Anabaena Flos-aquae Research Articles

A Chronic Aquatic Hazard Assessment for the Perfume Raw Material Octahydro-tetramethyl-naphthalenyl-ethanone.

Octahydro-tetramethyl-naphthalenyl-ethanone (OTNE) is a high-production volume fragrance material used in various down-the-drain consumer products. To assess aquatic risk, the Research Institute for Fragrance Materials (RIFM) uses a tiered data-driven framework to determine a risk characterization ratio, where the ratio of the predicted-environmental concentration to the predicted-no-effect concentration (PNEC) of <1 indicates an acceptable level of risk. Owing to its high production volume and the conservative nature of the RIFM framework, RIFM identified the need to utilize a species sensitivity distribution (SSD) approach to reduce the PNEC uncertainty for OTNE. Adding to the existing Daphnia magna, Danio rerio, and Desmodesmus subspicatus chronic studies, eight new chronic toxicity studies were conducted on the following species: Navicula pelliculosa, Chironomus riparius, Lemna gibba, Ceriodaphnia dubia, Hyalella azteca, Pimephales promelas, Anabaena flos-aquae, and Daphnia pulex. All toxicity data were summarized as chronic 10% effect concentration estimates using the most sensitive biological response. Daphnia magna was the most sensitive (0.032 mg/L), and D. subspicatus was the least sensitive (>2.6 mg/L, the OTNE solubility limit). The 5th percentile hazardous concentration (HC5) derived from the cumulative probability distribution of the chronic toxicity values for the 11 species was determined to be 0.0498 mg/L (95% confidence interval 0.0097-0.1159 mg/L). A series of "leave-one-out" and "add-one-in" simulations indicated the SSD was stable and robust. Add-one-in simulations determined that the probability of finding a species sensitive enough to lower the HC5 two- or threefold was 1/504 and 1/15,300, respectively. Given the high statistical confidence in this robust SSD, an additional application factor protection is likely not necessary. Nevertheless, to further ensure the protection of the environment, an application factor of 2 to the HC5, resulting in a PNEC of 0.0249 mg/L, is recommended. When combined with environmental exposure information, the overall hazard assessment is suitable for a probabilistic environmental risk assessment. Environ Toxicol Chem 2024;43:1378-1389. © 2024 SETAC.

Investigate Freshwater Algae Extract's Efficacy in Treating Diabetes Ulcers and Its Anti-Staphylococcal Properties.

Infection of diabetic foot ulcer is very common and leads in 20% of cases to amputation. Antibiotic-resistant Staphylococcus aureus is the main cause of severe infection. Antibiotic resistance is a major challenge to the global health system. This work aimed to investigate the antibacterial efficacy of some algae extracts against Staphylococcus aureus isolated from diabetic foot ulcers. freshwater river samples were collected to isolate the algae, and PCR was used for identification. The ethanol, water, and ethyl acetate extract of these algae were prepared and analyzed using high-performance liquid chromatography-mass spectrometry to determine the key components that have antibacterial properties. The antibacterial activity of these extracts against S. aureus was determined by broth dilution and well diffusion methods. Chlorella vulgaris and Anabaena flos-aquae were isolated from freshwater river and identified by PCR. Anabaena flos-aquae has a greater antibacterial efficacy against Staphylococcus aureus in comparison to Chlorella vulgaris, and the ethanolic extract demonstrated superior outcomes compared to the aqueous and ethyl acetate extracts. The MS spectrum of both algae had a very similar pattern, but the frequency of detected peaks was different. Ethanolic extract of A. flos-aquae and Chlorella vulgaris can be suggested to treat and control diabetic foot ulcer infection caused by S. aureus. Further studies are required to explore the full potential of these algae safely and extensively.

Fluorogenic “on-off” nanosensor based on dual-quenching effect for imaging intracellular metabolite of various microalgae

Sensing intracellular compounds such as ATP in living microalgal cells is of great importance in diverse fields. To achieve this, nanosensing platform composed of graphene oxide (GO) and ATP aptamer (APT) was applied to diverse microalgal cells (Chlamydomonas reinhardtii, Chlorella vulgaris, Anabaena flos-aquae, and Ochromonas danica). The nanosized GO was characterized with atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The nanosensing platform (GO-APT) was prepared by attaching fluorophore-labeled APT to GO. GO-APT was applicable to only cell wall-deficient species (O. danica and mutant strains of C. reinhardtii) and the existence of flagella did not affect the uptake of the GO-APT by the cells. These results indicate that the cell wall is the primary barrier of GO-APT internalization for sensing application. To reduce the background fluorescence signal elicited by nonspecific displacement of the fluorophore-labeled probe, APT was modified as molecular beacon (MB) type (APTMB). Owing to the double quenching effect (by GO and quencher-labeled complementary sequence), the background signal significantly reduced. Cytotoxicity of GO-APTMB on the microalgal species was also tested. The application of GO-APTMB had no effect on the growth of microalgae. Given that diverse aptamer sequences had been screened, the sensing platform is not limited for detecting ATP only, but also can be applied to other metabolite imaging by simply changing the aptamer sequences. Our research will contribute to broadening the application of GO and aptamer beacon complex for intracellular metabolite imaging and detecting.

FEATURES OF THE SEASONAL DYNAMICS OF PHYTOPLANKTON AT THE LEFT BANK OF THE VOLGA REACH OF KUIBYSHEV RESERVOIR (REPUBLIC OF TATARSTAN, RF)

Biocenosis of shallow waters of lowland reservoirs lives in various habitat regimes and are characterized by a special structural and functional organization. To fully elucidate these features, it is necessary to research several hydrologically different areas simultaneously. This study was conducted to evaluate the effect of seasonal dynamics on the phytoplankton community of the Volga reach of the Kuibyshev reservoir near the left bank. During the observation period, 112 taxa were found in the phytoplankton of the studied site. The greatest number of taxa were identified from the groups of diatoms (44%) and green (28%) algae. Some other less diverse groups are blue-green (16%), Chrysophyta (6%), cryptophyta and dinophyta (3%), etc. Cosmopolitan and planktonic species of algae prevail in terms of environmentally-geographical characteristics. Concerning halobility, most species are indifferent, and in terms of pH, the most common are the indifferent alkaliphile + alkalibiontic algae. The total abundance and biomass of planktonic algae range 8.49-1661.09 mln.cl./l and 10.28 -114.11 mg/l respectively. Some important dominant species are blue-green algae Microcystis aeruginosa f. flos-aquae, Aphanizomenon flos-aquae, Anabaena flos-aquae, Anabaena scheremetievi, Aulacoseira italica, Navicula sp., Carteria globosa, Chlamydomonas sp., Pandorina morum, Scenedesmus guadricauda. Seasonal dynamics of phytoplankton have two peaks of abundance and biomass which are at the end of the first decade of July and in the second decade of August. Both maxima are due to the massive development of blue-green algae, which causes water to “bloom”. The phytoplankton of the investigated section of the Kuibyshev reservoir is dominated by β-mesosaprobic organisms.

Effective biosorption of uranium from aqueous solution by cyanobacterium Anabaena flos-aquae.

Anabaena flos-aquae, a typical species of cyanobacterial bloom, was employed as a useful biosorbent for uranium removal. Batch experiments were conducted to examine the effects of different parameters on the uranium uptake amount of Anabaena flos-aquae. The maximum adsorption capacity of 196.4mg/g was obtained under the optimized experimental conditions. The calculations of kinetic and thermodynamic results proved the adsorption process was endothermic, chemisorption, and spontaneous. The adsorption of uranium onto Anabaena flos-aquae was better defined by the Langmuir model, which indicated the process was a monolayer sorption. In addition, the characterization of the biosorbent before and after uranium sorption implied that the dominant functional groups participated in the uranium adsorption process were hydroxyl, amino, and carboxyl. In conclusion, the environmentally friendly and biocompatible characteristics of Anabaena flos-aquae suggest that it can be a promising biosorbent for uranium removal.

Effect of limitation of iron and manganese on microalgae growth in fresh water.

Eutrophication is caused by the rapid growth of microalgae. Iron and manganese are important micronutrients for microalgae growth. However, the effect of the limitation of iron and manganese on microalgae growth in fresh water has not been well understood. In this study, natural mixed algae, Anabaena flosaquae and Scenedesmus quadricanda, were cultivated under different quotas of iron and manganese to reveal the effect of the limitation of iron and manganese on the growth of microalgae in fresh water. The results showed that the growth rate of algae is influenced more by iron than by manganese. However, the effect of manganese cannot be overlooked: when the initial manganese quota was replete, i.e. 0.6-0.8 mg l-1, manganese was able to relieve the effect of iron limitation on microalgae growth in fresh water. We further found that the microalgae showed an uptake preference for iron over manganese. Iron had a competitive effect on manganese uptake, while manganese had less impact on iron uptake by microalgae. The information obtained in the current study is useful for the provision of water quality warnings and for the control of microalgae bloom in fresh water.

Influence of light availability on the specific density, size and sinking loss of Anabaena flos-aquae and Scenedesmus obliquus

Harmful algal blooms in eutrophic waters pose a serious threat to freshwater ecosystems and human health. In-situ light availability control is one of the most commonly used technologies to suppress algae in lakes and reservoirs. To develop a better understanding of the effects of light on algal growth, specific density, colony size and sinking loss, Anabaena flos-aquae (cyanobacteria) and Scenedesmus obliquus (green algae) were evaluated in varying light scenarios. The results showed that the specific density and colony size of these two species varied during growth, and there were obvious differences among the light scenarios. At the end of exponential phase, S. obliquus incubated under light-limited condition maintained a higher specific density and formed larger aggregates, whereas A. flos-aquae formed a longer filament length. Both species exhibited higher sinking loss rates with lower light availability. These results implied that the sinking loss rate was not always constant but should be considered as a variable response to the change of light availability, and in-situ light availability control might result in a significant increase of the sinking loss of algae due to the change of size and specific density, thereby further affecting the algal biomass in the water column.

Ecological Status of Opa Reservoir, Obafemi Awolowo University, Ile Ife, based on the Abundance and Diversity of its Planktonic Flora

A study investigating the spatial and temporal distribution, composition and abundance of plankton in Opa reservoir, Obafemi Awolowo University, Ile-Ife, Southwest Nigeria, was conducted over a period of an annual cycle. The study was undertaken with a view of providing a more recent catalogue of planktonic flora and possibly an update of the reservoir’s trophic status. Quantitative net planktons were collected monthly from both the surface and bottom levels at three sampling stations established at the dam site (lacustrine), mid-lake (transition) and upper inflow (riverine) parts of the reservoir. The divisions recorded were Bacillariophyta &gt; Cyanophyta &gt; Chlorophyta &gt; Euglenophyta &gt; Myzozoa &gt; Ochrophyta = Charophyta &gt; Cryptophyta in order of abundance. Vertically, the highest occurrence of species was recorded at the lacustrine bottom station (71 species), while the least occurrence was observed in the transition bottom station (51 species). A total of sixteen plankton species showed significant seasonal variation in abundance during this study period, while only seven species had significant spatial variation (p ≤ 0.05). Higher abundance was observed during the rainy season (170,797,350 Org/m3 from seventy-two species) than dry season (5,138,400 Org/m3 from forty-nine species). Notable bio-indicator plankton species recorded were Anabaena circinalis, Anabaena flos-aquae, Microcystis sp., Aphanocapsa litoralis and Microcystis aeruginosa. Some other pollution indicator species recorded were Synedra ulna, Oscillatoria agardhii, Phacus sp., Surirella sp., Closterium sp., Aphanocapsa sp. and Euglena sp. Hence, Opa reservoir is very rich in Bacillariophyta (diatoms), followed by Cyanophyta (blue-green) and Chlorophyta (green algae), which are known to characterize eutrophic lakes.

Arsenic uptake, transformation, and release by three freshwater algae under conditions with and without growth stress

This study was carried out using indoor controlled experiments to study the arsenic (As) uptake, biotransformation, and release behaviors of freshwater algae under growth stress. Three freshwater algae, Microcystis aeruginosa, Anabaena flosaquae, and Chlorella sp., were chosen. Two types of inhibitors, e.g., Cu2+ and isothiazolinone, were employed to inhibit the growth of the algae. The algae were cultivated to a logarithmic stage in growth media containing 0.1mg/L P; then, 0.8mg/L As in the form of arsenate (iAsV) was added, while both inhibitors were simultaneously added at dosages of 0.1 and 0.3mg/L, with no addition of inhibitors in the control. After 2days of exposure, the average growth rate (μ2d) was measured to represent the growth rates of the algae cells; the extra- and intracellular As concentrations in various forms, i.e., arsenate, arsenite (iAsIII), monomethyl arsenic (MMA), and dimethyl arsenic (DMA), were also measured. Without inhibitors, the average growth rate followed the order of M. aeruginosa, Chlorella sp., and A. flosaquae, with the growth rate of M. aeruginosa significantly higher than that of the other two algae. However, when Cu2+ was added as an external inhibitor, the order of the average growth rate for the three algae became partially reversed, suggesting differentiation of the algae in response to the inhibitor. This differentiation can be seen by the reduction in the average growth rate of M. aeruginosa, which was as high as 1730% at the 0.3-mg/L Cu2+ dosage when compared with the control, while for the other two algae, much fewer changes were seen. The great reduction in M. aeruginosa growth rate was accompanied by increases in extracellular iAsV and iAsIII and intracellular iAsV concentrations in the algae, indicating that As transformation is related to the growth of this algae. Much fewer or neglectable changes in growth were observed that were consistent with the few changes in the extra- and intracellular As speciation for the other two algae with Cu2+ inhibition and all the three algae with isothiazolinone inhibition, corroborating the above hypothesis again. All the algae tested in this study demonstrated great abilities for As transformation and release, as seen by the much higher rates of 86.11-99.98% and 81.11-99.89% for transformation and release when compared to the control, respectively. When inhibitors were added, the transformation and release values of only A. flosaquae decreased remarkably down to 72.37-86.79% and 64.67-85.24%, respectively, while no changes were seen for these values in the other two algae, indicating that growth stress did not affect the As transformation and release of the other algae. The biological productivity of As by the three algae followed the order of M. aeruginosa, Chlorella sp., and A. flosaquae, which was generally consistent with the As transformation and release in conditions with and without inhibitors, suggesting that the As behavior in the algae that was related to growth stress largely differed among algae species.

Turbulent mixing mediates the photosynthetic activities and biochemical composition of Anabaena: implications for bioengineering

Cyanobacteria exhibit a variety of adaptive strategies that allow them to thrive in ever-changing aquatic environments. Here, successive steady states of continuous cultures were used to investigate the effects of quantified turbulence on the biochemical compounds and physiological processes of Anabaena flos-aquae in a photobioreactor under different dilution rates. A rapid increase in cell density was clearly observed following an increase in the turbulent dissipation rate at all growth rates of A. flos-aquae. The photosynthetic response to irradiance curves showed that the turbulence-treated strains exhibited lower photosynthetic oxygen evolution and saturating irradiance as well as higher respiration in rapidly growing young cells, indicating that they might not be very adaptable to high turbulent dissipation rates. Additionally, there was an increase in the protein levels of A. flos-aquae with increasing turbulence at all growth rates, whereas carbohydrate formation and lipid accumulation demonstrated the opposite trends. At a high growth rate, the level of carbohydrates decreased whereas that of lipids increased, which was interpreted as reflecting an adaptation to the turbulent environment. These findings suggest that turbulence sensitivity is shear regimen- and growth rate-dependent in A. flos-aquae. The high respiration capacity, low saturating irradiance, and conversion of carbohydrates to lipids represent effective measures for revealing the adaptive strategies of rapidly growing young cells under hydrodynamic regimes. The results regarding optimum lipid accumulation with specific growth traits have important implications for the design of cultivation methods of cyanobacteria resource utilization with respect to regulating turbulence.

Progress of research on the toxicology of antibiotic pollution in aquatic organisms

Antibiotics are widely used to improve human and animal health and treat infections. Antibiotics are often used in livestock farms and fisheries to prevent diseases and promote growth. Recently, there has been increasing interest in the presence of antibiotics in aquatic environments. Low levels of antibiotic components are frequently detected in surface water, seawater, groundwater, and even drinking water. Antibiotics are consistently and continually discharged into the natural environment as parent molecules or metabolites, which are usually soluble and bioactive, and this results in a pseudo and persistent pollution. The effects of environmental antibiotic toxicity on non-target organisms, especially aquatic organisms, have become an increasing concern. Although antibiotics have been detected worldwide, their ecological and developmental effects have been poorly investigated, particularly in non-target organisms. This review describes the toxicity and underlying mechanism of antibiotic contamination in aquatic organisms, including the effects on vertebrate development. A considerable number of antibiotic effects on aquatic organisms have been investigated using acute toxicity assays, but only very little is known about the long-term effects. Aquatic photosynthetic autotrophs, such as Pseudokirchneriella subcapitata, Anabaena flos-aquae, and Lemna minor, were previously used for antibiotic toxicity tests because of low cost, simple operation, and high sensitivity. Certain antibiotics show a different degree of potency in algal toxicity tests on the basis of different test algae. Antibiotics inhibit protein synthesis, chloroplast development, and photosynthesis, ultimately leading to growth inhibition; some organisms exhibit growth stimulation at certain antibiotic concentrations. Daphnia magna and other aquatic invertebrates have also been used for checking the toxicity priority of antibiotics. When investigating the acute effect of antibiotics (e.g., growth inhibition), concentrations in standard laboratory organisms are usually about two or three orders of magnitude higher than the maximal concentrations in the aquatic environment, resulting in the underestimation of antibiotic hazards. Vertebrate organisms show a promising potential for chronic toxicity and potentially subtle effects of antibiotics, particularly on biochemical processes and molecular targets. The adverse developmental effects of macrolides, tetracyclines, sulfonamides, quinolones, and other antibiotic groups have been evaluated in aquatic vertebrates such as Danio rerio and Xenopus tropicalis. In acute toxicity tests, low levels of antibiotics have systematic teratogenic effects on fish. The effects of antibiotics on oxidative stress enzymes and cytochrome P450 have been investigated. Cytotoxicity, neurotoxicity, and genotoxicity have been observed for certain antibiotic amounts. However, there are no firm conclusions regarding the chronic toxicity of antibiotics at environmentally relevant levels because of the lack of long-term exposure studies. Herein, future perspectives and challenges of antibiotic toxicology were discussed. Researchers should pay more attention to the following points: chronic toxicity and potentially subtle effects of environmentally relevant antibiotics on vertebrates; effects of toxicity on biochemical processes and mode of action; combined toxicity of antibiotics and other antibiotics, metabolites, and heavy metals; and environmental factors such as temperature and pH.

Occurrence of enrofloxacin in overflows from animal lot and residential sewage lagoons and a receiving-stream

Enrofloxacin (ENRO), a fluoroquinolone, was quantified in overflows from an animal lot and residential sewage lagoons and in a receiving-stream (Gans Creek). The concentrations of ENRO in samples was determined by high-performance liquid chromatography − tandem mass spectrometry. In total, ninety samples including duplicates were analyzed during several monthly sampling campaigns. The samples collected represented the residential sewage lagoon overflow (RLO), animal lot lagoon overflow (ALLO), the combined overflows (RLO and ALLO), and Gans Creek (upstream, midstream and downstream positions). The frequency of detection of ENRO was 90% for RLO and 100% for both ALLO and Gans Creek. The highest concentration of ENRO (0.44 μg/L) was found in ALLO sample collected during high precipitation. ENRO levels found in RLO samples ranged from < LOQ to 259 ng/L and the highest value observed also coincided with high flow. The levels of ENRO found in Gans Creek ranged from 17–216 ng/L. A preliminary ecotoxicological assessment was conducted through calculation of the risk quotients (RQs) for organisms based on the ratio of the measured environmental concentrations in this study to the predicted-no-effect-concentrations (acute and chronic effect) data. From the RQs, high risks were observed for Microcystis aeruginosa (cyanobacteria; RQ = 4.4); Anabaena flosaquae (cyanobacteria; RQ = 1.3); and Lemna minor (aquatic vascular plant; RQ = 2.0). The long-term effects of mixtures of PHCs on Gans Creek watershed are probable.

Computational embryology as an integrative platform for predictive DART

Enrofloxacin (ENRO), a fluoroquinolone, was quantified in overflows from an animal lot and residential sewage lagoons and in a receiving-stream (Gans Creek). The concentrations of ENRO in samples was determined by high-performance liquid chromatography − tandem mass spectrometry. In total, ninety samples including duplicates were analyzed during several monthly sampling campaigns. The samples collected represented the residential sewage lagoon overflow (RLO), animal lot lagoon overflow (ALLO), the combined overflows (RLO and ALLO), and Gans Creek (upstream, midstream and downstream positions). The frequency of detection of ENRO was 90% for RLO and 100% for both ALLO and Gans Creek. The highest concentration of ENRO (0.44 μg/L) was found in ALLO sample collected during high precipitation. ENRO levels found in RLO samples ranged from < LOQ to 259 ng/L and the highest value observed also coincided with high flow. The levels of ENRO found in Gans Creek ranged from 17–216 ng/L. A preliminary ecotoxicological assessment was conducted through calculation of the risk quotients (RQs) for organisms based on the ratio of the measured environmental concentrations in this study to the predicted-no-effect-concentrations (acute and chronic effect) data. From the RQs, high risks were observed for Microcystis aeruginosa (cyanobacteria; RQ = 4.4); Anabaena flosaquae (cyanobacteria; RQ = 1.3); and Lemna minor (aquatic vascular plant; RQ = 2.0). The long-term effects of mixtures of PHCs on Gans Creek watershed are probable.

New thermodynamic entropy calculation based approach towards quantifying the impact of eutrophication on water environment

Although the eutrophication phenomenon has been studied for a long time, there are still no quantifiable parameters available for a comprehensive assessment of its impacts on the water environment. As contamination alters the thermodynamic equilibrium of a water system to a state of imbalance, a novel method was proposed, in this study, for its quantitative evaluation. Based on thermodynamic analyses of the algal growth process, the proposed method targeted, both theoretically and experimentally, the typical algae species encountered in the water environment. By calculating the molar enthalpy of algae biomass production, the heat energy dissipated in the photosynthetic process was firstly evaluated. The associated entropy production (ΔS) in the aquatic system could be then obtained. For six algae strains of distinct molecular formulae, the heat energy consumed for the production of a unit algal biomass was found to proportionate to the mass of nitrogen (N) or phosphorus (P) uptake through photosynthesis. A proportionality relationship between ΔS and the algal biomass with a coefficient circa 44kJ/g was obtained. By the principle of energy conservation, the heat energy consumed in the process of algae biomass production is stored in the algal biomass. Furthermore, by measuring the heat of combustion of mature algae of Microcystis flos-aquae, Anabaena flos-aquae, and Chlorella vulgaris, the proportionality relationships between the heat energy and the N and P contents were validated experimentally at 90% and 85% confidence levels, respectively. As the discharge of excess N and P from domestic wastewater treatment plants is usually the main cause of eutrophication, the proposed impact assessment approach estimates that for a receiving water body, the ΔS due to a unit mass of N and P discharge is 268.9kJ/K and 1870.1kJ/K, respectively. Consequently, P discharge control would be more important for environmental water protection.

Effects of monosulfuron-ester on metabolic processes of nitrogen-fixing cyanobacteria Anabaena flos-aquae and Anabaena azotica.

Presence of the relatively new sulfonylurea herbicide monosulfuron-ester at 0.03–300 nmol/L affected the growth of two non-target nitrogen-fixing cyanobacteria (Anabaena flos-aquae and Anabaena azotica) and substantially inhibited in vitro Acetolactate synthase activity, with IC50 of 3.3 and 101.3 nmol/L for A. flos-aquae and A. azotica, respectively. Presenting in 30–300 nmol/L, it inhibited protein synthesis of the cyanobacteria with less amino acids produced as its concentration increased. Our findings support the view that monosulfuron-ester toxicity in both nitrogen-fixing cyanobacteria is due to its interference with protein metabolism via inhibition of branch-chain amino acid biosynthesis, and particularly Acetolactate synthase activity.

Effect of Small-Scale Turbulence on the Physiology and Morphology of Two Bloom-Forming Cyanobacteria.

The main goal of the present work is to test the hypothesis that small-scale turbulence affected physiological activities and the morphology of cyanobacteria in high turbulence environments. Using quantified turbulence in a stirring device, we conducted one set of experiments on cultures of two strains of cyanobacteria with different phenotypes; i.e., unicellular Microcystis flos-aquae and colonial Anabaena flos-aquae. The effect of small-scale turbulence examined varied from 0 to 8.01×10−2 m2s-3, covering the range of turbulence intensities experienced by cyanobacteria in the field. The results of photosynthesis activity and the cellular chlorophyll a in both strains did not change significantly among the turbulence levels, indicating that the potential indirect effects of a light regime under the gradient of turbulent mixing could be ignored. However, the experiments demonstrated that small-scale turbulence significantly modulated algal nutrient uptake and growth in comparison to the stagnant control. Cellular N and C of the two stains showed approximately the same responses, resulting in a similar pattern of C/N ratios. Moreover, the change in the phosphate uptake rate was similar to that of growth in two strains, which implied that growth characteristic responses to turbulence may be dependent on the P strategy, which was correlated with accumulation of polyphosphate. Additionally, our results also showed the filament length of A. flos-aquae decreased in response to high turbulence, which could favor enhancement of the nutrient uptake. These findings suggested that both M. flos-aquae and A. flos-aquae adjust their growth rates in response to turbulence levels in the ways of asynchronous cellular stoichiometry of C, N, and P, especially the phosphorus strategy, to improve the nutrient application efficiency. The fact that adaptation strategies of cyanobacteria diversely to turbulence depending on their physiological conditions presents a good example to understand the direct cause—effect relationship between hydrodynamic forces and algae.

Assessment of the Risks of Mixtures of Major Use Veterinary Antibiotics in European Surface Waters.

Effects of single veterinary antibiotics on a range of aquatic organisms have been explored in many studies. In reality, surface waters will be exposed to mixtures of these substances. In this study, we present an approach for establishing risks of antibiotic mixtures to surface waters and illustrate this by assessing risks of mixtures of three major use antibiotics (trimethoprim, tylosin, and lincomycin) to algal and cyanobacterial species in European surface waters. Ecotoxicity tests were initially performed to assess the combined effects of the antibiotics to the cyanobacteria Anabaena flos-aquae. The results were used to evaluate two mixture prediction models: concentration addition (CA) and independent action (IA). The CA model performed best at predicting the toxicity of the mixture with the experimental 96 h EC50 for the antibiotic mixture being 0.248 μmol/L compared to the CA predicted EC50 of 0.21 μmol/L. The CA model was therefore used alongside predictions of exposure for different European scenarios and estimations of hazards obtained from species sensitivity distributions to estimate risks of mixtures of the three antibiotics. Risk quotients for the different scenarios ranged from 0.066 to 385 indicating that the combination of three substances could be causing adverse impacts on algal communities in European surface waters. This could have important implications for primary production and nutrient cycling. Tylosin contributed most to the risk followed by lincomycin and trimethoprim. While we have explored only three antibiotics, the combined experimental and modeling approach could readily be applied to the wider range of antibiotics that are in use.

Comparing the sensitivity of chlorophytes, cyanobacteria, and diatoms to major-use antibiotics.

The occurrence of antibiotic residues in the aquatic environment is an emerging concern. In contrast to daphnia and fish, algae are known to be particularly sensitive to antibiotic exposure. However, to date, a systematic evaluation of the sensitivity of different algal species to antibiotics has not been performed. The aim of the present study was therefore to explore the sensitivity of a battery of algal species toward antibiotic exposures. The present study investigated the growth inhibition effects of 3 major-use antibiotics, tylosin, lincomycin, and trimethoprim, on 7 algal species from the chlorophyte, cyanobacteria, and diatom groups. Based on median effective concentration (EC50) values, cyanobacteria (EC50 = 0.095-0.13 μmol/L) were found to be the most sensitive group to lincomycin followed by chlorophytes (EC50 = 7.36-225.73 μmol/L) and diatoms (EC50 > 225.73 μmol/L). Cyanobacteria were also the most sensitive group to tylosin (EC50 = 0.09-0.092 μmol/L), but, for this compound, diatoms (EC50 = 1.33-5.7 μmol/L) were more sensitive than chlorophytes (EC50 = 4.14-81.2 μmol/L). Diatoms were most sensitive to trimethoprim (EC50 = 7.36-74.61 μmol/L), followed by cyanobacteria (EC50 = 315.78-344.45 μmol/L), and chlorophytes (EC50 > 344.45 μmol/L) for trimethoprim. Although these results partly support the current approach to regulatory environmental risk assessment (whereby cyanobacterial species are recommended for use with antibiotic compounds), they indicate that for some antibiotics this group might not be the most appropriate test organism. It is therefore suggested that environmental risk assessments consider data on 3 algal groups (chlorophytes, cyanobacteria, and diatoms) and use test species from these groups, which are consistently found to be the most sensitive (Pseudokirchneriella subcapitata, Anabaena flos-aquae, and Navicula pelliculosa). Environ Toxicol Chem 2016;35:2587-2596. © 2016 SETAC.

Effects of nutrient loading on Anabaena flos-aquae biofilm: biofilm growth and nutrient removals.

Effects of three different nutrient loadings (low nutrient loading, medium nutrient loading and high nutrient loading, denoted as LNS, MNS and HNS, respectively) on the structure and functions of algal biofilm using Anabaena flos-aquae were investigated using synthetic wastewater. Nutrients removal efficiencies, biofilm thickness, microalgae dehydrogenase activity (DHA) and exopolysaccharide (EPS) productions were examined. Results showed that the changes of nutrient concentration were insignificant after 4 days of experiment for the case of HNS condition; 9 days for the case of MNS condition, and 6 days for the case of LNS condition, respectively. The biofilm thickness, nutrient removal efficiencies, algae DHA and EPS productions increased with the increase of nutrient loadings in synthetic wastewater. For the case of HNS condition, the microalgal biofilm exhibited the best performance in terms of C, N and P removal efficiencies, reaching the removal rates of 68.45, 3.56 and 1.61 mg·L(-1)·d(-1) for C, N, P, respectively. This was likely because, fact with the high nutrient loading, the high biological activity could be achieved, thus resulting in high nutrient removals. The thickness of the biofilm in HNS condition was 75 μm, which was closely related to EPS production. DHA and EPS concentrations were 7.24 and 1.8 × 10(-2) mg·mm(-2), respectively. It was also shown that apart from the nutrient loading, the structure and functions of microalgal biofilm were also influenced by other factors, such as illumination and temperature.

Effect of four wetland plants on nutrient removal and growth of eutrophic algae

We studied the removal of chlorophyll-a and eutrophic alga Ankistrodesmus acicularis by mixed and monoculture constructed wetlands of four common wetland macrophytes, Echinodorus berteroi, Hydrocotyle sibthorpioides, Vallisneria natans and Hydrilla verticillata. We also tested the effects of the macrophyte culture solution on the growth of three common eutrophic algae: Chlorella pyrenoidosa, Scnedesmus obliquus and Anabaena flosaquae. The wetlands had significant effect on the removal of chlorophyll-a and A. acicularis. ANOVA results indicated a significant difference existed among different wetlands (P &amp;lt; 0.01). There was generally no significant difference between the mixed and the monoculture wetlands, while the mixed wetlands generally showed significant difference between them. Results also indicated that there were significant differences in the effect on the growth of three algae among the culture solutions of different wetlands (p &amp;lt; 0.01). Almost all mixed culture solutions had a significant difference from their monocultures. Similarly, the monoculture treatments generally showed significant differences from their corresponding mixed treatments. However, combinations of different macrophytes generally cannot increase the effect intensity. The results indicated that combinations of macrophytes can produce different effects on alga growth from their monocultures and from their combinations with other macrophytes. Different algae showed different levels of susceptibility to the plant culture solution, and a same culture solution had different effects on different algae, including inhibiting, promoting, or neutral effects.