Evaluation of abyssal meiobenthos in the eastern central Pacific (Clarion-Clipperton fracture zone)

Meiobenthos were sampled from 17 stations in the abyssal deep-sea system of the central Pacific centered around 14°N, 130°W at depths 4960–5154m, during the Nixo 47 R/V Jean Charcot cruise. Meiofaunal density range from 45–89 ind. 10cm². Predominant taxa are nematodes (84–100%) and copepods (0–10%). Rotifera, Polychaeta, and Acarina also occur. Nematodes are uniformly distributed spatially with 45 species or so; Monhysteridae is the dominant taxon, and Syringolaimus sp. (Ironidae) co-occurs faithfully. Low biomass (0.4–70.6μg 10cm²) are attributed to supposed dwarfism of metazoan meiofauna and very high proportion (60–80%) of juveniles and pre-adult forms. The majority of protozoans and metazoans are detritus- or deposit-feeders; in addition symbiotic associations, coprophagy and gardening activities are frequent. In such an oligotrophic environment, low food supply may limit meiofaunal abundance, biomass and maturation, and to a lesser extent species richness.     

The structure of Tuscarora fracture zone,northwestern Pacific

The Tuscarora fracture zone in the northwestern Pacific bounds parts of the Pacific plate that are characterized by linear (southwestern part) and non-linear (northeastern part) magnetic anomalies respectively. The fracture zone is traced from the oceanic plate across the Kuril-Kamchatka deep-sea trench into the shoreward trench slope. It therefore can not be considered as an ordinary transform fault.     

中国多金属结核开辟区沉积物地球化学特征

对中国多金属结核开辟区沉积物的详细研究表明,研究区内沉积物处于氧化至弱氧化环境,两种色调的沉积物在粒度分布特征以及化学组成上都存在着显著的差异,它们是不同沉积环境的反应.不同色调之间的界面为一沉积间断面.沉积物中的铁和锰具有不同的来源,铁可能以岩源碎屑为主,而锰则更可能是自生成因.钙和镁以生物成因为主.     

Discharge and surface plume measurements during manganese nodule mining tests in the north equatorial pacific

Rates, concentrations, and composition of mining discharge and the size and structure of the ensuing surface plumes were examined during North Pacific tests of scaled manganese nodule mining systems. Discharge was composed principally of bottom water and pelagic silts and clays, although nodule fragments with diameters less than 1 mm were also discharged at widely varying rates. Average flow rates of the discharge varied from 95 to 160 litres/s, with the solid fraction varying from 550 to approximately 2000g/s. The plume, as determined by particulate concentrations in excess of ambient oceanic conditions, extended approximately 5 km from the mining ship and had a width of about 1 km. Fe and Mn signatures allowed detection of the plume nearly 35 km from the source. The plume provided evidence of settling more rapidly than expected of silt and clay-size particles: a mean settling velocity of 6 × 10^?2 cm/s for the particulates in the plume and a mixed layer vertical turbulent eddy diffusivity of 1 × 10^?2m²/s have been inferred from the data. Field and laboratory data together suggest that the rapid settling was due to flocculation of the discharge particulates.     

Temporal and spatial distribution characteristics of nutrients in Clarion-Clipperton Fracture Zone in the Pacific in 2017

This research investigated eight stations in Clarion-Clipperton Fracture Zone(CCFZ) in the eastern tropical Pacific in 2017 to study the spatial distribution characteristics of nutrients and chlorophyll a(Chl a) concentration,and compared nutrient concentrations and molar ratios with those of other investigations 20 years ago in the same area. The study found that dissolved inorganic nutrient(N, P and Si) concentrations were lowest in the upper layer, and increased from surface to some depths, t...     

Submersible observations of manganese nodule and crust deposits on the Tenpo Seamount,Northwestern Pacific

Pavements of manganese nodules and crusts and outcrops of Miocene limestones were observed on the flanks and flat top of the Tenpo Seamount during three Shinkai 2000 dives. The pre‐Miocene volcano supplied nuclei of volcanic rocks and hydrothermal manganese deposits, and subsequent slow or no sedimentation promoted deposition of abundant hydrogenetic nodules and crusts, mainly on the upper flank of the seamount. Nodule pavements generally cover calcareous sand surface sediments, while crusts cover hard outcrops composed probably of volcanic rocks. The fields of crusts and nodules are sparsely distributed with each other on scales of meters to tens of meters. The on‐site observation suggests the deposits have encountered tectonic and/or mass movements that resulted in unusual occurrences of densely stacked nodules and occasionally the nodules resting directly on crusts or hard substrates. Mineralogical and chemical compositions reveal that for nodules and crusts the encrusting manganese layers of around 1 cm thickness are composed of hydrogenetic vernadite, and diagenetic influence is negligible.     

Major and trace element distributions in manganese nodules and micronodules as well as abyssal clay from the Clarion-Clipperton abyssal plain,Northeast Pacific

The contents of seven major components (TiO₂, Fe₂O₃, MgO, CaO, Na₂O, K₂O and P₂O₅) and 15 trace elements (Sc, V, Cr, Ni, Cu, Sr, Y, Zr, Ba, La, Ce, Nd, Eu, Yb and Th) were determined by ICP-AE spectrometry in 27 samples of manganese nodules, micronodules as well as abyssal clay collected by dredging from an area of nearly 1,9802 nautical miles in the central Clarion-Clipperton abyssal plain at a depth of about 4,500 m. Statistical analyses were used to compare among individual as well as pooled datasets, in addition to different indicators such as La/Th, Ni/Cu and LREE/HREE ratios for the Clarion-Clipperton samples, as well as between these and corresponding values for the upper continental crust (UCC), North America Shale Composite (NASC), and igneous Indian and Pacific Mid-Ocean Ridge Basalts (MORBs). The results show significant correlations between major components in the Clarion-Clipperton samples and Pacific Ocean MORB, whereas trace elements (excepting Ni and Cu) correlate better with the UCC and NASC. There is also depletion in LREEs, together with a Ce negative anomaly for all Clarion-Clipperton samples. The nodule, micronodule and abyssal clay datasets each reveal typical clusters of components such as P₂O₅ and Y, La, Nd, Eu, Tb, or Ni and Cu. Compared to abyssal clay, the nodule as well as micronodules show significant enrichment in Ni and Cu; nevertheless, an essentially constant Ni/Cu ratio indicates that all samples come from the sediment surface. The distributions of major components as well as trace elements for the Clarion-Clipperton samples present, to different degrees, characteristics common to both the upper continental crust and Mid-Ocean Ridge Basalt, strongly implying a hydrothermal origin, most probably from East Pacific Rise material transported by the Pacific North Equatorial Current.     

东太平洋中国多金属结核区锰结核样品中微生物群落结构的研究

通过非培养手段研究了东太平洋中国多金属结核区ES0303站点锰结核样品中的微生物群落结构.细菌16S rRNA基因克隆文库的研究结果表明：结核内细菌种群结构复杂,微生物种类丰富且各种群丰度不一（61个OTUs）,其中变形杆菌类群为优势种群,占所有细菌克隆子比例的64%,且主要分布于β/γ-、α-和δ-等3类变形杆菌（Proteobacteria）亚群之中,占比分别为34%、18%和12%.此外还存在包括酸杆菌（Acidobacteria）,放线菌纲（Actinobacteria）,绿弯菌门（Chloroflexi）,厚壁菌门（Firmicutes）,浮霉菌门（Planctomycetes）等在内的细菌类群的分布,克隆子比例依次为9%、7%、8%、2%和5%.古菌16S rRNA基因克隆文库的研究结果表明：古菌的群落结构单一（仅12个OTUs）,全部是由泉古菌海洋类群I（crenarchaeote marine group I,MGI）组成;其中MGI-η类群最为丰富,达到44%,而MGI-α、MGI-ζ和MGI-ε类群的克隆子比例分别为25%、18%和9%,另外还发现2个新的MGI分类类群.相关克隆子的数据库比对和系统发育树分析表明,并未发现已报道的直接参与铁锰氧化还原相关类群的存在,但它们大多数与来自多金属结核来源或深海来源的不可培养微生物具有较高的同源性.进一步的分析表明,锰结核内存在相当数量的氨氧化菌、硫酸盐还原菌、酸杆菌等能够改变pH值的细菌和古菌类群的存在,意味着它们可能在锰结核的形成过程中起到重要的作用.     

Mineralogy and composition of concentric layers within a manganese nodule from the North Pacific Ocean

The minor-element composition of concentric layers within a single ferromanganese nodule from the eastern North Pacific exhibits strong correlations with Fe and Mn contents but appears to be independent of pronounced mineralogic variations. On the basis of these correlations, the elemental composition of individual layers apparently is controlled by the relative contribution of two sources: seawater, and interstitial water of associated sediment. In contrast, the mineralogy of the nodule, consisting of birnessite in the outer few layers and todorokite in the inner layers, is considered to be a function of nodule diagenesis.     

‘Live’ benthic foraminifera at an abyssal site in the equatorial Pacific nodule province: Abundance,diversity and taxonomic composition

Replicate sediment samples were obtained from 3 closely spaced stations in the Kaplan East (KE) area of the abyssal eastern Equatorial Pacific (∼15°N, 119°W; ∼4100 m water depth), just below the carbonate compensation depth. At each site, 2 (Stns 827, 838) or 3 (Stn 824) complete cores (57 mm i.d.) were subsampled using 2–3 cut-off syringes of 6.6 cm³ cross-sectional area. The 0–1 cm sediment layers (>32 μm fraction) of these 20 subsamples together yielded 12,513 small, rose-Bengal stained benthic foraminifera dominated by agglutinated taxa, most of them morphologically simple monothalamous types or komokiaceans. Almost two-thirds (65%) of specimens were either obvious fragments, mainly of komokiaceans and tubular foraminifera, or single chambers or small groups of chambers believed to be fragments of very fragile komokiaceans. The remaining 4438 specimens (35%) were considered to be complete individuals. Most (78%) of these complete tests were indeterminate agglutinated spheres (termed ‘psammosphaerids’) that constituted 27.6% of all specimens (complete plus fragments). Complete individuals that could be assigned to either described or undescribed species accounted for 983 specimens (22% of complete tests=7.6% of all specimens); only 26 specimens (0.59% of complete individuals) were calcareous and these had invariably lost their tests through dissolution. Some groups exhibited considerable spatial heterogeneity. For example, 45% of the 3455 indeterminate psammosphaerids and 45% of the 3087 Komokiacean-like chambers occurred in single subcores. A total of 252 morphospecies was recognised; 168 were represented by complete individuals and 84 by fragments. There are clear differences between these Pacific assemblages and those from other oceans; in particular, psammosphaerids and isolated komokiacean chambers appear to be much more prevalent in the Pacific compared to the Atlantic Ocean. Some morphospecies present in Kaplan samples are known from the Atlantic but many are not. Such species may either (1) be ubiquitous but undersampled because they are rare or (2) have geographically patterned distributions. Without further sampling, there is no way to distinguish between these 2 possibilities. Fossilisable tests represent a very small component of the KE assemblage. Many of the delicate, monothalamous species that have little fossilisation potential, including the komokiaceans, accumulate stercomata (waste pellets) and may consume organic material and bacteria associated with sediment. Because of their enormous abundance at abyssal depths, these poorly known taxa probably play a substantial role in carbon cycling over vast areas of the Pacific seafloor.     

Chlorophyll distribution and photosynthetic activity in the north and equatorial Pacific Ocean along 155°W

The distribution of chlorophylla and photosynthetic characterestics of phytoplankters were investigated along 155°W between 50°N and 15°S during the KH-69-4 cruise of the R. V. Hakuh Maru (Aug. 12–Nov. 13, 1969). High concentrations of chlorophylla (more than 0.2 mg Chla/m³) were observed above the depths of 150 m at all stations except in 17°N, 5°S and 15°S. North of 20°N, the depths of chlorophyll accumulation shifted from near the surface to 50–100 m with southwards. In the equatorial region, chlorophyll accumulation centered at a depth of about 70 m and ranged vertically between 10 and 150 m. In all cases in the present study area, chlorophyll accumulation occurred within the euphotic zone (above the depth corresponding to 1% of the surface illumination), and except in the subarctic and some equatorial waters, this was usually prevalent in the lower half of the euphotic zone.The photosynthetic activities (initial slope of P vs I curve) of samples from the depths of chlorophyll accumulation were similar to, or lower than, those of shallow samples from the depths of upper half of the euphotic zone. At the depths of chlorophyll accumulation, calculatedin situ photosynthesis was high in the central Pacific and equatorial waters but low in the subarctic waters.     

Ferromanganese nodule fauna in the Tropical North Pacific Ocean: Species richness,faunal cover and spatial distribution

The poorly known ferromanganese nodule fauna is a widespread hard substratum community in the deep sea that will be considerably impacted by large-scale nodule mining operations. The objective of this study was to analyze the spatial distribution of the fauna attached to nodules in the Clarion-Clipperton Fracture Zone at two scales; a regional scale that includes the east (14°N, 130°W) and the west (9°N, 150°W) zones and a local scale in which different geological facies (A, B, C and west) are recognizable. The fauna associated with 235 nodules was quantitatively described: 104 nodules from the east zone (15 of facies A, 50 of facies B and 39 of facies C) and 131 nodules from the west zone. Percent cover was used to quantify the extent of colonization at the time of sampling, for 42 species out of the 62 live species observed. Fauna covered up to 18% of exposed nodule surface with an average of about 3%. While species richness increased with exposed nodule surface, both at the regional and at the facies scales (except for facies A), total species density decreased (again except for facies A). When all nodules were included in the statistical analysis, there was no relation between faunal cover and exposed nodule surface. Nevertheless, faunal cover did decrease with exposed nodule surface for the east zone in general and for both facies B and C in particular. Species distributions among facies were significantly different but explained only a very small portion of the variance (∼5%). We identified two groups of associated species: a first group of two species and a second group of six species. The other species (34) were independently distributed, suggesting that species interactions play only a minor role in the spatial distribution of nodule fauna. The flux of particulate organic carbon to the bottom is the only major environmental factor considered to vary between the two zones within this study. We conclude that the higher species richness and higher percent faunal cover of the east zone can be partially attributed to greater food availability derived from surface inputs. Moreover, the surfaces of facies B and C nodules had a complex, knobby micro-relief, creating microhabitat heterogeneity that may also have contributed to the greater species richness observed in the east zone.     

Silver in the subarctic northeast Pacific Ocean: Explaining the basin scale distribution of silver

Five vertical profiles of silver (Ag) in the subarctic northeast Pacific are presented. Dissolved (< 0.2 μm) Ag concentrations within the surface mixed layer range from 6–25 pM, with the highest observed values at the most coastal site. Elevated Ag concentrations at this station are most likely attributable to the estuarine circulation in the Juan de Fuca Strait. One open-ocean station (P20) exhibited a strong surface Ag maximum. The station was located at the edge of a Haida eddy which raises the possibility that such eddies transport Ag seaward from the coastal zone. Ag concentrations in the deep waters ranged from 60–80 pM. These measurements are consistent with other recent Ag data collected in the Pacific. Ag profiles throughout the Pacific Ocean yield a strong positive correlation between Ag concentration and dissolved silicic acid concentration. However, Ag is depleted relative to silicic acid at intermediate depths where dissolved O₂ concentrations are low, implying a possible removal of Ag from oxygen-depleted waters by scavenging and/or precipitation.     

东太平洋克拉里昂-克利帕顿断裂区多金属结核保留区的气象状况和预报规律

为保障我国大洋矿产资源的勘探和开采,文章根据我国于2017年对东太平洋克拉里昂-克利帕顿断裂区多金属结核保留区开展首次调查的志愿船观测数据,结合实际天气和预报过程,在对观测数据进行处理和分析的基础上,总结调查期间该保留区的气象状况和预报规律。研究结果表明:受冷高压及其外围的影响,保留区风向和风速变化较大,在预报过程中须实时关注冷空气的中心位置、走向和持续时间,适时调整作业方案;保留区气压与天气系统吻合较好,气温和湿度受降水影响,且降水频繁;除10月可能受到飓风影响外,保留区11月风速通常比10月大。     

Characterization of Deep-sea Macrofauna in the Korean Exploration Claim Area in the Clarion-Clipperton Fracture Zone,Northeastern Pacific Ocean

Macrofauna in the Clarion-Clipperton Fracture Zone remain poorly understood, due both to gross undersampling and to the fact that most species collected from the area are new to science. Evaluation of the diversity and species distribution of the benthic fauna in this area is critical to predicting and managing the impacts of manganese nodule mining. In this study, we investigated the distribution of macrofauna to understand the natural variability in the macrobenthic community and, by extension, to establish a baseline for environmental risk assessment. Samples were collected from the KR5 block of the Korea Contract Area, within the abyssal area of the Clarion-Clipperton Fracture Zone in the northeastern Pacific Ocean, by the RV Onnuri from 2012–2014. A total of 36 core samples were examined in the survey, from which we identified 183 macrobenthic species in 25 faunal groups with a mean density of 257 ind/m2. Not taking into account meio-faunal groups such as nematodes and harpacticoid copepods, the highest percentage of individuals was represented by Arthropoda. The dominant species (> 1% of total density) were the tanaids Typhlotanais sp.1, and Akanthophoreus spp. and Stenotanais sp., the isopod Macrostylis sp.1, and the polychaetes Cirratulidae spp. and Levinsenia uncinata. The abundances of the two dominant species, the tanaid Typhlotanais sp1. and isopod Macrostylis sp.1., were positively correlated with total organic carbon (TOC). There were no differences in macrofaunal density and community structure between preserved areas (PRA), the potential benthic impacted site (BIS), and other areas near the BIS. In general, higher diversity was associated with homogeneous environmental conditions, with high nodule coverage (> 50%) and TOC.     

东太平洋CC区板块构造和多金属结核资源效应探讨

利用东太平洋CC区多波束海底地形测量、结核覆盖率深拖系统探测、结核丰度地质采样和地球物理地震勘探资料,运用板块构造和沉积动力学理论,并与丰度趋势面和神经网络分析结果对比,对东太平洋CC区构造与多金属结核资源效应关系进行了探讨,并认为:(1)富集在研究区约200亿t结核的最主要控制因素是东太平洋海隆、莱恩山脉、克拉里昂-克利伯顿大断裂(Clarion-Clipperton Fracture Zone),东、西、南、北的四个构造单元为结核大量富集起到了框架性的关键作用;(2)本区经历了和遵循着海底扩张的基本过程,这个过程对结核物质来源、成矿作用、结核分布有重大影响,结核丰度、覆盖率与地形变化非常一致,重大相变距离为10～15km,基底自形成以来一直影响着地表结核;(3)地球深部地质作用过程对结核成矿作用也有一定影响,影响因素可能涉及基底岩浆房及其大小等.