High-resolution temporal detection of cyanobacterial blooms in a deep and oligotrophic lake by high-frequency buoy data.

Cyanobacterial blooms are increasing in magnitude, frequency, and duration worldwide. However, our knowledge of cyanobacterial blooms dynamics and driving mechanisms is still limited due to their high spatiotemporal variability. To determine the potential driving mechanisms of cyanobacterial blooms in oligotrophic lakes, we collected a high-frequency depth profile of chlorophyll fluorescence (ChlF) and synchronous water quality, hydrometeorological data in early spring 2016 in oligotrophic Lake Qiandaohu. The vertical distribution of ChlF exhibited two patterns, "aggregated" and "discrete", using Morisita's index, and the aggregated ChlF presented subsurface chlorophyll maxima during the thermal stratification period. The ChlF concentration was positively correlated with water temperature and negatively correlated with turbidity. Significantly linear relationships were observed between ChlF vertical structure parameters (e.g., Morisita's index, subsurface chlorophyll maxima depth and thickness) and thermal stratification parameters (e.g., mixing layer depth and relative water column stability). After rainstorm floods, the ChlF pattern suddenly change from "aggregated" to "discrete" and a ChlF concentration <1 µg/L was observed for 7-11 days with a significant increase in the mixing depth layer and turbidity. The results suggest that cyanobacterial blooms are robustly associated with thermal stratification and rainstorm floods in the deep and oligotrophic lake. Thermal stratification boosts surface phytoplankton accumulation by increasing water temperature, enhancing light availability and restricting phytoplankton vertical distribution. Rainstorm floods interrupt the accumulation by disrupting thermal stratification and decreasing the available light. Furthermore, wind speed and air temperature both regulate the phytoplankton dynamics by affecting thermal stratification. Our research quantifies the cyanobacterial bloom dynamics and their relationship between environmental factors, improving our knowledge of the driving mechanisms of cyanobacterial bloom for the protection of drinking water safety and aquatic organism health in lakes.

Contrasting assembly mechanisms explain the biogeographic patterns of benthic bacterial and fungal communities on the Tibetan Plateau.

The Tibetan Plateau characterized by high altitude and low temperature, where a great number of lakes are located, is a hotspot of global biodiversity research. Both bacterial and fungal communities are vital participants of biogeochemical cycling in lake ecosystems. However, we know very little about the large-scale biogeographic patterns and the underlying assembly mechanisms of lake benthic microbial communities on the Tibetan Plateau. To investigate the biogeographic patterns and their underlying assembly mechanisms of benthic bacterial and fungal communities, we collected sediment samples from 11 lakes on the Tibetan Plateau (maximum geographic distance between lakes over 1100 km). Benthic community diversity and composition were determined using the high-throughput sequencing technique. Our results indicated that there were contrasting distance-decay relationships between benthic bacterial and fungal communities on a regional scale. Benthic bacterial communities showed a significant distance-decay relationship, whereas no significant relationship was observed for benthic fungal communities. Deterministic processes dominated the bacterial community assembly, whereas fungal community assembly was more stochastic. pH was a dominant factor in influencing the geographic distribution of benthic microbial communities. Co-occurrence network analysis revealed that bacterial communities showed higher complexity and greater stability than those of the fungal communities. Taken together, this study contributes to a novel understanding of the assembly mechanisms underlying the biogeographic distribution of plateau benthic bacterial and fungal communities at a large scale.

Phosphorus acquisition strategy of Vallisneria natans in sediment based on in situ imaging techniques.

Phosphorus (P) availability is closely related to the distributions of pH, O2 and phosphatase activities in the rhizosphere of plants growing in soils and sediments. In this study, the P uptake processes and mechanisms of Vallisneria natans (V. natans) during two vegetation periods (i.e., week three and six) were revealed using three noninvasive 2D imaging techniques: planar optode (PO), diffusive gradients in thin films (DGT) and zymography. The results showed that increased phosphatase activity, O2 concentration and root-induced acidification were observed together in the rhizosphere of root segments and tips. In week three, when V. natans was young, the flux of DGT-labile P accumulated more in the rhizosphere in comparison with the bulk sediment. This was because increased phosphatase activity (of up to 35%) and root-induced acidification (with pH decreasing by up to 0.25) enhanced P acquisition of V. natans by the third week. However, the flux of DGT-labile P turned to depletion during weeks three to six of V. natans growth, after Fe plaque formed at the matured stage. The constant hydrolysis of phosphatase and acidification could not compensate for the P demand of the roots by the sixth week. At this stage, Fe plaque become the P pool, due to P fixation with solid Fe(III) hydroxides. Subsequently, V. natans roots acquired P from Fe plaque via organic acid complexation of Fe(III).

Quantitative assessment of background pollutants using a modified method in data-poor regions.

Heavy background pollutant loads pose a difficult problem for the assessment and management of regional water quality, especially in areas where surface water quality is less affected by anthropogenic pollution. Deducting background values from those derived from water quality monitoring is a new method for evaluating surface water environments in areas with heavy background loads. In this study, river source reserves in Heilongjiang province were evaluated with an export coefficient model (ECM) that considers the rainfall influence factor, has an improved timescale, and is based on synchronous rainfall monitoring data and concentrations. Moreover, the ECM was combined with a mechanism model. The chemical oxygen demand, ammonia nitrogen, and other water quality indices are affected by background environment, and therefore, suitable export coefficients for the study area were determined and a regression equation between the rainfall influence factor and precipitation was established. By combining the ECM and mechanism model, the concentrations entering the river during eight rainfall events in 2018 were predicted, and the background value was calculated to evaluate surface water quality. The predicted values were found to approximate the monitored values. Therefore, this study is of great significance for water quality assessment and management in areas with heavy background pollutant loads.

pH affects bacterial community composition in soils across the Huashan Watershed, China.

To investigate soil bacterial richness and diversity and to determine the correlations between bacterial communities and soil properties, 8 soil samples were collected from the Huashan watershed in Anhui, China. Subsequently, 454 high-throughput pyrosequencing and bioinformatics analyses were performed to examine the soil bacterial community compositions. The operational taxonomic unit richness of the bacterial community ranged from 3664 to 5899, and the diversity indices, including Chao1, Shannon-Wiener, and Faith's phylogenetic diversity ranged from 7751 to 15 204, 7.386 to 8.327, and 415.77 to 679.11, respectively. The 2 most dominant phyla in the soil samples were Actinobacteria and Proteobacteria. The richness and diversity of the bacterial community were positively correlated with soil pH. The Mantel test revealed that the soil pH was the dominant factor influencing the bacterial community. The positive modular structure of co-occurrence patterns at the genus level was discovered by network analysis. The results obtained in this study provide useful information that enhances our understanding of the effects of soil properties on the bacterial communities.

Using organic fertilizer to mitigate organic-inorganic fouling in agricultural saline wastewater irrigation systems.

Recycling saline wastewater for agricultural irrigation offer a promising solution to address both water scarcity and anthropogenic pollution. However, organic-inorganic fouling in saline wastewater irrigation systems (SWIS) poses significant technical and economic challenges. Traditional chemical biocides are currently insufficient for controlling composite organic-inorganic fouling and may pose environmental hazards. This study proposed a greener approach using organic acid (OA) fertilizers to alleviate organic-inorganic fouling in agricultural SWIS. The treatment performances were assessed employing four types of OA fertilizers (i.e., humic acid, alginic acid, nucleotide, and ammonia acid) and a negative control. Results showed that three types of OA, i.e., alginic acid, nucleotide, and ammonia acid, effectively reduced the total SWIS fouling content by 11.2%-57.4%, whereas humic acid exacerbated fouling by 11.2%-57.4%. Specifically, all types of OA significantly mitigated the content of inorganic fouling (precipitates and silicates) by 10.7%-42.3% by forming loosed and sparser structures. However, OA exhibited minimum effects on controlling silica fouling. Meanwhile, except the humic acid, other types of OA decreased the total content of organic fouling by 17.2%-39.5% by reducing the content of humic substances and building block fractions. In addition, the significant binary interactions of organic-inorganic fouling indicated the active role of calcium silica and biomineralization fouling. These findings provide insight into the development of appropriate and eco-friendly antifouling strategies for SWIS, with implications for recycling and reusing saline wastewater.

Impacts and mechanism of coal fly ash on kitchen waste composting performance: The perspective of microbial community.

Aerobic composting is eco-friendly and sustainable practice for kitchen waste (KW) disposal to restore soil fertility and reduce environmental risks. However, KW compact structure, perishable nature, acidification by anaerobic acidogens, inhibits the metabolism of aerobic microbes, insufficient breakdown of organic matters, and prolong the composting duration. This study, co-composted coal fly ash (FA), to regulate bacterial dynamics, co-occurrence patterns and nutrients transformation in KW composting. Our results indicated, FA created suitable environment by increasing pH and temperature, which facilitated the proliferation and reshaping of microbial community. FA fostered the relative abundances of phlya (Proteobacteria, Chloroflexi and Actinobacteriota) and genera (Bacillus, Paenibacillus and Lysinibacillus), which promoted the nutrients transformation (phosphorus and nitrogen) in KW compost. FA enhanced the mutualistic correlations between bacterial communities, promoted the network complexity (nodes & edges) and contains more positive connections, which reflect the FA amendment effects. KW mature compost seed germination index reached >85% of FA treatment, indicated the final products fully met the Chinese national standard for organic fertilizer. These findings might provide opportunity to advance the KW composting and collaborative management of multiple waste to curb the current environmental challenges.

Impacts and mechanism of biodegradable microplastics on lake sediment properties, bacterial dynamics, and greenhouse gasses emissions.

The accumulation of microplastics (MPs) in freshwater ecosystems plays a vital role in greenhouse gases (GHGs) emissions from lake sediment by altering sediment properties and microbial communities. Thus, a short-term microcosm experiment was performed to explore the effect of conventional polyethylene (PE) and biodegradable Poly (butylene-adipate-co-terephtalate) (PBAT) MPs on carbon dioxide (CO2) and methane (CH4) emissions from lake sediment and associated microbial community. The results indicated that at 1.0 % concentration, the cumulative CO2 emissions were increased by 16.8 % and the cumulative CH4 emissions were increased more than four times following the addition of biodegradable MPs compared to conventional MPs, which was due to the more dissolved organic carbon (DOC) provided by biodegradable MPs for microbial respiration. Furthermore, the cumulative CO2 and CH4 emissions significantly (p < 0.05) increased with the increasing concentrations of biodegradable MPs. Notably, the accumulation of MPs could weaken the microbial stress from requirements of energy and substrate, and increase the microbial biomass carbon (MBC) value, thus eventually improving the respiratory capacity of microbes. In addition, the biodegradable MPs significantly increased the abundance of microbes, such as Firmicutes, Myxococcota and Actinobacteriota, which were related to the function of anaerobic respiration. Overall, we concluded that the abundant DOC provided by biodegradable MPs could promote the growth of microbes in lake sediment, and they could change the structure and diversity of the microbial community, which would eventually enhance the anaerobic respiration of microbes and aggravate the GHGs emissions.

Influence of cyanobacterial bloom accumulation and dissipation on underwater light attenuation in a large and shallow lake.

Cyanobacterial bloom accumulation and dissipation frequently occur in Lake Taihu, a typically shallow, eutrophic lake due to wind wave disturbance. However, knowledge of the driving mechanisms of cyanobacterial blooms on underwater light attenuation is still limited. In this study, we collected a high-frequency in situ monitoring of the wind field, underwater light environment, and surface water quality to elucidate how cyanobacterial bloom accumulation and dissipation affect the variations in underwater light attenuation in the littoral zone of Lake Taihu. Results showed that cyanobacterial blooms significantly increased the diffuse attenuation coefficient of ultraviolet-B (Kd(313)), ultraviolet-A (Kd(340)), and photosynthetically active radiation (Kd(PAR)); the scattering of total suspended matter (bbp(λ)); and the absorption of phytoplankton (aph(λ)) and chromophoric dissolved organic matter (CDOM, ag(λ)) (p < 0.01). The Kd(PAR) decreased quickly during the processes of bloom dissipation, but the decrease of Kd(313) and Kd(340) lagged 0.5 day. Our results suggested that cyanobacterial blooms could increase particle matters and elevated the production of autochthonous CDOM, resulting in underwater light attenuation increase. Ultraviolet radiation (UVR) and PAR attenuation both have significant responses to cyanobacterial blooms, but the response processes were distinct due to the different changes of particle and dissolved organic matters. Our study unravels the driving mechanisms of cyanobacterial blooms on underwater light attenuation, improving lake ecosystem management and protection.

Dynamics of nitrogen and phosphorus profile and its driving forces in a subtropical deep reservoir.

Nitrogen and phosphorus stratification is crucial for ecosystem dynamics in deep lakes and reservoirs. It is critical for water quality management to understand the characteristics of nitrogen and phosphorus stratification and its driving forces. In this study, high-frequency total nitrogen (TN) and total phosphorus (TP) from January 2017 to October 2019 were estimated using the datasets of high-frequency buoy parameters, including water temperature, pH, chlorophyll-a, oxidation-reduction potential, dissolved oxygen, and fluorescent dissolved organic matter. The results revealed that both nitrogen and phosphorus in water column were periodically stratified. Specifically, the stratification of nitrogen and phosphorus occurred from April to December or January of the following year. Moreover, indices of TN stratification (IC-TN) and TP stratification (IC-TP) were - 0.29 ~ 0.05 and - 0.78 ~ 0.28, respectively. Significant (P < 0.01) positive correlations were observed between RWCS (an index of thermal stability) and IC-TN (or IC-TP), indicating thermal stratification may be the main driving force of nutrient stratification at inter-month scales. Further analysis indicated that the thermal stratification may affect nitrogen and phosphorus stratification though (1) influencing algal growth and (2) affecting the release of internal sources and the material exchange between water columns. Furthermore, precipitation is also suggested as an important factor affecting the stability of nitrogen and phosphorus vertical profile in the flood season. These findings may provide important information for optimizing water quality management efforts in Qiandaohu and other subtropical deep reservoirs. In addition, the knowledge of the effect of temperature and precipitation on nutrient stratification are essential to understand future ecosystem dynamics of deep reservoirs.

Reproductive toxicity in male mice exposed to Nanjing City tap water.

End points of reproductive toxicity were investigated in male mice (Mus musculus, ICR) fed Nanjing City tap water for 90 days. There was no significant alteration in body weights between treatment and control mice. In treated mice, flow cytometry analysis of testicular tissue indicated that the relative percentage of the elongated spermatid (HC) decreased significantly (P < 0.05). Also slight increases in the relative percentage of round spermatids (1C) and primary spermatocytes (4C) were noted. The ratios of 4C:2C (diploid germ cells) and 1C:2C increased, and testicular histopathology indicated an expansion of interstitial space and a decreased number and size of Leydig cells in treated mice. The current study suggests that Nanjing City tap water is toxic to the reproductive system of mice and additional study to evaluate its effects on other species, including human beings, would be warranted.

[Roles of monocyte chemoattractant protein-1, RANTES and Fractalkine on promoting vulnerability of atherosclerotic plaques].

OBJECTIVE: To elucidate the roles of monocyte chemotactic factors (MCP-1, RANTES and Fractalkine) on the vulnerability of atherosclerotic plaques in patients with stable (SAP) and unstable angina pectoris (UAP). METHODS: Patients with SAP (n = 50) and UAP (n = 50) underwent coronary angiography (CAG) and intravenous ultrasound (IVUS) were included in the study. Monocyte chemotaxis was assayed by the transwell chamber. Concentrations of hs-CRP, MCP-1, RANTES and Fractalkine were measured by Enzyme-linked-immunosorbent assay (ELISA). mRNA expression of MCP-1, RANTES and Fractalkine in the monocytes was detected by RT-PCR. RESULTS: IVUS evidenced soft lipid plaques in 48% UAP patients and in 16% SAP patients (P < 0.05). SAP patients had mainly fibrous and mixed plaques. Plaque burden and vascular remodeling index were significantly higher in UAP patients than in SAP patients (P < 0.01). The averaged number of migrated monocytes in the UAP patients were higher than that in patients with SAP (P < 0.01). Concentration of hs-CRP, MCP-1, RANTES and Fractalkine were significantly higher in UAP patients than those of SAP patients (P < 0.05 or P < 0.01). mRNA expression of MCP-1, RANTES and Fractalkine in patients with UAP was significantly higher than those of SAP patients (P < 0.05). CONCLUSION: Upregulated monocyte chemotactic factors (MCP-1, RANTES and Fractalkine) might promote coronary plaque vulnerability in UAP patients.

Knowledge Hiding: Current Research Status and Future Research Directions.

This article provides a review of scientific articles addressing the topic of knowledge hiding in organizations. Based on a descriptive analysis, bibliometric analysis, and content analysis of a sample of 81 articles published in the academic journals in the Web of Science from 2012 to 2020, we identify the main areas and current dynamics of knowledge hiding research. Our results show that the central research themes of knowledge hiding include five clusters: concept and dimensions, antecedents, consequences, theories, and influence mechanisms. Based on our findings, we suggest future research should further develop the concept and dimensions of knowledge hiding; probe deeper into the consequences of knowledge hiding; explore multilateral, cross-level, and collective knowledge hiding; employ innovative theoretical perspectives and research methods to study knowledge hiding; and address how cultural and other contextual factors may shape the knowledge hiding behavior.

The Perceived Impact of COVID-19 on Student Well-Being and the Mediating Role of the University Support: Evidence From France, Germany, Russia, and the UK.

The rapid and unplanned change to teaching and learning in the online format brought by COVID-19 has likely impacted many, if not all, aspects of university students' lives worldwide. To contribute to the investigation of this change, this study focuses on the impact of the pandemic on student well-being, which has been found to be as important to student lifelong success as their academic achievement. Student well-being has been linked to their engagement and performance in curricular, co-curricular, and extracurricular activities, intrinsic motivation, satisfaction, meaning making, and mental health. The purpose of this study was to examine how student perceptions of their degree completion and future job prospects during the pandemic impact their well-being and what role university support plays in this relationship. We used the conservation of resources theory to frame our study and to develop five hypotheses that were later tested via structural equation modeling. Data were collected from 2,707 university students in France, Germany, Russia, and UK via an online survey. The results showed that university support provided by instructors and administration plays a mediating role in the relationship between the perceived impact of COVID-19 on degree completion and future job prospects and levels of student well-being. Student well-being is decreased by their concerns for their degree completion but not by their concerns for future job prospects. In turn, concerns for future job prospects affect student well-being over time. These results suggest that in a "new normal," universities could increase student well-being by making support to student studies a priority, especially for undergraduates. Also, universities should be aware of the students' changing emotional responses to crisis and ensure visibility and accessibility of student support.

Compulsory Citizenship Behavior and Employee Creativity: Creative Self-Efficacy as a Mediator and Negative Affect as a Moderator.

Workplace stressors were identified to have critical impacts on employee creativity. However, little is known about how and when involuntary citizenship behavior [i.e., compulsory citizenship behavior (CCB)]-induced stress might exert an influence on employee creativity. To fill this knowledge gap, the present study firstly develops a moderated mediation model to investigate the CCB-employee creativity association as well as the underlying mechanism and contextual condition of this relationship. By integrating social cognitive theory such as self-efficacy theory and conservation of resources (COR) theory, we propose that CCB predicts employee creativity through the mediating role of creative self-efficacy (CSE), with the individual characteristics (i.e., personality traits) of negative affect acting as a boundary condition. Using two-wave time-lagged survey data collected from a sample of 251 frontline employees in 10 manufacturing firms in Southern China, the results show that: (a) CSE mediates the negative relationship between CCB and employee creativity; (b) negative affect moderates the relationship between CCB and CSE; (c) negative affect moderates the indirect influence of CCB on employee creativity through CSE. As the level of negative affect rises, this indirect relationship is stronger. Finally, important theoretical and managerial implications and promising avenues for future research are addressed.

Importance of Ssurface water background values for objectively assessing water quality in a unique basin.

Ignoring differences in surface water background values of different basins is a prominent shortcoming in water resource assessment and management systems in China. This study described the impact of this shortcoming on the results of water quality assessments by analysing water quality and the intensity of anthropogenic activities in 10 water resource basins in China. In particular, the Songhuajiang River Basin had a relatively undegraded natural environment with minimal anthropogenic activity. However, water quality assessment results showed the lowest water quality, and this basin is the most seriously affected by background values. The Huma River source water reserve was selected to conduct research of background value identification, concentration characteristics, migration and transformation laws, and output mechanism characteristics to enable the acknowledgment of the severe background value problem. Most data collected in basins with minimal anthropogenic pollution failed to meet Chinese water quality standard requirements, and high background values mainly resulted from litter leachate and soil erosion by rainfall or snowmelt runoff. A revised water quality assessment method was proposed in view of the particularity and heterogeneity of background values in the Songhuajiang River Basin. This study therefore clarified the negative impact of background values on water quality assessments, so that these values can be properly considered in Chinese water quality assessment and management systems.

[Accumulation Characteristics and Release Regularity of Nutrients in Sediments of a Surface-flow Constructed Wetland After Long-term Operation].

Sediments serve as an important carrier during the migration and transformation of pollutants in surface-flow constructed wetlands. Exploring the accumulation characteristics and release patterns of nutrients is of great significance for assessing the purification functions of constructed wetlands after long-term operation. The contents of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in sediments at various locations of the 5-year-old Yanlong Lake surface-flow constructed wetland were analyzed and static release experiments with cylindrical core samples were carried out. The results showed that after five years, sediments at this site have become moderately polluted and the nutrient accumulation level is mainly being affected by the influent flow, water depth, and plant effects. Additionally, ① nutrients in sediments were found to increase along the flow direction; ② they also increase as the depth of overlying water increases and are relatively affected by the carbon; ③ healthier growth of the wetland plants could lead to more nutrients being accumulated in sediments. The release trend of nutrients fell after a rise and basically reached equilibrium after 20 days, and the release rate was mainly affected by the accumulation level of nutrients, which is similar to the trend in light nutrient containing reservoirs. Plant residues contained in the sediments were associated with the stronger release of nutrients. These results can provide a scientific basis for solutions aimed at maintaining the purification capacity of long-running surface-flow constructed wetlands.

A risk assessment of water salinization during the initial impounding period of a proposed reservoir in Tianjin, China.

Water salinization of coastal reservoirs seriously threatens the safety of their water supply. To elucidate the mechanism of salinization and to quantitatively analyze the risk in the initial period of the impoundment of a proposed reservoir in Tianjin Binhai New Area, laboratory and field simulation experiments were implemented and integrated with the actual operation of Beitang Reservoir, which is located in the same region and has been operational for many years. The results suggested that water salinization of the proposed reservoir was mainly governed by soil saline release, evaporation and leakage. Saline release was the prevailing factor in the earlier stage of the impoundment, then the evaporation and leakage effects gradually became notable over time. By referring to the actual case of Beitang Reservoir, it was predicted that the chloride ion (Cl(-)) concentration of the water during the initial impounding period of the proposed reservoir would exceed the standard for quality of drinking water from surface water sources (250 mg L(-1)), and that the proposed reservoir had a high risk of water salinization.

[Accumulation of non-point source pollutants in ditch wetland and their uptake and purification by plants].

The study on the vertical and horizontal distribution of organic matters and total nitrogen (TN) in the sediment of ditch wetland naturally grown with reed (Phragmites communis) and wild rice (Zizania latifolia) showed that the sediment below 40 cm depth had a significant effectiveness in retaining and accumulating organic matters and TN, but in its surface layer, this effectiveness varied largely with seasons, and the maximum was more than twofold of the minimum. TN was highly correlated with organic matters, the correlation coefficient being 0.9876 in reed wetland and 0.9335 in wild rice wetland, and in water phase, it was positively related to NH4+ -N and NO3-N, indicating that the main composition of TN was organic N, and the mineralization of organic N was the sources of inorganic N. The harvest of reed in each autumn could take away 818 kg x hm(-2) of N and 103.6 kg x hm(-2) of P, and that of wild rice could take away 131 kg x hm(-2) of N and 28.9 kg x hm(-2) of P. Zizania caduci flora had a high assimilation ability of nutrients. Its cultivation in ditch wetland to replace wild helophytes would be a good approach to attain higher absorbing ability of N and P, and to resolve the secondary pollution problem of emerged plants, because farmers could harvest it voluntarily.