Organic Phosphate Concentrations Research Articles

Production of arabitol from glycerol by immobilized cells of Wickerhamomyces anomalus WC 1501.

Polyalcohols such as arabitol are among the main targets of biorefineries aiming to upcycle wastes and cheap substrates. In previous works Wickerhamomyces anomalus WC 1501 emerged as an excellent arabitol producer utilizing glycerol. Arabitol production by this strain is not growth associated, therefore, in this study, pre-grown cells were entrapped in calcium alginate beads (AB) and utilized for glycerol transformation to arabitol. Flasks experiments aimed to assess the medium composition (i.e., the concentration of inorganic and organic nitrogen sources and phosphates) and to establish the appropriate carrier-to-medium proportion. In flasks, under the best conditions of ammonium limitation and the carrier:medium ratio of 1:3 (w/v), 82.7g/L glycerol were consumed in 168h, yielding 31.2g/L arabitol, with a conversion of 38% and volumetric productivity of 186mg/mL/h. The process with immobilized cells was transferred to laboratory scale bioreactors with different configurations: stirred tank (STR), packed bed (PBR), fluidized bed (FBR), and airlift (ALR) bioreactors. The STR experienced oxygen limitation due to the need to maintain low stirring to preserve AB integrity and performed worse than flasks. Limitations in diffusion and mass transfer of oxygen and/or nutrients characterized also the PBR and the FBR and were partially relieved only in ALR, where 89.4g/L glycerol were consumed in 168h, yielding 38.1g/L arabitol, with a conversion of 42% and volumetric productivity of 227mg/mL/h. When the ALR was supplied with successive pulses of concentrated glycerol to replenish the glycerol as it was being consumed, 117g/L arabitol were generated in 500h, consuming a total of 285g/L glycerol, with a 41% and 234mg/L/h. The study strongly supports the potential of W. anomalus WC 1501 for efficient glycerol-to-arabitol conversion using immobilized cells. While the yeast shows promise by remaining viable and active for extended periods, further optimization is required, especially regarding mixing and oxygenation. Improving the stability of the immobilization process is also crucial for reusing pre-grown cells in multiple cycles, reducing dead times, biomass production costs, and enhancing the economic feasibility of the process.

Changes in bacterial community structure and carbon metabolism in sandy soil under the long-term application of chitin-rich organic material and attapulgite

Continuous expansion of sandy soil deeply threatens crop security and has become one of the main challenges facing modern society. Chitin-rich organic material and attapulgite have been considered efficient materials to improve degraded soil based on their rich nutrient contents and unique structures. However, their potential effects on microbial community and functions in sandy soil are poorly understood. Therefore, we conducted a 4-year field experiment featuring amendment with chitin-rich organic material and attapulgite and investigated the effect of amendments on microbial community diversity, structure and function using amplicons (16S and ITS) and metagenomic sequencing. The four treatments were as follows: (1) CK: no soil amendment; (2) SA: CK + attapulgite amendment; (3) SC: CK + chitin-rich organic material; and (4) SCA: CK + chitin-rich organic material + attapulgite amendment. The results indicated that the concentrations of soil organic carbon (SOC), total nitrogen, available phosphate (AP), available potassium, and enzyme activities increased while pH decreased in the treatments with chitin-rich organic material application (SC and SCA). Microorganisms have different responses to different soil amendments. Bacteria are the main components of microorganisms and their community structure was altered under chitin-rich organic material treatments (SC and SCA). Furthermore, 14 OTUs belonging to five phyla (Proteobacteria, Actinobacteriota, Firmicutes, Gemmatimonadota, and Patescibacteria) related to the decomposition of organic matter were enriched in SC, while 22 OTUs belonging to six phyla (Proteobacteria, Actinobacteriota, Firmicutes, Gemmatimonadota, Patescibacteria, and Cyanobacteria) were enriched significantly in SCA, suggesting that the combination of the two amendments had the potential to further alter the bacterial community compared with a single amendment. The metagenomic analysis revealed a decrease in the relative abundance of genes involved in carbon metabolism in SCA, with soil pH, AP, enzyme activity, SOC, and bacterial community structure identified as primary influencing factors. In conclusion, we conducted a comprehensive analysis of the effects of chitin-rich organic material and attapulgite on microorganisms in sandy soil and found a robust link between soil properties, bacterial community structure, and microbial carbon metabolism function.

The relationship of organic matter, nitrate, and phosphate content to diatom abundance in the eastern coastal waters of Rupat Island Province

This study was conducted in March 2023 in the coastal waters of the eastern part of the island of Rupat, Riau Province. The method used in this study used the purposive sampling method at 3 station points. Water samples were used to analyze nitrate and phosphate analyzed using Ultraviolet Spectrophotometry, and analysis of water organic matter using the titrimetric method. Diatom sampling using plankton net measuring 25 µm. The results of the study found 14 species from 3 classes of diatoms namely Bacillariophyceae, Cyanophyceae, and Conjugatophyceae. Diatom abundance ranged from 472.22 - 993.05 cells/L. The regression equation for nitrate on diatoms is Y= 929.151-3194.045x. The coefficient of determination (R2) of 0.080 indicates that the effect of nitrate on diatom abundance has a weak close relationship. The effect of phosphate on diatom abundance has a coefficient of determination (R2) of 0.105 and the effect of phosphate has weak proximity. The influence of water organic matter has a coefficient of determination (R2) of 0.033 with a very weak effect. The analysis shows that the concentration of nitrate (NO3) is included in the oligotrophic fertility level, namely the low fertility rate

Kinetic modeling and experiments on removal of COD/nutrients from dairy effluent using chlorella and co-culture.

A sustainable and cost-effective approach of waste water management is biological treatment for reducing organic carbon, nitrate, and phosphate content. Co-culturing of algae with bacteria in wastewater leads to higher biomass yield and improvement in COD/nutrients removal compared to the single strain counterparts. In this study, a mathematical modeling framework is proposed to predict the dynamic behavior of microbial co-culture in dairy waste water. Initially, the model has been developed to predict the biomass growth and COD/nutrients removal with discrete cultures (algae and bacteria). As an extension of the single strain kinetic model, Lotka-Volterra model was formulated to explore the symbiotic relationship between algae and bacteria in a co-culture and the impact of the interactions on the COD/nutrients removal efficiency and growth dynamics. Supporting experiments were carried out in 6 parallel sets (3 sets with triplicates) with standalone algae (Chlorella vulgaris, CV), bacteria (activated sludge), and co-culture in real-time dairy liquid effluent in lab flasks and predicted values from modeling were validated against experimental findings. Statistical analysis confirms reasonably good agreement between the model predictions and experimental findings indicating a positive synergistic effect of the algae-bacterial co-culture on COD removal.

Glyphosate and AMPA dynamics during the transition towards conservation agriculture: Drivers under shallow groundwater conditions

The environmental fate of glyphosate and its metabolite AMPA were investigated in buried lysimeters in a factorial combination of two cropping systems (conservation and conventional agriculture) and two water table depths (120 and 60 cm). Glyphosate was applied at a rate of 1.44 kg ha−1 a.i., and pore-water was sampled for 48 non-consecutive days along the soil profile (15, 30 and 60 cm) as well as the groundwater. Glyphosate and AMPA concentration in soil was detected to compare the effect of different soil-crop managements on transformation/dissipation dynamics and a full characterization of the soil profile was performed. Freundlich adsorption coefficients were calculated down to 110 cm depth and correlated to laboratory-estimated soil properties. Clay minerals, soil organic carbon, phosphate content, Al and Fe amount were the driving factors influencing most of the glyphosate sorption, regardless of the crop and water management system that did not differentiate between adsorption dynamics. In contrast, conservation practices differently affected glyphosate concentration in the soil profile, although its adoption was limited to two years. Moreover, the occurrence of a shallow water table influenced glyphosate transport in the vadose zone, and its detection in groundwater supported the hypothesis of fast transport of the molecule as mediated by preferential pathways, compromising groundwater quality, especially in agricultural lands. On the contrary, AMPA has never been detected in the groundwater, giving evidence of a diverse adsorption and transport dynamic compared to glyphosate.

An experimental oil spill at a tidal freshwater wetland along the St. Lawrence River re-visited after 21 years

In 1999, a tidal wetland located along the St. Lawrence River close to Ste. Croix de Lotbinière (Quebec, Eastern Canada) was the site of an experimental oil spill. Test plots were established and subjected to an experimental crude oil spill to evaluate natural attenuation, nutrient amendment and vegetation cropping as countermeasures. In 2020, this study re-visited the test plots to investigate residual oil and habitat recovery. Only concentrations of mid-chain length n-alkanes (C10–C36), but not of polycyclic aromatic hydrocarbons (PAHs), were significantly above detection limit, and were detected in both test plot and control sediments. Hydrocarbon, total organic carbon, nitrogen and phosphate contents did not differ significantly between test plot and control sediments. Microbial analyses did not detect significant differences in microbial load, microbial diversity or microbial community composition between test plot and control sediments. Key genes for the aerobic and anaerobic degradation of n-alkanes as well as for the aerobic degradation of PAHs were detected in all sediment samples. Associated gene abundances did not differ significantly between test plot and control sediments. This study shows that oil-exposed test plot sediments of the Ste. Croix wetland can be considered completely recovered after 21 years irrespective of the performed countermeasure.

Contrasting mobility of arsenic and copper in a mining soil: A comparative column leaching and pot testing approach.

The remediation of legacy metal(loid) contaminated soils in-situ relies on the addition of [organic] amendments to reduce the mobility and bioavailability of metal(loid)s, improve soil geochemical parameters and restore vegetation growth. Two vermicomposts of food and animal manure waste origin (V1 and V2) were amended to an arsenic (As) and copper (Cu) contaminated mine soil (≤1500mgkg-1). Leaching columns and pot experiments evaluated copper and arsenic in soil pore waters, as well as pH, dissolved organic carbon (DOC) and phosphate (PO43-) concentrations. The uptake of As and Cu to ryegrass was also measured via the pot experiment, whilst recovered biochars from the column leaching test were measured for metal sorption at the termination of leaching. Vermicompost amendment to soil facilitated ryegrass growth which was entirely absent from the untreated soil in the pot test. All amendment combinations raised pore water pH by ∼4 units. Copper concentrations in pore waters from columns and pots showed steep reductions (∼1mgL-1), as a result of V1 & V2 compared to untreated soil (∼500mgL-1). Combined with an increase in DOC and PO43-, As was mobilised an order of magnitude by V1. Biochar furthest reduced Cu in pore waters from the columns to <0.1mgL-1, as a result of surface sorption. The results of this study indicate that biochar can restrict the mobility of Cu from a contaminated mine soil after other amendment interventions have been used to promote revegetation. However, the case of As, biochar cannot counter the profound impact of vermicompost on arsenic mobility.

The Differential Responses of Coastal Diatoms to Ocean Acidification and Warming: A Comparison Between Thalassiosira sp. and Nitzschia closterium f.minutissima.

Marine diatoms are one of the marine phytoplankton functional groups, with high species diversity, playing important roles in the marine food web and carbon sequestration. In order to evaluate the species-specific responses of coastal diatoms to the combined effects of future ocean acidification (OA) and warming on the coastal diatoms, we conducted a semi-continuous incubation on the large centric diatom Thalassiosira sp. (~30 μm) and small pennate diatom Nitzschia closterium f.minutissima (~15 μm). A full factorial combination of two temperature levels (15 and 20°C) and pCO2 (400 and 1,000 ppm) was examined. The results suggest that changes in temperature played a more important role in regulating the physiology of Thalassiosira sp. and N. closterium f.minutissima than CO2. For Thalassiosira sp., elevated temperature significantly reduced the cellular particulate organic carbon (POC), particulate organic nitrogen (PON), particulate organic phosphate (POP), biogenic silica (BSi), chlorophyll a (Chl a), and protein contents, and the C:N ratio. CO2 only had significant effects on the growth rate and the protein content. However, for the smaller pennate diatom N. closterium f.minutissima, the growth rate, POC production rate, and the C:P ratio significantly increased with an elevated temperature, whereas the cellular POP and BSi contents significantly decreased. CO2 had significant effects on the POC production rate, cellular BSi, POC, and PON contents, the C:P, Si:C, N:P, and Si:P ratios, and sinking rate. The interaction between OA and warming showed mostly antagonistic effects on the physiology of both species. Overall, by comparison between the two species, CO2 played a more significant role in regulating the growth rate and sinking rate of the large centric diatom Thalassiosira sp., whereas had more significant effects on the elemental compositions of the smaller pennate diatom N. closterium f.minutissima. These results suggest differential sensitivities of different diatom species with different sizes and morphology to the changes in CO2/temperature regimes and their interactions.

Sediment organic matter properties facilitate understanding nitrogen transformation potentials in East African lakes

East African lakes include the most productive and alkaline lake group in the world. Yet, they generally receive fewer nutrient inputs than the densely populated subtropical and temperate lakes in the northern hemisphere. In these lakes with insufficient supplies of inorganic nitrogen, the mineralization of benthic organic matter can play an important role in driving the nutrient cycle and nitrogen loss. Using a suite of stable 15N isotope dilution and tracer techniques, we examined five main processes of the sediment nitrogen cycle in 16 lakes and reservoirs of Tanzania and Kenya, East Africa: gross nitrogen mineralization, ammonium immobilization, dissimilatory nitrate reduction to ammonium (DNRA), and the dinitrogen (N2) production via denitrification and anaerobic ammonium oxidation (anammox). Gross nitrogen mineralization and ammonium immobilization showed the maximum values of 9.84 and 12.39 μmol N kg−1 h−1, respectively. Potential DNRA rates ranged from 0.22 to 8.15 μmol N kg−1 h−1 and accounted for 10 %–74 % (average 25 %) of the total dissimilatory nitrate reduction. Potential nitrate reduction rates in most lakes were dominated by denitrification with a contribution of 26 %–85 % and a mean of 65 %. We further found that the sediment nitrogen transformations were driven mainly by benthic organic matter properties and water column phosphate concentrations, reflecting microbial metabolic responses to the changing carbon and nutrients availability. For instance, autochthonous production of protein-like organic matter attributed to active sediment nitrogen mineralization, DNRA, and denitrification. In contrast, the high degree of humification caused by the inputs of terrestrial humic-like substances slowed down the sediment nitrogen transformations. The contribution of DNRA to total dissimilatory nitrate reduction was significantly positively correlated to sediment C: N ratios. These results indicate that predictions of sediment N supply and loss in East African lakes can be improved by incorporating sediment organic matter properties.

Thermodynamics and Kinetics of pH-dependent Dissolution of Sparingly Soluble Alkaline Earth Hydroxides in Source-Separated Human Urine Collected in Decentralised Sanitation Systems

Alkaline earth hydroxides are widely used in water and wastewater treatment. Within the emerging niche of source-separating sanitation, these chemicals have found a new application—to prevent urease-catalysed degradation of urea present in freshly excreted human urine. However, little is known about the dissolution behaviour of these hydroxides in biological fluids like human urine. Herein, we investigate the solubility of Mg(OH)2 and examine factors that govern its dissolution in different types of urine (real fresh urine, synthetic fresh urine, synthetic dephosphatised fresh urine and real fresh urine concentrated by CO2-free drying). We report experimentally determined as well as thermodynamically simulated data on Mg(OH)2 solubility, dissolution kinetics, and chemical speciation in urine. We find that it takes between 6 and 16 min for Mg(OH)2 to dissolve and the average solubility in real fresh urine at 25°C to be 650 mg L−1. We show that solubility is influenced mainly by concentration of organic compounds, soluble phosphate, and magnesium excreted in fresh urine. When fresh urine is supersaturated with Mg(OH)2, the pH increases to &amp;gt;10.5 and urease-catalysed degradation of urea is inhibited for &amp;gt;14 days. Removing 95% water present in urine increases the solubility of Mg(OH)2 to 16,240 mg L−1 but reduces pH to &amp;lt; 10. Because relative increase in Mg(OH)2 solubility decreases as more water is removed and the solubility is retrograde with respect to temperature, to increase the urine pH to &amp;gt;10 and prevent enzymatic ureolysis, the temperature must be kept &amp;lt; 29°C at 75% water removal and &amp;lt; 22°C at 95% water removal. We find this dissolution behaviour of Mg(OH)2 in concentrated urine solutions to be unlike other alkaline earth hydroxides. These findings have significant implications for the design of new sanitation systems that separately collect and recycle plant-essential nutrients present in human urine.

Isolation, Classification, and Growth-Promoting Effects of Pantoea sp. YSD J2 from the Aboveground Leaves of Cyperus Esculentus L. var. sativus.

Plant growth-promoting (PGP) bacteria are an environmental-friendly alternative to chemical fertilizers for promoting plant development. We isolated and characterized a PGP endophyte, YSD J2, from the leaves of Cyperus esculentus L. var. sativus. Specific PGP characteristics of this strain, such as phosphate solubilization ability, potassium-dissolving ability, siderophore and indole-3-acetic acid (IAA) production, and salt tolerance, were determined in vitro. In addition, positive mutants were screened using the atmospheric and room-temperature plasma (ARTP) technology, with IAA level and organic phosphorus solubility as indices. Furthermore, the effect of the positive mutant on biomass production and antioxidant abilities of greengrocery seedling was evaluated and the genome was mined to explore the underlying mechanisms. The strain YSD J2 showed a good performance of PGP characteristics, such as the production of indole acetic acid and siderophores, solubilization ability of phosphate, and potassium-dissolving ability. It was recognized through 16S rRNA sequencing together with morphological and physiological tests and confirmed as Pantoea sp. The strain exposed to a mutation time of 125 s by ARTP had the highest IAA and organic phosphate (lecithin) concentrations of 10.34 mg/L and 16.52 mg/L, 42.06% and 34.15% higher than those of the initial strain. Inoculation of mutant strain YSD J2 significantly increased plant growth attributes and the activities of peroxidase and superoxide dismutase, respectively, but decreased the content of malondialdehyde significantly compared with the control. Furthermore, genome annotation and functional analysis were performed through whole-genome sequencing and PGP-related genes were identified. Our results indicated that the YSD J2 with PGP characteristics is a potential candidate for the development of biofertilizers.

Prospecting the plant growth–promoting activities of endophytic bacteria Franconibacter sp. YSD YN2 isolated from Cyperus esculentus L. var. sativus leaves

PurposePlant growth–promoting (PGP) bacteria are an environment-friendly alternative to chemical fertilizers for promoting plant growth and development. We isolated and characterized a PGP endophyte, YSD YN2, from the leaves of Cyperus esculentus L. var. sativus.MethodsSpecific PGP characteristics of this strain, such as phosphate solubilization ability, potassium-dissolving ability, siderophore and indole-3-acetic acid (IAA) production, and salt tolerance, were determined in vitro. In addition, positive mutants were screened using the atmospheric and room temperature plasma (ARTP) technology, with IAA level and organic phosphate solubility as indices. Furthermore, the effect of the positive mutant on seed germination, biomass production, and antioxidant abilities of greengrocery seedling was evaluated, and the genome was mined to explore the underlying mechanisms.ResultsThe strain YSD YN2 showed a good performance of PGP characteristics, such as the production of indole acetic acid and siderophores, solubilization ability of phosphate, and potassium-dissolving ability. It was recognized through 16S rRNA sequencing together with morphological and physiological tests and confirmed as Franconibacter sp. The strain exposed to a mutation time of 125 s by ARTP had the highest IAA and organic phosphate (lecithin) concentrations of 9.25 mg/L and 16.50 mg/L, 50.41% and 30.54% higher than those of the initial strain. Inoculation of mutant strain YSD YN2 significantly increased the seed germination, plant growth attributes, and the activities of peroxidase (POD) and superoxide dismutase (SOD), respectively, but decreased the content of malondialdehyde (MDA) significantly compared with the control. Furthermore, genome annotation and functional analysis were performed through whole-genome sequencing, and PGP-related genes were identified.ConclusionOur results indicated that the mutant strain YSD YN2 with PGP characteristics is a potential candidate for the development of biofertilizers.

Functional responses of biological soil crusts to simulated small precipitation pulses in the Monte desert, Argentina

In arid areas, biological activity responds to precipitation pulses, with different activation thresholds for different organisms. Biocrusts, communities of cyanobacteria, green algae, lichens and mosses living in the soil surface, contribute to soil fertilization by fixing atmospheric nitrogen (N), carbon (C), and solubilizing phosphorus (P). In this study, we hypothesized that biocrusts respond to low simulated precipitation pulses, lower than 10 mm, increasing nutrient availability. We expected biocrust organisms to increase soil net CO2 exchange, N fixation, soil N and P availability in response to small water pulses.In order to evaluate these predictions, we artificially irrigated soils with different covers, including those dominated by bare soil, mosses, and lichens, simulating precipitation pulses of 1, 3, 5, and 10 mm. We measured variables that change at short time scales (hourly), such as net CO2 exchange, N fixation and soil nitrate and phosphate availability, and those that change at larger time scales (years), such as organic matter and total N. Organic matter, total N, and phosphate concentrations were higher in soils with moss dominated biocrusts than in bare soils, indicating their importance to soil fertility in the long term. Soil net CO2 exchange, phosphate, and nitrate availability responded to the simulated precipitation pulses in all soil covers. Net CO2 exchange increased in all soil covers, but phosphate availability decreased in response to precipitation in moss dominated biocrusts. Nitrate availability was lower in lichen dominated biocrusts, although it increased in all soil covers in response to precipitation. These results show that although all the soils analyzed respond to low simulated precipitation pulses, biocrust organisms may retain soil nutrients and decrease availability to other organisms.

Ratio of Elements Carbon (C), Nitrogen (N), and Phosphorus (P) At Sediment in Seagrass Ecosystem Nirwana Beach Padang West Sumatera

This research was conducted in November 2020 at Nirwana Beach, Teluk Bayur, Padang City, West Sumatra Province. The organic carbon concentration in the sediments at Nirwana Beach ranges from 1.0320 – 3.03550%, the nitrate content ranges from 0.8599– 0.9577 mg/L, the phosphate 1.8231– 2.7616 mg/L. The C:N:P ratio of sediment is 18.75:1:2.25. The type of sediment found in this study is gravel-sand and seagrass found in the research location was Thalassia hemprichii with a density of 105 - 312 stands/m2. The correlation between the concentration of organic carbon, nitrate, and phosphate on the density of seagrass species is positive

Zooplankton indices in the evaluation of the ecological state of the eutrophic lake (Case study: Karasikha Lake, Russia)

Long-term (1998-2018) studies have been carried out on the small lake, Karasikha, located in the territory of the Volga-Kama State Nature Biosphere Reserve. Physicochemical characteristics of the lake water classify it as eutrophic, polluted, with a low oxygen content, but a high content of organic matter and phosphates. In parallel, some studies were carried out on its zooplankton community. Karasikha Lake is the habitat of 70 species of planktonic rotifers and crustaceans identified. Based on the number of species, rotifers predominated and their largest number belonged to Brachionidae family. On average 3-4 species were dominant, as indicators of eutrophic and polluted waters. However, with a relatively high species richness of zooplankton, the community has low quantitative indicators. The low oxygen content in the water column makes zooplankton concentrate mainly in the epilimnion layer (up to 2-3 m in depth). The lowest quantitative indicators of zooplankton are characteristic of the under-ice period, which is also associated with a lack of oxygen in the water. The community is dominated by indicators of dirty waters. The structure of zooplankton communities is typical of highly polluted lakes. Indices based on the taxonomic structure of zooplankton classify the reservoir as highly eutrophic and even hypertrophic.

210Po/210Pb disequilibria influenced by production and remineralization of particulate organic matter around Prydz Bay, Antarctica

Dissolved and particulate 210Po and 210Pb were measured to reveal the particle dynamics around Prydz Bay in the austral summer of 2015. The spatial variations of 210Po activity concentration and 210Po/210Pb disequilibria are mainly controlled by 210Po absorption and particle scavenging, and particulate organic matter (POM) remineralization. Different water masses around Prydz Bay show different characteristics of 210Po/210Pb disequilibria. The activity ratios of total 210Po to total 210Pb (expressed as TPoTPbAR) in Antarctic Surface Water, Winter residual Water, Shelf Water and Thermocline Water are all less than 1.0, indicating that biological absorption and particle adsorption preferentially scavenge 210Po from these waters. Circumpolar Deep Water shows the highest TPoTPbAR characteristics, and the total 210Po is in equilibrium or excess to the total 210Pb, which reflects the effect of POM remineralization. The TPoTPbAR value in the Antarctic Bottom Water is less than 1.0, and it falls between the ratios of Shelf Water and Circumpolar Deep Water, which proves that the formation of Antarctic Bottom Water has an impact on the 210Po/210Pb disequilibria. fretained is defined to represent the proportion of 210Po scavenging from the dissolved phase to the particulate phase but suspended in seawater; we found that there is a linear relationship between fretained and particulate organic carbon (POC), silicic acid and phosphate concentrations, indicating that the balance between input (POM remineralization) and removal (biological absorption and particle adsorption) determines the disequilibrium between 210Po and 210Pb. Based on the 210Po/210Pb disequilibria, the POC export from the euphotic zone is estimated to be 4.11–47.82 mmol C m−2 d−1, showing large spatial variability. The POC export on the shelf is generally higher than that on the slope and basin, which corresponds to the spatial variations of phytoplankton biomass and primary productivity.

Effect of operational parameters, environmental conditions, and biotic interactions on bacterial communities present in urban wastewater treatment photobioreactors

The effects of water depth, operational and environmental conditions on bacterial communities were analyzed in microalgal-bacterial outdoor photobioreactors treating urban wastewaters from March to August 2014. Three raceway photobioreactors inoculated with Scenedesmus sp. and with different water depths (20, 12, and 5 cm) were used at different dilution rates (0.15, 0.3, 0.4, and 0.5 d−1). A thin-layer reactor with 2 cm water depth and operated at 0.3 d−1 was used as a control. The results showed that biomass productivity increased as water depth decreased. The highest biomass productivity was 0.196 gL−1d−1, 0.245 gL−1d−1, and 0.457 gL−1d−1 for 20, 12, and 5 cm depth raceway photobioreactors, respectively. These values were lower than the maximum productivity registered in the control reactor (1.59 gL−1d−1). Bacterial communities, analyzed by high-throughput 16S rRNA sequencing, were not affected by water depth. A decrease in community evenness was related to a decrease in nutrient removal. Hetetrotrophs and phototrophs, mainly from the family Rhodobacteraceae, dominated bacterial diversity. The community changed due to increasing temperatures, irradiance, and organic carbon, ammonia, and phosphate contents in the photobioreactor-influent as well as, microalgae inhibition and higher organic carbon in the effluent. The photobioreactors shared a core-biome that contained five clusters of co-occurring microorganisms. The bacteria from the different clusters were taxonomically and ecologically different but functionally redundant. Overall, the drivers of the community changes could be related to abiotic variables and complex biological interactions, likely mediated by microalgae excretion of organic substances and the microorganisms’ competence for substrates.

Changes in Soil Chemical Properties of Rice Paddy, Upland Field, and Greenhouse in Incheon from 2015 to 2019

This study was performed with the monitoring data of soil chemical properties of rice paddy, upland field and greenhouse soils in Ganghwa, Incheon metropolitan city from 2015 to 2019. Soil pH values tended to increase gradually in three soils, but there was no significant change in that of greenhouse soil. The concentration of organic matter (OM) and available phosphate (Av. P2O5) have fluctuated from 2015 to 2019, showing significant differences. In 2019, the average value of OM and Av. P2O5 were distributed within the appropriate level suggested by Rural Development Administration. In rice paddy field, the available silicate (SiO2) were found to be proper within the standard concentration every year. The contents of exchangeable cations were higher than the proper standard, showing significant differences among the years, except greenhouse soil. The mean concentration of EC for five years in upland and greenhouse soils were 2.5 and 5.9 dS m-1 above the proper standard. The optimal frequencies of pH were 46.8% and 47.1% at rice paddy and upland soil, but the excessive frequency ratio of pH was 48.5% at greenhouse soil in 2019. The exchangeable cations seemed to be seriously disproportionate exceeding the optimal level by 95%. In Pearson correlation matrix, the value of exchangeable Ca had a significantly positive correlation with exchangeable Mg content at upland and greenhouse soils. By principal component analysis, the exchangeable K, Mg and OM could distinguish between greenhouse and other soils on the first principal component and the pH and Av. P2O5 could differentiate between rice paddy and upland soils on the second principal component. Scatter plot of chemical properties investigated from rice paddy (P), upland (U) field and greenhouse (F) soils from 2015 to 2019.

Phosphate-lanthanum coated sewage sludge biochar improved the soil properties and growth of ryegrass in an alkaline soil

The reclamation of alkaline soils remains challenging while the application of biochar has been proposed as a viable measure to rehabilitate soil fertility. The objective of the current pot study was to evaluate the efficacy of various P-La modified sewage sludge biochars (SSBC, La-SSBC, SSBC-P, La-SSBC-P) on soil phosphate-retention and ryegrass (Lolium perenne L.) growth in an alkaline soil (excess CaCO3). The results revealed that germination percentage, plant dry biomass, plant height, and the total amount of P in the ryegrass leaves were significantly (P < 0.05) improved under La-SSBC-P treatment as compared to other treatments. La-SSBC-P treatment significantly altered the chemical characteristics of post-harvest alkaline soil, such as pH, electrical conductivity (EC), cation exchange capacity (CEC), soil organic matter (SOM), limestone (CaCO3), phosphate, and lanthanum contents. In comparison to the SSBC treatment, soil available phosphorous (AP) contents under La-SSBC-P were enhanced by 6.7 times after loading biochar with P and La (La-SSBC-P). After the plantation of ryegrass, concentration of lanthanum in the soil was negligible. The contents of CaCO3 reduced by 76.2% after La-SSBC-P biochar treatment, compared to the cultivated control. This phenomenon clearly indicated that lanthanum was reduced due to the precipitation with limestone, which was proposed based on the data of X-ray diffraction (XRD) analysis. Overall, results showed that the P-loaded lanthanum decorated biochar (La-SSBC-P) could be used as a potential substitute for P-fertilizer under the experimental conditions. However, field experiments are required to confer the efficiency of La-SSBC-P as P fertilizer in different soils.

Identifying roles of the scion and the rootstock in regulating plant development and functioning under different phosphorus supplies in grapevine

Phosphorus is essential for plant life and plants have developed numerous strategies to maximise phosphate (Pi) acquisition and use under limited Pi supply. Here we have used reciprocal grafting to determine whether the shoot and root have different roles in regulating some of these strategies. Reciprocal grafts of two grapevine genotypes (Vitis vinifera cv. Pinot noir and V. berlandieri x V. rupestris cv. 1103 Paulsen) were produced as well as the corresponding homo-graft controls; the plants were grown in hydroponic culture and subjected to two levels of Pi supply (high (0.6 mM) or low (0.001 mM)). Biomass accumulation, root morphology, and root, stem and leaf organic acid, phosphate, nitrate and sulphate concentrations were measured. The transcript abundance of orthologues of known phosphate starvation induced (PSI) genes from Arabidopsis was also quantified. Under high Pi, the scion genotype had a large impact on plant growth, but the morphology of roots (such as root tip density) was not affected. Low Pi supply affected growth, tissue organic acid concentration, the activity of acid phosphatases released by the roots and the expression of PSI genes. Rootstock genotypes showed differences in root responses to low Pi supply, but the scion also exerted long-distance regulation of rootstock responses to low Pi, for example, modifying PSI gene expression, sulphate acquisition efficiency, the activity of acid phosphatases released by the roots and root organic acid concentrations. This work shows for the first time that the grapevine genotypes differ in their response to low Pi supply and that the scion can modify rootstock responses to the nutrient availability. This work highlights that genetic variation in shoot-borne signals can regulate root responses to Pi supply and that understanding rootstock responses to the environment must be done considering scion influence.