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A number of reefs are found along the coast of northern Norway, and a cluster of particularly high reefs off Troms County at 70°N are known collectively as the Fugløy Reef. The reefs, up to 40 m high and more than 200 m wide, consist mainly of the reef-building Lophelia pertusa . Most of the reefs identified in the study area are located on moraine ridges in water depths of 140–190 m, and in water masses dominated by the relatively warm and saline Norwegian Current. Several of the reefs are located on the flanks of channels incising the moraine highs, where currents are tidally dominated and periodically reach velocities of 30 cm/s. Gravity cores were acquired from the reefs and their surroundings, and thorough analyses of the sampled sediments provide valuable information about three (paleo-) sedimentary environments surrounding the reefs. The immediate vicinity of the reefs consists of coarse and unsorted deposits that are interpreted to be moraine material deposited by the retreating inland ice. Elevated current velocities have prevented fine sediments from settling since the ice retreated. The second province is a pockmarked basin at water depths down to ∼300 m. Gravity cores from the basin reveal silty sand deposits of more than 4 m thickness representing postglacial sedimentation in the area. Gas analyses reveal that the hydrocarbons found in the sediments clearly are of biogenic origin, although it is somewhat enigmatic whether biogenic gas is the sole driving force behind the pockmarks in the area. No direct link between the reefs and the pockmarks is found. The third sedimentary province is characterised by resedimentation of coral debris, clearly illustrated by sorted deposits and U/Th-datings from the allochthonous deposits. Remobilisation of coral debris is modest in areal extent, but an important mechanism linked to the occurrence of the coral reefs.

During the ACES (Atlantic Coral Ecosystem Study) European Programme, various molecular methods were used to assess the genetic diversity of deep-water corals, by focusing on Lophelia pertusa , the main reef-building species in the northeast Atlantic. Investigations at a high taxonomic level aimed at understanding the evolutionary history of azooxanthellate corals by placing them in the phylogenetic tree of scleractinian corals, using partial sequences of the mitochondrial 16S region. The taxonomy of L. pertusa was consistent with morphological studies at the family level. However, eastern and western Atlantic specimens were genetically highly differentiated. Madrepora oculata was found to be incorrectly classified by morphological analysis. Intraspecific analyses were undertaken for L. pertusa , using specific microsatellite markers, to screen individuals collected at 10 different sampling sites, distributed along the European margin and in Scandinavian fjords. Sequencing of the ribosomal Internal Transcribed Spacer (ITS) 1 and 2 nuclear DNA regions was used as a complementary method. Both microsatellite and gene sequence data showed that L. pertusa is not constituted by one panmictic population in the northeast Atlantic, but instead forms distinct, offshore and fjord populations. Along the continental slope, the subpopulations are moderately differentiated. Although larvae might be dispersed along the European margin, the gene flow occurring among these subpopulations is likely to be sporadic, and must be considered in the light of the age of these coral communities, the prevalence of asexual reproduction in the development of the reefs and the longevity of individual clones. Inbreeding was shown at several sites, suggesting a high degree of self-recruitment. The level of genetic diversity and the contribution of asexual reproduction to the maintenance of the subpopulations were highly variable from site to site. These results are of major importance in the generation of a sustainable management strategy for these diversity-rich deep-sea ecosystems.

Seamount fauna are threatened by destructive fisheries practices, yet little is known about the physical and biological processes (e.g., dispersal and connectivity) that maintain species on seamounts. Gorgonian octocorals are among the dominant epifaunal taxa of many seamounts and represent a model taxon with which to understand processes of dispersal and gene flow in seamount fauna. One of the more common deep-sea octocorals on the seamounts and islands of the Hawaiian Archipelago is the precious coral Corallium lauuense . Here, we present results of a preliminary study to examine the population genetic structure of widely-distributed populations of C. lauuense within and among eight Hawaiian seamounts using three highly polymorphic microsatellite loci. Genic diversity and population differentiation estimated from the number of alleles, heterozygosity, and a hierarchical analysis of molecular variance revealed relatively high levels of genetic diversity as well as low yet significant levels of population differentiation among several of the seamounts and islands (predominantly among population comparisons with any site and the Kauai and Makapu’u coral beds). Despite these genetic differences between sites, population differentiation based on F _ST and R _ST for all sites was not significant at any locus. No linkage disequilibrium or pattern of isolation by distance was observed, and heterozygote deficiency was found in every population within at least one locus. The low heterozygosity throughout the Hawaiian Archipelago raises the concern that this species may be suffering from inbreeding depression. Further investigation of precious coral population demographic structure is needed to assess the risk of habitat loss and fisheries activities on these seamounts.

Many deep-water coral species have very broad global distributions and are eurybathic from depths of meters to kilometers. Such ecological breadth may be confounded by the presence of cryptic species. We are currently comparing the genetic distances between Paragorgia sp. and Primnoa sp. across their distribution and depth range in Canada using 18S ribosomal DNA (rDNA) sequences. Initial results show a confusing picture amongst the geographically distant Paragorgia taxa. Specimens of P. arborea from the Canadian Atlantic are very divergent from the specimen from the Canadian Pacific. The placement of Pennatula and Anthomastus relative to these taxa is also unexpected. We expect this topology to alter with the addition of more taxa and further testing.

Little is known of the basic biology and ecology of the numerous species of deep-water scleractinians found in all the world’s oceans. Of all the biological processes, reproduction is the most fundamental. Without knowledge of a species’ reproduction, we know little about how they survive both the environment that is the deep-sea, and the increasing anthropogenic effects of man’s exploration for new fisheries and energy reserves. This review collates current knowledge of the reproductive processes of deep-water scleractinians. Only fifteen deep-water species as yet have had their reproduction described in the literature. Gametogenesis, reproductive seasonality and larval ecology are summarised and compared briefly to shallow-water counterparts. A summary table of all deep-water scleractinian species, for which the reproductive strategy is known, and their sample locations, is presented here. It is hoped this knowledge will be used as a basis for further understanding of how the deep-sea species of this order survive and disperse. These data are also directly applicable to the conservation and management of these deep-sea ecosystems.

Reproductive ecology was examined in three deep-sea, reef-forming corals, Goniocorella dumosa, Solenosmilia variabilis and Enallopsammia rostrata from the ‘ Graveyard’ seamount complex on the Chatham Rise, New Zealand. Samples were collected from 890–1130 m depth in April 2001 using an epibenthic sled from the research vessel Tangaroa. S. variabilis was found to be gonochoric and this sexual trait was also suggested for E. rostrata and G. dumosa , although only colonies of one sex were collected. The likely mode of reproduction is broadcast spawning and fertilisation is likely to occur in late April or May coinciding with pelagic biomass accumulations at the end of summer. Reproductive development displayed a high level of synchrony among species and between seamount localities. E. rostrata was observed to contain both stage III and stage IV oocytes, indicating overlapping cohorts of oocyte growth, possibly related to food resources available. High fecundities were estimated for E. rostrata (>144 oocytes polyp^−1), G. dumosa (>480 oocytes polyp^−1) and S. variabilis (>290 oocytes polyp^−1), with a negative correlation between oocyte size and number observed for all three species.

The lipid and organic nitrogen isotopic (δ^15N) compositions of two common deep-water corals ( Lophelia pertusa and Madrepora oculata ) collected from selected locations of the NE Atlantic are compared to the composition of suspended particulate organic matter, in order to determine their principle food source. Initial results suggest that they may feed primarily on zooplankton. This is based on the increased abundances of mono-unsaturated fatty acids and alcohols and the different ratios of the polyunsaturated fatty acids, 22:6/20:5 of the corals when compared to those of the suspended particulate organic matter. There is enrichment in L. pertusa of mono-unsaturated fatty acids and of δ^15N relative to M. oculata . It is unclear whether this reflects different feeding strategies or assimilation/storage efficiencies of zooplankton tissue or different metabolism in the two coral species.

Colonial non-zooxanthellate corals from deep-water coral reefs, Lophelia pertusa and Madrepora oculata , produce large amounts of extracellular mucus (EMS). This mucus has various functions, e.g., an antifouling capability protecting the coral skeleton from attacks of endolithic and boring organisms. Both corals show thick epithecal and exothecal skeletal parts with a clear lamellar growth pattern. The formation of the epitheca is unclear. It is supposed that the EMS play a central role during the calcification process of the epithecal skeletal parts. Staining with the fluorochrome tetracycline has shown an enrichment of Ca^2+ ions in the mucus. In order to investigate this hypothesis, the protein content of the mucus and the intracrystalline organic matter from newly formed epithecal aragonite of Madrepora oculata was determined via sodium dodecyl sulfate (SDS) gel electrophoresis. Identical band patterns within both substances could be detected, one around 45 kDa molecular weight and a cluster around 30–35 kDa molecular weight. The occurrence of identical protein patterns within the mucus and in the newly formed aragonite confirms the idea that the mucus plays an important role during the organomineralization of the coral epitheca.

High densities of fishes in aggregations of deep-water corals (e.g., of the genera Primnoa, Paragorgia, Paramuricea ) do not necessarily indicate that corals are important habitats in terms of population processes. Frequency dependent distribution models provide a basis for assessing the role of deep-water corals. It is necessary to understand the overall habitat-related distributions of fish species, at particular life history stages, in order to assess the particular role of corals. Examining the landscape for ecologically equivalent habitats is one approach for assessing the importance of coral habitats. Measures of the functional equivalence of habitats are demonstrated, as an example, for sites from the Gulf of Maine on the northeast United States continental shelf. Fish census data based on surveys with a remotely operated vehicle in 2003 showed that communities in habitats dominated by dense corals and dense epifauna were functionally equivalent when compared with five other less complex habitats (e.g., boulder with sparse coral cover). Comparison of species-individual curves showed that sites with dense coral and dense epifauna habitats supported only moderate levels of fish diversity when compared with other sites. Further, density of Acadian redfish ( Sebastes fasciatus ) in dense coral and dense epifauna habitats, where this species was dominant, was not statistically different but was higher than an outcrop-boulder habitat with sparse epifauna (the only other site where this species was abundant). Such data suggest that coral habitats are not necessarily unique but have attributes similar to other important habitats. However, the level of their importance in the demography of fish populations and communities remains to be demonstrated. Focusing conservation efforts for deep-water corals on their perceived value to exploited species, without good demographic information on fish populations, may ultimately leave corals open to destructive fishing practices if new and contrary information emerges. Conservation efforts for corals, in the absence of explicit ties to managed fish species, might do better emphasizing the intrinsic value of corals, their slow growth, high sensitivity to disturbance, and the questionable potential for recovery.

Seamounts are drowned volcanoes rising from abyssal depths. Fishes on seamounts exploit a range of landscape features that likely enhance probabilities of prey capture and reduce predator success. The epifaunal community on seamounts is dominated by suspension-feeders of which deep-water corals are a dominant element. Such taxa are widespread components of seamount landscapes but their functional role in mediating the distribution and abundance of fishes remains unknown. Here we propose a hierarchical habitat classification matrix, which includes deep-water corals, as a foundation for partitioning seamount landscapes in which fishes are observed. This scheme is based on our observations of fish distributions from the New England Seamounts, as well as literature review. Features of an idealized seamount landscape were divided at multiple spatial scales and included features at habitat class, subclass and microhabitat levels. Habitat classes were divided by major sediment types (i.e., basalt, fine grained sediments). Habitat subclasses included pavement, ridges, walls, ledges and tubes for basalt substrates and flat sediment, ripples and waves for fine-grained sediments. Microhabitat features were classified as flow related features, emergent structures (i.e., geologic and biologic including deep-water corals), and other biogenic structures (e.g., coral debris, depressions, burrows). Variations in the distribution of structures at multiple spatial scales can influence boundary flows and the ability of fishes to search for prey (e.g., where active searching by swimming can occur, where pelagic prey delivery is sufficient when station-keeping) and avoid predators (e.g., the ability to efficiently exhibit various avoidance behaviors such as shelter seeking). Placing fish abundance data in such a matrix of habitat types enables a variety of statistical approaches for testing for non-random distributions of fishes on seamounts and quantifying the functional role of corals as fish habitat.