Search Results (72)

Although the sediment–water interface of deep and large reservoirs is recognized as a dominant source of internal phosphorus (P) loading, the quantitative hierarchy of environmental drivers and their interaction thresholds remains poorly resolved. Here, we integrate 512 studies to provide the first process-based synthesis that partitions P release fluxes among temperature, pH, dissolved oxygen, salinity, sediment properties, and microbial activity across canyon, valley, and plain-type reservoirs. By deriving standardized effect sizes from 61 data-rich papers, we show that (i) a 1 °C rise in bottom-water temperature increases soluble reactive P (SRP) flux by 12.4% (95% CI: 10.8–14.0%), with sensitivity 28% lower in Alpine oligotrophic systems and 20% higher in warm monomictic basins; (ii) a single-unit pH shift—whether acid or alkaline—stimulates P release through distinct desorption pathways,; and (iii) each 1 mg L⁻¹ drop in dissolved oxygen amplifies release by 31% (25–37%). Critically, we demonstrate that these drivers rarely act independently: multi-factor laboratory and in situ analyses reveal that simultaneous hypoxia and warming can triple the release rate predicted from single-factor models. We further identify that >75% of measurements originate from dam-proximal zones, creating spatial blind spots that currently limit global P-load forecasts to ±50% uncertainty. To close this gap, we advocate coupled metagenomic–geochemical observatories that link gene expression (phoD, ppk, pqqC) to real-time SRP fluxes. The review advances beyond the existing literature by (1) establishing the first quantitative, globally transferable framework for temperature-, DO-, and pH-based management levers; (2) exposing the overlooked role of regional climate in modulating temperature sensitivity; and (3) providing a research agenda that reduces forecasting uncertainty to <20% within two years. Full article

In this study, the distribution patterns of the nitrifying and denitrifying microbiome in a large-scale biofilter (587.24 m³) in a cold freshwater recirculating aquaculture system (RAS) was investigated. Previous studies have revealed that the water quality, nitrification, and denitrification rates in the front (BFF), middle (BFM), and back (BFB) of this biofilter are different. The results showed the highest diversity of the denitrifying microbiome in the BFB, followed by BFF and BFM, whereas nitrifying microbiome diversity remained consistent across different positions. Two genera, Nitrosomonas and Nitrosospira, dominated the nitrifying microbiome, while Pseudomonas, Thauera, Cupriavidus, Dechloromonas, Azoarcus, and Paracoccus comprised the top six denitrifying genera. Principal coordinate analysis indicated a distinct spatial distribution pattern of the denitrifying microbiome but not the nitrifying microbiome. The genera Pseudomonas and Dechloromonas were the biomarkers of the BFF and BFB, respectively. Redundancy analysis showed that nitrite, nitrate, dissolved oxygen, and soluble reactive phosphorus influenced the functional microbiome distribution pattern. Network correlation analysis identified one nitrifying hub (Nitrosospira) in the BFF, five denitrifying hubs (Aromatoleum, Dechloromonas, Paracoccus, Ruegeria, and Thauera) in the BFM, and three denitrifying hubs (Azoarcus, Magnetospirillum, and Thauera) in the BFB. Exclusively negative correlations were found between hubs and its adjacent nodes in the BFF and BFB. This study demonstrates that habitat can shape the distribution patterns of the nitrifying and denitrifying microbiome in the biofilter of the RAS, with the BFF exhibiting greater benefits for the nitrification process. Full article

Background/Objectives: Chronic kidney disease–mineral and bone disorder (CKD-MBD) and systemic inflammation contribute to mortality in hemodialysis (HD) patients. The primary aim of this study was to determine whether specific CKD-MBD markers and inflammatory biomarkers are associated with increased mortality risk in HD patients. Methods: We conducted a retrospective cohort study on 63 stage 5D CKD patients undergoing maintenance HD. Serum intact parathyroid hormone (iPTH), soluble Klotho, calcium, phosphorus, 25(OH)D (25-hydroxyvitamin D), transforming growth factor-beta (TGF-β), vascular endothelial growth factor (VEGF), C-reactive protein (CRP), and interleukin-6 (IL-6) were analyzed. A Cox regression analysis assessed mortality predictors, and linear regression analysis evaluated CKD-MBD–inflammation correlations. Results: Lower iPTH (<329.3 pg/mL) levels were the only significant mortality predictor (p = 0.042). Other CKD-MBD markers (calcium, phosphorus, 25(OH)D, VEGF, TGF-β) did not impact survival. Soluble Klotho correlated positively with IL-6 (r = 0.57, p < 0.001), suggesting a compensatory inflammatory response. Conclusions: Our findings demonstrate that low iPTH levels and advanced age are independent predictors of mortality in hemodialysis patients. The positive association between soluble Klotho and IL-6 suggests a potential compensatory inflammatory response. These results highlight the need for further research to clarify underlying mechanisms and to explore novel therapeutic strategies. Full article

The forecasting of river flows and pollutant concentrations is essential in supporting mitigation measures for anthropogenic and climate change effects on rivers and their environment. This paper addresses two aspects receiving little attention in the literature: high-resolution (sub-daily) data-driven modeling and the prediction of phosphorus compounds. It presents a series of artificial neural networks (ANNs) to forecast flows and the concentrations of soluble reactive phosphorus (SRP) and total phosphorus (TP) under a wide range of conditions, including low flows and storm events (0.74 to 484 m³/s). Results show correct forecast along a stretch of the River Swale (UK) with an anticipation of up to 15 h, at resolutions of up to 3 h. The concentration prediction is improved compared to a previous application of an advection–dispersion model. Full article

By incubating the soil without living roots in situ at two spruce forest sites, we simulated the effects of tree dieback and interrupted mycorrhizal associations following forest disturbance on the soil microbiome and phosphorus leaching. We observed the retreat of ectomycorrhizal fungi and increased proportion of saprotrophs without changes in community richness and the Shannon diversity index. This was accompanied by a pronounced decomposition of organic matter, associated with an increased activity of carbon-mining hydrolases and acid phosphatase. The nonexistent phosphorus uptake and immobilization by ectomycorrhizal associations led to its substantial increase in the soil, in the labile fractions, such as microbial biomass and water-soluble reactive phosphorus, but also in the fraction bound to organometallics (extractable by oxalate), and caused considerable phosphate leaching, as estimated using ion-exchange resin traps. The results show that the retreat of the root-specific environment, characterized by the input of available carbon and effective nutrient uptake and by the specific microbiome, has profound effects on phosphorus dynamics and loss. Furthermore, we suggest that ectomycorrhiza plays an equally important role in controlling phosphorus-mining from organic matter and subsequent immobilization and/or leaching from soils concurrently to its known role in nitrogen cycling and immobilization in spruce forests. Full article

Reduced-oxidation-state phosphorus (reduced P, hereafter) compounds were likely available on the early Earth via meteorites or through various geologic processes. Due to their reactivity and high solubility, these compounds could have played a significant role in the origin of various organophosphorus compounds of biochemical significance. In the present work, we study the reactions between reduced P compounds and their oxidation products, with the three nucleosides (uridine, adenosine, and cytidine), with organic alcohols (glycerol and ethanolamine), and with the tertiary ammonium organic compound, choline chloride. These reactions were studied in the non-aqueous solvent formamide and in a semi-aqueous solvent comprised of urea: ammonium formate: water (UAFW, hereafter) at temperatures of 55–68 °C. The inorganic P compounds generated through Fenton chemistry readily dissolve in the non-aqueous and semi-aqueous solvents and react with organics to form organophosphites and organophosphates, including those which are identified as phosphate diesters. This dual approach (1) use of non-aqueous and semi-aqueous solvents and (2) use of a reactive inorganic P source to promote phosphorylation and phosphonylation reactions of organics readily promoted anhydrous chemistry and condensation reactions, without requiring any additive, catalyst, or other promoting agent under mild heating conditions. We also present a comparative study of the release of P from various prebiotically relevant phosphate minerals and phosphite salts (e.g., vivianite, apatite, and phosphites of iron and calcium) into formamide and UAFW. These results have direct implications for the origin of biological P compounds from non-aqueous solvents of prebiotic provenance. Full article

Catchment models are essential tools to identify and predict water quality problems linked to excessive nutrient applications (in this case phosphorus (P)). The Catchment Runoff Attenuation Flux Tool (CRAFT) has been successfully used to model nutrient fluxes and concentrations in north-western European catchments. The model is extremely parsimonious due to the relatively small number of parameters. However, an improvement to the representation of soluble P and particulate P fluxes in the fast-subsurface and surface runoff flow pathways was required. A case study in the north of Ireland applied the original and the new, enhanced (Dynamic) version of the CRAFT to the trans-border Blackwater catchment (UK and Republic of Ireland) covering nearly 1500 km², with the land use predominantly livestock grazing. The larger size of the Blackwater also required a nested modeling approach to be implemented using a multiple sub-catchment variant (MultiCRAFT). P load reductions in the different sub-catchments were first identified using a simple approach based on the gap between the Water Framework Directive (WFD) limits for “Good” ecological status for soluble reactive P (SRP) concentrations and the recently observed concentrations. Modeling of different mitigation scenarios was then conducted using the MultiCRAFT framework with the best-performing variant of the CRAFT model embedded. The catchment was found to have flashy, episodic delivery of high concentrations of SRP and PP during runoff events which will require different sources (i.e., diffuse and point) of P to be targeted to achieve the WFD targets by the end of the decade. The modeling results thus showed that the required SRP load reductions could be best achieved using a combined scenario of mitigation measures that targeted diffuse sources contributing to both the surface runoff and fast-subsurface flow pathways, with point sources also identified as needing reduction in some sub-catchments. Full article

One of the main problems arising in inland waterbodies is nutrient enrichment that accelerates eutrophication, causing massive cyanobacteria blooms and degrading aquatic ecosystems. This study focused on physical/chemical factors that affect cyanobacteria of 30 reservoirs in the Ebro River basin within the Iberian Peninsula of northeastern Spain. The abundance of cyanobacteria was assessed as total cell number, total biovolume, and the indicator pigment, total phycocyanin (PC). In addition, empirical measurements for PC were compared to PC estimated from remote sensing. Variables assessed for correlation with cyanobacteria abundance included temperature, pH, light availability inferred from Secchi depth, water residence time, total nitrogen, dissolved inorganic nitrogen, total phosphorus, soluble reactive phosphorus, silica, and total phytoplankton biomass as chlorophyll a. These variables were also assessed with a multi-statistical principal component analysis for relationships with cyanobacteria abundance. Cyanobacteria cell number and biovolume were positively correlated with temperature, total nitrogen, total phosphorus, and water residence time, and negatively correlated with silica. High PC concentrations were documented in the reservoirs, and satellite images from remote sensing showed the PC spatial distribution and heterogeneity in the reservoirs. The PCA results show that some variables, such as nitrogen and phosphorus, are closely related to the abundance of cyanobacteria, while other variables such as silica do not show a clear relationship. This study contributes to the knowledge base about inland waterbodies from a physical/chemical perspective, which had not been done before in the Ebro Basin, including the application of analytic tools such as remote sensing. Full article

In order to further close nutrient cycles of aquaponic systems, it could be possible to integrate a third trophic level in the form of insect larvae production (i.e., black soldier fly larvae) to recycle internal waste streams into valuable nutrients. This would present opportunities to formulate sustainable circular aquafeeds that combine these internally available nutrients with complementary external raw materials. The ingredient composition of feeds for such circular multitrophic food production systems (CMFS) may affect fish performance as well as excretion of important dissolved plant nutrients such as N, P and K. Hence, fish meal from catfish processing (CM) as base ingredient was combined with variable levels of poultry by-product meal (PM) and black soldier fly larvae meal (BSFM) into three marine-ingredient-free experimental diets corresponding to hypothetical production scenarios of a CMFS that aims to integrate aquaponics with insect larvae production. These experimental diets and a commercial diet (COM) were compared using isonitrogenous and isolipidic formulations. They were fed to African catfish (Clarias gariepinus) in recirculating aquaculture systems (RAS) and evaluated concerning growth performance and nutrient excretion. All diets resulted in similar total inorganic nitrogen (TIN) excretion, whereas the increase of dietary PM inclusion from 0% (BSF diet) to 20% (MIX diet) and to 41% (PM diet) and concomitant reduction of BSFM inclusion led to increasingly higher soluble reactive phosphorus (SRP) excretion per unit of feed compared to the COM diet. While the PM diet enabled the best growth and feed conversion performance, the MIX and especially the BSF diet produced more similar performance to the COM diet, which generated the highest dissolved K excretion. The MIX and the PM diet resulted in the highest Ca and P, yet lower N content in the fish feces. Results indicate that combining CM with elevated levels of PM in the diet of African catfish could improve growth performance and reduce the need for P fertilization in aquaponics when compared to industrial diets optimized for low environmental impact. Findings are discussed regarding their implications for CMFS and aquaponic feed formulation. Full article

Fertilizer management is one of the easiest and most practical ways of combating salt stress. This study was done to evaluate the alleviative effects of nitrogen and phosphorus on the growth and salt tolerance of salt-affected sorghum. A controlled study organized in a randomized block design with three replications was conducted, testing three nitrogen rates (N0: 0 kg ha⁻¹, N1: 180 kg ha⁻¹, N2: 360 N kg ha⁻¹) and phosphorus rates (P0: 0 P₂O₅ kg ha⁻¹, P1: 60 P₂O₅ kg ha⁻¹, P2: 120 P₂O₅ kg ha⁻¹). Nitrogen and phosphorus application had positive effects on morphological indexes (plant height, stem diameter), some physiological and biochemical attributes (the content of proline and soluble protein, and the activities of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase), and aerial biomass (fresh and dry weight) of sorghum grown in saline soils. Reactive oxygen species accumulation and cell membrane damage were decreased with the application of nitrogen and phosphorus. Compared with sole fertilizer, the combined application of nitrogen and phosphorus showed better performance in alleviating salt damage on sorghum. Despite the fact that the maximum of most of the measured parameters and the minimum of reactive oxygen species accumulation and cell membrane damage were generally obtained at N1P1 and N2P2 treatment, N1P1 was recommended to be the suitable treatment considering economic benefits and environmental protection. Full article

The aim of the presented research was the assessment of phosphorus speciation impact on the precipitation of phosphorus in reject water using Ca(OH)₂. To achieve this, phosphorus speciation (organic and inorganic phosphorus in suspension and in dissolved form) in reject water that is produced during sludge dewatering, after methane digestion in wastewater treatment plants (WWTPs), was determined. This study covered the materials from four WWTPs with different compositions of feedstock for anaerobic digestion (AnD). In one, the AnD process of primary and secondary sludge was carried out without co-substrate, while in three others, co-substrate (waste from the agri-food industry and external waste-activated sludge and fats from industrial plants) was examined. The investigation was conducted in batch reactors using doses of Ca(OH)₂ ranging from 2500 to 5500 mg Ca/dm³. The percentage of phosphorus forms determined in the raw reject water was similar, with the dominant form being soluble reactive phosphorus (SPR) (percentage from 87 to 96%). The small differences observed were dependent on the composition of the AnD feedstock. The results showed that, in all analysed wastewater, very high (exceeding 99.9%) phosphate phosphorus removal efficiencies were obtained using Ca(OH)₂ for short reaction times (t = 1 h). The efficiency of phosphate removal depended on pH but not on the forms of phosphorus in the analysed reject water. Full article

New technologies allow for the in situ monitoring of nutrients, specifically nitrogen and phosphorus, in water systems at increasingly higher temporal frequencies. These technologies allow for the near-continuous monitoring of water quality, which can potentially provide new perspectives on temporal variations in nutrient concentrations and transport dynamics, ultimately supporting more targeted and sustainable water management. The current study investigated the utility of monitoring nitrate-N and soluble reactive phosphorus (SRP) in situ using wet analytical chemistry for one year at 2-h intervals in a small agricultural watershed located in northwestern Ohio. While we saw large variability in the estimated nutrient loads due to daily variations in the high-temporal resolution nutrient concentrations, the nutrient loads were fundamentally driven by high-flow events for this agricultural watershed. Concentration–discharge relations were then developed to help identify how nutrients are stored and released over time scales ranging from low-flow seasonal responses to event-driven high-flow storms. The patterns in the concentration–discharge relations indicated a potential shift in the timing of the mobilization responses for SRP at the event scale over the course of the year. These results suggest that SRP-targeted management practices would need to intercept the dominant delivery pathways of phosphorus in the watershed, such as the tile drainage runoff, to help reduce phosphorus loading. For nitrate-N, patterns in the concentration–discharge relations revealed an increased mobilization response, which was seen during the growing season with low-flow conditions, indicating the potential role of biological uptake instreams across the lowest flows and concentrations of the year. Collectively, high-frequency temporal nutrient data monitored over individual events and across seasons offer guidance for management decisions while allowing us to track progress toward water quality goals. Full article

The bacterial community in sediment is sensitive to artificial disturbance, and they respond differently to human disturbance, such as changing the nutrient cycling and energy flow in marine ecosystems. However, little is known about the dynamics and distribution of bacterial community structures in marine sediments and potential biogeochemical functions during the long-time succession in marine ranching. In the present study, we compared the dynamics of the bacterial composition and potential biogeochemical functions of sediment to ten years (TR) and one-year new artificial reef (NR) areas using metagenomic next-generation sequencing technology. Results revealed that NR reduces the Pielou’s evenness and Shannon index. Similarly, nonmetric multidimensional scaling showed that the beta diversity of sediment bacterial communities in NR significantly differed between TR and non-artificial reef areas. Previously, TR biomarkers were frequently associated with organic matter decomposing and assimilating in the organically enriched sediments (i.e., Acinetobacter). The soluble reactive phosphate (SRP) and total phosphorus (TP) concentrations were thought to be the primary driving forces in shaping the microbial community in sediment. Pseudomonas, Lactobacillus, and Ralstonia have a significant positive correlation with SRP, TP, nitrate, and TN, but a negative association with pH, Salinity, Hg, and depth. NR was found to have more negative correlation nodes, indicating that taxa face more competition or predation press. Vibrio served as the module-hubs in the network in all areas. In addition, chemoheterotrophy, aerobic chemoheterotrophy, and fermentation were the three most prominent functions of the three areas, accounting for 59.96% of the relative abundance of the functional annotation. Different bacteria in sediments may change the amount of biogeochemical cycle in the marine ranching ecosystem. These findings can increase our understanding of the succession of the microecosystem for the marine ranching sedimentary environment by revealing how artificial reefs affect the indigenous sediment bacterial community and their responses to environmental variation. Full article

In aquaponics and circular multitrophic food production systems, dietary protein source, as well as fish species choice, particularly in cases of different nutritional physiology, could be factors affecting excreted nutrient profiles. Accordingly, growth performance, dissolved nutrient accumulation and feces nutrient profiles were evaluated for African catfish (Clarias gariepinus) reared in recirculating aquaculture systems (RAS) and fed single protein source diets based on black soldier fly larvae meal (BSF), poultry by-product meal (PM), poultry blood meal (PBM) and fish meal (FM) and the results were compared to previous findings for Nile tilapia (Oreochromis niloticus). All diets resulted in significantly different growth performances of African catfish, with FM producing the best growth performance, followed by PM, BSF and PBM. PM resulted in the highest soluble reactive phosphorus concentrations (SRP) in the RAS water; whereas, BSF resulted in the highest K, Mg and Cu concentrations. The highest feces nutrient density was recorded for PBM; whereas, FM and PM yielded the lowest feces nutrient density. Comparing African catfish to Nile tilapia revealed that the former showed significantly better growth performance with FM and PM, however, significantly weaker performance with BSF. Although dissolved K accumulation was similar between species across diets, significant differences were recorded for total inorganic nitrogen and SRP production per unit of feed for individual diets. Despite similar feces nutrient profiles, African catfish produce significantly less feces dry matter per unit of feed for each diet compared to Nile tilapia. Findings are discussed regarding their implications for aquafeed development in the context of circular multitrophic food production systems. Full article

We evaluated whether sediment excavation improved water quality in a former (pre-European settlement) wetland complex that was a farm in the early 1900s and then later in the 1990s/early 2000s was allowed to naturally refill with water and became nutrient-rich ponds plagued by legacy phosphorus issues. Two ponds were recently restored via dewatering, excavation of the surface sediment, and hydrologic reconnection to an adjacent creek to re-establish a flow-through marsh. The removal of ~103,000 m³ of phosphorus-laden sediment and reconnection to the adjacent stream resulted in improved water quality, with a reduction in total phosphorus concentration from ~1000 μg/L to ~20 μg/L and a 40% reduction in specific conductivity in both former ponds. Soluble reactive phosphorus concentrations declined substantially in one pond, from ~720 μg/L to 3 μg/L, but not in another pond, which was partially dredged by the landowner prior to restoration. Additionally, phosphorus concentration in the downstream receiving water body also declined but to a much more modest degree. Sediment excavation was an effective restoration tool in this former agricultural system, but given the expense and potential impact on pre-existing biota, a full-system diagnosis, including cost, sediment characterization, and control of external nutrient loading, is recommended before its implementation elsewhere. Full article