Phosphorus Ratio Research Articles

Nitrogen availability and its related enzyme activities affect microbial residue nitrogen accumulation during Chinese fir plantation development

Microbial growth, metabolism, and reproductive activities have a significant role in the generation, transformation, and storage of soil nitrogen (N). However, the time-integrated effect of microorganisms on long-term N sequestration in plantation forests remains poorly understood. We investigated the microbial residue N (MRN) and its contribution to soil total N (TN) among the young (8-year), middle (16-year), near-mature (24-year), mature (34-year), and over-mature (106-year) stands of Chinese fir plantation (CFP) in subtropical China. The soil TN content showed a general pattern of increasing with stand age, ranging from 2.61 to 3.42 g kg−1, and was higher in the over-mature and mature stands than in the other three stands (p < 0.001). In addition, soil carbon (C), N, phosphorus (P), and hydrolase stoichiometric ratios indicated that P limitation was widespread during all stages of CFP development. The average ratio of soil fungal residue N (FRN) to bacterial residue N (BRN) was 3.64:1. The MRN content and its contribution to soil TN exhibited a falling and then rising pattern from young to over-mature stands, ranging from 1.24 to 1.70 g kg−1 and 38.8 % to 57.5 %, respectively. Soil N fraction contents and hydrolase activities were higher in the 0–5 cm soil layer than in the 5–30 cm soil layer (p < 0.05). Regression analysis showed that soil MRN content increased with soil N fraction contents, C-N-P stoichiometric ratios, and hydrolase activities (p < 0.001). Redundancy analysis and partial least squares path modeling revealed that soil available N (AN) and N hydrolase were the main factors affecting MRN accumulation. These parameters may partially indicate the dynamics of MRN accumulation. Our study discovered that the long-term development of CFP promotes soil N sequestration, with microbial residues playing a significant role in contributing to N pools.

Optimizing biofuel production from algae using four-element framework: Insights for maximum economic returns

This paper introduces a Four Element Strategy (FES) focused on concentration of CO2 gas (Cc,g), energy input to the process, concentration of nutrients, and the type of algal strain to maximize biofuel production (BYP) from algae strains and evaluate associated economic benefits. Two algal strains encompassing slain algae Nannochloropsis sp. (Ns), and freshwater strain Chlorella vulgaris (Cv) were used in the current study. Response Surface Methodology (RSM) and Box Behnkin Design (BBD) are integrated with a biokinetic model to explore the relationships among growth parameters in the ranges; Cc,g ∼ 0.03–20 %), Nitrogen (N) to phosphorus (P) ratio (RN/P)∼1–11, and light intensity (LI)∼ 100–400 µE m⁻² s⁻¹ with corresponding CO2 bio-fixation rate (RCO2, g L⁻¹ d⁻¹), biomass accumulation (X, g L⁻¹), and algal growth rate (µ, d⁻¹). Optimization results indicate that the most productive conditions involve LI in the range of 100–270 µE m⁻² s⁻¹, Cc,g between 0.03 % and 15 %, and RN/P of 3.5–11, achieving maximum RCO2, X, and µ at 1 g L⁻¹ d⁻¹, 6 g L⁻¹, and 1.6 d⁻¹, respectively. Further optimization using the desirability function supports achieving RCO2 of 1.2 g L⁻¹ d⁻¹, X of 1.8 g L⁻¹, and µ of 1.7 d⁻¹, with RN/P, Cc,g, and LI at 11, 4.5 %, and 200 µE m⁻² s⁻¹, respectively. Notably, Ns demonstrated higher nutrient uptake rates and BYP compared to Cv, with total production costs of $0.629/L and respective required cost coverages of $0.138 and $0.375 for Ns and Cv. This study offers a comprehensive guideline for large-scale microalgae cultivation technology (MCT) processes, providing insights into optimizing conditions for biofuel production while considering economic viability.

Mixed planting of subtropical Chinese fir in South China improves microbial carbon source metabolism and functional diversity through the accumulation of nutrients from soil aggregates.

Soil microbial functional traits are key indicators of soil microbial ecological traits; however, how mixing patterns of Chinese fir and broadleaved trees drive soil microbial functional trait variation at the aggregate scale and how soil microbial functional traits are linked to soil fertility factors have largely not been determined. In this study, soil from the 0-20 cm depths in three Chinese fir plantations was collected, and the soil samples were separated into >2 mm (large macro-aggregate), 0.25-2 mm (macro-aggregate) and <0.25 mm (micro-aggregate) by complying with an optimal moisture sieving procedure. The metabolic activities, functional diversity and different carbon sources utilization characteristics of the soil microorganisms were determined by the Biolog Eco microplate method. In all Chinese fir plantations, micro-aggregates (<0.25 mm) consistently exhibited the highest levels of microbial metabolic activity, a more uniform carbon source utilisation capacity, and the highest microbial diversity. Micro-aggregates also showed elevated levels of soil organic carbon (OC), total nitrogen (TN), total phosphorus (TP), and higher ratios of C/N and C/P compared to large macro-aggregates and macro-aggregates, indicating that micro-aggregates contain more resources available to soil microorganisms. Soil OC, TN, and TP content were enhanced by integration with Michelia macclurei, suggesting that this combination promotes relatively favourable soil conditions for microbial growth and multiplication. This, in turn, promotes microbial metabolic activity. Furthermore, redundancy and correlation analyses showed that soil OC, TN, and TP were identified as principal determinants of soil microbial functional properties in Chinese fir plantations. In summary, mixed cultivation and aggregate size influenced microbial functional properties via soil nutrient alterations. Consequently, adopting a mixed cultivation approach of Chinese fir and broadleaved trees is advocated in the subtropical regions of Guangxi. Employing a diversity of tree species, including M. macclurei, is recommended for optimal soil quality preservation.

Macronutrients dynamics in copper-contaminated soils: Implications for hemp growth and its phytoremediation potential

Fibrous plants with higher biomass, particularly industrial hemp, have ability to withstand and accumulate significant quantities of heavy metals from contaminated environments. The present study aimed to evaluate the dynamics of different levels (ratios) of macronutrients nitrogen, phosphorus and potassium (NPK) viz., NPK1NPK (1:1:1); NPK2NPK (2:1:1); NPK3NPK (3:1:2); NPK4NPK (4:1:2) on hemp growth and Cu contents under various levels of Cu stress (100, 400 and 800 mg kg−1 on dry soil basis using CuSO4·5H2O). Results revealed that by increasing the Cu stress, growth and biomass decreased linearly and lipid per oxidation and enzymatic antioxidants increased. Balanced application of NPK improved the biomass and decreased the membrane damage by the modulation of malonaldehyde contents. Maximum concentration of Cu in roots (377.47 ± 4.90 mg kg−1), shoots (137.45 ± 5.60 mg kg−1) and (150.07 ± 3.57 mg kg−1) was recorded at Cu3NPK2 treatment as compared to control. Maximum translocation factor (TF) and bioaccumulation coefficients (BAC) in the shoots and leaves of hemp plant were noticed where Cu stress was applied at the rate of 100 mg kg−1. However, BAC and TF were below 1. The NPK2 treatment enhanced biomass and increase Cu content both in leaves and stems, rather than the roots. Our study suggests that balanced application of NPK is a practicable approach to alleviate Cu stress and improve biomass production of industrial hemp plant. These findings indicate that optimum nutrient supply, under Cu stress, can maximize the growth potential and overall health of industrial hemp, making it a viable option for phytoremediation and sustainable agriculture on contaminated soils.

Effects of experimental in-office bleaching gels incorporated with co-doped titanium dioxide nanoparticles on dental enamel physical properties.

To evaluate the physical properties of enamel submitted to hydrogen peroxide (HP) incorporated with titanium dioxide nanoparticles (NP) co-doped with nitrogen and fluorine and irradiated with violet LED light (LT). Enamel-dentin disks were randomly allocated (T0) into groups, according to HP (HP6, HP15, or HP35) and NP (no NP, 5NP, or 10NP) concentrations, and irradiated or not with LT. A negative control (NC) group was set. After three bleaching sessions (T1, T2, and T3), specimens were stored in saliva for 14days (T4). Enamel surface microhardness number (KHN), surface roughness (Ra), cross-sectional microhardness (ΔS), energy-dispersive spectroscopy (EDS), scanning electron (SEM), and polarized light (PLM) microscopies were performed. Surface KHN was significantly influenced by NP over time, independently of LT irradiation. At T3 and T4, gels with 5NP and 10NP exhibited no KHN differences compared to NC and baseline values, which were not observed under the absence of NP. NP incorporation did not statistically interfere with the ΔS and Ra. PLM images exhibited surface/subsurface darkening areas suggestive of demineralizing regions. SEM demonstrated some intraprismatic affection in the groups without NP. EDS reported a higher enamel calcium to phosphorus ratio following 10NP gels applications. Gels with NP maintained the enamel surface microhardness levels and seemed to control surface morphology, upholding the mineral content. None of the proposed experimental protocols have negatively influenced the enamel surface roughness and the cross-sectional microhardness.

A Quality Improvement Project to Decrease Fractures Secondary to Metabolic Bone Disease of Prematurity.

Osteopenia of prematurity is common in the neonatal intensive care unit, with an incidence of up to 54% in extremely low birthweight infants. The baseline fracture rate in our level IV midwestern neonatal intensive care unit was 13%, with poor compliance with recommended intakes of calcium, calcium:phosphorus ratio, and Vitamin D. A multidisciplinary team implemented a screening guideline through four Plan-Do-Study-Act cycles, which addressed staff education, vitamin D screening, and incorporation of calcitriol. In total, 150 patients born between October 1, 2019 and April 30, 2023 were screened for mineral intakes, laboratory abnormalities, and the development of fractures or osteopenia. The incidence of fractures decreased from 13% to 5.3%. Compliance with mineral intakes improved for calcium, calcium: phosphorus ratio, and Vitamin D. Infants born after the guideline were 4.8 times less likely to develop fractures. Quality improvement methodology successfully decreased the rate of fractures due to osteopenia of prematurity and increased compliance with recommended mineral intakes.

144. Impact of phosphorus levels and calcium to available phosphorus ratio on growth performance and bone mineralization in broilers from 0 to 35 days of age

144. Impact of phosphorus levels and calcium to available phosphorus ratio on growth performance and bone mineralization in broilers from 0 to 35 days of age

Riparian plant-soil-microbial C:N:P stoichiometry: are they conserved at plant functional group level?

As a consequence of the tight linkages between plants, soil, and microorganisms, we hypothesized the variations in plant species would change soil and microbial stoichiometry. Here, we examined the plant leaf carbon (C):nitrogen (N):phosphorus (P) ratios of nine species coming from three plant functional groups (PFGs) in the riparian zones of Hulunbuir steppe during near-peak biomass. The soil C:N:P, microbial biomass carbon (MBC):microbial biomass nitrogen (MBN), and extracellular enzyme's C:N:P were also assessed using the soils from each species. We found that plant tissue, soil nutrient, microbial, and enzyme activity stoichiometry significantly differed among different PFGs. Plant leaf and soil nutrient ratios tended to be similar (p > 0.05) between different species within the same PFGs. The variations in leaf C:N:P significantly correlated with the changes in soil C:N:P and MBC:MBN ratios. The homeostatic coefficients (H) < 1 suggested the relationships between plants and their resources C:N:P ratios might be non-homeostatic in the examined riparian zone. By assessing plant tissue and its soil nutrient stoichiometry, this study provided a perspective to understand the linkages of plant community, soil nutrient, and microbial characteristics.

Complete exhaustion of dissolved nutrients in a large lowland river

Riverine phytoplankton takes up phosphate, dissolved silicate, and nitrate. We investigated which nutrients are depleted during a Lagrangian sampling in the free-flowing part of the River Elbe in 2023. As part of this study, we tested the hypotheses that nutrient depletion might be caused by (1) above-average phytoplankton biomass or by (2) decreased nutrient load of the river during previous years. Phytoplankton biomass increased up to 350 km in rivers and stopped increasing exactly when soluble reactive phosphorus had been completely consumed, and molar carbon to phosphorus ratios of seston indicated the beginning phosphorus limitation. The concentrations of dissolved silicate and nitrate dropped below the detection limit as well. In contrast to the results from eight previous longitudinal samplings taken in 2018–2022, nitrate exhaustion was detected for the first time in 2023 within the transect. This was caused neither by an above-average phytoplankton biomass nor by a declined overall nutrient load of the river in 2018–2023. Instead, denitrification appears to be the most plausible explanation for the downstream decrease of nitrate and the loss of total nitrogen which was supported by enrichment of nitrate stable isotopes and a decreasing ratio of nitrate 15N/18O.

Cobalt as a potential limiting factor for heterocyst frequency in nitrogen‐limited Aphanizomenon and Dolichospermum: Evidence from experimental and field studies

Abstract Evidence suggests that low cobalt (Co) may limit heterocyst frequency (HF) in filamentous diazotrophic cyanobacteria. Therefore, the effect of three Co concentrations on HF in four species in the genera Aphanizomenon and Dolichospermum was examined in N‐depleted (N was not added) culture. Long‐term HF data were also analysed in experimentally fertilised N‐limited Lake 227. HF ranges and means at 0.17, 17, and 170 nmol Co/L were 4.1%–5.7% (4.6%), 5.4%–7.4% (6.4%), and 5.9%–9.3% (7.4%), respectively, after 11 days of growth in batch cultures suggesting that Co plays a role in regulating HF. HF at 0.17 nmol/L was significantly different from HF at the two higher concentrations in all species implicating Co in heterocyst differentiation. However, growth rates and final biovolume yields were not significantly affected by Co in any of the species. Applying the ratio of total phosphorus (TP)/Co in culture media (106) at 0.17 nmol Co/L to an N‐limited system implies that dissolved Co would have to be less than 1 pmol/L to severely limit HF at 1 μmol TP/L. This Co concentration is much lower than dissolved Co in Lake 227 during an Aphanizomenon skujae bloom with 1 μmol TP/L in 2017. Furthermore, Co increased from 0.7 to 2.0 nmol/L simultaneously increasing with HF and cyanobacteria biomass suggesting that Co probably did not limit HF and bloom biomass in Lake 227. Mean summer HFs in Lake 227 during 2000–2020 were 3.4% (epilimnion) and 4.0% (metalimnion), similar to HF at the lowest Co in the cultures. However, HF was significantly higher after 2015 following a shift in dominant bloom species from A. schindlerii to the smaller A. skujae. Calculations suggest that the decrease in cell size may have prompted a higher HF in A. skujae in order to fix an amount of N per unit biomass similar to that fixed by the larger A. schindlerii. Thus, two previously unidentified factors, Co and cell size, can be added to the list of factors that affect HF.

Linking eucalyptus stump decomposition to microbial diversity, community composition, and metabolites

In terrestrial ecosystems, microorganisms serve as primary decomposers of stumps, influencing carbon and nutrient cycling. However, our understanding of alterations in microbial communities driven by microbial-mediated metabolites within eucalyptus stump substrates of varying decay classes remains limited. Therefore, we conducted a 90-day laboratory incubation experiment using eucalyptus stump substrates representing five decay classes. Employing high-throughput sequencing and metabolomics, we evaluated microbial metabolites, community composition, diversity, and their interconnections. In the different decay classes of substrates, Proteobacteria, Actinobacteria, and Bacteroidetes were the dominant bacterial phyla. Despite the gradual increase of Basidiomycota across decay classes, Ascomycota persisted as the dominant fungal phylum. Acidothermus and Talaromyces genera were identified as primary microorganisms strongly associated with microbial metabolites. Partial least squares path modelling (PLS-PM) analysis revealed that microbial communities were primarily influenced by microbe-mediated metabolites, and available resource stoichiometry directly affected microbial alpha and beta diversity. The variations in stump bacterial and fungal community structures were explained by the presence of dissolved organic carbon (DOC) and ellagic acid. Random forest analysis indicated that total carbon (TC) of the stump was the most significant predictor of bacterial diversity. Moreover, total carbon to total phosphorus (TC:TP) and total nitrogen to total phosphorus (TN:TP) ratios of stumps were identified as pivotal factors influencing fungal diversity. Overall, our findings suggest that stump decomposition involves dynamic cross-kingdom succession and is significantly influenced by changes in substrate quality, with microbial-mediated metabolites exerting a pronounced and direct impact on microbial community diversity during the process.

Phytoplankton stoichiometry along the salinity gradient under limited nutrient and light supply.

Ongoing climate warming alters precipitation and water column stability, leading to salinity and nutrient supply changes in the euphotic zone of many coastal ecosystems and semi-enclosed seas. Changing salinity and nutrient conditions affect phytoplankton physiology by altering elemental ratios of carbon (C), nitrogen (N) and phosphorus (P). This study aimed to understand how salinity stress and resource acquisition affect phytoplankton stoichiometry. We incubated a phytoplankton polyculture composed of 10 species under different light, inorganic nutrient ratio and salinity levels. At the end of the incubation period, we measured particulate elemental composition (C, N and P), chlorophyll a and species abundances. The phytoplankton polyculture, dominated by Phaeodactylum tricornutum, accumulated more particulate organic carbon (POC) with increasing salinity. The low POC and low particulate C:N and C:P ratios toward 0psu suggest that the hypoosmotic conditions highly affected primary production. The relative abundance of different species varied with salinity, and some species grew faster under low nutrient supply. Still, the dominant diatom regulated the overall POC of the polyculture, following the classic concept of the foundation species.

Watershed grassland fires drive nutrient increases in replicated experimental ponds

Kelly, AG, Harris, TD. 2024. Watershed grassland fires drive nutrient increases in replicated experimental ponds. Lake Reserv Manage. 40:303–316. Forest and grassland fires have been increasing in frequency due to anthropogenic climate change and fire suppression-focused land management practices. Fire has frequently been observed in lake watersheds, yet links between fire ecology and limnology are not well understood, especially in grassland ecosystems. We conducted a 21-d replicated whole pond experiment to determine the effects of burning on lakes within grassland ecosystems. We examined physicochemical parameters and the phytoplankton concentration and community composition in control and treatment (burned) ponds. Total phosphorus, total dissolved phosphorus, soluble reactive phosphorus, and nitrate increased significantly following burning. The total nitrogen:total phosphorus and total dissolved nitrogen:total dissolved phosphorus ratios decreased significantly following burning. Increased nutrient inputs from burned material led to greater mean phytoplankton concentrations in the treatment ponds compared to the control ponds; however, no statistically significant changes were observed in phytoplankton concentration nor the community composition. Increases in nutrient concentrations in the treatment ponds were observed within the first half of the study and were short-lived, whereas increases in phytoplankton concentrations were not observed until experiment day 21. Our results indicate that increased prevalence of fire may worsen eutrophication issues in grassland water bodies, but more research is needed to understand the persistence of these impacts in pond ecosystems.

Altitude Distribution Characteristics of Farmland Soil Bacteria in Loess Hilly Region of Ningxia

It is of great significance for the conservation of biodiversity in farmland ecosystems to study the diversity, structure, functions, and biogeographical distribution of soil microbes in farmland and their influencing factors. High-throughput sequencing technology was used to analyze the distribution characteristics of soil bacterial diversity, community structure, and metabolic function along elevation and their responses to soil physicochemical properties in farmland in the loess hilly areas of Ningxia. The results showed that:① The Alpha diversity index of soil bacterial was significantly negatively correlated with elevation (P &lt; 0.05) and showed a trend of decreasing and then slightly increasing along the elevation. ② Seven phyla, including Proteobacteria, Actinobacteria, and Acidobacteria, were the dominant groups, and five of them showed highly significant differences between altitudes (P &lt; 0.01). ③ At the secondary classification level, there were 36 metabolic functions of bacteria, including membrane transport, carbohydrate metabolism, and amino acid metabolism, of which 22 showed significant differences, and 12 showed extremely significant differences among different altitudes. ④ Pearson correlation analysis showed that soil water content, bulk density, pH, and carbon-nitrogen ratio had the most significant effects on bacterial Alpha diversity, whereas soil nutrients such as total organic carbon, total nitrogen, and total phosphorus had significant effects on bacterial Beta diversity. ⑤ Mantel test analysis showed that the soil water content, total organic carbon, and carbon-nitrogen ratio affected bacterial community structure at the phylum level, and soil pH, total organic carbon, total nitrogen, total phosphorus, and carbon-nitrogen ratio were significantly correlated with bacterial metabolic function. Variance partitioning analysis showed that soil water content had the highest explanation for the community structure of soil bacteria, whereas soil pH had the highest explanation for metabolic function. In conclusion, soil water content and pH were the main factors affecting the diversity, community composition, and metabolic function of soil bacteria in farmland in the loess hilly region of Ningxia.

Correlation of methane production with physiological traits in Trichodesmium IMS 101 grown with methylphosphonate at different temperatures.

The diazotrophic cyanobacterium Trichodesmium has been recognized as a potentially significant contributor to aerobic methane generation via several mechanisms including the utilization of methylphophonate (MPn) as a source of phosphorus. Currently, there is no information about how environmental factors regulate methane production by Trichodesmium. Here, we grew Trichodesmium IMS101 at five temperatures ranging from 16 to 31°C, and found that its methane production rates increased with rising temperatures to peak (1.028 ± 0.040 nmol CH4 μmol POC-1 day-1) at 27°C, and then declined. Its specific growth rate changed from 0.03 ± 0.01 d-1 to 0.34 ± 0.02 d-1, with the optimal growth temperature identified between 27 and 31°C. Within the tested temperature range the Q10 for the methane production rate was 4.6 ± 0.7, indicating a high sensitivity to thermal changes. In parallel, the methane production rates showed robust positive correlations with the assimilation rates of carbon, nitrogen, and phosphorus, resulting in the methane production quotients (molar ratio of carbon, nitrogen, or phosphorus assimilated to methane produced) of 227-494 for carbon, 40-128 for nitrogen, and 1.8-3.4 for phosphorus within the tested temperature range. Based on the experimental data, we estimated that the methane released from Trichodesmium can offset about 1% of its CO2 mitigation effects.

Antibacterial activity of microwave synthesized hydroxyapatite against cariogenic bacteria: A preliminary study

IntroductionThe effects of hydroxyapatite (HA) on oral bacteria and biofilm remains inconclusive, with conflicting results. Studies assessing its effect against caries-causing bacteria are limited. ObjectiveThis study aimed to explore the antibacterial activity of HA synthesized using microwave against two of the most common cariogenic bacteria, Streptococcus mutans (S. mutans) and Streptococcus sobrinus (S. sobrinus). MethodsHA was chemically synthesized using a microwave. To verify the existence of the crystalline phase and the calcium and phosphate content, X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) analysis were employed, respectively. Reduction in bacterial growth was used to assess the antibacterial effects of 10 %, 20 %, and 30 % HA against the tested bacteria. ResultsThe presence of the hydroxyapatite crystallite phase was verified using XRD, while EDX revealed the Calcium to Phosphorus (Ca/P) ratio to be 1.6. In response to the 10 %, 20 %, and 30 % HA, S. mutans were reduced by 14.5 %, 15.6 %, and 23.4 %, whereas S. sobrinus decreased by 17.1 %, 60.8 %, and 98.6 %, respectively. ConclusionMicrowave-synthesized HA could have antibacterial properties against caries-causing bacteria with different potencies depending on concentration and bacteria.

Anthropogenically Driven Changes in the Carbon to Phosphorus Ratio of Marine Dissolved Organic Matter

AbstractMarine dissolved organic matter (DOM) cycles play a pivotal role in sustaining marine ecosystems and regulating the ocean's carbon sequestration from the atmosphere. However, the response of DOM cycles, including dissolved organic carbon (DOC) and dissolved organic phosphorus (DOP), to future climate change remains highly uncertain. Using the Community Earth System Model version 2 large ensemble simulations, we find that the C:P ratios in DOM are projected to increase by up to two‐fold in oligotrophic gyres by 2100. Increased upper ocean stratification reduces surface phosphate availability, thereby elevating phytoplankton C:P ratios and enhancing phytoplankton utilization of DOP, both acting to deprive DOM of P. Moreover, ocean stratification has a direct effect on exporting less DOC to the subsurface while accumulating more DOC at the sea surface. As a result of the strong sensitivity to ocean surface warming, the anthropogenically driven trends in upper ocean DOM concentration and its C:P ratios are estimated to emerge earlier from the simulated natural variability than upper ocean phosphate concentrations and net primary production—two key biogeochemical variables that are frequently monitored. This study suggests that changes in the C:P ratios of DOM could serve as a sensitive fingerprint of anthropogenic ocean warming, potentially exerting broad impacts on marine microbes. Our estimated 4% reduction in the globally integrated DOC export below 100 m is comparable to a 2% reduction in particulate organic carbon (POC) export by 2100, implying that global warming is likely to weaken the biological carbon pump through both DOC and POC.

Improving microalgal growth and nitrogen, and phosphorus removal by electric field in municipal wastewater

The promoting effect of electric fields on the growth and lipid production of microalga provides a new research direction for biorefining. However, researchers have rarely applied this technology to the treatment of actual wastewater. In this study, the dry weight and lipid content of microalgae increased by 47.45 % and 28.28 %, respectively, when optimized for light, growth phase and energization time. By optimizing the initial microalgal concentration and the ratio of nitrogen and phosphorus, the removal of total nitrogen (TN) and ammonia nitrogen (NH4+) increased by 18.5 % and 10.9 %, respectively. Compared to peroxidase (POD), significant changes in the relative activities of catalase (CAT) and total superoxide dismutase (T-SOD) were observed after the application of an electric field to the microalgae. Along with the cultivation, the relative activities of T-SOD and CAT showed a tendency of an increase and then a decrease compared with the control. This was mainly due to the increased internal secretion of T-SOD and CAT by the microalgae in response to the oxidative stress of the electric field on the microalgae, while the lack of nutrients at the later stages of cultivation also led to the increase of the content of the two enzymes in the control.

Response of carbon, nitrogen, and phosphorus in leaves of different life forms to altitude and soil factors in Tianshan wild fruit forest

IntroductionThe ecological stoichiometric ratio of carbon, nitrogen, and phosphorus is an important index to understand the utilization and distribution of plant nutrients.MethodTo explore how leaf carbon, nitrogen, and phosphorus contents, along with the stoichiometric ratio of different life forms of plants, respond to variations in altitude and soil physical and chemical properties, leaves and soil samples were collected from different life forms of plants at different altitudes (1,100~1,700 m) within the Guozigou region of the forest. Subsequently, the contents and ratios of carbon, nitrogen, and phosphorus in the leaves, as well as the physicochemical properties of the soil, were determined.ResultsThe results showed the following: (1) The three life forms of plants in the study area showed that the coefficient of variation of leaf carbon content was the smallest and the distribution was the most stable, while the coefficient of variation of carbon–nitrogen ratio was the largest. (2) Altitude had a significant effect on the carbon, nitrogen, and phosphorus contents of different life form of plants, among which the leaf nitrogen content of trees, shrubs, and herbs increased significantly with altitude (p &amp;lt; 0.01), the leaf phosphorus content of trees increased significantly with altitude (p &amp;lt; 0.01), and the leaf C:N of the three life form of plants decreased significantly with altitude (p &amp;lt; 0.01). The C:P of the arbor decreased significantly with altitude (p &amp;lt; 0.05), and the N:P of shrub and herb leaves increased significantly with altitude (p &amp;lt; 0.01). (3) Soil organic carbon and soil moisture content were the main environmental factors affecting the changes of carbon, nitrogen, and phosphorus in leaves of arbors, and nitrate nitrogen was the main environmental factor affecting the changes of carbon, nitrogen, and phosphorus in leaves of shrubs. Available phosphorus affected the changes of carbon, nitrogen, and phosphorus in the leaves of herbaceous plants.DiscussionThe results provide new insights into community-level biogeographical patterns and potential factors of leaf stoichiometry among plant life forms.

#1048 Why are felids at such a high risk of chronic kidney disease?

Abstract Background and Aims Felids are obligatory hyper-carnivorous mammals, representing the utmost manifestation of a carnivorous dietary adaptation. Chronic kidney disease (CKD) could be characterized as an epidemic amongst domestic and captive wild felids, affecting up to 87%. However, its aetiology remains yet unknown. The aim of the study was to assess how various diets influence the development of CKD in felids. Method Ninety adult, captive non-domestic felids (tigers, leopards, cheetahs, and lions) from zoological parks were examined under anaesthesia. Their examination and sampling were part of planned annual health evaluations, not related to experiments. Husbandry and dietary information, as well as medical history were collected through a questionnaire. Blood serum and urine were taken. For the staging of CKD, symmetric dimethylarginine (SDMA), the level of azotaemia (serum creatinine) and the level of proteinuria with the urinary protein creatinine ratio were evaluated and correlated to dietary, biological and management factors. Results Sixty percent of the felids were diagnosed with CKD. The risk for developing CKD was much higher in animals fed primarily with skeletal muscle meat only compared to animals being fed with meat containing bones or whole pray carcasses. Furthermore, the incorporation of fasting days was significantly linked to a lower CKD prevalence. In addition, feeding a combination of white and red meat showed a lesser association with CKD presence compared to exclusively feeding red meat. Conclusion Non-domestic felids in captivity are exposed to different feeding practices. Diets closer to natural, wild diets resulted in lower risks of developing CKD. Feeding strategies such as whole-body prey, the inclusion of white meat and the implementation of fasting days were associated to significantly lower risks of developing CKD in captive wild felids. Future studies on investigating the benefits of dietary supplements, the impact of the Calcium:Phosphorus ratio, the composition of meat and the structure of fasting days is needed. In addition, the role of chronic low-grade inflammation (inflammatory biomarker analysis) as well as the impact of various dietary regimes on the microbiota composition should be explored further.