strong or strong to very strong for a year may depress growth due to reduced feeding efficiency. But, given the long-lived nature of Lophelia colonies, an increase in water flow for one year is probably tolerable and an intolerance of low has been recorded, albeit with low confidence. Other epifaunal species may be swept away in very strong water flow although the Lophelia coral matrix would probably provide a refuge, however, some species may be lost and species richness decline.

Decrease in water flow rate
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Strong current flow appears to be required for growth in Lophelia, which occurs in areas of strong water flow. Lophelia 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). Frederiksen et al. (1992) suggested that topographical highs create internal waves, depending on slope, that resuspended 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 and other suspension feeders. Water flow is important for suspension feeders, such as Lophelia, to provide adequate food, oxygen and nutrients, to remove waste products and prevent sedimentation but the optimum current speed varies with species (see Hiscock, 1983 for discussion). For example, Mortensen (2001) observed no polyp mortality in the vicinity of his aquaria inlets but high mortality at the opposite end. Similarly, the death of coral polyps within a coral coppice is thought to be due to reduced water flow within the colony (Wilson 1979b).

Therefore, a decrease in water flow from e.g. moderately strong to negligible for a year would probably result in death of at least a proportion of the coral polyps, depending on their position within the reef, i.e. polyps within the coral matrix would be more intolerant of. Other suspension feeding invertebrates would also be adversely affected. Decreased water flow would also result in a increase in siltation, potentially resulting in smothering of Lophelia and other suspension feeders, and potentially interfering with Lophelia recruitment (Rogers, 1999). Although, a change for a year (see benchmark) is probably only a short period of time in the life of a Lophelia colony, Mortensen (2001) observed polyp mortality within a short 2.5 yr. experiment. Therefore, an intolerance of intermediate has been recorded, albeit at low confidence. Recovery would probably take considerable time.

Increase in temperature
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Lophelia pertusa is found in water between 4 and 12 °C (Rogers, 1999; Roberts et al., 2003) but records from the Mediterranean suggest it can survive up to 13 °C (Mortensen, 2001). In fjords the upper limit of the Lophelia reefs coincides with the level of the thermocline. Rogers (1999) suggested that death of the coral on the upper reaches of the reef may reflect changes in the depth of the thermocline. But the upper limit of the Lophelia 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.). The requirement of Lophelia for oceanic waters suggested that Lophelia was probably intolerant of salinity and temperature change (Rogers, 1999). Lophelia pertusa was reported on single point moorings of 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 corresponded with 8 °C and a salinity of 35 ppt. He suggested that Lophelia 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).

Offshore, deep-water Lophelia reefs are probably isolated from naturally occurring rapid acute changes in temperature due to their depth. But they are probably intolerant of an increase in temperature at the benchmark level caused by an activity that increases temperatures in their locality, e.g. from thermal discharges. The long term effects of climate change on deep-water currents could have far ranging effects (see water flow above). Therefore, an intolerance of high has been recorded.

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 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).
Decrease in temperature
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Lophelia pertusa is found in water between 4 and 12 °C (Rogers, 1999). Rogers (1999) noted that Lophelia is not usually found in waters colder than 6 °C but that it may encounter lower temperatures at the lower limits of its depth range. In a recent study, Roberts et al. (2003) noted a strong correlation between the occurrence of Lophelia and temperature. With a single exception, Lophelia had not been recorded in waters colder than 4 °C and was absent from depths of greater than 500 m in the Faeroe-Shetland Channel, presumably due to the influence of cold Nordic waters (e.g. the Arctic Intermediate Water and/or Norwegian Sea Arctic Water with temperatures of 1-5 °C or -0.5 to 0.5 °C respectively) (Roberts et al., 2003). The only record of Lophelia in the Faeroe-Shetland Channel below 500 m occurred in an area subject to temperatures below 4 °C for 52% of a 10 month period of observations and below zero for 4% of the same period. Roberts et al. (2003) suggested that the above record probably represented the limit of this Lophelia pertusa's range but that present evidence suggested that seabed mounds associated with coral growth were unlikely at depths influenced by cold Nordic waters.

Offshore Lophelia reefs are probably isolated from naturally occurring rapid acute changes in temperature due to their depth but are probably intolerant of a decrease in temperature at the benchmark level. Any activity or event that changed the circulation of deep-water currents (e.g. climate change) could have wide ranging effects. Therefore, an intolerance of high has been recorded.

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 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).
Increase in turbidity
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Offshore Lophelia reefs occur at considerable depth, below the photic zones of the temperate oceans, and hence in perpetual darkness. An increase in turbidity at the surface may decrease phytoplankton productivity. However, Lophelia and its associated suspension feeders utilize other sources of organic particulates and are unlikely to be significantly affected. Lophelia reefs may also occur at about 50 m in fjords, where an increase in turbidity may further inhibit algal growth, although the effects are unlikely to be significant. Therefore, not sensitive has been recorded.
Decrease in turbidity
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Offshore Lophelia reefs occur at considerable depth, below the photic zones of the temperate oceans, and hence in perpetual darkness. A decrease in the turbidity of surface or deeper waters in unlikely to affect offshore reefs since light will still not penetrate to the depth occupied by Lophelia reefs. However, a decrease in turbidity may allow algae to colonize shallow Lophelia reefs in fjords, increasing competition for space with other suspension feeders and coral larvae, and potentially smothering the coral at its upper limit. Therefore, deep-water Lophelia reefs are probably not sensitive to a decrease in turbidity, while shallow water examples may be degraded, and an overall intolerance of intermediate has been recorded. Recovery would take many years (see additional information below).
Increase in wave exposure
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Offshore Lophelia 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 penetrate to greater depths. However, Draper (1967) estimated that as far out as the continental shelf, for one day a year, storm conditions could generate a oscillatory water movement on the seabed of only ca 0.4 m/s at 180 m.

In Norwegian fjords where Lophelia 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 larvae. However, Lophelia occurs at depths at which even the wave action generated by storm conditions is unlikely to penetrate. Therefore, not relevant has been recorded.
Decrease in wave exposure
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In shallow, fjordic, examples of the biotope a decrease in wave action may allow the Lophelia reef to increase in height. The prevailing oceanic or tidal currents are probably far more important sources of water movement in areas occupied by Lophelia reefs than wave action alone. Therefore, a decrease in wave action is unlikely to have any detrimental effects and not sensitive has been recorded.
Noise
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Few marine invertebrates have been shown to respond to sound, although they do respond to pressure fluctuations similar to hydrodynamic water flow and currents. Close proximity to powerful sound sources, such as seismic survey arrays and underwater explosions will result in damage due to the pressure wave created, however, marine invertebrates are unlikely to be sensitive at the benchmark level (Vella et al., 2001). Fish species associated with the reef may temporarily avoid sites affected by noise from vessels but would probably return once the vessel has passed. Therefore, not sensitive has been recorded.
Visual Presence
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Offshore Lophelia reefs occur at great depth, below 200m, from very low light levels to perpetual darkness. Lophelia polyps showed no diurnal behaviour patterns in aquaria (Roberts & Anderson, 2002b) and have no known response to light or shading. Therefore, not relevant has been recorded.
Abrasion & physical disturbance
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Although Lophelia reefs occur a 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 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 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 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 reefs are either impacted or destroyed by bottom trawling in western Norway. Mechanical damage by fishing gear would also damage or kill the associated epifaunal species, and 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 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 was also "markedly reduced" on heavily fished seamounts (Koslow et al. (2001).

Overall, there is significant evidence of damage to Lophelia and other cold-water coral reefs due to deep-sea trawling, and an overall intolerance of high has been recorded. Recovery would probably take several hundreds to thousands of years (see additional information below).

Displacement
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Some fragmentation of the coral skeleton is probably a natural part of the development of the reef system. Similarly, if large pieces of coral were removed to a new location, as long as the new are was suitable for growth, the coral would probably survive and continue to grow. Pieces of the coral reef transported by trawls or by-catch returned to the sea, may also survive if it was transplanted to a suitable area for growth, potentially forming a new coral coppice or reef in time (see Rogers, 1999), although survival is probably very limited (Dr Alex Rogers, pers comm.). Mortensen (2001) reported that 50% of the polyps of Lophelia, sampled by dredge and transported to aquaria remained closed for up to 3 weeks, while in samples collected by grab, the polyps opened within a few hours. Therefore, displacement is likely to result in an energetic cost and stress to the coral. However, the associated epifauna and infauna are likely to be lost, or damaged in the process, resulting in a loss of species richness. Displacement is unlikely to leave the reef intact. Therefore, an intolerance of intermediate has been recorded at the benchmark level. Although, individual pieces or fragments of the coral will probably survive, it would still take considerable time for a coral coppice or reef to develop.

Chemical Factors

Synthetic compound contamination
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No information was available concerning the effects of synthetic chemicals on Lophelia or other cold-water coral species. Evidence from a variety of sources suggests that hydroids, crustaceans, gastropods, and ascidians are probably intolerant of tri-butyl tin (TBT) contamination while bryozoans are probably intolerant of chemical pollution (see £CR.Bug£ or £MCR.Flu£ for details) (Smith, 1968; Hoare & Hiscock, 1974; Boero, 1984; Bryan & Gibbs, 1991; Gili & Hughes, 1995; Rees et al., 2001). It is likely that exposure to synthetic chemical contaminants may result in loss or degradation of populations of associated suspension feeding invertebrates, while there is no evidence to suggest either the presence or absence of adverse affects on Lophelia itself. Overall, in the absence of evidence of the effects of synthetic contaminants on the key structural species within the biotope (Lophelia), no assessment of intolerance has been made.
Heavy metal contamination
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Deep-water corals could potentially be exposed to heavy metal contamination as a result of spoil dumping or exposure to drill muds and drill cuttings. For example, barium sulphate from drilling muds has been found up to 6 km from an individual platform in the North Sea, covering an area of 100 km² (Olsgard & Gray, 1995; Rogers, 1999). Olsgard & Gray (1995) demonstrated four categories of contamination (from gross, severe, moderate to initial) radiating from oil rigs, which were mirrored by the benthic fauna. The effects were mainly due to total hydrocarbons, barium, strontium, and other metals such as zinc, copper, cadmium, and lead. The initial effects of pollution were the severe reduction of species that were key components of benthic communities (Olsgard & Gray, 1995).

Bryozoans may be tolerant to heavy metals while hydroids studied manifest only sublethal effects (Ryland, 1967; Soule & Soule, 1979; Stebbing, 1981; Bryan, 1984; Holt et al., 1995; Ringelband, 2001). Echinoderms may be intolerant of heavy metal contamination which has been shown to reduce reproduction and recruitment in starfish and sea urchins (see £CR.Bug£; Kinne, 1984; Dinnel et al., 1988; Besten, et al., 1989, 1991; Gomez & Miguez-Rodriguez 1999). Sea urchin larvae are used to test water quality and may be expected to be intolerant of. Gastropod molluscs have been reported to be relatively tolerant of heavy metals while a wide range of sublethal and lethal effects have been observed in larval and adult crustaceans (Bryan, 1984).

However, no information concerning the effects of heavy metal contamination on Lophelia or other cold-water corals was found. Roberts (2002a) noted that colonies of Lophelia growing on the Beryl Alpha platform in the North Sea were ca 2 km away from the site of drilling and its associated drill cuttings, although a single colony occurred 210 m upstream of the drill cuttings pile. It appears that heavy metal contamination from oil exploitation may reduce the abundance of marine invertebrates within its vicinity, and may adversely effect the species richness of a nearby reef. But the direct effects on the corals themselves remain unknown. Therefore, no assessment of intolerance has been made.
Hydrocarbon contamination
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Lophelia reefs are protected from the effects of oil spills by their depth but may encounter hydrocarbon contamination resulting from oil and gas exploitation. Corals were reported to exhibit a range of effects to oil contamination including mortality if contamination was severe, or reduced growth, tissue damage, disruption of cell structure, damage to feeding behaviour, and excessive mucus production in response to chronic contamination. Oil contamination was also reported to cause corals to release brooded planula larvae prematurely, and affect the settlement of larvae, decrease the coral's fecundity, and even result in reproductive failure (for reviews see Loya & Rinkevich, 1980; Rogers, 1999).

The effects of oil contamination of a numbers of species from numerous taxonomic groups has been studied. Overall, several species of bryozoans, amphipods, echinoderms and soft corals may be highly intolerant of hydrocarbon contamination, while some species of hydroid may demonstrate sublethal effects and anemones and some species of sponge are probably relatively tolerant (for examples see £CR.Bug£ and £MCR.Flu£).

No information on the effects of hydrocarbon contamination on cold-water corals was found. However, the above evidence suggests that chronic contamination may result in sub-lethal effects and interfere with reproduction and hence recruitment in cold-water corals. Similarly, hydrocarbon contamination is likely to effect other members of the biotope adversely, reducing species richness and changing the composition of the community. Therefore, in the absence of further evidence an intolerance of intermediate has been recorded, albeit with low confidence.
Radionuclide contamination
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No information concerning the effects of radioactive contamination on Lophelia was found. However, Hall-Spencer et al. (2002) noted that although all shallow water organisms had accumulated nuclear bomb test related 14C, the Lophelia specimens collected from deep-waters off west Ireland were not contaminated by anthropogenic 14C, presumably because the water bodies they occupy are ancient. Therefore, Lophelia at sites in west Ireland could provide a useful background or baseline level for studies of radioactive contamination.
Changes in nutrient levels
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No information concerning the effects of nutrient levels on Lophelia and its associated community was found.
Increase in salinity
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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 to be stenohaline. The Lophelia reef and its associated fauna occur in relatively stable waters, that are not subject to fluctuations in salinity. While Lophelia is probably highly intolerant of changes in salinity at the benchmark level, it is unlikely to experience an increase in salinity except is rare cases such as the unlikely production of hypersaline effluents by offshore installations. Therefore, not relevant has been recorded.
Decrease in salinity
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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 to be stenohaline. The Lophelia reef and its associated fauna occur in relatively stable waters, that are not subject to fluctuations in salinity. While Lophelia is probably highly intolerant of changes in salinity at the benchmark level, it is unlikely to experience an increase in salinity except is rare cases such as the unlikely production of hyposaline effluents by offshore installations. However, in shallow fjordic water Lophelia 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 death of the upper extent of the reef. Therefore, an intolerance of intermediate has been recorded. Recovery would probably take several hundred years (see additional information below).
Changes in oxygenation
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It has been suggested that the lower limit of Lophelia's bathymetric distribution was probably determined by the oxygen minimum zone (Freiwald, 1998; Rogers, 1999) . However, Roberts et al. (2003) suggested the lower depth limit of Lophelia's distribution in the northeast Atlantic was related to temperature. Without information concerning the levels of hypoxia to which a Lophelia reef may be exposed, and its subsequent tolerance to hypoxia, no intolerance assessment has been made.

Biological Factors

Introduction of microbial pathogens/parasites
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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 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 no assessment of intolerance has been made.
Introduction of non-native species
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No alien or non-native species are known to compete with Lophelia pertusa or other cold-water corals.
Extraction
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Extraction of Lophelia pertusa colonies from the reef would result in fragmentation of part of the coral, and destruction of parts of the reef structure. Although not directly exploited, indirect removal of the coral as by-catch in bottom trawling has been shown result in damage to cold-water reefs (see physical disturbance above). Destruction of the cold-water reefs resulted in a marked reduction in the species richness of seamounts off Tasmania (Koslow et al., 2001). Reefs are considered to be good fishing places for net and long-line fisheries, and fishermen often set their gear as close as possible to reefs but not on them to avoid damaging their fishing gear. However, 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 (Rogers, 1999). In the UK, monkfish is a major fishery in the vicinity of the Lophelia reefs around Rockall (Dr Jason Hall-Spencer, pers comm.).

Overall, there is significant evidence of damage to Lophelia and other cold-water coral reefs due to deep-sea trawling, and an overall intolerance of high has been recorded. Recovery would probably take several hundreds to thousands of years (see additional information below).

Additional information icon Additional information

Recoverability
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. However, Lophelia pertusa exhibits extremely slow growth rates. For example, a single colony 1.5 m high may take between 200 -366 years to develop depending on growth rate. Large reefs may take several hundred to several thousand years to develop (see 'time for community to reach maturity') (Rogers, 1999).

If areas of the cold-water coral reef are removed, the area may be colonized by expansion from the remaining reef, or by recruitment by larvae. Although recent evidence suggests that Lophelia pertusa has a dispersive, pelagic larva (Roberts, 2002), the larval biology of Lophelia pertusa is completely unknown, and effective recruitment rates can not be predicted (Rogers, 1999). However, recent molecular genetic data suggests that larval recruitment is probably low or sporadic (Le Goff-Vitry & Rogers, 2002, summary only; Dr Alex Rogers, pers comm.). Even if recruitment is successful, it would still take considerable time for the new colony to grow, and even longer for a reef to recover. Rogers (1999) noted that if a cold-water coral reef was damaged by excessive sedimentation, then surface sediment would probably preclude larval settlement, preventing recovery.

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 may be able to colonize the substratum in the meantime, it would still take many years to replace the original reef.

Overall, any damage sustained by the cold-water coral reef may take at least decades but most probably hundreds of years to repair. The recovery of a destroyed large cold-water coral reef to its former size would probably take several hundred to several thousands of years.


This review can be cited as follows:

Tyler-Walters, H. 2005. Lophelia reefs. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 24/11/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=294&code=1997>