Natural Seeps Research Articles

Inversion Model for Permeability Coefficient Based on Random Forest–Secretary Bird Optimization Algorithm: Case Study of Lower Reservoir of C-Pumped Storage Power Station

The geological complexity of the karst regions presents significant challenges, with the permeability coefficient being a critical parameter for accurately analyzing seepage behavior in hydraulic engineering projects. To overcome the limitations of traditional inversion methods, which often exhibit low computational efficiency, poor accuracy, and instability, this study utilizes a finite-element forward model and orthogonal experimental design to establish a sample set for permeability-coefficient inversion. A surrogate model for seepage calculation based on the Random Forest (RF) algorithm is subsequently developed. Furthermore, the Secretary Bird Optimization Algorithm (SBOA) is incorporated to propose an intelligent RF–SBOA inversion method for permeability-coefficient estimation, which is validated through a case study of the C-pumped storage power station. The results demonstrate that the RF model’s predictions for water levels at four boreholes closely align with the measured data, outperforming models such as CART, BP, and SVR. The SBOA effectively identifies the optimal geological permeability coefficient, with the borehole water-level inversion achieving a maximum relative error of only 0.128%, which meets the accuracy requirements for engineering applications. Additionally, the computed distribution of the natural seepage field is consistent with the typical distribution patterns observed in mountain seepage systems. During the normal water-storage phase, both the calculated seepage flow and gradient comply with engineering standards, while the seepage-field distribution aligns with empirical observations. This inversion model provides a rapid and accurate method for estimating the permeability coefficient of strata in the project area, with potential applicability to permeability inversion in other engineering geology contexts, thus demonstrating considerable practical value for engineering applications.

Vertical stratification of arctic microbial communities near potential hydrocarbon seepage off Cape Dyer, Nunavut

AbstractClimate change disproportionately affects the Arctic, where warming is up to four times greater than the global annual average experienced in southern regions. Baffin Bay in the Canadian Arctic Archipelago is an ecologically and biologically significant area that will likely experience an increase in marine vessel traffic as a result of consistent declines in annual sea ice coverage. Along the western coast of Baffin Bay is known to be a region of active, natural hydrocarbon seeps where elevated levels of methane have been detected in previous surveys. Petroleum hydrocarbons released from the seafloor can fuel microbial production and shape the baseline microbiome. Establishing a microbial baseline is highly valuable as it contributes to a fundamental understanding of the existing microbial diversity that may be impacted in the future by anthropogenic stressors. In this study, 16S and 18S rRNA gene amplicon sequencing surveys revealed that the vertical stratification of the water column is largely driven by differences in depth, temperature, salinity, and inorganic nutrient concentrations. Chemical analysis provides further support that active petrogenic methane seepage occurs around Cape Dyer but not in areas targeted in this study. Presence of n-alkanes and toluene in association with hydrocarbon-synthesizing phytoplankton suggests biogenic production of these compounds. These findings provide a baseline for future environmental monitoring assessments to evaluate how the prokaryotic and eukaryotic microbiome may be impacted by ongoing climate change and anthropogenic stressors in western Baffin Bay.

Geochemical analysis of surface natural seepages and hydrocarbon fields of technogenic origin in the Amga River Basin (Siberian platform)

The presence of substantial accumulations of bitumen is critically significant as they serve as direct indicators of oilbearing regions. However, in the context of environmental studies, their existence complicates the assessment of technogenic soil contamination by oil and petroleum products. The objective of this research was to identify informative geochemical parameters that would facilitate the differentiation between natural surface seepages and technogenic hydrocarbon fields resulting from commercial oil spills. This study examined natural surface oil seepages in the Amga River Basin and technogenic oil contamination near the Amga Oil Depot. Employing classical bituminology, Fourier transform infrared spectroscopy, gas chromatography, and mass spectrometry, a comparative analysis of their compositional characteristics was conducted. Notably, significant differences in geochemical parameters, such as the concentrations of hydrocarbons, resins, asphaltenes, and oxygen-containing compounds, were observed when comparing oil pollution to natural surface seepages for the first time. Furthermore, it was demonstrated that genetic parameters for diagnosing soil contamination by oil, based on biomarker composition, could include the presence of 12- and 13-methylalkanes in the hydrocarbon profile of the pollutant. These compounds are recognized as distinctive biological markers of Cambrian and Early Paleozoic oils from the Nepsko-Botuobinsk oil and gas region. Conversely, these biomarkers were absent in the natural surface oil seepages of Amga. The findings of this research may prove valuable in environmental studies, particularly in monitoring efforts aimed at identifying technogenic oil contamination in soils that are not associated with natural oil seeps.

Experimental study on controlling basement leakage for urban flooding mitigation

Intense summer rainstorms can result in short-term urban flooding, leading to localized groundwater level rise and subsequent floor cracking and leakage in basements. Rational control of the surrounding water level is crucial for addressing existing basement leaks caused by short-term urban flooding. In this study, a combined approach of interception and seepage control using waterproof curtains and negative-pressure wells is proposed. Four different scenarios were considered, and experimental and numerical investigations were conducted on a 1.2 m × 1.2 m × 1.1 m model. The study analyzed the influence of factors such as water content, pore water pressure, soil properties, waterproof curtain insertion depth, and length of the filter section in the negative-pressure well on controlling the upward water level in the basement.The results showed that the installation of waterproof curtains alone can impede rainwater infiltration into the basement, delaying its penetration by approximately 48 h. The combined approach of interception and seepage control outperformed the sole use of waterproof curtains, with the reduction in water level becoming smaller as the insertion depth of the waterproof curtain increased. The reduction in water level decreased at a slower rate with increasing waterproof curtain insertion depth. The recommended waterproof curtain insertion ratio was equal to or greater than 83.5 %, while the filter section length ratio in the negative pressure well should be less than 64 %. Compared to natural seepage drainage, negative-pressure pumping could maintain the basement floor's water content within the initial range 32 h earlier. The water-blocking and depressurization effect is best in sandy soil and worst in clay. Water-blocking and depressurization provide a new approach for controlling the uplift caused by summer urban waterlogging, especially offering a new method for controlling leaks in the basement.

Bioremediation of contaminated soil by crude oil of Baiji refinery by extraction of the local dominant bacteria

Abstract In most communities, soil contamination is a problem as it affects people and the environment. Because oil spills on soil substantially impact the environment, accidental infusions and spills of ore oils frequently result in a complete or partial exchange of the soil pore fluid by oil-contaminated soils, altering the geotechnical engineering characteristics. Therefore, efficiently removing petroleum hydrocarbon pollutants from contaminated soil is urgently needed. A novel technique that is gaining popularity worldwide to clean up places polluted with petroleum hydrocarbons is known as bioremediation. This study browser the fundamental processes involved in bioremediation and removal efficiency of TPH (Total Petroleum Hydrocarbon) within different periods for (the Baiji refinery) which is polluted with crude oil as a result of numerous oil wells, oil drilling, pipeline, and storage tank damage, natural seepage, and spills during the conflict and Noory channel which content crude oil, waste of refinery process and sludge. The research aims to extract the dominant bacteria in the contaminated soil and use the last in bioremediation and find out the differences in its effectiveness in treating total petroleum hydrocarbons (TPH) later. The result indicates that the dominant bacteria are Stutzerimonas balearica and Bacillus subtilis which are used later in bioremediation and can digest TPH. The removal efficiency of TPH during the study period was 55, 65, 68, 78, 82, 85, and 92% for spilled samples and 50, 62, 66, 70, 80, 84, and 90% for the Noory channel, respectively.

Determination of the Nature of Hydrocarbons in the Barents Sea (Verification of Remote Sensing Data)

Based on remote sensing data on the distribution of oil spills obtained using synthetic aperture radar (SAR) imagery of the Sentinel-1A and Sentinel-1B satellites in 2016–2022 and the results of the analysis of aliphatic hydrocarbons (AHCs) and polycyclic aromatic hydrocarbons (PAHs) in bottom sediments taken in 2019–2022, the nature of oil slicks in various areas of the Barents Sea has been established. It is shown that the distribution of oil slicks in coastal areas is greatly influenced by anthropogenic hydrocarbon inflow (mainly from shipping and fishing), which is confirmed by elevated AHC concentrations in coastal sediments (up to 73 μg/g) and in the composition of Corg (up to 3.6%). In the central and northern regions of the Barents Sea (station 7105, in the coordinates 75.2–75.3 N, 31.5–31.8 E), the grouping of oil slicks is due to natural seepage of oil and gas. This is confirmed by the anomalous concentration of PAHs in the lower horizons of the obtained sediment column, and their composition (the dominance of 2-methylnaphthalene, a marker of their oil genesis). At the same time, the proportion of light homologues in the composition of alkanes increased, which may indicate their formation in the sedimentary sequence.

Quantitative analysis of the upwelling behavior of methane bubbles in nature and numerical simulations

In recent years, methane gas released from the seafloor has been considered a sub-oceanic resource, and comprehending the dynamics of methane bubbles in the ocean has garnered increasing attention. Therefore, in this study, we conducted a quantitative analysis of the behavior of ascending methane bubbles with and without a hydrate layer. The bubbles were filmed at two natural gas seep sites and reproduced by numerical simulations using two-dimensional motion analysis software. The simulations were performed with gas bubbles and methane hydrate (MH)1 bubbles spouting from a nozzle in a computational domain filled with pure water to assess the validity of image analysis for in-situ data, whereas numerical models and physical properties were utilized for the current two-phase (gas-liquid) simulations. The rising velocity, size, circumference, circularity, and maximum diameter of the methane bubbles were examined to understand the effects of the MH layer on the statistical and stochastic features of ascending methane bubbles. Based on the statistics of the above variables, the gas bubbles had a higher rising velocity and smaller circularity than the MH bubbles when the bubble sizes were identical. In addition, stochastic analysis indicated that the circularity of the MH bubble was uniquely determined by their size, due to the more rigid skin of the MH bubbles compared to that of gas bubbles. Consequently, discrepancies in bubble dynamics between methane gas and MH bubbles were clarified in this study.

Anti-seepage measures for the upper reservoir of one pumped-storage power station

Abstract Seepage control plays an important role in the design of pumped storage power station. In this paper, the seepage characteristics and geological conditions of the upper reservoir of a pumped storage power station are analyzed, and the natural seepage of the upper reservoir is calculated. According to the characteristics and amount of leakage, the upper reservoir can be controlled by local seepage control scheme, and the anti-seepage treatment scheme of the south reservoir bank is compared and analyzed. After the local anti-seepage treatment of upper reservoir, the daily seepage volume decreased from 5585m3/d to 2304m3/d, which indicates that the selected anti-seepage scheme is suitable. This paper can provide useful reference for similar projects in the future.

Analysis of Seepage Field Characteristics of Water Diversion Power Generation System of Pumped Storage Power Station

Based on the diversion power generation system project of the Hami pumped storage Hydropower Station, the drainage substructure method is used to accurately simulate the drainage holes of the plant area, and the three-dimensional finite element model of the plant area including the main faults and reflecting the seepage characteristics of complex rock mass is established. Based on the inversion analysis of the natural seepage field, the distribution characteristics of the three-dimensional seepage field in the plant area were studied, and the rationality of the layout of the anti-seepage drainage system was evaluated. The results show that under the action of the anti-seepage drainage system, the groundwater level of the mountain is greatly reduced, and the descending funnel is formed in the three caverns, the seepage flow is controllable overall, and the permeability stability meets the engineering safety requirements.

Correlation between Natural Seepage and Ionic Diffusion in Shales

Correlation between Natural Seepage and Ionic Diffusion in Shales

Long non-coding RNAs mediate fish gene expression in response to ocean acidification.

The majority of the transcribed genome does not have coding potential but these non-coding transcripts play crucial roles in transcriptional and post-transcriptional regulation of protein-coding genes. Regulation of gene expression is important in shaping an organism's response to environmental changes, ultimately impacting their survival and persistence as population or species face global change. However, the roles of long non-coding RNAs (lncRNAs), when confronted with environmental changes, remain largely unclear. To explore the potential role of lncRNAs in fish exposed to ocean acidification (OA), we analyzed publicly available brain RNA-seq data from a coral reef fish Acanthochromis polyacanthus. We annotated the lncRNAs in its genome and examined the expression changes of intergenic lncRNAs (lincRNAs) between A. polyacanthus samples from a natural CO2 seep and a nearby control site. We identified 4728 lncRNAs, including 3272 lincRNAs in this species. Remarkably, 93.03% of these lincRNAs were species-specific. Among the 125 highly expressed lincRNAs and 403 differentially expressed lincRNAs in response to elevated CO2, we observed that lincRNAs were either neighboring or potentially trans-regulating differentially expressed coding genes associated with pH regulation, neural signal transduction, and ion transport, which are known to be important in the response to OA in fish. In summary, lncRNAs may facilitate fish acclimation and mediate the responses of fish to OA by modulating the expression of crucial coding genes, which offers insight into the regulatory mechanisms underlying fish responses to environmental changes.

Automatic target recognition and geolocalisation of natural gas seeps using an autonomous underwater vehicle

Autonomous Underwater Vehicles (AUVs) have proven to be a precious resource for oceans preservation thanks to their ability to accomplish survey missions on wide areas without the need of human supervision. This also includes the detection and mapping of underwater gas emissions, whether these are due to damaged offshore structures or naturally released from the seafloor. Indeed, submarine seepage have severe repercussions on the surrounding marine habitat and contribute to greenhouse gas emissions, hence the need to identify and monitor them. This work focuses on the online Automatic Target Recognition (ATR) and geolocalisation of underwater gas leakages utilising an AUV equipped with a Forward Looking Sonar (FLS). With the aim to accurately position the seeps, it was necessary to address the problem of navigating the vehicle in areas with the presence of gas bubbles. In fact, bubbles adversely affect acoustic sensors typically exploited by underwater robots for navigation. The paper investigates the effects that seepage have on the performance of navigation solutions based on two different acoustic sensors: a Doppler Velocity Log (DVL) sensor and an Ultra-Short BaseLine (USBL) device. Afterwards, a solution to autonomously recognise in real-time gas seeps on FLS acoustic imagery utilising a Single Shot MultiBox Detector (SSD) is presented. The relative position of the detected seep with respect to the vehicle is then retrieved and combined with the estimated AUV position to obtain the geodetic location of the seep. Finally, the proposed algorithm was tested during at sea experiments, where gas leaks were artificially reproduced, and the achieved results prove the validity of the proposed method to autonomously detect and accurately geolocate underwater seeps in real time using an AUV.

Manifestation of Gas Seepage from Bottom Sediments on the Sea Surface: Theoretical Model and Experimental Observations

The key area of the Arctic Ocean for atmospheric venting of CH4 is the East Siberian Arctic Shelf (ESAS). Leakage of methane through shallow ESAS waters needs to be considered in interactions between the biogeosphere and a warming Arctic climate. The development of remote sensing techniques for gas seepage detection and mapping is crucially needed for further applications in the ESAS and other areas of interest. Given the extent of the seepage areas and the magnitude of current and potential future emissions, new approaches are required to effectively, rapidly, and quantitatively survey the large seepage areas. Here, we consider the main features of gas seep detection on the sea surface in the characteristics of wind waves and radar signals. The kinematics of wave packets based on the kinetic equation for the spectral density of the wave action of surface waves is described. The results of a full-scale experiment on the remote radar observation of a model gas seep to the sea surface in the radar equipment signals are considered. The characteristic radar signatures of the gas seep in a wide range of hydrometeorological conditions, the parameters of which were recorded synchronously with the radar mapping, were determined. The results of the first radar observations of natural methane seeps on the ESAS are presented, and their radar contrasts are evaluated. The theoretical conclusions are in good qualitative agreement with the results of the model experiment and field studies and can be used for further research in aquatic areas with potential gas seepage, both of natural or anthropogenic origin, such as bubbling release from broken underwater gas pipelines.

Bonny Light Crude Oil Toxicity: Histopathological and Biochemical Upshots on Cardiac and Hepatocellular Tissues

Aim: Evaluate the acute toxicity effect of bonny light crude oil on histopathological and biochemical disrupting effects on cardiac and hepatocellular tissues. Oil spills, gas flaring, natural seeps, industrial discharge, and the destruction of ecosystems have led to ecological devastation, health problems, and socioeconomic challenges for communities in the Niger Delta; one of the world's largest oil-producing regions. Crude oil spillage has been a persistent and severe environmental concern in the Niger Delta for many years. The spilled oil covers water surfaces, diminishes oxygen levels, and poses significant health risks to aquatic life, birds, loss of biodiversity, and the well-being of the human population that heavily relies on these resources for their sustenance. Study Design: A total of 50 albino rats were randomly divided into three (3) groups; control group, low dose group, and high dose group. The control group consisted of 10 albino rats while the low dose and high dose groups consisted of 20 albino rats each. The control group was fed with normal (uncontaminated) rat feeds and sterile water only (that is, a dosage of 0.00mL/g of rat feed), and the low dose (0.005mL/g) group was fed with 300g of rat feeds mixed with 1.5mL of BLCO while high dose (0.01mL/g) group was fed with 300g of feeds mixed with 3.0mL of BLCO. The treated feeds were administered once every day for 35 days. Methodology: After day 35, the rats were allowed to fast overnight and anesthetized with chloroform (CHCl3). Blood specimens (5 ml) were collected by slitting the neck of the rats into an anticoagulant labeled bottle. The livers and hearts of the experimental rats were harvested and preserved in 10% formalin in different labeled plastic containers prior to tissue processing and histological examinations. Blood specimens were centrifuged at 4500 rpm for 10 minutes to obtain plasma. Plasma levels of ALT, AST, ALP, cTnT, cTnI, MDA, and SOD were estimated. All weights were measured in grams. Results: The result indicated that low and high-dose treated groups showed a significant decrease in body weight. The SOD and MDA indicated significantly lower and higher values respectively in the low and high-dose treated groups when compared to the control rats. However, no significant difference in SOD values was seen between the low and high dose treated groups. The ALT, AST, and ALP values indicated significantly higher values in the low and high-dose treated groups compared to the control group. More so, dose-dependent increases were also observed in AST and ALT. However, ALP indicated no significant difference between the control and the low-dose treated rats. In addition, cTnT and cTnI values indicated significantly higher values in the low and high-dose treated groups compared to the control group. However, cTnT and cTnI indicated no significant difference between the high-dose and the low-dose treated rats. The P value was set to P=.05 Conclusion: Bonny light crude oil in feed at small doses over a period of 35 days induced myocardial and hepatic injuries indicated by increased levels of AST, ALT, ALP, cTn-T, and cTn-I. More so, histopathological changes further showed the disrupting changes in hepatic and cardiac tissues.

A Comprehensive Analysis of Marine Life Pollution Using Machine Learning Techniques on historical shipping Pollutants data

Oil spills significantly threaten marine and coastal ecosystems, resulting in devastating ecological and economic consequences. The current research highlights the key aspects surrounding oil spills, including their causes, environmental impacts, and mitigation strategies. Oil spills, resulting from accidents during offshore drilling, transportation, or natural seepage, pose severe ecological and societal challenges. These incidents release vast quantities of oil into marine ecosystems, leading to widespread environmental degradation. The impact of oil spills is influenced by factors such as spill volume, oil type, environmental conditions, and response effectiveness. Ecologically, oil spills harm marine life through toxic effects, habitat destruction, and interference with reproductive cycles. Birds, marine mammals, fish, and shoreline organisms suffer from oil exposure, leading to long-term population declines. The economic consequences are significant, affecting fishers, tourism, and coastal industries. The clean-up process involves mechanical removal, chemical dispersants, and controlled burns, each with its environmental trade-offs. Oil spill assessment methods encompass satellite monitoring, modeling, and ecological surveys to estimate damages and aid restoration efforts. Prevention measures include stricter regulations, technological advancements, and industry best practices. Public awareness and international cooperation are vital for enhancing spill preparedness and response. In the paper, oil spills continue to challenge environmental sustainability and economic stability. Addressing their multifaceted impacts demands an integrated approach involving mitigation, rigorous assessment, and global collaboration to prevent future disasters and safeguard our oceans and coastlines. An expansive dataset gathered from Queensland, Australia, incorporating intricate information about ships, regions, longitudes, latitudes, and pollutants, the study markedly advances the capability to identify oceanic oil spills and enhances our understanding of the resulting impact on marine life. In that, algorithms are used of machine learning techniques such as SVC and LogisticRegression. In the course of the study, machine learning techniques are applied, featuring algorithms like Support Vector Classification (SVC) and Logistic Regression. These algorithms play a crucial role in the analysis, contributing to the extraction of valuable insights from the dataset. Keywords: Bilge, Diesel, Hydraulic Oil, Types of Ship, Machine learning algorithms

A natural hydrogen seep in Western Australia: Observed characteristics and controls

Natural hydrogen (H2) is a promising resource for the energy industry’s transition to zero-carbon fuels. However, its extent and feasibility for exploitation remain unclear. A key step towards discovering subsurface dihydrogen accumulations is detecting H2 seeps. This study presents the first autonomous, multi-gas monitoring of a natural hydrogen seep in Australia, where dihydrogen, carbon dioxide, and hydrogen sulphide were measured together. The research revealed significant H2 seepage on the Yilgarn Craton in Western Australia, with seasonal fluctuations: high emissions after dry summers and reduced emissions following rainfall due to increased groundwater levels. Groundwater appears to act as a seasonal inhibitor to H2 seepage through the near subsurface potentially leading to false negatives in soil gas surveys post-rainfall and in low-lying areas. This work provides fundamental data for natural hydrogen exploration and therefore aids in the implementation of a large-scale hydrogen economy.

Novel oil spill indices for sentinel-2 imagery: A case study of natural seepage in Qaruh Island, Kuwait

Oil spills are a paramount and immediate challenge affecting marine ecosystems globally. Effective and timely monitoring tools, such as oil detection indices, offer a swift means to track oil spill spread across vast oceanic expanses. Moreover, these indices enhance data clarity, making it more conducive for machine learning and deep learning algorithms.This study leverages the natural seepage occurring around Qaruh Island, Kuwait as a unique context for the spectral analysis of oil spills using Sentinel-2 multispectral imagery due to repeated occurrences in the same region. This research evaluated 859 single band and 455 multichannel combinations to identify the most effective combinations in oil-water separability, employing the Jeffries-Matusita (JM) distance measure as a key metric. Bands 1, 2, 3, 8A, 11, and 12 consistently featured among the top-performing indices combinations B1−B11B1+B11;B1+B2B3+B11;B1+B2B3+B12;B1+B2B3+B8A affirming the significant effect of oil spills on visible, Near-Infrared (NIR), and Shortwave Infrared (SWIR) bands. Notably, the indices developed in this study outperformed those from prior research in terms of suitability to unsupervised classification algorithms. A significant conclusion of this study is that incorporating a higher number of bands in the analysis did not correlate with an increase in JM values, suggesting that the selection of specific, informative bands is more critical than the volume of input data. These findings underscore the indispensable role of Sentinel-2 imagery in environmental investigations and highlight the potential for focused, efficient analysis using strategic band combinations for effective oil spill detection.•This study identified optimized Sentinel-2 band combinations for oil-water separability, benefiting from naturally occurring spills around Qaruh Island.•The proposed indices outperformed the previous indices for oil spill visualization and clustering.•The new indices highlighted the critical role of specific band selection over the volume of input data for effective oil spill detection.

Dispersal and Distribution of Thermophilic Endospores in Deep-Sea Ecosystems

The distance-decay relationship is a central concept in biogeography and spatial biodiversity, describing how two distinct entities decrease in similarity as the distance between them increases. The decay of community similarity with geographical distance is driven by multiple factors, such as gene drift, environmental selection, and the accumulation of mutations over time. While the distance-decay relationship has been recognized for several decades, there are certain circumstances where the biogeographical patterns of certain species and communities cannot be predicted by this relationship. The example addressed in this project is the case of thermophilic endospore-forming bacteria found in permanently cold deep ocean sediments. Thermophilic endospores (thermospores) are routinely found on the deep ocean floor, a permanently cold environment that does not support their metabolic activity (Hubert et al. 2009). Thermospores are metabolically dormant states developed by some thermophilic bacteria having optimal growth temperatures between 40°C and 70°C. There is evidence that these heat-loving bacteria originate from the deep subsurface and are transported upward to the deep ocean via geological features of the oceanic crust including geofluid fluxes in high-temperature axial systems and natural hydrocarbon seeps (Gittins et al. 2022). Due to the ability of endospores to stay viable for thousands of years and resist a wide range of physicochemical stressors, they can disperse over long distances while remaining unaffected by changing factors such as selection, drift, or mutation (Gittins et al. 2022; Fig. 1). Consequently, these thermospores have the potential to challenge the distance-decay relationship and exhibit unique biogeographical patterns. This work quantifies endospores in sediment cores at and around hydrocarbon seeps using cores from deep-sea Scotian Slope sediments. Given the challenge of quantifying specific groups of endospores (e.g., thermophiles but not mesophiles), high-temperature germination assays that allow tracking of an exponential increase in signal as spores in marine sediment samples germinate and grow can be used. Distinct exponential increases can be attributed to different populations of germinated thermospores in the post-germination growth phase and are being monitored through measurements of sulfate reduction rates (using radiolabelled 35SO4), strain-specific quantitative PCR (qPCR), and fluorescence in-situ hybridization (FISH) (Rezende et al. 2017). These measurements revealed growth dynamics enabling an estimation of the initial cell numbers using exponential functions. These approaches are being applied to samples obtained via push coring using a remotely operated vehicle at different distances from deep sea hydrocarbon seeps, to test for the presence of abundance gradients of different thermospores. Current results already show a difference in thermospore abundance between sites at different distances from the seep. Quantitative tracking of the dispersal of thermospores by oceanic currents in the deep sea provides an excellent opportunity to investigate their distribution and potential to colonize more remote habitats, improving the understanding of microbial biodiversity and biogeography on our planet. By investigating thermospores and their interactions with the geophysical features of the deep sea and deep subsurface, this study aims to challenge the canonical idea that speciation occurs with distance and presents new perspectives on the theme of microbial biogeography. The evidence supporting the subsurface origin of thermophilic endospores, along with the proposed model for their dispersal and distribution, will contribute toward improving an integrated understanding of ecology and geology and their intersection in the microbial realm.

Potential for the anaerobic oxidation of benzene and naphthalene in thermophilic microorganisms from the Guaymas Basin.

Unsubstituted aromatic hydrocarbons (UAHs) are recalcitrant molecules abundant in crude oil, which is accumulated in subsurface reservoirs and occasionally enters the marine environment through natural seepage or human-caused spillage. The challenging anaerobic degradation of UAHs by microorganisms, in particular under thermophilic conditions, is poorly understood. Here, we established benzene- and naphthalene-degrading cultures under sulfate-reducing conditions at 50°C and 70°C from Guaymas Basin sediments. We investigated the microorganisms in the enrichment cultures and their potential for UAH oxidation through short-read metagenome sequencing and analysis. Dependent on the combination of UAH and temperature, different microorganisms became enriched. A Thermoplasmatota archaeon was abundant in the benzene-degrading culture at 50°C, but catabolic pathways remained elusive, because the archaeon lacked most known genes for benzene degradation. Two novel species of Desulfatiglandales bacteria were strongly enriched in the benzene-degrading culture at 70°C and in the naphthalene-degrading culture at 50°C. Both bacteria encode almost complete pathways for UAH degradation and for downstream degradation. They likely activate benzene via methylation, and naphthalene via direct carboxylation, respectively. The two species constitute the first thermophilic UAH degraders of the Desulfatiglandales. In the naphthalene-degrading culture incubated at 70°C, a Dehalococcoidia bacterium became enriched, which encoded a partial pathway for UAH degradation. Comparison of enriched bacteria with related genomes from environmental samples indicated that pathways for benzene degradation are widely distributed, while thermophily and capacity for naphthalene activation are rare. Our study highlights the capacities of uncultured thermophilic microbes for UAH degradation in petroleum reservoirs and in contaminated environments.

Exploring natural hydrogen hotspots: a review and soil-gas survey design for identifying seepage

Exploration for natural hydrogen seepages has grown rapidly, with surface seepages being seen as a primary indication of an underlying resource. While soil gas sampling has proven successful in detecting hydrogen in the soil, current understanding of hydrogen in the subsurface remains incomplete, with various potential sources of origin. This paper presents a selected review of published hydrogen hotspots around the world, examining their distribution with respect to two main features commonly associated with natural seepages: sub-circular depressions (SCD) and fault zones. Based on the findings, the paper proposes a conceptual soil-gas survey design for efficiently identifying potential hydrogen hotspots. The proposed scheme is tested on a SCD and a fault zone located in Western Australia. The study findings near the Perth Basin and the Yilgarn Craton highlight the presence of anthropogenic artifacts in hydrogen measurement, necessitating further investigation to constrain the possible sources of hydrogen generation. The study of the SCD in the Perth Basin supports the development of a statistical understanding of hydrogen distribution around surface features associated with hydrogen hotspots. Such a framework can guide soil-gas surveys and target areas with a higher likelihood of detecting natural hydrogen seepage. By addressing these points, prospective areas for natural hydrogen seepage can be better identified and evaluated, ultimately contributing to the development of hydrogen as a sustainable energy resource. Thematic collection: This article is part of the Hydrogen as a future energy source collection available at: https://www.lyellcollection.org/topic/collections/hydrogen