Water Temperature Fluctuations Research Articles

Simulated cold spell: Changes of lipid metabolism on silver pomfret during cooling and rewarming

In recent decades, frequent extreme cold spells have led to fluctuations in water temperature. As poikilotherm, fish adapt to the environmental temperature through a series of physiological and metabolic regulation. Silver pomfret (Pampus argenteus) is an economical marine fish, a potential candidate for aquaculture. To investigate the impact of cold stress and subsequent rewarming on the energy metabolism of silver pomfret, we simulated an extreme cold spell by gradually lowering water temperature from 18 °C to 6 °C, followed by a gradual rise to 12 °C. The findings revealed notable trends: as the water temperature dropped to 12 °C, there was a significant increase in fatty acid content. However, upon reaching 6 °C, the condition factor (CF) decreased, accompanied by a reduction in liver mass. During the rewarming phase, severe tissue damage was observed in both muscle and liver tissues, alongside elevated AST and ALT activity. Besides, silver pomfret consumed stored fatty acids, CF, hepatosomatic index and n-3/n-6 fatty acid ratio were higher than other groups once the water temperature returned to 12 °C. Further transcriptome sequencing of the liver revealed significant enrichment in numerous metabolism-related pathways through KEGG and GO analyses. Ten differentially expressed genes (DEGs), encoding pivotal enzymes in lipid metabolism, were identified from pathways such as the PPAR signaling pathway and fatty acid degradation. Based on these results, it was hypothesized that silver pomfret shields against injury by modulating fatty acid composition. This hypothesis found validation in P. argenteus liver cells, where acsl1, cpt1 and cpt2 were identified to facilitate lipid activation and transportation. Knocking down acsl1 impacted the utilization of lipid droplets, further affirming this mechanism. This study sheds light on the adaptive strategies of economically significant fish species in confronting extreme cold spells, providing valuable insights for future reference.

Infection dynamics of Shewanella spp. in Nile tilapia under varied water temperatures: A hematological, biochemical, antioxidant-immune analysis, and histopathological alterations

In aquaculture, fluctuating water temperatures can act as a potent stressor, influencing the virulence and transmission dynamics of pathogenic bacteria, potentially triggering outbreaks and impacting fish health. The purpose of this work was to examine the impact of Shewanella spp. infection on hematological, biochemical, and antioxidant-immune parameters of Nile tilapia (Oreochromis niloticus) under different water temperatures. For this purpose, 180 fish were divided into 6 groups in triplicate (30 fish per group; 10 fish per replicate). Group 1 (G1), G2, and G3 were reared at varying water temperatures (22 °C, 28 °C, and 31 °C, respectively) without infection. While G4, G5, and G6 were IP-injected with 0.2 mL of Shewanella spp. (0.14 × 105) and reared at 22 °C, 28 °C, and 31 °C, respectively. Shewanella spp. infection induced significant lowering (p < 0.05) in hematological parameters (red and white blood cells, hemoglobin, and packed cell volume%) and immune-antioxidant responses (phagocytic activity%, phagocytic index, lysozyme, nitric oxide), total antioxidant capacity, catalase, and reduced glutathione, especially at 22 °C. Moreover, a significant increase (p < 0.05) in the hepato-renal function indicators (alanine aminotransferase, aspartate aminotransferase, urea, and creatinine), stress biomarkers (glucose and cortisol), malondialdehyde, and pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor-α) were the consequences of the Shewanella spp. infection, especially at 22 °C. The Shewanella spp. infection exhibited marked histopathological changes in the hepatic and renal tissues. Worthily, Shewanella spp. can cause detrimental alterations in Nile tilapia's hematological, biochemical, and antioxidant-immune parameters at various water temperatures, but the major detrimental changes were observed at a water temperature of 22 °C. Consequently, we can conclude that the infection dynamics of Shewanella spp. are exaggerated at 22 °C. These outcomes could help in understanding the nature of such an infection in Nile tilapia.

Growth, phytochemical concentration, nutrient uptake, and water consumption of butterhead lettuce in response to hydroponic system design and growing season

Two hydroponic system designs (nutrient film technique: NFT, and deep water culture: DWC) were set up in a climate-controlled greenhouse to compare growth, nutrients and water uptake patterns, yield and quality of lettuce (Lactuca sativa cv. Butterhead) during fall (October through November) and summer (July-August) growing conditions. The research was conducted with four system replicates for each hydroponic design and each system contained nine lettuce plants. Plant photosynthetic properties, growth parameters, and irrigation solution nutrient concentrations were measured weekly. At the end of the production cycle, plants were harvested for leaf area, fresh and dry yield of shoots and roots, nutritional and phytochemical concentrations. In the study, DWC system had better water quality properties than NFT including less seasonal water temperature fluctuation, which supported lettuce with better photosynthetic rates, growth rate and fresh yield in fall. Tipburn symptoms were only observed in summer, and NFT grown lettuce had significantly lower shoot calcium and magnesium concentrations than DWC in both fall and summer seasons, which led to more severe tip burn symptom in summer. In addition, better water quality in DWC also benefited lettuce with higher antioxidant concentrations than NFT, which included 9.4 % higher vitamin C in fall, 34.6 % higher total carotenoids in fall, 40.6 % higher non-acidified phenols in fall, as well as 12.9 % higher total chlorophyll in summer. Although there were marginal differences in fresh yield, most types of mineral nutrients and antioxidants between DWC and NFT, DWC performed better than NFT with less tipburn in summer as well as increased yield, total carotenoids, vitamin C and non-acidified phenols in fall.

Environmental evaluation of the Reloncaví estuary in southern Chile based on lipophilic shellfish toxins as related to harmful algal blooms

The Reloncaví estuary in southern Chile is famous for its aquaculture. However, recurring harmful algal blooms have adversely affected mussel production. Therefore, regular monitoring of algal toxins is urgently needed to better understand the contamination status of the estuary. In this study, we quantified 15 types of lipophilic shellfish toxins in Metri Bay in the Reloncaví estuary on a biweekly basis for 4 years. We identified algal species using microscopy and metabarcoding analysis. We also measured water temperature, salinity, chlorophyll-a, and dissolved oxygen to determine the potential relationships of these parameters with algal toxin production. Our results revealed the presence of a trace amount of pectenotoxin and the causal phytoplankton Dinophysis, as well as yessotoxin and the causal phytoplankton Protoceratium. Statistical analysis indicated that fluctuations in water temperature affected the detection of these toxins. Additionally, metabarcoding analysis detected the highly toxic phytoplankton Alexandrium spp. in some samples. Although our results suggest that the level of lipophilic shellfish toxins in Metri Bay during the study period was insignificantly low using our current LC-MS method, the confirmed presence of highly toxic algae in Metri Bay raises concerns, given that favorable environmental conditions could cause blooms.

Characterizing seasonal, environmental and human-induced factors influencing the dynamics of Rispana River's water quality: Implications for sustainable river management

This study will comprehensively evaluate the Rispana River's aquatic environment from February to June 2021, integrating physicochemical, biological, and hydrological data. Key objectives include identifying pollution sources, assessing climate change impacts, and evaluating health effects on humans and aquatic life. Analysis of 50 water samples reveals significant pH variations across five sampling sites influenced by natural and human factors. Fluctuating water temperatures (16.41 °C–20.81 °C) impact various parameters, including dissolved oxygen (DO), total dissolved solids (TDS), and biochemical oxygen demand (BOD). Microbiological assessment detects coliforms, indicating contamination with potential health risks. The study highlights the degradation of the Rispana River due to pollution and climate change. Urgent action is needed to mitigate impacts and safeguard human and aquatic health. Sustained monitoring and strategic management approaches are crucial for the river's sustainability. Collaborative efforts are necessary to address pollution sources and restore the river's health, emphasizing the importance of protecting this vital resource for current and future generations.

Recent Advances in the Crosstalk between Brassinosteroids and Environmental Stimuli.

Due to their sessile lifestyle, plants need to optimize their growth in order to adapt to ever-changing environments. Plants receive stimuli from the environment and convert them into cellular responses. Brassinosteroids (BRs), as growth-promoting steroid hormones, play a significant role in the tradeoff between growth and environmental responses. Here, we provide a comprehensive summary for understanding the crosstalk between BR and various environmental stresses, including water availability, temperature fluctuations, salinization, nutrient deficiencies and diseases. We also highlight the bottlenecks that need to be addressed in future studies. Ultimately, we suppose to improve plant environmental adaptability and crop yield by excavating natural BR mutants or modifying BR signaling and its targets.

Optimization of Chlorine Injection Schedule in Water Distribution Networks Using Water Age and Breadth-First Search Algorithm

Chlorine decay over time and distance travelled poses challenges in maintaining consistent chlorine levels from treatment plants to demand nodes in water distribution networks (WDNs). Many studies have focused on optimizing chlorine booster systems and addressing dosage and location. This study proposes a chlorine injection optimization model for maintaining spatial and temporal chlorine residuals within an acceptable range. First, the approach involves identifying potential pathways from the source to demand nodes using a breadth-first search (BFS) algorithm. Subsequently, the required chlorine injection to maintain a 0.2 mg/L residual chlorine level at demand nodes is estimated based on water age. Finally, a single-objective genetic algorithm optimizes the chlorine injection schedule at the source. The results demonstrated that chlorine estimation based on water age exhibited promising results with an average error below 10%. In addition, the four-interval injection scheme performed well in adapting to changing demand patterns, making the method robust to varying demand patterns. Moreover, the model could accommodate fluctuating water temperature conditions according to operating seasons. This study provides valuable insights into effectively managing chlorine levels and operations of WDNs, and paves the way for using water age for chlorine estimation.

Comparing temperature fluctuation attenuation capabilities and feasible parameter regions of indirect- and direct-contact heat exchangers for an ultra-high precision constant-temperature chilled water system: An experimental and Modelica-based study

Constant temperature and humidity rooms have widespread applications in high-end manufacturing and scientific research. Conventional wisdom primarily focuses on controlling the air temperature at the terminals, i.e., the supplied outlets. For achieving ultra-high precision (e.g., ±0.1 °C), it becomes essential to pre-control the temperature of the chilled water of the air-conditioning system. Nevertheless, there is still limited understanding of this matter. This paper investigated two common temperature fluctuation attenuators for the chilled water system: indirect- and direct-contact heat exchangers, e.g., a plate heat exchanger (PHE) and a water mixing pump (WMP), respectively, as follows. First, Modelica models of the two systems were established and validated by an experimental set-up capable of switching between the PHE and WMP loops. Second, an orthogonal analysis was conducted to evaluate the attenuation effects of four key factors. Results indicated that both attenuators can provide the required constant temperature precision with nuanced differences. The MWP system demonstrated faster settling time, primarily affected by valve adjustment accuracy. In contrast, PHE exhibited superior fluctuation control, with valve adjustment accuracy and input chilled water temperature fluctuation amplitude as critical factors. Finally, feasible parameter regions for the two types of attenuators under ultra-high precision targets were delineated and analyzed.

Refined machine learning modeling of reservoir discharge water temperature

Water temperature is a controlling factor for physical, biological, and chemical processes in rivers, and is closely related to hydrological factors. The construction of reservoirs interferes with natural water temperature fluctuations. Hence constructing a model to accurately and efficiently predict the reservoir discharge water temperature (DWT) is helpful for the protection of river water ecology. Although there have been studies on constructing efficient and accurate machine learning prediction models for DWT, to our knowledge, there is currently no research focused on hourly scales. The study proposed in this paper is based on high-frequency monitoring data of vertical water temperature in front of a dam, water level, discharge flow, and DWT. In this study, six types of machine learning algorithms, namely, support vector regression, linear regression, k-nearest neighbor, random forest regressor, gradient boosting regression tree, and multilayer perceptron neural network, were used to construct a refined prediction model for DWT. The results indicated that the SVR model using the radial basis function as the kernel function had the best modeling performance. Based on the SVR model, we constructed a 1–24 h early warning model and optimized the scheduling of DWT based on changing discharge flow. In summary, a machine learning model for DWT that can provide short-term forecasting and decision support for reservoir managers was refined in this study.

Current state of juvenile roach (Rutilus rutilus caspicus)

Fluctuations in water temperature in the Northern Caspian Sea, especially in the shallow zone, are mainly due to fluctuations in air temperature and during the trawling period, in the fall, the water temperature at observation stations showed a decrease in water temperature, which caused the formation of dense aggregations in juvenile roach. To study the nutritional status of juvenile fish living in the Kazakh part of the Caspian Sea, material was selected from different depths of the sea from trawl catches during comprehensive research in the fall of 2022. In the course of studies conducted to assess nutrition using quantitative and qualitative indicators, it was determined that the nutritional spectrum of juvenile roach in the water Caspian Sea is represented mainly by the same bottom organisms with a dominance of crustaceans, with their preference for bivalves, which give a good growth rate. A parasitological study of juvenile roach showed the absence of pathogen circulation in the ecosystem of this reservoir. Based on the results of pathomorphological studies of fish gills, it was found that fragmentary hyperplasia is caused by the presence of protozoal invasion rather than by the influence of environmental factors.

Determination Of Variables Endangering Ecological Living By Application Of Data–Mining Models: In Case Of Turkish Geography

The concept of ecological balance refers to the state in which various organisms coexist harmoniously within a given ecosystem. In recent times, there have been significant environmental challenges that pose a threat to the global ecosystem. It has come to attention that Turkey is experiencing adverse effects of global warming, particularly in the form of water scarcity and temperature fluctuations. Moreover, Turkey is categorized as one of the nations at risk in terms of the detrimental impacts of global warming on the environment. In light of this, the objective of this study is to employ multiple regression analysis and time series analysis to identify the variables that have a negative influence on ecological life in Turkey during the period spanning from 1960 to 2020. The findings of the regression analysis suggest that there is insufficient statistical evidence to support the notion that industrial waste and construction activities have a significant impact on carbon emissions in Turkey. Furthermore, in Turkey, various factors such as population expansion, energy consumption, electricity usage, income levels, reliance on fuel-powered cars, lack of education, energy production, and gas emissions have been identified as having a negative impact on the environment.

Breaking seed dormancy for sustainable food production: Revisiting seed priming techniques and prospects

Seed dormancy represents a pivotal challenge in seed germination, standing as a significant impediment to attaining SDG 2 - the zero-hunger goal. This dormancy arises from a range of environmental stressors, including restricted water conditions, temperature fluctuations, and light exposure. Consequently, the disruption of seed dormancy assumes paramount importance to ensure consistent germination and the cultivation of high-quality crops. Seed priming, an approach involving the treatment and desiccation of seeds, serves to augment pre-germination metabolism and expedite the germination process. Traditional priming methods encompass hydro-priming, halo-priming, hormonal-priming, and osmo-priming, each contributing to enhanced seed germination. Recent strides in priming technology have yielded even more effective outcomes concerning germination, germination timing, and seedling vigor. Novel approaches such as nano-priming (employing nanoparticle-infused solutions) and magneto-priming (involving magnetic fields) have surfaced, fostering uniform seed germination. Preeminent among these strategies is seed bio-priming, which not only alleviates seed dormancy but also augments nutrient uptake efficiency in germinating seedlings. This review paper delineates diverse priming methodologies applicable across a spectrum of crops, serving as an environmentally benign alternative to mitigate dormancy-linked predicaments and enhance plant growth. Additionally, we delve into the latest advancements in priming techniques and offer future perspectives. The central objective of this review article is to enhance comprehension of seed priming as a potent and invaluable tool for surmounting seed dormancy, consequently fostering sustainable global food production.

Modeling the Effects of River Inflow Dynamics on the Deep Layers of Lake Biwa, Japan

Climate change-induced extreme weather events, including prolonged droughts and intense rainfall, exert a significant influence on river inflows. These inflows act as vital conduits for nutrient transport, water quality modulation, and the regulation of thermal dynamics in lakes and oceans. In this context, this study conducts a comprehensive examination of the multifaceted effects stemming from river water characteristics, snowmelt water influence, and shifts in precipitation patterns on the stratification dynamics of Lake Biwa in Japan. To facilitate these investigations, a hydrodynamic model was developed to simulate thermal stratification in Lake Biwa. The results demonstrate that an increase in precipitation and river water flow, specifically doubling these factors, leads to noticeable cooling of the lake’s surface layer and a consequent destabilization of stratification during the stratification period. Conversely, halving these factors stabilizes stratification. Furthermore, elevating river water temperature by 5 °C raises water temperature near the upper thermocline, encouraging vertical mixing within the surface layer. Conversely, a 5 °C decrease induces significant temperature fluctuations and an unstable stratification extending from the surface to deeper layers. Notably, the spatial variance in water temperature within Lake Biwa is profoundly influenced by fluctuations in river water temperature. This study underscores the critical importance of considering river plumes in the study of material circulation, stratification dynamics, and ecological well-being in lakes and oceans. Given the mounting concerns related to eutrophication and the prevalence of anoxia in aquatic ecosystems, this research provides invaluable insights into assessing the impacts of river plumes on Lake Biwa’s stratification structure and seasonal dynamics.

Observing and modelling dynamic changes in temperature and volumetric fluxes within a riverbank aquifer under the influence of seasonal river stage fluctuations

AbstractSeasonal variation causes regular fluctuations in river water levels and water temperatures, which affects the distribution of temperature fields and seepage fields in riparian zones. In this paper, the monitoring device was used to continuously monitor Dongting Lake for a period of 1 year, and the temperature distribution characteristics of the riparian hyporheic zone under seasonal variation were analysed. Ten riparian hydrothermal coupling models based on different soil thermal conductivity models were verified, and the optimal model was used to simulate the influence of the flood process on the temperature field and seepage field of the riparian hyporheic zone. The results show that the changes in groundwater level and temperature in the riparian hyporheic zone had obvious lag and attenuation phenomena compared with the changes in river water level and ambient temperature. The temperature field of the riparian hyporheic zone changed obviously in the year. The vertical temperature gradient was large in summer and winter, the stratification phenomenon was obvious, and the temperature field fluctuation was small. The effect of the flood process on the temperature field and seepage velocity in the riparian hyporheic zone was obviously hysteretic. The effect of the flood‐withdrawing process on the temperature change of the shallow layer was greater than that of the flood‐rising process, while the response of the deep layer temperature change to flood‐rising and flood‐withdrawing processes was the opposite. The effect of floods on the variation in groundwater velocity was that the flood‐rising process was greater than the flood‐withdrawing process.

Shrinking pupal cocoons of Rhyacophila lezeyi (Trichoptera, Rhyacophilidae) in a highly acidic stream during the summer season

Shrinking pupal cocoons of Rhyacophila lezeyi were often found during summer in Shibukuro Stream, a highly acidic mountain stream in northern Japan (pH = 2.82 on average). We performed both field surveys and laboratory rearing experiments to clarify the mechanisms of R. lezeyi cocoon shrinkage. The R. lezeyi cocoon shrinkage proportion increased in years with high stream water temperatures and was related to water temperatures before and after pupation at the study site. Approximately 90% of the prepupae and pupae inside the shrinking cocoons died during the rearing experiment, implying that cocoon shrinkage caused by high water temperature strongly influenced R. lezeyi pupal survival. Laboratory experiments showed that R. lezeyi’s pupal cocoon membranes were semi-permeable and that the cocoon fluids were always hyperosmotic, indicating that water molecules can continuously enter the cocoon fluids from the stream water until the turgor of the cocoon wall is reached. However, the shrinking cocoons showed lower fluid volume and higher osmolarity than the normal turgescent cocoons. The reduction of osmotic gradient across the membrane during decreased stream flow due to less precipitation and/or the damage to the cocoon membrane and pupal body from high and fluctuating water temperatures and low pH are possible mechanisms for R. lezeyi pupal cocoon shrinkage.

Utilizing hydrothermal time models to assess the effects of temperature and osmotic stress on maize (Zea mays L.) germination and physiological responses

The application of germination models in economic crop management makes them extremely useful for predicting seed germination. Hence, we examined the effect of varying water potentials (Ψs; 0. − 0.3, − 0.6, − 0.9, − 1.2 MPa) and temperatures (Ts; 20, 25, 30, 35, 40 °C) on maize germination and enzymatic antioxidant mechanism. We observed that varying Ts and Ψs significantly influenced germination percentage (GP) and germination rate (GR), and other germination parameters, including germination rate index (GRI), germination index (GI), mean germination index (MGI), mean germination time (MGT), coefficient of the velocity of germination (CVG), and germination energy (GE) (p ≤ 0.01). Maximum (87.60) and minimum (55.20) hydro-time constant (θH) were reported at 35 °C and 20 °C, respectively. In addition, base water potential at 50 percentiles was highest at 30 °C (15.84 MPa) and lowest at 20 °C (15.46 MPa). Furthermore, the optimal, low, and ceiling T (To, Tb and Tc, respectively) were determined as 30 °C, 20 °C and 40 °C, respectively. The highest θT1 and θT2 were reported at 40 °C (0 MPa) and 20 °C (− 0.9 MPa), respectively. HTT has a higher value (R2 = 0.43 at 40 °C) at sub-optimal than supra-optimal temperatures (R2 = 0.41 at 40 °C). Antioxidant enzymes, including peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione peroxidase (GPX), increased with decreasing Ψs. In contrast, CAT and POD were higher at 20 °C and 40 °C but declined at 25, 30, and 35 °C. The APX and GPX remained unchanged at 20, 25, 30, and 40 °C but declined at 35 °C. Thus, maintaining enzymatic activity is a protective mechanism against oxidative stress. A decline in germination characteristics may result from energy diverting to anti-stress tools (antioxidant enzymes) necessary for eliminating reactive oxygen species (ROS) to reduce salinity-induced oxidative damage. The parameters examined in this study are easily applicable to simulation models of Z. mays L. germination under extreme environmental conditions characterized by water deficits and temperature fluctuations.

Enhancements in Cloud Condensation Nuclei Activity From Turbulent Fluctuations in Supersaturation

AbstractThe effect of aerosols on the properties of clouds is a large source of uncertainty in predictions of weather and climate. These aerosol‐cloud interactions depend critically on the ability of aerosol particles to form cloud droplets. A challenge in modeling aerosol‐cloud interactions is the representation of interactions between turbulence and cloud microphysics. Turbulent mixing leads to small‐scale fluctuations in water vapor and temperature that are unresolved in large‐scale atmospheric models. To quantify the impact of turbulent fluctuations on cloud condensation nuclei (CCN) activation, we used a high‐resolution Large Eddy Simulation of a convective cloud chamber to drive particle‐based cloud microphysics simulations. We show small‐scale fluctuations strongly impact CCN activity. Once activated, the relatively long timescales of evaporation compared to fluctuations causes droplets to persist in subsaturated regions, which further increases droplet concentrations.

Temperature fluctuation alters immuno-antioxidant response and enhances the susceptibility of Oreochromis niloticus to Aeromonas hydrophila challenge

In Egypt, the temperature of the water fluctuates drastically, reaching a daytime high of 25 °C and a nighttime low of 15 °C, respectively, in the spring and the fall. To understand the mechanism behind fish kill in fish farms, an indoor experiment was conducted wherein 240 Nile tilapia weighing 24 ± 2.5 g were stocked in 12 glass aquaria (20 fish/aquarium). Water temperature was regulated throughout the day at 27 ± 1.5 °C for 12 h from 8:00 a.m. to 8:00 p.m. and at 18 ± 1.5 °C for the remaining 12 h. Fish samples (mucus and tissues) were collected four times with a week interval. Proinflammatory tumor necrosis factor-α and interleukin (IL)-1β were decreased during the 4 weeks, while anti-inflammatory IL-10 was highly upregulated during the first week and then decreased compared to the control. Heat shock protein-70 was significantly raised, but IL-8 was unaffected. The gene expressions of antioxidant enzymes catalase and glutathione peroxidase were markedly elevated in the first week and then decreased linearly until they no longer differed from the control group. Mucus lysozyme significantly decreased in weeks 1 and 2 and then began to increase in weeks 3 and 4. Every week, Aeromonas hydrophila infection resulted in clinical signs that were delayed by over 2 days compared to the control group. The mortality rate increased from 35 to 40%, and bacteria were isolated at a rate of 61.54 to 75% from the surviving fish, compared to a rate of 41.67% in the control group. Fluctuations in water temperature suppress the immunity of Nile tilapia, making them vulnerable to bacterial infection.

Experimental analysis on the collaborative operation of fuel cell and adsorption chiller composite system under multi-operating conditions

At present, researches on fuel cell-based combined cooling, heating and power (CCHP) systems mostly adopt simulation. In order to study the coupling relationship of various components in the CCHP system under actual operation, an experimental platform for the fuel cell and adsorption chiller composite system is established, and performance experiments are conducted on the system under various operating conditions. The experimental results show good agreement with the simulation results, with a maximum error of only 3.02 % at rated power. However, due to the significant hysteresis of heat transfer in the fuel cell, cooling water temperature fluctuations are observed about 100 s after the electric power switch, which intensify with higher electric power. Next, by using a typical variation curve of fuel cell electric power as input, the dynamic performance of the system under low and high-power conditions is studied. The variation in electric power leads to fluctuations in the cooling and heating power of the chiller. During the entire dynamic variation period, the cooling power decreases by about 20.76 % when the heating power supplied to the chiller is halved, which is also consistent with the simulation results. Therefore, the study provides constructive suggestions for stationary fuel cell-based CCHP systems.

Betaproteobacteria are a key component of surface water biofilters that maintain sustained manganese removal in response to fluctuations in influent water temperature

The health risks associated with manganese (Mn) in drinking water, and an improved understanding of Mn accumulation within, and subsequent release from, distribution systems, have increased the need for robust, sustainable treatment options to minimize Mn concentrations in finished water. Biofiltration is an established and effective method to remove Mn in groundwater however, Mn removal in surface water biofilters is an emerging treatment process that has not been extensively studied. Seasonal variations in water temperature can present an operational challenge for surface water biofilters which may see reduced Mn removal under colder conditions. This study examined the microbiomes of surface water biofilters at three utilities (ACWD WTP, WTP B, and WTP D) which all experienced similar seasonal fluctuations in influent water temperature. High Mn removal was observed at the ACWD WTP for much of the year, but Mn removal decreased with a concurrent decrease in the influent water temperature (58% ± 22%). In contrast, both WTP B and WTP D achieved year-round Mn removal (84% ± 5% and 93% ± 8% respectively). Marker gene (16S rRNA) sequencing analysis of the biofilter microbiomes identified a high abundance of Betaproteobacteria in WTP B and WTP D (37% ± 12% and 21% ± 3% respectively), but a low abundance of Betaproteobacteria in the ACWD WTP (2% ± 2%). The microbiomes of new bench-scale biofilters, in operation at the ACWD WTP, were also investigated. The abundance of Betaproteobacteria was significantly greater (p < 0.05) after the biofilters had acclimated than before acclimation, and differential abundance analysis identified 6 genera within the Betaproteobacteria class were enriched in the acclimated microbiome. Additionally, the acclimated biofilters were able to maintain high Mn removal performance (87% ± 10%) when the influent water temperature decreased to 10 °C or less. Further analysis of previously published studies found the abundance of Betaproteobacteria was also significantly greater (p < 0.001) in biofilters with sustained Mn removal than in biofilters which did not treat for Mn as a contaminant, despite differences in design scale, source water, and media type. Microbiome network analysis identified multiple co-occurrence relationships between Betaproteobacteria and Mn oxidizing bacteria in the WTP B and WTP D biofilters, suggesting indirect contributions by Betaproteobacteria to biological Mn oxidation. These co-occurrence relationships were not present in the full-scale ACWD WTP microbiome. Whether the role of Betaproteobacteria in biological Mn oxidation is direct, indirect, or a combination of both, they are consistently present at a high abundance in both groundwater and surface water biofilters with sustained Mn removal, and their absence may contribute to the seasonal fluctuations in Mn removal observed at the ACWD WTP. This new insight to Betaproteobacteria and their role in Mn biofiltration could contribute to water innovation and design that would improve the reliability of Mn removal.