东湖富营养化的成因分析和治理对策

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,东湖富营养化的成因分析和治理对策,Eutrophication of Lake Donghu :,Cause Analysis and Remedy Strategy,刘 建 康,Jiankang LIU,Institute of Hydrobiology, the Chinese Academy of Sciences,1,Serious eutrophication,in Lake Donghu,东湖富营养化,十分严重,2,1二十年前东湖富营养化的综合评价和氮磷收支,Comprehensive evaluation of Donghus eutrophication in the 1980s and its N, P budgets,3,Eutrophication of the lake began in the mid-1950s and proceeded rather fast.,东湖的富营养化,开始于五十年代中期，进程颇为快速。,4,Early 1980s:,NO,3,-N, NO,2,-N, NH,4,-N, TN, PO,4,-P, TP, SiO,2,Phytoplankton,Average daily primary gross production,Biomass,Chlorophyll,a,A comprehensive evaluation of status of eutrophication: on the way of transition from eutrophic to hyper-eutrophic (Cai,1993),八十年代初期,NO,3,-N, NO,2,-N, NH,4,-N, TN, PO,4,-P, TP, SiO,2,浮游植物:,日平均初级生产量 生物量 叶绿素a,东湖当时已处于富营养化向超富营养化过渡的阶段（蔡庆华，1993）,5,氮的总输入量: 536 t/a,总负荷量:19.22g/m,2,磷的总输入量:87.8 t/a,总负荷量:3.15 g/m,2,输入-输出差:总氮323.2 t/a,（占总输入量60.3%）,总磷67.7 t/a,（占总输入量77.1%）,（张水元等，1984）,N input: 536 t/a,Total loading:19.22g/m,2,P input:87.8 t/a,Total loading:3.15 g/m,2,Difference in input and output:,N323.2 t/a,（60.3% of total input）,P 67.7 t/a,（77.1% of total input）,（Zhang et al，1984）,6,Abundance and species composition of phytoplankton in Lake Donghu during 19561975, and the dynamics of primary productivity,2,1956-1975,年东湖浮游藻类数量和种类组成情况，和初级生产力的演变,7,The average annual total number of phytoplankton was steadily on the increase,1950s:27-949 ind/ml,1960s:156-4662 ind/ml,1970s：1000-35000ind/ml,浮游藻类年平均总数不断增加,50年代：27-949个/ml,60年代：156-4662个/ml,70年代：1000-35000个/ml,（饶欽止、章宗涉，1980）,（Jao and Zhang，1980）,8,Pronounced change occurred in the species composition of phytoplankton,1956-1957:Pyrrophyta Bacillariophyta,1960s:Cyanophyta Chlorophyta,Microcystis Aphanizomenon Anabaena,etc.,种类组成明显改变,19561957:甲藻 硅藻,60年代：蓝藻绿藻,（饶欽止、章宗涉，1980）,微囊藻（,Microcystis,）,束丝藻（,Aphanizomenon,）,鱼腥藻（,Anabaena,）等,（Jao and Zhang，1980）,9,Primary productivity of phytoplankton increased rapidly,浮游藻类初级生产量急剧增加,19631990年:最高生产层日产量平均每年增长0.256 mg O,2,/天,水柱最高日产量平均每年增长0.243 g O,2,/m,2,天19731985年:水柱日产量平均每年增长0.554 g/m,2,天,（,戎克文等，,1995,）,1963-1990: Average daily production at the layer of maximum production increased by 0.256 mg O,2,per day,Maximum daily production of water column increased by 0.243 g O,2,/m,2,per day.,1973-1985: Daily production of water column increased by 0.554 g O,2,/m,2,per day.,（,Rong et al.，,1995,）,10,Aggravation of,exogenic,pollution through the discharge of urban household sewage as well as industrial wastewater in an immense amount;,The disappearance of aquatic,macrophytes,reduced the competition for nutrients, causing the luxuriant proliferation of phytoplankton;,Dike construction within the lake diminished the exchange of water mass between,Guozhenghu,area and other lake areas with lower loading of N and P .,(,Rong,et al., 1995),1）城市生活污水和工业废水大量排入，外源污染加剧；,2）水草的消失减轻了对养料的竞争，促使浮游藻类大量繁殖；,3）湖内人工堤的修筑，减少了郭郑湖区与其他氮磷含量较低的湖区之间的水团交流,（,戎克文等，,1995,）,11,The distinction between “fish-stocking” and “intense fish-farming”,3鱼类“放养”与“精养”的区别,12,不同养殖类型的划分,Different types of fish culture,放养密度,Density,天然饵料,Natural food,精养,Intensive,半精养,Semi-intensive,粗养,Extensive,管理水平,投入和回收,抗病能力,人工饲料,Artificial feed,13,4放养不同种类的鱼给湖泊生态系统带来的不同影响,Impacts on lake ecosystems are different when different fish species are stocked,14,Grass carp stocking resulted in the disappearance of macrophytes,草鱼,（,Ctenopharyngodon idellus,）,的放养导致水生植物的消失,15,沉水植物的消失给水生态系统带来了一系列的影响,1）水生大型植物能起到净化水质的作用，它的消失直接削弱了水体自净的能力,2）水生大型植物是与浮游植物竞争养料的，前者的消失使后者能独享养料资源，导致浮游藻类的大量孳生，反过来通过在养料和光照方面的竞争优势，进一步压制水草的恢复,1) Aquatic macrophytes play the role of purifying the water quality, their disappearance attenuates directly the self purification capability of the water body.,2) Aquatic macrophytes compete for nutrients and light with phytoplankton,16,3) Macrophyte is the substratum on which the adhesive eggs of many fish, snail, and aquatic insect species are deposited; lacking of macrophytes would deprive these eggs of such substratum and depress the hatching rates substantially;,4）Macrophytes also serve as a sort of refuge for the fry of fish and larvae of aquatic invertebrates. The mortality of these animals would be markedly increased in the absence of such refuge, thus would further affect the biodiversity of the ecosystem,沉水植物的消失给水生态系统带来了一系列的影响,3）水草是好几种产粘性卵的鱼类、螺类以及水生昆虫卵粒附着的基质，产出的鱼卵、虫卵、和螺的卵囊没有水草可资附着，卵的孵化率大大降低,4）水草也是许多幼鱼和水生无脊椎动物躲避敌害的隐蔽场所，少了这样的避难所，这类动物死亡的机率大增，进而影像响到该生态系统的生物多样性。,17,Donghu :,团头鲂（,Megalobrama amblvcephaia,Yih）,是草食性鱼类,Blunt snout bream (,Megalobrama amblicephala,), also known as “Wuchang Fish”, is likewise a grass eater, though less voracious; its stocking in lake is not recommended.,18,鲤鱼（,Cyprinus carpio,）是生活在水体底层的鱼类。它以螺蚌等底栖动物为食，习惯在底泥中觅食，动辄把水搅浑。鲤鱼在泥底中的掘进习性使它易于从围圈边缘逃逸；鲤鱼的捕捞也比较困难。,湖泊放养对象中不包括鲤鱼,The common carp (,Cyprinus carpio,) is a fish living on the bottom of water body, feeding on benthic animals like snails, clams, and insect larvae. Searching for food in the sediment, the fish is very likely to stir up the bottom deposit and makes the water turbid. It is also difficult to capture.,It is not a target fish for lake stocking.,19,鲫鱼（,Carassius auratus,）的食性较广，肉味也较好，但野生的品种生长缓慢，一般不是放养对象，但鲫鱼有些品种生长明显较快，有些品种主食浮游生物，,将来有可能发展成为放养对象。,The crucian carp, i.e., the wild variety of goldfish (,Carassius auratus,), has a wider food spectrum, and tastes better, but the wild breed grows up slowly, hence not a choice for stocking.,20,鳜鱼（,Siniperca chuatsi,）是吃鱼的鱼类，肉味好，又少细刺，经济价值较高。,现在已有科研部门在小杂鱼类,丰多的湖泊中放养鳜鱼，,效果看来较好。,The mandarin fish (,Siniperca chautsi,) is a piscivorous fish, feeding on other fish species. It is tasty, devoid of fine skeletal spines, and fetches high price.,Certain research institutes have tried to stock this fish into lakes with plenty of trash fishes, and the result seems promising.,21,Donghu :,河蟹、虾等是有潜力的放养对象,Crab and prawn are some other potential stocking species,22,重要的是，不论哪种对象，都要衡量其放养后的生态影响,就水体中氮、磷的负荷而论，只要输出水体的渔获物中氮、磷的含量大大超过输入水体的全部“鱼种”的氮、磷含量加上这些“鱼种”生长代谢过程中所排泄的氮磷总量，那么这种放养对延缓富营养化的进度还有积极意义,The important point is:,whatever the animal may be, we should give heed to its,ecological impact,following the stocking. Taking the loading of,N and P,into consideration , so long as the content of N and P in the fish crop (i.e., the output) plus the N and P excreted by the stocked fish during their stay in the lake exceeds enormously those contained in the stocked fingerling (i.e., the input), then such stocking will be of positive significance for retarding the process of eutrophication.,23,5放养鲢、鳙的生态影响,Ecological effects of the stocking of silver carp and big-head carp,24,Both silver carp (,Hypophthalmichys molitrix,) and big-head carp (,Aristichthys nobilis,) are plankton feeders,鲢鱼（,Hypophthalmichthys molitrix,）和鳙鱼（,Aristichthys nobilis,）都是吃浮游生物的鱼类，前者食譜以浮游植物为主，杂有少量浮游动物；后者主要也吃浮游植物，但其肠道中浮游动物的数量多于鲢鱼肠道中的数量。这两种鱼都是我国“四大家鱼”的成员，其人工繁殖的技术也已经普及，所以在我国的湖泊、水库里广泛放养，产量较大，缺点是产值不高。,25,西方国家（不产鲢、鳙）的水生生物学家受传统“食物链”的影响，长期以来把控制藻类过盛的希望寄托在浮游动物身上，所以认为，为了遏制藻类水华，应该保护浮动物，这样就需要清除吃浮游动物的鳙和鲢。实际上，鲢、鳙控制大型浮游藻类（如微囊藻）所形成的水华的本领，比起浮游动物来要高强得多,鲢鳙滤食大型浮游藻类,小型藻类发展旺盛,小型藻类水华,Carps are capable of filtering medium-sized and large-sized phytoplankton,Small-sized algae,increases,Water bloom of small-sized algae appears,26,6在东湖里进行的围隔实验,Enclosure experiments inside the lake,27,什么导致了东湖蓝藻“水华”的消失？,营养盐的变化？,牧食浮游动物的变化？,滤食性鱼类的变化？,自1985年夏季，蓝藻水华消失,The diappearance of,Microcystis,bloom from Lake Donghu in 1985,What is the cause of the disappearance of waterbloom?,Nutrients？,Predator？,Filtering fishes？,28,Enclosure experiment in the summer of 1989,Eight,cubiform,enclosures were installed within the lake,The enclosures with bottom and sides were made of impermeable polyethylene cloth, each measuring 2.5 m square at the four vertical sides and at the bottom.,The enclosures are filled with lake-water to the depth of 2 m; thus each enclosure held 12.5 m,3,of lake-water.,The lake-water was filtered through a plankton net before being introduced into the enclosures in order to prevent the unintended introduction of fish fry.,1989年夏季的实验,围隔用不透水的聚乙烯材料制成2.5 m见方,上面敞开、下面有底的水箱，,湖水2.0 m深（湖水容积12.5 m,3）,湖水用浮游生物网滤过，以避免把小鱼苗带进围隔。,29,Purpose:,How does the stocking of silver carp and big-head carp influence the community structure of phytoplankton in the enclosure?,Can the dense stocking of fish eliminate water bloom?,目的：,1）鲢和鳙的放养如何影响围隔内浮游植物的群落结构？,2）鱼的密集放养能否消灭水华？,30,Fig.,藻类体积 (Algal volume (mm,3,L,-1,),1989年5-10月各围隔中和周围湖水中浮游植物总量、蓝藻生物量和鞭毛藻生物量变动情况,Changes in the biomass of total phytoplankton, cyanobacteria and flagellates in the enclosures and the surrounding lake water in the Donghu Lake during May-Oct. 1989 (after Shei and Liu, 1991),E3,E5,E7,Lake water,31,1989年5-10月各围隔中和周围湖水中浮游植物总量、蓝藻生物量和鞭毛藻生物量变动情况,Changes in the biomass of total phytoplankton, cyanobacteria and flagellates in the enclosures and the surrounding lake water in the Donghu Lake during May-Oct. 1989 (after Shei and Liu, 1991),32,The fluctuation of chlorophyll-a content and the biovolume of the total phytoplankton in the three enclosures was similar in pattern, but in the fish-free,#,7, the values were much higher than in the enclosures stocked with fish and in the ambient lake-water. The introduction of fish brought about marked changes not only in the biovolume of total phytoplankton, but also in the composition of the dominant group. In the enclosures stocked with fish, the proportion of Cyanophyceae was meager. In the enclosures without fish, large colony-forming,Microcystis,was predominant,(Shei and Liu, 1991).,三个围隔中叶绿素a的含量和浮游植物总体积的波动情况相似，但在无鱼的,#,7中，数值要比有鱼的围隔和周围湖水中高的多，鱼的引入，不仅给浮游植物的总体积而且对优势类群的组成带来了明显的改变。养了鱼的围隔中，蓝藻的比例很小，没有鱼的围隔，微囊藻属（,Microcystis,）的大型群体独占优势,（Shei and Liu,1991）,33,Experiment in the summer of 1990,The purpose of this experiment was:,1) to restore water-bloom in more of the enclosures;,2) to introduce silver carp and big-head carp into those enclosures covered already with water-bloom, to see if the bloom can be consumed by the fish;,3) to monitor the change in the size structure of phytoplankton community in enclosures after the introduction of fish.,1990年夏季的实验,目的：,1）使更多的围隔里重现水华；,2）在水华已覆盖水面的围隔里引进鲢和鳙，看水华能否被鱼吃掉；,3）监测围隔中引入鱼以后浮游植物群落在大小结构方面的变化。,34,#,1,Silver carp,6 (average body weight 148 g), total stocking density,71 g/m,3,#,2,Big-head carp,6 (average weight 176 g), total stocking density,64.5 g/m,3,#,3,Silver carp,4 (average 21g), big-head carp, 2 (average weight 32 g), total stocking density,12 g/m,3,#,4,Silver carp,4 (average 23 g), big-head carp 2 (average weight 32 g). total stocking density,13 g/m,3,#,5,Silver carp,3 (average 152 g), big-head carp,3 (average weight 172g), total stocking density,78 g/m,3,#,6,No fish,用了6个围隔，围隔的位置和大小与1989年相同，各围隔放养鱼类的情况如下：,#,1 鲢鱼6尾（平均体重 148 g）,#,2 鳙鱼6尾（平均176 g）,#,3 鲢鱼4尾（平均 21g）,#,4 鲢鱼4尾（平均23 g）,#,5 鲢鱼3尾（平均不152 g）,#,6 不放鱼,35,Luxuriant,Microcystis,bloom occurred in enclosures,#,l,#,2,#,5 and,#,6.,In enclosures,#,1,#,2 and,#,5, the biomass of phytoplankton was substantially reduced.,In the enclosures without fish (,#,6), the bloom, once formed, persisted to the end of the experiment.,In enclosures,#,3 and,#,4,total chlorophyll-a amount remained low throughout the experiment, and on the average, more than 80% of the total phytoplankton was composed of those smaller than 30 ,(,Shei,and Liu,1992).,微囊藻水华大量出现在,#,1、,#,2、,#,5 和,#,6围隔里。,养了鱼的第1、2、5号围隔里，浮游植物的生物量大为减少,在没有养鱼第号围隔里，水华一经出现，就持续到实验终了,（,Shei,and Liu,1992）,36,Fig. l Changes in chlorophyll-a amount in both total phytoplankton and those smaller than 30m in the enclosure and surrounding lake water in Donghu Lake during April-August, 1990. Arrow indicates the introduction of fish (after Xie 1996),37,Enclosure experiment in the summer of 1992,This experiment was aimed:,1) to ascertain the role of silver carp and big-head carp in the elimination of,Microcystis,bloom,2) to find out whether the stocking of grass carp had the same effect.,1992年夏季的实验,目的：,）证实鲢、鳙在消除微囊藻水华中所起的作用；,）找出放养草鱼是否有同样效应。,38,#,1 and,#,2 Blank test, no fish,was stocked in.,#,3,Grass carp, 3 (average body weight 187 g), total stocking density 45 g/m,3,#,4,Grass carp,3 (average 229 g), total stocking density 55g/m,3,#,5,Silver carp,3 (average 137 g), total stocking density 33 g/m,3,#,6,Silver carp,2 (average 133 g), total stocking density 21 g/m,3,#,7,Big-head carp,4 (average 233 g), total stocking density 75 g/m,3,#,8,Big-head carp,4 (average 216 g), total stocking density 69 g/m,3,实验用了个围隔，在七月份至九月份进行，月21日，各围隔养入鱼类如下：,#,和,#,空白试验，不放入鱼类,#,3 草鱼尾（平均体重187g）,#,4草鱼尾（平均229g）,#,5 鲢鱼尾（平均137g）,#,6 鲢鱼尾（平均133g）,#,7鳙鱼尾（平均233g）,#,8鳙鱼尾（平均216g）,39,Enclosures,40,41,There was no water-bloom in all these enclosures when the experiment started on July 6,th,.,Two weeks afterwards, a thin layer of bloom occurred in most of the enclosures; the dominant phytoplankton later turned to be,Microcystis,in all cases.,By the end of July, there was thick layer of water-bloom in most of the enclosures.,In mid-August all enclosures were covered with a thick bloom layer.,月日开始时所有围隔都没有水华,两星期后，大多数围隔出现一层薄薄的水华后来，优势浮游植物成为微囊藻,月底，大多数围隔里有厚层水华,月中旬全部围隔都有稠密水华层,42,In the enclosures stocked with big-head carp (,#,7 and,#,8, with stocking rate of 63-75 g fish per cubic meter of water), the total biomass of phytoplankton diminished rapidly.,Water bloom in these two enclosures disappeared two weeks after the introduction of fish.,Grass carp stocked into enclosures,#,3 and,#,4 did not reduce the biomass of phytoplankton at all, and the water-bloom, once formed, lasted to the end of the experiment,(,Sheil,et al.,1993).,放入鳙鱼的7号和8号围隔（放养密度为每立方米水含鱼6575克）克，导致浮游植物总生物量迅速减少。这两个围隔在鱼放入两星期后水华全部消失。第3号和第4号围隔里放养的草鱼，完全没有减少浮游植物的生物量，水华一经形成，就持续到实验终了（Shei et al.,1993）。,43,With big-head carp, water-bloom was completely eliminated at the stocking density (biomass) of 6975 g/m,3,; with silver carp, the amount of water-bloom in the enclosures was materially diminished at the stocking density of 2133g/m3, but there was remnant bloom persisting to the end of experiment.,Accordingly, the effective biomass of silver carp and big-head carp for the control of water-bloom should be 3369 g/m3.,Effective stocking density (biomass) for silver carp and big-head carp should be 4650g/m,3,(Liu and Xie, 1999),当鳙鱼的放养密度（用生物量表示）为6576g/m,3,时，水华全部被消灭；当鲢鱼的放养密度为2133g/m,3,时，围隔中水华的量大为减少，但直到实验终了仍有少量群体残留。因此，鲢、鳙控制水华的有效生物量应在3365g/m,3,的范围内。,有效放养密度（生物量）应该是4650g/m,3,(刘、谢1999)。,44,7为什么微囊藻水华17年来没有在东湖重现？,Why,Microcystis,bloom did not recur in Lake Donghu in the past 17 years?,45,武汉东湖渔产量,Fish yield in Lake Donghu,46,鲢鳙生物量的稳步增长导致微囊藻水华的消失,Increase in the yield of bighead carp and silver carp resulted in the disappearance of,Microcystis,bloom,47,The strategy adopted by the upholders of conventional “biomanipulation” is:,to stock,piscivorous fish,species into the water body to suppress the planktivorous fish ,so as to reinforce the zooplankton population, which is to be relied upon for water-bloom control (Starling,1993),常轨的生物操纵（Biomanipulation）论者用来控制水体富营养化的对策是：,在水体中放养食鱼性鱼类（piscivorous fish）以抑制食浮游生物的鱼类（planktivorous fish），借此壮大浮游动物种群，然后依靠浮游动物来控制藻类（Starling,1993）,48,As to the control of filamentous algae and large, colonial algae like,Microcystis,then zooplankton including,Daphnia,are utterly helpless.,Filter-feeding fishes,like silver carp and big-head carp, under appropriate stocking density, are capable of suppressing,Microcystis,bloom effectively,(Liu and Xie,1999).,浮游动物只能摄食细菌、较小的浮游动物、和小型藻类，因而有助于增进水的透明度。,控制丝状藻类和像微囊藻之类的大型群体，那么包括,Daphnia,在内的浮游动物是完全无能为力的。,滤食浮游浮生物的鱼类像鲢和鳙，在适当的放养密度下，是能有效地遏止微囊藻水华的,（刘、谢，1999）,49,8.东湖富营养化的治理对策,Countermeasures for the control of eutrophication in Lake Donghu,50,Start from the central treatment of household sewage,On the basis of the effectiveness of sewage treatment, to decide whether a selective dredging of the bottom deposit is necessary.,Prior to the fulfillment of central sewage treatment, prevention against the resurrection of,cyanobacteria,bloom at present can only resort to the stocking of silver carp and big-head carp.,根据东湖富营养化当前情况，治理首先应该从生活污水的集中处理着手，然后视处理的效果而决定是否需要对湖底淤泥进行重点清除。在污水处理尚未到位之前，防止蓝藻水华的暴发目前还只能依赖鲢、鳙的放养措施.,51,From a long-term point of view, the repair of the ecosystem, including the recovery of macrophytes in the lake, the rehabilitation of benthic invertebrate community, as well as the construction of vertical wetland sewage treatment installation (to be integrated with tourism construction) in residential area beyond the reach of sewage pipeline system, and the selective rectification of the lakes watershed, so as to reduce the source of pollution, to lessen the P and N loading of the lake-water, etc.,从长远来说，生态系统的整治，包括修复湖内水生植被，重建底栖无脊椎动物群落，结合旅游景点建设，在截污管道系统以外的零星居民点建立人工垂直湿地污水处理设施，在东湖流域（汇水区）进行重点整治，减少污染源，以降低东湖湖水中的磷、氮负荷，是治理富营养化的必由之路。,52,?,What does IETC “,Planning and Management of Lakes and Reservoirs: An Integrated Approach to Eutrophication Abridged Version - A Students Guide,” (2000) say about,“,Constructed Wetland,”?,53,Constructed Wetlands,The transition zones between lakes and terrestrial ecosystems are crucial for protection of lakes against anthropogenic impacts. Transition zones prevent, to a certain extent, entry of undesirable substances into lakes, and, therefore, should be preserved. Hence, construction should not be permitted in a zone 50 to 100 m from shorelines.,54,Non-point or diffuse pollutants from the environment flows toward lakes, but the transition zone is able to transform or absorb the pollutants.,Most important processes occurring in the transition zone:,Nitrate is denitrified by the anaerobic conditions.,Clay minerals adsorb ammonium.,Organic matter adsorbs phosphorus compounds.,Biodegradable organic matter is decomposed aerobically or,anaerobically,by microorganisms.,Macrophytes,store nutrients.,Soils with a high calcium, magnesium, aluminum or iron content can absorb phosphorus.,Suspended matter is removed along with associated nitrogen and phosphorus.,55,The denitrification potential of wetland is often high.,2,000-3,000 kg nitrate-N/ ha/year,Denitrification is accompanied by oxidation of organic matter.,However, phosphorus, bound in organic matter or adsorbed to the organic matter, may be released.,56,The,siting,of artificial wetlands must be carefully planned because their effects are dependent on the hydrology and on the landscape pattern.,Non-fertile land of moderate cost should be used.,Constructed wetlands can be either surface or subsurface wetlands.,57,Subsurface wetlands are based on flow of water through the soil, and oxygen is provided for biological decomposition via the root network.,Subsurface wetlands are usually of higher efficiency than surface wetlands but require more maintenance to avoid clogging.,58,When wetlands with open water are used, mosquitoes should be controlled, for instance, by stocking of insectivorous fish.,Harvest of wetland plant will increase the efficiency of nitrogen and phosphorus removal.,The harvested plants can be used to feed domestic animals, to produce methane or be composted.,59,THANK YOU FOR YOUR ATTENTION,谢谢大家！,60,