Microbial Community and Urban Water Quality

BCASVol.26 No.1 2012Microbial Community and Urban WaterQualityYANG Jun, ZHANG Yongyu, LIU Lemian, WANG Changfu & YU XiaqingAquatic Ecohealth Group, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of SciencesXiamen 361021, ChinaAbstract Urbanization of China is substantial and growing, and water resources are crucial for botheconomic and social sustainable development. Unfortunately, the frequency and intensity of watercontamination events are increasing at an unprecedented rate and often accompanied by increasedpollutant loading due to human activities such as ireversible industrialization and urbanization.The impacts of human pollution are most evident and of greatest concern at the microbial level.The research of the Aquatic Ecohealth Group, Key Laboratory of Urban Environment and Health,Institute of Urban Environment, Chinese Academy of Sciences, has been focusing mainly on aquaticmicroorganisms in the urban environment, from drinking water and landscape water to waste water. Itsprojects fall into three categories: biomonitoring and bioassessment, microbial ecology and diversity,ecotoxicology and environmental microbiology. Its scientific topics include the aquatic ecological safetyand microbial food web.Keywords freshwater ecology, biomonitoring and bioassessment, microbial ecology and diversity,ecotoxicology and environmental microbiologyDr YANG Jun is a professor of environmental biology at the Xiamen basedCAS Institute of Urban Environment. His research has been focusing onaquatic microorganisms in the urban environment, from drinking water andlandscape water to waste water. Scientific topics include eutrophication,biomonitoring and bioassessment, microbial ecology and diversity,ecotoxicology.Dr Yang received a B. A. from Hebei University (2001)，and Ph.D. fromInstitute of Hydrobiology, Chinese Academy of Sciences (2006). From2006 to 2008, he worked as a Kllm Postdoctoral Fellow at Earth SciencesDepartment, Dalhousie University iE-mail:lyang@iue.ac.cn中国煤化工fHCNMHG76 Bulletin of the Chinese Academy of Sciences.图BCASVol.26 No.1 2012Bacillariophyta, Chlorophyta, Chrysophyta, Cryptophyta,Freshwater eutrophication is likely to intensify in theCyanophyta, Euglenophyta, Pyrrophyta, Xanthophyta) werecoming decades due to rapid increase in human population,observed and the most diverse groups were Chlorophytademand for more food, land conversion, and fertilizer use.(52 taxa), Cyanophyta (20 taxa), Euglenophyta (17For different purposes, therefore, the integrated monitoringtaxa), Chrysophyta (14 taxa). The dominant groups wereand assessment methods of surface water quality forChlorophyta (40.58%), Cyanophyta (22.91%), Bacillariophytareservoirs are needed to support various decision making(21.61%), Chrysophyta (6.91%). Algae communities wereprocesses in local government agencies. Eutrophicationstructurally different between study reservoirs. The speciesinformation on the Fujian's water resources is critical torichness, abundance, diversity, and evenness of algaeensuring long-term availability of water that is safe forvaried significantly between reservoirs. These differencesdrinking and recreation. Algae species composition mayindicated a regional effect, which was related to trophic state,be an important facet of water quality for the users andenvironmental factors, and human influences.consumers because some species can impair the quality ofUnfortunately, neither oligotrophic nor mesotrophicdrinking water. Further, the degradation of water qualityreservoirs were found, and all investigated reservoirsassociated with excess levels of nitrogen and phosphoruswere eutrophicated based on the TSIc values, thus ourin Fujian reservoirs may be impacted by interactionsresults provided an early warning of water degradationamong agriculture and urban factors. A watershed-basedin Fujian reservoirs. Shallow reservoirs generally havemanagement strategy, especially phosphorus control,higher values of trohpic state index (TSI) and appear toshould be developed for drinking water source protectionbe more susceptible to anthropogenic disturbance thanand sustainable reservoirs in the future.deeper reservoirs. Trophic state is not the same thing asThe transparency and chlorophyll a were the strongestwater quality, but trophic state determination certainlyenvironmental factors in explaining the algae communityis an important aspect of water quality assessment. TSIdata. The chlorophyll a itself was related to the abundanceresults indicated that all 11 reservoirs were eutrophic, threeor frequency of Euglenophyta (hyper-eutrophicationof them were hypereutrophic, six were middle eutrophic,indicators). Accordingly, it might be recommended thatand two were light eutrophic. The comprehensive trophicregular biological monitoring should concentrate on thestate index (TSIc) was not correlated to taxa richness andabundance, species richness and species diversity ofabundance but signifcant correlations to Shannon-WienerEuglenophyta and Cyanophyta (bloom-forming species),diversity and Pielou's evenness were found.rather than the whole algal flora; and that regular chemicalOur results also illustrated that temperature,monitoring should concentrate on TN, TP and Chl a.transparency, conductivity, dissolved oxygen (DO),This limited number of variables seems to contain alltotal carbon (TC), NH-N, NOx-N, total phosphorusthe information necessary to establish the cutrophication(TP), and chlorophyll a were significant environmentalstatus of these Fujian reservoirs. Therefore, long-termvariables affecting the distribution of algae communities.and regular monitoring of Euglenophyta, Cyanophyta,Furthermore, the trophic state plays an important role inTN, TP and chlorophyll a in reservoirs is urgently neededshaping community structure and in determining speciesto further understand the future trend of eutrophicationdiversity of algae. Our TSIc was positively corelated withand to develop a watershed-based strategy to manage thenitrogen, phosphorus and Chl a.Cyanophyta bloom hazards.2. Microbial ecology and diversity in a subtropical river Jiulong River)It is important to investigate changes in microbialtemperate lakes. On the other hand, studies focusedcommunity for asssing aquatic ecosystem health. In theon patterns of n“中国煤化iposition inpast few decades, we have developed a good knowledge oflarge subtropicalMH_eters) are farthe temporal and spatial patterms of microbial abundanceless common.c N M H Ged microbialand production in some coastal regions, oceans andplanktonic communities by using denaturing gradient gel78 Bulletin of the Chinese Academy of Sciences| 中国煤化工YHCNMHG囡BCASVol.26 No.1 2012importance of agricultural pollution (TN, NH4-N, NO,-N,In conclusion, our data indicate that great variations inTP and PO4-P) and saltwater intrusion (conductivityenvironmental conditions of the Jiulong River throughoutand salinity) in determining community structure ofspace resulted in different microbial communities.prokaryotes or eukaryotes, variation partitioning wasThe agricultural activities in the upper Jiulong Riverperformed. The results of variation partitioning revealedWatershed are the major sources of nitrogen andthat agricultural pollution (phosphorus and nitrogen)phosphorus due to heavy chemical fertilizer applicationand saltwater intrusion (conductivity and salinity)and intensive livestock production. The genetic structurewere the main factors impacting microbial communityof both prokaryotic and eukaryotic microbial communitiescomposition, by explaining more than two-thirds of thechanged significantly from the upper Jiulong River sitestotal variation in both prokaryotic (67.0%) and eukaryoticto the estuarine sites. These changes were closely related(70.5%) communities. The relative contribution ofo the agricultural pollution and saltwater intrusion.agricultural pollution factors was considcrably larger thanSomewhat surprising was the finding that the geneticthat of saltwater intrusion factors in both communities.diversity patterns were similar between prokaryoticFor prokaryotic communities, the pure variance explainedand eukaryotic communities. Moreover, the robust andby agricultural pollution (39.0%) was higher than thatquantifiable relationship between DGGE results andexplained by pure saltwater intrusion (19.0%). Similarly,environmental variables indicated that the community-for eukaryotic communities the pure variance explainedlevel molecular fingerprinting techniques could supportby agricultural pollution (44.3%) was substantially higherthe physicochemical assessment of riverine water qualitythan that explained by pure saltwater intrusion (14.6%).and ecosystem health.3. Microbial ecotoxicology; Arsenate toxicity in a freshwater protozoanNowadays, water pollution is a part of our life whichhailed as environmentally friendly and cost effective, asheavily destroys the aquatic ecosystem and threatenscompared to the physico-chemical methods. In additionour health. Toxicity tests are an important component forto the popular phyto-remediation method, aquaticassessing the impact of chemicals on aquatic ecosystems.microorganisms are considered to be reliable candidates forGroups of selected biological organisms are employed toarsenic bioremediation in waters.determine the potential adverse effects of different kindsUnderstanding the responses of varied microorganismsof pollutants, such as heavy metals, persistent organicto arsenic will be an important knowledge base forpollutants (POPs) and microcystins, etc. Meanwhile,developing efficient and selective bioremediationbiological remediation is also considered as one of the mostapproaches. Arsenic metabolism in microbes, such aspotential efective approaches for the recovery of pollutedarchaca, bacteria, fungi and algae, has been extensivelyaquatic environment. Currently, one of our research interestsstudied in the past. Microbes respond to arsenic in a varietyis studying the arsenic (As) toxicity and metabolisms inof different ways, such as chelation, compartmentalization,a freshwater protozoan, Tetrahymena pyriformis. Arsenicexclusion, and immobilization. Most of them can methylate(As) is a ubiquitous and potentially toxic element inarsenic giving rise to monomethyl, dimethyl, and/or tri-the environment. Chronic exposure to arsenic throughmethyl derivatives, which are volatile and are rapidlycontaminated drinking water occurs worldwide, and isreleased to the atmosphere. However, it is a pity that oneassociated with a variety of diseases, including cancer,of the dominant players in global aquatic ecosystems,diabetes and developmental disorders. In natural waters,protozoa, was neglected in the past. So far, litle is knownAs exists predominantly as the pentavalent state, As (V).about arsenic metabolism in aquatic protozoan cells.Its mobility and bioavailability is influenced not only byThe uncellu中国煤化Tle largest andabiotic factors, but also by the activities of aquatic plants,most complex ofCN MH G° ecosystems,animals and microbes. Recently, bioremediation to cleanfollowing bactenla ana alr ouner smaller microbes. Asup arsenic-contaminated environments has been widelydominant bacterial grazers in microbial food webs, they80 Bulletin, ofthe Chinese Academy of SciencesVol.26 No.1 2012 Urban Water & Environmentinfluence to a great extent the bacterial community sizemost intracelular As (V) of T. pyriformis was transformedand population structure, and play important roles into As (I), and the methylated derivates of MMA (V) andthe biogeochemical cycles of elements, such as carbon,DMA (V). The transformation rate reached as high as 94%nitrogen, and sulfur, etc.. Moreover, as unicellularand 98% in the cells under treatments with 0.67 and 40 μMorganisms with a short regeneration time, protozoa respondof As (V), respectively. Among them, the most abundantrapidly with great sensitivity to the presence of pollutantsspecies were DMA (V) and MMA (V). As the toxicity ofin nature. This has resulted in them being used as testAs (V) is much higher than DMA (V) and MMA (V), wesystems for assessing ecological risk.consider that oxidation/reduction and methylation is likelyIn natural waters, the W idespread presence of arsenicone of the major detoxification pathways in T. pyriformis.has forced most organisms, from bacteria to mammals, toMoreover, we found that both As (I) and DMA (V) coulddevelop various strategies to counter-act arsenic toxicitybe continuously excreted from the cell, effectively reducingor to utilize arsenic as an electron donor/receptor inthe arsenic cytotoxicity. Finally, comparative proteomicsenergy production. Considering the important ecologicalwas employed to investigate the stress responses of T.status of protozoan in aquatic system, protozoan maypyriformis to arsenate exposure, and unveiled significanthave also developed certain approaches to respond to thechanges in the expression of multiple proteins involved inwidespread existence of arsenic. On this basis, a ciliatedanti- oxidation, sugar and energy metabolism, proteolysis,model protozoan Tetrahymena pyriformis was employedand signal transduction.as one case to study the arsenic metabolism. Our aim is toIt revealed multiple pathways of arsenate detoxificationevaluate the toxic effects of the As (V) to T. pyriformis, andin T. pyriformis. Arsenic oxidation/reduction andexplore the potential arsenic detoxification mechanisms inbiomethylation is the major detoxification pathway. Also,T pyriformis culture, which may have hopes to be appliedthe effective effux for As (I) and DMA can reduce thein technology for bioremediation of arsenic-contaminatedarsenic cytotoxicity. In addition, the following pathwayslocalities.were considered as the potential detoxification approaches,The most easily recognized symptom of arsenatesuch as: 1) enhancing the scavenging activity of freetoxicity was the growth inhibition of T. pyriformis. Theradicals to prevent oxidative damages; 2) employing the18-hour EC50 arsenate concentration, causing a 50%ubiquitin-dependent proteolysis to avoid accumulation ofdecrease in growth rate of T. pyriformis, was calculated tomisfolded or damaged polypeptides that are toxic to cells;be ca. 40 μM. Under the treatment with 40 μM arsenate,3) raising the sugar metabolic efficiency to supply morethe cell mobility of T. pyriformis was slowed downenergy for arsenic extrusion.significantly. Meanwhile, at above 18 h of exposure,Because protozoan is abundant and widespread insignificant morphological changes were found in mostglobal aquatic environment, if the arsenic detoxifyingof the treated cells. The cell body became a ltle shorterprocess of T. pyriformis is not just a special case, butand stouter, and the cell surface became riddled with acommonly exists among other protozoan, the protozoan-number of depressions ranging in diameter from 0.3-0.5mediated transformation is proposed to have an importantμm. However, interestingly we found that T. pyriformisimpact on the global arsenic cycle. Also, the high efficientcould still grow reasonably well in a medium containingbiotransformation of arsenic by T. pyriformis providesup to 30 μM of arsenate, revealing this protozoan hasbaseline information for further explorations regardingsome capacity to mitigate against arsenic toxicity. Arsenicthe exploitation of protozoa for arsenic removal inspeciation analysis by using HPLC ICP-MS showed thatcontaminated water.4. Environmental microbiology: Nitrogen and phosphorous removal by microa中国煤化工Human activities, particularly urbanization,eutrophicationns of nitrogenhave increased the entry of chemical and biologicaland phosphorulMYHCNMHGtem.Sothesecontaminants into the water systems. It is easy to causeeffuents should be treated properly to reduce contaminantsBulletin of the Chinese Academy of Sciences 81.困BCASVol.26 No.1 2012to environment. Special attention has been focused onincludes both eukaryotic microalgae and the prokaryoticnitrogen and phosphorus removal from wastewater usingcyanobacteria. The most important common feature ofbiological, physical and chemical methods. Conventionalall eukaryotic microalgae and cyanobacteria is that theytreatment of wastewater goes through primary physical andhave oxygen-evolving photosynthesis and that they usechemical methods, secondary biological process, removinginorganic nutrients and carbon. Microalgal biomassonly a fraction of nutrient in the wastewater. Some harmfulcan be used for hydrogen gas production, bioenergymaterial are not effective eliminated as the conventionalconversion and production of pharmaceutical substancestechnology of treatment used in wastewater treatmentor food. During the U.S. Department of Energy's Aquaticplants. More often, the effluent from the wastewaterSpecies Programme (ASP), it was found that for the algaetreatment plant fail to meet with the effluent standardsremediation of wastewater, energy outputs were twiceset by the local government. Microalgae can be used forthe energy inputs, based on digester gas production andtreatment of wastewater due to their capacity to assimilaterequirements for pumping the wastewater, mixing thenutrients including nitrogen and phosphorus. Moreover,ponds, etc. The overall economics were very favorablethese inorganic nutrients are suitable and cost-effective forbecause of the wastewater treatment credits. In Virginiamicroalgae cultivation. Algae are important bioremediation(USA), researchers at Old Dominion University haveagents, and are already being used by many wastewatersuccessfully piloted a project to produce biodieselfacilities. Microalgae treatment of wastewater does notfeedstock by growing algae at municipal wastewatergenerate additional pollution which can offer a moretreatment plants.ecologically safer, cheaper and efficient means to removeTo construct algac based wastewater treatment system,nutrients than conventional methods. Moreover, microalgaeit is essential to consider both wastewater treatment as wellcultures offer an interesting alternative for w astewateras algal cultivation. Cell retention time, nutrient additiontreatment because they provide a biotreatment coupledrate, water depth, and degree of mixing are the commonwith the production of potentially valuable biomassparameters consider for growth of algae. In addition toand reduction of greenhouse gas emission. The majorthese parameters BOD (biochemical oxygen demand)disadvantages associated with current wastewater treatmentreduction, TDS (total dissolved solids) reduction, pH,practices are: 1) Many wastewater treatment processesnitrogen removal rate and phosphorus removal rate aregenerate large amounts of biological waste sludge thatcommonly considered for wastewater treatment. Hence themust be sent off-site for disposal. Handling and disposal ofsystem should be designed accordingly to allow the growththis sludge is typically the largest single cost componentof algae as well as wastewater treatment. Algae-basedin the operation of a wastewater treatment plant. 2)wastewater treatment technology is suited for tropicalMost wastewater treatment processes cannot effectivelycountries where the temperature is warmer and sunlightrespond to diurmal, seasonal, or long-term variations in theis optimum. Environmental factors play a major role incomposition of wastewater. A treatment process that mayalgae cultivation. Maintenance of optimum temperaturebe effective in treating wastewater during one time of theand lighting in algae ponds are dificult. Apart from theseyear may not be as effective at treating wastewater duringenvironmental factors, there are a number of biologicalanother time of the year. 3) High energy requirementsproblems and operational problems can arise in the masswill make many wastewater treatment methods unsuitablecultivation of microalgae using wastewater. These issuesfor low per-capita energy consumption countries. 4)include contamination and grazing. Control measuresHigh operation and maintenance requirements, includingfor avoiding contamination by bacteria and other algalproduction of large volumes of sludge, make them .species are sterilization and ultra-filtration of the cultureeconomically unviable for many regions.medium. Grazing by protozoans and diseases like fingi canTo use microalgae for wastewater treatment is not aeventually be treated chemically.new idea, and many researchers have developed techniquesIn our laboratorv, a freshwater unicellular microalgaefor exploiting the fast growth and nutrient removalChlorella sp.中国煤化工nitrogen andcapacity. The term microalgae refers to all algae toophosphorus fromYHC N M H Gpal wastewatersmall to be seen properly without microscope, and oftenwhich were diluted to four different proportions, namely,82 Bulletin of the Chinese Academy of sciencesVol.26 No.1 2012 Urban Water & Environment100%, 75%, 50% and 25%. The growth of Chlorella sp.different in different proportions wastewaters. Chlorella sp.in different proportions wastewaters was monitored overgrew well after PO4-P was exhausted which indicated thata period of 24 days. The level of wastewater proportionsPOfP is not the limiting factor for growth of this alga. Thesegreatly infuenced algal growth. Interestingly, Chlorella sp.results indicate good prospects for being able to cultivategrew fastest in 50% wastewater both in influent and effluentChlorella sp. in both influent and efluent wastewater towastewater. Chlorella sp. showed a fairly high nutrientremove nutrients and produce microalgae biomass. In future,removal eficiency. The removal efficiencies of nitrogen (TN,Chlorella sp., Botryococus braunii and Scenedesmus sp.NH-N, and NOx-N) and phosphorus (TP and PO.-P) werewill be employed for wastewater treatment.ReferencesLiu L.M., Yang J.. Zhang Y. Y., 2011. Genetic diversity patterns of microbial communities of in a subtropical riverine ecosystem (Jiulong River,southeast China). Hydrobiologia 678:113-125Yang J.,. YuX. Q, Liu L. M.. Zhang W. J.. Guo P. Y.. 2012. Algae community and trophic state of subtropical reservoirs in southeast Fujian,China. Environmental Science and Pollution Research (in press).Zhang Y. Y., Yang J, Yin X. X., Yang S.P., Zhu Y.G..2012. Arsenate toxicity and stress responses in a freshwater ciliate Tetrahymenapyriformis. European Journal of Protistology (in press).中国煤化工MYHCNMHGBulletin of the Chinese Academy of Sciences 83.