Lake System Research Articles

Changes in total sulfur of lake sediments from central-eastern China linked to volcanic aerosol and human activity

Investigations into the repercussions of human activities on global climate and the ecological environment have received widespread attention. Over the past century, research has primarily focused on the impact of heavy metals and nutrients on lake ecosystems, along with their links to human activities. However, there is a noticeable dearth in explorations of historical variations in sulfur (S), an element that also has complex adverse effects on the environment and ecosystems. Here, we present an approximately 1800-year record of the total S (TS) content of sediments in Lake Nvshan, central-eastern China. The results provide evidence to indicate that high (low) TS contents in Lake Nvshan sediments are associated with strong (weak) volcanism in the Northern Hemisphere on multi-century scales. We also observed significant enhancement of TS content at 1750 and 1900 CE, which corresponded to a significant increase in the regional population at these times. We thus infer that elevations in TS levels prior to the increase in human activities likely resulted from increased volcanisms that led to greater inputs of sulfate from the stratosphere into the lake. Subsequently, the increases in TS contents could be attributed to intensified human industrial activities. Our findings revealed that volcanically derived sulfates have been supplanted by anthropogenically driven increases in the levels of sulfides as the primary factor influencing sediment TS contents in Lake Nvshan. These findings could elucidate how human activities have steered lake systems away from their natural baseline, thereby augmenting our understanding of their broader environmental impact.

Terrestrial dissolved organic matter inputs affect the nitrous oxide emission revealed by FT-ICR MS

Nitrous oxide (N2O) emission from lake systems could be affected via intrusion of terrestrial organic matter, causing impairment in biogeochemical cycling. The sources and mechanisms by which DOM (Dissolved organic matter) alters emissions of N2O are poorly understood. Here, we simulate different terrestrial DOM (anthropogenic sources, natural sources, and surface runoff) to assess the mechanisms affecting N2O emissions with variations of DOM. We used a combination of absorption spectroscopy, excitation-emission matrix fluorescence, and Fourier transform ion cyclotron resonance mass spectrometry to characterize DOM comprehensively. For the characterization of DOM, a combination of absorption spectroscopy, excitation-emission matrix fluorescence, and Fourier transform ion cyclotron resonance mass spectrometry was used. Microbial analysis was conducted to identify the potential microbial mechanisms. Different terrestrial DOM inputs primarily impact N2O emissions through the denitrification process (14.52 %, p < 0.05), with significant effects on the abundance of narG (12.97 %, p < 0.05) and nirK+S (10.13 %, p < 0.05). The biodegradable components in sediments directly promote N2O emissions, while in aquatic systems, the labile components (proteins, sugars, and lipids-like) were preferentially metabolized, producing reluctant derivatives. The biodegradable components (i.e., protein-like) from anthropogenic sources rapidly facilitate N2O production. Natural and surface runoff sources were the significant drivers for the continuous release and metabolism of DOM. N2O Loss emissions are negatively influenced by the regulation of carbon and nitrogen metabolism by nitrifiers and denitrifies in the sediment (p < 0.001). Metabolism of carbon and nitrogen regulated by nitrifier and denitrifies in the sediments negatively influences N2O flux (p < 0.001). N2O emissions were mainly influenced by bioavailability of inputs: DOM and varying terrestrial conditions. The results provide a theoretical base for the management of greenhouse gas emissions from lakes.

Ecology and biogeochemistry of the microbial underworld in two sister soda lakes

BackgroundApproximately 3.7 billion years ago, microbial life may have emerged in phosphate-rich salty ponds. Surprisingly, analogs of these environments are present in alkaline lake systems, recognized as highly productive biological ecosystems. In this study, we investigate the microbial ecology of two Canadian soda lake sediment systems characterized by naturally high phosphate levels.ResultsUsing a comprehensive approach involving geochemistry, metagenomics, and amplicon sequencing, we discovered that groundwater infiltration into Lake Goodenough sediments supported stratified layers of microbial metabolisms fueled by decaying mats. Effective degradation of microbial mats resulted in unexpectedly low net productivity. Evaporation of water from Last Chance Lake and its sediments led to saturation of brines and a habitat dominated by inorganic precipitation reactions, with low productivity, low organic matter turnover and little biological uptake of phosphorus, leading to high phosphate concentrations. Highly alkaline brines were found to be dominated by potentially dormant spore-forming bacteria. These saturated brines also hosted potential symbioses between Halobacteria and Nanoarchaeaota, as well as Lokiarchaea and bacterial sulfate reducers. Metagenome-assembled genomes of Nanoarchaeaota lacked strategies for coping with salty brines and were minimal for Lokiarchaea.ConclusionsOur research highlights that modern analogs for origin-of-life conditions might be better represented by soda lakes with low phosphate concentrations. Thus, highly alkaline brine environments could be too extreme to support origin of life scenarios. These findings shed light on the complex interplay of microbial life in extreme environments and contribute to our understanding of early Earth environments.

δ13C and δ18O-based interpretation of Miocene carbonates of the Miranda-Trebiño basin, NE Iberia: preliminary insights

The stable isotopes (C and O), bulk mineralogy and sedimentary facies types of the Miocene lacustrine palustrine carbonates of the Cucho Section (Miranda-Trebiño basin, N Iberia) are studied. The results indicate deposition in a freshwater carbonate lake recording significant biogenic CO2 input, changing Precipitation/Evaporation rates and variations in vegetation cover and pedogenesis on palustrine areas. Short-lived stages of higher salinity and evaporative conditions are recorded by the relative abundance of fine-grained dolomite. The highest δ13C values suggest 12C sequestration in anoxic bottom waters due to water column stratification. These new data support the general deepening trend of the lake system established from previous sedimentological analyses.

Restoration of submerged vegetation modulates microbial communities to decrease nitrogen and phosphorus loads in sediment-water systems

The release of nitrogen and phosphorus from sediments, known as internal nutrient loading, plays a crucial role in determining the eutrophic state of lakes and the timeframe for their ecological recovery. The restoration of submerged macrophytes is considered an effective measure to improve lake eutrophication. However, the impact of submerged macrophytes restoration on the storage and transformation mechanisms of nitrogen and phosphorus in lake sediment-water systems has not yet been systematically studied. This study constructed two submerged macrophyte communities with species richness of either two or five and monitored the physicochemical characteristics, nitrogen and phosphorus dynamics, and the structural and functional changes of sediment microbiomes in the plant-water-sediment system during three growth stages of the plants (May, July, and October). Our results demonstrated that the presence of submerged vegetation effectively reduced the nitrogen and phosphorus loads in the sediment-water system, encompassing their chemical forms, active concentrations, and release fluxes. Simultaneously, the restoration of submerged vegetation altered the composition of sediment microbial communities and the nitrogen and phosphorus cycling functions. Following the restoration, the abundance of functional genes associated with nitrogen fixation, organic nitrogen metabolism, nitrate reduction, and nitrification exhibited an average decrease of 2.95 %. In contrast, the abundance of genes involved in denitrification and nitrogen limitation response regulation increased by 20.24 %, while those related to phosphorus cycling processes showed a 7.29 % increase. Additionally, submerged macrophyte communities with varying richness differentially affected lake nitrogen and phosphorus loads, as well as the structure and function of sediment microbiomes, primarily related to the life cycle stages of the submerged macrophytes. These findings highlight the crucial role of submerged plants in maintaining lake nutrient balance and sediment microbiomes, providing valuable insights into how the restoration of submerged vegetation affects nutrient cycling in aquatic ecosystems.

Lake surface water temperature in China from 2001 to 2021 based on GEE and HANTS

Warming of lakes' surface water leads to accelerated loss of biodiversity and eco-environmental collapse of aquatic systems. Changes in lack surface water temperature (LSWT) are a crucial indicator of lake warming. LSWT growth potentially leads to a higher greenhouse gas emissions and deterioration of the ecological environment within lake systems. However, the magnitude of these changes remains uncertain due to data limitations, particularly for small lakes (1–5 km2). Small lakes will experience increasing perturbation with accelerating climate change and our methods demonstrate how the impacts of changes in lakes can be accurately measured and monitored. Our study assessed the spatial and temporal patterns of LSWT in China from 2001 to 2021. We utilized Google Earth Engine (GEE) and the Harmonic Analysis of Time Series (HANTS) algorithm to reconstruct LSWT series and detect spatiotemporal dynamics. The innovative connection of GEE and HANTS provides powerful tool for LSWT analysis. Our results show LSWT increased at a rate of 0.24 °C per decade, albeit with notable spatial and temporal variations. The nighttime rate of increase was greater than the daytime rate of increase. However, there was an abrupt change in daytime LSWT in approximately 2010 and this occurred earlier than an abrupt change in nighttime LSWT. Geographically, the lakes in the Eastern Plain zone exhibited the most significant LSWT warming trend. The majority of lakes warmed more rapidly between 2011 and 2021 as compared to 2001 to 2010. We found a concurrent and pronounced increase in the frequency of algal bloom occurrences after 2010. Our results demonstrate how GEE and HANTS can deliver the continued monitoring and assessment of LSWT trends needed to inform management strategies aimed at mitigating potential negative impacts of climate change on lake ecosystems, both locally and globally. Building on this method, future research should explore the underlying mechanisms driving LSWT trends and their long-term impacts on lake health.

Urban transformation of lakes and its impacts on a lake series: A case study of the yele mallappa shetty lake series Bengaluru, India.

The interconnected systems of lakes of Bengaluru, India, experience tremendous stress due to unsustainable urbanisation. Traditional lake-centric research approach struggles to capture and address this issue due to the cascaded nature of impacts in interconnected lake systems. Hence, this study assesses the impact of urbanisation on a lake series scale, focusing on the Yele Mallappa Shetty Lake series (YMSLS). Land use land cover change analysis (1993-2023) showed that in 1993, the YMSLS catchment area was dominated by open spaces (53.4%) and agriculture land and vegetation (35%), with built-up areas covering only 7.2%. By 2023, the built-up area has expanded to 34.6% and became the dominant land use. This rapid urbanisation has led to increased water surface area from wastewater influx, causing significant weed growth and water pollution in the lakes. Lake water quality assessment showed that faecal coliform, total coliform, dissolved oxygen, and biochemical oxygen demand levels exceeded standard limits with spatio-temporal variations driven by interconnectivity. Pollutant flushing during monsoon reduced pollution load in upstream lakes, but high wastewater inflow made downstream lakes, particularly the end lake, highly polluted but perennial. Increased water availability expanded the user base of the end lake, but traditional uses have declined and coping strategies of users, such as wastewater lift irrigation from the lake, became unsustainable. The study indicates that spatial interdependence and cascading effects necessitate a lake series approach for assessing the impacts of urbanisation on interconnected lake system, which is crucial for enhancing water security and preparedness for future extreme events.

Genetic Features of the Bream Abramis brama from the Lake System of the Sebezhsky National Park

For the first time, the analysis of the genetic variability of microsatellite DNA for five loci in the bream Abramis brama (L.) from lakes Sebezhskoye and Necheritsa of the Sebezhsky National Park, Sebezhsky district of the Pskov region, included in the lake system, was carried out. The results obtained demonstrate the uniformity of estimates of the genetic variability of bream in the lake system. Estimates of the allelic diversity of microsatellite loci and the expected heterozygosity of local bream groups did not differ significantly. The total genetic differentiation of bream was θ = 0.004. 95% CI (-0.01; 0.01) and was significantly insignificant. The population-genetic structure based on the studied multilocus genotypes has not been revealed by the Bayesian analysis method. The result indicate a high level of gene flow between local bream groupings and make it possible to assume the presence of a genetically unified panmixed population in the Sebezh lakes system.

The State of Thermophylic Ichthyofauna in the Water Bodies of Arkhangelsk Oblast: Report 1. Formation and Distribution

Materials determining the possible pathways of Arctic zone colonization by representatives of thermophilic ichthyofauna are presented. The previously proposed hypothesis that the fish of the thermophilic complex that lived in the White Sea basin during the Subboreal period (sterlet, blue bream, common rudd, white-eye bream, and asp) and were considered extinct during the subsequent cooling in the Subatlantic period, adapted to changed conditions, stayed in particular areas of their range, and became part of the modern ichthyofauna in limited numbers have been elaborated and confirmed. The possible pathways of spontaneous introduction of the Caspian thermophilic species, white-eye bream, and asp to the Northern Dvina basin are considered. Populations of rudd and blue bream, rare thermophilic species for the region, have been detected and studied in the lakes of the Kenozersky National Park. Rudd, a relict species of the Holocene thermal maximum, was previously recorded only in several floodplain lakes of the middle reaches of the Northern Dvina River. The Kenozero population of rudd is the first case of finding epresentatives of this species in the Onega River basin. Blue bream can be also considered a relict found in the territory of the region only in one lake system of the Kenozersky National Park and several small lakes of the Siysky State Nature Reserve.

Midge Paleo-Communities (Diptera Chironomidae) as Indicators of Flood Regime Variations in a High-Mountain Lake (Italian Western Alps): Implications for Global Change

Sediments of alpine lakes serve as crucial records that reveal the history of lacustrine basins, offering valuable insights into the effects of global changes. One significant effect is the variation in rainfall regimes, which can substantially influence nutrient loads and sedimentation rates in lacustrine ecosystems, thereby playing a pivotal role in shaping biotic communities. In this study, we analyze subfossil chironomid assemblages within a sediment core from an alpine lake (western Italian Alps) to investigate the effects of rainfall and flood regime variations over the past 1200 years. Sediment characterization results highlight changes in sediment textures and C/N ratio values, indicating phases of major material influx from the surrounding landscape into the lake basin. These influxes are likely associated with intense flooding events linked to heavy rainfall periods over time. Flooding events are reflected in changes in chironomid assemblages, which in our samples are primarily related to variations in sediment texture and nutrient loads from the surrounding landscape. Increased abundances of certain taxa (i.e., Brillia, Chaetocladius, Cricotopus, Psectrocladius, Cricotopus/Orthocladius Parorthocladius) may be linked to higher organic matter and vegetation inputs from the surrounding landscape. Biodiversity decreased during certain periods along the core profile due to intense flood regimes and extreme events. These results contribute to our understanding of alpine lake system dynamics, particularly those associated with intense flooding events, which are still understudied.

Zirconium-Modified Attapulgite Composite for Phosphorus Removal and Algae Control in Lake Water

Phosphorus removal is critical for effective water treatment and the prevention of eutrophication. This study focuses on the modification of attapulgite, an economical clay material, with zirconium (Zr@ATP) to enhance its phosphorus adsorption capacity. Zr@ATP was comprehensively characterized, and its phosphorus-removal mechanisms were investigated. Additionally, its performance in water treatment was evaluated using a lake water-sediment system. Zr@ATP exhibited a high surface area of 329.29 m2/g. The static adsorption experiments revealed that Zr@ATP achieved a phosphorus-removal efficiency of 95.8% at an adsorbent dosage of 5 g/L. Kinetic studies indicated that the adsorption followed a pseudo-second-order model, with the primary mechanism being chemisorption via ion exchange. Application of Zr@ATP in a lake water-sediment system resulted in an 83.6% reduction in total phosphorus. The chlorophyll concentration significantly decreased from 32.33 μg/L to 8.56 μg/L, and the algal density decreased by 84.6%, effectively inhibiting algal growth. These results suggest that Zr@ATP is a promising adsorbent for sustainable phosphorus removal and eutrophication control in aquatic environments.

Decoding lake water dynamics to optimize watershed agriculture through isotopic analyses of memory effects and hydrological connectivity

Understanding the complex spatiotemporal dynamics of lake water systems is critical in the context of intensifying global environmental changes. In this study, a novel stable isotope analysis method, combined with Bayesian mixing models, is applied to investigate hydrological connections and water source contributions in a specific area on the southwest shore of Dianchi Lake, China, at a monthly scale. The study reveals a significant “memory effect,” where 56.76% of the lake water volume in the current month is associated with the lake water volume in the prior month, with notable seasonal variations. The relative contributions of precipitation, surface water, soil water for different agricultural land uses, and groundwater to the lake water balance are assessed. The hydrological processes in Dianchi Lake are significantly influenced by agricultural land use, with greenhouse soils contributing less water than open field soils. Water outflow, rather than evaporation, is the primary factor reducing the nearshore lake volume, highlighting the impact of human activities. The dependency of water source contributions on meteorological factors is also examined, with seasonal and weather effects on lake water dynamics and agricultural water availability observed. By integrating isotope data with meteorological records and advanced modeling techniques, a quantitative framework for evaluating hydrological changes in lake catchments is developed. The developed approach enhances our understanding of lake water system dynamics and can enhance agricultural water management strategies, water resource allocation, irrigation planning, and climate change adaptation in agricultural watersheds.

A novel hybrid model for long-term water quality prediction with the ‘decomposition–inputs–prediction’ hierarchical optimization framework

ABSTRACT Accurate, stable, and long-term water quality predictions are essential for water pollution warning and efficient water environment management. In this study, a hierarchical water quality prediction (HWQP) model was developed based on ‘data decomposition–predictor screening–efficient prediction’ via wavelet decomposition, Spearman correlation analysis, and long short-term memory network, respectively. The observed data from 14 stations in the Huaihe River–Hongze Lake system, including ammonia nitrogen (AN) and chemical oxygen demand (COD), were used to make long-term water quality predictions. The results suggested that, compared to existing water quality prediction models, the HWQP model has higher accuracy, with the root mean square errors of 6 and 17% for simulating AN and COD, respectively. The AN and COD concentrations will range from 0 to 1 mg/l and from 3 to 5 mg/l at 12 stations, respectively, and the COD concentrations will exceed the water quality target at Stations 4 and 5. The established model has great potential to address the challenges associated with the water environment.

Remediation of biochar-supported effective microorganisms and microplastics on multiple forms of nitrogenous and phosphorous in eutrophic lake

Lots of studies on eutrophication, but there is a lack of comprehensive research on the repair of multiple forms of nitrogen and phosphorus under combined heavy metals (HMs) pollution. This work investigated the various forms of nitrogen and phosphorus in the water-sediment systems of eutrophic lakes with the application of biochar, Effective Microorganisms (EMs) and microplastics, aiming to deliberate the repair behavior of multiple forms of nitrogen/phosphorus and the integrated repairment of these nutrients and HMs in different remediations. For amended-groups, the application of biochar-supported EMs (BE) achieved the most desirable remediation for removing nitrogen, phosphorus and HMs in water and improved their stability in sediment due to the improved microbial activity and the developed biofilm system created by biochar. The addition of aging microplastics (MP) obviously reduced the systematic levels of nitrogen, phosphorus and HMs due to the stimulation of microbial activity and the adsorption of biofilm/EPS, but its high movability also increased the Fe(II) and S(-II) levels and the pollutants' ecological risks in sediment. The co-application of BE and MP (MBE) destroyed the ecosystem and decreased the removal of nitrogen and phosphorus, while greatly removing HMs by the superfluous biofilms/EPS. The application of biochar (BC) preferentially adsorbed and degraded dissolved nitrogen and phosphorus, releasing HMs into water. From these amended-groups, it's also knew that the removal of nitrogen and phosphorus mainly came from the degradation/assimilation of NH3-N, SRP and dissolved matters, particularly those molecular weight below 3 kDa; the higher removal of phosphorus than nitrogen was attributed to the coprecipitation of Fe-S-P hydroxides and the adsorption of particulates; however, the colloidal (3–100 kDa) nitrogen and phosphorus had low accessibility and bioavailability, and it also showed the competitive adsorption with colloidal HMs, causing their relatively low removal in water. This study provides insight into the comprehensive repair of nitrogen, phosphorus and HMs in various forms by biochar-immobilized microbes and the influence of microplastics on nutrients and HMs in eutrophic lakes.

Emergence of Potential Anadromous Arctic Charr (Salvelinus alpinus) Habitats in the Svalbard Archipelago After the End of the Little Ice Age

AbstractGlaciers in the Svalbard Archipelago are retreating rapidly in response to climate change. This retreat leads to the alteration of the hydrological and thermal regimes of freshwater ecosystems. In this delicate context, existing anadromous Arctic charr (Salvelinus alpinus) populations are at severe risk and might disappear from the archipelago. However, the retreat of glaciers also promotes the formation of new lake systems that might be suitable for colonization by anadromous Arctic charr. These systems may provide a substantial opportunity for the establishment of new populations of anadromous charr, potentially buffering the decline in existing systems. To date, there is a lack of information on the number of recently deglaciated lake systems that have emerged since the end of the Little Ice Age (ca. 1920) that might be suitable for charr colonization. Therefore, the goal of this paper is to provide an initial assessment of the number of these lakes. To this end, and in accordance with previously published research, this study assesses whether a recently deglaciated lake system is potentially open to colonization based on gradient, river length, and lake surface area. Depending on the applied threshold (four in total), up to 24 lake systems are classified as potentially open to colonization by anadromous Arctic charr, with Spitsbergen emerging as a potential hotspot for colonization. The findings of this paper might serve as basis for new studies and for implementing proactive management and conservation strategies to protect anadromous charr populations.

Unveiling the paleosalinity constraints on southern peri-Pannonian Lower Miocene lacustrine systems in Serbia and Bosnia and Herzegovina: Lopare (Dinaride Lake System) versus Toplica basin (Serbian Lake System)

Early Neogene saline lakes were widely developed across Central Paratethys, particularly across its „Dinaride-Anatolide“ landbridge (area of Dinarides, Balkans). The constraints on Lopare (western part of Jadar block; eastern Bosnia and Herzegovina) and Toplica (Jastrebac Mt., central Serbia) Neogene paleolakes provide a better understanding of deep-time climate evolution. The study focused on early Neogene paleolacustrine configuration, paleogeography, and the factors affecting a considerable paleosalinity increase. The study integrated available records on the predominantly Lower Miocene sedimentary sequence by analyzing and interpreting several paleosalinity markers (inorganic geochemical proxies, mineralogical data). The constraints on paleosalinity markers are afterward coupled with rather complex tectonic inferences. The two wellbores drilled in the Lopare and Toplica basins expose Neogene sections from which the critical paleosalinity markers are extracted (drillhole depths up to 350 and 1000 m, respectively). The mineral searlesite (NaBSi2O5(OH)2), and high B/Ga, markers of alkaline and arid paleoenvironmental lacustrine conditions, suggested intense evaporation (frequent drought periods). The evaporation was associated with paleoclimatic conditions during the Miocene Climatic Optimum. The Early Neogene arid climate and frequent evaporation episodes resulted in significant salinization of the Lower Miocene Lopare lacustrine sequence. The salinity in the Lopare sequence changed its character between brackish and saline, as evidenced by S/TOC and Ca/(Ca + Fe) ratios (TOC—Total Organic Carbon). At the same time, the salinity in the early Toplica basin was significantly lower and characterized by freshwater and brackish environments. The salinity variations between Toplica and Lopare were further exposed by Fe/(Ca + Mg), (Al + Fe)/(Ca + Mg), and C-value, yielding the change in the (paleo)water column. These markers further indicated the influence of warm climate conditions, consistent with the Miocene paleoclimatic record. Regarding paleogeography and Early Neogene tectonics, the results showed that before the Middle Miocene Badenian transgression, the Paratethyan Sea had no interference with the investigated intramontane lacustrine basins.

Evaporitic–lacustrine mudstone laminites and prodelta mudlobes – continuity and change in the Hartmann's Valley interval, Murray formation, Gale crater, Mars

ABSTRACTThe sedimentary fill of Gale crater on Mars is dominated by lacustrine strata that are the focus of investigations into surface processes, climate change and habitability early in the planet's history. This study focuses on the lower part of the explored portion of the Murray formation on Aeolis Mons (Mount Sharp) in the Pahrump Hills and Hartmann's Valley field areas. At Pahrump Hills, sedimentary features and geochemical attributes of exposed mudstones suggest accumulation in an underfilled lake basin in which lake levels, shorelines and salinities fluctuated greatly at various temporal scales. The immediately superjacent stratigraphic interval, designated by the rover team as the Hartmann's Valley member, has previously been interpreted as an aeolian‐deposited sandstone interval. This fresh examination of all available data, however, suggests that the Hartmann's Valley member is strongly dominated by the same mudstone facies that compose most of the underlying Pahrump Hills member. The one novel facies element encountered in the Hartmann's Valley member are undulose bedded to convex bodies of mudstone that are oriented roughly north–south, suggestive of sediment supply from a northern fluvial source. Mudstones analogous in scale and character to these undulose mudstones occur on Earth in multiple modern and ancient lacustrine successions, and are related to deposition of prodelta mud lobes. The mudstones of the Hartmann's Valley member record a continuation of the underfilled evaporitive lake system proposed previously for the underlying Pahrump Hills member but with somewhat more variable environmental conditions. Hartmann's Valley mudstones contain more abundant matrix CaSO4, suggesting more severe evaporitic conditions, whereas the interbedded undulose bedded mudstones signify intermittent freshening and buildout of mud‐dominated deltas into the lake. The textural similarities between Pahrump Hills and Hartmann's Valley strata suggest that the Gale lacustrine system operated at a stable depositional mode with similar environmental parameters during both stratigraphic intervals.

Spread and frequency of explosive silicic volcanism of the Carpathian-Pannonian Region during Early Miocene: Clues from the SW Pannonian Basin and the Dinarides

Explosive silicic volcanism of the Carpathian-Pannonian Region (CPR) is increasingly recognized as the primary source of tephra across the Alpine-Mediterranean region during the Early and Middle Miocene. However, the tephrostratigraphic framework for this period of volcanic activity is still incomplete. We present new multi-proxy data from Lower Miocene ignimbrites and tephra fallout deposits from the southwestern CPR and the Dinaride Lake System and integrate them into existing datasets to better resolve the regional extent and scale of these eruptions of the CPR. Volcanic glass geochemistry indicates distal fallout tuffs deposited in the Sinj Basin are correlative with the proximal Ostoros ignimbrites from the Bükkalja Volcanic Field, indicative of regionally extensive volcanism at 17.295 ± 0.028 Ma, based on CA-ID-TIMS UPb zircon geochronology. Based on integrated tephrostratigraphic data, newly identified 17.064 ± 0.010 Ma massive rhyolitic ignimbrite deposits from the Kalnik Volcaniclastic Complex located in the southwestern CPR are correlative with the 17.062 ± 0.010 Ma Mangó massive ignimbrite found in the Bükkalja Volcanic Field located in the northern CPR. Based on these new observations of its potential areal distribution and estimated thicknesses, these two widespread ∼17.1 Ma ignimbrites represent intermediate to large caldera-forming ignimbrites, larger than previously suggested. Finally, volcanic glass geochemistry of fallout deposits from the Dinaridic Sinj and Livno-Tomislavgrad Basins have similar volcanic glass geochemistry as the rhyolitic pumices from the lowermost part of the Bogács ignimbrite unit of the Bükkalja Volcanic Field. However, high-precision geochronology indicates that these distal ashfalls were deposited at 16.9567 ± 0.0074 Ma, significantly predating the 16.824 ± 0.028 Ma emplacement of the fiamme-bearing part of the Bogács ignimbrite. These distinct ages suggest that the Bogács unit represents multiple eruptive events and indicating that further work is required to deconvolve this portion of the CPR volcanic record. Together, these data suggest that large volume CPR ignimbrite volcanism was more frequent and widespread than previously understood, enhancing the existing volcanic framework and history of the source region for this time period.

Longitudinal Investigation of Groundwater and Surface Water Interaction of Two Gravel Pit Lakes in Central Texas: Chemical and Flow Implications

Two gravel pit lakes in central Texas were examined over the course of two years with upgradient and downgradient piezometer installations. Groundwater and lake water were sampled bimonthly for nutrients, water levels, and groundwater chemistry, and in addition, rain and lake gauges and mini-piezometers were installed, depth surveys were conducted, and a simple 2D flow model was constructed. The project goal was evaluating and examining flow dynamics and chemical effects as groundwater flows to surface water and back to groundwater with the intent to understand the effects that gravel pit lake systems have on connected shallow groundwater. Both lake systems were shown to be flow-through systems that influence the water quality by decreasing the dissolved nutrients in the groundwater in their vicinity while oxygenating the water and altering the pH. However, the lakes are also prone to high levels of evaporation, meaning that minor improvements to water quality come at the cost of decreasing the quantity of water in storage within the aquifer. Similar groundwater and mine lake systems may show comparable tendencies, providing new information for water managers, regulators, and stake-holders about the potential roles that non-remediated gravel pit lakes may play in local ecosystems and aquifer dynamics.

Lessons from long‐term research: Diptera species turnover and dominance shifts with respect to climate‐driven changes

Abstract The diverse pressures of climate change have influenced many habitats, especially freshwater ones, due to their greater sensitivity to stressors. Aquatic Diptera make up more than 50% off all aquatic insect species described, which makes them an ideal group to monitor changing climate as their diverse assemblages can reflect functions within the entire community. The aim of this research was to identify variations in the aquatic dipteran community during a 15‐year period at a tufa barrier in a karst barrage lake system and to determine the environmental factors that have the highest influence on this community. We analysed monthly data collected between 2007 and 2021, when we collected adult specimens using 6 pyramid‐type emergence traps. In total, 167 taxa from 13 different families were gathered. NMDS based on Bray–Curtis similarity analysis amongst assemblages revealed the segregation of samples based on different current velocities and substrates, indicating the importance of microhabitats in dipteran community structuring. Dipteran taxa indicative of specific 5‐year time periods within the research were identified and were associated with changes in environmental conditions especially discharge. The threshold indicator taxa analysis revealed specific species' responses to changing discharge rates. The study shows that discharge rate, not water temperature, is the critical factor shaping dipteran composition, whether by removing or adding taxa to the community. Species turnover showed an overall decrease in species numbers, that is, species richness, throughout the research period. We conclude that changes in the dipteran community, because of the vast functional traits, niches, adaptations and species diversity of the group, are not visible when analysing just the diversity indices. When determining environmental influence on the community in long‐term research, they should be combined with other data such as the overall abundance, the total number of species, as well as the species turnover.