Visioning a framework for effective environmental management of deep-sea polymetallic nodule mining: Drivers, barriers, and enablers

The anthropogenic impact of polymetallic nodule harvesting in the Clarion-Clipperton Fracture Zone is expected to strongly affect the benthic ecosystem. To predict the long-term, industrial-scale impact of nodule mining on the deep-sea environment and to improve the reliability of the sediment plume model, information about the specific characteristics of deep-sea particles is needed. Discharge simulations of mining-related fine-grained (median diameter ≈ 20 μm) sediment plumes at concentrations of 35–500 mg L–1 (dry weight) showed a propensity for rapid flocculation within 10 to 135 min, resulting in the formation of large aggregates up to 1100 μm in diameter. The results indicated that the discharge of elevated plume concentrations (500 mg L–1) under an increased shear rate (G ≥ 2.4 s–1) would result in improved efficiency of sediment flocculation. Furthermore, particle transport model results suggested that even under typical deep-sea flow conditions (G ≈ 0.1 s–1), rapid deposition of particles could be expected, which would restrict heavy sediment blanketing (several centimeters) to a smaller fall-out area near the source, unless subsequent flow events resuspended the sediments. Planning for in situ tests of these model projections is underway.

Download Full-text

Biological responses to disturbance from simulated deep-sea polymetallic nodule mining

PLoS ONE ◽

10.1371/journal.pone.0171750 ◽

2017 ◽

Vol 12 (2) ◽

pp. e0171750 ◽

Cited By ~ 96

Author(s):

Daniel O. B. Jones ◽

Stefanie Kaiser ◽

Andrew K. Sweetman ◽

Craig R. Smith ◽

Lenaick Menot ◽

...

Keyword(s):

Deep Sea ◽

Polymetallic Nodule ◽

Biological Responses ◽

Nodule Mining

Download Full-text

Deep-sea Polymetallic Nodule Mining: Challenges Ahead for Technologists and Environmentalists

Marine Georesources and Geotechnology ◽

10.1080/716100481 ◽

2003 ◽

Vol 21 (2) ◽

pp. 81-91 ◽

Cited By ~ 12

Author(s):

ANIL B. VALSANGKAR

Keyword(s):

Deep Sea ◽

Polymetallic Nodule ◽

Nodule Mining

Download Full-text

From sea surface to seafloor: a benthic allochthonous eDNA survey for the abyssal ocean

10.1101/2020.05.07.082602 ◽

2020 ◽

Cited By ~ 1

Author(s):

Olivier Laroche ◽

Oliver Kersten ◽

Craig R. Smith ◽

Erica Goetze

Keyword(s):

Water Column ◽

Deep Sea ◽

Anthropogenic Impacts ◽

Spatial Scales ◽

Deep Ocean ◽

Environmental Dna ◽

Benthic Boundary Layer ◽

Large Sample Size ◽

Polymetallic Nodule ◽

Nodule Mining

AbstractDiverse and remote deep-sea communities are critically under-sampled and increasingly threatened by anthropogenic impacts. 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), deriving both from the high biomass upper ocean as well as deep pelagic residents. While most pelagic eDNA found in sediments and on nodules could be sourced from the epipelagic for metazoans, 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.

Download Full-text

Experimental Investigation Into Soil and Mechanical Pick-up Device Interaction in Nodule Mining of Deep Seabed

Marine Technology Society Journal ◽

10.4031/mtsj.55.6.7 ◽

2021 ◽

Vol 55 (6) ◽

pp. 73-92

Author(s):

Krishnan Sudarvelazhagan ◽

Kuchibhotla Srinivas ◽

Murugesan Pradeep Kumar ◽

Senthamari Raju Raguraman ◽

Chullickal Raphael Deepak ◽

...

Keyword(s):

Experimental Investigation ◽

Deep Sea ◽

Large Scale ◽

Experimental Investigations ◽

Operating Parameters ◽

Variable Parameters ◽

Polymetallic Nodule ◽

Research Outcome ◽

Nodule Mining ◽

Device Interaction

Abstract This research is focused to experimentally analyze the nodule picking efficiency of a deep sea mechanical pick-up device developed by National Institute of Ocean Technology, India. Experiments were conducted in a simulation tank with different operating parameters on a bentonite soil bed simulating the deep seabed and artificial nodules. Digging depth of the pick-up device, its angle and haulage velocity were the input variable parameters. From the experimental investigations, the values of the operating parameters that result in the highest pick-up efficiency were identified. The nodule picking efficiency increased as the pick-up device inclination was increased and reduced when the digging depth and haulage velocity were increased. The maximum nodule picking efficiency was 85% when the haulage speed, digging depth, and pick-up device inclination were 0.0375 m/s, 25 mm, and 30°, respectively. The research outcome would be useful in actual deep seabed conditions for efficient polymetallic nodule mining. Multiple mining machines with increased working width are proposed for large-scale operations.

Download Full-text

DNA barcoding and cryptic diversity of deep-sea scavenging amphipods in the Clarion-Clipperton Zone (Eastern Equatorial Pacific)

Marine Biodiversity ◽

10.1007/s12526-021-01170-3 ◽

2021 ◽

Vol 51 (2) ◽

Author(s):

Inga Mohrbeck ◽

Tammy Horton ◽

Anna M. Jażdżewska ◽

Pedro Martínez Arbizu

Keyword(s):

Dna Sequences ◽

Deep Sea ◽

Molecular Data ◽

Equatorial Pacific ◽

Cryptic Diversity ◽

Species Identity ◽

Mining Sites ◽

Polymetallic Nodule ◽

Eastern Equatorial Pacific ◽

Nodule Mining

AbstractThe Clarion-Clipperton Zone (CCZ), located in the abyssal equatorial Pacific, has been subject to intensive international exploration for polymetallic nodule mining over the last four decades. Many studies have investigated the potential effects of mining on deep-sea ecosystems and highlighted the importance of defining environmental baseline conditions occurring at potential mining sites. However, current information on biodiversity and species distributions in the CCZ is still scarce and hampers the ability to effectively manage and reduce the potential impacts of mining activities. As part of the regulatory regimes adopted by the International Seabed Authority, concession holders are required to conduct an environmental impact assessment and gather baseline data on biodiversity and community structure in relation to their license areas. In the present study, we used an integrative molecular and morphological approach to assess species richness and genetic variation of deep-sea scavenging amphipods collected in two nodule-mining exploration areas (UK-1 and OMS-1 areas) and one Area of Particular Environmental Interest (APEI-6) in the eastern part of the CCZ. We analyzed the DNA sequences of the cytochrome c oxidase subunit I gene of 645 specimens belonging to ten distinct morphospecies. Molecular data uncover potential cryptic diversity in two investigated species, morphologically identified as Paralicella caperesca Shulenberger & Barnard, 1976 and Valettietta cf. anacantha (Birstein & Vinogradov, 1963). Our study highlights the importance of using molecular tools in conjunction with traditional morphological methods for modern biodiversity assessment studies, particularly to evaluate morphologically similar individuals and incomplete specimens. The results of this study can help determine species identity and ranges, information which can feed into environmental management.

Download Full-text

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

Communications Earth & Environment ◽

10.1038/s43247-021-00213-8 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Carlos Muñoz-Royo ◽

Thomas Peacock ◽

Matthew H. Alford ◽

Jerome A. Smith ◽

Arnaud Le Boyer ◽

...

Keyword(s):

Fracture Zone ◽

Deep Sea ◽

Environmental Concern ◽

Field Studies ◽

Research Activity ◽

Polymetallic Nodule ◽

Commercial Scale ◽

Clipperton Fracture Zone ◽

Clarion Clipperton Fracture Zone ◽

Nodule Mining

AbstractDeep-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.

Download Full-text

Impact of deep-sea polymetallic nodule mining on benthic microbial community and mediated biogeochemical functions

10.5194/egusphere-egu2020-13789 ◽

2020 ◽

Author(s):

Massimiliano Molari ◽

Tobias R. Vonnahme ◽

Felix Janssen ◽

Frank Wenzhöfer ◽

Matthias Haeckel ◽

...

Keyword(s):

Microbial Communities ◽

Deep Sea ◽

Large Scale ◽

Ecological Integrity ◽

Environmental Standards ◽

Metal Cycling ◽

Polymetallic Nodule ◽

Habitat Integrity ◽

Benthic Microbial Community ◽

Nodule Mining

Industrial-scale mining of deep-sea polymetallic nodules will remove nodules in large areas and impact the physical integrity of the seafloor. However, environmental standards for seafloor integrity and studies of recovery from environmental impacts are still largely missing. Further we have only a poor understanding of the role of nodules in shaping benthic microbial diversity and element cycles. We revisited the deep-sea disturbance and recolonization experiment carried out with a towed plough harrow in 1989 in the Peru Basin nodule field within a circular area of approx. 3.5 km diameter (>4100 m water depth). In the experimental area, the 26 years old plough tracks were still visible and showed different types and levels of disturbance such as removal and compaction of surface sediments. Microbial communities and their diversity were studied in disturbance tracks and undisturbed sites and related to habitat integrity, remineralization rates, and carbon flow. Locally, microbial activity was reduced up to 4 times in the impacted areas. Microbial cell numbers were reduced by ~50% in fresh, and by <30% in the old tracks. Our data suggest that microbially-mediated biogeochemical functions need more than 50 years to return to undisturbed levels in the sediments. In areas with nodules (i.e., outside the disturbance tracks) microbial communities in the nodules themselves were studied. Nodule communities were distinct from sediments and showed a 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), as well as bacterial sequences typically found in ocean crust, hydrothermal deposits and sessile fauna. Our results confirm that nodules host specific microbial communities with potentially significant contributions to organic carbon remineralization and metal cycling. This study contributes to developing environmental standards for deep-sea mining and highlights the limits for maintaining and recovering ecological integrity and functions during large-scale nodule mining.

Download Full-text