为探讨水文过程对水库硅藻异常增殖的影响,对江苏宜兴横山水库的硅藻生消过程中浮游植物、水质、降水、水位、气温等指标进行观测研究.结果表明,横山水库硅藻年际生物量波动很大,9月出现明显的异常增殖,总生物量达到14.27 mg/L,硅藻的优势属为针杆藻（Synedra）、小环藻（Cyclotella）、曲壳藻（Achnanthes）和直链藻（Melosira）,以针杆藻的优势度最高;浮游植物生物量与营养盐浓度关系不明显,与总氮浓度甚至呈负相关,但小环藻生物量与水体溶解性磷浓度呈正相关;水库的换水率与浮游植物生物量、硅藻的异常增殖过程和营养盐浓度水平均密切关联,总氮、溶解性磷浓度与水库换水率呈正相关,而硅藻生物量与水库换水率呈指数负相关.数值拟合分析显示硅藻生物量可以用换水率和磷浓度推算而得.研究表明,对于中营养水平的水库,硅藻生物量变化可能受水文过程与水质条件共同控制,在水库的硅藻水华防控中,既要加强营养盐水平的严格控制,也需考虑水文过程的调控手段.

为了解我国东南湿润区丘陵山地型水库硅藻的群落结构特征和控制因素,于2015年6月硅藻水华敏感期对苏南地区18座水库的浮游植物群落结构和水质进行调查,分析了营养盐、水深、库容等因素与硅藻及其它浮游生物的关系.结果表明,硅藻达到轻度水华水平(硅藻细胞含量介于100~1 000万cells·L-1)的水库有10座,对供水和景观功能产生明显影响;苏南地区水库普遍处于中营养和富营养水平,总氮浓度普遍偏高,磷及营养状态指数与硅藻生物量的关系密切;苏南地区水库中的浮游植物在数量上以蓝藻门中的席藻为主,在生物量上则以硅藻门、绿藻门和蓝藻门为主,其中硅藻门浮游植物平均占总浮游植物生物量的46.8%,是浮游植物异常增殖的主要门类;硅藻门中,主要是针杆藻、小环藻、曲壳藻和直链藻这4个种属占优,特别是针杆藻和小环藻,平均占硅藻总生物量的51.6%和21.4%;较深的水体,利于硅藻成为主要优势藻门;较大的水库流域库容比和较高总磷水平会导致水库营养水平和叶绿素浓度增加,促进浮游植物从硅藻门向绿藻门、蓝藻门演替,增加藻类危害的风险.因此,对于该地区水库,需要加强流域管理,并且针对水库自身的特点,包括水深、流域库容比等,确定其特定的富营养化控制策略,从而减少硅藻等藻类水华发生的风险,提升水源地水质安全保障能力.

基于溧阳市天目湖沙河水库2009—2014年的硅藻群落结构及水质调查,以及宜兴横山水库等硅藻水华期藻类和水质调查数据,分析了太湖流域水库中硅藻水华群落结构特征及受气温、水位、营养盐等环境条件的影响.结果表明,太湖流域硅藻水华的主要发生期为5—7月,快速生长期发生在气温为16~26℃期间,当气温超过26℃时,硅藻的生物量开始下降.硅藻的优势属包括针杆藻、曲壳藻、小环藻和颗粒直链藻.其中沙河水库和横山水库中针杆藻是主要危害,其生物量主导了硅藻总生物量.大溪水库有时以针杆藻为主,有时以颗粒直链藻为主.当总氮浓度低于1.0 mg/L的Ⅲ类水上限时,水体氮浓度能大大限制硅藻生物量,当总磷浓度低于0.025 mg/L的Ⅱ类水上限时,也可能对硅藻生物量产生限制.高于此营养水平,硅藻水华的严重程度主要受气温、降雨等因素影响.研究表明,对于处于中营养水平的太湖流域水库而言,硅藻生物量既受气温、降雨、水位等气象水文条件的控制,又受氮、磷、硅等营养盐供给的影响.硅藻水华的防控既要关注气候和气象条件,也要尽量削减氮、磷营养盐入湖通量,维持较低营养盐水平是确保硅藻水华不形成危害的关键.

The DYRESM-CAEDYM model was used to quantify the potential effects of reductions in external nutrient loads to the Shahe Reservoir in China, with an emphasis on effects on phytoplankton biomass. DYRESM-CAEDYM was calibrated using field data for a 2-year period and validated against a separate 1-year period. Simulated values for water temperature, dissolved oxygen, total nitrogen, total phosphorus, and chlorophyll a showed good agreement with field measurements. The model tended to underestimate peak values of inorganic nutrients such as ammonium, nitrate, and phosphate, with phosphate levels close to detection limits in both observed and simulated values. The model successfully captured seasonal phytoplankton succession, indicating spring peaks of diatom biomass and summer peaks of cyanophytes. Scenarios in which different reductions in external loading were applied suggest that simultaneous reductions in both external nitrogen and external phosphorus loading is more effective in controlling phytoplankton biomass than reducing input of either nutrient alone. Diatoms responded more strongly to load reductions in phosphorus input than nitrogen load, whereas cyanophytes showed the opposite pattern. A combined 25% reduction in the external loading of both nutrients could significantly decrease phytoplankton biomass in the reservoir below the 7 mu g/L chlorophyll a required by drinking water standards, and the study indicated that DYRESM-CAEDYM can be a useful management tool for eutrophication control.

在我国东南诸省，水库是极重要的可控水资源。特别是近来河流和平原湖泊污染加重，水库在城市供水等方面作用日显。但水库中有害蓝藻、硅藻等浮游植物在适宜营养盐和气象条件下异常增殖，甚而形成水华，对水库的城市供水功能影响甚大。本项目围绕降水等气候因素对东南地区水库中有害藻类的影响规律问题，以江苏溧阳天目湖沙河水库和浙江淳安千岛湖(新安江水库)为重点，兼顾苏南地区18个水源地型水库和宜兴市横山水库，基于水库藻类群落结构组成、相关水质、同步气象的长期监测与收集，结合原位营养盐条件实验，采用统计分析、水库生态模型模拟等手段，探讨了东南地区水库有害藻类的种群特征、异常增殖的水文气象及营养盐条件、有望采取的应对措施等问题，取得了如下主要认识:1)硅藻和蓝藻是东南水库常见有害门类，其中硅藻门中的小环藻、针杆藻、曲壳藻、直链藻属，蓝藻门中的束丝藻、微囊藻、尖头藻、席藻属，甚至拟柱胞藻，是江浙地区水库中常见有害属;2)不同门的藻类，同一门中不同属的藻类，适宜生长季节不同，以硅藻门为例，针杆藻的主要生长季为5-6月，小环藻的主要生长季为4月，而蓝藻门的几个优势种往往在6-8月形成生长高峰;3)由于水库换水周期较短，水文气象条件对水库藻类的影响很大，影响程度甚至超过营养盐，同时水文气象过程对营养盐影响也是决定性的;4)应对措施上，基于生态模型分析，进一步降低水库中的营养盐是应对藻类异常增殖风险的关键，调控水库渔业，限制鲢鳙鱼放养规模，对藻类异常增殖控制有效。项目研究中与新西兰、芬兰、丹麦等开展合作，发表SCI论文3篇，英文EI文章1篇，中文CSCD文章10篇，培养研究生6名。研究成果直接服务于江苏省太湖水污染防治办公室、溧阳市天目湖水源地生态环境保护领导小组办公室、淳安县环境保护局等相关水库环境管理部门，促成了溧阳市与中科院联合设立溧阳天目湖流域生态系统观测研究站以及南京地理与湖泊研究所与淳安县人民政府战略合作协议的签署。

为探索尿素在淡水生态系统中的作用,于2013年3月—2014年2月调查了江苏溧阳天目湖沙河水库及中田河入库河口中,尿素氮和不同形态氮素的含量和分布特征.结果表明,沙河水库中尿素普遍存在,全库年平均尿素氮浓度为0.016 mg·L-1（0.007—0.029 mg·L-1）;河、库尿素氮含量在不同月份波动较大,施肥期的2月、6月、11月含量较高,而在非施肥期含量较低,且河、库含量更加接近;沙河水库尿素氮的空间分布随季节变化而变化,一般在下游旅游集中区和上游靠近农业区出现尿素氮含量高值.此外,沙河水库溶解性氮以无机氮库为主,有机氮占29.09%,硝态氮是库体的主要氮形态;其中尿素氮占总氮、溶解性总氮、溶解性有机氮和生物可利用氮的年平均百分比分别为1.80%、2.21%、8.31%、3.54%.相关分析表明,沙河水库尿素含量与溶解氧含量呈显著负相关,与溶解性有机氮呈显著正相关.研究表明,天目湖沙河水库尿素含量的时空变化主要受外源输入（人类活动）的影响,其时间变化规律与农业活动密切相关,空间分布差异主要受污染源（河道入库口、农业、旅游业和养殖业）分布及其活动的影响.

A five-year (January 2009-December 2013) monthly monitoring program was undertaken in Shahe Reservoir to study phytoplankton dynamics and their relation to several key controlling factors including nutrient content and temperature. The results revealed that the phytoplankton biomass showed a significant single peak (mean of 30 mg/L) during May-July. The predominant genera showed significant seasonal succession, with the peak value of diatom biomass appearing in late spring and the peak value of cyanobacterial biomass appearing at early summer. Upon reduction of nitrogen and phosphorus, the biomass of phytoplankton in the reservoir decreased drastically. Based on correlation analysis and ordination analysis, biomass of the dominant genera showed significant positive relationships to temperature. The biomass of three dominant genera of Bacillariophyta, Cyclotella, Synedra, and Achnanthes, were significantly and positively related to ammonium concentration, while the biomass of three dominant genera from Cyanophyta, Aphanizomenon, Phormidium, and Raphidiopsis, were significantly and positively correlated to dissolved total P concentration. The results suggested that the phytoplankton biomass in Shahe Reservoir was mainly controlled by climatic factors, such as temperature and precipitation. However, N and P also had a strong influence on biomass and population structure of the phytoplankton as well as on proliferation of blooms. To avoid algal blooms in reservoirs located in southeast China, we suggest that both N and P should be reduced to grade II level of the Chinese surface water standard; more specifically, total N needs to be lower than 0.50 mg/L and total P needs to be lower than 0.025 mg/L.

Excessive nitrogen (N) and phosphorus (P) loading of aquatic ecosystems is a leading cause of eutrophication and harmful algal blooms worldwide, and reducing nutrient levels in water has been a primary management objective. To provide a rational protection strategy and predict future trends of eutrophication in eutrophic lakes, we need to understand the relationships between nutrient ratios and nutrient limitations. We conducted a set of outdoor bioassays at the shore of Lake Taihu. It showed that N only additions induced phytoplankton growth but adding only P did not. Combined N plus P additions promoted higher phytoplankton biomass than N only additions, which suggested that both N and P were deficient for maximum phytoplankton growth in this lake (TN:TP = 18.9). When nutrients are present at less than 7.75-13.95. mg/L TN and 0.41-0.74. mg/L TP, the deficiency of either N or P or both limits the growth of phytoplankton. N limitation then takes place when the TN:TP ratio is less than 21.5-24.7 (TDN:TDP was 34.2-44.3), and P limitation occurs above this. Therefore, according to this ratio, controlling N when N limitation exists and controlling P when P deficiency is present will prevent algal blooms effectively in the short term. But for the long term, a persistent dual nutrient (N and P) management strategy is necessary.
© 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.

Nitrogen (N) and phosphorus (P) over-enrichment has accelerated eutrophication and promoted cyanobacterial blooms worldwide. The colonial bloom-forming cyanobacterial genus Microcystis is covered by sheaths which can protect cells from zooplankton grazing, viral or bacterial attack and other potential negative environmental factors. This provides a competitive advantage over other phytoplankton species. However, the mechanism of Microcystis colony formation is not clear. Here we report the influence of N, P and pH on Microcystis growth and colony formation in field simulation experiments in Lake Taihu (China). N addition to lake water maintained Microcystis colony size, promoted growth of total phytoplankton, and increased Microcystis proportion as part of total phytoplankton biomass. Increases in P did not promote growth but led to smaller colonies, and had no significant impact on the proportion of Microtystis in the community. N and P addition together promoted phytoplankton growth much more than only adding N. TN and TP concentrations lower than about TN 7.75-13.95 mg L-1 and TP 0.41-0.74 mg L-1 mainly promoted the growth of large Microcystis colonies, but higher concentrations than this promoted the formation of single cells. There was a strong inverse relationship between pH and colony size in the N&P treatments suggesting CO2 limitation may have induced colonies to become smaller. It appears that Microcystis colony formation is an adaptation to provide the organisms adverse conditions such as nutrient deficiencies or CO2 limitation induced by increased pH level associated with rapidly proliferating blooms. (C) 2013 Elsevier B.V. All rights reserved.

基于2012年天目湖沙河水库逐月水质及浮游植物群落结构的监测,采用主成分分析及典范对应分析,对沙河水库水质时空分布特征及其对浮游植物群落演替的影响进行了分析。结果表明,沙河水库透明度（SD）、悬浮物（SS）、高锰酸盐指数（CODMn）、叶绿素a（Chl a）、总磷（TP）、总氮（TN）等主要水质因子既有明显的季节变化,也存在显著的空间分布差异,浮游植物生物量和群落结构也表现出显著的季节演替。从丰度上看,蓝藻门的席藻全年都是优势种,但冬、春季节硅藻门和隐藻门藻类丰度显著增高。从生物量上看,春季的优势种为硅藻门的针杆藻,是沙河水库水体透明度的主要影响因子。主成分分析表明,沙河水库的氮和磷具有明显不同的时间变化规律。典范对应分析表明,水温、pH、溶解性总氮、SD与藻类生物量的季节演替关系密切,蓝藻、硅藻生物量与水温、溶解性总磷呈正相关,与硝态氮浓度呈负相关。研究结果表明,天目湖沙河水库水质时空差异与浮游植物种群结构的时空分布关系密切,降低氮、磷浓度对沙河水库富营养化控制及水质的保护都非常重要,但在不同季节氮、磷的相对重要性不同。农业活动,如茶园的大面积开发及旅游业活动是影响天目湖水质的两个重要因素。