180 results on '"Fanxiang, Kong"'
Search Results
2. Secure UAV Communications Under Uncertain Eavesdroppers Locations.
- Author
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Silei Wang, Fanxiang Kong, and Qiang Li 0017
- Published
- 2021
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3. Community structure of aerobic anoxygenic phototrophic bacteria in algae- and macrophyte-dominated areas in Taihu Lake, China
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Limei Shi, Yuanfeng Cai, Xiaoli Shi, Min Zhang, Qingfei Zeng, Fanxiang Kong, and Ping Xu
- Subjects
Oceanography ,Water Science and Technology - Published
- 2022
4. UV-B Exposure Affects the Biosynthesis of Microcystin in Toxic Microcystis aeruginosa Cells and Its Degradation in the Extracellular Space
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Zhen Yang and Fanxiang Kong
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UV-B radiation ,microcystin ,gene transcription ,degradation ,Medicine - Abstract
Microcystins (MCs) are cyclic hepatotoxic heptapeptides produced by cyanobacteria that can be toxic to aquatic and terrestrial organisms. MC synthesis and degradation are thought to be influenced by several different physical and environmental parameters. In this study, the effects of different intensities of UV-B radiation on MC biosynthesis in Microcystis cells and on its extracellular degradation were investigated by mRNA analysis and degradation experiments. Exposure to UV-B at intensities of 1.02 and 1.45 W/m2 not only remarkably inhibited the growth of Microcystis, but also led to a decrease in the MC concentration. In addition, mcyD transcription was decreased under the same UV-B intensities. These results demonstrated that the effects of UV-B exposure on the biosynthesis of MCs in Microcystis cells could be attributed to the regulation of mcy gene transcription. Moreover, the MC concentration was decreased significantly after exposure to different intensities of UV-B radiation. Of the three MC variants (MC-LR, -RR and -YR, L, R and Y are abbreviations of leucine, arginine and tyrosine), MC-LR and MC-YR were sensitive to UV-B radiation, whereas MC-RR was not. In summary, our results showed that UV-B radiation had a negative effect on MC production in Microcystis cells and MC persistence in the extracellular space.
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- 2015
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5. The Dynamics of Microcystis Genotypes and Microcystin Production and Associations with Environmental Factors during Blooms in Lake Chaohu, China
- Author
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Li Yu, Fanxiang Kong, Min Zhang, Zhen Yang, Xiaoli Shi, and Mingyong Du
- Subjects
Microcystis ,microcystin ,16S rDNA ,mcyD ,qPCR ,environmental factors ,Lake Chaohu ,Medicine - Abstract
Lake Chaohu, which is a large, shallow, hypertrophic freshwater lake in southeastern China, has been experiencing lake-wide toxic Microcystis blooms in recent decades. To illuminate the relationships between microcystin (MC) production, the genotypic composition of the Microcystis community and environmental factors, water samples and associated environmental data were collected from June to October 2012 within Lake Chaohu. The Microcystis genotypes and MC concentrations were quantified using quantitative real-time PCR (qPCR) and HPLC, respectively. The results showed that the abundances of Microcystis genotypes and MC concentrations varied on spatial and temporal scales. Microcystis exists as a mixed population of toxic and non-toxic genotypes, and the proportion of toxic Microcystis genotypes ranged from 9.43% to 87.98%. Both Pearson correlation and stepwise multiple regressions demonstrated that throughout the entire lake, the abundances of total and toxic Microcystis and MC concentrations showed significant positive correlation with the total phosphorus and water temperature, suggesting that increases in temperature together with the phosphorus concentrations may promote more frequent toxic Microcystis blooms and higher concentrations of MC. Whereas, dissolved inorganic carbon (DIC) was negatively correlated with the abundances of total and toxic Microcystis and MC concentrations, indicating that rising DIC concentrations may suppress toxic Microcystis abundance and reduce the MC concentrations in the future. Therefore, our results highlight the fact that future eutrophication and global climate change can affect the dynamics of toxic Microcystis blooms and hence change the MC levels in freshwater.
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- 2014
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6. Involvement of NADH Oxidase in Biofilm Formation in Streptococcus sanguinis.
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Xiuchun Ge, Xiaoli Shi, Limei Shi, Jinlin Liu, Victoria Stone, Fanxiang Kong, Todd Kitten, and Ping Xu
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Medicine ,Science - Abstract
Biofilms play important roles in microbial communities and are related to infectious diseases. Here, we report direct evidence that a bacterial nox gene encoding NADH oxidase is involved in biofilm formation. A dramatic reduction in biofilm formation was observed in a Streptococcus sanguinis nox mutant under anaerobic conditions without any decrease in growth. The membrane fluidity of the mutant bacterial cells was found to be decreased and the fatty acid composition altered, with increased palmitic acid and decreased stearic acid and vaccenic acid. Extracellular DNA of the mutant was reduced in abundance and bacterial competence was suppressed. Gene expression analysis in the mutant identified two genes with altered expression, gtfP and Idh, which were found to be related to biofilm formation through examination of their deletion mutants. NADH oxidase-related metabolic pathways were analyzed, further clarifying the function of this enzyme in biofilm formation.
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- 2016
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7. Differences in growth and alkaline phosphatase activity between Microcystis aeruginosa and Chlorella pyrenoidosa in response to media with different organic phosphorus
- Author
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Yang YU, Min ZHANG, Fanxiang KONG, Xiaoli SHI, and Shanqin QIAN
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Microcystis aeruginosa, Chlorella pyrenoidosa, organic phosphorus, alkaline phophatase, Lake Taihu ,Geography. Anthropology. Recreation ,Physical geography ,GB3-5030 ,Environmental sciences ,GE1-350 - Abstract
The growth of Microcystis aeruginosa and Chlorella pyrenoidosa in three dissolved organic phosphorus sources (glucose-1- phosphate, adenosine triphosphate, cyclic-adenosine monophosphate) were studied in cultures separated by a dialysis membrane. Results showed that M. aeruginosa and C. pyrenoidosa could utilize those three forms of organic phosphorus, but their growth rates and cell abundances were low in comparison with those in the orthophosphate control. M. aeruginosa had a higher growth rate than C. pyrenoidosa in glucose-1-phosphate, and then became dominate in the separate cultures. In contrast, those two algal species didn’t show any significant differences in the growth rate and cell abundance in the medium with adenosine triphosphate and cyclicadenosine monophosphate. Alkaline phosphatase was an important enzyme for hydrolyzing glucose-1-phosphate, adenosine triphosphate and cyclic-adenosine monophosphate, the activity of which was positively correlated with the growth rate of algae. Considering the big proportion of glucose-1-phosphate in the Lake Taihu, the capability of M. aeruginosa to efficiently utilize this type of organic phosphorus source might be one of reason that why M. aeruginosa is the dominant species in this hyper-eutrophic lake.
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- 2011
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8. Jamming Strategy Generation for Hidden Communication Modes Via Graph Convolution Networks
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Huaizong Shao, Fanxiang Kong, and Qiang Li
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symbols.namesake ,Computer science ,Gaussian ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,Feature extraction ,Modulation (music) ,symbols ,Graph (abstract data type) ,Reinforcement learning ,Jamming ,Focus (optics) ,Algorithm ,Convolution - Abstract
Optimal jamming has important applications in both military and civil communications. There have been a brunch of works investigating the optimal jamming signal design when the signal modes of the opponent are known. In this work, we focus on the less studied hidden mode jamming problem. That is, the jammer has partially recorded the signal modes of the opponent, but there are some hidden modes not revealed to the jammer as of the appearance of these modes. As such, when the hidden modes appear, the jammer has to quickly adapt its jamming strategy to achieve effective jamming. However, it is challenging to do so due to incomplete knowledge of the intrinsic relation between the known and the hidden modes. In this work, a learning-based approach is proposed to attack this problem. Specifically, we custom-devise a jamming network (J-Net) to automatically learn the intrinsic relation among different modes and transfer the jamming strategy from the known modes to the hidden ones. Experimental results demonstrate that the J-Net attains much better jamming effect than pulsed Gaussian jamming and random jamming, and is comparable to the reinforcement learning-based approach, which assumes all the (known and hidden) modes available at the jammer.
- Published
- 2021
9. Diversity and dynamics of picocyanobacteria and the bloom-forming cyanobacteria in a large shallow eutrophic lake (lake Chaohu, China)
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Yuanfeng Cai and Fanxiang Kong
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bloom-forming cyanobacteria, picocyanobacteria, Microcystis, Anabaena, dynamics. ,Geography. Anthropology. Recreation ,Physical geography ,GB3-5030 ,Environmental sciences ,GE1-350 - Abstract
The diversity and succession pattern of cyanobacteria, particularly picocyanobacteria and bloom-forming cyanobacteria, were examined monthly in a eutrophic lake (lake Chaohu) in China using a combination of light microscopy and 16S ribosomal RNA (rRNA) sequence analysis. The results showed that both picocyanobacteria and bloom-forming cyanobacteria have high levels of diversity. Microcystis and Anabaena were the two predominant bloom-forming genera, and two obvious shifts occurred between them from spring to winter. Anabaena was dominant in spring, then it was rapidly replaced by Microcystis in summer and became dominant again in late autumn and early winter. Apart from water temperature, three forms of dissolved nitrogen (NO3-N, NO2-N, and NH4-N) were important driving factors for their seasonal succession, as demonstrated by redundancy analysis. Clone libraries and sequence analysis revealed that picocyanobacteria (mainly Synechococcus-like) are also important cyanobacteria members in lake Chaohu. All 8 picocyanobacterial phylotypes belonged to the Cyanobium clade. The phylotypes could be further grouped into at least 7 distinct clusters, and 4 of these clusters do not belong to any of the previously described clusters. Picocyanobacteria accounted for more than 70% (percentage in the clone library) in March and April but only accounted for less than 10% from June to October during the Microcystis bloom. The relative abundance of picocyanobacteria was positively correlated with the mass ratio of dissolved inorganic nitrogen and phosphorus (r=0.965, P
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- 2013
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10. Nitrate limitation and accumulation of dissolved organic carbon during a spring-summer cyanobacterial bloom in Lake Taihu (China)
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Xiaodong Wu, Fanxiang Kong, Xiaoli Shi, and Linlin Ye
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cyanobacterial bloom, dissolved organic carbon, nitrate limitation, water temperature. ,Geography. Anthropology. Recreation ,Physical geography ,GB3-5030 ,Environmental sciences ,GE1-350 - Abstract
Lake Taihu, high-molecular-weight dissolved organic matter (HMW-DOM), with sizes between 1 kDa and 0.2 μm, were collected using cross-flow ultrafiltration, from three different eutrophic regions. The DOC, and HMW-DOC concentrations, as well as environmental factors, including water temperature, nitrate, phosphate, and Chlorophyll-a (Chl-a), were analyzed. A significant negative relationship was observed between Chl-a and nitrate concentration, suggesting that cyanobacterial bloom was limited by nitrate. The high phosphate concentration can probably be attributed to phosphorus released from the sediment or can be a result of the accumulation of bloom. Furthermore, DOC concentration significantly increased with water temperature, and was negatively related to nitrate concentration, indicating that these two environmental factors are well correlated to DOC dynamics. DOC concentration did not significantly corresponded with the Chl-a concentration in Lake Taihu. Moreover, the relationship between HMW-DOC and Chl-a concentration was only observed in Gonghu Bay, suggesting that DOC and HMW-DOC are not solely derived from cyanobacterial bloom. Other organic carbon origins, such as terrestrial input, were also assumed to play an important role in Lake Taihu.
- Published
- 2012
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11. Formation of large colonies: a defense mechanism of Microcystis aeruginosa under continuous grazing pressure by flagellate Ochromonas sp.
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Fanxiang Kong and Zhen Yang
- Subjects
morphological change, aggregation of algal cells, grazed-induced, relative gas vesicle, buoyancy. ,Geography. Anthropology. Recreation ,Physical geography ,GB3-5030 ,Environmental sciences ,GE1-350 - Abstract
Induced colony formation under grazing pressure has been reported in our previous results. However, the colonies induced in these studies comprised only tens of cells which are far smaller than the naturally occurring colonies. In this work, unicellular Microcystis aeruginosa Kützing were co-cultivated with flagellate Ochromonas sp. for 50 d to investigate colony formation in M. aeruginosa under continuous grazing pressure. Results revealed that colonial M. aeruginosa formed on the 10th d under the grazing pressure of flagellate. These algal colonies resulted from the daughter cells of freshly dividing cells that failed to separate during the reproductive process. The diameters and cell numbers of the colonies increased slowly with time. Under continuous grazing pressure by Ochromonas sp. for 50 d, the diameter of some colonies reached over 180 μm. Analysis showed that the extracellular polysaccharide (EPS) content and relative gas vesicle (RGV) of each cell increased significantly after colony formation. However, there was no significant difference on the monosaccharide composition between unicellular and colonial M. aeruginosa. The loose aggregation of cells in the floating colonies suggests that a correlation probably exists between cell compactness and colony buoyancy.
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- 2012
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12. Stocks and dynamics of particulate and dissolved organic matter in a large, shallow eutrophic lake (Taihu, China) with dense cyanobacterial blooms
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Fanxiang Kong, Yang Yu, Yaping Lu, Feizhou Chen, Yaxin Huang, Limei Shi, and Min Zhang
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0106 biological sciences ,chemistry.chemical_classification ,Total organic carbon ,Chlorophyll a ,010504 meteorology & atmospheric sciences ,biology ,010604 marine biology & hydrobiology ,Particulates ,Oceanography ,biology.organism_classification ,01 natural sciences ,chemistry.chemical_compound ,chemistry ,Microcystis ,Dissolved organic carbon ,Environmental science ,Organic matter ,Eutrophication ,Bloom ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
Cyanobacterial blooms occur in eutrophic lakes worldwide, and greatly impair these ecosystems. To explore influences of cyanobacterial blooms on dynamics of both particulate organic matter (POM) and dissolved organic matter (DOM), which are at the base of the food chain, an investigation was conducted from December 2014 to November 2015 that included various stages of the seasonal cyanobacterial blooms (dominated by Microcystis ) in a large-shallow eutrophic Chinese lake (Taihu Lake). Data from eight sites of the lake are compiled into a representative seasonal cycle to assess general patterns of POM and DOM dynamics. Compared to December, 5-fold and 3.5-fold increases were observed in July for particulate organic carbon (POC, 3.05–15.37 mg/L) and dissolved organic carbon (DOC, 5.48–19.25 mg/L), respectively, with chlorophyll a (Chl a ) concentrations varying from 8.2 to 97.7 μg/L. Approximately 40% to 76% of total organic carbon was partitioned into DOC. All C, N, and P in POM and DOC were significantly correlated with Chl a. POC:Chl a ratios were low, whereas proportions of the estimated phytoplankton-derived organic matter in total POM were high during bloom seasons. These results suggested that contributions of cyanobacterial blooms to POM and DOC varied seasonally. Seasonal average C:P ratios in POM and DOM varied from 79 to 187 and 299 to 2 175, respectively. Both peaked in July and then sharply decreased. Redundancy analysis revealed that Chl a explained most of the variations of C:N:P ratios in POM, whereas temperature was the most explanatory factor for DOM. These findings suggest that dense cyanobacterial blooms caused both C-rich POM and DOM, thereby providing clues for understanding their influence on ecosystems.
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- 2018
13. Association between temporal and spatial beta diversity in phytoplankton
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Fanxiang Kong, Feizhou Chen, Zhen Yang, Xiaoli Shi, and Min Zhang
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0106 biological sciences ,Geography ,Ecology ,010604 marine biology & hydrobiology ,Association (object-oriented programming) ,Phytoplankton ,Beta diversity ,010603 evolutionary biology ,01 natural sciences ,Ecology, Evolution, Behavior and Systematics - Published
- 2017
14. Bacterial community dynamics and functional variation during the long-term decomposition of cyanobacterial blooms in-vitro
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Fanxiang Kong, Yaxin Huang, Yaping Lu, Limei Shi, Yang Yu, and Min Zhang
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0301 basic medicine ,Microcystis ,Environmental Engineering ,Nitrogen ,Fresh Water ,010501 environmental sciences ,Biology ,01 natural sciences ,Mineralization (biology) ,03 medical and health sciences ,Nutrient ,Dissolved organic carbon ,Environmental Chemistry ,Organic matter ,Waste Management and Disposal ,Nitrogen cycle ,0105 earth and related environmental sciences ,chemistry.chemical_classification ,Phosphorus ,Eutrophication ,biology.organism_classification ,Pollution ,Carbon ,Lakes ,030104 developmental biology ,chemistry ,Environmental chemistry ,Nitrification ,Nitrospira - Abstract
Cyanobacterial blooms drastically influence carbon and nutrient cycling in eutrophic freshwater lakes. To understand the mineralization process of cyanobacteria-derived particulate organic matter (CyanPOM), the aerobic degradation of cyanobacterial blooms dominated by Microcystis sp. was investigated over a 95-day microcosm experiment. Approximately 91%, 95% and 83% of the initial particulate organic carbon (POC), particulate organic nitrogen (PON), and particulate organic phosphorus (POP) were decomposed, respectively. The POC:PON ratio gradually increased from 5.9 to 13.5, whereas the POC:POP ratio gradually decreased from 230.3 to 120. These results indicated that the coupling of POC, PON, and POP changed during the decomposition of CyanPOM. Moreover, approximately 29%, 51% and 46% of POC, PON, and POP were mineralized to dissolved organic carbon, NO3-, and PO43-, respectively. Rhodospirillales (10.9%), Burkholderiales (16.5%), and Verrucomicrobiales (14.3%) dominated during the rapid phase (days 0-21), whereas Sphingomonadales (12.8%), Rhizobiales (11.8%), and Xanthomonadales (36.5%) dominated during the slow phase (days 21-50) of CyanPOM decomposition. Nitrospira (16.6%-32.9%) dominated and NO3- increased during the refractory phase (days 50-95), thus suggesting the occurrence of nitrification. Redundancy analysis revealed that bacterial communities during rapid decomposition were distinct from those during the slow and refractory periods. POC:POP, NH4+, and NO3- were the major driving factors for the patterns of bacterial communities. Furthermore, increase in nitrogen metabolism, methane metabolism, amino acid related enzymes and pyruvate metabolism characterized the functional variation of bacterial communities during degradation. Therefore, CyanPOM is an important nutrient source, and its decomposition level shapes bacterial communities.
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- 2017
15. Temporal and spatial variations in the composition of freshwater photosynthetic picoeukaryotes revealed by MiSeq sequencing from flow cytometry sorted samples
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Shengnan Li, Cécile Lepère, Gisèle Bronner, Xiaoli Shi, and Fanxiang Kong
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0301 basic medicine ,biology ,Zoology ,Chlorophyta ,Seasonality ,biology.organism_classification ,Bioinformatics ,medicine.disease ,Microbiology ,6. Clean water ,Ostreococcus ,03 medical and health sciences ,030104 developmental biology ,Algae ,Phycocyanin ,medicine ,Mantel test ,Turbidity ,Cercozoa ,Ecology, Evolution, Behavior and Systematics - Abstract
The diversity and composition of photosynthetic picoeukaryotes (PPEs) in two large shallow lakes in China (Lake Taihu and Lake Chaohu) were investigated from flow cytometry sorted samples using Miseq high-throughput sequencing. We collected 65 samples covering different regions of the two lakes over four seasons to unveil spatial and temporal patterns of PPEs community composition. The use of flow cytometry sorting largely improved the efficiency of detecting PPEs sequences and over 70% of the retrieved reads belonged to PPEs. Chlorophyta and Bacillariophyta dominated PPEs in most of the samples. A distinct but complex seasonality of PPEs composition emerged at the OTUs level. NGS-based Miseq sequencing facilitates an in-depth view of numerous rare OTUs. Nearly 80% of the PPEs OTUs were rare and lots of them were detected only in one season, whereas most of the abundant OTUs were frequently detected in all seasons but only changed in relative abundances. Besides, a close relative of the marine PPEs species Ostreococcus sp. (OTU_1144, 99% identity) was discovered in freshwater systems for the first time and was abundant especially in winter. The diversity and community composition of PPEs were more dependent on season rather than sampling sites. Temperature, phycocyanin and NO3 N concentrations in Lake Taihu explained the PPE composition variations, whereas in Lake Chaohu TN/TP ratios, temperature, pH and nephelometric turbidity units (NTU) seemed to be the most important factors. In addition, a great number of OTUs belong to nonpigmented picoeukaryotes, especially Chytridiomycota, Perkinsozoa, Ciliophora and Cercozoa, which are known to include algae parasites as well as predators. The results of mantel test also showed that the community of photosynthetic and nonpigmented picoeukaryotes were significantly correlated in both lakes.
- Published
- 2017
16. Growth, physiochemical and antioxidant responses of overwintering benthic cyanobacteria to hydrogen peroxide
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Min Zhang, Fanxiang Kong, Chao Chen, Yang Yu, Xiaoli Shi, and Zhen Yang
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Chlorophyll ,inorganic chemicals ,0106 biological sciences ,Cyanobacteria ,Chlorophyll a ,Health, Toxicology and Mutagenesis ,010501 environmental sciences ,Toxicology ,Photosynthesis ,01 natural sciences ,Antioxidants ,chemistry.chemical_compound ,Malondialdehyde ,Phytoplankton ,Phycocyanin ,Botany ,Biomass ,Overwintering ,0105 earth and related environmental sciences ,biology ,Superoxide Dismutase ,Chlorophyll A ,010604 marine biology & hydrobiology ,fungi ,Esterases ,Hydrogen Peroxide ,General Medicine ,Catalase ,biology.organism_classification ,Pollution ,Oxidative Stress ,chemistry ,Benthic zone ,bacteria ,Seasons - Abstract
The recruitment of overwintering benthic cyanobacteria from the sediment surface is important for the development of cyanobacterial blooms during warm spring seasons. Thus, controlling the growth of cyanobacteria at the benthic stage to inhibit their recruitment is vital to control or delay the formation of summer blooms. In this study, overwintering benthic cyanobacteria were exposed to ascending hydrogen peroxide (H2O2) concentrations (0, 1, 5, and 20 mg/L) in a simulated overwintering environment. Photosynthetic pigments, physiochemical features, and antioxidant responses were evaluated to determine the inhibitory effects of H2O2 on the growth of benthic cyanobacteria and to identify the potential mechanisms thereof. These H2O2-treated cyanobacteria were then collected through filtration and transferred to an optimum environment to evaluate their recovery capacity. The results showed that chlorophyll a and phycocyanin contents, photosynthetic yield, and esterase activity decreased significantly in H2O2 treated groups compared to the control. The activities of superoxide dismutase (SOD) and catalase (CAT) in benthic cyanobacteria were inhibited after 72 h exposure to H2O2, while the malondialdehyde (MDA) contents were stimulated at the same time. These results indicate that H2O2 can inhibit the growth of benthic cyanobacteria, and H2O2-induced oxidative damage might be one of the mechanisms involved. The recovery experiment showed that the impairment of benthic cyanobacteria was temporary at a low dose of 1 mg/L H2O2, but permanent damage was induced when H2O2 concentrations were increased to 5 and 20 mg/L. Overall, our results highlight that H2O2 is a potential cyanobacteria inhibitor and can be used to decreasing the biomass of overwintering cyanobacteria, and could further control the intensity of cyanobacteria during the growth seasons.
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- 2016
17. CO2 alters picophytoplankton community structure in freshwater ecosystems
- Author
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Xiujuan Wang, Mixue Liu, Shengnan Li, Xiaoli Shi, and Fanxiang Kong
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Ecology ,Community structure ,Environmental science ,Aquatic Science ,Freshwater ecosystem ,Ecology, Evolution, Behavior and Systematics - Published
- 2016
18. Nutrient reduction magnifies the impact of extreme weather on cyanobacterial bloom formation in large shallow Lake Taihu (China)
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Ronghua Ma, Xiaoli Shi, Min Zhang, Yang Yu, Zhen Yang, and Fanxiang Kong
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Cyanobacteria ,China ,Environmental Engineering ,010504 meteorology & atmospheric sciences ,education ,010501 environmental sciences ,01 natural sciences ,Extreme weather ,Nutrient ,Animals ,Shallow lake ,Weather ,Waste Management and Disposal ,0105 earth and related environmental sciences ,Water Science and Technology ,Civil and Structural Engineering ,Hydrology ,Biomass (ecology) ,Sheep ,biology ,Ecological Modeling ,Eutrophication ,Cyanobacterial bloom ,biology.organism_classification ,Pollution ,Lakes ,Agronomy ,Environmental science ,Female ,Bloom - Abstract
Cyanobacterial bloom formation is dependent on nutrient levels and meteorological conditions. In this study, we elucidated the effects of extreme weather events (EWEs, heavy rainfall and strong winds) on the cyanobacterial blooms in Lake Taihu in recent years based on an analysis of the meteorological, nutrient, and bloom area data from 2007 to 2015. The levels of total phosphorus (TP) and total nitrogen (TN) decreased by 42.5% and 31.2%, respectively, in the water of Lake Taihu over the past nine years. However, the frequency and intensity of cyanobacterial blooms did not significantly decrease. A total of 50.5% of the extended blooms (>300 km(2)) were associated with EWEs from 2007 to 2015, 36.2% of which were due to heavy rainfall and 38.3% of which were due to strong winds (25.5% were due to both). Interestingly, the frequency of the EWE-induced extended blooms significantly increased after 2012. Principal component analysis (PCA) showed that this frequency correlated positively with EWE-induced nutrient increases in the water, indicating that the complement from nutrient increases induced by EWE allow cyanobacterial cells to reach high biomass under relatively low nutrient condition. Our results suggest that EWEs play a more important role in extended bloom formation after the nutrient levels in shallow lakes are reduced.
- Published
- 2016
19. Hydrological regulation drives regime shifts: evidence from paleolimnology and ecosystem modeling of a large shallow Chinese lake
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Yu-Jiao Jiang, Min Zhang, Ning Qin, Wolf M. Mooij, Bin Yang, Luuk P. A. van Gerven, Qi-Shuang He, Fanxiang Kong, Fu-Liu Xu, Xiang-Zhen Kong, Annette B.G. Janssen, Wei He, Ze-Lin Bai, J.H. Janse, Chen Yang, Jan J. Kuiper, Wen-Xiu Liu, and Aquatic Ecology (AqE)
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Aquatic Ecology and Water Quality Management ,China ,010504 meteorology & atmospheric sciences ,PCLake ,regime shift ,water level control ,Lake Chaohu ,010501 environmental sciences ,01 natural sciences ,nutrient loading ,Ecosystem model ,Humans ,Environmental Chemistry ,Regime shift ,Ecosystem ,0105 earth and related environmental sciences ,General Environmental Science ,Ecological stability ,Global and Planetary Change ,paleolimnology ,Ecology ,Aquatic ecosystem ,Aquatische Ecologie en Waterkwaliteitsbeheer ,Eutrophication ,Water level ,Lakes ,international ,Environmental science ,Hydrology - Abstract
Quantitative evidence of sudden shifts in ecological structure and function in large shallow lakes is rare, even though they provide essential benefits to society. Such ‘regime shifts’ can be driven by human activities which degrade ecological stability including water level control (WLC) and nutrient loading. Interactions between WLC and nutrient loading on the long-term dynamics of shallow lake ecosystems are, however, often overlooked and largely underestimated, which has hampered the effectiveness of lake management. Here, we focus on a large shallow lake (Lake Chaohu) located in one of the most densely populated areas in China, the lower Yangtze River floodplain, which has undergone both WLC and increasing nutrient loading over the last several decades. We applied a novel methodology that combines consistent evidence from both paleolimnological records and ecosystem modeling to overcome the hurdle of data insufficiency and to unravel the drivers and underlying mechanisms in ecosystem dynamics. We identified the occurrence of two regime shifts: one in 1963, characterized by the abrupt disappearance of submerged vegetation, and another around 1980, with strong algal blooms being observed thereafter. Using model scenarios, we further disentangled the roles of WLC and nutrient loading, showing that the 1963 shift was predominantly triggered by WLC, whereas the shift ca. 1980 was attributed to aggravated nutrient loading. Our analysis also shows interactions between these two stressors. Compared to the dynamics driven by nutrient loading alone, WLC reduced the critical P loading and resulted in earlier disappearance of submerged vegetation and emergence of algal blooms by approximately 26 years and 10 years, respectively. Overall, our study reveals the significant role of hydrological regulation in driving shallow lake ecosystem dynamics, and it highlights the urgency of using multi-objective management criteria that includes ecological sustainability perspectives when implementing hydrological regulation for aquatic ecosystems around the globe.
- Published
- 2016
20. Unexpected predominance of photosynthetic picoeukaryotes in shallow eutrophic lakes
- Author
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Shengnan Li, Cécile Lepère, Xiujuan Wang, Fanxiang Kong, Xiaoli Shi, Mixue Liu, Nanjing Institute of Geography Limnology, Chinese Academy of Sciences [Beijing] (CAS), Laboratoire Microorganismes : Génome et Environnement (LMGE), Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), Institut Paoli-Calmettes, Fédération nationale des Centres de lutte contre le Cancer (FNCLCC), Mathématiques Appliquées aux Systèmes - EA 4037 (MAS), Ecole Centrale Paris, and 31270507, 31070242, National Natural Science Foundation of China
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0106 biological sciences ,0301 basic medicine ,Ecology ,010604 marine biology & hydrobiology ,Aquatic Science ,Photosynthesis ,[SDV.MP.PRO]Life Sciences [q-bio]/Microbiology and Parasitology/Protistology ,[SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology ,01 natural sciences ,03 medical and health sciences ,030104 developmental biology ,Environmental science ,[SDE.BE]Environmental Sciences/Biodiversity and Ecology ,Eutrophication ,ComputingMilieux_MISCELLANEOUS ,Ecology, Evolution, Behavior and Systematics - Abstract
International audience
- Published
- 2016
21. The responses of phytoplankton communities to elevated CO2 show seasonal variations in the highly eutrophic Lake Taihu
- Author
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Fanxiang Kong, Xiaoli Shi, Min Zhang, Xu-Hui Zhao, Ping Xu, and Zhou Yang
- Subjects
0106 biological sciences ,010504 meteorology & atmospheric sciences ,Range (biology) ,Ecology ,010604 marine biology & hydrobiology ,Aquatic Science ,01 natural sciences ,Oceanography ,Phytoplankton ,Environmental science ,Eutrophication ,Microcosm ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
From April 2012 to January 2013 (over four seasons), in situ microcosm experiments were conducted in Lake Taihu, perturbed over a range of pCO2 scenarios (270, 380, and 750 μatm; 1 atm = 101.325 kPa). The influence of CO2 level on microcosms was greatest during the spring because of the high growth rate of phytoplankton. In this season, rising CO2 levels caused a pH reduction, and the maximum reduction was 0.6 units when CO2 level was enhanced from the present level to 750 μatm. The doubling of CO2 level could increase the net primary production (NPP) by 65% during spring when the concentrations of other nutrients were maintained. The rise of NPP could cause a decline of dissolved inorganic carbon (DIC) concentration, and CO2 enrichment might mitigate the extent of this decline. Meanwhile, higher CO2 may slow or prevent a loss of diversity of phytoplankton in microcosms in this season. During the other three seasons, Microcystis predominated, and the percentage of cyanobacteria did not alter with the change of CO2. We did not observe a significant increase in the abundance of any taxa with the rise of CO2 during the in situ microcosm experiments.
- Published
- 2016
22. Spatial and seasonal shifts in bloom-forming cyanobacteria in Lake Chaohu: Patterns and driving factors
- Author
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Wenbin Yang, Chao Chen, Zhen Yang, Yuchao Zhang, Lijun Wei, Fanxiang Kong, and Min Zhang
- Subjects
0106 biological sciences ,Cyanobacteria ,biology ,Anabaena ,Ecology ,010604 marine biology & hydrobiology ,Plant Science ,010501 environmental sciences ,Aquatic Science ,biology.organism_classification ,Spatial distribution ,01 natural sciences ,Agricultural and Biological Sciences (miscellaneous) ,chemistry.chemical_compound ,Nitrate ,chemistry ,Microcystis ,Dominance (ecology) ,Turbidity ,Bloom ,0105 earth and related environmental sciences - Abstract
Summary The patterns of spatial and temporal shifts in bloom-forming cyanobacteria and the driving factors for these patterns were determined by analyzing the distribution of these cyanobacteria in Lake Chaohu using data from satellite images and field samples collected during 2012 and 2013. The cyanobacterial blooms primarily occupied the western region of Lake Chaohu, and the direction and speed of the prevailing wind determined the spatial distribution of these blooms. The cyanobacteria in Lake Chaohu were dominated by species of Microcystis and Anabaena. Microcystis reached its peak in June, and Anabaena had peaks in May and November, with an overall biomass that was higher than that of Microcystis. Microcystis generally occupied the western region of the lake in summer, whereas Anabaena dominated in other regions and seasons. Temperature may be responsible for these seasonal shifts. However, total phosphorus (TP), pH, temperature, turbidity and nitrate/nitrite nitrogen determined the coexistence of the two genera in different regions in summer. TP was correlated with Microcystis dominance, and pH and light availability were correlated with Anabaena dominance. Our results contribute to the understanding of shifts in bloom-forming cyanobacteria and are important for the control of cyanobacterial blooms.
- Published
- 2015
23. UV-B Exposure Affects the Biosynthesis of Microcystin in Toxic Microcystis aeruginosa Cells and Its Degradation in the Extracellular Space
- Author
-
Fanxiang Kong and Zhen Yang
- Subjects
Cyanobacteria ,Microcystis ,microcystin ,Microcystins ,Arginine ,Ultraviolet Rays ,Health, Toxicology and Mutagenesis ,lcsh:Medicine ,Microcystin ,Toxicology ,UV-B radiation ,Article ,Microbiology ,chemistry.chemical_compound ,Biosynthesis ,Extracellular ,Microcystis aeruginosa ,degradation ,chemistry.chemical_classification ,Microbial Viability ,biology ,lcsh:R ,Dose-Response Relationship, Radiation ,biology.organism_classification ,gene transcription ,chemistry ,Biochemistry ,Leucine ,Extracellular Space - Abstract
Microcystins (MCs) are cyclic hepatotoxic heptapeptides produced by cyanobacteria that can be toxic to aquatic and terrestrial organisms. MC synthesis and degradation are thought to be influenced by several different physical and environmental parameters. In this study, the effects of different intensities of UV-B radiation on MC biosynthesis in Microcystis cells and on its extracellular degradation were investigated by mRNA analysis and degradation experiments. Exposure to UV-B at intensities of 1.02 and 1.45 W/m2 not only remarkably inhibited the growth of Microcystis, but also led to a decrease in the MC concentration. In addition, mcyD transcription was decreased under the same UV-B intensities. These results demonstrated that the effects of UV-B exposure on the biosynthesis of MCs in Microcystis cells could be attributed to the regulation of mcy gene transcription. Moreover, the MC concentration was decreased significantly after exposure to different intensities of UV-B radiation. Of the three MC variants (MC-LR, -RR and -YR, L, R and Y are abbreviations of leucine, arginine and tyrosine), MC-LR and MC-YR were sensitive to UV-B radiation, whereas MC-RR was not. In summary, our results showed that UV-B radiation had a negative effect on MC production in Microcystis cells and MC persistence in the extracellular space.
- Published
- 2015
24. Dynamics and drivers of phytoplankton richness and composition along productivity gradient
- Author
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Fanxiang Kong, Xiaoli Shi, Zhen Yang, Jinlei Yu, Yongjiu Cai, Dietmar Straile, Feizhou Chen, and Min Zhang
- Subjects
0106 biological sciences ,China ,Environmental Engineering ,Range (biology) ,media_common.quotation_subject ,010603 evolutionary biology ,01 natural sciences ,Competition (biology) ,Altitude ,Phytoplankton ,Environmental Chemistry ,Waste Management and Disposal ,media_common ,Driving factors ,Ecology ,010604 marine biology & hydrobiology ,Temperature ,Biodiversity ,Pollution ,Lakes ,Productivity (ecology) ,Environmental science ,Composition (visual arts) ,Species richness ,Environmental Monitoring - Abstract
The shape of the productivity–richness relationship (PRR) for phytoplankton has been suggested to be unimodal, that is, the richness peaks at intermediate productivity levels. However, the mechanistic understanding for this pattern is still widely debated. In this study, we observed a unimodal PRR within 71 lakes along the Yangtze River encompassing an altitude range of 0–2700 m, and an over 2200 km distance from the upper reaches to the lower reaches. At low productivity, the competition for resources and regulatory processes jointly affected phytoplankton richness and composition, and their explanatory power depend on the gradient scale of driving factors. The variation of temperature attributing to altitudinal difference explained the majority of the variations of phytoplankton. If the altitude variation in temperature was eliminated, the explanatory power of temperature decreased from 31.7 to 7.6, and the independent effect of each resource and regulatory variable were limited and not decisive. At high productivity, the negative feedback of increased productivity (light limitation) affected the phytoplankton species richness and composition. The light-sensitive species disappeared, low-light-adapted species was retained and the phytoplankton composition gradually became similar with an increase in productivity. The findings contribute to an increased understanding of the mechanisms resulting in a hump-shaped PRR for phytoplankton.
- Published
- 2017
25. Large buoyant particles dominated by cyanobacterial colonies harbor distinct bacterial communities from small suspended particles and free-living bacteria in the water column
- Author
-
Feizhou Chen, Fanxiang Kong, Yaxin Huang, Xiangming Tang, Yaping Lu, Xiaoli Shi, Min Zhang, Shengling Gao, Yuanfeng Cai, and Limei Shi
- Subjects
0301 basic medicine ,Cyanobacteria ,China ,030106 microbiology ,Biology ,Microbiology ,Actinobacteria ,03 medical and health sciences ,chemistry.chemical_compound ,Diversity index ,Water column ,Nitrate ,Botany ,Phylogeny ,Original Research ,particles ,Alphaproteobacteria ,Biodiversity ,Original Articles ,biology.organism_classification ,Lakes ,030104 developmental biology ,chemistry ,illumina sequencing ,Seasons ,Eutrophication ,cyanobacterial aggregates ,Bacteria - Abstract
Worldwide cyanobacterial blooms greatly impair ecosystems in many eutrophic lakes and impact the microbial environment. In particular, large cyanobacterial colonies that are buoyant on the water surface may provide a distinct habitat for bacteria from other small particles that are suspended stably in the water column. To test this hypothesis, bacterial communities (excluding cyanobacteria) attached to large particles dominated by cyanobacterial colonies (>120 μm, LA), small particles (3–36 μm, SA), and free‐living bacteria (0.2–3 μm, FL) were investigated monthly for a year in Lake Taihu, China. Results confirmed that the Shannon diversity index of LA was significantly lower than that of FL, which was lower than that of SA. Cytophagia and Alphaproteobacteria were specially enriched in LA. Although samples in each habitat collected during high‐ (May to November) and low‐bloom seasons (December to April) were separated, all samples in LA were clustered and separated from SA and FL, which were also clustered during the same sampling seasons. In addition, the bacterial communities in LA were correlated with nitrate level, whereas FL and SA were correlated with nitrate level and temperature. Mantel analysis revealed that bacterial composition significantly correlated with the cyanobacterial composition in LA and FL but not in SA. These results indicate that LA provides distinct niches to bacteria, whereas the differentiation of bacterial communities in FL and SA is seasonally dependent.
- Published
- 2017
26. Dynamics and sources of dissolved organic carbon during phytoplankton bloom in hypereutrophic Lake Taihu (China)
- Author
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Bo Liu, Fanxiang Kong, Dezhi Yan, Xiaodong Wu, and Linlin Ye
- Subjects
Total organic carbon ,Hydrology ,Cyanobacteria ,Biomass (ecology) ,Chlorophyll a ,biology ,Aquatic Science ,biology.organism_classification ,Algal bloom ,chemistry.chemical_compound ,chemistry ,Isotopes of carbon ,Environmental chemistry ,Phytoplankton ,Dissolved organic carbon ,Environmental science - Abstract
To establish the influence of phytoplankton blooms on the dynamics and sources of dissolved organic carbon (DOC) in Lake Taihu, the concentrations and stable carbon isotope values (δ13C) of DOC and particulate organic carbon (POC) were analyzed, along with environmental factors, including water temperature, chlorophyll a (Chl a) concentration, phytoplankton community and total bacterial abundance, from March to August 2013 at five sites in Lake Taihu. Significant differences were observed in the DOC concentrations and δ13CDOC values at the sampling sites. On average, the proportion of DOC in the total organic carbon (TOC) pool ranged from 30% ± 10% to 81% ± 7%. POC was positively associated with both Chl a concentration and cyanobacteria biomass, suggesting that cyanobacteria blooms contribute to the POC pool in Lake Taihu. Depleted 13C in DOC relative to POC was observed in August, indicating that DOC was partially derived from POC in August. However, Chl a explained only 40% of the variation in DOC in the entirety of Lake Taihu, and at two sites far from the estuary, the contribution of allochthonous carbon was less than 50% in August. These results suggested a greater influence of allochthonous sources on the DOC pool. Moreover, the biodegradability of DOC was further determined by the total dissolved carbohydrates to DOC ratio (TCHO/DOC), specific UV absorbance (SUVA254), and the concentrations of bioavailable DOC (BDOC). On average, 17% of the variation in DOC was attributable to the BDOC pool, and the BDOC concentration correlated positively with Chl a, cyanobacteria biomass, and total bacterial abundance, suggesting that cyanobacteria–derived DOC is biodegradable and is preferentially utilized by bacteria.
- Published
- 2015
27. Effects of temperature fluctuation on the development of cyanobacterial dominance in spring: implication of future climate change
- Author
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Baoli Qin, Fanxiang Kong, Zhen Yang, Xiaoli Shi, Yang Yu, and Min Zhang
- Subjects
0106 biological sciences ,biology ,Ecology ,010604 marine biology & hydrobiology ,Global warming ,Aquatic Science ,biology.organism_classification ,Atmospheric sciences ,010603 evolutionary biology ,01 natural sciences ,Algae ,Phytoplankton ,Environmental science ,Dominance (ecology) ,Chlorella pyrenoidosa ,Microcystis aeruginosa ,Bloom ,Diel vertical migration - Abstract
Global warming is predicted to increase the intensity and frequency of short-term temperature fluctuation. However, the effect of temperature fluctuation on phytoplankton is rarely considered. We analyzed the effect of fluctuating temperature on cyanobacterial dominance and blooms in spring (March–May) with long-term data analyses, laboratory simulation, and field observation. Our results showed that the magnitude of air temperature fluctuation in spring has increased in Lake Taihu over the past 58 years (1956–2013) and was negatively correlated with cyanobacterial blooms onset time (1987–2013). Air temperature fluctuation was one of the predictors of the best model for the variability in the bloom size in spring (2000–2011). The results from the field observation (2009–2013) also indicated that there was a positive correlation between diel air temperature difference and the ratio of cyanobacteria to total algae. Laboratory experiments suggested that water temperature fluctuation slowed the growth rates of Chlorella pyrenoidosa and Cyclotella meneghiniana but not Microcystis aeruginosa, which confirmed our findings of field observation and long-term data analysis. Therefore, the increased temperature fluctuation under global warming may promote cyanobacterial dominance. Our findings provide further understanding of inter-annual difference of cyanobacterial blooms onset time in the warming world.
- Published
- 2015
28. The effects of CO2 on sestonic stoichiometry and community structure of crustacean zooplankton in a eutrophic lake: Increased competitive ability of Bosmina
- Author
-
Xiaoli Shi, Shengnan Li, Fanxiang Kong, Ping Xu, and Long-Sheng Tang
- Subjects
biology ,Ecology ,Bosmina ,Phytoplankton ,Community structure ,biology.organism_classification ,Eutrophication ,Microcosm ,Biochemistry ,Zooplankton ,Crustacean ,Daphnia ,Ecology, Evolution, Behavior and Systematics - Abstract
To explore the effects of CO2 concentration on the sestonic stoichiometric values and the community structure of crustacean zooplankton in a eutrophic lake, in situ microcosm experiments were conducted at the Lake Taihu Ecosystem Station in spring and summer of 2012. The experimental treatments were three concentrations of CO2, 270, 380 and 750 ppm, which represented preindustrial and present levels and the level predicted for the end of this century, respectively. The elevated atmospheric CO2 concentration increased the sestonic C:P ratio, particularly in the spring when the C:P ratio was two-fold greater at the high level of CO2 than at the low level of CO2. As a result, the contribution of Bosmina to total crustacean zooplankton abundance increased, most likely because of the low phosphorus content and high adaptability to foods with large elemental ratio variation. The other dominant crustacean zooplankton genera, including Daphnia, Ceriodaphnia, Diaphanosoma and Sinocalanus, had no response to the change in pCO2 during the microcosm experiments. The shift in crustacean zooplankton community structure between two seasons was primarily due to the transition of the phytoplankton community.
- Published
- 2015
29. Dynamics of dissolved organic carbon in eutrophic Lake Taihu and its tributaries and their implications for bacterial abundance during autumn and winter
- Author
-
Bo Liu, Xiaodong Wu, Fanxiang Kong, Linlin Ye, and Dezhi Yan
- Subjects
Chlorophyll a ,geography ,geography.geographical_feature_category ,Ecology ,Aquatic Science ,chemistry.chemical_compound ,chemistry ,Isotopes of carbon ,Abundance (ecology) ,Environmental chemistry ,Dissolved organic carbon ,Tributary ,Environmental science ,Transect ,Eutrophication ,Surface water ,Ecology, Evolution, Behavior and Systematics - Abstract
Surface water samples of Lake Taihu and its tributaries were collected from September 2012 to February 2013 to investigate the effects of dissolved organic carbon (DOC) dynamics on bacterial abundance. DOC concentrations, stable carbon isotope values (δ13CDOC), dissolved carbohydrates, and specific ultraviolet absorbance (SUVA254) were analyzed along with several environmental factors: water temperature, electrical conductivity (EC), chlorophyll a, and bacterial abundance. The highest DOC concentrations were observed in January 2013 at all sampling sites except at lake center. DOC concentrations decreased along both transects from the tributaries to the lake center in January 2013. In addition, the evidence from the positive correlation between DOC and EC in Lake Taihu suggests the input of river water into the lake. The variation in DOC concentration can be explained by temperature-dependent bacterial utilization of organic compounds. The δ13CDOC values ranged from −26.9‰ to −23.4‰ in Lake Taihu and its ...
- Published
- 2014
30. Effects of rice straw on the cell viability, photosynthesis, and growth of Microcystis aeruginosa
- Author
-
Fanxiang Kong, Wen Su, Yaping Lu, Johannes A. Hagström, and Yuhong Jia
- Subjects
Cyanobacteria ,biology ,food and beverages ,Oceanography ,Photosynthesis ,biology.organism_classification ,Esterase ,Enzyme assay ,Microbiology ,Cytosol ,Microcystis ,biology.protein ,Microcystis aeruginosa ,Viability assay ,Water Science and Technology - Abstract
Rice straw is supposed to be an environment-friendly biomaterial for inhibiting the growth of harmful blooms of the cyanobacterium Microcystis aeruginosa. However, its potential mechanism is not well known. To explore this mechanism, the growth, cell viability (esterase activity, membrane potential, and membrane integrity), photosynthesis, and cell size of M. aeruginosa were determined using flow cytometry and Phyto-PAM after exposure to rice straw extracts (RSE). The results show that doses from 2.0 to 10.0 g/L of RSE efficiently inhibited the alga for 15 days, while the physiologic and morphologic responses of the cyanobacteria were time-dependent. RSE interfered with the cell membrane potential, cell size, and in vivo chlorophyll-a fluorescence on the first day. After 7 days of exposure, RSE was transported into the cytosol, which disrupted enzyme activity and photosynthesis. The cyanobacteria then started to repair its physiology (enzyme activity, photosynthesis) and remained viable, suggesting that rice straw act as an algistatic agent.
- Published
- 2014
31. Controlling of cyanobacteria bloom during bottleneck stages of algal cycling in shallow Lake Taihu (China)
- Author
-
Yuhong Jia, Wen Su, Fanxiang Kong, Dan L. Johnson, and Zhen Yang
- Subjects
Cyanobacteria ,Biomass (ecology) ,biology ,fungi ,food and beverages ,Aquatic Science ,Straw ,biology.organism_classification ,Algal bloom ,Agronomy ,Phytoplankton ,Botany ,Eutrophication ,Water pollution ,Ecology, Evolution, Behavior and Systematics ,Overwintering - Abstract
To suppress the occurrence of phytoplankton blooms dominated by cyanobacteria, control measures were implemented during the bottleneck stages of algal succession, overwintering and pre-recruitment, using a combination of chemical and biological algicides. First, water and sediment samples were incubated in the laboratory to determine the threshold temperature for cyanobacteria recruitment. Second, the functional characteristics of candidate algicides were screened. Third, an in situ pilot experiment was conducted to test the feasibility of this method. Our results indicated that (1) the recruitment of cyanophytes was initiated at 15°C, (2) H2O2 and rice straw were the optimum algicides and their optimal concentrations were 10 mg/L and 1 g/L, respectively, and (3) following the combined application of H2O2 and rice straw during overwintering and pre-recruitment, the biomass of cyanobacteria decreased by 27.1% during recruitment and by 53.2% during the first algal bloom. These results suggested that the com...
- Published
- 2013
32. Abiotic factors in colony formation: effects of nutrition and light on extracellular polysaccharide production and cell aggregates of Microcystis aeruginosa
- Author
-
Fanxiang Kong and Zhen Yang
- Subjects
Abiotic component ,biology ,Cell ,Oceanography ,biology.organism_classification ,Light intensity ,medicine.anatomical_structure ,Nutrient ,Microcystis ,Botany ,Phytoplankton ,medicine ,Microcystis aeruginosa ,Eutrophication ,Water Science and Technology - Abstract
Colony morphology is important for Microcystis to sustain a competitive advantage in eutrophic lakes. The mechanism of colony formation in Microcystis is currently unclear. Extracellular polysaccharide (EPS) has been reported to play an important role in cell aggregate formation of some phytoplankton. Microcystis aeruginosa was cultivated under varied abiotic conditions, including different nutrient, light, and temperature conditions, to investigate their effects on EPS production and morphological change. The results show that nutrient concentration and light intensity have great effects on EPS productionin M. aeruginosa. There was a considerable increase in EPS production after M. aeruginosa was cultivated in adjusted culture conditions similar to those present in the field (28.9 mg C/L, 1.98 mg N/L, 0.65 mg P/L, light intensity: 100 μmol/(m2 · s)). These results indicate that abiotic factors might be one of the triggers for colony formation in Microcystis.
- Published
- 2013
33. Inhibition of Camellia sinensis (L.) O. Kuntze on Microcystis aeruginosa and isolation of the inhibition factors
- Author
-
Yaping Lu, Fanxiang Kong, Jin Wang, Yang Yu, and Wen Su
- Subjects
Cyanobacteria ,Microcystis ,Bioengineering ,Microbial Sensitivity Tests ,complex mixtures ,Applied Microbiology and Biotechnology ,Algal bloom ,High-performance liquid chromatography ,Camellia sinensis ,Mass Spectrometry ,Botany ,Microcystis aeruginosa ,Food science ,Chromatography, High Pressure Liquid ,Allelopathy ,biology ,Polyphenols ,food and beverages ,General Medicine ,biology.organism_classification ,Anti-Bacterial Agents ,Polyphenol ,Chromatography, Gel ,Chromatography, Liquid ,Biotechnology - Abstract
Low concentration of tea (Camellia sinensis (L.) O. Kuntze) was shown to inhibit the growth of the toxic cyanobacterium Microcystis aeruginosa. The inhibition efficiency was 40 % at 0.1 g dry tea/L and 90 % at 0.2 g/L after a 12-day culture. All varieties of tea used in the test could inhibit Microcystis growth, in which the inhibitory effect of green tea was greater than that of black tea. Antialgal allelochemicals were isolated from tea by solvent extraction, gel-chromatography and high performance liquid chromatography. Two algal-inhibition compounds were identified by liquid chromatography/mass spectrometry as epigallocatechin-3-gallate, epicatechin-3-gallate respectively. These are the main polyphenols in tea that have inhibitory effects on the growth of cyanobacteria. The combined effect of these polyphenols makes tea a promising source of algicide to inhibit the growth of algal blooms.
- Published
- 2013
34. Estimating spatial variation in the abundance of potential microcystin-producing Microcystis spp. using real-time PCR during summer bloom in Lake Taihu
- Author
-
Fanxiang Kong, Daming Li, Yuhong Jia, Zhen Yang, and Xiaoli Shi
- Subjects
chemistry.chemical_classification ,education.field_of_study ,biology ,Population ,General Medicine ,Microcystin ,biology.organism_classification ,chemistry ,Abundance (ecology) ,Microcystis ,Phycocyanin ,Botany ,education ,Eutrophication ,Bloom ,Bay - Abstract
Lake Taihu, which is the third largest freshwater lakes in China, is a hypertrophic shallow lake in eastern China that has experienced lake-wide cyanobacterial blooms annually during the last few decades. In this study, quantitative real-time PCR assays targeting on phycocyanin intergenic spacer ( PC - IGS ) and a microcystin synthetase gene mcyD were established, respectively. Water samples collected from eight sampling sites (including Zhushan Bay (N5), Meiliang Bay (N2), Gonghu Bay (N4), West lake areas (W2 and W4), south-middle lake areas (S2, S4 and S5)) in August of 2009 and 2010 were analyzed using real time PCR for the distribution and abundance of toxic and total Microcystis populations. The results showed that Microcystis exists as a mixed population of potential toxic and non-toxic genotypes, and there was significant spatial changes in the abundance of potential toxic Microcystis on the basis of quantification by quantitative real-time PCR analysis: the abundance of toxic Microcystis population in 2009 and 2010 varied from 4.08 × 10 4 to 8.28 × 10 6 copies mL −1 , from 4.45 × 10 5 to 5.22 × 10 7 copies mL −1 , respectively. Meanwhile the ratio of the mcyD subpopulation to the total Microcystis varied considerably, from 5.7% to 41.1% in 2009 and from 10.3% to 65.8% in 2010 in all sampling sites, and the value is high in Zhushan Bay and Meiliang Bay with the high level of eutrophication. Correlation analysis showed the abundance of toxic and total Microcystis being strongly related ( P Microcystis populations. The abundance of toxic and total Microcystis populations were positively correlated with chlorophyll-a (Chl-a) concentration ( P Microcystis is dominated genera of cyanobacterial bloom in Lake Taihu. It was also found that the abundance of toxic Microcystis and the proportion of toxic subpopulation to the total Microcystis were positively correlated with total phosphorus and orthophosphate concentrations ( P P > 0.05). All data suggest that phosphorus concentration is a critical factor for determining the abundance of toxic Microcystis population.
- Published
- 2012
35. The distribution of phytoplankton along trophic gradients and its mediation by available light in the pelagic zone of large eutrophic lakes
- Author
-
Fanxiang Kong, Zhen Yang, Min Zhang, Yang Yu, and Xiaoli Shi
- Subjects
Biomass (ecology) ,Available light ,Abundance (ecology) ,Ecology ,Phytoplankton ,Pelagic zone ,Aquatic Science ,Plankton ,Biology ,Eutrophication ,Ecology, Evolution, Behavior and Systematics ,Trophic level - Abstract
We describe the pattern and the principal factors affecting the phytoplankton biomass–nutrient relationship in the pelagic zone of large lakes. The results showed that the phytoplankton abundance and biomass of Cyanophyta, Cryptophyta, and Pyrrophyta were significantly correlated with trophic states. The total phosphorus (TP)–biomass relationship curves showed that the increment of biomass with TP is weak at high TP levels. The decrease in biomass at the high end of the curves might be a synthesis of the pattern of responses of the major taxonomic groups (except cyanobacteria) to environmental variables. Light limitation might be one of the important factors causing the decrease in the TP–biomass curve at high TP concentrations. If the mean underwater available light is lower than ∼250 µmol photons·m–2·s–1, clear-water species decline and cyanobacteria become dominant. The responses to available light of these key species play a central role in modulating the biomass–nutrient relationship. Our results contribute to the understanding of this relationship in the pelagic zone of large eutrophic lakes and have important practical implications for lake management.
- Published
- 2012
36. Temporal and spatial variations in the composition of freshwater photosynthetic picoeukaryotes revealed by MiSeq sequencing from flow cytometry sorted samples
- Author
-
Shengnan, Li, Gisèle, Bronner, Cécile, Lepère, Fanxiang, Kong, and Xiaoli, Shi
- Subjects
Diatoms ,China ,Lakes ,Nitrates ,Chlorophyta ,Phycocyanin ,Temperature ,Seasons ,Photosynthesis ,Flow Cytometry - Abstract
The diversity and composition of photosynthetic picoeukaryotes (PPEs) in two large shallow lakes in China (Lake Taihu and Lake Chaohu) were investigated from flow cytometry sorted samples using Miseq high-throughput sequencing. We collected 65 samples covering different regions of the two lakes over four seasons to unveil spatial and temporal patterns of PPEs community composition. The use of flow cytometry sorting largely improved the efficiency of detecting PPEs sequences and over 70% of the retrieved reads belonged to PPEs. Chlorophyta and Bacillariophyta dominated PPEs in most of the samples. A distinct but complex seasonality of PPEs composition emerged at the OTUs level. NGS-based Miseq sequencing facilitates an in-depth view of numerous rare OTUs. Nearly 80% of the PPEs OTUs were rare and lots of them were detected only in one season, whereas most of the abundant OTUs were frequently detected in all seasons but only changed in relative abundances. Besides, a close relative of the marine PPEs species Ostreococcus sp. (OTU_1144, 99% identity) was discovered in freshwater systems for the first time and was abundant especially in winter. The diversity and community composition of PPEs were more dependent on season rather than sampling sites. Temperature, phycocyanin and NO
- Published
- 2016
37. Groundwater contamination by microcystin from toxic cyanobacteria blooms in Lake Chaohu, China
- Author
-
Min Zhang, Zhen Yang, and Fanxiang Kong
- Subjects
0106 biological sciences ,Cyanobacteria ,China ,Microcystins ,Harmful Algal Bloom ,Microcystin ,010501 environmental sciences ,Management, Monitoring, Policy and Law ,01 natural sciences ,Algal bloom ,parasitic diseases ,polycyclic compounds ,Ecotoxicology ,Water Pollutants ,Groundwater ,0105 earth and related environmental sciences ,General Environmental Science ,chemistry.chemical_classification ,Hydrology ,geography ,geography.geographical_feature_category ,biology ,010604 marine biology & hydrobiology ,Phosphorus ,General Medicine ,biology.organism_classification ,Pollution ,Lakes ,chemistry ,Environmental science ,Bloom ,Eutrophication ,Environmental Monitoring ,Water well - Abstract
Lake Chaohu is a eutrophic lake that experiences massive cyanobacterial blooms. The high concentrations of microcystin observed in this lake are the result of the bloom's high proportion of toxic cyanobacteria strains. Groundwater is the important source of water for drinking, washing, and irrigation in the watershed of Lake Chaohu. This study examines the space-time distribution of microcystins and related environmental factors in wells near Lake Chaohu. All collected groundwater samples from the Lake Chaohu region had detectable concentrations of microcystins. The highest concentration of microcystins, 1.07 μg L(-1), occurred in a well hundreds of meters from the western coast of the lake in September. The distance from the lake shore to the well was significantly and positively correlated with the microcystin concentration in the groundwater. Moreover, a correlation analysis shows that the microcystin concentration in the groundwater was positively correlated with the total dissolved phosphorus (TDP) and microcystin concentration of the nearby lake water. Therefore, the microcystin in the groundwater likely originates from penetration by nearby lake water. Our results suggest that the groundwater near Lake Chaohu poses a significant health risk for the local residents when used for drinking water.
- Published
- 2016
38. CHANGES IN THE MORPHOLOGY AND POLYSACCHARIDE CONTENT OF MICROCYSTIS AERUGINOSA (CYANOBACTERIA) DURING FLAGELLATE GRAZING(1)
- Author
-
Zhou, Yang, Fanxiang, Kong, Xiaoli, Shi, Min, Zhang, Peng, Xing, and Huansheng, Cao
- Abstract
To investigate the changes in the morphology and polysaccharide content of Microcystis aeruginosa (Kütz.) Kütz. during flagellate grazing, cultures of M. aeruginosa were exposed to grazing Ochromonas sp. for a period of 9 d under controlled laboratory conditions. M. aeruginosa responded actively to flagellate grazing and formed colonies, most of which were made up of several or dozens of cells, suggesting that flagellate grazing may be one of the biotic factors responsible for colony formation in M. aeruginosa. When colonies were formed, the cell surface ultrastructure changed, and the polysaccharide layer on the surface of the cell wall became thicker. This change indicated that synthesis and secretion of extracellular polysaccharide (EPS) of M. aeruginosa cells increased under flagellate grazing pressure. The contents of soluble extracellular polysaccharide (sEPS), bound extracellular polysaccharide (bEPS), and total polysaccharide (TPS) in colonial cells of M. aeruginosa increased significantly compared with those in single cells. This finding suggested that the increased amount of EPS on the cell surface may play a role in keeping M. aeruginosa cells together to form colonies.
- Published
- 2016
39. THE ACCLIMATIVE CHANGES IN PHOTOCHEMISTRY AFTER COLONY FORMATION OF THE CYANOBACTERIA MICROCYSTIS AERUGINOSA
- Author
-
Min, Zhang, Xiaoli, Shi, Yang, Yu, and Fanxiang, Kong
- Abstract
Microcystis aeruginosa (Kütz.) Kütz. commonly occurs as single cells at early recruitment but forms large colonies in summer. Colony formation will induce many acclimative changes. In this study, we demonstrated the photochemical changes before and after colony formation. In the laboratory, light curves showed that colonies were more responsive to high light than single cells. The values of the maximal slope of electron transport rate (ETR)-light curve (α), relative maximal electron transport rate (rETR
- Published
- 2016
40. Photochemical responses of phytoplankton to rapid increasing-temperature process
- Author
-
Zhen Yang, Min Zhang, Fanxiang Kong, and Yang Yu
- Subjects
Cyanobacteria ,biology ,Plant Science ,Aquatic Science ,Atmospheric temperature range ,biology.organism_classification ,Photosynthesis ,Agricultural and Biological Sciences (miscellaneous) ,Chlorella ,Microcystis ,Phytoplankton ,Botany ,Chlorella pyrenoidosa ,Microcystis aeruginosa - Abstract
SUMMARY Phytoplankton is sensitive to rapidly increasing temperature in spring. However, studies on the effect of temperature on phytoplankton have mainly focused on constant temperatures. It is necessary to clarify the determining parameters of phytoplankton shifts during temperature increases, as temperatures are predicted to fluctuate more intensively and frequently in the future. In the study, we analyzed the responses of photosynthetic properties and growth in a cyanobacterium (Microcystis aeruginosa) and a green alga (Chlorella pyrenoidosa), the dominant species in Taihu, to rapid increasing-temperature process in the laboratory and in the field. The results show that gradually increasing temperature inhibited photosynthesis and the growth of C. pyrenoidosa and had almost no effect on M. aeruginosa. Elevated increasing temperature range also had more significant effects on the photosynthetic properties and growth rates of C. pyrenoidosa than those of M. aeruginosa in the laboratory and in the field. All of these results suggest that the photosynthetic performance of M. aeruginosa is more suitable to gradually increasing temperature and relatively strong temperature variations than that of C. pyrenoidosa, which might partially contribute to Microcystis excluding Chlorella competitively in aquatic ecosystem. Our findings point out the possible importance of the rapid and dramatic increasing-temperature process to the formation of cyanobacterial blooms.
- Published
- 2012
41. Quantification of microcystin-producing and non-microcystin producing Microcystis populations during the 2009 and 2010 blooms in Lake Taihu using quantitative real-time PCR
- Author
-
Fanxiang Kong, Yang Yu, Daming Li, Linlin Ye, Zhen Yang, and Xiaoli Shi
- Subjects
China ,Veterinary medicine ,Microcystis ,Environmental Engineering ,Genotype ,Microcystins ,Harmful Algal Bloom ,Population ,chemistry.chemical_element ,Microcystin ,Polymerase Chain Reaction ,Algal bloom ,Microbiology ,chemistry.chemical_compound ,Nitrate ,Phycocyanin ,Environmental Chemistry ,education ,General Environmental Science ,chemistry.chemical_classification ,education.field_of_study ,biology ,Phosphorus ,Hepatotoxin ,General Medicine ,biology.organism_classification ,Lakes ,chemistry - Abstract
Lake Taihu, a large, shallow hypertrophic freshwater lake in eastern China, has experienced lake-wide toxic cyanobacterial blooms annually during summer season in the past decades. Spatial changes in the abundance of hepatotoxin microcystin-producing and nonmicrocystin producing Microcystis populations were investigated in the lake in August of 2009 and 2010. To monitor the densities of the total Microcystis population and the potential microcystin-producing subpopulation, we used a quantitative real-time PCR assay targeting the phycocyanin intergenic spacer (PC-IGS) and the microcystin synthetase gene (mcyD), respectively. On the basis of quantification by real-time PCR analysis, the abundance of potential toxic Microcystis genotypes and the ratio of the mcyD subpopulation to the total Microcystis varied significantly, from 4.08 x 10(4) to 5.22 x 10(7) copies/mL, from 5.7% to 65.8%, respectively. Correlation analysis showed a strong positive relationship between chlorophyll-a, toxic Microcystis and total Microcystis; the abundance of toxic Microcystis correlated positively with total phosphorus and ortho-phosphate concentrations, but negatively with TN:TP ratio and nitrate concentrations. Meanwhile the proportion of potential toxic genotypes within Microcystis population showed positive correlation with total phosphorus and ortho-phosphate concentrations. Our data suggest that increased phosphorus loading may be a significant factor promoting the occurrence of toxic Microcystis bloom in Lake Taihu.
- Published
- 2012
42. Contributions of meteorology to the phenology of cyanobacterial blooms: Implications for future climate change
- Author
-
Hongtao Duan, Min Zhang, Fanxiang Kong, Yang Yu, and Xiaoli Shi
- Subjects
China ,Time Factors ,Environmental Engineering ,Meteorology ,Climate Change ,Climate change ,Cyanobacteria ,Freshwater ecosystem ,Wind speed ,Nutrient ,Spacecraft ,Waste Management and Disposal ,Water Science and Technology ,Civil and Structural Engineering ,Phenology ,Ecological Modeling ,Eutrophication ,Pollution ,Lakes ,Climatology ,Sunshine duration ,Regression Analysis ,Environmental science ,Seasons ,Bloom ,Environmental Monitoring - Abstract
Cyanobacterial blooms are often a result of eutrophication. Recently, however, their expansion has also been found to be associated with changes in climate. To elucidate the effects of climatic variables on the expansion of cyanobacterial blooms in Taihu, China, we analyzed the relationships between climatic variables and bloom events which were retrieved by satellite images. We then assessed the contribution of each climate variable to the phenology of blooms using multiple regression models. Our study demonstrates that retrieving ecological information from satellite images is meritorious for large-scale and long-term ecological research in freshwater ecosystems. Our results show that the phenological changes of blooms at an inter-annual scale are strongly linked to climate in Taihu during the past 23 yr. Cyanobacterial blooms occur earlier and last longer with the increase of temperature, sunshine hours, and global radiation and the decrease of wind speed. Furthermore, the duration increases when the daily averages of maximum, mean, and minimum temperature each exceed 20.3 °C, 16.7 °C, and 13.7 °C, respectively. Among these factors, sunshine hours and wind speed are the primary contributors to the onset of the blooms, explaining 84.6% of their variability over the past 23 yr. These factors are also good predictors of the variability in the duration of annual blooms and determined 58.9% of the variability in this parameter. Our results indicate that when nutrients are in sufficiently high quantities to sustain the formation of cyanobacterial blooms, climatic variables become crucial in predicting cyanobacterial bloom events. Climate changes should be considered when we evaluate how much the amount of nutrients should be reduced in Taihu for lake management.
- Published
- 2012
43. Phytoplankton Cell Lysis after Water Bloom in a Eutrophic Freshwater Lake Taihu (China)
- Author
-
Xiaoli Shi, Linlin Ye, Fanxiang Kong, and Xiaodong Wu
- Subjects
Chlorophyll a ,Lysis ,Ecology ,fungi ,Aquatic Science ,Biology ,chemistry.chemical_compound ,Nitrate ,chemistry ,Water temperature ,Environmental chemistry ,Phytoplankton ,Eutrophication ,Bloom ,Bay ,Ecology, Evolution, Behavior and Systematics - Abstract
The phytoplankton lysis rates in the different eutrophic regions of Lake Taihu were determined based on the activities of particle and dissolved esterase, as well as the decay rate of the latter, from August 2009 to March 2010. Two peaks were observed for the chlorophyll a concentration, one in September 2009 and another in January 2010. The highest phytoplankton lysis rates observed in October were associated with the decay of the summer bloom, whereas the minimum lysis rates observed in January were associated with the winter bloom. The highest cell lysis rates in Meiliang Bay, Lake centre, and Gonghu Bay were 0.67, 0.77, and 0.68 d–1, respectively, whereas the lowest lysis rates in these regions were 0.03, 0.01, and 0.05 d–1, respectively. Water temperature showed an apparent indirect effect on lysis rate. In addition, a significant inverse relationship was observed between lysis rates and nitrate concentration in the three lake regions, which suggests that phytoplankton cell lysis is associated with changes in nitrate concentration. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
- Published
- 2011
44. Dynamics of dissolved organic carbon after a cyanobacterial bloom in hypereutrophic Lake Taihu (China)
- Author
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Fanxiang Kong, Min Zhang, Xiaodong Wu, Xiao Shi, Yang Yu, Daming Li, and Linlin Ye
- Subjects
Chlorophyll a ,Carbon-to-nitrogen ratio ,Ecology ,Ultrafiltration ,food and beverages ,chemistry.chemical_element ,Carbon to nitrogen ratio ,Aquatic Science ,Cyanobacterial bloom ,chemistry.chemical_compound ,Lake Taihu ,chemistry ,Nitrate ,Environmental chemistry ,High molecular weight dissolved organic carbon ,Dissolved organic carbon ,Eutrophication ,Bloom ,Carbon ,Bay - Abstract
a b s t r a c t To establish the influence of the cyanobacterial bloom collapse on the characteristics of dissolved organic carbon (DOC) in Lake Taihu, high-molecular-weight dissolved organic matter (HMW-DOM), with sizes between 1 kDa and 0.5 m, were collected using cross-flow ultrafiltration, from three different eutrophic regions. Isolated HMW-DOM was further characterized by atomic carbon to nitrogen ratio and neu- tral sugars composition by gas chromatography and mass spectrometry. The results indicated that the cyanobacterial cell lysis induced by nitrate depletion is the likely mechanism for DOC release. The rela- tively high DOC level was associated with the high chlorophyll a concentration in Meiliang Bay, one of the most eutrophic bays in the northern part of the lake. However, no significant correlations were observed between chlorophyll a concentration and HMW-DOC concentration during the demise of the cyanobac- terial bloom in Lake Taihu. No significant differences were found in the HMW-DOC concentration among the three sampling sites, which were selected to represent different eutrophic status. However, a sig- nificant difference in the HMW-DOC concentration was found between October 2009 and January 2010 in all three sampling sites (p = 0.02). The HMW-DOC release may be attributed to the cyanobacterial cell lysis after the peak of summer bloom. The similarity in neutral sugar composition between the HMW- DOM and cyanobacterial exopolysaccharides suggests that the cyanobacterial bloom is the source of HMW-DOM. However, the significant correlation between the carbon to nitrogen ratio in HMW-DOM and chlorophyll a concentration was only observed in Meiliang Bay, which implies that apart from the cyanobacteria-derived DOC, a fraction of DOC was from riverine input. The decline of the cyanobacterial bloom also changed the overall DOM pool, leading to a shift in the component of HMW-DOM from a C-enriched material to an N-enriched material, as revealed by the variation in the carbon to nitrogen ratios. Overall, these results demonstrate that the quantitative and qualitative DOM is affected by the post-cyanobacterial bloom in Lake Taihu.
- Published
- 2011
45. Role of Cell Hydrophobicity on Colony Formation in Microcystis (Cyanobacteria)
- Author
-
Hualin Yang, Pengfu Li, Fanxiang Kong, Limei Shi, Xingyu Wang, Yuanfeng Cai, and Meng Xia
- Subjects
Cyanobacteria ,chemistry.chemical_classification ,biology ,Cell ,Proteolytic enzymes ,Aquatic Science ,biology.organism_classification ,Polysaccharide ,Microbiology ,medicine.anatomical_structure ,chemistry ,Microcystis ,Extracellular ,medicine ,Incubation ,Ecology, Evolution, Behavior and Systematics ,Bacteria - Abstract
Colony formation is highly import ant for the competitive advantage of the cyanobacterium Microcystis over other phytoplankton species. The laboratory-grown colonial Microcystis strains isolated from Lake Taihu (China) maintained colonial forms under the low light condition (10 μE m–2 s–1). The cell surface hydrophobicities of the Microcystis colonies were measured by cyanobacterial adherence to xylene in comparison with unicellular Microcystis strains. The cells of the tested colonial strains were all hydrophobic, while the cells of the tested unicellular strains were all hydrophilic. Incubation under the higher light condition (75 μE m–2 s–1) leaded to the significant decrease in the cell hydrophobicities of the colonial Microcystis and the transition from colonial forms to unicellular forms. These findings indicated that the cell hydrophobicity of Microcystis may play a role in cell-cell adherence and colony formation. Phosphate-limitation, nitrate-limitation and pH did not affect cell hydrophobicities of colonial Microcystis. Treatment with proteolytic enzymes had no effect on the cell hydrophobicity, indicating that cell surface proteins did not contribute to high cell hydrophobicity. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
- Published
- 2011
46. THE ACCLIMATIVE CHANGES IN PHOTOCHEMISTRY AFTER COLONY FORMATION OF THE CYANOBACTERIA MICROCYSTIS AERUGINOSA1
- Author
-
Fanxiang Kong, Xiaoli Shi, Yang Yu, and Min Zhang
- Subjects
Cyanobacteria ,Photoinhibition ,biology ,Microcystis ,Phycocyanin ,Darkness ,Ultrastructure ,Microcystis aeruginosa ,Plant Science ,Aquatic Science ,biology.organism_classification ,Photochemistry ,Photosynthesis - Abstract
Microcystis aeruginosa (Kutz.) Kutz. commonly occurs as single cells at early recruitment but forms large colonies in summer. Colony formation will induce many acclimative changes. In this study, we demonstrated the photochemical changes before and after colony formation. In the laboratory, light curves showed that colonies were more responsive to high light than single cells. The values of the maximal slope of electron transport rate (ETR)-light curve (α), relative maximal electron transport rate (rETRmax ), and onset of light saturation (Ik ) of colonies were significantly higher than those of single cells (P
- Published
- 2011
47. Changes in abundance and community structure of bacteria associated with buoyantMicrocystiscolonies during the decline of cyanobacterial bloom (autumn–winter transition)
- Author
-
Fanxiang Kong, Yang Yu, Yuanfeng Cai, and Limei Shi
- Subjects
biology ,Ecology ,Microcystis ,Gammaproteobacteria ,Botany ,Alphaproteobacteria ,Bacteroidetes ,Dominance (ecology) ,Aquatic Science ,biology.organism_classification ,Bloom ,Temperature gradient gel electrophoresis ,Bacteria - Abstract
The structure and composition of the bacterial community associated with buoyant Microcystis colonies were monitored during the decline of a cyanobacterial bloom (from October 13, 2009 to January 27, 2010). When temperature decreased, the ratio between the colony-associated bacteria and the Microcystis gradually decreased as estimated by a quantitative real-time polymerase chain reaction (qRT-PCR)-based approach. Diversity of bacterial communities was determined through denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. Cluster analysis of the DGGE profiles showed that most of the bacterial communities associated with Microcystis colonies collected on the nearby dates were clustered together. The bacterial clones from four clone libraries in different months were classified into 5, 12, 6 and 12 operational taxonomic units, most of which were affiliated with Gammaproteobacteria , Alphaproteobacteria and Bacteroidetes . Shift in dominance from pathogenic Aeromonas sp. to Shewanella sp. capable of remineralization of many organic materials was observed, and both species seemed to be associated with Microcystis colonies along with the bloom decline. These results indicated that the potential harmful effects of the Microcystis bloom on the safety of lake water during the decline period should be taken into account.
- Published
- 2011
48. Effect of Excess Light on Colony Size and Photosynthetic Quantum Yield ofMicrocystisspp. during a Summer Bloom
- Author
-
Fanxiang Kong and Xiao-Dong Wu
- Subjects
Cyanobacteria ,biology ,Quantum yield ,Aquatic Science ,biology.organism_classification ,Photosynthesis ,Light intensity ,Horticulture ,Microcystis ,Botany ,Bloom ,Incubation ,Surface water ,Ecology, Evolution, Behavior and Systematics - Abstract
Variation of Microcystis spp. (Cyanobacteria) colony size and photosynthetic quantum yield were examined during a summer bloom in a large shallow lake (Lake Taihu). After exposure to direct solar radiation for four hours, about 60% of the colonies larger than 36 μm had changed into smaller colonies and single cells. Meanwhile, the photosynthetic quantum yields of Microcystis spp. decreased rapidly. Under a treatment of 30% of the light intensity ofthat at the surface, only about 10% of the large colonies changed into smaller colonies and single cells, and the photosynthetic quantum yields showed only a slight decrease. When the samples were incubated at the surface layer and 0.5 m depth from 0800 h to 1800 h, the number of small colonies and single cells increased more markedly than that at 1.0 m depth. During this incubation, the photosynthetic quantum yields of the Microcystis spp. at the surface water were significantly lower than that at the 0.5 m and 1.0 m depths from 1000 h to 1800 h. Direc...
- Published
- 2010
49. Diversity and abundance of aerobic anoxygenic phototrophic bacteria in two cyanobacterial bloom-forming lakes in China
- Author
-
Limei Shi, Fanxiang Kong, Yawei Zhou, Pengfu Li, Zhuting Chen, and Yuanfeng Cai
- Subjects
Cyanobacteria ,biology ,Ecology ,Alphaproteobacteria ,Aquatic Science ,biology.organism_classification ,Anoxygenic photosynthesis ,Microcystis ,parasitic diseases ,Gammaproteobacteria ,Botany ,Aerobic anoxygenic phototrophic bacteria ,Bacteria ,Betaproteobacteria - Abstract
Aerobic anoxygenic phototrophic (AAP) bacteria are widely distributed in marine and freshwater ecosystems. The aims of this study were to investigate the diversity and abundance of AAP bacteria in cyano- bacterial bloom-forming eutrophic lakes and to study the association of AAP bacteria with the bloom- forming cyanobacteria. Analysis of pufM gene (the light-reaction center gene) clone libraries indicated that in eutrophic lakes (Lake Taihu and Lake Chaohu, China) with cyanobacterium Microcystis blooms, the AAP bacteria were related to members of Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. In Lake Taihu and Lake Chaohu, Alphaproteobacteria accounted for 81.5% and 75.0% of Microcystis- associated AAP bacteria, respectively, and 84.6% and 72.5% of free-living AAP bacteria, respectively. The predominance of Alphaproteobacteria in the two lakes was different from the previously reported predominance of Betaproteobacteria in freshwater lakes. Quantitative real-time PCR analysis indicated that in Lake Taihu and Lake Chaohu, AAP bacteria represented an important part of the bacterial community associated with Microcystis, and the abundance of Microcystis-associated AAP bacteria (18.3% and 11.7%, respectively) was higher than that of free-living AAP bacteria (5.1% and 7.9%, respectively). The abundance of AAP bacteria in the two bloom-forming lakes was higher than the previously reported level in other eutrophic freshwater bodies.
- Published
- 2010
50. Assessing the combination effects of environmental estrogens in fish
- Author
-
Xiaoli Shi, Hong-Er Tian, Fanxiang Kong, Hui Zhang, Min Zhang, and Yang Yu
- Subjects
Male ,Carps ,Health, Toxicology and Mutagenesis ,Management, Monitoring, Policy and Law ,Biology ,Toxicology ,Models, Biological ,Risk Assessment ,Vitellogenins ,In vivo ,Animals ,Ecotoxicology ,Potency ,Models, Statistical ,Chromatography ,Dose-Response Relationship, Drug ,Concentration Response ,Estrogens ,Regression analysis ,Environmental Exposure ,General Medicine ,Confidence interval ,Dose–response relationship ,Environmental chemistry ,Regression Analysis ,Nonlinear regression ,Water Pollutants, Chemical - Abstract
The method on combined effects of environmental estrogens and mixture environmental risk assessment was discussed. Batch tests were conducted to assess the in vivo potency of mixtures of estrogens using plasma vitellogenin concentrations in male crucian carp (Carassius carassius) as the endpoint. A nonlinear regression was determined on the concentration response relationship for the single chemical of 17β-estradiol (E(2)), 17α-ethynylestradiol (EE(2)), 4-tert-octylphenol (OP), bisphenol A (BPA), and that of the mixed compounds at equipotent concentrations (E(2)-EE(2), E(2)-EE(2)-OP-BPA), the mixture was tested using a fixed-ratio design. On the basis of statistical selection criteria, the best-fit model is chosen individually for each set of data. Furthermore, the bootstrap methodology is applied for constructing confidence intervals for the estimated effect concentrations. The combined effects of the mixture can be predicted using biomathematical models based on the concentration and potency of the individual mixture components. The finding of non-monotonic dose-response relationship and the combined effects can be accurately predicted in whole range of exposure concentration by the reference models, whereas the outcome of simple effect summation with a great deal of indetermination. Results suggested that there can be a risk of mixture effects. The potential impact of components on mixture would depend predominantly on its concentration, the mixture ratio, and its relative potency. Existing environmental risk assessment procedures are limited in their ability to evaluate the combined effects of chemical mixtures, therefore further improvement is needed.
- Published
- 2010
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