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More than 7000 demosponge species have been described to date globally but <2% are known from the abyssal plains, which occupy some 50% of the Earth's surface. The demosponge fauna in the abyssal nodule fields at Clarion‐Clipperton Zone (CCZ) in the Pacific Ocean, a region being explored for potential deep‐sea mining, is a case in point. A total of 21 species belonging to 13 genera in nine families and seven orders were identified from the eastern region of the CCZ, of which most are new to science. They are small in size (<5 mm), with simple skeletons and poor spicule diversity. All ordinal representatives of Demospongiae were utilized to determine taxonomic position of the highly homoplasious tiny demosponges in our molecular phylogenetic analyses. Our results indicated Plenaster craigi, the most common and abundant species in the eastern CCZ, represents a new family, and possibly in a new order. Interestingly, P. craigi and members of the families Polymastiidae and Hamacanthidae, all filter‐feeding demosponge species, are far more abundant in nodule fields than the carnivorous sponges (Cladorhizidae) which were widely known to be the most dominant demosponge group in the abyssal depths. Lastly, it is highly likely that such tiny demosponges are present in other habitats. They might have been overlooked and/or ignored by sponge researchers in the past due to their tiny size and nondescript habitus. These demosponges could be distinct new species, not juveniles or indeterminates and warrant full taxonomic treatment. [ABSTRACT FROM AUTHOR]

Valettietta Lincoln & Thurston, 1983 (Amphipoda: Alicelloidea) is an infrequently sampled genus of scavenging amphipod, with a known bathymetric range from 17–5467 m encompassing a variety of habitats from anchialine caves to abyssal plains. Molecular systematics studies have uncovered cryptic speciation in specimens collected from the abyssal Pacific, highlighting uncertainty in the description of Valettietta anacantha (Birstein & Vinogradov, 1963). Here, we apply an integrative taxonomic approach and describe two new species, Valettietta trottarum sp. nov. and Valettietta synchlys sp. nov. collected at abyssal depths in the Clarion-Clipperton Zone, Pacific Ocean. Both species can be distinguished by characters of the gnathopods, uropod 3, and the inner plate of the maxilliped. Further, molecular phylogenetic analyses of two mitochondrial (16S rDNA and COI) and two nuclear (Histone 3 and 28S rRNA) regions found both new species to form well-supported clades and allowed us to re-identify previously published records based on genetic species delimitation. The biogeography of Valettietta is discussed in light of these re-evaluated records, and a new taxonomic key to the genus is provided. These new taxa highlight the strength of applying an integrated taxonomic approach to uncover biodiversity, which is critical in regions being explored for potential industrial purposes. [ABSTRACT FROM AUTHOR]

Orienting vertically with the head facing upward allows fish to look for the shadow of their prey against ambient light, while also making their own shadow smaller to predators beneath them. Here, we describe the in situ behavior of three midwater fish in the family Neoscopelidae, Neoscopelus macrolepidotus, Neoscopelus microchir, and Scopelengys tristis, all of which were observed facing vertically with the head downward. This behavior allows the fish to diminish its shadow to hide from predators while hunting prey below. Assessing unique behaviors helps us better understand the role of these and other poorly studied deep-sea fishes. [ABSTRACT FROM AUTHOR]

Experienced ship roll during loading is the easiest parameter to observe and measure on board of a loaded ship. Therefore, the ship’s significant roll amplitudes should be the key limiting factor in view of the safety and efficiency of cargo handling operations at sea. For the example of three standard bulk carriers, the authors prepared a method of assessment of bulk carrier suitability to perform safe and efficient cargo handling operations in the Clarion-Clipperton Zone in view of significant amplitudes of roll. Via a calculation of the efficiency index for a set of limiting amplitudes of roll during loading simulation, we are able to analyze ship effectiveness. The application of the above-mentioned method can be employed as a useful tool to predict the lowest allowable significant amplitudes of roll when the required efficiency level is specified. Additionally, a calculation is made for the operable days where cargo operations are possible. Investigations show that, according to applied criteria, the effectiveness drops, and not every bulk carrier can perform safe cargo handling operations at sea. [ABSTRACT FROM AUTHOR]

Collections of the amphipod genus Oedicerina were obtained during six expeditions devoted to the study of deep-sea environments of the Pacific Ocean. The material revealed four species new to science. Two species (Oedicerina henrici sp. nov. and Oedicerina teresae sp. nov.) were found at abyssal depths of the central eastern Pacific in the Clarion-Clipperton Zone; one species (Oedicerina claudei sp. nov.) was recovered in the Sea of Okhotsk (north-west Pacific), and one (Oedicerina lesci sp. nov.) in the abyss adjacent to the Kuril-Kamchatka Trench (KKT). The four new species differ from each other and known species by the shapes of the rostrum, coxae 1 and 4, basis of pereopod 7, armatures of pereonite 7, pleonites and urosomites. An identification key for all known species is provided. The study of the cytochrome c oxidase subunit I gene of the four new species and Oedicerina ingolfi collected in the North Atlantic confirmed their genetic distinction. However, small intraspecific variation within each of the studied species was observed. In the case of the new species occurring across the KKT, the same haplotype was found on both sides of the trench, providing evidence that the trench does not constitute an insurmountable barrier for population connectivity. None of the species have so far been found on both sides of the Pacific. [ABSTRACT FROM AUTHOR]

Based on a combination of morphological and molecular data, we describe five new species and two new genera of xenophyophores from the Clarion–Clipperton Zone (abyssal eastern Pacific), an area with commercially valuable seafloor deposits of polymetallic nodules. Bizarria bryiformis gen. et sp. nov. displays unusual features, notably an organic-walled test, largely devoid of agglutinated particles, comprising interconnected branches growing upwards from the nodule substrate; the bases of the branches contain dark masses of waste material (stercomare) and pale strands of cytoplasm (granellare), the whitish, tuft-like extremities contain sediment particles. Tendalia reteformis gen. et sp. nov. forms a delicate network of agglutinated tubes. Shinkaiya contorta sp. nov. is characterized by a contorted, partly reticulated plate-like test while the simpler plate-like test of Galatheammina interstincta sp. nov. combines characters typical of Galatheammina and Psammina. In Semipsammina mattaeformis sp. nov. , a thin, delicate test with one or more tubular extensions forms a flat canopy over the mat-like stercomare encrusting the nodule substrate. Tendalia reteformis and S. contorta are free-living; the other species are sessile on nodules. Together, they illustrate the considerable morphological diversity of xenophyophores in a region where they dominate the megafauna, and highlight some major taxonomic challenges posed by these giant monothalamous foraminifera. [ABSTRACT FROM AUTHOR]

We describe Aschemonella monile Gooday and Holzmann sp. nov. from the Clarion-Clipperton Zone (CCZ, abyssal eastern equatorial Pacific), a region characterized by commercially significant concentrations of polymetallic nodules. The new species is the most abundant xenophyophore (giant agglutinated foraminifera) in our main sampling area (12-14°N; 116°30'-117°26'W). Additional specimens originate from the central CCZ, and from a third area, ~900 km NW of the main area, where A. monile numerically dominates the megabenthos in photographic surveys of the seafloor (average densities 1.54 individuals/m2; peak densities > 3 individuals/m2). Aschemonella monile is much larger (≥ 7 cm in length) than previously described species of the genus, with a test comprising an irregular sequence of self-contained, partly overlapping 'segments', creating a multichambered structure. A similar, much rarer species from the main study area, described here as Aschemonella aspera Gooday and Holzmann sp. nov., has an unsegmented test with a very rough, coarsely agglutinated wall. Genetic data suggest that A. monile is distinct from A. aspera and most closely related to a group comprising Rhizammina algaeformis and Aschemonella ramuliformis. Both new species have delicate tests that are often attached to nodule surfaces, making them particularly vulnerable to seafloor disturbances. [ABSTRACT FROM AUTHOR]

The global surge in demand for metals such as cobalt and nickel has created unprecedented interest in deep-sea habitats with mineral resources. The largest area of activity is a 6 million km2 region known as the Clarion-Clipperton Zone (CCZ) in the central and eastern Pacific, regulated by the International Seabed Authority (ISA). Baseline biodiversity knowledge of the region is crucial to effective management of environmental impact from potential deep-sea mining activities, but until recently this has been almost completely lacking. The rapid growth in taxonomic outputs and data availability for the region over the last decade has allowed us to conduct the first comprehensive synthesis of CCZ benthic metazoan biodiversity for all faunal size classes. Here we present the CCZ Checklist, a biodiversity inventory of benthic metazoa vital to future assessments of environmental impacts. An estimated 92% of species identified from the CCZ are new to science (436 named species from a total of 5,578 recorded). This is likely to be an overestimate owing to synonyms in the data but is supported by analysis of recent taxonomic studies suggesting that 88% of species sampled in the region are undescribed. Species richness estimators place total CCZ metazoan benthic diversity at 6,233 (+/−82 SE) species for Chao1, and 7,620 (+/−132 SE) species for Chao2, most likely representing lower bounds of diversity in the region. Although uncertainty in estimates is high, regional syntheses become increasingly possible as comparable datasets accumulate. These will be vital to understanding ecological processes and risks of biodiversity loss. • We provide the first checklist for the Clarion Clipperton Zone (CCZ) metazoan fauna • 5,142 unnamed species (informal names) are recorded from the CCZ • Total estimates of species richness range from >6,000–>8,000 • An estimated 88%–92% of species in the CCZ region in total are undescribed Species-level biodiversity information is key to understanding ecosystems and tracking environmental impacts. Rabone et al. provide the first checklist (436 species) and total species estimates (>6,000–>8,000) for the world's largest mineral exploration region, the CCZ. Estimates provide a baseline to build biodiversity knowledge at a regional scale. [ABSTRACT FROM AUTHOR]

Growing interest in polymetallic nodule mining has intensified the need to characterize the abundance, community structure and vertical flux of meroplankton in the Clarion-Clipperton Zone (CCZ) to facilitate the estimation of larval supply and potential connectivity of benthic populations. These ecological parameters are essential to predict recolonization processes following the expected large-scale, high intensity disturbances associated with nodule extraction. Here, we present the first description of the composition, abundance, temporal variability, and mesoscale distribution of dispersing stages of the benthos in two study areas in the eastern CCZ. Samples from free-vehicle plankton pumps showed little variation in meroplankton diversity and abundance over scales of 30–100 km for time scales of days to weeks. However, sediment-trap samples revealed high temporal variability in vertical flux over weeks to months. Larval abundances and fluxes measured in the abyssal CCZ are ~ 1–2 orders of magnitude lower than observed at deep-sea ridge and hydrothermal-vent habitats. We found significantly higher downward larval fluxes at 11 m above the bottom (mab) than at 146 mab, indicating accumulation or retention of meroplankton within the Benthic Boundary Layer (BBL). The high abundance of meroplankton in the BBL emphasizes its importance to dispersing stages and suggests that the creation of large sediment plumes in the BBL during nodule mining could compromise the dispersal and recruitment abilities of the abyssal benthos, potentially slowing rates and altering patterns of benthic community recovery following mining disturbance. [ABSTRACT FROM AUTHOR]

Xenophyophores, giant, fragile, agglutinated foraminifera (protists), are major constituents of the abyssal megafauna in the equatorial Pacific Clarion-Clipperton Zone (CCZ), a region where seabed mining of polymetallic nodules may occur in the future. As part of a baseline study of benthic communities we made extensive collections of xenophyophores in two areas (UK-1 and OMS) licensed for exploration by the International Seabed Authority. Based on test morphology, we distinguished 36 morphospecies (34 new to science) among 130 specimens. Twenty of these morphospecies yielded 184 DNA sequences, a 14-fold increase in genetic data for xenophyophores that confirms their high diversity in the eastern CCZ. A further 15 morphospecies (8 new to science) were recognised in samples from two other areas (APEI-6 and Russian exploration license area) within or adjacent to the CCZ. This large number of species confirms that the CCZ is a focal area for xenophyophore diversity. More broadly, it represents an unprecedented increase in the known global diversity of xenophyophores and suggests that many species remain undiscovered in the World's oceans. Xenophyophores are often sessile on nodules in the CCZ, making these delicate organisms particularly vulnerable to mining impacts. They can also play a crucial role in deep-sea ecosystems, providing habitat structures for meiofaunal and macrofaunal organisms and enhancing the organic content of sediments surrounding their tests. The loss of xenophyophores due to seabed mining may therefore have wider implications for the recovery of benthic communities following major human disturbances on the abyssal seafloor. [ABSTRACT FROM AUTHOR]

Abyssal polymetallic nodule fields represent a unique deep-sea habitat. The hard substratum provided by nodules is thought to increase habitat complexity, promoting the occurrence of highly diverse abyssal assemblages. However, hard substratum in these habitats is also available as outcropping rock fragments, but their contribution to habitat heterogeneity has been largely overlooked. Here, we assessed if the type and size of hard substratum can modulate benthic biodiversity at local scales within the Clarion Clipperton Zone (N Pacific abyss). We compared megafauna (animals >10 mm) assemblages in nodule bearing habitats with those in areas containing rocks in addition to nodules. We found a lower faunal density but a clearly higher diversity and more heterogenous composition in the assemblages of rock bearing areas compared to those with only nodules. In addition, hard substratum patch size appeared to positively influence the size of some taxa, like bamboo corals. These results suggest that rocks, in addition to nodules, constitute keystone structures enhancing habitat heterogeneity at local scales within nodule fields. Rock areas appear common in some abyssal plains and may make regionally-important contributions to abyssal biodiversity, suggesting that they may be relevant to include in conservation efforts. • We compared megafauna from Nodule and Rocks areas in an abyssal nodule field. • Rock bearing areas exhibit a higher diversity than those with only nodules. • Hard substratum patch size positively influences the size of some taxa. • Rocks and nodules are keystone structures enhancing abyssal habitat heterogeneity. • Rock areas in abyssal environments should be considered in conservation efforts. [ABSTRACT FROM AUTHOR]

In 1987, Slovakia bought part of the ocean bottom with the occurrence of mineral resources future - polymetallic nodules. The polymetallic nodule is a geological term for naming natural features consisting of more than 40 metals and other chemical elements. These special services originated in the ocean for two to three million years and nowadays, they are of main interest for countries whose mineral wealth is little or no available. Nodules contain about 30% manganese, 1.2% copper, 1.2% nickel, 0.2% cobalt, rare earth elements, etc. The existence of submarine nodules was found by the British ship HMS "Challenger" by oceanographic research in 1872 - 1876. Research and the subsequent mining of nodules were particularly points of interest for Western countries as well as the USSR. Rules for the use of mineral resources of the seabed beyond the limits of national jurisdiction were codified in the Convention on the Law of 1982, which came into force on 16.11.1994, and in the Slovakia on 21.7.1996. The seabed is one of the international space next to the high seas, Antarctica, outer space and celestial bodies, which are not subject to the sovereignty of any state authority. [ABSTRACT FROM AUTHOR]

The geochemical properties of sinking particles and sediments in the Clarion-Clipperton Zone were examined to develop a quantitative indicator with which to evaluate the contribution of sediment resuspended by nodule mining activity to sinking particles. The ratio of lithogenic material to organic carbon varies from ∼3 in sinking particles to ∼211 in sediments. This ratio is easily measured and is not easily affected by degradation and/or dissolution in the water column. A mixing model indicates that the ratio may be used as a potential proxy for estimating the contribution of resuspended sediment derived from mining operations to sinking particles. [ABSTRACT FROM PUBLISHER]

Abstract: Polymetallic/ferromanganese nodules (Mn-nodules) provide a rich source for manganese. It is not yet known if the nodules have a biogenic or an abiogenic origin. Here we applied the technique of high-resolution scanning electron microscopy, in combination with energy dispersive X-ray spectroscopical (EDX) analysis, to trace the existence of microbial biofilms. Two spatially separated assemblies exist, the exolithobiontic- and endolithobiontic colonizations. The exolithobiontic colonization is seen in the micro-canals, which traverse the outer surface layer of the nodules and are formed by elongated filamentous organisms, which show no signs of mineralization. In the center of the nodules three types of endolithobiontic microbial biofilms exist: first, cone-like microorganisms forming biofilms, second stone/pillar-like microorganisms and finally paving stone-like, hexagonal microorganisms. All are covered by brick-like mineral deposits. By EDX analysis we could measured the highest relative level of carbon (C) with respect to manganese (Mn) and sodium on the microorganisms. Our data are in perfect agreement with the assumption that the Mn deposits in the nodules are of biogenic origin. In a first approach, DNA from microorganisms from the interior of those Mn-nodules was isolated by PCR, and sequenced with respect to the 16S ribosomal RNA gene. Sequence comparison revealed that the sequence from the Mn-nodule, studied here, shares highest similarity to a bacterium living in soil, rich in iron and manganese. We propose that the microorganisms form a biofilm within the nodules onto which Mn is deposited due to an oxidation from Mn(II) to Mn(III)/Mn(IV). [Copyright &y& Elsevier]

The relationship between polymetallic nodules (Mn nodules) and deep-sea stratigraphy is relatively poorly studied and the role of sediment thickness in determining nodule occurrence is an active field of research. This study utilizes geophysical observations from three types of autonomous underwater vehicle (AUV) data (multi-beam bathymetry, sub-bottom profiles and underwater photography) in order to assess this relationship. Multi-beam bathymetry was processed with a pattern recognition approach for producing objective geomorphometric classes of the seafloor for examining their relation to sediment thickness and nodule occurrence. Sub-bottom profiles were used for extracting sediment thickness along a dense network of tracklines. Close-range AUV-photography data was used for automated counting of polymetallic nodules and their geometric features and it served as ground truth data. It was observed that higher nodule occurrence were related to layers with increased sediment thickness. This evidence reveals the role of local seafloor heterogeneity in nodule formation and suggests that unique patterns of local stratigraphy may affect geochemical processes that promote polymetallic nodule development at local scales. • AUV geophysical mapping reveals complex patterns of Mn nodule distribution. • Geophysical and image-based data suggest that Mn nodule occurrence relates to sediment thickness. • The role of sediment thickness in nodule development requires detailed geochemical investigation. [ABSTRACT FROM AUTHOR]

• All known observations for Area of Particular Environmental Interest 6 presented. • Assess morphology, sediments, nodules, oceanography, biogeochemistry and ecology. • APEI-6 partially representative of nearby exploration areas yet clear differences. • Present scientific synthesis and management implications for Clarion Clipperton Zone. To protect the range of habitats, species, and ecosystem functions in the Clarion Clipperton Zone (CCZ), a region of interest for deep-sea polymetallic nodule mining in the Pacific, nine Areas of Particular Environmental Interest (APEIs) have been designated by the International Seabed Authority (ISA). The APEIs are remote, rarely visited and poorly understood. Here we present and synthesise all available observations made at APEI-6, the most north eastern APEI in the network, and assess its representativity of mining contract areas in the eastern CCZ. The two studied regions of APEI-6 have a variable morphology, typical of the CCZ, with hills, plains and occasional seamounts. The seafloor is predominantly covered by fine-grained sediments, and includes small but abundant polymetallic nodules, as well as exposed bedrock. The oceanographic parameters investigated appear broadly similar across the region although some differences in deep-water mass separation were evident between APEI-6 and some contract areas. Sediment biogeochemistry is broadly similar across the area in the parameters investigated, except for oxygen penetration depth, which reached >2 m at the study sites within APEI-6, deeper than that found at UK1 and GSR contract areas. The ecology of study sites in APEI-6 differs from that reported from UK1 and TOML-D contract areas, with differences in community composition of microbes, macrofauna, xenophyophores and metazoan megafauna. Some species were shared between areas although connectivity appears limited. We show that, from the available information, APEI-6 is partially representative of the exploration areas to the south yet is distinctly different in several key characteristics. As a result, additional APEIs may be warranted and caution may need to be taken in relying on the APEI network alone for conservation, with other management activities required to help mitigate the impacts of mining in the CCZ. [ABSTRACT FROM AUTHOR]

The abyssal seafloor makes up three quarters of the ocean floor, and it is generally characterized as a food-limited habitat with low numbers of megafauna, particularly fishes. Baited camera observations from three abyssal seamount summits in the equatorial Pacific challenge this idea. On each of two deployments at the southernmost seamount, over 100 synaphobranchid eels (Ilyophis arx) were recorded feeding on standard bait (1 kg mackerel). This is the highest number of fishes per kg of bait ever recorded below 1000 m, including observations from large organic falls such as cetacean and shark carcasses. It is also the highest number that has ever been recorded at carrion of any kind or size at abyssal depths. We suggest an abyssal 'seamount effect' may be responsible, highlighting the potential importance of seamounts in structuring abyssal communities. • Over 100 synaphobranchid eels were observed at a 1kg bait package deployed on an abyssal seamount summit in the southwestern Clarion-Clipperton Zone. • Synaphobranchid eels, identified as Ilyophis arx, were exclusively observed on abyssal seamount summits, not on surrounding abyssal plains. • This is the highest number of fishes ever recorded per kg of bait/carrion below 1000 m. • This is the highest number of fishes that has ever been recorded at carrion of any kind or size at abyssal depths. • An abyssal 'seamount' effect may be responsible. [ABSTRACT FROM AUTHOR]

The amount and accuracy of nodule resources estimation in the Pacific Ocean are among the main factors conditioning the future exploitation. The estimates are based on the results of classical, direct seafloor sampling. Due to the large distance between sampling sites, the accuracy of assessing nodule resources in small parts of the deposit is low. The accuracy can be increased by using a large number of seafloor photographs taken along the route of the research vessel performing classic sampling. The study conducted for a part of the area administered by Interoceanmetal Joint Organization (IOM) included: (i) determining a model of the relationship between nodule abundance and seafloor nodule coverage using statistical methods, (ii) assessing the accuracy of nodule resources estimation using a geostatistical kriging procedure, (iii) proposing a preliminary classification of resources referring to International Seabed Authority (ISA) classification standards as material for further discussion. It was found that achievement of high accuracy in the estimation of nodule resources (with relative standard error <5%) in blocks planned for annual exploitation based on direct sampling is difficult. While the use of seafloor photographs increases the accuracy of estimating nodule resources, this improvement is not radical due to the unfavorable, preferential arrangement of photographic data. [ABSTRACT FROM AUTHOR]