Seepage Areas Research Articles

Tracing the Century-Long Evolution of Microplastics Deposition in a Cold Seep.

Microplastic (MP) pollution is one of the greatest threats to marine ecosystems. Cold seeps are characterized by methane-rich fluid seepage fueling one of the richest ecosystems on the seafloor, and there are approximately more than 900 cold seeps globally. While the long-term evolution of MPs in cold seeps remains unclear. Here, how MPs have been deposited in the Haima cold seep since the invention of plastics is demonstrated. It is found that the burial rates of MPs in the non-seepage areas significantly increased since the massive global use of plastics in the 1930s, nevertheless, the burial rates and abundance of MPs in the methane seepage areas are much lower than the non-seepage area of the cold seep, suggesting the degradation potential of MPs in cold seeps. More MP-degrading microorganism populations and functional genes are discovered in methane seepage areas to support this discovery. It is further investigated that the upwelling fluid seepage facilitated the fragmentation and degradation behaviors of MPs. Risk assessment indicated that long-term transport and transformation of MPs in the deeper sediments can reduce the potential environmental and ecological risks. The findings illuminated the need to determine fundamental strategies for sustainable marine plastic pollution mitigation in the natural deep-sea environments.

CAGE16-5 Cruise Report: ROV-based Geological and Biological Investigations of Methane Seeps at Prins Karls Forland, Storfjordrenna Pingos and Bjørnøyrenna Craters

The cruise was an activity in of the Centre of Excellence for Gas Hydrate, Environment and Climate (CAGE) at UiT – The Arctic University of Norway. The overall aim of the cruise was to utilize the NTNU/AMOS SK30k ROV for seafloor mapping and targeted sample collection at selected CAGE sites, focusing on methane seepage areas west and south of Svalbard. More specific objectives of the cruise were to: Use an ROV-mounted multibeam system to acquire very high resolution (10cm) seabed bathymetry in areas of methane seepsConduct detailed visual seabed surveys for habitat mapping and photomosaicking at specific seep featuresCollect seabed samples of authigenic carbontate crusts, sediments, microbes, foraminifera and macro organisms associated with methane seeps from the ROV, and complimented with more traditional sampling methodsContinue time series investigations of water column measurements of methane concentrations, and of methane oxidizing microbes in the seawaterNet sampling for planktic forams at seeps Sampling activities were designed with a multi-disciplinary approach, with research groups from all CAGE work packages working together in the same locations to develop a holistic understanding of the geological, oceanographic and biological components at key methane seep sites. This cruise prioritized the acquisition of information for mapping seabed features and habitat characterizations (e.g. photomosaicking, visual information) combined with in-situ site sampling using ROV technologies, and complimented by our ‘traditional’ technologies (e.g. CTD, net, and coring devices). With these objectives in mind, the strategy for each of the selected locations is to first carry out visual survey work to acquire framework measurements and data to be of use for all groups within CAGE, followed by a consolidated sampling plan to satisfy the needs of individual researchers for sample material The cruise may be known as: CAGE16_5

Macrofauna community of the cold seep area at Site F, South China Sea

A cold seep is one of the typical deep-sea chemical energy ecosystems and a hotspot for studying unique life processes and biogeochemical cycles in the deep sea. Macrofauna, which is one of the most important components of the cold seep ecosystem, has not been thoroughly studied. We examined the macrofauna community at Site F using images collected in 2016 by an imaging and laser profiling system and biological samples collected in 2020 and 2021 by TV grab and a remotely operated vehicle. In total, 41 species were found. The overall number of macrofauna identified at Site F (20,000 m2) reached 252,943 individuals, and the biomass reached 726.15 kg by dry weight. As the dominant species, Gigantidas platifrons and Shinkaia crosnieri reached their highest densities of 629 and 396 individuals/m2, respectively. The comparisons between different stations revealed that the diversity and density, even the biomass of dominant species, were much higher in the south than in the north at Site F in 2020. Correlation analysis showed that methane had a positive effect on macrofauna density. Compared with S. crosnieri, G. platifrons seems to be more adapted to the harsh cold seep environment. Methane consumption rates of the dominant species show that macrofauna are important in influencing seafloor methane fluxes. Our findings provide valuable insights into the ecology, community structure, and biota-environment interaction in the cold seep at Site F.

CAGE20-7 Cruise Report: Sediment and water column analyses around flares at Norskebanken, Hinlopen and offshore Prins Karls Forland

During the cruise CAGE 20-7 (November 2nd to 16th 2020), we observed and investigated a large active methane seepage area south from the Yermak plateau (Northern Svalbard), in particular to characterize the water column and the sediment near known flares in Norskebanken (Geissler et al., 2016). Some flares were targeted for gas composition, DNA and bubble size distribution. The combination of the R/V Kronprins Haakon and the ROV ÆGIR 6000 from the Norwegian Marine Robotics Laboratory at the University of Bergen allowed this investigation to happen in this rough environment, while collecting invaluable data from the ROV. The cruise may be known as: CAGE20_7

CAGE 20-1 Cruise Report: K-lander recovery and water column survey offshore Svalbard and in the Barents Sea

The cruise was conducted from June 22nd to July 1th 2020 as part of the Centre of Excellence for Arctic Gas Hydrate, Environment and Climate (CAGE) at UiT – The Arctic University of Norway. The main objective of the research cruise was to recover the K-lander that was deployed offshore Prins Karls Forland on an extensive methane seepage area. The sub-objective was to performed single and multibeam surveys around the lander in order to locate the origin of the signal seen in the collected data, and map the seepages to compare with our horizontally-looking multibeam mounted on the lander. In addition, we collected water from Niskin bottles during CTD casts to measure methane concentration in the water column along and across the lander. Other areas of interest were the “MASOX” site, and other sites where methane seepages are suspected
 The cruise may be known as: CAGE20_1

Novel and unusual genes for nitrogen and metal cycling in Planctomycetota- and KSB1-affiliated metagenome-assembled genomes reconstructed from a marine subsea tunnel.

The Oslofjord subsea road tunnel is a unique environment in which the typically anoxic marine deep subsurface is exposed to oxygen. Concrete biodeterioration and steel corrosion in the tunnel have been linked to the growth of iron- and manganese-oxidizing biofilms in areas of saline water seepage. Surprisingly, previous 16S rRNA gene surveys of biofilm samples revealed microbial communities dominated by sequences affiliated with nitrogen-cycling microorganisms. This study aimed to identify microbial genomes with metabolic potential for novel nitrogen- and metal-cycling reactions, representing biofilm microorganisms that could link these cycles and play a role in concrete biodeterioration. We reconstructed 33 abundant, novel metagenome-assembled genomes (MAGs) affiliated with the phylum Planctomycetota and the candidate phylum KSB1. We identified novel and unusual genes and gene clusters in these MAGs related to anaerobic ammonium oxidation, nitrite oxidation, and other nitrogen-cycling reactions. Additionally, 26 of 33 MAGs also had the potential for iron, manganese, and arsenite cycling, suggesting that bacteria represented by these genomes might couple these reactions. Our results expand the diversity of microorganisms putatively involved in nitrogen and metal cycling, and contribute to our understanding of potential biofilm impacts on built infrastructure.

The composition of gas emissions at Petite Terre (Mayotte, Comoros): inference on magmatic fingerprints

The Comoros archipelago is an active geodynamic region located in the Mozambique Channel between East continental Africa and Madagascar. The archipelago results from intra-plate volcanism, the most recent eruptions having occurred on the youngest island of Grande Comore and on the oldest one of Mayotte. Since 2018, the eastern submarine flank of Mayotte has been the site of one of the largest recent eruptive events on Earth in terms of erupted lava volume. On land, the most recent volcanic activity occurred in Holocene on the eastern side of Mayotte, corresponding to the small Petite Terre Island, where two main and persistent gas seep areas are present (Airport Beach, namely BAS, and Dziani Dzaha intracrateric lake). The large submarine eruption at the feet of Mayotte (50 km offshore; 3.5 km b.s.l.) is associated with deep (mantle level) seismic activity closer to the coast (5–15 km offshore) possibly corresponding to a single and large magmatic plumbing system. Our study aims at characterizing the chemical and isotopic composition of gas seeps on land and assesses their potential link with the magmatic plumbing system feeding the Mayotte volcanic ridge and the recent submarine activity. Data from bubbling gases collected between 2018 and 2021 are discussed and compared with older datasets acquired between 2005 and 2016 from different research teams. The relation between 3 He/ 4 He and δ 13 C-CO 2 shows a clear magmatic origin for Mayotte bubbling gases, while the variable proportions and isotopic signature of CH 4 is related to the occurrence of both biogenic and abiogenic sources of methane. Our new dataset points to a time-decreasing influence of the recent seismo-volcanic activity at Mayotte on the composition of hydrothermal fluids on land, whose equilibrium temperature steadily decreases since 2018. The increased knowledge on the gas-geochemistry at Mayotte makes the results of this work of potential support for volcanic and environmental monitoring programs.

Laboratory study of the factors affecting hydraulic fracturing effect for inter-salt oil shale layers, Qianjiang Depression, China

This study aims to investigate the potential factors affecting hydraulic fracturing of inter-salt oil shale reservoirs in the Qianjiang Depression, China. Using the inter-salt shale samples, the re-crystallization seepage tests, rock mechanical tests under high temperature and pressure, salt rock creep tests, and direct shear tests were conducted. The testing results suggest several major factors that affect hydraulic fracturing effects in the end. First, the seepage of reservoir and fracturing fluid through hydraulic fractures leads to salt dissolution and crystallization, reducing the effective seepage area of fractures. Second, the salt crystal may block the pore throats or micro fractures after brine invades the shale, decreasing the overall permeability. Third, the low strength and obvious plasticity of inter-salt shale and the strong creep characteristics of salt rock raise difficulties for proppant to effectively support fracture walls, thereby sharply narrowing the hydraulic fracture width. Lastly, the weak interfaces (bedding planes and lithology interfaces) in inter-salt oil shale reservoirs restrict the height of hydraulic fractures, resulting in the disconnection of seepage channels between multiple inter-salt shale reservoirs. Thus, several factors together reduce reservoir permeability, weaken the fluid flow capacity in the fracture, narrow the fracture width, and limit the effective stimulation volume, resulting in weaken the effect hydraulic fracturing.

The development and applications of a controllable lander for in-situ, long-term observation of deep sea chemosynthetic communities

Understanding the evolution of chemosynthetic communities and environmental changes near fluid seepages in the deep sea requires in-situ long-term observation data. However, in-situ detection or sampling for the investigation of cold seeps, hydrothermal vents, and nearby chemosynthetic ecosystems, by manned submersibles and remotely operated vehicles (ROVs), has great restrictions in terms of time. The observation parameters of a free-fall mode Lander cannot be adjusted in real time because there is no communication channel once the Lander is separated from the vessel. A long-term ocean observation platform (LOOP), that uses a new controllable mode for launching and recovery with the aid of a research vessel and submarine vehicles, has been developed and used in the cold seep area of the South China Sea. The LOOP can be operated in an online real-time control mode allowing landing site selection and adjustment of observation parameters during the launching process, with subsequent switched to an offline stand-alone operation mode for long-term, continuous observation. The effective observation times were 375 days and 414 days, respectively, during the 2016 and 2018 deployments in the cold seep area in the South China Sea. Results of these deployments show that salinity and dissolved oxygen parameters have strong spatial heterogeneity in both the horizontal and vertical directions within the cold seep vent. The spatial heterogeneity of environmental parameters may be one of the main driving factors for the uneven spatial distribution of chemosynthetic communities in cold seep areas. Overall, the LOOP provides an innovative and controllable launching and recovery mode and is expected to become a universal underwater observation platform for in-situ, long-term, and continuous data acquisition.

Yam Seep at Four-Way Closure Ridge: a prominent active gas seep system at the accretionary wedge SW offshore Taiwan

Hydroacoustic surveys at the accretionary wedge southwest of Taiwan reveal a confined active hydrocarbon seepage area of ~ 49,000 m2 in ~ 1350 m water depth on the northern crest of the Four-Way Closure Ridge, which we call Yam Seep. In this study, multibeam and side-scan sonar data acquired during surveys with an autonomous underwater vehicle during an expedition with R/V Ocean Researcher I in 2017 showed that the area is characterized by rough topography and high seafloor backscatter. Seafloor observations with a video sled and sediment sampling with gravity corers and the MeBo seafloor drill rig during an expedition with R/V SONNE in 2018 revealed that the area is almost entirely covered by intensely fractured methane-derived carbonates, which indicate that seepage has been ongoing for thousands of years. Hydroacoustic anomalies (‘flares’) in the water column indicated the presence of several gas bubble emission sites mostly at the center and eastern flank of the area in 2019. Drilling through massive carbonates in the northwestern part of Yam Seep induced free gas escape from a depth of ~ 5.1 m. This suggests the presence of gas hydrates in the subsurface as the seep area is located well within the gas hydrate stability zone. The inter-disciplinary investigations of the Yam Seep demonstrate that upward migration of light hydrocarbons and seafloor discharge has a considerable influence on the seabed properties.

CAGE18-2 Cruise Report: LoVe site – exploration around node 7

The cruise was conducted from May 20th to 27th 2018 as part of the Centre of Excellence for Arctic Gas Hydrate, Environment and Climate (CAGE) at UiT – The Arctic University of Norway.
 The main goal of the cruise was to explore the area around Node 7 as part of the LoVe (Lofoten-Vesterålen) observatory. The first phase of the LoVe project was founded by Statoil in was first launched in 2013 to observe a cold coral reef. This area is known to be an oceanographic hotspot because the shelf is very narrow and northern drift of warm Atlantic water is concentrated and very dynamic in this area. It is also a biological hotspot because the large oceanic fish stocks are passing through or spawn in the area. It is finally an economic hotspot because the area is expected to hold large oil and gas resources but exploitation of these resources is controversial because of the importance for fish and fishermen in this region. The observatory has 12 sensors on the platform today including a camera looking at the coral reef and echosounders to study the biology.
 The second phase of LoVe was granted by the Research Council of Norway in 2015 through the Infrastructure programme, with a network of nodes crossing the main oceanographic and biological processes. The various nodes of the planned transect have specific objectives, and in particular, node 7 is located on top of methane seepages which CAGE is in charge.
 The present cruise aimed at performing echosounder and multibeam surveys as well as performing water samples and CTD casts around node 7 and known seepage area. The addressed scientific topics include quantification of methane concentration in the water column, temperature and salinity (via CTD casts), echosounder and multibeam signals and current (amplitude and direction)
 The cruise may be known as: CAGE18_2

CAGE21-6 Cruise Report: Hydrocarbon leakage in Hopendjupet, central Barents Sea

CAGE21-6 will visit the Hjopendjupet Seepage area between 5-16th December and use an ROV to study the seafloor for the first time. The cruise may be known as: CAGE21_6

Design and study of a deep-sea multi-depth in-situ pore water pressure-retaining sampler

A high-standard pore water sampling in deep-sea sediments is essential for scientific and technical studies such as determining geochemical anomalies on the seafloor. This paper designed a multi-depth in-situ pore water pressure-retaining sampler (MIPPS). It can sample deep-sea in situ pore water with multiple depths, high resolution, and low disturbance. We evaluated the indicators and functions of the sampler through simulation calculations, laboratory, offshore and deep-sea experiments. The diffusion between pore water and deionized water was determined using Ansys Fluent simulation to select a suitable tube to reduce contamination. The pressure test shows that the sampler has a pressure-retaining capacity of 30 MPa. The experiments show the laboratory sampling rate in sediment at different temperatures. Furthermore, in the offshore experiment, we analyze the reasons for the decrease in the offshore sampling rate. Finally, the sampler was carried on board the heavy-duty ROV-Jellyfish for a deep-sea experiment in the South China Sea. The deep-sea experiment’s success indicates that the MIPPS is accurate and trustworthy in practice. Then the sampler continued to be used for the sea area of methane seepage for in-depth scientific applications.

Degradation potential of alkanes by diverse oil-degrading bacteria from deep-sea sediments of Haima cold seep areas, South China Sea.

Marine oil spills are a significant concern worldwide, destroying the ecological environment and threatening the survival of marine life. Various oil-degrading bacteria have been widely reported in marine environments in response to marine oil pollution. However, little information is known about culturable oil-degrading bacteria in cold seep of the deep-sea environments, which are rich in hydrocarbons. This study enriched five oil-degrading consortia from sediments collected from the Haima cold seep areas of the South China Sea. Parvibaculum, Erythrobacter, Acinetobacter, Alcanivorax, Pseudomonas, Marinobacter, Halomonas, and Idiomarina were the dominant genera. Further results of bacterial growth and degradation ability tests indicated seven efficient alkane-degrading bacteria belonging to Acinetobacter, Alcanivorax, Kangiella, Limimaricola, Marinobacter, Flavobacterium, and Paracoccus, whose degradation rates were higher in crude oil (70.3-78.0%) than that in diesel oil (62.7-66.3%). From the view of carbon chain length, alkane degradation rates were medium chains > long chains > short chains. In addition, Kangiella aquimarina F7, Acinetobacter venetianus F1, Limimaricola variabilis F8, Marinobacter nauticus J5, Flavobacterium sediminis N3, and Paracoccus sediminilitoris N6 were first identified as oil-degrading bacteria from deep-sea environments. This study will provide insight into the bacterial community structures and oil-degrading bacterial diversity in the Haima cold seep areas, South China Sea, and offer bacterial resources to oil bioremediation applications.

Numerical Simulation of Hydraulic Fracturing in Unconventional Reservoirs

Hydraulic fracturing is a well-stimulation technique that uses a large amount of water mixed with proppants at high pressure to enhance and boost oil and gas production. Proppants, in conjunction with water, facilitate the cracking process, acting as a catalyst for the oil and gas to pass through the formation and into the producing well. The primary goal of this research is to look into the parameters that influence hydraulic fracturing quality. Moreover, such parameters that improve the productivity of oil in unconventional reservoirs are evaluated. The field properties of the Eagle Ford Shale were used to create a geological model on the Navigator software for this purpose. This software is used to simulate three different horizontal and vertical wells to observe the production of oil and gas. Then, hydraulic fracturing is performed on the same wells with different scenarios using three parameters, namely the length of fracture, the width of fracture, and the height of fracture. These parameters are selected because the usage of proppants can be dependent on them. The findings are quite convincing and demonstrate the importance of hydraulic fracturing in an unconventional reservoir. Besides, it is observed that the greater the width, length, or height of the fracture, the greater the productivity of oil and gas in an unconventional reservoir due to the increment of the seepage area of the hydrocarbons. Thus, hydraulic fracturing can make any potential unconventional reservoir economically viable.

Novel use of unique minerals to reveal an intensified methane seep during the last glacial period in the South China Sea

Globally, research aiming to reveal the unique biogeochemical processes and gas hydrate potential in methane seep areas is well established. Furthermore, methane seeps discovered in the South China Sea (SCS) have been widely studied and have achieved significant results. Herein, by systematically analyzing sedimentary samples from the Shenhu area, SCS, we discovered a methane seep that was once active during the last glacial period, particularly the Last Glacial Maximum (LGM) period, and fixed at the seafloor for ∼10 ka. This discovery was achieved by integrating the features of the glauconite within the foraminifera chamber, different morphologies of pyrites, and unique framboid goethites (pyrite pseudomorphs). In addition, this study accounted for the high chromium-reducible sulfur content and extremely negative δ34S values (from −50.78 to −46.92%) between 121 and 231 cmbsf, the Mo content and its correlation with total sulfur (TS) and total organic carbon (TOC), the TS/TOC ratios of sediments, the results of AMS 14C dating, and the results of planktonic foraminifera analysis in the case of carbon and oxygen isotopes. Glauconite, which is usually considered a product associated with transgressive deposits and condensed sections, is widely found in warm climatic intervals. However, these intervals are generally associated with methane emission events. Thus, our results demonstrate another mechanism for the formation of glauconite in methane seeps during the LGM. Furthermore, the existence of framboid goethites implies that this methane seep has been subsiding since the end of the LGM and that few pyrites that formed previously were reoxidized. Notably, this study is the first to report a systematic investigation of methane seep activity during the last glacial period by the indication of authigenic minerals, such as glauconite and framboid goethite, in the SCS. Overall, our results show a direct relationship between methane seep activity and climatic variation.

Extraction of Submarine Gas Plume Based on Multibeam Water Column Point Cloud Model

The gas plume is a direct manifestation of sea cold seep and one of the most significant symbol indicators of the presence of gas hydrate reservoirs. The multibeam water column (MWC) data can be used to extract and identify the gas plume efficiently and accurately. The current research methods mostly start from the perspective of image theory, which cannot identify the three-dimensional (3D) spatial structure features of gas plumes, reducing the efficiency and accuracy of detection. Therefore, this paper proposes a method for identifying and extracting the gas plume based on an MWC point cloud model, which calculates the spatially resolved homing of MWC data and constructs a 3D point cloud model of MWC containing acoustic reflection intensity information. It first performs noise suppression of the 3D point cloud of the MWC based on the symmetric subtraction and Otsu algorithm by leveraging the noise distribution of the MWC and the reflection intensity characteristics of the gas plume. Then, it extracts the point cloud clusters containing the gas plume based on Density-Based Spatial Clustering of Applications with Noise (DBSCAN) according to the density difference between the gas plume point cloud and the background MWC point cloud and next identifies the point cloud clusters by feature matching based on fast point feature histograms (FPFHs). Finally, it extracts the gas plume point cloud set in the MWC. As evidenced by the MWC data collected from gas hydrate enrichment zones in the Gulf of Mexico, the location of gas plume extracted by this method is highly consistent with that of gas leakage points measured during the cruise. Using this method, we obtained the point cloud data set of gas plume for the first time and accurately characterized the 3D spatial morphology of the subsea gas plume, providing technical support for gas hydrate exploration, subsea gas seepage area delineation, and subsea seepage gas flux estimation.

Experimental Study on Grouting and Flow Characteristics of Rough Vertical Fractures

It is of great engineering significance to study the seepage characteristics and flow field distribution of rough fractured rock masses for grouting to stop leakage. Through the visual fracture seepage test device we developed, the visual seepage characteristics of tension fractures under vertical angles and different stress paths of grout and water were studied. Through silica gel secondary mould turning technology, the fracture morphology is accurately reprinted; based on GIS simulation technology, the visualization of the fracture surface spatial data is realized; the actual seepage area and flow path of the fluid are measured accurately by using digital image self-recognition technology, and the variation law of the grout and water seepage area under the coupling of normal stress and water pressure is obtained. Through visualization, it is pointed out that, with the increase of normal stress, the fracture water can be divided into three stages, archipelago flow, transition flow, and groove flow, while the grout has no capillary permeability and no archipelago flow effect because of its high viscosity. The critical point of grout antiseepage is defined and calibrated by data. Based on the analysis of the cross-sectional velocity of the groove flow, it is pointed out that the relationship between the velocity on the flow path and JRC is an exponential function. The main flow path is mainly distributed in the area where the JRC is relatively small. As the normal stress increases, the first deflection point of the grout flow path appears in the maximum region of JRC (6.42); the secondary deflection point appears in the second largest region of the flow path JRC (4.53), and the fluid of deflection point has the maximum kinetic energy on the main flow path. The current study can accurately obtain the relevant parameters of vertical fracture grouting seepage characteristics and provide theoretical guidance for solving the key scientific problems in grouting engineering, such as invisible flow paths and unmeasurable velocity vectors.

Shell-bearing Gastropoda from the methane seeps and hydrothermal vents of the Bering Sea: A preliminary description

The first description of the fauna of shell-bearing gastropod from chemosynthesis-based communities of the Bering Sea is given. The work includes materials collected during the cruises of the RV Akademik M.A. Lavrentyev in 2016 and 2018 in two types of the reducing biotopes: hydrothermal fields on the underwater Piip Volcano and the methane seeps on the Koryak slope of the Bering Sea. The Piip Volcano (∼ 368–495 m) is the northernmost (55°22’ – 55°24’ N) hydrothermal region in the Pacific. Methane seep fields of the Koryak slope found between 400 and 700 m depth are the northernmost chemosynthesis-based habitats known to date in the Pacific (60°49–61°10). In total, 27 recognizible taxonomic units (RTUs) of shell-bearing gastropods were identified from both areas, at least six of them presumably belong to species new to science. Also, five species are new to the fauna of the Bering Sea and adjacent areas of the Pacific Ocean. Only nine RTUs were found on the Piip Volcano, among which there was one species, Provanna sp. nov., belonging to the family known only from chemosynthesis-based communities and another species, Parvaplustrimwareni, was potentially obligate for chemosynthesis-based communities. Nineteen RTUs have been identified in the methane seeps of the Koryak slope, however no taxa specific for chemosynthesis-based communities had been recorded. Gastropods have less aggregated population structure on the Koryak slope than on the Piip Volcano, where four times as many specimens have been collected. In general, the pattern of distribution of taxonomic and functional groups in the area of methane seeps of the Koryak slope is presumably the same as in the background communities while in the hydrothermal zone of the Piip Volcano it is similar to other types of extreme communities. Majority of gastropods from both regions feed on detritus or invertebrates. Most RTUs have a lecitothropic protoconch, which corresponds to a short period or absence of pelagic stage in their development. This makes the species associations of gastropods vulnerable.

Geophysical studies of permafrost conditions of the Kangalassky coal mine dam

Problem statement. Geophysical studies of the ground dam body and base at the Kangalassky coal mine were carried out as part of monitoring related to the dam’s destruction, propagation of flank release fractures parallel to the ledge, and water seepage into the open pit. The main function of the ground dam is to protect the mining site from the inflow of surface water and preserve frozen rocks of the geological base. The mine workings of the coal mine are watered due to precipitation in the summer, snow melting and frozen rock thawing in the spring. Research objective is to assess the permafrost-ground conditions of the site according to geophysical methods and establish the boundaries of seepage flows that seep through the body and base of the ground dam. Methods of research. Electrical sounding at the dam site were performed by the electrical resistivity tomography method. The research was carried out with the Omega-48 equipment. Ground Penetrating Radar (GPR) study was carried out with a georadar of the OKO-2 series (AB-250M, central frequency 250 MHz). Georeferencing for comparative analysis of GPR parameters and positioning was carried out by the Geobox Fora Smart high-precision (geodetic) GNSS receiver. The cryogenic condition of rock was determined from the drilling data and FLIR SC660 thermal imaging camera data (device by the Shared core facilities of the Federal Research Center “Yakutsk Science Center SB RAS”, grant no. 13.TsKP.21.0016). Results. The results of GPR studies by the method of multi-season measurements in spring and autumn made it possible to objectively assess open pit permafrost conditions that reflect rock mass condition features (frozen or thawed rocks) and the position of the weakness zones (seepage areas and the presence of waterlogged soils). The analysis of geoelectric sections has identified anomalous areas with reduced electrical resistivity interpreted as zones of suprapermafrost surface water penetration into the embankment body with further dam base soil erosion. Possible surface waters migration routes and frozen rock degradation areas have also been identified. Scope of results. The described technique can be used at the enterprises of the mining complex in the North of Russia for engineering-geological and geocryological monitoring of mining and engineering structures.