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2030Statisticalanalysis
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(320/SET-1pH-meter)andconductivity(LF95withaTetra-Con96electrode)
weremeasuredevery100mofdepth0Watervisibilitywasmeasuredusing
aSecchidisc0Thefollowingsedimentpropertiesweretakenintoaccount:
pH,conductivity,redoxpotential,concentrationsofcalcium,nitrogen,phos-
phorusandhumicacids,organicandmineralmattercontentandhydration0
Waterandsedimentsamplesweretakenfromdepthzonesevery100mof
increasingdepth(3samplesfromeachzone)0Itwasassumedthatforevery
depthzone(representedby10–20plantsamples)environmentalconditions
areequal,sothattheywerecharacterisedbythemeanof3samplesofwater
and3samplesofsediment0
Watercolour,concentrationsofdissolvedinorganiccarbon(CO
2and
HCO
3
-),calcium,nitrogen,phosphorusandhumicacids,aswellasorganic
andmineralmattercontentinthesedimentweredeterminedaccordingto
Wetzel(2001)andEatonetal0(2005)0
2.3.Statisticalanalysis
Inordertocharacterisethevegetationofthestudiedlakesthebiomassofspe-
ciesinsampleswascompared,andthefrequencyofspeciesanddominance
indexinthesampleswerecalculated0Thefrequencyofspecies(F)intheplant
samplesasawholewascalculatedfromtheratiobetweenthenumberof
sampleswithagivenspeciesandthetotalnumberofcollectedsampleswith
submergedplants(n=10603)0Inaddition,thefrequencyofspecieswascom-
putedfordepthzonesastheratiobetweenthenumberofthespecies’occur-
rencesandthetotalnumberofsamplesinadepthzone0Speciesdominance
(DI)inthesamplewascalculatedaccordingtotheformula:DI
i=n
i/N•100%,
whereDI
i–dominanceindexofspeciesi,n
i–itsbiomassinthesample,N–
totalbiomassofspeciesinthesample(Kasprzak,Niedbała1981)0
Onlyspecieswithafrequencyvaluehigherthan5%inthetotalnumber
ofplantsampleswereconsideredwhencommunitiesweredifferentiated0
Intotal,only15plantspeciessatisfiedthiscondition0Inordertodetectthe
generalpatternofspeciesoccurrence,theCorrespondenceAnalysis(CA)was
conducted(inMVSP),andtakingintoaccountspeciesoccurrenceandbio-
mass,the15specieswereanalysedbyhierarchicalagglomerationclassifica-
tionbymeansofWard’smethodwiththeManhattandistance(STATISTICA8)0
Thismethodisdistinctfromallothermethodsbecauseitusesananalysisof
thevarianceapproachtoevaluatethedistancesbetweenclusters0Themeth-
odattemptstominimisethesumofsquaresofanytwoclustersthatcanbe
