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The abyssal seafloor (3500–6000m) remains largely unexplored but with deep-sea mining imminent, anthropogenic impacts may soon reach abyssal communities. Thus, there is a growing need for baseline studies of biodiversity, ecosystem functioning, and connectivity in both potential mining and no-mining areas across the Clarion-Clipperton Zone (CCZ), a key target region for polymetallic nodule mining. In this study, in situ pulse-chase lander experiments were conducted for 1.5 days in three no-mining areas (called Areas of Particular Environmental Interest, or APEIs) in the western CCZ, a region with a seafloor particulate organic carbon (POC) flux gradient. A decreasing trend was seen in mean seafloor respiration, macrofaunal abundance, and biomass from the more eutrophic APEI 7 to the more oligotrophic APEI 1, although this trend was not statistically significant (p = 0.18) most likely due to small samples sizes and high variability. In this study, most (96%) of the 13C-labeled processed phytodetritus was respired within 1.5 days. Experimental uptake of phytodetritus by macrofauna and bacteria was detected but was lower than in the previously studied and more eutrophic eastern CCZ over similar time scales (1.5 d). Bacteria dominated the short-term (∼1.5 d) uptake of organic carbon at the seafloor, yet macrofauna processed more organic carbon per unit biomass than previously found in the eastern CCZ (0.003 mg C m −2 d −1 and 0.5 × 10 −5 mg C m −2 d −1 for the western and eastern CCZ, respectively). Our study provides important information on C-uptake and respiration rates in areas set aside from mining in the western CCZ and suggests high variability may occur in the rates of benthic Corg-cycling across the CCZ. We recommend that benthic ecosystem functions be explored across gradients of POC flux which may be a major environmental factor driving ecosystem dynamics in the CCZ.

The evident shedding of the SARS-CoV-2 RNA particles from infected individuals into the wastewater opened up a tantalizing array of possibilities for prediction of COVID-19 prevalence prior to symptomatic case identification through community testing. Many countries have therefore explored the use of wastewater metrics as a surveillance tool, replacing traditional direct measurement of prevalence with cost-effective approaches based on SARS-CoV-2 RNA concentrations in wastewater samples. Two important aspects in building prediction models are: time over which the prediction occurs and space for which the predicted case numbers is shown. In this review, our main focus was on finding mathematical models which take into the account both the time-varying and spatial nature of wastewater-based metrics into account. We used six main characteristics as our assessment criteria: i) modelling approach; ii) temporal coverage; iii) spatial coverage; iv) sample size; v) wastewater sampling method; and vi) covariates included in the modelling. The majority of studies in the early phases of the pandemic recognized the temporal association of SARS-CoV-2 RNA concentration level in wastewater with the number of COVID-19 cases, ignoring their spatial context. We examined 15 studies up to April 2023, focusing on models considering both temporal and spatial aspects of wastewater metrics. Most early studies correlated temporal SARS-CoV-2 RNA levels with COVID-19 cases but overlooked spatial factors. Linear regression and SEIR models were commonly used (n = 10, 66.6 % of studies), along with machine learning (n = 1, 6.6 %) and Bayesian approaches (n = 1, 6.6 %) in some cases. Three studies employed spatio-temporal modelling approach (n = 3, 20.0 %). We conclude that the development, validation and calibration of further spatio-temporally explicit models should be done in parallel with the advancement of wastewater metrics before the potential of wastewater as a surveillance tool can be fu

Initiated by the SCAR scientific research programme “Antarctic Thresholds – Ecosystem Resilience and Adaptation” (AnT-ERA, 2013-2021), 26 experts synthesized knowledge on impacts and risks of climate-change on biological processes and ecosystem functions in the Antarctic. The ten main scientific messages that emerged addressed (1) accelerating marine and terrestrial biogeochemical cycles, (2) response to ocean acidification, (3) ecological changes in climate change hot spots, (4) unexpected dynamism of marine seafloor communities, (5) biodiversity shifts, (6) low temperature limitation of protein synthesis, (7) life intrinsically linked to changing sea ice conditions, (8) pollution, (9) genetically distinct terrestrial populations under threat, and (10) newly discovered habitats. Two-thirds of the literature included in this synthesis was published between 2010 and 2020 and only one-third was published earlier. The fast mounting, recent decadal evidence indicates various Antarctic biological communities now experience climate stress, or will experience such stress in the coming decades. The responses of organisms, ecosystem functions and services to environmental changes are complex and varied. Key knowledge gaps remain and need addressing to adequately assess future prospects for life in the Antarctic.

Highlights: • Camera observations document regional deposition of cephalopod remains on the abyssal plain. • More than 300 Argonauta egg cases were observed at 3970–4551 m in the central east Pacific between 2010 and 2020. • Shells were in various states of disintegration owing to damage, scavenging and dissolution. • Sinking epipelagic Argonauta egg cases to abyssal depths is a pathway in the carbon pump. • In situ observations show that shell decomposition takes about 90 days in this region. Calcifying plankton in the upper ocean produce calcium carbonate (CaCO3) shells that sink to the seafloor after death resulting in the vertical transport of inorganic carbon in shells and organic carbon in carcasses. In situ observations of pelagic detritus on the abyssal plain are very scarce. Carcasses are rapidly scavenged and shells may dissolve owing to undersaturation of deep waters with respect to CaCO3. We observed more than 300 egg cases of the epipelagic cephalopod Argonauta sp. in 9 large seafloor image surveys investigated across the Clarion Clipperton Zone in the Pacific between 2010 and 2020. Females of this octopus produce calcite egg cases that are used for buoyancy and as substrate on which to attach their eggs in the water column. These cases sink to the seafloor, presumably upon death of the octopus. In one area, between 3970 and 4551 m water depth surveyed in 2019, we documented more than 200 complete and fragments of egg cases (5.84 ± 1.8 cm in size) on the seafloor, complete and broken and in various states of dissolution. Here, we present observations of egg case dissolution in situ and of 99 white deposits that were likely largely dissolved egg cases. Our observations reveal a previously undocumented pathway of epipelagic inorganic carbon to the abyssal plain. Preliminary estimations indicate that the local contribution of Argonauta egg cases to the vertical transport of carbonates is likely small compared to other planktonic calcifiers, but the geograp

Remote deep-ocean sediment (DOS) ecosystems are among the least explored biomes on Earth. Genomic assessments of their biodiversity have failed to separate indigenous benthic organisms from sinking plankton. Here, we compare global-scale eukaryotic DNA metabarcoding datasets (18S-V9) from abyssal and lower bathyal surficial sediments and euphotic and aphotic ocean pelagic layers to distinguish plankton from benthic diversity in sediment material. Based on 1685 samples collected throughout the world ocean, we show that DOS diversity is at least threefold that in pelagic realms, with nearly two-thirds represented by abundant yet unknown eukaryotes. These benthic communities are spatially structured by ocean basins and particulate organic carbon (POC) flux from the upper ocean. Plankton DNA reaching the DOS originates from abundant species, with maximal deposition at high latitudes. Its seafloor DNA signature predicts variations in POC export from the surface and reveals previously overlooked taxa that may drive the biological carbon pump.

Scientific misconceptions are likely leading to miscalculations of the environmental impacts of deep-seabed mining. These result from underestimating mining footprints relative to habitats targeted and poor understanding of the sensitivity, biodiversity, and dynamics of deep-sea ecosystems. Addressing these misconceptions and knowledge gaps is needed for effective management of deep-seabed mining.

The cycling of carbon (C) by benthic organisms is a key ecosystem function in the deep sea. Pulse‐chase experiments are designed to quantify this process, yet few studies have been carried out using abyssal (3500–6000 m) sediments and only a handful of studies have been undertaken in situ. We undertook eight in situ pulse‐chase experiments in three abyssal strata (4050–4200 m water depth) separated by tens to hundreds of kilometers in the eastern Clarion‐Clipperton Fracture Zone (CCFZ). These experiments demonstrated that benthic bacteria dominated the consumption of phytodetritus over short (~ 1.5 d) time scales, with metazoan macrofauna playing a minor role. These results contrast with the only other comparable in situ abyssal study, where macrofauna dominated phytodetritus assimilation over short (2.5 d) time scales in the eutrophic NE Atlantic. We also demonstrated that benthic bacteria were capable of converting dissolved inorganic C into biomass and showed that this process can occur at rates that are as high as the bacterial assimilation of algal‐derived organic C. This demonstrates the potential importance of inorganic C uptake to abyssal ecosystems in this region. It also alludes to the possibility that some of the C incorporation by bacteria in our algal‐addition studies may have resulted from the incorporation of labeled dissolved inorganic carbon initially respired by other unstudied organisms. Our findings reveal the key importance of benthic bacteria in the short‐term cycling of C in abyssal habitats in the eastern CCFZ and provide important information on benthic ecosystem functioning in an area targeted for commercial‐scale, deep‐sea mining activities.

The biodiversity, ecosystem services and climate variability of the Antarctic continent and the Southern Ocean are major components of the whole Earth system. Antarctic ecosystems are driven more strongly by the physical environment than many other marine and terrestrial ecosystems. As a consequence, to understand ecological functioning, cross-disciplinary studies are especially important in Antarctic research. The conceptual study presented here is based on a workshop initiated by the Research Programme Antarctic Thresholds – Ecosystem Resilience and Adaptation of the Scientific Committee on Antarctic Research, which focussed on challenges in identifying and applying cross-disciplinary approaches in the Antarctic. Novel ideas and first steps in their implementation were clustered into eight themes. These ranged from scale problems, through risk maps, and organism/ecosystem responses to multiple environmental changes and evolutionary processes. Scaling models and data across different spatial and temporal scales were identified as an overarching challenge. Approaches to bridge gaps in Antarctic research programmes included multi-disciplinary monitoring, linking biomolecular findings and simulated physical environments, as well as integrative ecological modelling. The results of advanced cross-disciplinary approaches can contribute significantly to our knowledge of Antarctic and global ecosystem functioning, the consequences of climate change, and to global assessments that ultimately benefit humankind.

Commercial-scale mining for polymetallic nodules could have a major impact on the deepseaenvironment, but the effects of these mining activities on deep-sea ecosystems are verypoorly known. The first commercial test mining for polymetallic nodules was carried out in1970. Since then a number of small-scale commercial test mining or scientific disturbancestudies have been carried out. Here we evaluate changes in faunal densities and diversity ofbenthic communities measured in response to these 11 simulated or test nodule mining disturbancesusing meta-analysis techniques. We find that impacts are often severe immediatelyafter mining, with major negative changes in density and diversity of most groupsoccurring. However, in some cases, the mobile fauna and small-sized fauna experiencedless negative impacts over the longer term. At seven sites in the Pacific, multiple surveysassessed recovery in fauna over periods of up to 26 years. Almost all studies show somerecovery in faunal density and diversity for meiofauna and mobile megafauna, often withinone year. However, very few faunal groups return to baseline or control conditions after twodecades. The effects of polymetallic nodule mining are likely to be long term. Our analysesshow considerable negative biological effects of seafloor nodule mining, even at the smallscale of test mining experiments, although there is variation in sensitivity amongst organismsof different sizes and functional groups, which have important implications for ecosystemresponses. Unfortunately, many past studies have limitations that reduce their effectiveness in determining responses. We provide recommendations to improve futuremining impact test studies. Further research to assess the effects of test-mining activitieswill inform ways to improve mining practices and guide effective environmental managementof mining activities.

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.