Cold-water coral reefs - WWF UK

Cold-water coral reefs
are beyond any regional management influence but are
related to global change affecting all environments.
Therefore, defining environmental boundary conditions
for corals is essential for:
❏ the assessment of coral habitats living at biogeographic
boundaries
❏ conducting probability studies of potential coral
habitats in yet unexplored regions of the oceans (for
example remote seamounts and oceanic banks).
NUTRITION AND FOOD SOURCES
Little information on the nutrition and food sources of
cold-water corals is available. It is most likely the corals
feed on live plankton and suspended particulate organic
matter that is captured by the polyp tentacles. Visual
observations carried out with boreoscope cameras
mounted on the manipulator (robotic arm) of a manned
submersible next to a living colony, and in aquaria
experiments, showed that the polyps of L. pertusa prey
upon zooplankton up to 2 cm in size (Freiwald, 2002;
Mortensen, 2001). It has been suggested that the coral
may acquire nutrients from bacteria associated with
hydrocarbon seeps (Hovland et al., 1997). A preliminary
biochemical study of the soft tissue of L. pertusa and M.
oculata, however, yielded no evidence to support this
supposition (Kiriakoulakis et al., in press). We also have
little or no information on what prey items different
species of coral utilize, or how significant the input
of resuspended material could be (Frederiksen et
al., 1992).
Unlike tropical coral reef habitats, where almost
all nutrients and food are generated and subsequently
utilized within the system through photosymbiosis, coldwater
habitats depend on pelagic production. The quality
and availability of nutrients and food particles determine
the fitness of coral habitats. To improve understanding of
Box 3: Lophelia growth rates from colonization of man-made structures
L. pertusa has been reported to have colonized manmade
structures such as submarine cables (Duncan,
1877; Wilson, 1979a) and shipwrecks (Roberts et al.,
2003) as well as the Brent Spar oil storage buoy (Bell
and Smith, 1999) and other oil platforms in the North
Sea (Roberts, 2002; and see Chapter 4). Since these
colonization events must have happened after the hard
substrate was introduced, the maximum time that coral
growth could have taken place is known.
This information, summarized in Table 5, gives estimates
of the rate of skeletal linear extension of between 5 and
26 mm per year. Clearly these estimates are based on
the assumption that the coral settled as soon as the
structure was in place, and as such they are minimum
extension rates. If a coral larva settled several years
later, its extension rate must have been significantly
higher than estimated. This could explain the discrepancy
in estimates between the Beryl and Brent Field
corals (Table 5).
Additional evidence on the rate of skeletal linear
extension of L. pertusa has come from analysis of carbon
and oxygen stable isotopes. These estimates vary from
5 mm per year (Mortensen and Rapp, 1998) to 25 mm per
year (Mikkelsen et al., 1982; Freiwald et al., 1997; Spiro
et al., 2000) and so support linear extension rate
estimates from colonization data.
Table 5: Summary of data on Lophelia pertusa colonization of man-made structures
Location Substrate Maximum growth Maximum linear Linear extension Reference
(depth, m) time (years) extension (mm) rate (mm/year)
Northwest Spain Cable 6 45 8 Duncan, 1877
(955-1 006)
Bay of Biscay (800) Cable 38 230 6 Wilson, 1979b
West of Shetland Shipwreck 82 ~1 000 12 Roberts et al.,
(400) 2003
North Sea Brent Spar 20 540 26 Bell and Smith,
(60) storage buoy 1999
North Sea Beryl Alpha 23 120 5 Roberts, 2002
(100) SPM2
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