Recorded distribution in Britain and Ireland
Reefs of %Lophelia pertusa% have been recorded on raised offshore seabed features from the Shetland-Faroe Basin, Rockall Bank and Rockall Trough, Anton Dohrn Seamount, Rosemary Bank, Hatton Bank, Bill Bailey's Bank, and the Wyville-Thomson Ridge in the north Atlantic off Britain, and in the Porcupine Seabight and Porcupine Basin off west Ireland. The map shows the recorded distribution of Lophelia pertusa, including isolated colonies as well as reefs.
Temperature range preferences - 4 - 12 °C
Other preferences - Oceanic water
Lophelia pertusa has been recorded globally from the North Atlantic, parts of the Mediterranean, along the coasts of west Africa, the United States, east Canada and around the mid Atlantic islands south to Tristan da Cunha. It is also recorded from the Pacific, southern California, Cobb Seamount, and from the Island of St Paul in the Indian Ocean. There is also a single record from the Macquarie Ridge, south of New Zealand (Rogers, 1999). However, records often refer to dead or subfossil remains, may not represent reefs in all cases, and Lophelia often occurs as isolated patches over large areas of seabed, making it difficult to detect. Therefore, its living distribution may be inaccurate (Rogers, 1999). Recent genetic evidence suggests that Brazilian records of Lophelia are genetically distinct and may represent a different species or sub-species (Le Goff-Vitry et al., in press; Dr Alex Rogers, pers comm.).
Lophelia pertusa has been recorded from the continental shelf of the north east Atlantic more frequently than any other place in the world (Rogers, 1999). In addition, to records in British and Irish waters, Lophelia reefs have also been recorded from Norwegian fjords, and on raised offshore seabed features from Haltenbanke, Froyabanken and the Sula Ridge in south and west Norway, the Faroes shelf, and from the Porcupine Basin south along the continental shelf edge to North Africa (Rogers, 1999; ICES, 2002; Roberts, 2002b; A. Grehan pers. comm.). Scattered records also occur in the North Sea, the Outer Hebrides, Stanton Bank, and Donegal Basin (Rogers, 1999; Roberts et al., 2003). A review of the distribution of cold water coral in European waters is provided by Zibrowius (1980) and a detailed list of records is presented by Rogers (1999).
- Lophelia pertusa requires hard substrata (e.g. rock, coral fragments, artificial substrata, or hydrocarbon seep associated carbonates) on which to settle. Colonies that occur in sedimentary habitats have settled on small pieces of hard substrata such as pebbles, shells or worm tubes (Rogers, 1999).
- Lophelia pertusa appears to prefer the presence of oceanic waters. For example, Lophelia only occurs in Norwegian fjords that allow deep oceanic water into the fjord; its upper limit determined by the depth of coastal waters (Rogers, 1999).
- Its preference for oceanic waters suggested that Lophelia was sensitive to salinity and temperature (Rogers, 1999). Lophelia pertusa is found in water between 4 and 12 °C (Rogers, 1999) but records from the Mediterranean suggest it can survive up to 13 °C (Mortensen, 2001). 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 (Bett, 2000). Roberts et al. (2003) suggested that the above record probably represented the limit of 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.
- 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).
- The upper limit of Lophelia in fjords corresponds to the position of the thermocline (Rogers, 1999). However, Frederiksen et al. (1992) considered the origin of the water masses to be more important, while Mortensen et al. (2001) suggested that the pycnocline between lower salinity, warmer coastal waters and deeper, cooler oceanic water resulted in more stable conditions within the fjords, and a strong influx of oceanic waters.
- The upper limit of Lophelia in oceanic waters is probably seen on oil platforms in the North Sea. Lophelia pertusa was reported growing 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 physical conditions, competition from other epifauna (e.g. sponges and sea anemones) and possibly by wave action during storms (Roberts, 2002a).
- 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 such as seamounts and banks and where the channel narrows in Norwegian fjords (Rogers, 1999). For example, soft corals were reported to reach higher densities near the peaks of seamounts rather than the slopes, or along the edges of wide peaks (see 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, however, 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. Food availability may be of greater importance than current speed alone.
- Around the Norwegian /Scottish Shelf and Faroes, Lophelia most commonly occurs at depths between 200 -400 m, and between 200 -1000 m in the Massifs off west Ireland and the Bay of Biscay, and in some records extends to 3000 m (Rogers, 1999). Rogers (1999) suggested that its deepest limit may coincide with the oxygen minimum zone.
- In deep waters the upper limit of Lophelia is probably controlled by the transition from oceanic to coastal or surface waters (see Rogers, 1999). However, Lophelia reefs occur as shallow as 50 m in Norwegian fjords. Frederiksen et al. (1992) suggest that its upper limit is controlled by wave action. 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. Wave mediated currents are oscillatory and possibly more likely to result in damage to rigid corals than water flow (see Hiscock, 1983), although their skeletons are quite robust (Dr Jason Hall-Spencer pers comm.). 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.). Rogers (1999) noted that the upper limit of Lophelia in the Norwegian fjords also coincided with the thermocline, and that the turbidity of the coastal surface water also reduced competition from algae.
- It has been suggested that Lophelia reefs are associated with hydrocarbon or methane seeps (Hovland & Thomsen, 1997; Hovland, et al., 1998). But Rogers (1999) concluded that the evidence was equivocal. For example, occurrences of Lophelia in the Rockall Bank and elsewhere are not associated with hydrocarbon seeps (Rogers, 1999). Analysis of stable radiocarbon isotope (13C) levels in the skeleton of Lophelia pertusa and 13C/12C ratios in tissue is not consistent with a food chain based on hydrocarbon seeps (see Rogers, 1999 and Roberts et al., 2003 for discussion). Rogers (1999) suggested that most of the hydrocarbons are utilized by other organisms at the sediment-water interface. However, in some locations the hydrocarbon seep associated carbonates may provide hard substrata for settlement in an otherwise sedimentary habitat.
reefs require hard substrata, the presence strong currents and a good food supply, usually associated with raised seabed features, banks and sea mounts. Lophelia
occupies a relatively narrow range of temperatures (stenothermal) and salinity (stenohaline), although its upper limit may be determined by a number of factors.
This review can be cited as follows:
Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line].
Plymouth: Marine Biological Association of the United Kingdom.
Available from: <http://www.marlin.ac.uk/habitatpreferences.php?habitatid=294&code=1997>