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6 pages, 2 figures, 2 tables, supplementary information https://doi.org/10.1186/s41200-021-00210-y, The living and dead fauna of Valencia Seamount, a deep promontory in the middle of the Balearic Basin which summit is at ca. 1100 m depth, is described by first time based in a rock dredge perfomed in a sedimentary area of the summit Mount. Surface-feeder polychaetes (the Paraonidae Levinsenia gracilis and Terebellidae as dominant), and taxodont bivalves (Ledella messanensis and Yoldiella ovulum) were the main species of benthos. We found alive remains of the bamboo coral Isidella elongata, a vulnerable, habitat-forming species in the deep Mediterranean. Benthos density was low (0.6 organisms/2 dm3 mud). Thanatocoenosis evidenced a rather moderate diversity of benthic bivalves (11 species) and gastropods (9 species) also dominated by surface deposit feeders. Fish (identified/quantified from sedimented otoliths) showed diversified and abundant mesopelagic fauna, mainly Myctophidae. More interestingly, we highlighted among benthopelagic fish the occurrence of recruits of Merluccius merluccius, Micromesistius poutassou, or Hymenocephalus italicus, all species that live in the neighboring slopes of the Iberian Peninsula and the Balearic Islands at quite shallower depths (at 100-700 m) than their distribution in the Valencia Seamount summit (1102–1130 m) based on the deposited otoliths found. Some ecological aspects were discussed and the necessity to consider the deep Valencia Seamount as a potential area that should be under protection, The study was financed by the MICYT project RECOMARES (RTI2018-094066-B-I00) funded by Ministerio de Ciencia e Innovación, MICYIT. [...]. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI), With the institutional support of the ‘Severo OchoaCentre of Excellence’ accreditation (CEX2019-000928-S)

The relationships between infaunal diversity and ecosystem function of biogenic structures in the Eastern Canadian Arctic remain poorly documented. Our study investigated the influence of sponge gardens at the Frobisher Bay site (137 m) and bamboo corals at the Baffin Bay site (1007 m) on the infaunal community structure and benthic ecosystem functioning. The occurrence of both types of biogenic structure type enhanced particular taxa and/or feeding guilds. A large density of suspension filter feeders was observed in bamboo coral sediment, whereas bare sediment exhibited a large proportion of nematodes and deposit-detritus feeders. Sponge gardens’ sediment showed a high proportion of isopods, Paraonidae polychaetes and up/down conveyors whereas bare sediment exhibited a large density of filter feeders. Through incubation cores, we measured ex situ benthic nutrient and oxygen fluxes at the sediment-water interface in each habitat and site. Biogeochemical fluxes varied significantly between habitats in the Baffin Bay site with a significant impact of bamboo coral habitat on nutrient fluxes (nitrate, ammonium, and silicate). Surprisingly, the sediment hosting bamboo corals acted as a source of nitrate and ammonium reaching values similar or higher to the Frobisher site despite the difference in water depth, and thus food supply between the two sites. These significant releases could derive from (i) a high organic matter deposition in bamboo coral habitat, allowed by their erected structure, (ii) a high efficiency of bioturbators (surficial modifiers and burrowers) mixing the surface layer of the sediment, and (iii) the difference in sediment type. Our study highlighted that, compared to its adjacent habitat, the presence of bamboo corals appeared to enhance the infaunal density and nutrient release of its sediment. In contrast, the impact of sponge gardens was not as clear as for bamboo coral habitat, likely due to the relatively significant presence of megabiota in the sponge garden adjacent habitat. Thus, our results based on a relatively small sample size, indicate that the bamboo coral habitat seems to increase the efficiency of deep-benthic ecosystem functioning, while that of sponge garden on the shallow ecosystem functioning remains uncertain.

Environmental conditions of deep-sea corals were monitored with instruments placed in and adjacent to three Hawaiian deep-sea coral patches dominated by gorgonian octocorals and zoanthid gold coral. Temperature, backscatter, and flow differed among and within the patches and highlighted distinctions in distribution of focus taxa (Hemicorallium laauense, Pleurocorallium secundum, Narella spp., Acanella dispar, Kulamanamana haumeaae). Two of the patches (Barbers Pt., Makapuʻu Pt.) had more than double the sustained mean flow of the third patch (Keahole Pt.), where backscatter levels of the passing water mass showed scattering strengths a third higher, suggesting greater food supply in the water at the Keahole Pt. patch. Further, spectral analysis of flow speed and direction suggests that flow at the first two high-flow sites (Barbers Pt., Makapuʻu Pt.) are dominated by semi-diurnal tidal forcing (flow changing 4x daily, direction 2x daily), while Keahole Pt. patch shows a distinct pattern more typical of diurnal forcing. Of the focus taxa, the two coralliids occupied a similar temperature range but differed in dominance between sites along a flow/scatter gradient, with the “red” coral, Hemicorallium laauense, found at the site with low flow (0.5-4.9 cm/s) and higher scatter (-28 dB) and the “pink” coral, Pleurocorallium secundum, seen at the patch with higher sustained flow (12.6-18.4 cm/s) and lower backscatter (-43 dB). Narella spp. spanned a 10 °C temperature range but were found more frequently at sites with the highest mean flow (18.4-21.7 cm/s). The final two corals, the parasitic zoanthid “gold” coral, Kulamanamana haumeaae, and its most common host, bamboo coral, Acanella dispar, were found at all three sites over a wide temperature range with flow ranging from 2.8 to 18.9 cm/s. The number of gold colonies was negatively correlated with flow even though that relationship was not apparent for the bamboo coral. These patterns were considered in relation to what is known about the life history of deep-sea corals and how they might influence community settlement, growth, and diversity.

13 pages, 8 figures, 5 tables, 1 appendix, We present an initial reconstruction of recent (last few centuries) mud-bottom faunal communities on the upper slope (398–667 m) of the continental margin off Catalonia (western Mediterranean), including periods free of any trawling impact. Radiometric dating of marine sediments and identification of faunal remains (e.g., fish otoliths, pteropod shells, coral sclerites) were performed to obtain a sediment geochronology in a 56 cm sediment core (MC4) taken at 398 m off the Ebro Delta in 2011. Core MC4 was especially rich in faunal remains, including, for example, 247 identifiable otoliths. A fine-scale chronology of MC4 was not possible due to sediment mixing. However, the depth of 210Pbxs penetration (20–22 cm) identified sediments older (below 22 cm depth) and younger (from core top to 22 cm) than ca. 100 years. Mass Accumulation Rate (MAR) from the 210Pbxs profile was estimated as 0.23±0.02 g cm−2 y−1. A significant peak of sclerites of the bamboo coral Isidella elongata was found between 4 and 8 cm in MC4, with remains of the axes and bases of Isidella colonies exclusively found at core depths >8–10 cm, which would correspond (MAR results) to the period 1980–1985. Such structures were not found in the 0–8 cm layer, likely an effect of trawling that started in the area in the 1980s. Other changes both in benthos (corals and cirripedes) and zooplankton (pteropods) seemed to be related with Ebro river discharge, with changes coinciding with massive damming of the Ebro and tributary rivers in the 1950s and until 1965. Mesopelagic fish also showed temporal oscillations in MC4. Abundance of some myctophid remains (Lampanyctus croccodilus and Benthosema glaciale) was related with positive NAO periods and with rather high temperature in Levantine Intermediate Waters. By contrast, periods of higher dominance of Ceratoscopelus maderensis off Catalonian coasts could indicate lower salinity during the past and a progressive degree of eutrophication in intermediate waters in recent decades. A general decline in myctophids otolith abundance during the last ca. 100 years could be related to changes in the temperature and salinity of deep-water masses and a decline in ocean productivity that would also have affected open-water fish stocks, This study was financed within the framework of the MICYT project ANTROMARE, but it was especially possible thanks to the multi-methological work designed in proposals like TRENDSEAS and PELMAR (CTM2014-54018-C3, which were not funded by Ministerio de Economía y Competitividad)

Seamounts represent ecologically important marine environments and undeniably play a crucial role in the functioning of the deep-sea ecosystems, thanks primarily to their contribution in supporting offshore benthic and pelagic biodiversity. In the last decades, these features have received attention in all oceans of the world, but they were relatively overlooked in the Mediterranean Sea. In particular, the Ligurian Sea hosts six major structures, whose summits, ranging from 150 to nearly 2000 m depth, are virtually unknown from the biological point of view. The summit region of the Janua Seamount, located approximately at 40 nautical miles off the harbour of Genoa at 810 m depth, was explored for the first time using Remotely Operated Vehicles. The sea bed topography is characterized by a heterogeneous hard bottom, dominated by sub-fossil thanatocoenoses of Lophelia pertusa (Linnaeus, 1758) covered in a thick Ferrous-Manganese crust, and colonized by a scattered bathyal assemblage dominated by hexactinellids and benthic cnidarians showing a distinct regionalization around the summit. Cnidarians observed in this site include a rare Atlantic bamboo coral (Isididae, Chelidonisis aurantiaca Studer, 1890), described herein for the first time for the Mediterranean Basin. These findings provide new information on the biogeographic patterns of colonization of the bathyal Mediterranean fauna but also highlight the large knowledge gap that still exists for deep-sea biodiversity of this basin.

Keratoisis grayi is one of the most abundant large gorgonian corals found off Newfoundland and Labrador, yet we know little regarding the factors influencing its distribution, abundance, and condition. We employed remotely operated vehicle (ROV) transect data collected in three canyons off the Grand Banks, Newfoundland to quantitatively examine the influence of depth, bottom type, canyon, and trawling intensity on K. grayi abundance, height, and condition at small spatial scales. While surveying 105 km of seafloor with a ROV, we observed 5770 K. grayi colonies and 167 trawl marks. We found that K. grayi were significantly more likely to occur in boulder areas than in cobble or gravel. Bottom depth related positively and significantly with colony height and our models predict that the largest bamboo coral colonies occur in boulders in Halibut Channel, and in boulders and cobble in Haddock Channel. The majority of colonies observed were alive and undamaged, but tipped, broken, dead and partially dead colonies were also recorded. K. grayi were more likely to occur in trawled areas, but these colonies were more likely to be damaged, broken, smaller in size, and less abundant than colonies outside trawled areas. These results demonstrate a negative impact of bottom trawling on K. grayi colonies off Newfoundland and Labrador and that fishers may specifically target areas where these corals occur.

The bamboo coral Isidella elongata is a key structuring species on deep muddy bottoms, which has suffered severe consequences from bottom-fishing activities, as it often co-occurs with precious fishery resources such as red shrimps. A five-year series of data collected during a scientific trawl survey was used to localize the presence and to characterize the associated megafauna over a wide spatial scale in the Western and Central Mediterranean (Sardinia, South-Central Tyrrhenian, Western Ionian and Southern Adriatic). In addition, the overlap of I. elongata hotspots with nursery and spawning areas of three selected species (Aristaeomorpha foliacea, Aristeus antennatus and Galeus melastomus) was analysed. The sizes of the colonies were analysed in the South-Central Tyrrhenian and the Southern Adriatic. No significant variation over time was observed in the former, while in the latter, the colonies were bigger but showed a decreasing trend over time.

During two expeditions to seamounts near the Mariana Trench in the tropical western Pacific, several trochiform shells from the upper bathyal zone were sampled. Morphological observations of these specimens suggest that they represent two new species that belong to the family Trochidae, but the shell morphology, radular plan, and external anatomy differ considerably from those of closely related genera. A new subfamily, Carinotrochinae subfam. nov., and a new genus, Carinotrochus gen. nov., are proposed herein to accommodate these two species. Carinotrochus marianaensis sp. nov., the type species, was associated with coral debris at a depth of 865 m, and Carinotrochus williamsae sp. nov. was discovered crawling on a hydroid Stegolaria sp. that was attached to a dead bamboo coral at a depth of 1332 m. Genertic analysis of mitochondrial COI, 16S rRNA, and nuclear 28S rRNA genes using maximum likelihood, Bayesian inference, and pairwise uncorrected p-distances confirmed that the new taxa are trochids but do not belong to any existing defined subfamily. Molecular clock analysis based on concatenated sequences (COI, 16S, and 28S) indicated that Carinotrochinae subfam. nov. split from its shallow water sister subfamily Trochinae roughly 80 Mya during the Late Cretaceous.

A mono-specific population of Isidella elongata in the Ventotene Basin (Pontine Islands, western Mediterranean Sea) was recently revealed by ROV survey. This vulnerable marine community was found on top of a 3.6 km long morphological high, in water depths between 510 and 560 m. Side scan sonar data showed the presence of several trawl marks suggesting a high anthropogenic impact of the study area. Furthermore, multibeam and high-resolution seismic data revealed the presence of widespread pockmarks, indicating occurrence of fluids in the sub-seafloor.

Radiocarbon ( 14 C) measurements are an important tool for determining growth rates of bamboo corals, a cosmopolitan group of calcitic deep-sea corals. Published growth rate estimates for bamboo corals are highly variable, with potential environmental or ecological drivers of this variability poorly constrained. Here we systematically investigate the application of 14 C for growth rate determinations in bamboo corals using 55 14 C dates on the calcite and organic fractions of six bamboo corals (identified as Keratoisis sp.) from the western North Atlantic Ocean. Calcite 14 C measurements on the distal surface of these corals and five previously published bamboo corals exhibit a strong one-to-one relationship with the 14 C of dissolved inorganic carbon (DI 14 C) in ambient seawater ( r 2 =0.98), confirming the use of Keratoisis sp. calcite 14 C as a proxy for seawater 14 C activity. Radial growth rates determined from 14 C age-depth regressions, 14 C plateau tuning and bomb 14 C reference chronologies range from 12 to 78 µm y −1 , in general agreement with previously published radiometric growth rates. We document potential biases to 14 C growth rate determinations resulting from water mass variability, bomb radiocarbon, secondary infilling (ontogeny), and growth rate nonlinearity. Radial growth rates for Keratoisis sp. specimens do not correlate with ambient temperature, suggesting that additional biological and/or environmental factors may influence bamboo coral growth rates.

Special issue Bridging the gap between the shallow and deep oceans: The key role of submarine canyons.-- 13 pages, 9 figures, 2 tables, The impacts of fishing activities on ecosystems represent an acknowledged environmental issue, especially considering the increasing demands for the conservation of biodiversity. Submarine canyons are complex environments that can harbor high biodiversity of benthic ecosystems and high biomass of fish species, thus representing preferential fishing areas for bottom trawling fleets. The effects of bottom trawling on the benthic epifauna were investigated over the soft-bottom margins of the Gioia Canyon (Southeastern Tyrrhenian Sea) by means of quantitative analysis of Remote Operated Vehicle (ROV) video transects and compared with the recent pattern of trawling intensity, reconstructed through processing of data collected with the Vessel Monitoring System (VMS). Four ROV transects were then performed at 320–540 m depth in areas affected by different trawling pressure. The analysis was focused on the bamboo coral Isidella elongata and the sea pen Funiculina quadrangularis, which are considered indicator taxa of Vulnerable Marine Ecosystems (VMEs) and relevant in terms of sustainable management priorities. I. elongata only occurred at the two deeper stations, below 400 m depth. This species showed a clear relationship with trawling intensity, since its abundance was significantly higher under low trawling intensity, where coexistence of large (>20 cm height) and small colonies was observed. The relatively high prevalence of small colonies in areas exposed to higher trawling effort was interpreted as a consequence of the trawling activity that removed the larger colonies. However, the frequent occurrence of dead colonies and the diffuse presence of epibionts (e.g. the anemone Amphianthus dohrnii and the hydroid Clytia linearis) on living colonies indicate stressful conditions for I. elongata even in areas where trawling intensity was lower. Conversely, the relationship between trawling intensity and species abundance was not straightforward for F. quadrangularis; despite the lowest abundance of this species was recorded in areas subject to high trawling intensity, relatively high abundances were observed in areas with intermediate trawling effort. Although such distribution may be driven by other environmental factors, it suggests that vulnerability to bottom trawling can be different for the two species

Keratoisis is a genus of bamboo coral commonly reported in the northwest (NW) Atlantic as a result of fishing bycatch or by in situ observations. In 1999, a scientific trawl survey recovered fragments of Keratoisis sp. in southeast Baffin Bay (NW Atlantic), but colonies had never been seen in situ at this location until 2013, when a remotely operated vehicle (ROV) was used to survey this location. Here we report the presence of dense forests of Keratoisis sp. in a muddy environment at depths >900 m. Colonies were found as dense patches up to ~55 m long along the ROV track and were estimated to reach ~1 m in height. At this location, Keratoisis sp. appears to have branched root-like structures probably used for anchorage on mud. The majority of colonies were alive, but fragments of dead colonies were also observed, especially in the path of the 1999 bottom trawl tow. Based on visual observation, the dense stands of Keratoisis sp. in this environment seem to form structure and habitat for other invertebrates and fishes in an otherwise mainly muddy environment.

The critically endangered “bamboo coral” Isidella elongata is a near-endemic protected species for which limited information exists in the Eastern Mediterranean Sea. The aim of this work was to update the known geographical distribution of I. elongata in the Eastern Mediterranean by combining literature data with unpublished records (from experimental fisheries surveys and ROV observations) made within the last two decades. Our study revealed 35 records of I. elongata occurrence spanning across the entire Aegean ecoregion. It has been found at a depth range of 126–1125 m. A considerable number of records, in some cases with multiple colonies, were identified in the North Aegean Sea and the Hellenic Trench. This study showed that the distribution range of this key species in the Eastern Mediterranean Sea is wider than previously thought and provides a baseline for future research and conservation initiatives in Eastern Mediterranean deep waters.

This study presents the results of seafloor habitat identification and mapping of a NE Atlantic deep seamount. An “assemble first, predict later” approach has been followed to identify and map the benthic habitats of the Galicia Bank (NW Iberian). Biotic patterns inferred from the survey data have been used to drive the definition of benthic assemblages using multivariate tools. Eight assemblages, four hard substrates and four sedimentary ones, have been described from a matrix of structural species. Distribution of these assemblages was correlated with environmental factors (multibeam and backscatter data) using binomial GAMs. Finally, the distribution model of each assemblage was applied to produce continuous maps and pooled in a final map with the distribution of the main benthic habitats. Depth and substrate type are key factors when determining soft bottom communities, whereas rocky habitat distribution is mainly explained by rock slope and orientation. Enrichment by northern water masses (LSW) arriving to GB and possible zooplankton biomass increase at vertical-steep walls by “bottom trapping” can explain the higher diversity of habitat providing filter-feeders at slope rocky breaks. These results concerning vulnerable species and habitats, such as Lophelia and Madrepora communities and black and bamboo coral aggregations were the basis of the Spanish proposal of inclusion within the Natura 2000 network. The aim of the present study was to establish the scientific criteria needed for managing and protecting those environmental values, This study was financed by the EC contract INDEMARES-LIFE (07/NAT /E/000732)

Little is known about the factors that affect the growth rates of deep-water corals. Analysis of 23 specimens of bamboo corals, a ubiquitous deep-water group, that were reliably aged using radiometric techniques or validated increment counts indicates that the radial growth rate of the coral's calcite internode declines with depth and increases logistically with ambient temperature. Temperature alone accounts for about half of the variance among specimens in lifetime mean growth rates. Growth rates plateau below 2°C and above 5°C, which likely reflects physiological constraints on growth and calcification. Thus far, the only other effect on growth rate identified is a tendency for colonies from the NE Pacific to grow faster relative to ambient temperature than colonies in other regions. Analysis of elemental composition of the calcite internode, based on data available for 16 of the 23 specimens, shows that, contrary to suggestions in the literature, growth rate does not correlate with Sr/Ca ratios, neither among or within colonies. Rather, within-colony ontogenetic variability in increment width, an index of short-term growth rate, correlates positively with calcium weight-frac- tions and negatively with the ratio between P and S, an index of organic content. The underlying mechanism is likely to be a link between crystal ultrastructure, which varies with growth rate, and the ratio between CaCO3 and organic matrix in different crystal types. Between colonies, composi- tion correlates poorly with growth rate. This could reflect spatial and temporal heterogeneity in other environmental factors that determine internode composition, as well as difficulties in standardising P measurements across specimens.

Bamboo corals from Davidson Seamount and from the Gulf of Alaska were aged using a refined 210 Pb dating technique. The goal was to determine growth rates and age for several bam- boo corals with higher precision. Radiometric results for 2 Davidson Seamount corals (Keratoisis sp.) converged on a radial growth rate of ~0.055 mm yr -1 . One colony was aged at 98 ± 9 yr, with an aver- age axial growth rate of ~0.7 cm yr -1 . The age of a large colony was >145 yr with an estimated axial growth rate of 0.14 to 0.28 cm yr -1 . Inconsistent rates may indicate nonlinear axial growth. A Keratoi- sis sp. specimen from the Gulf of Alaska was aged at 116 ± 29 yr from a radial growth rate of ~0.056 mm yr -1 , which led to an average axial growth rate of ~1.0 cm yr -1 . An Isidella tentaculum colony was aged at 53 ± 10 yr and grew most rapidly with a radial growth rate of ~0.10 mm yr -1 and an average axial growth rate of ~1.4 cm yr -1 ; however, the 210 Pb decay pattern may have provided evidence for either a hiatus in radial growth or environmental changes in 210 Pb. Our findings of slow growth and long life compared favorably with other bamboo coral studies and provided age estimates with greater precision. The high longevity of bamboo coral is an indication that recovery from dis- turbance or removal may take decades to a century. These age data provide a basis for a defensible position on the protection of bamboo coral and essential information for describing other life history characteristics.

Bamboo corals (Family Isididae) are an important component of seamount benthos south of Tasmania. Besides having lifespans of up to 400 yr, little is known about their basic ecology, nor how to decode potential climate signals encoded in their skeletons. We explored the stable nitrogen isotope and radiocarbon compositions of the skeletal organic fraction of the genera Isidella, Keratoisis and Lepidisis collected from 3 Tasmanian seamounts. Analyses were performed on tissues and organic node growth rings sampled at a temporal resolution of 1 to 4 yr. Radiocarbon chronologies exhibited nuclear bomb signals characteristic of surface waters and constrained radial growth rates to ~35 ± 10 µm yr–1 for 3 specimens of the genus Lepidisis and 113 ± 17 µm yr–1 for 1 specimen of Isidella. δ15N values of the living tissue and underlying gorgonin were similar and averaged 9 to 12‰. Records of δ15N from 8 different specimens showed subtle, quasi-decadal patterns over the last ~100 yr, although the amplitude of these features (~1‰) was similar to the average intra- and intercolony reproducibility. These results demonstrate the utility of deep-sea corals to track seamount biogeochemical processes over long time scales, and suggest that the extent of nutrient depletion of surface waters and associated trophic dynamics have remained relatively constant in this region over centuries. This provides an important baseline for the evaluation of the impacts of anthropogenic climate change.

The DNA barcoding initiative has advocated the use of the 5′-end (∼ 658 bp) of mitochondrial (mt) cytochrome c oxidase subunit 1 ( cox1 ) to genetically distinguish species. However, this has proven difficult within the subclass Octocorallia due to extraordinarily low substitution rates within mt protein-coding genes. Intergenic regions (IGRs), which have been little examined among octocorals, may be subject to high mutation rates and have proven useful target regions at both the interspecific and population levels of metazoans. Herein we examine a mt IGR ( igr4 ) between the cytochrome b ( cob ) and NADH dehydrogenase subunit 6 ( nad6 ) genes among species of the bamboo coral subfamily Keratoisidinae to evaluate its utility for barcoding and phylogenetic studies. Among 77 keratoisidin specimens, we found igr4 to vary in length between either 42 bp ( Acanella Gray, 1870 and Orstomisis Bayer, 1990) or 302–605 bp ( Isidella Gray, 1857 , Lepidisis Verrill, 1883, Keratoisis Wright, 1869 , and two undescribed genera). We interpreted the short igr4 sequence of Acanella eburnea (Pourtales, 1868) as potentially indicative of additional mt genome-related novelties and thus sequenced its entire mt genome; gene content and gene order were the same as in a previously-sequenced bamboo coral mt genome. Alignment of the longer igr4 sequences included 108 parsimony-informative characters, as well as numerous indels ranging from 2–262 bp in length. Uncorrected pairwise ‘ p ’ distances indicated sequence variation of 0–27.2%, as compared to 0–4.8% among the same specimens for the MutS homolog ( msh1 ), currently the most widely sequenced octocorallian mt gene, and cox1 for a subset of the taxa. Despite the greater levels of variation, fewer unique haplotypes were observed at igr4 compared to msh1 ; however, in combination, the two gene regions revealed increased mt haplotype diversity relative to either gene region on their own.

We test two hypotheses, that annual environmental cycles produce periodic variability in the skeletal composition of deep-water gorgonians, and that these cycles can be counted to determine the coral's age. Annual periodicity of deposition was tested by comparing the internode composition of bamboo corals live-collected 10 years apart in the Southern Ocean. The validity of the comparison was substantiated by growth rates for the 10-year interval (77–121 μm/yr) that were confirmed by radiocarbon analysis. Variability in Mg/Ca and possibly S/Ca, but not Sr/Ca or P/Ca, was consistent with annual cycles of deposition. However, spectral analysis of Mg/Ca data for a larger coral showed little or no spectral peak associated with an annual cycle of deposition (though there were peaks at periods of 4–5 and 11–15 years). The absence of an annual peak is likely to reflect growth rates that vary over time, coral cross-sections that change shape over time, and interannual differences in the seasonal range of environmental variability. The resulting subjectivity in what defines an annulus, along with evidence that the nature and extent of annual periodicity differs among sites, means that the technique is likely to be inherently imprecise and to require independent validation for each site and taxon before it can be applied.

Using bomb-14C dating and growth ring counting methods, we calculate life spans and growth rates of six species of deep-sea corals collected at depths of between 400 and 900 m from the continental slope of Newfoundland and Labrador. Bamboo corals ( Acanella arbuscula , Keratoisis ornata ) and antipatharians ( Stauropathes arctica ) secrete concentric growth rings in their axial skeletons, which were proven to form annually for K. ornata and S. arctica. These species had the lowest radial growth rates of 33 ± 11 to 75 ± 11 μm·year–1. Primnoa resedaeformis and Paramuricea spp. had higher radial growth rates of 83 ± 6 to 215 ± 37 μm·year–1. Paragorgia arborea had the highest radial growth rate of 830 ± 120 μm·year–1. Axial growth rates ranged from 0.56 ± 0.05 cm·year–1 for a specimen of Paramuricea spp. to 2.61 ± 0.45 cm·year–1 for a specimen of Primnoa resedaeformis . Life spans ranged from 18 ± 4 years for a live-collected P. resedaeformis to 200 ± 30 years for a subfossil specimen of K. ornata. Because all of the corals were from heavily fished areas, it is likely that age distributions are biased towards smaller and younger colonies. Recovery of deep-sea corals from fishing-induced damage will take decades to centuries.

Fabric and growth mode of deep-water isidid gorgonian skeletons showing bright Mg-calcitic internodes and dark proteinageous nodes were investigated on modern, subrecent and fossil skeletons. The internodial microstructure is characterised by three-dimensionally interfingering calcitic fascicles accreting around a central axis. Macroscopic colour banding results from varying orientations of organic-rich fascicle bundles and intercalated bands of organic-poor granular crystals. This skeletal structure of isidid gorgonians strikingly differs from the density banding of scleractinians. Radiocarbon dating of a fossil skeleton gave an age of 3,985±35 to 3,680±35 years before present (BP) with a record of 305±35 years (±range). Linear extension rates of 0.4 mm year−1 average allow for an annual to sub-annual resolution on micrometer scale of colour bands or fascicles, respectively. The growth mode of branched skeletons is characterised by simultaneous secretion of vertically alternating nodes/internodes and lateral accretion of concentric increments enveloping the entire skeleton. Bifurcations at various growth stages imply that adjacent branches have different ages and show varying numbers of growth bands at any skeletal cross section. The scleroprotein gorgonin plays a crucial role in the formation of organic nodes and the secretion of calcitic internodes by providing a structural framework in the biomineralisation process.

The Keratoisidinae are a poorly known, but phenotypically diverse group of deepwater corals. Recent developments in deepwater trawling in the southwest Pacific have provided many more specimens of bamboo corals. Two sub-regions of the mitochondrial genome were sequenced to test genetic relationships among specimens collected over a wide geographical range (27–50° S): a sub-region of the large-subunit rRNA (16S rRNA), characterized by a highly variable insertion/deletion (INDEL#2) region; and a non-coding region between COII and COI. Based on DNA haplotypes, 14 species of Keratoisidinae were recognized among 88 specimens from deep water in the southwest Pacific Ocean. The common haplotypes also appeared in specimens collected in the northwest Pacific Ocean and may indicate that some bamboo coral species are widespread in the Pacific, or that the mitochondrial markers are insensitive to recent speciation events. Many specimens were taken from flat bottom areas and, contrary to assumptions, the bamboo corals are not endemic to seamounts. The closure of some seamounts to trawling will protect bamboo corals from extinction, but not from local depletion.

Sustainable fisheries require (1) viable stock populations with appropriate harvest limits and (2) appropriate habitat for fish to survive, forage, seek refuge, grow and reproduce. Some deep-water habitats, such as those formed by deep-water stands of coral, may be vulnerable to fishing disturbance. The rate at which habitat can be restored is a critical aspect of fishery management. The purpose of this study was to characterize growth rates for a habitatforming deep-sea coral. Two nearly complete colonies of red tree coral (Primnoa resedaeformis) collected from waters off southeast Alaska were used for an analysis of age and growth characteristics. CAT scans revealed that colonies consisted of multiple settlement events, where older basal structures provided for settlement of new colonies. The decay of 210 Pb over the length of the colony was used to validate age estimates from growth ring counts. Age estimates were over 100 yr for sections near the heavily calcified base. Based on validated growth ring counts, growth of red tree coral ranged from 1.60 to 2.32 cm per year in height and was approximately 0.36 mm per year in diameter. These growth rates suggest that the fishery habitat created by red tree coral is extremely vulnerable to bottom fishing activities and may take over 100 years to recover.

A subfossil fragment of the deep-sea gorgonian coral Primnoa resedaeformis was 14C AMS dated along a radial growth transect. Dates ranged from 2600±50 at the outside, to 2920±60 14C years BP near the interior, suggesting an age of

The deep-sea gorgonian coral Primnoa resedaeformis has an arborescent skeleton composed of both calcite and a horn-like structural protein called gorgonin. We have investigated potential climate records in corals from Alaska, the eastern seaboard of Canada and the United States, and a Southern Ocean (Pacific sector) seamount. Temperatures at these sites range from 4 to ∼10 °C. δ18O values of the calcite show strong evidence for isotopic disequilibrium. Extraction of δ18O paleotemperatures is therefore not straightforward. Sr/Ca data, analyzed by Secondary Ion Mass Spectrometry (SIMS), suggest that temperature might be a control on calcite Sr/Ca in Primnoa resedaeformis, but that growth-related kinetic effects could also be important. Based on previous 14C, δ13C and δ15N measurements, it has been suggested that particulate organic matter (POM) from the surface is an important carbon source to the polyps and the gorgonin fraction of the Primnoa skeleton. δ15N and δ13C of polyps and gorgonin show similar regional differences to δ15N and δ13C of surface POM. Polyps and contemporaneous gorgonin correlate strongly for both δ13C and δ15N. The influence of nutrient isotopic composition and climate and productivity variations on the isotopic composition of surface POM may therefore be recorded in gorgonin layers. These corals have very long lifespans (several centuries). The potential exists, therefore, to obtain extended records of surface productivity, deep ocean temperature and chemistry of value to climatologists and fisheries managers.

The variability of magnesium, strontium and calcium concentrations in the two skeleton types (sclerites and axis) of the red coral (Corallium rubrum) was assessed by using X-ray fluorescence spectroscopy and microprobe analysis as a prerequisite for their use as ecological indicators. Axis cross sections showed light and dark circular growth bands corresponding to fast and slow growth, respectively. Using microprobe analyses the Mg and Sr concentrations ranged from 2.8 to 3.0% and from 0.21 to 0.29%, respectively, in the sclerites and from 2.4 to 3.0% and from 0.1 to 0.28%, respectively, in the axis. Mg/Ca and Sr/Ca ratios varied within sclerites (average, 12% for both ratios) and within the axis of single colonies (average, 20% for Mg/Ca and 48% for Sr/Ca). Sr/Ca ratios in the axis were lower in fast-growing branch tips than in older, more basal parts of the colonies, whereas the Mg/Ca ratio did not differ significantly between colony regions. Mg/Ca and Sr/Ca ratios in the axis decreased significantly with depth, and we estimated an increase of the Mg/Ca ratio of 0.004–0.006 per degree Celsius. In all depth layers, Sr/Ca ratios showed a significant direct relationship with skeleton density in axis cross sections, whereas there was no significant relationship for Mg/Ca. Overall, our data indicate that temperature promotes the incorporation of Mg in C. rubrum as in other calcite skeletons, whereas Sr concentrations are inversely related to growth rate. This preliminary study suggests that Mg and Sr concentrations in the axis of the red coral have a strong potential as ecological indicator for temperature and growth rate.