Hydrothermal Activity Research Articles

Ecological risk of Cd and Cr in the black rock series should be noticed: Based on the study of enrichment mechanism, occurrence form in the Lower Cambrian Lujiaping formation

The heavy metals in soils developed from the black rock series originate from the parent rock, but their sources and enrichment mechanisms in the parent rock remain unclear. This study explores the enrichment mechanisms, occurrence forms, and ecological environmental effects of cadmium (Cd) and chromium (Cr) in the black rock series. Results revealed average concentrations of 1.15 mg/kg for Cd and 193.08 mg/kg for Cr. Cd showed moderate enrichment (CdEF=31.03), while Cr had slight enrichment (CrEF=4.42). Both metals were mainly in the residual fraction (44.22 % for Cd, 69.02 % for Cr), followed by the Fe-Mn oxide-bound fraction (24.07 % for Cd, 18.51 % for Cr). The Risk Assessment Code (RAC) indicated moderate risk for Cd (10 %≤RAC<30 %) and low risk for Cr (1 %≤RAC<10 %). The Secondary Phase to Primary Phase ratio (RSP) suggested mild Cd pollution (1 <RSP≤2) and no Cr pollution (RSP≤1). Cd poses a significant release risk, necessitating attention to its ecological safety. Hydrothermal and volcanic activities were primary sources of Cd, while TOC and volcanic activities influenced Cr. Anoxic conditions in the Lower Cambrian Ocean facilitated Cd and Cr enrichment. This study enhances understanding of heavy metal enrichment in black rock series and guides pollution management.

There and there again: Hydrothermal vent communities at Mokuyo Seamount, 30 years apart

There and there again: Hydrothermal vent communities at Mokuyo Seamount, 30 years apart

Geochronology, in-situ elements and sulfur isotopes of sulfides from the Songjiashan cobalt-iron deposit in the Zhongtiao mountains of North China Craton: Implications for cobalt occurrence and ore genesis

The Songjiashan Co-Fe deposit in the central part of the “Tongshan skylight” on the southeastern edge of the Zhongtiao Mountains is hosted by the volcanic-sedimentary rock series of the Paleoproterozoic Songjiashan Group. The spatial distribution of the orebodies is controlled by south-north trending rock units. Based on microscopic observations, the dominant ore minerals included magnetite, pyrite, chalcopyrite, carrollite, and linnaeite, while gangue minerals comprised quartz, calcite, sericite, and chlorite. Cobalt-iron ores had massive, banded, disseminated, and veinlet texture, and alteration of the host rocks included silicification, sericitization, pyritization, carbonation, and chloritization. Mineralization processes of the Songjiashan deposit were grouped into three periods: sedimentation, metamorphism, and hydrothermal. The Co concentrations in hydrothermal pyrite (Py-III) varied from 1.05 % to 3.75 %, with an average of 2.45 %. Cobalt in pyrite was homogeneously distributed and inversely correlated to Fe, indicating that Co isomorphically replaced Fe in pyrite. The characteristic Co/Ni ratio of pyrite varied greatly, ranging from 0.1 to 1000, reflecting various genetic types of sedimentation, metamorphism, and hydrothermal mineralization, with the main mineralization period primarily related to hydrothermal activities. Zircon U-Pb geochronology of the host rock and Re-Os isochron of Co-bearing pyrites indicate that Co mineralization mainly occurred at ∼2100 Ma. In-situ S isotopic analysis of sulfides reveals two peak δ34S values of 5–9 ‰ and 12–16 ‰. We interpret that the former value reflects the mixing of volcanic and marine sulfate sources, while the latter value is mainly artributted to marine sulfate sources. All δ34S values were lower than those of Proterozoic marine sulfates (15–20 ‰). Accordingly, we infer that thermochemical sulfate reduction plays a key role in marine sulfate reduction, and that the formation of Co-rich ore bodies in the Songjiashan deposit have undergone processes of initial sedimentation, metamorphism-deformation, and subsequent hydrothermal overprinting. Genetically, we suggest that the Songjiashan deposit belongs to a sedimentary-metamorphic hydrothermal superposition type Co-Fe deposit.

Plastic-Degrading Enzymes from Marine Microorganisms and Their Potential Value in Recycling Technologies.

Since the 2005 discovery of the first enzyme capable of depolymerizing polyethylene terephthalate (PET), an aromatic polyester once thought to be enzymatically inert, extensive research has been undertaken to identify and engineer new biocatalysts for plastic degradation. This effort was directed toward developing efficient enzymatic recycling technologies that could overcome the limitations of mechanical and chemical methods. These enzymes are versatile molecules obtained from microorganisms living in various environments, including soil, compost, surface seawater, and extreme habitats such as hot springs, hydrothermal vents, deep-sea regions, and Antarctic seawater. Among various plastics, PET and polylactic acid (PLA) have been the primary focus of enzymatic depolymerization research, greatly enhancing our knowledge of enzymes that degrade these specific polymers. They often display unique catalytic properties that reflect their particular ecological niches. This review explores recent advancements in marine-derived enzymes that can depolymerize synthetic plastic polymers, emphasizing their structural and functional features that influence the efficiency of these catalysts in biorecycling processes. Current status and future perspectives of enzymatic plastic depolymerization are also discussed, with a focus on the underexplored marine enzymatic resources.

Fluid overprints and mineralization of the Zhuguangshan granite-related U district in China: Recorded by cathodoluminescence textures and chemistry of quartz

Most high-grade U ores are mined from quartz veins hosted in granites. The veins formed at shallow depths during episodic hydrothermal activity, however, the evolution of multiple stage fluids is not well constrained. In this study, we collected 56 quartz samples from the world-class, granite-related, Zhuguangshan U district (>17,000 t U from seven deposits) in southern China. Their textures and compositions were analyzed using scanning electron microscope cathodoluminescence (SEM-CL, n = 98) and laser ablation-induction coupled plasma-mass spectrometry (LA–ICP–MS, n = 643). Four types of quartz were identified, including magmatic quartz, early hydrothermal euhedral quartz, ore stage hydrothermal quartz (U-rich), and late hydrothermal quartz. New quartz textures and chemical compositions show that the transition of early hydrothermal quartz from the magmatic to hydrothermal stages is discontinuous, unlike the continuous trend observed in most magmatic-hydrothermal systems. Ore stage quartz is CL dark (with a peak at 650 nm), occurs as rims on early barren quartz, and has high contents of Mn, Al, and Sb. Altered textures of magmatic quartz developed through fluid-rock reactions at low temperatures, while rimmed textures of hydrothermal quartz formed during subsequent late-stage U-bearing fluid events, which played a crucial role in U mineralization. Quartz in the Zhuguangshan U district has distinct features compared to other magmatic-hydrothermal systems that can guide exploration for high-grade ore in this, and perhaps other, granite-related U systems.

Osmotic energy conversion in serpentinite-hosted deep-sea hydrothermal vents

Cells harvest energy from ionic gradients by selective ion transport across membranes, and the same principle is recently being used for osmotic power generation from salinity gradients at ocean-river interfaces. Common to these ionic gradient conversions is that they require intricate nanoscale structures. Here, we show that natural submarine serpentinite-hosted hydrothermal vent (HV) precipitates are capable of converting ionic gradients into electrochemical energy by selective transport of Na+, K+, H+, and Cl-. Layered hydroxide nanocrystals are aligned radially outwards from the HV fluid channels, constituting confined nanopores that span millimeters in the HV wall. The nanopores change the surface charge depending on adsorbed ions, allowing the mineral to function as a cation- and anion-selective ion transport membrane. Our findings indicate that chemical disequilibria originating from flow and concentration gradients in geologic environments generate confined nanospaces which enable the spontaneous establishment of osmotic energy conversion.

The paleo-oceanic environment and organic matter enrichment mechanism of the early Cambrian in the southern Lower Yangtze platform, China

This study focuses on the Lower Yangtze Platform located in southern Anhui Province, focusing on the black shale of the early Cambrian Hetang Formation as the primary research subject. Three field sections representing distinct sedimentary structural units were selected for investigation. Analytical methodologies encompassing organic geochemistry, elemental geochemistry, and scanning electron microscopy were employed to reconstruct paleo-oceanic environmental conditions. These analyses aimed to elucidate the characteristics of marine surface productivity and identify the factors controlling organic matter formation, thereby establishing a model for organic matter accumulation processes. These findings suggest that the Jiangnan paleo-uplift exerted differentiated control over organic matter formation and accumulation. Specifically, the barrier function of the paleo-uplift fostered a relatively enclosed and restricted water environment in certain regions, which proved conducive to the formation, accumulation, and preservation of organic matter. Furthermore, the paleo-upwelling system and hydrothermal groundwater circulation triggered by the activation of the Jiangnan deep fault played crucial roles in controlling the formation and accumulation of organic matter in the early Cambrian. Notably, the research also revealed that intermittent hydrothermal activity had a dual impact on organic matter accumulation within various paleo-oceanic settings. This process potentially facilitated organic matter enrichment and led to the dilution of organic matter concentrations.

The structural elements controlling the subsurface mineralization as deduced from the integration of magnetic and self-potential methods, Wadi Khosh El-Daba area, southern Sinai, Egypt

Significant copper mineralization are observed to be associated, in most cases, with some radioactive anomalies related to increased uranium and thorium contents in Southern Sinai, Egypt. These mineralizations are related to intense post-magmatic, structurally controlled hydrothermal activities in many localities. Wadi Khosh El-Daba area is one of these locations which is mainly composed of monzogranites dissected by andesite dyke and pegmatite vein. This work deals with the application of ground magnetic and self-potential methods to establish the magnetic sources governing the mineralization, to interpret the significant trends that affected the study area, and to delineate the mineralized zones. The magnetic data were processed, enhanced and interpreted using advanced techniques, such as the first-order vertical derivative (FVD), the tilt derivative (TD), Euler deconvolution (ED), and source parameter image (SPI). The main structural lineaments/contacts that control the distribution of hydrothermal alterations and mineral distributions are oriented to the NW–SE, NE–SW, and NNW–SSE directions. The self-potential (SP) data show that there are numerous mineralized zones; most of them are distributed mainly along the structural lineaments deduced from the magnetic study. The quantitative interpretation revealed that the mineralized bodies are at shallow depths ranging from 5.6 m to 12.7 m, with half-width from 5 m to 13 m. These bodies are shallow to moderate dipping towards the south and north directions. Based on this study an anomaly map is originated to locate the preferred structural elements that may be controlling the mineralization in the area for further future exploration.

Geochemical Evidence of Ore-Forming Processes in the Shuiyindong Gold Deposit of Southwest Guizhou Province, China.

The Shuiyindong deposit is one of the ultralarge Carlin-type gold deposits in Southwest Guizhou Province, China. Gold mineralization mainly occurs in the Permian Longtan Formation and the early Triassic Yelang Formation. It is controlled by both strata and faults. Detailed studies of the mineralogy and geochemistry characteristics of the Shuiyindong deposit are conducted to investigate the ore-forming process. Arsenian pyrite and arsenopyrite are the main Au-hosting minerals. Three types of pyrite can be recognized, including euhedral and subhedral pyrite, framboidal pyrite, and bioclastic pyrite. The euhedral and subhedral pyrite is the main Au-hosting type. The Au appears as a solid solution (Au+) and natural nanoscale gold (Au0) in the sulfide minerals. The Co/Ni ratios of sulfides (0.07-3.13) reveal that the ore-forming fluids were mainly affected by hydrothermal activity, but magmatic activity cannot be excluded. Organic matter in the ores is abundant (0.11-3.04%), which might provide sulfur for pyrite and favor an increase in the porosity and permeability of the host rocks by releasing organic acids. The REE and trace element results suggest that halogens (F and Cl) were contained in the reducing magmatic hydrothermal fluids. The sulfur isotopic data (from -8.64‰ to 27.17‰) suggest that the source of sulfur is complicated and is probably a combination of a magmatic source, the reduction of marine sulfate, and bacterial sulfate reduction. The Pb isotopic data of the sulfides indicate that Pb is from a mixture of crust and mantle sources. The obvious enrichment zones exist along the boundary faults in the geochemical map of As, implying that As may originate from the deep crust and then move to the strata with basinal fluids. By combining these results, it can be inferred that the ore-forming fluids were a mixture of basinal and deep source fluids. A probable ore-forming model of the Shuiyindong gold deposit is established.

High-resolution bathymetry coupled with 3D models of hydrothermal vents from opportunistically-acquired imagery: Aurora vent field, Arctic Ocean

ABSTRACT Active venting at the Aurora hydrothermal field was first located in 2014. In July 2023, the AUV/ROV Nereid Under Ice (NUI) expanded the known size of the Aurora hydrothermal field, discovering 7 ‘black smokers’ together with associated lower-temperature flow. In this study, we present a new high-resolution bathymetric map acquired from NUI which has allowed us to identify morphological features previously undetectable from ship multibeam. All known active vents are aligned along a single 230 m-long ridge, parallel to the Gakkel Ridge strike direction and intersected by a scarp following the general trend of the Lena Trough. The new vents were measured at up to 17 m height from 3D models generated using structure-from-motion techniques applied to opportunistically acquired imaging data collected while in exploration mode. The extent of extinct sulfides present, together with the towering height of vents are consistent with a period of sustained high-temperature venting at Aurora.

Advances in Extremophile Research: Biotechnological Applications through Isolation and Identification Techniques.

Extremophiles, organisms thriving in extreme environments such as hot springs, deep-sea hydrothermal vents, and hypersaline ecosystems, have garnered significant attention due to their remarkable adaptability and biotechnological potential. This review presents recent advancements in isolating and characterizing extremophiles, highlighting their applications in enzyme production, bioplastics, environmental management, and space exploration. The unique biological mechanisms of extremophiles offer valuable insights into life's resilience and potential uses in industry and astrobiology.

UPPER CRETACEOUS–LOWER EOCENE MUDSTONES OF THE OUTER CARPATHIANS (PETROCHEMICAL AND PALEOGEODYNAMIC ASPECTS)

The mineral types of the Upper Cretaceous–Lower Eocene greenish-gray mudstones of the Skyba and Boryslav-Pokuttya nappes of the Outer Carpathians were studied. According to sedimentological features, these mudstones belong to hemipelagites and contain information about the background sedimentation conditions of the deep-sea oceanic basin. The purpose of the work is to clarify the paleogeodynamic features of the basin based on the results of studying the material composition of the Upper Cretaceous–Lower Eocene background mudstones, which in particular are part of the variegated-colored horizons. Research methods were geological mapping, X-ray structural, sedimentological, lithostratigraphic, petrogeochemical, geodynamic analysis. On the classification module diagram (Na2O+K2O)/Al2O3–(FeO*+MnO+MgO)/SiO2, the figurative points of the contents of the Upper Cretaceous–Lower Eocene mudstones of the Stryi, Yamna, and Manyava suites fall into the fields corresponding to two mineral types: a mixture with a predominance of montmorillonite and three-component mixture of chlorite+montmorillonite+hydromica composition. According to the obtained data, a gradual change in the conditions of the sedimentary environment from the Late Cretaceous to the Eocene can be traced, with a successive increase in the normalized alkalinity modulus and a decrease in the phemic modulus. On the paleogeodynamic discriminant diagrams (FeO*+MgO)–TiO2 and F1–F2, figurative points of Upper Cretaceous–Lower Eocene mudstones form petrochemical distribution trends that cover the fields of geodynamic conditions from passive to active margins of the sedimentation basin. The Cretaceous–Paleogene pelagic mudstones of the Sicilian domain of the Alpine Belt have a similar distribution of petrochemical components. The mineral assemblages found in the mudstones of the Skyba and Boryslav-Pokuttya nappes are typical for deep-sea clay sediments of modern oceans. The presence of montmorillonite and chlorite in the background argillites indicates a high probability of a contribution to the background petrofund of the sedimentatary basin by a femic magmatic component of endogenous origin, realized as a manifestation of volcanic and hydrothermal activity, synchronous to sedimentogenesis. An exogenous source could be the magmatic material transferred or changed by the processes of halmyrolysis, which is not synchronous with sedimentation. The Late Cretaceous–Early Eocene geodynamic events of the Outer Carpathian sedimentary basin developed in front of the ALCAPA and Tisza-Dacia terranes of the Alpine Tethys. Convergence, which caused the formation of the accretionary prism in front of the terranes, could contribute to the riftogenic (?) opening, deepening of the Outer Carpathian Basin, where the penetration of synsedimentary endogenous material, mainly of the basic composition, took place. This material could be the rock-forming source of the basin substrate, on which the mineral assemblages of the background hemipelagic mudstones were formed.

Hydrothermal activity near the Permian–Triassic transition in the south‐western Ordos Basin, China: Evidence from carbonate cementation in Upper Permian sandstones

ABSTRACTCarbonate cementation in the Upper Permian sandstones informs the timing and temperature of hydrothermal activity in the south‐western Ordos Basin. This study presents a detailed examination of these hydrothermally influenced carbonate cements, constraining their age, carbonate diagenesis and relationship with regional geodynamic evolution. Sedimentological analyses demonstrate the development of deltaic plain and front sand bodies in the study area, which resulted in interbeds of volcanic matrix‐rich sandstones with matrix‐free sandstones. Petrography and electron microprobe analysis reveal four carbonate mineral growth phases of matrix‐free sandstones in the following sequence; scarce pure siderite, scarce Mg‐rich siderite, abundant blocky calcite and moderately abundant grain‐replacing calcite. The fluid inclusion data show anomalies of homogenization temperature of blocky carbonate cements during early diagenesis, over a wide range of ca 148 to 228°C. In addition, blocky carbonate cements show low δ13C (−5.9 to −13.1‰ Vienna PeeDee Belemnite) and δ18O (clustered tightly from −12.4 to −14.6‰ Vienna PeeDee Belemnite) values, interpreted to result from elevated temperatures during cementation, associated with activation of basement faults and concomitant hydrothermal fluid intrusion triggered by oceanic crust subduction in the south‐west margin of the Ordos Basin. Using in situ calcite U–Pb geochronology, the timing of hydrothermal activity was constrained to ca 247.0 ± 11 to 248.2 ± 4.7 Ma. This work provides a case study for applying intergranular calcite U–Pb dating to determine the absolute timing of fluid flow in sedimentary basins, offering tremendous potential to capture snapshots of various diagenetic evolution stages in sediments. The proposed diagenetic model can also provide new insights and understanding regarding hydrothermally influenced sediments. More importantly, hydrothermal activity may have commenced earlier than previously thought. The North Qinling Orogen uplift and associated Mianlue oceanic crust subduction may have begun at the Permian–Triassic transition with a protracted hydrothermal event in the south‐western Ordos Basin.

Carbon-containing pyrite spherules: mineral biosignatures in black smokers?

Abstract. Sulfide- and sulfate-rich hydrothermal vents are involved in Earth's major geochemical cycles. An outstanding scientific question consists of finding out whether certain minerals found in hydrothermal chimneys are influenced more or less directly by microorganisms living at high temperatures (thermophiles or hyperthermophiles) in these environments. Here we report the morphological, textural and chemical characterization of pyrite crystals collected across a section of a chimney from the Trans-Atlantic Geotraverse hydrothermal site, sampled from the inner, hotter portion to the external, cooler portion, providing a promising approach to the search for hyperthermophilic biosignatures. The internal and middle portions of the chimney mainly harbour cube-shaped pyrite containing low quantities of hydrocarbons and thermally matured organic compounds. In contrast, the samples from the external portion contain pyrite spherules composed of a mosaic of slightly disoriented domains that include large amounts of organic material chemically consistent with thermally matured biogenic organic compounds. These characteristics make them comparable but not identical to pyrite spherules produced in the laboratory in the presence of hyperthermophilic archaea of the order Thermococcales. Differences include larger crystalline domains and more thermally matured organic compounds. Such features could be consistent with the thermal transformation of pyrite spherules produced by (or at least in the presence of) living cells. However, it remains impossible to completely rule out an abiotic origin without further isotopic investigation and experimental studies on the abiotic production of pyrite spherules in the presence of organic compounds and under hydrothermal conditions.

Anatomy of a fumarole field: drone remote-sensing and petrological approaches reveal the degassing and alteration structure at La Fossa cone, Vulcano, Italy

Abstract. Hydrothermal alteration and mineralization processes can affect the physical and chemical properties of volcanic rocks. Aggressive acidic degassing and fluid flow often also lead to changes in the appearance of a rock, such as changes in surface coloration or intense bleaching. Although hydrothermal alteration can have far-reaching consequences for rock stability and permeability, limited knowledge exists on the detailed structures, extent, and dynamic changes that take place near the surface of hydrothermal venting systems. By integrating drone-based photogrammetry with mineralogical and chemical analyses of rock samples and surface gas flux, we investigate the structure of the evolving volcanic degassing and alteration system at the La Fossa cone on the island of Vulcano, Italy. Our image analysis combines principal component analysis (PCA) with image classification and thermal analysis through which we identify an area of approximately 70 000 m2 that outlines the maximum extent of hydrothermal alteration effects at the surface, represented by a shift in rock color from reddish to gray. Within this area, we identify distinct gradients of surface coloration and temperature that indicate a local variability in the degassing and alteration intensity and define several structural units within the fumarole field. At least seven such larger units of increased activity could be constrained. Through mineralogical and geochemical analysis of samples from the different alteration units, we define a relationship between surface appearance in drone imagery and the mineralogical and chemical composition. Gradients in surface color from reddish to gray correlate with a reduction in Fe2O3 from up to 3.2 % in the unaltered regime to 0.3 % in the altered regime, and the latter coincides with the area of increased diffuse acid gas flux. As the pixel brightness increases towards higher alteration gradients, we note a loss of the initial (igneous) mineral fraction and a change in the bulk chemical composition with a concomitant increase in sulfur content from close to 0 % in the unaltered samples to up to 60 % in samples from the altered domains. Using this approach of combined remote-sensing and in situ analyses, we define and spatially constrain several alteration units and compare them to the present-day thermally active surface and degassing pattern over the main crater area. The combined results permit us to present a detailed anatomy of the La Fossa fumarole field, including high-temperature fumaroles and seven larger units of increased alteration intensity, surface temperature, and variably intense surface degassing. Importantly, we also identify apparently sealed surface domains that prevent degassing, likely as a consequence of mineral precipitation from degassing and alteration processes. By assessing the thermal energy release of the identified spatial units quantitatively, we show that thermal radiation of high-temperature fumaroles accounts for &lt; 50 % of the total thermal energy release only and that the larger part is emitted by diffuse degassing units. The integrated use of methods presented here has proven to be a useful combination for a detailed characterization of alteration and activity patterns of volcanic degassing sites and has the potential for application in alteration research and for the monitoring of volcanic degassing systems.

Novel isolates of hydrogen-oxidizing chemolithoautotrophic Sulfurospirillum provide insight to the functions and adaptation mechanisms of Campylobacteria in shallow-water hydrothermal vents.

Enhancing the availability of representative isolates from hydrothermal vents (HTVs) is imperative for comprehending the microbial processes that propel the vent ecosystem. In recent years, Campylobacteria have emerged as the predominant and ubiquitous taxon across both shallow and deep-sea vent systems. Nevertheless, only a few isolates have been cultured, primarily originating from deep-sea HTVs. Presently, no cultivable isolates of Campylobacteria are accessible in shallow water vent systems (<200 m), which exhibit markedly distinct environmental conditions from their deep-sea counterparts. In this study, we enriched a novel isolate (genus Sulfurospirillum, Campylobacteria) from shallow-water HTVs of Kueishan Island. Genomic and physiological analysis revealed that this novel Campylobacteria species grows on a variety of substrate and carbon/energy sources. The pan-genome and phenotypic comparisons with 12 previously isolated Sulfurospirillum species from different environments supported the identification of functional features in Sulfurospirillum genomes crucial for adaptation to vent environments, such as sulfur oxidation, carbon fixation, biofilm formation, and benzoate/toluene degradation, as well as diverse genes related with signal transportation. To conclude, the metabolic characteristics of this novel Campylobacteria augment our understanding of Campylobacteria spanning from deep-sea to shallow-water vent systems.IMPORTANCECampylobacteria emerge as the dominant and ubiquitous taxa within vent systems, playing important roles in the vent ecosystems. However, isolated representatives of Campylobacteria have been mainly from the deep-sea hydrothermal fields, leaving a significant knowledge gap regarding the functions, activities, and adaptation strategies of the vent microorganisms in shallow-water hydrothermal vents (HTVs). This study bridges this gap by providing insights into the phenomics and genomic diversity of genus Sulfurospirillum (order Campylobacterales, class Campylobacteria) based on data derived from a novel isolate obtained from shallow-water HTVs. Our mesophilic isolate of Sulfurospirillum not only augments the genus diversity of Campylobacteria pure cultures derived from vent systems but also serves as the inaugural reference isolate for Campylobacteria in shallow-water environments.

Complex hydrothermal vent microbial mat communities used to assess primer selection for targeted amplicon surveys from Kama‘ehuakanaloa Seamount

The microbiota of hydrothermal vents has been widely implicated in the dynamics of oceanic biogeochemical cycling. Lithotrophic organisms utilize reduced chemicals in the vent effluent for energy, which fuels carbon fixation, and their metabolic byproducts can then support higher trophic levels and high-biomass ecosystems. However, despite the important role these microorganisms play in our oceans, they are difficult to study. Most are resistant to culturing in a lab setting, so culture-independent methods are necessary to examine community composition. Targeted amplicon surveying has become the standard practice for assessing the structure and diversity of hydrothermal vent microbial communities. Here, the performance of primer pairs targeting the V3V4 and V4V5 variable regions of the SSU rRNA gene was assessed for use on environmental samples from microbial mats surrounding Kama‘ehuakanaloa Seamount, an iron-dominated hydrothermal vent system. Using the amplicon sequence variant (ASV) approach to taxonomic identification, the structure and diversity of microbial communities were elucidated, and both primer pairs generated robust data and comparable alpha diversity profiles. However, several distinct differences in community composition were identified between primer sets, including differential relative abundances of both bacterial and archaeal phyla. The primer choice was determined to be a significant driver of variation among the taxonomic profiles generated. Based on the higher quality of the raw sequences generated and on the breadth of abundant taxa found using the V4V5 primer set, it is determined as the most efficacious primer pair for whole-community surveys of microbial mats at Kama‘ehuakanaloa Seamount.

Флюидный режим образования вторичных доломитов в палеозойских карбонатных коллекторах Хасырейского месторождения (вал Гамбурцева)

The search for hydrocarbon deposits in the sediments of the Lower Paleozoic complex of the Timan-Pechora oil and gas province, which are associated with the main prospects for increasing reserves, is a relevant topic for research. It is necessary to understand the formation processes of carbonate reservoirs within the complex under consideration to develop a strategy for predicting the structure of the complex reservoirs. Obtaining data on the parameters of the fluid regime of the formation of secondary dolomites in the Paleozoic carbonate reservoirs of the Khasyrey field (Gamburtsev swell) was the aim of the study. We studied primary fluid inclusions in dolomite and anhydrite cements filling vuggy voids in reservoir rocks. We showed that the inclusions contained up to 10 vol. % of the gas phase, which was represented by methane and water vapor. The liquid phase was characterized by a substantially chloride-calcium composition, the salinity is 13.5–23.5 wt. % NaCl-eq. These data might indicate the formation of cavities and cements of secondary dolomites from moderate-temperature solutions of high salinity, which were formed as a result of mixing sedimentation (primary marine) waters and brines of hydrothermal vents. The products of evaporite dissolution in the presence of hydrocarbons and sulfate reduction processes were the most likely source and supplier of the fluids, both the formation of leaching caverns in the rock and the cements performing them. Fluids could enter the upper floors of the section from hydrothermal sources in the basement zones and lower horizons of the sedimentary cover through a system of faults and cracks during tectonic activation.

Oxidation of sulfur, hydrogen, and iron by metabolically versatile Hydrogenovibrio from deep sea hydrothermal vents.

Chemolithoautotrophic Hydrogenovibrio are ubiquitous and abundant at hydrothermal vents. They can oxidize sulfur, hydrogen or iron, but none are known to use all three energy sources. This ability though would be advantageous in vents hallmarked by highly dynamic environmental conditions. We isolated three Hydrogenovibrio strains from vents along the Indian Ridge, which grow on all three electron donors. We present transcriptomic data from strains grown on iron, hydrogen or thiosulfate with respective oxidation and autotrophic CO2 fixation rates, RubisCO activity, SEM, and EDX. Maximum estimates of one strain's oxidation potential were 10, 24, and 952mmol for iron, hydrogen and thiosulfate oxidation and 0.3, 1, and 84mmol CO2 fixation, respectively, per vent per hour indicating their relevance for element cycling in-situ. Several genes were up- or downregulated depending on the inorganic electron donor provided. Although no known genes of iron-oxidation were detected, upregulated transcripts suggested iron-acquisition and so far unknown iron-oxidation-pathways.

Landscape of the metaplasmidome of deep-sea hydrothermal vents located at Arctic Mid-Ocean Ridges in the Norwegian-Greenland Sea: ecological insights from comparative analysis of plasmid identification tools.

Plasmids are one of the key drivers of microbial adaptation and evolution. However, their diversity and role in adaptation, especially in extreme environments, remains largely unexplored. In this study, we aimed to identify, characterize, and compare plasmid sequences originating from samples collected from deep-sea hydrothermal vents located in Arctic Mid-Ocean Ridges. To achieve this, we employed, and benchmarked three recently developed plasmid identification tools-PlasX, GeNomad, and PLASMe-on metagenomic data from this unique ecosystem. To date, this is the first direct comparison of these computational methods in the context of data from extreme environments. Upon recovery of plasmid contigs, we performed a multiapproach analysis, focusing on identifying taxonomic and functional biases within datasets originating from each tool. Next, we implemented a majority voting system to identify high-confidence plasmid contigs, enhancing the reliability of our findings. By analysing the consensus plasmid sequences, we gained insights into their diversity, ecological roles, and adaptive significance. Within the high-confidence sequences, we identified a high abundance of Pseudomonadota and Campylobacterota, as well as multiple toxin-antitoxin systems. Our findings ensure a deeper understanding of how plasmids contribute to shaping microbial communities living under extreme conditions of hydrothermal vents, potentially uncovering novel adaptive mechanisms.