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We review the current knowledge of the biodiversity of the ocean as well as the levels of decline and threat for species and habitats. The lack of understanding of the distribution of life in the ocean is identified as a significant barrier to restoring its biodiversity and health. We explore why the science of taxonomy has failed to deliver knowledge of what species are present in the ocean, how they are distributed and how they are responding to global and regional to local anthropogenic pressures. This failure prevents nations from meeting their international commitments to conserve marine biodiversity with the results that investment in taxonomy has declined in many countries. We explore a range of new technologies and approaches for discovery of marine species and their detection and monitoring. These include: imaging methods, molecular approaches, active and passive acoustics, the use of interconnected databases and citizen science. Whilst no one method is suitable for discovering or detecting all groups of organisms many are complementary and have been combined to give a more complete picture of biodiversity in marine ecosystems. We conclude that integrated approaches represent the best way forwards for accelerating species discovery, description and biodiversity assessment. Examples of integrated taxonomic approaches are identified from terrestrial ecosystems. Such integrated taxonomic approaches require the adoption of cybertaxonomy approaches and will be boosted by new autonomous sampling platforms and development of machine-speed exchange of digital information between databases.

The HACON cruise is a major component of the FRINATEK HACON project, which aims at investigating the role of the Gakkel Ridge and Arctic Ocean in biological connectivity amongst ocean basins and global biogeography of chemosynthetic ecosystems. The HACON cruise was designed to conduct a multidisciplinary survey of the Aurora seamount centred around the identified black smokers in 2014. The scientific goal was to obtain visual and physical samples of the different habitats on the seamount to better understand hydrothermal vent communities on the Gakkel ridge and abyssal communities of an Arctic seamount, to assess the sphere of influence of the Aurora vent field across the seamount and adjacent seafloor regions The cruise may be known as: Hacon19

The HACON cruise is a major component of the FRINATEK HACON project, which aims at investigating the role of the Gakkel Ridge and Arctic Ocean in biological connectivity amongst ocean basins and global biogeography of chemosynthetic ecosystems. The HACON cruise was designed to conduct a multidisciplinary survey of the Aurora seamount centred around the identified black smokers in 2014. The scientific goal was to obtain visual and physical samples of the different habitats on the seamount to better understand hydrothermal vent communities on the Gakkel ridge and abyssal communities of an Arctic seamount, to assess the sphere of influence of the Aurora vent field across the seamount and adjacent seafloor regions. The cruise may be known as: Hacon21

As the United Nations develops a post-2020 global biodiversity framework for the Convention on Biological Diversity, attention is focusing on how new goals and targets for ecosystem conservation might serve its vision of ‘living in harmony with nature’1,2. Advancing dual imperatives to conserve biodiversity and sustain ecosystem services requires reliable and resilient generalizations and predictions about ecosystem responses to environmental change and management3. Ecosystems vary in their biota4, service provision5 and relative exposure to risks6, yet there is no globally consistent classification of ecosystems that reflects functional responses to change and management. This hampers progress on developing conservation targets and sustainability goals. Here we present the International Union for Conservation of Nature (IUCN) Global Ecosystem Typology, a conceptually robust, scalable, spatially explicit approach for generalizations and predictions about functions, biota, risks and management remedies across the entire biosphere. The outcome of a major cross-disciplinary collaboration, this novel framework places all of Earth’s ecosystems into a unifying theoretical context to guide the transformation of ecosystem policy and management from global to local scales. This new information infrastructure will support knowledge transfer for ecosystem-specific management and restoration, globally standardized ecosystem risk assessments, natural capital accounting and progress on the post-2020 global biodiversity framework.

We review the current knowledge of the biodiversity of the ocean as well as the levels of decline and threat for species and habitats. The lack of understanding of the distribution of life in the ocean is identified as a significant barrier to restoring its biodiversity and health. We explore why the science of taxonomy has failed to deliver knowledge of what species are present in the ocean, how they are distributed and how they are responding to global and regional to local anthropogenic pressures. This failure prevents nations from meeting their international commitments to conserve marine biodiversity with the results that investment in taxonomy has declined in many countries. We explore a range of new technologies and approaches for discovery of marine species and their detection and monitoring. These include: imaging methods, molecular approaches, active and passive acoustics, the use of interconnected databases and citizen science. Whilst no one method is suitable for discovering or detecting all groups of organisms many are complementary and have been combined to give a more complete picture of biodiversity in marine ecosystems. We conclude that integrated approaches represent the best way forwards for accelerating species discovery, description and biodiversity assessment. Examples of integrated taxonomic approaches are identified from terrestrial ecosystems. Such integrated taxonomic approaches require the adoption of cybertaxonomy approaches and will be boosted by new autonomous sampling platforms and development of machine-speed exchange of digital information between databases.

12 pages, 3 figures, supplementary information https://doi.org/10.1038/s41559-019-1091-z.-- The dataset generated and analysed during the current study is available from the corresponding author on reasonable request, The deep sea (>200 m depth) encompasses >95% of the world’s ocean volume and represents the largest and least explored biome on Earth (, This work was supported by the H2020 project MERCES (GA N. 689518) and IDEM (GA N. 11.0661/2017/750680/SUB/EN V.C2.). E.R.-L. was supported by the Norwegian project MarMine (247626), the Norwegian Institute for Water Research and the H2020 project MERCES (GA N. 689518). P.V.R.S. was supported by the NSERC Canadian Healthy Oceans Network and CFREF Ocean Frontier Institute. L.T. is supported by JPI Oceans2 and ONC. J.A. is supported by ARIM (Autonomous Robotic sea-floor Infrastructure for bentho-pelagic Monitoring; MartTERA ERA-Net Cofound). L.L. acknowledges NSF grant OCE 1634172 and the Deep-Ocean Observing Strategy subcontract from the Consortium for Ocean Leadership. H.R. was supported by the EMSO-Link project of the European Commission (Grant agreement ID: 731036), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

15 pages, 12 figures, supplementary data https://doi.org/10.1016/j.dsr.2020.103433, Kelp forests produce large amounts of macroalgal detritus, ranging from whole plants to small particles (1 mm). The role of this kelp detritus in fueling deep-sea communities adjacent to healthy kelp forests was investigated in a region in the north of Norway by comparing the community structure and biodiversity of meio-, macro-, and megafauna in two deep (450 m) areas with different expected input of kelp detritus: a deep fjord basin surrounded by kelp forests and the adjacent continental shelf 15 km offshore from the kelp forests. The results showed that, although the fjord received a significantly higher amount of large kelp detritus (i.e. blades) than the shelf area, the amount of small kelp detritus available on the sediment was similar in both areas. There were significant differences in the multidimensional scaling analyses on the community structure for meio-, macro-, and megafauna between the fjord and the shelf. Significant differences were also found in biomass, abundance and biodiversity indices for some groups. However, no clear pattern emerged in the community structure and biodiversity between the fjord and the shelf, and the observed differences could not be linked directly to kelp detritus availability. The similar amounts of small particles of kelp detritus in the fjord and shelf area suggest that kelp detritus can provide organic matter to ecosystems further away than initially hypothesized, thus potentially shaping the structure and functioning of deep benthic communities distant from the kelp forests. Yet, the direct (trophic) links of kelp detritus and the studied benthic fauna need to be further analysed. The results are discussed in relation to current global changes in kelp forest, including regime shifts from healthy kelp reefs to turfs or barren areas, which reduce drastically the amount of macroalgal detritus produced and exported, This study was funded by the Norwegian Research Council through the KELPEX project (NRC Grant no. 255085/E40). With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

2 pages.-- Reply to: Ecological variables for deep-ocean monitoring must include microbiota and meiofauna for effective conservation, J. Ingels et al. Nature Ecology & Evolution 5: 27-29 (2021), doi: 10.1038/s41559-020-01335-6, Meiofauna and microbes are key components of deep-sea ecosystem assessments and were included among the list of essential variables in our recent comprehensive assessment and prioritization of a global deep-ocean monitoring and conservation strategy1. Meiofauna ranked in the top three variables, whereas microbes (bacteria, and archaea) were reported as key variables for some aspects of monitoring the deep sea. However, larger components of the deep-sea fauna (such as macro- and megafauna) received the highest priority. In their Matters Arising, Ingels and co-workers2 criticized the ranking because, in their opinion, macro- and megafaunal components cannot be considered higher-priority variables than microbes and meiofauna. They concluded that this result reflects an unequal distribution of the competence of the authors and of the respondents to the elicitation survey. However, their criticisms are unjustified for conceptual, methodological and operational reasons. On semantic and theoretical grounds, Ingels et al. confused the concept of priority with that of relevance/importance. Ingels et al. seem also to confound the concept of monitoring and protecting with the importance of research for advancing scientific knowledge; these are two partly related, but distinct, objectives. Indeed, recognizing the ecological importance of one biological component is one thing, but identifying the monitoring variables where capacity to deliver for conservation management globally is well established, is quite another. We cannot apply the same monitoring and conservation approach to all biological components because small organisms, such as prokaryotes, protists and meiofauna encompass massive numbers of undescribed species with largely unknown ecologies3,4 and shorter turnover times, which may make them more resilient to disturbance than larger biota. Even an ocean completely depleted of large fauna, for example, sharks and all predators, would remain flush with meiofauna and microbes. Yet, a deep-sea system with abundant meiofauna and prokaryotes would almost certainly function poorly without higher trophic levels. This well-known ecological principle is certainly one of the reasons there was a wide consensus among the 112 experts (including the microbiologists and meiofauna experts who participated in the expert elicitation) on censusing larger species to protect vulnerable habitats they inhabit or create. The much more limited evidence for microbial and meiofaunal endemicity, the great proportion of unidentified species and the lack of life-history information, greatly compromise any proposal to use these components as proxies for monitoring and mapping conservation areas. Thus, the results of the expert elicitation, on the one hand, reflect the maturity of the disciplines and the capability to deliver indicator information and, on the other hand, recognize the role of larger organisms in current conservation priorities, while acknowledging fundamental roles of all groups., Another important aspect overlooked by Ingels et al. is that deep-sea biodiversity was only one of the five main research areas addressed by the study. In the second research area we considered, which was dedicated to ecosystem functions, benthic faunal biomass and benthic faunal production were ranked as top variables (see table 1 in Danovaro et al.1). Because meiofauna and microbes typically dominate benthic faunal biomass at abyssal depths5,6, we took care to emphasize the functional role of microbial components: “microbes (primarily bacteria followed by archaea) largely dominate overall biomass and production. These microscopic components, essential for deep-sea ecosystem functions … we stress microbial heterotrophic and chemoautotrophic C production as two essential ecological variables needed for understanding the key processes sustaining the functioning of deep-sea food webs and biogeochemical cycles”. We also strongly disagree with the methodological criticisms of Ingels et al. As scientists, we endeavour to remove all potential sources of bias in the framework of standard good practices for data evaluation. Our study is based on expert elicitation, which is a procedure to find consensus on priorities, not an experiment with treatments and controls; thus, standard deviations cannot be treated as in ecological experimental designs. Our Perspective describes how we endeavoured to achieve an objective methodology (that is, coverage of different research fields and knowledge for each of the five main themes, scientists covered a broad range of geographic regions, different taxonomic expertise, academic qualifications and years of experience). These aspects, including statistical treatment, were discussed in detail using multiple rounds of enquiries, following rigorous procedures7, and were presented transparently in the supplementary information of our paper1. To our knowledge, the 112 scientists participating in this elicitation make this study the widest deep-sea community ever to participate in defining priorities based on standardized questions. Ingels et al. assumed that microbial and meiofaunal components were not prioritized because most of the respondents were macrofaunal or megafaunal experts. However, this is not evident in our data, because a large fraction of respondents covered multiple fields of expertise (note that the supplementary information1 reported only one main topic per scientist). Their criticism suggests that deep-sea scientists are divided into two groups: micro- meiofaunal experts competing against macro- megafaunal experts, fighting to prioritize their own work, rather than a community working together towards a common objective. Obtaining expert opinions for comprehensive deep-sea management, as we did, requires the involvement of scientists working in different sectors (such as deep-sea technologies, conservation biology, biological oceanography, biogeochemistry, policy and management), thus participants cannot simply be classified as experts by faunal size category. The fact that many scientists, in responding to the questionnaire, did not automatically prioritize their own research specialty for deep-ocean monitoring, conservation and impact assessment suggests that this is a false and non-productive dichotomy. Accordingly, we reaffirm that the expert elicitation reported in Danovaro et al.1 is robust, accurate and balanced, and simply reflects the prioritization of the groups of organisms/habitats and associated variables to monitor in light of anthropogenic impacts, conservation needs and currently available technology, feasibility and knowledge. In operational terms, environmental monitoring, especially in the deep sea, requires ready-to-use technologies and methods that are employable, which greatly influences the choice of monitoring priorities and rankings of the consulted experts. Our paper innovatively coupled this need with the readiness levels of the described technologies. We agree that the scientific community should do more to document the importance of small organisms, to establish and disseminate the best standardized practices for collecting such observations and to increase our knowledge of undescribed species and their ecological roles to use them more effectively in future monitoring plans, particularly in light of the ongoing effects of global change8,9,10. At the same time, no marine protected area (in both shallow waters and in the open ocean) or other conservation initiative anywhere targets the loss of meiofaunal or microbial diversity. The reference to the Marine Strategy Framework Directive (MSFD 2008/56/EC), designed to address the Good Environmental Status of marine ecosystems (including the deep sea), does not support the position of Ingels et al.2 as the analysis of deep-sea biodiversity in the MSFD is, at present, limited to species of commercial interest and deep-water corals. None of the European directives prioritize meiofauna or microbes. Moreover, to the best of our knowledge, there is no single ongoing, nor planned, monitoring strategy of a national agency based on or prioritizing microbial or meiofaunal diversity in their standard protocols. Given the current limitation in the use of high-throughput sequencing (for example, for the identification of meiofauna3), further efforts are thus necessary to better integrate microbes and meiofauna in future monitoring and conservation programmes. To do this, the global deep-sea community must encourage joint efforts, share common goals and use standardized tools, This work was supported by the H2020 projects MERCES (Grant agreement no. 689518), and IDEM (Grant agreement no. 11.0661/2017/750680/SUB/EN V.C2.), by the Norwegian Institute for Water Research, by the NSERC Canadian Healthy Oceans Network and CFREF Ocean Frontier Institute, by JPI Oceans2 and ONC, by ARIM (MartTERA ERA-Net Cofound), by NSF grant OCE 1634172, by DOOS from the Consortium for Ocean Leadership, by the EMSO-Link EU project (Grant agreement ID: 731036) and by the Faculty of Science RAE Improvement Fund of The University of Hong Kong, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

So far, the natural recovery of vent communities at large scales has only been evaluated at fast spreading centers, by monitoring faunal recolonisation after volcanic eruptions. However, at slow spreading ridges, opportunities to observe natural disturbances are rare, the overall hydrothermal system being more stable. In this study, we implemented a novel experimental approach by inducing a small-scale disturbance to assess the recovery potential of vent communities along the slow-spreading northern Mid-Atlantic Ridge (nMAR). We followed the recovery patterns of thirteen Bathymodiolus azoricus mussel assemblages colonising an active vent edifice at the Lucky Strike vent field, in relation to environmental conditions and assessed the role of biotic interactions in recolonisation dynamics. Within 2 years after the disturbance, almost all taxonomic richness had recovered, with the exception of a few low occurrence species. However, we observed only a partial recovery of faunal densities and a major change in faunal composition characterised by an increase in abundance of gastropod species, which are hypothesised to be the pioneer colonists of these habitats. Although not significant, our results suggest a potential role of mobile predators in early-colonisation stages. A model of post-disturbance succession for nMAR vent communities from habitat opening to climax assemblages is proposed, also highlighting numerous knowledge gaps. This type of experimental approach, combined with dispersal and connectivity analyses, will contribute to fully assess the resilience of active vent communities after a major disturbance, especially along slow spreading centers targeted for seafloor massive sulphide extraction.

Healthy oceans are essential to maintain a healthy planet, but the ocean is facing many challenges that need urgent attention. Robust scientific data and innovative technological, policy, and industrial solutions are essential to support sound management of the deep-ocean natural capital, both within and beyond national jurisdiction, to ensure future healthy and productive oceans. As with many systems on Earth, there is a delicate ecological balance in the deep ocean that must be maintained. Understanding the interactions of the different components of natural capital in the deep sea is complex, as many of the variables are interlinked and many have cumulative and synergistic effects on the ecosystem. Add to this the global and changing effects of climate change and ocean acidification, and legislators and managers have a tough job ahead to account for all of these issues when designing appropriate conservation measures. It is important that scientists work hand in hand with multiple stakeholders to identify issues and research needs that contribute to enhancing knowledge and the science needed for decision-making to help towards securing a healthy future for our deep-ocean ecosystems and their long-term natural capital.

There has never been a time like the present when there is so much media, scientific, and economic interest in the deep waters of the world ocean and the animals that live there. It is increasingly important for students and new researchers, as well as experienced scientists, to understand how their research can help to address pressing societal challenges. It is beneficial for deep-sea scientists, social scientists, lawyers, authorities, conservationists, industry, and civil society to have broad knowledge of the issues surrounding exploitation in the deep ocean, which has gradually become an increasingly important research focus. The current and future work of deep-sea scientists in all disciplines provides rigorous scientific data and knowledge to support sound management of human activities in this highly complex and variable realm. In this volume, we have brought together internationally recognised scientists, economists, and legal experts to describe the processes by which humans can benefit from the natural capital of the deep sea in a sustainable framework. For this to happen, communication between all deep-sea stakeholders is essential, and this volume aims to facilitate future discussions between the many different sectors of society who may influence the global deep ocean for future generations.

The recovery of populations and their ability to recolonise a disturbed habitat is mainly dependent on their reproductive biology (e.g., fecundity, frequency of reproduction, and time to maturity) and recruitment success. To assess recolonisation processes and connectivity of vent communities, and infer their resilience to natural and anthropogenic disturbances, we studied the life-history traits of two dominant species of vent gastropods from the northern Mid-Atlantic Ridge: Protolira valvatoides and Pseudorimula midatlantica. Gonad morphology, gametogenesis, and reproductive outputs related to shell length were described using histological analyses, and population structure was assessed from individuals’ size–frequency distributions. Samples were collected at different locations of the Montségur and Eiffel Tower edifices (Lucky Strike vent field) in April 2015, July 2017, and August 2018 to inform on spatial and temporal variations of their reproductive outputs and demography. All stages of oocyte development were found in the gonads of both species, suggesting a continuous gametogenesis and asynchronous reproduction. However, the two species showed contrasting reproductive strategies. Indeed, while P. midatlantica is gonochoric with a fecundity of up to 327 mature oocytes, P. valvatoides is hermaphrodite with an extremely low fecundity including a maximum of eight vitellogenic oocytes. Maximum oocyte size was 176 µm for P. midatlantica and 272 µm for P. valvatoides. We infer from previous knowledge and our results that both species exhibit a lecithotrophic development of larvae. There was no evidence of temporal variability of reproductive traits, but environmental conditions seem to affect gametogenetic maturity and oocyte size of P. midatlantica limpets. Variations in population structure at the edifice scale suggest habitat selection of individuals related to biotic and abiotic factors.

13 pages, 9 figures, 4 tables, 1 appendix, Crustacean suprabenthic abundance, community structure, α-diversity (both taxonomic and trophic) and β-diversity were studied along a West-East gradient of oligotrophy in the deep Mediterranean Sea. The assemblages were sampled with a suprabenthic sledge in three regions (western, central and eastern basins) at three water depths (1200, 2000 and 3000 m) in May-June 2009. Environmental data were obtained at each sampling location including sediment properties, oceanographic variables near the seafloor and in the water column, and proxies of epipelagic productivity at the surface. Our results, concerning the crustacean component of the suprabenthos, showed complex trends in community structure and biodiversity across different spatial scales (longitudinal, bathymetric, and near-bottom distribution). A decrease in the number of species and abundance, accompanied by changes in the trophic structure of the assemblages were observed from West to East. In the eastern region the assemblages were impoverished in number of trophic guilds and trophic diversity. The West-East oligotrophic gradient was identified as the main driver in community structure as shown by the significant correlation with trophic environmental variables. Differences in community structure across regions were more marked at greater depths, while at the shallower sites assemblages were more similar. Within each basin, abundance, number of species and number of trophic groups decreased with depth, showing high turnover rates between 1200 and 2000 m depths. The small-scale (0–150 cm) vertical distribution of the suprabenthos was interpreted in relation to the species’ functional traits (e.g. swimming activity, migratory behaviour, bottom dependence, feeding habits). Bottom-dependent and more mobile components of the suprabenthos were apparently responding differently to the various environmental challenges imposed by the large-scale longitudinal and bathymetric gradients. We propose that the bathyal suprabenthos in the Mediterranean Sea may be essentially modulated by environmental sorting, but while the more mobile faunal component has more efficient dispersal mechanisms, the bottom-dependent component may be affected by limited dispersal. However, this empirical interpretation has still to be proved given the important caveats of our study (e.g. typically low densities of the Mediterranean bathyal suprabenthos; limited number of samples; difficulties in standardization inherent to suprabenthic sampling operations in the deep sea), This work was funded through the BIOFUN project (CTM2007-28739-E) within the framework of the EuroCores EuroDEEP programme (European Science Foundation). This study was partially funded by Fundação para a Ciência e Tecnologia (FCT) under the projects PEst-C/MAR/LA0017/2013 and UID/AMB/50017/2013. The first author was funded by a PhD grant from FCT (SFRH/BD/69450/2010).

This research is part of POLARCSIC activities.-- 15 pages, 9 figures, 3 tables, supplementary data https://doi.org/10.1016/j.jmarsys.2019.103268, The flow of non-living carbon (detritus) is considered an important process because it connects ecosystems and fuels benthic communities. In Norwegian kelp forests, 90% of the kelp production is exported to adjacent ecosystems where it can play a significant role in shaping benthic communities. We quantified the major structural and functional traits of an Arctic deep-sea ecosystem associated with kelp exports and assessed the ecological role of kelp export into the deep-sea system. We first developed a food-web model using the Ecopath with Ecosim (EwE) approach to represent the state of the deep (450 m) ecosystem of the Malangen fjord (Northern Norway) in 2017. Subsequently, we used the temporal dynamic model Ecosim to explore the structure and functioning traits of a theoretical deep-sea ecosystem projecting a decrease of kelp detritus biomass reaching the deep-sea ecosystem. Overall, our findings reveal that kelp detritus from shallow coastal areas has a small but noticeable role structuring the deep-sea ecosystem of Malangen. The temporal simulations show important differences depending on the application of mediating effects, which allow considering the detritus as a mediating group in prey-predator interaction, in addition to its direct role in trophic relationships. When mediating effects are applied, biomass increases for benthopelagic shrimps and suprabenthos groups and decreases for rays and skates, velvet belly, rabbitfish and other commercial demersal fishes under the low kelp detritus scenarios. Biomass-based and trophic-based indicators reveal a noticeable impact on the deep-sea ecosystem structure due to depletion of kelp detritus. To further assess future changes of the Arctic deep-sea ecosystems, dependencies with adjacent ecosystems, such as kelp detritus production, should be included, This work was funded by MARINFORSK Norwegian Research Council through the KELPEX project (NRC Grant no. 255085/E40). [...] MC acknowledges partial funding by the European Union's Horizon research program grant agreement No 689518 for the MERCES project, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Disposal of mine tailings in marine shallow water ecosystems represents an environmental challenge, and the present paper reports results from a field study in Fraenfjorden, Norway, which is subject to such disposal. Structural and functional responses of benthic infauna and epifauna were investigated along a gradient from heavy tailings deposition to reference conditions. The tailings clearly impacted the faunal composition, with lowered species number close to the outfall. Total abundance of infauna increased in the most impacted area due to dominance of opportunistic species, whereas the epifauna was reduced and represented by a few scattered specimens only. In the most impacted area functional responses included an increase in mobile carnivores/omnivores and species utilizing symbionts. Sessile and tube-living taxa, and deposit and suspension feeders decreased, probably due to smothering in combination with tailings-associated changes of the substrate. Functional diversity decreased for both infauna and epifauna, but less than the structural diversity.

Increasing interest in deep-seabed mining has raised many questions surrounding its potential environmental impacts and how to assess the impacts’ significance. Under the United Nations Convention on the Law of the Sea (UNCLOS), the International Seabed Authority (ISA) is charged with ensuring effective protection of the marine environment as part of its responsibilities for managing mining in seabed areas beyond national jurisdiction (the Area) on behalf of humankind. This paper examines the international legal context for protection of the marine environment and defining the significant adverse change that can cause “serious harm”, a term used in the ISA Mining Code to indicate a level of harm that strong actions must be taken to avoid. It examines the thresholds and indicators that can reflect significant adverse change and considers the specific vulnerability of the four ecosystems associated with the minerals targeted for mining: (1) manganese (polymetallic) nodules, (2) seafloor massive (polymetallic) sulphides, (3) cobalt-rich (polymetallic) crusts and (4) phosphorites. The distributions and ecological setting, probable mining approaches and the potential environmental impacts of mining are examined for abyssal polymetallic nodule provinces, hydrothermal vents, seamounts and phosphorite-rich continental margins. Discussion focuses on the special features of the marine environment that affect the significance of the predicted environmental impacts and suggests actions that will advance understanding of these impacts.

Deep seabed mining is a major new intersection of human enterprise and deep-ocean ecosystems. This paper reviews the concept and process for a holistic approach to planning environmental management in the deep sea based on Strategic Environmental Goals and Objectives. Strategic planning around the environment can establish a vision for the future condition of the ocean floor for which the International Seabed Authority (ISA) can draw on a wealth of precedents and experience. By engaging stakeholders and applying current knowledge of deep ecosystems, the ISA can build meaningful strategic environmental goals and objectives that give guidance to its own operation and those of its contractors. This framework builds understanding of the organization’s aspirations at global, regional and contractor levels. Herein, some examples are suggested, but we focus on the process. To operationalize these goals and objectives, progress must be measurable; thus, targets are set, reports are assessed, and appropriate responses are awarded. Many management tools and actions are applicable for achieving environmental goals. To date, the ISA has considered marine spatial planning largely around the current exploration contract blocks. Other elements of environmental management, including the requirements for baseline studies, impact assessment, post-impact monitoring and the treatment of harmful effects and serious harm need to be implemented to support well-defined environmental goals and objectives. We suggest that this planning be executed for scales larger than individual blocks, through a Strategic Environmental Management Plan, to ensure sustainable use of ocean resources across the Area.

Highlights • Active hydrothermal vent ecosystems are extremely rare. • Vent ecosystems are recognized as vulnerable by international organizations. • Mineral resources at active vents would not contribute significantly to the global metal supply. • Effective networks that protect representative active vents cannot be ensured. • A prohibition on mining active vents is consistent with obligations for conservation. Abstract There is increasing interest in mining minerals on the seabed, including seafloor massive sulfide deposits that form at hydrothermal vents. The International Seabed Authority is currently drafting a Mining Code, including environmental regulations, for polymetallic sulfides and other mineral exploitation on the seabed in the area beyond national jurisdictions. This paper summarizes 1) the ecological vulnerability of active vent ecosystems and aspects of this vulnerability that remain subject to conjecture, 2) evidence for limited mineral resource opportunity at active vents, 3) non-extractive values of active vent ecosystems, 4) precedents and international obligations for protection of hydrothermal vents, and 5) obligations of the International Seabed Authority under the UN Convention on the Law of the Sea for protection of the marine environment from the impacts of mining. Heterogeneity of active vent ecosystems makes it extremely challenging to identify “representative” systems for any regional, area-based management approach to conservation. Protection of active vent ecosystems from mining impacts (direct and indirect) would set aside only a small fraction of the international seabed and its mineral resources, would contribute to international obligations for marine conservation, would have non-extractive benefits, and would be a precautionary approach.

Deep-sea tailings disposal (DSTD) and its shallow water counterpart, submarine tailings disposal (STD), are practiced in many areas of the world, whereby mining industries discharge processed mud- and rock-waste slurries (tailings) directly into the marine environment. Pipeline discharges and other land-based sources of marine pollution fall beyond the regulatory scope of the London Convention and the London Protocols (LC/LP). However, guidelines have been developed in Papua New Guinea (PNG) to improve tailings waste management frameworks in which mining companies can operate. DSTD can impact ocean ecosystems in addition to other sources of stress, such as from fishing, pollution, energy extraction, tourism, eutrophication, climate change and, potentially in the future, from deep-seabed mining. Environmental management of DSTD may be most effective when placed in a broader context, drawing expertise, data and lessons from multiple sectors (academia, government, society, industry, and regulators) and engaging with international deep-ocean observing programs, databases and stewardship consortia. Here, the challenges associated with DSTD are identified, along with possible solutions, based on the results of a number of robust scientific studies. Also highlighted are the key issues, trends of improved practice and techniques that could be used if considering DSTD (such as increased precaution if considering submarine canyon locations), likely cumulative impacts, and research needed to address current knowledge gaps.

Resource subsidies in the form of allochthonous primary production drive secondary production in many ecosystems, often sustaining diversity and overall productivity. Despite their importance in structuring marine communities, there is little understanding of how subsidies move through juxtaposed habitats and into recipient communities. We investigated the transport of detritus from kelp forests to a deep Arctic fjord (northern Norway). We quantified the seasonal abundance and size structure of kelp detritus in shallow subtidal (0‒12 m), deep subtidal (12‒85 m), and deep fjord (400‒450 m) habitats using a combination of camera surveys, dive observations, and detritus collections over 1 year. Detritus formed dense accumulations in habitats adjacent to kelp forests, and the timing of depositions coincided with the discrete loss of whole kelp blades during spring. We tracked these blades through the deep subtidal and into the deep fjord, and showed they act as a short-term resource pulse transported over several weeks. In deep subtidal regions, detritus consisted mostly of fragments and its depth distribution was similar across seasons (50% of total observations). Tagged pieces of detritus moved slowly out of kelp forests (displaced 4‒50 m (mean 11.8 m ± 8.5 SD) in 11‒17 days, based on minimum estimates from recovered pieces), and most (75%) variability in the rate of export was related to wave exposure and substrate. Tight resource coupling between kelp forests and deep fjords indicate that changes in kelp abundance would propagate through to deep fjord ecosystems, with likely consequences for the ecosystem functioning and services they provide.

Special issue Integrated study of a deep submarine canyon and adjacent open slopes in the Western Mediterranean Sea: an essential habitat.-- 15 pages, 10 figures, 2 tables, The distribution, type and quantity of marine litter accumulated on the bathyal and abyssal Mediterranean seafloor has been studied in the framework of the Spanish national projects PROMETEO and DOS MARES and the ESF-EuroDEEP project BIOFUN. Litter was collected with an otter trawl and Agassiz trawl while sampling for megafauna on the Blanes canyon and adjacent slope (Catalan margin, north-western Mediterranean) between 900 and 2700 m depth, and on the western, central and eastern Mediterranean basins at 1200, 2000 and 3000 m depth. All litter was sorted into 8 categories (hard plastic, soft plastic, glass, metal, clinker, fabric, longlines and fishing nets) and weighed. The distribution of litter was analysed in relation to depth, geographic area and natural (bathymetry, currents and rivers) and anthropogenic (population density and shipping routes) processes. The most abundant litter types were plastic, glass, metal and clinker. Lost or discarded fishing gear was also commonly found. On the Catalan margin, although the data indicated an accumulation of litter with increasing depth, mean weight was not significantly different between depths or between the open slope and the canyon. We propose that litter accumulated in the canyon, with high proportions of plastics, has predominantly a coastal origin, while litter collected on the open slope, dominated by heavy litter, is mostly ship-originated, especially at sites under major shipping routes. Along the trans-Mediterranean transect, although a higher amount of litter seemed to be found on the Western Mediterranean, differences of mean weight were not significant between the 3 geographic areas and the 3 depths. Here, the shallower sites, also closer to the coast, had a higher proportion of plastics than the deeper sites, which had a higher proportion of heavy litter and were often affected by shipping routes. The weight of litter was also compared to biomass of megafauna from the same samples. On the Blanes slope, the biomass of megafauna was significantly higher than the weight of litter between 900 and 2000 m depth and no significant differences were found at 2250 and 2700 m depth. Along the trans-Mediterranean transect, no significant differences were found between biomass and litter weight at all sites except in two sites: the Central Mediterranean at 1200 m depth, where biomass was higher than litter weight, and the Eastern Mediterranean at 1200 m depth, where litter weight was higher than biomass. The results are discussed in the framework of knowledge on marine litter accumulation, its potential impact on the habitat and fauna and the legislation addressing these issues, This study was funded by the PROMETEO project (CTM2007-66316-C02/MAR, CICYT), the BIOFUN project (CTM2007-28739-E, European Science Foundation and national funding agencies), the DOS MARES project (CTM2010-21810-C03-03) and the European Community’s Seventh Framework Programme under the HERMIONE project (Grant Agreement 226354). EZR is funded by a JAE-DOC CSIC postdoctoral grant with co-funding from the European Social Fund. MC was funded by EC Marie-Curie IOF Fellowship to ECOFUN and Spanish Fellowship Program Ramón y Cajal

Increasing exploration and industrial exploitation of the vast and fragile deep-ocean environment for a wide range of resources (e.g., oil, gas, fisheries, new molecules, and soon, minerals) raises global concerns about potential ecological impacts ( 1 – 3 ). Multiple impacts on deep-sea ecosystems (>200 m below sea level; ∼65% of the Earth's surface is covered by deep ocean) caused by human activities may act synergistically and span extensive areas. Cumulative impacts could eventually cause regime shifts and alter deep-ocean life-support services, such as the biological pump or nutrient recycling ( 2 , 4 , 5 ). Although international law and national legislation largely ignore the deep sea's critical role in the functioning and buffering of planetary systems, there are promising developments in support of deep-sea protection at the United Nations and the International Seabed Authority (ISA). We propose a strategy that builds from existing infrastructures to address research and monitoring needs to inform governments and regulators.

Este artículo contiene 12 páginas , 7 figuras, 3 tablas, This study reports the composition and distribution of demersal megafauna from various north-western Mediterranean submarine areas such as canyons, seamounts and landslides between 60–800 m depth, based on remotely operated vehicle (ROV) observations. From a total of 30 h of video, 4534 faunistic observations were made and analysed in relationship to environmental factors (i.e. topography, substrate type and depth). In addition, anthropogenic impact was quantified by grouping observations in four categories: fishing nets, longlines, trawl marks and other litter. The different targeted environments showed similarities in faunal composition according to substrate, depth and topography. Our results also indicated the presence of anthropogenic impact in all the sampled areas in which litter and trawl marks were the most observed artefacts.

26 pages, 7 figures, 2 tables, supplementary material https://www.frontiersin.org/article/10.3389/fmars.2017.00005/full#supplementary-material, Submarine canyons are major geomorphic features of continental margins around the world. Several recent multidisciplinary projects focused on the study of canyons have considerably increased our understanding of their ecological role, the goods, and services they provide to human populations, and the impacts that human activities have on their overall ecological condition. Pressures from human activities include fishing, dumping of land-based mine tailings, and oil and gas extraction. Moreover, hydrodynamic processes of canyons enhance the down-canyon transport of litter. The effects of climate change may modify the intensity of currents. This potential hydrographic change is predicted to impact the structure and functioning of canyon communities as well as affect nutrient supply to the deep-ocean ecosystem. This review not only identifies the ecological status of canyons, and current and future issues for canyon conservation, but also highlights the need for a better understanding of anthropogenic impacts on canyon ecosystems and proposes other research required to inform management measures to protect canyon ecosystems, UF was funded by the Balearic Government post-doctoral grant 2016, co-financed by European Social Plan; VH was supported by the CODEMAP project (ERC Starting Grant no 258482) and the NERC MAREMAP programme; PP has been funded by the ABIDES project (CTM2015-65142-R); AR was supported by NIWA research project “Impact of resource use on vulnerable deep-sea communities” (MBIE contract CO1X0906). IV was funded by Ifremer and Région Bretagne. ALA is supported by Science Foundation Ireland / Marine Institute IvP award 15/IA/3100

15 pages, 5 figures, 1 table, The oceans were observed to be deep during the great age of exploration in the early to mid-nineteenth century. Subsequent exploration demonstrated that the ocean was bisected by underwater mountain ranges and dotted with abyssal hills. With the advent of the echosounder and latterly multichannel swath bathymetry, we now know that the deep ocean has topography as diverse as found on land. In the last 30 years, with an increase in deep-sea scientific activity and the use of underwater vehicles, we have learned that the deep sea consists of a series of habitats and ecosystems interconnected by hydrography and topography. The more recent challenges have been how to sample and analyse these separate habitats and ecosystems. This chapter describes the different environments and briefly outlines the main methods of sampling for each habitat or ecosystem. More detailed aspects of these sampling methods are found in subsequent chapters

A test deployment of a time-lapse camera lander in the deep Oslofjord (431 m) was used to obtain initial information on the response of benthic fauna to macroalgal debris. Three macroalgal species were used on the lander baited plate: Fucus serratus, Saccharina latissima and Laminaria hyperborea and observed during 41.5 hours. The deep-water shrimp Pandalus borealis were attracted to the macroalgae rapidly (3 min after the lander reached the seafloor), followed by amphipods. Shrimp abundances were significantly higher in areas covered by macroalgae compared to the adjacent seafloor and the number of shrimp visiting the macroalgae increased with time. Amphipods arrived 13 hours later and were observed mainly on decaying L. hyperborea. The abundance of amphipods on L. hyperborea increased rapidly, reaching a peak at 31 h after deployment. These initial observations suggest that debris from kelp forests and other macroalgal beds may play an important role in fuelling deep benthic communities in the outer Oslofjord and, potentially, enhance secondary production of commercial species such as P. borealis.

Covering more than half the planet, the deep ocean sequesters atmospheric CO2 and recycles major nutrients; is predicted to hold millions of yet-to-be-described species; and stores mind-boggling quantities of untapped energy resources, precious metals, and minerals ( 1 ). It is an immense, remote biome, critical to the health of the planet and human well-being. The deep ocean (defined here as below a typical continental shelf break, >200 m) faces mounting challenges as technological advances—including robotics, imaging, and structural engineering—greatly improve access. We recommend a move from a frontier mentality of exploitation and single-sector management to a precautionary system that balances use of living marine resources, energy, and minerals from the deep ocean with maintenance of a productive and healthy marine environment, while improving knowledge and collaboration.

The composition and structure of megabenthic communities in the Blanes canyon and adjacent open margin (Northwestern Mediterranean) were studied. The aim was to assess the effect of the canyon and commercial fishing intensity on the community composition and structure of benthic megafauna by (i) describing the megabenthic community composition, (ii) quantifying faunal abundance and biomass and (iii) describing community structure with MDS analyses and biodiversity indices. The results are compared between three sites (canyon head, canyon wall and open margin) located between 435 m and 700 m. Samples were collected using a commercial bottom trawl between April 2003 and March 2004. These sites are exploited by the local fishing fleet that targets the rose shrimp Aristeus antennatus. A total of 131 megabenthic species were identified from the three sites, with fishes and decapod crustaceans being the most speciose, most abundant and of higher biomass. The species richness, abundance and biomass of non-crustacean invertebrates were low. There were no significant differences in total abundance and biomass between the three sites. However, community structure analysis suggests that the open margin community is significantly different from the canyon head and canyon wall, with a lower species richness, lower diversity and lower evenness. The open margin community also reflects a higher degree of disturbance compared to the two canyon habitats. The results indicate that there is a canyon effect on the community structure of benthic megafauna, but this may be modulated by differing fishing pressure, which adds an additional factor to margin heterogeneity.

12 páginas, 6 figuras, 5 tablas., There is a general hypothesis that species inhabiting deep-sea waters have lower fecundity and larger eggs than shallower species. However, there are few comparative studies which explore this trend because of the complexity of sampling in deep waters, especially in fishes. We present here the first analysis of fecundity and egg size with depth along an isothermal environment. We calculate the relative fecundity and egg size of 11 species of demersal deep-sea fish from the western Mediterranean and included in our analyses published data for an additional 14 species from the same geographic area. The results show that the relative fecundity (eggs per g of individual) of the analyzed fishes slightly decreased along the bathymetric gradient, whereas egg size increased with depth. When the analysis was conducted including only species from the order Gadiformes, the most speciose group in the region and with the widest depth range of distribution (50–2000 m), there was no relationship between relative fecundity and depth, while the deepest species had larger egg sizes than shallower ones. The finding of similar relative fecundities but larger egg sizes suggests that these deep-sea species are investing a higher amount of energy in the production of offspring than shallower water counterparts. The results are discussed in relation to the isothermal characteristics of the deep Mediterranean Sea and ecological adaptations for reproductive success., This study was conducted within the framework oft he RECS(REN02/04556/C02/MAR), PROMETEO(CTM2007-66316-C02/MAR) and DOSMARES (CTM2010-21810-C03-03/MAR) projects by the Spanish Science and Innovation Ministry respectively, to JBC.

Special issue on InterRidge.-- 12 pages, 5 figures, 1 table, The discovery of hydrothermal vents and the unique, often endemic fauna that inhabit them represents one of the most extraordinary scientific discoveries of the latter twentieth century. Not surprisingly, after just 30 years of study of these remarkable—and extremely remote—systems, advances in understanding the animals and microbial communities living around hydrothermal vents seem to occur with every fresh expedition to the seafloor. On average, two new species are described each month—a rate of discovery that has been sustained over the past 25–30 years (Van Dover et al., 2002; Fisher et al., this issue). Furthermore, the physical, geological, and geochemical features of each part of the ridge system and its associated hydrothermal-vent structures appear to dictate which novel biological species can live where. Only 10 percent of the ridge system has been explored for hydrothermal activity to date (Baker and German, 2004), yet we find different diversity patterns in that small fraction. While it is well known that species composition varies along discrete segments of the global ridge system, this >biogeographic puzzle> has more pieces missing than pieces in place (Figure 1, Table 1), E. Ramirez-Llodra is supported by the ChEss-Census of Marine Life program (A.P. Sloan Foundation), which is kindly acknowledged. C.R. German also acknowledges support from ChEss- Census of Marine Life and further support from the Natural Environment Research Council (UK) and from the US National Science Foundation (NSF) and National Oceanic and Atmospheric Administration (NOAA). T. Shank acknowledges support from NSF, the USNational Aeronautic and Space Administration Astrobiology Program, NOAAOcean Exploration, and the Deep-Ocean Exploration Institute at the Woods Hole Oceanographic Institution

Time-series studies (1989–2002) in the NE Atlantic have shown large-scale changes in the composition and structure of the benthic community on the Porcupine Abyssal Plain. Radical changes in the abundance of some species in 1996 led to a significant shift in the way in which organic matter was reprocessed at the seabed. This article examines the reproductive processes of the holothurian Oneirophanta mutabilis collected during the time series. The reproductive biology of O. mutabilis is reviewed. No males were evident in any of the samples. The sex ratio (females: ‘no gender’) was biased significantly towards no-gender individuals. The maximum egg size was 650 μm and there was no evidence of synchrony in reproduction. Significant changes in the oocyte-size distribution and the fecundity of O. mutabilis were noted through time, coinciding with the time of greatest faunal change in the benthic community. There was an increase in the proportion of previtellogenic oocytes and a decrease in the proportion of mature vitellogenic oocytes in 1997 and 1998, in parallel with a significant decrease in fecundity of the post-1996 samples. Samples from 2002 showed a reversal in the reproductive trends, with an increase in the proportion of mature vitellogenic oocytes and fecundity. The results are discussed in relation to large changes in abundance of the epibenthos on the Porcupine Abyssal Plain. It is suggested that the superabundance of certain megafaunal species on the abyssal seafloor affected the availability of trophic resources for O. mutabilis, leading to the changes in its reproductive effort.

The mining sector is growing in parallel with societal demands for minerals. One of the most important environmental issues and economic burdens of industrial mining on land is the safe storage of the vast amounts of waste produced. Traditionally, tailings have been stored in land dams, but the lack of land availability, potential risk of dam failure and topography in coastal areas in certain countries results in increasing disposal of tailings into marine systems. This review describes the different submarine tailing disposal methods used in the world in general and in Norway in particular, their impact on the environment (e.g. hyper-sedimentation, toxicity, processes related to changes in grain shape and size, turbidity), current legislation and need for future research. Understanding these impacts on the habitat and biota is essential to assess potential ecosystem changes and to develop best available techniques and robust management plans.