Cycling Of Elements Research Articles

Depth shapes microbiome assembly and network stability in the Mariana Trench.

Exploring microbial interactions and their stability/resilience from the surface to the hadal ocean is critical for further understanding of the microbiome structure and ecosystem function in the Mariana Trench. Vertical gradients did not destabilize microbial communities after long-term evolution and adaption. The uniform niche breadth, diversity, community complexity, and stability of microbiomes in both upper bathypelagic and hadal waters suggest the consistent roles of microbiomes in elemental cycling and adaptive strategies to overcome extreme environmental conditions. Compared with microeukaryotes, bacteria and archaea play a pivotal role in shaping the stability of the hadal microbiome. The consistent co-occurrence stability of microbiomes across vertical gradients was observed in the Mariana Trench. These results illuminate a key principle of microbiomes inhabiting the deepest trench: although distinct microbial communities occupy specific habitats, the interactions within microbial communities remain consistently stable from the upper bathypelagic to the hadal waters.

Tracing anthropogenic aerosol trace metal sources in the North Atlantic Ocean using Pb, Zn and Ni isotopes

Atmospheric deposition of trace metals of natural or anthropogenic origin is an important input of micronutrients to the surface ocean. However, understanding its direct impact on oceanic element cycles is challenging due to scarce data, coupled to diverse aerosol sources and variable solubilities. Here, we present a dataset that combines Ni, Zn and Pb isotopes for samples from the Moroccan and Senegalese coasts and in the high latitude North Atlantic Ocean. We combine the new with published data for other circum-North Atlantic sources to assess the processes that determine the isotope signatures in different types of aerosols. We then use open marine aerosol data to investigate the impact of these signatures in the open ocean. Isotope analyses were conducted on bulk aerosols (TSP), on their ultra-high-purity water leachates, and on rainwaters. Aerosols characterized by crustal elemental abundances have isotope compositions similar to Saharan mineral dust. Mixing with anthropogenic aerosols from Europe/North Africa results in lower 206Pb/207Pb and 208Pb/207Pb values for the Eastern North Atlantic region. Higher 206Pb/207Pb at a given 208Pb/207Pb, observed near the Canadian margin and occasionally at the Senegalese coast, points to anthropogenic inputs from North America. Based on trends in the aerosol data (e.g., δ66ZnJMC-Lyon versus 206Pb/207Pb, δ60NiSRM986 versus Ni/V), we identify several anthropogenic sources of Zn and Ni. The δ66ZnJMC-Lyon of low-temperature pollution (e.g., non-exhaust traffic emission) appears to be around −0.1‰ to 0.2‰, while leachate δ66ZnJMC-Lyon as low as −0.21‰ indicates contributions from high-temperature combustion or smelting processes. Among aerosols with good correlations between Ni and V, δ60NiSRM986 > 0.40‰ traces Ni contributions from oil combustion. Other Ni-enriched sources, possibly originating from laterite or sulfide, show relatively low δ60NiSRM986 (as low as −0.85‰) and low V/Ni. Generally, aerosol sources for Zn are consistent throughout the North Atlantic, while Ni can be highly heterogenous. Combining the new data with literature elemental data, ratios of soluble Zn/Pb in anthropogenic aerosols are 1–100 times surface ocean ratios, suggesting that the low δ66ZnJMC-Lyon observed in anthropogenic aerosol can be key in controlling the upper ocean Zn isotope composition. These aerosols have, however, much less significance for surface ocean Ni.

Современное состояние и перспективы развития систем предиктивной аналитики в области строительства

Introduction. The roots of modern predictive analytics go back to the 1940s, when governments began using the first computational models: Monte Carlo, neural network computational models, and linear programming. In the 1960s, corporations and research institutions began the era of computer-assisted commercialization of analytics. Then in the 1970s - 1990s it became more widespread in organizations. Tech startups have made Prescriptive Analytics and real-time analytics a reality.
 Materials and methods. Data from open sources was used. The subject of the study is the history, current state of predictive analytics systems and the prospects of the developed methodology for analyzing big data in order to predict changes in the stages of the life cycle of elements of engineering equipment of buildings and structures. The preparation and visualization of information was carried out using Microsoft Office Excel.
 Results. The terms, history of appearance, development and current state of predictive analytics systems are studied. The perspectives developed in the dissertation work, the methodology for analyzing big data in order to predict changes in the stages of the life cycle of elements of engineering equipment of buildings and structures, have been studied. The use of “Shewhart Control Charts”, methods of cluster and qualimetric analysis in scenarios unusual for them in the dissertation work allows us to count on the positive prospects of the developed methodology.
 Conclusions. Predictive analytics in the construction field is one of the most promising areas of big data analysis. The big data analysis technique developed in the dissertation in order to predict changes in the stages of the life cycle of elements of engineering equipment of buildings and structures is based on the use of modern algorithms.
 The scientific novelty lies in the approach to analysis, which uses a combined scheme in which cluster and qualimetric methods of analysis are used to search for equipment elements close to changing the stage of the life cycle.

Fossilized giant sulfide-oxidizing bacteria from the Devonian Hollard Mound seep deposit, Morocco.

The giant sulfide-oxidizing bacteria are particularly prone to preservation in the rock record, and their fossils have been identified in ancient phosphorites, cherts, and carbonates. This study reports putative spherical fossils preserved in the Devonian Hollard Mound hydrocarbon-seep deposit. Based on petrographical, mineralogical, and geochemical evidence the putative microfossils are interpreted as sulfide-oxidizing bacteria similar to the present-day genus Thiomargarita, which is also found at modern hydrocarbon seeps. The morphology, distribution, size, and occurrence of the fossilized cells show a large degree of similarity to their modern counterparts. Some of the spherical fossils adhere to worm tubes analogous to the occurrence of modern Thiomargarita on the tubes of seep-dwelling siboglinid worms. Fluorapatite crystals were identified within the fossilized cell walls, suggesting the intercellular storage of phosphorus analogous to modern Thiomargarita cells. The preservation of large sulfide-oxidizing bacteria was probably linked to changing biogeochemical processes at the Hollard Mound seep or, alternatively, may have been favored by the sulfide-oxidizing bacteria performing nitrate-dependent sulfide oxidation-a process known to induce carbonate precipitation. The presence of sulfide-oxidizing bacteria at a Devonian hydrocarbon seep highlights the similarities of past and present chemosynthesis-based ecosystems and provides valuable insight into the antiquity of biogeochemical processes and element cycling at Phanerozoic seeps.

The influence of cold seepage on the grain size and geochemistry of sediments from the Laptev Sea shelf

The East Siberian Arctic shelf is renowned for its active methane-rich fluid seeps, confirmed by numerous gas flares in the water column and direct observations of methane release from the seafloor. These cold-seep sites serve as natural laboratories for studying the impact of methane seepage on early diagenesis, authigenic mineral formation, and the geochemical cycles of carbon, sulfur, and other elements. This study examines the grain size and chemical composition of two sediment types from the Laptev Sea shelf: cold-seep sediments influenced by sulfate-driven anaerobic methane oxidation, and unaffected “seep-free” sediments (i.e., control site). High methane concentrations (up to 649 μM/L) in the surface layer of sediments indicate that the sulfate–methane transition zone is found close to the sediment–water interface approximately 5–6 cm below the seabed. At the cold-seep site, thin layers containing up to 40% sand fraction were discovered among the fine-grained sediments. We infer that upward-migrating fluids may contribute to the remobilization of the fine fraction, resulting in concentration of coarse particles. Cold-seep sediments are characterized by molybdenum (Mo) enrichment compared to the lithological background, although one “seep-free” core exhibits evidence of authigenic Mo deposition. The Mo concentration (up to 16.8 ppm) indicates that enrichment occurs under sulfidic conditions restricted to pore water, which are caused by anaerobic methane oxidation. The high Mo concentration in one “seep-free” core likely implies past cold-seep activity. A general Mo–U covariation indicates that the molybdenum enrichment in cold-seep sediments from the Laptev Sea outer shelf is controlled by a weak particulate shuttle process.

Turning a 3D Printer into a HPLC Fraction Collector: A Tool for Compound-Specific Stable Isotope Measurements

Compound-specific isotope analysis (CSIA) can provide unique insights into the cycling of elements including carbon and nitrogen. One approach for CSIA is the use of high-performance liquid chromatography (HPLC) to separate compounds of interest, followed by analysis of these compounds using an elemental analyser coupled to an isotope ratio mass spectrometer. A key component of this technique is the fraction collector, which automatically collects compounds as they are separated by HPLC. Here, we present a fraction collector that is a simple adaptation of a 3D printer, and, thus, can be easily adopted by any laboratory already equipped for HPLC. In addition to the much lower cost compared to commercial alternatives, this adaptation has the advantage for CSIA that the 3D printer is able to heat the collected fractions, which is not true for many commercial fraction collectors. Heating allows faster evaporation of the solvent, so that the dried compounds can be measured by EA–IRMS immediately. The procedure can be repeated consecutively so that diluted solutions can have the compounds concentrated for analysis. Any computer-controlled HPLC can be integrated to the fraction collector used here by means of AutoIt.

Are all copepods the same? Variation in copepod stoichiometry with taxonomy, ontogeny, latitude, and habitat

AbstractCopepods are the most abundant metazoans on Earth, driving cycles of key elements in aquatic systems, most prominently carbon (C), nitrogen (N), and phosphorus (P). One key factor determining nutrient cycling is copepod somatic stoichiometry, which can reflect ecological strategy. We conducted a systematic review that updates the seminal work of Båmstedt (1986) by summarizing the effects of latitude, habitat, life history stage, and taxonomy on C:N, C:P, and N:P ratios of field‐collected copepods. We found that differences among copepod families accounted for the greatest variation, with the Rhincalanidae and Diaptomidae being particularly C‐rich, while the Calanidae were more N‐ and P‐rich. Copepod C:N was higher in inland waters compared with animals from marine environments in both copepodites and adult females, matching the higher C content of seston in many inland freshwaters. For both copepodites and adult females, mid‐latitude animals had higher C:N and C:P than high‐latitude animals, which matched predictions based on the availability of nutrients or adaptation to cold environments. More data must be gathered to fill gaps in our knowledge of copepod stoichiometry, focusing particularly on younger life stages, non‐calanoids, low and high latitudes, the southern hemisphere, and estuarine and some inland water habitats, including large lakes. Such information will help better parameterize models of aquatic ecosystems and improve our understanding of how copepods influence consumer‐driven nutrient cycling and food web dynamics.

Geochemistry of dissolved rare earth elements in the Lancang River with cascade dams and implications for anthropogenic impacts

Anthropogenic effects like the construction of cascade dams are increasingly affecting the biogeochemical cycles of rare earth elements (REE) in rivers. However, our understanding on the REE compositions of dissolved loads in rivers under the effect of cascade dams remains limited. In this study, forty-four water samples in the Lancang River were analyzed for REE concentrations to assess the impact of cascade dams. The results showed that total dissolved REE concentrations ranged from 4.0 to 65.7 ng/L, with an average value of 21.8 ng/L. The concentrations in the middle (519.6 ng/L) and lower (331.5 ng/L) reaches were higher than those in the upper reaches (108.1 ng/L). All river samples showed (La/Yb)N values < 1, and the PAAS-normalized REE patterns indicated a substantial enrichment of heavy REE, characterized by negative Ce (0.1–0.9) and positive Eu (1.5–32.1) anomalies. The enrichment of heavy REE can be attributed to their preferential release from minerals during the weathering process and their interaction with inorganic complex anions. The negative Ce anomaly observed is likely the result of redox conditions, while the positive Eu anomaly was inherited from the REE characteristics of the source rocks. Moreover, the Ce anomaly decreased to 0.29 in the Huangdeng reservoir and 0.12 in the Dachaoshan reservoir. The value of Ce anomaly displayed a sharp decline in the middle and lower reaches affected by the cascade reservoirs. The effect of the dams played an important role in Ce anomaly by decreasing the DOC concentrations, and rivers with low DOC concentrations are commonly associated with negative Ce anomaly. This study revealed that cascade dams paly an essential role in the variation of REE in dissolved loads and REE anomaly may have the potential to track anthropogenic activities.

Resilience and functional redundancy of methanogenic digestion microbiome safeguard recovery of methanogenesis activity under the stress induced by microplastics.

Microplastics and nanoplastics are emerging pollutants that substantially influence biological element cycling in natural ecosystems. Plastics are also prevalent in sewage,and they accumulate in waste-activated sludge (WAS). However, the impacts of plastics on the methanogenic digestion of WAS and the underpinning microbiome remain underexplored, particularly during long-term operation. In this study, we found that short-term exposure to individual microplastics and nanoplastics (polyethylene, polyvinyl chloride, polystyrene, and polylactic acid) at a low concentration (10 particles/g sludge) slightly enhanced methanogenesis by 2.1%-9.0%, whereas higher levels (30-200 particles/g sludge) suppressed methanogenesis by 15.2%-30.1%. Notably, thecoexistence of multiple plastics, particularly at low concentrations, showed synergistic suppression of methanogenesis. Unexpectedly, methanogenesis activity completely recovered after long-term exposure to plastics, despite obvious suppression of methanogenesis by initial plastic exposure. The inhibition of methanogenesis by plastics could be attributed to the stimulated generation of reactive oxygen species. The stress induced by plastics dramatically decreased the relative abundance of methanogens but showed marginal influence on putative hydrolytic and fermentation populations. Nonetheless, the digestion sludge microbiome exhibited resilience and functional redundancy, contributing to the recovery of methanogenesis during the long-term operation of digesters. Plastics also increased the complexity, modularity, and negative interaction ratios of digestion sludge microbiome networks, but their influence on community assembly varied. Interestingly, a unique plastisphere was observed, the networks and assembly of which were distinct from the sludge microbiome. Collectively, the comprehensive evaluation of theinfluence of microplastics and nanoplastics on methanogenic digestion, together with the novel ecological insights, contribute to better understanding and manipulating this engineered ecosystem in the face of increasing plastic pollution.

An experimental study on monitoring of marine sediment transport by using a 3D sediment trap

The observation and analysis of sediment transport in oceans is an important means for the protection of the marine environment, resource development, construction engineering, and element cycling. However, traditional methods of observing sediment transport are either limited by the range of the instruments used or their own observational attributes, such that they cannot be used to accurately detect and analyze the process of transport of marine sediment. A 3D sediment trap has been proposed to compensate for the shortcomings of the various monitoring tools in our team, but no mature method for the analytical inversion of the data obtained from this device has been developed to date. In this paper, we developed analytical methods to invert sediment transport processes using corrected capture efficiency, sample inversion, and transport flux analysis. Through an annular flume test, we measured the turbidity, pressure, and particle size of the water stream and substituted them into the proposed analytical equations, thus verifying the applicability of the analytical methods. We used the slice experiment of the time series of the sediment samples, to determine the validity of the sample inversion, and establish the relationship between the particle size and concentration of the captured samples. We performed restoration tests on the process of sediment transport to establish a set of methods of flux analysis based on the velocity and turbidity of flow. And finally corrected for capture efficiency by particle size. The combination of analytical methods and 3D sediment trap could provide technological support for investigating the evolution of the sea, ecological cycle, and marine engineering.

Marine toxin domoic acid alters nitrogen cycling in sediments

As a red tide algal toxin with intense neurotoxicity distributed worldwide, domoic acid (DA) has attracted increasing concerns. In this work, the integrative analysis of metagenome and metabolome are applied to investigate the impact of DA on nitrogen cycling in coastal sediments. Here we show that DA can act as a stressor to induce the variation of nitrogen (N) cycling by altering the abundance of functional genes and electron supply. Moreover, microecology theory revealed that DA can increase the role of deterministic assembly in microbial dynamic succession, resulting in the shift of niches and, ultimately, the alteration in N cycling. Notably, denitrification and Anammox, the important process for sediment N removal, are markedly limited by DA. Also, variation of N cycling implies the modification in cycles of other associated elements. Overall, DA is capable of ecosystem-level effects, which require further evaluation of its potential cascading effects.

Metagenomic insight into the acidophilic functional communities driving elemental geochemical cycles in an acid mine drainage lake

Acidophiles play a key role in the generation, evolution and attenuation of acid mine drainage (AMD), which is characterized by strong acidity (pH<3.5) and high metal concentrations. In this study, the seasonal changes of acidophilic communities and their roles in elemental cycling in an AMD lake (pH∼3.0) in China were analyzed through metagenomics. The results showed eukaryotic algae thrived in the lake, and Coccomyxa was dominant in January (38.1%) and May (33.9%), while Chlorella in July (9.5%). The extensive growth of Chlamydomonas in December (22.7%) resulted in an ultrahigh chlorophyll a concentration (587 μg/L), providing abundant organic carbon for the ecosystem. In addition, the iron-oxidizing and nitrogen-fixing bacterium Ferrovum contributed to carbon fixation. Ammonia oxidation likely occurred in the acidic lake, as was revealed by archaea Ca. Nitrosotalea. To gain a competitive advantage in the nutrient-poor environment, some acidophiles exhibited facultative characteristics, e.g. the most abundant bacterium Acidiphilium utilized both organic and inorganic carbon, and obtained energy from organic matter, inorganic sulfur, and sunlight simultaneously. It was suggested that sunlight, rather than chemical energy of reduced iron-sulfur was the major driver of elemental cycling in the AMD lake. The results are beneficial to the development of bioremediation strategies for AMD.

Increased coral biomineralization due to enhanced symbiotic activity upon volcanic ash exposure

Coral reefs, which are among the most productive ecosystems on earth, are in global decline due to rapid climate change. Volcanic activity also results in extreme environmental changes at local to global scales, and may have significant impacts on coral reefs compared to other natural disturbances. During explosive eruptions, large amounts of volcanic ash are generated, significantly disrupting ecosystems close to a volcano, and depositing ash over distal areas (10s - 1000s of km depending on i.a. eruption size and wind direction). Once volcanic ash interacts with seawater, the dissolution of metals leads to a rapid change in the geochemical properties of the seawater column. Here, we report the first known effects of volcanic ash on the physiology and elemental cycling of a symbiotic scleractinian coral under laboratory conditions. Nubbins of the branching coral Stylophora pistillata were reared in aquaria under controlled conditions (insolation, temperature, and pH), while environmental parameters, effective quantum yield, and skeletal growth rate were monitored. Half the aquaria were exposed to volcanic ash every other day for 6 weeks (250 mg L−1 week−1), which induced significant changes in the fluorescence-derived photochemical parameters (ΦPSII, Fv/Fm, NPQ, rETR), directly enhanced the efficiency of symbiont photosynthesis (Pg, Pn), and lead to increased biomineralization rates. Enhancement of symbiont photosynthesis is induced by the supply of essential metals (Fe and Mn), derived from volcanic ash leaching in ambient seawater or within the organism following ingestion. The beneficial role of volcanic ash as an important micronutrient source is supported by the fact that neither photophysiological stress nor signs of lipid peroxidation were detected. Subaerial volcanism affects micronutrient cycling in the coral ecosystem, but the implication for coral ecophysiology on a reef scale remains to be tested. Nevertheless, exposure to volcanic ash can improve coral health and thus influence resilience to external stressors.

Hydrothermal amorphous silica, barite and orpiment from the crater area of seamount (SM-13) off Nicobar island, Andaman sea: Indications for the development of a new hydrothermal field

The Andaman sea characterized by trench-arc-backarc elements (Andaman-Nicobar island-arc, the Andaman back-arc spreading center, the seamount complex, and the back-arc basin) is a complex active basin and is known for hydrothermal activity in some of the seamounts (subaerial and submarine) of the volcanic arc. In the present study, 13 submarine seamounts (SM1- SM13) in the southern Andaman volcanic arc, extending from 6°47′N: 94°43′E to 7° 56′ N: 94° 2.47′E, were surveyed onboard RV Sindhu Sadhana (November 2021) to find the evidences for the hydrothermal activity. Out of the 13 seamounts, at one crater seamount (SM-13) we have observed evidence for hydrothermal activity characterized by plumes rich in dissolved gases (mainly CO2) in the water column, live chemosymbiotic organisms (Bathymodiolus species), and neoforming minerals such as amorphous silica, barite and orpiment. We observed two plumes rich in dissolved gases (mainly CO2), called GP1 and GP2, in the water column at two different water depths i.e. 400 and 380 mbsl respectively. Geochemical analysis of the water samples shows enhanced TCO2 concentrations within the plumes rich in dissolved gases (mainly CO2) observed in sub-bottom profiler data, however, the dissolved methane concentrations do not show any enrichment when compared with ambient seawater concentrations. Apart from the enhancement in the TCO2 concentrations, pH and total alkalinity data also show fluctuations within the same depth zone which may be attributed to the hydrothermal plume exhausting from the crater seamount. The occurrence of live chemosymbiotic organism Bathymodiolus species indicate an active and continuous supply of H2S. The precipitation of neoforming hydrothermal minerals such as amorphous silica, tabular barite, and orpiment on the surface of the rock samples further supports the hydrothermal activity. Previous studies carried out in 2007 have reported hydrothermal ferromanganese oxides precipitated from low-temperature hydrothermal fluids (Surya prakash et al., 2012) and inferred SM-13 as a dormant submarine volcano (Kamesh Raju et al., 2012). However, after 14 years, we observe volatile emissions to the water column, hydrothermal mineral precipitation and live chemosymbiotic organisms from the same seamount. These observations of the present study infer development of a new hydrothermal field in the least explored Andaman Sea. This study adds up a new active site to the global hydrothermal inventory which may allow better estimation of global hydrothermal flux and its role in oceanic elemental cycle.

To the transition zone and back: Records from diopside exsolution lamellae in chromite from Archean ophiolitic podiform chromitites

Plate tectonics and deep subduction provide the conveyor belt for elemental cycling between Earth's surface and deep interior. Here, we report Archean diopside exsolution lamellae in chromite grains from 2.5 billion years old (Ga) subducted then exhumed Archean oceanic crustal fragments in ophiolitic mélange. Diopside exsolution lamellae are a key indicator of a precursor ultra-high pressure (UHP) phase of chromite, known previously only from Phanerozoic subduction zones, indicating deep subduction and elemental cycling between the surface and deep Earth. These lamellae, along with trapped dolomite, and UHP TiO2(II)-bearing multi-phase solid crustal mineral inclusions in the host chromite, suggest that a precursor chromite polymorph (chenmingite) with a crystal structure stable only at conditions in the mantle transition zone (> 413 to 660 km) preserve the history of subduction, entrapment of UHP crustal mineral inclusions, and return flow to the surface in an Archean subduction/forearc system. These nano-scale diopside lamellae and UHP TiO2(II)-bearing multi-phase solid inclusions are strong evidence for deep and steep subduction in the Neoarchean, and early operation of the deep crustal material recycling, linking surface and deep environments, forging a habitable world.

Hydrothermal origin of heavy potassium isotope compositions in altered oceanic crust: Implications for tracing the elemental cycle

Stable potassium isotopes are easily fractionated by fluid-rock interactions and provide a tool to probe the role of hydrothermal alteration of the oceanic crust in modifying the chemical composition of seawater and, through subduction, the deep Earth. An in-depth understanding of K isotope fractionation during high-temperature hydrothermal oceanic crust alteration is necessary to refine the use of K isotopes to track geochemical processes. This study investigated a suite of samples of altered upper oceanic crust, that formed at the East Pacific Rise and is exposed at the Hess Deep, to constrain K isotope fractionation by combining mineralogical, elemental, isotopic, and synchrotron-based spectroscopic approaches. Relative to the protolith, isotopically heavy K is enriched in the sheeted dike complex (δ41K of -0.48 ± 0.15 to 0.14 ± 0.13‰, ave. -0.22‰) where the rocks are generally depleted in K through high-temperature (hundreds of °C) fluid-rock reaction. In contrast, samples from the lava/dike boundary (-0.59 ± 0.14 to -0.48 ± 0.12‰, ave. -0.54‰) and lavas (-0.54 ± 0.10 to -0.42 ± 0.09‰, ave. -0.46‰), commonly exhibit net enrichment of K relative to the protolith due to low-temperature (tens of °C) fluid-rock reaction and have δ41K similar to fresh basalts. We interpret the observed isotopic variation in the sheeted dikes as being primarily due to one or both of the following: (i) diffusive K loss, with 39K diffusing faster than 41K, and (ii) neoformation of albitic plagioclase, which is identified as an important 41K host in altered sheeted dikes. Using isotope mass balance calculation, we show that isotopic fractionation occurring during high-temperature alteration may be difficult to identify in hydrothermal vent fluids because the δ41K of the K leached from the rocks is similar to that of the protolith. Hydrothermal K outputs to the ocean may not contribute significantly to elevating the δ41K of modern seawater relative to the silicate Earth. In contrast to upper oceanic crust altered at low-temperature and seafloor sediments, subducting ocean crust altered at high-temperature adds rocks with δ41K higher than the protolith to the mantle. Because the high δ41K value of the sheeted dikes is generated during the loss of K from these rocks, hence expressed most strongly in K-depleted samples, tracking this signature in arc magma and the mantle will be challenging.

Short- and long-term plant and microbial uptake of 15N-labelled urea in a mesic tundra heath, West Greenland

Terrestrial animals are key elements in the cycling of elements in the Arctic where nutrient availability is low. Waste production by herbivores, in particular urine deposition, has a crucial role for nitrogen (N) recycling, still, it remains largely unexplored. Also, experimental evidence is biased toward short-term studies and Arctic regions under high herbivore pressure. In this study, we aimed to examine the fate of N derived from urine in a nutrient poor tundra heath in West Greenland, with historical low level of herbivory. We performed a pulse labelling with 15N-urea over the plant canopy and explored ecosystem N partition and retention in the short-term (2 weeks and 1 year) and longer-term (5 years). We found that all vascular plants, irrespective of their traits, could rapidly take up N-urea, but mosses and lichens were even more efficient. Total 15N enrichment was severely reduced for all plants 5 years after tracer addition, with the exception of cryptogams, indicating that non-vascular plants constituted a long-term sink of 15N-urea. The 15N recovery was also high in the litter suggesting high N immobilization in this layer, potentially delaying the nutrients from urine entering the soil compartment. Long-term 15N recovery in soil microbial biomass was minimal, but as much as 30% of added 15N remained in the non-microbial fraction after 5 years. Our results demonstrate that tundra plants that have evolved under low herbivory pressure are well adapted to quickly take advantage of labile urea, with urine having only a transient effect on soil nutrient availability.

Towards a mechanistic understanding of animal-ecosystem interactions.

Research Highlight: Ferraro, K. M., Welker, L., Ward, E. B., Schmitz, O. J., & Bradford, M. A. (2023). Plant mycorrhizal associations mediate the zoogeochemical effects of calving subsidies by a forest ungulate. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.14002. Animals play large roles in ecosystem elemental cycling but predicting effects in diverse contexts remains a substantial challenge. Fundamental to progress is (1) identifying mechanisms by which animals impact nutrient distribution and cycling, and (2) disentangling how environmental context mediates the operation of alternative mechanisms. In an elegant field experiment, Ferraro etal. (2023) provide the first detailed exploration of the impact of nutrient inputs from mammalian parturition on soil functioning and the stoichiometry of plant tissues. The authors find that nitrogen from experimental additions of ungulate parturition material (natal fluids) is rapidly incorporated into microsite soil organic pools and plant tissues. They also find that soil processes (soil microbial biomass, rates of carbon mineralization, nitrogen mineralization and nitrification) and the nitrogen content of plant tissues above- and belowground are increased by addition of parturition material. Notably, the authors identify that increases in some soil processes and plant tissue nitrogen are weaker in microsites dominated by ericoid mycorrhizal plants than those dominated by ectomycorrhizal plants. These findings demonstrate that parturition depositions, a ubiquitous but overlooked mechanism of mammalian impacts on ecosystems, impact ecosystem processes and plant tissue stoichiometry. Furthermore, plant-fungal associations are a predictive axis of context dependency mediating zoogeochemical effects at fine scales. Ferraro etal.'s (2023) novel approach simultaneously advances mechanistic understanding of animal-ecosystem interactions at fine scales and facilitates prediction of ungulate effects on nutrient availability at landscape extents.

Impact of drought on terrestrial ecosystem C-N-P stoichiometry and microbial nutrient limitation

Carbon (C), nitrogen (N), and phosphorus (P) stoichiometric traits are of critical importance to ecosystem functioning. Exploring the effects of drought on the C-N-P stoichiometric is of great significance for understanding element cycling and nutrient limitation in terrestrial ecosystems; however, it has not been uniformly and reliably concluded on a global scale. Here, based on 505 paired observational statistics, we systematically analyzed the effect of drought on terrestrial ecosystem C-N-P stoichiometry on the global scale. Drought greatly decreased the C:N ratio in soil (9.9%), enzymes (13.9%), shoots (7.9%), and roots (8.1%). Furthermore, soil microbes were limited by N, whereas plants were restricted by P under drought stress. Drought intensity and duration were significantly negatively correlated with shoot N:P and vector angle. Mean annual temperature (MAT) was negatively correlated with enzyme N:P and vector angle but had less effect on plant C:N:P stoichiometry. In conclusion, heavy drought intensity and long duration attenuated the P limitation in the shoot but enhanced the microbial N limitation.

Design for and from disassembly with timber elements: strategies based on two case studies from Switzerland

When a timber building gets disassembled and its elements either are burned or biodegrade, the carbon stored in the timber structure gets released to the atmosphere as CO2. Reusing timber elements prevents this process from happening and thus delays the global warming caused by greenhouse gas emissions. Even if there is a long historic tradition of timber reuse in Switzerland, currently a low fraction of a timber building’s elements is being reused after its disassembly. In this study, strategies that could facilitate circular use of timber elements are analyzed. The focus lies on the design process, which is investigated from two perspectives: strategies at the start-of-life of buildings to enable new timber element cycles to emerge (design for disassembly, or DforD), and strategies at the end-of-life of buildings to keep existing timber elements cycles closed (design from disassembly, or DfromD). Two case studies of recently completed multi-story timber-hybrid buildings in Switzerland were analyzed from both perspectives. Regarding DforD, a scoring system was developed that assesses single elements according to their disassembly and reuse potential. Regarding DfromD, a building design optimization tool was created that takes dimensional design tolerances of a building as an input and proposes a procurement-optimized and structurally safe arrangement of reused elements, which are taken from an inventory that is based on the two case studies. It was found that connections between reinforced concrete and timber parts play a crucial role in terms of DforD and that building layouts with DfromD elements may vary widely according to the chosen optimization variable. In conclusion, both applications have the potential to scale up the competitiveness of reused elements.