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题名: 三峡水库浮游藻类群落变化及水华控制原理
作者: 周广杰
答辩日期: 2009-06-05
导师: 胡征宇
授予单位: 中国科学院水生生物研究所
授予地点: 水生生物研究所
学位: 博士
关键词: 三峡水库 ; 香溪河库湾 ; 浮游藻类 ; 水华
其他题名: PHYTOPLANKTON COMMUNITY VARIATIONS AND ALGAL BLOOMS CONTROL THEORY IN THREE-GORGES RESERVOIR
摘要: 三峡工程是目前中国乃至世界上最大的水资源管理工程,在正常水位达到175 m时,库容将达到3.93×1010 m3。三峡建坝在防洪、发电、航运、灌溉等方面带来了巨大的经济效益,同时,也对库区生态环境产生了深刻而长远的影响。例如,蓄水以前,长江干流和支流均未出现过藻类水华,而蓄水以后,三峡水库每年都会出现藻类水华。浮游植物的过量生长会恶化库区水质、降低水库的自然功能,破坏水生态系统甚至威胁人类健康。因此,寻找安全有效的三峡水库藻类水华控制方法迫在眉睫。 本研究的目的是调查三峡水库浮游藻类的季节变动和空间分布,寻找水华发生的规律,跟踪春季浮游藻类变化的整个过程并分析其和环境因子之间的关系,最后提出三峡水库水华控制的技术理论。主要研究结果如下: 蓄水前,共采集到藻类7门77种,其中绿藻为30种,硅藻28种,分别占总种类数的38.96%和36.36%。蓄水后,藻类种类数急剧增加,共采集到藻类8门165种,其中,绿藻90种,硅藻41种,分别占总种类数的54.55%和24.85%。无论是蓄水前还是蓄水后,不管是干流还是支流,绿藻和硅藻始终是构成藻类的主要类群。蓄水前,干流和支流均未出现明显的优势种和藻类水华。而蓄水后,三峡水库多次出现藻类水华,尤其在支流库湾,藻类水华每年春天重复出现,而且在过去的五年里,藻类水华发生的范围和频率有增加的趋势。藻类水华可能是由于水体中高浓度的营养盐、缓慢的水流以及适宜的温度引发。 水华藻类包括铜绿微囊藻、惠氏微囊藻、水华束丝藻、新星形冠盘藻、美丽星杆藻、一种小环藻、倪氏拟多甲藻、另一种拟多甲藻、实球藻、空球藻、美丽团藻、湖沼红胞藻和延长鱼鳞藻。三峡库区多条支流库湾均出现过藻类水华,其中倪氏拟多甲藻水华最为严重。蓄水前五年,水华主要出现在春季,夏季、秋季和冬季也有,例如2008年的夏季和秋季香溪河便出现大面积的严重的藻类水华。 叶绿素a浓度、总生物量均与NO3--N浓度显著负相关,并且在水华发生前和水华发生期间硝酸盐的吸收非常高,这说明了香溪河浮游植物生长和硝酸盐的消耗存在密切的联系。强降雨能够强烈影响香溪河库湾春季浮游藻类的生长以及水体环境,降雨发生时,大量泥沙进入水体,导致浊度上升,浮游植物由于不能适应这种强烈的环境变化,大多数藻类死亡。所以强降雨使得叶绿素a浓度、藻类细胞密度和生物量急剧降低,同时引发藻类水华突然消失。同时,由于强降雨又能够引发水体中NO3--N浓度的明显上升,因此强降雨又为新一轮的水华爆发提供了足够的氮源。强降雨引发的强烈的水体环境变化可能不再适合先前优势种的生长,这样可能就会导致优势种之间的转变。 三峡水库干流江段属于P限制或者NP联合限制水体,而香溪河库湾属于N限制水体。另外,水体中添加Fe使得藻类的生长显著增加,而添加Ca对藻类的生长没有产生显著影响。这说明了Fe可能在三峡水库藻类水华出现与消失的过程中起了非常重要的作用。三峡水库干流江段和香溪河库湾水体中的原有藻类、羊角月牙藻和梅尼小环藻生长潜力均比较高,或许这就是三峡水库春季有时候会发生硅藻和绿藻水华的原因。 香溪河库湾的氮营养主要来源于面源污染,并且降雨是香溪河库湾氮输入的一种重要方式,因此,我们很难控制水体中氮营养的输入。和氮污染相比,香溪河库湾磷污染更为严重,它主要来源于大量的磷工业废水和生活污水的持续排放,而且水体中过量的磷浓度是香溪河库湾出现藻类水华的重要原因之一。因此,必须采取措施来控制香溪河库湾的点源磷污染,这样才可能会阻止藻类水华的发生。 春季主要的水华藻类倪氏拟多甲藻喜欢生长于静水区,并且每年春季其水华也是最先在静水区出现,然后再扩散到库湾的其他区域。这样看来,静水区是香溪河库湾甲藻水华的源头。静水区水体相对较浅,半封闭,水流几乎静止并且易于人为管理。因此重点控制静水区的甲藻水华,就能够积极有效的减少库湾甲藻水华的程度。基于我们的研究可以发现,强降雨导致的水体土沙含量的增多可以引发藻类水华消失。因此,在春季甲藻水华刚刚在静水区开始出现的时候,就利用当地的泥土去控制它,这或许是一个积极有效的办法。当然,为了避免营养输入和增加藻类去除效率,泥土必须经过特殊处理,例如,用壳聚糖进行粘土改性处理。 我们认为,利用生态水文调度来控制藻类水华最好参考当地的气象条件进行。当强降雨发生时,进行大坝蓄水,因为此时降雨可以引发藻类水华消失。当降雨逐渐减少,藻类水华日益加重时,进行大坝放水,这样水体水流加速,拟多甲藻水华可能会消失或减弱因为它不适合在流水环境中生长。
英文摘要: The Three-Gorges Dam (TGD) is the largest water conservancy project ever built in China, and so in the world. With the normal pool level at 175 m, the total storage capacity of the reservoir is 39.3 billion m3. Damming of the Three-Gorges brought many benefits in controlling flood, producing hydroelectric power, navigating, irrigating the field and other aspects. However, it also exerted far-reaching and profound impacts on the ecological environment. For example, in the mainstream and tributaries of the Yangtze River, there were no algal blooms reported before the building of TGD. However, phytoplankton blooms occurred repeatedly in TGR every spring since water storage started. The excessive growth of phytoplankton deteriorated the water quality, decreased reservoir natural functions, damaged water ecology system, and even threatened human health. Therefore, it was very urgent to develop safe and efficient ways to control blooms occurring in TGR. The present research aims to investigate spatial and temporal variability of phytoplankton, to explore the developmental discipline of algal blooms, to analyze the whole course of spring phytoplankton variability, to identify the main environmental factors which affected phytoplankton growth and algal blooms, and finally to provide the basis for controlling blooms in Three-Gorges Reservoir. The main results were as follows: Before water storage, a total of 77 algal taxa belonging to 7 phyla was identified. Green algae (30 species) and diatoms (28 species) were the dominant species, representing 38.96% and 36.36% of the total taxa. After water storage, algal taxa increased dramatically and a total of 165 algal taxa belonging to 8 phyla was identified. Green algae (90 species) and diatoms (41 species) were the dominant species, representing 54.55% and 24.85% of the total taxa. Whether in mainstream or tributary, green algae and diatoms were clearly the dominant phytoplankton population. Before water storage, obvious dominant species and algal blooms had never appeared in the mainstream and tributaries of TGR. However, algal blooms appeared frequently since water storage started in the year of 2003. Especially in some bays and tributaries, algal blooms occurred repeatedly every spring. Additionally, the spatial extents and frequency of algal blooms exhibited an increasing trend in last five years. Algal blooms seemed to be caused by high nutrients, slow current speed and suitable water temperature. The main taxa of algal blooms were Microcystis aeruginosa、Microcystis wesenbergii、Aphanizomenon flos-aquae、Stephanodiscus neoastraea、Asterionella formosa、Cyclotella sp.、Peridiniopsis niei、Peridiniopsis sp.、Pandorina morum、Eudorina elegans、Volvox aureus、Rhodomonas lacustris and Mallomonas elongata. Several bays and tributaries of TGR had suffered from algal blooms, where Peridiniopsis niei was the most serious dominant species. Algal blooms occurred mainly in spring and sometimes in other seasons in last five years. For example, the Xiangxi Bay suffered from serious algal blooms in summer and autumn of the year of 2008. Chlorophyll a concentration and phytoplankton biomass were both correlated significantly negatively with nitrate concentration, and nitrate uptake was extremely high during the pre-bloom and bloom periods. This phenomenon indicated phytoplankton growth was closely related to nitrate consumption. Heavy rainfalls affected seriously phytoplankton growth and the environment to which the cells were subjected. A large number of soil and sand from surrounding land entered the water body and caused turbidity to increase abruptly. Most of these species were dead because they did not adapt the sharply environmental change. Therefore, heavy rainfalls caused phytoplankton chlorophyll a concentration, abundance and biomass to decrease sharply and algal blooms to disappear. Heavy rainfalls also caused nitrate to increase sharply and this provided sufficient nitrogen for algae blooms occurring again. After heavy rainfalls, strong environmental changes may be no longer suitable for the growth of previous dominant species and thus resulted in variation of dominant species. The sampling sites in mainstream of TGR were co-limited by N and P or P-limited alone, and sites in Xiangxi bay were N-limited alone. Treatments that were enriched with Fe showed markedly increased growth in comparison to Fe not enriched treatments, but enrichment with Ca alone did not result in a significant increase in algal biomass. This showed Fe likely played an important role in determining the appearance and disappearance of algal blooms of TGR. Native algae, Selenastrum capricornutum and Cyclotella meneghinana had high growth potential in TGR. Maybe that was the reason that blooms of diatoms and green algae were sometimes detected in spring in TGR. Nitrogen nutrition came mainly from non-point source pollution and rainfall was a very important way of nitrogen input. Therefore, it was difficult to control nitrogen input because we could not change rainfall. Compared with nitrogen, the phosphorus pollution in Xiangxi Bay was more serious. Serious phosphorus pollution came from the continuous discharge of a large number of phosphorous industry wastewater and domestic sewage. Additionally, enough phosphorus nutrition was one of important causes of bloom occurring in Xiangxi bay. Necessary measures must be taken to control the point source of pollutants of phosphorus in Xiangxi bay in order to prevent the occurrence of water bloom. Peridiniopsis niei, the principal specie of water bloom, preferred standing water region and Peridiniopsis niei bloom also firstly occurred in standing water region every spring and then spread to the other regions of the Bay. It seemed that standing water regions was the source of Peridiniopsis niei bloom to diffuse in Xiangxi Bay. There were special geographical conditions for standing water regions which were shallow, almost static and closed. Therefore, the regions could be managed artificially easily. To control Peridiniopsis niei bloom in standing water regions maybe was an effective way to decrease blooms occurring in the whole bay. Based on our study, soil input caused by heavy rainfalls could trigger algal blooms disappear. Thus, it was maybe effective that using local soils to control Peridiniopsis niei bloom when it had just been found in standing water regions. Certainly, the local soils must be modified (for example, chitosan-modified) in order to avoid nutrient input and increase algae-removal efficiency. In our view, eco-hydraulic regulation should be performed according to local meteorological conditions. Dam storage was performed when heavy rainfall occurred because heavy rainfall could trigger algal blooms to disappear. Dam discharge was performed when rainfall reduced and algal blooms became serious. The disgusting Peridiniopsis bloom maybe disappear because it was not suitable to grow in flowing water region.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.ihb.ac.cn/handle/342005/12394
Appears in Collections:中科院水生所知识产出(2009年前)_学位论文

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三峡水库浮游藻类群落变化及水华控制原理.周广杰[d].中国科学院水生生物研究所,2009.20-25
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