Hot Springs Research Articles

Analysis of nearly 3000 archaeal genomes from terrestrial geothermal springs sheds light on interconnected biogeochemical processes

Terrestrial geothermal springs are physicochemically diverse and host abundant populations of Archaea. However, the diversity, functionality, and geological influences of these Archaea are not well understood. Here we explore the genomic diversity of Archaea in 152 metagenomes from 48 geothermal springs in Tengchong, China, collected from 2016 to 2021. Our dataset is comprised of 2949 archaeal metagenome-assembled genomes spanning 12 phyla and 392 newly identified species, which increases the known species diversity of Archaea by ~48.6%. The structures and potential functions of the archaeal communities are strongly influenced by temperature and pH, with high-temperature acidic and alkaline springs favoring archaeal abundance over Bacteria. Genome-resolved metagenomics and metatranscriptomics provide insights into the potential ecological niches of these Archaea and their potential roles in carbon, sulfur, nitrogen, and hydrogen metabolism. Furthermore, our findings illustrate the interplay of competition and cooperation among Archaea in biogeochemical cycles, possibly arising from overlapping functional niches and metabolic handoffs. Taken together, our study expands the genomic diversity of Archaea inhabiting geothermal springs and provides a foundation for more incisive study of biogeochemical processes mediated by Archaea in geothermal ecosystems.

Thermal‐mechanical properties of bamboo charcoal/recycled low‐density polyethylene composites

AbstractBamboo fiber has garnered considerable attention owing to its high specific strength and renewability. However, the hydrophilic nature of the material must be carefully managed to create a bamboo composite with usable thermal‐mechanical properties. Herein, the NaOH‐treated bamboo fiber (particle size ≤200 μm) was used to produce bamboo charcoal (BC). Then, recycled low‐density polyethylene containing BC composites was fabricated by varying the BC composition (between 2 and 8 wt%). Effects of different BC wt% in the BC/recycled low‐density polyethylene composites (denoted as xBCPE, where x indicates BC wt% in the composites) were analyzed for tensile strength, morphology, and thermal properties. In addition, the water absorption capacities of the BCPE composites were compared. These xBCPE composites showed excellent thermal stability and low water absorption properties. Therefore, they are potential candidate materials for electrical device packaging with partial degradability.Highlights Bamboo charcoal (BC) was prepared via low‐temperature pyrolysis of alkaline‐treated bamboo fiber. BC displayed strong interfacial interaction with recycled low‐density polyethylene. Proportion of BC on the composite properties was investigated and furnished. The xBCPE composites demonstrate low water absorption and excellent thermal stability. The reinforced composite (4BCPE) shows great promise as a functional material.

Representative High-Temperature Hydrothermal Activities in the Himalaya Geothermal Belt (HGB): A Review and Future Perspectives

Southern Tibet and western Yunnan are areas with an intensive distribution of high-temperature geothermal systems in China, as an important part of the Himalayan Geothermal Belt (HGB). In recent decades, China has conducted systematic research on high-temperature geothermal fields such as Yangbajing, Gudui, and Rehai. However, a comprehensive understanding has not yet been formed. The objective of this study was to enhance comprehension of the high-temperature geothermal system in the HGB and to elucidate the hydrogeochemical characteristics of geothermal fluids. This will facilitate the subsequent sustainable development and exploitation of domestic high-temperature hydrothermal geothermal resources. To this end, this study analysed geothermal spring and borehole data from the Yangbajing, Gudui, and Rehai geothermal fields. Based on previous research results, the source, evolution, and reservoir temperature characteristics of geothermal fluids are compared and summarised. The main high-temperature geothermal water in the geothermal field is derived from the deep Cl-Na geothermal fluid. Yangbajing’s and Gudui’s geothermal waters are primarily recharged by snow-melt water, while Rehai’s geothermal water is mainly recharged by local meteoric water. The average mixing ratios of magmatic water in the Yangbajing, Gudui, and Rehai geothermal fields are 17%, 21%, and 22%, respectively. The Yangbajing and Gudui geothermal fields have a relatively closed geological environment, resulting in a stronger water–rock interaction compared to the Rehai geothermal field. As geothermal water rises, it mixes with shallow cold water infiltration. The mixing ratios of cold water in the Yangbajing, Gudui, and Rehai geothermal fields are 60–70%, 40–50%, and 20–40%, respectively. Based on the solute geothermometer calculations, the maximum geothermal reservoir temperatures for Yangbajing, Gudui, and Rehai are 237 °C, 266 °C, and 282 °C, respectively. This study summarises and compares the hydrogeochemical characteristics of three typical high-temperature geothermal fields. The findings provide an important theoretical basis for the development of high-temperature geothermal resources in the Himalayan Geothermal Belt.

Granitoids of the western Himalaya and Karakoram as potential geothermal reservoirs – A petrological, geochemical and petrophysical study

Hot springs in various granitoid and gneissic complexes in northern Pakistan indicate elevated geothermal gradients, which warrants their evaluation for geothermal applications. Evaluation of such prospects requires extensive knowledge of rock properties and their interaction with reservoir fluids. Our contribution provides first-order information on petrophysical, geochemical, and petrographic descriptions derived from outcrop analogs. About seventy samples of (mostly) granitoids and gneisses from the Nanga Parbat Massif (NPM), the Kohistan-Ladakh Batholith (KLB), and the Karakoram Batholith (KB) were collected. Biotite, K-feldspar, and plagioclase in the granitoid and gneiss show weak to moderate alteration, which increases in shear zones, suggesting fracture-assisted fluid interaction. Geochemical results indicate that the gneisses and granites of the NPM are mostly peraluminous S-type and show enrichment in most LREEs and depletion in HREEs. In addition, depleted Sr and Ba and enriched Rb and U in granites indicate partial melting and high fractionation. On the contrary, granitoids from the KLB are of calc-alkaline I-type and characterized by the depletion of REEs and the enrichment in Ba and Sr. The granitoids of the KB, due to their different magmatic histories, are more diverse, ranging from older I-type calc-alkaline granodiorite, and younger I-type alkaline syenite and S-type calc-alkaline granite. They show an overall enrichment in HREEs along with Ba, Th, Ta, Sr, and Lu. Allanites from syenite of the KB show significant concentrations of Th and U.Petrophysical measurements reveal low matrix porosities (0.6–3.5 %), with primarily average thermal conductivities (1.48–3.37 W m−1K −1) and thermal diffusivities (0.68–1.95 ∙10–6 m2 s−1), with minor variation in specific heat capacities (744–767 J kg−1 K−1). The NPM displays higher average thermal conductivity, thermal diffusivity, and lower porosity than the KB, while the petrophysical properties of the KLB range between these two domains.The geothermal systems in the area operate due to the thickening of a granitoid-dominant crust, which is enriched with radiogenic elements. The fault zones provide channels for meteoric water to access deeply these hot and thermally conductive rocks in the subsurface. After heat exchange, the water is discharged back to the surface as hot springs. The present data set provides a better understanding of regional geothermal regimes from petrological, geochemical, and petrophysical perspectives and assists in numerical modeling for potential geothermal assessment.

Seasonal Scale Climatic Factors on Grassland Phenology in Arid and Semi-Arid Zones

Influenced by climate change, significant alterations in vegetation phenology have been observed globally. Grassland phenology is highly sensitive to climate change. However, research on the variations in grassland phenology and its responses to seasonal climatic changes in arid and semi-arid regions remains scarce. This study, utilizing Solar-Induced Chlorophyll Fluorescence (SIF) data, meteorological station data, and grassland type data, employs trend analysis and time series analysis to explore the trends of seasonal climatic variability and the sensitivity response of grassland phenology in Xinjiang to seasonal climates. The findings reveal the following: (1) The region experiences more pronounced warming in winter and spring than in summer and autumn, with ground temperature increments outpacing those of air temperatures. The summer season registers the peak in precipitation volume and rate of increase, where mountainous zones accrue more rainfall compared to basins and plains. The distribution of sunshine duration is characterized by higher values in eastern areas than in the west and more in the plains than in mountainous regions, potentially due to escalating cloudiness, which has contributed to a diminishing trend in sunshine hours across Xinjiang over the past 20 years. (2) Over the past two decades, the perennial greening phase of Xinjiang grasslands has predominantly occurred in early May, showing an overall trend of occurring earlier by approximately 5.47 days per decade, while the yellowing phase mainly occurs at the end of September and the beginning of October, demonstrating a delaying trend (6.61 days/decade). The average length of the growing season is 145 days, generally showing a slightly increasing trend (11.97 days/decade). (3) In spring, the rise in air and ground temperatures, along with increased sunshine duration, all promote grassland growth, leading to an earlier greening phase. Conversely, in autumn, increases in air temperature, ground temperature, and sunshine duration can inhibit grassland growth, resulting in an earlier yellowing phase. Increased precipitation in summer and autumn can delay the yellowing phase and extend the length of the grassland growing season. This research provides new insights into the factors influencing large-scale grassland phenology and offers references for grassland adaptation to future climate changes.

A Novel Numerical Model Considering Unsaturated Soil Properties and Computational Study on Heat and Moisture Transfer Characteristics of Helix Ground Heat Exchanger

Abstract A novel three-dimensional numerical simulation model for the helix ground heat exchanger was proposed in this paper, which takes into account unsaturated soil properties. This model is more suitable for real working conditions. To validate its accuracy, a miniature model heat transfer experimental platform was constructed. Additionally, the study conducted simulation research using three types of soil with significantly different thermal and moisture characteristics. Moreover, the comprehensive thermal conductivity and water diffusion coefficient of these three soil types were determined by relevant literature and experimental tests. The aim was to comprehensively explore the impact of different soil types on the heat and mass transfer of the helix ground heat exchanger. The results indicate that the numerical model developed in this paper accurately captures the heat and mass transfer characteristics of the helix ground heat exchanger to a certain extent. Increasing the comprehensive thermal conductivity and water diffusion coefficient of the soil can significantly enhance the heat exchange capacity of the exchanger. For instance, under sandy loam conditions, the heat exchange capacity is approximately 20.73% higher compared to clay loam conditions. The study also identifies two distinct areas around the helix ground heat exchanger: the severe change region and the soft change region. In the severe change region, there is a notable decrease in soil water content near the exchanger, which inevitably weakens the thermal conductivity of the soil. It is advised to minimize this effect through measures like active water spraying.

Modeling geothermal energy potential in the Ruwan-Zafi hot spring region of northeastern Nigeria using high-resolution aeromagnetic data

Modeling geothermal energy potential in the Ruwan-Zafi hot spring region of northeastern Nigeria using high-resolution aeromagnetic data

Shallow geothermal field multidisciplinary exploration: New data from Campi Flegrei caldera (CFc) for low—middle enthalpy resource exploitation

In the framework of the GeoGrid project, with the specific goal to look for shallow geothermal resources suitable to test the developed technologies, the Agnano geothermal field, a relatively unexplored sector of the eastern Campi Flegrei caldera, was investigated through a multidisciplinary geophysical, stratigraphic and hydro-chemical surveys. Such multidisciplinary approach allows us to reconstruct the subsurface morphology below the Agnano Hyppodrome (AH), interpreted by gravimetric, seismic and stratigraphic data, as a complex structure characterized by a gradual southward and south-eastward deepening of a high-density contrast interface. Moreover, the inferred models show two pronounced lateral depressions in agreement with the existence of known lateral faults bounding the western and eastern flanks of AH, while the hydro-chemical survey of the entire Agnano caldera revealed discontinuous manifestations of thermal waters along the groundwater flow direction. Furthermore, it was found that, within the southern sector of the Agnano caldera, mineralized waters predominantly align with a primary NE-SW buried structural lineament, a feature only hypothesized in previous studies and that in this sector local fresh groundwater likely receives endogenous inputs, including CO2 at elevated temperatures, potentially leading to the mixing of seawater or deep brine. Finally, our results individuate an area north of the Agnano Hippodrome characterized by a significant presence of higher temperature mineralized water, but lacking of seawater enrichment, making it a favorable site for further exploitation of low-to-medium-enthalpy geothermal sources.

Magnolol ameliorates fumonisin B1-induced oxidative damage and lipid metabolism dysfunction in astrocyte-like C6 cells

The neurotoxicity of fumonisin B1 (FB1), a commonly detected mycotoxin in crops and the environment, has attracted considerable attention in recent years. However, no effective method for eliminating FB1 completely exists due to the thermal stability and water solubility of this mycotoxin. Magnolol (MAG) is a neolignane with antioxidative and neuroprotective effects. It has been applied in neurotoxicity treatment. However, the application of MAG to attenuate FB1-induced toxicity has not been reported. This study explored the protective mechanism of MAG against FB1-induced damage in C6 cells through antioxidant and lipid metabolism modulation. Results showed that exposure to 15 μM FB1 caused oxidative stress by changing the levels of malondialdehyde, reactive oxygen species, total superoxide dismutase, catalase, and total glutathione. These changes were reversed by MAG addition, especially at the concentration of 80 μM. The protective effects of MAG were further confirmed by the reduction in the phosphorylation levels of proteins in the MAPK signaling pathway. Lipidomics analysis identified 263 lipids, which belong to 24 lipid classes. Among all of the identified lipids, triglycerides (TGs), diglycerides (DGs), phosphatidylcholines (PCs), wax monoesters (WEs), Cers, and phosphatidylethanolamines (PEs) were major categories. Moreover, nine categories of lipids showed the opposite change trend in the FB1 exposure and MAG 80 groups. A further investigation of the 34 co-occurring differential lipids with remarkable changes (P value < 0.05 and VIP value > 1) in the control, FB1 exposure, and MAG 80 groups was performed. Therein, nine lipids (PCs, LPCs, and SM) were screened out as potential biomarkers to reveal the cytoprotective effects of MAG. This work is the first to investigate the rescue mechanism of MAG in FB1-induced cytotoxicity. The obtained results may expand the application of MAG to alleviate the toxicity of mycotoxins.

Genomic and phenotypic characterization of Thermosynechococcus-like strains reveals eight species within the genus Thermosynechococcus and a novel genus Parathermosynechococcus gen. nov.

Thermophilic unicellular cyanobacteria of the family Thermosynechococcaceae are essential primary producers and integral components of many microbial mats found in hot springs of Asia and North America. Historically, based on their simple morphology, these organisms, along with members of taxonomically unrelated thermophilic Thermostichaceae have been described with a generic term, “Synechococcus”, used for elongated unicellular cyanobacteria. This has created significant misperception in the scientific literature regarding the taxonomic status of these essential thermophilic primary producers and their relationship with Synechococcus sensu stricto.In this manuscript, we attempted a genome-driven taxonomic reevaluation of the family Thermosynechococcaceae. Application of genomic analyses such as GTDB classification, ANI/AAI and phylogenomics support the delineation of eight species within genus Thermosynechococcus. Two subspecies were further identified within T. taiwanensis by dDDH and phylogenomics. Moreover, the results also suggest the presence of two putative new genera phylogenetically alongside genus Thermosynechococcus, a thermophilic genus Parathermosynechococcus represented by PCC 6715 and a non-thermophilic genus represented by PCC 6312. The proposed genospecies and new genera were further integrated with morphological and/or ecological information. Interestingly, the phylogeny of 16S-23S ITS achieved a better taxonomic relationship than that of 16S rRNA and supported the genome-based classification of Thermosynechococcus spp. Finally, the pan-genome analysis indicated a conserved pattern of genomic core among known members of Thermosynechococcus.

Sources, Fates, and Geochemical Cycling of Mercury in Geothermal Fields: Insights From Mercury Isotopes

AbstractGeothermal fields emit remarkable amounts of mercury (Hg) to the environment. To address the source, fate and geochemical cycling of Hg in geothermal fields, we investigated Hg concentrations and isotopic compositions of hot spring water and fumarole gases from Rehai and Dagejia in SW‐China. Elevated Hg concentrations in fumarole gases (10.0–167 ng m−3) and hot spring water (3.44–84.5 ng L−1) were observed, suggesting that both geothermal fields are of environmental concern. The variation in Δ199Hg (−0.06 to 0.23‰) and Δ200Hg (−0.09 to 0.19‰) in hot spring water supports Hg likely originating from endogenous volcanic degassing and/or rainwater. Negative and nearly zero Δ199Hg in fumarole gases (−0.32 to 0.03‰) supports volcanic degassing and background atmosphere origin. The ranges of δ202Hg in fumarole gases (−0.74 to 0.59‰) and hot spring water (−1.29 to 0.52‰) could reflect limited fluids boiling in geothermal fields. This study, thus, fills an important knowledge gap regarding Hg global cycling.

Extremophiles and their expanding biotechnological applications.

Microbial life is not restricted to any particular setting. Over the past several decades, it has been evident that microbial populations can exist in a wide range of environments, including those with extremes in temperature, pressure, salinity, and pH. Bacteria and Archaea are the two most reported types of microbes that can sustain in extreme environments, such as hot springs, ice caves, acid drainage, and salt marshes. Some can even grow in toxic waste, organic solvents, and heavy metals. These microbes are called extremophiles. There exist certain microorganisms that are found capable of thriving in two or more extreme physiological conditions simultaneously, and are regarded as polyextremophiles. Extremophiles possess several physiological and molecular adaptations including production of extremolytes, ice nucleating proteins, pigments, extremozymes and exopolysaccharides. These metabolites are used in many biotechnological industries for making biofuels, developing new medicines, food additives, cryoprotective agents etc. Further, the study of extremophiles holds great significance in astrobiology. The current review summarizes the diversity of microorganisms inhabiting challenging environments and the biotechnological and therapeutic applications of the active metabolites obtained as a response to stress conditions. Bioprospection of extremophiles provides a progressive direction with significant enhancement in economy. Moreover, the introduction to omics approach including whole genome sequencing, single cell genomics, proteomics, metagenomics etc., has made it possible to find many unique microbial communities that could be otherwise difficult to cultivate using traditional methods. These findings might be capable enough to state that discovery of extremophiles can bring evolution to biotechnology.

PRECIPITATION OF ARSENIC FROM THERMAL WATER

The presented scientific research reveals the results of experiments on the precipitation of arsenic in the form of sulfide (As2S3) from the Daridag thermal water using sodium sulfide as a reagent. The main factors impacting the precipitation of the As2S3 compound were determined: the amount of precipitant (Na2S), the ratio of solid and liquid phases (S:L), pH of the initial solution, precipitation time and temperature, also optimal parameters were obtained. According to the results obtained, the yield during precipitation of arsenic tri-sulfide from from thermal water under certain temperature conditions (t=30-450С, pH=1-2; S:L - 1:1000; = 30-50 min.) were 99.6 %. The properties of the samples were studied by physicochemical research methods (X-Ray, SEM/EDS). X-ray phase analysis showed that the sediment sample obtained under these conditions is X-ray amorphous. The composition and morphology of the obtained sample was confirmed by scanning electron microscopy and spectroscopy (SEM/EDS)

Integrating multi-platform assembly to recover MAGs from hot spring biofilms: insights into microbial diversity, biofilm formation, and carbohydrate degradation

BackgroundHot spring biofilms provide a window into the survival strategies of microbial communities in extreme environments and offer potential for biotechnological applications. This study focused on green and brown biofilms thriving on submerged plant litter within the Sungai Klah hot spring in Malaysia, characterised by temperatures of 58–74 °C. Using Illumina shotgun metagenomics and Nanopore ligation sequencing, we investigated the microbial diversity and functional potential of metagenome-assembled genomes (MAGs) with specific focus on biofilm formation, heat stress response, and carbohydrate catabolism.ResultsLeveraging the power of both Illumina short-reads and Nanopore long-reads, we employed an Illumina-Nanopore hybrid assembly approach to construct MAGs with enhanced quality. The dereplication process, facilitated by the dRep tool, validated the efficiency of the hybrid assembly, yielding MAGs that reflected the intricate microbial diversity of these extreme ecosystems. The comprehensive analysis of these MAGs uncovered intriguing insights into the survival strategies of thermophilic taxa in the hot spring biofilms. Moreover, we examined the plant litter degradation potential within the biofilms, shedding light on the participation of diverse microbial taxa in the breakdown of starch, cellulose, and hemicellulose. We highlight that Chloroflexota and Armatimonadota MAGs exhibited a wide array of glycosyl hydrolases targeting various carbohydrate substrates, underscoring their metabolic versatility in utilisation of carbohydrates at elevated temperatures.ConclusionsThis study advances understanding of microbial ecology on plant litter under elevated temperature by revealing the functional adaptation of MAGs from hot spring biofilms. In addition, our findings highlight potential for biotechnology application through identification of thermophilic lignocellulose-degrading enzymes. By demonstrating the efficiency of hybrid assembly utilising Illumina-Nanopore reads, we highlight the value of combining multiple sequencing methods for a more thorough exploration of complex microbial communities.

Amazon açaí fiber-Portland cement compatibility: a challenge to produce cement-bonded fiberboards?

The açaí waste from Amazon contains short fibers that show potential for reinforcing cement-bonded fiberboards (CBFBs), although their compatibility with cement matrix is still unknown. This work aimed to characterize raw and pretreated açaí fibers and analyze their compatibility with Portland cement by different techniques, besides developing a CBFB. The fibers were subjected to thermal (180, 200, and 220 °C), cold and hot water, alkaline (NaOH), and bleaching (NaOH-H2O2) pretreatments. The chemical and water pretreatments raised the fiber crystalline indexes (28%-57%). The chemical pretreatments individualized the fiber bundles and removed hemicelluloses. Alkali-pretreated and raw fibers had the highest (96%) and lowest (65%) cement compatibility indexes. Portlandite and ettringite appeared after 24 h for most pastes but were delayed for raw and 220 °C-pretreated fibers. In contrast, only the raw fiber specimens reached the required compression strength of 34 MPa after 28 days; hence, they were chosen to produce a CBFB. The boards showed proper thickness swelling (1.4%), but low bending strength (MOE = 647.8 MPa; MOR = 1.9 MPa). Overall, the fiber modifications improved the compatibility with cement, but not the composite's mechanical strength. Açai-fiber CBFB is a promising building material, but future studies must overcome its poor mechanical performance.

Exploring Medium and Low-Temperature Convective Geothermal Resources Through Controlled Source Audio Magnetotelluric Mothod

Medium and low-temperature convective geothermal resources are a crucial component of China's geothermal wealth, primarily concentrated in the eastern coastal regions. To maximize the utilization of these resources, geophysical surveys are essential, with controlled source audio magnetotelluric(CSAMT) being a prominent and effective method employed in geothermal resource assessments. This study focuses on applying CSAMT to survey specific geothermal sites, including the Xiu Yan Gou Tang Hot Spring, Fengcheng Gou Tang Hot Spring, and Hai Cheng Xi Huang di Geothermal Field. The results obtained through this method provide detailed insights into the distribution of both deep and shallow thermal storage spaces within these fields, shedding light on the intricate thermal circulation systems associated with them. These findings serve as a reliable foundation for planning and executing further geothermal resource development projects. CSAMT emerges as a comprehensive tool for understanding the nuances of medium and low-temperature convective geothermal resources.

Experimental Behavior of Solar Still Using Mixed Oxides Mn-Fe/Silicone Resin Composite as Selective Solar Absorber

In this research, the optical properties of a black pigment of mixed Mn-Fe oxides synthesized by the precipitation method dispersed in silicone resin at different concentrations for use as a solar absorber in a two-slope passive solar still were evaluated. The transmittance of different thicknesses of float glass with 0.1% Fe2O3 was also studied for use as a condenser in the construction of the solar still. Regarding the pigments, the absorbance and spectral emittance were evaluated, the floated. With the above information, both the absorbent surface and the condensers were optimized to propose the best design of the solar still. The novel hybrid material used as a selective coating in the still, which corresponds to 2.3% Mn-Fe mixed oxides, exhibited a high solar absorbance of 91.82% and a relatively low infrared thermal emission of less than 57.22%, as well as good stability to the corrosive and hot environment of the solar still, in addition to great durability over time and in real operating conditions. The float glass with the highest transmittance corresponds to a thickness of 3 mm and an average transmittance of 82.57%. The built prototype was characterized by obtaining the temperature profiles of the absorber and condensers, thermal efficiency, production and water quality. The prototype has a thermal efficiency of 29.6%, requiring only energy from the sun for its operation. The water produced by this device becomes an option for human use and consumption in accordance with current official standards, allowing supply in communities that do not have access to drinking water but have access to seawater or waters with high hardness.

Aquatic photosynthetic carbon pump driven by periodic temperature variations affects dissolved inorganic carbon and hydrochemical characteristics in a groundwater-fed reservoir

Under the influence of periodic temperature variations, biogeochemical cycling in water bodies is markedly affected by the periodic thermal stratification processes in subtropical reservoirs or lakes. In current studies, there is insufficient research on the influence and mechanism of dissolved inorganic carbon (DIC) distribution in karst carbon-rich groundwater-fed reservoirs under the coupled effects of thermal structure stratification and the biological carbon pump (BCP) effect. To address this issue, the Dalongdong (DLD) reservoir in the subtropical region of southern China was chosen as the site for long-term monitoring and research on relevant physicochemical parameters of water, DIC, and its stable carbon isotope (δ13CDIC), CO2 emission flux, as well as the reservoir's thermal stratification index. The results show that: (1) the DLD reservoir is a typical warm monomictic reservoir, which exhibits regular variations of mixing period-stratification period-mixing period on a yearly scale due to thermal structure changes; (2) DIC was consumed by aquatic photosynthetic organisms in the epilimnion during the stratification period, leading to a decrease in DIC concentration, partial pressure of CO2 (pCO2) and CO2 emission flux, and an increase in stable carbon isotope (δ13CDIC). During the mixing period, the trend was reversed; (3) During the thermal stratification, aquatic photosynthesis and water temperature were the primary factors controlling DIC variations in both the epilimnion and thermocline. Regarding the hypolimnion, calcite dissolution, organic matter decomposition, and water temperature were the dominant controlling factors. These results indicate that although carbon-rich karst groundwater provides a plentiful supply of DIC in the DLD reservoir, its availability is still influenced by variations in the reservoir's thermal structure and the metabolic processes of aquatic photosynthetic organisms. Therefore, to better estimate the regional carbon budget in a reservoir or lake, future studies should especially consider the combined effects of BCP and thermal structure variations on carbon variations.

Invisible invaders: range expansion of feral Neocaridina davidi offers new opportunities for generalist intracellular parasites

AbstractThe release of ornamental pets and associated pathogens outside their native range might directly or indirectly impact the recipient community. In temperate regions, e.g., central Europe, feral freshwater species of tropical and sub-tropical origins are mainly constrained to thermally polluted waters and thermal springs. However, species with high environmental plasticity and reproduction rates, such as the shrimp Neocaridina davidi, may adapt to colder water regimes over time. A widening thermal niche may eventually overcome thermal barriers, further expanding the range and enhancing transmission opportunities for host generalist parasites. This study assesses the observed (field observations) and theoretical (species distribution models) range expansion of N. davidi and associated parasites in Europe. We report three newly established N. davidi populations from thermally polluted waters in central Europe (Germany, Hungary, and Slovakia) and provide further evidence of its range expansion into colder environments. Species distribution models predict thermally suitable habitats in the Mediterranean and a foreseeable expansion into Western Europe and the Balkans by 2050. We confirm the presence of the microsporidian parasite Ecytonucleospora hepatopenaei in feral N. davidi populations across Europe and expand the list of microsporidians found in this host from two to four. Furthermore, we provide the first evidence of parasite spillover from/to the invasive crayfish Procambarus clarkii, suggesting that parasite exchange with native biota might be possible. Such possibility, coupled with an ongoing range expansion of N. davidi bolstered by human-mediated introductions and climate change, will likely exacerbate the impact on native biota.

Geotourism in Mount Pandan and Bledug Kuwu Hotspring as a potential resources for community development

Mount Pandan and Bledug Kuwu are popular tourist attractions in the central part of Java Island. Each location has an object that can be analyzed as a geotourism potential, as the manifestation of hot springs. These results indicate that Bledug Kuwu Mud Volcano, Crewek Hot Spring, Banyu Kuning Hot Spring, and Jari Kasinen Hot Spring sites can be geotourism-based tourist objects. Mount Pandan and Bledug Kuwu sites need to be improved in several aspects, especially in terms of infrastructure. Parameters that need to be considered for all objects are conservation values due to disaster risk factors that already exist and disaster risk factors that are still potential and have yet to occur, such as volcanic eruptions and landslides, as well as the process of destruction that appears in several objects that can threaten the sustainability of tourist sites. In addition, it is necessary to increase the understanding of residents and visitors who come about geological information related to the formation of hot springs, both in the form of information boards posted around the site and information displayed on local websites.