Algal Concentration Research Articles

Analysis of long-term changes in algal bloom pattern and their association with Ocean, atmosphere, and land-based processes across the northern Indian Ocean

Algal blooms are global phenomena in marine and fresh waters. An understanding of the impacts of climate change and anthropogenic activities on marine algal blooms is essential for protecting marine ecosystems. We have studied the long-term changes in the spatial patterns of algal blooms over the northern Indian Ocean and assessed the influence of the ocean, atmosphere, and land-based processes on them. We have analyzed multi-source satellite data (2003 – 2020) of various parameters such as algal concentration, temperature, salinity, sea level, particulate organic carbon, precipitation, wind speed, and river discharge on an open-source cloud computing platform. The seasonality of variables is assessed using a harmonic model, and their spatial trend is estimated using the non-parametric Mann-Kendall test. The spatial relationship between various geophysical parameters and algal bloom concentration is assessed by the cross-correlation test, and the prediction is done using a multivariate autoregression model. Results suggest that each variable exhibits distinguishable seasonal patterns. Algal bloom duration showed a significant increase over time. However, algal bloom coverage showed a significant decline in the coastal waters in all seasons except post-monsoon. The cross-correlation test unveils that lower temperatures, salinity, and sea level promote algal bloom occurrences in coastal waters rather than open waters. Furthermore, the statistical model with a time lag of 2 months shows better performance for prediction of bloom intensity (r2 = 0.86).

The rapid detection method of brown tide algae concentration based on unthresholded recurrence plots and improved broad learning system

In recent years, there have been frequent outbreaks of harmful algal blooms (HAB) in coastal areas, which have caused serious economic losses to the local community. Therefore, accurate and rapid prediction of microalgal concentrations is necessary for early warning and countermeasures before the occurrence of HAB. This paper presents a model for predicting microalgae concentration based on unthresholded recurrence plots (UTRPs) combined with an improved broad learning system (BLS). Spectral data acquisition of algae species at different concentrations using l-induced fluorescence spectroscopy. Then, the 1D spectral data are dimensionally lifted by UTRPs transformation, recurrence plots (RPs) transformation can fully extract the internal information of 1D sequence data, and at the same time, UTRPs avoids the influence of artificially selected thresholds on the feature transformation results of traditional (RPs). Finally, a lightweight flat network BLS was used for microalgae concentration regression prediction, at the same time the BLS regularization method was improved. When comparing the two most commonly used deep learning regression models and integrated learning models, UTRPs and elastic net (UTRPs-ENBLS) achieves convincing results.

Bioestimulante de algas melhora a tolerância à salinidade e a qualidade visual de espécies herbáceas ornamentais tropicais

ABSTRACT The use of biostimulants may mitigate the deleterious effects of salt stress on plant growth and physiological variables. Thus, the present study aimed to evaluate the growth, physiology, organic solutes, and visual characteristics of two tropical ornamental species (Celosia argentea and Catharanthus roseus) cultivated with brackish waters and treated with Ascophyllum nodosum extract. The experiment was performed in greenhouse conditions. The experimental design was a complete randomized block arranged in a split-plot scheme. The plots comprised three levels of electrical conductivity of the irrigation water (ECw - 0.5, 2.5, and 4.5 dS m-1), the subplots four concentrations of algae extract (0, 400, 800, and 1200 mg L-1), and the sub-subplots two tropical ornamental herbaceous species [C. argentea and C. roseus]. The salinity of the irrigation water negatively affects the morphological and physiological characteristics of the two species studied, mainly C. roseus. Irrigation with water up to 2.5 dS m-1 favored visual quality and increased the purchasing preference for C. argentea. The use of intermediate concentrations (400 mg L-1) of algae extract (A. nodosum) promoted partial mitigation of the effects of salt stress on biomass production and leaf gas exchange, especially for C. argentea, but these positive responses decreased or disappeared with the intensification of salt stress and the increase in algae extract concentration.

Ammonification by kelp associated microbes increases ammonium availability.

Microbes contribute biologically available nitrogen to the ocean by fixing nitrogen gas from the atmosphere and by mineralizing organic nitrogen into bioavailable dissolved inorganic nitrogen (DIN). Although the large concentration of plants and algae in marine coastal environments provides ample habitat and reliable resources for microbial communities, the role of the microbiome in host-microbe nitrogen cycling remains poorly understood. We tested whether ammonification by epiphytic microbes increased water column ammonium and improved host access to nitrogen resources by converting organic nitrogen into inorganic nitrogen that is available for assimilation by hosts. When bull kelp (Nereocystis luetkeana) in the northeast Pacific was incubated with 15N labelled amino acid tracers, there was accumulation of 15N in kelp tissue, as well as accumulation of 15NH4 in seawater, all consistent with the conversion of dissolved organic nitrogen to ammonium. Metagenomic analysis of surface microbes from two populations of Nereocystis indicated relative similarity in the percentage of genes related to ammonification between the two locations, though the stressed kelp population that had lower tissue nitrogen and a sparser microbiome had greater ammonification rates. Microbial communities on coastal macrophytes may contribute to the nitrogen requirements of their hosts through metabolisms that make ammonium available.

Anisotropic Green Tide Patch Information Extraction Based on Deformable Convolution

Green tides are marine disasters caused by the explosive proliferation or high concentration of certain large algae in seawater, which causes discoloration of the water body. Accurate monitoring of its distribution area is highly important for early warning and the protection of marine ecology. However, existing deep learning methods have difficulty in effectively identifying green tides with anisotropic characteristics due to the complex and variable shapes of the patches and the wide range of scales. To address this issue, this paper presents an anisotropic green tide patch extraction network (AGE-Net) based on deformable convolution. The main structure of AGE-Net consists of stacked anisotropic feature extraction (AFEB) modules. Each AFEB module contains two branches for extracting green tide patches. The first branch consists of multiple connected dense blocks. The second branch introduces a deformable convolution module and a depth residual module based on a multiresolution feature extraction network for extracting anisotropic features of green tide patches. Finally, an irregular green tide patch feature enhancement module is used to fuse the high-level semantic features extracted from the two branches. To verify the effectiveness of the AGE-Net model, experiments were conducted on the MODIS Green Tide dataset. The results show that AGE-Net has better recognition performance, with F1-scores and IoUs reaching 0.8317 and 71.19% on multi-view test images, outperforming other comparison methods.

Effect of Spirulina platensis on probiotic, nutritional, and quality properties of yogurt

The present work was carried out to investigate the changes in the microbiological, physicochemical, textural sensory properties, and antioxidant profile of probiotic yogurt enriched with different concentrations (0, 0.5, 0.75, and 1%) of Spirulina platensis. Results indicated that when the amount of S. platensis was increased, there was a corresponding increase in water retention ability. This could have been attributed to a significant increase in fibre content (p < 0.05). The ratio of the soluble/insoluble dietary fibre of the yogurt samples depended on the concentration of algae. Towards the end of storage, there was a decrease in pH which resulted from the combined effect of the starter culture and probiotics working together. The amounts of Lactobacillus acidophilus and Bifidobacterium animalis increased in groups with S. platensis throughout storage, which is essential for a product to possess probiotic properties. In the sensory evaluation, group D which contained 1% (w/v) Spirulina was ranked as the most preferred. Additionally, this group exhibited the highest DPPH activity. The addition of Spirulina to yogurt had a significant impact on its quality characteristics, and exhibited potent prebiotic properties.

Algae development in rivers with artificially constructed weirs: Dominant influence of discharge over temperature

Algal blooms contribute to water quality degradation, unpleasant odors, taste issues, and the presence of harmful substances in artificially constructed weirs. Mitigating these adverse effects through effective algal bloom management requires identifying the contributing factors and predicting algal concentrations. This study focused on the upstream region of the Seungchon Weir in Korea, which is characterized by elevated levels of total nitrogen and phosphorus due to a significant influx of water from a sewage treatment plant. We employed four distinct machine learning models to predict chlorophyll-a (Chl-a) concentrations and identified the influential variables linked to local algal bloom events. The gradient boosting model enabled an in-depth exploration of the intricate relationships between algal occurrence and water quality parameters, enabling accurate identification of the causal factors. The models identified the discharge flow rate (D-Flow) and water temperature as the primary determinants of Chl-a levels, with feature importance values of 0.236 and 0.212, respectively. Enhanced model precision was achieved by utilizing daily average D-Flow values, with model accuracy and significance of the D-Flow amplifying as the temporal span of daily averaging increased. Elevated Chl-a concentrations correlated with diminished D-Flow and temperature, highlighting the pivotal role of D-Flow in regulating Chl-a concentration. This trend can be attributed to the constrained discharge of the Seungchon Weir during winter. Calculating the requisite D-Flow to maintain a desirable Chl-a concentration of up to 20 mg/m3 across varying temperatures revealed an escalating demand for D-Flow with rising temperatures. Specific D-Flow ranges, corresponding to each season and temperature condition, were identified as particularly influential on Chl-a concentration. Thus, optimizing Chl-a reduction can be achieved by strategically increasing D-Flow within these specified ranges for each season and temperature variation. This study highlights the importance of maintaining sufficient D-Flow levels to mitigate algal proliferation within river systems featuring weirs.

Analysis of Algae and Bacteria Mixture in Removing Pollutants from Laundry Wastewater

Laundry detergents contain high nutrients, especially phosphate and nitrogen compounds. High concentrations of these nutrients can cause eutrophication to the water bodies and are toxic to aquatic organisms. Thus, this study aims to identify the characteristics of laundry wastewater and to enhance the treatment for the pollutants using algae and bacteria mixture. Moreover, the removal efficiency for this pollutant has been determined after the batch experiment. The characteristics of laundry wastewater were evaluated using in-situ and laboratory analysis. The in-situ testing included pH, temperature, and dissolved oxygen (DO) parameters. Laboratory experiments consist of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonia-nitrogen, nitrite-nitrogen, and nitrate-nitrogen. The results were recorded for the parameters before and after treatment. It can be revealed that the concentration of 2 g of algae had recorded 61% COD removal. For the concentration of 0.5 g algae, the highest percentage of removal recorded was 79.2% for ammonia-nitrogen. For total suspended solids (TSS), a maximum of 79% has been removed for a 0.5 g algae mixture. An average of 90% removal has been detected for 2 g algae and 1 g algae concentrations, respectively. Therefore, these algae and bacteria mixtures can be considered green technology to biodegrade the pollutants and enhance the quality of the laundry wastewater.

Design of compostable toughened PLA/PBAT blend with algae via reactive compatibilization: The effect of algae content on mechanical and thermal properties of bio‐composites

AbstractA binary blend of polylactic acid (PLA) and poly (butylene adipate‐co‐terephthalate) (PBAT), along with algae in their respective composites, were successfully produced using a melt extrusion process. The produced in‐house coupling agent was used to enhance interfacial adhesion and algae dispersion. The influence of algae content incorporated into the compatibilized binary blend was thoroughly investigated, focusing on the bio‐composites morphology, mechanical, and thermal properties. The addition of PLA‐g‐MA to the binary blend led to notable improvements in the storage modulus, mechanical strength, and thermal properties of the binary blend. Subsequently, the introduction of algae into the compatibilized binary blend further augmented the storage modulus, with an optimum algae concentration of 10 wt%. However, higher algae content led to decreased tensile strength, elongation at break, and impact resilience. The optimal balance of these properties was achieved at an optimal loading of 5–10 wt% of algae into the compatibilized binary blend. The thermal stability of the bio‐composites was notably impacted by algae concentration, with the 10 wt% algae bio‐composite exhibiting increased thermal stability. Increasing algae content correlated with decreased bio‐composite crystallinity. These findings underscore the potential of optimized biobased algae composites for achieving desired mechanical and thermal properties, contributing to the development of sustainable and eco‐friendly polymer bio‐composites.

Efficacy and mechanism of Microcystis aeruginosa removal by activated carbon fiber/nanoscale zero-valent iron/nickel foam cathodic electrochemical system

ABSTRACT Cyanobacterial outbreaks seriously affect drinking water safety. Therefore, developing effective algal removal technologies is urgently needed. The study aims to investigate the effects of pH, electrode distance, current density, and initial algal concentration on electrochemical algae collection. Consequently, we loaded nanoscale zero-valent iron (nZVI) on activated carbon fiber/nickel foam (ACF/Ni) to form an ACF/nZVI/Ni composite cathode using the liquid phase reduction method and used titanium-based platinum plating (Pt/Ti) as the anode to construct a novel Pt/Ti- ACF/nZVI/Ni electrochemical system. The results showed that on pH of 6.0, the electrode distance was 10 mm, the current density was 75 mA/cm2, and the initial algal concentration was OD680 = 0.100; the algal cell removal rate was 94.20% after electrolysis for 30 min. This paper provides an efficient and environmentally friendly electrochemical algal removal technology for protecting the safety of drinking water and dealing with cyanobacterial outbreaks.

Combined effect of algae and dust on snow spectral and broadband albedo

The optical properties of snow can be strongly modified by the presence of a variety of impurities including mineral dust and snow algae. We made use of measured concentration of snow algae and mineral dust to parameterize the BioSNICAR radiative transfer model. Surficial snow samples were gathered during a field campaign on 7th July 2020 at the Presena glacier (Rhaetian Alps). We collected 18 samples of surface snow containing different amount of snow algae and mineral dust. Through radiative transfer simulations we estimated an average broadband albedo reduction of 7.4 ± 6.1 % and 35.3 ± 7.4 % compared to clean snow, caused by snow algae and mineral dust presence, respectively. When we considered the combined effect of snow algae and dust, we estimated a broadband albedo reduction equal to 40.8 ± 8.4 %. We estimated an average instantaneous radiative forcing induced by snow algae, mineral dust and both impurities equals to 42.3 (± 36.1) W/m2, 203.7 (±45.5) W/m2, and 211.8 (±45.9) W/m2, respectively.Using BioSNICAR simulations, we also tested a series of narrowband spectral indices to determine the concentration of mineral dust and snow algae from multi- and hyper-spectral data. Results showed that most spectral indices used for snow algae mapping are correlated also with mineral dust concentration. We found that only an index correlates uniquely with snow algae: the scaled band integral at 680 nm. A new spectral index, namely the Green Blue Normalized Index, is therefore proposed to discriminate mineral dust from snow algae when both impurities are present. The high spectral resolution of current (e.g. PRISMA, EnMAP) and future (e.g. CHIME, SBG) hyperspectral satellite missions will be fundamental to decouple the effect of mineral dust and snow algae on the optical properties of snow. In fact, from those data it is possible to calculate all narrowband indices presented in this study.

Evaluation of antioxidant properties and cytotoxicity of brown algae (nizamuddinia zanardinii) in uterine (hela) and pancreatic cancer cell lines (paca-2).

Pancreatic cancer and cervical cancer are among the most common cancers. Brown algae have anti-inflammatory, anti-cancer, anti-fungal, antioxidant, and immune-boosting properties. This study investigated the antioxidant properties and the effect of brown algae extract on pancreatic and uterine cancer cells. In this study, Cervical (Hela) and pancreas (Paca-2) cancer cell lines were examined. The algae materials were extracted by sequential maceration method and amount of fucoxanthin content in the sample was determined by using High Performance Liquid Chromatography (HPLC) system. The cytotoxic effect of different concentrations of brown algae was measured by the MTT assay. All statistical calculations for comparing IC50 were analyzed using Graph Pad Prism software. the algal sample contained an average of 102.52 ± 0.12μg of fucoxanthin per 100g. IC50 for 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide free radical scavenging activity for methanolic extract was 2.02 and 11.98 ± 0.13 respectively. Brown algae in all fractions inhibited cell growth and survival. In Hela cell lines, the methanolic extract was the most effective inhibitor, while in Paca cell lines, hexane and methanolic extracts were particularly potent. The methanolic extract was more toxic than other fractions on Hela and Paca cell lines. This study highlights brown algae extracts strong anticancer effects on uterine and pancreatic cancer cells, suggesting its potential as a natural anticancer drug. Different fractions of the extract showed superior apoptotic and cytotoxic effects, with higher concentrations leading to increased apoptotic effects and reduced survival rates of cancer cells.

Feeding rates and carbon and nitrogen partitioning in crown-of-thorns sea star larvae (Acanthaster cf. solaris) during development

Crown-of-thorns sea star (CoTS; Acanthaster cf. solaris) outbreaks are a significant cause of coral decline. Enhanced food supply for the larvae via eutrophication is implicated as a cause of outbreaks, yet larval feeding ecology is poorly understood. In this study, feeding experiments were carried out at two algal food concentrations of 1000 cells mL−1 (~ 1.52 µg chl a L−1) and 3000 cells mL−1 (~ 4.56 µg chl a L−1) across six successive larval stages to investigate the effect of food concentration on filtration rate and ingestion rate for these stages. Filtration rate increased with larval stage and more than tripled from 127 ± 32 µL larva−1 h−1 (mean ± SE) of the youngest (2–3 dpf) larvae to 497 ± 109 µL larva−1 h−1 at late brachiolaria stage (9–10 dpf). Ingestion rate increased with food concentration and larval age, with advanced brachiolaria larvae consuming 313.5 ± 39.1 cells larva−1 h−1 in the higher algal food treatment. Organic carbon (C) and nitrogen (N) measured in larvae and their food indicated that the youngest feeding larvae ingested 13% their body carbon content daily, with that number almost doubling to 24% by advanced bipinnaria stage. The C/N ratio decreased sharply for brachiolaria larvae, reflecting developmental changes and greater dependence on exogenous nutrition. These results add to our understanding of the role food concentration plays in the growth and survivorship of CoTS larvae in the field.

Effect of catholyte on performance of photosynthetic microbial fuel cell for wastewater treatment and energy recovery

The performance of photosynthetic microbial fuel cell (PMFC) was assessed for wastewater treatment and energy recovery using two different catholytes; untreated domestic wastewater (UDW) and wetland treated wastewater (WTW). The performance was investigated under continuous light and 12/12 h light/dark cycle, employing Scenedesmus sp. as a biocatalyst. The results showed that PMFC with UDW as the catholyte outperformed the WTW under both types of illumination. Under continuous illumination, the PMFC with UDW achieved a maximum working voltage 33 % higher than that of WTW. The rates of chemical oxygen demand (COD) and nutrient removal in the cathode chamber were significantly higher for PMFC with UDW catholyte. Maximum dissolved oxygen (DO) reached 10 and 8.4 mg/L for UDW and WTW, respectively, with corresponding algae concentrations of 5165 and 3130 mg/L. Under the light/dark cycle, both the working voltage and DO concentration exhibited a diurnal pattern. The maximum algal growth, DO and power output in UDW were higher than WTW under 12/12 h light-dark cycle; however, these values remained lower compared to continuous illumination. These results demonstrate the feasibility of PMFC for both untreated and secondary treated domestic wastewater as catholytes.

Removal of arsenic from realgar-containing water by Spirogyra: Implications for in situ remediation of arsenic in the mine area

Realgar (As4S4) is an arsenic sulfide mineral, occurring widely in metamorphic-hydrothermal deposits, reductive soil and wetland sediments. The dissolution of realgar releases arsenic, which is toxic to the environment, so the process that causes this problem deserves attention. Native Spirogyra sp. was collected and cultured from a realgar mine area and used to create varying concentrations of algae to investigate the dissolution of realgar using a photosynthesis microcosm. Separately the dynamic adsorption and uptake processes of arsenic (III) and arsenic (V) were investigated. The dissolution rate equation of realgar under Spirogyra sp. is R = 10−6.36[DO]1.84[H+]−0.60. The diurnal growth of Spirogyra sp. increases arsenic release by as much as three times than the control group and significantly changes aqueous arsenic species by varying the dissolved oxygen and pH. The amounts of arsenic (III) and arsenic (V) removed from living Spirogyra sp. were 14605 μg⋅g−1⋅h−1 and 6511 μg⋅g−1⋅h−1. Increasing amounts of –COOH, CO and carbonyl groups from the live Spirogyra sp. also promoted the dissolution of realgar. The results suggest that filament Spirogyra sp. would be an effective method for in situ acceleration of arsenic sulfide dissolution and remediation of arsenic pollution in environments such as paddy soil.

A multifunctional cellulose- and starch-based composite hydrogel with iron-modified biochar particles for enhancing microalgae growth

A multifunctional polysaccharide-based hydrogel was studied as an additive for enhancing microalgae growth. The hydrogel was fabricated by physically and chemically crosslinking renewable ingredients of carboxymethyl cellulose (CMC), arrowroot starch, and activated biochar modified with iron using a bio-crosslinker of oxidized sucrose and a plasticizer of glycerol. The optimum formula for the hydrogel with a high swelling ratio, BET surface area, and electrical conductivity was found to include 1 g starch, 3 g CMC, 1.5 g biochar, 15 mL oxidized sucrose, and 1.5 mL glycerol in 200 mL deionized water. The algal yield and cell concentration after 14 days of growth in a Bold basal medium with an optimum concentration of 2.5 g hydrogel/L increased by 65.7 % and 92.2 %, respectively, compared to those of the control without the hydrogel. However, if the hydrogel concentration in the culture increased to 12.5 g/L, the algal yield was decreased by 67.8 % compared to the control due to oxidative injury. The hydrogel additive could significantly increase the nitrogen but decrease the carbon, hydrogen, and sulfur contents of the microalgae. The algal yield with 2.5 g/L hydrogel additive improved by 13.9 % compared to the algal yield with the same amounts of individual non–crosslinked hydrogel ingredients.

The microalgae’s ability to accumulate selected trace elements studied by ICP-MS/MS and chemometric methods

BackgroundMicroalgae can be used in different branches of industry, including cosmetology, pharmaceutics and the food industry, information on their ability to accumulate different elements becomes more important. The microalgae biomass grown in the media enriched in elements can increase the accumulation of different ions and give a possibility to control the contents of the various elements. MethodsThe aim of the study was to determine the total content of metals in microalgae by tandem mass spectrometry with inductively coupled plasma (ICP-MS/MS) and analysis of the contents of particular metals as a function of the type of microalgae and conditions of cultivation. As the adverse effects of metals on the health of humans and animals have been well-documented and the use of microalgae has increased, the knowledge of metal contents in them is of particular importance in control of their quality. ResultsAnalysis of results permitted distinction of three main groups of microalgae with similar total metal content levels. Moreover, the results revealed the ways of stimulating more significant accumulation of selected elements (for example, Se concentration in control algae 0.279 µg g−1, in the algae cultivated in enriched medium – 219.7 µg g−1). They indicated the possible correlations between the accumulation of different ions. The result obtained shows a significant effect of metal accumulation and has a considerable impact on the differentiation of Arthrospira platensis grown in the medium enriched in different elements (selenium, zinc, chromium) (p ≤ 0.05). ConclusionsParticular impact on the content of selected elements had the conditions of cultivation (type of support) and the microalgae species. Although the one species as the most significant source of selected elements cannot be indicated, it is possible to control the accumulation by the composition of the medium.

Algal organic matter induced photodegradation of tinidazole

Antibiotic pollution has become one of the most emerging problems of the modern era. Tinidazole (TDZ) is one the most important nitroimidazole derivative drugs whose use has tremendously increased in the last few years. The proposed research work provides a good alternative cost-effective method for wastewater treatment. In the present investigation, algae were used as a photosensitizer in the treatment of the wastewater that was contaminated with antibiotic residue. The proposed research also provides the probable mechanism involved in the photodegradation of tinidazole. The different factors like concentration and pH of the test solution which play a key role in the photodegradation of drug molecules are also discussed in the present investigation. The result of this study established that the maximum degradation of drug molecules was observed at the algal concentration of 1.6 × 108 Cell/L and approximately 58% of drug molecules were degraded. This study also established that in an acidic medium ie at pH 5 the degradation occurs more efficiently. Results of the current study indicated that the use of algae-induced photodegradation of drug residue became one of the most promising routes for wastewater treatment. The results of the present study provide a new way to treat wastewater contaminated with antibiotics residue.

Removal of Algae and Algal Toxins from a Drinking Water Source Using a Two-Stage Polymeric Ultrafiltration Membrane Process.

The release of algal toxins in algae-containing water sources poses a serious threat to drinking water safety and human health. The conventional water treatment processes of water plants have a limited ability to remove algae and algal toxins, especially algal toxins with a molecular weight (MW) of less than 1000 Da. To eliminate algal pollution from a water source, a two-stage ultrafiltration (UF) process with a large polysulfone hollow fiber membrane with a MW cut-off of 200 kDa and a small aromatic polyamide roll membrane with a MW cut-off of 1 kDa were applied after a traditional sand filter in a water treatment plant. UF operation conditions, including the operating time, pressure, and membrane flux, were investigated. With an operating pressure of 0.05-0.08 MPa, the polysulfone hollow fiber membrane removed algae effectively, as the influent algal cell concentration ranged from 1-30 cells/mL but exhibited a limited removal of algal toxins. With an operating pressure of 0.3-0.4 MPa, the elimination of microcystins (MCs) reached 96.3% with the aromatic polyamide roll membrane. The operating pressure, membrane flux, and operating time were selected as the experimental factors, and the effects on the UF efficiency to remove algal toxins and biodegradable dissolved organic carbon were investigated by the response surface methodology. The model showed that the order of influence on the membrane operating efficiency was operating pressure > membrane flux > running time. The optimal UF operating conditions were an operating pressure of 0.3 MPa, a membrane flux of 17.5 L/(m2·h), and a running time of 80 min.

Evidence of strobilurin fungicides and their metabolites in Dongjiang River ecosystem, southern China: Bioaccumulation and ecological risks

Despite the widespread application of strobilurin fungicides (SFs) in agriculture, little is known about their distribution and bioaccumulation in aquatic ecosystems. In this study, the concentrations of 12 SFs and two of their metabolites were determined in abiotic (water and sediment; n = 83) and biotic (plant, algae, zooplankton, and fish; n = 123) samples collected from a subtropical freshwater ecosystem, namely, Dongjiang River wetland, in southern China. Among the 12 SFs measured, azoxystrobin (AZ) was the major fungicide found in surface water (median: 2.20 ng/L) and sediment (0.064 ng/g dry wt.). Azoxystrobin acid (AZ-acid), a metabolite of AZ, was the major analyte in the plant samples and had a median concentration at 0.36 ng/g dry wt. In algae and zooplankton, (Z)-metominostrobin was the predominant fungicide and had median concentrations of 3.52 and 5.55 ng/g dry wt., respectively. In fish muscle, dimoxystrobin (DIMO) was the major SF and had a median concentration of 0.47 ng/g dry wt. The bioconcentration factor (BCF) values of AZ-acid, trifloxystrobin (TFS), and pyraclostrobin (PYR) in algae and zooplankton and AZ-acid, PYR, TFS, TFS-acid, picoxystrobin, and DIMO in fish muscle exceeded 1000 L/kg (algae, zooplankton, and fish concentrations were expressed on a dry weight basis), suggesting that these fungicides can accumulate in biota. A positive association between log BCFs of SFs in fish and logKow of SFs and a negative correlation between log BCFs and the log solubility index were observed. Additionally, the risk quotient (RQ) was calculated to evaluate the potential ecotoxicological risk of SFs to different aquatic organisms (algae, zooplankton, and fish). The PYR and DIMO concentrations at 19 sampling sites had RQ values >0.1, indicating moderate ecotoxicological risks to aquatic organisms. This study is the first to document the widespread occurrence of SFs and their metabolites in aquatic ecosystems and to elucidate the bioaccumulation potential of SFs in aquatic organisms.