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Cyanobacteria (Blue-Green Algae) Harmful Algal Blooms

JenniferM.DeBruyn,UTDepartmentofBiosystemsEngineeringandSoilScienceStevenW.Wilhelm,UTDepartmentofMicrobiology

AndreaLudwig,UTDepartmentofBiosystemsEngineeringandSoilScienceGregBoyer,StateUniversityofNewYorkDepartmentofChemistry

Whenpondsandlakesbecomeovergrownwithalgae,thebodyofwatercanbecomeunattractiveforrecreationandhavefoultastesorodorsthatrestricttheuseofthewaterasadrinkingsupply.Sometypesofalgaealsoproducecompoundsthataretoxictootherorganisms.Besidesimpactingpeople,algaecanalsocauseproblemsforfishandotheraquaticlife.Largeabundancesofalgaethatcauseadverseeffectsarecalledharmfulalgalblooms(HABs).Reportsoflivestockandpet(Backeretal.2013)illnessesanddeathsduetodrinkingtoxicwaterareknown.Althoughdocumentedreportsofhumanillnessesareinfrequent(Carmichael2008),thereisagrowingconcernthesafetyoffreshwateracrosstheUnitedStates.(ResourceMediaandNWF2013).Theincreasedfrequencyofalgalbloomsinsmalllakesaswellasinlargelakes(includinglakesErie,OntarioandMichigan)innumerousstateshasledtodrinkingwaterandrecreationalcontactbansaroundtheUnitedStates(Downing2013,KVAL2013).

Harmful Algal Blooms (HABs) Algae,orphytoplankton,aremicroscopicorganismsthatareanormalandimportantpartofponds,

streams,rivers,lakes,oceansandotheraquatichabitats.Theyformthebaseoftheaquaticfoodweb,providingfoodforinvertebratesandfish.Theygettheirenergythroughphotosynthesis,muchlikeplants,andintheprocessproduceasignificantamountoftheoxygenwebreatheeveryday.Inhealthyaquatichabitats,algaeareusuallypresentinlownumbersandthewaterappearsclear.

When your pond turns green … Undercertainconditions,algaecangrowexcessively,

resultinginanalgalbloom:avisible,densebuildupofalgae(Figure1).Bloomscanturnaclearpondcloudy,formingfoams,matsorscumsonthesurfaceofthewater.Somebloomshaveunpleasanttastesandodors.

Bloomsaremostcommoninstill,nutrient‐richwatersduringwarmweather.Oneofthemaincausesofalgalbloomsisexcessivenutrients.Justlikelandplants,algaerequirenutrients(suchasnitrogenandphosphorus)togrow.Runofffromlandcancarrynutrientsfromfertilizers,animalmanure,sewagetreatmentplants,failingseptictanks,andothersources.Whentheseextranutrientsendupinapondorlake,theystimulatethegrowthofalgae,causinganalgalbloom.

Figure1.AMicrocystisbloom.PhotoSWilhelm

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Algalbloomscancauseavarietyofproblems.Bloomscausingdetrimenttohumanoranimalhealthortotheenvironmentarereferredtoasharmfulalgalblooms(HABs),asshowninFigure2.Thickbloomsblocklightfromreachingtothebottomofthepondandmacrophytes(pondplantsrootedtothebottom,suchaswaterliliesorcattails)candiebackduetothelackoflight.Bloomsalsocanleadtoreducedoxygenlevelsinthewater.Whenthealgaedies,bacteriadecomposethedeadcells,usingupoxygenintheprocess.Thelowoxygen(hypoxic)“deadzones”killfishandotheraquaticspecies.Recurringdeadzoneshavebecomeamajorprobleminsomeofourlargewaterbodies,includingLakeErie,theChesapeakeBay,andtheGulfofMexico.Inmanycases,thosedeadzonesarelinkedtoalgalovergrowth.

Toxic cyanobacteria Therearemanytypesoffreshwateralgae;themost

commongroupsarediatoms,greenalgaeandcyanobacteria(alsoknownasblue‐greenalgae).Undersomeconditions,cyanobacteriaproducecompoundsthataretoxictoanimalsandhumans.Themostcommoncyanobacteriatoxinsincludethemicrocystins,cylindrospermopsins,anatoxinsandsaxitoxins.Microcystinsarehepatotoxins(affectingtheliver),andanatoxinsandsaxitoxinsareneurotoxins(affectingthenervoussystem).

Cyanobacteriadonotactivelyexcretethetoxin.Instead,mostofthetoxinisreleasedfromacyanobacterialcellwhenitisconsumedbyanotherorganismordiesandruptures.Whenalargecyanobacterialbloomdies,thewatermaylookclear,butthealgal‐producedtoxinmaystillpersistuntilsunlightorbacteriabreakthetoxindowntoanontoxicform.

Therearecurrentlyabout3,000knownspeciesofcyanobacteria,andsomeestimatethatthetotalnumberofspeciesistwicethatnumber.However,toxinformationisconfinedtoarelativelysmall(lessthan100)numberofcyanobacteriaspecies.Someofthemorecommontoxin‐producingcyanobacteriaincludeMicrocystis,Anabaena,PlanktothrixandLyngbya.Veryfewofthesetoxinsaffectfish,andwhycyanobacteriamaketoxinsisstillnotwellunderstood.Specieswiththecapabilityoftoxinproductiondonotalwaysmaketoxin.Somespeciesproduceasingletoxin,othersproducemultipletoxins.Evenwithinasinglespeciesbloom,somecellswillmaketoxinwhileotherswillnot.Thereasonfortoxinformationremainsamysterythatscientistsarestillworkingtounderstand.

Health effects of HAB toxin exposure Themostcommonroutesofexposuretocyanobacteriaandtheirtoxinsareskincontact,swallowing

waterwhileswimming,eatingcontaminatedfish,and,inthecaseofanimals,lickingwateroralgaeoffoffurafterswimming.WhenanimalsareexposedtooringestHABtoxinsinlargequantities,therecanbeadversehealtheffects.Somehumansareverysensitivetothealgalcellmaterial,leadingtoanallergicresponse.Directcontactwithhighlevelsofalgalcellsortheirtoxinscancauseirritationofskin,eyes,noseandthroatandinflammationoftherespiratorytract.Ingestioncancausenausea,vomitinganddiarrhea.Inhumans,toxinshavebeenlinkedtoliverdiseaseandneurologicaleffects.Theeffectsoflong‐term,chronicexposuretocyanobacterialtoxinsarenotyetunderstood;however,linksbetweenalgaltoxinsandincreasedratesoflivercancerhavebeensuggested(Grosse2006).Forthisreason,healthdepartmentsroutinelycautionthatyoushouldavoidcontactwithallblooms,toxicornot.

Figure2. AnalgalbloomonLakeErie. Photo:SWilhelm

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Toxiccyanobacterialbloomshavecausedthedeathofwildlife,livestockandpets.Dogsareespeciallysusceptible,astheyarenotrepulsedbyunsightlyorsmellyblooms.Dogstendtowadeordrinkinshallowareasofpondsandlakeswherealgalmatscanconcentrate.Theymayalsoeatalgalmaterialswasheduponshore,orlicktheirfurafterswimmingthroughabloom.Treatmentsforillnessesfromcyanobacteriatoxinsarelimitedastherearenoknownantidotestothetoxin.

Identifying Harmful Algal Blooms Notallalgalbloomsproducetoxins,andyoucannotvisuallydistinguishifabloomistoxic,evenundera

microscope.Ingeneral,freshwaterdiatomsandgreenalgaedonotmaketoxins,thoughtheycancauseharmthroughwaterfoulingorhypoxia.Smallaquaticplantsalsocangrowtohighdensitiesandcoverthesurfaceoffreshwaterbodiesbutarenotharmful.Unpleasanttastesandodorsarenotgoodindicatorsoftoxins:abloomthathastasteandodorproblemsisnotnecessarilytoxic;likewiseatoxicbloomdoesnotnecessarilyhaveunpleasanttasteandodor.Laboratoryanalysisisrequiredtodetectthesetoxiccompoundsinawatersample.Butsincemostharmfulalgalbloomsinfreshwatersarecausedbycyanobacteria,thebestprecautionistodetermineifyouhavecyanobacteria(potentiallytoxic)orsomeothertypeofgreenalgaeoraquaticplant(harmless).

Nontoxic algae and plants Duckweed(Lemnaspp).Thistinyaquaticplantactuallyisnotanalga.ItiscommonthroughoutNorthAmericaandisharmless.Itlooksliketinylobedleavesonthesurfaceofthepond,similartoaminiaturecloverorlilypads,withrootsextendingdownintothewater.

Wikipedia.org aquaplant.tamu.edu/plant‐identification/alphabetical‐index/common‐duckweed

PhotocreditA.Ludwig

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Greenalgae.Thisisabroadgroupofspecies.Greenalgaecanlooklikefilaments,stringsorhairs.Theycanformmatsonthesurfaceandsometimesairbubblesareapparent.Thereisaroughtexturelikefabricorcarpet.Whenyoudipastickintothepond,algaewillclingtoit.Thesebloomsaretypicallynottoxic.

PhotocreditA.Ludwig PhotocreditA.Ludwig

1aquaplant.tamu.edu/plant‐identification/alphabetical‐index/filamentous‐algae

PhotocreditA.LudwigPhotocreditA.Ludwig

Ahrens,Sara.img_1353.jpg.August2010.Pics4Learning.17Apr2015<pics.tech4learning.com>

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Potentially toxic cyanobacteria Cyanobacteriabloomslooklikegreenpaintorpeasoup.Thetextureissmooth.Whenyoudipastick

intoit,thegreendoesnotclingtothestick.Somecyanobacteriabloomscanbetoxic.SomecommontypesofpotentiallytoxiccyanobacteriaareMicrocystis,Anabaena,PlanktothrixandLyngbya.

Microcystis.Bloomsaregreen,thickandpaint‐like,sometimeswithagranulartexture.Attheironsetindividualcoloniescanbesometimesseenwiththenakedeye—theylooksomewhatlikesnowflakesinthewater.

Anabaena.LikeMicrocystis,populationsofthiscyanobacteriumarefoundworldwide.Thebloomsalsolooksimilar.However,theAnabaenacellsformlongfilamentsvisibleunderamicroscopeandoftencontainspecializedcellsthatconvertnitrogengasdirectlytoammoniabytheprocessofnitrogenfixation.

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Planktothrix.Thisorganismformslong,slender,straightfilamentsthatwillformdensesuspensionsbothinthewatercolumnandonsediments.ItiscommoninbothEuropeandNorthAmericaandcanbefoundinhighabundancesinagriculturallyimpactedbodiesofwater.

Lyngbya.Thishorse‐hairlikecyanobacteriumcanformlargedensematsonthebottomofwaterbodies,sometimeswashinguponshoretocreateunsightlymoundsofalgae.Oneofthebeststudiedspecies,Lyngbyawollei,wasfirstisolatedfromtheTVAGuntersvilleReservoir.

Foradditionalphotosofalgalbloomsandphotomicrographsofthevarioustypesofalgae,pleaseseethefollowing:

BloomCharacterizationGuide,OhioEPAepa.ohio.gov/portals/28/Documents/HAB/BloomCharacterizationGuide‐DRAFT.pdf

AlgalPlates,OhioEPAepa.ohio.gov/portals/35/inland_lakes/10000%20Algae%20Plates_1.pdf PhotoGalleryofGreenandBlue‐greenAlgae,NewYorkDECwww.dec.ny.gov/chemical/81962.html Cyanosite,PurdueUniversitywww‐cyanosite.bio.purdue.edu/images/images.html

Imagefromwww.outdooralabama.com

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I Think I Have a Cyanobacteria Bloom. What Should I Do? Itisimportanttorememberthatnotallcyanobacteriabloomsaretoxic.Buttobesafe,ifyouthinkyou

haveacyanobacteriabloom,youshouldtakethefollowingprecautions:

Donotletlivestock,petsorpeoplecomeincontactwithwaterwithvisiblecyanobacteriablooms.Ifyoudocomeintocontact,rinsethoroughlywithcleanwater.

Asageneralrule,neverdrinkuntreatedsurfacewaters,evenifalgalbloomsarenotvisible.Untreatedwatercancontainbacteriaandotherparasitesthatcancauseillness.

Donotallowpeople,petsorlivestocktodrinkwaterwhenabloomisvisible,evenifithasbeentreated.Boiling,chlorinedisinfection,UVtreatmentsandwaterfiltrationwillnotremovealgaltoxins.

Donotusetoxin‐contaminatedwaterforfoodcropirrigation. Donotusealgaecidessuchascoppersulfatetotreattheblooms;thiswillcausethecellstorupture

andcauseasubstantialreleaseoftoxinsintothewater,greatlyincreasingtheriskoftoxinexposure.Copperisalsotoxictootheraquaticwildlife.Mostbloomswilldieoffontheirown.

Becautiousofeatingfishcollectedfromcontaminatedwaters.Concentrationofthetoxinsinfishfleshishighlyvariable.Youmaygetafishwithaveryhighconcentrationoftoxins.

Ifyoucomeincontactwithwaterthathasvisiblecyanobacteriabloomsandexperienceanyofthesymptomslistedabove,seekmedicalattention.

How Can I Prevent Algal Blooms? Itisimportanttounderstandthatfreshwaterbodiesofwatergothroughanaturalagingprocess,which

includesperiodsofnutrientenrichmentcalledeutrophication.Naturalagingandeutrophicationoflakesgenerallytakeshundredsorthousandsofyears,butitmaybeenhancedbyhumanactivitiesontheland.Methodsofalgaecontrolorremoval(e.g.,drainingthepond,dredgingsedimentandscoopingalgalmats,chemicaltreatmentswithalumorherbicides)areoftenexpensiveandonlytreatthesymptomsoftheproblems,notthecause.Thebeststrategyforkeepingabodyofwaterclearofalgaebloomsistotreatthecauseoftheproblem:minimizingthenutrientinputsintoyourpond.Theprimarysourcesofnutrientrunofffromlandinclude:

Over‐applicationoffertilizer,manureand/orpoultrylitter. Leakingsepticsystems,drainfieldsandgraywaterdischarge. Animalwastefromlivestockormigratorybirds. Shorelineerosion.

Somebestmanagementpracticestoreducenutrientinputsandthepotentialforalgaebloomsinclude:

Usinggrass‐linedditchesorswalesbetweenfieldsandpondtoredirectnutrient‐richrunoff.Ifyourpondneedstobefedbythisrunoffinordertopersist,usesmallcheckdamsinthechanneltoslowdowntherunoffandencouragesettlingofsedimentsandabsorptionofnutrients.Checkbehindcheckdamsoftenandremovedepositsasneeded.

Ensuringthereisaborderofthickvegetationaroundthepondtointerceptandfilterrunoff.Amixofwarm‐andcool‐seasongrassesworksbetterthangroundcoverorsparsewoodyvegetation.

Keepingaminimummaintenancebufferaroundthepondof20feet.Reducemowingfrequencyanddonotusefertilizersinthisbufferarea.

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Plantingwetlandplantsalongtheperimeterofthepondtohelpfilterrunoffandstabilizepondbanks.Thiswillhelppreventerosionofbanksediments.Ifleftunmowed,wetlandplantswillusuallygrowupalongthepondperimeterovertimenaturally.Theseplantsarereferredtoasvolunteers.

Allowingvolunteerplantstocomein.These“emergents”willlikelyfillinshallowareasofupto18inchesdeepandwillsoakupnutrientsfromthepondwater.

Addingameansofaerationandcirculationtothepond.Addinganaeratororfountainwillhelpremoveexcessnitrogeninthewaterandimprovetheflowofwateraroundthepond.

Practicingwinterdrawdownanddrainingthepond,ifpossible.Thispracticewillhelpcyclethenutrientsaswellasfreezetherootsofnuisanceplants,suchascattails.

Skimmingthesurfacewithrakesornetsandremovingthebiomassfromthepond.Doingsowillpreventtheadditionalnutrientloadfromdecayingalgalbiomass.

Limitingthelightavailabilitytothepond.Thispracticecanbeaccomplishedbyplantingtreesortallshrubsaroundthepondorbycoveringwithopaqueplasticfabricforanextendedperiodoftime.

Deployingafloatingwetlandinthemiddleofthepondtohelpsoakupnutrients.Afloatingwetlandisafloatingapparatusthatisplantedwithwetlandplants.Thewetlandplantssendrootsdownintothepondwatercolumnandconstantlytakeupnutrientsdirectlyfromthewater.Floatingwetlandscanbemadeoffoammatsorwoodenpalletsfloatedwithbuoys.

Additional Resources Formoreinformationaboutharmfulalgalblooms,andtoseemoreimagestohelpwith

identification,pleaseseethefollowingwebsites:

NewYorkStateDepartmentofEnvironmentalConservation.“Blue‐GreenHarmfulAlgalBlooms”.www.dec.ny.gov/chemical/77118.html

OhioEPA.“HarmfulAlgalBlooms”.epa.ohio.gov/ddagw/HAB.aspx USEnvironmentalProtectionAgency.“CyanobacterialHarmfulAlgalBlooms”

www2.epa.gov/nutrient‐policy‐data/cyanohabs MichiganStateUniversityExtension."PondManagement:Anin‐depthresponsetofrequentlyasked

questionsfrompondownersandmanagers."articles.extension.org/sites/default/files/w/1/1d/Pond_Management_and_In‐depth_Response_to_FAQs_from_Pond_Owners_and_Managers.pdf

References (2013)ToxicAlgae:Comingsoontoalakenearyou?AJointReportbyResourceMediaandNationalWildlife

Federation

BackerLC,LandsbergJH,MillerM,KeelM,TaylorTK(2013)CanineCyanotoxinPoisoningsintheUnitedStates(1920s–2012):ReviewofSuspectedandConfirmedCasesfromThreeDataSources.Toxins5:1597‐1628

CarmichaelW(2008)Aworldoverview–onehundredtwentysevenyearsofresearchontoxiccyanobacteria,Wheredowegofromhere.In:K.H(ed)CyanobacterialHarmfulalgalblooms:Stateofthescienceandresearchneeds,p105‐125

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DowningB(2013)ToxicalgaestrikeOttawaCountywatersystem;threatprevalentacrossOhio.AkronBeacon

JournalOnlineGrosseY(2006)Carcinogenicityofnitrate,nitrite,andcyanobacterialpeptidetoxins.TheLancetOncology7:628‐629KVAL(2013)State:Don'tdrink‐ortouch‐thiswater.KVAL.comhttp://www.kval.com/news/local/wallowing‐or‐

inhaling‐water‐droplets‐as‐well‐as‐skin‐contact‐should‐be‐avoided‐214214351.html,Eugene,OR

ThispublicationwassupportedinpartbyNSFaward1451528.

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