Hot Springs Research Articles

Thermophilic Hadarchaeota grow on long-chain alkanes in syntrophy with methanogens

Methanogenic hydrocarbon degradation can be carried out by archaea that couple alkane oxidation directly to methanogenesis, or by syntrophic associations of bacteria with methanogenic archaea. However, metagenomic analyses of methanogenic environments have revealed other archaea with potential for alkane degradation but apparent inability to form methane, suggesting the existence of other modes of syntrophic hydrocarbon degradation. Here, we provide experimental evidence supporting the existence of a third mode of methanogenic degradation of hydrocarbons, mediated by syntrophic cooperation between archaeal partners. We collected sediment samples from a hot spring sediment in Tengchong, China, and enriched Hadarchaeota under methanogenic conditions at 60 °C, using hexadecane as substrate. We named the enriched archaeon Candidatus Melinoarchaeum fermentans DL9YTT1. We used 13C-substrate incubations, metagenomic, metatranscriptomic and metabolomic analyses to show that Ca. Melinoarchaeum uses alkyl-coenzyme M reductases (ACRs) to activate hexadecane via alkyl-CoM formation. Ca. Melinoarchaeum likely degrades alkanes to carbon dioxide, hydrogen and acetate, which can be used as substrates by hydrogenotrophic and acetoclastic methanogens such as Methanothermobacter and Methanothrix.

Sustainable wastewater recovery system employing geothermal energy – Performance and feasibility study

In this study, a sustainable wastewater recovery system employing geothermal energy has been proposed. The efficiency of the suggested sustainable system has been simulated using heat transfer. Then, component-wise validation has been carried out with the existing data available in the literature wherever applicable and estimated an error of ± 8 %. The proposed sustainable system’s parametric and performance analyses have employed the developed vapor. From the parametric study, it is observed that hot spring temperatures have a significant influence on sustainable systems. Further, through performance investigation, it is understood that low dam/river/sea water temperatures and enhancing the water condenser effectiveness and flow rate ratio simultaneously improve the system performance. For different climatic regions of India, explored the feasible geothermal hotspots near dams/rivers/seawater and analyzed that among the hot and dry, hot and humid, composite and cold regions, the proposed sustainable system is best suitable at a composite region with a maximum possible water extraction/freshwater generation rate of 0.78 L/h for the given specifications and operating range. Moreover, it is assessed that hot spring temperature is the deciding factor for sustainable system performance in different climatic regions. Further, the current study can be used as a reference for understanding the phenomenon of potential geothermal hotspots for wastewater recovery in various climatic areas

Tracing the orogenic sulfur cycle in the Andes using stable isotope composition of dissolved sulfate in thermal springs

The cycling of sulfur (S) to the upper crust and surface via thermal springs at convergent margins has not been explored outside areas with active arc volcanism, even though subduction plays a key role in the Earth's long-term S cycle. To address this knowledge gap, we analyzed stable sulfur and oxygen isotope compositions (δ34S and δ18O values) of dissolved sulfate (SO42−) in 55 thermal springs from five distinct settings in the Andean orogen. These regions are the Peruvian flat slab and backarc, transition between these two, Argentinian backarc, and Chilean forearc. Although the flat-slab settings had lower SO42− concentrations (<2000 mg/L) compared to the steep-slab settings (<12,700 mg/L), there was no significant relationship between isotope composition of SO42− and slab geometry. The δ34S and δ18O values of SO42− varied widely across the studied areas (+0.2 to +23.5 ‰ and − 3.3 to +16.0 ‰, respectively) and reflected the isotope compositions of local bedrock endmembers from dissolution of marine evaporites (+5 to +25 ‰ and + 10 to +20 ‰, respectively) and oxidation of magmatic and/or hydrothermal S and ore sulfide minerals with variable δ34S (0 to +16 ‰). The δ18O and δ2H values of thermal spring water (−18.5 to −3.3 ‰ and − 141.1 to −23.7 ‰, respectively) were consistent with meteoric precipitation, and in most cases decreased with increasing altitude following precipitation in the Andes. Generally, our isotope results do not support the direct transfer of slab-derived S/SO42− to thermal springs in the investigated settings. Rather, the δ34S and δ18O of SO42− in the thermal springs are a sensitive indicator of local water-rock interactions that remobilize bedrock S originating from a complex orogenic cycle reflecting tectonic uplift, erosion, weathering, and exhumation history across the duration of Andean Mountain building.

Characterization of cyanobacterial mats from an artificial hot spring in Uniejów (Poland) and the potential use of their biomass

Artificial geothermal water systems are an efficient and low-cost alternative to natural ecosystems for phototrophic microorganism biomass production on an industrial scale. Our study focused on the investigation of mat-forming cyanobacteria produced in an artificial pool with a geothermal water source from a hot spring in Uniejów, Poland. The microorganisms inhabiting this ecosystem tolerate the high salinity (approximately 50 ‰) and temperature (45-55.2 °C) of the water. The structure, composition, and growth rates of the cyanobacterial mats were investigated under natural and laboratory conditions. We tested whether cyanobacteria harvested from this habitat represent a safe source of vital biomolecules for industrial applications. We found that the layered mats consisted of simple filamentous cyanobacteria, mainly of the genera Leptolyngbya, Thermoleptolyngbya, and Anagnostidinema. In the isolated cyanobacteria, we did not detect commonly studied cyanotoxins (i.e., ATX-a, BMAA, CYN, MC, and SXT) that could pose a direct risk to human health and lead to indirect risks through the contamination of bioproducts. The extracts and filtrates of the strains did not reduce the survival of Daphnia. In addition, we found that temperatures of 40-50 °C and pH values of 7.2-7.7 were optimal for mat formation and the growth of the dominant cyanobacteria. In the case of the Desertifilum dzianense strain, the highest biomass yield was noted at 26 °C. In summary, our study indicates that mat-forming cyanobacteria inhabiting ecosystems powered by geothermal waters from the Uniejów hot spring have strong potential as bioresources for different industrial applications.

A Novel Species of the Genus Thermanaerothrix Isolated from a Kamchatka Hot Spring Possesses Hydrolytic Capabilities.

Hot springs are inhabited by specific microbial communities which are reservoirs of novel taxa. In this work strain 4228-RoLT was isolated from the Solnechny hot spring, Uzon Caldera, Kamchatka. Cells of the strain 4228-RoLT were Gram-negative rods forming multicellular filaments. The strain grew optimally at 60°C and pH 7.0 and fermented various organic compounds including polysaccharides (microcrystalline cellulose, xylan, chitin, starch, dextrin, dextran, beta-glucan, galactomannan, glucomannan, mannan). Major fatty acids were iso-C17:0, C16:0, C18:0, C20:0, iso-C19:0, anteiso-C17:0 and C22:0. Genome of the strain was of 3.25 Mbp with GC content of 54.2%. Based on the whole genome comparisons and phylogenomic analysis the new isolate was affiliated to a novel species of Thermanaerothrix genus within Anaerolineae class of phylum Chloroflexota, for which the name T. solaris sp. nov. was proposed with 4228-RoLT (= VKM B-3776T = UQM 41594T = BIM B-2058T) as the type strain. 114 CAZymes including 43 glycoside hydrolases were found to be encoded in the genome of strain 4228-RoLT. Cell-bound and extracellular enzymes of strain 4228-RoLT were active against starch, dextran, mannan, xylan and various kinds of celluloses, with the highest activity against beta-glucan. Altogether, growth experiments, enzymatic activities determination and genomic analysis suggested that T. solaris strain 4228-RoLT could serve as a source of glycosidases suitable for plant biomass hydrolysis.

Investigation on radon levels in soil and water associated with Mount Tampomas geothermal activity in Indonesia

ObjectiveTo investigate radon emanation in geothermal manifestations around Mount Tampomas, West Java, Indonesia, and assess radon concentrations in soil and water samples. MethodsRadon measurements were conducted using the Durridge Rad7 instrument, supplemented with a soil gas probe for in-situ soil radon measurements at a depth of 80 ​cm. In-situ water radon measurements were performed using the Rad Aqua instrument, while radon measurements for hot water samples were conducted separately. Radon measurements for hot water samples were corrected for decay using a radon decay correction factor. ResultsThe analysis of radon measurements revealed a wide range of concentrations in soil and water samples. Soil radon concentrations ranged from 15 Bq/m³ to 4,660 Bq/m³, with localized hotspots exhibiting exceptionally high concentrations. Water radon measurements showed elevated levels, ranging from 0.2 Bq/L to 13.4 Bq/L in-situ, particularly in hot springs. In collected water samples, radon concentrations ranged from 1 Bq/L to 6 Bq/L. These combined results highlight significant variability in radon levels across different water sources influenced by geothermal activity. ConclusionsThese findings indicate active emanation processes influenced by geological factors and underscore the role of subsurface geology and aquifer characteristics in radon transport mechanisms. The presence of localized radon hotspots suggests the need for comprehensive monitoring and proactive management strategies to mitigate environmental and public health risks associated with radon exposure.

Diversity analysis of cyanobacterial flora from the Tatapani Hot Spring of Chhattisgarh and exploration of their industrially as well as environmentally valuable properties

The present study investigates the cyanobacterial diversity of Tatapani hot spring, Chhattisgarh, India, using a polyphasic approach, their pigment system, biofuel properties and ability to bioremediate emerging pollutant triclosan. While the microscopic analyses of the natural samples reflected high cyanobacterial diversity with all morpho-forms, physicochemical studies revealed temperature being the major factor affecting the cyanobacterial distribution in the hot spring. Among the 22 collected cyanobacterial samples, 14 were grown successfully under laboratory conditions and 10 of them showed optimum growth at 45 °C. However, four strains displayed preference for lower temperature (27 °C) for optimum growth. The polyphasic characterization of 14 strains revealed that all the thermophiles belonged to the genus Mastigocladus whereas the strains Sytonema sp. TPJ-3, Calothrix sp. TPB-2, Westiellopsis sp. TPR-29 and Desikacharya sp. TPB-4 constituted the group of mesophiles. Calothrix sp. TPB-2 was identified as a novel genus (Neocalothrix thermalis) based on distinct morphology and phylogenetic position with unique ITS folding pattern. Additionally, our study disclosed the production of comparatively higher amounts of pigments and medium chain length fatty acids (C16 to C18) by the thermophilic strains, which indicated their potential to be used as feedstocks for pigments and biofuel production respectively. Although the triclosan bioremediation study reflected considerable triclosan removal efficiencies of all the strains, most impressive results were observed in case of Westiellopsis sp. TPR-29 (93.08 %) and Mastigocladus sp. TA-8 (91.92 %). Moreover, the in-silico study-based revelation of high triclosan binding ability of cyanobacterial laccase (−5.8 and − 5.4 kcal/mol) and catechol 2,3-dioxygenase (−5.9 and − 6.0 kcal/mol) suggested the probable triclosan degrading potential of Westiellopsis and Mastigocladus. Conclusively, the Tatapani hot spring represents a unique environment with the dominance of true-branched heterocytous thermophilic cyanobacteria that have enormous potential to remove triclosan and produce high amounts of pigments and medium chain length fatty acids.

Monitoring Multi-Drug Resistant Klebsiella pneumoniae in Kitagata Hot Spring, Southwestern Uganda: A Public Health Implication.

The concerning frequency of K. pneumoniae in various recreational settings, is noteworthy, especially regarding multi-drug resistant (MDR) strains. This superbug is linked to the rapid spread of plasmids carrying these resistance genes. The objective of this study was to evaluate the spatiotemporal prevalence of MDR-K. pneumoniae in the Kitagata hot spring, Southwestern Uganda. A laboratory-based descriptive longitudinal study was conducted between May and July 2023. During rainy and dry seasons, we collected eighty water samples in the morning and evening from the hot spring. The temperature at each point was measured prior to sample collection, and two samples were obtained at varying depths. 5 mL of each homogenized sample were pre-enriched in brain heart infusion broth, and subsequently in both blood and violet red bile agar. The Kirby-Bauer disk diffusion method was performed, followed by the detection of carbapenemase (CR) and extended-spectrum β-lactamase (ESBL) production. Polymerase chain reaction showed resistance genes viz. bla TEM, bla CTX-M and bla KPC. Data were analyzed using SPSS-20 to obtain chi-square tests and regression analysis. K. pneumoniae accounted for 30.0% of isolates obtained from Kitagata hot springs, with all isolates classified as multi-drug resistant. All isolates were resistant to ampicillin, rifampicin, ceftazidime, and azithromycin (79.2%). Additionally, 95.8% of isolates harbored bla TEM gene alone and both bla TEM and bla CTX genes, followed by bla KPC alone (33.3%), with 25% harboring all three resistance genes. During the dry season, K. pneumoniae had a higher prevalence (35.0%) compared to the wet season (25.0%). The prevalence of MDR-K. pneumoniae significantly increased over the course of the study. The presence of the three studied resistance genes in the isolates showed a positive correlation with the second phase of sample collection and the dry season but exhibited a negative correlation with temperature, except for isolates harboring either bla TEM alone or bla TEM+KPC+CTX genes. Kitagata hot spring serves as a hotspot for continuous dissemination and acquisition of MDR-K. pneumoniae harboring resistance genes that encode for ESBL and CR production. The healthcare sector ought to implement an ongoing monitoring and surveillance system as well as robust antimicrobial resistance stewardship programs aimed at delivering health education to the community.

Nizhne-Shсhapinsky Thermal Springs (Kamchatka) as an Example of Magnesium Carbon Dioxide Waters

Nizhne-Shсhapinsky Thermal Springs (Kamchatka) as an Example of Magnesium Carbon Dioxide Waters

A green extraction method for agar with improved thermal stability and water holding capacity

The conventional agar extraction method has drawbacks such as high energy consumption, low yield, poor quality, and possible residual harmful factors, which greatly limit its application in high-end fields such as biomedicine and high-end materials. This work explored a new freezing-thawing-high-temperature coupling technique for agar extraction. It increased the yield and the strength of agar by 10.6 % and 13.7 %, respectively, as compared to direct high-temperature extraction of agar (HA). The greater molecular weight and lower sulfate content of agar obtained from freeze-thaw cycles combined with high temperature extraction (FA) may be attributed to the desulfurization effect caused by freeze-thaw cycles and the preservation of the molecular chain structure. The reduction in sulfate content decreases the steric hindrance resistance of the polysaccharide chains, enhances their interactions, and promotes the regularity and density of the agar structure, while also improving its water retention and thermal stability. In conclusion, this research can offer a theoretical basis and guidance for the eco-friendly extraction of agar with improved agar characteristics and expended its applications.

Experimental study on the selection of coal-to-oil gasification ash slag gel gelling agent

The gasification ash slag (GAS) is a solid waste that is difficult to degrade and causes serious environmental pollution. In this study, a new type of mine fire prevention and extinguishing gel material was prepared from gasified ash as a base material for spontaneous combustion control of coal in the mining airspace. To better enhance the gel fire prevention process pipeline conveying efficiency, and fire extinguishing performance, the selection of seven gelling agent formulation gasification slag gel, through the thermal stability, water retention, and rheological experiments preferred the best performance of the gelling agent. Thermal stability experiments showed that the thermal decomposition of the gel was divided into three stages: water loss, gel decomposition, and secondary decomposition of decomposition products, and the analysis of the initial decomposition temperature and mass loss rate yielded the best thermal stability of CB-GAS; Water retention experiments show that XG-GAS still retains 72.33 % of water at the 11 h in high-temperature environment, which is the best water retention performance; The rheological experiments showed that the viscosity of the gel decreased continuously with the increase of shear stress, and the analysis of the parameters yielded the best rheological properties of CB-GAS. Combining the four performance indicators, the hierarchical analysis method was used to calculate the influence weight value of the indicators and carry out comprehensive scoring, which resulted in the best performance of the gasification ash fireproofing gel prepared with the optimal gelling agent CB, followed in order by XG, CMC, HPG, MC, SA, and HPMC. This study provides an important reference for gel grouting fireproofing.

Six novel species of the genus Methanoculleus isolated from various environments in Taiwan.

Taiwan is situated in the subtropical region and its geographical location and topographical features contribute to a rich ecological diversity and scenic landscapes. We investigated the diversity of methanogens in different environments of Taiwan using a culture-dependent method. This report presents the characterization and taxonomy of six hydrogenotrophic methanogens obtained from cold seep sediments (strain FWC-SCC1T and FWC-SCC3T), marine sediments (strain CWC-02T and YWC-01T), estuarine sediments (strain Afa-1T), and a hot spring well (strain Wushi-C6T) in Taiwan. The proposed names of the six novel species are Methanoculleus frigidifontis (type strain FWC-SCC1T=BCRC AR10056T=NBRC 113993T), Methanoculleus oceani (CWC-02T=BCRC AR10055T=NBRC 113992T), Methanoculleus methanifontis (FWC-SCC3T=BCRC AR10057T=NBRC 113994T), Methanoculleus nereidis (YWC-01T=BCRC AR10060T=NBRC 114597T), Methanoculleus formosensis (Afa-1T=BCRC AR10054T=NBRC 113995T), and Methanoculleus caldifontis (Wushi-06T=BCRC AR10059T= NBRC 114596T).

Production and Characterization of Extracellular Polysaccharide from Anoxybacillus flavithermus AAG-61 with Resistance to Sulfamethoxazole and Ofloxacin

Extracellular polysaccharide producers from Kursunlu (Manisa) thermal spring were identified and a total of nine isolates were selected. One isolate was selected based on its strong mucoid structure and identified as Anoxybacillus flavithermus (AAG61) by MALDI-TOF MS. A. flavithermus AAG-61 had multiple antibiotic resistance to both Sulfamethoxazole, and Ofloxacin. The polysaccharide produced by A. flavithermus AAG-61 was purified and characterized. It was an anionic heteropolysaccharide containing rhamnose, mannose, arabinose, and glucose. The polysaccharide was water-soluble and had a concentration of 3.1 g/L carbohydrate and 0.11 g/L protein. The EPS consisted of 32% carbon, 7% nitrogen, 5% hydrogen, and traces of sulfur (0.6%). The presence of protein and sulfur in the polysaccharide was confirmed by FT-IR. Zeta potential, mobility, and conductivity values were -8.3 (± 0.5) mV, -0.65 (± 0.04) µmcm/Vs, and 1.57 (± 0.08) mS/cm. The crystallinity pattern was also determined by XRD analysis. No effect on the viability of the human fibroblast cell line was observed.

Polyphosphate-kinase-1 dependent polyphosphate hyperaccumulation for acclimation to nutrient loss in the cyanobacterium, Synechocystis sp. PCC 6803.

Polyphosphate is prevalent in living organisms. To obtain insights into polyphosphate synthesis and its physiological significance in cyanobacteria, we characterize sll0290, a homolog of the polyphosphate-kinase-1 gene, in the freshwater cyanobacterium Synechocystis sp. PCC 6803. The Sll0290 protein structure reveals characteristics of Ppk1. A Synechocystis sll0290 disruptant and sll0290-overexpressing Escherichia coli transformant demonstrated loss and gain of polyphosphate synthesis ability, respectively. Accordingly, sll0290 is identified as ppk1. The disruptant (Δppk1) grows normally with aeration of ordinary air (0.04% CO2), consistent with its photosynthesis comparable to the wild type level, which contrasts with a previously reported high-CO2 (5%) requirement for Δppk1 in an alkaline hot spring cyanobacterium, Synechococcus OS-B'. Synechocystis Δppk1 is defective in polyphosphate hyperaccumulation and survival competence at the stationary phase, and also under sulfur-starvation conditions, implying that sulfur limitation is one of the triggers to induce polyphosphate hyperaccumulation in stationary cells. Furthermore, Δppk1 is defective in the enhancement of total phosphorus contents under sulfur-starvation conditions, a phenomenon that is only partially explained by polyphosphate hyperaccumulation. This study therefore demonstrates that in Synechocystis, ppk1 is not essential for low-CO2 acclimation but plays a crucial role in dynamic P-metabolic regulation, including polyP hyperaccumulation, to maintain physiological fitness under sulfur-starvation conditions.

Contributions to the knowledge of the geohydraulic model and geothermal potential of the São Vicente Medical Spa aquifer system (Central Portugal)

São Vicente Medical Spa is located in mainland Portugal (Southwest Europe) and has been using thermal waters for therapeutic purposes for a long time. The Romans were known to have used its sulphureous waters around 2000 years ago. The spa has a Roman bathhouse that is still visible today, and its ruins were discovered during recent excavations. In this work are presented some elements of the Roman baths, the current baths, as well as the main aspects of the thermal park, with the location of the sulphureous water abstractions, including the classic thermal spring, which discharges water at a temperature of 18.6 ºC. The geomorphological, geological, and hydrogeological aspects are outlined, giving particular attention to the water chemistry of the various abstractions to develop multiple applications of geothermometers to contribute to the knowledge of the geohydraulic model at depth and the geothermal potential of the aquifer system. The conclusions are drawn from a conceptual model, including the reservoir depth, which, according to various scenarios, will be between 3 km and 8 km, in a favorable situation, respectively, to reach groundwater with temperatures between 112 ºC and 118 ºC. Finally, some remarks are made about the location of the new groundwater abstraction and the depth to be reached to increase the exploitation flows and their temperature. Lastly, it outlined new studies to improve the current geohydraulic model and to investigate its relationship with the deep aquifer systems in its neighborhood, namely the Entre-os-Rios hydromineral system.

Sulfur Manufacturing at Hot Springs in Early Modern Chinese Borderlands

Sulfur Manufacturing at Hot Springs in Early Modern Chinese Borderlands

PENGARUH CUSTOMER EXPERIENCE, DIGITAL MARKETING DAN FASILITAS WISATA TERHADAP MINAT KUNJUNGAN PADA OBYEK WISATA SUBAN AIR PANAS KABUPATEN REJANG LEBONG.

The purpose of this research is to find out whether Customer Experience (X1), Digital Marketing (X2), and Tourist Facilities (X3) influence Visiting Interest (Y) at the Suban Hot Springs tourist attraction, Rejang Lebong Regency. The population in this study are students who at Muhammadiyah University of Bengkulu. totaling 180 respondents. The sampling technique used accidental sampling based on predetermined criteria, totaling 180 respondents. The processed data was analyzed using the SPSS 26 formula. Based on the results of research and analysis of the influence of the Customer Experience (X1), Digital Marketing (X2) and Tourist Facilities (X3) variables on interest in visiting the Suban Hot Springs tourist attraction, Rejang Lebong Regency. The following conclusion can be drawn: Customer Experience (X1) has a positive effect on consumer interest in visiting (Y) at the Suban Hot Springs tourist attraction, Rejang Lebong Regency. Digital Marketing (X2) has a positive effect on consumer interest in visiting (Y) at the Suban Hot Springs tourist attraction, Rejang Lebong Regency. Tourist Facilities (X3) have a positive effect regarding consumer interest in visiting (Y) at the Suban Hot Springs tourist attraction, Rejang Lebong Regency. Keywords: Customer Experience, and Digital Marketing of tourist facilities and interest in visiting.

Geothermal energy appraisal and subsurface structural mapping of the Rafin Rewa warm spring region, Precambrian basement complex of Nigeria

This research work aims at evaluating the geothermal energy potentials of the Rafin Rewa warm spring (RRWS) of the Precambrian Basement Complex in Nigeria as an alternative energy source using integrated aeromagnetic geophysical techniques. Four aeromagnetic dataset were acquired, assemblage, analyzed, and interpreted using integrated geophysical processing techniques of spectral analysis and Euler deconvolution. Qualitative interpretation of the residual anomalous map reveals a distribution of positive anomalies (> 53 nT) majorly in the central and southeastern regions, which are traced to the granitic rocks, while the low anomalies (< − 1.5 nT) have been traced to the RRWS location emanating from the coastal plain sands of the Pliocene, Pleistocene, Oligocene, and Miocene ages. Quantitatively, the depth to the top (DTT) of the anomalous bodies reveals a depression that is almost intersecting with the Curie point depth (CPD) plot at the RRWS location, which indicates high heat flow in the RRWS region. The Spectral Analysis results reveal that the DTT and the CPD in this area ranges from 0.512 to 0.761 km and 6.504 to 10.582 km, respectively while the average CPD is 8.543 ± 0.325 km. It is observed that the DTT and CPD decrease as one move away from the RRWS region. The computed heat flow average was 160.76 ± 19.09 mW/m2 within the RRWS region. The Euler deconvolution result reveals the presence of geological structures, which were interpreted as faults and fractures. The major fractures trend in the east–west (E-W) directions, while the minor fractures trend northeast-southwest (NE-SW) directions. The geochemical result presented shows that iconic compositions impact the convective heat transfer processes associated with geothermal systems. It was conclusively believed that regions with comparable shallow CPDs could be viable for further geothermal energy investigations.

Results of the CO2 diffuse degassing survey from the 2017 IAVCEI CCVG 13th volcanic gas workshop: Pululahua Dome Complex, Ecuador

Pululahua is a potentially active andesite and dacite lava dome complex. This paper presents the results of a survey focused on carbon dioxide (CO2) diffuse degassing at Pululahua, which was conducted during the 2017 International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) Commission of the Chemistry of Volcanic Gases (CCVG) 13th Gas Workshop. Our objective was to conduct a comprehensive investigation of CO2 diffuse degassing by employing standard methods for measuring CO2 flux and temperature, and data processing. These methods were applied to map the spatial distribution of the measured parameters, investigate the origin of CO2, and quantify the volcanic CO2 output within the surveyed area of Pululahua. We carried out a total of 350 soil CO2 flux and 329 soil temperature measurements and collected 12 gas samples for carbon isotopic composition analysis, surrounding the three youngest domes in the complex. In addition, seventeen CO2 flux measurements over a thermal water pool were performed. Our findings indicate that the diffuse emission at Pululahua's crater floor is fed by both biogenic and volcanic CO2. Fluxes from each source are similar in magnitude, with approximately 90% of the measurements falling into an intermediate flux range. The occurrence of volcanic CO2 emissions is supported by the carbon isotopic composition. Diffuse degassing distribution highlights a CO2 anomaly surrounding the younger domes within the crater. We estimated the CO2 diffuse emission using both statistical and geostatistical approaches over area of 3.36 km2, resulting in values of 154.2 t d−1 and 126.2 t d−1 respectively. Based on the geostatistical quantification of the total CO2 emission from soil degassing, Pululahua's crater volcanic CO2 contribution is estimated between 59 and 97 t d−1. Finally, the potential hazards associated with the release of cold CO2 at Pululahua's crater are also discussed.

Molecular Screening for Cyanobacteria and Their Cyanotoxin Potential in Diverse Habitats.

Cyanobacteria are adaptable and dominant organisms that exist in many harsh and extreme environments due to their great ecological tolerance. They produce various secondary metabolites, including cyanotoxins. While cyanobacteria are well studied in surface waters and some aerial habitats, numerous other habitats and niches remain underexplored. We collected 61 samples of: (i) biofilms from springs, (ii) aerial microbial mats from buildings and subaerial mats from caves, and (iii) water from borehole wells, caves, alkaline, saline, sulphidic, thermal, and iron springs, rivers, seas, and melted cave ice from five countries (Croatia, Georgia, Italy, Serbia, and Slovenia). We used (q)PCR to detect cyanobacteria (phycocyanin intergenic spacer-PC-IGS and cyanobacteria-specific 16S rRNA gene) and cyanotoxin genes (microcystins-mcyE, saxitoxins-sxtA, cylindrospermopsins-cyrJ), as well as amplicon sequencing and morphological observations for taxonomic identification. Cyanobacteria were detected in samples from caves, a saline spring, and an alkaline spring. While mcyE or sxtA genes were not observed in any sample, cyrJ results showed the presence of a potential cylindrospermopsin producer in a biofilm from a sulphidic spring in Slovenia. This study contributes to our understanding of cyanobacteria occurrence in diverse habitats, including rare and extreme ones, and provides relevant methodological considerations for future research in such environments.