71
4. Total suspended solids (TSS): Water samples
were analyzed gravimetrically for TSS
(APHA et al. 1998 ).
5. Chlorophyll-a: The green pigment chlorophyll- a has been reported to be a reliable
indicator of phytoplankton biomass (Trivedi
and Goel 1986 ). Chlorophyll was, therefore,
extracted in 90 % aqueous acetone and spectrophotometrically analyzed for its concentration
as described in APHA, AWWA ( 1998 ).
6. Nitrate nitrogen: In the present study, total
oxidized nitrogen was estimated using the
cadmium reduction method (APHA et al. 1998 ).
7. Phosphorus: Phosphorous occurs in natural
waters and in wastewater almost solely as phosphates. In the current study, the total reactive
phosphorus of the water was estimated using the
stannous chloride method (APHA et al. 1998 ).
8. Biological oxygen demand (BOD): The BOD
test is widely used to determine the pollution
strength of domestic and industrial wastes and
is one of the most important in stream pollution control activities. During the present
study, the BOD was estimated employing the
5-day BOD test (APHA et al. 1998 ).
Biological Sampling
Separate samples were collected by fi ltering a
volume of 10 L subsurface water through a plankton net made up of bolting silk cloth No. 20 (the
inside width of the meshes was 74 μm). Extreme
care was taken to keep water undisturbed at the
time of sampling and also to avoid spilling of
water from the net. The samples were immediately
preserved by adding a few drops of 5 % formalin.
The samples were then concentrated to 10 ml by
centrifugation. For fi nal analysis, 0.5 ml of sample
was taken on Sedgwick-Rafter chambers and
rotifers were enumerated and analyzed under a
Leica DMRB research microscope.
Results
The rotifer fauna of River Vishwamitri is represented by a total of 59 species belonging to 24
genera and 17 families.
Species Numbers
Station III has the highest number of rotifer
species. This station has 40 species (Table 6.1 )
out of a total of 59, thus harboring about 67.8 %
of the total rotifer species. This was followed by
station I which has 37 rotifer species (Table 6.2 ),
representing 62.7 % of the rotifer fauna. Next was
station II that had a total of 33 species (Table 6.3 ),
thus having about 56 % of the total rotifer species.
Station IV and station V had the least number of
rotifer species, a total of 12 (Table 6.4 ) and 10
species (Table 6.5 ), respectively, thus harboring
just about 20.3 % and 16.9 % of the total rotifer
fauna of the river.
Exclusive Species
Rotifer species that occurred at a single station
have been termed as “exclusive species” in the
present study. Twenty rotifer species out of a total
of 59 species have been found to occur exclusively at just one particular station. Thus, 33.9 %
of the species can be termed as exclusive species or
species occurring exclusively at a single station.
From the data (Table 6.1 ), it is evident that station
III supports the maximum number of such exclusive species. This station harbors a total of 12
such exclusive species accounting for 63 % of the
total exclusive species. This is followed by station
I having a total of fi ve exclusive species (Table 6.2 ),
thus accounting for 21 %; station II is next,
harboring three exclusive species (Table 6.3 )
and accounting for 15.8 % of these exclusive
species. Sites IV and V do not support any of the
exclusive species.
Distribution Pattern of Species
As stated earlier, 20 species out of a total of 59
species are exclusive. Six species of rotifers in
River Vishwamitri are common and found at
all five stations. Thus, 10.2 % of the species
are commonly found at all the stations. Four
species are such that they occur at four stations,
i.e., 6.8 % of the species can be found in at least
four stations. Seven species are such that they
6 Structure and Dynamics of Rotifer
4. Total suspended solids (TSS): Water samples
were analyzed gravimetrically for TSS
(APHA et al. 1998 ).
5. Chlorophyll-a: The green pigment chlorophyll- a has been reported to be a reliable
indicator of phytoplankton biomass (Trivedi
and Goel 1986 ). Chlorophyll was, therefore,
extracted in 90 % aqueous acetone and spectrophotometrically analyzed for its concentration
as described in APHA, AWWA ( 1998 ).
6. Nitrate nitrogen: In the present study, total
oxidized nitrogen was estimated using the
cadmium reduction method (APHA et al. 1998 ).
7. Phosphorus: Phosphorous occurs in natural
waters and in wastewater almost solely as phosphates. In the current study, the total reactive
phosphorus of the water was estimated using the
stannous chloride method (APHA et al. 1998 ).
8. Biological oxygen demand (BOD): The BOD
test is widely used to determine the pollution
strength of domestic and industrial wastes and
is one of the most important in stream pollution control activities. During the present
study, the BOD was estimated employing the
5-day BOD test (APHA et al. 1998 ).
Biological Sampling
Separate samples were collected by fi ltering a
volume of 10 L subsurface water through a plankton net made up of bolting silk cloth No. 20 (the
inside width of the meshes was 74 μm). Extreme
care was taken to keep water undisturbed at the
time of sampling and also to avoid spilling of
water from the net. The samples were immediately
preserved by adding a few drops of 5 % formalin.
The samples were then concentrated to 10 ml by
centrifugation. For fi nal analysis, 0.5 ml of sample
was taken on Sedgwick-Rafter chambers and
rotifers were enumerated and analyzed under a
Leica DMRB research microscope.
Results
The rotifer fauna of River Vishwamitri is represented by a total of 59 species belonging to 24
genera and 17 families.
Species Numbers
Station III has the highest number of rotifer
species. This station has 40 species (Table 6.1 )
out of a total of 59, thus harboring about 67.8 %
of the total rotifer species. This was followed by
station I which has 37 rotifer species (Table 6.2 ),
representing 62.7 % of the rotifer fauna. Next was
station II that had a total of 33 species (Table 6.3 ),
thus having about 56 % of the total rotifer species.
Station IV and station V had the least number of
rotifer species, a total of 12 (Table 6.4 ) and 10
species (Table 6.5 ), respectively, thus harboring
just about 20.3 % and 16.9 % of the total rotifer
fauna of the river.
Exclusive Species
Rotifer species that occurred at a single station
have been termed as “exclusive species” in the
present study. Twenty rotifer species out of a total
of 59 species have been found to occur exclusively at just one particular station. Thus, 33.9 %
of the species can be termed as exclusive species or
species occurring exclusively at a single station.
From the data (Table 6.1 ), it is evident that station
III supports the maximum number of such exclusive species. This station harbors a total of 12
such exclusive species accounting for 63 % of the
total exclusive species. This is followed by station
I having a total of fi ve exclusive species (Table 6.2 ),
thus accounting for 21 %; station II is next,
harboring three exclusive species (Table 6.3 )
and accounting for 15.8 % of these exclusive
species. Sites IV and V do not support any of the
exclusive species.
Distribution Pattern of Species
As stated earlier, 20 species out of a total of 59
species are exclusive. Six species of rotifers in
River Vishwamitri are common and found at
all five stations. Thus, 10.2 % of the species
are commonly found at all the stations. Four
species are such that they occur at four stations,
i.e., 6.8 % of the species can be found in at least
four stations. Seven species are such that they
6 Structure and Dynamics of Rotifer