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1.
《Harmful algae》2019
Microcystis spp., which occur as colonies of different sizes under natural conditions, have expanded in temperate and tropical freshwater ecosystems and caused seriously environmental and ecological problems. In the current study, a Bayesian network (BN) framework was developed to access the probability of microcystins (MCs) risk in large shallow eutrophic lakes in China, namely, Taihu Lake, Chaohu Lake, and Dianchi Lake. By means of a knowledge-supported way, physicochemical factors, Microcystis morphospecies, and MCs were integrated into different network structures. The sensitive analysis illustrated that Microcystis aeruginosa biomass was overall the best predictor of MCs risk, and its high biomass relied on the combined condition that water temperature exceeded 24 °C and total phosphorus was above 0.2 mg/L. Simulated scenarios suggested that the probability of hazardous MCs (≥1.0 μg/L) was higher under interactive effect of temperature increase and nutrients (nitrogen and phosphorus) imbalance than that of warming alone. Likewise, data-driven model development using a naïve Bayes classifier and equal frequency discretization resulted in a substantial technical performance (CCI = 0.83, K = 0.60), but the performance significantly decreased when model excluded species-specific biomasses from input variables (CCI = 0.76, K = 0.40). The BN framework provided a useful screening tool to evaluate cyanotoxin in three studied lakes in China, and it can also be used in other lakes suffering from cyanobacterial blooms dominated by Microcystis. 相似文献
2.
《Harmful algae》2016
This review summarizes the present state of knowledge regarding the toxic, bloom-forming cyanobacterium, Microcystis, with a specific focus on its geographic distribution, toxins, genomics, phylogeny, and ecology. A global analysis found documentation suggesting geographic expansion of Microcystis, with recorded blooms in at least 108 countries, 79 of which have also reported the hepatatoxin microcystin. The production of microcystins (originally “Fast-Death Factor”) by Microcystis and factors that control synthesis of this toxin are reviewed, as well as the putative ecophysiological roles of this metabolite. Molecular biological analyses have provided significant insight into the ecology and physiology of Microcystis, as well as revealed the highly dynamic, and potentially unstable, nature of its genome. A genetic sequence analysis of 27 Microcystis species, including 15 complete/draft genomes are presented. Using the strictest biological definition of what constitutes a bacterial species, these analyses indicate that all Microcystis species warrant placement into the same species complex since the average nucleotide identity values were above 95%, 16S rRNA nucleotide identity scores exceeded 99%, and DNA–DNA hybridization was consistently greater than 70%. The review further provides evidence from around the globe for the key role that both nitrogen and phosphorus play in controlling Microcystis bloom dynamics, and the effect of elevated temperature on bloom intensification. Finally, highlighted is the ability of Microcystis assemblages to minimize their mortality losses by resisting grazing by zooplankton and bivalves, as well as viral lysis, and discuss factors facilitating assemblage resilience. 相似文献
3.
《Harmful algae》2019
Non-diazotrophic Microcystis and filamentous N2-fixing Aphanizomenon and Dolichospermum (formerly Anabaena) co-occur or successively dominate freshwaters globally. Previous studies indicate that dual nitrogen (N) and phosphorus (P) reduction is needed to control cyanobacterial blooms; however, N limitation may cause replacement of non-N2-fixing by N2-fixing taxa. To evaluate potentially counterproductive scenarios, the effects of temperature, nutrients, and zooplankton on the spatio-temporal variations of cyanobacteria were investigated in three large, shallow eutrophic lakes in China. The results illustrate that the community composition of cyanobacteria is primarily driven by physical factors and the zooplankton community, and their interactions. Niche differentiation between Microcystis and two N2-fixing taxa in Lake Taihu and Lake Chaohu was observed, whereas small temperature fluctuations in Lake Dianchi supported co-dominance. Through structural equation modelling, predictor variables were aggregated into ‘composites’ representing their combined effects on species-specific biomass. The model results showed that Microcystis biomass was affected by water temperature and P concentrations across the studied lakes. The biomass of two filamentous taxa, by contrast, exhibited lake-specific responses. Understanding of driving forces of the succession and competition among bloom-forming cyanobacteria will help to guide lake restoration in the context of climate warming and N:P stoichiometry imbalances. 相似文献
4.
Mark J. McCarthy Peter J. Lavrentyev Longyuan Yang Lu Zhang Yuwei Chen Boqiang Qin Wayne S. Gardner 《Hydrobiologia》2007,581(1):195-207
Nitrogen dynamics and microbial food web structure were characterized in subtropical, eutrophic, large (2,338 km2), shallow (1.9 m mean depth), and polymictic Lake Taihu (China) in Sept–Oct 2002 during a cyanobacterial bloom. Population growth and industrialization are factors in trophic status deterioration in Lake Taihu. Sites for investigation were selected along a transect from the Liangxihe River discharge into Meiliang Bay to the main lake. Water column nitrogen and microbial food web measurements were combined with sediment–water interface incubations to characterize and identify important processes related to system nitrogen dynamics. Results indicate a gradient from strong phosphorus limitation at the river discharge to nitrogen limitation or co-limitation in the main lake. Denitrification in Meiliang Bay may drive main lake nitrogen limitation by removing excess nitrogen before physical transport to the main lake. Five times higher nutrient mineralization rates in the water column versus sediments indicate that sediment nutrient transformations were not as important as water column processes for fueling primary production. However, sediments provide a site for denitrification, which, along with nitrogen fixation and other processes, can determine available nutrient ratios. Dissimilatory nitrate reduction to ammonium (DNRA) was important, relative to denitrification, only at the river discharge site, and nitrogen fixation was observed only in the main lake. Reflecting nitrogen cycling patterns, microbial food web structure shifted from autotrophic (phytoplankton dominated) at the river discharge to heterotrophic (bacteria dominated) in and near the main lake. 相似文献
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6.
在太湖北部主要河口区及敞水区域采集纤毛虫样品, 并用定量蛋白银法进行分析。河口区设10个采样点, 敞水区设14个采样点。调查中共检出3纲15目60属的105种纤毛虫, 种类最多的是钩刺目(21种), 其次是寡毛目(20种)。纤毛虫优势种及其在河口区和敞水区占总丰度比例分别为: 寡毛目的双叉弹跳虫Halteria bifurcate Tamar (12.3%、18.1%)、大弹跳虫H. grandinella Dujardin (12.3%、10.9%)、短列裂隙虫Rimostrombidium brachykinetum Krainer (8.0%、13.4%)、圆筒状似铃壳虫Tintinnopsis cylindrata Kofoid Campbell (11.8%、4.5%)、盾纤目的银灰膜袋虫Cyclidium glaucoma Mller (3.1%、10.8%)。其他常见种类还有: 前口目的趣尾毛虫Urotricha farcta Claparde Lachmann、寡毛目的杯铃壳虫Codonella cratera Leidy、小裂隙虫R. humile Penard、奇异急游虫Strombidium mirabile Penard、小筒壳虫Tintinnidium pusillum Entz、缘毛目的水生钟虫复合种Vorticella aquadulcis complex和钟形钟虫V. campanula Ehrenberg。河口区和敞水区纤毛虫平均丰度分别为31407 cells/L(范围1 600-80 900 cells/L)和18618 cells/L(范围1225 -36000 cells/L), 平均生物量分别为1322.6 g/L(范围44.6-3119.7 g/L)和543.6 g/L(范围44.0-1570.4 g/L)。两个区域的优势类群相似, 均以寡毛目、前口目、盾纤目和缘毛目为主。但河口区纤毛虫生物多样性(种类丰富度、Simpson多样性指数、Margalef多样性指数、Shannon多样性指数)显著高于敞水区的(P0.05)。统计分析发现, 食藻种类与叶绿素a含量之间无显著相关, 而食菌种类的丰度和叶绿素a含量呈显著正相关关系(P0.001)。由此推测, 纤毛虫群落结构的空间差异可能与水华暴发程度有较大关系。 相似文献
7.
Field and experimental studies were conducted to evaluate the combined impacts of cyanobacterial blooms and small algae on
seasonal and long-term changes in the abundance and community structure of crustacean zooplankton in a large, eutrophic, Chinese
lake, Lake Chaohu. Seasonal changes of the crustacean zooplankton from 22 sampling stations were investigated during September
2002 and August 2003, and 23 species belonging to 20 genera were recorded. Daphnia spp. dominated in spring but disappeared in mid-summer, while Bosmina coregoni and Ceriodaphnia cornuta dominated in summer and autumn. Both maximum cladoceran density (310 ind. l−1) and biomass (5.2 mg l−1) appeared in autumn. Limnoithona sinensis, Sinocalanus dorrii and Schmackeria inopinus were the main species of copepods. Microcystis spp. were the dominant phytoplankton species and formed dense blooms in the warm seasons. In the laboratory, inhibitory effects
of small colonial Microcystis on growth and reproduction of Daphnia carinata were more remarkable than those of large ones, and population size of D. carinata was negatively correlated with density of fresh large colonial Microcystis within a density range of 0–100 mg l−1 (r = −0.82, P< 0.05). Both field and experimental results suggested that seasonal and long-term changes in the community structure of crustacean
zooplankton in the lake were shaped by cyanobacterial blooms and biomass of the small algae, respectively, i.e., colonial
and filamentous cyanobacteria contributed to the summer replacement of dominant crustacean zooplankton from large Daphnia spp. to small B. coregoni and C. cornuta, while increased small algae might be responsible for the increased abundance of crustacean zooplankton during the past decades. 相似文献
8.
水体富营养化和气候变暖是淡水生态系统面临的两大威胁。文章分别阐述了富营养化和气候变暖对淡水湖泊浮游藻类直接和间接效应, 并总结气候变暖可能通过影响水体理化性质、水生植物组成、食物链结构从而直接或间接改变浮游藻类生物量或群落结构。作者重点分析了气候变暖下湖泊生态系统蓝藻水华暴发机制, 比较了不同湖泊蓝藻对气候变暖和富营养化响应的异同点, 发现气候变暖和富营养化对湖泊生态系统影响存在相似性, 表现在均促进湖泊由清水-浊水稳态转变、增加蓝藻水华发生频率和强度。然而二者对湖泊浮游藻类影响的相对重要性取决于分层型湖泊和混合型湖泊的差异性、不同营养型湖泊和不同类群蓝藻组成差异性。作者认为, 开展气候变暖和富营养化下, 湖泊浮游藻类功能群响应研究亟待进行。 相似文献
9.
《Harmful algae》2016
Cyanobacteria can produce toxic metabolites known as cyanotoxins. Common and frequently investigated cyanotoxins include microcystins (MCs), nodularin (NOD) and saxitoxins (STXs). During the summer of 2011 extensive cyanobacterial growth was found in several fishponds in Serbia. Sampling of the water and fish (common carp, Cyprinus carpio) was performed. Water samples from 13 fishponds were found to contain saxitoxin, microcystin, and/or nodularin. LC–MS/MS showed that MC-RR was present in samples of fish muscle tissue. Histopathological analyses of fish grown in fishponds with cyanotoxin production showed histopathological damage to liver, kidney, gills, intestines and muscle tissues. This study is among the first so far to report severe hyperplasia of intestinal epithelium and severe degeneration of muscle tissue of fish after cyanobacterial exposure. These findings emphasize the importance of cyanobacterial and cyanotoxin monitoring in fishponds in order to recognize cyanotoxins and their potential effects on fish used for human consumption and, further, on human health. 相似文献
10.
《Harmful algae》2019
Lake Taihu, the third largest freshwater lake in China, suffers from harmful cyanobacteria blooms caused by Microcystis spp., which do not fix nitrogen (N). Reduced N (i.e., NH4+, urea and other labile organic N compounds) is an important factor affecting the growth of Microcystis. As the world use of urea as fertilizer has escalated during the past decades, an understanding of how urea cycling relates to blooms of Microcystis is critical to predicting, controlling and alleviating the problem. In this study, the cycling rates of urea-N in Lake Taihu ranged from non-detectable to 1.37 μmol N L−1 h−1 for regeneration, and from 0.042 μmol N L−1 h−1 to 2.27 μmol N L−1 h−1 for potential urea-N removal. The fate of urea-N differed between light and dark incubations. Increased 15NH4+ accumulated and higher quantities of the removed urea-15N remained in the 15NH4+ form were detected in the dark than in the light. A follow-up incubation experiment with 15N-urea confirmed that Microcystis can grow on urea but its effects on urea dynamics were minor, indicating that Microcystis was not the major factor causing the observed fates of urea under different light conditions in Lake Taihu. Bacterial community composition and predicted functional gene data suggested that heterotrophic bacteria metabolized urea, even though Microcystis spp. was the dominant bloom organism. 相似文献
11.
Different dynamics, of the vertical distribution of Microcystis aeruginosa colonies of different sizes, were examined in a large shallow lake (Taihu Lake) during a summer bloom. During the observation the Microcystis colonies, larger than 120 μm, were mainly concentrated in the upper layer both under calm and windy conditions. Colonies from 36 μm to 120 μm showed a clear relationship to wind conditions whereas colonies less than 36 μm showed a nearly uniform vertical distribution at the different depths. There was no clear relationship between the vertical distribution of colonies larger than 36 μm and light intensity. However, at solar noon, colonies less than 36 μm were mainly distributed in the middle layers of the water column. The results indicate that small colonies are easily affected by the wind‐induced mixing, and they show an ability for active movement in response to light intensity under calm conditions. In contrast, large colonies tend to show little diurnal repositioning to light intensity and thereby are mainly concentrated in the surface layer. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
Abundance, biomass and production of pelagic bacteria were examined over one year at monthly sampling intervals across a trophic profile in Meiliang Bay, Lake Taihu. With the lowest density in the open lake, the bacterial abundance showed a clear trend in relation to trophic status. The carbon content per cell was higher in autumn and winter, and the opposite was true for bacterial biomass. Bacterial 3[H]-TdR and 14[C]-Leu incorporation rates, cell production, turnover times and carbon production varied during the annual cycle at different sites. The ratio of bacterial production to primary production was high, independently of the method used, indicates that the microbial food web in Lake Taihu is an important component of the total food web of the lake and dominated by external inputs. Electronic supplementary material Supplementary material is available for this article at and is accessible for authorized users 相似文献
13.
Colonial Microcystis aeruginosa isolates tend to lose their typical colonial morph after some generations under laboratory conditions, one interesting but yet important question is whether unicellular M. aeruginosa, originally isolated from the field, can revert back to colonial morphology when growing back in natural waters. Based on this idea, we employed dialysis bags and plastic bottles to conduct an in situ experiment. Each of the dialysis bags and plastic bottles was filled with unicellular M. aeruginosa with high concentrations and then submerged to two natural lakes (Lake Caiyue and Lake Taihu) for 40 and 28 days, respectively. Results showed M. aeruginosa grew well in dialysis bags but not in plastic bottles; no colonies were observed in M. aeruginosa incubated in either dialysis bags or plastic bottles exposed in both lakes. This suggests laboratory maintained unicellular M. aeruginosa cannot revert back to colonial form after short-term exposure in natural conditions. 相似文献
14.
《Harmful algae》2019
Cyanobacterial blooms are intensifying global ecological hazards. The fine structure and dynamics of bloom community are critical to understanding bloom development but little understood. Here, the questions whether dominant bloomers have high diversity and whether dominant OTUs (operational taxonomical units) compete with one another were addressed. 16S rRNA gene amplicons from an annual bloom at five locations in Harsha Lake (Ohio, USA) showed cyanobacteria were the dominant phylum, and co-existing major bacterial phyla included Proteobacteria, Bacteroidetes, Actinoacteria, and Verrucomicrobia. On the genus level, the initial dominance by Dolichospermum in June yielded to Planktothrix in July, which were replaced by Microcystis and Cylindrospermopsis in August throughout the bloom. Based on the number of verified unique OTUs (a within-genus biodiversity metric), dominant genera tended to have high within-genus diversity. For example, Dolichospermum had 57 unique OTUs, Planktothrix had 36, Microcystis had 12, and Cylindrospermopsis had 4 unique OTUs. Interestingly, these different OTUs showed different dynamics and association with other OTUs. First, no between-OTU competitions were observed during the bloom cycle, and dominant OTUs were abundant throughout the bloom. Such biodiversity of OTUs and their dynamics were verified in Microcystis aeruginosa with two microcystin synthetase genes (mcyA and mcyG): the relative abundance of both genes varied during the bloom based on quantitative PCR. Two Dolichospermum circinale OTUs and one P. rubescens OTU were most abundant and persistently present throughout the entire bloom. Second, these OTUs differed in the OTUs they were associated with. Third, these OTUs tended to have different levels of association with the environmental factors, even they belonged to the same genera. These findings suggest the structure and dynamics of a cyanobacterial bloom community is complex, with only few OTUs dominating the bloom. Thus, high-resolution molecular characterization will be necessary to understand bloom development. 相似文献
15.
为揭示茶园间作果树对于节肢动物群落数量、空间格局的影响,2009年夏茶期间,于具有悠久茶-果间作历史、名茶洞庭碧螺春原产地的太湖东洞庭山选10种间作茶园,2010年春茶时节于西洞庭山选10种同类型间作茶园,调查果树的树丛之间、茶丛上层、茶丛中层、茶丛下层、地表和土壤层中各种节肢动物数量。发现:(1)两次调查结果具有较好的重现性;(2)每种供试茶园优势种害虫都是假眼小绿叶蝉Empoasca vitis Gthe和黑刺粉虱Aleurocanthus spiniferus(Quaintance)、其它主要害虫种类相同,东、西洞庭山优势种天敌相同;(3)10种茶园中茶丛上层、茶丛中层物种数多于其它层次;茶丛下层的个体数最大,主要是粉虱类和蚧类等小型同翅目昆虫;茶丛中层多样性指数稍高;(4)茶-桔、茶-板栗间作茶园物种较多;茶-腊梅间作茶园物种数、个体数较少。研究结果表明:茶园中合理地间作果树,可以增大生物多样性,即使在果树树丛之间、地表和土壤层中也拥有一定数量的节肢动物,间作明显地影响节肢动物群落的组成。 相似文献
16.
Seasonal dynamics of Anabaena flos-aquae (Lyngb.) Breb., including vegetative cells, akinetes and akinete envelopes, in bottom sediments and water column at both littoral and deeper central stations of a small Siberian reservoir was studied. Two types of akinetes were observed: in the first half of summer Anabaena formed akinetes, which served for vegetative reproduction and germinated in water column soon after differentiation, while in the second half of summer the akinetes produced served as a resting stages, which were deposited to bottom sediments. Canonical correlation analyses revealed that decrease of water temperature was the main environmental factor that stimulated the akinete formation. In contrast to the general opinion, concentration of inorganic phosphorus slightly, but positively influenced the akinete formation. Thus, akinetes formed in response to the temperature decrease, needs a certain level of this nutrient. At littoral and open-water stations abundance and seasonal dynamics of akinetes in water column and their sinking pattern were very similar. However, seasonal dynamics of abundance of akinetes in sediments in these two reservoir locations differed: whereas the abundance of akinetes in open water increased permanently during the summer, that in the littoral decreased soon after their sedimentation. The cause for decrease in abundance of akinetes in bottom sediments in winter is unknown. 相似文献
17.
采用普通牛肉汁培养基和 10倍稀释的普通牛肉汁培养基 (以下简称稀释培养基 )研究太湖沉积物中细菌多样性 ,发现在稀释培养基上生长的细菌数量普遍是在普通牛肉汁琼脂培养基上生长的细菌数量的 3~ 5倍。分离得到纯培养物的 16SrDNA部分序列 (5′端约 5 0 0bp)分析表明 ,不同培养基上生长的优势细菌类群存在差别 :普通培养基生长的细菌主要为γ_Proteobacteria(35. 1% ) ,其次为Actinobacteria(2 4 5 % )和Firmicutes(2 2 . 3% )等类群 ,其中大部分细菌与假单胞菌属 (Pseudomoas)、芽孢杆菌属 (Bacillus)和节杆菌属 (Archrobacter)细菌的系统关系密切 ;稀释培养基生长的细菌则主要为Actinobacteria(2 7. 1% )、Firmicutes(2 5 . 7% )、α_Proteobacteria(2 1. 4 % )和γ_Proteobacteria(15. 7% )等类群 ,与芽孢杆菌属 (Bacillus) (2 5. 7% )发育系统关系密切的细菌为优势属。研究结果表明同时采用两种培养基有助于从太湖沉积物中分离到更多种微生物。 相似文献
18.
近年来,随着全球气候变暖和水体富营养化程度加深,蓝藻水华频繁暴发。微囊藻毒素是有害蓝藻产生及释放的危害最大的一类蓝藻毒素,对生态环境和公众健康造成了严重的威胁。因此,寻求有效的微囊藻毒素降解方法已成为全球科学领域的研究热点。针对微囊藻毒素生物治理技术展开综述,阐述了微囊藻毒素的产生、理化性质及生物毒性,总结了微生物、水生植物、浮游动物等自然生物降解微囊藻毒素的能力。在此基础上概述了生物滤池、人工湿地、生态浮床、膜生物膜反应器等生物治理技术对微囊藻毒素的去除效果,分析了现有微囊藻毒素生物处理方法的优势和局限性,并对今后的研究方向提出展望,为解决水环境中微囊藻毒素的污染问题提供思路。 相似文献
19.
《Harmful algae》2019
The aim of the present research was to summarize the main reasons that explain the distribution of harmful blooms of cyanobacteria in Argentina. It is a large territory with climates ranging from humid tropical to cold temperate. We performed a meta-analysis of the published data and information in technical reports published from 1945 to 2015, and included additional data from personal non-published studies. A total of 122 water bodies affected by planktonic cyanobacterial blooms were recorded and geo-referenced. The analysis showed that blooms, defined as events exceeding 5000 cells/mL, occurred in different types of water bodies, including shallow lakes, rivers, streams, reservoirs, estuaries and storage facilities. Maximum bloom abundance and species and ecological strategies (dispersive, scum-forming, nitrogen fixer) responsible for each event were related to the geographic and climatologic characteristics and type and origin of water bodies. The Puna and the Andean Patagonia eco-regions were mostly free of blooms. The most impaired aquatic systems were shallow lakes and reservoirs (46.7 and 24.6%, respectively). Deep lakes had no reports of blooms and rivers were mainly affected at the regulated reaches, with intensities generally decreasing downstream the dams. Besides, 74.3% of the blooms reported in Argentina exceeded WHO Alert Level 2 for drinking and bathing waters (100,000 cells/mL). Thirty-nine species, identified by Komárek’s polyphasic approach to taxonomy, were responsible for the blooms. Microcystis aeruginosa, Dolichospermum spiroides, Dolichospermum circinale, Raphidiopsis mediterranea and Cylindrospermopsis raciborskii were frequently found participating in either mixed or single species blooms. The species distribution was associated with the eco-region and aquatic system typologies and affected by seasonality and climatological and geographic variables. The eco-strategies of cyanobacterial species showed stronger associations with the qualitative and quantitative indicators used in the meta-analysis, and appeared as useful tools for management measures. 相似文献