- Asian Journal of Experimental Biological Sciences

ASIAN J. EXP. BIOL. SCI. VOL 1(4) 2010:- 840- 844
© Society of Applied Sciences
ORIGINAL ARTICLE
Environmental factor effects on the seasonally changes of zooplankton
density in Parishan Lake (Khajoo Spring site), Iran
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Shayestehfar , A., Noori *, M., Shirazi , F
1
2
Department of Biology, Faculty of Science, University of Arak, Arak-Iran
Department of Microbiology, Faculty of Science, Islamic Azad University of Arak, Arak-Iran
ABSTRACT
Zooplankton communities are important constituents of aquatic ecosystems playing major roles in energy flow between the
various organisms of food chains. Studies were carried out on Khajoo Spring water flown in a closed freshwater lake
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(Parishan Lake) with 43 km area, 820 m altitude above sea level and 266.5 km in the South-West of the Fars Province, Iran, to
investigat changes in the zooplankton composition at different seasons. Ten samples were collected monthly from three
different sites of spring water from January to December 1998-1999. Some of the samples were used for identification and
purification without any fixation of zooplankton but some of them were fixed. Zooplanktons were identified using bright field
and dark-field microscopes. The relationship between environmental factors and population density of the species at different
times was also measured. Results showed existing 107 taxa in two Rotifera and Arthropoda phyla, 4 classes, 8 orders, 20
families and 50 genera of zooplankton that fluctuated based on environmental conditions. In autumn total zooplankton
density and zooplankton variation are higher than other seasons, but these were the lowest in spring.
KEYWORDS: Zooplankton, Fresh water, environmental factors, Khajoo spring (Parishan Lake), Iran
INTRODUCTION
Zooplankton constitutes an important food source for many aquatic organisms [1] consistings of protozoan,
cladocera, copepoda, rotifera, and others which also may serve as indicators of water quality [2]. They play a major
role in energy transfer from phytoplankton to economically important fish populations, control phytoplankton
production, and shap pelagic ecosystems. Because of their critical role as food source for larval and juvenile fish, the
dynamics of zooplankton populations, their reproductive cycles, growth, reproduction, and survival rates are all
important factors influencing recruitment to fish stocks [3]. Zooplanktons live in different environments where many
factors such as light availibity, temprature and nutrient uptake influence disribution [4 & 5]. The composition and
abundance of zooplankton are related to many factors, such as water hydrochemistry, season, lake morphology,
presence of macrophytes, predators etc. and particularly to the productivity of the lake that is lake trophic condition
[6]. The latter makes it very suitable and popular for monitoring programs devoted to record changes in the lake's
ecological quality [7]. A variety of both biotic and abiotic factors have been implicated in determining the boundaries
of species distributions. Biotic factors important to segregation include resources and predators. Abiotic factors such
as dissolved oxygen, temperature and light can also influence the distribution of species [8]. The purpose of this study
was to investigate changes of zooplankton in Parishan Lake (Khajoo Spring site) in Fars Province, Iran at different
seasons. The effect of different environmental factors, which potentially influence the population dynamic, was
evaluated by correlating these factors with zooplankton density.
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ASIAN J. EXP. BIOL. SCI. VOL 1 (4) 2010
Environmenta effects on the seasonally changes of zooplankton density in Parishan Lake Iran..........Shayestehfar et al
MATERIALSAND METHODS
Study site
Experiments were carried out in Parishan Lake (Khajoo Spring site) in south-west region of Fars Province, Iran (lat.
2
29° 32´ N, long. 51°48´ E) (Figure 1). The lake is a closed freshwater lake with 43 km sureface area, 820 m altitude
2
from sea surface and 266.5 Km water shed area that its water is provided from surface waters, rainfall and a
few spring such as Khajoo Spring.
Figure 1Topography of the sampling site, Parishan Lake (Khajoo Spring) in Fars Province, Iran.
Sampling andAnalyses
Ten samples were collected monthly from three different Khajoo Spring sites of water surface from January 1998 to
December 1999. Air and water temperature and pH were measured immediately after each water sampling, with a
standard thermometer and a pH meter (WTW, Metrohm). In addition some climatological data such as humidity,
evaporation and rain fall were obtained from the IRMO (Iran meteorological organization) [9]. Disolved oxygen
(DO), biological oxygen demand (BOD), chemical oxygen demand (COD), carbon di-oxide (CO2), total nitrogen
(NO2) and total dissolved solid were measured using the Winkler Method [10]. So, these two factors are deleted in our
analyses and just rainfall was taken into consideration.
Samples for identification and counts for abundance estimates of zooplanktons were fixed by adding glycoalkhol
(7%) and stored at 4C°. Some of samples were used without any fixation. Then counting and identification of samples
were undertaken using Gridded Sedgewick Rafter Counting Cells under stereo, bright field and dark field
microscopes based on Ward and Whipple (1966) [11], Jeje and Fernando (1986) [12] and other available references.
Data were analyzed using the EXCEL (2003 and 2007) software.
RESULTS
Change of family composition of zooplankton
One hundred and seven taxa were identified from Khajoo Spring, Iran in two Rotifera and Arthropoda phyla, 4 classes
(Bdelloidea, Branchiopoda, Ostracoda and Maxillopoda), 8 orders (Plomia, Flosculariaceae, Bdelloidae, Cladocera,
Podocera, Cyclopodia, Calanoida and Harpacticoida), 20 families and 50 genera of zooplankton that fluctuated based
on environmental conditions. The composition and abundance of dominant zooplankton families in winter, spring,
summer and autumn of study site are shown in Figure 2. The predominant zooplankton families in the Khajoo Spring,
Iran, in all of annual months were identified: Brachionidae, Cyclopidae, Daphnidae and notommatidae.
ASIAN J. EXP. BIOL. SCI. VOL 1 (4) 2010
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Environmenta effects on the seasonally changes of zooplankton density in Parishan Lake Iran..........Shayestehfar et al
oxygen demand (COD), pH, alkalinity, acidity, carbon di-oxide (CO2), total nitrogen (NO2), total dissolved solid
(TDS), total hardness (TH) and zooplankton density (ZD) (2281 in autumn and 266 in spring) are presented in Table 1.
The data showed wide variations in values and there were a dynamic fluctuation of the environmental factors in the
Parishan Lake (Khajoo Spring site), Iran. Figure 3 shows seasonal values of the various environmental
The composition and abundance of dominant zooplankton families in
winter, spring, summer and autumn of Khajoo Spring, Iran
Tustudinellidae
Temoridae
100%
Synchaetidae
F a m ily com p osit io n ( % )
Sididae
Philodinidae
80%
Notommatidae
Moinidae
Macrothricidae
60%
Lecanidae
Harpacticidae
Flosculariidae
Dicranophoridae
40%
Diaptomidae
Daphnidae
Cyprididae
20%
Cyclopidae
Chydoridae
Centropagidae
0%
ec
D
ov
N
ct
O
p
Se
ug
A
ly
Ju
n
Ju
ay
M
pr
A
ar
M
b
Fe
Ja
n
Brigeidae
Brachionidae
Asplanchnidae
Month of the year
Figure 2 Stacked column with a 3-D visual effect histogram for comprising the composition and abundance of dominant
zooplankton families in winter, spring, summer and autumn of Parishan Lake (Khajoo Spring site) in Fars Province, Iran.
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ASIAN J. EXP. BIOL. SCI. VOL 1 (4) 2010
Environmenta effects on the seasonally changes of zooplankton density in Parishan Lake Iran..........Shayestehfar et al
Figure 3 Seasonal values of the various environmental variables in Khajoo Spring, Iran. Abbreviations: air temperature (AT),
water temperature (WT), humidity (Hu), evaporation (Ev), rain fall (RF), dissolved oxygen (DO), biological oxygen demand
(BOD), chemical oxygen demand (COD), alkalinity (Al), total nitrogen (NO2), total dissolved solid (TDS), total hardness (TH)
and zooplankton density (ZD).The minimum air and water temperatures (8.6°C and 8.2°C in January) in Parishan Lake
(Khajoo Spring site), Iran were recorded. Recorded maximum air and water temperatures in the site were 29.8°C and
28.2°C in August. Minimum humidity was in August (32.68%) and maximum in February (79.2%). July had the
highest evaporation (250%) and the least was in February (48.5%). All of annual months, except spring and first
summer months, lacked rain fall. BOD, COD, Al, NO2, TDS, TH and ZD showed maximum ranges in autumn and
minimum in spring while DO was the reverse of this case and pH had the least variation (Table 1).
DISCUSSION
Results showed there were wide variations in monthly values of environmental parameters and there were a dynamic
fluctuation of the environmental factors in the Parishan Lake (Khajoo Spring site), Iran. It was well known that
determinations of the parameters that actually affect density of zooplankton are more complex and it is difficult to
establish one-to-one casual relationships between zooplankton associations and factors without supporting
experimental evidence [13 &14]. Temperature regulates the density and diversity of dominant zooplankton
population in the freshwater. Our data showed that annual air and water temperature ranges from 8.2 to 29.8°C are
suitable for all studied zooplankton but the both factors positively correlated with density of zooplankton by the
reason maximum mean air and water temperature were in autumn (28.1 and 26.5°C) and also maximum mean
zooplankton density was in autumn (2281). As shown Ahmad (1990) trend of fluctuations, these results confirm
zooplankton quickly reaction to atmospheric temperature changing. During the present investigation there was an
inverse relationship between the water temperature and dissolved oxygen [15]. So, air and water temperature
negatively correlated with dissolved oxygen and DO reduction is increased zooplankton density. This is in agreement
with the findings of Wang (1928) [16]. To date, little is known about the effects of climate warming on zooplankton in
cold-water ecosystems. However, evidence suggests zooplanktons are more sensitive to changes in temperature than
phytoplankton in other environments. For example, moderate warming enhances the growth and feeding rates of
many filter-feeding zooplankton species, such as Daphnia magna (e. g., McKee and Ebert 1996) [17]. Beisner et al
(1997) showed that a 50-d period of constantly warmer conditions (25°C vs. 18°C) accelerated the growth of Daphnia
populations in mesocosms, which resulted in over exploitation of their algal food supply and ultimately their
extinction [18 & 19]. Warmer temperature can favor smaller zooplankton because warming disproportionately
increases developmental (i. e., molting) and respiratory costs more than ingestion. In addition, large cladocerans and
copepods may show reduced fecundity at elevated temperatures. For example, Taylor and Mahoney (1988) showed
that total zooplankton abundance declined because lethal increases in water temperatures above 45°C resulted in
crustacean species being replaced by smaller rotifers [19 & 20]. In addition air and water temperature Al, BOD, COD,
NO2 and TDS parameters positively correlated with density of zooplankton, while increasing DO is linked with AT,
WT and ZD reduction. There is an inverse relationship between DO with BOD and COD. The quantities of COD were
relatively more than BOD which is in agreement with the findings of Uhlman (1979) [21].
Humidity was low in summer, high in winter and moderate in the autumn and spring respectively. All of annual
months, except spring and first summer month, lack rain fall. Specifically, increasing variation in rainfall might result
in diminished long-run growth rates for many animal species while increasing variation in temperature might result in
increased long-run growth rates. While the effect of rainfall is theoretically well understood and supported by data, the
hypothesized effect of temperature is not. Drake (2005) results are consistent with the prediction that fluctuating
temperatures should increase long-run growth rates and the frequency of extreme demographic events [22]. Also
Akin-Oriola (2003) showed environmental factors in two Nigerian rivers -included buffering capacity, trace metal
ions, pH-temperature/ transparency- were primarily influenced by rainfall [14]. The results of this study also revealed
that pH having the least variation did not exert any significant correlation with zooplankton density [13]. During the
present study we observed an inverse relationship between dissolved oxygen with alkalinity and pH. pH showed an
alkaline nature which is in agreement with Lakshminarayana (1965), the pH and alkalinity always showed a direct
relationship and CO2 showed an inverse relationship with DO [23]. There is a direct relationship between rotifera,
cladocera, ostracoda, copepoda with water temperature. In the present study we observed an inverse relationship
ASIAN J. EXP. BIOL. SCI. VOL 1 (4) 2010
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Environmenta effects on the seasonally changes of zooplankton density in Parishan Lake Iran..........Shayestehfar et al
between cladocera, ostracoda, copepoda, rotifera and DO. In the present study we found that, the population density of
arthropoda and rotifera as well as cladocera, copepoda and ostracoda are related to the seasons.
The predominant zooplankton families in the Khajoo Spring, Iran, in all of annual months are Brachionidae,
Cyclopidae, Daphnidae and notommatidae. Flosculariidae and Asplanchnidae family were the least. In autumn total
zooplankton density and zooplankton variation are higher than other seasons, but these were the lowest in spring.
Finally it is clear that environmental factors play an important role in zooplankton density in freshwater and
physicochemical factors determine the population dynamics in this environment. But, further work is needed using
one-to-one factors on one-to-one species with supporting experimental evidence.
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Correspondence to Author: Mitra Noori, Department of Bi ology, Faculty of Science, University of Arak, Arak -Iran.
Phone: 0098 861 4173401, Fax: 0098 861 4173406, Email address:[email protected]
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ASIAN J. EXP. BIOL. SCI. VOL 1 (4) 2010

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