Circadian Variation of Physicochemical Factors yvis-à-vis Zooplankton Abundance at Different

Seasons in A Freshwater Lake, at Saheb Bundh, , ,Purulia, West Bengal

Subhayan Dutta1,2, Aniruddha Mukhopadhyay2 & Tapan Saha1

1Institute of Environmental Studies & Wetland ManagementInstitute of Environmental Studies & Wetland Management B‐04 LA Block, Salt Lake City, Kolkata – 700 098

2Department of Environmental Science, University of Calcuttap f , y f51/2 Hazra Road, Kolkata –700 019

INTRODUCTIONINTRODUCTION•• SahebSaheb BundhBundh (Nibaran(Nibaran Sayer)Sayer) isis aa biodiversitybiodiversity--richrich rainrain fedfed freshfresh waterwater

lakelake ecosystemecosystem situatedsituated atat PuruliaPurulia districtdistrict inin WestWest BengalBengal.. TheThe lakelake waterwaterisis mainlymainly usedused forfor domesticdomestic asas wellwell asas drinkingdrinking purposespurposes duringduring summersummerisis mainlymainly usedused forfor domesticdomestic asas wellwell asas drinkingdrinking purposespurposes duringduring summersummerseasonseason..

•• TheThe lakelake asas statedstated aboveabove isis situatedsituated atat PuruliaPurulia districtdistrict inin WestWest BengalBengal atat2323ºº2020''4242"N"N latitudelatitude andand 8686ºº2121''3737"E"E longitudelongitude.. TheThe totaltotal landland andand waterwaterareaarea ofof thethe lakelake coverscovers anan areaarea ofof 6060 acresacres..

ThTh dd ii i di d d did di hh d id i ff hh DODO•• TheThe presentpresent studystudy isis aimedaimed atat understandingunderstanding thethe dynamicsdynamics ofof thethe DODOconcentration,concentration, pH,pH, TemperatureTemperature andand toto ascertainascertain theirtheir applicabilityapplicability asaswaterwater qualityquality indicesindices inin freshwaterfreshwater lakelake ecosystemecosystem..q yq y yy

•• PresentPresent investigationinvestigation alsoalso depictsdepicts thatthat thethe dynamicitydynamicity ofof biologicalbiological liveslives ininanan aquaticaquatic ecosystemecosystem withwith specialspecial referencereference toto zooplanktonszooplanktons alongalong withwiththeirtheir synchronizationsynchronization withwith physicochemicalphysicochemical environmentenvironment..

MATERIALS & METHODSMATERIALS & METHODSMATERIALS & METHODSMATERIALS & METHODS

Field Study:Field Study:TheThe mainmain objectiveobjective ofof thethe fieldfield

studystudy isis toto developdevelop aa clearclearunderstandingunderstanding ofof severalseveralphysicophysico--chemicalchemical andand biologicalbiologicalaspectsaspects ofof thethe lakelake ecosystemecosystemaspectsaspects ofof thethe lakelake ecosystemecosystemwithwith respectrespect toto differentdifferent visualvisualconditioncondition ofof thethe lakelake ecosystem,ecosystem,infrastructureinfrastructure andand surroundingsurroundinginfrastructureinfrastructure andand surroundingsurroundingactivitiesactivities.. FourFour samplingsampling sitessiteshavehave beenbeen chosenchosen forfor thethe studystudy..

Water AnalysisWater Analysis::TheThe waterwater ofof SahebSaheb BundhBundh waswas collectedcollected fromfrom subsurfacesubsurface (the(the depthdepth ofof 00 55TheThe waterwater ofof SahebSaheb BundhBundh waswas collectedcollected fromfrom subsurfacesubsurface (the(the depthdepth ofof 00..55

meters)meters) usingusing waterwater samplersampler fromfrom thethe aboveabove--mentionedmentioned sitessites followingfollowingAPHAAPHA.. ParametersParameters likelike pH,pH, Conductivity,Conductivity, DissolvedDissolved Oxygen,Oxygen, %% OxygenOxygenSaturationSaturation andand TemperaturesTemperatures werewere measuredmeasured onon thethe spotspot byby usingusing waterwateranalyzeranalyzer (WTW(WTW makemake ModelModel NoNo.. MultiMulti 340340i/SET)i/SET).. SamplingsSamplings werewereperformedperformed throughthrough oneone dayday atat twotwo hourshours intervalinterval.. TheThe samesame hashas beenbeenobservedobserved forfor allall threethree seasonsseasons thatthat isis PrePre monsoon,monsoon, Monsoon,Monsoon, andand PostPostmonsoonmonsoon..monsoonmonsoon..

ZooplanktonZooplankton AnalysisAnalysis::ForFor thethe studystudy ofof zooplanktonzooplankton diversitydiversity 5050LL ofof waterwater waswas filteredfiltered fromfrom eacheachyy pp yy

spotspot throughthrough aa boltingbolting silksilk zooplanktonzooplankton netnet (No(No..2020)) andand preservedpreserved inin 7070%%alcoholalcohol.. TheThe zooplanktonszooplanktons werewere identifiedidentified followingfollowing standardstandard literatureliterature(Needham(Needham andand Needham,Needham,19721972;; Tonapi,Tonapi,19801980 andand Battish,Battish,19921992))..AASedgwickSedgwick RafterRafter CountingCounting CellCell waswas usedused forfor quantificationquantification andand theirtheirSedgwickSedgwick--RafterRafter CountingCounting CellCell waswas usedused forfor quantificationquantification andand theirtheirabundanceabundance waswas expressedexpressed asas numbernumber individualindividual perper literliter..

StatisticalStatistical AnalysisAnalysis::yyTheThe observedobserved resultsresults werewere undergoneundergone differentdifferent statisticalstatistical analysisanalysis usingusing SPSSSPSS

(Version(Version 1111..00)) softwaresoftware..

ResultsResults && DiscussionsDiscussionsTable 1. Seasonal Variation of Different Parameters in the Lake

Seasons Post Monsoon 2006 Pre Monsoon 2007 Monsoon 2007

Temperature (0C) 21.12±0.54 30.72±0.65 28.85±0.3

pH 7.68±0.08 7.96±0.19 7.77±0.25pH 7.68±0.08 7.96±0.19 7.77±0.25

Conductivity (μS/cm) 425.75±8.03 418.5±5.14 339.29±11.3

Dissolved Oxygen (mg/l) 7.21±0.52 7.38±0.67 6.56±0.55

Oxygen Saturation (%) 68 48±6 09 120 34±20 6 54 22±8 97Oxygen Saturation (%) 68.48±6.09 120.34±20.6 54.22±8.97

Temperature of the lake varies from 21.12±0.54 to 30.72±0.65 0 C with minimum in post monsoon and maximum in pre monsoon.

DO show a general trend of high value of   7.38±0.67 mg/l during pre monsoon period and low values during post monsoon.

This is same for the oxygen saturation also.

The pH of the lake is almost in a range of neutral to alkaline. During the pre monsoon the pH shows maxima of 7 96±0 19pre monsoon the pH shows maxima of 7.96±0.19.

Conductivity also shows a seasonal variation.

Fig-1 DIURNAL VARIATION OF TEMPERATURE

30

35

40R

E

10

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25

TEM

PER

ATU

R

MONSOON

PRE MONSOON

POST MONSOON

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5

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TIME

TemperatureTemperature showsshows 2424 hrhr diurnaldiurnal variationvariation andand showsshowsdd i hi h hh ff i hi h dd ii ii dddecrementdecrement withwith thethe onsetonset ofof nightnight andand increasesincreases inin daydaytimetime (Fig(Fig-- 11))..

Fig - 2 DIURNAL VARIATION OF DISSOLVED OXYGEN

10

12

4

6

8

DO

(ppm

) MONSOON

PRE MONSOON

POST MONSOON

0

2

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8.00AMAM AM PM PM PM PM PM PM AM AM AM AM AM

TIME

Diurnal variation of dissolved oxygen also shows same trend as oftemperature (Fig- 2). With the decrease of temperature in the night therate of photosynthesis by phytoplankton decreased and as a result theamount of dissolved oxygen alsoalso getget reducedreduced..

Fig-3 DIURNAL VARIATION OF OXYGEN SATURATION

140

160

180

60

80

100

120

140

OXY

GEN

SA

T.(%

)

MONSOON

PRE MONSOON

POST MONSOON

0

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8.00AM

TIMETIME

Oxygen Saturation also shows same variation trend as of DOOxygen Saturation also shows same variation trend as of DO

Fig - 4 DIURNAL VARIATION OF pH

8.5

9

7

7.5

8

pH

MONSOON

PRE MONSOON

POST MONSOON

6

6.5

8.00AM

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TIME

Diurnal variation of surface pH also confirmed daytimeincrease and nocturnal decrease (Fig-4).

Fig - 5 DIURNAL VARIATION OF CONDUCTIVITY

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350

400

450C

M

100

150

200

250

300

MIC

RO

SIE

MEN

S/C

MONSOON

PRE MONSOON

POST MONSOON

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No significant variation for the parameter like conductivityNo significant variation for the parameter like conductivity(Fig - 5). From this we can conclude that conductivity maynot be associated with circadian changes, particularly for thepresent ecos stempresent ecosystem.

ROTIFERA COPEPODA CLADOCERA

Table – 2. Zooplankton Species of the Lake

Brachionus fulcatus Cyclops nauplius Ceriodaphnia

Brachionus forficula Mesocyclops leuckarti Daphnia carinata

Brachionus diversicornis Moina sp. Diphanosoma sarsi

Brachionus caudatus Moinodaphnia macleayi

Brachionus rubens

Filinia terminalis

K t ll t iKeratella tropica

Lecane sp.

Monostyla sp.

Fig- 6 SEASONAL VARIATION OF ZOOPLANKTON

300

350

100

150

200

250

NO./L

ROTIFERACOPEPODACLADOCERA

0

50

PRE MONSOON MONSOON POST MONSOON

SEASONS

Fig - 7 DIURNAL VARIATION OF ROTIFERA

120

140

40

60

80

100

120NO./L

SUMMER

MONSOON

WINTER

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Rotifera and Copepoda species are completely absent at the surface water atnight hours while during daytime they are present as expected (Fig – 7and 8).

Fig - 8 DIURNAL VARIATION OF COPEPODA

35

40

5

10

15

20

25

30

NO./L

SUMMER

MONSOON

WINTER

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5

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10.00AM

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2.00 PM 4.00 PM 6.00 PM 8.00 PM 10.00PM

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TIME

Fig-9 DIURNAL VARIATION OF CLADOCERA

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NO

./L

SUMMER

MONSOON

WINTER

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8.00AM

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Group Cladocera show a higher population density withrespect to the other groups at night (Fig –9). This may be dueto the fact that cladocerans move out from their shelter atnight to graze in the open water.g g p

ConclusionConclusionAlAl llll hh hh f ll df ll d hh dd dd ii dd i hi hAlmostAlmost allall thethe parametersparameters havehave followedfollowed thethe expectedexpected trendstrends inin dayday nightnightcyclecycle..

TheThe diurnaldiurnal cyclingcycling ofof pHpH TemperatureTemperature DissolvedDissolved OxygenOxygen andand %% OxygenOxygenTheThe diurnaldiurnal cyclingcycling ofof pH,pH, Temperature,Temperature, DissolvedDissolved OxygenOxygen andand %% OxygenOxygenSaturationSaturation areare positivelypositively correlatedcorrelated inin almostalmost allall seasonsseasons..

DissolvedDissolved oxygenoxygen andand OxygenOxygen SaturationSaturation havehave followedfollowed synchronizedsynchronized upsupsdd ddandand downsdowns..

PresentPresent investigationinvestigation alsoalso depictsdepicts thatthat thethe zooplanktonszooplanktons areare completelycompletelyabsentabsent atat thethe surfacesurface waterwater atat nightnight hourshours whilewhile duringduring daytimedaytime theythey areareabsentabsent atat thethe surfacesurface waterwater atat nightnight hourshours whilewhile duringduring daytimedaytime theythey arearepresentpresent asas expectedexpected..

TheThe onlyonly exceptionexception inin thethe aboveabove mentionedmentioned factfact isis thethe groupgroup CladoceraCladoceratiti th ith i t lt l iisupportingsupporting theirtheir nocturnalnocturnal grazinggrazing..

TheThe physicochemicalphysicochemical factorsfactors asas wellwell asas sunlightsunlight mightmight actact asas factorsfactorsinfluencinginfluencing thethe distributiondistribution andand abundanceabundance ofof zooplanktonszooplanktonsinfluencinginfluencing thethe distributiondistribution andand abundanceabundance ofof zooplanktonszooplanktons