淡水湖泊浮游藻类对富营养化和气候变暖的响应

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。     

星云湖枝角类群落变化的长期特征与驱动因素

以星云湖为代表的云南大中型湖泊近年来受到多个环境压力的胁迫,出现水质持续恶化、环境功能降低、生态系统退化等问题。目前针对这些湖泊生态环境的研究主要集中于以富营养化为代表的单一环境胁迫,且以短期监测为主,因此有效的湖泊治理与生态修复急需评价多重环境压力的长期驱动过程与特征。本文围绕星云湖枝角类群落沉积物记录,开展了多指标(如色素、粒度等)的综合分析,并结合湖泊调查、历史资料和多变量统计方法对主要环境压力与长期生态响应模式进行了识别。结果表明:沉积物分析中共鉴定出枝角类10属16种,其中盘肠溞属与象鼻溞属占绝对优势;在1890年之前湖泊沉积物色素浓度稳定在较低水平,随后湖泊生产力缓慢上升且沉积物颗粒(63μm)增加;1980年初开始沉积物色素含量快速上升,耐污种C.sphaericus明显增加并成为绝对优势种;随着湖泊生产力水平的上升,枝角类生物量持续增加(R2=0.753,P0.001,n=33),且枝角类群落出现显著变化(R2=0.953,P0.001,n=33);同时,随着外来鱼类的引入和鱼类捕食压力的变化,象鼻溞生物量总体下降但个体大小变化不明显;营养水平的持续增加与水生植物的逐渐消亡,可能导致了枝角类物种趋于单一,底栖枝角类生物量总体下降。总之,星云湖枝角类群落结构与生物量在过去100年来出现了显著变化,湖泊富营养化与生产力的变化是主要驱动因子,同时外来鱼类的引入、水文条件及水生植物的变化也对枝角类群落产生了重要的影响。     

基于硅藻功能群特征揭示海西海近现代生态环境变化

依据硅藻的形态、生理与生态特点而定义的功能群分类,可以更好地描述对湖泊环境胁迫的响应特征.本研究识别了海西海表层沉积物硅藻群的空间分布模式,并通过多指标分析探讨其与环境因子的关系.结果表明: 主成分分析和冗余分析,水深和沉积物总氮含量是硅藻功能群空间分布异质性的主要驱动因子;水深8 m左右可能是海西海硅藻出现功能群分异的阈值,与热力分层深度等湖泊水文特征相对应.上述表层沉积物硅藻功能群空间分布结果为沉积物化石记录的解释提供了依据.沉积物钻孔分析显示,近百年来海西海硅藻功能群呈现明显的阶段性波动,与年均气温、沉积物总氮含量、中值粒径等指标变化相对应.气候变暖、富营养化和水位上升是驱动海西海硅藻功能群长期变化的主要环境因子,协同促进了功能群D、P、MP占优势.硅藻功能群多样性变化的长期特征表明气候变暖和营养盐富集促进了硅藻功能群多样性的增加,而海西海1957年筑坝和1990年水库扩容两次典型水文调控显著增加了湖泊水深,导致硅藻功能群多样性降低.     

大型浅水富营养化湖泊中蓝藻水华形成机理的思考

湖泊富营养化依然是我国目前以及今后相当长一段时期内的重大水环境问题。研究蓝藻水华的形成机制 ,对于科学预测湖泊中蓝藻水华的产生 ,并采取相应措施减少其带来的影响具有重要的生态和环境意义。为探索富营养化湖泊中蓝藻水华形成机理 ,综述了目前对我国大型浅水湖泊蓝藻水华成因研究现状和对水华形成机理的一般认识。分析了导致蓝藻水华形成的化学、物理和生物等主要环境因素 ,论述了蓝藻 ,尤其是微囊藻成为水华优势种的可能原因。认为对水华的形成需要全面认识 ,营养盐浓度的升高可能仅是蓝藻水华形成、且人们可以加以控制的因素之一 ;在探索水华成因时 ,不能仅仅局限于夏季蓝藻水华发生时环境特征的研究与观察 ,而应该提前关注蓝藻的越冬生理生态特征、春季复苏的生态诱导因子及其阈值以及在复苏后 ,蓝藻如何在生长过程中形成群体 ,并逐步成为湖泊水生生态系统中的优势种乃至形成水华的过程。并需要对蓝藻越冬的生存对策、蓝藻群体的形成的条件、蓝藻在春季复苏的触发条件及其生态阈值、以及蓝藻在与其它藻类种群竞争中取胜的生理生化特征有足够的认识。蓝藻水华的“暴发”是表观现象 ,其前提还是藻类一定的生物量 ,且是一个逐渐形成的过程。根据生态学的基本理论和野外对水华形成过程的原位观测     

云南程海湖泊系统响应富营养化与水文调控的长期模式

流域开发和气候变化背景下,逐渐增强的人类活动已经显著影响湖泊系统演替及功能。本研究以云南程海为研究对象,通过对程海湖泊沉积物记录与现代调查数据相结合,重建了程海近250年来的生态环境变化过程,探讨了程海湖泊系统在富营养化以及水文波动等多重环境压力影响下的长期响应模式。结果表明: 1970年之前程海营养水平整体偏低,1970—2000年间缓慢增长,2000年后快速增加,初级生产力呈长期上升趋势。1993—2000年期间,引水工程显著增加了湖泊水动力强度和物种扩散能力,促进了直链藻和菱形藻的增加。程海沉积物记录的碳循环变化主要受内源输入的长期影响。富营养化是硅藻群落长期演替的主要驱动因子,其次是湖泊水动力条件的波动。对程海的生态修复与流域管理不仅需要关注水体营养盐的富集与流域污染物的控制,同时还要考虑到湖泊水文调控和水位波动的影响。     

玄武湖菹草种群的发生原因及人工收割对水环境的影响

利用以沉水植物为主的水生植物进行水体生态修复是目前研究的热点问题, 为研究南京玄武湖2005-2006年的菹草(Potamogeton crispus)种群发生的原因及人工收割对水体的影响, 对玄武湖不同湖区定期监测其透明度、溶解氧、pH、TN、TP等水质指标, 并进行分析, 结果表明: 对湖泊蓝藻水华的应急处理, 使水体透明度提高179.5%, DO含量增高24.1%, TN、TP分别降低54.1%、74.5%, pH由9.1降至8.7, 水质改善是菹草种群萌发并能大规模生长的主要原因。而菹草生长阶段短期内对菹草进行大规模收割使水体DO含量降低42.1%, 透明度下降51.5%(P0.05), 收割虽从水体中携带走部分氮、磷营养盐, 但差异不显著(P0.05), 且收割后TP出现升高现象。故在对草藻型湖泊生态修复过程中, 可先期通过物理或化学手段改善水体透明度、调节pH、降低营养盐, 使其满足水生植物萌发及幼苗生长的需求, 为水生植物后期存活并生长打下基础, 在后期生态管理过程中, 应逐步收割植株, 缓慢从水体携带营养盐, 以达到改善水质, 恢复及重建水生生态系统的目的。       

300年来鄱阳湖营养盐演化重建与模拟

水体富营养化已经成为全球性的问题而受到广泛关注,然而其发生的过程和机制尚未完全明了。在湖泊营养演化过程中,水文和生态是两个最基本的制约因素。相对于短期的和试验性的研究,长时间尺度的营养盐变化过程能更全面地揭示营养盐的演化机制。以我国最大的淡水湖——鄱阳湖为例,采用湖泊水体交换周期模型和湖泊生态-营养盐动力耦合模型,重建鄱阳湖营养盐的长期变化,并利用沉积钻孔代用指标加以验证。在此基础上探讨其演化机制,模拟的时间序列中营养盐变化对气候水文与生态系统存在两种不同的响应模式。敏感因子分析显示:典型同步响应期中(1812—1828 AD),气候水文因子的贡献率达79.1%,生态因子为20.9%;典型异步响应期中(1844—1860 AD),两者贡献率分别为36.4%和63.6%。在模拟的营养盐变化时间序列中同步期占62.5%,说明气候因子在营养盐演化过程中起重要的作用;异步期虽只占12.5%,但对湖泊营养盐作用、营养盐反馈生物量同样至关重要。相关分析结果显示,生物量增长与TP含量基本呈线性关系,但存在一个阈值。在没有超过阈值前,生物量对TP具有较好的调节作用;当超过阈值之后,生物量的调节作用减弱。     

大理西湖流域开发历史与硅藻群落变化的模式识别

有关云南湖泊的研究长期集中于高原九大湖泊和水体富营养化评价,缺少对中小型水体及多重环境压力胁迫的综合研究.本文以大理西湖为例,结合沉积物记录与现代监测资料,甄别了气候变化和人类活动干扰下硅藻群落结构的长期响应模式及其驱动强度.结果表明: 20世纪50年代以前,大理西湖总体处于自然演化阶段;1950年代开始,围湖造田和流域改造的增强导致了水体营养水平增加、水动力条件改变,硅藻优势种由扁圆卵型藻替代为脆杆藻属;而1997年以来营养水平的快速增加和湖泊水动力的改变,促进了浮游藻类大量生长、底栖硅藻持续减少,同时水生植物快速退化、生态系统稳定性明显降低.因此,在长期流域开发的背景下,对云南中小型高山湖泊的有效保护需要评价流域开发类型、强度及全球变暖的长期影响.     

湖泊蓝藻水华发生机理研究进展

蓝藻水华是富营养化湖泊常见的生态灾害,通过产生毒素、死亡分解时使水体缺氧和破坏正常的食物网威胁到饮用水安全、公众健康和景观,会造成严重的经济损失和社会问题,揭示其发生机理是进行防治的基础。综述了蓝藻水华发生机理的主要假说和证据,主要分为环境因子(营养盐、氮磷比、温度、微量元素、浮游动物牧食、水文和气象条件等)和生理生态特性(伪空泡、胶质鞘、CO2浓缩机制、适应低光强、贮藏营养物质、防晒、产毒素和固氮等)两个方面;评述了主要新理论,展望了今后的研究。到目前为止的研究表明寻找一两个关键因子并不能阐明蓝藻水华的发生机理。现存的理论或假说尽管已经在蓝藻水华的防治实践中产生重要作用,但仍然未能清楚地阐释其发生的客观规律。认为蓝藻水华是在各种环境因子(外因)的耦合驱动下,水华蓝藻由于其独特的生理生态特性(内因),产生巨大的生物量而在浮游植物群落中占绝对优势,在合适的水文气象条件下集聚于水表而形成。因此水华机理的研究应同时关注水华蓝藻的生理生态学规律和蓝藻水华发生的各种环境条件。不同环境因子协同影响水华蓝藻的不同生理生态特性的表达,从而影响水华的发生过程,将可能是以后研究的重点。蓝藻水华机理的研究在微观方面正趋向于应用分子生物学手段分析蓝藻生理过程,宏观方面则将广泛应用遥感遥测技术观测全湖蓝藻的变化规律。今后加强对水华蓝藻生理生态特性的基因表达与调控和环境多因子耦合作用于蓝藻水华过程的研究将有重要意义。蓝藻水华的机理研究包括现象、过程和原因3个层次的问题,通过大量的现象和过程的研究,不断揭示其发生过程中水华蓝藻的群落演替、种群发展、细胞活性和分子机理等变化规律,才能找到其发生的真正原因,为其防治提供理论依据和更好的治理措施。在蓝藻水华防治方面,控制营养盐和生态修复可能将是今后很长时间内最根本最有效和最具操作性的方法。     

附着生物在浅水富营养化湖泊藻-草型生态系统转化过程中的作用

不同营养盐水平下附着生物对水生植物影响的实验结果表明, 随营养盐浓度的升高, 附着生物的生物量随之增加, 且对水生植物光合作用的抑制作用也相应增强. 结合其他研究的风浪、光照、营养盐形态和鱼的牧食对水生植物的影响, 得出在浅水富营养化湖泊中, 草型生态系统与藻型生态系统互相转化的先决条件是营养盐水平, 当其浓度发生变化时, 对生态系统造成胁迫, 导致生态系统不稳定, 此时, 外部的任何一点扰动(如风浪、高水位、鱼等)就有可能使得原来的生态系统发生崩溃, 新的与环境相协调的生态系统得以建立. 从理论上解释了湖泊生态系统在草型和藻型之间转化的机理, 为湖泊富营养化治理与生态修复提供了理论依据.     

Asynchronous onset of eutrophication among shallow prairie lakes of the Northern Great Plains,Alberta, Canada

Coherent timing of agricultural expansion, fertilizer application, atmospheric nutrient deposition, and accelerated global warming is expected to promote synchronous fertilization of regional surface waters and coherent development of algal blooms and lake eutrophication. While broad‐scale cyanobacterial expansion is evident in global meta‐analyses, little is known of whether lakes in discrete catchments within a common lake district also exhibit coherent water quality degradation through anthropogenic forcing. Consequently, the primary goal of this study was to determine whether agricultural development since ca. 1900, accelerated use of fertilizer since 1960, atmospheric deposition of reactive N, or regional climate warming has resulted in coherent patterns of eutrophication of surface waters in southern Alberta, Canada. Unexpectedly, analysis of sedimentary pigments as an index of changes in total algal abundance since ca. 1850 revealed that while total algal abundance (as β‐carotene, pheophytin a) increased in nine of 10 lakes over 150 years, the onset of eutrophication varied by a century and was asynchronous across basins. Similarly, analysis of temporal sequences with least‐squares regression revealed that the relative abundance of cyanobacteria (echinenone) either decreased or did not change significantly in eight of the lakes since ca. 1850, whereas purple sulfur bacteria (as okenone) increased significantly in seven study sites. These patterns are consistent with the catchment filter hypothesis, which posits that lakes exhibit unique responses to common forcing associated with the influx of mass as water, nutrients, or particles.     

Predicting cyanobacterial dynamics in the face of global change: the importance of scale and environmental context

There is growing concern that harmful cyanobacterial blooms are increasing in frequency and occurrence around the world. Although nutrient enrichment is commonly identified as a key predictor of cyanobacterial abundance and dominance in freshwaters, several studies have shown that variables related to climate change can also play an important role. Based on our analysis of the literature, we hypothesized that temperature or water‐column stability will be the primary drivers of cyanobacterial abundance in stratified lakes whereas nutrients will be the stronger predictors in frequently mixing water bodies. To test this hypothesis, as well as quantify the drivers of cyanobacteria over different scales and identify interactions between nutrients and climate‐related variables, we applied linear and nonlinear mixed‐effect modeling techniques to seasonal time‐series data from multiple lakes. We first compared time series of cyanobacterial dominance to a published lake survey and found that the models were similar. Using time‐series data of cyanobacterial biomass, we identified important interactions among nutrients and climate‐related variables; dimictic basin experienced a heightened susceptibility to cyanobacterial blooms under stratified eutrophic conditions, whereas polymictic basins were less sensitive to changes in temperature or stratification. Overall, our results show that due to predictable interactions among nutrients and temperature, polymictic and dimictic lakes are expected to respond differently to future climate warming and eutrophication.     

Role of Predatory Bacteria in the Termination of a Cyanobacterial Bloom

Changes in cyanobacterial abundance and in the occurrence of bacteria of bacteria capable of lysing cyanobacteria were monitored over a period of 6 months (May to October 1998) in eutrophic Brome Lake (Quebec, Canada), in which dense cyanobacterial blooms recur regularly. By screening lake water, we isolated two strains of lytic bacteria, from the family Cytophagaceae. When tested on 12 cyanobacteria and 6 heterotrophic bacteria, strain 1 lysed only Anabaena flos-aquae and strain 2 lysed only Synechococcus cedorum, Synechococcus leopoliensis, Synechococcus elongatus, and Anacystic nidulans: both liquid and agar-grown cultures of these cyanobacteria were lysed. The number of plaque forming units of bacteria increased dramatically during the decline of the bloom. The results are consistent with an important role for these host-specific lytic bacteria in control and elimination of cyanobacterial blooms in this lake.     

Hindcasting cyanobacterial communities in Lake Okaro with germination experiments and genetic analyses

Cyanobacterial blooms are becoming increasingly prevalent worldwide. Sparse historic phytoplankton records often result in uncertainty as to whether bloom-forming species have always been present and are proliferating in response to eutrophication or climate change, or if there has been a succession of new arrivals through recent history. This study evaluated the relative efficacies of germination experiments and automated rRNA intergenic spacer analysis (ARISA) assays in identifying cyanobacteria in a sediment core and thus reconstructing the historical composition of cyanobacterial communities. A core (360 mm in depth) was taken in the central, undisturbed basin of Lake Okaro, New Zealand, a lake with a rapid advance of eutrophication and increasing cyanobacteria populations. The core incorporated a tephra from an 1886 volcanic eruption that served to delineate recent sediment deposition. ARISA and germination experiments successfully detected akinete-forming nostocaleans in sediment dating 120 bp and showed little change in Nostocales species structure over this time scale. Species that had not previously been documented in the lake were identified including Aphanizomenon issatschenkoi , a potent anatoxin-a producer. The historic composition of Chrococcales and Oscillatoriales was more difficult to reconstruct, potentially due to the relatively rapid degradation of vegetative cells within sediment.     

Vulnerability of pejerrey Odontesthes bonariensis populations to climate change in pampean lakes of Argentina

The vulnerability of the pejerrey Odontesthes bonariensis population in Lake Chasicó was assessed under different climate change conditions. During the sampling period, the water temperature was adequate for fish reproduction and to sustain an adequate sex ratio. Climate-driven higher temperatures, however, may severely distort population structure and cause drastic reduction or local extinction of stocks. Lake Chasicó can be classified as eutrophic with clear waters and cyanobacteria that regularly cause fish mortality were identified as Nodularia spumigena and Oscillatoria sp. Global warming may strengthen the effects of eutrophication (e.g. toxic blooms or anoxia). Since many Cyanophyta species tolerate higher temperatures better than other algae, toxic blooms could increase. Furthermore, cyanobacteria have low nutritional value and could decouple the low-diversity food web. Lake Chasicó has currently the salinity optimum (c. 20) for the development of the early life-history stages of O. bonariensis. Climate change, however, is likely to amplify the intensity of droughts or inundations. Floods can endanger O. bonariensis development due to its sub-optimal growth at low salinity and droughts could increase lake salinity and also temperature and nutrient concentration. In order to reduce some of the effects of climate change on the O. bonariensis population in Lake Chasicó, integrated basin management based on an eco-hydrological approach is proposed.     

Preliminary analysis to estimate the spatial distribution of benefits of P load reduction: Identifying the spatial influence of phosphorus loading from the Maumee River (USA) in western Lake Erie

Since the early 2000s, Lake Erie has been experiencing annual cyanobacterial blooms that often cover large portions of the western basin and even reach into the central basin. These blooms have affected several ecosystem services provided by Lake Erie to surrounding communities (notably drinking water quality). Several modeling efforts have identified the springtime total bioavailable phosphorus (TBP) load as a major driver of maximum cyanobacterial biomass in western Lake Erie, and on this basis, international water management bodies have set a phosphorus (P) reduction goal. This P reduction goal is intended to reduce maximum cyanobacterial biomass, but there has been very limited effort to identify the specific locations within the western basin of Lake Erie that will likely experience the most benefits. Here, we used pixel‐specific linear regression to identify where annual variation in spring TBP loads is most strongly associated with cyanobacterial abundance, as inferred from satellite imagery. Using this approach, we find that annual TBP loads are most strongly associated with cyanobacterial abundance in the central and southern areas of the western basin. At the location of the Toledo water intake, the association between TBP load and cyanobacterial abundance is moderate, and in Maumee Bay (near Toledo, Ohio), the association between TBP and cyanobacterial abundance is no better than a null model. Both of these locations are important for the delivery of specific ecosystem services, but this analysis indicates that P load reductions would not be expected to substantially improve maximum annual cyanobacterial abundance in these locations. These results are preliminary in the sense that only a limited set of models were tested in this analysis, but these results illustrate the importance of identifying whether the spatial distribution of management benefits (in this case P load reduction) matches the spatial distribution of management goals (reducing the effects of cyanobacteria on important ecosystem services).     

How important are trophic state,macrophyte and fish population effects on cladoceran community? A study in Lake Erhai

Environmental controls on cladoceran community structure in lake ecosystems are complex and may involve many environmental parameters including trophic state and fish populations. In Lake Erhai, a plateau lake located in southwest China, it was hypothesized that a combination of lake eutrophication and planktivorous fish introduction would increase the abundance of cladoceran, while also decreasing cladoceran size. To test this hypothesis, we examined temporal changes in cladoceran microfossils in the sediments of Lake Erhai over the past century. The influence of changing macrophyte coverage within the littoral region of the lake was also considered. Results demonstrated that cladoceran abundance (measured as flux of cladoceran fossils in the sediments) increased markedly accompanying eutrophication of the lake. In addition, there was a shift in the dominant cladoceran species from those species that prefer oligotrophic conditions to those that prefer mesotrophic and eutrophic conditions. A reduction in the ephippium length of Daphnia spp. was observed and attributed to the introduction of the planktivorous fish Neosalanx taihuensis. Our findings indicated that eutrophication and fish introduction were the main controls affecting cladoceran community structure during the recent decades, and predation by planktivorous fish had an important impact on Daphnia body size.     

Mesozooplankton and microzooplankton grazing during cyanobacterial blooms in the western basin of Lake Erie

Lake Erie is the most socioeconomically important and productive of the Laurentian (North American) Great Lakes. Since the mid-1990s cyanobacterial blooms dominated primarily by Microcystis have emerged to become annual, late summer events in the western basin of Lake Erie yet the effects of these blooms on food web dynamics and zooplankton grazing are unclear. From 2005 to 2007, grazing rates of cultured (Daphnia pulex) and natural assemblages of mesozooplankton and microzooplankton on five autotrophic populations were quantified during cyanobacterial blooms in western Lake Erie. While all groups of zooplankton grazed on all prey groups investigated, the grazing rates of natural and cultured mesozooplankton were inversely correlated with abundances of potentially toxic cyanobacteria (Microcystis, Anabaena, and Cylindrospermopsis; p < 0.05) while those of the in situ microzooplankton community were not. Microzooplankton grazed more rapidly and consistently on all groups of phytoplankton, including cyanobacteria, compared to both groups of mesozooplankton. Cyanobacteria displayed more rapid intrinsic cellular growth rates than other phytoplankton groups under enhanced nutrient concentrations suggesting that future nutrient loading to Lake Erie could exacerbate cyanobacterial blooms. In sum, while grazing rates of mesozooplankton are slowed by cyanobacterial blooms in the western basin of Lake Erie, microzooplankton are likely to play an important role in the top-down control of these blooms; this control could be weakened by any future increases in nutrient loads to Lake Erie.     

Biodegradability and adsorption on lake sediments of cyanobacterial hepatotoxins and anatoxin-a

Cyanobacterial hepatotoxins and anatoxin-a, a neurotoxin, were shown to be degraded when crude extracts of lysed toxic laboratory strains of cyanobacteria were exposed to natural populations of micro-organisms from lakes. While anatoxin-a decayed equally fast with all the inocula from lake sediment and water, the degradation rate of hepatotoxins was higher with inocula from places at which cyanobacterial water blooms had occurred than with inocula from places with no known mass occurrences of cyanobacteria. Degradation was slowest when an inoculum from a humic lake was used. A part of the loss of the toxins was shown to be due to adsorption on lake sediments.     

Targeted deep sequencing reveals high diversity and variable dominance of bloom-forming cyanobacteria in eutrophic lakes

Cyanobacterial blooms in eutrophic lakes are severe environmental problems worldwide. To characterize the spatiotemporal heterogeneity of cyanobacterial blooms, a high-throughput method is necessary for the specific detection of cyanobacteria. In this study, the cyanobacterial composition of three eutrophic waters in China (Taihu Lake, Dongqian Lake, and Dongzhen Reservoir) was determined by pyrosequencing the cpcBA intergenic spacer (cpcBA-IGS) of cyanobacteria. A total of 2585 OTUs were obtained from the normalized cpcBA-IGS sequence dataset at a distance of 0.05. The 238 most abundant OTUs contained 92% of the total sequences and were classified into six cyanobacterial groups. The water samples of Taihu Lake were dominated by Microcystis, mixed Nostocales species, Synechococcus, and unclassified cyanobacteria. Besides, all the samples from Taihu Lake were clustered together in the dendrogram based on shared abundant OTUs. The cyanobacterial diversity in Dongqian Lake was dramatically decreased after sediment dredging and Synechococcus became exclusively dominant in this lake. The genus Synechococcus was also dominant in the surface water of Dongzhen Reservoir, while phylogenetically diverse cyanobacteria coexisted at a depth of 10 m in this reservoir. In summary, targeted deep sequencing based on cpcBA-IGS revealed a large diversity of bloom-forming cyanobacteria in eutrophic lakes and spatiotemporal changes in the composition of cyanobacterial communities. The genus Microcystis was the most abundant bloom-forming cyanobacteria in eutrophic lakes, while Synechococcus could be exclusively dominant under appropriate environmental conditions.