Seasonal dynamics of rotifers in relation to physical - Limnoreferences

Hydrobiologia 491: 101–109, 2003.
E. van Donk, M. Boersma & P. Spaak (eds), Recent Developments in Fundamental and Applied Plankton Research.
© 2003 Kluwer Academic Publishers. Printed in the Netherlands.
Seasonal dynamics of rotifers in relation to physical and chemical
conditions of the river Yamuna (Delhi), India
J. Arora & N. K. Mehra ∗
Limnology Unit, Department of Zoology, University of Delhi, Delhi 110 007, India
E-mail: nareshmehra@hotmail.com ( ∗ Author for correspondence)
Received 13 June 2001; in revised form 27 December 2001; accepted 13 June 2002
Key words: backwaters, rotifers, species composition, seasonal variations, physical and chemical variables,
river Yamuna
Abstract
We examined the seasonal succession of the rotifer assemblages in the backwaters of the Delhi segment of the river
Yamuna in relation to 18 physical–chemical variables across one year. These shallow, weedy, and perennial aquatic
biotopes support a diverse and abundant zooplankton. A total of 89 rotifer species belonging to 34 genera and 18
families were recorded. Their seasonal dynamics were characterized by (i) maxima and minima in total densities
during spring–early summer and winter, respectively; (ii) individual species reaching maximum and minimum
densities during different seasons; and (iii) an absence of seasonal variation in species diversity. The relative
importance of various physical and chemical factors in determining rotifer community structure and seasonal
succession is evaluated and Pearson-product moment correlations between physical–chemical variates and rotifer
densities are analyzed and discussed.
Introduction
The spatial and temporal dynamics of rotifer communities
are influenced by a variety of physical, chemical
and biological factors, whose relative role in structuring
rotifer assemblages and controlling seasonal
dynamics may vary within or between biological systems
(Hunter & Price, 1992). In general, both biotic
and abiotic factors define the microhabitat boundaries
for rotifer species by partitioning the environment
and minimizing competitive interactions (Nogrady et
al., 1993). Biotic factors such as food quality and
quantity (Dumont, 1977), exploitative and interference
competition (May & Jones, 1989), predation
(Williamson, 1983) and parasitism (Ruttner-Kolisko,
1977) may inter alia induce changes in rotifer communities
favouring one species over another. Further,
rotifers are highly susceptible to physical and chemical
changes in their environment due to their small size
and permeable integument (Nogrady et al., 1993). The
various factors that influence the dynamics of natural
rotifer populations are: temperature, oxygen concentration,
light intensity and pH (Hofmann, 1977). In
101
addition, variables related to the trophic status of the
aquatic ecosystem such as nutrient and chlorophyll
concentrations and conductivity determine the presence
of particular species and seasonal succession of
rotifer assemblages (Berzins & Pejler, 1987, 1989a;
Devetter, 1998). Although physical–chemical and biological
conditions prevailing in the Delhi region of
river Yamuna have been studied by Rai (1974a, b),
de Zwart (1991) and Kaur (1996), these studies were
episodic and limited to a small number of physical,
chemical and biological factors. The present investigation
attempts to analyze the relative impact of a variety
of variables on rotifer assemblages in the backwaters
of the river Yamuna in the Delhi region by correlating
rotifer abundances with various abiotic factors.
Materials and methods
Study area
Our study was conducted in backwaters of the river
Yamuna upstream of the Wazirabad barrage (see

102
Fig. 1), at an average elevation of 216 m above sea
level, in the National Capital Territory of Delhi (Lat.
28 ◦ 12 ′ –28 ◦ 53 ′ N, Long. 76 ◦ 50 ′ –77 ◦ 23 ′ E).
These low-lying areas get inundated during monsoon
(July–September) due to heavy discharge from the
headwaters of the river. In addition, the overflowing
water of the river due to discharges from a reservoir
situated upstream of the barrage also replenishes
these backwaters. Due to the presence of agricultural
fields and a few human settlements in the vicinity of
the backwaters, the inflow from the catchment area
also influences the physical–chemical characteristics
of the backwaters. These shallow, perennial and weedy
aquatic biotopes can be designated as open, lentic ecosystem
with an inlet. They support luxuriant growth
of floating macrophytes, viz. Eichhornia crassipes
(Mart.) Solm and Salvinia molesta Mitch, along the
shore throughout the year. In addition, two submerged
macrophytes viz. Hydrilla sp. and Vallisnaria sp. were
also recorded.
The sampling sites viz. Site-I (S-I) and Site-II (S-
II), were located diagonally opposite to each other
(Fig. 1). S-I supported thick growth of macrophytes,
especially during spring and summer, whereas S-II
was located near the inlet point of the river Yamuna
and supported lesser growth of macrophytes. Also,
floating and submerged leaves of Salvinia were smaller
in size at S-II.
Sampling and analyses
Water samples for physical–chemical analysis and
plankton analysis were collected once a month from
the two sampling sites for one year.
Physical–chemical analysis
Water temperature (using dial thermometer) was recorded
in the field. In addition, the samples for estimation
of dissolved oxygen (DO) were collected directly
in the BOD bottles and fixed immediately. Water
samples were collected in clean 1L-polyethylene
bottles for analysis of other variables in the laboratory.
Samples were analyzed within 4–6 h of collection.
pH and conductivity were recorded using Control Dynamics
pH meter and conductivity meter, respectively.
Analyses of all factors except nitrates, colour and
turbidity were done according to the ‘Standard Methods
for the Examination of Water and Wastewater’
(APHA, 1989). Nitrates were analyzed according to
‘Water Analysis’ (Fresenius et al., 1988) and colour
and turbidity using Hellige’s Instruction Manual.
Figure 1. Map showing two sampling stations (Site-I and Site-II)
located on the backwaters of the Delhi segment of the river Yamuna
towards the eastern side of Wazirabad barrage.
Plankton analysis
The plankton was concentrated for quantitative analysis
by filtering 25 L of water through a 50 µm mesh
plankton net. In order to collect relatively rare species,
50 L of water was also filtered for qualitative
analysis. All the concentrated plankton samples were
preserved with 4% neutral formalin solution after anaesthesia
with CO2-saturated mineral water. Rotifers
were enumerated using a modified Sedgewick–Rafter
cell equipped with a grid base. Samples were diluted to
a desired volume and three counts taking 1ml aliquots
each time were examined. Densities were expressed
as ind. l −1 . Qualitative analysis of the rotifers was
done using a stereoscopic binocular microscope (Leitz
Wetzlar). Trophi were isolated, whenever necessary,
by dissolving the soft tissue with 4% sodium hypochlorite.
Entire animals and trophi were mounted in
glycerin on a glass slide, sealed with ‘nail polish’ and

examined under 50× or 100× magnification. Rotifers
were identified to species using Koste (1978).
Data analysis
Species diversity of rotifers was calculated using
Shannon–Wiener Index (H ′ )
H ′ s�
=−
pi Log2 pi
i=1
where s and pi are population parameters and s is the
number of species with known proportional abundance
(pi). α diversity was calculated as total number of
species present at each sampling site.
Maximum diversity (H ′ max ) was calculated as
H ′ max = Log 2 s
which assumes that all individuals in a collected
sample are distributed as evenly as possible among the
number of species present (Brower et al., 1990).
Species evenness or equitability was calculated as
J ′ = H ′ /Hmax
which has a minimum value of 0 when evenness is
low and a maximum value of 1 when evenness is high
(Brower et al., 1990).
The spatial and temporal variations in physical and
chemical factors as also rotifer abundance, diversity
and equitability were analyzed using two-way AN-
OVA. Also, data of rotifer abundances were analyzed
and correlated with non-biological variables using
Pearson-product moment correlations.
Results
Physical–chemical analyses
Mean values as well as ranges for various variates are
shown in Table 1. Temperature ranged from 11 ◦ Cto
30 ◦ C, and showed no substantial differences between
the two sampling sites. Generally, water temperature
was for most part of the year above 20 ◦ C except during
the period December–February. DO was inversely
related with temperature and recorded a maximum of
23.6 mg l −1 at S-II. pH ranged from neutral to slightly
alkaline (7.2–8.7) and its values significantly differed
in the different months (p

104
Figure 2. Seasonal variations in (a) Shannon–Weiner diversity
Index (H ′ ); (b) α diversity at S-I & S-II.
ity during different seasons (p < 0.01). However,
the spatial differences for all these parameters were
marginal.
The concentrations of NO3–N, PO4–P, silicates
and SO4 2− exhibited high temporal (p < 0.01) but
little spatial variability, except for PO4–P, which was
generally higher at S-I.
Rotifer species composition
Eighty-nine species of rotifers belonging to 34 genera
and 14 families were recorded. They were categorized
as common, frequent, occasional and rare on the
basis of frequency of their occurrence in the plankton
samples (Table 2). Species such as Colurella
uncinata bicuspidata (Ehrb.), Lecane closterocerca
(Schmarda), L. bulla (Gosse), L. leontina (Turner) and
Limnias melicerta Weisse were perennial, whereas
Filinia terminalis (Plate) and Notholca labis Gosse
(winter), Pompholyx sulcata (Hudson), Ascomorpha
saltans Bartsch (spring–early summer), Filinia opoliensis
(Zacharias) and Brachionus falcatus Zacharias
(late summer–monsoon) were recorded only during
certain seasons.
Table 2. List of planktonic rotifer species recorded at the two
study sites (Site-I and Site-II) from the backwaters of Delhi
segment of the river Yamuna
PHYLUM: ROTIFERA
CLASS: EUROTATORIA
SUBCLASS: DIGONONTA
ORDER: BDELLOIDEA
SITE-I SITE-II
FAMILY: PHILODINIDAE
Rotaria sp. C C
SUBCLASS: MONOGONONTA
ORDER: PLOIMIDA
FAMILY: ASPLANCHNIDAE
Asplanchna brightwelli Gosse, 1850 – R
A. intermedia Hudson, 1886 F F
A. priodonta Gosse, 1850 O O
FAMILY: BRACHIONIDAE
Anuraeopsis fissa (Gosse, 1851) F F
Brachionus angularis Gosse, 1851 O O
B. bidentatus Anderson, 1889 O O
B. caudatus (Hauer, 1937) O O
B. calyciflorus Pallas, 1766 F F
B. falcatus Zacharias, 1898 O O
B. leydigi Cohn, 1862 R R
B. quadridentatus Hermann, 1783 F F
Keratella cochlearis (Gosse, 1851) F F
K. quadrata (Müller, 1786) R –
K. tropica (Apstein, 1907) C C
Platyias leloupi (Gillard, 1957) F –
P. quadricornis (Ehrb., 1832) F F
Notholca labis Gosse, 1887 O O
FAMILY: COLURELLIDAE
Colurella uncinata f. bicuspidata
(Ehrb., 1832) C C
C. adriatica Ehrb., 1831 – R
C. obtusa (Gosse, 1886) C C
C. oxycauda Carlin, 1939 R R
Lepadella costatoides Segers, 1992 O R
L. heterostyla (Murray, 1913) O –
L. ovalis (Müller, 1786) C C
L. patella (Müller, 1786) C C
∗ L. quinquecostata (Lucks, 1912) R –
L. quadricarinata (Stenroos, 1898) F O
Squatinella lamellaris (Ehrb., 1832) R –

Table 2. Continued
SITE-I SITE-II
FAMILY: DICRANOPHORIDAE
Dicranophorus epicharis
Harring & Myers, 1928 R –
Encentrum sp. R –
FAMILY: EUCHLANIDAE
Dipleuchlanis propatula (Gosse, 1886) F R
Euchlanis dilatata Ehrb., 1832 C C
FAMILY: GASTROPODIDAE
Ascomorpha saltans Bartsch, 1870 O O
FAMILY: LECANIDAE
Lecane arcuata (Bryce, 1891) F O
L. arcula Harring, 1914 O O
L. bulla (Gosse, 1886) C C
L. closterocerca (Schmarda, 1859) C C
L. curvicornis (Murray, 1913) F F
L. furcata (Murray, 1913) F F
L. hamata (Stokes, 1896) C C
L. leontina (Turner, 1892) C C
L. ludwigii (Eckstein, 1883) C F
L. luna (Müller, 1776) C C
L. lunaris (Ehrb., 1832) C C
L. pyriformis (Daday, 1905) C F
L. quadridentata (Ehrb., 1832) F F
L. signifera (Jennings, 1896) O O
L. stenroosi (Meissner, 1908) O O
L. ungulata (Gosse, 1887) F F
L. unguitata (Fadeev, 1925) F F
FAMILY: MYTILINIDAE
Lophocharis salpina (Ehrb., 1834) R O
Mytilina bisulcata (Lucks, 1912) O O
M. mucronata (Müller, 1773) R R
M. ventralis (Ehrb., 1832) C C
FAMILY: NOTOMMATIDAE
Cephalodella catellina (Müller, 1786) F O
C. forficula (Ehrb., 1838) O –
C. gibba (Ehrb., 1838) C C
mucronata Myers, 1924 R –
Eosphora najas Ehrb., 1830 F O
Monommata sp. O O
Notommata copeus Ehrb., 1834 F F
Notommata sp. C C
Table 2. Continued
FAMILY: PROALIDAE
105
SITE-I SITE-II
Proales sp. O R
FAMILY: SCARIDIIDAE
Scaridium longicaudum Müller, 1786 C C
FAMILY: SYNCHAETIDAE
Polyarthra sp. F F
Synchaeta oblonga Ehrb., 1831 R R
FAMILY: TRICHOCERCIDAE
Trichocerca braziliensis (Murray, 1913) O O
T. brachyura (Gosse, 1851) O O
T. bicristata (Gosse, 1887) R –
T. cavia (Gosse, 1886) R R
T. iernis (Gosse, 1887) R R
T. longiseta (Schrank, 1802) O O
T. porcellus (Gosse, 1886) F F
T. rattus (Müller, 1776) O O
T. similis (Wierzejski, 1893) F O
T. tigris (Müller, 1776) R R
Trichocerca sp. O R
FAMILY: TRICHOTRIIDAE
Trichotria tetractis (Ehrb., 1830) C C
ORDER: FLOSCULARIACEAE
FAMILY: FILINIIDAE
Filinia opoliensis (Zacharias, 1898) O O
longiseta (Ehrb., 1834) O O
F. terminalis (Plate, 1886) R R
FAMILY: FLOSCULARIIDAE
Floscularia ringens Linnaeus, 1758 O O
Limnias melicerta Weisse, 1848 C C
∗ Ptygura kostei Jose De Paggi, 1996 R R
FAMILY: TESTUDINELLIDAE
Testudinella emarginula (Stenroos, 1898) C C
T. patina (Hermann, 1783) C C
Testudinella sp. R R
Pompholyx sulcata (Hudson, 1885) O O
The system of classification followed is after Koste (1978).
R = Rare; O = Occasional; F = Frequent; C= Common; – = Absent;
( ∗ = New record).

106
Rotifer diversity
Table 3. Correlations between rotifer
abundance (Individuals L −1 ) versus
physical-chemical parameters
Parameter Site-I Site-II
Temperature 0.383 0.206
DO −0.126 −0.139
pH 0.537 0.497
COD −0.780 ∗∗ −0.595 ∗
BOD −0.710 ∗∗ −0.684 ∗
Conductivity 0.414 0.588 ∗
Turbidity −0.343 −0.227
Colour 0.596 ∗ 0.270
Total hardness −0.149 −0.011
Total alkalinity −0.210 −0.241
Chlorides 0.090 0.220
Calcium −0.090 −0.093
Magnesium −0.162 −0.250
PO4–P 0.818 ∗∗ 0.935 ∗∗
NO3–N 0.868 ∗∗ 0.768 ∗∗
NO2–N 0.659 ∗ 0.452
Silicates −0.019 0.128
Sulphates 0.397 0.658 ∗
Correlations are Pearson product-moment
type ( ∗ = p

is supported by the presence of fewer species of
‘temperate-centered’ brachionid genera such as Keratella
and a restricted occurrence of the cold-water
genera Notholca and Synchaeta. These observations
are in concurrence with reports by Sharma & Michael
(1980) and Sharma (1998) with regard to Indian rotifer
fauna. Dumont (1983) and Green (1994) also reported
that Brachionus is predominantly tropical, whereas the
boreal Notholca is rarely present in tropical waters.
The presence of cold-water Notholca labis Gosse in
this segment of the river could be due to drift from
higher altitudes (Sharma, 1998).
During the one-year cycle, the rotifer density
reached maxima during spring–early summer and
minima during winter. In earlier studies on river
Yamuna, the rotifer density was found to be maximum
during summer (Rai, 1974b: Kaur, 1996). This
difference could reflect the different ecological conditions
prevailing in the backwaters. Although the rotifer
density observed definite seasonal variations, species
diversity (H ′ ) and equitability did not vary significantly
across the year. This can be attributed to the
different rotifer taxa registering their peak populations
at different times of the year.
The present study reveals no significant variations
in density, H ′ and equitability between the two study
sites. However, α diversity varied significantly at the
two study sites, possibly due to differential growth
of macrophytes. A number of investigators (Pontin
& Shiel, 1995; Duggan et al., 1998) also observed
that macrophytes in aquatic ecosystems provide a rich
variety of microhabitats for a diverse rotifer fauna.
In general, high densities of rotifers reflect the
availability of a wide range of natural sestonic food
particles, which rotifers may consume (Dumont, 1977;
Gulati, 1990). Various investigators reported that the
Figure 3. Seasonal variations in the abundance of rotifers at S-I and S-II.
107
rapid increase in rotifers numbers may be attributed to
their intrinsic high fecundity supported by favourable
food and environmental conditions (Dumont, 1977;
Lynch, 1979; Gulati, 1999). Thus, the presence of favourable
physical–chemical characteristics (e.g., temperature,
nutrients and pH) as also relative abundance
of diatoms viz. Cymbella and Gomphonema, followed
by green algae viz. Rhizoclonium and Spirogyra and
blue-green algae viz. Lyngbya and Anabaena (Arora,
1998), were possibly responsible for promoting the
growth of rotifers during spring–early summer seasons
during this study. In contrast, lower density of
rotifers recorded during winter could be due to low
temperatures, which do not favour their growth and
reproduction (Michaloudi et al., 1997).
Hofmann (1977) suggested that temperature (a
conditional factor) and oxygen (a material factor)
are the main but not the only determinative factors
which influence the occurrence and diversity of rotifers.
Influence of temperature on rotifer communities
was also confirmed by May (1983), Berzins & Pejler
(1989b) and Hessen et al. (1995). However, during
our study high rotifer density was weakly associated
with temperature and oxygen. This can be explained
on the assumption of Holland et al. (1983) that the
influence of temperature and oxygen on rotifer abundances
is less manifested in warmer climates as also
in shallow waters. Nevertheless, during the present
study, seasonal variations in species composition of
rotifers were mainly controlled by temperature. For instance,
cold stenotherm species viz. Filinia terminalis
(Plate) and Notholca labis Gosse were recorded during
winter, whereas warm stenotherm species viz.
Ascomorpha saltans Bartsch and Pompholyx sulcata
(Hudson) were observed during spring–early summer.
These observations are in accord with May (1983) and

108
Figure 4. Seasonal variations in the relative per cent abundance of different representative families of rotifers (a) at S-I and (b) at S-II. The
abbreviations of different rotifers families are as follows: Flos – Flosculariidae; Test – Testudinellidae; Euch – Euchlanidae; Lec – Lecanidae;
Brach – Brachionidae; Others – Rest of the families.
Berzins & Pejler (1989b), who have also regarded the
above-mentioned cold- and warm-stenotherm species
as ‘winter forms’ and ‘summer forms’, respectively.
The results of this study indicate that rotifer population
density was positively related with PO4–P,
NO3–N, NO2–N, SO4 2− , colour and conductivity, and
negatively associated with COD and BOD. Besides,
no significant correlation was observed between rotifer
abundance and alkalinity, pH, turbidity, silicates
and total hardness. NO3–N and PO4–P indicate the
trophic status, and may partly determine the species
presence and dynamics of rotifer assemblages (Berzins
& Pejler, 1987, 1989a). In addition, there are reports
of significant correlations of rotifer populations
with total nitrogen by Devetter (1998), and with phosphorus
by Stemberger (1995). Devetter (1998) did not
observe any correlation among rotifer populations and
the concentrations of anions (SO4 2− and Cl − )and
cations (Mg 2+ and Ca 2+ ). Our results are in agreement
with Devetter’s observations, except for SO4 2−
ions, for which we observed significant positive correlation
with rotifer density at S-II. In addition, water
colour may partly determine the occurrence of rotifer
species and hence their seasonal dynamics (Berzins &
Pejler, 1989c). An analysis of physical and chemical
data from a large number of water bodies (e.g., Berzins
& Pejler, 1987; Hessen et al., 1995; Pinel-Alloul
et al., 1995) revealed that alkalinity and pH are often
important in predicting zooplankton community composition,
which is contrary to the results obtained by
us. Perhaps relatively high values for pH and alkalinity
throughout the study period were important because
they indicate high photosynthetic activity, and rotifers
were not food-limited.
De Zwart (1991) and Kaur (1996) observed dominance
of rotifers with low species diversity in the

segments of the Yamuna having high levels of BOD
and COD. In comparison, the present study sites recorded
highly diverse rotifer fauna with relatively low
BOD and COD values. The levels of BOD and COD
were low exhibiting seasonal variations and negative
correlation with rotifer density.
Our study suggests that physical and chemical
factors largely influence the spatial and temporal dynamics
of the rotifer populations in the backwaters of
the Yamuna. However, an additional investigation of
some top-down factors and on the influence of competitive
interactions on the seasonal succession of rotifer
communities is required to reach a definite conclusion.
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