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4.1.TN/TPratio
CalculationofTN/TPratioisoneofthemethodsfordeterminingthelimiting
nutrient.IftheTN/TPratioislessthan7-nitrogenisthelimitingnutrienttophyto-
planktongrowth,between7and14-both,nitrogenandphosphorusarethelimiting
factors,andgreaterthan14-phosphorusisthelimitingfactor.ThesummerTN/TP
ratioinSouthBalticSeashorelakes(Tab.3.)washigherormuchhigherthanthe
criticalratio(e.a.TN/TP<7),anddidnotindicatethenitrogenlimitation.Onlyinthe
caseof6measuredlakes(Łebsko,Jamno,LiwiaŁuża,OstrowoandWickoMałe)the
TN/TPratioindicatesnitrogenandphosphoruslimitation.Additionally,TN/TPratio
wasgenerallylowerineutrophicandhypereutrophiclakesandhigherinmeso-and
meso-oligotrophiclakes(Fig.3.).AsimilarrelationshipwasobservedbyGalvez-Clo-
utierandSanchez(2007),whoanalyzedthetrophicconditionof154lakesinQuebec.
Thehypereutrophicoreutrophicconditionsoflakesincreasestheprobabilityofni-
trogenlimitation.Highphosphorusloadingcausesthatplanktonicnitrogenutiliza-
tioncanexcedinpusanddepletenitrogensuppliesinthetrophogeniczone[46].
Fig.3.TN/TPratioandmeanTSI’svaluerelationinSouthBalticSeashorelakes
Source:ownresearch.
4o2oTrophicconditionanddeviationinTSI’s
ThelakesofSouthBalticSeashorearemostlyeutrophicorhypertrophic.Only
twoof24measuredlakeswereoligo-mesoandmesotrophic.Trophicconditionof
lakeswasgenerallydependedonbothcatchmentareausageandmorphological
parametersoflakes.Highertrophylevelwasinlakesofagriculturalcatchmentarea.
Moreover,themeanTSI’svaluewaspositivelycorrelatedwiththelakesurfacearea
andthelakescatchmentarea,andnegativelycorrelatedwiththemeandepthofthe
lake.Significantrelationshipbetweenthetrophicstateandmorphologicalparame-
tersoflakeswasdescribedinmanystudies[26,28,44].
ThewideuseofCarlsontypeindicestocharacterizethetrophicstateofwater
bodiesresultsfromitssimplicityandeaseofuseandthenumerousexamplesofits
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