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Dissolved oxygen concentration is one of the important indicators of water quality. In order to achieve low-cost and stable measurement of dissolved oxygen in water, this paper reported a single-optical-path dissolved oxygen sensor based upon quenching of single optical path fluorescence. A sol-gel method was used to prepare an oxygen sensitive membrane with tetraethyl orthosilicate (TEOS) and triethoxy(octyl)silane (octyl-triEOS) as the precursor embedded with tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride (Ru(dpp)3Cl2) to optimize the nitrogen-oxygen quenching ratio and improve the performance of the sensor. Optical stability experiments were also conducted. A single-optical-path structure was adopted to reduce complexity, and the fluorescence intensity was calculated using the fast Fourier transform (FFT). The number of calculations were effectively reduced by measuring and storing the fluorescence intensity at 0 mg/L in advance. Calibration experiments were performed on the sensor, and the oxygen sensitive membrane with the highest sensitivity was prepared by the control variable method. The results showed that the fluorescence dyes in the prepared oxygen sensitive membrane were uniformly dispersed, and a fitted Stern–Volmer equation was obtained with a linearity of 0.994 and a sensitivity of 0.115; moreover, the light stability was good. Performance testing and anti-interference experiments were conducted, and the results showed that the standard deviation was 0.076 mg/L and the relative standard deviation was 0.805%. The errors due to changes in salinity and pH were both less than 0.25 mg/L. The sensor offers high accuracy and anti-interference ability, and is suitable for water quality monitoring and marine science. [ABSTRACT FROM AUTHOR]

The production of oxygen through phytoplankton photosynthesis is a crucial phenomenon in the dynamics of marine ecosystems. A generic oxygen-phytoplankton interaction model is considered to comprehend its underlying mechanism. This paper investigates the discrete-time dynamics of oxygen and phytoplankton in aquatic ecosystems, incorporating factors that cause phytoplankton mortality due to external influences. We explore the conditions for the local stability of steady states concerning the oxygen content in dissolved water and phytoplankton density. The analysis reveals that the model undergoes a co-dimension one bifurcation, encompassing flip and Neimark–Sacker bifurcations, utilizing the center manifold theorem and bifurcation theory. To manage the chaos resulting from the Neimark–Sacker bifurcation, we apply the OGY feedback control method and a hybrid control methodology. Finally, we present numerical simulations to validate the theoretical discussion. [ABSTRACT FROM AUTHOR]

Plant litter imported from forest headwater streams is an important supply of material and energy to the downstream aquatic ecosystems, affecting the storages and fluxes of carbon and nutrients of the whole forest ecosystems. However, our knowledge on the dynamics of plant litter potassium (K) storage is still limited. Here, we monitored the spatial and temporal characteristics of plant litter K concentration and storage in a subtropical forest headwater stream for an entire year. Results showed that: (1) the annual average concentration and storage of K in plant litter were 1.4 mg/kg and 19.6 mg/m2, respectively, with an overall decreasing trend throughout the year and from the source of the stream to the mouth; (2) riparian forest type (broadleaved vs. mixed forests) and the presence of a tributary showed significant effects on twig K concentration and storage, but did not affect those of other types of plant litter (total, fine woody debris, leaf, reproductive part, and twig); (3) water depth and active channel width positively correlated with litter K storage, while stream gradient, water dissolved oxygen, and alkalinity negatively corrected to litter K storage. Our results clearly demonstrated the spatiotemporal dynamics of plant litter K storage in the subtropical forest headwater stream, which provides basic data and scientific basis for an in-depth understanding of nutrient fluxes and cycling along with ecohydrological processes in subtropical forest ecosystems. [ABSTRACT FROM AUTHOR]

In this study, Z-type ZnIn 2 S 4 @CuO composites with a core–shell structure were synthesized. Under visible light irradiation, ZnIn 2 S 4 @CuO generates electron-hole pairs, and the presence of an internal electric field (IEF) improves the charge transfer mechanism of the composites and promotes the separation of charge carriers. The electrons on the conduction band of ZnIn 2 S 4 combine with dissolved oxygen in water to generate •O 2 –, and the holes on the valence band of CuO combine with OH– and H 2 O in water to generate •OH, and the generated reactive substances attack atoms on the TC to cause its ring-opening degradation, and ultimately mineralize the TC into CO 2 and H 2 O. [Display omitted] • A novel method for efficient construction of binary composites is proposed. • Z-type heterostructure reduces the photogenerated carrier complexation efficiency. • Verification of the Z-structure charge transfer mechanism. • TC degradation pathways proposed in combination with HR-MC and FEDs. In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core–shell structure ZnIn 2 S 4 @CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn 2 S 4 @CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn 2 S 4 alone, respectively, the reason is because of the introduction of ZnIn 2 S 4 , Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn 2 S 4 @CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification. [ABSTRACT FROM AUTHOR]

Hypoxia in coastal waters is a pressing ecological problem caused by continued eutrophication and climatic change that has widespread consequences for metazoan life and biogeochemical cycles. Numerous studies have investigated the controls on seasonal hypoxia formation and persistence in many of the world's large estuaries and coastal hypoxic zones, but far fewer studies have examined the controls on short-term oxygen variability that leads to diel-cycling hypoxia in shallow-water environments. We utilized a unique, comprehensive (181 stations) record of dissolved oxygen concentrations collected at shallow water sites (primarily < 2 m) at high frequency (15 min) throughout the estuarine complex of the Chesapeake Bay and its tributaries to quantify how internal and external variables co-varied with dissolved oxygen. We used a combination of time-series analysis, harmonic analysis, and machine learning (e.g., classification and regression trees (CART)) approaches to identify spatial patterns in major controls on oxygen variability and the duration of moderate hypoxia. We found that key controls on oxygen variability varied substantially over space. For example, photosynthetically active radiation (PAR) was a strong predictor of oxygen dynamics in the majority of mesohaline waters. In more fetch-exposed stations, wind strongly controlled hypoxic duration, but in eutrophic, inshore locations, chlorophyll a, or turbidity were often better predictors. Specifically, diel oxygen variability was muted in upstream regions characterized by high turbidity. The duration of low oxygen conditions, which we defined conservatively as less than 4.8 mg O2 L−1 (156 µM), was strongly controlled by temperature, and simple projections of regional warming and CART-derived oxygen thresholds suggest that the Bay could experience a 10% increase in this type of hypoxia duration by mid-to-late twenty-first century. The ratio of tidal to biological variability in oxygen was found to increase under conditions of higher turbidity, stronger wind, and lower salinity, but biological variability was typically a factor of two higher than tidal variability. Although chlorophyll-a generated high oxygen concentrations at some locations, those stations with exceptionally high chlorophyll a (> 30 µg L−1) were the most vulnerable to hypoxia. Because conventional water quality modeling frameworks are designed to capture hypoxia on relatively long time scales, these new insights can help inform updated oxygen models to support the management of shallow-water estuaries in the face of managed nutrient reductions and climate change. [ABSTRACT FROM AUTHOR]

Copyright of Environmental & Social Management Journal / Revista de Gestão Social e Ambiental is the property of Environmental & Social Management Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The literature has explored various methods for assessing minimum environmental flow. Implementing holistic approaches proves to be prohibitively expensive and impractical for many small and medium projects. Hence, desktop and cost-effective methods are commonly employed without an integrated decision-making system to justify the assessed values. This study introduces a systematic decision-making framework aimed at selecting the most suitable method for assessing the actual needs of river habitats. Employing a fuzzy technique known as the Order Preference Similarity to the Ideal Solution (FTOPSIS), the study considers factors such as physical, thermal, and dissolved oxygen habitat suitability, maximum habitat area, and water demand loss function to determine the most appropriate method among established ones, including the Tennant method, flow duration curve analysis method, wetted perimeter method, and physical habitat simulation method. The results prioritize physical habitat simulation, wetted perimeter by slope method, and flow indices of 70%, 75%, and 80% by flow duration curve analysis method as the optimal approaches for assessing minimum environmental flow. This proposed decision-making system offers a viable platform to explore the applicability of existing cost-effective methods for assessing minimum environmental flow. It also serves as an effective mechanism for reducing negotiations among stakeholders by comprehensively considering all relevant aspects in the environmental management of river ecosystem requirements. [ABSTRACT FROM AUTHOR]

Introduction: Hypoxia is defined as a critically low-oxygen condition of water, which, if prolonged, can be harmful to fish and many other aquatic species. In the context of ocean salmon fish farming, early detection of hypoxia events is critical for farm managers to mitigate these events to reduce fish stress, however in complex natural systems accurate forecasting tools are limited. The goal of this research is to use a machine learning approach to forecast oxygen concentration and predict hypoxia events in marine net-pen salmon farms. Methods: The developed model is based on gradient boosting and works in two stages. First, we apply auto-regression to build a forecasting model that predicts oxygen concentration levels within a cage. We take a global forecasting approach by building a model using the historical data provided by sensors at several marine fish farms located in eastern Canada. Then, the forecasts are transformed into binary probabilities that indicate the likelihood of a low-oxygen event. We leverage the cumulative distribution function to compute these probabilities. Results and discussion: We tested our model in a case study that included several cages across 14 fish farms. The experiments suggest that the model can detect future hypoxic events with a commercially acceptable false alarm rate. The resulting probabilistic predictions and oxygen concentration forecasts can help salmon farmers to prioritize resources, and reduce harm to crops. [ABSTRACT FROM AUTHOR]

Levels of dissolved oxygen in open ocean and coastal waters are decreasing (ocean deoxygenation), with poorly understood effects on marine megafauna. All of the more than 1000 species of elasmobranchs (sharks, skates, and rays) are obligate water breathers, with a variety of life‐history strategies and oxygen requirements. This review demonstrates that although many elasmobranchs typically avoid hypoxic water, they also appear capable of withstanding mild to moderate hypoxia with changes in activity, ventilatory responses, alterations to circulatory and hematological parameters, and morphological alterations to gill structures. However, such strategies may be insufficient to withstand severe, progressive, or prolonged hypoxia or anoxia where anaerobic metabolic pathways may be used for limited periods. As water temperatures increase with climate warming, ectothermic elasmobranchs will exhibit elevated metabolic rates and are likely to be less able to tolerate the effects of even mild hypoxia associated with deoxygenation. As a result, sustained hypoxic conditions in warmer coastal or surface‐pelagic waters are likely to lead to shifts in elasmobranch distributions. Mass mortalities of elasmobranchs linked directly to deoxygenation have only rarely been observed but are likely underreported. One key concern is how reductions in habitat volume as a result of expanding hypoxia resulting from deoxygenation will influence interactions between elasmobranchs and industrial fisheries. Catch per unit of effort of threatened pelagic sharks by longline fisheries, for instance, has been shown to be higher above oxygen minimum zones compared to adjacent, normoxic regions, and attributed to vertical habitat compression of sharks overlapping with increased fishing effort. How a compound stressor such as marine heatwaves alters vulnerability to deoxygenation remains an open question. With over a third of elasmobranch species listed as endangered, a priority for conservation and management now lies in understanding and mitigating ocean deoxygenation effects in addition to population declines already occurring from overfishing. [ABSTRACT FROM AUTHOR]

River water quality could be determined by understanding the capacity of pollutants in a water body. Fuzzy C-Means (FCM) is one of the fuzzy clustering methods for determining river water quality by measuring water quality parameters, that is, dissolved oxygen (DO) and total dissolved solids (TDS). The FCM algorithm is an effective fuzzy clustering algorithm for grouping data but often produces local and inconsistent optimal solutions due to the partition matrix's random initialisation process. Therefore, this study proposes to modify the FCM algorithm to be precise in the partition matrix initialisation process using several distance concepts. The purpose of the proposed algorithm modification is to get more consistent FCM clustering results and minimise stop iterations. The validation process for the clustering results uses the FCM algorithm, and the FCM modification algorithm uses three parameters, namely the Partition Coefficient Index (PCI), Partition Entropy Index (PEI) and Silhouette Score (SS). The experiments were conducted with three replications and using various distance concepts. The results showed that the number of iterations stopped in the FCM algorithm has different values for PCI, PEI, SS, and stop iterations and objective functions in each trial. On the contrary, the FCM modification algorithm has consistent PCI, PEI, and SS values, and the number of iterations stops with fewer iterations. Therefore, the modified algorithm for initialising the partition matrix can be used in the fuzzy C-means clustering algorithm. [ABSTRACT FROM AUTHOR]

The article focuses on the ecological factors affecting zooplankton diversity in the Ravi River and its implications for water quality. Topics include the dominant zooplankton species observed, the impact of environmental parameters like water temperature and turbidity on zooplankton distribution, and the influence of anthropogenic activities on river health and zooplankton diversity.

The article focuses on evaluating the seasonal changes in groundwater quality in the Al Hoceima region of northern Morocco, with an emphasis on physicochemical parameters and indicators of fecal contamination. Topics include seasonal variations in groundwater quality, analysis of physicochemical and bacteriological data, and the impact of environmental factors on water contamination.

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dye is a substance that imparts colour onto textiles, fabrics, paper, leather, etc. and is not altered by washing, heating, and light. Dyes were extracted from plants, animals, and minerals until synthetic dyes came to the market, as synthetic dyes were more stable, readily available, and inexpensive. Despite being extremely important to the economy, they have been among the most significant global polluters. Textile dye industries have become the chief source of water pollution, with their effluents increasing the turbidity of water and reducing photosynthesis and dissolved oxygen levels. This leads to significant damage to aquatic biodiversity, threatening the survival of many species. Synthetic dyes have carcinogenic, mutagenic, and genotoxic effects on animals and human beings, posing a severe health risk. The degradation of dyes is essential for ensuring the sustainability of the environment for future generations. The traditional physicochemical means of dye treatment are not convenient because of the high solubility in water, cost of method utilisation and other disadvantages related to these techniques. To overcome the disadvantages of physicochemical treatment, biological methods or bioremediation can be used as an alternative. The objective of this review article is to study the mechanisms involved in the degradation of textile dyes by bacteria to obtain sustainable, economically and ecologically sound solutions for dye treatment. This paper will explain the various types of natural and synthetic dyes utilised in the textile industry, their chemistry, and how they affect water and soil ecosystems. The treatment of textile dye by various physicochemical methods and their advantages and disadvantages are also discussed. In bioremediation, the microorganisms utilize organic pollutants as a source of food or energy. Bioremediation uses biosorption and enzymatic activity for dye degradation, which does not disturb natural processes and is thus sustainable. The microorganisms secrete crucial extracellular and intracellular enzymes that carry out decolourisation and degradation through a series of events, which include hydrolysis, acidogenesis, and methanogenesis. We will discuss how aerobic and anaerobic microorganisms degrade these textile dyes through the process of biodegradation and bioaugmentation and how this technology provides a clean and eco-friendly method for removing textile dyes. [ABSTRACT FROM AUTHOR]

A study was carried out in 345 water ecosystems (rivers, streams, ditches, lagoons, ponds, puddles, rockpools, and artificial containers) throughout the autonomous community of Galicia (NW Spain) during different seasons between 2020 and 2023. The results revealed the first detections of Anopheles (Anopheles) petragnani Del Vechio, 1939 (n  = 185) and Culex (Culex) mimeticus Noè, 1899 (n  = 12) in the territory, allowing to update and expand the overall knowledge about their distribution and ecology. The breeding preferences of the species were analyzed considering habitat characteristics (land use, water body type, and degree of insolation), geographical variables (latitude, longitude, and altitude), and physical–chemical water parameters (temperature, pH, dissolved oxygen, electrical conductivity, salinity, total dissolved solids, and turbidity). In addition, the relationship between the occurrence of these species and other mosquitoes present in the study area was discussed. Anopheles petragnani is widely distributed in the region and shows breeding preferences for water bodies of fluvial origin, forest environments, and shaded situations. Culex mimeticus was detected sporadically breeding in a pond and in a river in the south of the region, both in industrial and agricultural land uses, and always exposed to the sun. Although the presence of these species may not currently pose a health risk in the region, it is important not neglecting their study since the adequate characterization of their larval biotopes is relevant regarding vector surveillance and control measures. [ABSTRACT FROM AUTHOR]

The Siberian Arctic is warming rapidly, causing permafrost to thaw and altering the biogeochemistry of aquatic environments, with cascading effects on the coastal and shelf ecosystems of the Arctic Ocean. The Lena River, one of the largest Arctic rivers, drains a catchment dominated by permafrost. Baseline discharge biogeochemistry data is necessary to understand present and future changes in land-to-ocean fluxes. Here, we present a high-frequency, 4.5-year-long dataset from a sampling program of the Lena River's biogeochemistry, spanning April 2018 to August 2022. The dataset comprises 587 sampling events and measurements of various parameters, including water temperature, electrical conductivity, stable oxygen and hydrogen isotopes, dissolved organic carbon concentration and 14C, coloured and fluorescent dissolved organic matter, dissolved inorganic and total nutrients, and dissolved elemental and ion concentrations. Sampling consistency and continuity and data quality were ensured through simple sampling protocols, real-time communication, and collaboration with local and international partners. The data is available as a collection of datasets separated by parameter groups and periods at https://doi.org/10.1594/PANGAEA.913197 (Juhls et al., 2020b). To our knowledge, this dataset provides an unprecedented temporal resolution of an Arctic river's biogeochemistry. This makes it a unique baseline on which future environmental changes, including changes in river hydrology, at temporal scales from precipitation event to seasonal to interannual, can be detected. [ABSTRACT FROM AUTHOR]

Moving bed bioreactors are efficient for the removal of nitrogen effluents by simultaneous nitrification and denitrification (SND), which is particularly challenging for effluents with low C/N ratio due to insufficient carbon available for denitrification. The addition of external organic carbon in such cases increases treatment costs. Endogenous degradation of biomass offers a cost-effective and persistent source of carbon. Internal carbon leads to low denitrification rates and optimizing the biomass content leads to a sustainable solution for treating such effluents. The present study aims to optimize the process of SND using endogenous carbon by investigating the effect of operational parameters like dissolved oxygen, influent ammonium (NH4–N) loading, hydraulic retention time (HRT) and carrier filling ratio (CFR). The synthetic wastewater used in the study does not inherently contain any organic carbon, thus indicating the responsible carbon for denitrification to be of internal origin. Using a novel carrier for multispecies biofilm development, initial NH4–N concentration variation showed an insignificant effect on SND efficiency. At higher loading, nitrite accumulation due to incomplete denitrification was observed. The effect of CFR was investigated in a range of 20–35%, beyond which non-homogeneous mixing was caused in the reactor. Under controlled DO and temperature of about 5 mg/L and 28 ± 2°C, respectively, an optimum filling ratio of 35% was finalised, resulting in an SND efficiency of 97.9% at 22 h HRT for high influent NH4–N concentration of 500 mg/L. Bacteriological species identification revealed the coexistence of nitrogen-fixing, aerobic nitrifying and anaerobic denitrifying bacteria in the biofilm growing on the biocarrier. Mechanism of SND occurring in aerobic moving bed bioreactors: Laboratory-scale aerobic Moving Bed Bioreactor setup for a continuous study evaluating the influence of operational parameters on SND Occurrence of aerobic and anoxic zones in biofilm grown on the surface of novel carriers due to diffusional gradient of dissolved oxygen [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive approach to predicting short-term (for the upcoming 2 weeks) changes in estuarine dissolved oxygen concentrations via machine learning models that integrate historical water sampling, historical and upcoming 2-week meteorological data, and river discharge and discharge metrics. Dissolved oxygen is a critical indicator of ecosystem health, and this approach is implemented for the Neuse River Estuary, North Carolina, U.S.A., which has a long history of hypoxia-related habitat degradation. Through meticulous data preprocessing and feature selection, this research evaluates the predictions of dissolved oxygen concentrations by comparing a recurrent neural network with four other models, including a Multilayer Perceptron, Long Short-Term Memory, Gradient Boosting, and AutoKeras, through sensitivity experiments. The input predictors to our prediction models include water temperature, turbidity, chlorophyll-a, aggregated river discharge, and aggregated wind based on eight directions. By emphasizing the most impactful predictors, we streamlined the model-building processes and built a hindcast system from 2015 to 2019. We found that the recurrent neural network model was most effective in predicting the dissolved oxygen concentrations, with an R2 value of 0.99 at multiple stations. Different from our machine learning hindcast models that used observed upcoming meteorological and discharge data, an actual forecast system would use forecasted meteorological and discharge data. Therefore, an actual operational forecast may have lower accuracy than the hindcast, as determined by the accuracy of the predicted meteorological and discharge data. Nevertheless, our studies enhance our understanding of the factors influencing dissolved oxygen variability and set the basis for the implementation of a predictive tool for environmental monitoring and management. We also emphasized the importance of building station-specific models to improve the prediction results. [ABSTRACT FROM AUTHOR]

Microalgae-bacteria consortium for wastewater treatment has great potential for use in nutrient removal and biodiesel acquisition. In this study, the effect of four different light/dark regimes (6/18 h , 12/12 h , 18/6 h , 24/0 h) on biomass production and pollutant degradation during the treatment of oilfield wastewater by the algae-bacteria consortium was investigated. The maximum algal biomass (0.2 g/L) and total chlorophyll content (812.76 μgmg−1 cell dry weight−1) were obtained due to an appropriate illumination cycle (18 hlight/6 h dark) with enhanced dissolved oxygen content (5.87 mg/L), thus improving bacterial biomass (0.31 g/L). The ratio of microalgae to bacteria was essentially constant under different light/dark cycles. In addition, the highest removal rates of chemical oxygen demand (55.32%), ammonia nitrogen (50.75%), total nitrogen (64.53%), and total phosphorus (65.97%) were also obtained at the 18/6 h cycle, significantly different from the results of other light/dark cycles. The degradation efficiency of ammonia nitrogen by bacteria increased and then decreased with increasing light duration, while the removal rate of ammonia nitrogen by algae showed the opposite trend. The results indicated that the light and dark regimes had an important influence on the growth of the microalgae-bacteria consortium and their performance in treating oilfield wastewater. [ABSTRACT FROM AUTHOR]

The study investigated the impacts of dietary supplementation with two probiotics, PondToss® and LactéolFort®, on the growth performance and biochemical indices of the whiteleg shrimp (Litopenaeus vannamei) in clear water (CW) and biofloc technology (BFT) systems. Six different treatments were applied: T1 (CW without probiotics, control), T2 (BFT without probiotics), T3 (BFT with PondToss® at 0.5g g-1), T4 (BFT with PondToss® at 1g kg-1), T5 (BFT with LactéolFort® at 0.5gkg-1), and T6 (BFT with LactéolFort® at 1g kg-1). Over 90 days, shrimps with initial average weights of 3.9 to 4.10g were fed the experimental diets to satiety twice daily. The study found that neither rearing system nor probiotic treatment affected water temperature or dissolved oxygen (DO) levels. However, the treatments significantly influenced water pH, dissolved nitrogen forms (ammonia, nitrite, and nitrate), total suspended solids (TSS), total alkalinity (as CaCO3), and floc volume (VF). Biofloc and probiotic-enriched diets stimulated growth in terms of weight gain, specific growth rate (SGR), and survival rate. In biofloc conditions, shrimps fed with probiotics showed an increased feed intake and a better feed and protein utilization. Biochemical indices such as albumin, total protein, and globulin levels varied significantly among the groups, with the control group (T1) recording the lowest survival rate (66.89%), while the BFT and probiotic-enriched groups had higher survival rates, ranging from 87.35 (T6) to 90.21% (T2). The findings suggest that probioticsupplemented diets in BFT systems improve water quality, boost shrimp growth, enhance nutrient utilization, and positively affect biochemical characteristics. Thus, combining probiotics with biofloc technology appears to be a promising strategy for enhancing shrimp performance. [ABSTRACT FROM AUTHOR]

The Kuroshio-Oyashio confluence region of the Northwest Pacific Ocean is one of the most productive fishing areas, which is rich of fish resources. In order to understand the biodiversity of fish communities in the confluence region and to protect and exploit fishery resources properly' we used environmental DNA (eDNA) to analyze the fish diversity in the Kurishio-Oyashio confluence region during the summer. A total of 51 species of marine fishes (22 orders' 30 families and 44 genera) were detected among 22 water sampling stations using high-throughput sequencing analysis. The Myctophidae family was the richest in species, comprising 33.33% of the detected fish species. In addition' the primary species with higher relative abundance were Stenobrachius nannochir, Gonostoma atlanticum, Notoscopelus japonicus, Sardinops melanostictus, Takifugu poecilonotus, Ceratoscopelus warmingii, Hexagrammos agrammus, Scomber japonicus, Nematalosa japonica and Diaphus kuroshio. The alpha diversity among stations was obviously different, and there were higher biodiversity in low-latitude sections than that of high-latitude sections. Redundancy analysis showed that the content of dissolved oxygen was the main environment factor impacting the fish species composition. The results indicated that eDNA can be a useful method for monitoring fish diversity and spatial distribution in the Kuroshio-Oyashio confluence region. [ABSTRACT FROM AUTHOR]

This study tested the hypothesis of how the nanopore size of membranes and how the surface charge of nanobubbles responds to its pinch-off from the nanopore. This study also tested the hypothesis that nanobubbles that remain in solution after production may increase the dissolved oxygen content in water. The effect of membrane pore size, hydrodynamic conditions (gas and liquid flow rates), and physicochemical parameters (pH and temperature) on volumetric mass transfer coefficient (k L a) for oxygen nanobubbles formed by the nanopore diffusion technique was investigated. This study experimentally determined the k L a by carefully removing the dissolved oxygen by nitrogen purging from nanobubble suspension to examine the sole contribution of nanobubble dissolution in water to the reaeration. Scaling estimates indicate that the nanobubble pinch-off radius and nanopore radius have a power-law correlation and that nanobubble size declines with the nanopore size. This is in line with our experimental results. The surface charge of nanobubbles delays its pinch-off at the gas-liquid interface. Nanobubbles offered 3-4 times higher k L a than microbubbles. Standard oxygen transfer efficiency in water was found to be 78%, significantly higher than that in microbubbles. However, dissolving stable nanobubbles in water does not considerably increase dissolved oxygen levels. [ABSTRACT FROM AUTHOR]

While in situ toxicity testing with caged organisms has been used to assess surface water and sediment contamination, no successful application to benthic organisms exposed to highly contaminated groundwater plumes discharging to surface waters has been reported. The objective of this study was to demonstrate and evaluate this application using four sets of tests performed at three previously reported contaminated groundwater sites, which include one river site affected by volatile organic contaminant plumes, and two sites, one pond and one small urban stream, impacted by landfill plumes. The study examined multiple cage designs and orientations and two test organisms: an amphipod (Hyalella azteca) and midge larvae (Chironomus riparius; only one study). Cages were deployed for between 5 and 28 days and assessed for organism survival and growth. At all sites and for some deployment conditions, cages exposed to high contaminant concentrations in the plume footprint had greater mortality compared to those exposed to lower or background concentrations. Organism growth was less clear as a metric of toxicity. Vertically oriented cages typically showed high mortality to plume contaminants, but some were also affected by other non-target groundwater conditions (e.g., low dissolved oxygen, other contaminant sources), while horizontally oriented cages were rarely responsive to either groundwater influence. A hybrid cage design showed much promise in its single study. Useful observations on the test organisms and on potentially problematic site conditions were also made. The informed use of in situ toxicity cages could be an additional beneficial tool for groundwater contaminated site assessments. [ABSTRACT FROM AUTHOR]

Over 60 years of oceanographic observations from Ocean Station Papa (OSP) in the northeast Pacific indicate faster dissolved oxygen loss than the global average. The greatest negative trends in oxygen concentration occur on isopycnals in the upper water column (σθ = 26.1–26.8 kg m−3, ∼110–200 m) but have considerable uncertainty due to natural variability. In this paper, we use eight Argo profiling floats equipped with optode oxygen sensors to assess the 2008–2016 interannual variability of subsurface dissolved oxygen near OSP. We developed a method using high frequency Conductivity‐Temperature‐Depth data to correct optode profiles for slow response times and used reference profiles from the OSP time series to calibrate the optodes. Response time correction markedly improves subsurface bias caused by slow optode equilibration. Our analysis indicates that episodic shoaling of isopycnals can cause rapid reduction in dissolved oxygen concentration. Changes in ventilation, horizontal mixing, and water mass age are unlikely drivers for the rapid O2 loss events examined. We link dissolved oxygen loss during shoaling events to organic matter export, due to higher concentrations of organic matter and greater respiration rates at shallower depths. Reduced net community production during the "Blob" marine heatwave may have reduced the impact of the second shoaling event examined. Natural variations in dissolved oxygen in these layers provide context for uncertainty estimates of long‐term trends and insight toward the potential for future extreme oxygen minima from the combined impact of the long‐term decline and episodic shoaling. Plain Language Summary: Oxygen dissolved in the ocean is declining worldwide as temperatures increase. Widespread ecological stress and altered marine chemistry will be a likely result. The subarctic northeast Pacific Ocean has been losing oxygen even faster than the global average rate. In this study, we use data from ocean observing robots in this region to investigate factors causing episodes of faster oxygen depletion. To do this accurately, we developed and applied a method to correct the data for how slowly the oxygen sensor responds as it moves upward through the water column. We identify two periods of rapid oxygen loss in subsurface water layers of about 1.5 years each. Both episodes happen when regional wind patterns cause these water layers to move closer to the surface. When shallower, these layers experience faster oxygen consumption by respiration, because the supply of organic detritus from the surface is higher. Such oxygen depletion episodes, driven by periodic wind shifts, can be regarded as natural variations in the ocean's oxygen content and need to be considered when interpreting the potential for long‐term anthropogenic trends. Key Points: We observe two episodes of rapid oxygen loss in the upper pycnocline of the NE Pacific coincident with isopycnal shoalingWe propose enhanced respiration at shallower depths as the most likely driver of oxygen declines during these shoaling eventsHigh‐frequency Conductivity‐Temperature‐Depth data can be used to obtain float ascent velocities to correct oxygen optode lag [ABSTRACT FROM AUTHOR]

The Arctic Ocean plays an important role in the regulation of the earth's climate system, for instance by storing large amounts of carbon dioxide within its interior. It also plays a critical role in the global thermohaline circulation, transporting water entering from the Atlantic Ocean to the interior and initializing the southward transport of deep waters. Currently, the Arctic Ocean is undergoing rapid changes due to climate warming. The resulting consequences on ventilation patterns, however, are scarce. In this study we present transient tracer (CFC‐12 and SF6) measurements, in conjunction with dissolved oxygen concentrations, to asses ventilation and circulation changes in the Eurasian Arctic Ocean over three decades (1991–2021). We constrained transit time distributions of water masses in different areas and quantified temporal variability in ventilation. Specifically, mean ages of intermediate water layers in the Eurasian Arctic Ocean were evaluated, revealing a decrease in ventilation in each of the designated areas from 2005 to 2021. This intermediate layer (250–1,500 m) is dominated by Atlantic Water entering from the Nordic Seas. We also identify a variability in ventilation during the observation period in most regions, as the data from 1991 shows mean ages comparable to those from 2021. Only in the northern Amundsen Basin, where the Arctic Ocean Boundary Current is present at intermediate depths, the ventilation in 1991 is congruent to the one in 2005, increasing thereafter until 2021. This suggests a reduced ventilation and decrease in the strength of the Boundary Current during the last 16 years. Plain Language Summary: The Eurasian Arctic Ocean, the region of the Arctic Ocean connected to the European and Asian continents, is an important pathway for recently ventilated water from the Nordic Seas. These waters are exported back to the North Atlantic following their travel through the Arctic Ocean. Ventilation describes the process of surface waters being transported into the interior ocean due to increasing density, which affects the underlying water masses. In this study we investigate how the ventilation patterns have evolved in the Eurasian Arctic Ocean over the past three decades, using transient tracer (CFC‐12 and SF6) measurements. We observed a significant change in the intermediate layer (250–1,500 m) with older waters found in measurements in 1991 and 2021 compared to 2005 and 2015. Moreover, our data suggest a slowdown in ventilation throughout the three decades in the northern Amundsen Basin, implying a decrease in the circulation time‐scale of the Arctic Ocean Boundary Current over the past 16 years. This has potentially important implications for the transport of, for example, heat, salt or oxygen from the Atlantic Ocean around the Arctic Ocean, and back. Key Points: Temporal variability of ventilation in the Eurasian Arctic Ocean during the past 30 years is estimated by observations of transient tracersWe found a slow down of the ventilation between 2005 and 2021 in the intermediate watersEvidence of multidecadal variability of ventilation in the intermediate waters of the Eurasian Arctic Ocean is present [ABSTRACT FROM AUTHOR]

The seasonal variation of physico-chemical parameters of backwater from Yashwant Sagar reservoir were investigated during 3rd January 2023 to 25th December 2023 by using standardised parameters to determine its quality. Seasonal values of water colour, odor, turbity, temperature, pH, total alkalinity, total hardness, dissolved oxygen, free CO2 were observed from 5 different stations of Yashwant Sagar dam backwater area of Karjat and Shrigonda are presented in this paper. It was found that physicochemical parameters of water were almost at optimum level. [ABSTRACT FROM AUTHOR]

Electrocatalytic activities for the oxygen reduction reaction (ORR) of Au electrodes modified by as prepared and size selected (0.45–1.0, 0.22–0.45, and 0.1–0.22 µm) h-BN nanosheet (BNNS), which is an insulator, were examined in O2 saturated 0.5M H2SO4 solution. The overpotential was reduced by all the BNNS modifications, and the smaller the size, the smaller the overpotential for ORR, i.e., the larger the ORR activity, in this size range. The overpotential was reduced by as much as ∼330 mV compared to a bare Au electrode by modifying the Au surface by the BNNS of the smallest size range (0.1–0.22 µm). The overpotential at this electrode was only 80 mV more than that at the Pt electrode. Both the rotation disk electrode experiments with Koutecky–Levich analysis and rotating ring disk electrode measurements showed that more than 80% of oxygen is reduced to water via the four-electron process at this electrode. These results strongly suggest and theoretical density functional theory calculations support that the ORR active sites are located at the edges of BNNS islands adsorbed on Au(111). The decrease in size of BNNS islands results in an effective increase in the number of the catalytically active sites and, hence, in the increase in the catalytic activity of the BNNS/Au(111) system for ORR. [ABSTRACT FROM AUTHOR]

This study aimed to assess the trophic status of Pegametan Bay, Bali, Indonesia, as influenced by floating net cage aquaculture activities during June 2019 (dry season) and March 2021 (wet season). The trophic status was assessed using 24 parameters developed from a literature review, and water samples were collected from four observation stations. Data were analyzed using field measurements and laboratory analyses. The results showed that dissolved oxygen ranged between 2.6–9.1 mg/l in June 2019 and 3.4–7.7 mg/l during the March 2021 measurement period, salinity (33.6–34.4 ppt and 31–34 ppt), turbidity (0.77–6.33 FNU and 1.2–3.42 FNU), water clarity (4.18–11.92 m and 4.44–8.44 m), Biological Oxygen Demand (10.5–26 mg/l and 1–17 mg/l), Chemical Oxygen Demand (3.68–11 mg/l and 15.5–46.5 mg/l), chlorophyll-a (0.11–0.24 mg/l and 0–0.56 mg/l), Total Dissolved Solids (20,400–22200 mg/l and 21,300–53400 mg/l), ammonia (0.038–0.178 mg/l and 0.01–0.3 mg/l), nitrate (0.02–0.706 mg/l and 0.01–0.03 mg/l), orthophosphate (0.014–0.174 mg/l and 0.04–1.59 mg/l, and culturable bacteria (0–1.74 ∙ 105 CFU/mL and 0–1.61 ∙ 108 CFU/mL). Pegametan Bay exhibited a significant decrease in water quality between June 2019 and March 2021, with mesotrophic and eutrophic trophic states. The parameters determining changes in the trophic state of Pegametan Bay were orthophosphate, TSS, organic content, E. coli, Salmonella, and Vibrio. This trophic state assessment can be used for early detection, monitoring, water quality control, and eutrophication control, thereby ensuring sustainable aquaculture activities and optimal marine resource production. [ABSTRACT FROM AUTHOR]

Chlorophyceae is a class of plankton commonly discovered in aquaculture ponds in tropical aquatic regions. Therefore, this study aimed to analyze the abundance levels of Chlorophyceae in pen-culture ponds during the dry season using a dynamic modeling system. The method adopted was a causal ex-post facto design, and the observed parameters were water quality and plankton abundance. The results showed the presence of various plankton classes such as Chrysophyceae, Chyanophyceae, Chlorophyceae, Dynophyceae, and Oligotrichea, as well as the discovery of 17 plankton genera. Water quality parameters identified Total Dissolved Solids (TDS) concentrations, dissolved oxygen levels, temperature, pH levels, and salinity ranging from 3.06–7.37 mg·L-1, 4.39–6.30 mg·L-1, 26.21–31.17 °C, 7.7–8.1, and 10–25 ppt, respectively. The average plankton dominance index (D’) showed Chlorophyceae dominance at 4.55, followed by Chyanophyceae, Chrysophyceae, Dynophyceae, and Oligotrichea at 1.78, 0.08, 0.07, and 0.01, respectively, falling in the index category of 0.5 < D < 1. Furthermore, the average plankton abundance dominance level (pi) signified Chlorophyceae dominance at 7.11E-01, followed by Chyanophyceae, Chrysophyceae, Dynophyceae, and Oligotrichea at 4.68E-01, 1.30E-01, 8.05E-02, and 3.96–02, respectively. This implied that in pen-culture water, Chlorophyceae significantly dominated over other classes. Dynamic modeling results showed the abundance of Chlorophyceae in ponds A, C, and D to be relatively uniform (± 5.00E-02 cell/ ml) compared to pond B (± 0.10E-00 cell/ml). It was important to acknowledge that as Chlorophyceae dominance increased (0.10E-00–5.0E-02 cell/ml), the total plankton abundance in the water decreased contradictorily (0.01E00–100E-04 cell/ml) due to over-dominance. On the basis of the modeling description, Chlorophyceae sustained for 20 weeks during the culture period, with optimal growth observed from the 1st to the 5th week. In conclusion, this plankton class experienced dynamic fluctuations during the pen-culture cultivation period, and the life cycle stability was dependent on water quality and temperature. [ABSTRACT FROM AUTHOR]

Eutrophication has become a recurrent concern in reservoirs worldwide. This problem is intensified in tropical semiarid regions, where the reservoirs have high seasonal and annual variability of water level and volume. Therefore, an extensive understanding of the diel variation of water quality key-parameters can help improve management of such reservoirs. This study focuses on Castanhão reservoir with the largest multipurpose dam in the Brazilian semiarid. Its main water uses are irrigation, fish farming, and human supply. The reservoir faced a decline in water quality due to a prolonged drought period. While previous research has predominantly emphasized the seasonal dynamics of thermal and chemical stratification, our investigation provides diel assessments of multiple water quality parameters, including nutrient concentrations and phytoplankton abundance. Our primary objective is to compare seasonal and diel variations in stratification and nutrient distribution within the reservoir. Key findings reveal a diel cycle of thermal stratification, primarily during dry season, driven by higher wind speeds. This is corroborated by a significant negative correlation between wind speed and the relative water column stability index. In contrast, during the rainy season, the reservoir experiences continuous thermal stratification due to inflowing water being warmer than the reservoir's water temperature. Notably, a significant negative correlation between total phosphorus and chlorophyll-a, along with a two-fold increase of this nutrient throughout the day during the rainy season, underscores the influence of the phytoplankton community dynamics on the diel nutrient variation. Chemical stratification of dissolved oxygen occurred during dry and rainy seasons, indicating that even during the dry season, where there is no significant inflow, the internal nutrient loading can also significantly impact the water quality of a reservoir. This study advances the understanding of diel water quality dynamics in tropical semiarid reservoirs, shedding light on both climatic and anthropogenic influences on water resources. [ABSTRACT FROM AUTHOR]

Highlights : A clear negative correlation between the size of water clusters and the concentration of dissolved oxygen was observed. This implied that smaller clusters water exhibits higher concentrations of dissolved oxygen. Oxygen molecules are primarily existed at the surfaces or interfaces of water clusters and can rapidly traverse the gas liquid interface. A semi empirical formula relating the average number of water molecules in a cluster to 17O NMR half peak width was derived, demonstrating an approximate lin ear relationship. The structure of liquid water is primarily composed of three-dimensional networks of water clusters formed by hydrogen bonds, and dissolved oxygen is one of the most important indicators for assessing water quality. In this work, distilled water with different concentration of dissolved oxygen were prepared, and a clear negative correlation between the size of water clusters and dissolved oxygen concentration was observed. Besides, a phenomenon of rapid absorption and release of oxygen at the water interfaces was unveiled, suggesting that oxygen molecules predominantly exist at the interfaces of water clusters. Oxygen molecules can move rapidly through the interfaces among water clusters, allowing dissolved oxygen to quickly reach a saturation level at certain partial pressure of oxygen and temperature. Further exploration into the mechanism by molecular dynamics simulations of oxygen and water clusters found that oxygen molecules can only exist stably at the interfaces among water clusters. A semi-empirical formula relating the average number of water molecules in a cluster (n) to 17O NMR half-peak width (W) was summarized: n = 0.1 W + 0.85. These findings provide a foundation for exploring the structure and properties of water. [ABSTRACT FROM AUTHOR]

[Objective] The study was carried out to explore the effects of acute hypoxia on the survival of juvenile Eleutheronema tetradactylum and their spleen and heart tissue structure, with a view to providing technical support and theoretical references for the breeding and production of this species. [Method] Filling water with nitrogen to quickly overflow oxygen and reduce the content of dissolved oxygen in the water. Different levels of dissolved oxygen treatment were set in the experiment: normal oxygen group (6.33 ± 0.15 mg/L), moderate hypoxia group (3.99 ± 0.18 mg/L), and severe hypoxia group (2.05 ± 0.15 mg/L). Each treatment group was set up with 3 parallel devices. During the experiment, the flowing water was turned off, and the dissolved oxygen level in the water was monitored in real time by using a dissolved oxygen measuring instrument. The corresponding dissolved oxygen level was maintained by adjusting the size of the inflation valve. Using paraffin embedding, sectioning and hematoxylin eosin (HE) staining methods were used to observe the changes in tissue structure of the heart and spleen of juvenile E. tetradactylum. [Result] In terms of mortality rate, there was no mortality observed in the E. tetradactylum in the normal oxygen group; the mortality rates of juvenile fish under the stress in the moderate and severe hypoxia groups were 10.0%-13.3% at 23 hours, 30.0% - 40.0% at 26 hours, and 43.3%-53.3% at 29 hours. In terms of spleen tissue structure, compared with the normal oxygen group, the moderate hypoxia group showed an increase in white pulp and the number of lymphocyte in juvenile fish, sparse distribution of peripheral red pulp, and a decrease in the number of melanin macrophages; the red pulp area of juvenile fish in the severe hypoxia group expanded, with a decrease in the white pulp area and the number of lymphocytes, and melanin macrophages rarely appearing. In terms of heart tissue structure, the compact layer of heart tissue in juvenile fish in the moderate hypoxia group became thinner, the myocardial fibers in the sponge layer became thinner, and the spacing became wider, and partial myocardial fiber rupture phenomenon occurred; the degree of thinning of the compact layer and thinning of the myocardial fibers in the sponge layer of juvenile fish in the severely hypoxic group increased, and the degree of expansion of the interstitial space increased compared to the hypoxic group, with partial myocardial cell rupture, nucleus protrusion, myocardial fiber rupture, and disordered arrangement. [Conclusion] The study has shown that acute hypoxia stress can affect the survival rate of juvenile E. tetradactylum. The lower the dissolved oxygen level, the higher the mortality rate, and the degree of tissue structure damage increases with the level of hypoxia. [ABSTRACT FROM AUTHOR]

Headwater streams play a large role in aquatic greenhouse gas emissions. Carbon dioxide (CO2) and dissolved oxygen in streams often undergo changes through diel cycles. However, methane (CH4) and nitrous oxide (N2O) have unknown diel dynamics. Here, we reveal consistent patterns in CO2, CH4, and N2O over diel cycles and during flood events using high‐frequency continuous observations in a subtropical headwater stream. Diel cycles were most pronounced during baseflow. Increased nighttime discharge due to higher groundwater inputs enhanced gas transfer velocities and concentrations. Overall nocturnal emissions were 31%, 68%, and 32% greater than daytime for CO2, CH4, and N2O, respectively. Floods dampened diel signals. If both flood events and diel patterns are neglected, estimates of greenhouse gas emissions from headwaters may be greatly underestimated. Overall, CH4 and N2O emissions from headwater streams may be underestimated by ~ 20–40% due to a lack of observations during nighttime, floods, and in warmer climates. [ABSTRACT FROM AUTHOR]

The spread of industrial activities, especially electrical power generation stations on the banks of rivers, increases the pollution of the surrounding water environment as a result of the release of industrial water that is not treated adequately. Among these stations is the Al-Musayyib Thermal Power Station. The research focused on studying the quality of the water entering and leaving the station by installing two sensing stations. Remote monitoring of the Euphrates River, as the station contains several sensors, including measuring acidity, dissolved oxygen, turbidity, and the amount of total salts, in addition to a sensor for measuring refined fuel. These results are collected around the clock at a central station, where the results showed a decrease in the level of dissolved oxygen ranging between (3.5-5) RSD% 0.1-0.2 as well as an increase in The temperature of the excreted water ranging between from (30C°-33C°) RSD% 0.1-0.2, both of which negatively affect the environmental life of living organisms, as well as the appearance of a high percentage of pollutants resulting from refined fuel, ranging between (2.1-8.1) ppm, The findings will contribute to improving the efficiency of treatment plants to suit the environment surrounding the river, In order to preserve the water environment, it is necessary to place oil dispensers in the treatment units, as well as work to reduce the temperatures of the cooling water, which are at temperatures higher than the medical grades coming out of the station. [ABSTRACT FROM AUTHOR]

Accurate determination of reaeration coefficient in lakes is a key factor for accurate modeling of dissolved oxygen. This study developed a new numerical model to determine the lake reaeration coefficient of Sawa lake, Iraq based on solving the transform mechanisms of dissolved oxygen without the using the empirical and laboratory methods. The model solved the gas transport at the water-air surface numerically to predict the dissolved oxygen and the reaeration coefficient simultaneously. Results showed that the lake reaeration coefficient was 0.001 day-1 at 20 °C with low root mean squared errors (0.138, 0.137, and 0.168 mg/L for the three years of simulation 2007, 2012, and 2017, respectively) and absolute mean errors (0.121, 0.114, and 0.145 mg/L in 2007, 2012, and 2017, respectively). It was noticed that the lake habitat was impacted causing unhealthy conditions (low reaeration rate), and there was upward dissolved oxygen movement due to the presence of positive trend in the yearly cycle of temperature. In addition, including this numerical approach along with other water quality models can improve the predictions of other water quality parameters. [ABSTRACT FROM AUTHOR]

The formation of oxygen-depleted zones in the bottom waters is one of the most widespread phenomena in coastal areas. Upwelling episodes along India's west coast due to the southwest monsoon increase biological productivity, further lowering the dissolved oxygen in the upwelled waters, which intensifies annually between June and October. Here, we have determined the changes in the microbial community in response to the varying oxygen levels and other physicochemical parameters at the Candolim Time Series Station using highthroughput sequencing. Amplicon Sequence Variants across all the samples collected in different seasons were mostly affiliated to the phyla Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Chloroflexi, Firmicutes and Planctomycetes, with the most dominant being Proteobacteria (21-41%). Statistical analysis revealed that microbial diversity differed significantly with changing DO, ammonia, nitrate and nitrite concentrations during different seasons. The microbial community shift due to seasonal hypoxia results in the differential biogeochemical cycling of essential nutrients, with certain years seeing redox conditions up to sulphate reduction while certain years seeing only nitrogen loss. Future global warming scenarios will serve as a big challenge for understanding the role of microbial diversity and its implications in the cycling of natural elements. [ABSTRACT FROM AUTHOR]

Toxic cyanobacteria, specifically Microcoleus, are being found in rivers in Utah, California, and other states, posing a threat to humans and animals if ingested. The reasons for the increase in sightings are still unknown, but researchers are studying the factors that contribute to their population growth. These cyanobacteria are particularly dangerous as they hide in clean water and only release toxins when disturbed. Efforts are being made to monitor and inform the public about the presence of toxic cyanobacterial mats in rivers. Researchers are using sensors to monitor changes in dissolved oxygen and temperature, collecting samples for toxin testing, and developing models to predict cyanobacterial hotspots. Changes in the rivers, such as increased sediment inputs, may be contributing to their growth. The ultimate goal is to understand the triggers and controls of toxin production in these mats. [Extracted from the article]

Extreme precipitation is exacerbating the burden of infectious diarrhea in the context of climate change, it is necessary to identify the critical and easy-to-intervene intermediate factors for public health strategies. Water quality may be the most important mediator, while relevant empirical evidence is limited. This study aimed to examine the role of water quality in the process of infectious diarrhea caused by extreme precipitation. Weekly infectious diarrhea cases, meteorological factors and water quality data in Yangtze River Basin in China between October 29, 2007 to February 19, 2017 were obtained. Two-stage statistical models were used to estimate cityspecific extreme precipitation, water quality and infectious diarrhea relationships that were pooled to derive regional estimates. A causal mediation analysis was used to assess the mediation effect of water quality. In Yangtze River Basin, extreme precipitation events had a significant impact on infectious diarrhea (Incidence Rate Ratios [IRR]: 1.027, 95% Confidence Interval [CI]: 1.013 ~1.041). After extreme precipitation events, the dissolved oxygen (DO) in surface water decreased (-0.123 mg/L, 95%CI: -0.159 mg/L ~-0.086 mg/L), while the un-ionized ammonia (NH(3)-N) increased (0.004 mg/L, 95%CI: 0.001 mg/L ~0.006 mg/L). The combined overall effect of DO and NH(3)-N on infectious diarrhea showed that both low and high concentrations were associated with an increased risk of infectious diarrhea. The causal mediation analysis showed that the mediation proportion of the two water quality indexes (DO and NH(3)-N) is 70.54% ( P < 0.001). To reduce the health effects of extreme precipitation, in contrast to current population-oriented health strategies, those that take into account more direct and easy-to-intervene water quality indicators should be encouraged by future policies. [ABSTRACT FROM AUTHOR]

This study investigated the impact of lyophilized Euterpe oleracea (LEO) in the diet of tambaqui (Colossoma macropomum) on antioxidant capacity following transport stress. Six diets with varying LEO concentrations (0.00, 0.63, 1.25, 2.50, 5.00, and 10.0%) were administered. After a 30-day feeding period, the fish from each diet were subjected to simulated transport for 3, 6, 12, and 24 h. No mortality was observed during the posttransport simulation. Dietary LEO appeared to conserve dissolved oxygen in water. The inclusion of 1.25% and 10.0% LEO enhanced the hepatic total antioxidant capacity by 42% and 53%, respectively, compared to the control during transport for up to 12 h. Additionally, 5.00%–10.0% LEO mitigated lipid peroxidation in the brain, gills, and liver of tambaqui for up to 12 h, remaining effective in the gills for 24 h. Consequently, considering its potential to alleviate oxidative stress, the incorporation of 5.00% to 10.0% LEO into the diet is a promising strategy for enhancing the resilience of fish during transport lasting up to 12 h. [ABSTRACT FROM AUTHOR]

In recent decades, reports from around the globe indicate an increase in natural organic matters (NOMs) in surface waters, which has a negative impact on drinking water purification and causes problems such as the taste and color of water, reducing the amount of dissolved oxygen in water, causing membrane fouling in the filtration process, and acting as a precursor for the formation of an antiseptic by-product. This work used the adsorption process to evaluate the elimination of natural organic compounds in aquatic environments. Ethylenediaminetetraacetic acid (EDTA) as a crosslinker for chitosan (CTS) and N, N-methylenebisacrylamide as a crosslinker for polyacrylamide (PAM) were used to prepare humic acid (HA) adsorbents utilizing a two-step procedure. The FTIR spectroscopy proved the EDTA cross-linking agent was effective with the semicrosslinking CTS/PAM hydrogel. CTS/PAM/EDTA double network (DN) hydrogel exhibited a higher HA adsorption capacity ( q e = 107.7 mg/g) than CTS/PAM ( q e = 59.3 mg/g) at pH = 7 and an initial concentration of 60 mg·L−1 during 60 min. Also, results demonstrate that CTS/PAM/EDTA DN hydrogels showed faster adsorption kinetics than CTS/PAM. [ABSTRACT FROM AUTHOR]

• Domestic sewage contained more oxygen-consuming substances than industrial wastewater. • Small molecular amino acids potentially served as high oxygen-consuming substances. • Biological process played an important role in oxygen consumption for domestic sewage. • FED2 calculation was applied to explore the key oxygen-consuming group for amino acids. The dissolved oxygen content in water is an important indicator for assessing the quality of the water environment, and maintaining a certain amount of dissolved oxygen is essential for the healthy development of the ecological environment. When a water body is anoxic, the activity of anaerobic microorganisms increases and organic matter is decomposed to produce a large number of blackening and odorizing substances, resulting in black and odorous water bodies, which is a very common and typical phenomenon in China. Presently, there is still a relatively universal occurrence of illicitly connected stormwater and sewage pipes in the urban drainage pipe network in China, which makes oxygen-consuming substances be directly discharged into rivers through stormwater pipes and consume the dissolved oxygen in the water bodies, resulting in an oxygen deficiency of the water. This induces seasonal or year-round black and stink phenomena in urban rivers. Hence, identifying high oxygen-consuming substances, which lays the foundation for the subsequent removal of oxygen-consuming substances, is essential. Through a series of comparisons of water quality indicators and analysis of organic characteristics, it was found that the oxygen consumption capacity of domestic sewage was higher than that of industrial wastewater in the selected area of this study, and the oxygen-consuming substances of domestic sewage were small molecular amino acids. By comparing 20 conventional free amino acids, it was found that seven of them consumed oxygen easily, and compared with chemical oxygen consumption, biological oxygen consumption was in a leading position. [Display omitted] [ABSTRACT FROM AUTHOR]

Banyuwangi Regency has high potential for vannamei shrimp farming. Vannamei shrimp farming is susceptible to disease attack. Disease monitoring serves to determine the distribution of disease in vannamei shrimp ponds. The purpose of this study was to monitor disease in vannamei shrimp pond waters of Banyuwangi Regency. This research method uses descriptive method. Monitoring of water quality parameters insitu and exitu. Disease monitoring using Real-Time PCR Quant studio 5 to detect AHPND, WSSV, EHP, and IMNV. The analysis used was descriptive analysis. The results showed that the water quality in vannamei shrimp ponds in Banyuwangi Regency was an average temperature of 25.8℃, average salinity of 33.9 g.L-1, average dissolved oxygen (DO) 7.15 mg.L-1, average pH 8.15, average ammonia 0.257 mg.L-1, average nitrite 0.04 mg.L-1, average nitrate 4.9 mg.L-1. As for the disease, there are three types, namely AHPND, EHP, and IMNV. [ABSTRACT FROM AUTHOR]

Estuarine processes are key in modulating the riverine input of particle-reactive trace elements to the ocean. An important, but still under-utilized member of these elements is beryllium-9 (9Be) that together with cosmogenic 10Be has been suggested to serve as a quantitative tracer of present and past continental weathering flux. This study investigates different pathways of terrigenous 9Be through coastal areas into the ocean, based on dissolved 9Be concentrations in surface and bottom waters together with corresponding particulate 9Be concentrations along the salinity gradient in the Changjiang Estuary. Dissolved 9Be in the Changjiang Estuary shows a non-conservative behavior: At low to mid-salinity where water is well-mixed, 9Be is removed from both surface and bottom waters at low salinity and then released back into the water column at mid-salinity. At high salinity where water is stratified, dissolved 9Be is removed from surface waters, but is released back into bottom waters. In combination with hydrochemical (e.g., dissolved oxygen) and particulate 9Be data obtained from different extracted phases, we attribute the removal of dissolved 9Be at low salinity to salt-induced colloidal flocculation, whereas in surface waters at high salinity, we ascribe the removal to biological scavenging facilitated by phytoplankton blooms. The release of 9Be into mid- and high-salinity bottom waters is likely dominated by benthic processes, including porewater diffusion and/or submarine groundwater discharge. The contribution from desorption of 9Be from suspended particulate matter is negligible throughout the entire estuary. We propose that the release of 9Be through benthic processes potentially presents the most important contributor to the marine 9Be budget, where this benthic flux of 9Be is likely enhanced by hypoxic conditions in coastal bottom waters. [ABSTRACT FROM AUTHOR]

The coast of Tanjung Mas, Semarang City, is an industrial area used by the community to cultivate milkfish using stick-net pens. Furthermore, heavy metal contamination such as Cr, Cd, Cu, and Pb potentially disrupts milkfish meat's growth, quality, and safety. This study aims to determine heavy metals concentration in the waters and milkfish meat in stick-net pens cultivation in Tanjung Mas, Semarang City. The study was conducted using exploration, with five observation sites representing household waste disposal flow, industrial discharge, open sea, and intermediate areas. The observation sites were selected based on the milkfish cultivation activity. The sample and data, including water, milkfish, and environmental factors (temperature, pH, salinity, water current, and dissolved oxygen), were collected three times every two weeks. The heavy metals were detected using Atomic Absorption Spectrometry (AAS). The highest heavy metal concentration is Cr, which ranges from 1.70 ± 0.32 ppm to 2.36 ± 0.63 ppm in milkfish and 2.77 ± 0.65 ppm to 3.05 ± 0.58 ppm in the environment. The heavy metals contamination in Semarang City's water areas is still relatively low and has no impact on milkfish growth. Industrial waste, mainly heavy metals, potentially threatens the stick-net pens cultivation model developed by the community in Semarang City. This study can be used as an input for mitigation and adaptive action in anticipating future environmental changes and maintaining their business sustainability. [ABSTRACT FROM AUTHOR]

The construction of dams on large rivers significantly changes the hydrological regime. The morphology and functional features of floodplain water bodies have a significant impact on water quality parameters. The electrical conductivity, transparency, water temperature and dissolved oxygen content of 302 water bodies located in the Dnipro River floodplain were investigated. The variability of water quality indicators is explained by different sources of water supply to the floodplain reservoirs, as well as by the geological characteristics of the soil. The genesis of lakes of a certain shape is related to the geological and geomorphological conditions of the floodplain, which is the reason for the connection between the functional characteristics of water bodies and water quality indicators in them. Predictors of the probability of oxygen stress are the proximity of the sandy border to the reservoir and the elongated shape of the reservoir. [ABSTRACT FROM AUTHOR]

Preventing the rebound of black and odorous water bodies is critical for improving the ecological environment of water bodies. This study examined the effect and underlying mechanism of in-situ improvement of the sediment microenvironment by nitrate in the tailwater of wastewater treatment plants combined with aerobic denitrifying bacteria under low-DO regulation (TailN + CFM + LDO). On the 60th day of remediation, the levels of dissolved oxygen and oxidation–reduction potential in the overlying water rose to 5.6 mg/L and 300 mV, respectively, the concentration of acid volatile sulfide within the sediment significantly decreased by 70.4%, and the organic matter content in the sediment was reduced by 62.7%, in which the heavy fraction organic matter was degraded from 105 g/kg to 56 g/kg, and the potential risk of water reverting to black and odorous conditions significantly decreased. Amplicon sequencing analysis revealed that the relative abundance of the electroactive bacteria Thiobacillus and Pseudomonas with denitrification capacity was found to be significantly higher in the TailN + CFM + LDO group than in the other remediation groups. Functional prediction of the 16S sequencing results indicated that both the quantity and activity of critical microbial enzymes involved in nitrification and denitrification processes could be enhanced in the TailN + CFM + LDO group. These results improved our understanding of the improvement of the sediment microenvironment and could thus facilitate its application. [ABSTRACT FROM AUTHOR]

High-quality biofilm carriers are crucial for the formation of biofilm, but problems such as slow biofilm growth on the carrier surface have been troubling a large number of researchers. The addition of a carrier changes the flow state in the reactor, which in turn affects the microbial attachment and the quantity of microorganisms. Also, aerobic microorganisms need to use dissolved oxygen in the water to remove water pollutants. In this paper, a novel recirculating flow carrier with a hollow cylinder structure is proposed, with a certain number of hollow inverted circular plates placed at equal distances inside. In this paper, the hydraulic residence time, aeration volume, and the spacing of the inflow plates of the recirculating flow biofilm carrier, which are three important factors affecting the hydraulic characteristics of the reactor, are first investigated. At the same time, it was compared with the common combined carrier to find the optimal operating conditions for the hydraulic characteristics. Secondly, a reactor start-up study was carried out to confirm that the new recirculating flow biofilm carrier could accelerate the biofilm growth by changing the hydraulic characteristics. The results showed that under the same conditions, the hydraulic properties of the reactor were better with the addition of the recirculating flow carrier, with an effective volume ratio of 98% and a significant reduction in short flows and dead zones. The stabilized removal of COD, NH3-N, and TN in the reactor with the addition of the recirculating flow carrier reached about 94%, 99%, and 91% respectively, at the beginning of the 15th day, which effectively proved the feasibility of the recirculating flow carrier. [ABSTRACT FROM AUTHOR]

A massive bloom of the raphidophyte Heterosigma akashiwo occurred in summer 2022 in San Francisco Bay, causing widespread ecological impacts including events of low dissolved oxygen and mass fish kills. The rapidly evolving bloom required equally rapid management response, leading to the use of near-real-time image analysis of chlorophyll from the Ocean and Land Colour Instrument (OLCI) aboard Sentinel-3. Standard algorithms failed to adequately capture the bloom, signifying a need to refine a two-band algorithm developed for coastal and inland waters that relates the red-edge part of the remote sensing reflectance spectrum to chlorophyll. While the bloom was the initial motivation for optimizing this algorithm, an extensive dataset of in-water validation measurements from both bloom and non-bloom periods was used to evaluate performance over a range of concentrations and community composition. The modified red-edge algorithm with a simplified atmospheric correction scheme outperformed existing standard products across diverse conditions, and given the modest computational requirements, was found suitable for operational use and near-real-time product generation. The final version of the algorithm successfully minimizes error for non-bloom periods when chlorophyll a is typically <30 mg m−3, while also capturing bloom periods of >100 mg m−3 chlorophyll a. [ABSTRACT FROM AUTHOR]