Succession of aquatic microbial communities as a result of the water quality variations in continuou

ISSNS 1001- -0742Jounul of Entironmental Scienes Vol . l6, No.5,pp.772- 778,2004CNII- : 26291XArtiele D: 1074020050772-07CL number: XI31.2 Document code: ASuccession of aquatic microbial communities as a result of the water qualityvariations in continuous waterW ANG Rong-chang*, WEN Xiang-hua, QIAN Yi(Environment Stimulation and Pollution Control State Key Laboratory ，Department of Environmental Science and Engineering, Tsinghua University ，Bejing 00084, China. E-mail: richardwang00 @ mails. tsinghua . edu. cn)Abstract: The changes of structural and functional parameters of aquatic microbial communities in continuous wateron campus of Tsinghua University, China are investigated by polyurethane foam unit(PFU) method. The measuredcompositions of the communities include alga, protozoa, and some metazoa( such as rotifers). The measuredindicators of water quality include water temperature, pH value, dissolved oxygen( DO), potassium permanganateindex( CODmn ), total nitrogen(TN), total phosphorus(TP) and chlorophylIl- a( Chla). The trophic level, expressedby the trophic level indices( TL/c)，is assessed with analytic hierarchy process and principal component analysis(AHP-PCA) method. The changing trends of the structural and functional parameters of aquatic microbialcommunities, such as Margalef index of diversity( D), Shannon-weaver index of diversity ( H), Heterotropy index( H), number of species when the colonization gets equilibrium( S.), colonizing speed constant( G) and timespent when 90 percent of Sa colonized in PFU( To% ), are also analyzed. The experimental results showed thesuccession of aquatic microbial communities along the water flow is consistent with the water quality changes, so theparameters of microbial community can reflect the changes of water quality from the ecological view.Keywords: succession; aquatic microbial community; polyurethane foam unit ( PFU) method; water quality;biodiversity ; biomonitoringfreshwater microbiota is anformingIntroductionvirtually self- contained communities that exhibit manyA recent worldwide development is the introduction ofcharacteristics of structure and function of entire aquaticin-stream biological effects or response monitoring in waterecosystems ( Caimns，1980; Shen， 1990). Although oftenresources management. This type of response monitoring,neglected in water resources studies, it has been recognizedcommonly referred to as biomonitoring, is increasingly beingthat changes in these communities may significantly affectrecognized as an important component in the overallother components of the aquatic food web, and thus maymonitoring and assessment of water resources .influence the distribution and abundance of both lower andBiomonitoring uses biological variables to survey thehigher organisms( Caims, 1980; Carrick, 1992) . Therefore,environment and is a complement to chemical monitoring .to a certain extent，the changes of ecological characteristics ofAssessment of ecosystem responses to environmental stressesmicrobiota communities can reflect the aquatice ecosystemis a new branch of biomonitoring ( Gerhardt，1999). Thereresponses to the changes of water quality.are many methods to assess the ecosystem responses tThe objective of this investigation was to investigate theenvironmental stresses, one of them is the polyurethane foamsuccessionof aquatic microbial communities along aunit(PFU) method. This method was frst brought forward bycontinuous water before and after cascade aeration, by usingCairms, J. Jr.(Caims，1969). By comparison with a widethe PFU method , in order to show how the aquatic ecosystemsvariety of artificial substrates previously used in ecologicalresponse to the stresses of water quality changes .studies in freshwater ecosystem, it was found that PFUs were1 Materials and methodsbest suited for collecting complex aquatic microbialcommunities ( Cairms，1979; Pratt， 1985; Xu，1998;1.1 Materials1999). PFUs were used to sample the aquatic microbiotaArtificial substrates ( PFUs ) were used throughout thecommunities. The microbiota communities, which are easierstudy to ollct the aquatic microbial colonizers from theto be investigated， are important components of aquatic*ural” refuge from normalmierobial communities. Microbiota was defined as the中国煤化工ve method for sampling amicroorganisms in the aquatic ecosysterns， which can beneMY分C NMH Gf75mm x 65mm x 50inspected by optical microscopy, such as alga ，protozoa, andmm, the pore diameter of which is about 100- 150 micron .some metazoa( Shen，1990). From an ecological viewpoint ,1.2 Sampling sites and methodFoundaion item: The 985 Program of Tsingua Univerity: * Corresponding authorNo.5Succession of aquatic mierobial communities 88 a result of the water qualityvariations in continuous water773The investigation. was conducted in a continuous water according to Standard Methods ( American Public Healthon Tsinghua Campus. The surface area of the water is aboutAssociation, 1992).13700 m'. The lengh of the flow is about 1800 m. PFUsThe degree of eutrophication was asssed by trophicwere anchored 30 cm under the water surface at six sarmplinglevel index( TLI) method using analytic hierarchy process andsites( Fig.1). Sample site No.1 was set near the upstream ofprineipal component analysis ( AHP-PCA)(Jin, 1995). Thea2 m high water fll, other sample sites were set along theprincipal asessing factor included Chla， TP， TN andwater. flow direction. After the water flow reached theCODn. The trophic level index ( TLI ) was calculatedsampling site No.6, it was pumped back to the water falapplying Eq. (1).through a connecting pipe. Then the water flow formed aTL; = 10(a, + b,InC.),(1)loop. The direction of water flow is shown in Fig. 1.where TLI; is the trophic level index of asessing factor j;C。is the concentration of assessing factor j; aj， bj areNconstants determined by geographic features of the water. Theoverall trophic level index ( TU.) was calculated as EqFall aeration⑥国(2).@\↑ru。= 2 W,TL，(2)where TLI is the overall trophic level index of the waler; Wis the weight cofficient of asessing factor j; TLI, is the自Sampling sitestrophie level index of assessing factor j; m is the number of一》 Flow directionassessing factors. The values of a，b; and W, for eachassessing factor are listed in Table 1, which suited for watersin Beijing area(Jin, 1995). Table 2 lists the standard forFrg.1 Map of invesigated water( showing sanmpling sites 1 to 6)classifying trophic levels according to the TL。 values ( Jin,1995) .The PFUs were set in the water from 7 to 30 July, 2002Table 1 Values of ay, by and W; for each sesing factorand were sampled on the day 1, 2, 3, 5, 8，12, 15, 19,and 22 respectively after inmersion. When sampling, twaAssessing factorbChla2.5001.0860.54replicate PFUs were picked randomly from each samplingIP9.4361.6240.28site. Simultaneously， oxygen concentration and waterTN5.453 .1.6940.09temperature were measured with an O2/ temperature probeCODma0.109 .2.661(YSI MODELS 54 ARC). The water flow velocities wereTable 2 Classtflcation of trophication types according to TLI。 valuesmeasured with an tachometer. The collected PFUs werecarefully placed into clean plastic bags and immediately takenTrophication typeOligotrophicaion Mesotrophication EutrophicationTu.< 30<50> 50to the laboratory for microscopic inspection. For each site andtime, water and microorganisms absorbed in the two PFUs1.3.2Structural parameters of aquatic microbialwere squeezed into a 200 ml glass beaker, mixed and allowedcommunitiesto settle for about 10 min. Three drops of mixed materialThe main investigated structural paramelers of aquatictaken from the bottom of the setting beaker were examinedmicrobial communities comprised biodiversity indices ,for the microbiota species via microscopy within three hours.evenness index( EI) and heterotropy index( HI) .The river water was sampled at the same depth as PFUs withThe biodiversity of microbial communities at the sixself-made water sampling equipment . The water samples weresampling sites were compared using the Margalef index ofcarried back to laboratory and stored in refrigeratory at 4Cdiversity( D) and Shannon-weaver index of diversity( H),before they were examined for water quality indices .which were calculated respectively as Eq. (3) and (4)1.3 Analysis methods(Huang, 2001).1.3.1 Water quality indicesD=v，(3)The investigated water quality indicators includedtemperature( T), dissolved oxygen ( DO), pH， potassiumwhere S中国煤化工is the total numberpermanganate index ( CODMn )，total nitrogen ( TN)，totalof individMYHCNMHGphosphorus(TP) and chlorophylI-a(Chla). T and DO wereH= 2(n/N)og(n/N)，(4)measured using DO online monitor( YSI MODELS 54 ARC),pH values were determined using pH meter ( Thermo Orionwhere S is the number of species; n is the toltal number ofmodel 868). CODmo, TN，TP and Chla were determinedspecie i and N is the total number of individuals. It was774WANG Rong-chang et al .Vol. 16shown that community stability would esentially always riseshown in Fig.3 and Fig.4, pH value was about 7.8 andwith species diversity because of the statistical averaging ofwater temperature was about 25C. However， the . DOthe fluctuations in species' abundances( Doak, 1998 ; Chen,concentration at each sampling site ( Fig. 5) decreased2001 ). Biodiversity indices could partially reflect thegradually along the river except No .2 sampling site, the DOstability of the investigated community.concentration at No. 1 sampling site was 1- 2 mg/L higherThe Heterotrophy index( HI) was calculated as Eq. (5)than other sites as the result of cascade aeration, and along(Shen，1990; Huang, 2001).the river oxygen consumption was higher than oxygenATPdissolution，so the DO concentration decreased gradually .HI=CB2400(5)While at No .2 sampling site probably because the water flowChlavelocity was lower there and the oxygen dissolution effect was.where ATP is the concentration of Adenosine Triphosphatesmaller than No.3, so it had a lower DO concentration .(ATP) in the sample(pg/L); B is the biomass expressed by10.00ATP concentation ( mg/L); Chla is the concentration o9.00chlorophyl-a ( m/L). HI reflects the ratio of hetertrophicemicroorganisms in total aquatic microbial community biomass ..001.3.3Functional parameters of aquatic microbial7.00上communities6.00上The colonization of aquatic microorganisms in PFUs can00 Lbe described by MacArthur- Wilson island biogeographicalSamling sitescolonization equilibrium model ( MacArthur，1963 )，asfollows:Fig.3 pH values of ceach sampling siteS,= sn(1-ea)，(6)30.0 rwhere S, is the number of species at time l; Se is the28.0-number of species when the colonization gets equilibrium; Gis the colonization rate constant. Soq and G are used as。26.0一functional parameters of aquatic microbial community inbiomonitoring( GB/T 12990-91). San indicates the maximum22.0 Fnumber of species which can colonize in PFUs， while G20.0Lrepresents the colonization rate of microorganisms . Besides ,Sampling sitesthe time spent when 90 percent of Se colonized in PFUFig.4 Temperature of each sampling site(To% ) is also used as a functional parameter of aquaticmicrobial community. Saq， G and Tg0% are all investigated10.0in this research .8.002 Results and discussion6.004.002.1 Water fow velocity and water quality2.00The water flow velocity at each sampling site changeddue to the difference of their sectional area. The water flowvelocity was the highest at No.5 sampling site and was about0.06 m/s(Fig.2), but was below 0.01 m/s at No.2 and No.Fig.5 DO of each saumpling site6 sampling site .0.08 rThe potassium permanganate indices ( COD)，totali 0.07nitrogen (TN)，total phosphorus (TP ) and chorophylI-a: 0.06g 0.0(Chla) of each site are shown in Fig. 6, Fig.7, Fig.8 and.04上Fig.9 respectively . These water quality indicators showed the)03-0.02-) ↓similar changing trends along the water from sampling site00.0No.中国煤化工No.1 to No.4, all theseindilC N MH Gase. But at sarmpling siteNo.s, there Was a arop ot al tne values, then at samplingFig.2 Water Q0ow velocity of each sonpling sitesite No.6, all the values rebounded to a higher level. Thesetrends reflcted the water quality changes along the water.During the period of the experiment, pH value andThe water quality deteriorated along the flow except that therewaterrtepprere of each sampling site varied minutely, asNo.5. Succession of aquatic microbial communities as a result of the water quality variations in continuous water75was an amelioration at sampling site No.5.six sampling sites during the study period are listed in Table6.004 and Table 5 respectively .Table 3 Tropie level indices of each sampling siteTUTlTLTophie3.00 FhSanmpling sites(T(TN) (CODm)TUe14.03 39.46 85.83 31.69 29.20 Oligo1.50 F17.39 37.61 85.50 31.78 30.48 Meso14.35622.47 43.89 88.08 36.67 35.65 MesoSampling sites19.0342.19 87.20 34.23 32 .45 Meso21.3542.98 89.3633.30 34.60 MesoFig.6 CODyo of each sampling site15.00Table 4 Taxonomic compostion and total numbers of species ot12.00phytoplankton at the six sampling sitesNames of species123456_Chorophyceae3.000Pediastnum duplex5Scnedesmus opoliensisFig.7 TN of each sampling siteAnkistrodesmus faleatusGolenkinia radiata0.10Celastrum reicalauomCoelastrum microponum0.0Senedesmus quadricaudas 0.06Scenedesmus ecormisOocystis sp.0.02 tDimorpocr lunatusPediastrum BivaePediastrumduplexvar . ClathralumMicractinum pailunCrucigenia iregularisFig.8 TP of each sampling siteVolvocalesGonium sociale1.50Pandorina morumTetasporales曾0.900Sphaerecytis schrveteriClosteriopsis lngisin! 0.60一Ulotrichales0.30Ulothrir acgoalisConiugales3Spirogyra fluiatilisSpirogyra variansFig.9 Chla of ech sampling sieSt. etrcenmCyanophyceaeThe trophic level indices of each sampling sites wereChroococcalesHyella caepitosacalculated and the degrees of eutrophication were assessedD . nupestrisaccording to the standards listed in Table 3. Close to theNostocaleswater fall， No. 1，No. 2 and No. 3 sampling sites hadOseillatoriatenuiscomparatively lower trophic level than other sampling sitesDinophyceaethat were gradually polluted by non-point sources. ThePeridinis中国煤化工+++++overall trophic level of the investigated water was oligo- mesotrophic .EuglenophyCeratiumMHCNMHG.2.2 Structure of the microbial communitiesEuglenales2.2.1 CompositionEuglenaproaxymnaTrachelomonashispidaThe taxonomic composition and total number of speciesof phytoplagkzooplankton collected from PFUs at the?芳芳数据776WANG Rong-chang et al .Vol.16Sampling sitesshows. the Margalef biodiversity indices( D) of differentNames of speciessampling sites at different times. As a whole, the MargalefEuglena gracilisbiodiversity indices( D ) decline along the flow direction fromEuglena sanguineaesampling site No.l to No.6. Fig. 13 depicts the Shannon-PhacustrpanonWeaver biodiversity indices( H) of different sampling sites .Chlorgoniule longatumSynediarumpensBy comparing Fig. 12 and Fig. 13，it is evident that theDiatomvariation trends of H at different sites are similar to those ofAchnanthesD. But the flucluation of H values is smaller than that of DAnomocorneisvalues. Partly because the richness of each species isAsterionellaconsidered when calculating H， the changes of speciesBacillarianumber are counteracted by the changes of individual numberCoscinodiscusCyclotellaof each species， whereas the individual number is notconsidered when calculating D. Both of these figures showedCymbellathat the biodiversity decrease along the water as the waterDiatomaquality worsen graduallyDiploneisDitylum .Table 5Taxonomic composition and total numbers of specles ofEpithemiazooplankton at the six sampling sltesEucocconeisNanes of speciesEunotiaFragiariaPlytomastiophoraFrustuliaEuglena uiridisHantzschiaZoomastigophoreaMelosiraVoricella conallariaMeridionLitonotus abtusssNariculaGhecamoeba quailineataNeidiumProrodon viridesNitschiaLitonotus cygnusArella 印p.PinnulariaSteutor roeseliRhizosoleriaRotifer .RhoicospheniaBrachiorus sp.RhopalodiaSymchaetaSuriellaRotaria 邮.SynedraEuchlanisTabellariaOther algal generaColurella uncinataTotal number50535252BelloidaNots: Presence is denoted by (+ ), absence by (-)Conochilus sp.Lepadella sp.The ratio of the number of each main species to thePhilodina roseolawhole species number of phytoplankton and zooplankton areLene sp.showed in Fig.10 and Fig.11. It can be seen that the mainTrichocerca 印.phytoplankton species in the waters were Diatom andGastrotrichaChaetonnotus s.Chlorophyceae, at all the six sampling sites, this two types ofNematodaalgae together can take about 70% of the total algae speciesNenmatoda sp.number and their proportion to the whole phytoplanktonTarligradaspecies increase from sampling site No. 1 to No.4 andMacrobiotudecrease at sampling site No .5, this changing trend is similarCnustaceaDaphniato the water quality changing trend. Zoomastigophorea andAlona sp.Rotifer were the main species of zooplankton. They takeabout 60% of the whole species and the changing trend of中国煤化工their proportion to the whole zooplankton species is alsoOt:TYHCNMHG1Total numbel22similar to the changing trend of water quality indicators.2.2.2 BiodiversityNotes: Presence is denoted by ( + ), absence by (-)Thebiodiversityindices of aquaticmicrobial2.2.3 Heterotrophy indicescommunities in the PFUs at each site are calculated. Fig. 12The heterotrophy indices ( HI) of the total aquaticNo.5Succession of aquatic microbial communities as a result of the water quality variations in continuous water77microbial communities at six sampling sites are calculated and5.00llutrated in Fig. 14. As mentioned above, HI reflects the4.00ratio of hetertrophic microorganisms in total aquatic microbialcommunity biomass . The higher the trophic level is, the more2.00algae will emerge in the water, so the autotrophic species will1.00dominate in the aquatic microbial communities， the HIvalues will be lower. Therefore, in some sense, HI values6Sampling sitcswill increase when the trophic level decrease, as shown inFig.14，from sampling site No.4 to No.5, the HI valuesFig.13 Shannon- W eaver biodiversity indices of each sampling siteincrease while the TLIc values decrease. Although the HIchanging trend is in reverse to the trend of TLIc, it rellects9.00足8.0the responses of aquatic microbial communities to the changes7. .00 Fof water quality .6.005.00 F1104.00 F103.00-q号1.00中60，Sampling sites40L2ig.14 Heterotropy indices of each sampling site30平2.3 Function of the microbial communitiesThe process of colonization in PFU was simulated withSampling sites'Equation (6). The constants in the Equation (6) werecalculated by direct nonlinear regression analysis withzzBugMATLAB 6.1. The results are given in Table 6. It was clearFig. 10 Ratio of each main plytoplankton species at each sanpling sitehat from sampling site No. 1 to No. 6，S。and Tgo%decreased gradually on the whole, this eleced that thespecies number possibly existed in the water decreased fromsampling site No.1 to No.6, the time needed to get thebiogeographical equilibrium also decreased. This could beparially explained by the principle that it took much longer身6time for more species to colonize in the PFUs and get the541biogeographical equilibrium. However, the G values showed莒20an increasing trend on the whole. This indicated that thecolonization or immigration rates of the aquatic microbialcommunities were different at the six sampling sites. As theSamp1 Samp2 Samp3 Samp4 Samp5 Samp6compositions and structures of the aquatic microbialther speciesmplinsttcecommunities changed， their functions would changeCrustaceaaccordingly .NematodaPhytomastigophoreaTable 6 Functional parameters of aquatic microbial communitiesFig.11 Ratio of each main phytoplankon species at each sarmpling siteSampling siteSaTo%360.3067.530.4565.05q 4.00320.4994.62喜3.000.3796.085.13中国煤化工3CMHCNMHGIn the investigated water, the water quality deteriorategradually from sampling site No. 1 to No. 6，except atFig.12 Margalef bodiversity indices of each sampling sitesampling site No.5 there was a lttle amelioration. So thetrophic level, relected by TLIc values, varies accordingly .778WANG Rong-chang et al .Vol.I6Through analyzing thcompositions and proportions of theCaimnsJJr, Hart K M, Henebry M S, 1980. The efecs of a sublethal dose ofcopper sulfate on the colonization rate of freshwater protozoan communitiesaquatic microbial communities， it is evident that the[J]. The American Midland Nturalis, 104(1): 93- -101.structural parameters of the aquatic microbial communities ,Carrick H J，Fahnenstiel G L，1992. Growth and production of planktonicsuch as D, H and HI, change correspondingly as the waterprotozoa in Lake Michigan. In situ versus in titro comparisons andquality change. The functional parameters of the aquaticimportance 10 food web dynamics[J]. Limnology and Oceanography, 37(6);1221-1235.microbial communities， such as Sq，G and T%，alsoChen LZ, Ma K P, 2001. Biodivensity science: principles and aplications[M] .exhibit their changes. in response to the changes of waterShanghuai: Shanghai Science and Technology Press. 46- 50.quality. The remarkable consistency between the successionDoak DF, Biggerxr D, Harding E K et al.. 1998. The statistical inevitability ofof aquatic microbial communities and the water qualitystability-diversity relationships in community ecology[J]. Americanchanges indicated that the changes of water quality would leadNatralist, 151(3): 264- -276.CB/T 12990-91. Standards of water biomonioring of China， Water quality-to the structural and functional changes of aquatic microbialmicrobial comrounity biomonitoring-PFU method[S].communities，which reflct the ecological responses of aquaticGerhardt A, 199 Biononitoring for the 21st century[J] . Environmental! Scienceecosystems to the environmental changes, such as, the waterForum, 9: 1-12.quality changes. .Huang Y Y, 2001. Pllution ecology of inland waters- principles und aplieations[M]. Beiing: Seience Pres. 155- 156.Acknowledgements: The authors would like to thankJin X C, 1995. Lakes in China-- Research of their environment( Volume I and II)Professor Xu Muqi for helping us be familiar with the PFU[M]. 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