鲴对食微囊藻鲢鳙排泄物及藻活性的作用研究

中国环境科学2016,36(12)：3784~3792ChinaEnvironmentalScience鲴对食微囊藻鲢鳙排泄物及藻活性的作用研究郭艳敏1,高月香2,张毅敏2*,孙丽伟1*,何东2,巫丹2(1.东南大学能源与工程学院,江苏南京210096；2.环境保护部南京环境科学研究所,江苏南京210042)摘要：开展室内模拟实验,研究鲢、鳙和鲴不同混养系统中排泄物的量及微囊藻活性的变化.实验设置鲢鳙组合,鲢鳙鲴组合以及对照组,其中鲢鳙生物量放养比例为3:1,鲢鳙鲴组合中生物量放养比例为3:1:1,实验周期14d.结果显示,鲢鳙组和鲢鳙鲴组均能降低微囊藻密度,两组无显著差异(P0.05),但是均极显著小于对照组(P0.01).混养鲴鱼可以降低排泄物的量及微囊藻的被消化率,鲢鳙鲴组排泄物的量在第4d开始下降,实验结束时是鲢鳙组的16.08%.鲢鳙鲴组微囊藻的被消化率,第5d后快速增长,至实验结束达到85.9%,极显著高于鲢鳙组(P0.01).鲢鳙组和鲢鳙鲴组排泄物中的氨基酸和总氮含量相比未被摄食微囊藻减少率分别为33.17%、53.62%和34.97%、54.27%.鲢鳙鲴组和鲢鳙组排泄物光能活性(Fv/Fm、Fv/Fo、Yeld、qP及NPQ表示)和生长活性差异(EPS、Chla表示)较大,鲢鳙组微囊藻叶绿素荧光参数(除NPQ外)值经过短暂的下降后开始增长,而鲢鳙鲴组Fv/Fm、Fv/Fo、Yeld及qP在培养过程中下降显著,且至第5d后叶绿素荧光参数(除NPQ外)均极显著低于鲢鳙组(P0.01).鲢鳙鲴组NPQ呈上升的趋势,且第7d后极显著高于鲢鳙组(P0.01).在排泄物培养期间,鲢鳙鲴组排泄物中微囊藻的胞外多糖(EPS)含量、叶绿素a(Chla)浓度不断下降,至实验结束极显著低于鲢鳙组(P0.01).结果表明,在鲢鳙控藻的基础上,混养鲴鱼可以减少鲢鳙摄食微囊藻后的排泄物,同时降低排泄物中微囊藻活性,减少了因鲢鳙排泄物引起的水环境污染和生态影响.关键词：鲴鱼；鲢；鳙；混养；排泄物；藻活性中图分类号：X52文献标识码：A文章编号：1000-6923(2016)12-3784-09EffectofXenocyprismicrolepisonfecesandmicrocystisactivityfrommicrocystis-dietarysilvercarpandbigheadcarp.GUOYan-min1,GAOYue-xiang2,ZHANGYi-min2*,SUNLi-wei1*,HEDong2,WUDan2(1.SchoolofEnergyandEnvironment,SoutheastUniversity,Nanjing210096,China；2.NanjingInstituteofEnvironmentalScience,MinistryofEnvironmentalProtection,Nanjing210042,China).ChinaEnvironmentalScience,2016,36(12)：3784~3792Abstract：EffectsontheamountsoffecesandtheactivityofmicrocystisbytheintroductionofthedifferentcombinationofSilvercarp,bigheadcarpandXenocyprismicrolepiswerestudiedinindoorsimulationexperiments.Duringtheexperiment,threegroupsweresetup:silvercarpandbigheadcarpgroup,silvercarp、bigheadcarpandXenocyprismicrolepisgroup,blankcontrolgroup,andthebiomassproportionofsilvercarpandbigheadwascarp3:1.Theresultsshowedthatinbothexperimentalgroups,thedensitiesofMicrocystisaeruginosaweresignificantlyreducedthanblankcontrolgroup(P0.01).Thefecesweightinsilvercarpandbigheadcarpgroupcontinuallyincreased,however,whichofpolycultureofXenocyprismicrolepisgroupreachedmaximumonthe4thday,thendeclinedrapidly,andfinallywas16.08%ofsilvercarpandbigheadcarpgroupattheendoftheexperiment.Therewerenoobviouschangeinalgaedigestibilityinsilvercarpandbigheadcarpgroup,whilethealgaedigestibilityofthepolycultureofXenocyprismicrolepisgruoupappearedrapidgrowthfrom5thday,reached85.9%attheendoftheexperiment,whichwassignificantlyhigherthanthesilvercarpandbigheadcarpgroup(P0.01).TheaminoacidandnitrogencontentinthefecesofexperimentalgroupsdecreasedcomparedwiththoseundigestedMicrocystisaeruginosa:thedecrementinsilvercarpandbigheadcarpgroupwere33.17%and53.62%andthoseinpolycultureofXenocyprismicrolepiswere34.97%and53.62%,respectively.Furthermore,afterMicrocystisaeruginosawasdigestedbyfish,chlorophyllfluorescenceparameters(exceptNPQ)wassignificantlylowerthantheblankcontrolgroup(P0.05),butNPQwassignificantlyhigherthantheblankcontrolgroup(P0.05).Chlorophyllfluorescenceparameters(exceptNPQ)insilvercarpandbigheadcarpgroupincreasedafterabrief收稿日期：2016-05-06基金项目：国家水体污染控制与治理科技重大专项课题(2012ZX07101-007)*责任作者,张毅敏,研究员,[e-mail];孙丽伟,责任作者,副教授,[e-mail]12期郭艳敏等：鲴对食微囊藻鲢鳙排泄物及藻活性的作用研究3785decreasing.Fv/Fm、Fv/Fo、YieldandqPvaluesinpolycultureofXenocyprismicrolepisgroupearlyrapidlydeclinedatfirst,tendedtobestableafterthe11day,and5dayslaterweresignificantlylowerthanthatofsilvercarpandbigheadcarpgroup(P0.01).NPQinpolycultureofXenocyprismicrolepisgroupshowedascendanttrend,andthenwassignificantlyhigherthanthatofsilvercarpandbigheadcarpgroupafterthe7thday(P0.01).Duringthefecescultivation,theEPSandChlaoffecesinpolycultureofXenocyprismicrolepisgroupcontinuallydecreased,anduntiltheendoftheexperiment,theywassignificantlylowerthanthoseofsilvercarpandbigheadcarpgroup(P0.01).Besidetheintroductionofsilvercarpandbigheadcarp,thepolycultureofXenocyprismicrolepiscouldreducethefecesofsilvercarpandbigheadcarpbyfeedingMicrocystisaeruginosaandfurtherreducetheactivityofthealgaeinfecestherefore,improvedtheremovaleffectcausedbyMicrocystisaeruginosa,providedtheoreticalbasisforbiomanipulationmodeofpolycultureofXenocyprismicrolepis.Keywords：Xenocyprismicrolepis；silvercarps(Hypophthalmichthysmolitrix)；bigheadcarp；polyculture；feces；algaeactivity为控制藻类水华,遏制水体的富营养化进程,通过对武汉东湖的长期调查和围隔实验提出了非经典的生物操纵理论,即控制凶猛鱼类和放养食浮游生物的滤食性鱼类(鲢、鳙等)直接控藻,改善水生态环境[1-3].但其他研究表明鲢鳙对水华蓝藻(微囊藻)的消化利用率只有25%~30%[4],未消化的微囊藻随排泄物的分解重新进入水体.实验还表明,鲢鱼在10d之内排出的粪便重量几乎等于其自身的重量[5],并且发现未消化微囊藻经鲢、鳙代谢后其生长速率和光合活性均得到了增强[6-7],排泄物中大量的活性微囊藻重新进入水体,可能引起水华藻类生物量的激增[8-9].底层鱼类可以摄食利用水底碎屑,促进泥水界面的物质交换和水体的自净,在生态系统物质循环和能量流动中起着重要作用,因此构建底层鱼类—鲢鳙鱼—藻类食物链对富营养化水体的净化以及藻类的控制有很重要的意义.底层鱼类—细鳞斜颌鲴(Xenocyprismicrolepis,以下简称鲴鱼),俗名有沙姑子、黄尾刁子、黄片等,它肉质鲜美、生长快,是一种优良的养殖对象[10].研究发现该鱼鳃耙排列紧密,消化能力极强,下颌前有比较发达的角质边缘,能充分刮取和摄食能使水质污染的腐殖质、各种固有的藻类及上层鱼类排泄物的有机碎屑,有水底“清洁工之称”[11].张毅敏等[12]对鲴和三角帆蚌进行混养,结果表明鲴和三角帆蚌组合的协同控藻作用明显,藻细胞去除率最高可达(86.11±0.30)%,而且鲴鱼在不同水温条件下对铜绿微囊藻均具有较强的控制作用[14].在养殖池塘中混养鲴鱼,不仅明显提高养殖效益,而且有效改善水质,提高溶解氧含量,降低氨氮和亚硝酸盐氮的浓度[14-15].鲴鱼可以摄食消化鲢鳙摄食微囊藻后的排泄物,鲴鱼的摄食活动是否减少鲢鳙摄食微囊藻后的排泄物,并影响微囊藻的被消化率及活性有待进一步研究.基于鲴鱼的摄食特性,本文采用室内模拟实验,在模拟的富营养化水环境分别放养鲢鳙鲴和鲢鳙,研究鲴鱼对鲢鳙控藻过程中排泄物及微囊藻活性的变化,旨在了解鲴鱼在控藻食物链中的摄食作用,为鲢鳙鲴联合操纵控藻改善水质提供依据.1材料与方法1.1实验材料实验用鱼:鲢鱼(Hyp