Occurrence Of Corals Research Articles

First report of Devonian corals from the Bitlis-Pötürge Massif (SE Turkey): a rare occurrence of corals on the northern margin of Gondwana

The Bitlis-Pötürge Massif of SE Turkey is a metamorphic belt separating the Arabian Plate from the Taurides. It includes a non-metamorphic Palaeozoic sequence that contains locally fossiliferous strata. Here is reported for the first time an assemblage of Upper Devonian rugose and tabulate corals from the Meydan Formation, composed of the rugose Frechastraea schafferi (PENECKE), Peneckiella cf. teicherti HILL, Pseudopexiphyllum supradevonicum (PENECKE), and Macgeea desioi VON SCHOUPPÉ, and the tabulate Thamnopora reticulata (DE BLAINVILLE), Alveolites ex. gr. suborbicularis and Scoliopora sp. The rugose corals suggest a Late Frasnian age. The palaeobiogeographic affinities of corals are discussed. The species F. schafferi and the genus Pseudopexiphyllum –so far only reported from Turkey, Iran and Afghanistan– are probably limited to the northern margin of Gondwana and therefore diagnostic for this palaeogeographic area. Until now, the northern margin of Gondwana yielded very few Upper Devonian corals so this occurrence in SE Turkey is particularly important to estimate the relationship between these corals and the ones from the northern margin of the Palaeotethys Ocean.

Tidal Dynamics Control on Cold-Water Coral Growth: A High-Resolution Multivariable Study on Eastern Atlantic Cold-Water Coral Sites

Cold-water coral communities form complex benthic ecosystems in a distinct part of the water column. The exact processes supporting reef growth and changes with time are still partly unsolved. Recent studies have suggested a tidally driven hydraulic control of flow over topographic features as a driver for local downwelling at cold-water coral sites. This mechanism forms a link between surface and coral growth depths and is a driver of resuspension of the bottom material. Only few studies have concentrated on how these processes vary with the health status and structure of the cold-water coral occurrences. In this study, we explore the processes over tidal cycles by analysing in situ stratification, hydrography and velocity data which we then combine with local topography from seven Lophelia pertusa dominated eastern Atlantic cold-water coral sites. The “quality” of coral sites varies from thriving reefs to declining and dead coral sites. We show that living and healthy corals are concentrated at sites, where local hydrodynamics create overturning and mixing which support food supply for filter-feeding corals.

Stability and decline in deep-sea coral biodiversity, Gulf of Mexico and US West Atlantic

Characterizing deep-sea coral biodiversity is essential to evaluate the current state of deep-sea ecosystems and to assess vulnerability to anthropogenic threats such as offshore drilling and ocean acidification. Thousands of deep-sea coral records from the past 6 decades are compiled in the publicly accessible NOAA database, but few large-scale analyses of deep-sea coral biodiversity through time have been conducted. This study provides the longest temporal analysis of deep-sea coral generic biodiversity (58 yr), and the first such study for US waters. To mitigate missing temporal and spatial data, a machine learning model was employed to simulate deep-sea coral occurrences. Patterns of deep-sea coral generic biodiversity were calculated for observed and simulated data from 1960 to 2018 in the US marine ecoregions of the Gulf Stream Slope, Carolinian Atlantic Shelf and Slope, South Florida/Bahamian Atlantic Shelf and Slope, and Northern Gulf of Mexico (NGOM) Shelf and Slope. There were statistically significant decreases in deep-sea coral generic biodiversity for all ecoregion/depth pairs in simulated data and most ecoregion/depth pairs in observed data. There was relative stability in biodiversity from 1960 to the mid-2000s, followed by generally rapid decreases between 2007 and 2011. Biodiversity stabilized after 2011, though it remains at the lowest average level in the past 58 yr. Most ecoregions and depths show the lowest generic richness during the most recent time interval (2010–2018) compared to the preceding 5 decades. The most persistent deep-sea coral genera from 1960 to 2018 vary based on ecoregion and depth. Rapid decreases in biodiversity support previous work showing deep-sea corals can undergo biodiversity loss in less than 4 yr, which is alarming given their slow growth and decadal recovery times. This analysis provides a robust temporal framework for future researchers to evaluate casual mechanisms affecting deep-sea coral biodiversity and inform on conservation strategies.

Spatial-temporal variations in echinoderm diversity within coral communities in a transitional region of the northeast of the eastern pacific

Echinoderms associated with coral communities in the Easter Pacific compose a conspicuous assemblage that alters their ecosystem structure and composition. The environmental conditions in the transitional region of Central Mexican Pacific (CMP) present high variability associated with climatic seasons and El Niño-Southern Oscillation (ENSO) events. In order to understand it, a research was held during four years (2011-2014) throughout the CMP region with seven conspicuous echinoderm indicator species. Echinoderms diversity, distribution, and density were measured, and also their relation with benthic coverage, depth, rugosity, and temperature. The echinoderm assemblages changed in density and diversity among localities and regions over the years. Their presence was positive related with the occurrence of algal turf and corals, but absent in the presence of coral rubble and fleshy macro-algae. Also, during the negative phase of ENSO/2011, the increase of algal turf favored the abundance of echinoids. Subsequent to ENSO, their density decreased but the richness of the echinoderm assemblage remained stable, suggesting that coral communities in the study area possess a strong resilience, where local abiotic and biotic factors maintain a dynamic balance in echinoderm populations.

The Value of a Deep-Sea Collection of the Azores (NE Atlantic Ocean): Marine invertebrate biodiversity in an era of global environmental change

The deep ocean is the largest and least explored biome with the highest richness of species and phylogenetic biodiversity on Earth. The high costs of using sophisticated technological means to access deep-sea ecosystems gives an inestimable value to specimens collected in these environments. Azorean scientists have long started collaborating with fishermen to collect deep-sea marine invertebrate fauna accidentally captured during fishing activities, thus obtaining deep-sea organisms opportunistically. Specimens have been stored and catalogued at the Department of Oceanography and Fisheries – University of the Azores’ Marine Biological Reference Collection (COLETA) since 2006. The collection has been continuously growing through oceanographic cruises and fisheries observer programs in the framework of several national and international collaborations. Currently, COLETA has 14367 specimens and samples corresponding to 10827 databased entries representing mostly corals (3415) and sponges (1941) of the deep sea (Fig. 1), for which data are available until 2012 (Institute of Marine Research (IMAR - Azores), Portugal and Department of Oceanography and Fisheries (DOP) - UAC, Portugal 2015). Specimens and associated metadata have contributed for the the taxonomy, population genetics and life history (age, growth, reproduction) of corals and other organisms. The homonym COLETA database, besides the taxonomic identification and photography of the specimen, has metadata including geographic location, depth, and the method of collection (e.g. survey, fishing). Thus, COLETA has also been instrumental in the mapping of distribution of biodiversity and vulnerable marine ecosystems such as coral gardens, sponge grounds, hidrarian gardens and sea pen fields in the Azores Exclusive Economic Zone (EEZ). Efforts have been made to make COLETA compatible with other databases, such as the database of historical records of cold-water coral occurrences in the Azores (e.g. Prince Albert of Monaco Campaigns in the 19th century) and other fisheries databases, in order to maximize its potential to study trends in biodiversity loss related to climate change and fisheries impacts. Underwater images of live specimens from video surveys have also been cross-referenced with specimens stored at COLETA in an effort to join taxonomists and ecologists in the characterization of new habitats. Curated collections and datasets based on vouchered records, which can be continuously consulted, are essential to study deep-sea biodiversity. A continuously growing collection has also the potential of adding a time frame to the study of the impact of climate change, fishing and pollution on the deep-sea. In an era of biodiversity loss, COLETA represents a good example of where physical specimens and associated metadata databases can be combined to research and discover species, to achieve ecosystem conservation and guide marine spatial planning.

Occurrence and distribution of the coral Dendrophyllia ramea in Cyprus insular shelf: Environmental setting and anthropogenic impacts

Occurrence and abundance of deep-water corals in the Levantine Mediterranean Sea is still largely unknown. This is the first attempt to quantitatively describe a Dendrophyllia ramea population discovered in June 2015 during the CYCLAMEN expedition on board the Research Vessel Aegaeo. This population is the deepest ever described until now in the Mediterranean and was found on the outer insular shelf off eastern Cyprus (Protaras, 35°02′N; 34°05′E). Video transects conducted by means of a remotely operated vehicle revealed a well-developed population of D. ramea located on a sandy seabed at 125–170 m depth. The highest density was 6 colonies m−2 and on average 1.6 ± 1.4 (SD) colonies m−2. The population consists of isolated or piled up branches of various sizes and large colonies, some ∼50 cm max width. The corals thrive on soft bottoms, representing a rather novel aspect of the research on D. ramea, since the species is still considered to be mostly associated with rocky substrates. The occurrence of the species in sedimentary grounds makes it especially vulnerable to bottom contact fishing gears as bottom trawling. Spatial distribution of the coral population, as well as a first attempt to characterize its habitat, are explored as an approach to describe the habitat's suitability and the vulnerability for the species in the area.

Corals recruit onto live and dead shells of the bivalve Modiolus philippinarum

We report the occurrence of coral recruits on bivalve shells of Modiolus phillipinarum, which served as an effective substrate for coral larval settlement within the reef area Gulf of Mannar, India.

Occurrence of hard coral (Genus Montipora) common in Elphinstone Island and its adjacent areas of Myeik Archipelago, Myanmar

Occurrence of hard coral (Genus Montipora) common in Elphinstone Island and its adjacent areas of Myeik Archipelago, Myanmar

Effects of competition on the territorial behaviour of a farmer damselfish, Plectroglyphidodon lacrymatus (Perciformes: Pomacentridae).

Aggression and territory size of the farmer damselfish Plectroglyphidodon lacrymatus were examined in the presence of adjacent territories of conspecific and heterospecific farmers that maintain algal turf territories on the reefs of Anda, north-western Philippines. Plectroglyphidodon lacrymatus territories with no adjacent neighbours had a mean size of 1.2 m2 whereas those adjacent to conspecifics were 47% smaller. In contrast, the mean size of territories adjacent to a heterospecific farmer (i.e., Pomacentrus burroughi, Pomacentrus chrysurus) did not differ from that of solitary individuals. Aggression towards conspecific farmers (84% probability) was higher than heterospecific farmers (31%). The higher aggression towards conspecific farmers suggests that the energetic costs for defence increased, which may have caused a decrease in territory sizes. Despite the higher aggression towards conspecific farmers, the thickness and percentage cover of algae inside the territories of focal fish did not appear to vary according to type of neighbouring farmer although algal turf cover was higher and juvenile coral occurrence was lower inside than outside the territories. Our results show that the territorial behaviour of P. lacrymatus varies with conspecific and heterospecific farmers, which may influence their distribution and benthic habitat characteristics.

Holocene and Pleistocene fringing reef growth and the role of accommodation space and exposure to waves and currents (Bora Bora, Society Islands, French Polynesia)

AbstractHolocene fringing reef development around Bora Bora is controlled by variations in accommodation space (as a function of sea‐level and antecedent topography) and exposure to waves and currents. Subsidence ranged from 0 to 0·11 m kyr−1, and did not create significant accommodation space. A windward fringing reef started to grow 8·7 kyr bp, retrograded towards the coast over a Pleistocene fringing reef until ca 6·0 kyr bp, and then prograded towards the lagoon after sea‐level had reached its present level. The retrograding portion of the reef is dominated by corals, calcareous algae and microbialite frameworks; the prograding portion is largely detrital. The reef is up to 13·5 m thick and accreted vertically with an average rate of 3·12 m kyr−1. Lateral growth amounts to 13·3 m kyr−1. Reef corals are dominated by an inner Pocillopora assemblage and an outer Acropora assemblage. Both assemblages comprise thick crusts of coralline algae. Palaeobathymetry suggests deposition in 0 to 10 m depth. An underlying Pleistocene fringing reef formed during the sea‐level highstand of Marine Isotope Stage 5e, and is also characterized by the occurrence of corals, coralline algal crusts and microbialites. A previously investigated, leeward fringing reef started to form contemporaneously (8·78 kyr bp), but is thicker (up to 20 m) and solely prograded throughout the Holocene. A shallow Pocillopora assemblage and a deeper water Montipora assemblage were identified, but detrital facies dominate. At the Holocene reef base, only basalt was recovered. The Holocene windward–leeward differences are a consequence of less accommodation space on the eastern island side that eventually led to a more complex reef architecture. As a result of higher rates of exposure and flushing, the reef framework on the windward island side is more abundant and experienced stronger cementation. In the Pleistocene, the environmental conditions on the leeward island side were presumably unfavourable for fringing reef growth.

First report of a Messinian coralgal facies in a terrigenous setting of Central Apennines (Italy) and its palaeogeographic significance

The upper Miocene dominantly terrigenous succession cropping out at Monte San Fabrizio (Simbruini Mts.) shows peculiar, previously unreported bio‐sedimentological features, which bring fresh elements in a regional palaeogeographic/palaeotectonic key. Overlying the regional foredeep succession, an array of different lithofacies either form mappable outcrops or occur as clasts, remarkably not referable to any stratigraphic units already known in the Central Apennines. These lithologies, which include coral‐bearing siliciclastic sediments, mixed carbonate/siliciclastic deposits with benthic macrofaunas, rhodalgal facies, and conglomerates, essentially made of Mesozoic pelagic lithoclasts, are here grouped in a comprehensive informal unit, called Monte San Fabrizio Unit (MSFU). The most striking feature of the MSFU is a coralgal facies characterized by the occurrence of zooxanthellate (z) corals (Porites and Siderastrea crenulata). While the age of these deposits is not directly determinable due to the lack of biostratigraphic markers, their composition and field relationships clearly place their origin within a late‐orogenic setting: only the uplift, subaerial exposure, and erosion of large portions of the pre‐orogenic stratigraphy, also belonging to different geological domains, and subsequent sediment transport by rivers, can account for the heterogeneous composition of the conglomerates. Their sedimentological characters (i.e., shape and size of the clasts) suggest reworking of the pebbles in a shore environment. A shallow marine photic environment is confirmed by the presence of z‐corals, red algae, and abundant macrofauna. The occurrence of Porites and Siderastrea crenulata represents the first occurrence of corals subsequent to the drowning of the bryozoan limestone carbonate factory, being the youngest occurrence of corals in the Central Apennines and the first ever post‐Burdigalian z‐corals described in the region. This also constrains the age of the MSFU as early–middle (pre‐evaporitic) Messinian, due to the almost total demise of z‐corals known in the Mediterranean in response to the Messinian Salinity Crisis. In conclusion, sedimentology, palaeobiology, and field geology all point to a shallow‐water environment, close to a shoreline, for the MSFU. This unit can be interpreted as representing the vestiges of an ephemeral depositional environment, such as a small wedge‐top basin, an evidence that this portion of the Apennine chain was already structured in the early–middle Messinian.

High precision U-series dating of scleractinian cold-water corals using an automated chromatographic U and Th extraction

High-precision U-series dating of scleractinian cold-water corals is a key chronological tool for studies of past environmental and climate conditions. Here, we tested and optimized an automated chemical extraction system (ESI prepFAST-MC equipped with an Eichrom TRU-resin chromatographic column) for its ability to purify U and Th isotopes for mass spectrometric U-series dating at the sub-‰ precision level. Chemical yields are constantly high, on average around 90% for both U and Th. Analytical blanks are comparable to manual purification (<0.15pg U, 0.15pg Th for a typical sample of 50mg) and memory effects due to the recycling of the column are mostly insignificant as the carry-over fraction is about 10−5 for Th and 10−3 for U isotopes. However, it was found that the built-in UTh (TRU-resin) column must be pre-conditioned for analysis using >1μgg−1 Th and U in order to achieve the above mentioned chemical yields. This conditioning has no impact on the Th/U data. The automated chemical preparation protocol described here is compared to conventional high precision U-series dating with manual sample purification. For the 34 cold-water corals extracted from a sediment core collected from a coral mound off Angola, the differences between 230Th/238U- and 234U/238U-ratios and U-series ages measured with the two analytical methods are smaller than the respective analytical uncertainty of <3.0‰, 0.8‰ and 3.0‰, respectively. Overall, ages of the studied corals span 34,000years and perfectly meet quality control constrains, such as initial seawater δ234U0. Finally, our record of coral ages indicates vigorous coral growth under warm and cold climate conditions in the temperate south-eastern Atlantic, contrasting climate influenced coral occurrences in the north-eastern Atlantic.

Towards a new paleotemperature proxy from reef coral occurrences

Global mean temperature is thought to have exceeded that of today during the last interglacial episode (LIG, ~ 125,000 yrs b.p.) but robust paleoclimate data are still rare in low latitudes. Occurrence data of tropical reef corals may provide new proxies of low latitude sea-surface temperatures. Using modern reef coral distributions we developed a geographically explicit model of sea surface temperatures. Applying this model to coral occurrence data of the LIG provides a latitudinal U-shaped pattern of temperature anomalies with cooler than modern temperatures around the equator and warmer subtropical climes. Our results agree with previously published estimates of LIG temperatures and suggest a poleward broadening of the habitable zone for reef corals during the LIG.

Is substrate composition a suitable predictor for deep-water coral occurrence on fine scales?

Species distribution modelling can be applied to identify potentially suitable habitat for species with largely unknown distributions, such as many deep-water corals. Important variables influencing species occurrence in the deep sea, e.g. substrate composition, are often not included in these modelling approaches because high-resolution data are unavailable. We investigated the relationship between substrate composition and the occurrence of the two deep-water octocoral species Primnoa resedaeformis and Paragorgia arborea, which require hard substrate for attachment. On a scale of 10s of metres, we analysed images of the seafloor taken at two locations inside the Northeast Channel Coral Conservation Area in the Northwest Atlantic. We interpolated substrate composition over the sampling areas and determined the contribution of substrate classes, depth and slope to describe habitat suitability using maximum entropy modelling (Maxent). Substrate composition was similar at both sites - dominated by pebbles in a matrix of sand (>80%) with low percentages of suitable substrate for coral occurrence. Coral abundance was low at site 1 (0.9 colonies of P. resedaeformis per 100m2) and high at site 2 (63 colonies of P. resedaeformis per 100m2) indicating that substrate alone is not sufficient to explain varying patterns in coral occurrence. Spatial interpolations of substrate classes revealed the difficulty to accurately resolve sparsely distributed boulders (3–5% of substrate). Boulders were by far the most important variable in the habitat suitability model (HSM) for P. resedaeformis at site 1, indicating the fundamental influence of a substrate class that is the least abundant. At site 2, HSMs identified cobbles and sand/pebble as the most important variables for habitat suitability. However, substrate classes were correlated making it difficult to determine the influence of individual variables. To provide accurate information on habitat suitability for the two coral species, substrate composition needs to be quantified so that small fractions (<20% contribution of certain substrate class) of suitable substrate are resolved. While the collection and analysis of high-resolution data is costly and spatially limited, the required resolution is unlikely to be achieved in coarse-scale interpolations of substrate data.

MIOCENE SCLERACTINIAN CORALS OF GAVDOS ISLAND, SOUTHERN GREECE: IMPLICATIONS FOR TECTONIC CONTROL AND SEA-LEVEL CHANGES

Low-diversity scleractinian patch reefs that have been developed, during Early to Middle Tortonian, in Gavdos island are studied, aiming in a better understanding of the time and space relationships of the reef development and the associated basin fill evolution. Gavdos island consists part of a tectonically active setting constituting the southernmost extension of the Hellenic arc (Eastern Mediterranean). A representative Tortonian section (Bo section), located in the northwest part of the island, which hosts a mass occurrence of hermatypic corals, is studied. Scleractinian samples were collected from the upper 12 m of the section, which is characterized by interchanges of marly limestone and compact marls. The reefs are represented by the coral species Heliastraea oligophylla, Porites maicientensis, Thegioastraea roasendai and Porites collegniana. The microfacies analysis showed that the mediumto-thin-bedded carbonates of the limestone-marl alternations comprise patch reefs (boundstones-framestones, SMF 16, sensu Wilson, 1975, FZ 7-8, sensu Flügel 1982) consisted of screractinian corals. Corals are associated with corallinacean algae. Patch reefs are associated by bioclastic packstones-floatstones, characterized by benthic foraminifera, calcareous algae, spines of echinoids, gastropods and molluscs. Reefs are laterally associated by a bioclastic limestone rich in planktonic forams, associated by detrital material (fragments of quartz, feldspars, quartzites and cherts). The studied reef facies have been dolomitized and cemented in the meteoric realm. In places pseudomorphs after evaporites have been observed, tending to occlude cavities resulted after dissolution. The depositional environment corresponds to a moderate to high-energy inner platform setting, experiencing open-ocean influences. The pattern of coralgal reef development during Miocene, in the tectonically controlled Gavdos island, represents a complex interaction of tectonic activity and global sea-level changes.

Coastal Erosion in Yasawa Islands, Fiji

Coastal erosion may have many different causes. Wherever we came across erosion problems on the Yasawa Islands in Fiji, they had causes other than sea level rise. We present two case studies. At one site, the beach erosion was caused by the construction of a stonewall diverting the currents in a gyre that hit the shore causing local beach erosion. At another site, extensive erosion caused removal and lateral re-deposition of huge quantities of sand. From the Google Earth images we can infer a date between 2005 and 2009 for this change in shore conditions. We suggest that the shallow-water sand was destabilized by the commercial harvesting of thousands of sea cucumbers (Holothuria scabra). These animals, by their sheer numbers and ecological behavior, were exerting a stabilizing influence on the shallow-water sandy deposits off the beach at Yageta Village. In both cases, the erosion was caused by human action. The coasts all along the Yasawa Islands are characterized by coastal stability. The presence of extensive rock-cut platforms and notches, as well as the occurrence of corals grown into “mini-atolls” are indicative of a stable sea level throughout the islands.

Seven new species of sponges (Porifera) from deep-sea coral mounds at Campos Basin (SW Atlantic)

Deep-sea reefs and coral banks are increasingly known as highly biodiverse ecosystems where sponges constitute a significant proportion of builders and inhabitants. Albeit smaller in dimensions, Campos Basin coral mounds also harbor a rich associated fauna, whence only 16 species of sponges had been fully identified this far. Seven new species are described here, viz. Geodia garoupa sp. nov., Vulcanella stylifera sp. nov., Trachyteleia australis sp. nov., Echinostylinos brasiliensis sp. nov., Xestospongia kapne sp. nov., Sympagella tabachnicki sp. nov., and Leucopsacus barracuda sp. nov. Of the 24 species of sponges known from the area, only seven were found elsewhere too, thus suggesting a possible high endemism in Campos Basin. Nevertheless, the widespread occurrence of deep reef-framework building corals along a large sector of the Brazilian coast suggests these habitats and their associated fauna may be more widespread than currently appreciated. Echinostylinos patriciae nom. nov. is proposed for the New Zealand record of E. reticulatus.

Occurrence of azooxanthellate scleractinian corals off Goa, mid-west coast of India

West coast of India is characterized by the presence of rich rocky out-crops with a diversity of poorly illuminated vertical rocky walls, crevices, caves, tunnels and overhangs. Though these are the typical environment for azooxanthellate scleratinian corals, there is no report available on these corals from this region. In situ observations including photography were made by SCUBA diving Collected specimens were soaked in fresh water and then in sodium hypochlorite solution for cleaning. Finer details of coralla were photographed using a stereoscopic microscope. The present account reported three species of azooxanthellate corals namely Balanophyllia cumingii Milne Edwards & Haime, 1848, Dentrophyllia indica Pillai, 1969 and Paracyathus profundus Duncan, 1889 for the first time from the rocky out-crops off Goa, mid-west coast of India and illustrated with in situ morphological characters of the species recorded. Despite their rich biodiversity, the seas and the deep shelf regions adjacent to India have had few surveys and limited reports (34 species) only are available on the occurrence of azooxanthellate corals. Detailed further studies along the coast would unveil the presence of more number of species.

Effectiveness of a deep-sea cold-water coral Marine Protected Area, following eight years of fisheries closure

Pressure on deep-sea ecosystems continues to increase as anthropogenic activities move into ever deeper waters. To mitigate impacts on vulnerable habitats, various conservation measures exist, such as the designation of Marine Protected Areas (MPAs). So far, however, little evidence is available about their effectiveness. This paper presents a unique follow-up study assessing the status and recovery of a deep-sea fisheries closure and MPA at ~1000m water depth in the NE Atlantic, eight years after designation. The Darwin Mounds cold-water coral ecosystem was discovered in 1998, and closed to all bottom contact fisheries, especially trawling, in 2003. Our repeat survey in 2011 used both high-resolution sidescan sonar data collected by Autonomous Underwater Vehicle (AUV) and video footage from a Remotely Operated Vehicle (ROV) to evaluate recovery. The results demonstrate that (1) protection was successful and fishing impact was largely avoided in the Western Darwin Mounds, which contained similar proportions of live cold-water coral occurrence in 2011 as observed in 1998–2000; however (2) the Eastern Darwin Mounds suffered severe damage pre-closure, and by 2011 showed no coral recolonisation and very little regrowth. These results are further evidence for the low resilience and slow recovery potential of deep-sea ecosystems, and underline once again the importance of the precautionary principle in deep-sea conservation.

Distributions and habitat associations of deep-water corals in Norfolk and Baltimore Canyons, Mid-Atlantic Bight, USA

A multi-disciplinary study of two major submarine canyons, Baltimore Canyon and Norfolk Canyon, off the US mid-Atlantic coast focused on the ecology and biology of canyon habitats, particularly those supporting deep-sea corals. Historical data on deep-sea corals from these canyons were sparse with less than 750 records for the mid-Atlantic region, with most being soft sediment species. This study substantially increased the number of deep-sea coral records for the target canyons and the region. Large gorgonians were the dominant structure-forming coral taxa on exposed hard substrates, but several species of scleractinians were also documented, including first observations of Lophelia pertusa in the mid-Atlantic Bight region. Coral distribution varied within and between the two canyons, with greater abundance of the octocoral Paragorgia arborea in Baltimore Canyon, and higher occurrence of stony corals in Norfolk Canyon; these observations reflect the differences in environmental conditions, particularly turbidity, between the canyons. Some species have a wide distribution (e.g., P. arborea, Primnoa resedaeformis, Anthothela grandiflora), while others are limited to certain habitat types and/or depth zones (e.g., Paramuricea placomus, L. pertusa, Solenosmilia variabilis). The distribution of a species is driven by a combination of factors, which include availability of appropriate physical structure and environmental conditions. Although the diversity of the structure-forming corals (gorgonians, branching scleractinians and large anemones) was low, many areas of both canyons supported high coral abundance and a diverse coral-associated community. The canyons provide suitable habitat for the development of deep-sea coral communities that is not readily available elsewhere on the sedimented shelf and slope of the Mid-Atlantic Bight.