Circadian Variation of Physicochemical Factors vis-à-vis Zooplankton Abundance at Different Seasons in A Freshwater Lake, at Saheb Bundh, Purulia, West Bengal Subhayan Dutta 1,2 , Aniruddha Mukhopadhyay 2 & Tapan Saha 1 1 Institute of Environmental Studies & Wetland Management Institute of Environmental Studies & Wetland Management B‐04 LA Block, Salt Lake City, Kolkata – 700 098 2 Department of Environmental Science, University of Calcutta 51/2 Hazra Road, Kolkata –700 019
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Circadian Variation of Physicochemical Factors yvis-à-vis Zooplankton Abundance at Different
Seasons in A Freshwater Lake, at Saheb Bundh, , ,Purulia, West Bengal
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
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
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
15
20
25
TEM
PER
ATU
R
MONSOON
PRE MONSOON
POST MONSOON
0
5
8.00AM
10.00AM
12.00PM
2.00PM
4.00PM
6.00PM
8.00PM
10.00PM
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2.00AM
4.00AM
6.00AM
8.00AM
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
8.00AM
10.00AM
12.00PM
2.00PM
4.00PM
6.00PM
8.00PM
10.00PM
12.00AM
2.00AM
4.00AM
6.00AM
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
20
40
8.00AM
10.00AM
12.00PM
2.00PM
4.00PM
6.00PM
8.00PM
10.00PM
12.00AM
2.00AM
4.00AM
6.00AM
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
10.00AM
12.00PM
2.00PM
4.00PM
6.00PM
8.00PM
10.00PM
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2.00AM
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TIME
Diurnal variation of surface pH also confirmed daytimeincrease and nocturnal decrease (Fig-4).
Fig - 5 DIURNAL VARIATION OF CONDUCTIVITY
300
350
400
450C
M
100
150
200
250
300
MIC
RO
SIE
MEN
S/C
MONSOON
PRE MONSOON
POST MONSOON
0
50
100
8.00AM
10.00AM
12.00PM
2.00PM
4.00PM
6.00PM
8.00PM
10.00PM
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TIME
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 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
0
5
8.00AM
10.00AM
12.00PM
2.00 PM 4.00 PM 6.00 PM 8.00 PM 10.00PM
12.00AM
2.00AM
4.00AM
6.00AM
8.00AM
TIME
Fig-9 DIURNAL VARIATION OF CLADOCERA
40
50
60
20
30
40
NO
./L
SUMMER
MONSOON
WINTER
0
10
8.00AM
10.00AM
12.00PM
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4.00PM
6.00PM
8.00PM
10.00PM
12.00AM
2.00AM
4.00AM
6.00AM
8.00AM
TIME
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..