On the role of seamounts in upwelling deep-ocean waters through turbulent mixing.

Turbulent mixing in the ocean exerts an important control on the rate and structure of the overturning circulation. However, the balance of processes underpinning this mixing is subject to significant uncertainties, limiting our understanding of the overturning's deep upwelling limb. Here, we investigate the hitherto primarily neglected role of tens of thousands of seamounts in sustaining deep-ocean upwelling. Dynamical theory indicates that seamounts may stir and mix deep waters by generating lee waves and topographic wake vortices. At low latitudes, stirring and mixing are predicted to be enhanced by a layered vortex regime in the wakes. Using three realistic regional simulations spanning equatorial to middle latitudes, we show that layered wake vortices and elevated mixing are widespread around seamounts. We identify scalings that relate mixing rate within seamount wakes to topographic and hydrographic parameters. We then apply such scalings to a global seamount dataset and an ocean climatology to show that seamount-generated mixing makes an important contribution to the upwelling of deep waters. Our work thus brings seamounts to the fore of the deep-ocean mixing problem and urges observational, theoretical, and modeling efforts toward incorporating the seamounts' mixing effects in conceptual and numerical ocean circulation models.

First evidence of prickly shark, Echinorhinus cookei Pietschmann 1928, aggregation on seamounts in the eastern Pacific, Panama.

In May 2022, twelve prickly sharks, Echinorhinus cookei Pietschmann 1928, were sighted at 151-350 m depth in the Cordillera de Coiba seamounts, Pacific Panama. This discovery expands our knowledge of the distribution and habitat use of this rare deep-sea species. It underscores the potential significance of the Cordillera de Coiba seamounts, an offshore marine protected area, as a critical habitat for E. cookei, a species threatened by commercial fishing. Although unverified reports exist on its presence in the tropical eastern Pacific, this publication represents the first documented record of live specimens of E. cookei in Panama.

Diversity and Distribution of Harmful Algal Bloom Species from Seamount to Coastal Waters in the South China Sea.

Mount Xianbei is one of the largest shallow seamounts located in the middle of the South China Sea (SCS), which might play a role in shaping the biodiversity of surrounding continental coastal waters, particularly the diversity of phytoplankton species causing frequent harmful algal blooms (HABs) in northern SCS. However, the diversity, composition, and distribution of phytoplankton species in the seamount regions of Xianbei remain largely unexplored. In this study, samples around and outside the seamount regions were collected during a late summer cruise of 2021 to test whether seamounts play a role in HAB species propagation. In total, we identified 19 HAB species across all samples using the ASV-based DNA metabarcoding approach, 6 of which had not been reported previously in the SCS, suggesting a diverse HAB species in the SCS. Specifically, 16 HAB species were found in the seamount region of Xianbei, and 5 of them were also found in the coastal waters, indicating a close connection between seamount and coastal waters. This study was the first attempt to explore HAB species' spatial diversity and vertical distribution in the seamount region of Xianbei at single-nucleotide resolution, which provides a novel explanation for the coastal HAB occurrence in the northern SCS. IMPORTANCE There are a number of seamounts under the water of the South China Sea (SCS). The seamounts might play a role in shaping the biodiversity of surrounding continental coastal waters. However, there is no direct evidence revealing the relationship of the biodiversity of phytoplankton between seamounts and coastal waters in the SCS, especially those species having the potential to form harmful algal blooms (HABs). Some HAB species might proliferate in certain geographic locations, while others may be broadly distributed across oceanic provinces. In this study, we provided a detailed analysis of phytoplankton composition and molecular detection of HAB species from seamount to coastal waters in the SCS, which suggested a strong interaction in the HAB species between the two areas. This finding provides new insights into the diversity and distribution of HABs in seamounts and their role in shaping the composition and the occurrence of HABs in coastal water.

Going deeper and further: a range and depth extension for the deep-sea feather star Paratelecrinuscubensis (Carpenter, 1881) (Comatulida, Atelecrinidae), first record from the Western Pacific.

A specimen belonging to the deep-sea feather-star family Atelecrinidae was collected in April 2018 at the Kocebu Guyot at 1294 m deep. Based on its morphological characters, the specimen was identified as Paratelecrinuscubensis (Carpenter, 1881). This species of feather star is restricted to the deep sea and was known only from 12 records from the Bahamas and Cuba at depths of 567-892 m. The data represent the first record from the Western Pacific Ocean and the deepest record known, extending the depth where this feather star has been found to beyond 1000 m. The morphological characteristics of the Kocebu Guyot specimen were essentially identical to the morphology of the neotype, with a slight difference in the dorsal spine at the end of the cirri. The phylogenetic analysis based on the mitochondrial cytochrome c oxidase subunit I (COI), 16S rRNA genes, 28S rRNA genes, and 18S rRNA genes reveal a close relationship of P.cubensis with P.wyvilli. Results of our molecular phylogenetic analysis are consistent with our morphological identifications. Our find extends the known geographical distribution of the feather star P.cubensis to the Western Pacific Ocean and provide insights into deep-sea biodiversity in the Kocebu Guyot.

320,000 years of interaction between a fast-spreading ridge and nearby seamounts monitored using major, trace and isotope composition data from oceanic basalts: Zoom at 15.6°N on the East Pacific Rise.

Basaltic samples were collected by the French submersible ``Nautile'' during the "Parisub" cruise (2010, R/V L'Atalante, Ifremer) along a 25 km long sampling profile crossing perpendicularly the current axis of the East Pacific Rise at 15.6°N, as well as the trace of its two former parallel axes located further east. The total length of the profile corresponds to an approximate time interval of ∼ 320,000 years. The corresponding dataset documents the geochemical response of Mid-Ocean Ridge Basalts (MORB) related to the progressive convergence between the ridge segment and a nearby hotspot. It also represents one of the highest-sampling (and in turn geochemical) resolution efforts to date. The major, trace element and isotopic compositions determined through optical and mass spectrometry analysis of 52 samples are presented and compared to other previous data obtained from the same area. The data obtained strictly follow the conventions used in rock geochemistry in terms of data acquisition, reduction, and format, so that they can be compared to similar data from other regions. The different figures present (i) The geological context of study area, (ii) A classification of the samples according to their geochemical composition and geological context for a better legibility of the dataset, (iii) A comparison with data from other oceanic rises, (iv) A detailed method explaining the foundations of the chronology between samples established, and (v) A chronological representation of the geochemical composition of the basalts collected. These data can be useful for anyone interested in marine geosciences and more specifically scientists studying mantle geochemistry, oceanic lithosphere formation, and hotspot-ridge interactions. These data can also be used to model magmatic processes, crust-mantle interactions, and can be integrated in geophysical and geological models of seafloor accretion.

Trace elements and δ15N values in micronekton of the south-western Indian Ocean.

Trace elements and δ15N values were analysed in micronekton (crustaceans, fishes and squids) sampled in the south-western Indian Ocean. Myctophids were associated with high concentrations of arsenic at La Pérouse and MAD-Ridge seamounts, and with lead and manganese at MAD-Ridge and in the Mozambique Channel. The difference in cadmium, copper and zinc concentrations between micronekton broad categories reflected differing metabolic and storage processes. When significant, negative relationships were found between micronekton body size and trace element concentrations, which can possibly be attributed to differing metabolic activity in young and old individuals, dietary shifts and/or dilution effect of growth. No relationships were found between trace element concentrations and δ15N values of micronekton (except cobalt which decreased with increasing δ15N values), since most trace elements are not biomagnified in food webs due to regulation and excretion processes within organisms. All trace element pairs were positively correlated in fishes suggesting regulation processes.

Review of Ophioplinthaca Verrill, 1899 (Echinodermata, Ophiuroidea, Ophiacanthidae), description of new species in Ophioplinthaca and Ophiophthalmus, and new records from the Northwest Pacific and the South China Sea.

The ophiuroid genus Ophioplinthaca is well characterized by the deep incisions in the disc. Prior to this study, it contained 32 accepted species, but species limits and geographic distributions were not well understood. The manned submersible vehicle 'Shenhaiyongshi' was used to collect ophiuroid specimens from the deep-sea seamounts and cold seeps in the South China Sea and Northwest Pacific at 602-3600 m depth, during 2018 to 2020. The genus Ophioplinthaca was reviewed using both morphological data and a phylogenetic analysis, based on COI sequences. The taxonomic status of the genus Ophiophthalmus Matsumoto, 1917, a junior homonym of Ophiophthalmus Fitzinger, 1843 (a reptile) was clarified by proving prevailing usage of the ophiuroid name. A total of eight species were identified, including two new species, described asOphioplinthacabrachispina sp. nov. and Ophiophthalmusserratus sp. nov., and two new records. The new species are characterized by unique features of the arm skeletons. Tabular keys to all Ophioplinthaca and Ophiophthalmus species are provided. Interspecific and intraspecific genetic distance of Ophioplinthaca species ranged from 2.32% to 19.72%, and from 0.26% to 0.90%, respectively. The data suggest that species of the genus Ophioplinthaca are more widely spread around the Northwest Pacific region deep-sea seamounts than previously known.

Sponges of Western Mediterranean seamounts: new genera, new species and new records.

BACKGROUND: The seamounts Ses Olives (SO), Ausias March (AM) and Emile Baudot (EB) at the Mallorca Channel (Balearic Islands, western Mediterranean), are poorly explored areas containing rich and singular sponge communities. Previous works have shown a large heterogeneity of habitats, including rhodolith beds, rocky, gravel and sandy bottoms and steeped slopes. This diversity of habitats provides a great opportunity for improving the knowledge of the sponges from Mediterranean seamounts. METHODS: Sponges were collected during several surveys carried out by the Balearic Center of the Spanish Institute of Oceanography at the Mallorca Channel seamounts. Samples were obtained using a beam-trawl, rock dredge and remote operated vehicle. Additional samples were obtained from fishing grounds of the Balearic Islands continental shelf, using the sampling device GOC-73. Sponges were identified through the analysis of morphological and molecular characters. RESULTS: A total of 60 specimens were analyzed, from which we identified a total of 19 species. Three species and one genus are new to science: Foraminospongia balearica gen. nov. sp. nov., Foraminospongia minuta gen. nov. sp. nov. and Paratimea massutii sp. nov. Heteroxya cf. beauforti represents the first record of the genus Heteroxya in the Mediterranean Sea. Additionally, this is the second report of Axinella spatula and Haliclona (Soestella) fimbriata since their description. Moreover, the species Petrosia (Petrosia) raphida, Calyx cf. tufa and Lanuginella pupa are reported for the first time in the Mediterranean Sea. Petrosia (Strongylophora) vansoesti is reported here for the first time in the western Mediterranean Sea. Haliclona (S.) fimbriata is reported here for the first time in the north-western Mediterranean Sea. Hemiasterella elongata is reported here for the second time in the Mediterranean Sea. The species Melonanchora emphysema, Rhabdobaris implicata, Polymastia polytylota, Dragmatella aberrans, Phakellia ventilabrum and Pseudotrachya hystrix are reported for first time off Balearic Islands. Following the Sponge Barcoding project goals, we have sequenced the Cytochrome Oxidase subunit I (COI) and the 28S ribosomal fragment (C1-D2 domains) for Foraminospongia balearica sp. nov., Foraminospongia minuta sp. nov., H. cf. beauforti and C. cf. tufa, and the COI for Paratimea massuti sp. nov. We also provide a phylogenetic analysis to discern the systematic location of Foraminospongia gen. nov., which, in accordance to skeletal complement, is placed in the Hymerhabdiidae family. A brief biogeographical discussion is provided for all these species, with emphasis on the sponge singularity of SO, AM and the EB seamounts and the implications for their future protection.

Seafloor litter at oceanic islands and seamounts of the southeastern Pacific.

Seafloor litter in oceanic islands of the southeastern Pacific Ocean have rarely been described and quantified, mainly due to the associated logistical challenges. In this study, we describe and quantify the different kinds of litter from 60 to 320 m depths in Rapa Nui (RN) and Desventuradas Islands (DI), and evaluated the relationship of this litter with the local population in terms of demographic density and fishing activity. The study compiled data from 84 stations surveyed with a ROV representing a total distance of 22 km. Litter was grouped into six categories. 96 observations of litter and debris were taken around RN, most of which associated with local artisanal fishing activity, especially fishing anchors (56%). No tourism-associated debris were reported. Any kind of seafloor litter was observed at DI. The present study provides baseline information for the local community to improve management by understanding the potential sources of seafloor litter.

Improved bathymetry leads to >4000 new seamount predictions in the global ocean - but beware of phantom seamounts!

Seamounts are important marine habitats that are hotspots of species diversity. Relatively shallow peaks, increased productivity and offshore locations make seamounts vulnerable to human impact and difficult to protect. Present estimates of seamount numbers vary from anywhere between 10,000 to more than 60,000. Seamount locations can be estimated by extracting large, cone-like features from bathymetry grids (based on criteria of size and shape). These predicted seamounts are a useful reference for marine researchers and can help direct exploratory surveys. However, these predictions are dependent on the quality of the surveys underpinning the bathymetry. Historically, quality has been patchy, but is improving as mapping efforts step up towards the target of complete seabed coverage by 2030. This study presents an update of seamount predictions based on SRTM30 PLUS global bathymetry version 11 and examines a potential source of error in these predictions. This update was prompted by a seamount survey in the British Indian Ocean Territory in 2016, where locations of two putative seamounts were visited. These 'seamounts' were targeted based on previous predictions, but these features were not detected during echosounder surveys. An examination of UK hydrographic office navigational (Admiralty) charts for the area showed that the summits of these putative features had soundings reporting 'no bottom detected at this depth' where 'this depth' was similar to the seabed reported from the bathymetry grids: we suspect that these features likely resulted from an initial misreading of the charts. We show that 15 'phantom seamount' features, derived from a misinterpretation of no bottom sounding data, persist in current global bathymetry grids and updated seamount predictions. Overall, we predict 37,889 seamounts, an increase of 4437 from the previous predictions derived from an older global bathymetry grid (SRTM30 PLUS v6). This increase is due to greater detail in newer bathymetry grids as acoustic mapping of the seabed expands. The new seamount predictions are available at https://doi.pangaea.de/10.1594/PANGAEA.921688.

Deep-sea anglerfishes (Lophiiformes: Ceratioidei) from off northeastern Brazil, with remarks on the ceratioids reported from the Brazilian Exclusive Economic Zone

The deep-sea anglerfishes of the suborder Ceratioidei (Lophiiformes) are represented by about 170 valid species with some of the most extraordinary morphological and reproductive adaptations among vertebrates, including extreme sexual dimorphism and male parasitism. Here we report on the diversity and distribution of rare ceratioids collected during the ABRACOS (Acoustics along the BRAzilian COaSt) expeditions off northeastern Brazil and the Fernando de Noronha Ridge (Rocas Atoll, Fernando de Noronha Archipelago, and associated seamounts). Chaenophryne ramifera, Oneirodes anisacanthus, O. carlsbergi, Gigantactis watermani, and unidentified specimens of Caulophryne, Dolopichthys, and Rhynchactis are recorded for the first time in the Brazilian Exclusive Economic Zone. Ceratias uranoscopus, Melanocetus johnsonii, and Chaenophryne draco have their distributions extended in Brazilian waters. Caulophryne, O. anisacanthus, and G. watermani are also recorded for the first time in the western South Atlantic. The specimen of G. watermani reported here represents the third known specimen of the species, and variations of its escal anatomy in relation to the holotype are described. Based on specimens examined and a review of records in the literature, 20 species of the Ceratioidei, in addition to unidentified species of Caulophryne, Dolopichthys, and Rhynchactis, are confirmed in the Brazilian Exclusive Economic Zone.(AU)

Os peixes-pescadores de profundidade da subordem Ceratioidei (Lophiiformes) são representados por cerca de 170 espécies válidas que apresentam algumas das adaptações anatômicas e reprodutivas mais extraordinárias entre os vertebrados, incluindo extremo dimorfismo sexual e parasitismo masculino. No presente estudo reportamos sobre a diversidade e distribuição de espécies raras de Ceratioidei coletadas durante as expedições ABRACOS (Acoustics along the BRAzilian COaSt) realizadas ao largo do nordeste do Brasil e na Cadeia de Fernando de Noronha (Atol das Rocas, Arquipélago de Fernando de Noronha e montes submarinos associados). Chaenophryne ramifera, Oneirodes anisacanthus, O. carlsbergi, Gigantactis watermani e espécimes não identificados de Caulophryne, Dolopichthys e Rhynchactis são registrados pela primeira vez na Zona Econômica Exclusiva brasileira. Ceratias uranoscopus, Melanocetus johnsonii e Chaenophryne draco tiveram suas distribuições estendidas em águas brasileiras. Caulophryne, O. anisacanthus e G. watermani também são registrados pela primeira vez no Atlântico Sul ocidental. O espécime de G. watermani reportado aqui representa o terceiro espécime conhecido da espécie, e variações anatômicas de sua esca em relação à do holótipo são descritas. Com base nos espécimes examinados e na revisão de registros na literatura, 20 espécies de Ceratioidei, além de espécies não identificadas de Caulophryne, Dolopichthys, and Rhynchactis, são confirmadas na Zona Econômica Exclusiva brasileira.(AU)

Resilience of seamount benthic communities to trawling disturbance.

Despite bottom trawling being the most widespread, severe disturbance affecting deep-sea environments, it remains uncertain whether recovery is possible once trawling has ceased. Here, we review information regarding the resilience of seamount benthic communities to trawling. We focus on seamounts because benthic communities associated with these features are especially vulnerable to trawling as they are often dominated by emergent, sessile epifauna, and trawling on seamounts can be highly concentrated. We perform a meta-analysis to investigate whether any taxa demonstrate potential for recovery once trawling has ceased. Our findings indicate that mean total abundance can gradually increase after protection measures are placed, although taxa exhibit various responses, from no recovery to intermediate/high recovery, resistance, or signs of early colonisation. We use our results to recommend directions for future research to improve our understanding of the resilience of seamount benthic communities, and thereby inform the management of trawling impacts on these ecosystems.

Arthropoda; Crustacea; Decapoda of deep-sea volcanic habitats of the Galapagos Marine Reserve, Tropical Eastern Pacific.

BACKGROUND: The deep-sea biome (> 200 m depth) is the world's last great wilderness, covering more than 65% of the earth's surface. Due to rapid technological advances, deep-sea environments are becoming more accessible to scientific research and ocean exploration around the world and, in recent years, this is also true for the Galapagos Islands. Deep-sea habitats cover the largest proportion of Galapagos Marine Reserve (GMR), yet to date, no comprehensive baseline exists on the biodiversity of the benthic fauna associated with volcanic seafloor formations within this region. Closing this knowledge gap is essential to provide information for decision-making for the management of marine resources within the GMR and assessing any potential changes in biodiversity resulting from climate-driven alterations that deep-sea environments are expected to experience. In 2015, the Charles Darwin Foundation's Seamounts of the GMR Research Project, together with the Galapagos National Park Directorate (GNPD) and Ocean Exploration Trust (OET), conducted a joint expedition on board the EV Nautilus. Using Remotely operated vehicles (ROVs), the aim of the expedition was to characterise the geological formations and biological communities present on seamounts, lava flows and other deep-sea habitats (> 200 m) within the GMR. NEW INFORMATION: We provide the first comprehensive image inventory for the phylum Arthropoda from 260 to 3400 m of depth within the GMR. Past studies on deep-sea macroinvertebrates in the GMR have been limited to voucher samples collected from dredging (restricted to soft bottom environments) or by submersibles (only allowing limited biological sampling). The image inventory, presented here, is based on high-definition video transects conducted by the Hercules ROV on board the EV Nautilus. Images of macroinvertebrate morphospecies were captured, catalogued and identified, thus providing the first known image inventory of in-situ macroinvertebrate species from the deep-sea region of the GMR.We present 32 distinct morphospecies occurrences within the class Malacostraca and order Decapoda. We also report 17 different families, three species that are new records to the GMR, in-situ images of two new species to science recently described and one possible new squat lobster, as well as interesting behavioural observations.

Fungal diversity in deep-sea sediments from Magellan seamounts environment of the western Pacific revealed by high-throughput Illumina sequencing.

There are lots of seamounts globally whose primary production is disproportionally greater than the surrounding areas. Compared to other deep-sea environments, however, the seamounts environment is relatively less explored for fungal diversity. In the present study, we explored the fungal community structure in deep-sea sediments from four different stations of the Magellan seamounts environment by using high-throughput sequencing of the ITS1 region. A total of 1,897,618 ITS1 sequences were obtained. Among these sequences, fungal ITS1 sequences could be clustered into 1,662 OTUs. The majority of these sequences belonged to Ascomycota. In the genera level, the most abundant genus was Mortierella (4.79%), which was reported as a common fungal genus in soil and marine sediments, followed by Umbelopsis (3.80%), Cladosporium (2.98%), Saccharomycopsis (2.53%), Aspergillus (2.42%), Hortaea (2.36%), Saitozyma (2.20%), Trichoderma (2.12%), Penicillium (2.11%), Russula (1.86%), and Verticillium (1.40%). Most of these recovered genera belong to Ascomycota. The Bray-Curtis analysis showed that there was 37 to 85% dissimilarity of fungal communities between each two sediment samples. The Principal coordinates analysis clearly showed variations in the fungal community among different sediment samples. These results suggested that there was a difference in fungal community structures not only among four different sampling stations but also for different layers at the same station. The depth and geographical distance significantly affect the fungal community, and the effect of depth and geographical distance on the structure of the fungal community in the Magellan seamounts is basically same. Most of the fungi were more or less related to plants, these plant parasitic/symbiotic/endophytic fungi constitute a unique type of seamounts environmental fungal ecology, different from other marine ecosystems.

Asteroidea (Echinodermata) from shallow-waters of the remote oceanic archipelago Trindade and Martin Vaz, southeastern Atlantic, with taxonomic and zoogeographical notes.

Trindade and Martin Vaz (TMV) is a highly isolated, oceanic volcanic archipelago located approximately 1200 km off the Brazilian coast and about 4200 km away from the nearest African coast. It has been almost 70 years since the first sea star, "Astropecten sp.", was recorded from Trindade in 1951. In the following years (1955-1971; 2006) six sea star species were added to the archipelago's fauna. After that period, however, research on shallow water echinoderms has not been conducted in TMV and no further sea star species have been recorded from there since. From 2012 to 2019, 263 daytime SCUBA diving and intertidal samplings conducted at TMV yielded 91 lots of sea stars in 7 species: Linckia guildingi Gray, 1840; Oreaster reticulatus (Linnaeus, 1758); Astropecten aff. antillensis Lütken, 1859; Copidaster lymani A. H. Clark, 1948; Luidia alternata alternata (Say, 1825); Mithrodia clavigera (Lamarck, 1816); and Ophidiaster guildingi Gray, 1840. The last five species in this list represent new records to the archipelago, with C. lymani also being the first record of the species in the southwestern Atlantic. Five shallow water species previously known from TMV have not been observed in the present survey: Asterinides folium (Lütken, 1860), Astropecten brasiliensis Müller Troschel, 1842, Astropecten cingulatus Sladen, 1883, Linckia nodosa Perrier, 1875, and Ophidiaster alexandri Verrill, 1915. Twelve sea star species are currently known from shallow waters of TMV.                A list of all sea star species known from shallow waters (intertidal down to 100 meters) of the tropical southern-central Atlantic oceanic archipelagoes and islands (Ascension, Cape Verde, Fernando de Noronha, Gulf of Guinea, Rocas Atoll, Saint Helena, Trindade and Martin Vaz) with their gross distribution in the Atlantic Ocean was compiled in order to explore the existence of patterns of geographic distribution for the shallow water sea star species in the tropical southern-central Atlantic oceanic islands. It has been found that 44% of the species from TMV are of western Atlantic affinity, 33% amphi-Atlantic, and 22% circumtropical in distribution. No endemic sea star species are known from TMV to date. The even more remote Ascension (ASC) and Saint Helena (STH) are more of a mosaic than TMV. The ASC and STH fauna consist of 8 and 11 sea star species, respectively. Their endemic component totals to 25% and 27%, respectively. STH has more amphi-Atlantic and eastern Atlantic sea star species (27% each) than ASC (25% and 12.5%, respectively). Twenty-five percent of the sea star species in ASC are circumtropical in distribution, whereas no circumtropical species have been found in STH. The western Atlantic (WA) component comparatively to the eastern Atlantic (EA) one is of minor significance in STH (18% versus 27%, respectively), whereas the WA and EA components contribute equally to the taxonomic composition in ASC (12.5% each). However, patterns of faunal affinities in both islands are actually taxon-dependent.

Mariana serpentinite mud volcanism exhumes subducted seamount materials: implications for the origin of life.

The subduction of seamounts and ridge features at convergent plate boundaries plays an important role in the deformation of the overriding plate and influences geochemical cycling and associated biological processes. Active serpentinization of forearc mantle and serpentinite mud volcanism on the Mariana forearc (between the trench and active volcanic arc) provides windows on subduction processes.  Here, we present (1) the first observation of an extensive exposure of an undeformed Cretaceous seamount currently being subducted at the Mariana Trench inner slope; (2) vertical deformation of the forearc region related to subduction of Pacific Plate seamounts and thickened crust; (3) recovered Ocean Drilling Program and International Ocean Discovery Program cores of serpentinite mudflows that confirm exhumation of various Pacific Plate lithologies, including subducted reef limestone; (4) petrologic, geochemical and paleontological data from the cores that show that Pacific Plate seamount exhumation covers greater spatial and temporal extents; (5) the inference that microbial communities associated with serpentinite mud volcanism may also be exhumed from the subducted plate seafloor and/or seamounts; and (6) the implications for effects of these processes with regard to evolution of life. This article is part of a discussion meeting issue 'Serpentine in the Earth system'.

A new species of Atrimitra Dall, 1918 (Gastropoda: Mitridae) from seamounts of the recently created Nazca-Desventuradas Marine Park, Chile.

We describe Atrimitra isolata sp. n. (Gastropoda: Mitridae), collected on the summit of seamounts (~200 m water depth) in the vicinity of Desventuradas Islands, Chile insular territory. Additionally, we provide some insight into the habitat of this new species based on underwater imagery taken with a remotely operated vehicle. A. isolata sp. n. is characterized by its small size (up to 26 mm), elongate-ovate shape, solid shell and smooth appearance. It has a base brown color, with some specimens being tan or yellow. It is morphologically related to counterparts from shallow depths on the west coast of North, Central and South America (i.e., Atrimitra idae, Atrimitra orientalis and Atrimitra semigranosa), but has no affinities with species of the family reported from around Easter Island, on the far western side of the Salas y Gómez ridge (e.g., Strigatella flavocingulata, Imbricariopsis punctata and Neocancilla takiisaoi), or with other Indo-Pacific species. The present contribution adds to the knowledge of the poorly studied fauna of the seamounts in the southern portion of the Nazca ridge and easternmost section of the Sala y Gómez ridge, an area characterized by the high degree of endemism of its benthic fauna, and now protected within the large and newly created Nazca-Desventuradas Marine Park.

Black Corals (Anthozoa: Antipatharia) from the Southwestern Atlantic.

Black corals (Cnidaria: Hexacorallia: Antipatharia) occur in all oceans of the globe, especially at depths greater than 50 m. However, their richness is underestimated due to the scarcity of studies on this group, especially in deep waters. The south Atlantic is one of the most depauperate regions in terms of our knowledge of antipatharians. Herein, we report 34 antipatharian species for the Southwestern Atlantic. Additionally, based on the examination of museum specimens, three species are new records in the Atlantic (Parantipathes laricides; Stichopathes paucispina and S. spiessi); and 17 had their distribution expanded, representing six families (Antipathidae, Cladopathidae, Leiopathidae, Myriopathidae, Schizopathidae and Stylopathidae). Additionally, the richness, distribution and associations of antipatharians are briefly discussed. An artificial key to South Atlantic antipatharians is included.

Characterization of the acoustic community of vocal fishes in the Azores.

Sounds produced by teleost fishes are an important component of marine soundscapes, making passive acoustic monitoring (PAM) an effective way to map the presence of vocal fishes with a minimal impact on ecosystems. Based on a literature review, we list the known soniferous fish species occurring in Azorean waters and compile their sounds. We also describe new fish sounds recorded in Azores seamounts. From the literature, we identified 20 vocal fish species present in Azores. We analysed long-term acoustic recordings carried out since 2008 in Condor and Princesa Alice seamounts and describe 20 new putative fish sound sequences. Although we propose candidates as the source of some vocalizations, this study puts into evidence the myriad of fish sounds lacking species identification. In addition to identifying new sound sequences, we provide the first marine fish sound library for Azores. Our acoustic library will allow to monitor soniferous fish species for conservation and management purposes.

Pycnogonids (Arthropoda, Pycnogonida) from the Southwest Indian Ridge.

This report addresses sixty-two deep-sea pycnogonid specimens collected by the Southwest Indian Ocean Seamounts Expedition, November 7 to December 21, 2011 on-board the British research vessel R.S.S. James Cook (voyage numbers JC066, JC067). Pycnogonids were collected from four of six geological features sampled along the central section of the Southwest Indian Ridge (SWIR) in an area approximately 1500 km south-south east of Madagascar. Specimens were mostly gathered utilizing a remotely operated vehicle (ROV) and tethered video-sediment grab platforms. Additional specimens were gathered from sediment cores or hand-picked from whale bone and wood-fall experiment nets and mooring buoy ropes. Fifteen new species are described, illustrated and compared with their nearest relatives. Two previously described species belonging to the genera Colossendeis and Austrodecus are recorded. A specimen of Austrodecus bamberi represents the first record of the female and is the only species in the collection previously known from the SWIR. One species of Colossendeis remains unnamed pending further analysis. One subadult specimen of Sericosura showing strong morphological affinity with a specimen previously recorded from the Walvis Ridge remains undescribed pending availability of further material. One subadult specimen is tentatively assigned to Nymphon. Specimens are assigned to six families and eight genera. Colossendeis rostrata is synonymised with C. melancholicus. The methodology of counting palp segments in the genera Austrodecus and Rhynchothorax is reviewed.