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Cold‐water corals (CWCs) are important species that provide habitat for other taxa but are sensitive to mechanical damage from bottom trawling. CWC conservation has been implemented in the form of marine protected areas (MPAs), but recovery from impact may be particularly slow in the deep‐sea environment; consequently, the use of restoration techniques has been considered. To gain some insight into CWC recruitment and growth, in 2011 we deployed small seabed moorings in the Darwin Mounds MPA (~1,000 m water depth). This site hosts hundreds of CWC mounds, that had previously (until 2003) been impacted by deep‐water trawling. In 2019, we carried out in situ visual surveys of these moorings and the surrounding seabed environment, then recovered two of the moorings. The mooring buoys, glass floats with plastic covers, were extensively colonized by a diverse epifauna that included the CWCs Desmophyllum pertusum and D. dianthus. The presence of coral recruits indicated that environmental conditions, and larval supply, remained favorable for the settlement and growth of CWCs within the MPA. Based on our observations, we consider four possible restoration methods, together with a "do‐nothing" option, for the Darwin Mounds CWCs that have shown little, if any, natural recovery despite 16 years of protection. We conclude that seabed emplacement of high‐relief artificial substrata is likely to be the most efficient and cost‐efficient means of promoting enhanced recovery of the CWCs. [ABSTRACT FROM AUTHOR]

Climate change is reorganizing the planet's biodiversity, necessitating proactive management of species and habitats based on spatiotemporal predictions of distributions across climate scenarios. In marine settings, climatic changes will predominantly manifest via warming, ocean acidification, deoxygenation, and changes in hydrodynamics. Lophelia pertusa, the main reef‐forming coral present throughout the deep Atlantic Ocean (>200 m), is particularly sensitive to such stressors with stark reductions in suitable habitat predicted to accrue by 2100 in a business‐as‐usual scenario. However, with new occurrence data for this species along with higher‐resolution bathymetry and climate data, it may be possible to locate further climatic refugia. Here, we synthesize new and published biogeographic, geomorphological, and climatic data to build ensemble, multi‐scale habitat suitability models for L. pertusa on the continental margin of the southeast United States (SEUS). We then project these models in two timepoints (2050, 2100) and four climate change scenarios to characterize the occurrence probability of this critical cold‐water coral (CWC) habitat now and in the future. Our models reveal the extent of reef habitat in the SEUS and corroborate it as the largest currently known essentially continuous CWC reef province on earth, and also predict abundance of L. pertusa to identify key areas, including those outside areas currently protected from bottom‐contact fishing. Drastic reductions in L. pertusa climatic suitability index emerged primarily after 2050 and were concentrated at the shallower end (<~550 m) of the regional distribution under the Gulf Stream main axis. Our results thus suggest a depth‐driven climate refuge effect where deeper, cooler reef sites experience lesser declines. The strength of this effect increases with climate scenario severity. Taken together, our study has implications for the regional and global management of this species, portending changes in the biodiversity reliant on CWC habitats and the critical ecosystem services they provide. [ABSTRACT FROM AUTHOR]

Cold‐water coral reefs constitute important biodiversity hotspots in aphotic waters around the world. The complex, highly variable morphology of the reef habitat‐forming species has important implications for the communities they harbor and for the physical processes occurring therein. Lophelia pertusa (Desmophyllum pertusum) is one of the most common reef‐building cold‐water corals, but its morphological diversity has never been characterized on a broad scale. We qualitatively and quantitatively explored the patterns of morphological variation of this species over a wide geographic and ecological range, addressing corallite and colony traits and their interrelation. Geographic variation is evident at both corallite and colony level, although with distinct trends. By linking branching patterns to colony morphology, we identified three main morphotypes (asymmetrical, bushy, and columnar) with substantial geometric and architectural differences, which suggest high functional diversity of cold‐water coral reefs across regions. Colony morphology appears strongly governed by asexual budding of individual polyps, but largely decoupled from corallite morphology. We hypothesize that colony morphology is primarily driven by local hydrodynamic conditions and associated food supply. [ABSTRACT FROM AUTHOR]

Aim: The Deepwater Horizon disaster resulted in the largest accidental marine oil spill in history and caused extensive injury to deep‐sea habitats, including cold‐water coral communities dominated by Paramuricea species. One of the primary difficulties in assessing the full extent of the injury to cold‐water coral ecosystems is the extreme paucity of observational data and the subsequent lack of knowledge of their distribution within the affected region. The aim of this study was to use habitat suitability modelling to estimate the number of potentially affected Paramuricea sp. corals across the northern Gulf of Mexico. Location: Northern Gulf of Mexico. Taxon: Cold‐water corals in the genus Paramuricea. Methods: High‐resolution (12.5 m) models were built using the maximum entropy (Maxent) approach using remotely sensed data including seafloor topography, seismic reflectivity, temperature and the amount of productivity exported from the surface. Model outputs were used to estimate the number of potential coral sites in the northern Gulf of Mexico, delineated as areas with both high habitat suitability scores and the presence of hard substrate. The number of coral sites was further adjusted using a ground‐truthing procedure using autonomous underwater vehicle‐transect data. Results: Across the entire study area in the northern Gulf of Mexico, there were 558 predicted coral sites, covering an area of 14.2 km2. Within a 2,291 km2 region shown to have been directly affected by the spill and subsequent oil plume, there were 66 predicted coral sites covering an area of 1.2 km2 with an average of 63 corals per site. Main Conclusions: Our results indicate that the magnitude of injury stemming from the spill was likely far higher than previously known, and will help quantify the full extent of the losses incurred as well as prioritize disturbed areas for future research and restoration efforts. [ABSTRACT FROM AUTHOR]

Data from two experimental longline surveys and two video inspections carried out in Santa Maria di Leuca cold‐water coral province (Mediterranean Sea) during spring–autumn 2010 were used in order to compare the benthopelagic abundance and diversity between coral and non‐coral habitats and between different devices. The sampling was carried out in two types of habitat: a coral habitat with carbonate mounds and a non‐coral habitat characterized by intermound sea floor.A Bayesian hierarchical modelling approach to accommodate factors influencing community assemblages was used considering the number of species, the Shannon–Wiener diversity index and the two most abundant species represented by the European conger (Conger conger) and blackbelly rosefish (Helicolenus dactylopterus).A relevant effect of the habitat factor was observed for both the number of species and the diversity index, showing a higher species number and diversity index in the coral habitat than in the non‐coral habitat. Concerning the relevance of fixed effects from the model on the probability of observing non‐zero (positive) abundances, the devices considered, longline and baited lander, did not show different influence for either C. conger or H. dactylopterus. In the case of positive abundance, a relevant device effect was only observed for H. dactylopterus, showing higher abundances for longline than for baited lander. A habitat effect was detected, with positive abundances for both species in the coral habitat.This study proves that structurally complex habitats generated by cold‐water corals influence the distribution and diversity of the benthopelagic fauna, and that the use of different devices can provide complementary useful results. Increased knowledge about the role of cold‐water corals in the associated benthopelagic fauna could lead to better conservation of one of the most important hot spots of biodiversity in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Cold‐water coral (CWC) ecosystems are protected both in national and international waters. They are considered Vulnerable Marine Ecosystems and, in addition, meet the criteria to be defined ecological or biological significant areas.Two new sites of the "Sardinian CWC province" were discovered by means of remotely operated vehicle surveys in two submarine canyons in the north‐eastern portion of the Sardinian continental margin, at depths ranging from 230 to 430 m.Dense and healthy patches of small and medium‐sized Madrepora oculata colonies were found dwelling on rocky walls and inclined silted soft bottoms.A rich and diverse associated megafauna was found within both live and dead portions of the coral framework. In addition, the presence of benthic litter and derelict fishing gears were also documented.These results further extend the "Sardinian CWC province" extension, providing insights of a potential CWC network along the Sardinian continental margin with implications for the Mediterranean mosaic of CWC provinces, further stressing the need for urgent conservation measures for these habitats. [ABSTRACT FROM AUTHOR]

While ocean acidification is a global issue, the severity of ecosystem effects is likely to vary considerably at regional scales. The lack of understanding of how biogeographically separated populations will respond to acidification hampers our ability to predict the future of vital ecosystems. Cold-water corals are important drivers of biodiversity in ocean basins across the world and are considered one of the most vulnerable ecosystems to ocean acidification. We tested the short-term physiological response of the cold-water coral Lophelia pertusa to three pH treatments (pH = 7.9, 7.75 and 7.6) for Gulf of Mexico (USA) and Tisler Reef (Norway) populations, and found that reductions in seawater pH elicited contrasting responses. Gulf of Mexico corals exhibited reductions in net calcification, respiration and prey capture rates with decreasing pH. In contrast, Tisler Reef corals showed only slight reductions in net calcification rates under decreased pH conditions while significantly elevating respiration and capture rates. These differences are likely the result of environmental differences (depth, pH, food supply) between the two regions, invoking the potential for local adaptation or acclimatization to alter their response to global change. However, it is also possible that variations in the methodology used in the experiments contributed to the observed differences. Regardless, these results provide insights into the resilience of L. pertusa to ocean acidification as well as the potential influence of regional differences on the viability of species in future oceans. [ABSTRACT FROM AUTHOR]

The tall sea pen Funiculina quadrangularis has a patchy distribution around the UK, being found in sheltered waters below 20 m depth on the northwest coast of Scotland and Ireland. The limited distribution and sensitivity to bottom fishing activities make F. quadrangularis vulnerable to reduction in population numbers that may lead to genetic isolation and reduced diversity. Because of this vulnerability and low resilience to physical disturbance, the tall sea pen is recognised as a Species of Principle Importance under the Natural Environment and Rural Communities Act, 2006, UK. () and is also on the Biodiversity Action Plan list of Priority Species for the UK. In the Mediterranean it is recognised as a sensitive and essential fish habitat because it forms habitat for several commercially important crustaceans. The aim of this study was to understand the current state of the genetic structure and gene flow of F. quadrangularis in areas of NW Scotland. We developed 10 microsatellite markers and used them to genotype 176 samples from four populations. Overall, our results suggest that there is high genetic diversity and high gene flow between colonies of F. quadrangularis in and among locations in Loch Linnhe and Loch Duich. As a result of the high rates of gene flow, genetic differentiation between sites was low. This may provide resilience to human impacts if distant populations have a high connectivity. However, care must be taken, as small but significant isolation by distance was found between the most geographically distant sites and only a small part of the species range was examined in this study. The genetic tools developed here will provide a foundation for wider studies of this vulnerable species. [ABSTRACT FROM AUTHOR]

Aim The distribution of vulnerable marine ecosystems in the deep sea is poorly understood. This has led to the emergence of modelling methods to predict the occurrence of suitable habitat for conservation planning in data-sparse areas. Recent global analyses for cold-water corals predict a high probability of occurrence along the slopes of continental margins, offshore banks and seamounts in the north-eastern Atlantic, but tend to overestimate the extent of the habitat and do not provide the detail needed for finer-scale assessments and protected area planning. Using Lophelia pertusa reefs as an example, this study integrates multibeam bathymetry with a wide range of environmental data to produce a regional high-resolution habitat suitability map relevant for marine spatial planning. Location Irish continental margin (extended continental shelf claim). Methods Maximum entropy modelling was used to predict L. pertusa reef distribution at a spatial resolution of 0.002°. Coral occurrences were assembled from public databases, publications and video footage, and filtered for quality. Environmental predictor variables were produced by re-sampling of global oceanographic data sets and a regional ocean circulation model. Multi-scale terrain parameters were computed from multibeam bathymetry. Results Suitable habitat was predicted on mound features and in canyon areas along a narrow band following the slopes of the Irish continental margin, the Rockall Bank and the Porcupine Bank. Standard deviation of the seabed slope (54%), temperature (28%) and bottom shear stress (9%) were the most important variables to predict coral distribution. Main conclusions This is the first regional coral habitat suitability modelling study to incorporate full coverage multibeam bathymetry in the deep sea. The use of high-resolution environmental data and quality-controlled distribution data significantly reduces habitat overestimation demonstrated by global-scale analyses and produces detailed maps to support marine protected area network design. The strong response of the corals to local-scale terrain variability highlights the need to protect the seabed from anthropogenic impacts that may reduce its complexity, such as bottom trawling. [ABSTRACT FROM AUTHOR]

Cold-water coral mound morphology and development are thought to be controlled primarily by current regime. This study, however, reveals a general lack of correlation between prevailing bottom current direction and mound morphology (i.e. footprint shape and orientation), as well as current strength and mound size (i.e. footprint area and height). These findings are based on quantitative analyses of a high-resolution geophysical dataset collected with an Autonomous Underwater Vehicle from three cold-water coral mound sites at the toe of slope of Great Bahama Bank. The three sites (80 km2 total) have an average of 14 mounds km−2, indicating that the Great Bahama Bank slope is a major coral mound region. At all three sites living coral colonies are observed on the surface of the mounds, documenting active mound growth. Morphometric analysis shows that mounds at these sites vary significantly in height (1 to 83 m), area (81 to 6 00 000 m2), shape (mound aspect ratio 0·1 to 1) and orientation (mound longest axis 0 to 180°). The Autonomous Underwater Vehicle measured bottom current data depict a north-south flowing current that reverses approximately every six hours. The tidal nature of this current and its intermittent deviations during reversals are interpreted to contribute to the observed mound complexity. An additional factor contributing to the variability in mound morphometrics is the sediment deposition rate that varies among and within sites. At most locations sedimentation rate lags slightly behind mound growth rate, causing mounds to develop into large structures. Where sedimentation rates are higher than mound growth rates, sediment partially or completely buries mounds. The spatial distribution and alignment of mounds can also be related to gravity mass deposits, as indicated by geomorphological features (for example, slope failure and linear topographic highs) in the three-dimensional bathymetry. In summary, variability in sedimentation rates, current regime and underlying topography produce extraordinarily high variability in the distribution, development and morphology of coral mounds on the Great Bahama Bank slope. [ABSTRACT FROM AUTHOR]

Authigenic gypsum was found in a gravity core, retrieved from the top of Mound Perseverance, a giant cold-water coral mound in the Porcupine Basin, off Ireland. The occurrence of gypsum in such an environment is intriguing, because gypsum, a classic evaporitic mineral, is undersaturated with respect to sea water. Sedimentological, petrographic and isotopic evidence point to diagenetic formation of the gypsum, tied to oxidation of sedimentary sulphide minerals (i.e. pyrite). This oxidation is attributed to a phase of increased bottom currents which caused erosion and enhanced inflow of oxidizing fluids into the mound sediments. The oxidation of pyrite produced acidity, causing carbonate dissolution and subsequently leading to pore-water oversaturation with respect to gypsum and dolomite. Calculations based on the isotopic compositions of gypsum and pyrite reveal that between 21·6% and 28·6% of the sulphate incorporated into the gypsum derived from pyrite oxidation. The dissolution of carbonate increased the porosity in the affected sediment layer but promoted lithification of the sediments at the sediment-water interface. Thus, authigenic gypsum can serve as a signature for diagenetic oxidation events in carbonate-rich sediments. These observations demonstrate that fluid flow, steered by environmental factors, has an important effect on the diagenesis of coral mounds. [ABSTRACT FROM AUTHOR]

The Darwin Mounds are small (up to 70 m in diameter), discrete cold-water coral banks found at c. 950 m water depth in the northern Rockall Trough, north-east Atlantic. Formerly described in terms of their genesis, the Darwin Mounds are re-evaluated here in terms of mound growth processes based on 100 and 410 kHz side-scan sonar data. The side-scan sonar coverage is divided into a series of acoustic facies representing increasing current speed and sediment transport/erosion from south to north: pockmark facies, ‘mounds within depressions’ facies, Darwin Mound facies, stippled seabed facies and sand wave facies. Mound morphometric changes are quantified and show a south-to-north divergence from an inherited morphology, reflecting the outline of coral-colonized fluid escape structures, to developed, downstream elongated, elevated mound forms. It is postulated that increasing current speeds and bedload sand transport favour mound growth and development by a process of enhanced sand sedimentation within mounds due to current deceleration by frictional drag around coral colonies. Comparisons are made with similar growth processes attributed to comparably sized cold-water coral mounds in the Porcupine Seabight, offshore Ireland. [ABSTRACT FROM AUTHOR]

Aim The large biogenic structures formed by colonial cold-water scleractinian corals provide valuable habitat for marine invertebrates on seamounts and the continental slope of all world oceans. These patchily distributed long-lived structures are easily damaged by several human activities, particularly bottom trawling for fish, and are potentially vulnerable to ocean acidification caused by climate change. Consequently, an important conservation question is whether these structures support a specialized invertebrate fauna restricted to these habitats. Here we investigate the relationship between structures formed by the coral Solenosmilia variabilis and its associated ophiuroid (brittlestar) fauna, one of the dominant components of deep-sea ecosystems. Location Seafloor habitat around Southern Australia, New Zealand, and the Macquarie Ridge from 35 to 53° S and 117° E–176° W, 500–1500 m depth. Methods Data were derived from samples collected by numerous scientific expeditions to the study region. Because these samples were collected using a variety of gear and effort, a two-step approach was used. First, the largest consistently collected data set (73 ophiuroid species from 59 samples) was assembled for multivariate analysis. ANOSIM was used to test for differences in ophiuroid community composition between Solenosmilia and non- Solenosmilia habitat on seamounts and the continental slope, and SIMPER was used to identify species that characterized Solenosmilia habitat. Second, these results were validated against all known data to ensure that these characteristic species had not been found in non- Solenosmilia habitat elsewhere. Results The ophiuroid assemblages from Solenosmilia habitat were distinct from those found on other habitats on the continental slope and offshore seamounts across the study region. Although a suite of ophiuroid species characterized Solenosmilia habitat, most have also been collected from dead coral or other rubble, suggesting a physical rather than biological association between the coral matrix and its associated invertebrate fauna. Main conclusions Despite the lack of an exclusive ophiuroid–coral relationship, cold-water scleractinian coral remains the principal habitat for a number of ophiuroid species across southern Australia and New Zealand. The slow growth rate of the coral and the low dispersal potential of some associated species suggest that recovery of damaged cold-water coral assemblages will be a long-term process. [ABSTRACT FROM AUTHOR]

The azooxanthellate scleractinian coral Lophelia pertusa has a near-cosmopolitan distribution, with a main depth distribution between 200 and 1000 m. In the northeast Atlantic it is the main framework-building species, forming deep-sea reefs in the bathyal zone on the continental margin, offshore banks and in Scandinavian fjords. Recent studies have shown that deep-sea reefs are associated with a highly diverse fauna. Such deep-sea communities are subject to increasing impact from deep-water fisheries, against a background of poor knowledge concerning these ecosystems, including the biology and population structure of L. pertusa. To resolve the population structure and to assess the dispersal potential of this deep-sea coral, specific microsatellites markers and ribosomal internal transcribed spacer (ITS) sequences ITS1 and ITS2 were used to investigate 10 different sampling sites, distributed along the European margin and in Scandinavian fjords. Both microsatellite and gene sequence data showed that L. pertusa should not be considered as one panmictic population in the northeast Atlantic but instead forms distinct, offshore and fjord populations. Results also suggest that, if some gene flow is occurring along the continental slope, the recruitment of sexually produced larvae is likely to be strongly local. The microsatellites showed significant levels of inbreeding and revealed that 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. [ABSTRACT FROM AUTHOR]

The scleractinian coral, Lophelia pertusa, is distributed globally on continental slopes, mid-oceanic ridges and in fjords. This species forms cold-water reefs, which are associated with a diverse animal community. These communities are poorly understood but are currently under threat from human activities. Molecular markers are required to assess the spatial genetic population structure of this key species for management and conservation purposes. Ten polymorphic microsatellite loci were isolated for Lophelia pertusa using an enriched partial library technique. Nine loci showed significant differences from Hardy-Weinberg expected genotype frequencies, eight of which showed heterozygote deficiencies. [ABSTRACT FROM AUTHOR]