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  • 1
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    Has Phytodetritus Processing by an Abyssal Soft-Sediment Community Recovered 26 Years after an Experimental Disturbance? (2018)
    Frontiers
    In:  Frontiers in Marine Science, 5 . Art.Nr. 59.
    Details
    Publication Date: 2021-02-08
    Description: The potential harvest of polymetallic nodules will heavily impact the abyssal, soft sediment ecosystem by removing sediment, hard substrate, and associated fauna inside mined areas. It is therefore important to know whether the ecosystem can recover from this disturbance and if so at which rate. The first objective of this study was to measure recovery of phytodetritus processing by the benthic food web from a sediment disturbance experiment in 1989. The second objective was to determine the role of holothurians in the uptake of fresh phytodetritus by the benthic food web. To meet both objectives, large benthic incubation chambers (CUBEs; 50 × 50 × 50 cm) were deployed inside plow tracks (with and without holothurian presence) and at a reference site (holothurian presence, only) at 4100 m water depth. Shortly after deployment, 13C- and 15N-labeled phytodetritus was injected in the incubation chambers and during the subsequent 3-day incubation period, water samples were taken five times to measure the production of 13C-dissolved inorganic carbon over time. At the end of the incubation, holothurians and sediment samples were taken to determine biomass, densities and incorporation of 13C and 15N into bacteria, nematodes, macrofauna, and holothurians. For the first objective, the results showed that biomass of bacteria, nematodes and macrofauna did not differ between reference sites and plow track sites when holothurians were present. Additionally, meiofauna and macrofauna taxonomic composition was not significantly different between the sites. In contrast, total 13C uptake by bacteria, nematodes and holothurians was significantly lower at plow track sites compared to reference sites, though the number of replicates was low. This result suggests that important ecosystem functions such as organic matter processing have not fully recovered from the disturbance that occurred 26 years prior to our study. For the second objective, the analysis indicated that holothurians incorporated 2.16 × 10−3 mmol labile phytodetritus C m−2 d−1 into their biomass, which is one order of magnitude less as compared to bacteria, but 1.3 times higher than macrofauna and one order of magnitude higher than nematodes. Additionally, holothurians incorporated more phytodetritus carbon per unit biomass than macrofauna and meiofauna, suggesting a size-dependence in phytodetritus carbon uptake.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.3389/fmars.2018.00059
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Abyssal plain faunal carbon flows remain depressed 26 years after a simulated deep-sea mining disturbance (2018)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 15 (13). pp. 4131-4145.
    Details
    Publication Date: 2021-02-08
    Description: 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 seafloor within a 10.8km2 circular area of the nodule-rich seafloor in the Peru Basin (SE Pacific) was ploughed in 1989 to bury nodules and mix the surface sediment. This area was revisited 0.1, 0.5, 3, 7, and 26 years after the disturbance to assess macrofauna, invertebrate megafauna and fish density and diversity. We used this unique abyssal faunal time series to develop carbon-based food web models for each point in the time series using the linear inverse modeling approach for sediments subjected to two disturbance levels: (1) outside the plough tracks; not directly disturbed by plough, but probably suffered from additional sedimentation; and (2) inside the plough tracks. Total faunal carbon stock was always higher outside plough tracks compared with inside plough tracks. After 26 years, the carbon stock inside the plough tracks was 54% of the carbon stock outside plough tracks. Deposit feeders were least affected by the disturbance, with modeled respiration, external predation, and excretion rates being reduced by only 2.6% inside plough tracks compared with outside plough tracks after 26 years. In contrast, the respiration rate of filter and suspension feeders was 79.5% lower in the plough tracks after 26 years. The "total system throughput" (T..), i.e., the total sum of modeled carbon flows in the food web, was higher throughout the time series outside plough tracks compared with the corresponding inside plough tracks area and was lowest inside plough tracks directly after the disturbance (8.63 × 10−3±1.58 × 10−5mmolCm−2d−1). Even 26 years after the DISCOL disturbance, the discrepancy of T.. between outside and inside plough tracks was still 56%. Hence, C cycling within the faunal compartments of an abyssal plain ecosystem remains reduced 26 years after physical disturbance, and a longer period is required for the system to recover from such a small-scale sediment disturbance experiment.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: archive
    DOI: 10.5194/bg-15-4131-2018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Biological responses to disturbance from simulated deep-sea polymetallic nodule mining (2017)
    Public Library of Science
    In:  PLoS ONE, 12 (2). e0171750.
    Details
    Publication Date: 2020-02-06
    Description: Commercial-scale mining for polymetallic nodules could have a major impact on the deepsea 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.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1371/journal.pone.0171750
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Abyssal food-web model indicates faunal carbon flow recovery and impaired microbial loop 26 years after a sediment disturbance experiment (2020)
    Elsevier
    In:  Progress in Oceanography, 189 . Art.Nr. 102446.
    Details
    Publication Date: 2021-01-08
    Description: Highlights • Total modeled carbon cycling at disturbed sites is lower than at reference sites. • Projected microbial loop functioning is reduced 26 years after sediment disturbance. • Estimated faunal respiration has recovered from sediment disturbance. • Estimated microbial respiration has not recovered from the sediment disturbance. Abstract 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 was studied during the ‘DISturbance and reCOLonization’ (DISCOL) experiment in the Peru Basin in 1989 when 10.8 km2 of seafloor were ploughed with a plough harrow. Here, we present a detailed description of carbon-based food-web models constructed from various datasets collected in 2015, 26 years after the experiment. Detailed observations of the benthic food web were made at three distinct sites: inside 26-year old plough tracks (IPT, subjected to direct impact from ploughing), outside the plough tracks (OPT, exposed to settling of resuspended sediment), and at reference sites (REF, no impact). The observations were used to develop highly-resolved food-web models for each site that quantified the carbon (C) fluxes between biotic (ranging from prokaryotes to various functional groups in meio-, macro-, and megafauna) and abiotic (e.g. detritus) compartments. The model outputs were used to estimate total system throughput, i.e., the sum of all C flows in the food web (the ‘ecological size’ of the system), and microbial loop functioning, i.e., the C-cycling through the prokaryotic compartment for each site. Both the estimated total system throughput and the microbial loop cycling were significantly reduced (by 16% and 35%, respectively) inside the plough tracks compared to the other two sites. Site differences in modelled faunal respiration varied among the different faunal compartments. Overall, modelled faunal respiration appeared to have recovered to, or exceeded reference values after 26-years. The model results indicate that food-web functioning, and especially the microbial loop, have not recovered from the disturbance that was inflicted on the abyssal site 26 years ago.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
    DOI: 10.1016/j.pocean.2020.102446
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    The BenBioDen database, a global database for meio-, macro- and megabenthic biomass and densities (2020)
    Nature Research
    Details
    Publication Date: 2023-02-08
    Description: Benthic fauna refers to all fauna that live in or on the seafloor, which researchers typically divide into size classes meiobenthos (32/64 µm–0.5/1 mm), macrobenthos (250 µm–1 cm), and megabenthos (〉1 cm). Benthic fauna play important roles in bioturbation activity, mineralization of organic matter, and in marine food webs. Evaluating their role in these ecosystem functions requires knowledge of their global distribution and biomass. We therefore established the BenBioDen database, the largest open-access database for marine benthic biomass and density data compiled so far. In total, it includes 11,792 georeferenced benthic biomass and 51,559 benthic density records from 384 and 600 studies, respectively. We selected all references following the procedure for systematic reviews and meta-analyses, and report biomass records as grams of wet mass, dry mass, or ash-free dry mass, or carbon per m2 and as abundance records as individuals per m2. This database provides a point of reference for future studies on the distribution and biomass of benthic fauna.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    The SCOC database, a large, open, and global database with sediment community oxygen consumption rates (2019)
    Nature Research
    Details
    Publication Date: 2022-03-03
    Description: Sediment community oxygen consumption (SCOC) rates provide important information about biogeochemical processes in marine sediments and the activity of benthic microorganisms and fauna. Therefore, several databases of SCOC data have been compiled since the mid-1990s. However, these earlier databases contained much less data records and were not freely available. Additionally, the databases were not transparent in their selection procedure, so that other researchers could not assess the quality of the data. Here, we present the largest, best documented, and freely available database of SCOC data compiled to date. The database is comprised of 3,540 georeferenced SCOC records from 230 studies that were selected following the procedure for systematic reviews and meta-analyses. Each data record states whether the oxygen consumption was measured ex situ or in situ , as total oxygen uptake, diffusive or advective oxygen uptake, and which measurement device was used. The database will be curated and updated annually to secure and maintain an up-to-date global database of SCOC data.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Polymetallic nodules are essential for food-web integrity of a prospective deep-seabed mining area in Pacific abyssal plains (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: Polymetallic nodule fields provide hard substrate for sessile organisms on the abyssal seafloor between 3000 and 6000 m water depth. Deep-seabed mining targets these mineral-rich nodules and will likely modify the consumer-resource (trophic) and substrate-providing (non-trophic) interactions within the abyssal food web. However, the importance of nodules and their associated sessile fauna in supporting food-web integrity remains unclear. Here, we use seafloor imagery and published literature to develop highly-resolved trophic and non-trophic interaction webs for the Clarion-Clipperton Fracture Zone (CCZ, central Pacific Ocean) and the Peru Basin (PB, South-East Pacific Ocean) and to assess how nodule removal may modify these networks. The CCZ interaction web included 1028 compartments connected with 59,793 links and the PB interaction web consisted of 342 compartments and 8044 links. We show that knock-down effects of nodule removal resulted in a 17.9% (CCZ) to 20.8% (PB) loss of all taxa and 22.8% (PB) to 30.6% (CCZ) loss of network links. Subsequent analysis identified stalked glass sponges living attached to the nodules as key structural species that supported a high diversity of associated fauna. We conclude that polymetallic nodules are critical for food-web integrity and that their absence will likely result in reduced local benthic biodiversity.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    Format: other
    Format: text
    Format: text
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Major fine-scale spatial heterogeneity in accumulation of gelatinous carbon fluxes on the deep seabed (2023)
    Frontiers
    Details
    Publication Date: 2024-03-14
    Description: Abyssal plain communities rely on the overlying water column for a settling flux of organic matter. The origin and rate of this flux as well as the controls on its fine-scale spatial distribution following seafloor settlement are largely unquantified. This is particularly true across regions where anthropogenically-induced seafloor disturbance has occurred. Here, we observed, quantified and mapped a mass deposition event of gelatinous zooplankton carcasses (pyrosomes) in July-September 2015 across one such physically disturbed region in the Peru Basin polymetallic nodule province (4150 m). Seafloor in this area was disturbed with a plough harrow in 1989 (as part of the DISCOL experiment) causing troughs in the sediment. Other parts were disturbed with an epibenthic sled (EBS) during a cruise in 2015 resulting in steep-walled, U-shaped troughs. We investigated two hypotheses: a) gelatinous food falls contribute significantly to the abyssal plain carbon pump and b) physical seafloor disturbance influences abyssal distribution of organic matter. We combined optical and bathymetric seafloor observations, to analyze pyrosome distribution on seabeds with different levels of disturbance. 2954 pyrosome colonies and associated taxa were detected in 〉 14,000 seafloor images. The mean regional carbon (C) deposition associated with pyrosome carcasses was significant compared to the flux of particulate organic C (182 to 1543%), and the total respired benthic C flux in the DISCOL Experimental Area (39 to 184%). EBS-disturbed seafloor tracks contained 72 times more pyrosome-associated C than an undisturbed reference site, and up to 4 times more than an area disturbed in 1989. Deposited pyrosomes collected had a higher proportion of labile fatty acids compared to the sediment. We document the temporal and spatial extent of an abyssal food fall event with unprecedented detail and show that physical seafloor disturbance results in the accumulation of detrital material. Such accumulation may reduce oxygen availability and alter benthic community structure. Understanding both the relevance of large food falls and the fine scale topography of the seafloor, is necessary for impact assessment of technologies altering seafloor integrity (e.g. as a result of bottom-trawling or deep seabed mining) and may improve their management on a global scale.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Deconvolving feeding niches and strategies of abyssal holothurians from their stable isotope, amino acid, and fatty acid composition (2023)
    Springer
    Details
    Publication Date: 2024-05-14
    Description: Holothurians are the dominant megabenthic deposit feeders in the Peru Basin (SE Pacific) and feed to various degrees of selectivity on a heterogenous pool of sedimentary detritus, but drivers of feeding selectivity and diet preferences for most holothurian species are unknown. This study reconstructs the diets of 13 holothurian species of the orders Elasipodida, Holothuriida, and Synallactida. Bulk stable isotope analyses (δ13C, δ15N) of holothurian body wall and gut wall tissues, gut contents, and feces were combined with compound-specific stable isotope analyses of amino acids, phospholipid-derived fatty acids, and neutral-lipid-derived fatty acids in the body wall. We further assessed how holothurians in the Peru Basin partition their resources and calculated how much of the daily particulate organic carbon (POC) flux to the area is ingested by them using information about gut contents of nine species. To assess the dependence of holothurians on fresh phytodetritus, we performed in situ pulse-chase experiments using 13C- and 15N-enriched phytodetritus. By measuring the uptake of this phytodetritus in fatty acids and amino acids and by comparing it with the presence of these compounds in the sediment, we calculated net accumulation and net deficiency for specific fatty acids and amino acids and discussed how climate change might affect the dependence on specific compounds. A Sørensen–Dice coefficient-based cluster analysis using data from trophic levels, levels of heterotrophic re-synthesis of amino acids, feeding selectivity, and food sources/diet suggested two major trophic groups with two optional subgroups each. Species-specific traits of locomotion, tentacle morphology, and gut structure likely allow resource partitioning and differences in selectivity among the holothurians, of which a subpopulation of 65% of all specimens can ingest 4 to 27% of the daily POC flux to the Peru Basin. Holothurians are specifically dependent on the uptake of arachidonic acid from phytodetritus, while most essential amino acids are available in the Peru Basin in sufficient concentrations.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Abyssal food-web model indicates faunal carbon flow recovery and impaired microbial loop 26 years after a sediment disturbance experiment (2020)
    In:  EPIC3Progress in Oceanography, 189, pp. 102446, ISSN: 00796611
    Details
    Publication Date: 2021-01-26
    Description: 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 was studied during the ‘DISturbance and reCOLonization’ (DISCOL) experiment in the Peru Basin in 1989 when 10.8 km2 of seafloor were ploughed with a plough harrow. Here, we present a detailed description of carbon-based food-web models constructed from various datasets collected in 2015, 26 years after the experiment. Detailed observations of the benthic food web were made at three distinct sites: inside 26-year old plough tracks (IPT, subjected to direct impact from ploughing), outside the plough tracks (OPT, exposed to settling of resuspended sediment), and at reference sites (REF, no impact). The observations were used to develop highly-resolved food-web models for each site that quantified the carbon (C) fluxes between biotic (ranging from prokaryotes to various functional groups in meio-, macro-, and megafauna) and abiotic (e.g. detritus) compartments. The model outputs were used to estimate total system throughput, i.e., the sum of all C flows in the food web (the ‘ecological size’ of the system), and microbial loop functioning, i.e., the C-cycling through the prokaryotic compartment for each site. Both the estimated total system throughput and the microbial loop cycling were significantly reduced (by 16% and 35%, respectively) inside the plough tracks compared to the other two sites. Site differences in modelled faunal respiration varied among the different faunal compartments. Overall, modelled faunal respiration appeared to have recovered to, or exceeded reference values after 26-years. The model results indicate that food-web functioning, and especially the microbial loop, have not recovered from the disturbance that was inflicted on the abyssal site 26 years ago.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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