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Theroleofnutrientsinecologicalclassificationoffreshwaters:reportofECOSTATworkshop,Tallinn,29-30May2018

Introduction

Intheory,theroleofnutrientsintheclassificationoffreshwatersinvolvesastraightforwardapplicationofthetextinAnnexVoftheWFDwhichdescribeshowsupportingelementsingeneral,andnutrientsinparticular,shoulddeterminefinalstatusclassifications.Thenormativedefinitionsofecologicalstatusclassification(WFDAnnexV,Tables1.2.1–1.2.5)usesidenticalwordstodescribenutrientconcentrationsthatareconsistentwithhigh,goodandmoderatestatusirrespectiveofwaterbodytype.Theseare:

Highstatus:“Nutrientconcentrationsremainwithintherangenormallyassociatedwithundisturbedconditions”

Goodstatus:“Nutrientconcentrationsdonotexceedthelevelsestablishedsoastoensurethefunctioningoftheecosystemandtheachievementofthevaluesspecified[inthenormativedefinitions]forthebiologicalqualityelements.”

Moderatestatus:“Conditionsconsistentwiththeachievementofthevaluesspecified[inthenormativedefinitions]forthebiologicalqualityelements.”

The“oneout,allout”ruleappliestosupportingelementsaswellastobiologicalqualityelements,soanutrientconcentrationthatcorrespondedwiththenormativedefinitionformoderatestatusshouldleadtotheoveralldesignationforthewaterbodyinquestionbeingmoderatestatus,eveniftheBQEswereallathighorgoodstatus.

Inpractice,however,itisclearthatapproachestotheuseofsupportingelementsingeneral,andnutrientsinparticular,variesconsiderablyaroundtheEuropeanUnion.Forthisreason,akeyactivityofECOSTATinrecentyearshasbeentounderstandhowMemberStatesuseallsupportingelementsfortheassessmentofecologicalstatus,butwithaparticularfocusontheroleofnutrients.ThisstartedoutbyunderstandinghowMemberStatesestablishedthenutrientconcentrationsrequiredtosupportecologicalstatusandthen,havingnotedconsiderablevariationinapproaches,workingtowardsanunderstandingof“bestpractice”.This,inturn,requiredrecognitionofanumberofchallenges(notleastofwhichareweakrelationshipsbetweenbiologicalqualityelementsandinorganicnutrientsforavarietyofreasons,andtheroleofotherstressors)andhasresultedinaCISguidancedocumentduetobepublishedlaterin2018.

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Therewas,however,recognitionearlyinthisprocessthattheprocessofsettingstandardsfornutrientconcentrationswastightlylinkedtoacountry’sregulatorymechanisms.Thisisparticularlytrueforinorganicnutrients,whereweakrelationshipsbetweenthepressurevariableandthebiologicalresponsecreateuncertaintybothfordecidingwhetherthereisagenuineimpactasaresultofelevatednutrients,andthatthereisahighlikelihoodofanimprovementifstepsaretakentoreducenutrientconcentrations.

Inbrief,ifaMemberState’spolicyistotakeactionassoonasaregulatorystandardisbreached,thenitmakessensetosetarelativelystrictnutrientboundaryinordertominimizethelikelihoodofa“falsepositive”.Ontheotherhand,ifaMemberStaterequiresbothbiologyandchemistrytofallbelowgoodstatusbeforetakingaction,thenastrictnutrientstandardwillincreasetheriskofa“falsenegative”and,instead,amorerelaxednutrientstandardmaybeappropriate(Theseissuesarediscussedinmoredetailinsection2.2oftheCISguidance).

Thisreport(basedondiscussionsheldattheECOSTATworkshopinTallinn)explorestheinteractionsbetweenscienceandregulationthatleadtofinalstatusclassifications.Thisinvolvesrecognizingboththatnutrientsareamajorreasonforfreshwatersnotachievinggoodstatus(and,therefore,compromisethelong-termsustainablewaterresource)andthatnutrientandbiologicaldataarehighlyvariable,whichmeansthatarrivingattherightdecisionforanyindividualwaterbodymaynotbestraightforward.

Theroleof“expertjudgment”

Thephrase“expertjudgment”occurredseveraltimesduringdiscussionsattheworkshop,andaninitialconsiderationofwhatismeantbythisterm,andhowitappliestotheclassificationofwaterbodiesisnecessarybeforeproceeding.

Therearefourreferencestotheuseof“expertjudgment”inthetextoftheWFD(AnnexII,1.3,AnnexV,1.3.4(twice)andAnnexV,1.4.1)althoughthefirstandlastinstances(selectionofreferenceandintercalibrationsites)havebothbeensupersededbymorerecentCISguidelines.Theothertworeferencesto“expertjudgment”refertosamplingfrequenciesforsurveillanceandoperationalmonitoring,andgiveMemberStatesscopetovary(withinlimits)theintensityatwhichdifferentqualityelementsareevaluated.Thisbriefanalysisindicatesthat,whilstthereareprecedentsfortheuseof“expertjudgment”intheimplementationoftheWFD,therearealsosituationswhereexperiencegainedthroughimplementationmeansthat“expertjudgment”canbereplacedbymorerigorous,evidence-basedprocedures.Thecaseofreferenceconditionsisuseful,inthepresentcontext,because,here,expertjudgmentisallowedonlywhereotherapproaches(spatiallybasedorbasedonmodelingoracombination)arenotpossible(AnnexII,1.3paragraph3).Expertjudgementisnot,strictlyspeaking,analternative;ratheralastresortinsituationswherestrongevidenceisnotavailable.

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Thepresentdiscussionsdivideintotwobroadscenarios:

First,datafromalargenumberofspecificcases(i.e.individuallakesorrivers)wasusedtoinferageneralsituation(i.e.nutrientconcentrationsconsistentwithgoodstatus);

Second,thisgeneralsituationwasthenusedtopredictthenutrientstatusforindividuallakesandriverswhich,inturn,contributedtotheirfinalstatusassessment.

Inbothcases,thereshouldbeadirectpathwayfromtheevidencetotheoutcome.Inpractice,unaccountedvariation(partstochastic,partunmeasured)meansthatthereisrarelyanunambiguousoutcome,butratherarangeofprobabilities,recognizingthatthesamebiologicalstatecanoccuratseveralnutrientconcentrations.Theboundaryconcentrationissetfromamongstthesepossiblevaluesbased,partly,onanunderstandingofhowtheinformationwillbeusedintheregulatoryprocess(seech.7inCISGuidance).

Newcasesarethenevaluatedagainstthisboundarybut,again,variabilityinbothbiologicalandnutrientdatameansthataface-valueinterpretationmaybemisleading,especiallywheneitherthebiologicalorchemicalmeasurementsareclosetotheboundary.Inthissituation,adecisionmaynecessitatelookingbeyondthenarrowevidencebaseusedforformalassessments.

Bothsituationsrepresentthelegitimateuseof“expertjudgment”,recognizingthatitisnotpossibletocaptureallaspectsoftheinteractionsbetweennutrientsandbiologywithinthelimitedmeasurementsthatarepossiblewithinnationwidemonitoringnetworks.

Themeetingrecognizedthatexpertjudgmentcanplayanimportantrole,particularlywhenmakingdecisionsaboutindividualwaterbodieswheretherewaslowconfidenceinoutcomesfromformalqualityelements(i.e.ifanEQRwasclosetoastatusclassboundary)orifqualityelementsgaveconflictingresults.ThisexpertjudgmentmaytaketheformofadeeperunderstandingoftheecologyofparticularorganismsorcommunitiesthaniscapturedbytheBQEsorlocalknowledge.However,itisimportantthatthecriteriaonwhichsuchjudgmentsarebasedareclearandtheevidencerelevanttoeachcaseisdocumented.

Keyrecommendations:expertjudgment

• Genuinelyinformedexpertopinionisavaluableadjuncttoformalclassificationdata(BQEs,supportingelements)insomesituations.

• Useofexpertjudgmentneedstobeacknowledgedanddocumented.

• Thecriteriaonwhichjudgmentsarebasedneedtobeclear

• Mostappropriatewhenappliedatthelevelofindividualwaterbodies.

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Settingnutrientcriteria

ThenewCISGuidancedocumentandtoolkitaddresseshowtodevelopnutrientboundariesinlinewiththenormativedefinitions.TheunderlyingassumptionisthataMemberStatehasatleastoneBQEwithastatisticallysignificant(presumedtobecausal)relationshipwithinorganicnutrients.ThisshouldallowMemberStatestocheckexistingboundariesanddevelopnewboundarieswhereappropriate;however,problemswillremainwhenthereisno(oronlyaweak)relationshipbetweentheBQEandnutrients,andwherenutrientsareinteractingwithotherpressures.

ChallengesarisewhenaMemberStatehasonlyasmallnumberofsiteswithinaparticulartype,orwherethenutrientgradientisshort.SomesolutionsaresuggestedintheCISGuidance,allattemptingtoproducelargerdatasetswith,hopefully,strongerrelationshipswithpressure.Thismayentailmergingtypeswithinacountryorlookingbeyondnationalborderstoobtaindatafromsimilarwaterbodieselsewhere.DatasetsdevelopedfortheintercalibrationexerciseofferasignificantopportunityforMemberStatestoshareinformation.Thesehavesummarydata(intercalibrationcommonmetrics,chemistry)aggregatedtointercalibrationtypesthatcouldbeutilizedbyMemberStateswhosenationaldatasetsmaynotyieldsufficientlystrongrelationshipsintheirownright.Theguidelinesforfittingnewormodifiedmethodstoexistingintercalibrationexercises(CISGuidance#30)willalsoenablebetween-countrydifferencestobeminimized(e.g.throughuseoflinearfixed-effectmodels).

AnalternativetoaMemberState“borrowing”datafromneighbourswithsimilarwaterbodytypesistodevelopgenericnutrientboundariesthatareapplicableacrossthesamebroadtypeinseveralMemberStates.ThishasbeenattemptedaspartofECOSTAT’snutrientactivities(seePhillipsetal.,2016)but,atpresent,boundariesareonlyavailableforafewbroadtypes.Oncethesecondroundofreportingiscomplete,thereshouldbemoredataavailablefromwhichsuchrelationshipscanbederived,allowingthenumberofbroadtypesforwhichboundariesareavailabletobeexpanded.

Broadtypeboundariesneedtobetreatedwithcaution,asEQRshavetobe“translated”fromnationalmetrictointercalibrationcommonmetric(ICM)scalesandtheremayalsobedifferencesinthesampling,analysisandstatisticalaggregationofchemicalvariablesbetweenMemberStates.Nonetheless,theseofferamajoropportunitytosupportMemberStatesintheireffortstodevelopeffectivenutrientclassificationcriteria.Expertjudgmentshouldbealastresortwhensettingnutrientboundaries

Keyrecommendations:nutrientcriteria

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• EncourageuseofBPGforMemberStatestocheckanddeveloptheirownnutrientcriteria

• ProvidealibraryofICdatasetsthatMemberStatescanusetosupplementnationaldatawhendevelopingnutrientcriteria

• EncouragesharingdatabetweenneighbouringMemberStatestoenablestrongerrelationshipstobeestablished.

• Extendthecurrentrangeofnutrientboundariestocoverallbroadtype

Usingnutrientcriteriainclassification

Classificationincontext

Classificationisanadministrativesteponalongerjourneytowardsattaininggoodecologicalstatusand,thereby,securingasustainablewaterresourceforEurope.TheWFDandCISGuidancesetoutgeneralrulesforclassificationyetthereisalsoscopeforMemberStatestointerprettheserulesinamannerappropriatetotheirterritory.WhilstMemberStatesneedtoprovideasoundframeworkaroundwhichprogrammesofmeasurescanbeprioritizedanddesigned,theEUasawholeneedsconsistencyininterpretationoftheWFDtoenabletheEUtobettertrackprogressinWFDdeliveryandidentification.ThereisapotentialtensionbetweentheserightsandresponsibilitiesofMemberStatesandtheneedsoftheEuropeanCommission.

TherealsoappearstobeanissuewithimplementationofnutrientcriteriawithinMemberStates.Whilstallhaveproceduresforusingnutrientsintheirclassificationprocedures,thereisashortfallinthedatasubmittedtotheEEA,withdatamissingfor16%oflakes(byarea)and36%ofrivers(bylength).Whetherthisrepresentsanabsenceofdataorjustafailureincommunicationisnotclear.Theproportionofwaterbodieswith“unknown”statusfornutrientsvariesbetweenMemberStatesbutacomparisonofthenumberofwaterbodiesforwhichdataavailable,andthetotalareathattheserepresents,suggeststhat,ingeneral,smallerwaterbodiesarelesslikelytobemonitoredandreportedthanlargerones.

Afurtherissuewhencomparingclassificationresultsisthat,whilstBQEshave(largely)beenharmonizedasaresultoftheintercalibrationexercise,thereisnosuchconsistencyinsupportingelements.Differencesencompasschoiceofdeterminand(i.e.solubleversustotalnutrients),analyticalmethodsandsamplingfrequencyaswellasboundary-settingprocedures.Whilstthelatterisaddressedviathe“bestpracticeguide”andtoolkit,MemberStatesarenotboundtocomplytoanystandardapproach.Thereare,moreover,both

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differencesandambiguityintherulesusedwhencombiningdatafromBQEsandsupportingelementstodetermineafinalclassification,aswellasalackofclarityinhowresultsareextrapolatedtocoverwaterbodiesthathavenotbeenmonitored.Atthesametime,itisclearthatclassificationmethodsareevolvingwithinMemberStatesinthelightofexperience,whichraisesfurtherchallengesofensuringcomparabilitybetweenresultsovertime(and,particularly,betweenRBMP)inordertobeabletotrackprogresstowardsWFDobjectives.

Classificationoutcomesmustbothprovideasoundframeworkaroundwhichprogrammesofmeasurescanbeprioritizedanddesigned

ConsistencyininterpretationofWFDwillenableEUtobettertrackprogressinWFDdeliveryandidentificationofbestpracticewillhelpMSachieveWFDgoals

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Fig.1.Useofsupportingelementsinwaterbodyclassificationforlakes(top)andrivers

(bottom)in2ndRBMP.DatafromtheWISEFreshwatervisualizationtoolsummarizedby

area(lakes)orlength(rivers)forallMS(exceptGR,IE,LV)[finalversionswillberedrawn

andfocussolelyonnutrients]

Classificationinpractice

ECOSTATrepresentativeswerepresentedwiththreescenariosandaskedhowtheircountrywouldclassifyawaterbodyineachcase.Thescenariosandresponseswere:

• Biologyis“good”butnutrientsare“lessthangood”o Presentedwiththisscenario,mostMemberStatesclassifiedthewaterbody

as“lessthangood”status,withjustthree(AT,DE(freshwater),SK)allowingthehigh/goodbiologytooverrideevidenceofnutrientenrichment(Fig.2).

• biologyis“lessthangood”butnutrientsare“good”o TherewasgreaterunanimityamongstMemberStatesandbetweenwater

bodytypesforthisquestion,withallagreeingthatthissituationshouldresultina“lessthangood”finalclassification.

• bothbiologyandnutrientsare“lessthangood”o Asforthepreviousquestion,allMemberStateswouldclassifyawaterbody

withthesecharacteristicsaslessthangoodstatus.

ThefullresultsofthissurveyarepresentedinAppendix1.

Fig.2.MemberStateapproachestoclassificationofawaterbodywhenbiologyisathigh

orgoodstatuswhilstnutrientsarelessthangood.

SeveralMemberStatesaddedcaveatstotheiranswerswhichsuggestedareluctancetoactunlesstheywereconfidentintheface-valueclassificationgivenbyeithertheBQEor

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supportingelement.Theirimmediateresponse,insuchcircumstances,wastotrytoraisetheconfidenceintheclassificationandthenextsectionswilldescribethewaysthatthisisattempted.However,therealsoappearstobedifferencesinthewayconfidenceinteractswithclassificationresults.Insomecountries,lowconfidenceinaBQEorsupportingelementmeansthat“oneoutallout”isoverriddensothatawaterbodymaybereportedtobeat“goodstatus”despitetheface-valueclassificationofoneormoreelementsbeingatmoderatestatus.Inothercountries,thefacevalueclassificationwillbereportedirrespectiveoftheconfidenceinthatclassification,butmeasuresappliedtothatwaterbodymaybelimitedifconfidenceislow.IncreasingconfidenceintheclassificationwascitedbysomeMemberStatesasanappropriatefirst“measure”incaseswhereBQEsandsupportingelementsgaveconflictingresults.

Increasingconfidenceinclassifications

Statisticalaspects

Theissueofconfidencearisesbecausetermssuchas“goodstatus”and“moderatestatus”arecategoricalexpressionsofprobabilitydistributionsderivedfromcontinuousdata(EQRs,nutrientconcentrations).AmeanEQRornutrientconcentrationrepresentsthepointofmaximumprobabilitybutthetailsoftheprobabilitydistributionmayextendintoneighbouringstatusclasses.Asprogrammesofmeasuresinevitablyplacefinancialburdensonbothregulatorsandstakeholders,itisreasonabletorequireahighlevelofconfidenceinaclassification,andparticularlyinthelinkbetweenecologicalstatusandpressures,beforeactionistaken.

Confidenceinaclassificationdevolvesintotwocomponents:proximitytoaboundaryandthereliabilityofthesamplemeanasanestimateofthe“true”(i.e.population)mean.Fig.3representshypotheticaldistributionswithidenticalmeans(0.56,assumedtoindicate“moderatestatus”)butdifferentstandarderrors.Theproximityofthemeanleadstopartofbothdistributionsextendingintotheadjacentstatusclass.Forthewiderofthese,thereisa33%chancethatthe“true”meanisingoodstatus(aswellas0.7%chancethatitis“poorstatus”).Bycontrast,thechanceofthe“true”meanoccurringingoodstatusdropsto19%inthecaseofthenarrowerdistribution.Asstandarderrorisafunctionofsamplesize,astraightforwardoption,whenpresentedwithasituationsuchasthisis,therefore,toincreasethequantityofdatauponwhichthestatuspredictionisbased.

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Fig.3.ConfidencedensityofEQRvaluesforahypotheticalBQEassumingmean=0.56.

Curvesshowshapeofdistributionwhenthestandarderrorislarge(blue)andsmall

(green).Theverticalredlineindicatesthepositionofthegood/moderateboundary.

However,thoughtheriskofmisclassificationdropswithincreasingsamplesize,theproximityofthe“true”meantothegood/moderateboundaryinthiscasemeansthatitisunlikelytobeeliminatedentirely.Therefore,asecondoptionistolookatfurthereutrophicationindicatorstoseeifthese,too,indicateaproblem(Fig.4).Inthisexample,thecombinedlikelihoodofthetrueconditionofthewaterbodybeingatlessthangoodstatusdropsto16%.

RedrawFig.3has0.52not0.56–as1OAomeansthatFig.4isdifficulttointerpret.

BothstrategiesareusedbyMemberStatesinsituationswheretherearemismatchesbetweenstatusderivedfromBQEsandsupportingelementsandbothareclearlysensiblestrategiestoensuringconfidenceboththatawaterbodyislessthangoodstatusandthatnutrientsarethecause.However,whilstsomeMemberStatesseemtoapplytheserulestotheclassificationitself(i.e.requiring>1BQEto“fail”beforeawaterbodyisdowngraded),othersallow“oneoutallout”todeterminetheclassificationbutthenapplyrulessubsequentlytoensureconfidencebeforemeasuresareimplemented(effectively,raisingconfidenceistreatedasadefacto“measure”ininstanceswherethereareambiguousclassificationresults)

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Fig.4.ConfidencedensityofEQRvaluesfortwohypotheticalBQEswithmean=0.56

(solidline)and0.52(dashedline).Theverticalredlineindicatesthepositionofthe

good/moderateboundary.

Keyrecommendations:increasingconfidenceinclassifications

• Instanceswhere“oneout,allout”isoverriddenshouldbedocumented.

• HarmonisedapproachestoclassificationinsituationswhenthereislowconfidenceinBQEsand/ornutrientcriteriawouldbehelpful.

• Agreementisneededonwhetherstepstoraiseconfidenceshouldaffectclassificationresultsorrepresenta“measure”isneeded

• MemberStatesneedflexibilitywhenapplyingclassificationrulesbutsharedexperiencesshouldallow“bestpractice”tobedisseminated.

Overall,itwasclearthatitismorecommonforMemberStatestooverride1OAOtoupgradeawaterbody(e.g.moveittogoodstatuswhenoneBQEorsupportingelementindicatesmoderatestatus)thantheopposite.MemberStatesregardedsuchupgradesasalegitimateresponsetosituationswheretherewasalowconfidenceinaclassification(e.g.whenthefailingBQEwasnaturallyvariable).Theoppositecase(i.e.whenawaterbodyisclassifiedasmoderatestatusdespiteallBQEsandsupportingelementsbeingatgoodstatus)wasregardedasappropriateinsituationswheretherewereknowntobepressurestowhichintercalibratedBQEswerenotsensitive.

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Strengtheningtheevidence:BQEs

Theprevioussectionoutlinedtwobroadstrategiesadoptedincaseswhere1oAodictatedafailuretoachievegoodstatusbutwithlowconfidence:increasingthequantityofdatafortheBQEorsupportingelementconcernedortocollectabroaderrangeofBQEsandnon-biologicalevidence.

WhilstmonitoringthefullrangeofBQEsismandatoryforsurveillancemonitoring,MemberStateshavemoreflexibilitywhendesigningsamplingstrategiesforoperationalmonitoring.Inthecaseofasmall,homogeneouswaterbodywithasinglepressure,theuseofasingleBQEmightbedeemedtobearationaluseofalimitedbudget.However,eveniftheBQEmostsensitivetothepressureinquestionisadopted,therewillstillbealikelihoodofmismatchesbetweenBQEandsupportingelementclassifications,particularlyforsitesthatareclosetostatusclassboundaries.

Thismeansthat,exceptforafewcaseswhereimpactsareveryclear,monitoringmorethanoneBQEperwaterbodyprovidesaninsuranceagainstthescenariosoutlinedintheprevioussection.Ideally,theseBQEsshouldprovidecomplementaryecologicalinsightsintotheprincipalstressorgradient(presumedtobenutrients,inthiscase).WhilstKellyetal.(2016)suggestedadiminishingmarginalutilityfromemployingadditionalBQEsfortheassessmentoflakes(Fig.5),thisfocusedonbroad-scalesurveillancemonitoring,andthesituationwillbedifferentifthefocuswassolelyonlakesthatwereclosetokeyboundaries.Ontheotherhand,theincreaseinoverallstatisticalconfidenceasmoreBQEswereemployedmayberelativelymodest(##to##intheexampleinFig.#)andwilldependonboththerelativesensitivityofeachBQEandthestrengthofeachoftheirrelationshipstothepressuregradient.

Afinalcomplication,addressedlaterinthisreport,isthatBQEsmayberespondingtomorethanonepressure.Whilstthismaynotaffecttheoverallevaluationofstatus,itisaseriouscomplicationwhentryingtodemonstratethecausalrelationshipswithpressuresuponwhichprogrammesofmeasurescanbeplanned.

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Fig.5.DiminishingmarginalutilityofemployingextraBQEsinlakeassessment:

simulationsassuminga1:1relationshipbetweeneachslopeandeachmetrichaving

identicalresponsetostresses(fromKellyetal.,2016).

Strengtheningtheevidence:supportingelements

Similarargumentsapplytosupportingelements:intheory,asingleexceedanceofasupportingelementstandardshouldleadtothestatusofawaterbodybeingdowngraded.Inpractice,however,MemberStatesadoptavarietyofapproaches.

Inthesimplestcases,classificationsarebasedonasinglenutrientparameterperwaterbodytype,basedonanaprioriassumptionaboutthelimitingnutrient.Thisiscombinedwithotherphysico-chemicalparametersfollowingthe“oneout,allout”rule.

Inmanycases,however,severalnutrientparametersareassessed,representingbothnitrogenandphosphorusfractions.Thesemaybeeachtreatedasindependentcomponentsofasuiteofphysico-chemicalelementswhicharethenevaluatedfollowingthe“oneout,allout”rule(e.g.Romanianfreshwaters),orareaggregatedintoasingle“nutrient”elementwhichisthencomparedwithotheraggregationstodeterminethefinalphysico-chemicalstatus.

InFrance,forexample,fiveseparatenutrientparametersaremeasuredinrivers(“PO4”,TP,“NH4”,“NO2”,“NO3”).Insuchcases,theprincipleofthedowngradingparameterisapplied(i.e.theworstofthesedeterminesstatus.However,inordertoreduceclassificationerrorswhenvaluesareneartheboundarybetween“high”and“good”statusorbetween“good”and“moderate”status,thefollowingrulesareadopted:

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Ageneralphysico-chemicalqualityelementforwhichseveralparametersareinvolved,canbeclassifiedasHighif:

• AllBQEandtheothergeneralphysico-chemicalelementsclassifythewaterbodyasHighstatus;

• Onlyoneparameterisdowngradedto“Good”forthequalityelementinquestion.

Similarly,forGoodstatus:

Ageneralphysico-chemicalqualityelementforwhichseveralparametersareinvolved,canbeclassifiedasGoodifthefollowingconditionsaremet:

• AllBQEandtheothergeneralphysico-chemicalelementsareclassifiedasGood.

• Onlyoneparameterisdowngradedto“moderate”forthisqualityelement

Thisisnotvalidfornitratesinrivers:ifthe“nitrates”parameterisclassifiedlessthan"good"(concentration>50mg/l)thenthenutrientqualityelementisclassifiedasmoderate.

DenmarkusesnutrientdataonlyinlakeswhenoneormoreoftheBQEs(phytoplankton,macrophytesorfish)aremissing.IfthisisthecaseandtheoneortwomeasuredbiologicalelementsareinGES,butbothphosphorousandnitrogenexceedstheboundaries,thelakeisclassifiedasmoderatestatus.Demarkhasnotyetdevelopednutrientstandardsforrivers,butanewprojectisunderdevelopmentthat,basedonnutrienttoolkit,willtrytodevelopnutrients(andtheotherphysical-chemicalQEsaswell)inwatercourses.

Dissolvedoxygenisaparameterthatshould,intheory,providevaluablesupportingevidencewheneutrophicationissuspected.Inlakes,especially,hypolimneticdeoxygenationisasignificantconsequenceofeutrophication,butitcanbedifficulttogetmeasurementsthatarerobustenoughtoinfluenceclassifications.TherewaslittleevidenceinthequestionnairereturnsofMemberStatesusingthisroutinely,althoughGreecehaveanoptionforusing“expertjudgement”toincorporatehypolimneticoxygenintoclassifications.

Dissolvedoxygeninriversisprincipallyusedasanindicatoroforganicloading,ratherthanofconsequencesofinorganicnutrientsandoxygentargetsarebasedprimarilyonthetoleranceoffish.Nonetheless,recordsoffishkillsassociatedwithnighttimeanoxiaisaclear“undesirabledisturbance”resultingfromelevatednutrientconcentrationsandUKincorporatestheseaspartoftheirwider“weightofevidence”approachtoevaluatingeutrophicationimpactsinrivers.

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Conclusions

CISGuidance##addressedtheissuesassociatedwithsettingobjectivenutrientboundariesthatwouldhelpMemberStatestoachievegoodstatusintheirwaterbodies.Thisdemonstratedthat,inmostsituations,therewasconsiderablevariationintherelationshipbetweenBQEsandnutrients.TheGuidanceaddressedthequestionofhowtoselectappropriateboundaryvaluesinlightofthisuncertainty.However,whilsttherateofclassificationmismatchescouldbereducedbyfollowingthesemethods,itcouldneverbeeliminatedentirely.ThesemismatchescontributetoareductionintheoverallconfidenceofawaterbodyclassificationunlessMemberStatestakestepsoverandabovethoseprescribedintheWFDitself.Thesestepscantakeoneofthreeforms:

• MoredatafortheBQEand/orsupportingelement(s)–intheory,reducingthestandarderrorandresultinginamoreaccuratepredictionofthetruestatus;

• DatafromadditionalBQEsand/orsupportingelements–inordertoobtainamoreholisticpictureofthestatusofthewaterbody;or,

• AdditionalsourcesofevidencetothatprovidedbyBQEsandsupportingelements(e.g.hypolimneticdeoxygenation,fishkills).

TheuncertaintiesinherentinestablishingsupportingelementstandardsmeanthatMemberStatesmusthavetheflexibilitytouseadditionalinformation(and,inparticular,localknowledge)toqualifyfacevalueclassificationresults.Therewasbroadagreementthatresponsibleuseofexpertjudgementisappropriateinsuchcircumstances,solongasthisiswell-documentedandtransparent.

Therewas,however,lessagreementonwhetherthisadditionalinformationshouldbeusedtooverridetheclassificationbasedonastraightforward“1oAo”orwhetheritshouldbeusedtoinformdiscussionsaboutappropriatemeasurestobeappliedinacatchment.IfseenasastepinalongerjourneytowardsachievementofWFDobjectivesthenwhetherornotclassificationitselfisaffectedmaybeoflittlerelevance.However,variationsinnationalapproachescouldhavesignificantimpactsonthecomparabilityofdatasubmittedtotheEuropeanCommissionaspartofRBMPreportingrequirements.

References

Borja,A.&Rodríguez,J.G.(2010).Problemsassociatedwiththe‘one-out,all-out’principle,whenusingmultipleecosystemcomponentsinassessingtheecologicalstatusofmarinewaters.MarinePollutionBulletin60:1143-1146.

Moe,S.J.,LycheSolheim,A.,Soszka,H.,Gołub,M.,Hutorowicz,A.,Kolada,A.,Picinska-Fałtynowicz,J.&Białokoz,W.(2015).Integratedassessmentofecologicalstatusand

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misclassificationoflakes:Theroleofuncertaintyandindexcombinationrules.EcologicalIndicators48:605-615.

Prato,S.,LaValle,P.,DeLuca,E.,Lattanzi,L.,Migliore,G.,Morgana,J.G.,Munari,C.,Nicoletti,L.,Izzo,G.&Mistri,M.(2014).The‘‘one-out,all-out’’principleentailstheriskofimposingunnecessaryrestorationcosts:AstudycaseintwoMediterraneancoastallakes.MarinePollutionBulletin80:30-40.

Appendix:useofsupportingelementsinclassification–questionnaireresults

ECOSTATrepresentativeswerepresentedwiththreescenariosandaskedhowtheircountrywouldclassifyawaterbodyineachcase.Thescenarioswere:

Biologyis“good”butnutrientsare“lessthangood”biologyis“lessthangood”butnutrientsare“good”bothbiologyandnutrientsare“lessthangood”

Q1:Whatisthefinalstatusifbiologyis“good”butnutrients“lessthangood”?

19MemberStateshaveaunifiedapproachacrossbothfreshwaterandtransitional/coastalwaters(orarelandlocked)andafurtherfourdidnotspecifywhethertheirapproachappliedtoallwaterbodytypes.GermanyandItalyhavedifferentapproachestoclassificationinfreshwaterandtransitionalandcoastalwatersandtheremainingcountriesdidnotprovideinformationforallwaterbodytypes.

Presentedwiththisscenario,mostMemberStatesclassifiedthewaterbodyas“lessthangood”status,withjustthree(AT,DE(freshwater),SK)allowingthehigh/goodbiologytooverrideevidenceofnutrientenrichment(Fig.3).

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Fig.3.Classificationofawaterbodywhenbiologyisathighorgoodstatuswhilstnutrientsarelessthangood.

Nineresponses,however,offeredmorenuancedinterpretationsofthesituation.Thesearesummarizedbelow:

DK(lakes):NoactiononlyifallBQEsaregood

FI:StatuswouldbegoodiftherearespatialandtemporalreplicatesoftheBQEsandthereislessreplicationofnutrients.However,statuswouldbemoderateiftherewerelessdataforBQEsbutmorefornutrients.

FR:Forrivers,statuswouldbemoderateifthiswasindicatedbytwophysico-chemicalparametersorifthenitratethreshold(50mgL-1)wasexceeded.Ifasinglephysico-chemicalparameter(otherthannitrate)wasinmoderatestatus,thenstatuswouldbegood.Forlakes,coastalandtransitionalwaters,statuswouldbemoderateifindicatedbytwophysico-chemicalparametersorifoneparameterindicatedthatthestatuswasbelowmoderate.Again,ifasinglephysic-chemicalparameterindicatedmoderatestatus,thenthefinalstatuswouldbegood.

IE:Forrivers,twonutrientstandardsmustfailwithconfidencebeforethewaterbodyisclassifiedasmoderatestatus;forlakes,ifanynutrientstandard/parameterfails,thelakeisclassifiedatmoderatestatus;forcoastalandtransitionalwaters,ifanutrientstandardfailstheTraCwaterbodyisclassifiedatmoderatestatus.

IT(coastalandtransitionalwaters):TRIXcombinesO2,nutrientsandchlorophyll.

LT:StatusislessthangoodifBQEsarehighandgoodbutoneormorephysico-chemicalparametersaremoderate.Inthiscase,theconfidenceofclassificationwouldbelow.

0

4

8

12

16

20

high/good lessthangood other

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NO:StatuswouldbelessthangoodifBQEsindicatedgoodstatusbutgoodifBQEsindicatedhighstatus.

PL:Statuswouldbemoderate;however,ifonlyonephysico-chemicalparameterwasslightlybelowthemoderatestatusthresholditwouldbeignoredandstatuswouldbereportedasgood.

SI:Statuswouldbemoderate;however,iftherewaslimitednutrientdata,thewaterbodywouldbeclassifiedasgoodstatusandmonitoringfrequencywouldbeincreased.

Theseresponsesallfollowtheprincipleofclassifyingthewaterbodyaccordingtothelowestofbiologicalandphysico-chemicalcriteriabutoffervariousclausesthatincreaseconfidenceinthefinaloutcome.

Q2:Whatisthefinalstatusifbiologyis“lessthangood”butnutrientsare“good”?

TherewasgreaterunanimityamongstMemberStatesandbetweenwaterbodytypesforthisquestion,withalmostallagreeingthatthissituationshouldresultina“lessthangood”finalclassification(Fig.4).

Fig.4.Classificationofawaterbodywhenbiologyislessthangoodwhilstnutrientsareathighorgoodstatus.

Severalcountriesmadecommentsthatqualifiedtheirinterpretationofthisapproachandthesearelistedbelow.

BG:Ifthedifferenceispermanentitinitiatesinvestigativemonitoringand/orvalidationoftheclassificationsystem.

DE(coastalandtransitionalwaters):Thissituationhasneveroccurredasnutrientstandardsarestrict.

0

5

10

15

20

25

30

high/good lessthangood other

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DK:InthepresentRBMPnutrientsareusedonlyfortheclassificationoflakes.

EE:Iftheaveragestatusbasedonnutrientsis“good”butTNorTPismoderate,thisistakenintoaccountatthepermittingstage.

NL:Inthissituation,measureswouldbeplannedtorestorebiology,andthesemayincludeadditionalmeasurestoreducenutrientsifnecessary

PL:IfoneBQEsdifferssignificantly(atleasttwoclasses)andtherearedoubts,itcanbediscarded

Q3.Whatisthefinalstatusifbothbiologyandnutrientsare“lessthangood”

AllMemberStateswouldclassifyawaterbodywiththesecharacteristicsaslessthangoodstatus.

Inwhichsituationsaremanagementactionstakenandhowdothesedifferinthefollowingsituations?

ThenextquestionattemptedtolinkclassificationstotheactionstakenbyMemberStateswhenfacedwithcombinationsofBQEandsupportingelementfailures.Therewasaconsensusontheneedtoinitiatemanagementactionswhenbothbiologyandnutrientsindicatedconditionswerelessthangoodstatus.However,theprocedurefordealingwithmoreambiguousoutcomesvaried.Manycountriesrecognizetheinherentuncertaintiesinbothbiologicalandchemicaldataasareasonforfurthermonitoringwhenjustonecomponentindicatedfailure.Thesituationoffailingbiologyassociatedwithnutrientsthatshouldsupporthighorgoodstatusledtosuggestionsofinvestigatingotherpotentialpressures.

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Table1.Managementactivitiesassociatedwithdifferentoutcomesfrombiologicalandnutrientclassifications.

managementaction notes

BQE <good high/good <good

nutrients high/good <good <good

AT yes note yes moremonitoringdataneeded

BE-F yes yes yes

BE-W yes yes yes sometimesforHMWBtoo

BG note note yes investigatemonitoringbeforemeasures

CY yes yes yesMeasurestakenbasedonsignificantpressures,irrespectiveoffailedBQE

DE(freshwater)

note yes yes measuresforotherpressuresconsidered

DE(marine) note note yes thefirstcasehasoccurredjustoncewhilstthesecondisveryrare

DK yes note yes(lakesonly)NoactionistakenifallBQEs(phytoplankton,macrophytes,fish)aregood;actionisalsotaken(unlessexceptionsareused)iffewerBQEsareused,inconjunctionwithoperationalmonitoring.

EE note yes yes closerinvestigationrequiredifreasonforBQEfailureisnotclear.

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managementaction notes

BQE <good high/good <good

nutrients high/good <good <good

ES note yes yes Researchisinitiatedifcausesoffailurearenotclear.

FI note yes yes casespecific:dependsonqualityofdata

FR note yes yes Finaldecisionconsidersbothecologicalstatusandnutrients

GR(freshwater)

yes yes yes

HR yes yes yes

HU note yes yes

Furthermonitoringandcloserinvestigationrequired.

Note,too,thatnutrientsarenotusedtoclassifysodiclakes;BQEsandconductivityareusedtoderivestatusforthese.

IE(freshwater) yes yes yesThereisalsoanoptionformanagementactionwhenbothareathigh/goodstatus,iftrendsinthedatapredictafailureinthefuture

IT(freshwater) yes yes yes

LT note yes yes investigativemonitoringtoidentifycauses

LU Yes yes yes

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managementaction notes

BQE <good high/good <good

nutrients high/good <good <good

LV Yes yes yes

NO Yes yes yes

PL Yes yes yes

PT Note yes yes measuresfocusonappropriatepressures(e.g.hymooralienspecies)

RO Yes yes yes

SE Note no yesAgeneralrecommendationof10%nutrientreductionappliesifBQEsare<good

SI note(1) note(2) yes1)AdetailedanalysisofpressuresandimpactsisinitiatedincasesofBQEfailure;2)monitoringfrequencyisincreasedincasesoflowconfidence.

SK Yes note yes tofulfilrequirementsofUWWTDandNitratesDirective

UK note(1) note(2) yes1)Overall“weightofevidence”takenintoaccount(assessmentofclassificationandconfidence);2)Actiontakenwillberisk-based;low-risklow-costactionsmostlikely

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