Deep-sea mining, environmental impact and the DISCOL project

Delayed response of hermit crabs carrying anemones to a benthic impact experiment at the deep-sea nodule fields of the Peru Basin?

Article

Mar 2023
MAR ENVIRON RES

The deep Peru Basin is characterised by a unique abyssal scavenging community featuring large numbers of hermit crabs (Probeebei mirabilis, Decapoda, Crustacea). These are atypical hermit crabs, not carrying a shell, but on some occasions carrying an anemone (Actiniaria). The reason why some hermit crabs carry or not carry anemones is thought to be indicative of a changed environment, outweighing the cost/benefit of their relationship. Here we present the temporal variation of abundances of P. mirabilis with and without anemones, spanning more than two decades, following a benthic impact experiment. An overall decrease in hermit crab densities was observed, most noticeable and significant after 26 years and characterised by a loss of Actiniaria on the Probeebei mirabilis' pleon. Whether this is a delayed response to the benthic impact experiment carried out 26 years’ prior or a natural variation in the population remains to be corroborated by an extension of the time-series. Attention is drawn to the limitations of our knowledge over time and space of the abyssal community dynamics and the urgent necessity to fill in these gaps prior to any type of deep-sea exploitation.

Small-scale heterogeneity of trace metals including rare earth elements and yttrium in deep-sea sediments and porewaters of the Peru Basin, southeastern equatorial Pacific

Article

Full-text available

Dec 2019
BG

Due to its remoteness, the deep-sea floor remains an understudied ecosystem of our planet. The patchiness of existing data sets makes it difficult to draw conclusions about processes that apply to a wider area. In our study we show how different settings and processes determine sediment heterogeneity on small spatial scales. We sampled solid phase and porewater from the upper 10 m of an approximately 7.4×13 km2 area in the Peru Basin, in the southeastern equatorial Pacific Ocean, at 4100 m water depth. Samples were analyzed for trace metals, including rare earth elements and yttrium (REY), as well as for particulate organic carbon (POC), CaCO3, and nitrate. The analyses revealed the surprisingly high spatial small-scale heterogeneity of the deep-sea sediment composition. While some cores have the typical green layer from Fe(II) in the clay minerals, this layer is missing in other cores, i.e., showing a tan color associated with more Fe(III) in the clay minerals. This is due to varying organic carbon contents: nitrate is depleted at 2–3 m depth in cores with higher total organic carbon contents but is present throughout cores with lower POC contents, thus inhibiting the Fe(III)-to-Fe(II) reduction pathway in organic matter degradation. REY show shale-normalized (SN) patterns similar to seawater, with a relative enrichment of heavy REY over light REY, positive LaSN anomaly, negative CeSN anomaly, and positive YSN anomaly and correlate with the Fe-rich clay layer and, in some cores, also correlate with P. We therefore propose that Fe-rich clay minerals, such as nontronite, as well as phosphates, are the REY-controlling phases in these sediments. Variability is also seen in dissolved Mn and Co concentrations between sites and within cores, which might be due to dissolving nodules in the suboxic sediment, as well as in concentration peaks of U, Mo, As, V, and Cu in two cores, which might be related to deposition of different material at lower-lying areas or precipitation due to shifting redox boundaries.

Small-scale heterogeneity of trace metals including REY in deep-sea sediments and pore waters of the Peru Basin, SE equatorial Pacific

Article

Full-text available

Jul 2019
BGD

Due to its remoteness, the deep-sea floor remains an understudied ecosystem of our planet. The patchiness of existing data sets makes it difficult to draw conclusions about processes that apply to a wider area. In our study we show how different settings and processes determine sediment heterogeneity on small spatial scales. We sampled solid phase and pore water from the upper 10 m of an approximately 7.4 × 13 km² large area in the Peru Basin, south-east equatorial Pacific Ocean, at 4100 m water depth. Samples were analyzed for trace metals including rare earth elements and yttrium (REY) as well as for particulate organic carbon (POC), CaCO3, and nitrate. The analyses revealed a surprisingly high small-scale heterogeneity of the deep-sea sediment composition. While some cores have the typical green layer from Fe(II) in the clay minerals, this layer is missing in other cores, i.e. showing a tan color associated with Fe(III) in the clay minerals. This is due to varying organic carbon contents: nitrate is depleted at 2–3 m depth in cores with higher total organic carbon contents, but is present throughout cores with lower POC contents, thus inhibiting the Fe(III)-to-Fe(II) reduction pathway in organic matter degradation. REY show shale-normalized (SN) patterns similar to seawater with a relative enrichment of heavy REY over light REY, positive LaSN anomaly, negative CeSN anomaly, as well as positive YSN anomaly and correlate with the Fe-rich clay layer and in some cores also with P. We, therefore, propose that Fe-rich clay minerals, such as nontronite, as well as phosphates are the REY-controlling phases in these sediments. Variability is also seen in dissolved Mn and Co concentrations, which might be due to dissolving nodules in the suboxic sediment, as well as in concentration peaks of U, Mo, As, V, and Cu in two cores, which might be related to deposition of different material at lower lying areas.

Megabenthic ecology of abyssal polymetallic nodule fields

Thesis

Full-text available

Jun 2019

Erik Simon-Lledó

Abyssal polymetallic nodule fields constitute an unusual deep-sea habitat. The mix of soft sediment and the hard substratum provided by nodules increases the complexity of these environments, and is thought to promote the occurrence of some of the most biologically diverse seafloor assemblages in the abyss. This unusual and diverse habitat is potentially subject to imminent large-scale human impacts in the form of seafloor mining. Mining disturbances are likely to extend over extremely large seafloor areas and have a clear potential to drive major changes in the resident fauna. Predicting the nature of such changes remains difficult; the ecology of this remote and vast habitat is poorly understood. The large seafloor areal coverage that can be investigated using photographic surveys presents an opportunity to numerically quantify variation in megafaunal communities inhabiting these abyssal plain environments. In this thesis, the fundamental drivers of megabenthic community variations in abyssal polymetallic nodule fields are explored based on extensive acoustic and imagery data collected using autonomous underwater vehicles. First, baseline ecological patterns of megafaunal distribution are investigated at different factor-operating scales, i.e. different environmental factors, in the proposed conservation zone ‘Area of Particular Environmental Interest 6’ of the Clarion Clipperton Zone (NE Pacific; water depth: 3950-4250 m). Broad-scale (tens of kilometres) variations in seafloor geomorphology appear to control megabenthic standing stock, while fine-scale (tens of meters) variations in nodule occurrence appear more important in the regulation of diversity and community composition. Both of these factors seem to play a key role in the functional structuring of megafauna assemblages across a nodule field. Second, long term effects of disturbance on megafaunal distribution patterns are investigated in the Peru Basin (E Pacific; 3800-4300 m water depth), 26 years after simulated mining impacts were induced during the “DISturbance and reCOLonization” experiment. Distinct ecological patterns are found across different seafloor disturbance levels; i.e. suspension feeder standing stock remains strongly reduced in directly disturbed seafloor areas, suggesting that the megabenthos of the DISCOL area has not yet recovered from simulated mining impacts. The findings of this thesis provide evidence of the habitat heterogeneity of polymetallic nodule field ecosystems, which appears promoted by both geomorphological and nodule occurrence variations across space. The nodule field is likely better considered as a mosaic habitat where nodules act as keystone structures, modulating a continuous community variation across a gradient of this resource. Consequently, successful conservation actions will likely require the preservation of areas comprising the full range of nodule cover and not just the low cover areas that are least attractive to mining.

A historical perspective on deep-sea mining for manganese nodules, 1965–2019

Article

May 2019

Ole Sparenberg

Of late, there has been a rise in interest in deep-sea minerals such as manganese nodules. Commercial mining operations to extract such minerals may commence soon. However, deep-sea mining projects were already underway in the 1960s and in an advanced stage of development by the 1970s, only to be shelved again in the 1980s. This paper examines a half a century of history of deep-sea mining and discusses how changing political, legal, economic, and socio-cultural policy frameworks contributed to its rise, fall, and eventual rebirth. In doing so, it is shown that the path towards commercial mining is less straightforward or inevitable than it may seem to current proponents and critics of deep-sea mining. This paper also uses the case of manganese nodules to illustrate how mineral concentrations can gain, lose, and regain their status of a resource depending on social, political, legal, and economic factors. The “becoming” of resources is an open-ended, reversible and sometimes incomplete process.

Biogeochemical Regeneration of a Nodule Mining Disturbance Site: Trace Metals, DOC and Amino Acids in Deep-Sea Sediments and Pore Waters

Article

Full-text available

Apr 2018

Increasing interest in deep-sea mineral resources, such as polymetallic nodules, calls for environmental research about possible impacts of mineral exploitation on the deep-sea ecosystem. So far, little geochemical comparisons of deep-sea sediments before and after mining induced disturbances have been made, and thus long-term environmental effects of deep-sea mining are unknown. Here we present geochemical data from sediment cores from an experimental disturbance area at 4,100 m water depth in the Peru Basin. The site was revisited in 2015, 26 years after a disturbance experiment mimicking nodule mining was carried out and compared to sites outside the experimental zone which served as a pre-disturbance reference. We investigated if signs of the disturbance are still visible in the solid phase and the pore water after 26 years or if pre-disturbance conditions have been re-established. Additionally, a new disturbance was created during the cruise and sampled 5 weeks later to compare short- and longer-term impacts. The particulate fraction and pore water were analyzed for major and trace elements to study element distribution and processes in the surface sediment. Pore water and bottom water samples were also analyzed for oxygen, nitrate, dissolved organic carbon, and dissolved amino acids, to examine organic matter degradation processes. The study area of about 11 km2 was found to be naturally more heterogeneous than expected, requiring an analysis of spatial variability before the disturbed and undisturbed sites can be compared. The disturbed sites exhibit various disturbance features: some surface sediments were mixed through, others had the top layer removed and some had additional material deposited on top. Pore water constituents have largely regained pre-disturbance gradients after 26 years. The solid phase, however, shows clear differences between disturbed and undisturbed sites in the top 20 cm so that the impact is still visible in the plowed tracks after 26 years. Especially the upper layer, usually rich in manganese-oxide and associated metals, such as Mo, Ni, Co, and Cu, shows substantial differences in metal distribution. Hence, it can be expected that disturbances from polymetallic nodule mining will have manifold and long-lasting impacts on the geochemistry of the underlying sediment.

Deep seabed mining: Frontiers in engineering geology and environment

Article

Full-text available

Apr 2023

Ocean mining activities have been ongoing for nearly 70 years, making great contributions to industrialization. Given the increasing demand for energy, along with the restructuring of the energy supply catalyzed by efforts to achieve a low-carbon economy, deep seabed mining will play an important role in addressing energy- and resource-related problems in the future. However, deep seabed mining remains in the exploratory stage, with many challenges presented by the high-pressure, low-temperature, and complex geologic and hydrodynamic environments in deep-sea mining areas, which are inaccessible to human activities. Thus, considerable efforts are required to ensure sustainable, economic, reliable, and safe deep seabed mining. This study reviews the latest advances in marine engineering geology and the environment related to deep-sea mining activities, presents a bibliometric analysis of the development of ocean mineral resources since the 1950s, summarizes the development, theory, and issues related to techniques for the three stages of ocean mining (i.e., exploration, extraction, and closure), and discusses the engineering geology environment, geological disasters, in-situ monitoring techniques, environmental protection requirements, and environmental effects in detail. Finally, this paper gives some key conclusions and future perspectives to provide insights for subsequent studies and commercial mining operations.

Impact of returning scientific cruises and prolonged on-site presence on litter abundance at the deep-sea nodule fields in the Peru Basin

Article

Sep 2022
MAR POLLUT BULL

Marine litter can be found along coasts, continental shelves and slopes, down into the abyss. The absence of light, low temperatures and low energy regimes characterising the deeper habitats ensure the persistence of litter over time. Therefore, manmade items within the deep sea will likely accumulate to increasing quantities. Here we report the litter abundance encountered at the Pacific abyssal nodule fields from the Peru Basin at 4150 m depth. An average density of 2.67 litter items/ha was observed. Litter composed of plastic was the most abundant followed by metal and glass. At least 58 % of the items observed could be linked to the research expeditions conducted in the area and appeared to be mostly accidental disposals from ships. The data gathered was used to address temporal trends in litter abundance as well as the impact of human on-site presence and return cruises in the context of future deep-sea mining efforts.

Tidally Driven Dispersion of a Deep-Sea Sediment Plume Originating from Seafloor Disturbance in the DISCOL Area (SE-Pacific Ocean)

Article

Full-text available

Dec 2021

The purpose of the study was to measure in situ the background suspended particulate matter concentration (SPMC) in the DISCOL area (SE Pacific) and its increase due to mechanical mobilization of the seabed. The disturbance experiment imitated future manganese nodule exploitations and was designed to measure the sediment plume generated by such activities. In the direct vicinity of the disturbance, landers equipped with acoustic and optical sensors measured the current velocities and the SPMC. The SPMC at the disturbance was easily up to 10 mg/L and thus about 200 times higher than the background concentration. The downstream sediment plume, measured by the lander, had a SPMC of about 1 mg/L. After tide reversal, the sediment plume was recorded a second time. A sediment transport model reproduced the plume dispersion. After rapid settling of the coarser fraction, a plume of hardly settling fine particles remained in suspension (and no deposition–resuspension cycles). The transport was controlled by the tides and by the vertical velocity component that resulted from bathymetrical differences. The plume may continue to disperse up to 100+ days (up to hundreds of km) depending on the particle size and until background concentration is reached.

Recovery of Paleodictyon patterns after simulated mining activity on Pacific nodule fields

Article

Full-text available

Dec 2021

Since the late 1980s, various experiments have been conducted in polymetallic nodule fields of the Pacific Ocean to assess the potential environmental impacts of future mining, specifically in two areas: the Peru Basin and the Clarion-Clipperton Fracture Zone (CCZ). Two expeditions, SO242/2 in 2015 (Peru Basin) and SO268/1 + 2 in 2019 (CCZ), deployed a towed camera system to collect imagery from both areas. These expeditions aimed to assess recovery of fauna in the short (few weeks) and long term (several years) following physical seafloor disturbance actions designed to mimic potential mining, by ploughs, dredges and epibenthic sleds. Within the collected image data, several strikingly hexagonal hole patterns were observed and identified as Paleodictyon nodosum , and an irregular form of Paleodictyon traces, both on undisturbed and disturbed areas of seafloor. Recent forms occur abundantly in various deep-sea regions, but their origin, and how they represent the mode of life of the forming organism, remains unknown. In this study, the imaged occurrences of Paleodictyon traces on disturbed seafloor sheds light on the lifecycle of the forming organism, demonstrating that they can recolonize disturbed habitat and produce the trace network in a few weeks. Nevertheless, the density of these patterns on disturbed substrates was lower than observed on undisturbed substrates in both nodule regions. We therefore hypothesize that, along with other benthic deep-sea fauna, these structures and the forming organism are impacted by physical seafloor disturbance, and even 26 years after disturbance, densities on disturbed sediments have not recovered to undisturbed levels.

Copper-binding ligands in deep-sea pore waters of the Pacific Ocean and potential impacts of polymetallic nodule mining on the copper cycle

Article

Full-text available

Sep 2021

The release of potentially toxic metals, such as copper (Cu), into the water column is of concern during polymetallic nodule mining. The bioavailability and thus toxicity of Cu is strongly influenced by its speciation which is dominated by organic ligand (L) complexation in seawater, with L-complexes being considered less bioavailable than free Cu2+. The presence of CuL-complexes in deep-sea sediments has, however, not been systematically studied in the context of deep-sea mining. We thus analyzed the Cu-binding L concentration ([L]) in deep-sea pore waters of two polymetallic nodule provinces in the Pacific Ocean, the Peru Basin and the Clarion-Clipperton-Zone, using competitive ligand equilibration–adsorptive stripping voltammetry. The pore-water dissolved Cu concentration ([dCu]) ranged from 3 to 96 nM, generally exceeding bottom water concentrations (4–44 nM). Based on fitting results from ProMCC and Excel, Cu was predominantly complexed by L (3–313 nM) in bottom waters and undisturbed pore waters. We conclude that processes like deep-sea mining are unlikely to cause a release of toxic Cu2+ concentrations ([Cu2+]) to the seawater as > 99% Cu was organically complexed in pore waters and the [Cu2+] was < 6 pM for 8 of 9 samples. Moreover, the excess of L found especially in shallow pore waters implied that even with a Cu release through mining activities, Cu2+ likely remains beneath toxic thresholds.

Assessing the temporal scale of deep-sea mining impacts on sediment biogeochemistry

Article

Full-text available

May 2020
BG

Deep-sea mining for polymetallic nodules is expected to have severe environmental impacts because not only nodules but also benthic fauna and the upper reactive sediment layer are removed through the mining operation and blanketed by resettling material from the suspended sediment plume. This study aims to provide a holistic assessment of the biogeochemical recovery after a disturbance event by applying prognostic simulations based on an updated diagenetic background model and validated against novel data on microbiological processes. It was found that the recovery strongly depends on the impact type; complete removal of the reactive surface sediment reduces benthic release of nutrients over centuries, while geochemical processes after resuspension and mixing of the surface sediment are near the pre-impact state 1 year after the disturbance. Furthermore, the geochemical impact in the DISturbance and reCOLonization (DISCOL) experiment area would be mitigated to some degree by a clay-bound Fe(II)-reaction layer, impeding the downward diffusion of oxygen, thus stabilizing the redox zonation of the sediment during transient post-impact recovery. The interdisciplinary (geochemical, numerical and biological) approach highlights the closely linked nature of benthic ecosystem functions, e.g. through bioturbation, microbial biomass and nutrient fluxes, which is also of great importance for the system recovery. It is, however, important to note that the nodule ecosystem may never recover to the pre-impact state without the essential hard substrate and will instead be dominated by different faunal communities, functions and services.

The Ecological Impacts of Submarine Tailings Placement

Chapter

Full-text available

Dec 2016

Deep-sea macrofaunal impacts of a large-scale physical disturbance experiment in the Southeast Pacific

Article

Jan 1998
DEEP-SEA RES PT II

Future human use of the deep sea potentially threatens benthic communities on large spatial and temporal scales. As a first approach to investigating the effects of large-scale sediment disturbance from deep-sea mining, the environmental risk assessment experiment DISCOL (DISturbance and ReCOLonization) was started in 1989 at 4150m depth in the tropical southeastern Pacific Ocean. A specially constructed disturber was towed 78 times through a 10.8km2 experimental field. The reestablishment of the impacted macrofaunal assemblages in the disturber tracks, with particular emphasis on the Polychaeta, was monitored three times over 3yr. Mean macrofaunal densities (>500μm, 0–5cm sediment depth range) in undisturbed sediments ranged from 77 to 122.8inds./0.25m2 at the three sampling times. After the impact, the animal abundances in the plow tracks were reduced to 39% of undisturbed densities. Polychaeta (48.6% of undisturbed densities) were less impacted than Tanaidacea (28.0%), Isopoda (18.5%), and Bivalvia (9.3%). Abundances of most higher taxa increased rapidly in the tracks, and after 3yr were comparable to those of undisturbed sediments. Dominance shifts in polychaete families level were observed in the early post-impact phases. Significant displacement of macrofaunal depth distributions after 3yr indicated sustained disturbance effects. Single species reactions within the Polychaeta did not allow clear interpretation of long-term disturbance effects, but Hurlbert rarefaction, used in a nonstandard way, demonstrated significantly reduced “diversity” after 3yr. The reestablishment of a semi-liquid surface sediment layer is proposed as a potentially controlling factor for the reestablishment of the macrofaunal community after physical disturbance. Although the DISCOL experiment did not fully simulate full-scale industrial impacts, it has provided insights into macrofaunal recolonization following large-scale disturbance of deep-sea environments.

Short and decadal impacts of seafloor physical perturbation on the abundances of Lebensspuren ‘traces of life’ in the Peru Basin manganese nodule province

Article

Full-text available

Feb 2024

Interest in deep-sea mining for polymetallic nodules as an alternative source to onshore mines for various high-technology metals has risen in recent years, as demands and costs have increased. The need for studies to assess its short- and long-term consequences on polymetallic nodule ecosystems is therefore also increasingly prescient. Recent image-based expedition studies have described the temporal impacts on epi-/megafauna seafloor communities across these ecosystems at particular points in time. However, these studies have failed to capture information on large infauna within the sediments or give information on potential transient and temporally limited users of these areas, such as mobile surface deposit feeders or fauna responding to bloom events or food fall depositions. This study uses data from the Peru Basin polymetallic nodule province, where the seafloor was previously disturbed with a plough harrow in 1989 and with an epibenthic sled (EBS) in 2015, to simulate two contrasting possible impact forms of mining disturbance. To try and address the shortfall on information on transient epifauna and infauna use of these various disturbed and undisturbed areas of nodule-rich seafloor, images collected 6 months after the 2015 disturbance event were inspected and all Lebensspuren , ‘traces of life’, were characterized by type (epi- or infauna tracemakers, as well as forming fauna species where possible), along with whether they occurred on undisturbed seafloor or regions disturbed in 1989 or 2015. The results show that epi- and endobenthic Lebensspuren were at least 50% less abundant across both the ploughed and EBS disturbed seafloors. This indicates that even 26 years after disturbance, sediment use by fauna may remain depressed across these areas.

The Effect of Air Chamber Geometrical Design for Enhancing the Output Power of Oscillating Water Column Wave Energy Converter

Article

Full-text available

Feb 2023
MAR TECHNOL SOC J

This paper represents the effects of geometry and design of an oscillating water column energy converter air chamber on the airflow response. The primary goal of this research is to use different shapes of air chambers, such as rectangular, cylindrical, and conical air chambers with varying cross sections, to optimize the air velocity entering the turbine, to obtain the maximum power available in a progressive wave with a constant period and wavelength. Modeling and numericalsimulation are performed by using the commercial software ANSYS. Since this paper is concerned with the effect of air flow velocity, a vent is located at the chamber's outlet rather than a turbine. In order to obtain the exit air velocity results, the wave system air characteristics results are applied as an input air flowfor three air chamber cases. The results show that the air velocity flow increasedsignificantly from 7.14 m/s in the rectangular air chamber to 10.4 m/s in cylindrical air chamber and reached a maximum of 14.2 m/s in the conical airchamber.

Research on the Control Algorithm of Full Sea Heavy Load Proportional Seven-Function Hydraulic Manipulator Based on Load Sensing

Article

Full-text available

Feb 2023
MAR TECHNOL SOC J

An underwater manipulator is one of the most commonly used tools in offshore operations. In the face of the unknown environment of the deep sea and the uncertainty of the operation target, the underwater manipulator needs good control stability and higher control efficiency to prevent accidents, which puts forward higher requirements for the control of the manipulator. Underwater manipulators often need to work under heavy loads and to perform tasks efficiently under light loads, which is crucial for efficient control under load. In this paper, a control algorithm based on proportion and derivative feedback control for an all sea depth load proportional hydraulic manipulator is proposed. The feasibility and progressiveness of this algorithm are verified by building kinematic and dynamic models, building physical platforms for tests, and building sea trial acceptance.

Ophiotholia (Echinodermata: Ophiuroidea): A little-known deep-sea genus present in polymetallic nodule fields with the description of a new species

Article

Full-text available

Mar 2023

Introduction The Clarion Clipperton Zone (CCZ) in the Northeast Pacific Ocean holds the largest deposits of polymetallic nodules at abyssal depths. These nodules are rock formations containing valuable metals and minerals targeted for mining. They further provide diverse habitat for a range of deep-sea species. Little is known so far on the taxonomy, natural history and biogeography of these deep-sea animals which is vital for accurate assessment of the risk of species extinctions from large-scale mining. One of the most abundant megafaunal groups in the CCZ is the Ophiuroidea (brittle stars), of which Ophiotholia is one of the more abundant genera found in the area. The genus Ophiotholia has a world-wide distribution and currently holds six species. Methods Material collected from seven scientific cruises to the CCZ was examined, morphologically, together with comparative material from all the known species. The small size and the damage caused during sampling often impeded their identification. The specimens were also genetically analyzed using a fragment of the mitochondrial COI gene. Scanning Electron Microscope images of the key microstructural characters were made using selected specimens from CCZ as well as from the comparative material. Result and discussion One morphotype was identified as the known species Ophiotholia supplicans Lyman, 1880, while the second is new to science and is described in this paper. The umbrella spines and the arrangement of their articulations on the lateral arm plate, were selected as the most relevant morphological characters in the taxonomy of the genus Ophiotholia and a revised identification key of all characters from all known Ophiotholia species is provided as a table in the supplement material. The identification and description of such a little-known genus improves the evaluation of the biodiversity not only in the CCZ but also for the deep sea.

Taxonomic assessment of deep-sea decapod crustaceans collected from polymetallic nodule fields of the East Pacific Ocean using an integrative approach

Article

Full-text available

Oct 2022

Deep-sea decapod crustaceans (Crustacea: Decapoda) collected during nine research cruises to the Clarion-Clipperton Zone (CCZ) in the NE Pacific Ocean and the Peru Basin in the SE Pacific Ocean were studied comprehensively using an integrative taxonomic approach. The abyssal seafloors of both areas are rich in economically interesting polymetallic nodules. All specimens were morphologically identified and genetically analysed using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI). Eight species were collected, comprising three anomurans, three carideans, one dendrobranchiate, and one brachyuran, from water depths ranging between 4089 and 4511 m. COI sequences for representatives of the genera Parapagurus Smith, 1879, Ethusina SI Smith, 1884, and Bathystylodactylus Hanamura & Takeda, 1996 are provided for the first time. The molecular barcodes of the species provided herein will be valuable for the full taxonomic assignment of sequences produced in future metabarcoding and eDNA monitoring work. The new records extend the geographical distributional ranges or fill geographical gaps of the species reported, although none of the species is endemic to polymetallic nodule areas. This study is part of a taxonomic series aiming to describe the biodiversity of areas targeted for future deep-sea mining.

Numerical Simulation of Deep-Sea Sediment Transport Induced by a Dredge Experiment in the Northeastern Pacific Ocean

Article

Full-text available

Aug 2021

Predictability of the dispersion of sediment plumes induced by potential deep-sea mining activities is still very limited due to operational limitations on in-situ observations required for a thorough validation and calibration of numerical models. Here we report on a plume dispersion experiment carried out in the German license area for the exploration of polymetallic nodules in the northeastern tropical Pacific Ocean in 4,200 m water depth. The dispersion of a sediment plume induced by a small-scale dredge experiment in April 2019 was investigated numerically by employing a sediment transport module coupled to a high-resolution hydrodynamic regional ocean model. Various aspects including sediment characteristics and ocean hydrodynamics were examined to obtain the best statistical agreement between sensor-based observations and model results. Results show that the model is capable of reproducing suspended sediment concentration and redeposition patterns observed during the dredge experiment. Due to a strong southward current during the dredging, the model predicts no sediment deposition and plume dispersion north of the dredging tracks. The sediment redeposition thickness reaches up to 9 mm directly next to the dredging tracks and 0.07 mm in about 320 m away from the dredging center. The model results suggest that seabed topography and variable sediment release heights above the seafloor cause significant changes especially for the low sedimentation pattern in the far-field area. Near-bottom mixing is expected to strongly influence vertical transport of suspended sediment.

Deep-sea mining: processes and impactsprocesses and impacts

Chapter

Aug 2020

Mining the extensive accumulations of minerals on the seafloor of the deep ocean might provide important resources, but it also has the potential to lead to widespread environmental impacts. Some of these impacts are unknown, and some may differ for the three main resource types: polymetallic nodules, seafloor massive sulphides, and polymetallic (cobalt-rich) crusts. Here, we detail the mining processes and describe the ecosystems associated with the minerals of interest. We then explain the expected impacts of mining, and discuss their potential effects on deep-ocean ecosystems. We also highlight the missing evidence needed to underpin effective environmental management and regulation of the nascent deep-sea mining industry.

Impacts of deep‐sea mining on microbial ecosystem services

Article

Full-text available

Jan 2020

Interest in extracting mineral resources from the seafloor through deep‐sea mining has accelerated in the past decade, driven by consumer demand for various metals like zinc, cobalt, and rare earth elements. While there are ongoing studies evaluating potential environmental impacts of deep‐sea mining activities, these focus primarily on impacts to animal biodiversity. The microscopic spectrum of seafloor life and the services that this life provides in the deep sea are rarely considered explicitly. In April 2018, scientists met to define the microbial ecosystem services that should be considered when assessing potential impacts of deep‐sea mining, and to provide recommendations for how to evaluate and safeguard these services. Here, we indicate that the potential impacts of mining on microbial ecosystem services in the deep sea vary substantially, from minimal expected impact to loss of services that cannot be remedied by protected area offsets. For example, we (1) describe potential major losses of microbial ecosystem services at active hydrothermal vent habitats impacted by mining, (2) speculate that there could be major ecosystem service degradation at inactive massive sulfide deposits without extensive mitigation efforts, (3) suggest minor impacts to carbon sequestration within manganese nodule fields coupled with potentially important impacts to primary production capacity, and (4) surmise that assessment of impacts to microbial ecosystem services at seamounts with ferromanganese crusts is too poorly understood to be definitive. We conclude by recommending that baseline assessments of microbial diversity, biomass, and, importantly, biogeochemical function need to be considered in environmental impact assessments of deep‐sea mining.

Unexpected high abyssal ophiuroid diversity in polymetallic nodule fields of the Northeast Pacific Ocean, and implications for conservation

Preprint

Full-text available

Apr 2020

The largest and commercially appealing mineral deposits can be found in the abyssal sea floor of the Clarion-Clipperton Zone (CCZ), a polymetallic nodule province, in the NE Pacific Ocean, where experimental mining is due to take place. In anticipation of deep-sea mining impacts, it has become essential to rapidly and accurately assess biodiversity. For this reason, ophiuroid material collected during eight scientific cruises from five exploration licence areas within CCZ, one area being protected from mining (APEI3, Area of Particular Environmental Interest) in the periphery of CCZ and the DISturbance and re-COLonisation (DISCOL) Experimental Area (DEA), in the SE Pacific Ocean, was examined. Specimens were genetically analysed using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI). Maximum-likelihood and neighbour-joining trees were constructed, while four tree-based and distance-based methods of species delineation (automatic barcode gap discovery, ABGD; barcode index numbers, BINs; general mixed Yule–coalescent, GMYC; multi-rate Poisson tree process, mPTP) were employed to propose secondary species hypotheses (SSHs) within the ophiuroids collected. The species delimitation analyses' concordant results revealed the presence of 43 deep-sea brittle star SSHs, revealing an unexpectedly high diversity and showing that the most conspicuous invertebrates in abyssal plains have been so far considerably underestimated. The number of SSHs found in each area varied from five (IFREMER area) to 24 (BGR (Federal Institute for Geosciences and Natural Resources, Germany) area) while 13 SSHs were represented by singletons. None of the SSHs were found to be present in all seven areas while the majority of species (44.2 %) had a single-area presence (19 SSHs). The most common species were Ophioleucidae sp. (Species 29), Amphioplus daleus (Species 2) and Ophiosphalma glabrum (Species 3), present in all areas except APEI3. The biodiversity patterns could be mainly attributed to particulate organic carbon (POC) fluxes that could explain the highest species numbers found in BGR (German contractor area) and UKSRL (UK Seabed Resources Ltd, UK contractor area) areas. The five exploration contract areas belong to a mesotrophic province, while conversely the APEI3 is located in an oligotrophic province, which could explain the lowest diversity as well as very low similarity with the other six study areas. Based on these results the representativeness and the appropriateness of APEI3 to meet its purpose of preserving the biodiversity of the CCZ fauna are questioned. Finally, this study provides the foundation for biogeographic and functional analyses that will provide insight into the drivers of species diversity and its role in ecosystem function.

DISCOL experiment revisited: Assessing the temporal scale of deep-sea mining impacts on sediment biogeochemistry

Article

Full-text available

Sep 2019
BGD

Deep-sea mining for polymetallic nodules is expected to have severe environmental impacts because in addition to the nodules, benthic fauna as well as the upper reactive sediment layer is removed through the mining operation, and blanketed by resettling material from the suspended sediment plume. This study aims to provide a holistic assessment of the biogeochemical recovery after a disturbance event by applying prognostic simulations based on an updated diagenetic background model and validated with novel (micro)-biological data. It was found that the recovery strongly depends on the impact type; complete removal of the reactive surface sediment reduces seafloor nutrient fluxes over centuries, while geochemical processes after resuspension and mixing of the surface sediment are near pre-impact state one year after the disturbance. Furthermore, the geochemical impact in the DISCOL area would be mitigated to some degree by a clay-bound Fe(II)-reaction layer, impeding the downward diffusion of oxygen, thus stabilizing the redox zonation of the sediment during transient post-impact recovery. The interdisciplinary (geochemical, numerical and biological) approach highlights the closely linked nature of benthic ecosystem functions, e.g. through bioturbation, microbial biomass and nutrient fluxes, which is also of great importance for the system recovery.

Impacts of Deep-Sea Mining on Microbial Ecosystem Services

Preprint

Full-text available

Nov 2018

Interest in extracting mineral resources from the seafloor through deep-sea mining has accelerated substantially in the past decade, driven by increasing consumer demand for various metals like copper, zinc, manganese, cobalt and rare earth elements. While there are many on-going discussions and studies evaluating potential environmental impacts of deep-sea mining activities, these focus primarily on impacts to animal biodiversity. The microscopic spectrum of life on the seafloor and the services that this microbial realm provides in the deep sea are rarely considered explicitly. In April 2018, a community of scientists met to define the microbial ecosystem services that should be considered when assessing potential impacts of deep-sea mining, and to provide recommendations for how to evaluate these services. Here we show that the potential impacts of mining on microbial ecosystem services in the deep sea vary substantially, from minimal expected impact to complete loss of services that cannot be remedied by protected area offsets. We conclude by recommending that certain types of ecosystems should be off limits until initial characterizations can be performed, and that baseline assessments of microbial diversity, biomass, and biogeochemical function need to be considered in environmental impact assessments of all potential instances of deep-sea mining.

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

Article

Full-text available

Feb 2017
PLOS ONE

Commercial-scale mining for polymetallic nodules could have a major impact on the deep-sea environment, but the effects of these mining activities on deep-sea ecosystems are very poorly known. The first commercial test mining for polymetallic nodules was carried out in 1970. Since then a number of small-scale commercial test mining or scientific disturbance studies have been carried out. Here we evaluate changes in faunal densities and diversity of benthic communities measured in response to these 11 simulated or test nodule mining disturbances using meta-analysis techniques. We find that impacts are often severe immediately after mining, with major negative changes in density and diversity of most groups occurring. However, in some cases, the mobile fauna and small-sized fauna experienced less negative impacts over the longer term. At seven sites in the Pacific, multiple surveys assessed recovery in fauna over periods of up to 26 years. Almost all studies show some recovery in faunal density and diversity for meiofauna and mobile megafauna, often within one year. However, very few faunal groups return to baseline or control conditions after two decades. The effects of polymetallic nodule mining are likely to be long term. Our analyses show considerable negative biological effects of seafloor nodule mining, even at the small scale of test mining experiments, although there is variation in sensitivity amongst organisms of different sizes and functional groups, which have important implications for ecosystem responses. Unfortunately, many past studies have limitations that reduce their effectiveness in determining responses. We provide recommendations to improve future mining impact test studies. Further research to assess the effects of test-mining activities will inform ways to improve mining practices and guide effective environmental management of mining activities.

Tailings and their disposal in deep-sea mining

Article

Jan 2013

Although not yet commercially practiced, deep-sea mining is under development for metalliferous sediments, massive sulphides and polymetallic nodules. Ore extraction is to be achieved by sediment suction, rock cutting and nodule collection, and transport from the seafloor to the mining platform is planned to be carried out by airlifting up the water - ore slurry. Water, accompanying particulate matter and dissolved substances comprising the fluid-particle mixture tailings, is to be ejected back into the ocean. Environmental studies for impact evaluation were conducted for water column and seafloor effects. This paper concentrates on the fluid tailings and their discharge back into the sea. We also address potential environmental effects of large-scale environmental impact experiments in due time before industry conducts pilot mining operations, as well as the disposal of mud and concrete tailings, the processing wastes. Copyright © 2013 by The International Society of Offshore and Polar Engineers (ISOPE).

Anthropogenic impacts on the deep sea

Article

Jan 2003

Hjalmar Thiel

The deep sea has received broad attention in the preceding chapters of this volume, a recognition that it is the largest, continuous ecological unit on earth. However, it is also of all environments the most remote and least well known, both to scientists and to the public. But this remoteness has not protected the deep sea from anthropogenic impacts. Wastes released anywhere on the high seas or into the atmosphere may rapidly sink into the abyss, to be out of sight and out of mind. Invisible and visible wastes penetrate this vast volume of water from a variety of sources and via different pathways. There are few areas of the world's oceans that have not received any anthropogenic impact, invisibly and by slow-paced transport. Life is ubiquitous in the oceans. Since most species require oxygen, this essential gas must be transported to all locales with the currents; and these same currents transport invisible contaminants. These invisible substances have travelled for long distances and periods of time, and may affect organisms many degrees of latitude and longitude away from their origin and their entrance to the oceans. In contrast, human intrusions into the deep sea are already direct sources of environmental disturbances, and these intrusions, visible and made with consciousness of their impact, may become more numerous and more serious in coming years. Anthropogenic impacts in the deep sea deserve serious consideration and international legal regulation. Invisible deep-sea contaminants may eventually return to the ocean surface, add to the local pollution, and disturb species or communities and eventually man through direct or synergistic effects. Turn-over times in the oceans, depending on regional peculiarities, are estimated at a few hundreds to one thousand years or so. One has no idea what the pollution status of the ocean surface will be when contaminants resurface after such long time periods. Visible contaminants, intentionally dumped into the deep sea, cannot be retrieved. Any realization that specific substances may not have found their final storage at great ocean depth will inevitably come too late; there would be no possibility to redress the situation. Similarly, impacts occurring in the deep sea as a consequence of mining mineral resources will have long-term effects. A thorough knowledge of the ecology of the deep sea is essential to arrive at the right decisions. However, effective protective measures for the deep sea will be possible only if the impacts are known or their extent can be estimated. These are certainly difficult tasks, but impact prediction must be undertaken a long time in advance. Oceanographers of all disciplines must think ahead. Appropriate deep-sea research must be conducted, targeted so as to understand potential impacts, and experimental large-scale approaches are essential. From a conservation point of view the deep sea is firmly within the ambit of the human commu-nity despite its remoteness. Besides ocean scientists, politicians, economists, and engineers must take the potential disturbance of the far-distant deep sea into account. They all share responsibility for the deep sea as part of the oceans and the human environment.

Data Support for Modelling of Deep-Sea Mining Impacts

Article

Full-text available

Oct 2011

The paper critically reviews the presently available experimental data from various tests and experiments connected with the deep-sea mining issue with regard to their feasibility in supporting and validating the developed numerical models. Numerical modelling is applied mainly to predetermining the plume development a n d seaaoor blanketing caused by v arious sediment discharges. The paper describes processes included in these models and discusses the experimental acquisition of needed model parameters. The existing models and their validation are shortly reviewed and parameters essential to operate and validate them are pointed out. Recommendations for further studies are given in order to improve the quality of model forecasts.

Impact of Bottom Trawling on Deep-Sea Sediment Properties along the Flanks of a Submarine Canyon

Article

Full-text available

Aug 2014
PLOS ONE

The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400-800 m depth range. To explore the degree of alteration of surface sediments (0-50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y-1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea.

Effects of scallop dredging on a soft sediment community: A large-scale experimental study

Article

Full-text available

Apr 1996

Changes to benthic infauna caused by scallop dredging at a site in Port Phillip Bay, southeastern Australia, were examined experimentally using a BACI (before, after, control, impact) design. The experimental dredging was undertaken by commercial fishermen and was typical of normal commercial operations in its spatial extent, intensity and duration. Changes to benthic community structure following dredging were monitored using grab samples taken on 3 occasions pre-dredging and 6 occasions post-dredging. The significance of changes was assessed using ANOVA for the more abundant species and, for pooled groups of species, Bray-Curtis community dissimilarities and multidimensional scaling (MDS). The abundance of 7 of the 10 most common species changed significantly (ANOVA p < 0.10) after dredging; 6 species decreased in abundance while 1 species increased. The size and persistence of dredging impacts varied between species, but most species decreased in abundance by 20 to 30%. Dredging impacts became undetectable for most species following their next recruitment. Most species recruited within 6 mo of the dredging impact, but a small number of species still had not recruited after 14 mo. These latter species appeared to cause a persistent change in community structure which was still detectable after 14 mo using Bray-Curtis dissimilarities. MDS ordination indicated that changes to community structure caused by dredging were smaller than those that occur between seasons and years.

Epibenthic Foraminifera from elevated microhabitats: Cibicidoides wuellerstorfi and Planulina ariminensis

Article

Apr 1989

Planulina ariminensis and Cibicidoides wuellerstorfi prefer an elevated position above the sediment-water interface for a better chance to catch food particles from slightly streaming water. They are attached to sponge skeletons, stones, hydroids and other objects protruding above the sediment surface. This elevated habitat explains why they are underrepresented in live populations collected from standard samples of loose sediment. -from Authors

Atmospheric and Oceanographic Characteristics of the BGR Exploration Area for Polymetallic Nodules in the Northeastern Tropical Pacific Ocean and Model Simulations of Dredge-Induced Suspended Sediment Transport

Chapter

Jun 2024

This chapter provides an overview on atmospheric and hydrographic conditions, and temporal variations of bottom water currents in the exploration area for polymetallic nodules of the German Federal Institute for Geosciences and Natural Resources (BGR) in the northeastern tropical Pacific Ocean. Furthermore, we compare in situ resuspension experiments with numerical model results on transport pathways and deposition patterns of the suspended sediments to assess the reliability of model predictions with respect to future deep-sea mining. The BGR area underlies seasonal climate variations due to meridional migrations of the Intertropical Convergence Zone (ITCZ) and changes in the subtropical high. In March, when the ITCZ is weakest near the equator, sea level pressure is high and precipitation and northeast winds are low, while in August and September, when the ITCZ is most northerly, pressure is low, precipitation increases, and winds are variable. The frequency of tropical storms and hurricanes peaks in June through August. Tropical storm magnitude is usually reached once a year, and hurricanes occur every other year. The two parts of the exploration area are located at the equatorward edge of the westward flowing North Equatorial Current. Water temperatures reach as high as 27 °C and salinity as low as 33.9 psu in the mixed layer with an average depth of 30 m. The thermo- and haloclines are sharp and separate the surface layers from cooler, saltier waters that are devoid of oxygen to a depth of 700 m to 900 m. These water masses overlie Pacific Intermediate waters, the deeper Antarctic Intermediate water, and Lower Circumpolar waters closest to the ocean bottom. Analysis of near-bottom current data recorded by moored ADCPs between 2013 and 2019 indicates low velocities of 1–5 cm s−1 on average and maximum values of 8–14 cm s−1. Current directions are strongly influenced by semidiurnal tidal cycles and near-inertial oscillations, with predominant southeasterly to southwesterly flow. The bottom currents can be amplified and change their predominant direction by mesoscale eddies that form under the influence of Central American Gap Winds and travel several 1000 km westward. Coupled ocean-circulation and sediment-transport models, taking into account local sediment particle properties, were used to simulate the near-field and far-field transport and settling of suspension plumes on the seafloor generated by dredging experiments in the BGR exploration area and by an epibenthic sledge tow in the Peru Basin. Comparison of the observed and predicted deposition patterns showed satisfactory agreement and increased confidence in the model’s ability to adequately predict the spread of suspension plumes and particle redeposition resulting from future industrial-scale deep-sea mining.

Can the well-studied environmental impacts of bathyal bottom trawling be used in assessing the unknown environmental effects of deep-sea mining on the abyssobenthic environment?

Preprint

Full-text available

Sep 2021

Lauren Geiser

The deep-sea is the largest continuous ecosystem on Earth, yet it remains one of the least understood by scientists. Exploitation of the deep-sea takes several forms including commercial fishing and, in the near future, mining. Bottom trawling is a destructive, nonselective fishing method that is well established all over the world. Consequently, its environmental impacts have been well studied. Deep-sea mining (DSM), on the other hand, has not yet begun commercially, but is expected to commence in both national and international waters within the next few decades. Since no large-scale seabed mining has yet taken place, its environmental impacts remain uncertain. This thesis explores the similarities of bathyal deep-sea bottom trawling (DSBT) and abyssal DSM to determine if the well-known environmental impacts of DSBT can be used to predict those of DSM. Methodologies are compared, as well as the biotic and faunal aspects of their respective benthic ecosystems. It is likely that the environmental effects of DSBT can and should be used in assessing the impacts of DSM. Because full-scale in situ testing remains challenging and expensive for submarine mining, this insight may prove helpful in establishing preliminary regulations and environmental protections for DSM.

Oxford Encyclopedia - Article - Rahul Sharma

Article

Full-text available

May 2020

Rahul Sharma

Deep-sea mining pertains to underwater minerals such as polymetallic nodules, ferromanganese crusts, and hydrothermal sulfides that are considered as alternative sources for metals such as Cu, Ni, Co, Pb, Zn, Cd, Mn, Fe, and rare earths that could be exploited in the future by developing suitable technologies. Many of these deposits occur in international waters in which several “contractors” have staked claims over large tracts of the seafloor under the United Nations Law of the Sea, whereas attempts are also being made to develop the deposits within the Exclusive Economic Zone of some countries. However, several concerns have emerged over potential impacts of mining these deposits, leading to regulations being framed as well as measures being devised for conserving the marine ecosystems. The likely sources of environmental impact of deep-sea mining include those from the mining ship where handling of ore, machinery, oil will take place; the lift mechanism that would transfer the minerals from the sea bottom to the surface through the entire water column; as well as the mining machine that would actually scrape the seafloor for minerals. This article describes the likely impacts that could be caused due to mining of three different types of deep-sea minerals, viz. polymetallic nodules, hydrothermal sulfides and ferromanganese crusts. It further shows the estimation of impacts in terms of mining area, volume and weight of associated substrates; and goes on to suggest mitigation measures to minimize the potential impacts of deep-sea mining. Finally, the national and international environmental regulations for deep-sea mining have been discussed.

Persistence of plastic debris and its colonization by bacterial communities after two decades on the abyssal seafloor

Article

Full-text available

Jun 2020

The fate of plastic debris entering the oceans is largely unconstrained. Currently, intensified research is devoted to the abiotic and microbial degradation of plastic floating near the ocean surface for an extended period of time. In contrast, the impacts of environmental conditions in the deep sea on polymer properties and rigidity are virtually unknown. Here, we present unique results of plastic items identified to have been introduced into deep-sea sediments at a water depth of 4150 m in the eastern equatorial Pacific Ocean more than two decades ago. The results, including optical, spectroscopic, physical and microbial analyses, clearly demonstrate that the bulk polymer materials show no apparent sign of physical or chemical degradation. Solely the polymer surface layers showed reduced hydrophobicity, presumably caused by microbial colonization. The bacterial community present on the plastic items differed significantly (p < 0.1%) from those of the adjacent natural environment by a dominant presence of groups requiring steep redox gradients (Mesorhizobium, Sulfurimonas) and a remarkable decrease in diversity. The establishment of chemical gradients across the polymer surfaces presumably caused these conditions. Our findings suggest that plastic is stable over extended times under deep-sea conditions and that prolonged deposition of polymer items at the seafloor may induce local oxygen depletion at the sediment-water interface.

Environmental Impacts of Nodule, Crust and Sulphide Mining: An Overview

Chapter

Full-text available

May 2019

The new industry of deep-sea mining (DSM) potentially offers abundant supplies of several metals from the deep ocean, but the ores will need to be recovered from pristine environments in which the ecosystems are often poorly known. Information that is available for some of these environments suggests that organisms may struggle to recover from the impacts of DSM, whilst in other areas the impacts may be somewhat less.

Evaluation of Physical Environmental Consequences of Deep-sea Mining

Article

Jan 2001

The environmental consequences of deep-sea mining have been a matter of thorough research since the first pilot mining tests in the 1910th. Despite numerous efforts by the engineering and the scientific community, the technical means for in-situ observation and control as well as the possibilities for onboard or laboratory investigations vary greatly and fail to assist to answer these questions satisfactorily. Therefore, in the frame of the "German Interdisciplinary Deep-Sea Protection (TUSCH)"-programme special subprojects were launched to make new attempts to answer the above mentioned questions. This contribution summarizes the results from these investigations. By means of a new sediment sampler especially developed for this purpose, large volume, undisturbed cores were recovered, which allowed the necessary geotechnical investigations. The results indicated that the moveable sediment layer thickness barely surmounts the nodule diameter, that only a fraction of the recent sediment layer will be resuspended and form a cloud, that the near-bottom tailings will be caught by the wake flow of the miner, that most of the resuspended material will rapidly aggregate and resettle relatively fast, and that the chemical changes are negligible.

Trawl Fishing Disturbance and Medium-Term Macroinfaunal Recolonization Dynamics: A Functional Approach to the Comparison between Sand and Mud Habitats in the Adriatic Sea (Northern Mediterranean Sea)

Chapter

Full-text available

Dec 2005

Demersal fishing gear affects seabed habitats both directly and indirectly and modifies the processes and dynamics of benthic communities. At present, scientific attention is focused on using the functional approach to better understand the constraints that drive the recolonization of benthic fauna subjected to fishing disturbance. The Northern Adriatic Sea has an extensive trawlable area that is intensively exploited by a variety of trawling gear. Among these, the rapido, a beam trawl used to catch flatfishes on mud substrate and pectinids on sand, appears to have the greatest impact on the benthic habitat. We used various functional indicators (diversity indices, community structure, trophic groups, production analysis, and exergy) to compare the medium-term (9-month) macroinfaunal recolonization processes in sand and mud habitats treated with a single experimental rapido haul. Recolonization was found to be a community-wide process. The early successional stages in the sand habitat were dominated by scavenging organisms that peaked in abundance 7 d after the treatment. In the mud habitat, the trend in scavenger activity was less distinct, although a peak in abundance was recorded 1 month after the treatment. The functional analyses revealed that complete recovery required at least 9 months in both habitats. Finally, data collected on the fishing ground near the sand experimental area were analyzed in order to investigate the chronic disturbance caused by commercial trawling. The fishing ground samples showed a higher spatial heterogeneity than the sand experimental samples. Total abundance, total biomass, and production values in the fishing ground were comparable with the lowest recorded values in the sand experimental area, and the exergy differences suggested that the fishing ground’s benthic community remained in an early successional stage.

The Biology of Lophelia pertusa (Linnaeus 1758) and Other Deep-Water Reef-Forming Corals and Impacts from Human Activities.

Article

Full-text available

Jan 1999
INT REV HYDROBIOL

Alex David Rogers

Over the last twenty years, human exploitation has begun to have an impact in the deep sea, especially in the upper bathyal zone. This has mainly taken the form of deep-sea fishing but more recently oil exploration has extended beyond the continental shelf. Deep-water coral reefs occur in the upper bathyal zone throughout the world. These structures, however, are poorly studied with respect to their occurrence, biology and the diversity of the communities associated with them. In the North-East Atlantic the coral Lophelia pertusa has frequently been recorded. The present review examines the current knowledge on L. pertusa and discusses similarities between its biology and that of other deep-water, reef-forming, corals. It is concluded that L. pertusa is a reef-forming coral that has a highly diverse associated fauna. Associated diversity is compared with that of tropical shallow-water reefs. Such a highly diverse fauna may be shared with other deep-water, reef-forming, corals though as yet many of these are poorly studied. The main potential threats to L. pertusa in the North-East Atlantic are considered to be natural phenomena, such as slope failures and changes in ocean circulation and anthropogenic impacts such as deep-sea fishing and oil exploration. The existing and potential impacts of these activities on L. pertusa are discussed. Deep-sea fishing is also known to have had a significant impact on deep-water reefs in other parts of the world.

Why are there so many species in deep-sea sediments?

Article

Nov 1996
J EXP MAR BIOL ECOL

J. D. Gage

High species diversity in samples of macrobenthos of deep-sea sediments is now well established. But a consensus on the processes regulating this unexpectedly species-rich coexistence in metazoan species at the deep-sea bed is still elusive. This review takes a broad approach by examining differences between marine and terrestrial biodiversity in the context of the following: scale of sampling effort on which our knowledge is based; the species concept as applied in the past to taxonomic studies on deep-sea benthic organisms; scaling differences and size related patterns in community structure and habitat complexity and differences in potential for co-evolution. Latitudinal and bathymetric patterns are summarised in relation to habitat variability and distributional range and in relation to J.S. Gray's (1994) claim that benthic diversity may be equally high on the continental shelf.

Deep-sea benthic community and environmental impact assessment at the Atlantic Frontier

Article

May 2001
CONT SHELF RES

J. D. Gage

The seabed community provides a sensitive litmus for environmental change. North Sea analysis of benthic populations provides an effective means for monitoring impacts from man's interventions, such as offshore oil exploitation and fishing, against baseline knowledge of the environment. Comparable knowledge of the benthic biology in the deep waters of the Atlantic Frontier beyond the N.E. Atlantic shelf edge is poorly developed. But uncertainties should not encourage assumptions and extrapolations from the better-known conditions on the continental shelf. While sampling at present still provides the best means to assess the health of the deepwater benthic habitat, protocols developed for deep-sea fauna should be applied. These are necessary because of (a) lower faunal densities, (b) higher species richness, (c) smaller body size, and (d) to ensure comparability with other deep-sea data. As in the North Sea, species richness and relative abundance can be analysed from quantitative samples in order to detect impacts. But analysis based on taxonomic sufficiency above species level is premature, even if arguably possible for coastal communities. Measures also need to ensure identifications are not forced to more familiar coastal species without proper study. Species-level analysis may be applied to seabed photographs of megafauna in relation to data on bottom environment, such as currents and the sediment, to monitor the health of the deep-water community. Although the composition of higher taxa in the benthic community is broadly similar to soft sediments on the shelf, concordance in sensitivities is speculative. Moreover, new organisms occur, such as giant protozoan xenophyophores, unknown on the continental shelf, whose sensitivities remain conjectural. Past knowledge of the benthic biology of the deep-water areas off Scotland is based on scattered stations and some more focussed, multidisciplinary studies, and should be significantly augmented by the results from the oil industry-funded Atlantic Margin Environmental Study cruises in 1996 and 1998. A predominantly depth-related pattern in variability applies here as found elsewhere in the deep ocean, and just sufficient knowledge-based predictive power exists to make comprehensive, high-resolution grid surveys unnecessary for the purpose of broad-scale environmental assessment. But new, small-scale site surveys remain necessary because of local-scale variability. Site survey should be undertaken in the context of existing knowledge of the deep sea in the UK area of the Atlantic Frontier and beyond, and can itself usefully be structured as tests of a projection from the regional scale to reduce sampling effort. It is to the benefit of all stakeholders that environmental assessment aspires to the highest scientific standards and contributes meaningfully to context knowledge. By doing so it will reduce uncertainties in future impact assessments and hence contribute usefully to environmental risk management.

New deep-sea Nematoda (Enoplida, Thoracostomopsidae, Oncholaimidae, Enchelidiidae) from a manganese nodule area of the eastern South Pacific

Article

Jan 1995
ZOOL SCR

Christian Bussau

Five new nematode species are described from a mangancsc nodule area of the abyssal eastern South Pacific: Enoploides tyrannis sp. n., Paramesacanthion abyssorum sp. n., P. forcepssp. n. (all three Thoracostomopsidae), Phylloncholaimus immanis gen. et sp. n. (Oncholaimidac), and Eurystomina absoluta sp. n. (Enchelidiidae). They are characterized by large size (body length 5000–23000 μm), short tails (c = 17–33), and strongly cuticularizcd, barrel-shaped buccal cavities with large teeth. With the exception of one male of E. tyrannis from the surface of a manganese nodule, all other specimens were found in the sediment. The new species are sporadic in distribution and represented by few individuals.

Environmental effects of marine fishing

Article

Full-text available

Sep 1995
AQUAT CONSERV

Some effects of fisheries on the associated biological systems are reviewed and management options and their inherent risks are considered. In addition to the effects on target species, other sensitive groups impacted by fishing are considered including marine mammals, turtles, sea birds, elasmobranchs and some invertebrates with low reproductive rates. Other impacts discussed include the destruction of benthic habitat, the provision of unnatural sources of food and the generation of debris. Management options are considered including the designation of marine protected areas, risk aversion, and the burden of proof. A balanced consideration of the risks and consequences of ‚Type 1’︁ and ‚Type II’︁ errors is advocated.

Numerical modeling of suspended sediment due to deep-sea mining

Article

Full-text available

Feb 1996

A numerical model was developed in order to estimate the residence time of a sediment plume generated by potential deep-sea mining activities with special attention to discharges in the bottom boundary layer. The site of the Disturbance and Recolonization Experiment (DISCOL) in the Peru Basin in the southeast Pacific Ocean was chosen as a case study. The model includes the actual bathymetry, as well as the characteristic flow patterns in this region. Various aspects affecting the transport and sedimentation of the plume, such as stratification, flocculation in a sediment-laden water column, and the hydrodynamics are discussed in conjunction with field data and studied with the overall aim of providing a reliable risk assessment of deep-sea mining environmental impacts.

Stratégie des peuplements bathyaux face aux courants de turbidité: Un exemple dans le bassin des Loyauté, au large de la Nouvelle-Calédonie (SW Pacifique)

Article

Dec 1997
Geobios

Benthonic communities and sediments have been sampled off New Caledonia island (SouthwesternPacific), along a SW-NE route crossing the Loyalty basin between Thio and Lifou islands. This basin is 2 300 to 2 350 m deep, with even bottoms excepted in the NE part, 20 km off Lifou, where a tectonic ridge (Lévi ridge) rises up to 150 m above surrounding areas. Present and recent deposits are composed of beige, brown-yellow or reddish hemipelagic muds interlayered with sandy turbidites issued from neighbouring slopes. At 9 sites previously reached by turbidity currents, benthonic faunas are composed mostly with monospecific populations regarded as opportunist: either Ophiurids, or Porcellanasteridae (Asterids). These two species rise up to 98% of the total population in proximal sites and to 73% in distal ones located in the center of Loyalty basin. On the top of Levi Ridge, devoid of turbidites, the proportion falls to 24% within a normally diversified population. According to several researches located in the world ocean, the dominance of two Echinoïdea species in an abyssal plain is exceptional. When abnormal faunal compositions are sometimes observed, they are related to local factors such as important detrital inputs, low temperature of deep waters, isolation, high trophic level. In the Loyalty basin, a sedimentary factor only is reliable; so, East and West of Levi Ridge and toward this structure, evolution of communities seems to illustrate different steps of a bottom recolonization by opportunist species after the major disturbance caused by turbidite deposition, the youngest of which being about 1 000 years old. This would imply a very slow reconstruction of original communities following this disturbance.

Scientific requirements for an abyssal benthic laboratory

Article

Mar 1994
J MARINE SYST

For over thirty years man has studied ''outer space'' and installed satellites which watch the surface of the Earth. The great depths of the world ocean are, however, practically unknown and there is an urgent need to put abyssal benthic laboratories into ''inner space'' in order to study basic phenomena of interest to marine science and climatology as well as man's impact on the oceans. In view of the numerous problems related to global change, as a first step emphasis should first be on the role of the oceans and their inherent processes, which are the focus of such international programmes as the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS). Multi-disciplinary registration of key events at selected key sites investigating the variability in time and pace are of the utmost importance. The same methods and techniques must be used for the study of human impacts on the deep oceans caused by mining of metalliferous resources and by waste disposal as well as in basic studies. However, the investigation of the inner space of our planet has certain requirements. As long-term and large-sc-le investigations become more and more important, development of automized systems, largely independent from research vessels will be required. This will demand high capacities of energy for all technical functions as well as high storage capacities for data and samples. As a consequence the needs for.two different-although overlapping-functional approaches are defined for future deep-sea deployments. (A) A system for long-term registration of the natural variability and long-term monitoring of human impacts; (B) A system for short-term observations and short-time experimentations. This report summarizes their technological demands. The envisioned interdisciplinary technology should deliver information on physical, biological and geochemical processes and their variabilities in the deep oceans. The prospected systems need to have the ability for real time video observation, data transfer and experimental manipulation, as well as sensing and sampling facilities with large storage capacities for long-term deployments. Prospective costs of the described multipurpose abyssal benthic laboratory will presumably exceed the funds for deep-sea research of a single country. A joint European effort could solve this problem and help to manifest a leading role for European marine science in international deep-sea and global change research.

Evaluation of the environmental consequences of polymetallic nodule mining based on the results of the TUSCH Research Association

Article

Dec 2001
DEEP-SEA RES PT II

H. Thiel

Realising a need for increased general knowledge of the deep sea for environmental impact assessments related to the permanent storage of waste products and mining of metal resources, the German Bundesministerium für Bildung und Forschung has funded targeted research in the deep sea for more than 10 years. The research was carried out in an area in the Southeast Pacific Ocean close to and within a German mining claim, to match the interests of German deep-sea polymetallic nodule mining enterprises and the developing mining code of the Preparatory Commission for the International Seabed Authority and the International Tribunal for the Law of the Sea. The “TUSCH (abbreviation for ‘Tiefsee-Umweltschutz’—deep-sea environmental protection) Research Association”, with members from various university and governmental institutions, was part of the ATESEPP (Effects of Technical Interventions into the Ecosystem of the Deep Sea in the Southeast Pacific Ocean) Project between 1996 and 1998. Geotechnical, sedimentological, geochemical, hydrographic, numerical modelling and ecological studies relevant to environmental impact assessment studies of polymetallic nodule mining were undertaken. Since general oceanographic knowledge of the deep sea is rather limited, these various projects also have increased our general understanding of this region.

Use and protection of the deep sea - An introduction

Article

Dec 2001
DEEP-SEA RES PT II

H. Thiel

Consequences of hydraulic dredging for a razor clam Ensis siliqua (L.) bed in the north-west Irish sea

Article

Dec 2007

The Gormanstown razor clam bed, which measured 21km2 in extent in 1998, provided more than half the razor clams harvested in Europe for three years, 1999-2001. Exploitation of the bed commenced in late 1997. As a result of hydraulic dredging, the sediments have higher sorting coefficients and some larger grades were added in the form of shell fragments in the intervening years. The macrobenthos of the bed was monitored over a period of seven years, beginning one year after exploitation commenced. Throughout that time the dominant species, Ensis siliqua, which had accounted for up to 90% of the biomass in the first year of the study, declined to approximately 50% in 2005. Ensis siliqua displays the characteristics of a K-selected species: heavy standing biomass, type one survivorship curve and slow replication. Coinciding with exploitation, the bed was invaded by other deposit and suspension-feeding bivalves, notably Pharus legumen and Lutraria lutraria, whose population expansion can be traced to the early dredge fishery. The ratio of Ensis to Lutraria sampled weights was 124:1 in 1998, but it steadily advanced to 1.2:1 in 2005. Thus Lutraria, another suspension feeder, has displaced the razor clam. The Shannon-Wiener index of diversity rose as exploitation of the bed progressed, and in 2005 (eight years after dredging commenced), it had not returned to its 1998 level. However, the trend over the period was downwards, suggesting that a new stability involving a different species composition may be achieved. An age length key applied to length-frequency distributions of E. siliqua indicated that no age class older than age eleven has accounted for 10% of the population since 2001, although that was usually the case in the four preceding years.

Deep-sea mining, environmental impact and the DISCOL project

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