Environmental Engineering Reference
In-Depth Information
Fig. 4.2
Taxonomic
composition of benthic
macroinvertebrate community
(order level) among the
different basins of the
Himalayan region (acronyms:
River basins;
A
Alaknanda,
B
Bhagirathi, M Mandakini,
P
Pindar, R Ramganga,
Y
Yamuna, Taxa;
B
Basommatophora,
C
Coleoptera,
D
Diptera,
E
Ephemeroptera,
O
Others,
P
Plecoptera,
T
Trichoptera)
Basins
%
50
40
30
20
T
10
E
D
O
C
0
Taxa
P
B
YBAMPR
River basins
are equally abundant in the Supin. Decrease in
the relative abundance of Trichoptera corre-
sponded to increase of Ephemeroptera at all
the locations (Fig.
4.3
). Besides, the abun-
dance of Ephemeroptera marginally exceeds
that of Trichoptera. In contrast, the abundance
of Trichoptera is considerably higher than
Ephemeroptera.
Trichoptera is dominating in the pine and
pine-dominating forest types in most of the
streams of all the river basins except Rupin and
Supin (in the Yamuna basin), Dharasu Gad
(Bhagirathi basin) and Damar Gad (Mandakini
basin) where Ephemeroptera is dominant.
Functionally, all Trichoptera recorded during
the study are shredders and collectors which
process the coarse particulate organic matter
(CPOM) so important to the detritus chain. On
the other hand most of the Ephemeroptera
observed are basically scrapers, and only few
feed on the FPOM component of the detritus.
Diptera is abundant after Ephemeroptera and
Trichoptera in the Yamuna, Bhagirathi, Pindar
and Ramganga basins. The relative abundance
of Trichoptera is higher with respect to
Ephemeroptera in all river basins examined
during the study (Table
4.2
).
This is quite contrary to the observation that
the relative abundance of Ephemeroptera exceeds
Trichoptera in glacier-fed Himalayan rivers, the
Bhilangana (Man Mohan and Bisht
1991
), the
Ganga near the foothills at Hardwar (Nautiyal
et al.
1997b
) and the Bhagirathi (Nautiyal et al.
2007
), while Diptera is abundant in the Alaknanda
(Nautiyal et al.
2004
). The spring-fed Himalayan
streams are also dominated by Ephemeroptera,
Khanda Gad (Kumar
1991
), Alikhad stream
(Joshi
1994
) and the Gaula (Sunder
1997
),
while Trichoptera is the abundant taxon in the
headwater zone of Vindhyan (Central Highlands)
river Paisuni (Shivam
2006
). Contrarily, Ward
(
1994
) observed that Ephemeroptera precede
Trichoptera in the alpine glacier-fed streams.
Thus, headwaters are not necessarily dominated
by Trichoptera, nor do they appear to be related
to lower temperatures in the alpine zone. The
higher relative abundance of Trichoptera in this
study could be attributed to the fact that most of
the locations studied earlier are located below
800 m above sea level compared with an eleva-
tion range of 800-2,000 m asl which is also quite
below the alpine zone. As forest is usually the
major land use in these elevations, the abundance
of Trichoptera seems reasonable as they feed on
the coarse to fi ne particulate organic matter gen-
erated from the forest detritus, thus functioning
as shredder, collector and gatherer in the detritus
food chain.
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