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Arguments for an abiotic origin of low-molecular weight organic compounds in deep-sea hot springs are compelling owing to implications for the sustenance of deep biosphere microbial communities and their potential role in the origin of life. Theory predicts that warm H ₂-rich fluids, like those emanating from serpentinizing hydrothermal systems, create a favorable thermodynamic drive for the abiotic generation of organic compounds from inorganic precursors. Here, we constrain two distinct reaction pathways for abiotic organic synthesis in the natural environment at the Von Damm hydrothermal field and delineate spatially where inorganic carbon is converted into bioavailable reduced carbon. We reveal that carbon transformation reactions in a single system can progress over hours, days, and up to thousands of years. Previous studies have suggested that CH ₄ and higher hydrocarbons in ultramafic hydrothermal systems were dependent on H ₂ generation during active serpentinization. Rather, our results indicate that CH ₄ found in vent fluids is formed in H ₂-rich fluid inclusions, and higher n- alkanes may likely be derived from the same source. This finding implies that, in contrast with current paradigms, these compounds may form independently of actively circulating serpentinizing fluids in ultramafic-influenced systems. Conversely, widespread production of formate by ΣCO ₂ reduction at Von Damm occurs rapidly during shallow subsurface mixing of the same fluids, which may support anaerobic methanogenesis. Our finding of abiogenic formate in deep-sea hot springs has significant implications for microbial life strategies in the present-day deep biosphere as well as early life on Earth and beyond. Significance Arguments for an abiotic origin of organic compounds in deep-sea hot springs are compelling because of their potential role in the origin of life and sustaining microbial communities. Theory predicts that warm H ₂-rich fluids circulating through serpentinizing systems create a favorable thermodynamic drive for inorganic carbon reduction to organic compounds. We show that abiotic synthesis proceeds by two spatially and temporally distinct mechanisms. Abundant dissolved CH ₄ and higher hydrocarbons are likely formed in H ₂-rich fluid inclusions over geologic timescales. Conversely, formate production by ΣCO ₂ reduction occurs rapidly during subsurface mixing, which may support anaerobic methanogenesis. We confirm models for abiotic metastable organic compound formation and argue that alkanes in all ultramafic-influenced vents may form independently of actively circulating serpentinizing fluids.

Hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise is transported several thousand kilometres westward across the South Pacific Ocean; global hydrothermal dissolved iron input is estimated to be more than four times what was previously thought and modelling suggests it must be physically or chemically stabilized in solution. Trans-Pacific transport of hydrothermal metals Deep-sea hydrothermal vents are an important source of iron, an essential trace element that can limit marine productivity. Recent studies have questioned the long-standing view that most of the iron discharged from such vents is removed from seawater close to its source, and is therefore of limited importance for ocean biogeochemistry. Joseph Resing et al . report on the lateral transport of hydrothermal dissolved iron and other trace metals from the southern East Pacific Rise more than 4,000 km across the South Pacific Ocean. Using data from samples collected from 35 hydrographic stations between Manta, Ecuador and Papeete, Tahiti, the authors estimate an input of global hydrothermal dissolved iron to the ocean at least four times greater than previously reported. With the help of a model study, they suggest that physicochemical stabilization of iron enables hydrothermal activity to significantly affect the carbon cycle by supporting phytoplankton growth in the Southern Ocean. Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean 1 , 2 , 3 . Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle 4 . It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources 2 , 5 and is thus of limited importance for ocean biogeochemistry 6 . This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its long-range oceanic transport 7 , 8 , 9 , 10 . Such transport has been subsequently inferred from spatially limited oceanographic observations 11 , 12 , 13 . Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed 6 , 14 . Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates 7 , 11 , 14 . Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export production.

Hydrothermally sourced dissolved metals have been recorded in all ocean basins. In the oceans’ largest known hydrothermal plume, extending westwards across the Pacific from the Southern East Pacific Rise, dissolved iron and manganese were shown by the GEOTRACES program to be transported halfway across the Pacific. Here, we report that particulate iron and manganese in the same plume also exceed background concentrations, even 4,000 km from the vent source. Both dissolved and particulate iron deepen by more than 350 m relative to 3 He—a non-reactive tracer of hydrothermal input—crossing isopycnals. Manganese shows no similar descent. Individual plume particle analyses indicate that particulate iron occurs within low-density organic matrices, consistent with its slow sinking rate of 5–10 m yr −1 . Chemical speciation and isotopic composition analyses reveal that particulate iron consists of Fe( III ) oxyhydroxides, whereas dissolved iron consists of nanoparticulate Fe( III ) oxyhydroxides and an organically complexed iron phase. The descent of plume-dissolved iron is best explained by reversible exchange onto slowly sinking particles, probably mediated by organic compounds binding iron. We suggest that in ocean regimes with high particulate iron loadings, dissolved iron fluxes may depend on the balance between stabilization in the dissolved phase and the reversibility of exchange onto sinking particles. The largest known hydrothermal plume moves dissolved iron halfway across the Pacific. In situ measurements show that dissolved and particulate iron transport is facilitated by reversible exchange of dissolved iron onto organic compounds.

To assess the potential impact of the Deepwater Horizon oil spill on offshore ecosystems, 11 sites hosting deep-water coral communities were examined 3 to 4 mo after the well was capped. Healthy coral communities were observed at all sites >20 km from the Macondo well, including seven sites previously visited in September 2009, where the corals and communities appeared unchanged. However, at one site 11 km southwest of the Macondo well, coral colonies presented widespread signs of stress, including varying degrees of tissue loss, sclerite enlargement, excess mucous production, bleached commensal ophiuroids, and covering by brown flocculent material (floc). On the basis of these criteria the level of impact to individual colonies was ranked from 0 (least impact) to 4 (greatest impact). Of the 43 corals imaged at that site, 46% exhibited evidence of impact on more than half of the colony, whereas nearly a quarter of all of the corals showed impact to >90% of the colony. Additionally, 53% of these corals’ ophiuroid associates displayed abnormal color and/or attachment posture. Analysis of hopanoid petroleum biomarkers isolated from the floc provides strong evidence that this material contained oil from the Macondo well. The presence of recently damaged and deceased corals beneath the path of a previously documented plume emanating from the Macondo well provides compelling evidence that the oil impacted deep-water ecosystems. Our findings underscore the unprecedented nature of the spill in terms of its magnitude, release at depth, and impact to deep-water ecosystems.

The Aurora hydrothermal system, Arctic Ocean, hosts active submarine venting within an extensive field of relict mineral deposits. Here we show the site is associated with a neovolcanic mound located within the Gakkel Ridge rift-valley floor, but deep-tow camera and sidescan surveys reveal the site to be ≥100 m across—unusually large for a volcanically hosted vent on a slow-spreading ridge and more comparable to tectonically hosted systems that require large time-integrated heat-fluxes to form. The hydrothermal plume emanating from Aurora exhibits much higher dissolved CH 4 /Mn values than typical basalt-hosted hydrothermal systems and, instead, closely resembles those of high-temperature ultramafic-influenced vents at slow-spreading ridges. We hypothesize that deep-penetrating fluid circulation may have sustained the prolonged venting evident at the Aurora hydrothermal field with a hydrothermal convection cell that can access ultramafic lithologies underlying anomalously thin ocean crust at this ultraslow spreading ridge setting. Our findings have implications for ultra-slow ridge cooling, global marine mineral distributions, and the diversity of geologic settings that can host abiotic organic synthesis - pertinent to the search for life beyond Earth. The Aurora hydrothermal field (Arctic Ocean) is hosted in volcanic rocks but also shows evidence of mantle rock influence in the shallow sub-surface. Our discovery is pertinent to disciplines from marine mining to the search for life beyond Earth.

Several moons in the outer solar system host liquid water oceans. A key next step in assessing the habitability of these ocean worlds is to determine whether life’s elemental and energy requirements are also met. Phosphorus is required by all known life and is often limited to biological productivity in Earth’s oceans. This raises the possibility that its availability may limit the abundance or productivity of Earth-like life on ocean worlds. To address this potential problem, here we calculate the equilibrium dissolved phosphate concentrations associated with the reaction of water and rocks—a key driver of ocean chemical evolution—across a broad range of compositional inputs and reaction conditions. Equilibrium dissolved phosphate concentrations range from 10 −11 to 10 −1  mol/kg across the full range of carbonaceous chondrite compositions and reaction conditions considered, but are generally > 10 −5  mol/kg for most plausible scenarios. Relative to the phosphate requirements and uptake kinetics of microorganisms in Earth’s oceans, such concentrations would be sufficient to support initially rapid cell growth and construction of global ocean cell populations larger than those observed in Earth’s deep oceans. Is phosphorous a limiting factor for life on ocean worlds (e.g. Europa and Enceladus)? Calculated dissolved phosphate concentrations from a wide range of possible water-rock reactions suggest cell populations larger than those observed in Earth’s deep oceans could be supported.

This paper reviews the scientific motivation and challenges, development, and use of underwater robotic vehicles designed for use in ice-covered waters, with special attention paid to the navigation systems employed for under-ice deployments. Scientific needs for routine access under fixed and moving ice by underwater robotic vehicles are reviewed in the contexts of geology and geophysics, biology, sea ice and climate, ice shelves, and seafloor mapping. The challenges of under-ice vehicle design and navigation are summarized. The paper reviews all known under-ice robotic vehicles and their associated navigation systems, categorizing them by vehicle type (tethered, untethered, hybrid, and glider) and by the type of ice they were designed for (fixed glacial or sea ice and moving sea ice).

Tectonic uplift of mantle rocks along slow- and ultraslow-spreading mid-ocean ridges facilitates diverse styles of hydrothermal circulation. Here, we report on Lucky B, an ultramafic-hosted hydrothermal field on the ultraslow-spreading Lena Trough at 81°N in the ice-covered Arctic Ocean. At the seafloor we observed diffuse, metal-poor fluid discharge with abundant vent fauna alongside sites of massive sulfide deposits and hydrothermal chimneys, extending laterally over at least 1.9 km. The overlying water column exhibited two geochemically distinct plumes, the stronger of which showed strong redox and particle anomalies. We hence identify Lucky B as ‘black smoker’-type system featuring distinct styles of venting from several major fluid sources. The strongest plume also contained high concentrations of dissolved hydrogen (H 2 ) and methane (CH 4 ), distinguishing Lucky B from other ultramafic-hosted systems that primarily emit serpentinization-derived H 2 . Low H 2 /CH 4 ratios and high CH 4 relative to dissolved Mn suggest an involvement of sediment in the subseafloor fluid–rock reactions. Our analysis of the plume microbiology revealed abundant chemoautotrophs that use primarily hydrothermal H 2 and sulfide as energy sources. Collectively, these findings reveal multifaceted hydrothermal venting at Lucky B, driven by geological and biogeochemical processes in the subseafloor and extending into the Arctic Ocean water column.

Describes the research that has enabled an advance in understanding of the nature and factors controlling the biogeography and biodiversity of the ecosystems in four geographic locations: the Atlantic Equatorial Belt (AEB), the New Zealand region, the Arctic and Antarctic, and the SE Pacific off Chile. Source: National Library of New Zealand Te Puna Matauranga o Aotearoa, licensed by the Department of Internal Affairs for re-use under the Creative Commons Attribution 3.0 New Zealand Licence.

Bioactive trace metals are critical micronutrients for marine microorganisms due to their role in mediating biological redox reactions, and complex biogeochemical processes control their distributions. Hydrothermal vents may represent an important source of metals to microorganisms, especially those inhabiting low-iron waters, such as in the southwest Pacific Ocean. Previous measurements of primordial 3He indicate a significant hydrothermal source originating in the northeastern (NE) Lau Basin, with the plume advecting into the southwest Pacific Ocean at 1500–2000 m depth (Lupton et al., 2004). Studies investigating the long-range transport of trace metals associated with such dispersing plumes are rare, and the biogeochemical impacts on local microbial physiology have not yet been described. Here we quantified dissolved metals and assessed microbial metaproteomes across a transect spanning the tropical and equatorial Pacific with a focus on the hydrothermally active NE Lau Basin and report elevated iron and manganese concentrations across 441 km of the southwest Pacific. The most intense signal was detected near the Mangatolo Triple Junction (MTJ) and Northeast Lau Spreading Center (NELSC), in close proximity to the previously reported 3He signature. Protein content in distal-plume-influenced seawater, which was high in metals, was overall similar to background locations, though key prokaryotic proteins involved in metal and organic uptake, protein degradation, and chemoautotrophy were abundant compared to deep waters outside of the distal plume. Our results demonstrate that trace metals derived from the NE Lau Basin are transported over appreciable distances into the southwest Pacific Ocean and that bioactive chemical resources released from submarine vent systems are utilized by surrounding deep-sea microbes, influencing both their physiology and their contributions to ocean biogeochemical cycling.