Water Sediment Research Articles

Palaeoenvironmental implications and genesis of lacustrine Lower Triassic giant ooids

The sedimentary environment and mechanisms of formation of giant ooids (> 2 mm) are not well understood. Here, we use petrographical, mineralogical and geochemical data of giant ooids from the Lower Triassic Buntsandstein Formation of central Germany to develop a coherent formation model. Structural preservation of calcite crystallites in ooid cortices in combination with comparatively low strontium concentrations (< 545 μg/g) and the absence of dolomite in the cortex suggest a primary low-Mg calcite composition. Shale-normalised rare earth elements plus yttrium (REE + Y) patterns lack a pronounced heavy REE over light REE enrichment and show a positive cerium anomaly (Ce/Ce*SN = 1.9–3.9). Together with a missing yttrium anomaly and low Y/Ho ratios (< 40), these data are largely consistent with ooid formation in a lacustrine environment. Positive cerium and lanthanum anomalies further point to formation and deposition in an alkaline to hypersaline playa-lake environment. Based on our findings, a five-stage formation model is proposed. We suggest nucleus formation by microbial spheres, followed by calcite crystal nucleation on biofilm templates at the sediment–water interface, and crystal/cortex growth inside the sediment pile. The spherical ooid form is achieved by wave-induced physical rolling motion after exhumation. Ooid growth ceases when the ooid reaches a critical size (here 4 mm), depending on local hydrodynamic properties. Inhomogeneous crystal growth and the inclusion of exogenous particles lead to structural and geochemical anomalies in the ooid cortex. Results presented here have far-reaching implications for the application of REE and other trace elements as environmental proxies in ancient carbonates.

Potential Socioeconomic Impacts of the Grand Ethiopian Renaissance Dam Operation on Inland Fisheries in the High Aswan Dam Reservoir

ABSTRACTThe High Aswan Dam (HAD) reservoir is considered as the most vital reservoir in Egypt and as a source of freshwater fish. It contributes 69% of the total inland fisheries production. The annual fish production from the HAD reservoir is estimated by the General Authority for Fishery Resources Development (GAFRD) as 12,000 ton/year. The HAD reservoir is the main source of freshwater fisheries in Egypt. That amount of fish in the reservoir guarantees a constant source of income and employment since the HAD establishment. Fish production is significantly affected by three environmental key parameters: water level fluctuation, water temperature change, and sedimentation amount. Any alteration in these three parameters will significantly affect the social and economic status of the HAD reservoir fisheries. This study aims to quantify the potential socioeconomic consequences of the Grand Ethiopian Renaissance Dam (GERD) operation on the HAD reservoir fishery. To quantify these potential impacts, this research utilizes pre‐GERD socioeconomic data gathered by national and international organizations such as WorldFish (https://worldfishcenter.org/) and GAFRD, to establish baseline data. The change in predicted socioeconomic assessment is carried out based on the water level, temperature change, and sedimentation, after the GERD operation. A significant reduction in fish production is anticipated, with an estimated average decline by 48.5% compared to current production rates. This decline is expected to lead to a decrease in the overall socioeconomic value of the HAD reservoir fishery, potentially resulting in job losses for 25% to 72% of the fishermen and distributors employees. The total fishing income is expected to decrease, because of the decrease in fish production. The research findings highlight the importance of policy considerations to mitigate the possible socioeconomic impacts. Potential policy interventions could include stricter fishing regulations, alternative livelihood programs for affected communities, and collaborative management strategies with upstream dam operators.

Spatiotemporal Changes and Trade-Offs/Synergies of Waterfront Ecosystem Services Globally

The types of ecosystem services are complex and diverse. This study estimated four ecosystem services, their trade-offs, and their synergistic outcomes in 2010, 2015, and 2020 using the InVEST model. Globally, results showed that waterfront ecosystem services are high (low) in the north (south), and that high-value areas are mainly in Sweden and Finland in Europe; the Congo in Africa; Russia, Southwest China, and Indonesia in Asia; the Northwestern United States and Canada in North America, and northeastern Peru and northwestern Brazil in South America. Overall, ecosystem services changed little during 2010–2020. Additionally, a notable trade-off was found between water yield and habitat quality, and strong synergies were found between water yield and carbon storage and sequestration, water yield and sediment delivery ratio, carbon storage and sequestration and sediment delivery ratio, and carbon storage and habitat quality. The results of this study could help promote sustainable development of waterfronts globally.

Surface water infiltration and sediment degradation shaping dissolved organic matter in groundwater related to chronic kidney disease of unknown etiology

Surface water infiltration and sediment degradation shaping dissolved organic matter in groundwater related to chronic kidney disease of unknown etiology

Linkage detection between climate oscillations and water and sediment discharge of 10 rivers in Eastern China

Water discharge and sediment load are often controlled by a combination of factors. However, the relationship between water and sediment load changes and meteorological oscillations has rarely been explored for different river sizes. Explanations for the various responses of water-sediment changes to meteorological factors in different rivers is important for understanding global hydrology. In this study, we analyzed data from 2002-2022 using cross-wavelet and wavelet coherence in an attempt to characterize the effects of large-scale climatic oscillations on 10 rivers in eastern China. Comparing the results shows that water releases lag three months or more behind SST variations. It also oscillates interannually (mostly every 8-16 months). Most rivers runoff lags changes in PDO by three months or more. The impact of ENSO (El Niño-Southern Oscillation) on each river basin gradually decreases from south to north. The impacts on northern rivers such as the Yellow River, Huai Riverand Liao River are weaker. At the same time, the water discharge changes in the Pearl River and Minjiang River basins in southeastern China are extremely rapid and sensitive to ENSO events. Meanwhile, the impacts of ENSO on large rivers lasted throughout the study period, while the impacts of ENSO on smaller rivers had intermittent periods, and the response rates of geographically similar mountain and stream-type rivers were not the same. The effect of the PDO (Pacific Decadal Oscillation) warm and cold phases was different for each region. Our research contributes to understanding the relationship between rivers and climate oscillations, advancing Water-Sediment Balance and Global Sustainability—key goals of the United Nations 2030 Agenda for Sustainable Development.

A simple approach to quantifying whole‐lake methane ebullition and sedimentary methane production, and its application to the Canadian Lake Pulse dataset

AbstractAquatic sediments represent a key component for understanding CH4 dynamics and emission to the atmosphere. Once produced in the sediments, CH4 is released either by diffusion at the sediment–water interface or by bubbling out to the atmosphere when total gas pressure in the sediment exceeds local ambient pressure due to high CH4 production. Although bubbling is one of the dominant CH4 emission pathways in lakes, direct measurements of this flux are hampered by its high spatiotemporal variability and methodological limitations. Here, we develop a conceptual approach to quantify CH4 production in lake sediments and particularly its release as bubbles based on simple measurements of bubble gas content and depth. Its main assumptions were empirically tested using &gt; 200 long‐term bubble trap deployments collected from 4 temperate lakes. We then applied the developed methodology to a suite of 408 Canadian lakes to produce the first standardized large‐scale assessment of lakes CH4 ebullitive flux during summer. Our results show that lake sediments produced CH4 at a median rate of 3.3 mmol m−2 d−1 (ranged from 0.2 to 11.8 mmol m−2 d−1), releasing 33% via ebullition to the atmosphere. These rates are remarkably similar in magnitude to other regional estimates in the literature. Moreover, our approach revealed that catchment slope was an important determinant of both the lake‐wide ebullitive fluxes and the fraction of sediment CH4 production released as bubbles.

Congo River: Analysis of suspended sediment flux in a multichannel megasystem in Central Africa

Tropical mega rivers play a crucial role in transferring water and sediment to the oceans. The Congo River is the second largest in the world by volume of water, playing a significant role in the export of fresh water and sediment from the continent to the Atlantic Ocean. This paper aims to analyze the variability of the suspended sediment flux of the Congo River between 2005 and 2018. Suspended Sediment Concentration (SSC), water discharge and water level data were used at the Brazzaville station, which represents 97% of the basin area, and precipitation data for the entire basin. Solid discharge, specific sediment yield and denudation rate of the basin were estimated. The estimated water discharge was 41 268 m³.s-1 for the period between 1947 and 2023, with a bimodal river regime with a flood peak in December and a secondary peak in May. The mean annual SSC estimated for the Congo River was 27.20 mg.L-1. A moderate (r = 0.48) and weak (r = -0.26) correlation was observed between SSC and precipitation, and SSC and water level, respectively, possibly influenced by the basin's terrain characteristics. During the year, the Congo River transfers 33.66 × 106 ton.year-1 of sediment to the ocean, has a specific sediment yield of 9.62 ton.km-2.year-1 and a very low denudation rate (3.37 mm.ky-1).

Climatic and Anthropogenic Influences on Long-Term Discharge and Sediment Load Changes in the Second-Largest Peninsular Indian Catchment

In recent decades, understanding how climate variability and human activities drive long-term changes in river discharge and sediment load has become a crucial field of research in fluvial geomorphology, particularly for South Asia’s densely populated and environmentally sensitive regions. This study analyses spatio-temporal trends in water discharge (Qd) and sediment load (Qs) in the Krishna basin, Peninsular India’s second-largest catchment. Using nearly 50 years of daily discharge, sediment concentration, and rainfall data from the Central Water Commission (CWC) and India Meteorological Department (IMD), we applied Mann–Kendall, Pettitt tests, and double mass equations to detect long-term trends, abrupt changes, and the relative influence of climate and anthropogenic effects. Results showed a notable decline in the annual discharge, with 15 of 20 stations showing decreasing trends, especially along the Bhima, Ghataprabha, and lower Krishna rivers. The annual stream flow data showed a 53% decline in the mean Qd from 26.01 × 109 m3 year−1 before 2000 to 12.32 × 109 m3 year−1 after 2000 at the terminal station. Eight of ten gauging stations showed a significant decrease (p-value &lt; 0.05) in their annual sediment load, with a 76% reduction across the Krishna basin after its changepoint in 1983. The Pettitt test identified a statistically significant downward shift in discharge at seven stations. Double mass plots indicate that anthropogenic factors, such as large-scale reservoirs and water diversion, are the main contributors, accounting for 82.7% of sediment decline, with climatic factors contributing 17.1%. The combined trend analysis and double mass plots confirm these findings, underscoring the need for further study of human impacts on the basin’s hydro-geomorphology. This study offers a clear and robust approach to quantifying the relative effects of climate and human activities, providing a versatile framework that can enhance understanding in similar studies worldwide.

Methane and sulfide sulfur in water and bottom sediments of streams of the steppe zone of the European part of Russia

The results of long-term studies of the conjugate distribution of concentrations of methane (CH 4 ) and sulfide sulfur (S sulfide ) in bottom sediments of streams of the steppe zone of the European part of Russia are analyzed. In addition to CH 4 and S sulfide , Eh and pH values, humidity and density were determined in various sediment horizons; CH 4 , dry residue and pH values were determined in water. Concentrations of CH 4 in the water of watercourses vary from 0.1 to 2007.0 µl/l (median 24.3 µl/l), with the largest number of values (72 %) in the range 10.1–100.0 µl/l. The concentrations of CH 4 and Ssulfide in the bottom sediments of watercourses are quite high and vary, respectively, from 0.01 to 51.0 µg/g of wet sediment (median 1.35 µg/g) and from 0.001 to 4.50 mg/g of wet sediment (median 0.813 mg/g). Usually, there is an increase in CH 4 and S sulfide from the surface layer to the subsurface horizons, after which their concentrations decrease. The difference between the distribution of sulfides and the distribution of CH 4 is the more frequent occurrence of maximum concentrations of sulfides in less deep sediment horizons. Seasonal changes in the distribution of CH 4 and S sulfide along the vertical of sediments were recorded not only in terms of their concentrations, but also in the location of maximum and minimum values. There is a weak direct relationship between the concentrations of CH 4 and S sulfide , which indicates synchronous processes of formation of these gases in separate layers of sediments of the studied watercourses. The direct relationship established between the concentrations of CH 4 in water and the 0–2 cm layer of bottom sediments indicates sediments as an important source of CH 4 entering water and its emission into the atmosphere.

Geochemical distribution of elements in the environmental media from the surroundings of open pit areas

The results of geochemical investigations - carried out within the framework of the European project LIFE IP RESTART - in the degraded areas of the Kopriva (deposit of natural stone-limestone) and Lipovški vrh (deposit of limestone for industrial purposes) open pits are presented. There test sites of the installation of secondary raw materials (a mixture of recycled materials and mineral raw materials) with the aim of revitalizing degraded surfaces are planned. The main goal of this study is to define the baseline geochemical distribution of elements in environmental materials (rocks, soil, stream sediment and surface water) for the purpose of monitoring the potential environmental impacts of installed secondary raw materials. In rocks Ca content predominates due to the geological setting (predominantly limestone) of the studied areas. According to the legislative guidelines for soil, exceedances have been found for Pb in one sample (origin can be natural or anthropogenic) and Ni in two samples (presumably natural origin) from the area of Kopriva. In the area of Lipovški vrh in the stream Suhi Potok, higher contents of Mg, Na, Sr, Ca, Mn and S occur in the downstream sediment compared to upstream sediment. It is assumed higher contents occur due to anthropogenic contribution of carbonate material along the stream (washing of materials from nearby open pit and road). In the surface water of Suhi Potok, higher concentrations of S, Sr, B, U and Zn were determined. However, the concentrations did not exceed the legislative guidelines.

Spatial Trends of Cadmium and Zinc Concentrations in Water and Enrichments in Surficial Sediments within Nyanza (Winam) Gulf of Lake Victoria (East Africa)

Metal pollution contributes significantly to the environmental degradation of lake ecosystems. The study evaluated the spatial trends in cadmium and zinc concentrations in surface water, un-fractioned and the &lt;63µm grain size fraction (silt and clay) of surficial sediments within Nyanza Gulf, from lake monitoring stations in 2010 and 2012 surveys. Significantly higher Zn total concentrations were found in surface lake water compared to earlier surveys, but cadmium levels were low and not detectable as in previous studies. Variable contents of Zn and Cd were found in un-fractioned and finer sediment fractions. “Much higher sediment Cd contents were found in 2010 compared to other surveys. Major areas under river and urban influences recorded much higher sediment Cd contents than offshore sediments. However, there were no significant differences between Cd and Zn contents between the gulf and main lake zones. Cd sediment enrichment factors were highly variable compared to Zn, which showed a more uniform trend in most of the gulf areas, but Cd sediment enrichment factors appear to increase when compared to previous data. The spatial distribution of Cd and Zn in the surficial sediments show unpolluted to moderate pollution levels, according to geo-accumulation index. Only 4% of Zn samples exceeded the sediment quality threshold effect concentration (TEC) values, but all were below the mid-range effect values. Cadmium is a recognized toxicant and there are potential ecological concerns regarding the variable sediment Cd contents since it has been found previously in bioavailable forms in surficial sediments and 2% of the samples contained Cd (un-fractioned sediment) above the threshold effect concentration during the 2012 survey compared to 51 % in 2010, but none exceeded the severe effect levels”. Continuous monitoring of priority heavy metals is of relevance on the understanding of potential long-term ecological impacts to the lake ecosystem.

The Teichichnus Ichnofacies: Its neoichnological basis and identification in the rock record

AbstractResearch on the ichnology of brackish‐water environments began in the 1930s and has led to the identification of predictable infaunal patterns. Brackish‐water deposits characteristically display low‐diversity tracefossil assemblages consisting of both vertical and horizontal structures. These salinity‐reduced ecosystems are dominated by opportunistic euryhaline‐tolerant species. Osmoregulation‐related selective pressures lead to decreased diversity and an abundance of infaunal organisms. In environments with fluctuating or low salinity, fauna adopt r‐selected strategies and are characterized by rapid colonization dynamics, high population densities, elevated mortality rates and low‐diversity assemblages. Tides in brackish‐water settings contribute a plentiful food supply with tidal currents transporting marine‐sourced and terrestrially sourced organic matter that settles on the sediment–water interface during slack‐water periods. This increased food availability favours trophic generalists using various feeding strategies to exploit both intrastratal and surficial food resources. The ichnological characteristics of modern and ancient brackish‐water strata are used to propose the Teichichnus Ichnofacies; they are temporally and spatially recurrent and reflect the biology of brackish‐water settings. The Teichichnus Ichnofacies is recognized by reduced trace‐fossil diversity, smaller trace sizes, dominance of structures reflecting trophic generalist behaviours, sporadic distributions of ichnofossils, locally high bioturbation intensities and opportunistic colonization. This ichnofacies is characterized by trace fossils interpreted to be associated with surface deposit feeding, intrastratal deposit feeding and subordinate filter feeding.

Lithium extraction from low-quality brines.

In the quest for environmental sustainability, the rising demand for electric vehicles and renewable energy technologies has substantially increased the need for efficient lithium extraction methods. Traditional lithium production, relying on geographically concentrated hard-rock ores and salar brines, is associated with considerable energy consumption, greenhouse gas emissions, groundwater depletion and land disturbance, thereby posing notable environmental and supply chain challenges. On the other hand, low-quality brines-such as those found in sedimentary waters, geothermal fluids, oilfield-produced waters, seawater and some salar brines and salt lakes-hold large potential owing to their extensive reserves and widespread geographical distribution. However, extracting lithium from these sources presents technical challenges owing to low lithium concentrations and high magnesium-to-lithium ratios. This Review explores the latest advances and continuing challenges in lithium extraction from these demanding yet promising sources, covering a variety of methods, including precipitation, solvent extraction, sorption, membrane-based separation and electrochemical-based separation. Furthermore, we share perspectives on the future development of lithium extraction technologies, framed within the basic principles of separation processes. The aim is to encourage the development of innovative extraction methods capable of making use of the substantial potential of low-quality brines.

The Microfungal Communities in Deep-Sea Sediments from the Equatorial Atlantic

Microfungi of deep-sea sediments, and especially those several meters below the water–sediment interface, are poorly studied. In this work, for the first time, microfungal communities isolated by cultivation from deep-sea sediments of the eastern part of the Equatorial Atlantic (the Romanche and Chain Fracture Zones) were investigated. Fungi were isolated from sediments sampled at each of 12 stations from horizons 1.0–4.7 m below the sediment–water interface. To study microscopic fungi, one sediment horizon was isolated from each core. The fungal abundances were within the range of 0.0–3300.0 CFU g-1 sediment dry weight. A total of 19 fungal taxa from the phyla Ascomycota (18) and Basidiomycota (1) were identified, and Mycelia sterilia 1 strain was also isolated. Seven fungal species were encountered only once. In this case, the maximum similarity of species composition, in terms of the Bray – Curtis coefficient, was 57.14% (horizons 1.0 and 3.6 m, four common species). A comparison of the taxonomic structures of fungal communities from the study area was made with those from sediments of the Indian and Pacific Oceans and other areas of the Atlantic. The fungal communities from sediments in the study area were compared with those from the Indian and Pacific Oceans and other areas of the Atlantic. From the literature data and present study results, a list of fungal species with 180 names was compiled. The fungi belonged to 97 genera, 57 families, 32 orders and 13 classes of the phyla Ascomycota, Basidiomycota, and Mucoromycota. The diversity of fungal communities was assessed using indicators of taxonomic richness (number of taxa from different ranks), proportions (genera/families, species/families, species/genera), Average Taxonomic Distinctness index (AvTD, Δ+) and Variation in Taxonomic Distinctness index (VarTD, Λ+). Four and twelve fungal classes were identified in sediments in the Eastern Equatorial Atlantic and the Indian Ocean, respectively. The species/genera proportions in the communities varied from 1.33 (Indian Ocean) to 3.8 (other areas of the Atlantic Ocean). For the fungal communities of the Eastern Equatorial Atlantic, the AvTD index value was minimal (Δ+ = 50.19), the VarTD index was maximal (Λ+ = 945.38), and they were beyond the 95% confidence interval. This was due to the small number of the fungal classes and vertical and horizontal unevenness of species distribution along taxonomic branches, which was manifested in the dominance of species of the family Aspergillaceae (78.9% of the species in the class Saccharomycetes and Eurotiomycetes), only two species belonging to the classes Sordariomycetes and one species belonging to the class Microbotryomycetes (phylum Basidiomycota). Consequently, statistically significant differences were found between the taxonomic structures of the fungal communities of the Eastern Equatorial Atlantic and the other regions of the World Ocean, which are due to the insufficient amount of data obtained on the species composition of fungi in the sediments of this area. The study did not reveal any pattern in the change in the number of fungal species and their abundance in relation to the water characteristics (temperature, pH, and salinity), horizon depth in the sediment core, sediment type, or sampling station location in the Romanche and Chain Fracture Zones.

Chlorophyll in water and bottom sediments as an indicator of the trophic state of Busse Lagoon (Sakhalin Island)

New associated data on the content of chlorophyll a and its derivatives in the water and bottom sediments of Busse Lagoon (Sakhalin Island) have been obtained. Chlorophyll a and chlorophyll degradation products (Chl a + Ph) in the water column is represented predominantly by the active form (61.4 ± 1.1%), in bottom sediments – by a product of its degradation (84.7 ± 2.5%). The connection between pigments in water and bottom sediments, as well as the abiotic conditions of primary production, has been revealed. For the first time, for a unique reservoir characterized by overgrowth of aquatic vegetation, silt accumulation and regular death of aquatic organisms, the similarity of the average annual sedimentation rate in the lagoon with the ratio of pelagic and benthic pigments was shown. The prevailing importance of the biotic factor in the formation of trophic conditions has been established. Based on the average content of Chl a + Ph in water (4.1 ± 0.8 mg/dm3) and in bottom sediments (13.5 ± 4.0 μg/g d.s.), Busse Lagoon is a mesotrophic reservoir. Trophic state of benthic in the period 2013–2021 is preserved, remaining oligotrophic in the shallow coastal zone and mesotrophic in the central part of the lagoon.

Heavy metal characteristics and ecological threat assessment in water and sediments of Eniong Creek, Niger Delta, Nigeria

Heavy metal characteristics and ecological threat assessment in water and sediments of Eniong Creek, Nigeria was studied between August 2022 and January 2023 in 3 stations. Seven heavy metals were analyzed with standard methods and compared with quality Standard. Ecological threat was assessed in water using two metal pollution indices while six sediment quality assessment indices were used to access the sediment quality. Results showed that the mean concentrations of nickel, copper, cadmium and zinc in water sample exceeded the permissible limits set by National environmental (surface and groundwater) quality regulations for aquatic life, while copper and cadmium exceeded the permissible limits set by Canadian sediment standards quality for the protection of aquatic life in sediments in all the stations. The heavy metal pollution index (HPI) values exceeded the threshold (100) across the stations, ranging between 469.53 and 686.74 while comprehensive pollution index (CPI) ranged between 1.405 and 1.854, indicating moderate contaminated water. The sediment indices indicated that cadmium and copper were the major metallic pollutants. The indices indicated the following –contamination factor: copper (moderate) and cadmium (very high), degree of contamination (very high); ecological risk: cadmium and copper (high) while lead and zinc were moderate; potential ecological risk (high); quantification of contamination: cadmium and copper (anthropogenic); geo-accumulation index: cadmium (very highly polluted). The study revealed that the water body and sediments were polluted, attributed to anthropogenic activities.Keywords: Eniong Creek; Heavy Metals, Nigeria; Sediment; Water

Three-Dimensional Hydrodynamic Modelling to Estimate Sediment Rate in Lamong Bay

Abstract Lamong Bay Terminal, part of Tanjung Perak Port in Surabaya, functions as a container terminal. The port in the Surabaya area causes high ship traffic activity in the waters of Lamong Bay and sediment may be carried away from rivers heading towards the sea. The sedimentation process in waters can cause problems because it can cause shallowing of the waters, so it is necessary to maintain and monitor the depth of shipping lanes to maintain the safety of sea traffic. Therefore, understanding the hydrodynamics of seawater and sediment movement in the water region is necessary for successful dredging operations and assessing the impact of silt on port areas. In this research, the approach used to determine current patterns and sediment distribution was through the application of a numerical model with three– dimensional baroclinic hydrodynamic equations. The numerical modeling study in this research uses tidal data, sediment samples, salinity, and temperature to determine current patterns and the rate of sediment distribution. This process is carried out periodically and continuously as part of the evaluation of Lamong Bay Terminal. The results can serve as a reference for dredging planning to maintain the depth of the waters at the Lamong Bay Terminal. In this study, the highest current velocity was obtained at the time of spring tide reaching 0.9 ms−1 and at the neap tide of 0.4 ms−1. The sediment distribution pattern in the waters of Lamong Bay affected the existence of the pier and the morphological conditions of the seabed. The largest siltation or sedimentation that has occurred at Lamong Bay Port is 0.055 m/month near the jetty, thus depth monitoring is needed in this area, regularly. This study supports SDG 9 by advancing resilient infrastructure solutions to manage the sedimentation process in waters.

Rheological characterization and modeling of ultra-high-velocity fluidized submarine landslides

Submarine landslides are critical phenomena due to their potential to reshape seabed topography, trigger tsunamis, and compromise offshore infrastructure. Understanding the rheological properties, particularly shear stress and viscosity under high shear rates, is essential for comprehending the dynamics of these landslides, a topic often underexplored in previous research. This study explores the rheological behavior of fluidized submarine landslides, with a focus on in-site sediments from the South China Sea and the Western Pacific Ocean. Samples prepared with varying densities were subjected to extensive rheological testing in the laboratory and analyzed under shear rates of up to 2000 s−1. Results indicated that all samples exhibited non-Newtonian fluid characteristics, showing shear-thinning behavior at low shear rates and shear-thickening behavior at higher shear rates. This transition is attributed to the breakdown of internal sediment structures, leading to changes in viscosity. This study also found that higher water content generally results in lower yield stress and consistency coefficients, while increasing the shear rate reduces the nonlinearity of the fluid's behavior. To model this complex behavior, a piecewise rheological model based on the Herschel-Bulkley framework was proposed. This model effectively captures the variations in rheological properties across different shear rate stages, with critical shear rates influenced by the sediment type and water content. These findings contribute to a deeper understanding of submarine landslides under extreme conditions, and the proposed model offers a more accurate tool for predicting the behavior of fluidized submarine landslides.

Nitrogen, sulfur, iron, and microbial communities co-shape the seasonal biogeochemical behaviors of As and Sb in coastal tidal flat wetlands associated with rivers

Arsenic (As) and antimony (Sb) are affected by complex biogeochemical processes in coastal ecosystems. However, the influence of N, S, Fe, and microbial communities on the biogeochemistry of As and Sb in coastal tidal flat wetlands remain uncertain, particularly when rivers flow into these areas. This study combined diffusive gradients in the thin-film technique with high-throughput sequencing to investigate the release and vertical distribution of As and Sb in river and coastal tidal flat wetland sediments. The results indicated a distinct stratification phenomenon in the As release at depths ranging from 20 mm to −150 mm. At river sites, the release of As occurred in the upper layer (above −40 mm), with peak values of 4.3 and 9.3 μg/L at HS and SY sites in summer, respectively, likely due to anaerobic ammonium oxidation. In the lower layer (below −40 mm), both As and Sb were released, and this was possibly due to Fe reduction. However, at the coastal tidal flat sites, the release of As and Sb may have been driven by anaerobic ammonium oxidation, dissimilatory nitrate reduction to ammonium, sulfate reduction, and Fe reduction. At the river sites, As exhibited increased activity during the summer, and the residual forms were converted more easily into mobile forms. Sb remained relatively stable during both winter and summer. Conversely, both As and Sb primarily existed in residual forms and exhibited higher stability during summer in the coastal tidal flat sites. The microbial phyla Nitrospirota (3.6−7.0 %) and Acidobacteriota (9.5−10.2 %) were more prevalent at the river sites, whereas Desulfobacterota (8.8−12.0 %) and Firmicutes (0.13−27.9 %) were more prevalent at the coastal tidal flat sites. The bacterial genera involved in the N, S, and Fe transformation processes differed between the two sites, and they were primarily Thiobacillus, Limnobacter, and Sulfurovum at the river sites and Sva1033, Anaeromyxobacter, and Sva0485 at the coastal tidal flat sites. In this study, the microorganisms that mediated N, S, and Fe complex processes at various depths in the sediment–water interface were decoupled to elucidate the effect of these processes on the biogeochemical behavior of As and Sb as they move from rivers to coastal tidal flat wetlands.

Shewanella youngdeokensis sp. nov. Isolated from Marine Sediment and Sea Water of East Sea in Republic of Korea

The strain DAU334T, which was obtained from samples of sea water and sediments collected from the East Sea in the Republic of Korea, is a rod-shaped, Gram-stain-negative bacterium. It is facultative and positive for the oxidase and catalase enzymes. Based on the analysis of 16S rRNA sequences, it was determined that strain DAU334T had the highest degree of similarity to several strains of Shewanella species, i.e., S. schlegeliana HRKA1T (99%), S. halifaxensis HAE-EB4T (99%), S. pneumatophori SCRC-2738T (99%), S. sairae SM2-1T (99%), and S. marinintestina IK-1T (1419/1440, 99%), respectively. The complete genome sequence consisted of one contig with 4 343 646 bp, and the genome G+C content was 43.12%. The average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), and average amino acid identity (AAI) between strain DAU334T and its closest relatives were 77.85‒71.10, 82.14‒67.07, and 22.60‒19.70%, respectively. The major fatty acids (>10%) of strain DAU334T were iso-C13:0 and Summed feature 3 (C16:1 w7c and/or C16:1 w6c). The respiratory quinones were ubiquinone 7 (Q7), ubiquinone 8 (Q8), menaquinone 7 (MK-7), menaquinone 8 (MK-8), methylated menaquinone 7 (MMK-7), and an unidentified one. According to the results of polyphasic analyses, the strain DAU334T belongs to a novel species within the genus Shewanella, for which the name Shewanellayoungdeokensis sp. nov. (type strain DAU334T = KCTC 72428T = JCM 35745T = KCCM 43479T) is proposed.