Biological effects 26 years after simulated deep-sea mining

Potential biomarkers of metal toxicity in deep-sea invertebrates - A critical review of the omics data

Deep-sea mining (DSM) activities are expected to release potentially toxic metal mixtures through the generation of sediment plumes to the marine environment. This may disrupt the normal functioning of biological mechanisms, adversely affecting deep-sea invertebrate organisms. It is thus essential to understand the ecotoxicological effects from these toxic elements in deep-sea organisms and the omics approaches applied to ecotoxicology are seen as promising tools. Here, we provide an overview of the principal biological modifications identified in deep-sea invertebrates when exposed to metals and critically evaluate the current knowledge and discuss which potential biomarkers may be useful after metal exposure. Most of the 50 omics studies on deep-sea invertebrates revised are comparative transcriptomes (n = 41). Forty-three potential biomarker candidates are highlighted from immune system, 46 from cellular metabolism and 29 from oxidative stress. The processes mostly affected by metal toxicity in deep-sea invertebrates are related to innate immune defense; sulfur, chitin, and catabolic metabolism; antioxidation; and detoxification. We acknowledge the current limitations and future perspectives for their uses and emphasize the need to invest in further ecotoxicological studies using the omics approaches.

The long-lived deep-sea bivalve Acesta excavata is sensitive to the dual stressors of sediment and warming

Human influence in the deep-sea is increasing as mining and drilling operations expand, and waters warm because of climate change. Here, we investigate how the long-lived deep-sea bivalve, Acesta excavata responds to sediment pollution and/or acute elevated temperatures. A. excavata were exposed to suspended sediment, acute warming, and a combination of the two treatments for 40 days. We measured O2 consumption, NH4+ release, Total Organic Carbon (TOC), and lysosomal membrane stability (LMS). We found suspended sediment and warming interacted to decrease O:N ratios, while sediment as a single stressor increased the release of TOC and warming increased NH4+ release in A. excavata. Warming also increased levels of LMS. We found A. excavata used protein catabolism to meet elevated energetic demands indicating a low tolerance to stress. A. excavata has limited capacity for physiological responses to the stressors of warming and sediment which may lead to decreased fitness of A. excavata.

Evaluating ecological benefits of oceanic protected areas

Oceans beyond the continental shelf represent the largest yet least protected environments. The new agreement to increase protection targets to 30% by 2030 and the recent United Nations (UN) High Seas Treaty try to address this gap, and an increase in the declaration of oceanic Marine Protected Areas (oMPAs) in waters beyond 200 m in depth is likely. Here we find that there is contradictory evidence concerning the benefits of oMPAs in terms of protecting pelagic habitats, providing refuge for highly mobile species, and potential fisheries benefits. We discover a mismatch between oMPA management objectives focusing on protection of pelagic habitats and biodiversity, and scientific research focusing on fisheries benefits. We suggest that the solution is to harness emerging technologies to monitor inside and outside oMPAs.

Carbonate compensation depth drives abyssal biogeography in the northeast Pacific

Abyssal seafloor communities cover more than 60% of Earth's surface. Despite their great size, abyssal plains extend across modest environmental gradients compared to other marine ecosystems. However, little is known about the patterns and processes regulating biodiversity or potentially delimiting biogeographical boundaries at regional scales in the abyss. Improved macroecological understanding of remote abyssal environments is urgent as threats of widespread anthropogenic disturbance grow in the deep ocean. Here, we use a new, basin-scale dataset to show the existence of clear regional zonation in abyssal communities across the 5,000 km span of the Clarion-Clipperton Zone (northeast Pacific), an area targeted for deep-sea mining. We found two pronounced biogeographic provinces, deep and shallow-abyssal, separated by a transition zone between 4,300 and 4,800 m depth. Surprisingly, species richness was maintained across this boundary by phylum-level taxonomic replacements. These regional transitions are probably related to calcium carbonate saturation boundaries as taxa dependent on calcium carbonate structures, such as shelled molluscs, appear restricted to the shallower province. Our results suggest geochemical and climatic forcing on distributions of abyssal populations over large spatial scales and provide a potential paradigm for deep-sea macroecology, opening a new basis for regional-scale biodiversity research and conservation strategies in Earth's largest biome.

Seamount mining test provides evidence of ecological impacts beyond deposition

In July 2020, Japan undertook the first deep-sea mining test of cobalt-rich crusts on the summit of Takuyo-Daigo Seamount within their exclusive economic zone (EEZ). Seabed mining regulations are currently being developed by the International Seabed Authority (ISA)¹; however, a lack of experimental data has so far constrained our understanding of the associated impacts, particularly from the release of sediment plumes.² The area of sediment re-deposition from the crust mining test was determined using modeled data and in situ observations. To investigate biological impacts, variations in seabed megafauna (animals > 1 cm) were quantified from seabed imagery collected around the excavation site before, 1 month, and 13 months after the test in areas both inside and outside (adjacent) expected deposition. Observable responses varied across community components: densities of sessile animals were similar between deposition and adjacent areas throughout the study; mobile epifauna were less abundant only in the deposition area following disturbance; and highly mobile swimmers showed reduced densities after the test in both deposition and adjacent areas following disturbance. These results stress that monitoring of highly mobile taxa may be essential to fully assess disturbance extent and magnitude. Fish may avoid areas even outside plume deposition, possibly owing to the creation of suboptimal feeding patches resulting from deposition. Our findings suggest sufficiently large (>300 × 300 m), distant, and representative control areas are essential to optimally map deep-sea mining impacts in ferromanganese crust habitats to ensure impact assessments encompass the full range of functional components in the megabenthic community (including mobile fishes) that typically inhabit seamounts.

Stressors of emerging concern in deep-sea environments: microplastics, pharmaceuticals, personal care products and deep-sea mining

Although most deep-sea areas are remote in comparison to coastal zones, a growing body of literature indicates that many sensitive ecosystems could be under increased stress from anthropogenic sources. Among the multiple potential stressors, microplastics (MPs), pharmaceuticals and personal care products (PPCPs/PCPs) and the imminent start of commercial deep-sea mining have received increased attention. Here we review recent literature on these emerging stressors in deep-sea environments and discuss cumulative effects with climate change associated variables. Importantly, MPs and PPCPs have been detected in deep-sea waters, organisms and sediments, in some locations in comparable levels to coastal areas. The Atlantic Ocean and the Mediterranean Sea are the most studied areas and where higher levels of MPs and PPCPs have been detected. The paucity of data for most other deep-sea ecosystems indicates that many more locations are likely to be contaminated by these emerging stressors, but the absence of studies hampers a better assessment of the potential risk. The main knowledge gaps in the field are identified and discussed, and future research priorities are highlighted to improve hazard and risk assessment.

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

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

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

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

Benthic megafauna of the western Clarion-Clipperton Zone, Pacific Ocean

There is a growing interest in the exploitation of deep-sea mineral deposits, particularly on the abyssal seafloor of the central Pacific Clarion-Clipperton Zone (CCZ), which is rich in polymetallic nodules. In order to effectively manage potential exploitation activities, a thorough understanding of the biodiversity, community structure, species ranges, connectivity, and ecosystem functions across a range of scales is needed. The benthic megafauna plays an important role in the functioning of deep-sea ecosystems and represents an important component of the biodiversity. While megafaunal surveys using video and still images have provided insight into CCZ biodiversity, the collection of faunal samples is needed to confirm species identifications to accurately estimate species richness and species ranges, but faunal collections are very rarely carried out. Using a Remotely Operated Vehicle, 55 specimens of benthic megafauna were collected from seamounts and abyssal plains in three Areas of Particular Environmental Interest (APEI 1, APEI 4, and APEI 7) at 3100-5100 m depth in the western CCZ. Using both morphological and molecular evidence, 48 different morphotypes belonging to five phyla were found, only nine referrable to known species, and 39 species potentially new to science. This work highlights the need for detailed taxonomic studies incorporating genetic data, not only within the CCZ, but in other bathyal, abyssal, and hadal regions, as representative genetic reference libraries that could facilitate the generation of species inventories.

Impact of resuspended mine tailings on benthic biodiversity and ecosystem processes: The case study of Portmán Bay, Western Mediterranean Sea, Spain

Industrial seabed mining is expected to cause significant impacts on marine ecosystems, including physical disturbance and the generation of plumes of toxin-laden water. Portmán Bay (NW Mediterranean Sea), where an estimated amount of 60 Mt of mine tailings from sulphide ores were dumped from 1957 to 1990, is one of the most metal-polluted marine areas in Europe and worldwide. This bay can be used to assess the impact on marine ecosystems of particle settling from sediment plumes resulting from mine tailings resuspension. With this purpose in mind, we conducted a field experiment there to investigate subsequent effects of deposition of (artificially resuspended) contaminated sediments on (i) prokaryotic abundance and meiofaunal assemblages (in terms of abundance and diversity), (ii) the availability of trophic resources (in terms of organic matter biochemical composition), and (iii) a set of ecosystem functions including meiofaunal biomass, heterotrophic C production and C degradation rates. The results of this study show that mine tailings resuspension and plume deposition led to the decline of prokaryotic abundance and nematode's biodiversity. The later decreased because of species removal and transfer along with particle resuspension and plume deposition. Such changes were also associated to a decrease of the proteins content in the sediment organic matter, faster C degradation rates and higher prokaryotic C production. Overall, this study highlights that mine tailing resuspension and ensuing particle deposition can have deleterious effects on both prokaryotes and nematode diversity, alter biogeochemical cycles and accelerate C degradation rates. These results should be considered for the assessment of the potential effects of seabed mineral exploitation on marine ecosystems at large.

Ethical opportunities in deep-sea collection of polymetallic nodules from the Clarion-Clipperton Zone

Infrastructure supporting the transition of human societies from fossil fuels to renewable energy will require hundreds of millions of tons of metals. Polymetallic nodules on the abyssal seabed of the Clarion-Clipperton Zone (CCZ), eastern North Pacific Ocean, could provide them. We focus on ethical considerations and opportunities available to the novel CCZ nodule-collection industry, integrating robust science with strong pillars of social and environmental responsibility. Ethical considerations include harm to sea life and recovery time, but also the value of human life, indigenous rights, rights of nature, animal rights, intrinsic values, and intangible ecosystem services. A "planetary perspective" considers the biosphere, hydrosphere, and atmosphere, extends beyond mineral extraction to a life-cycle view of impacts, and includes local, national, and global impacts and stakeholders. Stakeholders include direct nodule-collection actors, ocean conservationists, companies, communities, interest groups, nations, and citizens globally, plus counterfactual stakeholders involved with or affected by intensification of terrestrial mining if ocean metals are not used. Nodule collection would harm species and portions of ecosystems, but could have lower life-cycle impacts than terrestrial mining expansion, especially if nodule-metal producers explicitly design for it and stakeholders hold them accountable. Participants across the value chain can elevate the role of ethics in strategic objective setting, engineering design optimization, commitments to stakeholders, democratization of governance, and fostering of circular economies. The International Seabed Authority is called to establish equitable and transparent distribution of royalties and gains, and continue engaging scientists, economists, and experts from all spheres in optimizing deep-sea mineral extraction for humans and nature. Nodule collection presents a unique opportunity for an ambitious reset of ecological norms in a nascent industry. Embracing ethical opportunities can set an example for industrial-scale activities on land and sea, accelerate environmental gains through environmental competition with land ores, and hasten civilization's progress toward a sustainable future. Integr Environ Assess Manag 2022;18:634-654. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

How do we best synergize climate mitigation actions to co-benefit biodiversity?

A multitude of actions to protect, sustainably manage and restore natural and modified ecosystems can have co-benefits for both climate mitigation and biodiversity conservation. Reducing greenhouse emissions to limit warming to less than 1.5 or 2°C above preindustrial levels, as outlined in the Paris Agreement, can yield strong co-benefits for land, freshwater and marine biodiversity and reduce amplifying climate feedbacks from ecosystem changes. Not all climate mitigation strategies are equally effective at producing biodiversity co-benefits, some in fact are counterproductive. Moreover, social implications are often overlooked within the climate-biodiversity nexus. Protecting biodiverse and carbon-rich natural environments, ecological restoration of potentially biodiverse and carbon-rich habitats, the deliberate creation of novel habitats, taking into consideration a locally adapted and meaningful (i.e. full consequences considered) mix of these measures, can result in the most robust win-win solutions. These can be further enhanced by avoidance of narrow goals, taking long-term views and minimizing further losses of intact ecosystems. In this review paper, we first discuss various climate mitigation actions that evidence demonstrates can negatively impact biodiversity, resulting in unseen and unintended negative consequences. We then examine climate mitigation actions that co-deliver biodiversity and societal benefits. We give examples of these win-win solutions, categorized as 'protect, restore, manage and create', in different regions of the world that could be expanded, upscaled and used for further innovation.

No recovery of a large-scale anthropogenic sediment disturbance on the Pacific seafloor after 77 years at 6460 m depth

Habitat restoration and recolonisation of benthic communities after physical perturbation in the deep sea has long been thought to be extremely slow. This study reports on a serendipitous opportunity to survey the current state of a large mechanical disturbance of sediments at 6460 m in the Pacific Ocean. The impact was caused 77 years ago by the sinking of the USS Johnston. The surrounding debris field had little impact on the sedimentary habitat, other than in the provision of artificial hard substrates, while the troughs that formed as the ship impacted the seafloor and slid down the slope of the Philippine Trench were still completely void of animal tracks and burrows, or any observable epifauna, and in some areas subsurface stratification was still exposed at the surface. This suggests that mechanical perturbations of sediments in the deep Pacific may remain ecologically significant for, at the very least, 100 years.

Importance of Spatial Autocorrelation in Machine Learning Modeling of Polymetallic Nodules, Model Uncertainty and Transferability at Local Scale

Machine learning spatial modeling is used for mapping the distribution of deep-sea polymetallic nodules (PMN). However, the presence and influence of spatial autocorrelation (SAC) have not been extensively studied. SAC can provide information regarding the variable selection before modeling, and it results in erroneous validation performance when ignored. ML models are also problematic when applied in areas far away from the initial training locations, especially if the (new) area to be predicted covers another feature space. Here, we study the spatial distribution of PMN in a geomorphologically heterogeneous area of the Peru Basin, where SAC of PMN exists. The local Moran’s I analysis showed that there are areas with a significantly higher or lower number of PMN, associated with different backscatter values, aspect orientation, and seafloor geomorphological characteristics. A quantile regression forests (QRF) model is used using three cross-validation (CV) techniques (random-, spatial-, and cluster-blocking). We used the recently proposed “Area of Applicability” method to quantify the geographical areas where feature space extrapolation occurs. The results show that QRF predicts well in morphologically similar areas, with spatial block cross-validation being the least unbiased method. Conversely, random-CV overestimates the prediction performance. Under new conditions, the model transferability is reduced even on local scales, highlighting the need for spatial model-based dissimilarity analysis and transferability assessment in new areas.

Underwater Hyperspectral Imaging (UHI): A Review of Systems and Applications for Proximal Seafloor Ecosystem Studies

Marine ecosystem monitoring requires observations of its attributes at different spatial and temporal scales that traditional sampling methods (e.g., RGB imaging, sediment cores) struggle to efficiently provide. Proximal optical sensing methods can fill this observational gap by providing observations of, and tracking changes in, the functional features of marine ecosystems non-invasively. Underwater hyperspectral imaging (UHI) employed in proximity to the seafloor has shown a further potential to monitor pigmentation in benthic and sympagic phototrophic organisms at small spatial scales (mm–cm) and for the identification of minerals and taxa through their finely resolved spectral signatures. Despite the increasing number of studies applying UHI, a review of its applications, capabilities, and challenges for seafloor ecosystem research is overdue. In this review, we first detail how the limited band availability inherent to standard underwater cameras has led to a data analysis “bottleneck” in seafloor ecosystem research, in part due to the widespread implementation of underwater imaging platforms (e.g., remotely operated vehicles, time-lapse stations, towed cameras) that can acquire large image datasets. We discuss how hyperspectral technology brings unique opportunities to address the known limitations of RGB cameras for surveying marine environments. The review concludes by comparing how different studies harness the capacities of hyperspectral imaging, the types of methods required to validate observations, and the current challenges for accurate and replicable UHI research.

Causal Approach to Determining the Environmental Risks of Seabed Mining

Mineral deposits containing commercially exploitable metals are of interest for seabed mineral extraction in both the deep sea and shallow sea areas. However, the development of seafloor mining is underpinned by high uncertainties on the implementation of the activities and their consequences for the environment. To avoid unbridled expansion of maritime activities, the environmental risks of new types of activities should be carefully evaluated prior to permitting them, yet observational data on the impacts is mostly missing. Here, we examine the environmental risks of seabed mining using a causal, probabilistic network approach. Drawing on a series of expert interviews, we outline the cause-effect pathways related to seabed mining activities to inform quantitative risk assessments. The approach consists of (1) iterative model building with experts to identify the causal connections between seabed mining activities and the affected ecosystem components and (2) quantitative probabilistic modeling. We demonstrate the approach in the Baltic Sea, where seabed mining been has tested and the ecosystem is well studied. The model is used to provide estimates of mortality of benthic fauna under alternative mining scenarios, offering a quantitative means to highlight the uncertainties around the impacts of mining. We further outline requirements for operationalizing quantitative risk assessments in data-poor cases, highlighting the importance of a predictive approach to risk identification. The model can be used to support permitting processes by providing a more comprehensive description of the potential environmental impacts of seabed resource use, allowing iterative updating of the model as new information becomes available.

Evolving the narrative for protecting a rapidly changing ocean, post-COVID-19

The ocean is the linchpin supporting life on Earth, but it is in declining health due to an increasing footprint of human use and climate change. Despite notable successes in helping to protect the ocean, the scale of actions is simply not now meeting the overriding scale and nature of the ocean's problems that confront us.Moving into a post-COVID-19 world, new policy decisions will need to be made. Some, especially those developed prior to the pandemic, will require changes to their trajectories; others will emerge as a response to this global event. Reconnecting with nature, and specifically with the ocean, will take more than good intent and wishful thinking. Words, and how we express our connection to the ocean, clearly matter now more than ever before.The evolution of the ocean narrative, aimed at preserving and expanding options and opportunities for future generations and a healthier planet, is articulated around six themes: (1) all life is dependent on the ocean; (2) by harming the ocean, we harm ourselves; (3) by protecting the ocean, we protect ourselves; (4) humans, the ocean, biodiversity, and climate are inextricably linked; (5) ocean and climate action must be undertaken together; and (6) reversing ocean change needs action now.This narrative adopts a 'One Health' approach to protecting the ocean, addressing the whole Earth ocean system for better and more equitable social, cultural, economic, and environmental outcomes at its core. Speaking with one voice through a narrative that captures the latest science, concerns, and linkages to humanity is a precondition to action, by elevating humankind's understanding of our relationship with 'planet Ocean' and why it needs to become a central theme to everyone's lives. We have only one ocean, we must protect it, now. There is no 'Ocean B'.

Giant, highly diverse protists in the abyssal Pacific: vulnerability to impacts from seabed mining and potential for recovery

Xenophyophores, giant deep-sea agglutinated foraminifera, dominate the benthic megafauna in the eastern equatorial Pacific Clarion-Clipperton Zone. This abyssal (>4000 m depth) region hosts major deposits of polymetallic nodules targeted for future seabed mining, an activity that would destroy these highly diverse and delicate protists, particularly those living on the nodules themselves. Since the cell occupies only a small proportion of their test volume, xenophyophores may make a fairly modest contribution to benthic biomass and carbon cycling. Nevertheless, xenophyophore tests can passively enhance particle deposition, concentrate food, and provide habitat structure utilized by diverse organisms. Their destruction could therefore influence the recovery of benthic communities. Species requiring nodule substrates will likely not recover, since nodules take millions of years to form. However, xenophyophores can grow quickly and colonize extensive volcanic ash deposits within years, suggesting that sediment-dwelling species could be among the first large immobile organisms to reappear in mining-impacted areas.

Impact of historical sulfide mine tailings discharge on meiofaunal assemblages (Portmán Bay, Mediterranean Sea)

Portmán Bay is one of the most contaminated and chronically impacted coastal marine areas of the world. Here, from the 1957 to 1990, about 60 million tons of mine tailings from the processing of sulfide ores were dumped directly at the shoreline. The resulting deposit provides a unique opportunity to assess the impact of mine tailings on coastal marine ecosystems after ca 30 years since the discharge has ceased. We investigated meiofaunal abundance, biomass and biodiversity along a gradient of metal concentration that overlaps with a bathymetric gradient from 30 to 60 m depth. Despite the localized presence of extremely high concentration of metals, the bay was not a biological desert, but, nevertheless, was characterized by evident signs of impact on benthic diversity. Meiofaunal variables increased significantly with decreasing metal contamination, eventually reaching values comparable to other uncontaminated coastal sediments. Our results show that mine tailings influenced the spatial distribution of meiofaunal taxa and nematode species composition. In particular, we report here that the bay was characterized by the dominance of nematode opportunistic species tolerant to high metal concentration. The effects of mine tailing discharge on meiofaunal biodiversity and composition were still evident ca 30 years after the end of the mining activities. Overall, this study provides new insights on the potential impact of mine tailings disposal and metal contamination in coastal sediments, and, can also contribute to predict the potential long-term consequences of ever-expanding deep-sea mining industry on benthic environments.

Climate change considerations are fundamental to management of deep-sea resource extraction

Climate change manifestation in the ocean, through warming, oxygen loss, increasing acidification, and changing particulate organic carbon flux (one metric of altered food supply), is projected to affect most deep-ocean ecosystems concomitantly with increasing direct human disturbance. Climate drivers will alter deep-sea biodiversity and associated ecosystem services, and may interact with disturbance from resource extraction activities or even climate geoengineering. We suggest that to ensure the effective management of increasing use of the deep ocean (e.g., for bottom fishing, oil and gas extraction, and deep-seabed mining), environmental management and developing regulations must consider climate change. Strategic planning, impact assessment and monitoring, spatial management, application of the precautionary approach, and full-cost accounting of extraction activities should embrace climate consciousness. Coupled climate and biological modeling approaches applied in the water and on the seafloor can help accomplish this goal. For example, Earth-System Model projections of climate-change parameters at the seafloor reveal heterogeneity in projected climate hazard and time of emergence (beyond natural variability) in regions targeted for deep-seabed mining. Models that combine climate-induced changes in ocean circulation with particle tracking predict altered transport of early life stages (larvae) under climate change. Habitat suitability models can help assess the consequences of altered larval dispersal, predict climate refugia, and identify vulnerable regions for multiple species under climate change. Engaging the deep observing community can support the necessary data provisioning to mainstream climate into the development of environmental management plans. To illustrate this approach, we focus on deep-seabed mining and the International Seabed Authority, whose mandates include regulation of all mineral-related activities in international waters and protecting the marine environment from the harmful effects of mining. However, achieving deep-ocean sustainability under the UN Sustainable Development Goals will require integration of climate consideration across all policy sectors.

Protist diversity and function in the dark ocean - Challenging the paradigms of deep-sea ecology with special emphasis on foraminiferans and naked protists

The dark ocean and the underlying deep seafloor together represent the largest environment on this planet, comprising about 80% of the oceanic volume and covering more than two-thirds of the Earth's surface, as well as hosting a major part of the total biosphere. Emerging evidence suggests that these vast pelagic and benthic habitats play a major role in ocean biogeochemistry and represent an "untapped reservoir" of high genetic and metabolic microbial diversity. Due to its huge volume, the water column of the dark ocean is the largest reservoir of organic carbon in the biosphere and likely plays a major role in the global carbon budget. The dark ocean and the seafloor beneath it are also home to a largely enigmatic food web comprising little-known and sometimes spectacular organisms, mainly prokaryotes and protists. This review considers the globally important role of pelagic and benthic protists across all protistan size classes in the deep-sea realm, with a focus on their taxonomy, diversity, and physiological properties, including their role in deep microbial food webs. We argue that, given the important contribution that protists must make to deep-sea biodiversity and ecosystem processes, they should not be overlooked in biological studies of the deep ocean.

Effects of a deep-sea mining experiment on seafloor microbial communities and functions after 26 years

Future supplies of rare minerals for global industries with high-tech products may depend on deep-sea mining. However, environmental standards for seafloor integrity and recovery from environmental impacts are missing. We revisited the only midsize deep-sea disturbance and recolonization experiment carried out in 1989 in the Peru Basin nodule field to compare habitat integrity, remineralization rates, and carbon flow with undisturbed sites. Plough tracks were still visible, indicating sites where sediment was either removed or compacted. Locally, microbial activity was reduced up to fourfold in the affected areas. Microbial cell numbers were reduced by ~50% in fresh "tracks" and by <30% in the old tracks. Growth estimates suggest that microbially mediated biogeochemical functions need over 50 years to return to undisturbed levels. This study contributes to developing environmental standards for deep-sea mining while addressing limits to maintaining and recovering ecological integrity during large-scale nodule mining.

Macrostylis metallicola spec. nov.-an isopod with geographically clustered genetic variability from a polymetallic-nodule area in the Clarion-Clipperton Fracture Zone

Background

The Clarion-Clipperton Fracture Zone (CCFZ) in the Northeast Central Pacific Ocean is a region of heightened scientific and public interest because of its wealth in manganese nodules. Due to a poor ecological understanding at the abyssal seafloor and limited knowledge of the organisms inhabiting this area, huge efforts in alpha taxonomy are required. To predict and manage potential hazards associated with future mining, taxonomy is an essential first step to grasp fundamental ecosystem traits, such as biogeographic patterns, connectivity, and the potential for post-impact recolonization. Amongst samples from the Global Sea Mineral Resources NV exploration area (EA) in the CCFZ an undescribed species of the isopod crustacean family Macrostylidae was discovered. Previously, it has been reported from two other nearby regions, the Institut Français de Recherche pour l’Exploitation de la Mer and BGR EAs. There it was one of the more widely distributed and abundant species of the benthic macrofauna and exhibited geographically structured populations. It nevertheless remained taxonomically undescribed so far.

Methods

The new species is described by means of integrative taxonomy. Morphologically, macro photography, confocal microscopy, scanning electron microscopy and light microscopy were used to describe the species and to get first insights on its phylogenetic origin. Additionally, mitochondrial DNA markers were used to test the morphological allocation of the two dimorphic sexes and juvenile stages, to analyze geographic patterns of genetic differentiation, and to study intra-and inter-species relationships, also in light of previously published population genetics on this species.

Results

The new species, Macrostylis metallicola spec. nov., is a typical representative of Macrostylidae as recognizable from the fossosoma, prognathous cephalothorax, and styliform uropods. It can be morphologically distinguished from congeners by a combination of character states which include the autapomorphic shape of the first pleopod of the copulatory male. A sexual dimorphism, as expressed by a peculiar sequence of article length-width ratios of the male antennula, indicates a relationship with M. marionaeKniesz, Brandt & Riehl (2018) and M. longipesHansen (1916) amongst other species sharing this dimorphism. Mitochondrial genetic markers point in a similar direction. M. metallicola appears to be amongst the more common and widely distributed components of the benthic macrofauna in this region which may suggest a resilience of this species to future mining activities because of its apparent potential for recolonization of impacted sites from adjacent areas of particular environmental interest. The genetic data, however, show geographic clustering of its genetic variability, pointing towards a limited potential for dispersal. Local extinction of populations could potentially not be compensated quickly and would mean a loss of genetic diversity of this species.