Organic Phosphate Research Articles

Flood Risk Mapping: Quantifying Topographic Wetness Index to Determine Flood Risk Zones for Mutoko District in Zimbabwe

Slope and topography help to describe the shape and relief of the land, allowing the hydrological and terrain analysis of a region by generating topographic wetness index (TWI). In this study the TWI is calculated using a digital elevation model raster layer. Spatial analyst tool and map algebra in ArcGIS was utilized to calculate slope, flow direction, flow accumulation, radian of slope, flow accumulation scaled, tan of slope, and ultimately TWI. Given that the TWI concept is less suitable in flat areas due to undefined flow directions, Mutoko District was chosen for this study due to its variations in topography. The index helps to quantify topographic control on hydrologic processes, terrain driven variation in soil moisture, and is highly correlated with several soil attributes such as horizon depth, silt percentage, organic matter content and phosphorous. However, TWI utilizes topographic elements of landscape to determine water flow and accumulation, and does not take into account additional information such as soil type or rainfall, which would be necessary for comprehensive assessment of flood risk zones. Availability of meteorological and hydrological data in addition to a digital elevation model (DEM), provides a more dynamic approach for comprehensive analysis, allowing dynamic simulations of spatially distributed water storage that can be used to derive alternative wetness indices

MICROBIOLOGICAL TRANSFORMATION OF PHOSPHORUS IN THE ROOT ZONE OF SUNFLOWER UNDER THE ACTION OF BACILLUS SP. 2473 AND DIFFERENT DEGREES OF CROP FERTILIZATION

Objective. To study the peculiarities of the microbiological transformation of phosphorus compounds in the root zone of sunflower plants under the action of Bacillus sp. 2473 and different degrees of crop fertilization. Methods. Field experiment; microbiological (accounting for bacteria capable of dissolving insoluble phosphate complexes with Ca2+, Al3+, Fe3+ and hydrolysing organic phosphates in the rhizosphere soil of sunflower plants); biochemical (determination of soil phosphatase activity); chemical (determination of phosphorus content in soil and plants); statistical. Results. Under the conditions of the field experiment on leached chornozem, it was established that during the growing season of sunflower in the soil after the introduction of Bacillus sp. 2473 into the agrocenosis, the number of bacteria capable of dissolving insoluble complexes of phosphates with Ca2+, Al3+, Fe3+ and bacteria hydrolysing organic forms of phosphates increases compared to the indicators of the control variants. Phosphatase activity increases during the growing season of plants and reaches the highest values during the seed ripening phase. The lowest levels of phosphorus content in the rhizosphere soil of sunflower plants were registered after presowing inoculation with Bacillus sp. 2473. The content of Р2О5 decreased from 0.25 mg Р2О5/dm3 of the soil solution (in the control) to 0.21 mg Р2О5/dm3 in the phase of 7–8 leaves under the action of the inoculant; from 0.42 mg Р2О5/dm3 to 0.31 mg Р2О5/dm3 in the flowering phase; from 0.24 mg Р2О5/dm3 to 0.21 mg Р2О5/dm3 in the seed ripening phase, respectively, which indicates the strengthening of phosphorus assimilation by bacterized plants. The optimal agricultural background, taking into account the effect of fertilizers on the development of phosphate-mobilizing microorganisms, is the use of mineral fertilizers in a rate not exceeding N90P90K90. Conclusion. Under the influence of the phosphate-mobilizing bacterium Bacillus sp. 2473, the processes of phosphorus transformation are activated in the root zone of sunflower plants, which is indicated by an increase in the number of phosphate-mobilizing bacteria, phosphatase activity and the degree of phosphate mobility in the rhizosphere soil of plants. As a result, the assimilation of phosphorus by plants is enhanced, which is confirmed by the increase in its removal with crop yield from 47.3 kg/ha to 74.8 kg/ha, while the efficiency of phosphorus nutrition of plants is 53.8 % (against the background of N90P90K90).

Plant Growth-Promoting Soil Bacteria: Nitrogen Fixation, Phosphate Solubilization, Siderophore Production, and Other Biological Activities.

This review covers the literature data on plant growth-promoting bacteria in soil, which can fix atmospheric nitrogen, solubilize phosphates, produce and secrete siderophores, and may exhibit several different behaviors simultaneously. We discuss perspectives for creating bacterial consortia and introducing them into the soil to increase crop productivity in agrosystems. The application of rhizosphere bacteria-which are capable of fixing nitrogen, solubilizing organic and inorganic phosphates, and secreting siderophores, as well as their consortia-has been demonstrated to meet the objectives of sustainable agriculture, such as increasing soil fertility and crop yields. The combining of plant growth-promoting bacteria with mineral fertilizers is a crucial trend that allows for a reduction in fertilizer use and is beneficial for crop production.

Coordinated phosphate uptake by extracellular alkaline phosphatase and solute carrier transporters in marine diatoms.

Marine diatoms express genes encoding potential phosphate transporter and alkaline phosphatase (APase) under phosphate-limited (-P) condition. This indicates that diatoms use high-affinity phosphate uptake system with organic phosphate hydration. The function of molecules playing roles for Pi uptake was determined in this study. Pi uptake and APase activity of two marine diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana, were monitored during acclimation to -P condition. The transcript levels of Pi transporter were analyzed, and Pi transporters were localized with GFP tagging in diatom cells. KO mutants of plasma membrane solute carrier proteins (SLC34s) or APase were established, and their phenotype was evaluated. Some Na+ /Pi transporter candidates, SLC34s in P. tricornutum and T. pseudonana, increased transcript under -P condition. Whole-cell Pi transport was specifically stimulated by sodium ion but independent of potassium, lithium, or proton. Genome-editing KO of PtSLC34-5 and APase (Pt49678) in P. tricornutum was highly inhibitory for Pi uptake, and KO of TpSLC34-2 was also highly inhibitory for Pi uptake in T. pseudonana. SLC34s and APase were co-expressed under -P conditions in marine diatoms. SLC34s play a major role in the initial acclimation stage of diatom cells to -P condition and APase plays an increasing role in the prolonged Pi-starved condition.

Biotreatment of Industrial Wastewater using Microalgae: A Tool for a Sustainable Bioeconomy.

Fresh water is one of the essential sources of life, and its requirement has increased in the past years due to population growth and industrialization. Industries use huge quantities of fresh water for their processes, and generate high quantities of wastewater rich in organic matter, nitrates, and phosphates. These effluents have contaminated the freshwater sources and there is a need to recycle this wastewater in an ecologically harmless manner. Microalgae use the nutrients in the wastewater as a medium for growth and the biomass produced are rich in nutrition that can cater growing food and energy needs. The primary and secondary metabolites of microalgae are utilized as biofuel and as active ingredients in cosmetics, animal feed, therapeutics, and pharmaceutical products. In this review, we explore food processing industries like dairy, meat, aquaculture, breweries, and their wastewater for the microalgal growth. Current treatment methods are expensive and energy demanding, which indirectly leads to higher greenhouse gas emissions. Microalgae acts as a potential biotreatment tool and mitigates carbon dioxide due to their high photosynthetic efficiency. This review aims to address the need to recycle wastewater generated from such industries and potentiality to use microalgae for biotreatment. This will help to build a circular bioeconomy by using wastewater as a valuable resource to produce valuable products.

Livestock movement driven phosphorus transitions as core drivers of grassland vegetation dynamics

The Banni grasslands, located in the Kachchh district of India, have experienced significant degradation and a decrease in grassland productivity. Phosphorus is a crucial nutrient for grassland productivity, and its availability is often limited in these ecosystems. The study is a maiden attempt to understand the link between phosphorus availability, measured by the phosphorus activation coefficient (PAC), phosphate solubilizing microorganisms (PSM), vegetation patterns, indicated by normalized difference vegetation index (NDVI) and its relationship with livestock movement. Soil samples were collected from 45 locations spread across the three divisions of Banni grassland, and various soil parameters including phosphorus content, organic carbon, and microbial activity were analyzed. The results showed that the concentration of available phosphorus (AP) varied significantly among different divisions of the grassland, with division 1 having the highest AP concentration. The phosphorus activation coefficient (PAC) was also highest in division 2. Additionally, PSM diversity was significantly different among divisions, with division 2 exhibiting the highest PSM values. The NDVI values, representing vegetation density, varied across divisions, with division 1 having the highest overall NDVI. Statistical analysis revealed significant positive correlations between PAC, PSM, and NDVI. The research emphasizes the significance of PSM driven phosphorus availability in influencing vegetation dynamics within the Banni grassland ecosystem. The movement of livestock emerges as a key factor in introducing organic matter and phosphate solubilizing microorganisms, thereby facilitating the conversion of total phosphorus (TP) into forms accessible to plants. The study indicates that implementing effective phosphorus management practices, taking into account livestock movement and organic contributions, could enhance grassland productivity and ensure the long-term sustainability of the ecosystem. These findings offer valuable insights for more holistic and nuanced understanding of the complex relationships between phosphorus availability, phosphate solubilizing microorganisms, vegetation patterns, and sustainable management in the Banni grasslands and potentially in other ecosystems facing similar challenges.

Potential of a novel endophytic diazotrophic Serratia sp. Wed4 for pyrene biodegradation

Endophytic diazotrophic Serratia sp. Wed4 with high nitrogenase activity (1260.9 ± 8.3 nmol C2H4 mL−1h−1) was isolated from Glycine max Linn growing in PAH contaminated soil for improving PAH removal and crop growth. Strain Wed4 biodegraded 37.0% of pyrene within 14 d via phthalate pathway in vitro and could biodegraded other PAHs with 2–5 rings effectively. Its capabilities on promoting crop growth included indole acetic acid (IAA) production (30.8 ± 3.3 μg mL−1), iron carrier production (A/Ar = 0.841 ± 0.002), inorganic phosphate dissolution (D/d = 1.184 ± 0.032) and organic phosphate dissolution (D/d = 1.154 ± 0.025). Strain Wed4 successfully colonized in barley tissues (>104 CFU g−1 FW), significantly promoted barley growth and nitrogen nutrition, reduced pyrene residues especially in shoots. Under sufficient nitrogen condition, strain Wed4 significantly promoted the dry weight of barley by 18.9%–33.9%, and decreased the pyrene residues by 46.4% in shoots and by 32.1% in roots. Meanwhile, under the deficient nitrogen condition, strain Wed4 significantly promoted the dry weight of barley by 40.1%–63.3% and decreased the pyrene residues by 39.0% in shoots and by 28.0% in roots. The pyrene contents were significantly negatively correlated with the total nitrogen contents in barley tissues, suggesting that nitrogen fixation of strain Wed4 also stimulated the pyrene removal. Based on its performance, Serratia sp. Wed4 provided a great potential to increasing crop yield and reducing PAH pollution in nitrogen deficient soils.

Novel self-stratifying bioelectrochemical system for municipal wastewater treatment halves nitrous oxide emissions

Reducing carbon footprint and greenhouse gas emissions are prime global goals. Wastewater treatment contributes significantly, and this study developed a technology with a focus on utilisation in small-decentralised plants. Bioelectrochemical systems (BES) utilise bacteria to remove pollutants while generating power and a range of experiments were performed to investigate their suitability compared to conventional trickling filters. A lab-based trickling filter was inferior to one adapted with electrodes both in terms of organic matter (COD) and phosphate reduction, but the BES did not generate electrical output due to inferior cathode configuration. An enhanced, novel, dual-BES system was developed with improved cathode positioning and operated as a cascade. This demonstrated improved COD (79 %) and total nitrogen (102 %) removal over the trickling filter. Concomitantly it emitted 47 % less N2O and generated an electrical output of 0.62 mA at 311 mV. Further work is needed to optimise BES but these results are encouraging in the development of sustainable biotechnologies.

Response of soil micro-food web to nutrient limitation along a subtropical forest restoration

Forest ecosystem productivity and function is strongly influenced by the interaction between soil organisms and their resource use that can be impeded by an imbalance of ecological stoichiometry. Soil microorganisms are known to have an important role in biogeochemical cycling which is strongly influenced by ecological stoichiometry. However, there is limited understanding of how soil micro-food web respond to stoichiometric imbalances during forest restoration. Here, we investigated the effect of forest restoration on soil physio-chemical properties and the structure and function of soil micro-food web along a chronosequence of transformation stages: (i) early stage monoculture plantation of Chinese fir (Cunninghamia lanceolata) comprised of three age classes (5, 10 and 20 years); (ii) mid-stage conifer-broadleaved mixed forest; and (iii) late-stage mixed species broadleaved forest in south China. Results showed that forest restoration from C. lanceolata monocultures to mixed species broadleaved forest significantly increased soil organic carbon and total nitrogen. Soil bacteria, fungi, protists and nematodes abundance increased and the co-occurrence networks of soil biota became more complex and stable along the restoration chronosequence. In contrast, soil nitrogen and phosphorus limitations, particularly phosphorus limitation, increased along the chronosequence. In addition, soil exoenzyme activity suggested that the microbial investment in resource acquisition shifted from C- to nutrient-acquiring enzymes from the earlier to the later restoration stages. Availability of soil resources (e.g., dissolved organic carbon, ammonium, and available phosphate) appeared to have an important role in regulating soil food web composition, structure and stability during forest restoration. We conclude that nutrient limitation, particularly phosphorus limitation, likely has an important role in determining the stability of soil food webs during forest restoration. These findings contribute to our understanding of the relationships between soil nutrient limitation and soil micro-food web, and have implications for carbon sequestration through forest restoration and management in southern China.

The synergistic effect of an organic phosphate salt nucleating agent and CaCO3 in isotactic polypropylene

The synergistic effect of an organic phosphate salt nucleating agent and CaCO3 in isotactic polypropylene

Synergistic effect of organic phosphate salt nucleating agents and inorganic fillers on isotactic polypropylene

Synergistic effect of organic phosphate salt nucleating agents and inorganic fillers on isotactic polypropylene

Determination of degradation/reaction rate for surface water quality of recycled water using Lake2K model for large-scale water recycling.

The depletion of groundwater resources in the water-stressed regions has led to the overuse of surface water reservoirs. Recharging groundwater by rejuvenating dried surface reservoirs using recycled water is a new sustainable solution. To ensure the prevention of groundwater contamination and associated health risks (as recycled water is used), it is crucial to assess the surface reservoir water quality. The study for the first time suggests the Lake2K model, a one-dimensional mechanistic mass-balance model, to simulate the changes in water quality in a series of man-made surface water reservoirs where recycled water flows under an indirect groundwater recharge scheme (soil aquifer treatment system). The model was developed, calibrated, and validated using field observations to estimate degradation/reaction rate constants for various water quality parameters. The observed average degradation/reaction rate constants for parameters including ammonia-N, nitrate-N, total nitrogen, total organic carbon, and organic phosphorous were 0.043day-1, 0.04day-1, 0.043day-1, 0.055day-1, and 0.056day-1, respectively, which were found to be relatively high compared to existing literature, indicating a greater degradation of these parameters in warmer climates. The results showed that the water quality improved significantly as the water progressed through the reservoirs, aligning with field observations. Additionally, the simulated seasonal variations revealed that the maximum growth rate of phytoplankton occurred during July, August, and September for each reservoir, while the nutrient pool (nitrate-N and orthophosphates) experienced the greatest depletion during this growth period. These findings shed light on the dynamics of surface water quality in regions facing water scarcity and contribute to the development of sustainable groundwater management strategies.

Phosphorus Solubilizing Microbes: Propitious Strategy For Biofertilization

Phosphorus (P) is crucial for plant growth and development, it is a macroelement that is required for plants to function physiologically. Even though there are a lot of P-containing organic and inorganic molecules in soil, most of them are inert, making them unavailable to plants. Phosphorus (P) deficiency is widely acknowledged as a critical constraining factor in agricultural production, primarily due to its essential role in various biochemical pathways, including ATP synthesis, nucleic acid formation, and energy transfer processes within plant cells. In rhizosphere soil a diverse community of plant-growth-promoting rhizobacteria (PGPR), particularly phosphate-solubilizing bacteria (PSB) are present, by increasing nutrient bioavailability—especially in the case of phosphate—these bacteria have a beneficial effect on plant growth, increasing total plant productivity and yield. Phosphate-solubilizing microorganisms (PSMs) aid in the hydrolysis of resistant organic and inorganic phosphate (P) forms into soluble forms that are easily absorbed by plants. Despite decades of research on PSMs, the practical implementation of PSM-based strategies to enhance soil phosphorus fixation and improve crop yields at the field scale remains largely undeveloped. This review aims to deepen our comprehension of the pivotal role played by PSMs as biofertilizers in the context of crop production.

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.

Intercalation vs Adsorption Strategies of Myo-Inositol Hexakisphosphate into Zn-Fe Layered Double Hydroxide: A Tiff between Anion Exchange and Coprecipitation.

Myo-inositol hexakisphosphates (IHPs) or phytates are the most abundant organic phosphates having the potential to serve as a phosphorus reserve in soil. Understanding the fate of IHP interaction with soil minerals tends to be crucial for its efficient storage and utilization as a slow-release organic phosphate fertilizer. We have systematically compared the effective intercalation strategy of a phytate onto Zn-Fe layered double hydroxide (LDH) acting as storage/carrier material through coprecipitation and anion exchange. Powder X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, thermogravimetric analysis, FTIR spectra, and molecular modeling demonstrated the formation of phytate-intercalated Zn-Fe LDH through coprecipitation with a maximum loading of 41.34% (w/w) in the pH range of ∼9-10 in a vertical alignment through monolayer formation. No intercalation product was obtained from the anion exchange method, which was concluded based on the absence of shifting in the XRD (003) peak. A change in the zeta potential values from positive to negative and subsequent increase in solution pH, with decreasing phytate concentration, are suggestive of adsorption of IHP onto the LDH surface. The batch adsorption data were best fitted with Langmuir isotherm equation and followed the pseudo-second-order kinetic model. The maximum adsorption capacity was found to be 45.87 mg g-1 at a temperature of 25 ± 0.5 °C and pH 5.63.

Influence mechanism of sludge bed position on microalgal-bacterial granular sludge process

Sludge bed position in the reactor is one of the key parameters for microalgal-bacterial granular sludge (MBGS) process, which lacks of study. To fill this gap, this study investigated the influence of sludge bed position on MBGS. The sludge bed located closer to the bottom of the bioreactor demonstrated the optimal pollutant removal performance due to a close synergistic effect between microalgae and bacteria, resulting in the high growth rate as well as agglomeration rate of MBGS. Specifically, organics and ammonia removals were closely related to the sludge bed position. For the bottom bed position, the removals of organic matter, ammonia, and phosphate were 75.1 %, 73.1 %, and 82.5 %, whereas for the top bed position, they were only 13.2 %, 9.6 %, and 68.9 %, respectively. Additionally, a significant correlation between the position of the sludge bed and the relative abundance of Rotifera (R2 = 0.931) and Chlorophyta (R2 = 0.733) was observed, while the microbial communities at the lower sludge bed positions underwent rapider succession. It can be inferred that that a sludge bed located closer to the bottom of the bioreactor ensures that the light source and substrate matrix are transmitted in the same direction, thereby resulting in a close synergistic effect between microalgae and bacteria for achieving the excellent performance of MBGS. These results can provide basis knowledge for engineering application of MBGS process.

Plant growth promotion under phosphate deficiency and improved phosphate acquisition by new fungal strain, Penicillium olsonii TLL1.

Microbiomes in soil ecosystems play a significant role in solubilizing insoluble inorganic and organic phosphate sources with low availability and mobility in the soil. They transfer the phosphate ion to plants, thereby promoting plant growth. In this study, we isolated an unidentified fungal strain, POT1 (Penicillium olsonii TLL1) from indoor dust samples, and confirmed its ability to promote root growth, especially under phosphate deficiency, as well as solubilizing activity for insoluble phosphates such as AlPO4, FePO4·4H2O, Ca3(PO4)2, and hydroxyapatite. Indeed, in vermiculite containing low and insoluble phosphate, the shoot fresh weight of Arabidopsis and leafy vegetables increased by 2-fold and 3-fold, respectively, with POT1 inoculation. We also conducted tests on crops in Singapore's local soil, which contains highly insoluble phosphate. We confirmed that with POT1, Bok Choy showed a 2-fold increase in shoot fresh weight, and Rice displayed a 2-fold increase in grain yield. Furthermore, we demonstrated that plant growth promotion and phosphate solubilizing activity of POT1 were more effective than those of four different Penicillium strains such as Penicillium bilaiae, Penicillium chrysogenum, Penicillium janthinellum, and Penicillium simplicissimum under phosphate-limiting conditions. Our findings uncover a new fungal strain, provide a better understanding of symbiotic plant-fungal interactions, and suggest the potential use of POT1 as a biofertilizer to improve phosphate uptake and use efficiency in phosphate-limiting conditions.

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

Phosphorus starvation response and PhoB-independent utilization of organic phosphate sources by Salmonella enterica.

Phosphorus (P) is the fifth most abundant element in living cells. This element is acquired mainly as inorganic phosphate (Pi, PO4 3-). In enteric bacteria, P starvation activates a two-component signal transduction system which is composed of the membrane sensor protein PhoR and its cognate transcription regulator PhoB. PhoB, in turn, promotes the transcription of genes that help maintain Pi homeostasis. Here, we characterize the P starvation response of the bacterium Salmonella enterica. We determine the PhoB-dependent and independent transcriptional changes promoted by P starvation and identify proteins enabling the utilization of a range of organic substrates as sole P sources. We show that transcription and activity of a subset of these proteins are independent of PhoB and Pi availability. These results establish that Salmonella enterica can maintain Pi homeostasis and repress PhoB/PhoR activation even when cells are grown in medium lacking Pi.

GIS Analysis of spatial-temporal variation of the ecological risk caused by element and organic pollutants in Lake Marmara (TURKIYE)

Located in western Anatolia (Turkey), Lake Marmara is a wetland with high ecological value. Lake Marmara, which was exposed to intense anthropogenic effects after 1940, is experiencing ecological deterioration in recent years. This study aimed to analyze the ecological risk level of the lake by using Enrichment Factor (EF), Toxic Risk Index (TRI), Modified Potential Ecological Risk Index (mER) etc. The research hypothesized that the discharge of water from the Gediz River and Kum Stream to the lake after 1940 triggered ecological risk problems. Moderate toxic risk, low potential ecological risk, moderate element contamination were detected throughout the lake. It was determined that Mo, P and Hg of anthropogenic origin and As, Ni, Cr, Cu of lithological origin created ecological risk at a regional scale. Domestic-industrial wastes and agriculture in the Gediz River basin and around the lake were identified as the dominant anthropogenic activity. The temporal variation of the ecological risk indices based on the elements did not reflect the anthropogenic traces of water discharge into the lake from the Gediz River basin. However, the temporal variation of TOC, N, P and CDP showed the effects of anthropogenic interventions in the lake. According to the threshold values; P is highly contaminated and N is close to the severely contaminated limit. The findings, while confirming the research hypothesis, showed that the dominant ecological risk factor in Lake Marmara is not elemental contamination, but organic pollutants, nitrogen and phosphate.