Deep-sea Ecosystems Research Articles

Effects of sediment pulses on the deep-sea coral Goniocorella dumosa

ABSTRACT Seabed-contact activities operating in the deep sea can generate sediment plumes that pose varying levels of threat to benthic fauna. Corals are important components of deep-sea ecosystems and can be particularly sensitive to elevated suspended sediment concentrations. In this study, we exposed colony fragments of the New Zealand deep-sea scleractinian Goniocorella dumosa to four-day pulses of four target sediment concentrations: 0 mg l−1 (representing control conditions) and 45, 102 and 435 mg l−1 (targeting concentrations expected from mining and trawling disturbance). All coral fragments survived. Oxygen consumption rates were not affected by treatments and time. No visible detrimental effects on coral health were noted after the first pulse of sediment exposure. However, both a loss of coenosarc and instances of polyp mortality were observed on fragments exposed to suspended sediments during the following sediment pulses. This observed decline in coral health over time indicates that G. dumosa could cope with sediment disturbance from human activities that disturb the seafloor for periods of up to four days, but that repeated, or prolonged sediment exposure could cause a deterioration in the health condition of this species. This hypothesis should be further investigated in following studies.

Genomic and transcriptomic analyses illuminate the molecular basis of the unique lifestyle of a tubeworm, Lamellibrachia satsuma.

Vestimentiferan tubeworms are representative members of deep-sea chemosynthetic ecosystems. In this study, we developed a draft genome and gene models and performed genomic and transcriptomic analyses of Lamellibrachia satsuma, the only vestimentiferan reported from the euphotic zone. The quality of the genome assembly and gene models is comparable to or higher than those of previously reported vestimentiferan tubeworms. Tissue-specific transcriptome sequencing revealed that Toll-like receptor genes and lineage-specific expanded bacteriolytic enzyme genes are highly expressed in the obturacular and vestimental regions, respectively, suggesting the importance of these tissues in defense against pathogens. On the other hand, globin subunit genes are expressed almost exclusively in the trunk region, supporting the hypothesis that the trophosome is the site of haemoglobin biosynthesis. Vestimentiferan-specific expanded gene families included chitinases, ion channels, and C-type lectins, suggesting the importance of these functions for vestimentiferans. C-type lectins in the trunk region, in particular, may be involved in recognition of pathogens, or in interactions between tubeworms and symbiotic bacteria. Our genomic and transcriptomic analyses enhance understanding of molecular mechanisms underlying the unique lifestyle of vestimentiferan tubeworms, particularly their obligate mutualism with chemosynthetic bacteria.

Distribution Patterns of Benthic Protist Communities Depending on Depth Revealed by Environmental Sequencing-From the Sublittoral to the Deep Sea.

Protists are key components of the microbial food web in marine pelagic systems because they link algal and bacterial production to higher trophic levels. However, their functioning and bathymetric distribution in benthic deep-sea ecosystems are still only poorly understood. However, biogeographical patterns of communities can be coupled to the functioning of ecosystems and are therefore important to understand ecological and evolutionary processes. In this study, we investigated the diversity and distribution of benthic protist communities from the sublittoral down to the deep seafloor (50-2000 m) around three islands of the Azores in the North Atlantic Ocean. Using amplicon sequencing of the V9 region (18S rDNA) of 21 samples, we found that protist community compositions from different depths were significantly different. Three assemblages were separated along the following depths: 50 m, 150-500 m and 1000-2000 m, which indicate that deep-sea areas surrounding islands might act as isolating barriers for benthic protist species. A limited gene flow between the communities could favor speciation processes, leading to the unique protist communities found at the different investigated islands.

Editorial: Data acquisition and processing strategies for the development of ecological indicators in the exploration and monitoring of deep-sea ecosystems under natural and anthropogenic changes

Editorial: Data acquisition and processing strategies for the development of ecological indicators in the exploration and monitoring of deep-sea ecosystems under natural and anthropogenic changes

Long distance dispersal and oceanographic fronts shape the connectivity of the keystone sponge Phakellia ventilabrum in the deep northeast Atlantic

Little is known about dispersal in deep-sea ecosystems, especially for sponges, which are abundant ecosystem engineers. Understanding patterns of gene flow in deep-sea sponges is essential, especially in areas where rising pressure from anthropogenic activities makes difficult to combine management and conservation. Here, we combined population genomics and oceanographic modelling to understand how Northeast Atlantic populations (Cantabrian Sea to Norway) of the deep-sea sponge Phakellia ventilabrum are connected. The analysis comprised ddRADseq derived SNP datasets of 166 individuals collected from 57 sampling stations from 17 different areas, including two Marine Protected Areas, one Special Area of Conservation and other areas with different levels of protection. The 4,017 neutral SNPs used indicated high connectivity and panmixis amongst the majority of areas (Ireland to Norway), spanning ca. 2,500-km at depths of 99–900 m. This was likely due to the presence of strong ocean currents allowing long-distance larval transport, as supported by our migration analysis and by 3D particle tracking modelling. On the contrary, the Cantabrian Sea and Roscoff (France) samples, the southernmost areas in our study, appeared disconnected from the remaining areas, probably due to prevailing current circulation patterns and topographic features, which might be acting as barriers for gene flow. Despite this major genetic break, our results suggest that all protected areas studied are well-connected with each other. Interestingly, analysis of SNPs under selection replicated results obtained for neutral SNPs. The relatively low genetic diversity observed along the study area, though, highlights the potential fragility of this species to changing climates, which might compromise resilience to future threats.

A dataset of micro biodiversity in benthic sediment at a global scale

Microorganisms, occupying the largest biomass in deep sea, play essential roles in deep-sea ecosystem. It is believed that the microbes in deep-sea sediments are more representative of deep-sea microbial communities, the microbial composition of which is seldom affected by ocean currents. However, the community of benthic microbes on a global scale has not been adequately explored. Herein, we build a comprehensive global dataset determined by 16S rRNA gene sequencing to characterize the biodiversity of microorganisms in benthic sediment. The dataset comprised 212 records from 106 sites, included sequencing of bacteria and archaea for each site and yielded 4,766,502 and 1,562,989 reads, respectively. Through annotation, a total of 110,073 and 15,795 OTUs of bacteria and archaea were obtained, and 61 bacterial phyla and 15 archaeal phyla were identified, of which the dominant phyla were Proteobacteria and Thaumarchaeota in deep-sea sediment. Therefore, our findings provided a biodiversity data of microbial communities in deep-sea sediment at global-scale and laid a foundation to further reveal the structures of microorganism communities in deep sea.

On the paradox of thriving cold-water coral reefs in the food-limited deep sea.

The deep sea is amongst the most food-limited habitats on Earth, as only a small fraction (<4%) of the surface primary production is exported below 200 m water depth. Here, cold-water coral (CWC) reefs form oases of life: their biodiversity compares with tropical coral reefs, their biomass and metabolic activity exceed other deep-sea ecosystems by far. We critically assess the paradox of thriving CWC reefs in the food-limited deep sea, by reviewing the literature and open-access data on CWC habitats. This review shows firstly that CWCs typically occur in areas where the food supply is not constantly low, but undergoes pronounced temporal variation. High currents, downwelling and/or vertically migrating zooplankton temporally boost the export of surface organic matter to the seabed, creating 'feast' conditions, interspersed with 'famine' periods during the non-productive season. Secondly, CWCs, particularly the most common reef-builder Desmophyllum pertusum (formerly known as Lophelia pertusa), are well adapted to these fluctuations in food availability. Laboratory and in situ measurements revealed their dietary flexibility, tissue reserves, and temporal variation in growth and energy allocation. Thirdly, the high structural and functional diversity of CWC reefs increases resource retention: acting as giant filters and sustaining complex food webs with diverse recycling pathways, the reefs optimise resource gains over losses. Anthropogenic pressures, including climate change and ocean acidification, threaten this fragile equilibrium through decreased resource supply, increased energy costs, and dissolution of the calcium-carbonate reef framework. Based on this review, we suggest additional criteria to judge the health of CWC reefs and their chance to persist in the future.

Habitat heterogeneity effects on microbial communities of the Gulf of Maine

Many biological and physical variables influence microbes at the sediment-water interface, whose response to those variables affects the overall fate and residence time of organic matter (OM) in the marine environment. In addition to the many ecological roles microbes play in deep-sea sediments, further studies are needed to address microbial community diversity and its influence on seafloor organic matter remineralization rates. We explored microbial diversity, distribution, and associated organic matter remineralization among contrasting habitats and following 24-h experimental phytodetrital enrichment of sediments from Canyon, Inter-Canyon, and Channel habitats of the Gulf of Maine, Northwest Atlantic. Based on multivariate analyses of community composition we found that habitat heterogeneity influenced microbial community composition but not microbial diversity. Similarly, the phytodetrital addition did not translate to significant differences in microbial diversity but altered nitrate flux in Inter-canyon sediments and phosphate flux in Channel sediments. Bacteria were dominant over Archaea and, of the environmental variables we measured, quantity and quality of organic matter best explained overall microbial community variation. Proteobacteria, Bacteroidae, Acidobacteriota, Planctomycetota, and NB1-J Deltaproteobacteria dominated all habitats, but variation in the microbial community at our study sites explained only 7% of nutrient fluxes. Our exploratory study did not suggest a strong contribution of microbial community composition to OM remineralization variation both among contrasting habitats and in response to phytodetrital addition, and thus to this aspect of deep-sea ecosystem functioning, at least over short-term incubations.

Combining morphological and mitochondrial DNA data to describe a new species of Austroniscus Vanhöffen, 1914 (Isopoda, Janiroidea, Nannoniscidae) linking abyssal and hadal depths of the Puerto Rico Trench.

Hadal trenches are perceived as a unique deep-sea ecosystem with fundamentally different communities compared to the nearby abyss. So far, however, scarce information exists about how populations are genetically linked within a trench and about mechanisms for species divergence. The present study presents the morphological and molecular-genetic characterization and description of a new nannoniscid species within the genus Austroniscus Vanhöffen, 1914 obtained from abyssal and hadal depths of the Puerto Rico Trench, NW Atlantic. Samples were collected as part of the Vema-TRANSIT expedition onboard RV Sonne in January 2015. Because of the large depth differences between sampling locations (4,552-8,338 m), we expected to find different species within the genus inhabiting abyssal and hadal sites. Initial morphological examination using traditional light microscopy and Confocal Laser Scanning Microscopy was paired with subsequent molecular analysis based on mtDNA (COI and 16S). Contrary to our assumptions, combined morphological and molecular species delimitation analyses (sGMYC, mPTP, ABGD) revealed the presence of only one species spanning the abyssal and hadal seafloor of the Puerto Rico Trench. In addition, comparison with type material could show that this species belongs to a new species, Austroniscus brandtae n. sp., which is described herein. Incongruence between some species delimitation methods suggesting the presence of multiple species is interpreted as strong genetic population structuring within the trench, which is also supported by the analysis of the haplotype networks. The geographic and bathymetric distribution of Austroniscus species is discussed. The species described herein represents the first in the genus Austroniscus from the Atlantic Ocean and the deepest record of the genus to date, and hence significantly expanding previously known limits of its geographic and bathymetric range.

A standardised ecosystem services framework for the deep sea

Despite its remoteness, human activity has impacted the deep sea and changes to the structure and function of deep-sea ecosystems are already noticeable. In terrestrial and shallow water marine environments, demonstrating how ecosystems support human well-being has been instrumental in setting policy and management objectives for sustainable resource use. Foundational to this approach is a framework of ecosystem service (ES) classification and a synthesis of the knowledge base, which can then be used to structure decision-support tools such as ecosystem accounts or Environmental Impact Assessments. At present, no such framework exists for the deep sea. There is thus an urgent need to determine and assess the ES provided by deep-sea habitats and species before (potentially irreversible) decisions are made about deep-sea habitat use and governance. As a first step towards the incorporation of ES in such decision-making, we undertake two systematic reviews of the scientific literature based on the principles of the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) systematic process. This was to define a comparative ES framework and synthesise the current evidence base for how deep-sea habitats support ecosystem services. Our framework proposes four supporting services, three regulating services, four provisioning services and three cultural services for which there is an established and growing body of evidence for the role of deep-sea habitats. The ES framework presented here provides a structure for deep-sea ecosystem services. In its next phase of development, this could provide the foundation for the development of habitat-ecosystem service matrices, which are a critical component for truly accounting for ES in decision-making, particularly spatial management. This framework has significant implications for deep-sea management, conservation and policy, as it provides an ecosystem services-based tool that can be used in any deep-sea ecosystems management across the planet, and it also shows how critical these data gaps are for today’s decisions and how seriously they should be considered in decision-making processes.

Deep-sea benthic megafauna hotspot shows indication of resilience to impact from massive turbidity flow

Sediment density flows are large scale disturbances that can have dramatic impacts on seafloor animal communities in the deep sea. Seafloor imagery collected in Kaikōura Canyon (New Zealand), before and after a sediment density flow event that included debris and turbidity flows triggered by a 2016 Mw 7.8 Kaikōura Earthquake, shows the recovery trajectory of the animal community in the canyon head in the weeks, months, and years following the disturbance. The canyon community appears resilient to this event, with models estimating full recovery within a minimum of 4.5–5.1 years and as long as 12 years. The implications of the resilience of this deep-sea community are discussed in the context of the local marine protected area, the surrounding fishery, and global seabed mining.

Combined use of carbon, nitrogen and sulfur stable isotopes reveal trophic structure and connections in deep-sea mesopelagic and demersal fish communities from the Southeastern Pacific Ocean

The trophic structure of deep-sea fish communities has been poorly studied in the Southeastern Pacific Ocean. Here, using the analysis of multiple (CNS) stable isotopes, we provide a first approach to characterize the structure of a marine food web including mesopelagic (9 species) and demersal (13 species) fishes. At a species level, Dissostichus eleginoides were the most 13C-depleted and the grenadier Coryphaenoides ariommus the most 13C-enriched species. The most 15N-depleted species was the lanternfish Diogenichthys laternatus and macrourid fishes Trachyrincus villagai and C. ariommus the most 15N-enriched. δ34S values showed less variation, but ranged considerably, varying between 10.5 and 17.7‰: C. ariommus was the most 34S-depleted species and D. eleginoides the most 34S-enriched. At a whole study level, individual δ13C and δ15N values were positively correlated. Relationships between δ13C and δ34S, and δ15N and δ34S were both negative. When analyses were conducted separately for demersal and mesopelagic fishes, δ13C showed a positive correlation with δ15N. There was a negative relationship between δ13C and δ34S in demersal fish but no apparent relationship between δ15N and δ34S. In mesopelagic fishes, there was no statistical support for relationships between δ13C and δ34S or δ15N and δ34S. Mean log-transformed total length (TL) and mean δ15N were related in mesopelagic fishes, but there was no apparent relationship between TL and δ13C or δ34S values. In the case of demersal fishes there was no relationship between TL and either δ15N, δ13C or δ34S. Using cluster analysis, species were classified into 4 distinct trophic groups (G1 - G4) that display different trophic strategies according to the literature. Groups G1 and G2 included zooplanktivorous, micronektonivorous and gelatinovorous fishes associated with pelagic habitats. Groups G3 and G4 include micronektonivorous, piscivorous and generalist fishes foraging in benthic habitats. The demersal fish Dissostichus eleginoides was classified as a member of G1, suggesting that its diet in northern Chile is likely dominated by pelagic prey. In addition, Macrourus holotrachys (G3) showed very marked individual variability in δ15N values indicating considerable intraspecific variation in diet and foraging behavior. Given that this species had isotope values that extended across values typical of benthic and pelagic habitats, it suggests that some individuals may perform vertical migrations. Our results also highlighted that some demersal species (M. holotrachys and Coryphaenoides ariommus) had δ34S values that indicate the assimilation of some chemosynthetic-derived sulfur.Our results provide isotopic information on deep-water species in this region and show likely coupling between the demersal and mesopelagic assemblages. This information improves our understanding of deep-sea ecosystem functioning and provides key information for fisheries management and conservation initiatives.

An annotated and illustrated identification guide to common mesophotic reef sponges (Porifera, Demospongiae, Hexactinellida, and Homoscleromorpha) inhabiting Flower Garden Banks National Marine Sanctuary and vicinities.

Sponges are recognized as a diverse and abundant component of mesophotic and deep-sea ecosystems worldwide. In Flower Garden Banks National Marine Sanctuary region within the northwestern Gulf of Mexico, sponges thrive among diverse biological and geological habitats between 16-200+ m deep (i.e., coral reefs and communities, algal nodules, and coralline algae reefs, mesophotic reefs, patch reefs, scarps, ridges, soft substrate, and rocky outcrops). A synoptic guide is presented, developed by studying common sponge species in the region, through direct sampling and in-situ photographic records. A total of 64 species is included: 60 are Demospongiae (14 orders), two are Hexactinellida (one order), and two are Homoscleromorpha (one order). Thirty-four taxa are identified to species and 13 were identified to have affinity with, but were not identical to, a known species. Fifteen taxa could only be identified to genus level, and the species remain as uncertain (incerta sedis), with the potential to represent new species or variants of known species. One specimen received only a family assignation. This study extends geographic or mesophotic occurrence data for eleven known species and includes several potentially new species. This work improves our knowledge of Gulf of Mexico sponge biodiversity and highlights the importance of the region for scientists and resource managers.

A global review of ocean ecosystem accounts and their data: Lessons learned and implications for marine policy

Given the ocean ecosystem’s contribution to the environment, economy and human wellbeing, its condition and value need to be accounted for in decision making for a healthy and sustainable society. Ocean accounting aims to incorporate the ocean environment into national accounts by tracking natural assets, the services they provide, and their links to our economies, and social wellbeing. Around the world, adoption of National Ocean Accounts is gathering momentum, taking national accounts “Beyond GDP” to produce more holistic statistics to inform ocean policy. We conducted the first review of publicly available ocean ecosystem accounts, including ten case studies to identify key opportunities and challenges. The spatial scale, scope, methods, and reporting quality of data within the case studies varied greatly and poor data documentation generally hindered the review. Case studies typically focussed on ecosystem assets that were inherently easy to map (e.g., nearshore or intertidal areas) and excluded deeper continental shelf waters, pelagic and offshore deep-sea ecosystems. The focus on easy to map ecosystems suggests that ocean accounts will have difficulty representing national marine jurisdictions with large extents of deeper continental shelf waters, pelagic and offshore deep-sea ecosystems. Ecosystem extent accounts consistently had limited transparency of methods and absent reporting on uncertainty or data variance. We recommend future ocean ecosystem account case studies should consider 1) open science 2) FAIR (Findability, Accessibility, Interoperability and Reusability) data principles 3) reporting error around data. By addressing these points, ocean ecosystem accounts will be more robust, and comparability of case studies through space and time will be improved, making future case studies better tools for decision makers.

Epibenthic faunal community dynamics and seasonal species turnover in a deep-sea coral ecosystem

Deep-sea coral ecosystems represent oases of life in the deep ocean, often hosting abundant and diverse faunal communities. Although mounting evidence indicates that deep-sea benthic communities are highly dynamic and can change over scales of a few hours to seasons or years, such dynamics have never been characterized in deep-sea coral ecosystems. We used a time-lapse camera deployed for a year at a depth of 1230 m on Sur Ridge (Monterey Bay National Marine Sanctuary) to characterize hourly changes in megafaunal abundance and diversity in a deep-sea coral assemblage. The response of community dynamics to variation in environmental factors, including surface net primary production as well as current speed/direction, temperature and acoustic backscatter (a proxy for particle and zooplankton density) at depth, was also evaluated. Overall, 33 taxa from 6 phyla, including multiple commercially valuable species, were observed throughout the study period. The strong seasonal pattern and periodicities in the occurrence of the most abundant taxa likely drove the observed temporal trends in overall abundance and diversity. Fluctuations in food availability may have, at least partially, driven these trends, as indicated by the significant relationship between community dynamics, surface net primary production and acoustic backscatter at depth. However, the low explanatory power of environmental parameters tested here suggest that biotic factors such as individual behaviors and species interactions had a strong influence on community dynamics. This study emphasizes the role of deep-sea coral as habitat and the need for monitoring to better understand how environmental and biological processes interact to shape associated faunal communities.

Extending deep-sea benthic biodiversity inventories with environmental DNA metabarcoding

Inventories of biodiversity are crucial for helping support conservation and management efforts, yet the deep-sea, which is the largest biome on earth remains vastly understudied. Recent advances in molecular detection methods offer alternative techniques for studying inaccessible ecosystems, including those at depth. In this study we utilized environmental DNA metabarcoding, a first for studying deep-sea benthic environments in southern Africa, to assess biological diversity and to test the effects of depth and historical trawling activities on deep-sea communities. Utilising 29 sediment samples (thus focussing on predominantly meiofaunal and epifaunal biodiversity) and targeting a 313 bp region of the mtDNA cytochrome oxidase I gene, we recovered 444 OTUs across a wide array of species and genera. Even though many OTUs could only be assigned to higher taxonomic levels, results showed that biodiversity differed significantly across depth, suggesting that even at relatively small spatial scales (~ 6 km, across a depth gradient of 355 m to 515 m), eDNA derived biodiversity detected variation linked to the depth gradient. Comparison of the OTU database with known species inventories from the sampled area revealed little overlap, highlighting the need for expanding barcoding efforts of deep-sea species to aid future eDNA survey efforts. Overall our results suggest that within a South African context, increased barcoding efforts, in combination with eDNA metabarcoding and physical sampling could capture a greater proportion of benthic deep-sea biodiversity. This provides additional opportunities to underpin conservation and management decision-making in the region, such as evaluating potential sites for future protection.

Energetic connectivity of diverse elasmobranch populations - implications for ecological resilience.

Understanding the factors shaping patterns of ecological resilience is critical for mitigating the loss of global biodiversity. Throughout aquatic environments, highly mobile predators are thought to serve as important vectors of energy between ecosystems thereby promoting stability and resilience. However, the role these predators play in connecting food webs and promoting energy flow remains poorly understood in most contexts. Using carbon and nitrogen isotopes, we quantified the use of several prey resource pools (small oceanic forage, large oceanics, coral reef, and seagrass) by 17 species of elasmobranch fishes (n = 351 individuals) in The Bahamas to determine their functional diversity and roles as ecosystem links. We observed remarkable functional diversity across species and identified four major groups responsible for connecting discrete regions of the seascape. Elasmobranchs were responsible for promoting energetic connectivity between neritic, oceanic and deep-sea ecosystems. Our findings illustrate how mobile predators promote ecosystem connectivity, underscoring their functional significance and role in supporting ecological resilience. More broadly, strong predator conservation efforts in developing island nations, such as The Bahamas, are likely to yield ecological benefits that enhance the resilience of marine ecosystems to combat imminent threats such as habitat degradation and climate change.

Environmental viromes reveal global virosphere of deep-sea sediment RNA viruses

IntroductionViruses are the most abundant and diverse life forms on the earth. Both DNA viruses and RNA viruses play important roles in marine ecosystems via regulating biogeochemical cycles. ObjectivesHowever, the virome of marine RNA viruses has been rarely explored so far. In this study, therefore, the environmental viromes of deep-sea sediment RNA viruses were characterized on a global scale to reveal the global virosphere of deep-sea RNA viruses. MethodsThe viral particles were purified from each of 133 deep-sea sediment samples and then characterized based on metagenomes of RNA viruses. ResultsIn this study, we established the global virome dataset of deep-sea RNA viruses purified from 133 sediment samples that were collected from typical deep-sea ecosystems of three oceans. A total of 85,059 viral operational taxonomic units (vOTUs) were identified, of which only 1.72% were hitherto known, indicating that the deep-sea sediment is a repository of novel RNA viruses. These vOTUs were classified into 20 viral families, including prokaryotic (7.09%) and eukaryotic (65.81%) RNA viruses. Furthermore, 1,463 deep-sea RNA viruses with complete genomes were obtained. The differentiation of RNA viral communities was driven by the deep-sea ecosystems as opposed to geographical region. Specifically, the virus-encoded metabolic genes took great effects on the differentiation of RNA viral communities by mediating the energy metabolism in the deep-sea ecosystems. ConclusionsTherefore, our findings indicate that the deep sea is a vast reservoir of novel RNA viruses for the first time, and the differentiation of RNA viral communities is driven by the deep-sea ecosystems through energy metabolism.

Environmental viromes reveal the global distribution signatures of deep-sea DNA viruses

IntroductionViruses are abundant and ecologically significant in marine ecosystems. However, the virome of deep-sea sediments is not extensively investigated. ObjectivesTo explore the distribution pattern of deep-sea viruses on a global scale, the viromes of DNA viruses isolated from 138 sediments of 5 deep-sea ecosystems were characterized. MethodsThe viral particles were purified from each sediment sample. Then the viral DNAs were extracted and subjected to viral metagenomic analysis. ResultsHere, we constructed a global deep-sea environmental virome dataset by analyzing the viral DNA of 138 sediment samples. A total of 347,737 viral operational taxonomic units (vOTUs) were identified, of which 84.94% were hitherto unknown, indicating that deep sea was a reservoir of novel DNA viruses. Furthermore, circular viral genome analysis revealed 98,581 complete genomes. The classified vOTUs included eukaryotic (44.55%) and prokaryotic (25.75%) viruses, and were taxonomically assigned to 63 viral families. The composition and abundance of the deep-sea sediment viromes were dependent on the deep-sea ecosystem as opposed to geographical region. Further analysis revealed that the viral community differentiation in different deep-sea ecosystems was driven by the virus-mediated energy metabolism. ConclusionOur findings showed that deep-sea ecosystems are a reservoir of novel DNA viruses and the viral community is shaped by the environmental characteristics of deep-sea ecosystems, thus presenting critical information for determining the ecological significance of viruses in global deep-sea ecosystems.

Estimating preferences for Mediterranean deep-sea ecosystem services: A discrete choice experiment

The deep sea represents Earth’s largest (but least explored) biome. It is increasingly affected by anthropogenic stressors and climate change, which threaten the provision of essential ecosystem services. The monetary value of these benefits has rarely been assessed. High biodiversity is hosted in the deep sea and, more generally, in the oceans. This paper uses a hypothetical choice experiment to investigate Italian households’ preferences for deep-sea ecosystem services. The data show wide heterogeneity of the preferences for preserving the Mediterranean deep sea. Many respondents indicate that they would refuse to pay to support the protection of biodiversity and scientific research in this remote and unfamiliar environment. Overall, global warming was of little concern for most respondents, who would not be willing to pay to limit the increase in global temperatures. High income and formal education positively influenced the willingness of the respondents to donate to Non-Governmental Organization’s initiatives to support the Mediterranean deep sea. Deep-water corals appear more ‘charismatic’ to respondents than submarine canyons among deep-sea habitats.