Search Results (124)

This article analyzes the information provided by the sedimentary sequences of 29 lakes in central Mexico, 10 of which are currently paleolakes. During the Late Quaternary, the lakes of central Mexico experienced environmental changes driven by global and local climatic and geological processes, showing regional trends of wet and dry periods. Paleoenvironmental reconstructions are based on the use of 20 indicators, including diatoms, pollen, geochemistry, mineralogy, granulometry, magnetic susceptibility, and isotopes. Seven major episodes are recognized in the historical evolution of the lakes of central Mexico: i. Late Miocene–Pliocene: A period that includes the formation of large lakes in central Mexico by volcano tectonic activity under a regime of continuous humidity. ii. Pleistocene–Drought and climatic variability of the interglacial period. iii. Drying and successive lacustrine transgression during the Last Glacial Maximum. iv. Spatial climate variability in the Heinrich 1 period. v. Lake regression and expansion of terrestrial vegetation in the Bølling–Allerød period. vi. Transgression of lakes of central Mexico during the Younger Dryas and mid-Holocene periods. vii. Late Holocene: A period that includes lake desiccation influenced by the impact of human activities. The analysis of the data allows us to propose six challenges for the scientific community in future research of central Mexico. Full article

Hydrologic models are instrumental in understanding the behavior of the Nile River Basin (NRB), yet their effectiveness is often limited by the basin’s complex hydrology and sparse observational records. This study applies a basin-scale hydrological modeling approach to simulate near-natural, pre-reservoir flow conditions in the NRB, while incorporating lake and wetland submodels. The basin was discretized into 34 sub-watersheds with an outlet at Aswan. The conceptual GR4J rainfall–runoff model was implemented within the Raven modeling framework, chosen for its parsimony and suitability for data-limited conditions. Multi-objective calibration used discharge data from the Global Runoff Data Centre (GRDC), supplemented by digitized historical records to improve spatial and temporal coverage. A stepwise calibration strategy was applied at 18 sites, focusing on pre-reservoir periods to capture natural flow dynamics. The calibrated model reproduces observed discharges with high skill. At the Aswan outlet, Nash–Sutcliffe Efficiency (NSE) values were 0.87 (calibration) and 0.80 (validation), with percent bias (PBIAS) values of 6.1% and 5.0%, respectively. Model performance was strongest in the Blue Nile, White Nile headwaters, and the Nile main stem. The model also successfully simulated the hydrological step-change observed in Lake Victoria during the 1960s, underscoring its robustness in simulating regional hydroclimate disruptions. This calibrated model enables reconstruction of historical Nile discharge and simulation of past hydrologic disturbances, including those driven by major volcanic eruptions over the past millennia. Full article

The hydrogeochemical characterization of shallow volcanic lakes at the Sete Cidades Volcano (São Miguel, Azores) provides new insights into the processes controlling water chemistry in low-depth lacustrine systems within active volcanic environments. Fourteen lakes (0.6–4 m deep) were sampled during two campaigns (winter 2024 and spring/summer 2025), combining in situ physicochemical measurements and major ion analyses along vertical profiles. The lakes are holomictic, cold (11.3–17.6 °C), slightly acidic (pH 5.66–5.95), and weakly mineralized (EC ~65–69 µS/cm), indicating dilute waters of predominantly meteoric origin. Hydrochemical facies are dominated by Na–Cl type, with strong correlations between chloride and conductivity (r = 0.857), supporting a major contribution from marine atmospheric deposition. To move beyond correlation-based interpretation, Gibbs diagrams and saturation indices (PHREEQC) were applied to constrain the dominant geochemical processes. Most samples plot within the precipitation dominance field, while all calculated saturation indices are negative (SI < 0), indicating undersaturation with respect to carbonate, evaporite, and silicate minerals. These results demonstrate that water chemistry is primarily controlled by atmospheric inputs, with only minor contributions from water–rock interaction and negligible influence of evaporation or mineral equilibrium processes. Seasonal increases in HCO₃⁻ and dissolved CO₂ at depth suggest enhanced organic matter decomposition during warmer periods, highlighting the role of biogeochemical processes in modulating carbon dynamics in shallow systems. The absence of a clear hydrothermal signature further distinguishes these lakes from deeper volcanic systems in the Azores. This study provides the first integrated hydrogeochemical framework for shallow volcanic lakes in the region, combining classical hydrochemistry with process-based tools. The results establish a quantitative baseline for assessing environmental change and improve the interpretation of external (atmospheric) versus internal (geochemical and biological) controls in volcanic lake systems. Full article

This study provides sedimentological and stratigraphic insights into the Ediacaran fluviolacustrine successions of the Amane-n’Tourhart and Tifernine basins. The Amane-n’Tourhart Basin developed in a post-caldera volcanic setting along the margin of the Oued Dar’a Caldera, whereas the Tifernine Basin formed in a pre-caldera tectono-volcanic context associated with caldera development. The successions provide valuable information about the sedimentary processes operating in late Ediacaran continental environments. Field observations, facies analysis, and petrography reveal a variety of siliciclastic, carbonate, mixed siliciclastic–carbonate, and volcaniclastic facies. These facies form associations indicative of alluvial fan, floodplain, and shallow-water lacustrine settings. Alluvial fan deposits are dominated by conglomerates and sandstones forming braided systems. Fluviolacustrine successions show a transition from clay-rich siltstones with calcareous nodules to nodular and massive limestones, marking a gradual shift from fluvial to lacustrine conditions. Laminated limestones and stromatolites indicate intermittent microbial activity that contributed to carbonate precipitation. Sedimentation was strongly influenced by volcanic inputs and climatic fluctuations, alternating between humid and arid conditions. These factors drove cycles of channel incision, sediment infill, and lake expansion–contraction, illustrating the dynamic interplay of volcanism and climate that modulated deposition in these Ediacaran continental basins, with broad relevance to our understanding of this critical window in the Earth’s history. Full article

Soil fungi are pivotal drivers of biogeochemical cycling, mediating nutrient transformation, plant–soil feedbacks, and ecosystem stability. Understanding their responses to vegetation succession is essential for predicting ecosystem recovery in fragile volcanic landscapes. We investigated soil fungal communities across five successional stages on the Jingpo Lake lava plateau—grassland (GL), shrubland (SL), deciduous broad-leaved forest (DB), coniferous and broad-leaved mixed forest (CB), and coniferous forest (CF)—using high-throughput ITS sequencing and soil physicochemical analysis. Basidiomycota and Ascomycota dominated at the phylum level, with Sebacina, Cortinarius, and Mortierella as core genera. Alpha diversity (Shannon, Simpson, Chao1) was significantly higher in early-successional GL and SL than in DB (p < 0.05), while CB exhibited the lowest community evenness (Pielou-e). Co-occurrence networks revealed greater connectivity in GL, whereas forest types showed simplified topologies. LEfSe identified distinct fungal biomarkers for each vegetation type. PICRUSt2-based functional prediction indicated biosynthesis as the dominant pathway (>40%), with significant variation among vegetation types. Redundancy analysis (RDA) identified soil organic matter (SOM) as the primary predictor of fungal community composition. Our findings indicate that vegetation succession is associated with changes in fungal diversity and function primarily linked to variations in SOM, with moisture regimes as a secondary contextual factor. Notably, advanced forest stages exhibited reduced fungal diversity and simplified community structure—highlighting a trade-off between nutrient enrichment and microbial complexity in volcanic ecosystems. These insights advance our understanding of plant–soil–microbe coupling during ecosystem restoration on lava plateaus. Full article

Continental rift lacustrine basins typically feature multiple sediment sources under the combined controls of volcanism, tectonics, water balance and sediment supply, resulting in complex stratigraphic successions. This complexity is particularly pronounced in fine-grained successions, which are of high interest for their potential to generate and accumulate hydrocarbons. Nevertheless, the mechanisms governing the sedimentary transition from volcaniclastic to siliciclastic-dominated fills within a rift cycle remain poorly constrained. The Lower Cretaceous Xiguayuan Formation in the Luanping Basin accumulated in a lacustrine setting influenced by explosive volcanism, providing an excellent archive of siliciclastic–volcaniclastic interaction. Based on field observations, core descriptions, and petrographic analysis, sixteen lithofacies have been grouped into seven facies associations, including subaqueous ignimbrite, volcanically sourced turbidites, subaqueous volcanic ridge, central-lake sedimentation, shallow-lacustrine margin deposits, low-density turbidites, and high-density turbidites. Their spatial relationships reveal two volcanic pulses and document the lake’s environmental evolution, with deep-water background sediments overlying volcaniclastics and a marked increase in siliciclastic input upsection, reflecting a transition from an underfilled, volcaniclastic-dominated underfilled lake to a siliciclastic-dominated lake. Notably, the fine-grained sediments associated with volcanism exhibit excellent hydrocarbon potential. Organic-rich claystones and carbonate laminae form a microscopic source–reservoir system, in which volcanic inputs appear to enhance organic matter preservation and promote the development of reservoir-quality layers. This study elucidates how volcanic activity modulates sedimentation and sediment supply in a deep-lacustrine rift, offering new insights into volcano-sedimentary interactions and related hydrocarbon systems in continental rift basins. Full article

Monitoring the hydrochemistry of groundwater and the H-O isotopes in the Jingpo Lake volcanic area, China, is fundamental to studying the mechanisms of volcanic and seismic events, as well as the associated hazards. To study the hydrogeochemistry of fluids in the Jingpo Lake volcanic area, water samples from seven sites were tested for hydrogeochemistry, H-O isotopes, and radon (Rn) content. The genesis and evolution of the groundwater system were elucidated through an integrated approach employing Gibbs diagrams, ionic ratio analyses, reservoir temperature estimation (silica–enthalpy method), and inverse geochemical modeling with PHREEQC. The results showed that the dominant water chemistry type was HCO₃⁻, primarily influenced by volcanic rock weathering and deep hydrothermal activity. Spring and well water were influenced by cation exchange, adsorption, and rock weathering dissolution. The H-O isotope composition and radon content indicate that atmospheric precipitation is the main source of supply, while well water is influenced by deep fluids. According to the Na-K-Mg triangle diagram, most of the groundwater was shallow and immature, whereas the well water was partially balanced. The temperature of the geothermal water was controlled by the geothermal gradient, depending on its occurrence and circulation depth. Additionally, the equilibrium temperature of the thermal reservoir was calculated using the silica–enthalpy equation method, with the concentrations of dissolved components in the water taken into account. The temperature of the thermal reservoir of the well water and the depth of groundwater circulation were estimated. The original reservoir temperature in the study area was calculated to range from 108 °C to 156 °C, with a geothermal water-to-shallow groundwater mixing ratio of between 71% and 85%. The estimated shallow temperature ranged from 64.9 °C to 74.9 °C. These hydrogeochemical signatures reflect active water–rock interactions and the contribution of deep-seated geothermal fluids, providing robust evidence for ongoing geothermal activity in the Jingpo Lake volcanic system. The findings enhance our understanding of the recent geological evolution and present-day hydrothermal processes of this potentially active volcanic field, which establishes a crucial hydrogeochemical baseline for future monitoring and hazard assessment studies. Full article

The lack of high-precision imaging data for lunar volcanic regions currently hinders the detailed characterization of lava tube systems and their associated fine-scale geomorphology. To address this information deficit, this study establishes the Jingpo Lake Volcanic Field (JLVF) in Northeast China as a primary terrestrial analog for the lunar Marius Hills complex. We systematically characterize the basaltic morphometric continuum, tracing the geological evolution from proximal scoria cones through medial lava tube skylights to distal lava plateaus. Focusing on the subsurface transport system, we identify a linear chain of discontinuous skylights that structurally mirrors the “proto-rille” stage of lunar sinuous rilles. Quantitative morphometry reveals that these terrestrial vents reproduce the geometric duality of lunar pits, ranging from stable “deep shafts” to degraded “funnel pits,” effectively validating the mechanical diversity of the lunar inventory. Critically, the “U-to-V” cross-sectional transition observed in JLVF collapse trenches serves as diagnostic ground-truth evidence, confirming that lunar rilles originate from the catastrophic roof failure of subsurface tubes rather than purely thermal erosion. Regarding the lava plateau, our field investigation resolves sub-meter micro-textures—including laminar pahoehoe ropes and inflation fissures—that are typically obscured by the resolution limits of current lunar orbiters. These findings suggest that the seemingly “smooth” lunar maria likely host complex, rugged micro-terrains. Therefore, comparing lunar volcanic regions with simulated volcanic fields from Earth is crucial. Analyzing potential volcanic products from angles undetectable by some lunar satellites can offer vital insights for future lunar exploration. Full article

The Cuitzeo Groundwater Flow System, located in central Mexico within a volcanic rock region, encompasses two of the largest lakes in the country: Lake Cuitzeo and Lake Pátzcuaro. These lakes are sustained by both surface water and groundwater discharge, playing a critical role in local ecosystems and the surrounding population. Groundwater is particularly important for maintaining the lakes’ existence. However, the behavior of the groundwater flow system in this region has not been previously described. This study compiles historical data from 170 groundwater sites within the system from different years and includes temperature (°C), pH, total dissolved solids (TDS), major ions, and geology in detail. The historical data provide a spatial analysis and initial characterization to study the hydrochemistry of the system, identify recharge and discharge zones, assess water-rock interaction processes, and trace the evolution of groundwater. The results highlight distinct chemical behaviors across the different zones of the study area, with the most notable being ion exchange consistent with the weathering of volcanic silicates and interaction with lacustrine sediments. This study is crucial as it offers valuable insights into the hydrochemistry and water levels of the groundwater flow system and highlights areas where additional data are needed to better understand its dynamics. Full article

Lake Batur, located within a volcanic caldera in Bali, Indonesia, is subjected to anthropogenic pressures related to agriculture, aquaculture, tourism, and religious activities, which may affect its water quality and ecology condition. This study investigates the physicochemical properties of lake water and diatom assemblages preserved in lake sediments to provide insight into environmental conditions in this volcanic alkaline ecosystem. Water quality parameters, including pH, temperature, electrical conductivity (EC), and total dissolved solids (TDS), were measured. Vertical profiles of temperature and conductivity revealed stable stratification, with minimal variation below 20 m water depth. Elevated nitrogen concentrations, including nitrate (NO₃⁻), nitrite (NO₂⁻), and ammonium (NH₄⁺), were observed, particularly in the southern basin, suggesting localized nutrient enrichment. Scanning electron microscopy (SEM) analysis of lake sediment samples identified ten diatom genera, including Ulnaria, Denticula, and Discostella, which are commonly associated with nutrient-enriched freshwater environments. Overall, the results indicate that Lake Batur exhibits conditions consistent with early-stage eutrophication in localized areas, highlighting the importance of continuous monitoring and targeted management strategies to protect the ecological integrity of this volcanic lake system. Full article

Seasonal temperature reconstructions provide a critical approach for reconciling discrepancies between paleoclimate model simulations and proxy records. However, cold-season temperature variations remain poorly constrained due to the scarcity of robust cold-season temperature proxies. This study provides critical insights into lake ice-covered season temperature dynamics in Northeast China, a region where cold-season climate variability has remained poorly constrained in paleoclimate reconstructions. We collected total organic carbon sequences from seven closed lakes in Northeast China over the last 10,000 years to evaluate the lake ice cover duration as a proxy for lake ice-covered season temperature during the early–middle Holocene. Our results show that the lake ice cover duration decreased from ~8 ka BP, reaching a minimum at around 4 ka BP. This pattern is linked to ice-covered season temperature changes, with warmer ice-covered seasons leading to shorter ice cover durations and increased lake productivity, which were driven by orbital forcing (seasonal insolation changes) and greenhouse gas concentrations. Orbital forcing played a dominant role in winter warming between 8 and 4 ka BP, while greenhouse gas also contributed, but to a lesser extent. Full article

Volcanic eruptions can mobilize naturally occurring toxic elements such as arsenic into surrounding ecosystems, contaminating soil, water, and food webs. Despite increasing evidence of arsenic enrichment in volcanic regions, comprehensive exposure assessments that integrate dietary and drinking water pathways remain limited, particularly in post-eruption contexts where baseline data are scarce. Following the 2020 Taal Volcano eruption, this study conducted a probabilistic risk assessment to quantify aggregate exposure to inorganic arsenic (iAs) among residents of Batangas, Philippines. A Monte Carlo simulation framework (10,000 iterations) integrated post-eruption environmental data on total arsenic in soil, lake water, drinking water and clam tissues with modeled bioaccumulation and transfer factors for fish and major terrestrial crops. Two exposure scenarios, lower bound (50% iAs fraction) and upper bound (90% iAs fraction), were applied to capture uncertainty in arsenic speciation and bioavailability. Simulated iAs concentrations followed the order rice > corn > vegetables > root crops. Aggregate daily iAs doses averaged 3.0 ± 1.4 µg/kg bw/day (lower bound) and 4.0 ± 2.0 µg/kg bw/day (upper bound), with females showing slightly higher exposures and pregnant women exhibiting lower doses. Sensitivity analysis identified clam intake, rice intake, and iAs in rice, clams, and drinking water as dominant determinants of total exposure. All simulated individuals exceeded the U.S. EPA non-cancer reference dose (HQ > 1) and cancer risk benchmark (10⁻⁶–10⁻⁴), indicating substantial health concern. These findings highlight the urgent need for sustained environmental monitoring, arsenic speciation analyses, biomonitoring, and public health programs to guide evidence-based management in arsenic-affected volcanic regions. Full article

Volcanic crater interiors in Nicaragua’s Pacific region are a valuable, understudied, and threatened native plant resource. Laguna de Apoyo Nature Reserve encompasses a crater and lake formed following a Quaternary volcanic explosion in Pacific Nicaragua. The flora of the tropical dry forest in the crater’s interior surrounding the lake has not been extensively assessed. We identified 403 native and 72 introduced plant species and their uses through a combination of survey plots, unstructured interviews, expert consultations, and targeted searches for plant species coordinated with key informants in the Reserve. Fabaceae, Euphorbiaceae, and Asteraceae were the most represented native species, whereas the most significant numbers of introduced species were found in Poaceae, Euphorbiaceae, and Fabaceae. Forty-one species have conservation priority status. Documented uses were found for 70% of the native species and 88% of the introduced species. The most significant numbers of plant species with reported use types were ornamentals and fuelwood. This study constitutes the most comprehensive plant species inventory in a protected area of Nicaragua’s tropical dry forest biome. These findings indicate native plant diversity is high, introduced species pose considerable risks, and most species are integrated into local uses. Consequently, management decisions should explicitly promote native diversity, protect threatened species, better control introduced species, and encourage sustainable use. Full article

A novel bacterial strain, Lysinibacillus sp. JNUCC 51, was isolated from volcanic soil collected at Baengnokdam Crater Lake, Mt. Halla, Jeju Island, Republic of Korea. Phylogenetic, ANI (88.76%), and dDDH (70.4%) analyses indicated that the strain represents a distinct genomic lineage closely related to L. xylanilyticus. The complete genome (5.12 Mb; 37% G+C) encoded 4912 genes, including ten biosynthetic gene clusters (NRPS, β-lactone, RiPP, terpene, and T3PKS types), suggesting strong metabolic versatility. Cells were Gram-positive rods (1.5–3.0 × 0.5–0.7 µm) growing at pH 4.0–9.0 and up to 5% NaCl. Chemotaxonomic profiles revealed iso-C₁₅:₀, iso-C₁₇:₀, and iso-C₁₆:₀ as dominant fatty acids; MK-6/MK-7 as major quinones; and phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylcholine as main polar lipids. Bioactivity-guided fractionation of the culture extract led to the isolation of Diolmycin A2 (phenolic polyketide) and maculosin (diketopiperazine), both exhibiting anti-inflammatory and melanogenesis-inhibitory effects consistent with their PKS/NRPS gene clusters. The culture broth suppressed nitric oxide production in LPS-stimulated RAW 264.7 macrophages and reduced melanin synthesis in α-MSH–induced B16F10 melanocytes. A human patch test (5% extract) confirmed dermatological safety. Overall, Lysinibacillus sp. JNUCC 51 is a volcanic-origin bacterium producing structurally diverse bioactive metabolites with promising postbiotic and cosmeceutical potential, particularly for skin inflammation and pigmentation control. Full article

Jeju Island, a volcanic island located off the southern coast of the Korean Peninsula, harbors highly specialized microbial communities shaped by its unique geological and climatic diversity. In particular, Baengnokdam Crater Lake at the summit of Mt. Halla represents an extreme, oligotrophic volcanic habitat characterized by intense UV radiation, temperature fluctuations, and limited nutrients. From this environment, a novel bacterial strain, Brevibacillus sp. JNUCC 42, was isolated and subjected to comprehensive taxonomic, genomic, and biochemical analyses. The strain is a Gram-positive, aerobic, rod-shaped bacterium that grows optimally at 30 °C and pH 7.0–9.0 with moderate NaCl tolerance (≤3%). Phylogenetic analysis based on 16S rRNA gene sequencing and genome-scale GBDP confirmed its affiliation to the genus Brevibacillus, forming a distinct lineage closely related to B. laterosporus DSM 25^T. Whole-genome sequencing generated a 4.93 Mb circular chromosome with a GC content of 40.7%. Comparative genomic analyses revealed ANI (87.1%) and dDDH (32.8%) values far below the species threshold, supporting its delineation as a novel species. Chemotaxonomic data further distinguished JNUCC 42 by its predominance of anteiso-C₁₅:₀ (37.24%) and iso-C₁₅:₀ (27.78%) fatty acids and the presence of a unique unidentified aminolipid not detected in the type strain. Genome mining identified 21 biosynthetic gene clusters, including NRPS, PKS, and NRPS–PKS hybrids, suggesting its potential to produce structurally diverse secondary metabolites. One of these metabolites, the cyclic dipeptide maculosin [cyclo(L-Pro-L-Tyr)], was purified from the culture extract and structurally characterized by NMR spectroscopy. Functional assays demonstrated that maculosin significantly inhibited α-MSH-induced melanogenesis and intracellular tyrosinase activity in B16F10 melanoma cells without cytotoxicity up to 100 µM. Collectively, these findings indicate that Brevibacillus sp. JNUCC 42 represents a novel species within the genus Brevibacillus and a promising microbial source of bioactive compounds with potential cosmeceutical applications. Full article