ap biology lab 12
DESCRIPTION
Lab on dissolved oxygen and primary productivityComplete lab write up with discussion/conclusionTRANSCRIPT
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APLab#12:DissolvedOxygenandPrimaryProductivityPaulaZdanowski,IvyZhou,KylieOHara,SaraKuramitsu
April13,2015Gold1
Mr.Hilvert
AbstractTheobjectiveofthislabwastocalculatedissolvedoxygenconcentrationanddetermine
theprimaryproductivityofanaquaticecosystem.Toaccomplishthis,thedissolvedoxygeninwateratdifferenttemperaturesfirstwasdeterminedthroughtitration.Then,tomeasuretheproductivityofanaquaticenvironment,differentbottleswithvaryingdegreesoflightwereleftunderalightfor24hours,andtitratedagaintodeterminethedissolvedoxygenconcentration.Theresultsofthislabdemonstratednostrongcorrelationbetweentheintensityofthelightandthenetproductivity,sosomethingotherthanlightmusthavebeeninfluencingtheproductivityintheaquaticenvironment.
Introduction
Oxygenisanecessarypartinaquaticaswellasterrestrialenvironments.Becauseitisneededinvirtuallyallmetabolicprocesses,dissolvedoxygenisagreatindicatorofwaterquality(Robson).Becausewaterisnotasefficientatholdingoxygenasairis,itisimperativethatoxygenisconstantlyreplenishedfromtheatmosphereandsurroundingbiologicalactivity.Thisdissolvedoxygenisabyproductofphotosynthesis.Therearevariousfactorsthatimpactthedissolvedoxygencontentofabodyofwater,includingtemperature,wind,turbulence,andthetrophicstate(HargreavesandTucker).Ameasureoftheproductionofoxygenoveraperiodoftimeisfoundbycalculatingtheamountofcarbonthathasbeenfoundonorganiccompoundsovertime(Sanchez).Theobjectivesofthisexperimentweretodemonstrateimportanceofcarbonandoxygencyclesinanecosystem,theeffectoflightandnutrientsonphotosynthesis,andtoidentifythefactorsthataffectthesolubilityofdissolvedgassesinaquaticenvironments..Wehypothesizedthatthetemperatureofthewaterwouldimpacttheamountofdissolvedoxygen,andthatthebottleswithlowerlightwouldbelessproductive.Procedure/Materials/Methods
Theobjectiveofthislabistomeasurethedissolvedoxygenconcentration,calculateproductivityandrespirationrate,anddemonstratethisknowledgeincorrespondencewiththeecosystem.Inthisfirstpartofthislab,wemeasuredtheamountofdissolvedoxygen.Todoso,wefirstpreparedasamplingwaterbottle.Wefilledabottlewith20Cwatertothetop.Wedidnotallowanyairbubblestobetrappedinsideandthencappeditbottle.Thenweplacedthebottleinawhiteshallowpanandaddedeightdropsofmanganoussulfateandeightdropsofalkalineiodide.Thesolutionwasanorangecolor.Whenwedidthis,aprecipitateformed
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immediately.Nextwemixedtheingredientsbyinvertingitseveraltimes.Welettheprecipitatesettleandthenaddedonescoopofacidintothebottleandalsomixeditbyinvertingthebottle.
Whenweaddedtheacid,theprecipitatedissolvedandthesolutionturnadarkyellow.Wethenmeasured20mLofthesampleandplaceditintoatitrationvial.Apieceofwhitepaperwasplacedunderthevialtoseethecolorbetter.Next,weaddedeightdropsofstarchindicatortothesamplewhichcausedthecolortochangetoapurple.Atitrationsyringewasfilledwithsodiumthiosulfateandwasusedtotitratethesampleuntilthecolorchangedfrompurpletopaleyellow/clear.Wethenmeasuredtheamountofdissolvedoxygenbymeasuringtheamountoftitrantused.Wealsogatheredclassdata.
Inthesecondpartofthelabwemeasuredproductivity.Firstwefilledsevensamplingbottlesbysubmergingtheminthedirtygreenfishtankonthesideoftheroom.Weplacedeachbottleinsideuntilalltheairbubblescameoutandthenwecappedthebottleunderwater.Thenwelabeledeachbottlewith17.Afterwards,wewrappedthebottleswiththeappropriateamountofscreenforthelightintensities.Thiscanbeseeninthetableonpage11.(Bottle2hadfoilaroundit,bottle3had1screen,etc...)Weliedbottles27downontheirsidesunderalightovernight.Next,wepreparedawetmountofthewatersampleinbottle1andobserveditunderamicroscope.Weidentifiedtheorganismswefoundanddrewthem.Wealsopreparedbottle1thesameasthesamplebottleinthepreviousexperimentandtitratedthesolution.Onthenextdaywepreparedtheotherbottlesaccordingtothesamestepsasbeforeinthepreviouslabandbottle#1.Afterwards,wemeasureddissolvedoxygenineachbottleandtitratedeachsample.Usingspecificformulaswecalculatedtheproductivityandrespirationratesofthesamples.Classdatawasalsoobtained.Inthelastpartofthelab,wegraphedthedatagiventomeasuretheproductivityofabodyofwater.DataTable1:DissolvedOxygenConcentration,LabGroupSample
Temperature DissolvedOxygen(mg/L) %Saturation
20C 1mg/L 10%
Table2:DissolvedOxygenConcentration,ClassSample
Temperature(Celsius) DissolvedOxygen(mg/L) %Saturation
0(Group1) 0.7 5%
0(Group6) 0.9 8%
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20(Group2) 0.97 10%
20(Group5) 0.88 10%
30(Group3) 0.96 12%
30(Group4) 0.75 11%
Astemperatureincreases,thedissolvedoxygenandthe%saturationalsogenerallyincreases.Table3:GrossandNetProductivity/RespirationRate,ClassSample
PercentLight DissolvedOxygen(mg/L)
NetProductivity GrossProductivity(mlO2/L)
GrossProductivity(mgC/m^3)
Initial 0.83
Dark 0.80
100% 0.79 0.04 0.01 5.36
65% 0.83 0 0.03 16.08
25% 0.78 0.05 0.02 10.72
10% 0.91 0.08 0.11 58.96
2% 0.69 0.14 0.11 58.96
Respiration=InitialBottleDarkBottleNetPrimaryProduction=LightBottleInitialBottleGrossProduction=LightBottleDarkBottleThereisnotastrongcorrelationbetweenthepercentlightexposedandthedissolvedoxygen.Thecurveincreasesanddecreasesoftensothatapatternisdifficulttoidentify.Thereisalsonospecificcorrelationbetweenlightpercentageandnetproductivityaswellaslightpercentageandgrossproductivity.
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Discussion/ConclusionForPartA,ourfindingsshowthatthetemperatureofthewaterdidimpactthedissolved
oxygencontent.Theoveralltrendshowsthatthelowerthetemperature,thehigherthedissolvedoxygencontentinthewater.Thisishoworganismsinaquaticenvironmentssurviveincoldweatherwhenthewaterfreezes.Becauseofthehighoxygencontentinthewater,theyareabletoslowdowntheirmetabolisms,whilestillmaintainingahighenoughoxygenintaketosurvive.
ForpartB,ourfindingsshowthatlighthaslittleeffectontheproductivityofaquaticenvironments,whichdisprovesourhypothesis.Thereasonforthisisbecauselightcannotpenetratewaterverywell,whichmeansthatorganismslivingdeepinwaterarelimitednotbylight,butbynutrients.Thevaryingdissolvedoxygencontentsforeachbottledemonstratesthattheamountoflightdidnotreallylimittheproductivity.WorksCitedHargreaves,JohnA.,andCraigS.Tucker."MeasuringDissolvedOxygenConcentrationin
Aquaculture."TheFishSite.5mPublishing,09Jan.2006.Web.20Apr.2015.Robson,MarkG."DissolvedOxygen."Encyclopedia.com.HighBeamResearch,01Jan.2003.Web.20
Apr.2015.Sanchez,Enrique."UseoftheWaterQualityIndexandDissolvedOxygenDeficitasSimpleIndicators
ofWatershedsPollution."UseoftheWaterQualityIndexandDissolvedOxygenDeficitasSimpleIndicatorsofWatershedsPollution.ElsevierLtd.,21Nov.2005.Web.20Apr.2015.
Questions
1) Howdoestemperatureaffectthesolubilityofoxygeninwater?Thelowerthetemperature,themoresolubleoxygenisinwater.
2)Howdoessalinityaffectthesolubilityofoxygeninwater?Thehigherthesalinity,thelowerdissolvedoxygenthereisinwater.
3)Wouldyouexpecttofindhigherdissolvedoxygencontentinabodyofwaterinwinteror summer?
Iwouldexpecttheretobeahigherdissolvedoxygencontentinabodyofwaterinthewinterbecausethewateriscolder.4)Discusshoweachofthefollowingfactorscouldinfluencethedissolvedoxygen concentrationinabodyofwater:
Wind:Windwouldincreasethedissolvedoxygenconcentrationbecauseitmovesairacrossthesurfaceofthewaterallowingmoreoxygentobeintroduced.Temperature:Thehigherthetemperature,thelowertheamountofdissolvedoxygenin
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water.Altitude:Asaltitudeincreases,thedissolvedoxygencontentwoulddecreasebecauseofthedropinpressure.
5)Doyouthinkitwouldbewisetostockapondwithgamefishifithadadissolvedoxygencontentof3ppm?Whyorwhynot?Itwouldnotbewisebecausemostfishneedadissolvedoxygencontentofatleast5or6ppm.
6)Ichosetolabelthelowdissolvedoxygencontentassummer,andthehighdissolvedoxygencontentaswinterbecausetemperatureisindirectlyrelatedtothelevelofdissolvedoxygeninwater.
7)InpartB,wereanyofthesampleslightlimited?Why?
Itdoesntappearthatanyofthesampleswerelightlimited,becausetherewasnotrendindissolvedoxygencontentforvaryingdegreesoflight.Thisisbecausemostaquaticenvironmentsaremorelimitedbytheirnutrientssincelightcannotpenetratedeeplyintowater.
8)BasedonyouranalysisofthelakespresentedinpartCofthelab,whichlakeismoreproductive?Lake2appearstobemoreproductivebecauselightcanpenetratedeeperintothewaterthaninlake1.
9)Whatisusedasthebasisformeasuringprimaryproductivity?DissolvedoxygencontentisusedasthebasisformeasuringprimaryproductivitybecauseitcandemonstratetheamountofO2usedinrespiration.
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10)
11)a.additionofmanganoussulfate:producesmanganoushydroxidewhenaddedwithwater
b.additionofalkalineiodide:oxidizesmanganoushydroxidetomanganichydroxidec.additionofsulfamicacid:convertsmanganichydroxidetomanganicsulfated.additionofstarchindicator:makestitrationendpointmorevisiblee.titrationwithsodiumthiosulfate:freeiodinecombinesintosodiumiodide