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(a) Mean faunal carbon ingestion (mmol C m −2 d −1 ) as suspended detritus, sedimentary labile and sedimentary semi-labile detritus outside and inside plough tracks 0.1-year post-disturbance (PD 0.1 ), 0.5-year post-disturbance (PD 0.5 ), 3-year post-disturbance (PD 3 ), 7-year post-disturbance (PD 7 ), and 26-year post-disturbance events (PD 26 ). (b) Mean carbon losses (mmol C m −2 d −1 ) from the food webs as predation, feces, scavenging on the carcass, and faunal respiration outside and inside plough tracks during PD 0.1 , PD 0.5 , PD 3 , PD 7 , and PD 26. In both figures, the error bars represent 1 standard deviation.
Source publication
Future deep-sea mining for polymetallic nodules in abyssal plains will
negatively impact the benthic ecosystem, but it is largely unclear whether
this ecosystem will be able to recover from mining disturbance and if so, to
what extent and at what timescale. During the DISturbance and
reCOLonization (DISCOL) experiment, a total of 22 % of the seaflo...
Contexts in source publication
Context 1
... respiration (mmol C m −2 d −1 ) ranged from 6.0 × 10 −3 ± 6.8 × 10 −5 (inside plough tracks, PD 0.5 ) to 3.9 × 10 −2 ± 3.7 × 10 −4 (outside plough tracks, PD 3 ). During the 26 years after the DISCOL experiment, mod- eled faunal respiration was always higher outside plough tracks than inside plough tracks (Table 3, Fig. 5b). Over time, non-polychaete macrofauna contributed least to total faunal respiration (Table 3), except inside plough tracks during PD 0.5 and at both sites during PD 3 . During this PD 3 sampling campaign, macrofauna contributed 50 % outside plough tracks and 58 % inside plough tracks to total faunal respiration. Polychaetes respired between 19 % of the total fauna respiration outside plough tracks during PD 26 and Table 3. Faunal respiration rate (mmol C m −2 d −1 ) and contribution (%) of the size classes macrofauna, polychaetes, invertebrate megafauna, and fish to the respiration outside plough tracks (outside PT) and inside plough tracks (inside PT) directly after the disturbance event in March 1989 (PD 0.1 ), 0.5-year post-disturbance (September 1989, PD 0.5 ), 3-year post-disturbance (January 1992, PD 3 ), 7-year post-disturbance ( February 1996 Figure 6. Development of T .. (mmol C m −2 d −1 ), i.e., the differ- ence in "total system throughput" T .. outside plough tracks com- pared to inside plough tracks, over time. PD 0.1 corresponds to 0.1- year post-disturbance, PD 0.5 is 0.5-year post-disturbance, PD 3 is 3-year post-disturbance, PD 7 is 7-year post-disturbance, and PD 26 is 26-year post-disturbance ...
Context 2
... % of total faunal respiration inside plough tracks during PD 0.5 . Invertebrate megafaunal contribution to respiration was highest during PD 26 , when they respired 65 % of the total faunal respiration inside plough tracks and 79 % of the total faunal respiration outside plough tracks. The contri- bution of fish to total faunal respiration was always < 2 %. Besides respiration, feces production contributed between 20 % inside plough tracks during PD 3 and 35 % outside plough tracks during PD 0.1 to total carbon outflow from the food web (Fig. 5). The contribution of the combined outflow of predation by external predators and scavengers on carcasses to the total C loss from the food web ranged from 50 % inside plough tracks during PD 7 to 65 % inside plough tracks during PD 0.1 ...
Context 3
... respiration (mmol C m −2 d −1 ) ranged from 6.0 × 10 −3 ± 6.8 × 10 −5 (inside plough tracks, PD 0.5 ) to 3.9 × 10 −2 ± 3.7 × 10 −4 (outside plough tracks, PD 3 ). During the 26 years after the DISCOL experiment, mod- eled faunal respiration was always higher outside plough tracks than inside plough tracks (Table 3, Fig. 5b). Over time, non-polychaete macrofauna contributed least to total faunal respiration (Table 3), except inside plough tracks during PD 0.5 and at both sites during PD 3 . During this PD 3 sampling campaign, macrofauna contributed 50 % outside plough tracks and 58 % inside plough tracks to total faunal respiration. Polychaetes respired between 19 % of the total fauna respiration outside plough tracks during PD 26 and Table 3. Faunal respiration rate (mmol C m −2 d −1 ) and contribution (%) of the size classes macrofauna, polychaetes, invertebrate megafauna, and fish to the respiration outside plough tracks (outside PT) and inside plough tracks (inside PT) directly after the disturbance event in March 1989 (PD 0.1 ), 0.5-year post-disturbance (September 1989, PD 0.5 ), 3-year post-disturbance (January 1992, PD 3 ), 7-year post-disturbance ( February 1996 Figure 6. Development of T .. (mmol C m −2 d −1 ), i.e., the differ- ence in "total system throughput" T .. outside plough tracks com- pared to inside plough tracks, over time. PD 0.1 corresponds to 0.1- year post-disturbance, PD 0.5 is 0.5-year post-disturbance, PD 3 is 3-year post-disturbance, PD 7 is 7-year post-disturbance, and PD 26 is 26-year post-disturbance ...
Context 4
... % of total faunal respiration inside plough tracks during PD 0.5 . Invertebrate megafaunal contribution to respiration was highest during PD 26 , when they respired 65 % of the total faunal respiration inside plough tracks and 79 % of the total faunal respiration outside plough tracks. The contri- bution of fish to total faunal respiration was always < 2 %. Besides respiration, feces production contributed between 20 % inside plough tracks during PD 3 and 35 % outside plough tracks during PD 0.1 to total carbon outflow from the food web (Fig. 5). The contribution of the combined outflow of predation by external predators and scavengers on carcasses to the total C loss from the food web ranged from 50 % inside plough tracks during PD 7 to 65 % inside plough tracks during PD 0.1 ...
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Due to the predicted future demand for critical metals, abyssal plains covered with polymetallic nodules are currently being prospected for deep-seabed mining. Deep-seabed mining will lead to significant sediment disturbance over large spatial scales and for extended periods of time. The environmental impact of a small-scale sediment disturbance wa...
Citations
... We applied the four wildly used physiological constraints in LIM studies Stratmann et al., 2018) in the food web model, including respiration (R), assimilation efficiency (AE), production (P ), and net growth efficiency (NGE). ...
... On the other hand, the organic matter degradation in sediments exhibits high variability, influenced by factors such as organic matter chemistry, sediment physical characteris-tics, and biological agents involved in decomposition (Middelburg and Meysman, 2007). As a result, the proportions of detrital organic carbon components (i.e., labile, semi-labile, and refractory fractions) typically differ across study locations and cannot be directly inferred from previous literature (e.g., van Oevelen et al., 2011;Dunlop et al., 2016;Stratmann et al., 2018;Durden et al., 2020). Due to lacking empirical data, we aggregated all detritus into a single compartment, consistent with the approach in other benthic food web model studies (e.g., Rowe et al., 2008). ...
... However, most LIM studies used reference constraints due to technical difficulties in physiological experiments on benthic species (van Oevelen et al., 2010). For example, Stratmann et al. (2018) studied the abyssal plain food web of the Peru Basin; however, some physiological constraints of benthos in the food webs were derived from the shallow water or intertidal species (e.g., Drazen et al., 2007;Koopmans et al., 2010). In other food web studies, the physiological constraint of the dominant species was used as the representative for the entire size group (e.g., De Smet et al., 2016). ...
The Gaoping Submarine Canyon (GPSC) off southwest Taiwan has been extensively studied due to its unique geology, its role in transferring terrestrial material to the deep sea, and its diverse biological communities. However, there is a lack of understanding of carbon cycling across the sediment–water interface in the canyon. This study aims to fill the gap by utilizing the field data collected between 2014 and 2020 and a linear inverse model (LIM) to reconstruct the benthic food web (i.e., carbon flows through different stocks) in the head of GPSC and the upper Gaoping slope (GS). The biotic and abiotic organic carbon (OC) stocks were significantly higher on the slope than in the canyon, except for the bacteria stock. The sediment oxygen utilization was similar between the two habitats, but the magnitude and distribution of the OC flow in the food web were distinctively different. Despite a significant input flux of ∼ 2020 mg C m−2 d−1 in the canyon, 84 % of the carbon flux exited the system, while 12 % was buried. On the slope, 84 % of the OC input (∼ 109 mg C m−2 d−1) was buried, and only 7 % exited the system. Bacteria processes play a major role in the carbon fluxes within the canyon. In contrast, the food web in the upper slope exhibited stronger interactions among metazoans, indicated by higher fluxes between meiofauna and macrofauna compartments. Network indices based on the LIM outputs showed that the canyon head had higher total system throughput (T..) and total system throughflow (TST), indicating greater energy flowing through the system. In contrast, the slope had a significantly higher Finn cycling index (FCI), average mutual information (AMI), and longer OC turnover time, suggesting a relatively more stable ecosystem with higher energy recycling. Due to sampling limitations, the present study only represents the benthic food web during the “dry” period. By integrating the field data into a food web model, this study provides valuable insight into the fates of OC cycling in an active submarine canyon, focusing on the often overlooked benthic communities. Future studies should include “wet” period sampling to reveal the effects of typhoons and monsoon rainfalls on OC cycling.
... Morato et al. 2016, Hanz et al. 2022 and energy flow webs (e.g. , Stratmann et al. 2018, de Jonge et al. 2020, Stratmann 2023, whereas NTIs have been studied via interaction webs (e.g. Salinas et al. 2023). ...
Deep-sea sponges are important contributors to carbon and nitrogen cycling due to their large filtration capacity. Species of the suborder Astrophorina form dense sponge grounds in the North Atlantic, where they serve as prey for spongivores, but also have non-trophic interactions with commensal epi- and endobionts. At the Flemish Cap (NW Atlantic), Astrophorina sponges are present in 4 previously described deep-sea epifaunal assemblages: the deep-sea coral assemblage, lower slope assemblages 1 and 2, and the deep-sea sponge assemblage. To investigate their role in trophic and non-trophic interactions at the Flemish Cap, we developed trophic and non-trophic interaction web models for each of the 4 faunal assemblages using the published literature. By excluding the sponges from the models, we estimated how many trophic, and facultative and obligatory non-trophic, interactions would be lost, and how this removal affected food-web properties (number of compartments, links, link density, and connectance). Astrophorina sponges were mostly linked via facultative non-trophic interactions to 59, 58, 84, and 90 compartments in the deep-sea coral, the lower slope 1 and 2, and the deep-sea sponge assemblages, respectively. Direct trophic interactions only existed with Syllidae, Echinasteridae, and Pterasteridae. Astrophorina sponges were considered highest impact taxa in all faunal assemblages and, together with sea pens, they were identified as structural species/habitat formers and foundation species in the deep-sea coral and deep-sea sponge habitat. Hence, even less abundant, or non-representative (indicator), species can be important for food-web integrity via trophic and non-trophic interactions.
... Although areas of potentially commercially viable nodule abundances are known, commercial extraction has yet to commence, though experimental works with nodule-gathering vehicles and on investigating the potential disturbance impacts on seafloor structure and communities are ongoing. The topic remains controversial as it is assumed that mining will have negative impacts on the deep-sea ecosystem, at least on the local scale, with the hard substrate provided by the nodules being wholly removed from the seafloor/ ocean interface (Amon et al. 2016;Jones et al. 2017;Stratmann et al. 2018;Smith et al. 2020). In general, soft sediments form much of this interface across the abyssal plains, though in regions where polymetallic nodules occur, these nodules provide a hard substrate, creating a complex which supports a highly diverse range of sessile fauna (Vanreusel et al. 2016), as well as adding complexity to the local hydrodynamic regime on the local scale. ...
... In 1996, 7 years post-disturbance, hemi-sessile animals had returned to ploughed areas, whereas the number of soft-bottom animals was still lower in the ploughed area than were present before ploughing. Even 26 years after the disturbance experiment, in September 2015, macrofauna and megafauna densities were still significantly depressed within the disturbance area (Stratmann et al. 2018). Sediment porewater chemistry had recovered, but the microbial biogeochemical activities still showed negative impacts and also metal distributions within the sediments continued to differ from those at undisturbed reference sites. ...
... In general, faunal groups in the DISCOL area have shown varying degrees of recovery (Bluhm 2001;Stratmann et al. 2018;Simon-Lledó et al. 2019). Mobile species were found to recover faster than sessile species with large individuals, which either did not recover at all or only recovered at comparably slow rates (Jones et al. 2017). ...
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.
... At the annual meeting in 2004, the Executive Board of the International Marine Minerals Society (IMMS, incorporated in 1987) voted to change the name of the annual meeting to its current designation as the UMC. For more than half a century, over 25 nations have represented at this annual forum to exchange ideas, seek expertise, and share in the achievement of the evolving industry [11]. The UMC is more than an annual forum; it has, through the years, fostered cooperation, assistance and understanding among those who compose the marine minerals community. ...
... The journal Marine Policy edited a special section ''Deep-Sea Mining Activities in the Pacific Region" to provide the current state of deep-sea mining at the Pacific [10]. A special issue ''Assessing environmental impacts of deep-sea mining-revisiting decade-old benthic disturbances in Pacific nodule areas" edited by the journal Biogeosciences presents the scientific results of the biological, biogeochemical, geological, and oceanographic investigations carried out in the mining impact project (consisting of 25 institutes from 11 European countries) [11]. Review on the development of deep-sea mining equipment is neither complete nor systematic, and therefore a comprehensive review is essential for research leading to a deeper understanding and commercial development of deep-sea mining. ...
... In 1996, 7 years post-disturbance, hemi-sessile animals had returned to ploughed areas, whereas the number of soft-bottom animals was still low compared to before the ploughing (Bluhm 2001). Even 26 years after the experiment was conducted, in September 2015, macrofauna and megafauna densities were still signi cantly depressed within the disturbance area (Stratmann et al. 2018). Sediment porewater chemistry had recovered, but the microbial biogeochemical activities still showed negative impacts and also metal distributions within the sediments continued to differ from those at undisturbed reference sites. . ...
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 disturbed in 1989 and 2015 to simulate mining disturbance. To try and address the shortfall on transient fauna and infauna use of these various disturbed and undisturbed regions 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 and logged, along with whether they occurred on undisturbed seafloor, or regions disturbed in 1989 or 2015. The results show that traces of surface/ocean interface use of disturbed areas by infauna and mobile fauna are at least 50% lower, even 26 years after disturbance, with many trace categories not present in even low numbers on disturbed seafloor areas.
... In a global context, there are several initiatives that use benthic invertebrate data for research, observing, and statutory monitoring including GEO BON, the International Seabed Authority (ISA) and related needs for observing and model data to understand baseline and impact assessment for its Reserved Areas for prospective seafloor mining (Stratmann et al. 2018), the Intergovernmental Panel on Climate Change (IPCC; Yool et al. 2017;Tittensor et al. 2021;Cooley et al. 2022), the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), the CBD, the Coastal and Estuarine Research Federation (CERF), the OSPAR Commission, the International Council for the Exploration of the Sea (ICES), the Deep Ocean Stewardship Initiative (DOSI), and those implementing the Deep Ocean Observing Strategy (DOOS; Levin et al. 2019). National and regional initiatives are also evaluating the status and trends in marine invertebrate variables including the European Marine Strategy Framework Directive (MSFD), the US Magnuson-Stevens Fishery Conservation and Management Act and related Integrated Ecosystem Assessments, the US National Marine Sanctuaries Act and related Condition Reports. ...
Invertebrate animals living at the seafloor make up a prominent component of life globally, spanning 10 orders of magnitude in body size over 71% of Earth's surface. However, integrating information across sizes and sampling methodologies has limited our understanding of the influence of natural variation, climate change and human activity. Here, we outline maturing practices that can underpin both the feasibility and impact of establishing Benthic Invertebrate Abundance and Distribution as a Global Ocean Observing System—Essential Ocean Variable, including: (1) quantifying individual body size, (2) identifying the well‐quantified portions of sampled body‐size spectra, (3) taking advantage of (semi‐)automated information processing, (4) application of metadata standards such as Darwin Core, and (5) making data available through internationally recognized access points. These practices enable broader‐scale analysis supporting research and sustainable development, such as assessments of indicator taxa, biodiversity, biomass, and the modeling of carbon stocks and flows that are contiguous over time and space.
... One of the largest and most studied disturbance experiments was the "DISturbance and reCOLonization experiment" (DISCOL) in the nodule-covered Peru Basin, in 1989 (Thiel et al. 2001). The disturbance showed significant effects, such as a modelled reduction of carbon flow in the food web and variations in the recovery of organisms with different feeding types, with suspension and filter feeders showing the lowest recovery rates (Stratmann et al. 2018a). Investigations of the same area based on AUV photo mosaics conducted 26 years after the impact confirmed the significant reduction in megafaunal suspension feeders, whereas the densities of deposit feeders as well as scavengers and predators had recovered to pre-impact values (Simon-Lledó et al. 2019c). ...
The Clarion Clipperton Fracture Zone (CCZ) is an abyssal region in the north-east Pacific that is currently being explored for metal-rich polymetallic nodules, but also harbors a highly diverse megabenthic community. This community is influenced by multiple environmental gradients including bathymetric structures as well as differences in habitat and food availability. This study focuses on the benthic megafauna investigated in an exploration area positioned in the very east of the CCZ, which exhibits the lowest water depths (mean: 4200 m) and the highest flux of particulate organic carbon (POC) of the CCZ. Case studies using seafloor images for the detection of megafauna have revealed differences between seamounts and abyssal hills compared to nodule fields, as well as differences in the community composition between areas with and without nodule coverage and rock outcrop. Extrapolations suggest a richness of more than 300 morphotypes in the study area, including multiple invertebrate groups such as corals, sponges, echinoderms, and crustaceans as well as fish. Focusing on sampled specimens, diversities of Ophiuroidea, Porifera, and Bryozoa are high and more species are likely to be discovered in the study area. This also applies for the taxon Ophiuroidea, which is among the taxa investigated in the greatest detail so far. In the context of deep-sea mining, megafauna has been in the focus of a variety of environmental studies including baseline analyses, disturbance experiments, and/or testing of mining components or systems. These studies identify and address key factors responsible for the observed natural and impacted distribution patterns and thereby help to constrain expected anthropogenic impacts to the deep-sea environment in the context of deep-sea mining. Specifically in the area of focus of this study, 10 years of megafauna analyses have shown that the biodiversity in the selected preservation reference zone (PRZ) is not as similar to that of the impact reference zone (IRZ) as originally hypothesized based mainly on geological parameters. We suggest that recent area-wide habitat classifications and faunal mapping exercises (e.g., Uhlenkott et al. 2020, 2022) are used to designate a new PRZ that is more similar to the IRZ to meet its purpose, but that the current PRZ is maintained for scientific and conservation purposes.
... In contrast, the LIM type 2 involved a more detailed food web reconstruction of the low, medium and heavy impacted sites, all 26 years after the disturbance in which additionally available data could be used. Results from LIM type 1 showed that even 26 years after the disturbance, the total carbon cycling remained depressed inside the heavily disturbed sites was only 56 % compared to the low impacted sites (Stratmann et al. 2018). Hence, a longer period is required for the system recovery from such a disturbance experiment. ...
... Deep-sea mining will significantly disturb the seafloor because of nodule removal and because the generated sediment plumes from a single mining operation will affect ~1500 km 2 of seabed and benthic boundary layer per year (Levin et al., 2016;Drazen et al., 2020;Smith et al., 2020). Substantial impacts are expected on benthic microbiota (Stratmann et al. 2018b(Stratmann et al. , 2018aVonnahme et al., 2020), meiofauna (Miljutin et al., 2011;Stratmann et al., 2018a), macrofauna, megafauna (Jones et al., 2017;Stratmann et al. 2018bStratmann et al. , 2018a and food web dynamics (de Jonge et al., 2020). Deep-sea mining will result in habitat removal, turbidity in the water column, and burial of seafloor biota; these could lead to losses of connectivity and biodiversity and contribute to species extinctions (Borowski and Thiel 1998;Niner et al., 2018;Ardron et al., 2019;Smith et al., 2020). ...
... Deep-sea mining will significantly disturb the seafloor because of nodule removal and because the generated sediment plumes from a single mining operation will affect ~1500 km 2 of seabed and benthic boundary layer per year (Levin et al., 2016;Drazen et al., 2020;Smith et al., 2020). Substantial impacts are expected on benthic microbiota (Stratmann et al. 2018b(Stratmann et al. , 2018aVonnahme et al., 2020), meiofauna (Miljutin et al., 2011;Stratmann et al., 2018a), macrofauna, megafauna (Jones et al., 2017;Stratmann et al. 2018bStratmann et al. , 2018a and food web dynamics (de Jonge et al., 2020). Deep-sea mining will result in habitat removal, turbidity in the water column, and burial of seafloor biota; these could lead to losses of connectivity and biodiversity and contribute to species extinctions (Borowski and Thiel 1998;Niner et al., 2018;Ardron et al., 2019;Smith et al., 2020). ...
... Deep-sea mining will significantly disturb the seafloor because of nodule removal and because the generated sediment plumes from a single mining operation will affect ~1500 km 2 of seabed and benthic boundary layer per year (Levin et al., 2016;Drazen et al., 2020;Smith et al., 2020). Substantial impacts are expected on benthic microbiota (Stratmann et al. 2018b(Stratmann et al. , 2018aVonnahme et al., 2020), meiofauna (Miljutin et al., 2011;Stratmann et al., 2018a), macrofauna, megafauna (Jones et al., 2017;Stratmann et al. 2018bStratmann et al. , 2018a and food web dynamics (de Jonge et al., 2020). Deep-sea mining will result in habitat removal, turbidity in the water column, and burial of seafloor biota; these could lead to losses of connectivity and biodiversity and contribute to species extinctions (Borowski and Thiel 1998;Niner et al., 2018;Ardron et al., 2019;Smith et al., 2020). ...
The abyssal seafloor (3500–6000m) remains largely unexplored but with deep-sea mining imminent, anthropogenic impacts may soon reach abyssal communities. Thus, there is a growing need for baseline studies of biodiversity, ecosystem functioning, and connectivity in both potential mining and no-mining areas across the Clarion-Clipperton Zone (CCZ), a key target region for polymetallic nodule mining. In this study, in situ pulse-chase lander experiments were conducted for 1.5 days in three no-mining areas (called Areas of Particular Environmental Interest, or APEIs) in the western CCZ, a region with a seafloor particulate organic carbon (POC) flux gradient. A decreasing trend was seen in mean seafloor respiration, macrofaunal abundance, and biomass from the more eutrophic APEI 7 to the more oligotrophic APEI 1, although this trend was not statistically significant (p = 0.18) most likely due to small samples sizes and high variability. In this study, most (96%) of the 13C-labeled processed phytodetritus was respired within 1.5 days. Experimental uptake of phytodetritus by macrofauna and bacteria was detected but was lower than in the previously studied and more eutrophic eastern CCZ over similar time scales (1.5 d). Bacteria dominated the short-term (∼1.5 d) uptake of organic carbon at the seafloor, yet macrofauna processed more organic carbon per unit biomass than previously found in the eastern CCZ (0.003 mg C m−2 d−1 and 0.5 × 10−5 mg C m−2 d−1 for the western and eastern CCZ, respectively). Our study provides important information on C-uptake and respiration rates in areas set aside from mining in the western CCZ and suggests high variability may occur in the rates of benthic Corg-cycling across the CCZ. We recommend that benthic ecosystem functions be explored across gradients of POC flux which may be a major environmental factor driving ecosystem dynamics in the CCZ.
... The 'Impact and impact assessment' subcategory comprises 103 publications (36.9%) and contains both assessment of observed or predicted environmental impact [102][103][104][105][106][107], as well as methodology, strategies and challenges for environmental impact assessment (EIA) [107][108][109][110]. The latter includes the work by Clark et al. [110], who summarises some of the key problems raised by previous EIA reviews and examines recent deep-sea mining EIAs. ...
... In the absence of experience from actual seabed mining operations, several studies ( [102][103][104]) seek to infer potential impacts from the large-scale disturbance and recolonization experiment (the DISCOL project) that was conducted in a ferromanganese nodule area in the South-East Pacific Ocean off Peru in 1989. Other experimental or evidence-based approaches include Spearmann et al. [105], who conducted plume experiments on the tropic seamount 300 nautical miles SSW of the Canary Islands, and Mestre et al. [106], who used the sulphide mine tailings deposit in Portmán Bay (Spain) as a shallow-water analogue to study the potential ecotoxicological impact of deep-sea mining. ...
Deep-sea mining is a multidimensional concept that requires interdisciplinary research and development to close the current knowledge gaps. This study conducts a bibliometric analysis of the research focus, publishing structures and international and inter-institutional cooperation as evident in academic publishing. This could aid in the identification of knowledge gaps, research opportunities, potential inter-institutional cooperation and the need for strategic investment and policy development. The analysis is based on a sample of 1935 journal papers (from 1968 to 2021) obtained by searching Elsevier’s Scopus database for publications containing an explicit reference to deep-sea mining (or equivalent terms) in their title, abstract or keywords. Publication numbers are broken down by publication year, subject area, author affiliations and source. The scientific output mirrors the commercial interest and the growing environmental concern. A detailed analysis of content is performed on the 2017-2021 subset, containing one third of the total publications. Here, China (152 publ.), the United Kingdom (133), the United States (115) and Germany (107) are the top contributors. China has had a comparatively stronger focus on engineering aspects and produces very few publications with international co-authorship. Almost half of the 2017-2021 publications focus on environmental aspects, whereas engineering aspects (especially vertical transport) are addressed by close to one third. Little is published on site remediation and ore processing, or specifically on ferromanganese crusts.
