Incorporation of hydrogen-producing magnesium into minced beef meat protects the quality attributes and safety of the product during cold storage

The impact of hydrogen (H2) producing magnesium (Mg) incorporation into minced beef meat (MBM) on the quality and safety of the product was investigated. The H2-producing Mg (H2-P-Mg)-incorporated MBMs were vacuumed (VP) and stored at 4 °C for 12 days. Other MBMs were vacuumed and gassed with H2 or N2. At the end of storage, the lowest browning index values were for H2 and H2-P-Mg samples. H2- PMg and VP methods generally decreased the counts of mesophilic and psychrotrophic bacteria and yeast molds and restricted the formation of thiobarbituric acid reactive substances and biogenic amines. Heat mapping, PCA, and multivariate analysis methods confirmed chemical analysis results. The volatile compounds were at their highest levels in the control samples at the end of storage, followed by H2, N2, H2-P-Mg, and VP samples. Using the H2-P-Mg method in MBM preparation could protect the quality characteristics and safety of the product during cold storage.

Miyata (Porphyra haitanensis)

The quality of Pyropia haitanensis (T. J. Chang & B. F. Zheng) N. Kikuchi & M. Miyata (Porphyra haitanensis) is directly affected by nutrient availability. However, the molecular mechanism underlying the synergistic regulatory effects of nitrogen (N) and phosphorus (P) availability on P. haitanensis quality is unknown. Here, we performed physiological and multi-omics analyses to reveal the combined effects of N and P on P. haitanensis quality. The pigments accumulated under high N because of increases in N metabolism and porphyrin metabolism, ultimately resulting in intensely colored thalli. High N also promoted amino acid metabolism and inosine 5'-mononucleotide (IMP) synthesis, but inhibited carbohydrates accumulation. This resulted in increased amino acid, IMP and decreased agaro-carrageenan and cellulose contents, thereby improving the nutritional value and taste. Furthermore, high P promoted carbon metabolism and amino acid metabolism.This study provided the basis for elucidating the mechanism behind N and P regulating the seaweed quality.

The pH acidity and nitrate accumulation by plasma discharge enhanced the growth and phytochemicals of soybean sprouts grown in reused water

This study investigated the effect of plasma treatment on reused water and evaluated the interactions of the plasma-treated water (PTW) with plants or microbes to determine the optimal PTW for reuse. The repeated treatment gradually accumulated nitrate (NO3-) in the PTW and lowered its pH; afterward, it led to the sprouted soybeans accumulating other inorganic ions in the PTW. The biomass of soybean sprouts was enhanced by the accumulated NO3- but decreased due to the pH effect. Meanwhile, the acidic pH reduced the microbial counts, but they increased after sprinkling the PTW over the sprouts. The optimal PTW in our study, which had a gradual increase of NO3- (≤321.8 mg·L-1) with an acceptable pH (≥pH 3), significantly enhanced the biomass by 4.2% compared to the untreated control. Additionally, it increased the total content of amino acids and isoflavones by 9% and 18% in the growing part, respectively.

Nutrient dynamics in wetland systems associated with hydrological and anthropogenic variations in the south of Samborombón Bay, Argentina

Wetlands provide numerous ecosystem services to the environment, such as nutrient removal and storage. The aim of this work is to evaluate the nutrient dynamics in different sectors within wetland systems in the south of the Samborombón Bay (Argentina) based on hydrological and/or anthropogenic variations. For this purpose, the hydrological features of the wetland were defined through the analysis of satellite images, precipitation and tidal data, and field surveys. Three sectors were identified in the wetland: one with tidal influence, another which is dependent on rainfall, and another that receives inputs from rainfall and from a sewage effluent treatment plant. In order to analyze the nutrient dynamics, samples of surface water, groundwater, and sediments were collected from these sectors. Measurements of pH and electrical conductivity were determined in situ in water samples, while the concentration of inorganic forms of phosphorus and nitrogen, soluble reactive silica, and organic carbon were determined through laboratory analysis. Also, bioavailable phosphorus, organic matter, pH, and electrical conductivity were determined in the sediment samples collected. Statistical analysis of the data reveals differences between the sectors and allows the interpretation of the dynamics of the studied components in the wetland. Electrical conductivity distinguishes the intertidal sectors of the wetland while components associated with P and N discriminate the sectors with inputs from the sewage effluent treatment plant. On the other hand, soluble reactive silica, organic carbon, and organic matter do not seem to be influenced by the tide or effluent discharge. This study demonstrates that the studied wetland works as a nutrient retention area, providing ecosystem services to local inhabitants. Although these services can be utilized, they require a continuous monitoring over time to provide an early warning in case the variations in P and N cycles could lead to eutrophication or wetland degradation.

Developing simple indicators of nitrogen and phosphorus removal in constructed stormwater wetlands

Quantifying pollutant removal by stormwater wetlands requires intensive sampling which is cost-prohibitive for authorities responsible for a large number of wetlands. Wetland managers require simple indicators that provide a practical means of estimating performance and prioritising maintenance works across their asset base. We therefore aimed to develop vegetation cover and metrics derived from monitoring water level, as simple indicators of likely nutrient pollutant removal from stormwater wetlands. Over a two-year period, we measured vegetation cover and water levels at 17 wetlands and used both to predict nitrogen (N) and phosphorus (P) removal. Vegetation cover explained 48 % of variation in total nitrogen (TN) removal; with a linear relationship suggesting an approximate 9 % loss in TN removal per 10 % decrease in vegetation cover. Vegetation cover is therefore a useful indicator of TN removal. Further development of remotely-sensed data on vegetation configuration, species and condition will likely improve the accuracy of TN removal estimates. Total phosphorus (TP) removal was not predicted by vegetation cover, but was weakly related to the median water level which explained 25 % of variation TP removal. Despite weak prediction of TP removal, metrics derived from water level sensors identified faults such as excessive inflow and inefficient outflow, which in combination explained 50 % of the variation in the median water level. Monitoring water levels therefore has the potential to detect faults prior to loss of vegetation cover and therefore TN removal, as well as inform the corrective action required.

Dependence of evolution of Cyanobacteria superiority on temperature and nutrient use efficiency in a meso-eutrophic plateau lake

Algal blooms in lakes have been a challenging environmental issue globally under the dual influence of human activity and climate change. Considerable progress has been made in the study of phytoplankton dynamics in lakes; The long-term in situ evolution of dominant bloom-forming cyanobacteria in meso-eutrophic plateau lakes, however, lacks systematic research. Here, the monthly parameters from 12 sampling sites during the period of 1997-2022 were utilized to investigate the underlying mechanisms driving the superiority of bloom-forming cyanobacteria in Erhai, a representative meso-eutrophic plateau lake. The findings indicate that global warming will intensify the risk of cynaobacteria blooms, prolong Microcystis blooms in autumn to winter or even into the following year, and increase the superiority of filamentous Planktothrix and Cylindrospermum in summer and autumn. High RUETN (1.52 Biomass/TN, 0.95-3.04 times higher than other species) under N limitation (TN < 0.5 mg/L, TN/TP < 22.6) in the meso-eutrophic Lake Erhai facilitates the superiority of Dolichospermum. High RUETP (43.8 Biomass/TP, 2.1-10.2 times higher than others) in TP of 0.03-0.05 mg/L promotes the superiority of Planktothrix and Cylindrospermum. We provided a novel insight into the formation of Planktothrix and Cylindrospermum superiority in meso-eutrophic plateau lake with low TP (0.005-0.07 mg/L), which is mainly influenced by warming, high RUETP and their vertical migration characteristics. Therefore, we posit that although the obvious improvement of lake water quality is not directly proportional to the control efficacy of cyanobacterial blooms, the evolutionary shift in cyanobacteria population structure from Microcystis, which thrives under high nitrogen and phosphorus conditions, to filamentous cyanobacteria adapted to low nitrogen and phosphorus levels may serve as a significant indicator of water quality amelioration. Therefore, we suggest that the risk of filamentous cyanobacteria blooms in the meso-eutrophic plateau lake should be given attention, particularly in light of improving water quality and global warming, to ensure drinking water safety.

Effects of different dwarfing interstocks on the rhizosphere, endophytic bacteria, and drought resistance of apple trees

Rootstock is commonly used to enhance plant resistance to drought stress. However, it is necessary to investigate the effects of different rootstock, interstock, and scion combinations on rhizosphere and root endophytic bacteria under drought stress. We conducted a pot experiment to investigate how interstock [SH40, Jizhen 1 (J1), and Jizhen 2 (J2)] affects the drought tolerance and nitrogen (N) uptake and utilization of apple trees under drought stress. The results showed that the total dry weight, total chlorophyll content, carotenoid content, photosynthesis rate, and N absorption and utilization efficiency of apple trees decreased significantly, whereas relative electrolyte leakage increased significantly under drought stress. Membership function analysis showed that the apple plants with the J1 interstock had the greatest drought resistance. In addition, drought treatment significantly affected the diversity and composition of rhizosphere and root endophytic communities in all three rootstock/interstock/scion combinations. Further analysis revealed that the relative abundance of the plant pathogen Ralstonia was significantly increased in J2 drought-treated roots, compared to the other groups, whereas those of some potentially beneficial bacteria (0134_terrestrial_group, Phenylobacterium, Ellin6067, Kribbella, Chloronema, and Streptomyces) increased significantly in the J1 drought-treated sample. Co-occurrence network analysis showed that some potentially beneficial bacteria (Ellin6067, S0134_terrestrial_group, Pedomicrobium, and Subgroup_10) were significantly positively correlated with N content. These modifications of the rhizosphere and endophytic bacterial communities may influence the drought resilience and N uptake efficiency of different combinations of interstocks and scions. This study is a much-needed step towards understanding the stress response mechanism of scion-rootstock combinations.

Nutrients addition decreases soil fungal diversity and alters fungal guilds and co-occurrence networks in a semi-arid grassland in northern China

Anthropogenic eutrophication is known to impair the diversity and stability of aboveground community, but its effects on the diversity, composition and stability of belowground ecosystems are not yet fully understood. In this study, we conducted a 9-year nitrogen (N) and phosphorus (P) addition experiment in a semi-arid grassland of Northern China to elucidate the impacts of nutrients addition on soil fungal diversity, functional guilds, and co-occurrence networks. The results showed that N addition significantly decreased soil fungal diversity and altered fungal community composition, whereas P addition had no impact on them. The relative abundance of arbuscular mycorrhizal fungi and leaf_saprotroph were reduced by N and P addition, but P addition enhanced the abundance of saprotrophic fungi. Co-occurrence network analysis revealed that N addition destabilized fungal network complexity and stability, while P addition slightly increased the network complexity. Additionally, the network analysis of N × P interaction revealed that P addition mitigated negative effects of N addition on network complexity and stability. Structural equation modeling (SEM) results suggested that nutrients addition directly or indirectly influenced the fungal community structure through the loss of plant richness and the increase of perennial grass biomass. These findings indicate that in comparison to P addition, N addition exhibits a pronounced negative effect on soil fungal communities. Our findings also suggest that changes in plant functional groups under nutrients deposition are pivotal in shaping soil fungal community structure in semi-arid grassland and highlight the need for a better understanding of the belowground ecosystem dynamics.

Microbial mechanisms in nitrogen fertilization: Modulating the re-mobilization of clay mineral-bound cadmium in agricultural soils

Soil cadmium (Cd) can affect crop growth and food safety, and through the enrichment in the food chain, it ultimately poses a risk to human health. Reducing the re-mobilization of Cd caused by the release of protons and acids by crops and microorganisms after stabilization is one of the significant technical challenges in agricultural activities. This study aimed to investigate the re-mobilization of stabilized Cd within the clay mineral-bound fraction of soil and its subsequent accumulation in crops utilizing nitrogen ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3--N), at 60 and 120 mg kg-1. Furthermore, the study harvested root exudates at various growth stages to assess their direct influence on the re-mobilization of stabilized Cd and to evaluate the indirect effects mediated by soil microorganisms. The results revealed that, in contrast to the NO3--N treatment, the NH4+-N treatment significantly enhanced the conversion of clay mineral-bound Cd in the soil to NH4NO3-extractable Cd. It also amplified the accumulation of Cd in edible amaranth, with concentrations in roots and shoots rising from 1.7-6.0 mg kg-1 to 4.3-9.8 mg kg-1. The introduction of NH4+-N caused a decrease in the pH value of the rhizosphere soil and stimulated the production and secretion organic and amino acids, such as oxalic acid, lactic acid, stearic acid, succinic acid, and l-serine, from the crop roots. Furthermore, compared to NO3--N, the combined interaction of root exudates with NH4+-N has a more pronounced impact on the abundance of microbial genes associated with glycolysis pathway and tricarboxylic acid cycle, such as pkfA, pfkB, sucB, sucC, and sucD. The effects of NH4+-N on crops and microorganisms ultimately result in a significant increase in the re-mobilization of stabilized Cd. However, the simulated experiments showed that microorganisms only contribute to 3.8-6.6 % of the re-mobilization of clay mineral-bound Cd in soil. Therefore, the fundamental strategy to inhibit the re-mobilization of stabilized Cd in vegetable cultivation involves the regulation of proton and organic acid secretion by crops.

Emerging nitrogen-fixing cyanobacteria for sustainable cotton cultivation

Amid growing environmental concerns and the imperative for sustainable agricultural practices, this study examines the potential of nitrogen-fixing cyanobacteria as biofertilizers, particularly in cotton cultivation. The reliance on synthetic nitrogen fertilizers (SNFs), prevalent in modern agriculture, poses significant environmental challenges, including greenhouse gas emissions and water system contamination. This research aims to shift this paradigm by exploring the capacity of cyanobacteria as a natural and sustainable alternative. Utilizing advanced metabarcoding methods to analyze the 16S rRNA gene, we conducted a comprehensive assessment of soil bacterial communities within cotton fields. This study focused on evaluating the diversity, structure, taxonomic composition, and potential functional characteristics of these communities. Emphasis was placed on the isolation of native N2-fixing cyanobacteria strains rom cotton soils, and their subsequent effects on cotton growth. Results from our study demonstrate significant plant growth-promoting (PGP) activities, measured as N2 fixation, production of Phytohormones, Fe solubilization and biofertilization potential of five isolated cyanobacterial strains, underscoring their efficacy in cotton. These findings suggest a viable pathway for replacing chemical-synthetic nitrogen fertilizers with natural, organic alternatives. The reintegration of these beneficial species into agricultural ecosystems can enhance crop growth while fostering a balanced microbial environment, thus contributing to the broader goals of global sustainable agriculture.

Nitrogen in landfills: Sources, environmental impacts and novel treatment approaches

Nitrogen (N) accumulation in landfills is a pressing environmental concern due to its diverse sources and significant environmental impacts. However, there is relatively limited attention and research focus on N in landfills as it is overshadowed by other more prominent pollutants. This study comprehensively examines the sources of N in landfills, including food waste contributing to 390 million tons of N annually, industrial discharges, and sewage treatment plant effluents. The environmental impacts of N in landfills are primarily manifested in N2O emissions and leachate with high N concentrations. To address these challenges, this study presents various mitigation and management strategies, including N2O reduction measures and novel NH4+ removal techniques, such as electrochemical technologies, membrane separation processes, algae-based process, and other advanced oxidation processes. However, a more in-depth understanding of the complexities of N cycling in landfills is required, due to the lack of long-term monitoring data and the presence of intricate interactions and feedback mechanisms. To ultimately achieve optimized N management and minimized adverse environmental impacts in landfill settings, future prospects should emphasize advancements in monitoring and modeling technologies, enhanced understanding of microbial ecology, implementation of circular economy principles, application of innovative treatment technologies, and comprehensive landfill design and planning.

Lingtou Dancong) leaf quality under different nitrogen fertilization regimes

Our study investigated the impact of nitrogen fertilization at 0, 150, 300, and 450 kg/ha on the non-volatile and volatile substances, as well as gene expression in fresh leaves from Lingtou tea plants. We found that applying nitrogen at 450 kg/ha notably increased total polyphenols (TPs) and free amino acids (AAs) while decreasing the TP to AA ratio (TP/AA) and total catechins (TC) contents. Chlorophyll, caffeine (CAF) and theanine accumulated to a greater extent with nitrogen application rates of 150, 300, and 450 kg/ha, respectively, six substances - TP, CAF, TC, theanine, epigallocatechin (EGC), and AA - as key contributors to the taste quality of LTDC. Additionally, five substances with variable importance in projections (VIP) ≥ 1 and odor activation values (OAV) ≥ 1, notably linalool and cis-linalool oxide (furanoid), significantly contributed to the tea's overall aroma. Furthermore, applying 300 kg/ha nitrogen upregulated the dihydroflavonol reductase (DFR)gene, likely causing catechin decrease.

Hemiparasite Phtheirospermum japonicum growth benefits from a second host and inflicts greater host damage with exogenous N supply

While parasites are likely to connect to multiple host plants in nature, parasitism dynamics under multiple association conditions remain unclear and are difficult to separate from competitive effects. In this study, a five-compartment split root-box was constructed to allow a single facultative root hemiparasite, Phtheirospermum japonicum, to connect to zero, one or two Medicago sativa hosts while maintaining constant plant number and independently controlling nutrient supply. In the first experiment, we found that P. japonicum derived equal, additive benefits from attachment to a second host irrespective of parasite N status. In the second experiment, parasites were grown at four N levels in either parasitic or control conditions. Attachment caused a constant, absolute increase in parasite mass at all N levels, while host damage increased at higher parasite N levels despite an apparent decrease in host to parasite N transfer. Our findings suggest that host damage caused by P. japonicum may be strengthened by exogenous nitrogen supply to the parasite.

Interaction of reed litter and biochar presences on performances of constructed wetlands

Constructed wetlands (CWs) are frequently used for effective biological treatment of nitrogen-rich wastewater with external carbon source addition; however, these approaches often neglect the interaction between plant litter and biochar in biochar-amended CW environments. To address this, we conducted a comprehensive study to assess the impacts of single or combined addition of common reed litter and reed biochar (pyrolyzed at 300 and 500 °C) on nitrogen removal, greenhouse gas emission, dissolved organic matter (DOM) dynamics, and microbial activity. The results showed that combined addition of reed litter and biochar to CWs significantly improved nitrate and total nitrogen removal compared with biochar addition alone. Compared to those without reed litter addition, CWs with reed litter addition had more low-molecular-weight and less aromatic DOM and more protein-like fluorescent DOM, which favored the enrichment of bacteria associated with denitrification. The improved nitrogen removal could be attributed to increases in denitrifying microbes and the relative abundance of functional denitrification genes with litter addition. Moreover, the combined addition of reed litter and 300 °C-heated biochar significantly decreased nitrous oxide (30.7 %) and methane (43.9 %) compared to reed litter addition alone, while the combined addition of reed litter and 500 °C-heated biochar did not. This study demonstrated that the presences of reed litter and biochar in CWs could achieve both high microbial nitrogen removal and relatively low greenhouse gas emissions.

Comparative analysis of the effects of microplastics and nitrogen on maize and wheat: Growth, redox homeostasis, photosynthesis, and AsA-GSH cycle

Microplastics (MPs) pose a significant threat to the function of agro-ecosystems. At present, research on MPs has mainly focused on the effects of different concentrations or types of MPs on a crop, while ignoring other environmental factors. In agricultural production, the application of nitrogen (N) fertilizer is an important means to maintain the high yield of crops. The effects of MPs and N on growth parameters, photosynthetic system, active oxygen metabolism, nutrient content, and ascorbate-glutathione (AsA-GSH) cycle of maize and wheat were studied in order to explicit whether N addition could effectively alleviate the effects of MPs on maize and wheat. The results showed that MPs inhibited the plant height of both maize and wheat, and MPs effects on physiological traits of maize were more severe than those of wheat, reflecting in reactive oxygen metabolism and restriction of photosynthetic capacity. Under the condition of N supply, AsA-GSH cycle of two plants has different response strategies to MPs: Maize promoted enzyme activity and co-accumulation of AsA and GSH, while wheat tended to consume AsA and accumulate GSH. N application induced slight oxidative stress on maize, which was manifested as an increase in hydrogen peroxide and malonaldehyde contents, and activities of polyphenol oxidase and peroxidase. The antioxidant capacity of maize treated with the combination of MPs + N was better than that treated with N or MPs alone. N could effectively alleviate the adverse effects of MPs on wheat by improving the antioxidant capacity.

Distribution of hydrogen sulfide, nitrogen and phosphorous species in inshore and offshore sediments of the south Caspian Sea

This study aimed to geochemically investigate the sediments of the south Caspian Sea at different depths in summer and winter 2020. Sampling was conducted in 5 transects along the south coastline of the Caspian Sea and sediment grain size, hydrogen sulfide, Oxidation-reduction potential (Eh), total nitrogen, nitrite, nitrate, ammonium, total phosphorus, organic and inorganic phosphorous were measured. Eh values showed significant differences between seasons and between different transects (p < 0.05). Hydrogen sulfide ranged from 1.87 to 307.00 ppm. No significant difference was observed in hydrogen sulfide between seasons and among depths (p > 0.05). Total, inorganic and organic phosphorus contents were 782.96-1335.79 ppm, 639.66-1183.60 ppm, and 42.58-205.46 ppm, respectively. Total nitrogen revealed significant differences among transects (p < 0.05). Based on sediment quality guidelines, most sampling sites had alerting conditions for organic matter, and phosphorous contamination was detected at all stations. Anoxic condition was seen at most sites according to sedimentary Eh.

Nitrogen addition does not alter symmetric responses of soil respiration to changing precipitation in a semi-arid grassland

Concurrent changing precipitation regimes and atmospheric nitrogen (N) deposition can have profound influences on soil carbon (C) cycling. However, how N enrichment regulates the responses of soil C fluxes to increasing variability of precipitation remains elusive. As part of a field precipitation gradient experiment with nine levels of precipitation amounts (-60 %, -45 %, -30 %, -15 %, ambient precipitation, +15 %, +30 %, +45 %, and +60 %) and two levels of N addition (0 and 10 g N m-2 yr-1) in a semi-arid temperate steppe on the Mongolian Plateau, this work was conducted to investigate the responses of soil respiration to decreased and increased precipitation (DP and IP), N addition, and their possible interactions. Averaged over the three years from 2019 to 2021, DP suppressed soil respiration by 16.1 %, whereas IP stimulated it by 27.4 %. Nitrogen addition decreased soil respiration by 7.1 % primarily via reducing microbial biomass C. Soil respiration showed symmetric responses to DP and IP within all the four precipitation variabilities (i.e., 15 %, 30 %, 45 %, and 60 %) under ambient N. Nevertheless, N addition did not alter the symmetric responses of soil respiration to changing precipitation due to the comparable sensitivities of microbial biomass and root growth to DP and IP under the N addition treatment. These findings indicate that intensified precipitation variability does not change but N addition could alleviate soil C releases. The unchanged symmetric responses of soil respiration to precipitation variability under N addition imply that N deposition may not change the response pattern of soil C releases to predicted increases in precipitation variability in grasslands, facilitating the robust projections of ecosystem C cycling under future global change scenarios.

Nitrogen and phosphorus limitations promoted bacterial nitrate metabolism and propagation of antibiotic resistome in the phycosphere of Auxenochlorella pyrenoidosa

Despite that nitrogen (N) and phosphorus (P) play critical roles in the lifecycle of microalgae, how N and P further affect the distribution of bacteria and antibiotic resistance genes (ARGs) in the phycosphere is still poorly understood. In this study, the effects of N and P on the distribution of ARGs in the phycosphere of Auxenochlorella pyrenoidosa were investigated. Results showed that the growth and chlorophyll synthesis of microalgae were inhibited when N or P was limited, regardless of the N/P ratios, but the extracellular polymeric substances content and nitrate assimilation efficiency were enhanced in contrast. Metagenomic sequencing revealed that N or P limitation resulted in the recruitment of specific bacteria that highly contribute to the nitrate metabolism in the phycosphere. Besides, N or P limitation promoted the propagation of phycosphere ARGs, primarily through horizontal gene transfer mediated by mobile genetic elements. The enrichment of specific bacteria induced by changes in the algal physiology also contributed to the ARGs proliferation under nutrient limitation. Our results demonstrated that the reduction of algal cells caused by nutrient limitation could promote the propagation of ARGs, which provides new insights into the occurrence and spread of ARGs in the phycosphere.

Temporal and spatial differences in nitrogen and phosphorus biogeochemistry and ecosystem functioning of a hypertrophic lagoon (Curonian Lagoon, SE Baltic Sea) revealed via Ecological Network Analysis

In coastal lagoons, eutrophication and hydrology are interacting factors that produce distortions in biogeochemical nitrogen (N) and phosphorus (P) cycles. Such distortions affect nutrient relative availability and produce cascade consequences on primary producer's community and ecosystem functioning. In this study, the seasonal functioning of a coastal lagoon was investigated with a multielement approach, via the construction and analysis of network models. Spring and summer networks, both for N and P flows, have been simultaneously compiled for the northern transitional and southern confined area of the hypertrophic Curonian Lagoon (SE Baltic Sea). Ecological Network Analysis was applied to address the combined effect of hydrology and seasonality on biogeochemical processes. Results suggest that the ecosystem is more active and presents higher N and P fluxes in summer compared to spring, regardless of the area. Furthermore, larger internal recycling characterizes the confined compared to the transitional area, regardless of the season. The two areas differed in the fate of available nutrients. The transitional area received large riverine inputs that were mainly transferred to the sea without the conversion into primary producers' biomass. The confined area had fewer inputs but proportionally larger conversion into phytoplankton biomass. In summer, particularly in the confined area, primary production was inefficiently consumed by herbivores. Most phytoplanktonic N and P, in the confined area more than in the transitional area, were conveyed to the detritus pathway where P, more than N, was recycled, contributing to the unbalance in N:P stoichiometry and favouring N-fixing cyanobacteria over other phytoplankton groups. The findings of this study provide a comprehensive understanding of N and P circulation patterns in lagoon areas characterized by different hydrology. They also support the importance of a stoichiometric approach to trace relative differences in N and P recycling and abundance, that promote blooms, drive algal communities and whole ecosystem functioning.

Measurements and analysis of nitrogen and phosphorus in oceans: Practice, frontiers, and insights

Nitrogen and phosphorus concentrations in oceans have been extensively studied, and advancements in associated disciplines have rapidly progressed, enabling the exploration of novel and previously challenging questions. A keyword analysis was conducted using the Scopus database to examine chronological trends and hotspots, offering comprehensive insights into the evolution of marine nitrogen and phosphorus research. For this purpose, author keyword networks were developed for the periods before 1990, 1990 to 2000, 2001 to 2011, and 2012 to 2022. Furthermore, analytical techniques employed in the recent decade to determine nitrogen and phosphorus concentrations in seawater were assessed for their applicability and limitations through a critical review of more than 50 journal articles. Taxonomy and nitrogen biogeochemistry were the prominent research interests for the first two periods, respectively, while stable isotopic tracking of nitrogen and phosphorus processes emerged as the dominant research focus for the last two decades. The integration of macroeconomic factors in research development and the chronological rise of interdisciplinary research were identified. Conventional analytical techniques such as spectrophotometry, colorimetry, fluorometry, and elemental analysis were noted, along with emerging techniques like remote sensing and microfluidic sensors.

Ectomycorrhiza and ethylenediurea reduced the impact of high nitrogen and ozone stresses and increased the growth of Cedrus deodara

Cedrus deodara is the central conifer plant affected by ozone and nitrogen pollutants among forest species worldwide. The growth of C. deodara depends upon the ectomycorrhizal (ECM) association, which is usually disturbed by these factors. This study aims to understand how these factors affect plants at physiological and biochemical levels. Three fungal strain consortiums were inoculated with two-year-old C. deodara seedlings. The stresses of 100 kg N h-1and 100 ppb O3 were applied for six months to study their impact on chlorophyll and antioxidant enzymes (SOD, CAT, and APX). The results showed that C2 (Consortium of Cedrus deodara) positively impacted the growth of selected plant species. The high photosynthesis rate was determined by enhanced chlorophyll content, and C2-treated plants showed high chlorophyll content. Relatively, chlorophyll a and b contents increased significantly in the seedlings treated with Ethylenediurea (EDU) alone and with ozone stress. In addition, a significant difference was observed between EDU and O3-treated plants (14% EDU400-O3 and 23% EDU600-O3) and the control. Overall, antioxidant activities were higher in the treated samples than in the control. The order of SOD activity was C2 (448 U/gFW) and lowest (354.7 U/gFW) in control. APX also showed higher activity in treated plants in C1 ≥ C2 ≥ C3+O3, whereas CAT activity was the highest in C2 treatments. Ozone and nitrogen-stressed plants showed higher activities than EDU-treated plants compared to non-treated ones. Our findings highlight the importance of understanding the signaling effects of numerous precursors. Moreover, an extended investigation of seedlings developing into trees must be conducted to verify the potential of ectomycorrhizal strains associated with C. deodara and comprehend EDU's role as a direct molecular scavenger of reactive toxicants.

Redox regulation in primary nitrate response: Nitric oxide in the spotlight

Nitrogen (N) is the main macronutrient of plants that determines growth and productivity. Nitrate is the major source form of N in soils and its uptake and assimilatory pathway has been extensively studied. The early events that occur after the perception of nitrate is known as primary nitrate response (PNR). In this review, new findings on the redox signal that impacts PNR are discussed. We will focus on the novel role of Nitric Oxide (NO) as a signal molecule and the mechanisms that are involved to control NO homeostasis during PNR. Moreover, the role of Reactive Oxygen Species (ROS) and the possible interplay with NO in the PNR are discussed. The sources of NO during PNR will be analyzed as well as the regulation of its intracellular levels. Furthermore, we explored the relevance of the direct action of NO through the S-nitrosation of the transcription factor NLP7, one of the master regulators in the nitrate signaling cascade. This review gives rise to an interesting field with new actors to mark future research directions. This allows us to increase the knowledge of the physiological and molecular fine-tuned modulation during nitrate signaling processes in plants. The discussion of new experimental data will stimulate efforts to further refine our understanding of the redox regulation of nitrate signaling.

Quinones-enhanced humification in food waste composting: A novel strategy for hazard mitigation and nitrogen retention

The harmless and high-value conversion of organic waste are the core problems to be solved by composting technology. This study introduced an innovative method of promoting targeted humification and nitrogen retention in composting by adding p-benzoquinone (PBQ), the composting without any additives was set as control group (CK). The results indicated that the addition of exogenous quinones led to a 30.1% increase in humic acid (HA) content during the heating and thermophilic phases of composting. Spectroscopic analyses confirmed that exogenous quinones form the core skeleton structure of amino-quinones in HA through composting biochemical reactions. This accelerated the transformation of quinones into recalcitrant HA in the early stages of composting, and reduced CO2 and NH3 by 8% and 78%, respectively. Redundancy analysis (RDA) revealed that the decrease in carbon and nitrogen losses primarily correlated with quinones enhancing HA formation and greater nitrogen incorporation into HA (P < 0.05). Furthermore, the compost treated with quinones demonstrated a decrease in phytotoxicity and earthworm mortality, alongside a significant increase in the relative abundance of actinobacteria, which are associated with the humification process. This research establishes and proposes that co-composting with quinones-containing waste is an effective approach for the sustainable recycling of hazardous solid waste.

Utilizing plasma-generated N2O5 gas from atmospheric air as a novel gaseous nitrogen source for plants

Fixing atmospheric nitrogen for use as fertilizer is a crucial process in promoting plant growth and enhancing crop yields in agricultural production. Currently, the chemical production of nitrogen fertilizer from atmospheric N2 relies on the energy-intensive Haber-Bosch process. Therefore, developing a low-cost and easily applicable method for fixing nitrogen from the air would provide a beneficial alternative. In this study, we tested the utilization of dinitrogen pentoxide (N2O5) gas, generated from oxygen and nitrogen present in ambient air with the help of a portable plasma device, as a nitrogen source for the model plant Arabidopsis thaliana. Nitrogen-deficient plants supplied with medium treated with N2O5, were able to overcome nitrogen deficiency, similar to those provided with medium containing a conventional nitrogen source. However, prolonged direct exposure of plants to N2O5 gas adversely affected their growth. Short-time exposure of plants to N2O5 gas mitigated its toxicity and was able to support growth. Moreover, when the exposure of N2O5 and the contact with plants were physically separated, plants cultured under nitrogen deficiency were able to grow. This study shows that N2O5 gas generated from atmospheric nitrogen can be used as an effective nutrient for plants, indicating its potential to serve as an alternative nitrogen fertilization method for promoting plant growth.

Identifying leverage points for sustainable nutrient policy integration in Canada

Addressing the 'wicked problem' of nutrient pollution requires coordinated policies spanning across diverse sectors and environmental systems. Using a case study of Canadian legislation, we apply semantic network analysis to identify thematic links across an inventory of 245 nutrient-related policies. Our analysis identifies twelve topics with unique types of connections across multiple facets of Canadian society. 'Hub' policies include broad environmental protection, land use planning, and climate-related legislation with close ties to multiple other topics. 'Bridge' policies create connections among otherwise disconnected topics in the network, representing opportunities to inform new policy proposals. Some legislation, such as food processing regulations, indirectly relates to nutrient use but could inform policy integration towards more coordinated and holistic nutrient management across the food system. A computational text network approach can be useful for addressing challenges in complex policy analysis, including by identifying unique entry points to guide more cross-cutting nutrient policy development.

Nitrogen enrichment changed the biogeochemical role of sesarmid crabs by shifting their diets in tropical mangrove ecosystems

Sesarmid crabs modulate nutrient dynamics of tropical mangroves through their leaf-eating habit. How N enrichment may alter this regulatory role, and the implications for mangrove nutrient dynamics, remain unclear. Using a mesocosm experiment, we tested how N enrichment could change the microphytobenthos (MPB) communities, thus modifying the crabs' diet and their role in nutrient dynamics. The factorial experiment combined with field investigation revealed a significant increase in the relative abundance of cyanobacteria. Stable isotope analysis suggested that the main carbon source of crabs shifted from leaf litter to cyanobacteria in mesocosms under both high (20×) and low (2×) N enrichment treatments. The significantly lower total cellulase activity of crabs in the mesocosms might explain the decreased carbon assimilation from leaf litter. The changes in the MPB and the microbiome with N enrichment in the presence of crabs may drive significantly higher carbon processing rate in tropical mangroves.

Phytoplankton assemblage responses to nitrogen following COVID-19 stay-in-place orders in western Long Island Sound (New York/Connecticut)

This study evaluated water quality, nitrogen (N), and phytoplankton assemblage linkages along the western Long Island Sound (USA) shoreline (Nov. 2020-Dec. 2021) following COVID-19 stay-in-place (SIP) orders through monthly surveys and N-addition bioassays. Ammonia-N (AmN; NH3+NH4+) negatively correlated with total chlorophyll-a (chl-a) at all sites; this was significant at Alley Creek, adjacent to urban wastewater inputs, and at Calf Pasture, by the Norwalk River (Spearman rank correlation, p < 0.01 and 0.02). Diatoms were abundant throughout the study, though dinoflagellates (Heterocapsa, Prorocentrum), euglenoids/cryptophytes, and both nano- and picoplankton biomass increased during summer. In field and experimental assessments, high nitrite + nitrate (N + N) and low AmN increased diatom abundances while AmN was positively linked to cryptophyte concentrations. Likely N + N decreases with presumably minimal changes in AmN and organic N during COVID-19 SIP resulted in phytoplankton assemblage shifts (decreased diatoms, increased euglenoids/cryptophytes), highlighting the ecological impacts of N-form delivered by wastewater to urban estuaries.

Controlling effects of terrestrial organic matter on metal contamination and toxicity risks in port sediments

The contents of metals, total carbon, total nitrogen (TN), total organic carbon (TOC), and stable isotope composition (δ13Corg and δ15N) of sediment organic matter (SOM) were investigated to explore the sources and spatial distribution of metals and SOM in the surface sediments (Kaohsiung Port, Taiwan). Results showed that TOC and metals in estuarine sediments are high, gradually decreasing toward the port entrances. The δ13Corg, δ15N, and TOC/TN ratios indicate that SOM comes mainly from terrestrial sources. This study proposes a befitting model between metal pollution and toxicity risk index and SOM sources in port sediments by combining stable isotope composition, correlation matrix, and multiple linear regression analysis. The model indicates that the degree of metal pollution and toxicity risk in sediments are mainly affected by TOCterr content and SOM source. The results help to understand the influence of organic matter sources in port sediments on metal concentration distribution.

Trophic ecology of sympatric sea turtles in the tropical Atlantic coast of Brazil

The Tropical Atlantic coast of Brazil is a hotspot area for multiple sea turtle species at all life stages. The multiple nearshore reefs and beaches, oceanic islands, and the only atoll in the south Atlantic Ocean, are suitable for year-round foraging, migration corridors, and nesting activities of five sea turtle species. Still, relatively few studies have assessed trophic niche among sympatric sea turtles which can provide a better understanding of how closely related species compete/partition the available resources. Using multiple biogeochemical tracers (i.e., nitrogen (δ15N) and carbon (δ13C) stable isotopes, and mercury (Hg)), we disentangled the trophic niches of four sea turtle species - the green turtle (Chelonia mydas), the loggerhead turtle (Caretta), the hawksbill turtle (Eretmochelys imbricata), and the olive ridley turtle (Lepidochelys olivacea) - co-occurring in nesting and foraging habitats along the northeastern coast of Brazil. We found interspecific differences in isotopic and contamination niches, as well as intraspecific niche variation associated with life stage. Differences in the estimation niche models associated to life-stage in C. caretta support the notion of ontogenetic shift in habitat and diet composition previously reported for this species. Oceanic habitat signatures were observed in juvenile green turtles and adult olive turtles, while nearshore habitat signatures were observed in adult hawksbill turtles.

A series of high-sensitivity radon detection systems and their applications in nitrogen as well as the boil-off liquid nitrogen measurement

In modern rare-event search experiments such as neutrino experiments and dark matter search experiments, radon is one of the most important radiation backgrounds since it can emanate from nearly all the materials containing radium and migrate freely in the experiment system. To support the China Dark Matter Experiment (CDEX) at China Jinping Underground Laboratory (CJPL), a series of high-sensitivity radon detection systems with different electrostatic collection chambers were designed, and radon in nitrogen as well as boil-off liquid nitrogen was measured after accurate calibration and enrichment. Results showed that the calibration factors were 2.1 ± 0.2 (counts/h)/(Bq/m3), 21.1 ± 0.7 (counts/h)/(Bq/m3), 186.2 ± 2.2 (counts/h)/(Bq/m3), 387 ± 7 (counts/h)/(Bq/m3) and the 90% confidence level detection limits were 27.22 mBq/m3, 1.89 ∼ 3.06 mBq/m3, 0.41 ∼ 0.68 mBq/m3, 0.44 mBq/m3 for CJPL-HR2, CJPL-HR20, CJPL-HR140 and CJPL-HR300 measurement systems, respectively. Combined with an enrichment system consisting of twenty g CarboACT activated charcoals in a cold trap, the lower level detection limit (LLD) of typical No.1 CJPL-HR140 could reach 1.8 μBq/m3 with three days' enrichment time and three days' measurement time at 20 L/min sampling flowrate. For verification and application, the radon activity concentrations in nitrogen were 0.6 ∼ 1.9 mBq/m3 with an average of 1.1 ± 0.1 mBq/m3.While in boil-off liquid nitrogen, the radon activity concentrations ranged from 0.04 to 0.62 mBq/m3, and they were significantly lower in old-decayed liquid nitrogen compared to newly-filled liquid nitrogen, with a nearly five-fold decrease.

Control of nitrogen and odor emissions during chicken manure composting with a carbon-based microbial inoculant and a biotrickling filter

Although aerobic composting is usually utilized in livestock manure disposal, the emission of odorous gases from compost not only induces harm to the human body and the environment, but also causes loss of nitrogen, sulfur, and other essential elements, resulting in a decline in product quality. The impact of biotrickling filter (BTF) and insertion of carbon-based microbial agent (CBMA) on compost maturation, odor emissions, and microbial population during the chicken manure composting were assessed in the current experiment. Compared with the CK group, CBMA addition accelerated the increase in pile temperature (EG group reached maximum temperature 10 days earlier than CK group), increased compost maturation (GI showed the highest increase of 41.3% on day 14 in EG group), resulted in 36.59% and 14.60% increase in NO3--N content and the total nitrogen retention preservation rate after composting. The deodorization effect of biotrickling filter was stable, and the removal rates of NH3, H2S, and TVOCs reached more than 90%, 96%, and 56%, respectively. Furthermore, microbial sequencing showed that CBMA effectively changed the microbial community in compost, protected the ammonia-oxidizing microorganisms, and strengthened the nitrification of the compost. In addition, the nitrifying and denitrifying bacteria were more active in the cooling period than they were in the thermophilic period. Moreover, the abundance of denitrification genes containing nirS, nirK, and nosZ in EG group was lower than that in CK group. Thus, a large amount of nitrogen was retained under the combined drive of BTF and CBMA during composting. This study made significant contributions to our understanding of how to compost livestock manure while reducing releases of odors and raising compost quality.

Nutrient reduction by eastern oysters exhibits low variability associated with reproduction, ploidy, and farm location

Enhancement of shellfish populations has long been discussed as a potential nutrient reduction tool, and eastern oyster aquaculture was recently approved as a nutrient reduction best management practice (BMP) in Chesapeake Bay, USA. This study addressed BMP-identified data gaps involving variation in nutrient concentration related to ploidy, effects of reproductive development, and a paucity of phosphorus concentration data. Diploid and triploid oysters were collected from farms in Maryland and Virginia across the typical local reproductive cycle. The nutrient concentration of tissue and shell was consistent with the currently implemented BMP. Minor variation observed in nitrogen and phosphorus concentration was within the previously reported range, for farm location, ploidy, and reproductive cycle timing. Ploidy-based differences in tissue dry weight were not observed at either farm, which contrasts with current nutrient reduction estimates. These results suggest separate crediting values for diploids and triploids may need further investigation and potential re-evaluation.

Nutrient transport, shear strength and hydraulic characteristics of topsoils amended with mulch, compost and biosolids

Anthropogenic disturbance of soils can disrupt soil structure, diminish fertility, alter soil chemical properties, and cause erosion. Current remediation practices involve amending degraded urban topsoils lacking in organic matter and nutrition with organic amendments (OA) to enhance vegetative growth. However, the impact of OAs on water quality and structural properties at rates that meet common topsoil organic matter specifications need to be studied and understood. This study tested three commonly available OAs: shredded wood mulch, leaf-based compost, and class A Exceptional Quality stabilized sewage sludge (or biosolids) for nutrient (nitrogen and phosphorus) water quality, soil shear strength, and hydraulic properties, through two greenhouse tub studies. Findings showed that nitrogen losses to leachate were greater in the biosolids amended topsoils compared to leaf-compost, mulch amended topsoils, and control treatments. Steady-state mean total nitrogen (N) concentrations from biosolids treatment exceeded typical highway stormwater concentrations by at least 25 times. Soil total N content combined with the carbon:nitrogen ratio were identified to be the governing properties of N leaching in soils. Study soils, irrespective of the type of amendment, reduced the applied (tap) water phosphorus (P) concentration of ∼0.3 mg-P/L throughout the experiment. Contrary to the effects on N leaching, P was successfully retained by the biosolids amendment, due to the presence of greater active iron contents. A breakthrough mechanism for P was observed in leaf compost amended soil, where the effluent concentrations of P continued to increase with each rainfall application, possibly due to an saturation of soil adsorption sites. The addition of OAs also improved the strength and hydraulic properties of soils. The effective interlocking mechanisms between the soil and OA surfaces could provide soil its required strength and stability, particularly on slopes. OAs also improved soil fertility to promote turf growth. Presence of vegetative root zones can further reinforce the soil and control erosion.

Reviewing impacts of biotic and abiotic stresses on the regulation of phosphate homeostasis in plants

Adapting to varying phosphate levels in the environment is vital for plant growth. The PHR1 phosphate starvation response transcription factor family, along with SPX inhibitors, plays a pivotal role in plant phosphate responses. However, this regulatory hub intricately links with diverse biotic and abiotic signaling pathways, as outlined in this review. Understanding these intricate networks is crucial, not only on a fundamental level but also for practical applications, such as enhancing sustainable agriculture and optimizing fertilizer efficiency. This comprehensive review explores the multifaceted connections between phosphate homeostasis and environmental stressors, including various biotic factors, such as symbiotic mycorrhizal associations and beneficial root-colonizing fungi. The complex coordination between phosphate starvation responses and the immune system are explored, and the relationship between phosphate and nitrate regulation in agriculture are discussed. Overall, this review highlights the complex interactions governing phosphate homeostasis in plants, emphasizing its importance for sustainable agriculture and nutrient management to contribute to environmental conservation.

Biochar influences nitrogen and phosphorus dynamics in two texturally different soils

Nitrogen (N) and phosphorus (P) are vital for crop growth. However, most agricultural systems have limited inherent ability to supply N and P to crops. Biochars (BCs) are strongly advocated in agrosystems and are known to improve the availability of N and P in crops through different chemical transformations. Herein, a soil-biochar incubation experiment was carried out to investigate the transformations of N and P in two different textured soils, namely clay loam and loamy sand, on mixing with rice straw biochar (RSB) and acacia wood biochar (ACB) at each level (0, 0.5, and 1.0% w/w). Ammonium N (NH4-N) decreased continuously with the increasing incubation period. The ammonium N content disappeared rapidly in both the soils incubated with biochars compared to the unamended soil. RSB increased the nitrate N (NO3-N) content significantly compared to ACB for the entire study period in both texturally divergent soils. The nitrate N content increased with the enhanced biochar addition rate in clay loam soil until 15 days after incubation; however, it was reduced for the biochar addition rate of 1% compared to 0.5% at 30 and 60 days after incubation in loamy sand soil. With ACB, the net increase in nitrate N content with the biochar addition rate of 1% remained higher than the 0.5% rate for 60 days in clay loam and 30 days in loamy sand soil. The phosphorus content remained consistently higher in both the soils amended with two types of biochars till the completion of the experiment.

The cumulative effects of cascade reservoirs control nitrogen and phosphorus flux: Base on biogeochemical processes

The reservoir serves as a water source, a flood control structure, a navigational aid, and also impacts the downstream ecosystem as well as the reservoir zone. However, debate exists about effectiveness of cascade reservoirs in controlling the transportation of nutrients, particularly in the Yangtze River basin, which has been significantly affected by reservoir development. This research develops a new model X-NPSEM (X with Nitrogen and Phosphorus Steady-state Reservoir Model) based on biogeochemical processes of nitrogen and phosphorus reaction for investigating the dynamic storage capacity of cascade reservoirs at both reservoir- and watershed scales. Then the cumulative effects of cascade reservoirs and the related mechanism were investigated in Fujiang watershed, China. Based on the results, cascade reservoirs retained 16.3 % of nitrogen fluxes and 37.6 % of phosphorus fluxes annually. Downstream reservoirs have higher retention rates of phosphorus (0.48/d) compared to upstream reservoirs (0.10/d), mainly due to inflow sediment. Nitrogen retention rates show seasonal variations: wet season (0.21/d) and dry season (0.17/d). These fluctuations in nitrogen retention are primarily influenced by changes in temperature rather than other factors such as operation period, nitrogen and phosphorus concentration, or the nitrogen/phosphorus ratio. In upstream, the concentration of sediment entering the reservoir plays a decisive role in the transformation of P retention from sink to source. The X-NPSRM coupler model could be used for global reservoir operation and watershed management.

Does a hydropower reservoir cascade really harm downstream nutrient regimes

River damming is believed to largely intercept nutrients, particularly retain more phosphorus (P) than nitrogen (N), and thus harm primary productivity, fishery catches, and food security downstream, which seriously constrain global hydropower development and poverty relief in undeveloped regions and can drive geo-political disputes between nations along trans-boundary rivers. In this study, we investigated whether reservoirs can instead improve nutrient regimes downstream. We measured different species of N and P as well as microbial functions in water and sediment of cascade reservoirs in the upper Mekong River over 5 years and modelled the influx and outflux of N and P species in each reservoir. Despite partially retaining total N and total P, reservoirs increased the downstream flux of ammonium and soluble reactive phosphorus (SRP). The increase in ammonium and SRP between outflux and influx showed positive linear relationships with the hydraulic residence time of the cascade reservoirs; and the ratio of SRP to dissolved inorganic nitrogen increased along the reservoir cascade. The lentic environment of reservoirs stimulated algae-mediated conversion of nitrate into ammonium in surface water; the hypoxic condition and the priming effect of algae-induced organic matter enhanced release of ammonium from sediment; the synergy of microbial phosphorylation, reductive condition and sediment geochemical properties increased release of SRP. This study is the first to provide solid evidence that hydropower reservoirs improve downstream nutrient bioavailability and N-P balance through a process of retention-transformation-transport, which may benefit primary productivity. These findings could advance our understanding of the eco-environmental impacts of river damming.

Intensification of harmful cyanobacterial blooms in a eutrophic, temperate lake caused by nitrogen, temperature, and CO2

Warmer temperatures can significantly increase the intensity of cyanobacterial harmful algal blooms (CHABs) in eutrophic freshwater ecosystems. However, few studies have examined the effects of CO2 enrichment in tandem with elevated temperature and/or nutrients on cyanobacterial taxa in freshwater ecosystems. Here, we observed changes in the biomass of cyanobacteria, nutrients, pH, and carbonate chemistry over a two-year period in a shallow, eutrophic freshwater lake and performed experiments to examine the effects and co-effects of CO2, temperature, and nutrient enrichment on cyanobacterial and N2-fixing (diazotrophic) communities assessed via high throughput sequencing of the 16S rRNA and nifH genes, respectively. During both years, there were significant CHABs (50-500 μg cyanobacterial chlorophyll-a L-1) and lake CO2 levels were undersaturated (≤300 μatm pCO2). NH4+ significantly increased the net growth rates of cyanobacteria as well as the biomass of the diazotrophic cyanobacterial order Nostocales under elevated and ambient CO2 conditions. In a fall experiment, the N2 fixation rates of Nostocales were significantly higher when populations were enriched with CO2 and P, relative to CO2-enriched populations that were not amended with P. During a summer experiment, N2 fixation rates increased significantly under N and CO2 - enriched conditions relative to N-enriched and ambient CO2 conditions. Nostocales dominated the diazotrophic communities of both experiments, achieving the highest relative abundance under CO2-enriched conditions when N was added in the first experiment and when CO2 and temperature were elevated in the second experiment, when N2 fixation rates also increased significantly. Collectively, this study indicates that N promotes cyanobacterial blooms including those formed by Dolichospermum and that the biomass and N2 fixation rates of diazotrophic cyanobacterial taxa may benefit from enhanced CO2 levels in eutrophic lakes.

The fate of nitrogen in the urban area - The case of Zielona Góra, Poland

The anthropogenic change of the nitrogen (N) cycle is strongly triggered by urban demand (such as food and meat consumption, energy demand and transport). As a consequence of high population density, impacts on human health through water and air pollution also concentrate on a city environment. Thus, an urban perspective on a predominantly rural pollution becomes relevant. Urban N budgets may be considered less intrinsically connected, so that separation of an agri-food chain and an industry-combustion chain is warranted. Results have been obtained for Zielona Góra, Poland, a city of 140,000 inhabitants characterized by domestic and transport sources and forest-dominated surroundings. In addition to food imports in Zielona Gora amounting to about 30 %, in the suburban area a significant share of N amounting to 41 % is related to fertilizer imports. The remaining imports are in fuel, electronics, textiles, plastics and paper. Most of the agri-food N (45 %) is denitrified in wastewater treatment. N associated with combustion (mainly NOx emissions from vehicles) represents a much smaller share than N entering via the agri-food system, amounting to 22 % of the total N imports. This overall picture is maintained also when specifically addressing the city center, with the exception of mineral fertilizer that plays a much smaller role, with just 7 % of N imports to the city.

Effects of storm runoff on the spatial-temporal variation and stratified water quality in Biliuhe Reservoir, a drinking water reservoir

Stormflow runoff is an important non-point source of pollution in drinking water reservoirs. Storm runoff is usually very turbid and contains a high concentration of organic matter, therefore affecting water quality when it enters reservoirs. In order to investigate the impact of storm runoff on spatial-temporal variation and stratification of water quality during this rainstorm event, the inflow process of the storm runoff was studied through a combination of field investigation and simulation using the Delft3D-Flow model. Water samples were collected from Biliuhe Reservoir at four different periods: before storm runoff, storm runoff flood peak period, 1 week after storm runoff, and 5 weeks after storm runoff. The results showed that the input of storm runoff resulted in a significant increase in the nitrogen (N) and phosphorus (P) in the reservoir water, especially in the reservoir entrance. The concentrations of total nitrogen (TN) and total phosphorus (TP) gradually decreased after the flood peak period; however, the average concentrations of TN and TP in the entire reservoir remained higher than those before the storm runoff levels for an extended duration. The storm runoff will greatly contribute to the contamination of water quality in a reservoir, and the water quality cannot be quickly restored by self-purification in the short term. During the flood peak period, under the influence of density current, the electrical conductivity (EC) and turbidity increased significantly in the water depth of 10-15 m, so that the reservoir water had obvious stratification between 10 and 15 m. The form of pollutants in storm runoff was mostly in particle phosphorus. Total particulate phosphorus (TPP) concentration was 0.015 ± 0.011 mg/L, accounting for 44.12% of total phosphorus (TP) concentration in storm runoff flood peak period. The process of a rainstorm caused runoff, which carried high levels of turbidity, particulate phosphorus, and organic matter. The storm runoff disrupts the stratification of the reservoir water. In terms of vertical distribution, the turbidity in the reservoir area increased to 73.75 NTU. Therefore, the occurrence of significant turbidity density flow in the reservoir is frequently accompanied by intense rainfall events. Gaining insights into the impact of storm runoff on the vertical distribution of reservoir turbidity can help managers in selecting an appropriate inlet height to mitigate high turbidity outflow.

Assessment of the performance of a symbiotic microalgal-bacterial granular sludge reactor for the removal of nitrogen and organic carbon from dairy wastewater

Cheese whey (CW) is a nutrient deficient dairy effluent, which requires external nutrient supplementation for aerobic treatment. CW, supplemented with ammonia, can be treated using aerobic granular sludge (AGS) in a sequencing batch reactor (SBR). AGS are aggregates of microbial origin that do not coagulate under reduced hydrodynamic shear and settle significantly faster than activated sludge flocs. However, granular instability, slow granulation start-up, high energy consumption and CO2 emission have been reported as the main limitations in bacterial AGS-SBR. Algal-bacterial granular systems have shown be an innovative alternative to improve these limitations. Unfortunately, algal-bacterial granular systems for the treatment of wastewaters with higher organic loads such as CW have been poorly studied. In this study, an algal-bacterial granular system implemented in a SBR (SBRAB) for the aerobic treatment of ammonia-supplemented CW wastewaters was investigated and compared with a bacterial granular reactor (SBRB). Mass balances were used to estimate carbon and nitrogen (N) assimilation, nitrification and denitrification in both set-ups. SBRB exhibited COD and ammonia removal of 100% and 94% respectively, high nitrification (89%) and simultaneous nitrification-denitrification (SND) of 23% leading to an inorganic N removal of 30%. The efficient algal-bacterial symbiosis in granular systems completely removed COD and ammonia (100%) present in the dairy wastewater. SBRAB microalgae growth could reduce about 20% of the CO2 emissions produced by bacterial oxidation of organic compounds according to estimates based on synthesis reactions of bacterial and algal biomass, in which the amount of assimilated N determined by mass balance was taken into account. A lower nitrification (75%) and minor loss of N by denitrifying activity (<5% Ng, SND 2%) was also encountered in SBRAB as a result of its higher biomass production, which could be used for the generation of value-added products such as biofertilizers and biostimulants.

Impact of wildfire recurrence on soil properties and organic carbon fractions

The recurrence and severity of wildfire is on the rise due to factors like global warming and human activities. Mediterranean regions are prone to significant wildfire events, which cause extensive damage to ecosystems and soil properties. This study focuses on the municipality of Allande in south-western Asturias (Spain), a region highly affected by recurrent wildfires. In this regard, we sought to examine how the recurrence of such fires influences soil organic carbon fractionation and other soil parameters, such as nitrogen fractionation, pH, and cation exchange capacity. The study involved six sampling plots with between varying fire recurrence levels, from 0 to 4 events between 2005 and 2022. The results revealed some significant effects of wildfires recurrence on soil texture, inorganic elemental composition and CEC, but not on pH and CE. In soil affected by recurrent fires, labile carbon fractions (cold-water extractable & hot-water extractable), and fulvic acid concentrations decreased by up to 36%, 5%, and 45%, respectively in comparison with undisturbed soil. In contrast, humic acid concentration remained stable or increased in soils damaged by fire. Additionally, nitrogen species in soil were observed to decrease significantly in high recurrence scenarios, especially nitrate. On the basis of our findings, we conclude that wildfires impact the distinct fractions of organic carbon and nitrogen in soils and that this effect is aggravated by increasing recurrence.

A new set of N isotopic reference values for monitoring Ulva green tides in coral reef ecosystems

Green tides occurrence has increased in coral reefs, yet few reference values have been documented to support bloom management in these ecosystems. Here, we took advantage of recent Ulva green tides that occurred in New Caledonia to (i) identify the elements limiting the growth of Ulva spp. during these blooms; and (ii) validate the use of isotopic markers for identifying sources of nutrients that generated blooms. N/P ratios highlighted a stronger limitation of algae by phosphorus than by nitrogen on sites under oceanic influence, while the proportions of N and P were optimal for algal growth at sites where green tides occurred. Macroalgae highly exposed to sewage water was characterized by higher δ15N than macroalgae collected in areas exposed to synthetic inorganic fertilizers. From these results, we established a new set of threshold values for using δ15N in Ulva species as an indicator of nitrogen source type in coral reefs.

Water pollution scenarios and response options for China

China has formulated several policies to alleviate the water pollution load, but few studies have quantitatively analyzed their impacts on future water pollution loads in China. Based on grey water footprint (GWF) assessment and scenario simulation, we analyze the water pollution (including COD, NH3-N, TN and TP) in China from 2021 to 2035 under different scenarios for three areas: consumption-side, production-side and terminal treatment. We find that under the current policy scenario, the GWF of COD, NH3-N, TN, and TP in China could be reduced by 15.0 % to 39.9 %; the most effective measures for GWF reduction are diet structure change (in the consumption-side area), and the wastewater treatment rate and livestock manure utilization improvement (in the terminal treatment area). However, the GWF will still increase in 8 provinces, indicating that the current implemented policy is not universally effective in reducing GWF across all provinces. Under the technical improvement scenario, the GWF of the four pollutants will decrease by 54.9 %-71.1 % via improvements in the current measures related to current policies and new measures in the production-side area and the terminal treatment area; thus, GWF reduction is possible in all 31 provinces. However, some policies face significant challenges in achieving full implementation, and certain policies are only applicable to a subset of provinces. Our detailed analysis of future water pollution scenarios and response options to reduce pollution loads can help to inform the protection of freshwater resources in China and quantitatively assess the effectiveness of policies in other fields.

River ecological status is shaped by agricultural land use intensity across Europe

Agriculture impacts the ecological status of freshwaters through multiple pressures such as diffuse pollution, water abstraction, and hydromorphological alteration, strongly impairing riverine biodiversity. The agricultural effects, however, likely differ between agricultural types and practices. In Europe, agricultural types show distinct spatial patterns related to intensity, biophysical conditions, and socioeconomic history, which have been operationalised by various landscape typologies. Our study aimed at analysing whether incorporating agricultural intensity enhances the correlation between agricultural land use and the ecological status. For this, we aggregated the continent's agricultural activities into 20 Areas of Farming-induced Freshwater Pressures (AFFP), specifying individual pressure profiles regarding nutrient enrichment, pesticides, water abstraction, and agricultural land use in the riparian zone to establish an agricultural intensity index and related this intensity index to the river ecological status. Using the agricultural intensity index, nearly doubled the correlative strength between agriculture and the ecological status of rivers as compared to the share of agriculture in the sub-catchment (based on the analysis of more than 50,000 sub-catchment units). Strongest agricultural pressures were found for high intensity cropland in the Mediterranean and Temperate regions, while extensive grassland, fallow farmland and livestock farming in the Northern and Highland regions, as well as low intensity mosaic farming, featured lowest pressures. The results provide advice for pan-European management of freshwater ecosystems and highlight the urgent need for more sustainable agriculture. Consequently, they can also be used as a basis for European Union-wide and global policies to halt biodiversity decline, such as the post-2027 renewal of the Common Agricultural Policy.

Interactive effects of climate-atmospheric cycling on aquatic communities and ecosystem shifts in mountain lakes of southeastern Tibetan Plateau

Recent climate warming and atmospheric reactive nitrogen (Nr) deposition are affecting a broad spectrum of physical, ecological and human systems that may be irreversible on a century time scale and have the potential to cause regime shifts in ecological systems. These changes may alter the limnological conditions with important but still unclear effects on lake ecosystems. We present changes in cladoceran with comparisons to diatom assemblages over the past ~200 years from high-resolution, well-dated sediment cores retrieved from six high mountain lakes in the southeastern (SE) margin of the Tibetan Plateau. Our findings suggest that warming and the exponential increase of atmospheric Nr deposition are the major drivers of ecological regime changes. Shifts in cladoceran and diatom communities in high alpine lakes began over a century ago and intensified since 1950 CE, indicating a regional-scale response to anthropogenic climate warming. Zooplankton in the forest lakes showed asynchronous trajectories, with increased Nr deposition as a significant explanatory factor. Forest lakes with higher dissolved organic carbon (DOC) concentrations partially buffered the impacts of Nr deposition with little structural change, while lakes with low DOC display symptoms of resilience loss related to Nr deposition. Biological community compositional turnover in subalpine lakes has shown marked shifts, equivalent to those of low-elevation lakes strongly affected by direct human impacts. This suggests that local effects override climatic forcing and that lake basin features modified by anthropogenic activity act as basin-specific filters of common forcing. Our results indicate that snow and glacial meltwaters along with nutrient enrichment related to climate warming and atmospheric Nr deposition, represent major threats for lake ecosystems, even in remote areas. We reveal that climate and atmospheric contaminants will further impact ecological conditions and alter aquatic food webs in higher altitude biomes if climate and anthropogenic forcing continue.

Phenotypic, genomic and in planta characterization of Bacillus sensu lato for their phosphorus biofertilization and plant growth promotion features in soybean

Bacillus sensu lato were screened for their capacity to mineralize organic phosphorus (P) and promote plant growth, improving nitrogen (N) and P nutrition of soybean. Isolates were identified through Type Strain Genome Server (TYGS) and Average Nucleotide Identity (ANI). ILBB95, ILBB510 and ILBB592 were identified as Priestia megaterium, ILBB139 as Bacillus wiedmannii, ILBB44 as a member of a sister clade of B. pumilus, ILBB15 as Peribacillus butanolivorans and ILBB64 as Lysinibacillus sp. These strains were evaluated for their capacity to mineralize sodium phytate as organic P and solubilize inorganic P in liquid medium. These assays ranked ILBB15 and ILBB64 with the highest orthophosphate production from phytate. Rhizocompetence and plant growth promotion traits were evaluated in vitro and in silico. Finally, plant bioassays were conducted to assess the effect of the co-inoculation with rhizobial inoculants on nodulation, N and P nutrition. These bioassays showed that B. pumilus, ILBB44 and P. megaterium ILBB95 increased P-uptake in plants on the poor substrate of sand:vermiculite and also on a more fertile mix. Priestia megaterium ILBB592 increased nodulation and N content in plants on the sand:vermiculite:peat mixture. Peribacillus butanolivorans ILBB15 reduced plant growth and nutrition on both substrates. Genomes of ILBB95 and ILBB592 were characterized by genes related with plant growth and biofertilization, whereas ILBB15 was differentiated by genes related to bioremediation. Priestia megaterium ILBB592 is considered as nodule-enhancing rhizobacteria and together with ILBB95, can be envisaged as prospective PGPR with the capacity to exert positive effects on N and P nutrition of soybean plants.

Microbial pathways of nitrous oxide emissions and mitigation approaches in drylands

Drylands refer to water scarcity and low nutrient levels, and their plant and biocrust distribution is highly diverse, making the microbial processes that shape dryland functionality particularly unique compared to other ecosystems. Drylands are constraint for sustainable agriculture and risk for food security, and expected to increase over time. Nitrous oxide (N2O), a potent greenhouse gas with ozone reduction potential, is significantly influenced by microbial communities in drylands. However, our understanding of the biological mechanisms and processes behind N2O emissions in these areas is limited, despite the fact that they highly account for total gaseous nitrogen (N) emissions on Earth. This review aims to illustrate the important biological pathways and microbial players that regulate N2O emissions in drylands, and explores how these pathways might be influenced by global changes for example N deposition, extreme weather events, and climate warming. Additionally, we propose a theoretical framework for manipulating the dryland microbial community to effectively reduce N2O emissions using evolving techniques that offer inordinate specificity and efficacy. By combining expertise from different disciplines, these exertions will facilitate the advancement of innovative and environmentally friendly microbiome-based solutions for future climate change vindication approaches.

Identifying the external N and Hg inputs to the estuary ecosystem based on the triple isotopic information (δ15NNO3, Δ17ONO3 and δ18ONO3)

The supply and sources of N and Hg in the Geum estuary of the western coast of Korea were evaluated. Triple isotope proxies (δ15NNO3, Δ17ONO3 and δ18ONO3) of NO3- combined with conservative mixing between river and ocean waters were used to improve isotope finger-printing methods. The N pool in the Geum estuary was primarily influenced by the Yellow Sea water, followed by riverine discharge (821 × 106 mol yr-1) and atmospheric deposition (51 × 106 mol yr-1). The influence of the river was found to be greater for Hg than that of the atmosphere. The triple isotope proxies revealed that the riverine and atmospheric inputs of N have been affected by septic wastes and fossil fuel burning, respectively. From the inner estuary towards offshore region, the influence of the river diminishes, thus increasing the relative impact of the atmosphere. Moreover, the isotope proxies showed a significant influence of N assimilation in February and nitrification in May.

Nitrogen, sulfur-doped carbon quantum dots with large Stokes shift for real-time monitoring of pH in living cells

Construction of carbon quantum dots-based (CQDs) fluorescent probes for real-time monitoring pH in cells is still unsatisfied. Here, we propose the synthesis of nitrogen, sulfur-doped CQDs (N,S-CQDs) using one-pot hydrothermal treatment, and serve it as fluorescent probes to realize the real-time sensing of intracellular pH. These pH-responsive N,S-CQDs were proved exhibited a diversity of admirable properties, including great photostability, nontoxicity, favorable biocompatibility, and high selectivity. Particularly, due to the doping of nitrogen and sulfur, N,S-CQDs possessed long-wavelength emission and large Stokes Shift (190 nm), which could avoid self-absorption of tissue to realize high contrast and resolution bioimaging. The response of the probes to pH showed a good linear in range of 0.93-7.00 with coefficient of determination of 0.9956. Moreover, with advantages of high signal-to-noise ratio and stability against photobleaching, the as-prepared N,S-CQDs were successfully applied to monitor pH in living cells via bioimaging. All findings suggest that N,S-CQDs have significant potential for practical application for sensing and visualizing pH fluctuation in living systems.