Environmental Engineering Reference
In-Depth Information
the pollution load increases drastically as evi-
denced by the biological oxygen demand values
(Table 6.16 ), and the dissolved oxygen levels are
too low to support many organisms. At these
sites, the suspended solid levels are also very
high which greatly reduces the transparency. This
would in turn affect the light penetration required
by the primary producers. All these factors
combined probably account for the low diversity
at these stations.
Apart from the physicochemical factors, biotic
factors might also play an important role in con-
trolling the zooplankton community structure.
The presence or absence of predators also affects
the rotifer populations. The negative relation
between the presence of Daphnia and rotifers
has been well documented (Fussmann 1996 ).
As already discussed earlier during the post-
monsoon period, the cladoceran density is quite
low, probably affected by the high levels of sus-
pended solids, as the result of which the rotifers
are found in high numbers.
Presence of macrophytes also affects the zoo-
plankton diversity. Lougheed et al. ( 1998 ) stated
that patchy distribution of aquatic vegetation
contributes to seasonal variability in water qual-
ity characteristics and the amount of habitat
available for aquatic invertebrates. Development
of vegetation increases structural complexity, so
providing more niches for rotifers. In a large
body with a complex littoral zone, the numbers of
rotifer species can reach over 200 (Segers and
Dumont 1995 ; Dumont and Segers 1996 ).
The macrophytes provide more diverse habitat
(Van den Berg et al. 1997 ). This was well
observed by Kuczyriska-Kippen ( 2007 ) that
shallow lakes with a good macrophyte density
offered a wide choice of habitat for the rotifer
community, thus enhancing their diversity and
density in such habitats.
In River Vishwamitri, macrophytes are present
in highest numbers at station III followed by station
II and station I. Station IV and station V have
negligible macrophyte population (Dhuru et al.,
2003 ). This could be yet another reason for higher
diversity in the fi rst three stations. Telesh ( 1995 )
also found rotifer diversity high in reed beds, the
most common type of aquatic vegetation. Typha
angustata beds seen at stations II and III of River
Vishwamitri could be another factor contributing
to the higher rotifer number often present in these
stations. Telesh ( 1995 ) further describes that spe-
cies like Brachionus calycifl orus , B. quadridenta-
tus , and Filinia longiseta are commonly found in
areas where macrophytic vegetations are plenty.
All the above species were found at sampling sta-
tions II and III. Phytophilous species like Platyias
quadricornis and Mytilina ventralis are abundant
in macrophyte beds (Telesh 1995 ). Platyias
quadricornis was found at station III, while
Mytilina ventralis was located at station II of
Vishwamitri.
Thus, it can be seen that by and large station
III seems to provide a better habitat with diverse
niche for the rotifer community. This station
besides receiving domestic sewage has relatively
good levels of dissolved oxygen throughout the
year. Moreover, there is water throughout the year
at this station. The reed beds provide more varied
microhabitat which is needed for the survival of
the periphytic rotifers. This could be the reason
for a high number of exclusive species found at
this station.
From the above discussion, it could be con-
cluded that pH and chlorophyll-a play a major
role in infl uencing the rotifer community structure.
Additionally, both abiotic and biotic factors could
be interacting with each other and their combined
effect may be infl uencing the rotifer community
structure.
References
APHA, AWWA, WEF (1998) Standard methods for the
examination of water and wastewater. American
Public Health Association, Washington, DC
Archibald M (1972) Diversity in some South African dia-
tom associations and its relation to water quality.
Water Res 6:1229-1238
Arora HC (1966) Studies on Indian Rotifera - Part III. On
Brachionus calycifl orous and some varieties of the
species. J Zool Soc India 16:1-6
Arora J, Mehra NK (2003) Seasonal dynamics of rotifers
in relation to physical and chemical conditions of the
river Yamuna (Delhi). India Hydrobiol 491:101-109
Banerjea S, Motwani MP (1960) Some observations on
pollution of the Suvaon stream by the effl uents of a
sugar factory, Balrampur (UP). Ind J Fish 7:107-128
 
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