Flux Of Matter Research Articles

East-Siberian Sea–Chukchi Sea Prograded Margin Tectono-Sedimentary Element and Makarov Oceanic Basin Composite Tectono-Sedimentary Element, Siberian and Central Arctic

The East Siberian Sea–Chukchi Sea Prograded Margin (ESCPM) and Makarov Oceanic Basin (MOB) include interconnected sedimentary accumulations with gradual facies transitions that occupy a significant part of the Amerasia Basin and the adjacent Siberian Arctic continental margin. The ESCPM contains a succession of Cenozoic clinothem featuring shelf-margin progradation caused by a rapid influx of siliciclastic material from NE Asia into the adjacent Amerasia Basin and represents a single tectono-sedimentary element (TSE) as per the volume's terminology. The MOB is a most distant and isolated from continental depositional systems part of the Arctic Ocean. It consists of two first-order sedimentary accumulations with distinct depositional styles and provenances. The lower, Passive margin TSE is composed of a fragment of the presumably Paleozoic-Mesozoic Barents and North Kara passive continental margin. The upper, Synoceanic TSE was formed following the separation of continental block of the Lomonosov Ridge from the Eurasian continental margin at ∼ 56 Ma and during the opening of the Eurasian Basin. It includes mostly Eocene to Holocene hemipelagic and pelagic deposits and ice-rafted sediments. Each of these accumulations is characterised as a TSE, and the MOB itself is considered as a composite TSE (CTSE). Assessments of petroleum potential in both elements rely on regional geological constraints, sedimentary architecture, and modelling. Direct hydrocarbon indicators have been detected in seismic profiles in both ESCPM and MOB. In the latter, petroleum generation likely began in the Jurassic or Late Cretaceous, peaking in the Paleocene and possibly extending into the Miocene. Reservoir rocks are inferred in Cretaceous and Cenozoic strata. In ESCPM TSE, Paleocene-middle Eocene sedimentary successions are considered to include potential source rocks, associated with main flooding surfaces and clinothem bottomset deposits.

Multiple stressor effects act primarily on microbial leaf decomposers in stream mesocosms.

At the global level, stream ecosystems are influenced by multiple anthropogenic stressors such as eutrophication, habitat deterioration, and water scarcity. Multiple stressor effects on stream biodiversity are well documented, but multiple stressor effects on stream ecosystem processes have received only limited attention. We conducted one mesocosm (stream channel) and one microcosm (feeding trial) experiment to study how combinations of reduced flow, increased nutrient concentrations, and increased fine sediment coverage would influence fungal and macroinvertebrate decomposer assemblages and their active contribution to leaf decomposition. In the stream channels, increased fine sediment coverage significantly reduced fungal biomass, occurrence frequencies of most aquatic hyphomycete species, and microbial leaf decomposition rates compared to untreated controls. Macroinvertebrate-induced leaf decomposition rates were mainly correlated to total fungal biomass and community composition. Neither increased nutrient concentrations, nor reduced flow conditions significantly influenced leaf decomposer communities or decomposition rates. The feeding trials revealed significantly reduced leaf consumption in the freshwater amphipod Gammarus pulex when feeding on leaf material from treatments with increased fine sediment coverage in the mesocosm experiment. When offered a food choice between sterile, unconditioned leaf material and leaf material from treatments with increased fine sediment coverage, G. pulex foraged mainly on sterile material. This study showed that increased fine sediment coverage can alter the flux of energy and material in the detrital food chain through bottom-up regulation of leaf conditioning by fungal decomposers. Our results suggest that increasing attention should be given to mitigating fine sediment transport and deposition in stream systems to preserve ecosystem functioning within the detrital food chain.

Surface Suspended Particulate Matter Flux in the Northern Gulf of Mexico from Satellite Observations

Surface Suspended Particulate Matter Flux in the Northern Gulf of Mexico from Satellite Observations

Biodiversity Change in Cultural Landscapes-The Rural Hotspot Hypothesis.

A dramatic decrease of biodiversity is currently questioning human-environment interactions that have shaped ecosystems over thousands of years. In old cultural landscapes of Central and East European (CEE) countries, a vast species decline has been reported for various taxa although intensive land cultivation has been reduced in favor of agroecological transformation, nature conservation and sustainable land management in the past 30 years. Thus, in the recent history, agricultural intensification cannot solely be discussed as the major driver controlling biodiversity. In cultural landscapes, we state that drivers and pressures mainly emerge from the backyards of rural settlements that act as interconnected rural hotspots and therefore form an ecological metapopulation in which small-scale backyard habitats are capable of preserving and exchanging species pools of the historical cultural landscape. We further argue that shifting sociocultural norms significantly affecting the survival of source populations in rural hotspots and drastically limit their dispersal pathways, which triggers the degradation of the rural metapopulation in recent times. Pressures of cultivation shift, landscape decoupling, structural homogenization, and use of technology and agrochemicals are identified as backyard ecological drivers negatively affecting biodiversity preservation, particularly in the surrounding rural landscape. Spatiotemporal dimensions of backyard pressures involving material fluxes, species exchange and retention, alternation of site conditions, and local genetic adaptation are delineated for different backyard features, including building structures, gardens, lawns, and paved grounds. Finally, we propose a future research agenda to quantify effects and trends of rural hotspots and followed patterns of altered species dynamics. We give an example on the use of satellite time series to remotely map rural backyard habitats and reveal significant spatiotemporal trends induced by small-scale human behavior that may lead to a new socioecological perception and stimulate actions to shape ecological dynamics emerging from the backyards of human settlements.

Sink or break: Oil increases resistance of phytoplankton aggregates to fragmentation

AbstractFragmentation of marine snow affects the downward flux of organic matter, and other aggregate‐associated compounds such as oil. Using phytoplankton aggregates, we demonstrate that marine snow with oil, termed marine oil snow, had a higher resistance to fragmentation compared to marine snow without oil when exposed to turbulence ex situ. At moderate shear levels, typical of the ocean mixed layer, 17% of marine snow without oil broke, whereas 63% of marine snow fragmented at intermediate shear. In contrast, only 17% and 33% of marine oil snow fragmented at the intermediate and highest shear levels, respectively. Our results suggest that oil increases the cohesion and stability of aggregates making them less susceptible to breaking. This work contributes toward explaining the exceptional oil sedimentation event following the 2010 spill in Gulf of Mexico. It also enhances our understanding of the factors that determine the probability of sinking aggregates to fragment.

Characterizing regional oceanography and bottom environmental conditions at two contrasting sponge grounds on the northern Labrador Shelf

Abstract. Deep-sea sponge grounds are distributed globally and are considered hotspots of biological diversity and biogeochemical cycling. To date, little is known about the environmental conditions that allow high sponge biomass to develop in the deep sea. Here, we characterize oceanographic conditions at two contrasting sites off the northern Labrador Shelf with respective high and low sponge biomass. Data were collected by year-long benthic lander deployments equipped with current meters, a turbidity and chlorophyll-a measuring device, and a sediment trap. Additionally, regional oceanography was described by analysing vertical conductivity–temperature–depth (CTD) casts, Argo float profiles, and surface buoy drifter data for the northern Labrador Shelf from 2005 to 2022. The stable isotopic composition of benthic fauna was determined to investigate food web structure at the sponge grounds. Our results revealed strong (0.26±0.14 m s−1; mean ± SD) semidiurnal tidal currents at the high-sponge-biomass site but 2-fold weaker currents (0.14±0.08 m s−1; mean ± SD) at the low-sponge-biomass site. Tidal analysis suggests that kinetic energy is dissipated from barotropic tide to baroclinic tide/turbulence at the high-sponge-biomass site, which could enhance food availability for benthic organisms. Bottom nutrient concentrations were elevated at the high-sponge-biomass site, which would benefit growth in deep-sea sponges. Organic matter flux to the seafloor was increased at the high-sponge-biomass site and consisted of fresher material. Finally, both sponge grounds demonstrated tight benthic–pelagic coupling prior to the onset of stratification. Stable isotope signatures indicated that soft corals (Primnoa resedaeformis) fed on suspended particulate organic matter, while massive sponges (Geodia spp.) likely utilized additional food sources. Our results imply that benthic fauna at the high-sponge-biomass site benefit from strong tidal currents, which increase the food supply, and favourable regional ocean currents, which increase the nutrient concentration in bottom waters.

Food-web dynamics of a floodplain mosaic overshadow the effects of engineered logjams for Pacific salmon and steelhead.

Food webs vary in space and time. The structure and spatial arrangement of food webs are theorized to mediate temporal dynamics of energy flow, but empirical corroboration in intermediate-scale landscapes is scarce. River-floodplain landscapes encompass a mosaic of aquatic habitat patches and food webs, supporting a variety of aquatic consumers of conservation concern. How the structure and productivity of these patch-scale food webs change through time, and how floodplain restoration influences their dynamics, are unevaluated. We measured productivity and food-web dynamics across a mosaic of main-channel and side-channel habitats of the Methow River, WA, USA, during two study years (2009-2010; 2015-2016) and examined how food webs that sustained juvenile anadromous salmonids responded to habitat manipulation. By quantifying temporal variation in secondary production and organic matter flow across nontreated river-floodplain habitats and comparing that variation to a side channel treated with engineered logjams, we jointly confronted spatial food-web theory and assessed whether food-web dynamics in the treated side channel exceeded natural variation exhibited in nontreated habitats. We observed that organic matter flow through the more complex, main-channel food web was similar between study years, whereas organic matter flow through the simpler, side-channel food webs changed up to ~4-fold. In the side channel treated with engineered logjams, production of benthic invertebrates and juvenile salmonids increased between study years by 2× and 4×, respectively; however, these changes did not surpass the temporal variation observed in untreated habitats. For instance, juvenile salmonid production rose 17-fold in one untreated side-channel habitat, and natural aggregation of large wood in another coincided with a shift to community and food-web dominance by juvenile salmonids. Our findings suggest that interannual dynamism in material flux across floodplain habitat mosaics is interrelated with patchiness in food-web complexity and may overshadow the ecological responses to localized river restoration. Although this dynamism may inhibit detection of the ecological effects of river restoration, it may also act to stabilize aquatic ecosystems and buffer salmon and other species of conservation concern in the long term. As such, natural, landscape-level patchiness and dynamism in food webs should be integrated into conceptual foundations of process-based, river restoration.

The estimation of desulphurization property of boron-containing slags of the reduction period of the AOD process

Now the main industrial method for producing stainless steel is smelting in an argon-oxygen decarburization (AOD) furnace, therefore the paper presents the results of thermodynamic modeling of the desulfurization process of low-carbon semi-finished stainless steel during the reduction period of AOD process by treating it with boron-containing slags. The use of boron oxide as a fluxing material instead of fluorspar reduces the environmental harm and decrease the viscosity of the formed slags. Using the simplex lattice method of experiment planning, a matrix was constructed containing 16 compositions of the oxide system СаО–SiO2–(3-6%)В2О3–12%Cr2O3–3%Al2O3–8%MgO with variable basicity of 1.0–2.5. Based on the generalization of the thermodynamic modeling results, approximating mathematical models in the form of a reduced third-degree polynomial were constructed. The adequacy of the models is verified by three control points not included in the experimental design matrix using the t-criterion at a significance level of 0.01. The results of mathematical modeling are presented graphically in the form of diagrams of the dependence of the equilibrium sulfur distribution on the slag composition at temperatures of 1600 and 1700°C. The constructed diagrams made it possible to quantitatively estimate the effect of temperature, basicity and boron oxide content on the equilibrium interphase distribution coefficient of sulfur. It is found that an increase in slag basicity from 1.0 to 2.5 in the considered range of boron oxide content (3.0–6.0%) improves the metal desulfurization process, ensuring an increase in the equilibrium interphase distribution coefficient of sulfur from 0.1 to 5.0–7.0 at temperatures of 1700 and 1600°C. It’s shown that the process of metal desulfurization in slags with low basicity of 1.05–1.15 is accompanied by a slight decrease in the sulfur content in the metal. At the same time, the concentration of boron oxide has virtually no negative effect on the process of metal desulfurization. Slags with increased basicity up to 2.0–2.5 have more favorable refining properties. The sulfur concentration in the metal during their formation decreases from 0.015 to 0.007–0.008%.

Disorder–Order transition and Metal-to-Metal charge transfer induced rare Orangish-Red emission in Bi3+-Activated double perovskite phosphors

Revealing and regulating the photoluminescence behaviors of Bi3+-activated phosphors play a crucial role in the exploration of high-quality photoluminescent materials for phosphor-converted white light-emitting diodes (pc-WLEDs). However, the existing development strategies of Bi3+-doped red phosphors are still scarce. Herein, a series of excellent NaLaScNbO6:Bi3+, Li+ orangish-red phosphors were synthesized via a high-temperature solid-state reaction. Under 370 nm NUV excitation, the optimal sample emits an orangish-red light with a peak wavelength of 625 nm, full width at half maximum of 123 nm. The A-site disorder–order transition induced by Bi3+ doping in NaLaScNbO6 double perovskite was first confirmed through Rietveld refinements and high-resolution transmission electron microscopy. The co-doped Li+ as an alkali flux material can effectively promote the layer ordering of the A-site and considerably elevate the inner quantum efficiency from 38.97 to 76.10 %. This remarkable orangish-red luminescence can be attributed to the metal-to-metal charge transfer (between Bi3+ and Nb5+) in conjunction with structural disorder–order transition. The luminous efficiency of the fabricated pc-WLED is 7.63 lm/W. The fabricated pc-WLED shows a high color rendering index (Ra = 92, R9 = 92) that can used in warm white pc-LED. The obtained results provide a fresh perspective and valuable insights into the design of Bi3+-doped red phosphors, establishing a correlation between disorder–order transition and luminescence phenomena.

Advancing an integrated understanding of land–ocean connections in shaping the marine ecosystems of coastal temperate rainforest ecoregions

AbstractLand and ocean ecosystems are strongly connected and mutually interactive. As climate changes and other anthropogenic stressors intensify, the complex pathways that link these systems will strengthen or weaken in ways that are currently beyond reliable prediction. In this review we offer a framework of land–ocean couplings and their role in shaping marine ecosystems in coastal temperate rainforest (CTR) ecoregions, where high freshwater and materials flux result in particularly strong land–ocean connections. Using the largest contiguous expanse of CTR on Earth—the Northeast Pacific CTR (NPCTR)—as a case study, we integrate current understanding of the spatial and temporal scales of interacting processes across the land–ocean continuum, and examine how these processes structure and are defining features of marine ecosystems from nearshore to offshore domains. We look ahead to the potential effects of climate and other anthropogenic changes on the coupled land–ocean meta‐ecosystem. Finally, we review key data gaps and provide research recommendations for an integrated, transdisciplinary approach with the intent to guide future evaluations of and management recommendations for ongoing impacts to marine ecosystems of the NPCTR and other CTRs globally. In the light of extreme events including heatwaves, fire, and flooding, which are occurring almost annually, this integrative agenda is not only necessary but urgent.

A pronounced deep water cooling in the Indian Ocean at ∼ 3.3–2.3 Ma linked to a major increase in the Antarctic ice volume

This study investigates changes in the bottom water circulation of the Indian Ocean since 6.5 Ma, based on benthic foraminiferal relative abundances and their stable isotope ratios from Ocean Drilling Program (ODP) Sites 709 and 758. A significant shift, from dominant North Indian Deep Water (NIDW) to Antarctic Bottom Water (AABW) circulation, is documented at ∼3.3 Ma. Principal Component Analysis (PCA) reveals two major benthic foraminiferal assemblages (PCA1 and PCA2). PCA2 is dominated by Nuttallides umbonifera, Globocassidulina subglobosa, and Epistominella exigua, representing cold and well‑oxygenated bottom water conditions between 3.3 and 2.3 Ma. The increased δ18O values of Cibicides wuellerstorfi and high relative abundance of N. umbonifera between ∼3.3 and 2.3 Ma at both sites, indicate an increased influence of AABW in the Indian Ocean due to a major increase in Antarctic ice volume. PCA1 is dominated by Uvigerina proboscidea, Fissurina spp., and miliolids, indicating oxygen-poor bottom waters and high surface productivity between 1.7 and 0.5 Ma associated with an influence of NIDW. The high relative abundance of U. proboscidea and low relative abundance of E. exigua signify low seasonality and sustained flux of organic matter with a signature of strong South Equatorial Counter Current formed by the seasonal reversal of winds during 1.7–0.5 Ma at Site 709.

Effect of Al2O3 and ZrO2 nanoparticles on microstructure and mechanical properties of Mg-AZ91 hybrid nanocomposites

In the present study, magnesium (Mg) hybrid nanocomposites containing alumina (Al2O3: 1 wt%) and zirconia (ZrO2: 0.5 and 1 wt%) nanoparticles (<50 nm) are fabricated using the stir casting technique under the protection of flux material. Role of two different nanoparticles is analysed on the performance of developed hybrid nanocomposites for implant applications. Compared to the monolithic Mg alloy, microstructural characterization revealed a reasonably uniform dispersion of nanoparticles in the matrix and a reduction in grain size in the hybrid nanocomposites. The addition of nanoparticles enhanced the microhardness and ductility of the composites. SEM, XRD and EDS are used to characterize the prepared composites. The contribution of both nanoparticles to the strengthening mechanisms are analyzed. The microhardness of AZ91 was increased from 61.4 (base alloy) to 68.79 in hybrid nanocomposites. The tensile strength of hybrid nanocomposites was found to increase from 65 MPa to 80 MPa. Adding Al2O3 nanoparticles resulted in improved grain refinement while adding ZrO2 led to an increase in microhardness. Overall, the addition of hybrid reinforcement resulted in better mechanical properties by balancing the strength and ductility of the developed nanocomposites.

Study the Dynamics of the Transformation Processes for Nitrogen and Phosphorus Compounds in the Ecosystem of the Vistula Lagoon of the Baltic Sea using the Methods of Mathematical Modeling

By using mathematical modeling methods, a systematic study of the interaction of hydrobiological, hydrochemical, hydrological and hydrophysical processes that occur in the ecosystem of the Vistula Lagoon (VL) of the Baltic Sea was carried out, taking into account the processes in the active layer of bottom sediments (BS). The features of the dynamics of nitrogen and phosphorus compounds, the turnover time and the components of the balance of compounds of biogenic elements in the VL ecosystem, as well as the degree of their temporal variability have been analyzed. It is shown that the variability of nitrogen and phosphorus compounds in the aquatic environment increases in spring and autumn periods. This is due to an increase in river flow into the lagoon and an increase in the level of external biogenic load on the water area of the VL. Model calculations of matter fluxes allow us to state that the inputs of dissolved organic and suspended matter into the lagoon from external sources and the removal to the Baltic Sea are important processes that significantly affect their content in the VL ecosystem. It has been established that under strong winds the process of sedimentation of suspensions can be largely blocked, and the intensity of BS resuspension can increase significantly. An analysis of the main qualitative and quantitative features of the nature of the temporal dynamics of the DON and DOP turnover times, as well as the mineral compounds of nitrogen and phosphorus, indicates a close conjugation of the processes of transformation of dissolved organic and inorganic substances in the water of the VL. A quantitative assessment of the processes of consumption and excretion of compounds of biogenic elements by different groups of aquatic organisms has been performed, and the important role of heterotrophic bacterioplankton and protozoa in the processes of transformation of compounds of nutrients in the VL ecosystem has been shown. The model can be used to perform scenario modeling and analysis of possible changes in the VL ecosystem under changing climatic and anthropogenic conditions.

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.

Heterogeneous marine environments diversify microbial-driven polymetallic nodule formation in the South China Sea

Most studies on the genesis of polymetallic nodules suggested that nodules in the South China Sea (SCS) are hydrogenetic; however, the complexity and the heterogeneity in hydrology and geochemistry of the SCS might cause different processes of nodule formation, impacting their application and economic value. Microbial-mediated ferromanganese deposition is an important process in nodule formation, but the related microbial potentials are still unclear in the SCS. In this study, we sampled in three typical regions (A, B, and C) of the SCS enriched with polymetallic nodules. Firstly, we investigated environmental and microbial characteristics of the water columns to determine the heterogeneity of upper seawater that directly influenced deep-sea environments. Then, microbial compositions and structures in sediment cores, overlying waters, and nodules (inside and outside) collected within the same region were analyzed for inferring features of nodule environments. Microbial interactions between nodules and surrounding environments were estimated with collinear network analysis. The microbial evidence indicated that geochemical characteristics in deep sea of the SCS that were key to the polymetallic nodule formation were severely affected by organic matter flux from upper water column. The sediment in region A was sub-oxic due to the large input of terrigenous and phytoplankton-derived organic matter, potentially enhancing the overflow of reduced metals from the porewater. The intense microbial interaction between nodules and surface sediment reinforced the origin of metals for the ferromanganese deposition from the sediment (diagenetic type). Contrarily, the sediments in regions B and C were relatively rich in oxygen, and metal ions could be majorly supplied from seawater (hydrogenetic type). The large discrepancy in microbial communities between nodule inside and remaining samples suggested that nodules experienced a long-term formation process, consistent with the feature of hydrogenetic nodules. Overall, distributions and interactions of microbial communities in nodules and surrounding environments significantly contributed to the nodule formation in the SCS by manipulating biogeochemical processes that eventually determined the source and the fate of metal ions.

Precursory crater contraction associated with the 2017 eruption of Shinmoe-dake volcano (Japan) detected by PALSAR-2 and Sentinel-1 InSAR

The time series of PALSAR-2 and Sentinel-1 images reveal inflation at the volcanic flank and contraction at the crater for approximately 5 months before the 2017 eruption of Shinmoe-dake volcano, Japan. While the observation of inflation at the volcano’s flank is ubiquitous, few studies have reported crater contraction preceding an eruption. The flank inflation stopped after the 2017 eruption, while the contraction at the crater continued until the 2018 eruption. We found that a pipe-shaped deformation source above sea level best fits the observation preceding the 2017 eruption. Suppose the flux of ejected materials constrains the conduit radius during the previous 2011 eruption. In that case, the amount of deformation of the pipe-shaped deformation source, whether open or closed at its top, is too large to be realistic. Although constraining the conduit radius from the eruption flux overestimates the pressure change of the pipe-shaped deformation source, water-saturated fractures along the volcanic conduit could extend the effective conduit radius of the pressure source. We propose one potential scenario for the mechanism of the crater contraction preceding volcanic eruptions based on the combination of compaction due to cooling by ambient groundwater and material withdrawal within the conduit. The groundwater inflows from the ambient aquifer through cracks in the porous conduit wall, which are generated by conduit expansion during the magma ascent. Decoupling from the conduit wall due to a decrease in volume of the material promotes material instability and crater contraction. The interaction between the groundwater and the magma triggers the 2017 eruption of Shinmoe-dake volcano, as previous studies have reported.Graphical

Sedimentation cycles, tectonic phases and progradation trends: Late Pannonian deposition in the Drmno Basin, Serbia

The Drmno Basin is characterized by siliciclastic deposition and coal accumulation during the Late Pannonian and Pliocene, which resulted in the formation of numerous coal seams that lack lateral continuity, challenging traditional research methods. The cyclicity and geometry of the coal seams suggest several phases of peat accumulation, interrupted by the influx of siliciclastic material from the Carpathians. Siliciclastic deposition began in the upper delta plain environment and developed into an alluvial plain with river channels and swamps. The coal seams in the Drmno field within the Kostolac open-cast mine show a northward shift of the peat accumulation centre and, together with the coarsening upward trend in the interburden sediments, indicate a south-northward progradation. Biostratigraphic results confirmed the progradation trend with Prosodacnomya carbonifera indicating an age of 7.5–8 Ma in the southern part of the field and with Prosodacnomya elongata indicating an age of 7.2 Ma in the northern part. The influence of recent tectonic activity in the peri-Pannonian domain is reflected by the presence of compressional tectonic structures observed in the basin fill.

Riverine connectivity modulates elemental fluxes through a 200- year period of intensive anthropic change in the Magdalena River floodplains, Colombia

Tropical floodplain lakes are increasingly impacted by human activities, yet their pathways of spatial and temporal degradation, particularly under varying hydrological connectivity regimes and climate change, remain poorly understood. This study examines surface-sediment samples and 210Pb-dated sediment cores from six floodplain lakes, representing a gradient in hydrological connectivity in the lower Magdalena River Basin, Colombia. We analysed temporal and spatial variations in several sediment biogeochemical indicators: the concentration and flux of nutrients, heavy metals, and organic matter (OM), and redox conditions, flooding and erosion. Multiple factor analysis (MFA) of surface-sediments identified redox conditions, OM, flooding, heavy metals and lake connectivity as the main contributors to spatial variability within- and between-lakes sediments, accounting for 48 % of the total variation. Additionally, no clear distinction was found between littoral and open-water sediment characteristics. Isolated lakes sediments exhibited reductive conditions rich in OM and nutrients, whereas connected lakes sediments showed greater heavy metal enrichment and higher concentrations of coarse river-fed material. Generalised additive models identified significant changes in the biogeochemical indicators since the late 1800s, that accelerated post-1980s. Shifts in OM, erosion, flooding, redox conditions, land-cover change, heavy metals and climate were identified by MFA as the main drivers of change, explaining 60 %-71 % of the variation in the connected lakes and 53 %-72 % in the isolated lakes. Post-1980s, connected lakes transitioned from conditions of higher accumulation of OM and little erosion to higher accumulation of heavy metals and river-fed material. Conversely, isolated lakes, shifted from detrital-heavy metal-rich sediments to OM-, and nutrient-rich, reductive sediments. Sedimentation rates also surged post-1980s, particularly in highly connected lakes, from 0.14 ± 0.07 g cm² yr⁻¹ to 0.5 ± 0.5 g cm² yr⁻¹, with elevated fluxes of metals, OM and nutrients. These changes in sediment biogeochemistry align with deforestation, river regulation and prolonged dry periods, highlighting the complexities behind establishing reliable reference conditions for pollution assessments in large, human-impacted tropical river systems.

Upper mantle scale enrichment of Cenozoic intraplate magmatism in Northeast Asia: He-Sr-Nd-Pb-O isotope geochemistry of the basalts around the Korean peninsula

The Earth’s mantle is considered to be geochemically heterogeneous, which is reflected by the diverse compositions of oceanic island basalts (OIB). The mantle enrichment resulting in this is primarily attributed to the influx of recycled crustal materials into the mantle through subduction. Additionally, the sub-continental lithospheric mantle (SCLM) complicates the elucidation of mantle heterogeneity. From this perspective, Northeast Asia, where the Pacific stagnant slab in the mantle transition zone and the SCLM distribution are presented, is the suitable site for examining the upper mantle scale enrichment. Here we report He-Sr-Nd-Pb-O isotope compositions of Cenozoic basalts found around the Korean Peninsula to illustrate the source lithology and components that caused mantle heterogeneity. Our measured helium isotope ratios ranging from 5.7 to 7.3 Ra (3He/4He ratio of air, Ra = 1.39 x 10-6) are mostly within the SCLM range (6.1 ± 0.9 Ra) but lower than the mid-ocean ridge basalt range (MORB; 8 ± 1 Ra). The Sr-Nd-Pb isotope compositions of the basalts generally display a mixture of depleted MORB mantle (DMM), enriched mantle 1 (EM1), and enriched mantle 2 (EM2) components. In addition, the basalts have δ18Oolivine (vs. V-SMOW) values ranging from 4.7 to 5.7 ‰ that deviate from the DMM range (δ18Oolivine = 5.1 ± 0.2 ‰). Our isotopic analysis results highlight the role of a pyroxenite source in the metasomatized SCLM in the genesis of basalts, and the low 3He/4He ratios of the basalts indicates a significant contribution of SCLM. Moreover, the delaminated cratonic SCLM and asthenosphere-lithosphere interaction are scenarios for the low 3He/4He ratios. Therefore, we propose that mixing of DMM (high 3He/4He ratio; 7 to 9 Ra) and the metasomatized SCLM (low 3He/4He ratio; 5 to 7 Ra) allowed enrichment within the upper mantle scale for the Cenozoic intraplate magmatism in Northeast Asia.

Terrestrial generalist predators have larger isotopic niches but rely less on aquatic prey at a natural compared to a post-mining lakeshore

The flooded pits from former opencast mining (post-mining lakes) are young aquatic ecosystems often with low primary productivity due to the high acidity. The limited availability of nutrients and simplified aquatic food webs in these artificial lakes may affect the matter fluxes towards food webs in adjacent terrestrial habitats. To understand the impact of emerging prey from a post-mining lake on terrestrial food webs and associated arthropod communities, we compared the emergence and activity of arthropods as well as the isotopic niches of generalist predators and their potential prey between lakeshores of a post-mining and a natural lake. We used aquatic and terrestrial emergence tents to sample potential prey that emerged locally (Collembola and Diptera) and pitfall traps to sample terrestrial arthropod predators (Carabidae and Araneae) from lakeshores. Community and stable isotope (δ13C and δ15N) analyses were performed to compare diversity and isotopic niches of generalist arthropod predators between the natural and post-mining lakeshores. The number of emerging aquatic and terrestrial prey did not differ significantly between lakes, but the δ15N values of aquatic emerging dipterans differed between the two lakes. Predator community diversity did not differ significantly between lakeshores, but generalist predator species from the natural lakeshore generally had larger isotopic niche sizes than the same species at the post-mining lakeshore indicating a more diverse diet. Additional estimates of diet composition suggest that predators at the natural lakeshore utilized aquatic prey to a lesser degree than at the post-mining lake, but still had a more diverse diet.