东湖富营养化的成因分析和治理对策.ppt

东湖富营养化的成因分析和治理对策EutrophicationofLakeDonghu:CauseAnalysisandRemedyStrategy刘建康JiankangLIU中科院水生生物研究所InstituteofHydrobiology,theChineseAcademyofSciences,SeriouseutrophicationinLakeDonghu,东湖富营养化十分严重,1二十年前东湖富营养化的综合评价和氮磷收支ComprehensiveevaluationofDonghuseutrophicationinthe1980sanditsN,Pbudgets,Eutrophicationofthelakebeganinthemid-1950sandproceededratherfast.,东湖的富营养化开始于五十年代中期，进程颇为快速。,Early1980s:NO3-N,NO2-N,NH4-N,TN,PO4-P,TP,SiO2PhytoplanktonAveragedailyprimarygrossproductionBiomassChlorophyllaAcomprehensiveevaluationofstatusofeutrophication:onthewayoftransitionfromeutrophictohyper-eutrophic(Cai,1993),八十年代初期NO3-N,NO2-N,NH4-N,TN,PO4-P,TP,SiO2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）,氮的总输入量:536t/a总负荷量:19.22g/m2磷的总输入量:87.8t/a总负荷量:3.15g/m2输入-输出差:总氮323.2t/a（占总输入量60.3%）总磷67.7t/a（占总输入量77.1%）（张水元等，1984）,Ninput:536t/aTotalloading:19.22g/m2Pinput:87.8t/aTotalloading:3.15g/m2Differenceininputandoutput:N323.2t/a（60.3%oftotalinput）P67.7t/a（77.1%oftotalinput）（Zhangetal，1984）,AbundanceandspeciescompositionofphytoplanktoninLakeDonghuduring19561975,andthedynamicsofprimaryproductivity,21956-1975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,Theaverageannualtotalnumberofphytoplanktonwassteadilyontheincrease1950s:27-949ind/ml1960s:156-4662ind/ml1970s：1000-35000ind/ml,浮游藻类年平均总数不断增加50年代：27-949个/ml60年代：156-4662个/ml70年代：1000-35000个/ml,（饶欽止、章宗涉，1980）,（JaoandZhang，1980）,Pronouncedchangeoccurredinthespeciescompositionofphytoplankton1956-1957:PyrrophytaBacillariophyta1960s:CyanophytaChlorophytaMicrocystisAphanizomenonAnabaenaetc.,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,（JaoandZhang，1980）,Primaryproductivityofphytoplanktonincreasedrapidly,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0.256mgO2/天水柱最高日产量平均每年增长0.243gO2/m2天19731985年:水柱日产量平均每年增长0.554g/m2天,（戎克文等，1995）,1963-1990:Averagedailyproductionatthelayerofmaximumproductionincreasedby0.256mgO2perday,Maximumdailyproductionofwatercolumnincreasedby0.243gO2/m2perday.1973-1985:Dailyproductionofwatercolumnincreasedby0.554gO2/m2perday.,（Rongetal.，1995）,Aggravationofexogenicpollutionthroughthedischargeofurbanhouseholdsewageaswellasindustrialwastewaterinanimmenseamount;Thedisappearanceofaquaticmacrophytesreducedthecompetitionfornutrients,causingtheluxuriantproliferationofphytoplankton;DikeconstructionwithinthelakediminishedtheexchangeofwatermassbetweenGuozhenghuareaandotherlakeareaswithlowerloadingofNandP.(Rongetal.,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）,Thedistinctionbetween“fish-stocking”and“intensefish-farming”,3鱼类“放养”与“精养”的区别,不同养殖类型的划分Differenttypesoffishculture,放养密度Density,天然饵料Naturalfood,精养Intensive,半精养Semi-intensive,粗养Extensive,人工饲料Artificialfeed,4放养不同种类的鱼给湖泊生态系统带来的不同影响Impactsonlakeecosystemsaredifferentwhendifferentfishspeciesarestocked,Grasscarpstockingresultedinthedisappearanceofmacrophytes,草鱼（Ctenopharyngodonidellus）的放养导致水生植物的消失,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)Aquaticmacrophytesplaytheroleofpurifyingthewaterquality,theirdisappearanceattenuatesdirectlytheselfpurificationcapabilityofthewaterbody.2)Aquaticmacrophytescompetefornutrientsandlightwithphytoplankton,3)Macrophyteisthesubstratumonwhichtheadhesiveeggsofmanyfish,snail,andaquaticinsectspeciesaredeposited;lackingofmacrophyteswoulddeprivetheseeggsofsuchsubstratumanddepressthehatchingratessubstantially;4）Macrophytesalsoserveasasortofrefugeforthefryoffishandlarvaeofaquaticinvertebrates.Themortalityoftheseanimalswouldbemarkedlyincreasedintheabsenceofsuchrefuge,thuswouldfurtheraffectthebiodiversityoftheecosystem,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。,Donghu:,团头鲂（MegalobramaamblvcephaiaYih）是草食性鱼类,Bluntsnoutbream(Megalobramaamblicephala),alsoknownas“WuchangFish”,islikewiseagrasseater,thoughlessvoracious;itsstockinginlakeisnotrecommended.,鲤鱼（Cyprinuscarpio）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,Thecommoncarp(Cyprinuscarpio)isafishlivingonthebottomofwaterbody,feedingonbenthicanimalslikesnails,clams,andinsectlarvae.Searchingforfoodinthesediment,thefishisverylikelytostirupthebottomdepositandmakesthewaterturbid.Itisalsodifficulttocapture.,Itisnotatargetfishforlakestocking.,鲫鱼（Carassiusauratus）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。,Thecruciancarp,i.e.,thewildvarietyofgoldfish(Carassiusauratus),hasawiderfoodspectrum,andtastesbetter,butthewildbreedgrowsupslowly,hencenotachoiceforstocking.,鳜鱼（Sinipercachuatsi）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。,Themandarinfish(Sinipercachautsi)isapiscivorousfish,feedingonotherfishspecies.Itistasty,devoidoffineskeletalspines,andfetcheshighprice.Certainresearchinstituteshavetriedtostockthisfishintolakeswithplentyoftrashfishes,andtheresultseemspromising.,Donghu:,河蟹、虾等是有潜力的放养对象,Crabandprawnaresomeotherpotentialstockingspecies,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,Theimportantpointis:whatevertheanimalmaybe,weshouldgiveheedtoitsecologicalimpactfollowingthestocking.TakingtheloadingofNandPintoconsideration,solongasthecontentofNandPinthefishcrop(i.e.,theoutput)plustheNandPexcretedbythestockedfishduringtheirstayinthelakeexceedsenormouslythosecontainedinthestockedfingerling(i.e.,theinput),thensuchstockingwillbeofpositivesignificanceforretardingtheprocessofeutrophication.,5放养鲢、鳙的生态影响Ecologicaleffectsofthestockingofsilvercarpandbig-headcarp,Bothsilvercarp(Hypophthalmichysmolitrix)andbig-headcarp(Aristichthysnobilis)areplanktonfeeders,鲢鱼（Hypophthalmichthysmolitrix）和鳙鱼（Aristichthysnobilis）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。,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,Carpsarecapableoffilteringmedium-sizedandlarge-sizedphytoplankton,Small-sizedalgaeincreases,Waterbloomofsmall-sizedalgaeappears,6在东湖里进行的围隔实验Enclosureexperimentsinsidethelake,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ThediappearanceofMicrocystisbloomfromLakeDonghuin1985,Whatisthecauseofthedisappearanceofwaterbloom?Nutrients？Predator？Filteringfishes？,Enclosureexperimentinthesummerof1989EightcubiformenclosureswereinstalledwithinthelakeTheenclosureswithbottomandsidesweremadeofimpermeablepolyethylenecloth,eachmeasuring2.5msquareatthefourverticalsidesandatthebottom.Theenclosuresarefilledwithlake-watertothedepthof2m;thuseachenclosureheld12.5m3oflake-water.Thelake-waterwasfilteredthroughaplanktonnetbeforebeingintroducedintotheenclosuresinordertopreventtheunintendedintroductionoffishfry.,1989年夏季的实验围隔用不透水的聚乙烯材料制成2.5m见方上面敞开、下面有底的水箱，湖水2.0m深（湖水容积12.5m3）湖水用浮游生物网滤过，以避免把小鱼苗带进围隔。,Purpose:Howdoesthestockingofsilvercarpandbig-headcarpinfluencethecommunitystructureofphytoplanktonintheenclosure?Canthedensestockingoffisheliminatewaterbloom?,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？,Fig.,藻类体积(Algalvolume(mm3L-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Changesinthebiomassoftotalphytoplankton,cyanobacteriaandflagellatesintheenclosuresandthesurroundinglakewaterintheDonghuLakeduringMay-Oct.1989(afterSheiandLiu,1991),E3,E5,E7,Lakewater,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Changesinthebiomassoftotalphytoplankton,cyanobacteriaandflagellatesintheenclosuresandthesurroundinglakewaterintheDonghuLakeduringMay-Oct.1989(afterSheiandLiu,1991),Thefluctuationofchlorophyll-acontentandthebiovolumeofthetotalphytoplanktoninthethreeenclosureswassimilarinpattern,butinthefish-free#7,thevaluesweremuchhigherthanintheenclosuresstockedwithfishandintheambientlake-water.Theintroductionoffishbroughtaboutmarkedchangesnotonlyinthebiovolumeoftotalphytoplankton,butalsointhecompositionofthedominantgroup.Intheenclosuresstockedwithfish,theproportionofCyanophyceaewasmeager.Intheenclosureswithoutfish,largecolony-formingMicrocystiswaspredominant(SheiandLiu,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（SheiandLiu,1991）,Experimentinthesummerof1990Thepurposeofthisexperimentwas:1)torestorewater-bloominmoreoftheenclosures;2)tointroducesilvercarpandbig-headcarpintothoseenclosurescoveredalreadywithwater-bloom,toseeifthebloomcanbeconsumedbythefish;3)tomonitorthechangeinthesizestructureofphytoplanktoncommunityinenclosuresaftertheintroductionoffish.,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。,#1Silvercarp,6(averagebodyweight148g),totalstockingdensity71g/m3#2Big-headcarp,6(averageweight176g),totalstockingdensity64.5g/m3#3Silvercarp,4(average21g),big-headcarp,2(averageweight32g),totalstockingdensity12g/m3#4Silvercarp,4(average23g),big-headcarp2(averageweight32g).totalstockingdensity13g/m3#5Silvercarp,3(average152g),big-headcarp,3(averageweight172g),totalstockingdensity78g/m3#6Nofish,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148g）#2鳙鱼6尾（平均176g）#3鲢鱼4尾（平均21g）#4鲢鱼4尾（平均23g）#5鲢鱼3尾（平均不152g）#6不放鱼,LuxuriantMicrocystisbloomoccurredinenclosures#l,#2,#5and#6.Inenclosures#1,#2and#5,thebiomassofphytoplanktonwassubstantiallyreduced.Intheenclosureswithoutfish(#6),thebloom,onceformed,persistedtotheendoftheexperiment.Inenclosures#3and#4,totalchlorophyll-aamountremainedlowthroughouttheexperiment,andontheaverage,morethan80%ofthetotalphytoplanktonwascomposedofthosesmallerthan30(SheiandLiu,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（SheiandLiu,1992）,Fig.lChangesinchlorophyll-aamountinbothtotalphytoplanktonandthosesmallerthan30mintheenclosureandsurroundinglakewaterinDonghuLakeduringApril-August,1990.Arrowindicatestheintroductionoffish(afterXie1996),Enclosureexperimentinthesummerof1992Thisexperimentwasaimed:1)toascertaintheroleofsilvercarpandbig-headcarpintheeliminationofMicrocystisbloom,2)tofindoutwhetherthestockingofgrasscarphadthesameeffect.,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。,#1and#2Blanktest,nofishwasstockedin.#3Grasscarp,3(averagebodyweight187g),totalstockingdensity45g/m3#4Grasscarp,3(average229g),totalstockingdensity55g/m3#5Silvercarp,3(average137g),totalstockingdensity33g/m3#6Silvercarp,2(average133g),totalstockingdensity21g/m3#7Big-headcarp,4(average233g),totalstockingdensity75g/m3#8Big-headcarp,4(average216g),totalstockingdensity69g/m3,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）,Enclosures,Therewasnowater-bloominalltheseenclosureswhentheexperimentstartedonJuly6th.Twoweeksafterwards,athinlayerofbloomoccurredinmostoftheenclosures;thedominantphytoplanktonlaterturnedtobeMicrocystisinallcases.BytheendofJuly,therewasthicklayerofwater-bloominmostoftheenclosures.Inmid-Augustallenclosureswerecoveredwithathickbloomlayer.,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,Intheenclosuresstockedwithbig-headcarp(#7and#8,withstockingrateof63-75gfishpercubicmeterofwater),thetotalbiomassofphytoplanktondiminishedrapidly.Waterbloominthesetwoenclosuresdisappearedtwoweeksaftertheintroductionoffish.Grasscarpstockedintoenclosures#3and#4didnotreducethebiomassofphytoplanktonatall,andthewater-bloom,onceformed,lastedtotheendoftheexperiment(Sheiletal.,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（Sheietal.,1993）。,Withbig-headcarp,water-bloomwascompletelyeliminatedatthestockingdensity(biomass)of6975g/m3;withsilvercarp,theamountofwater-bloomintheenclosureswasmateriallydiminishedatthestockingdensityof2133g/m3,buttherewasremnantbloompersistingtotheendofexperiment.Accordingly,theeffectivebiomassofsilvercarpandbig-headcarpforthecontrolofwater-bloomshouldbe3369g/m3.Effectivestockingdensity(biomass)forsilvercarpandbig-headcarpshouldbe4650g/m3(LiuandXie,1999),当鳙鱼的放养密度（用生物量表示）为6576g/m3时，水华全部被消灭；当鲢鱼的放养密度为2133g/m3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/m3的范围内。有效放养密度（生物量）应该是4650g/m3(刘、谢1999)。,7为什么微囊藻水华17年来没有在东湖重现？WhyMicrocystisbloomdidnotrecurinLakeDonghuinthepast17years?,武汉东湖渔产量FishyieldinLakeDonghu,鲢鳙生物量的稳步增长导致微囊藻水华的消失IncreaseintheyieldofbigheadcarpandsilvercarpresultedinthedisappearanceofMicrocystisbloom,Thestrategyadoptedbytheupholdersofconventional“biomanipulation”is:tostockpiscivorousfishspeciesintothewaterbodytosuppresstheplanktivorousfish,soastoreinforcethezooplanktonpopulation,whichistoberelieduponforwater-bloomcontrol(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（piscivorousfish）以抑制食浮游生物的鱼类（planktivorousfish），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）,Astothecontroloffilamentousalgaeandlarge,colonialalgaelikeMicrocystis,thenzooplanktonincludingDaphniaareutterlyhelpless.Filter-feedingfisheslikesilvercarpandbig-headcarp,underappropriatestockingdensity,arecapableofsuppressingMicrocystisbloomeffectively(LiuandXie,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）,8.东湖富营养化的治理对策CountermeasuresforthecontrolofeutrophicationinLakeDonghu,StartfromthecentraltreatmentofhouseholdsewageOnthebasisoftheeffectivenessofsewagetreatment,todecidewhetheraselectivedredgingofthebottomdepositisnecessary.Priortothefulfillmentofcentralsewagetreatment,preventionagainsttheresurrectionofcyanobacteriabloomatpresentcanonlyresorttothestockingofsilvercarpandbig-headcarp.,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.,Fromalong-termpointofview,therepairoftheecosystem,includingtherecoveryofmacrophytesinthelake,therehabilitationofbenthicinvertebratecommunity,aswellastheconstructionofverticalwetlandsewagetreatmentinstallation(tobeintegratedwithtourismconstruction)inresidentialareabeyondthereachofsewagepipelinesystem,andtheselectiverectificationofthelakeswatershed,soastoreducethesourceofpollution,tolessenthePandNloadingofthelake-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。,?,WhatdoesIETC“PlanningandManagementofLakesandReservoirs:AnIntegratedApproachtoEutrophicationAbridgedVersion-AStudentsGuide”(2000)sayabout“ConstructedWetland”?,ConstructedWetlandsThetransitionzonesbetweenlakesandterrestrialecosystemsarecrucialforprotectionoflakesagainstanthropogenicimpacts.Transitionzonesprevent,toacertainextent,entryofu