between the dead coral framework, either pelagic or
hemipelagic, largely contributes to the relief-forming
growth of a given reef structure. Without this additive,
pure coral framework would disintegrate by processes like
bioerosion (see above) and would end as a low-relief coral
rubble substrate. Sediment trapping is facilitated by the
current velocity decelerating effect of the coral framework, by the mucus binding of particles, and is probably
enhanced by large quantities of arborescent agglutinated
benthic foraminifers, which live attached to coral skeletons, thus enhancing the baffling capacities considerably
(Messing et al., 2008). Particle flux in cold-water coral settings shows a pronounced seasonality as a matter of
pelagic production cycles in the fertile surface waters
(Duineveld et al., 2007). In general, the current regime at
depths of the corals keeps sedimentary particles in suspension and therefore, off-reef sedimentation rates are low if
any. The intermingling of biological with geological processes, such as new colonization, coral growth, with subsequent trapping and deposition of suspended finegrained particles within the loci of coral reefs, is regarded
as the main driver to enhance the formation of elevated
reef structures within fairly short time scales (Roberts
et al., 2006, 2009a and see above).
Coral habitats, some key species and trophic webs
Mature reefs provide a variety of macro- and microscale
habitats, which enhance biodiversity compared to adjacent
off-reef habitats. According to Mortensen and Fosså
(2006), macro-habitats in a typical reef consist of the live
coral zone on top and upper flanks, then the dead coral
zone, which consists of older in situ or fragmented coral
framework underneath, and at the base, a belt of coral rubble zone mixed with background sediments that surround
the structure. Micro-habitats are the surfaces of tissue covered living corals, the detritus laden surface of dead corals,
the cavities inside dead coral skeleton, and the free space
between coral branches. The live coral zone shows only
few characteristic species that cope with the protective
and reactive coenosarc of the corals. The eunicid polychaete Eunice norvegica is regarded as a non-obligate
mutualist that takes food from the corals, cleans the polyps
from sediment particles, and stimulates precipitation of
coral skeleton to build a protective tube inhabited by
the worm (Mortensen, 2001). Moreover, E. norvegica is
able to actively aggregate pieces of small coral colonies,
thus enhancing coral patch formation (Roberts, 2005).
Another polychaete frequently observed on living corals
is the polynoid Harmothoe oculinarum (Jensen and
Frederiksen, 1992). The rosalinid foraminifer Hyrrokkin
sarcophaga is known as a common parasite of cold-water
corals and associated fauna, such as the file clam Acesta
excavata (Cedhagen, 1994; Freiwald and Schönfeld,
1996; Beuck et al., 2008). Predatory gastropods in the living coral zone, probably grazing coral tissue and mucus
are several coralliophilinid species such as Babelomurex
sentix and Coralliophila richardi (Taviani et al., 2009).
Other characteristic grazers commonly observed in the living coral zone are starfishes like Porania pulvillus
(Wienberg et al., 2008). Sponges strongly associated with
live corals are Hexadella detritifera, Lissodendoryx
diversichela, Hymeraphia verticillata, and Mycale lingua
(e.g., van Soest et al., 2005, 2007). None of the species
mentioned above is obligate to cold-water corals, but
seemingly they occur in greater abundances in this habitat.
The dead coral zone shows highest diversity of coral associates (Mortensen and Fosså, 2006), which use the complex coral framework in various ways but mostly as hard
substrate. Only focusing on bivalves here, some characteristic species are A. excavata, Asperarca nodulosa,
Bathyarca pectunculoides, Chlamys sulcata, and
Delectopecten vitreus, among many others. Moreover,
the coral skeleton is utilized by a vast array of boring
organisms; the ones which have an endolithic lifestyle
among them are fungi, sponges, polychaetes, and bryozoans (see Beuck and Freiwald, 2005; Beuck et al.,
2007, 2010; Wisshak et al., 2005).
Along with increasing research efforts on cold-water
coral reef systems, it became increasingly clear that especially the framework-building L. pertusa acts as an ecological engineer by providing a variety of habitats,
shelter, substrates, and by provision of particulate and
dissolved organic matter, thereby attracting a myriad of
species (Roberts et al., 2009a; Wild et al., 2008). Regional
species filing useful for estimations of gamma diversity
found with Lophelia started with 895 species (see the seminal review of Rogers, 1999), and later on with 1,300
coral-associates. A current database for the HERMIONE
Project of the European Commission listed nearly 2,900
species sorted out for synonyms and calibrated taxonomy
using the World Register of Marine Species database
(www.marinespecies.org; Freiwald, in preparation) of
which 140 species were described new to science from
this reef system during the past 15 years. The most diverse
taxa are crustaceans (493 species), mollusks (420 species),
sponges (386 species), cnidarians (338 species), and fishes
including sharks and rays (278 species). It should be noted
that many taxa are yet not sufficiently treated and validated by experts, and that even in well-studied coral sites
sampling efforts are yet under-representative to provide
a solid base for quantitative biodiversity studies to better
understand the entire community and their ecological
functioning. Most advanced biodiversity studies from
cold-water reefs were provided by Jonsson et al. (2004)
from the Swedish Kosterfjord, from Mortensen and Fosså
(2006) comparing several reefs from within and off the
Norwegian Trondheimsfjord, and from Roberts et al.
(2009b) with a study on the Scottish Mingulay reef
system.
Unlike warm-water reefs, which also rely on solar radiation as intimate energy resource, cold-water coral reefs
are largely dependent on the export of organic matter from
primary production in photic surface waters to the seafloor
(Duineveld et al., 2007; Davies et al., 2009). In a first comprehensive study of the trophic food web and food supply
COLD-WATER CORAL REEFS
227
hemipelagic, largely contributes to the relief-forming
growth of a given reef structure. Without this additive,
pure coral framework would disintegrate by processes like
bioerosion (see above) and would end as a low-relief coral
rubble substrate. Sediment trapping is facilitated by the
current velocity decelerating effect of the coral framework, by the mucus binding of particles, and is probably
enhanced by large quantities of arborescent agglutinated
benthic foraminifers, which live attached to coral skeletons, thus enhancing the baffling capacities considerably
(Messing et al., 2008). Particle flux in cold-water coral settings shows a pronounced seasonality as a matter of
pelagic production cycles in the fertile surface waters
(Duineveld et al., 2007). In general, the current regime at
depths of the corals keeps sedimentary particles in suspension and therefore, off-reef sedimentation rates are low if
any. The intermingling of biological with geological processes, such as new colonization, coral growth, with subsequent trapping and deposition of suspended finegrained particles within the loci of coral reefs, is regarded
as the main driver to enhance the formation of elevated
reef structures within fairly short time scales (Roberts
et al., 2006, 2009a and see above).
Coral habitats, some key species and trophic webs
Mature reefs provide a variety of macro- and microscale
habitats, which enhance biodiversity compared to adjacent
off-reef habitats. According to Mortensen and Fosså
(2006), macro-habitats in a typical reef consist of the live
coral zone on top and upper flanks, then the dead coral
zone, which consists of older in situ or fragmented coral
framework underneath, and at the base, a belt of coral rubble zone mixed with background sediments that surround
the structure. Micro-habitats are the surfaces of tissue covered living corals, the detritus laden surface of dead corals,
the cavities inside dead coral skeleton, and the free space
between coral branches. The live coral zone shows only
few characteristic species that cope with the protective
and reactive coenosarc of the corals. The eunicid polychaete Eunice norvegica is regarded as a non-obligate
mutualist that takes food from the corals, cleans the polyps
from sediment particles, and stimulates precipitation of
coral skeleton to build a protective tube inhabited by
the worm (Mortensen, 2001). Moreover, E. norvegica is
able to actively aggregate pieces of small coral colonies,
thus enhancing coral patch formation (Roberts, 2005).
Another polychaete frequently observed on living corals
is the polynoid Harmothoe oculinarum (Jensen and
Frederiksen, 1992). The rosalinid foraminifer Hyrrokkin
sarcophaga is known as a common parasite of cold-water
corals and associated fauna, such as the file clam Acesta
excavata (Cedhagen, 1994; Freiwald and Schönfeld,
1996; Beuck et al., 2008). Predatory gastropods in the living coral zone, probably grazing coral tissue and mucus
are several coralliophilinid species such as Babelomurex
sentix and Coralliophila richardi (Taviani et al., 2009).
Other characteristic grazers commonly observed in the living coral zone are starfishes like Porania pulvillus
(Wienberg et al., 2008). Sponges strongly associated with
live corals are Hexadella detritifera, Lissodendoryx
diversichela, Hymeraphia verticillata, and Mycale lingua
(e.g., van Soest et al., 2005, 2007). None of the species
mentioned above is obligate to cold-water corals, but
seemingly they occur in greater abundances in this habitat.
The dead coral zone shows highest diversity of coral associates (Mortensen and Fosså, 2006), which use the complex coral framework in various ways but mostly as hard
substrate. Only focusing on bivalves here, some characteristic species are A. excavata, Asperarca nodulosa,
Bathyarca pectunculoides, Chlamys sulcata, and
Delectopecten vitreus, among many others. Moreover,
the coral skeleton is utilized by a vast array of boring
organisms; the ones which have an endolithic lifestyle
among them are fungi, sponges, polychaetes, and bryozoans (see Beuck and Freiwald, 2005; Beuck et al.,
2007, 2010; Wisshak et al., 2005).
Along with increasing research efforts on cold-water
coral reef systems, it became increasingly clear that especially the framework-building L. pertusa acts as an ecological engineer by providing a variety of habitats,
shelter, substrates, and by provision of particulate and
dissolved organic matter, thereby attracting a myriad of
species (Roberts et al., 2009a; Wild et al., 2008). Regional
species filing useful for estimations of gamma diversity
found with Lophelia started with 895 species (see the seminal review of Rogers, 1999), and later on with 1,300
coral-associates. A current database for the HERMIONE
Project of the European Commission listed nearly 2,900
species sorted out for synonyms and calibrated taxonomy
using the World Register of Marine Species database
(www.marinespecies.org; Freiwald, in preparation) of
which 140 species were described new to science from
this reef system during the past 15 years. The most diverse
taxa are crustaceans (493 species), mollusks (420 species),
sponges (386 species), cnidarians (338 species), and fishes
including sharks and rays (278 species). It should be noted
that many taxa are yet not sufficiently treated and validated by experts, and that even in well-studied coral sites
sampling efforts are yet under-representative to provide
a solid base for quantitative biodiversity studies to better
understand the entire community and their ecological
functioning. Most advanced biodiversity studies from
cold-water reefs were provided by Jonsson et al. (2004)
from the Swedish Kosterfjord, from Mortensen and Fosså
(2006) comparing several reefs from within and off the
Norwegian Trondheimsfjord, and from Roberts et al.
(2009b) with a study on the Scottish Mingulay reef
system.
Unlike warm-water reefs, which also rely on solar radiation as intimate energy resource, cold-water coral reefs
are largely dependent on the export of organic matter from
primary production in photic surface waters to the seafloor
(Duineveld et al., 2007; Davies et al., 2009). In a first comprehensive study of the trophic food web and food supply
COLD-WATER CORAL REEFS
227