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The rate of discovery of reefs of the cold-water coral Lophelia pertusa (Linnaeus, 1758) has been remarkable, and attributable to the increased use of underwater video. These reefs form a major three-dimensional habitat in deeper waters where little other ‘cover’ for fish is available. They are common in the eastern North Atlantic, and occur at least in the western North Atlantic and off central Africa. There are also other non-reef records of Lophelia in the Atlantic, and in Indian and Pacific oceans. Thus, not only are these reefs a significant habitat on a local scale, but they may also provide an important habitat over a very wide geographic scale. The present study examined the association of fish species with Lophelia in the Northeast Atlantic, including the Trondheimsfjord and Sula Ridge in Norway, Kosterfjord in Sweden, Darwin Mounds west of Scotland, and Rockall Bank, Rockall Trough and Porcupine Seabight off Ireland. The fish fauna associated with a shipwreck west of Shetland was also studied. Data were collected from 11 study sites at 8 locations, using 52 hours of video and 15 reels of still photographs. Video and still photographs were collected from (1) manned submersible, (2) surface controlled remotely operated vehicle (ROV), (3) a towed “hopper” camera, (4) wide angle survey photography (WASP), (5) seabed high resolution imaging platform (SHRIMP), and (6) an in situ time-lapse camera “Bathysnap”. It was possible to identify 90 % of fish observed to species level and 6.5 % to genus or family level. Only 3.5 % of the fish were not identifiable. A guide to the fishes is given at http://www.ecoserve.ie/projects/aces/. Twenty-five species of fishes from 17 families were recorded over all the sites, of which 17 were of commercial importance and comprised 82 % of fish individuals observed. These commercial fish species contribute 90 % of commercial fish tonnage in the North Atlantic. The habitats sampled were comprised of 19 % reef, 20 % transitional zone (i.e. between living coral and debris zone), 25 % coral debris and 36 % off-reef seabed. Depth was the most significant parameter in influencing the fish associated with the reefs, both at the species and family level. There was a complete separation of sites above and below 400–600 m depth by multi-dimensional scaling (MDS) analysis. Less distinct assemblages of fish species were associated with each habitat. Fish species richness and abundance was greater on the reef than surrounding seabed. In fact, 92 % of species, and 80 % of individual fish were associated with the reef. The present data indicates that these reefs have a very important functional role in deep-water ecosystems as fish habitat.

Deep-sea dredging of sediment-starved steep reliefs in the Strait of Sicily (cruise CS96 of RV Urania ) recovered various benthic organisms previously unknown or poorly documented in the Mediterranean basin. This Mediterranean case-study refers to deep coral substrates represented by loose or cemented skeletal remains of Desmophyllum, Lophelia and Madrepora , subfossil giant oyster shells, micriticised sponges, from c. 250–1000 m depth. Here we present some of the more remarkable species: one foraminiferan ( Planogypsina ?); the sponges Stylocordyla pellita, Sphinctrella gracilis and Siphonidium ramosum ; a bioluminescent zoantharian (still unidentified); the boring actinian Fagesia loveni ; the stoloniferous octocoral Scleranthelia musiva ; the gorgonian Dendrobrachia fallax ; and the holothurian Psolidium complanatum .

The metazoan meiofauna associated with Lophelia pertusa reef degradation zones in the Belgica Mound province (Porcupine Seabight, North-East Atlantic) was studied in the framework of the Atlantic Coral Ecosystem Study (ACES; EC Fifth Framework Research Program). Attention was focused on the influence of and differences between different microhabitat types: dead coral fragments, glass sponge skeletons and the underlying sediment. This study demonstrates the importance of dead Lophelia pertusa framework and associated substrates for meiofauna along the European continental margins. The presence of these large biogenic structures on the seafloor of the continental margin (1) enables more taxa to be present and (2) particularly favours harpacticoid copepods, naupliar larvae and polychaetes. The meio-epifaunal community on these substrates significantly differs from the meio-infaunal community in the underlying sediment. This is mainly due to a much lower dominance of nematodes and a higher relative abundance of most other taxa, especially harpacticoids, naupliar larvae and polychaetes, in the latter habitat. This situation is comparable to that of epiphytic assemblages. Dominance of nematodes is low. The meio-infaunal assemblage in the underlying sediment is characterized by low densities. There are clear indications that cold-water coral degradation zones are biologically very diverse, in terms of species richness as well as equitability. Of all microhabitat types, coral fragments support the most diverse communities, whereas the underlying sediment is the least diverse.

This paper describes the associated fauna of the deep-sea gorgonian corals Paragorgia arborea and Primnoa resedaeformis . Composition and distribution of this fauna is described based on material from the continental shelf and slope off Atlantic Canada (300–600 m depth). Samples were collected from five areas with Remotely Operated Vehicle, video grab, and bottom trawl. The collected material consists of 25 samples, 13 from P. arborea and 12 from P. resedaeformis . A total of 114 species and 3915 individuals were recorded. The P. resedaeformis fauna was more abundant and diverse than the fauna of P. arborea , with 2651 specimens and 97 species found on the former and 1264 specimens and 47 species on the latter. Rarefaction analysis indicated that many more associated species are still to be found. Species richness and abundance was significantly correlated with coral morphology (e.g., number of branches, wet weight, and % exposed skeleton). Crustaceans dominated the fauna, contributing 46 % to the total number of individuals and 26 % to the total number of species. Two coral microhabitats were identified: 1) young and live parts of colonies and, 2) old parts with deposits and exposed skeleton. Most of the associated fauna was found in the latter habitat. There was a clear difference in fauna composition of the two coral species. Sessile hydroids, anemones, and molluscs were more abundant on P. resedaeformis . These organisms occurred attached to the hard substratum provided by the exposed skeleton. Parasitic copepods and polychaetes were more common on P. arborea . Two copepods, a lichomolgid ecto-parasite and a lamippid gall-forming endoparasite, were associated with P. arborea . The echinoderm Gorgonocephalus lamarckii was found in the high current environment on the outer branches of P. arborea . The shrimp Pandalus propinquus was hiding and resting on colonies of both coral species. Many of the associated taxa are also found on tropical gorgonians but the deepsea gorgonians lack the diverse decapod and gastropod-fauna of their tropical counterparts. The species richness of the deep-sea gorgonian coral fauna was higher than what has been observed for tropical gorgonians. In contrast to the tropical associates very few are obligate symbionts. Nevertheless, several of the species are rare in other habitats and have been recorded on the same and other gorgonian species in early studies from the eastern North Atlantic. The sampling gear collected the fauna differently. Corals from bottom trawls had a poorer associated fauna that differed in composition with material collected by ROV or video assisted grab.

Benthic Foraminifera found attached to the deep-sea coral Primnoa resedaeformis may be used to establish paleo-coral locations long after the coral has disappeared. Recent coral research cruises have revealed that the coral on the Scotian Margin is in peril and in many cases no longer exists. Sea floor video footage suggests various fishing methods have destroyed much of the coral as it has in coastal areas off Norway and Alaska. To date deep-sea corals are sparse on the Scotian Margin; therefore evidence preserved in the sediment may establish whether corals were present and more abundant in the past. A representative assemblage of benthic foraminiferans found attached to the deep-sea coral Primnoa resedaeformis may be the evidence necessary to provide presence/absence indicators long after the coral has disappeared. Both foraminiferal species are known to be only associated with the coral, and distortion of the ventral side (attached) of common foraminiferal species found in the sediment, may provide a clue to past coral habitat. Identifying a deep-sea coral paleo-habitat indicator provides insight into the extent to which it existed. Video footage from coral cruises over the last three years indicates that coral and fish go hand in hand, an important observation for a region where fishing comprises 23 % of the local economy. Twenty-eight foraminiferal species were found in a range of abundances on nine deep-sea coral specimens of Primnoa resedaeformis . Attached foraminiferans are found on the basal sections of the coral where they colonize onto the hard calcite substrate. One of the more common and consistent foraminiferal species found attached to the coral, Discanomalina semipunctata , is not found commonly on the continental margin in non-coral areas and may provide in situ evidence of past coral habitat.

Samples of Lophelia were taken at two localities in the Lindos Bay Clay (Lower Pleistocene) of the Rhodes Formation on the Dodecanese Island of Rhodes. At a coastal exposure at Vasphi, northeast Rhodes, about 200 fragments of Lophelia were collected in situ from the clay and surface preservation of these is consequently particularly fine. The second collection of material was made at an exposure south of Lardos, about 35 km further south. This material comprised some 800 fragments of Lophelia collected both in situ and loose; preservation quality of the surfaces of these is variable. Both collections derive from single fl at beds of coral fragments. Bioerosion of the corals shows a good diversity, comprising about 18 ichnotaxa, five in open nomenclature, including: Orthogonum lineare, Saccomorpha clava and other microborings (probably exclusively of endolithic fungi), Oichnus isp. (pits and holes of various forms, probably all deriving from foraminifers), dish-shaped etchings possibly produced by the foraminifer Hyrrokkin sarcophaga, Palaeosabella prisca (polychaete worm borings), Caulostrepsis isp. (polychaete borings), probable Maeandropolydora isp. (polychaete borings), Talpina isp. (phoronid borings), Podichnus centrifugalis (attachment scars of brachiopods), Centrichnus eccentricus (attachment scars of anomiid bivalves), Gnathichnus pentax (tooth scratches by regular echinoids), and Entobia ispp. (borings of endolithic sponges). Three small, radiating forms around a millimetre in size are difficult to attribute to particular tracemaking organisms. They are retained in open nomenclature as Semidendrina -form (possibly foraminifera borings), a non-camerate radiating form and a hirsute camerate form. No ctenostome bryozoan borings were observed. Talpina isp. is abundant at Vasphi but scarce at Lardos. Otherwise the relative abundance of the trace fossils is comparable at the two localities. The total amount of bioerosion varies considerably in different parts of the coral skeleton. On the basis of SEM imagery, three categories of bioerosional intensity are introduced: 1, slight bioerosion; 2, medium bioerosion, and 3, heavy bioerosion. The distribution of Gnathichnus pentax and the absence of Radulichnus inopinatus indicates an aphotic environment. The microbioerosional assemblage correlates with the Saccomorpha clava / Orthogonum lineare Ichnocoenosis, which also indicates an aphotic seafl oor.

This study focuses on bioerosion of an aphotic deep-water coral mound, the Propeller Mound, in the northern Porcupine Seabight. The predominant framework builder is the cosmopolitan cold-water coral Lophelia pertusa . We demonstrate bioerosion patterns within the skeleton of L. pertusa using a new embedding method under vacuum conditions with subsequent scanning electron microscope analysis. Following this method, 23 ichnospecies are documented and related to heterotrophic organism groups such as Bacteria (1), Fungi (12), Bryozoa (1), Foraminifera (3), and Porifera (6). Predominant endolithic sponges in the framework of L. pertusa are Alectona millari and Spiroxya heteroclita . Owing to its characteristic growth and surface ornamentation, trace casts of Spiroxya heteroclita are correlated to the well-known trace fossil Entobia laquea . Investigations of thin sections of post-mortem skeletons show a clearly pronounced endolithic tiering of three penetration depths. The analysed samples are divided into three macroscopic preservational stages differing in post-mortem age, and exposure of the framework. Bioerosion affects bare parts of the coral skeleton. Bioeroders preferably settle on one side of an upright growing colony. A succession usually starts with the infestation by bacteria and fungi. Contact zones of epiliths are preferred areas for penetration by endoliths. Sponges and foraminifers appear 10 cm below the zone of living polyps, followed by boring bryozoans 15 cm below. However, in one case the sponge Spiroxya heteroclita is documented in the skeleton of living polyps. Frameworks exposed to water host 19 ichnospecies, thus forming the most diverse ichnocoenosis, whereas nine ichnospecies are documented in coral specimens buried by sediment. Mapping of epi- and endoliths in living and freshly necrotic colonies represents a useful tool for monitoring environmental conditions and define ecological “health” of deep-water corals in a rapid large-scale assessment of the state of coral reefs.

We report an unusually shallow-water occurrence of habitat-forming Desmophyllum dianthus (Esper, 1794) from the Chilean fjord region. Most occurrences of the cosmopolitan D. dianthus are known from the bathyal zone. In the northern Chilean fjord region, however, this coral is reported within the euphotic zone. The upper limit of distribution was found at 7 m water depth and is confined to the lower boundary of the low salinity layer. Large accumulations both as living aggregations and as sediment-formers typically occur from 20 m water depth and beyond. The corals prefer to colonise the undersides of rock ledges with downwardfacing corallites. The motivation of this study is to analyse and discuss the existence of an azooxanthellate coral that generally thrives in aphotic environment but here extends into the photic zone by means of screening of bioerosion patterns. Based on the detailed analysis of scratching and boring traces, we compare the ichnocoenosis found within the Chilean D. dianthus with the established bathymetrically indicative ichnocoenoses from other areas around the world. These indicator ichnocoenoses are widely used to reconstruct relative water depths of depositional settings in the geological past. The study of the bioeroding assemblage from two living D. dianthus collected at 28 m water depth in the Reñihue Fjord, Chile, shows some remarkable patterns that shed light on the complex way in which the coral’s soft tissue expands and retracts at the apical zone of the corallum in response to in vivo infestation of endolithic algae. The role of this heterotypic interaction is discussed. To visualise the endolithic ichnocoenoses, we applied several methodologies such as the vacuum cast embedding technique combined with scanning electron microscopy, fluorescence microscopy and x-ray analyses. In total, 20 different trace makers are identified. Based on the analysis of the indicator ichnospecies, the endolithic community is indicative for the dysphotic zone. This result is compatible with the sciaphile environment of D. dianthus , living under rock ledges in the photic zone.

The habitat-forming scleractinian coral Lophelia pertusa supports an ecosystem that is widely known to occur in the bathyal marine ecologic realm along deep shelves, oceanic banks, seamounts and continental margins. Therefore, L. pertusa is generally considered a ‘deep-water’ or ‘deep-sea’ coral. In contrast, this study analyses the environmental controls of this bathyal ecosystem where it is thriving well in the non-bathyal shallow-water setting of the Swedish Kosterfjord area (NE Skagerrak). This is one of several shallow-water L. pertusa occurrences in Scandinavian waters where saline and temperature stable oceanic waters intrude as topographically-guided underflows onto the inner shelf and adjacent fjords, driven by an estuarine circulation. The L. pertusa occurrence of the Säcken site in the northern Kosterfjord exists at 80–90 m water depth and only a few tens of metres beneath a permanently brackish surface water layer. At the depth of the coral patches, however, the hydrographic data reveal fully marine conditions, which are ensured by a deeper inflow of Atlantic water through the Norwegian Trench into the Skagerrak. SEM analyses of resin casts taken from dead L. pertusa skeletons yield an endolith assemblage dominated by boring sponges such as Cliona spp. (trace: Entobia ispp.), the boring bryozoan Spathipora , the fungus Dodgella priscus (trace Saccomorpha clava ) and an unknown fungus (trace: Orthogonum lineare ). Such a composition exclusively of heterotroph organisms resembles the Saccomorpha clava / Orthogonum lineare ichnocoenosis which is regarded as indicative for fossil and Recent, open marine, aphotic environments. This interpretation is supported by direct light measurements at the Säcken site, which indicate aphotic conditions for at least most of the year. The finding of bathyal communities in comparatively shallow waters is linked to factors that force deeper oceanic water masses to surface. Such situations are likely to be expected where an estuarine circulation prevails, or in deep-sea basins bordered by narrow shelves and with local upwelling cells driven by the wind regime, facilitating the intrusion of eutrophic deeper waters to shallow depths — including the benthic communities. This circumstance reveals a major potential pitfall in the palaeobathymetric interpretation of fossil L. pertusa occurrences, which tend to be interpreted as bathyal palaeoenvironments. Strikingly, almost all known exposed ancient L. pertusa locations (e.g. Rhodes and Messina Strait in the Mediterranean Sea or the Cook Strait, New Zealand) derive from tectonically active regions with steep bathymetric gradients and a specific confined topography which could have forced deep water to the near surface.

Lophelia pertusa is a deep-sea scleractinian coral (azooxanthellate) found on the continental margins of the major world oceans. Built of aragonite it can be precisely dated and measured for stable isotope composition (C–O) to reconstruct past oceanic conditions. However, the relation between stable isotope and skeleton microstructures, i.e. centres of calcification and surrounding fibres, is crucial for understanding the isotopic patterns. Values for δ^18O and δ^13C in Lophelia pertusa were determined at a micrometer scale using an ion microprobe (SIMS - Secondary Ion Mass Spectrometry). In this coral species, centres of calcification are large (50 µm) and arranged in lines. The centres of calcification have a restricted range of variation in δ^18O (−2.8 ± 0.3 ‰ (V-PDB)), and a larger range in δ^13C (14.3 to 10.9 ‰ (V-PDB)). Surrounding skeletal fibres exhibit large isotopic variation both for C and O (up to 12 ‰) and δ^13C and δ^18O are positively correlated. The C and O isotopic composition of the centres of calcification deviate from this linear trend at the lightest δ^18O values of the surrounding fibres. The fine-scaled variation of δ^18O is probably the result of two processes: (1) isotopic equilibrium calcification with at least 1 pH unit variation in the calcification fluid and (2) kinetic fractionation. The apparent δ^13C disequilibrium in Lophelia pertusa may be the result of mixing between depleted δ^13C metabolic CO_2 (respiration) and DIC coming directly from seawater. This study underlines the close relationship between microstructure and stable isotopes in corals. This relationship must also be taken into consideration for major elements like Mg and trace elements (U-Sr-Ba) increasing the reliability of the geochemical tools used in paleoceanography.