Deep-sea Polymetallic Nodule Research Articles

Simulation Experiment of Environmental Impact of Deep-Sea Mining: Response of Phytoplankton Community to Polymetallic Nodules and Sediment Enrichment in Surface Water.

In this paper, simulation experiments were conducted to study the response of phytoplankton biomass and community composition to the influence of polymetallic nodules and sediment at four stations in the western Pacific in 2021. Chlorophyll a, pico-phytoplankton cell abundance, and metal concentration were measured before and after 24 h of deck incubation. The results show that there were three different patterns of response, namely, restrained, stimulated, and unaffected patterns. The restrained pattern appeared in the filtered treatments at station Incub.01, and the stimulated pattern appeared in the unfiltered treatments at station Incub.02. The response of the phytoplankton was not detectable at stations Incub.03 and 04. Regardless, positive and negative responses were found in the dominant pico-phytoplankton group—Prochlorococcus—and with slight variation in Synechococcus. The concentration of manganese varied among the treatments compared to that of iron and other metals. The factors affecting the growth of the phytoplankton in this study were metal concentrations and turbidity. The phytoplankton biomass baseline may also have played an important role: the lower the biomass, the higher the growth rate. This study proved that deep-sea polymetallic nodule mining will have a specific impact on surface phytoplankton biomass, but turbidity and particle retention time could be important factors in mitigating the extent of the impact.

Effects of Migration and Diffusion of Suspended Sediments on the Seabed Environment during Exploitation of Deep-Sea Polymetallic Nodules

With the increase in demand for metal resources, research on deep-sea polymetallic nodule mining has been reinvigorated, but the problem of its environmental impact cannot be ignored. No matter what method is used for mining, it will disturb the surface sediments of the seabed, thereby increasing the concentration of suspended solid particles and metal ions in the water body, changing the properties of the near-bottom water body and sediments, and affecting biological activity and the living environment. Focusing on the ecological and environmental impacts of deep-sea polymetallic nodule mining, taking as our main subject of focus the dynamic changes in sediments, we investigated the environmental impacts of nodule mining and their relationships with each other. On this basis, certain understandings are summarized relating to the ecological and environmental impacts of deep-sea polymetallic nodule mining, based on changes in the engineering geological properties of sediment, and solutions for current research problems are proposed.

Deep-sea polymetallic nodules as opportunity for future supply with critical raw materials

The renewed importance of polymetallic nodules in the context of forecasted increasing demands for metals are discussed. Based on the Interoceanmetal Joint Organization’s (IOM) site-specific data obtained during the exploration activity in the Clarion-Clipperton Fracture Zone, a total of 272.5 Mt of nodules were estimated as economically reasonable for future mining for Ni, Cu, Co, and Mn. Additionally, data for REE and other critical elements in nodules as potential by-products are presented.

Prospective life cycle assessment of metal commodities obtained from deep-sea polymetallic nodules

Sustainable metal supply will be essential to achieve climate and sustainability goals (e.g., Paris agreement), for instance by providing the necessary raw materials for renewable energy infrastructure systems. The potential exploitation of mineral resources from the deep sea (e.g., polymetallic nodules) can play a major role in this supply. A holistic environmental analysis is needed, in order to consider the entire value chain of the products obtained out of deep-sea exploitation. Therefore, the objective of this study was to perform a prospective life cycle assessment (LCA) of deep-sea-sourced commodities and compare it to equivalent products obtained from terrestrial mining. It considered as reference flow one tonne of (dry) nodules, using a cradle-to-gate approach up to the final metal commodities, analyzing the delivery to the market of 10.5 kg of copper, 12.8 kg of nickel, 2.3 kg of cobalt and 311.3 kg of ferromanganese. Three environmental impact categories were analyzed, i.e., climate change, acidification and photochemical oxidant formation. Overall, onshore activities (e.g., hydrometallurgical processing) are the main hotspots for environmental impacts of metals sourced from the deep sea; offshore activities play a minor role in the value chain. While photochemical oxidant formation impacts would be similar to terrestrial alternatives, the deep-sea-sourced commodities can bring environmental gains in the order of 38% for climate change and up to 72% for acidification. As this study shows, a strategic selection of the location for onshore processing of the polymetallic nodules is key to target cleaner production, not only because of the distance from the nodules site, but especially because of the available energy mix. The results should be interpreted with care, though, due to intrinsic limitations of the LCA study, e.g., the prospective nature of this study, the limited access to terrestrial mining data, amongst others. Nonetheless, regardless the limitations a prospective LCA imposes, this study highlights some important potential benefits that commodities from deep-sea polymetallic nodules can bring to society with respect to three important environmental impacts.

Importance of Spatial Autocorrelation in Machine Learning Modeling of Polymetallic Nodules, Model Uncertainty and Transferability at Local Scale

Machine learning spatial modeling is used for mapping the distribution of deep-sea polymetallic nodules (PMN). However, the presence and influence of spatial autocorrelation (SAC) have not been extensively studied. SAC can provide information regarding the variable selection before modeling, and it results in erroneous validation performance when ignored. ML models are also problematic when applied in areas far away from the initial training locations, especially if the (new) area to be predicted covers another feature space. Here, we study the spatial distribution of PMN in a geomorphologically heterogeneous area of the Peru Basin, where SAC of PMN exists. The local Moran’s I analysis showed that there are areas with a significantly higher or lower number of PMN, associated with different backscatter values, aspect orientation, and seafloor geomorphological characteristics. A quantile regression forests (QRF) model is used using three cross-validation (CV) techniques (random-, spatial-, and cluster-blocking). We used the recently proposed “Area of Applicability” method to quantify the geographical areas where feature space extrapolation occurs. The results show that QRF predicts well in morphologically similar areas, with spatial block cross-validation being the least unbiased method. Conversely, random-CV overestimates the prediction performance. Under new conditions, the model transferability is reduced even on local scales, highlighting the need for spatial model-based dissimilarity analysis and transferability assessment in new areas.

The Development History and Latest Progress of Deep-Sea Polymetallic Nodule Mining Technology

Deep-sea polymetallic nodules are a mineral resource with potential for commercial development. Due to the unique deep-sea environment in which they are found, specialized technology and equipment are required for their extraction. In this paper, firstly, the development of deep-sea polymetallic nodule mining technology is classified into three stages, and its characteristics are summarized. Moreover, the results from research into deep-sea polymetallic nodule mining technology are analyzed, including proposals for mining systems, research into key technologies, basic scientific problems, and proof of technical feasibility from sea tests. Secondly, the testing of the collector prototype and the environmental impact assessment study of Global Sea Mineral Resources NV, as well as the progress of the deep-sea polymetallic nodule mining test project in China, are introduced. On this basis, the opportunities and challenges brought by the fast-growing demand for electric vehicles to the development of deep-sea polymetallic mining technology is analyzed, and a possible technical scheme for a mining system and the trends in its development towards high reliability and high standards of environmental protection according to the requirements of commercial exploitation are explored. This provides a reference for the research and development of high-efficiency technology and equipment for the mining of deep-sea polymetallic nodules.

Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds

Deep-sea polymetallic nodule mining research activity has substantially increased in recent years, but the expected level of environmental impact is still being established. One environmental concern is the discharge of a sediment plume into the midwater column. We performed a dedicated field study using sediment from the Clarion Clipperton Fracture Zone. The plume was monitored and tracked using both established and novel instrumentation, including acoustic and turbulence measurements. Our field studies reveal that modeling can reliably predict the properties of a midwater plume in the vicinity of the discharge and that sediment aggregation effects are not significant. The plume model is used to drive a numerical simulation of a commercial-scale operation in the Clarion Clipperton Fracture Zone. Key takeaways are that the scale of impact of the plume is notably influenced by the values of environmentally acceptable threshold levels, the quantity of discharged sediment, and the turbulent diffusivity in the Clarion Clipperton Fracture Zone.

Environment, ecology, and potential effectiveness of an area protected from deep-sea mining (Clarion Clipperton Zone, abyssal Pacific)

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.

Mesopelagic Scattering Layer Behaviors Across the Clarion-Clipperton Zone: Implications for Deep-Sea Mining

The Clarion-Clipperton Zone (CCZ) is a 4 million km2 area in the eastern Central Pacific Ocean exhibiting large variability in environmental parameters, particularly oxygen and primary production, that is being targeted for deep-sea polymetallic nodule mining. This remote region’s pelagic biology is very poorly sampled, including for micronekton and zooplankton that provide essential ecosystem services such as carbon flux and support for commercial fisheries. We built a baseline of deep scattering layer (DSL) depths and vertical migration behaviors, proxies for mesopelagic micronekton and zooplankton communities, using shipboard acoustic Doppler current profiler datasets. Acoustic data (38 kHz, 75 kHz) were compiled from research cruises passing near or through the CCZ (2004–2019), and environmental data (mean midwater oxygen partial pressure, surface chlorophyll-a, and sea surface height anomaly) were assembled from the World Ocean Atlas and satellite oceanographic datasets. Our results suggest that midwater oxygen, associated with the Eastern Tropical Pacific Oxygen Minimum Zone (OMZ), is the strongest predictor of daytime DSL depths and the proportions of midwater populations that undergo vertical migration in this region. We used these relationships to predict micronekton and zooplankton behaviors across the CCZ, including licensed mining exploration areas and no-mining reserves. While the OMZ encompasses most licensed exploration areas, the current network of reserves lies outside of the core OMZ and ultimately may not represent or protect the pelagic OMZ fauna at highest risk from mining impacts. This research will further assist in developing resource exploitation regulations by the International Seabed Authority, and will provide mesopelagic baseline information for monitoring changes that may occur in the CCZ once industrial-scale mining begins.

Analysis of the Effect of Payment Mechanism on Exploitation of Polymetallic Nodules in the Area

The international seabed area (i.e., the “Area”) is rich in mineral resources. According to the United Nations Convention on the Law of the Sea (UNCLOS) and the relevant implemented agreements, in 2012, the International Seabed Authority (ISA) began to develop the regulations for the exploitation of mineral resources in the Area. The most important part of the regulations involves determining the distribution of benefits from the exploitation of mineral resources in the Area between the ISA and the contractors. The establishment of a financial model to evaluate the economic benefits and compare the distribution scheme was the basic method relied on in the current study of payment mechanism. According to the characteristics of the exploitation project of mineral resources in the Area, the discounted cash flow method was selected to construct the financial model. Taking China’s deep-sea mineral resources development project in the Area as the background, the main parameters of the model were determined. A comparative study of similar financial models with Massachusetts Institute of Technology (MIT) and other foreign countries was carried out, in addition to a sensitivity analysis of parameters. On the basis of the assurance that the contractor’s internal rate of return was not lower than the level of the land mining enterprise, the financial model was used to calculate the internal rate of return and the revenue of royalty under different payment mechanisms and rates. The advantages and disadvantages of different payment mechanisms in the exploitation of mineral resources in the area were analyzed. Lastly, the possible impacts of deep-sea polymetallic nodule mining on Terrestrial metal markets were highlighted.

Meiofauna in a Potential Deep-Sea Mining Area—Influence of Temporal and Spatial Variability on Small-Scale Abundance Models

In large areas of the Clarion Clipperton Fracture Zone (northeast Pacific), exploration of deep-sea polymetallic nodules as a potential source of high-technology metals is ongoing. Deep-sea mining may have a severe impact on the benthic communities. Here, we investigated meiofauna communities in the abyss at the scale of a prospective mining operation area. Random forest regressions were computed to spatially predict continuous layers of environmental variables as well as the distribution of meiofauna abundance across the area. Significant models could be computed for 26 sediment and polymetallic nodule parameters. Meiofauna abundance, taxon richness and diversity were also modelled, as well as abundance of the taxon Nematoda. Spatial correlation is high if the predictions of meiofauna are either based on bathymetry and backscatter or include sediment and nodule variables; Pearson’s correlation coefficient varies between 0.42 and 0.91. Comparison of differences in meiofauna abundance between different years shows that spatial patterns do change, with an elevated abundance of meiofauna in the eastern part of the study area in 2013. On the spatial scale of a potential mining operation, distribution models prove to be a useful tool to gain insight into both temporal variability and the influence of potential environmental drivers on meiofauna distribution.

Silurian metalliferous nodules from the region of Asaritsa peak, West Balkan mountain – preliminary results

First data for polymetallic nodules and host sediments in Silurian sequence from the region of Asaritsa peak, West Balkan mountain are presented. The nodules are rich of Fe, Mn, Co and Ni. Both sediments and nodules have high content of REE. The described Silurian nodules and sediments show a number of similarities with modern deep-sea polymetallic nodule bearing sediments. Some differences such as probable depth of deposition, mechanism of nodule formation, degree of lithification are also established.

From Sea Surface to Seafloor: A Benthic Allochthonous eDNA Survey for the Abyssal Ocean

Environmental DNA (eDNA) metabarcoding could facilitate rapid and comprehensive biotic surveys in the deep ocean, yet many aspects of the sources and distribution of eDNA in the deep sea are still poorly understood. In order to examine the influence of the water column on benthic eDNA surveys in regions targeted for deep-sea polymetallic nodule mining, we investigated the occurrence of pelagic eDNA across: (1) two different deep-sea habitat types, abyssal plains and seamounts, (2) benthic sample types, including nodules, sediment, and seawater within the benthic boundary layer (BBL), and (3) sediment depth horizons (0-2 cm, 3-5 cm). Little difference was observed between seamounts and the adjacent abyssal plains in the proportion of legacy pelagic eDNA sampled in the benthos, despite an > 1000 m depth difference for these habitats. In terms of both reads and amplicon sequence variants (ASVs), pelagic eDNA was minimal within sediment and nodule samples (< 2 %), and is unlikely to affect benthic surveys that monitor resident organisms at the deep seafloor. However, pelagic eDNA was substantial within the BBL (up to 13 % ASVs, 86% reads), derived both from the high-biomass upper ocean as well as deep pelagic residents. While most pelagic metazoan eDNA found in sediments and on nodules could be sourced from the epipelagic, protist legacy eDNA sampled on these substrates appeared to originate across a range of depths in the water column. Some evidence of eDNA degradation across a vertical sediment profile was observed for protists, with higher diversity in the 0-2 cm layer and a significantly lower proportion of legacy pelagic eDNA in deeper sediments (3-5 cm). Study-wide, our estimated metazoan sampling coverage ranged from 40 % to 74 %, despite relatively large sample size. Future deep-sea eDNA surveys should examine oceanographic influences on eDNA transport and residence times, consider habitat heterogeneity at a range of spatial scales in the abyss, and aim to process large amounts of material per sample (with replication) in order to increase the sampling coverage in these diverse deep ocean communities.

Life cycle climate change impacts of producing battery metals from land ores versus deep-sea polymetallic nodules

• Cradle-to-gate life cycle assessment of metals from land ores versus deep-sea nodules. • Using nodules can reduce CO2 emissions by 80% (Ni), 76% (Cu), 29% (Co), and 22% (Mn). • Nodules put 94% less sequestered carbon at risk and disrupt sequestration by 88% less. • Making 1 billion EV batteries from nodules could reduce atmospheric CO2 by 11.5 Gt.

High fungal-mediated leaching efficiency of valuable metals from deep-sea polymetallic nodules

Abstract Polymetallic nodules on abyssal seafloor represent a major reservoir of valuable metals. Here we analysed fungal-mediated leaching of metals from nodules collected at ca. 5000 m depth in the Clarion-Clipperton Fracture Zone of the Pacific Ocean. The bioleaching efficiency of Aspergillus and a mixed cultures of A. niger and Trichoderma sp., at different growing conditions, were investigated and compared to chemical treatments using citric acid. 11 days of treatment with A. niger growing in optimal medium conditions, produced the best result with the extraction of more than 80% of Mn, Cu, Ni, and 70% and 30% of Co and Fe, respectively. Our findings suggest that biotechnological processes can be a sustainable approach in terms of carbon footprint reduction compared to chemical strategies. Results presented here provide the potential of fungal-mediated leaching and pave the way for the development of effective and eco-sustainable biotechnologies for the metal recovery from deep-sea nodules.

The contribution of microbial communities in polymetallic nodules to the diversity of the deep-sea microbiome of the Peru Basin (4130–4198 m depth)

Abstract. Industrial-scale mining of deep-sea polymetallic nodules will remove nodules in large areas of the sea floor. The regrowth of the nodules by metal precipitation is estimated to take millions of years. Thus, for future mining impact studies, it is crucial to understand the role of nodules in shaping microbial diversity and function in deep-sea environments. Here we investigated microbial-community composition based on 16S rRNA gene sequences retrieved from sediments and nodules of the Peru Basin (4130–4198 m water depth). The nodule field of the Peru Basin showed a typical deep-sea microbiome, with dominance of the classes Gammaproteobacteria, Alphaproteobacteria, Deltaproteobacteria, and Acidimicrobiia. Nodules and sediments host distinct bacterial and archaeal communities, with nodules showing lower diversity and a higher proportion of sequences related to potential metal-cycling Bacteria (i.e. Magnetospiraceae, Hyphomicrobiaceae), bacterial and archaeal nitrifiers (i.e. AqS1, unclassified Nitrosomonadaceae, Nitrosopumilus, Nitrospina, Nitrospira), and bacterial sequences found in the oceanic crust, nodules, hydrothermal deposits, and sessile fauna. Sediment and nodule communities overall shared a low proportion of operational taxonomic units (OTUs; 21 % for Bacteria and 19 % for Archaea). Our results show that nodules represent a specific ecological niche (i.e. hard substrate, high metal concentrations, and sessile fauna), with a potentially relevant role in organic-carbon degradation. Differences in nodule community composition (e.g. Mn-cycling bacteria, nitrifiers) between the Clarion–Clipperton Fracture Zone (CCZ) and the Peru Basin suggest that changes in environmental setting (e.g. sedimentation rates) also play a significant role in structuring the nodule microbiome.

Environmental predictors of deep-sea polymetallic nodule occurrence in the global ocean

Abstract Polymetallic nodules found on the abyssal plains of the oceans represent one of the slowest known geological processes, and are a source of critical and rare metals for frontier technologies. A quantitative assessment of their occurrence worldwide has been hampered by a research focus on the northeastern Pacific Ocean and the lack of a global open-access data set of nodules. We have compiled a global data set of &amp;gt;10,000 seabed nodule and control samples, and combine it with digital grids of key environmental parameters to generate a predictive machine-learning model of nodule occurrence. In order of decreasing parameter ranking, we find that nodules are associated with very low sedimentation rates (&amp;lt; 0.5 cm/k.y.), moderately high oxygen values (150 and 210 mmol/m3), lithologies of clay followed by calcareous ooze, low summer surface productivity (&amp;lt;300 mgC/m2/day), low benthic biomass concentration (&amp;lt;1 log mgC/m2), water depths &amp;gt;4500 m, and low total organic carbon content (0.3–0.5 wt%). Competing hypotheses for nodule sustention and thus continued growth on the seafloor are the removal of sediment by bottom-water currents and biological activity. Using a high-resolution eddy-resolving ocean circulation model, we find that the bottom-current speeds over nodule fields are too low (&amp;lt;5 cm/s) to remove sediment, implicating the activity of epibenthic megafauna as the most likely mechanism. Our global nodule probability map combined with the assessment of a range of environmental drivers provides an improved basis for decision and policy making in the controversial area of deep-sea exploration.

Deep-Sea Mining Equipment in China: Current Status and Prospect

There are abundant mineral resources at the seafloor. These resources have rich varieties, vast reserves, high grade, and great development and utilization prospects. Countries in the world are accelerating the development of deep-sea mining equipment nowadays. This study analyzes the development status of the deep-sea mining equipment in China and abroad and investigates the deficiencies in technologies and equipment in China from the perspectives of fundamental scientific research, key technology development, and sea trial verification. Moreover, it summarizes the key scientific and technological issues to be resolved, and proposes the developing trends of deep-sea heavy operation equipment, ore transport equipment, and sea surface support vessels. We propose that deep-sea mining should adhere to the concepts of heavy equipment, collaboration, intelligence, and green development, and key technology innovation and independent research and development of the mining equipment should be promoted. Demonstration projects should be constructed for deep-sea polymetallic nodule mining to accelerate the development of deep-sea mining technologies and equipment, so as to realize large-scale sea trials, conduct system design for long-term operation, and promote commercial seabed mining.

Environmental considerations for impact and preservation reference zones for deep-sea polymetallic nodule mining

Development of guidance for environmental management of the deep-sea mining industry is important as contractors plan to move from exploration to exploitation activities. Two priorities for environmental management are monitoring and mitigating the impacts and effects of activities. International regulation of deep-sea mining activities stipulates the creation of two types of zones for local monitoring within a claim, impact reference zones (IRZ) and preservation reference zones (PRZ). The approach used for allocating and assessing these zones will affect what impacts can be measured, and hence taken into account and managed. This paper recommends key considerations for establishing these reference zones for polymetallic nodule mining. We recommend that zones should be suitably large (Recommendation 1) and have sufficient separation (R2) to allow for repeat monitoring of representative impacted and control sites. Zones should be objectively defined following best-practice and statistically robust approaches (R3). This will include the designation of multiple PRZ and IRZ (R4) for each claim. PRZs should be representative of the mined area, and thus should contain high -quality resource (R5) but PRZs in other habitats could also be valuable (R6). Sediment plumes will influence design of PRZ and may need additional IRZ to monitor their effects (R7), which may extend beyond the boundaries of a claim (R8). The impacts of other expected changes should be taken into account (R9). Sharing PRZ design, placement, and monitoring could be considered amongst adjacent claims (R10). Monitoring should be independently verified to enhance public trust and stakeholder support (R11).

The community structure of the deep-sea nematode community associated with polymetallic nodules in the Central Indian Ocean Basin

Technological advances have led to an increase in the number of investigations in the deep sea over the last two decades. However, despite a large number of scientific cruises, few published data on the nematode biodiversity and community structure are available from the abyssal nodule fields of the Central Indian Ocean Basin (CIOB). It is well known that CIOB harbors one of the largest high-grade nodule reservoirs and has therefore gained the most attention from industries and governments. Therefore, to adequately assess the potential environmental impacts of deep-sea polymetallic nodule mining in CIOB, more quantitative samples are needed to better understand trends in nematode diversity, abundance, and community structure in the nodule fields. Recently, on the basis of detailed surveys and analysis, a Test Mine Site (TMS) and Reference Mining Site (TRS) have been identified within the First Generation Mine Site (FGM) for further detailed studies. According to ISA guidelines, the TMS and TRS need to be similar in faunal abundance, composition and diversity, nodule abundances, metal grade and environmental data. As per the deep-sea environment conservation point of view, particularly to plan mining operations, the study has been done to check whether TMS and TRS have a similar type of faunal assemblage so that impacts and the ensuing loss of biota are minimized. To address this, we compared the composition and distribution of nematode communities at genus/species level from TMS and TRS. The average nematode density ranged from 71.68 ± 1.7 inds/10 cm2 in the TRS and 91.23 ± 1.3 inds/10 cm2 in the TMS. A total of 63 nematode genera belonging to 24 families were identified from TMS. The TRS samples supported 52 genera belonging to 20 families. A homogeneous community was observed at family/genus level from the TMS and TRS, particularly dominated by cosmopolitan nematode genera like Acantholaimus, Halalaimus, Thalasomonhystera and Leptolaimus. The TRS and TMS samples did exhibit a similar evenness (J'), and diversity (H’) suggesting a homogeneous nematode community throughout the area. Taxon diversity and richness estimators revealed that the current sampling design was able to characterize the majority of the nematode genera present. It can be suggested that the entire area of sampling is inhabited by a single, uniformly distributed, nematode assemblage at the genus level.This study also addresses whether or not nematode assemblages at genus/ species level inhabiting the bare sediment (soft sediment without nodules) in abyssal nodule fields are unique and differ from those found in the crevices of polymetallic nodules. As expected, there were fewer numbers of total genera recorded from the crevices with the differences being found in the dominant genera and families. Thalassomonhystera, Acantholaimus and Desmoscolex were noted as characteristic of the bare sediment while Leptolaimus and Camacolaimus showed the highest likelihood in nodule crevices. Hard nodule crevice substratum does favor some species level morphotypes of the genus Leptolaimus and Camacolaimus since these morphotypes were found exclusively in nodule crevices. However, owing to the still limited sampling effort in the deep sea, it is premature to suggest that these species are endemic to nodules. Implications of the present findings for environmental management and future research needs are provided.